- New insight on an old reaction - The aqueous hydrolysis of acetic anhydride
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Studies have shown that aqueous reactions generating a change in pH can be accurately monitored using a fast-response pH electrode. This technique has been successfully applied in this work to the aqueous hydrolysis of acetic anhydride, which is a reaction that has been studied using a variety of techniques for nearly one hundred years. Many of these techniques involve elaborate equipment and sophisticated analyses, making the pH technique an attractive alternative. Studies here have focused on the temperature effects of the simple hydrolysis and acetate-catalyzed hydrolysis reactions. Data analyses suggest the notion that if simple hydrolysis occurs by a two-step mechanism, it does so only at low temperatures, whereas acetate-catalyzed hydrolysis occurs almost assuredly by a single step mechanism. Results of this work yield the following values for the activation parameters for simple hydrolysis (subscripted with a "w") and acetate-catalyzed hydrolysis (subscripted with an "a") at atmospheric pressure: ΔHw?=39.90. 7kJ×mol-1,ΔSw?=-227(2)J×K-1×mol-1, ΔHa?=49.7(0.3)kJ×mol-1 and ΔS?a=-1571J×K- 1×mol-1. Implications of these results are discussed in this article. Copyright
- Wiseman, Floyd Landis
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- Peroxy Acid Oxidations. II. A Kinetic and Mechanistic Study of Oxidation of α-Diketones
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The kinetics of Baeyer-Villiger oxidation of biacetyl and benzil by peroxomonophosphoric acid and peroxomonosulfuric acid have been studied in different pH ranges at 308 K.The reactions are second order; first order each in peroxy acid and in diketone concentrations at constant pH.The oxidation rate is strongly pH-dependent; the rate increases with increase in pH.From the pH-rate data the reactivity of different peroxo species, in the oxidation, has been determined.A mechanism consistent with rate-detemining nucleophilic attack of peroxo species on carbonyl carbon of the diketone molecule has been proposed.Acetic acid and benzoic acid are respectively found to be the products of oxidation of biacetyl and benzil.
- Panda, Radhasyam,Panigrahi, Akhil Krishna,Patnaik, Chakrapani,Sahu, Sabita Kumari,Mahapatra, Sabita Kumari
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- Synthesis of Pd-Pt Ultrathin Assembled Nanosheets as Highly Efficient Electrocatalysts for Ethanol Oxidation
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Control over composition and morphology of nanocrystals (NCs) is significant to develop advanced catalysts applicable to polymer electrolyte membrane fuel cells and further overcome the performance limitations. Here, we present a facile synthesis of Pd?Pt alloy ultrathin assembled nanosheets (UANs) by regulating the growth behavior of Pd?Pt nanostructures. Iodide ions supplied from KI play as capping agents for the {111} plane to promote 2-dimensional (2D) growth of Pd and Pt, and the optimal concentrations of cetyltrimethylammonium chloride and ascorbic acid result in the generation of Pd?Pt alloy UANs in high yield. The prepared Pd?Pt alloy UANs exhibited the remarkable enhancement of the catalytic activity and stability toward ethanol oxidation reaction compared to irregular-shaped Pd?Pt alloy NCs, commercial Pd/C, and commercial Pt/C. Our results confirm that the Pd?Pt alloy composition and ultrathin 2D morphology offer high accessible active sites and favorable electronic structure for enhancing electrocatalytic activity.
- Choi, Sang-Il,Han, Yeji,Hong, Jong Wook,Kim, Jeonghyeon,Lee, Su-Un
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- Kinetics of formation of peroxyacetic acid
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The kinetics of the reaction of acetic acid with hydrogen peroxide, leading to peroxyacetic acid, were studied at various molar reactant ratios (AcOH-H2O2 from 6 : 1 to 1 : 6) at 20, 40, and 60°C and sulfuric acid (catalyst) concentrations of 0 to 9 wt %. The reaction is reversible, and the equilibrium constant decreases as the temperature rises: K = 2.10 (20°C), 1.46 (40°C), 1.07 (60°C); Δr H 0 = - 13.7±0.1 kJ mol-1, Δr S = -40.5±0.4 J mol-1 K-1. The maximal equilibrium concentration of peroxyacetic acid (2.3 M) is attained at 20°C and a molar AcOH-to-H2O2 ratio of 2.5 : 1. The rate constants of both forward and reverse reactions increase with increase in sulfuric acid concentration from 0 to 5 wt %. Further raising the catalyst concentration does not affect the reaction rate. The reaction mechanism is discussed. 2005 Pleiades Publishing, Inc.
- Dul'neva,Moskvin
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- Rapid Aqueous Synthesis of Large-Size and Edge/Defect-Rich Porous Pd and Pd-Alloyed Nanomesh for Electrocatalytic Ethanol Oxidation
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In this work, a facile aqueous synthesis strategy was used (complete in 5 min at room temperature) to produce large-size Pd, PdCu, and PdPtCu nanomeshes without additional organic ligands or solvent and the volume restriction of reaction solution. The obtained metallic nanomeshes possess graphene-like morphology and a large size of dozens of microns. Abundant edges (coordinatively unsaturated sites, steps, and corners), defects (twins), and mesopores are seen in the metallic ultrathin structures. The formation mechanism for porous Pd nanomeshes disclosed that they undergo oriented attachment growth along the ?111? direction. Owing to structural and compositional advantages, PdCu porous nanomeshes with certain elemental ratios (e. g., Pd87Cu13) presented enhanced electrocatalytic performance (larger mass activity, better CO tolerance and stability) toward ethanol oxidation.
- Teng, Yuxiang,Guo, Ke,Fan, Dongping,Guo, Hongyou,Han, Min,Xu, Dongdong,Bao, Jianchun
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- A high-throughput pH-based colorimetric assay: application focus on alpha/beta hydrolases
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Research involving α/β hydrolases, including α-amino acid ester hydrolase and cocaine esterase, has been limited by the lack of an online high throughput screening assay. The development of a high throughput screening assay capable of detecting α/β hydrolase activity toward specific substrates and/or chemical reactions (e.g., hydrolysis in lieu of amidase activity and/or synthesis instead of thioesterase activity) is of interest in a broad set of scientific questions and applications. Here we present a general framework for pH-based colorimetric assays, as well as the mathematical considerations necessary to estimate de novo the experimental response required to assign a ‘hit’ or a ‘miss,’ in the absence of experimental standard curves. This combination is valuable for screening the hydrolysis and synthesis activity of α/β hydrolases on a variety of substrates, and produces data comparable to the current standard technique involving High Performance Liquid Chromatography (HPLC). In contrast to HPLC, this assay enables screening experiments to be performed with greater efficiency.
- Paye, Mariétou F.,Rose, Harrison B.,Robbins, John M.,Yunda, Diana A.,Cho, Seonggeon,Bommarius, Andreas S.
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- Polyoxometalate-Modified Fabrics: New Catalytic Materials for Low-Temperature Aerobic Oxidation
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The polyoxometalate H5PV2Mo10O40 (1) is deposited on cotton cloth, polyacrylic fiber, nylon fiber, carbon powder (Ambersorb 572), and the Japanese "self-deodorizing" fabric Smoklin by immersion of these materials in aqueous solutions of 1 followed by evaporation of the water. DRIFT spectra and chemical reactivity indicate that 1 is not damaged during deposition on the materials. More significantly, they catalyze O2-based oxidations of two representative and common toxics in air, acetaldehyde and 1-propanethiol, in addition to a representative thioether, tetrahydrothiophene. These aerobic oxidations proceed heterogeneously with the substrates in the liquid phase and under unusually mild conditions (mostly ambient temperature and pressure). One representative reaction, CH3CHO+O2→CH3COOH, catalyzed by several 1-fabric materials is examined in some detail. Kinetics, radical scavenging, and other experiments are consistent with the 1-fabric functioning primarily as a radical chain initiator. Surface area measurements and scanning electron microscopy of two representative materials, 1-polyacrylic and 1-Smoklin, before and after deposition of 1 and after catalysis indicate that the fibers are not demonstrably altered by deposition of 1, and that the 1-fabric catalysts are not significantly deactivated by use. In all cases, the surface areas are 2/g by BET N2 adsorption, and the deposition morphology is clumps of 1 microcrystals covering 2 oxidations in our evaluations. In contrast, 1-Smoklin is quite acti ve for all these processes.
- Xu, Ling,Boring, Eric,Hill, Craig L.
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- Kinetic studies on the oxidation of iodide by peroxyacetic acid
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The kinetics of the oxidation of iodide by peroxyacetic acid (PAA) in aqueous media in the presence and absence of the heptamolybdate has been studied by a high time resolution spectrophotometric stopped-flow method. The time-dependent concentration of the liberated iodine was monitored by the change in absorbance at 352 nm. The effect of ammonium heptamolybdate as well as pH on the rate of the reaction was also studied and it was found that the rate of the reaction is independent of pH and molybdate concentration under the examined conditions. The results obtained show that the rate law of the reaction can be expressed as rate=k[PAA][I-] with a value of k=4.22×102 (mole/l)-1 s-1 at pH 3.5-5.4 and 25°C.
- Awad, Mohamed Ismail,Oritani, Tadato,Ohsaka, Takeo
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- Substrate Specificity and Leaving Group Effect in Ester Cleavage by Metal Complexes of an Oximate Nucleophile
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Deprotonated zinc(II) and cadmium(II) complexes of a tridentate oxime nucleophile (1, OxH) show a very high reactivity, breaking by 2-3 orders of magnitude the previously established limiting reactivity of oximate nucleophiles in the cleavage of substituted phenyl acetates and phosphate triesters, but are unreactive with p-nitrophenyl phosphate di- and monoesters. With reactive substrates, these complexes operate as true catalysts through an acylation-deacylation mechanism. Detailed speciation and kinetic studies in a wide pH interval allowed us to establish as catalytically active forms [Cd(Ox)]+, [Zn(Ox)(OH)], and [Zn(Ox)(OH)2]? complexes. The formation of an unusual and most reactive zinc(II) oximatodihydroxo complex was confirmed by electrospray ionization mass spectrometry data and supported by density functional theory calculations, which also supported the previously noticed fact that the coordinated water in [Zn(OxH)(H2O)2]2+ deprotonates before the oxime. Analysis of the leaving group effect on the cleavage of phenyl acetates shows that the rate-determining step in the reaction with the free oximate anion is the nucleophilic attack, while with both zinc(II) and cadmium(II) oximate complexes, it changes to the expulsion of the leaving phenolate anion. The major new features of these complexes are (1) a very high esterolytic activity surpassing that of enzyme hydrolysis of aryl acetate esters and (2) an increased reactivity of coordinated oxime compared to free oxime in phosphate triester cleavage, contrary to the previously observed inhibitory effect of oxime coordination with these substrates.
- Lugo-González, José Carlos,Gómez-Tagle, Paola,Huang, Xiaomin,M. Del Campo, Jorge,Yatsimirsky, Anatoly K.
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- Activity, recyclability, and stability of lipases immobilized on oil-filled spherical silica nanoparticles with different silica shell structures
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Candida antarctica lipaseA was immobilized on spherical silica nanoparticles with oil-filled core and oil-induced mesoporous silica shell with different silica shell structures. The immobilization of enzymes was achieved by directly adding enzymes to the oil-in-water emulsion system under ambient synthesis conditions, and the silica shell structure was controlled by the addition of the cosolvent ethanol to the initial synthesis medium. Detailed structural analysis revealed the formation of oil-filled spherical silica nanoparticles with 3.4-4.2nm mesopores randomly arranged in the silica shell; the thickness and pore characteristics of these pores markedly changed with the addition of ethanol. The retention of the enzyme activity during biocatalysis was significantly affected by the structural properties of the silica shells, and it was found that a thick and dense silica shell is essential to afford an active, recyclable, and stable biocatalyst. Furthermore, the oil encapsulated within the core cavity was found to play an important role in achieving a high catalytic efficiency. Trapped oil: Candida antarctica lipaseA is immobilized on oil-filled spherical silica nanoparticles with different silica shell structures through an anionic surfactant-induced self-assembly approach (see scheme) with ethanol as a cosolvent. The entrapped enzymes mostly retain their activities and exhibit recyclability and thermal and chemical stability, depending on the thickness and pore characteristics of the silica shells. TEOS=Tetraethoxyorthosilicate, APTES=3-aminopropyl triethoxysilane.
- Kuwahara, Yasutaka,Yamanishi, Takato,Kamegawa, Takashi,Mori, Kohsuke,Yamashita, Hiromi
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- Exceptionally stable Rh-based molecular catalyst heterogenized on a cationically charged covalent triazine framework support for efficient methanol carbonylation
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Direct carbonylation of methanol into methyl acetate and acetic acid using Rh-based heterogeneous catalysts is of great interest due to their effective levels of activity and stability. Here, a Rh-based molecular catalyst heterogenized on a charged 1,3-bis(pyridyl)imidazolium-based covalent triazine framework (Rh-bpim-CTF) was synthesized and characterized to have a single-site distribution of metal molecular species throughout the support by its ligation to abundant N atom sites. Methanol carbonylation was performed using the Rh-bpim-CTF catalyst in a plug-flow reaction in the gas phase, affording a turnover frequency of up to 3693 h-1 and a productivity of 218.9 mol kg-1 h-1 for acetyl products with high stability.
- Park, Kwangho,Lim, Sangyup,Baik, Joon Hyun,Kim, Honggon,Jung, Kwang-Deog,Yoon, Sungho
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- Radical catalyzed debromination of bromo-alkanes by formate in aqueous solutions via a hydrogen atom transfer mechanism
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CO2·- radicals catalyze the dehalogenation of bromo-alkanes by formate via a hydrogen atom transfer mechanism.
- Shandalov, Elisabetha,Zilbermann, Israel,Maimon, Eric,Nahmani, Yeoshua,Cohen, Haim,Adar, Eilon,Meyerstein, Dan
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- Critical phenomena in acetone oxidation by nitric acid
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The kinetic regularities of acetone oxidation by aqueous nitric acid solutions (5.86-58.31 wt.%) were studied using a differential automatic microcalorimeter. The critical phenomena were discovered, which manifest themselves as a abrupt change in the initial heat release rate at a minor change in the temperature or acid concentration. The abrupt change in the oxidative activity of the reactant at a minor change in the system parameter was assumed to be related to changes in the structure of the solution and, as a consequence, in the solvation energy of the reactants at a certain acid/water ratio in the solution.
- Rubtsov, Yu. I.,Kazakov,Sorokina,Manelis
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- A Highly Efficient Copper(II) Complex catalysed Hydrolysis of Methyl Acetate at pH 7.0 and 25 deg C
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The turnover time for 2+ (1 mM) catalysed hydrolysis of methyl acetate (1 M) is 23 min at pH 7, 25 deg C.
- Chin, Jik,Jubian, Vrej
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- Efficient production of acrylic acid by dehydration of lactic acid over BaSO4 with crystal defects
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BaSO4 catalysts with different micromorphologies and crystal texture were prepared and used to investigate the structure-activity relationship in the dehydration reaction of lactic acid (LA) to acrylic acid (AA). SEM and N2 physisorption were used to study the micromorphology. XRD and photoluminescence spectra were employed to analyze the crystal texture of samples prepared with different methods and treatments. The results revealed that BaSO4 with smaller crystals and more defects had higher activity and selectivity to AA. It was likely that the crystal defects provided the active acid sites for dehydration of LA to AA, as evidenced by XPS and NH3-TPD measurements. Using ethanol as the solvent and ultrasound treatment during the preparation of BaSO4, imperfect small crystals with more defects were formed, which increased the AA selectivity to 78.8%.
- Lyu, Shuting,Wang, Tiefeng
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- Selective oxidation of ethane to acetic acid selective oxidation of ethane to acetic acid catalyzed catalyzed by by a c-scorpionate c-scorpionate iron(Ii) iron(ii) complex: Complex: A ahomogeneous vs.vs.heterogeneous comparison
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The direct, one-pot oxidation of ethane to acetic acid was, for the first time, performed using a C-scorpionate complex anchored onto a magnetic core-shell support, the Fe3O4/TiO2/[FeCl2{κ3 -HC(pz)3}] composite. This catalytic system, where the magnetic catalyst is easily recovered and reused, is highly selective to the acetic acid synthesis. The performed green metrics calculations highlight the “greeness” of the new ethane oxidation procedure.
- Martins, Luísa M. D. R. S.,Matias, Inês A. S.,Ribeiro, Ana P. C.
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- Single-pot ethane carboxylation catalyzed by new oxorhenium(V) complexes with N,O ligands
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The oxorhenium(V) chelates [ReOCl-(N,O-L)(PPh3] [N,O-L = (OCH2CH2)N(CH2CH2,OH)-(CH 2COO) (2), (OCH2CH2)N(CH2COO) (CH2-COOCH3) (3)] and [ReOCl2(N,O-L)(PPh 3] [N,O-L = C5H4N(COO-2) (4) C 5H3(COOCH3-2)(COO-6) (5)] have been prepared by reaction of [ReOCl3(PPh3)2] (1), in refluxing methanol, with N,N-bis(2-hydroxy-ethyl)glycine [bicine; N(CH2CH 2OH)2(CH2COOH)], N-(2-hydroxyethyl) iminodiacetic acid [N(CH2CH2-OH)(CH2COOH) 2], picolinic acid [NC5H4(COOH-2)] or 2,6-pyridinedicarboxylic acid [NC5H3(COOH-2,6) 2], respectively, with ligand esterification in the cases of 3 and 5. All these complexes have been characterized by IR and multinuclear NMR spectroscopy, FAB+-MS, elemental and X-ray diffraction structural analyses. They act as catalysts, in a single-pot process, for the carboxylation of ethane by CO, in the presence of potassium peroxodisulfate K 2S2O8, in trifluoroacetic acid (TFA), to give propionic and acetic acids, in a remarkable yield (up to ca. 30%) and under relatively mild conditions, with some advantages over the industrial processes. The picolinate complex 4 provides the most active catalyst and the carboxylation also occurs, although much less efficiently, by the TFA solvent in the absence of CO. The selectivity can be controlled by the ethane and CO pressures, propionic acid being the dominant product for pressures about ca. 7 and 4 atm, respectively (catalyst 4), whereas lower pressures lead mainly to acetic acid in lower yields. These reactions constitute an unprecedented use of Re complexes as catalysts in alkane functionalization.
- Kirillov, Alexander M.,Haukka, Matti,Kirillova, Marina V.,Pombeiro, Armando J. L.
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- Hydrothermal process for increasing acetic acid yield from lignocellulosic wastes
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To increase the acetic acid yield in a wet oxidation of lignocellulosic wastes, a new two-step reaction process is proposed. The first step produces 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (2-FA) by dehydration of monosaccharides which are f
- Jin, Fangming,Zheng, Junchao,Enomoto, Heiji,Moriya, Takehiko,Sato, Naohiro,Higashijima, Hisao
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- Effect of ammonium perfluorooctanoate on acetylcholinesterase activity and inhibition using MALDI-FTICRMS
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Ammonium perfluorooctanoate (APFO) is a commercially important compound, but its harm to people's health has raised widespread concern. In the past, the investigations into APFO and its degradation product (perfluorooctanoic acid, PFOA) were all about their effect on indicator compounds in animals and enzyme activities. Here, we provided a new suggestion to investigate the influence of APFO and PFOA. Acetylcholinesterase (AChE) was chosen as research subject to reflect the effect of external perfluorochemicals. We applied matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICRMS) to detect the activity of AChE rapidly and accurately. On this basis, not only AChE activity but also AChE inhibition was studied carefully. The presence of APFO and PFOA showed obvious increase of AChE activity. Moreover, addition of both APFO and PFOA had enhanced AChE inhibition from organophosphorous (OP) pesticide (irreversible inhibitor). Otherwise, the participation of APFO and PFOA had not increased AChE inhibitions from reversible inhibitor galantamine. These results might provide new insights into the effect of APFO and encourage the deep understanding about effect of APFO on human being.
- Cai, Tingting,Zhang, Li,Wang, Rong,Liang, Chen,Zhang, Yurong,Guo, Yinlong
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- Adsorption and catalytic properties of the inner nanospace of a gigantic ring-shaped polyoxometalate cluster
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Functional inner space: A gigantic ringshaped {Mo154} polyoxometalate cluster anion can be stabilized by encapsulation in dimethyldioctadecylammonium (DODA) cations. Its inner nanospace enables adsorption of gases and vapors, and it acts as a water-tolerant solid acid catalyst (see scheme).
- Noro, Shin-Ichiro,Tsunashima, Ryo,Kamiya, Yuichi,Uemura, Kazuhiro,Kita, Hidetoshi,Cronin, Leroy,Akutagawa, Tomoyuki,Nakamura, Takayoshi
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- Oxidative decarboxylation of levulinic acid by cupric oxides
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In this paper, cupric oxides was found to effectively oxidize levulinic acid (LA) and lead to the decarboxylation of levulinic acid to 2-butanone. The effects of cupric oxide dosage, reaction time and initial pH value were investigated in batch experiments and a plausible mechanism was proposed. The results showed that LA decarboxylation over cupric oxides at around 300 °C under acidic conditions produced the highest yield of butanone (67.5%). In order to elucidate the catalytic activity of cupric oxides, XRD, AFM, XPS and H 2-TPR techniques was applied to examine their molecular surfaces and their effects on the reaction process.
- Gong, Yan,Lin, Lu,Shi, Jianbin,Liu, Shijie
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- Amavadin and other vanadium complexes as remarkably efficient catalysts for one-pot conversion of ethane to propionic and acetic acids
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Synthetic amavadin Ca[V{ON[CH(CH3)COO]2}2] and its models Ca[V{ON(CH2COO)2}2] and [VO{N(CH2CH2O}3)], in the presence of K 2S2O8 in trifluoroacetic acid (TFA), exhibit remarkable catalytic activity for the one-pot carboxylation of ethane to propionic and acetic acids with the former as the main product (overall yields up to 93%, catalyst turnover numbers (TONs) up to 2.0×104). The simpler V complexes [VO(CF3SO3)2], [VO(acac)2] and VOSO4 are less active. The effects of various factors, namely, C2H6 and CO pressures, time, temperature, and amounts of catalyst, TFA and K2S2O 8, have been investigated, and this allowed optimisation of the process and control of selectivity. 13C-labelling experiments indicated that the formation of acetic acid follows two pathways, the dominant one via oxidation of ethane with preservation of the C-C bond, and the other via rupture of this bond and carbonylation of the methyl group by CO; the C-C bond is retained in the formation of propionic acid upon carbonylation of ethane. The reactions proceed via both C- and Ocentred radicals, as shown by experiments with radical traps. On the basis of detailed DFT calculations, plausible reaction mechanisms are discussed. The carboxylation of ethane in the presence of CO follows the sequential formation of C2H5 ., C2H5CO., C2H 5COO. and C2H5COOH. The C 2H5COO. radical is easily formed on reaction of C2H5CO. with a peroxo V catalyst via a V{η-OOC(O)C2H5) intermediate. In the absence of CO, carboxylation proceeds by reaction of C2H5. with TFA. For the oxidation of ethane to acetic acid, either with preservation or cleavage of the C-C bond, metal-assisted and purely organic pathways are also proposed and discussed.
- Kirillova, Marina V.,Kuznetsov, Maxim L.,Da Silva, Jose A. L.,Guedes Da Silva, Maria Fatima C.,Frausto Da Silva, Joao J. R.,Pombeiro, Armando J. L.
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- Single-pot conversion of methane into acetic acid in the absence of CO and with vanadium catalysts such as amavadine
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Although its biological function is still unknown, the naturally occurring vanadium complex amavadine may be suitable for industrial applications: This compound (as well as other VIV and VV complexes with N,O and O,O ligands) are shown to act as catalysts for the direct conversion of methane into acetic acid, without requiring CO, under very mild conditions and in high yields (see scheme).
- Reis, Patricia M.,Silva, Jose A. L.,Palavra, Antonio F.,Frausto da Silva, Joao J. R.,Kitamura, Tsugio,Fujiwara, Yuzo,Pombeiro, Armando J. L.
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- A facile post-synthetic modification of ordered mesoporous carbon to get efficient catalysts for the formation of acetins
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Highly active and stable solid acid catalysts based on ordered mesoporous carbons were synthesized via hard template method and further functionalization with sulfonic (SO3H) groups. Two post-synthetic modification strategies were applied. In the first one, the pristine carbon was modified with concentrated sulfuric acid. The second approach included the reaction of carbon with aryl diazonium cation generated in situ from sulfanilic acid. The morphology, structure, composition, and surface functionalities of the resulting carbons were determined by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, N2 adsorption-desorption measurement, elemental analysis, potentiometric titration, X-ray photoelectron spectroscopy and FT-IR method. The obtained samples were further tested in acetylation of glycerol with acetic acid under various conditions, and were found to efficiently produce acetins, valuable fuel additives. An excellent catalytic activity was shown especially by the SO3H-bearing mesoporous carbon prepared by a facile method with the use of 4-benzenediazonium sulfonate under ambient conditions. Furthermore, very good recycling properties of this catalyst was demonstrated by four consecutive runs. It is supposed that acidic catalytic activity of the synthesized materials can be further extended to other acid-catalyzed reactions.
- Goscianska, Joanna,Malaika, Anna
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- Reactor kinetics studies via process raman spectroscopy, multivariate chemometrics, and kinetics modeling
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The deployment of in situ analytics for monitoring chemical reactions in process chemistry development and scale-up is facilitated by advanced instrumentation such as Raman spectrometry. Furthermore, greater process understanding can be engendered by coupling in situ Raman data with multivariate chemometrics analyses and kinetics modeling. Such information is important for devising science-based process control strategies along the concept of quality by design (QbD) initiated through the U.S. FDA process analytical technology (PAT) framework. A series of experiments using varied glass reactors, stirring speeds, and isothermal reaction temperatures were designed with acetic anhydride hydrolysis as the model reaction to successfully demonstrate the efficacy of combining in situ Raman spectroscopy, multivariate analyses, and kinetics modeling. Two different Raman measurement methods, using immersion and noncontact probe optics, were tested through a process Raman spectrometer with multiplexing capability. Information-theoretic multivariate chemometrics were applied to elicit pure component spectra and transient concentrations of chemical species, and two differential-algebraic equations modeling approaches were adopted for elucidating chemical and dissolution kinetics information. The variations in reactor vessel type and sizes, stirring speeds, Raman measurements, and kinetics models were compared in this study.
- Assirelli, Melissa,Xu, Weiyin,Chew, Wee
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- Effect of Pd loading and precursor on the catalytic performance of Pd/WO3-ZrO2 catalysts for selective oxidation of ethylene
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The structure and properties of Pd/WO3-ZrO2 (W/Zr = 0.2) catalysts with different Pd loadings and precursors were investigated. The results indicate that Pd/WO3-ZrO2 prepared from a PdCl2 precursor was optimum for high activity and selectivity. Moreover, ethylene conversion increased with the Pd loading. The structure and nature of the catalysts were characterized using X-ray diffraction, BET N2 adsorption, H2 temperature-programmed reduction and H2 pulse adsorption techniques. The results reveal that the higher catalytic performance of Pd/WO3-ZrO2 prepared from PdCl2 could be related to the formation of polytungstate species and the existence of well-dispersed Pd particles.
- Wang, Lixia,Xu, Shuliang,Chu, Wenling,Yang, Weishen
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- Temperature Dependence of Collisional Energy Transfer in Ethyl Acetate
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Results are reported for the temperature and pressure dependence of the rate coefficient for the thermal unimolecular decomposition of ethyl acetate, obtained by using very low-pressure pyrolysis (VLPP) over the range 800-1150 K, both under conditions where only gas/wall collision occur and also (at 837 K) dilute in a number of bath gases (He, Ar, Ne, Kr, N2, and C2H4).Solution of the appropriate reaction-diffusion master equation yields from these data both the extrapolated high-pressure rate coefficient (1012.7 exp(-201.5 kJ mol-1/RT) s-1) and the average downward collisional energy transfer, down>.The down> values are compared with those obtained for the same collision partners at ca. 340 K using multiple-photon dissociation (mpd).It is found that, for mon- and diatomic bath gases, down> is approximately proportional to T-(0.1-0.3) (for He, Ne) and to T-(0.3-0.5) (for Ar, Kr, N2).The combination of thermal and mpd techniques used here is generally applicable to obataining collisional energy-transfer data of highly vibrationally excited molecules over a wide range of temperatures and collision partners.
- Brown, Trevor C.,Taylor, John A.,King, Keith D.,Gilbert, Robert G.
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- Dissociative nucleophilic substitution of η2-olefin complexes via a novel η2-vinyl cation inTermediate
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A series of η2-[Os(NH3)5(vinyl ether)]2+ complexes have been prepared by three independent methods that involve direct coordination of a vinyl ether, alcohol addition to an η2-alkyne complex, or nucleophilic substitution of an η2-vinyl ether species. In the presence of an acid catalyst, the vinyl ether ligand undergoes a novel acid-catalyzed substitution reaction at the α-carbon with a broad range of nucleophiles that includes alcohols, amines, carboxylates, hydrides, silylated enols, nitriles, phosphines, and dialkyl sulfides. These reactions appear to proceed through an elimination-addition process where the first step is loss of an alcohol to form an η2-vinyl cation intermediate. In cases where the α-carbon bears an alkyl group, an η2-vinyl cation species can be isolated and characterized. For example, protonation of [Os(NH3)5(η2-2-methoxypropene)]2+ (3) in neat HOTf allows the characterization of the substitution reaction intermediate η2-[Os(NH3)5(C3H5)]3+ (32), formally a metallocyclopropene that behaves chemically like a vinyl cation. In contrast, when the α-carbon of the vinyl ether bears a hydrogen such as with [Os(NH3)5(η2-ethoxyethene)]2+ (1), the hypothetical vinyl cation intermediate, in absence of a suitable nucleophile, undergoes an intramolecular 1,2-hydrogen shift to yield the Fischer carbyne [(NH3)5Os≡CCH3]3+ (33). Examples of nucleophilic substitution reactions for other types of η2-[Os(NH3)5(olefin)](n+) complexes are also demonstrated.
- Chen, Huiyuan,Harman, W. Dean
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- Oxidations by the system 'hydrogen peroxide-[Mn2L2O3][PF6] 2 (L=1,4,7-trimethyl-1,4,7-triazacyclononane)-carboxylic acid'. Part 10: Co-catalytic effect of different carboxylic acids in the oxidation of cyclohexane, cyclohexanol, and acetone
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Hydrogen peroxide oxidation of cyclohexane in acetonitrile solution catalyzed by the dinuclear manganese(IV) complex [LMn(O)3MnL](PF6)2 (L=1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN) at 25 °C in the presence of a carboxylic acid affords cyclohexyl hydroperoxide as well as cyclohexanone and cyclohexanol. A kinetic study of the reactions with participation of three acids (acetic acid, oxalic acid, and pyrazine-2,3-dicarboxylic acid, 2,3-PDCA) led to the following general scheme. In the first stage, the catalyst precursor forms an adduct. The equilibrium constants K1 calculated for acetic acid, oxalic acid, and 2,3-PDCA were 127±8, (7±2)×104, and 1250±50 M-1, respectively. The same kinetic scheme was applied for the cyclohexanol oxidation catalyzed by the complex in the presence of oxalic acid. The oxidation of cyclohexane in water solution using oxalic acid as a co-catalyst gave cyclohexanol and cyclohexanone, which were rapidly transformed into a mixture of over-oxidation products. In the oxidation of cyclohexanol to cyclohexanone, varying the concentrations of the reactants and the reaction time we were able to find optimal conditions and to obtain the cyclohexanone in 94% yield based on the starting cyclohexanol. Oxidation of acetone to acetic acid by the system containing oxalic acid was also studied.
- Shul'pin, Georgiy B.,Matthes, Marianne G.,Romakh, Vladimir B.,Barbosa, Marília I.F.,Aoyagi, Jonatas L.T.,Mandelli, Dalmo
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- Dioxygen activation at room temperature during controllable and highly efficient acetaldehyde-to-acetic acid oxidation using a simple iron(III)-acetonitrile complex
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We show that highly efficient acetaldehyde-to-acetic acid oxidation is achieved in a diluted FeCl3-acetonitrile solution (5-100 μM), which proceeds rather rapidly and follows the enzymatic-like Michaelis-Menten kinetics. Interestingly, by adjusting the concentration of FeCl3, we are able to accelerate or shut down the oxidation process conveniently. Based on the catalytic results, spectroscopic evidences and successive DFT calculations, a reactant-initiated, putative mononuclear non-heme iron-oxygen complex, [FeCl(MeCN)4(O)]2+, is proposed as the active oxidizing species to conduct the room temperature reaction with relatively high TOF values (~1.2 s-1). Finally, the putative iron-oxygen complexes are employed to the selective oxidation of benzyl alcohol under ambient conditions.
- Li, Renhong,Kobayashi, Hisayoshi,Yan, Xiaoqing,Fan, Jie
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- Solar-Powered Organic Semiconductor–Bacteria Biohybrids for CO2 Reduction into Acetic Acid
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An organic semiconductor–bacteria biohybrid photosynthetic system is used to efficiently realize CO2 reduction to produce acetic acid with the non-photosynthetic bacteria Moorella thermoacetica. Perylene diimide derivative (PDI) and poly(fluorene-co-phenylene) (PFP) were coated on the bacteria surface as photosensitizers to form a p-n heterojunction (PFP/PDI) layer, affording higher hole/electron separation efficiency. The π-conjugated semiconductors possess excellent light-harvesting ability and biocompatibility, and the cationic side chains of organic semiconductors could intercalate into cell membranes, ensuring efficient electron transfer to bacteria. Moorella thermoacetica can thus harvest photoexcited electrons from the PFP/PDI heterojunction, driving the Wood–Ljungdahl pathway to synthesize acetic acid from CO2 under illumination. The efficiency of this organic biohybrid is about 1.6 %, which is comparable to those of reported inorganic biohybrid systems.
- Gai, Panpan,Li, Feng,Liu, Libing,Lv, Fengting,Qi, Ruilian,Wang, Shu,Yu, Wen,Zhao, Hao
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- Structure and characterization of amidase from Rhodococcus sp. N-771: Insight into the molecular mechanism of substrate recognition
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In this study, we have structurally characterized the amidase of a nitrile-degrading bacterium, Rhodococcus sp. N-771 (RhAmidase). RhAmidase belongs to amidase signature (AS) family, a group of amidase families, and is responsible for the degradation of amides produced from nitriles by nitrile hydratase. Recombinant RhAmidase exists as a dimer of about 107?kDa. RhAmidase can hydrolyze acetamide, propionamide, acrylamide and benzamide with kcat/Km values of 1.14 ± 0.23?mM- 1s- 1, 4.54 ± 0.09?mM- 1s- 1, 0.087 ± 0.02?mM- 1s- 1 and 153.5 ± 7.1?mM- 1s- 1, respectively. The crystal structures of RhAmidase and its inactive mutant complex with benzamide (S195A/benzamide) were determined at resolutions of 2.17?A? and 2.32?A?, respectively. RhAmidase has three domains: an N-terminal α-helical domain, a small domain and a large domain. The N-terminal α-helical domain is not found in other AS family enzymes. This domain is involved in the formation of the dimer structure and, together with the small domain, forms a narrow substrate-binding tunnel. The large domain showed high structural similarities to those of other AS family enzymes. The Ser-cis Ser-Lys catalytic triad is located in the large domain. But the substrate-binding pocket of RhAmidase is relatively narrow, due to the presence of the helix α13 in the small domain. The hydrophobic residues from the small domain are involved in recognizing the substrate. The small domain likely participates in substrate recognition and is related to the difference of substrate specificities among the AS family amidases.
- Ohtaki, Akashi,Murata, Kensuke,Sato, Yuichi,Noguchi, Keiichi,Miyatake, Hideyuki,Dohmae, Naoshi,Yamada, Kazuhiro,Yohda, Masafumi,Odaka, Masfumi
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- A highly efficient catalyst precursor for ethanoic acid production: [RhCl(CO)(PEt3)2]; X-ray crystal and molecular structure of carbonyldiiodo(methyl)bis(triethylphosphine)rhodium(III)
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Under mild conditions, [RhI(CO)(PEt3)2], is more active for the carbonylation of methanol to ethanoic acid than [Rh(CO)2I2]-, which is widely used industrially; intermediates in the catalytic cycle have been identified and characterised.
- Rankin, Joanne,Poole, Andrew D.,Benyei, Attila C.,Cole-Hamilton, David J.
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- Coenzyme Models. 33. Evidence for Retro-acyloin Condensation as Catalyzed by Thiazolium Ion and Cationic Micelle. Oxidative Trapping of the "Active Aldehyde" Intermediates by Flavin
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N-Hexadecylthiazolium bromide (HxdT) in the CTAB micelle, which is known as an excellent catalytic system for acyloin condensation of aldehydes, catalyzes the reverse reaction (i.e., retro-acyloin condensation) to give aldehydes from α-ketols via the active aldehyde intermediates.The existence of the novel, HxdT-mediated process was proposed on the basis of an experimental discovery that flavin (3-methyltetra-O-acetylriboflavin: MeFl), which is capable of oxidatively trapping the active aldehyde intermediates, is reduced by α-ketols such as acetoin and 3-hydroxy-3-methyl-2-butanone in the micellized HxdT solution.It was further substantiated by detection of acetaldehyde in the final reaction mixture.Based on the diasappearance rate of the absorbance of MeFl, we spectrophotometrically estimated the rate constants for the retro-acyloin condensation.Similarly, biacetyl, the monohydrated species of which is analogous to α-ketol, afforded acetaldehyde and acetic acid in the micellized HxdT solution, the rate constant being greater by factors of 102-103 than those for α-ketols.The relevance of the retro-acyloin condensation to biological systems (e.g., the mechanism of transketolase catalysis) is discussed.
- Shinkai, Seiji,Hara, Youichiro,Manabe, Osamu
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- Nitrogen isotope effects on acetylcholinesterase-catalyzed hydrolysis of o-nitroacetanilide
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The nitrogen-15 isotope effect on V/K for Electrophorus electricus acetylcholinesterase-catalyzed hydrolysis of o-nitroacetanilide has been determined by isotope ratio mass spectrometry. The effect determined in buffered H2O (0.1 M sodium phosphate, 0.1 N NaCl, pH 7.3, 25 °C) is 15V/K = 1.0119 ± 0.0005. A small though palpable decrease of the isotope effect is observed when the reaction is run in equivalently buffered D2O (pD = 7.7), 15V/K = 1.0106 ± 0.0002. The corresponding solvent isotope effect is DV/K = 1.56 ± 0.03. The solvent isotope effect on the nitrogen isotope effect is interpreted in terms of a mechanism in which successive transition states for induced fit and for formation and decomposition of a uninegative tetrahedral intermediate contribute to rate determination of V/K. Numerical modeling allows relatively narrow limits to be placed on the isotope effects for the chemical steps. The solvent and substrate isotope effects for the formation of the tetrahedral intermediate are DK5 = 2.6-3.7 and 15k5 = 1.000-1.009, respectively. The corresponding isotope effects for the decomposition of the intermediate are Dk7 = 1.0-1.5 and 15k7′ = 15k515k7/15k6 = 1.027-1.053. The value of 15k7′ is consistent with a transition state for decomposition of the tetrahedral intermediate in which C-N bond breaking is occurring.
- Rao, Muralikrishna,Barlow, Paul N.,Pryor, Alton N.,Paneth, Pyotr,O'Leary, Marion H.,Quinn, Daniel M.,Phillip Huskey
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- Photoelectrochemistry of Levulinic Acid on Undoped Platinized n-TiO2 Powders
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The photoelectrochemistry of levulinic (4-oxopentanoic) acid, the major product of controlled degradation of cellulose by acids, has been investigated.Since this acid can be present in waste streams of biomass processing, we investigated the photoelectrochemical reactions of this acid on slurries composed of semiconductor/metal particles.The semiconductor investigated was platinized undoped n-TiO2, as anatase, anatase-rutile mixture, or rutile.The effects of the level of platinization, pH, acid concentration, and the semiconductor surface area were investigated.In addition to the decarboxylation reaction leading to methyl ethyl ketone, we have also observed novel cleavages of the C-C backbone leading to propionic acid, acetic acid, acetone, and acetaldehyde as major products.These lower molecular weight carboxylic acids undergo decarboxylation at the slurry diodes to ethane and methane.The organic product distribution is a complex function of the crystallographic phase of n-TiO2 and of the level of metallization of the semiconductor powder.
- Chum, H. L.,Ratcliff, M.,Posey, F. L.,Turner, J. A.,Nozik, A. J.
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- Formic Acid Promotion of Transition-metal Catalysed Isomerization of Methyl Formate
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MeI-HCO2H is an extremely effective promoter/solvent combination for the transition-metal catalysed conversion of methyl formate to acetic acid in the absence of initial carbon monoxide pressure.
- Cheong, Minserk,Bae, Seong-ho,Lee, Kang B.
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- Kinetics and Mechanism of the Acetylperoxy + HO2 Reaction
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The reaction of HO2 with CH3C(O)O2 is examined using flash photolysis and FTIR smog chamber techniques. Time-resolved UV spectroscopy is used to follow the transient peroxy species. It yields reasonable concentration versus time profiles for CH3C(O)O2 and HO2, but indicates anomalously high levels of secondary CH3O2 radicals. Transient IR diode laser absorption confirms the HO2 decay rates; however, the anticipated reaction model substantially underestimates the observed decay. The model is augmented by assuming that, in analogy with formaldehyde, there exists a reaction between HO2 and acetaldehyde (the precursor for CH3C(O)O2). Consistent with this, the fitted rate for the hypothesized reaction increases with increasing initial acetaldehyde level. Relative rate measurements reveal that chlorine atoms remove more CH3CHO relative to CH2OH in air as compared to nitrogen diluent. This supports the hypothesis since, in the presence of oxygen, HO2 is formed and presents an additional acetaldehyde removal pathway. Employing the augmented model, analyses of HO2 decay traces yield a CH3C(O)O2 + HO2 rate constant of k1 = (3.9-2.3+5.0) × 10-13e(1350±250)/T cm3 s-1. Reasons are discussed for why the present rate constants are 2 - 3 times larger than previously reported. FTIR - smog chamber studies reveal the reaction to proceed via two channels to (a) peracetic acid and O2 and to (b) acetic acid and O2, with a branching fraction at 295 K that is less than half of the literature value. Time-resolved UV absorption measurements support this smaller fraction; averaged together the two methods give k1b/k1 = 0.12 ± 0.04. As part of this work, relative rate techniques are used to measure k(Cl+CH3C- (O)OH) = (2.5 ± 0.3) × 10-14 cm3 s-1and k(Cl+CH3C(O)OOH) = (4.5 ± 1.0) × 10-15 cm3 s-1 at 295 K.
- Crawford, Mary A.,Wallington, Timothy J.,Szente, Joseph J.,Maricq, M. Matti,Francisco, Joseph S.
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- Application of band-target entropy minimization to on-line raman monitoring of an organic synthesis. An example of new technology for process analytical technology
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The hydrolysis of acetic anhydride to acetic acid in water as solvent was monitored by Raman microscopy. Both static and flow-through configurations were used in the experiments, and various experimental designs, i.e., multiple-experimental runs and multiple-perturbation semibatch mode, were considered. Various spectral data preprocessing was performed and band-target entropy minimization (BTEM) was used in the spectral analysis to recover the pure-component spectra from the multicomponent data. Good and consistent spectral estimates of the solutes acetic anhydride and acetic acid were recovered. In addition, the pure-component spectrum of white-light interference was recovered. Together, these estimates permitted very good estimates of the individual time-dependent signal contributions. Taken together, the present results suggest that the combination of Raman spectroscopy and BTEM has considerable potential for organic syntheses and process analysis. The combination of Raman spectroscopy and BTEM represents another approach for reaction monitoring in process analytical technologies (PAT).
- Widjaja, Effendi,Ying, Yan Tan,Garland, Marc
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- Keggin-type molybdovanadophosphoric acids loaded on ZSM-5 zeolite as a bifunctional catalyst for oxidehydration of glycerol
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Glycerol is a promising renewable feedstock for the manufacture of C3 derivatives. We investigated the one-pass oxidehydrarion of glycerol through the dehydration of glycerol into acrolein, followed by the oxidation of acrolein. A novel bifunctional catalyst for this reaction was prepared by loading the Keggin-type molybdovanadophosphoric acid H3+xPVxMo12-xO40 (x = 0–3) on ZSM-5 (MFI) zeolite (Si/Al = 45) exhibiting both dehydration and oxidation activity. H5PV2Mo10O40 and H6PV3Mo9O40 were stable and dispersed on ZSM-5 zeolite, and the acidic property of the ZSM-5 zeolite was retained. The oxidehydration of glycerol was catalyzed by H5PV2Mo10O40 loaded on the ZSM-5 zeolite with high selectivity of acrylic acid. In-situ IR analysis suggests that acrolein molecules adsorbed on H5PV2Mo10O40/ZSM-5 were converted into acrylic acid due to the inhibition of side-reactions such as polymerization and auto-condensation, which induced coke formation, compared with the other Mo and V-based oxides loaded on ZSM-5 zeolite.
- Suganuma, Satoshi,Hisazumi, Takuya,Taruya, Kohtaro,Tsuji, Etsushi,Katada, Naonobu
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- Reaction coordinate analysis for β-diketone cleavage by the non-heme Fe2+-dependent dioxygenase Dke1
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Acetylacetone dioxygenase from Acinetobacter johnsonii(Dke1) utilizes a non-heme Fe2+ cofactor to promote dioxygen-dependent conversion of 2,4-pentanedione (PD) into methylglyoxal and acetate. An oxidative carbon-carbon bond cleavage by Dke1 is triggered from a C-3 peroxidate intermediate that performs an intramolecular nucleophilic attack on the adjacent carbonyl group. But how does Dke1 bring about the initial reduction of dioxygen? To answer this question, we report here a reaction coordinate analysis for the part of the Dke1 catalytic cycle that involves O2 chemistry. A weak visible absorption band (ε ≈ 0.2 mM-1 cm-1) that is characteristic of an enzyme-bound Fe2+-β-keto-enolate complex served as spectroscopic probe of substrate binding and internal catalytic steps. Transient and steady-state kinetic studies reveal that O2-dependent conversion of the chromogenic binary complex is rate-limiting for the overall reaction. Linear free-energy relationship analysis, in which apparent turnover numbers (kcatapp) for enzymatic bond cleavage of a series of substituted β-dicarbonyl substrates were correlated with calculated energies for the highest occupied molecular orbitals of the corresponding β-keto-enolate structures, demonstrates unambiguously that k catapp is governed by the electron-donating ability of the substrate. The case of 2′-hydroxyacetophenone (2′HAP), a completely inactive β-dicarbonyl analogue that has the enol double bond delocalized into the aromatic ring, indicates that dioxygen reduction and C-O bond formation cannot be decoupled and therefore take place in one single kinetic step.
- Straganz, Grit D.,Nidetzky, Bernd
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- Crystalline Mo3VOx mixed-metal-oxide catalyst with trigonal symmetry
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Outstanding catalytic activity for the selective oxidation of acrolein (see picture) is observed with a crystalline metal oxide, Mo3VO x (x ≤ 11.1). The catalyst is synthesized from a solution containing pentagonal units of {Mo(Mo5O27)} (blue), which further react with molybdenum and vanadium species (red) to form a 3D metal oxide. (Chemical Equation Presented).
- Sadakane, Masahiro,Watanabe, Nobufumi,Katou, Tomokazu,Nodasaka, Yoshinobu,Ueda, Wataru
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- Photothermal strategy for the highly efficient conversion of glucose into lactic acid at low temperatures over a hybrid multifunctional multi-walled carbon nanotube/layered double hydroxide catalyst
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The conversion of carbohydrates into lactic acid has attracted increasing attention owing to the broad applications of lactic acid. However, the current methods of thermochemical conversion commonly suffer from limited selectivity or the need for harsh conditions. Herein, a light-driven system of highly selective conversion of glucose into lactic acid at low temperatures was developed. By constructing a hybrid multifunctional multi-walled carbon nanotube/layered double hydroxide composite catalyst (CNT/LDHs), the highest lactic acid yield of 88.6% with 90.0% selectivity was achieved. The performance of CNT/LDHs for lactic acid production from glucose is attributed to the following factors: (i) CNTs generate a strong heating center under irradiation, providing heat for converting glucose into lactic acid; (ii) LDHs catalyze glucose isomerization, in which the photoinduced OVs (Lewis acid) in LDHs under irradiation further improve the catalytic activity; and (iii) in a heterogeneous-homogeneous synergistically catalytic system (LDHs-OH-), OH- ions are concentrated in LDHs, forming strong base sites to catalyze subsequent cascade reactions.
- Duo, Jia,Jin, Binbin,Jin, Fangming,Shi, Xiaoyu,Wang, Tianfu,Ye, Xin,Zhong, Heng
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p. 813 - 822
(2022/02/09)
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- 2-(4-Nitrophenyl)-1H-indolyl-3-methyl Chromophore: A Versatile Photocage that Responds to Visible-light One-photon and Near-infrared-light Two-photon Excitations
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Due to cell damage caused by UV light, photoremovable protecting groups (PPGs) that are removed using visible or near-infrared light are attracting attention. A 2-(4-nitrophenyl)- 1H-indolyl-3-methyl chromophore (NPIM) was synthesized as a novel PPG. Various compounds were caged using this PPG and uncaged using visible or near-infrared light. Low cytotoxicity of NPIM indicates that it may be applied in physiological studies.
- Abe, Manabu,Guo, Runzhao,Hamao, Kozue,Lin, Qianghua,Takagi, Ryukichi
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supporting information
p. 153 - 156
(2022/02/14)
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- Nanoconfinement Engineering over Hollow Multi-Shell Structured Copper towards Efficient Electrocatalytical C?C coupling
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Nanoconfinement provides a promising solution to promote electrocatalytic C?C coupling, by dramatically altering the diffusion kinetics to ensure a high local concentration of C1 intermediates for carbon dimerization. Herein, under the guidance of finite-element method simulations results, a series of Cu2O hollow multi-shell structures (HoMSs) with tunable shell numbers were synthesized via Ostwald ripening. When applied in CO2 electroreduction (CO2RR), the in situ formed Cu HoMSs showed a positive correlation between shell numbers and selectivity for C2+ products, reaching a maximum C2+ Faradaic efficiency of 77.0±0.3 % at a conversion rate of 513.7±0.7 mA cm?2 in a neutral electrolyte. Mechanistic studies clarified the confinement effect of HoMSs that superposition of Cu shells leads to a higher coverage of localized CO adsorbate inside the cavity for enhanced dimerization. This work provides valuable insights for the delicate design of efficient C?C coupling catalysts.
- Li, Jiawei,Liu, Chunxiao,Xia, Chuan,Xue, Weiqing,Zeng, Jie,Zhang, Menglu,Zheng, Tingting
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supporting information
(2021/12/06)
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- Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation
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MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.
- Calvino, José J.,Constantinescu, Gabriel,Frade, Jorge R.,Kovalevsky, Andrei V.,Labrincha, Jo?o A.,Lajaunie, Luc,Lopes, Daniela V.,Sergiienko, Sergii A.,Shaula, Aliaksandr L.,Shcherban, Nataliya D.,Shkepu, Viacheslav I.,Tobaldi, David M.
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p. 626 - 639
(2022/01/22)
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- Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis
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The two-electron reduced forms of perylene diimides (PDIs) are luminescent closed-shell species whose photochemical properties seem underexplored. Our proof-of-concept study demonstrates that straightforward (single) excitation of PDI dianions with green
- Li, Han,Wenger, Oliver S.
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supporting information
(2021/12/23)
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- The influence of different carbonate ligands on the hydrolytic stability and reduction of platinum(
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Pt(iv) complexes bearing axial carbonate linkages have drawn much attention recently. A synthetic method behind this allows the hydroxyl group of bioactive ligands to be attached to the available hydroxyl group of Pt(iv) complexes, and the rapid release of free drugs is achieved after the reduction of carbonate-linked Pt(iv) complexes. Further understanding on the properties of Pt(iv) carbonates such as hydrolytic stability and reduction profiles, however, is hindered by limited research. Herein, six mono-carbonated Pt(iv) complexes in which the carbonate axial ligands possess various electron-withdrawing powers were synthesized, and the corresponding mono-carboxylated analogues were also prepared as references to highlight the different properties. The influence of the coordination environment towards the hydrolysis and reduction rate of Pt(iv) carbonates and carboxylates was explored. The mono-carbonated Pt(iv) complexes are both less stable and reduced faster than the corresponding mono-carboxylated ones. Moreover, the hydrolysis and reduction profiles are dependent not only on the electron-withdrawing ability of the carbonates but also on the nature of the opposite axial ligands. Besides, the exploration of the hydrolytic pathway for Pt(iv) carbonates suggests that the process proceeds by an attack of OH? on the carbonyl carbon, followed by elimination, which is different from that of Pt(iv) carboxylates. This study provides some information on the influence of axial carbonate ligands with different electron-withdrawing abilities on the properties of the Pt(iv) center, which may inspire new thoughts on the design of “multi-action” Pt(iv) prodrugs.
- Chen, Shu,Deng, Zhiqin,Ng, Ka-Yan,Tse, Man-Kit,Yao, Houzong,Zhou, Qiyuan,Zhu, Guangyu
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supporting information
p. 885 - 897
(2022/02/01)
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- Solvent-free oxidation of straight-chain aliphatic primary alcohols by polymer-grafted vanadium complexes
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Oxidovanadium(IV) complexes [VO(tertacac)2] (1), [VO(dipd)2] (2), and [VO(phbd)2] (3) were synthesized by reacting [VO(acac)2] with 2,2,6,6-tetramethyl-3,5-hepatanedione, 1,3-diphenyl-1,3-propanedione, and 1-phenyl-1,3-butanedione, respectively. Imidazole-modified Merrifield resin was used for the heterogenization of complexes 1–3. During the process of heterogenization, the V4+ center in complex 2 converts into V5+, whereas the other two complexes 1 and 3 remain in the oxidovanadium(IV) state in the polymer matrix. Theoretically, calculated IPA values of 1–3 suggest that 2 is prone to oxidation compared with 1 and 3, which was also supported by the absence of EPR lines in 5. Polymer-supported complexes Ps-Im-[VIVO(tertacac)2] (4), Ps-Im-[VVO2(dipd)2] (5), and Ps-Im-[VIVO(phbd)2] (6) were applied for the solvent-free heterogenous oxidation of a series of straight-chain aliphatic alcohols in the presence of H2O2 at 60°C and showed excellent substrate conversion specially for the alcohols with fewer carbon atoms. Higher reaction temperature improves the substrate conversion significantly for the alcohols containing more carbon atoms such as 1-pentanol, 1-hexanol, and 1-heptanol while using optimized reaction conditions. However, alcohols with fewer carbon atoms seem less affected by reaction temperatures higher than the optimized temperature. A decreasing trend in the selectivity(%) of carboxylic acid was observed with increasing carbon atoms among the examined alcohols, whereas the selectivity towards aldehydes increased. The order of efficiency of the supported catalysts is 4 > 6 > 5 in terms of turnover frequency (TOF) values and substrate conversion, further supported by theoretical calculations.
- Chaudhary, Nikita,Haldar, Chanchal,Kachhap, Payal
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- Synthesis and characterization of Merrifield resin and graphene oxide supported air stable oxidovanadium(IV) radical complexes for the catalytic oxidation of light aliphatic alcohols
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Imidazole modified Merrifield resin and (3-Aminopropyl)trimethoxysilane-modified graphene oxide supported oxidovanadium(IV) radical complexes PS-im-[VIVO(tbnC[rad])(acac)] (1) and GO-ATPMS-[VIVO(tbnO[rad])(acac)] (2) were synthesized and characterized by various spectroscopic, thermal and chemical techniques. The radical nature of 1 and 2 was established by trapping experiments in addition to EPR spectroscopy. In EPR analysis, complex 2 shows a prominent signal with g = 2.005, characteristic of an oxygen-centered radical. The neat complex [VIVO(tbnC[rad])(acac)] (A) displays an EPR signal at g = 2.0025, typical of carbon-centered radical. On the contrary, such characteristic EPR signal of a radical is absent in complex 1, presumably due to spin pairing. XPS analysis confirms the +4 oxidation state of vanadium in fresh as well as recycled catalysts 1 and 2. Both the supported complexes show excellent catalytic activity towards a variety of aliphatic alcohols. Comparatively, the polymer-supported complex displays better substrate conversion than the graphene oxide-supported complex. However, 2 shows better selectivity towards aldehydes, whereas carboxylic acids are obtained as major products in the presence of 1. Interestingly, catalyst 1 is almost equally effective towards all the examined alcohols, but its effectiveness reduces slightly for longer carbon chain alcohols. On the other hand, catalyst 2 shows better substrate conversion for the alcohols with a longer carbon chain. During the catalytic oxidation of alcohols, the active intermediate species oxidoperoxidovanadium(V) complex ([VO(O2)(tbn)(acac-H)]?) was detected by FT-IR, UV–vis, and LC–MS analysis.
- Chaudhary, Nikita,Haldar, Chanchal,Kesharwani, Neha
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- Hydrolysis of amides to carboxylic acids catalyzed by Nb2O5
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Hydrolysis of amides to carboxylic acids is an industrially important reaction but is challenging due to the difficulty of cleaving the resonance stabilized amidic C-N bond. Twenty-three heterogeneous and homogenous catalysts were examined in the hydrolysis of acetamide. Results showed that Nb2O5was the most effective heterogeneous catalyst with the greatest yield of acetic acid. A series of Nb2O5catalysts calcined at various temperatures were characterized and tested in the hydrolysis of acetamide to determine the effects of crystal phase and surface properties of Nb2O5on catalytic performance. The high catalytic performance observed was attributed mainly to the facile activation of the carbonyl bond by Lewis acid sites that function even in the presence of basic inhibitors (NH3and H2O). The catalytic studies showed the synthetic advantages of the present method, such as simple operation, catalyst recyclability, additive free, solvent free, and wide substrate scope (>40 examples; up to 95% isolated yield).
- Siddiki,Rashed, Md. Nurnobi,Touchy, Abeda Sultana,Jamil, Md. A. R.,Jing, Yuan,Toyao, Takashi,Maeno, Zen,Shimizu, Ken-Ichi
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p. 1949 - 1960
(2021/03/26)
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- Combination of Highly Efficient Electrocatalytic Water Oxidation with Selective Oxygenation of Organic Substrates using Manganese Borophosphates
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One of the key catalytic reactions for life on earth, the oxidation of water to molecular oxygen, occurs in the oxygen-evolving complex of the photosystem II (PSII) mediated by a manganese-containing cluster. Considerable efforts in this research area embrace the development of efficient artificial manganese-based catalysts for the oxygen evolution reaction (OER). Using artificial OER catalysts for selective oxygenation of organic substrates to produce value-added chemicals is a worthwhile objective. However, unsatisfying catalytic performance and poor stability have been a fundamental bottleneck in the field of artificial PSII analogs. Herein, for the first time, a manganese-based anode material is developed and paired up for combining electrocatalytic water oxidation and selective oxygenations of organics delivering the highest efficiency reported to date. This can be achieved by employing helical manganese borophosphates, representing a new class of materials. The uniquely high catalytic activity and durability (over 5 months) of the latter precursors in alkaline media are attributed to its unexpected surface transformation into an amorphous MnOx phase with a birnessite-like short-range order and surface-stabilized MnIII sites under extended electrical bias, as unequivocally demonstrated by a combination of in situ Raman and quasi in situ X-ray absorption spectroscopy as well as ex situ methods.
- Menezes, Prashanth W.,Walter, Carsten,Chakraborty, Biswarup,Hausmann, Jan Niklas,Zaharieva, Ivelina,Frick, Achidi,von Hauff, Elizabeth,Dau, Holger,Driess, Matthias
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- (Hexamethylbenzene)Ru catalysts for the Aldehyde-Water Shift reaction
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The Aldehyde-Water Shift (AWS) reaction uses H2O as a benign oxidant to convert aldehydes to carboxylic acids, producing H2, a valuable reagent and fuel, as its sole byproduct. (Hexamethylbenzene)RuIIcomplexes are demonstrated to have higher activity and selectivity (up to 95%) for AWS over disproportionation than previously reported catalysts.
- Phearman, Alexander S.,Moore, Jewelianna M.,Bhagwandin, Dayanni D.,Goldberg, Jonathan M.,Heinekey, D. Michael,Goldberg, Karen I.
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supporting information
p. 1609 - 1615
(2021/03/09)
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- Honeycomb-structured solid acid catalysts fabricated via the swelling-induced self-assembly of acidic poly(ionic liquid)s for highly efficient hydrolysis reactions
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The development of heterogeneous acid catalysts with higher activity than homogeneous acid catalysts is critical and still challenging. In this study, acidic poly(ionic liquid)s with swelling ability (SAPILs) were designed and synthesized via the free radical copolymerization of ionic liquid monomers, sodium p-styrenesulfonate, and crosslinkers, followed by acidification. The 31P nuclear magnetic resonance chemical shifts of adsorbed trimethylphosphine oxide indicated that the synthesized SAPILs presented moderate and single acid strength. The thermogravimetric analysis results in the temperature range of 300–345 °C revealed that the synthesized SAPILs were more stable than the commercial resin Amberlite IR-120(H) (245 °C). Cryogenic scanning electron microscopy testing demonstrated that SAPILs presented unique three-dimensional (3D) honeycomb structure in water, which was ascribed to the swelling-induced self-assembly of the molecules. Moreover, we used SAPILs with micron-sized honeycomb structure in water as catalysts for the hydrolysis of cyclohexyl acetate to cyclohexanol, and determined that their catalytic activity was much higher than that of homogeneous acid catalysts. The equilibrium concentrations of all reaction components inside and outside the synthesized SAPILs were quantitatively analyzed using a series of simulated reaction mixtures. Depending on the reaction mixture, the concentration of cyclohexyl acetate inside SAPIL-1 was 7.5–23.3 times higher than that outside of it, which suggested the high enrichment ability of SAPILs for cyclohexyl acetate. The excellent catalytic performance of SAPILs was attributed to their 3D honeycomb structure in water and high enrichment ability for cyclohexyl acetate, which opened up new avenues for designing highly efficient heterogeneous acid catalysts that could eventually replace conventional homogeneous acid catalysts.
- Chen, Bihua,Deng, Xi,Ding, Tong,Gao, Guohua,Ma, Sanguan,Ni, Bing,Wang, Xin,Zhang, Dawei,Zhang, Yongya
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p. 297 - 309
(2020/07/25)
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- Membrane transport inspired hydrolysis of non-activated esters at near physiological pH
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A positively charged micelle loaded with substrates was transported selectively to the reaction site (cathode) to promote the proximity and localization of the reactants (ester and hydroxide). The guided vehicular delivery coupled with electrolysis allows the hydrolysis of non-activated esters at near physiological pH with significant yields along with recyclability.
- De Sarkar, Suman,Mahanty, Kingshuk,Mandal, Raki,Mandal, Subhendu,Tarafdar, Pradip K.
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supporting information
p. 11088 - 11091
(2021/10/30)
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- Selectivity Switch in the Aerobic 1,2-Propandiol Oxidation Catalyzed by Diamine-Stabilized Palladium Nanoparticles
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Palladium nanoparticles stabilized by a sterically demanding secondary diamine ligand have been synthesized by hydrogen reduction of a palladium acetate complex bearing the corresponding diimine ligand. The obtained nanoparticles were used to catalyze the aerobic oxidation of 1,2-propandiol in n-hexane, and after their heterogenization onto a high surface area carbon, in water. In n-hexane (2,4-dimethyl-1,3-dioxolan-2-yl) methanol has been obtained as major product, whereas in water acetic acid with a selectivity of >85 % has been achieved. The selectivity switch observed was a clear induced by water. The robustness of diamine-stabilized palladium nanoparticles under real aerobic oxidation conditions has been proved by recycling experiments, TEM measurements of the recovered catalysts and by comparison of its performance with that of palladium nanoparticles generated by the metal vapor synthesis technique and supported onto the same carbon in the absence of the stabilizing diamine ligand.
- Oberhauser, Werner,Evangelisti, Claudio,Capozzoli, Laura,Manca, Gabriele,Casaletto, Maria Pia,Vizza, Francesco
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p. 2896 - 2906
(2021/05/06)
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- Catalytic Aerobic Oxidation of Lignocellulose-Derived Levulinic Acid in Aqueous Solution: A Novel Route to Synthesize Dicarboxylic Acids for Bio-Based Polymers
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The world is facing grand and ever-increasing pressures on energy and environmental issues. Using carbon-neutral biomass to prepare monomers such as dicarboxylic acids for degradable polymers is of great significance and an urgent but challenging task. Herein, we report a catalytic route for the synthesis of 2-hydroxy-2-methylsuccinic acid, an excellent monomer: e.g., it is able to remarkably enhance the comprehensive properties of polybutylene succinate as shown herein. By catalytic aerobic oxidation of levulinic acid, a bulk platform chemical derived from lignocellulose, the target product was obtained with a very high selectivity of up to ca. 95%. The mild reaction conditions below 100 °C in water and the low-cost reusable heterogeneous catalyst further make the process highly attractive for applications. This process was also found to be effective for the conversion of homologues of levulinic acid to dicarboxylic acids. We studied the C-C bond rearrangement and the roles of catalysts in the reaction that are highly likely involved in a superoxide anion radical mechanism. This study may provide inspiration for the synthesis of bio-based dicarboxylic acids via alternative routes.
- Che, Li,Jiang, Min,Jiang, Yu,Pang, Jifeng,Song, Lei,Wang, Rui,Zhang, Tao,Zhao, Yu,Zheng, Mingyuan,Zhou, Guangyuan,Zhou, Mo
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p. 11588 - 11596
(2021/09/22)
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- Efficient Assay for the Detection of Hydrogen Peroxide by Estimating Enzyme Promiscuous Activity in the Perhydrolysis Reaction
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Hydrogen peroxide is an ideal oxidant in view of its availability, atom economy, or green aspects. Furthermore, it is produced by the cell mitochondria and plays a meaningful role in controlling physiological processes, but its unregulated production leads to the destruction of organs. Due to its diverse roles, a fast and selective method for hydrogen peroxide detection is the major limitation to preventing the negative effects caused by its excess. Therefore, we aimed to develop an efficient assay for the detection of H2O2. For this purpose, we combined the enzymatic method for the detection of hydrogen peroxide with the estimation of the promiscuity of various enzymes. We estimated the activity of an enzyme in the reaction of p-nitrophenyl esters with hydrogen peroxide resulting in the formation of peracid. To our knowledge, there is no example of a simple, multi-sensor demonstrating the promiscuous activity of an enzyme and detecting hydrogen peroxide in aqueous media.
- Wilk, Monika,Ostaszewski, Ryszard
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p. 1464 - 1469
(2021/02/01)
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- Biochemical and biophysical characterisation of a small purified lipase from Rhizopus oryzae ZAC3
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The characteristics of a purified lipase from Rhizopus oryzae ZAC3 (RoL-ZAC3) were investigated. RoL-ZAC3, a 15.8 kDa protein, which was optimally active at pH 8 and 55 °C had a half-life of 126 min at 60 °C. The kinetic parameters using p-nitrophenylbuty
- Ayinla, Zainab A.,Ademakinwa, Adedeji N.,Gross, Richard A.,Agboola, Femi K.
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- Mo–V–O nanocrystals synthesized in the confined space of a mesoporous carbon
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Ternary Mo–V oxide nanocrystals (Nano-MoVO) were hydrothermally synthesized in the confined space of a mesoporous carbon template and tested in the oxidative dehydrogenation (ODH) of ethane and propane. The synthesized nanocrystals are approximately 60 nm in length, 20 nm in diameter on average, and possess a structure resembling orthorhombic MoVO (Orth-MoVO) as indicated by spectroscopic and microscopy characterization. The Nano-MoVO catalyst has a 5-fold higher mesopore volume and a 4-fold larger external surface area than an Orth-MoVO synthesized by a conventional method (Orth-MoVO) as characterized through N2 adsorption analysis. Nano-MoVO shows similar activation energy in the ODH of ethane compared with other conventional MoVO catalysts. However, Nano-MoVO exhibits significantly higher propane/ethane activation rate ratio and higher propene selectivity even in the absence of elements such as Te and Nb that suppress overoxidation of propane-derived species to COx. The results suggest the benefits of the nanocrystalline morphology to limit overoxidation.
- Mukai, Shin R.,Obunai, Ryo,Ogino, Isao,Tamura, Keisuke,Ueda, Wataru
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- Influence of Solvents on the Oxidation Kinetics of Aldehydic Group Compounds by Diethylammonium Chloro-chromate
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The redox studies of some compounds containing aldehydic functional groups by diethylammonium chloro-chromate (DEACC) in dimethylsulfoxide leading a product forming to acid of correspondimg order. Reactions are found to be in unit order with oxidant while a fractional order (less than unity) was found w. r. t. reductants. The redox reactions are influenced with acid, the acid dependence is governed by this equation: kobs = a + b[H+]. When isomeric form of aldehyde, that is Me-CDO is oxidised with the same oxidant it was observed a considerable K. I.E. (Deuterium effect; kH/kD = 05.69 at 298 K). The reaction of Acetaldehyde was done in various non aqueous medium, soluble or miscible in DMSO. The effect of solvent is studied fitting our data in the solvent model of Taft's and Swain's applied for this purpose. Rate constants are correlating very well with already reported Taft's values of s*; further the reaction constants are negative in nature. Suitable mechanism involving are proposed with transfer of hydride ion.
- Bishnoi, Pramila,Chandora, Divya,Ganpatram,Prakash, Om,Sharma, Vinita
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p. 1329 - 1335
(2022/01/24)
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- Steric effect induces CO electroreduction to CH4on Cu-Au alloys
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The electrocatalytic reduction of carbon monoxide (CO) is an emerging direction with new catalyst structures, among which the bimetallic component catalysts feature both functional diversity and high-density of active sites. In this work, we demonstrate that the fine tuning of adjacent bimetallic sites can allow us to select different reaction pathways toward C1or C2products in the electroreduction of CO. Cu and Cu-Au alloy catalysts with different atomic ratios were fabricated and investigated for appropriate molecular distances. The pure Cu catalyst was found to be active for electroreducing CO to C2H4, as the adjacent Cu sites were beneficial for adsorbing multiple CO molecules and subsequent C-C coupling. On the other hand, alloying Cu with Au introduced steric hindrance and a larger intermolecular distance between adjacent adsorbed *CO intermediates, thus leading to a decrease of C2H4selectivity but an enhanced CH4pathway. Our work revealed the importance of spacing between active sites for CO electroreduction, which can benefit the catalyst design to further improve activities and selectivities in electrocatalytic CO reduction.
- Guan, Anxiang,Ji, Yali,Li, Si,Qian, Linping,Wang, Qihao,Wu, Limin,Yang, Chao,Zhang, Lijuan,Zheng, Gengfeng
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supporting information
p. 21779 - 21784
(2021/10/12)
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- Gas-phase oxidative carbonylation of methane to acetic acid over zeolites
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Gas-phase oxidative carbonylation of methane was first performed on ZSM-5 zeolites. The addition of water vapor to a mixture of carbonylation gases leads to a multiple (by two orders of magnitude) increase in acetic acid yield. Zeolites with high acidity, primarily Br?nsted acidity, favor the target product formation.
- Ezhova, Natalia N.,Golubev, Konstantin B.,Kolesnichenko, Natalia N.,Yashina, Olga V.
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p. 712 - 714
(2021/11/26)
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- Highly efficient visible-light photocatalytic ethane oxidation into ethyl hydroperoxide as a radical reservoir
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Photocatalytic ethane conversion into value-added chemicals is a great challenge especially under visible light irradiation. The production of ethyl hydroperoxide (CH3CH2OOH), which is a promising radical reservoir for regulating the oxidative stress in cells, is even more challenging due to its facile decomposition. Here, we demonstrated a design of a highly efficient visible-light-responsive photocatalyst, Au/WO3, for ethane oxidation into CH3CH2OOH, achieving an impressive yield of 1887 μmol gcat?1in two hours under visible light irradiation at room temperature for the first time. Furthermore, thermal energy was introduced into the photocatalytic system to increase the driving force for ethane oxidation, enhancing CH3CH2OOH production by six times to 11?233 μmol gcat?1at 100 °C and achieving a significant apparent quantum efficiency of 17.9% at 450 nm. In addition, trapping active species and isotope-labeling reactants revealed the reaction pathway. These findings pave the way for scalable ethane conversion into CH3CH2OOH as a potential anticancer drug.
- Zhu, Yao,Fang, Siyuan,Chen, Shaoqin,Tong, Youjie,Wang, Chunling,Hu, Yun Hang
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p. 5825 - 5833
(2021/05/07)
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- Tuning the Lewis acidity of ZrO2for efficient conversion of CH4and CO2into acetic acid
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The conversion of CH4 and CO2 into acetic acid is a dream reaction, but it remains a great challenge owing to the inertness of both CH4 and CO2. The formation of acetic acid requires efficient activation of CH4 and CO2. In this work, we demonstrated that enhanced acetic acid production from CH4 and CO2 is achieved via improving the Lewis acidity of ZrO2-containing catalysts. Definitely, the best catalyst (SZ-3) exhibits about 14 times higher activity for acetic acid formation than that of pure ZrO2, owing to its strongest Lewis acidity that facilitates the activation of both CH4 and CO2. The mechanism of acetic acid formation is revealed via DFT calculations. CH4 is activated at Lewis acid sites to form Zr-CH3 and O-H species, and subsequently, the O-H species could readily hydrogenate CO3 species formed from CO2 activation at Lewis acid sites to give HCO3, followed by facile coupling with Zr-CH3 yielding acetic acid with a lower energy barrier.
- Li, Yufeng,Liu, Bing,Liu, Jie,Wang, Ting,Shen, Yu,Zheng, Ke,Jiang, Feng,Xu, Yuebing,Liu, Xiaohao
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supporting information
p. 8978 - 8985
(2021/06/02)
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- ACETIC ACID FORMATION BY SELECTIVE OXIDATION OF METHANE
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The invention relates to methods and a reactor system for producing acetic acid in a selective oxidation (SO) reactor. One example process is to provide a fresh feed stream to the SO reactor, the fresh feed stream consisting of a methane feed stream, a carbon dioxide feed stream, and a steam feed stream. Acetic acid is formed in the SO reactor. A stream of acetic acid product is separated from a stream of reactor effluent in a scrubber. A recycling gas stream is obtained from the scrubber. At least part of the recycling gas stream is combined into the fresh feed stream at the SO reactor.
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Page/Page column 17-19
(2021/12/31)
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- Hydroformylation and one-pot hydroformylation/epoxy ring cleavage of limonene oxide: A sustainable access to biomass-based multi-functional fragrances
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Naturally occurring, renewable limonene oxide is converted into aldehydes with pleasant scent under oxo (hydroformylation) conditions. Good activity and selectivity are only reached by the careful choice of the catalytic system and the reaction conditions. [Rh(COD)(OMe)]2 was used as the catalyst precursor and PPh3 or (2,4-di-tBuC6H3O)3P as auxiliary ligands, the latter showing better results. The process can be carried in eco-friendly solvents such as anisole, ethanol, dimethylcarbonate (DMC) and diethylcarbonate (DEC). Employing Rh/(2,4-di-tBuC6H3O)3P catalytic system and acetic anhydride or acetic acid as co-reactants, a concomitant one-pot epoxide opening takes place along with hydroformylation, resulting in new acetylated aldehydes potentially useful for the fragrance industry. With the former co-reactant diacetylated products are preferred, while with the latter co-reactant hydroxy acetoxy aldehydes are formed in high yields. The one pot hydroformylation/epoxy ring cleavage process can be also performed in green solvents: DMC, DEC and anisole.
- de Oliveira, Mileny P.,Delolo, Fábio G.,Villarreal, Jesus A.A.,dos Santos, Eduardo N.,Gusevskaya, Elena V.
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- Core-shell nanoparticles with tensile strain enable highly efficient electrochemical ethanol oxidation
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The ethanol oxidation reaction (EOR), the anode reaction of direct ethanol fuel cells, suffers from sluggish oxidation kinetics and low selectivity toward complete oxidation to CO2. The key to solving the above problems is to design and synthesize high-performance catalysts. In this work, we synthesize Ag@AgPd core-shell nanoparticles that exhibit a significant improvement in catalytic performance. Specifically, in 1.0 M KOH + 1.0 M EtOH, the mass activity of the Ag@AgPd core-shell catalyst reaches up to 12.7 A mgPd?1with a significantly improved selectivity toward CO2by 4.5 times compared with commercial Pd/C. This superior performance guarantees that this Ag@AgPd core-shell nanoparticle is among the best-reported catalysts. Mechanism study by density functional theory shows that the tensile strain that originates from the unique core-shell structure decreases the potential determining step by 39%, which plays the most important role in increasing the activity and selectivity. This work demonstrates the effect of the tensile strain in promoting the kinetics and selectivity of the EOR, which may serve as a guide for the design of highly efficient electrocatalysts for general alcohol oxidation reactions by controlled nanoparticle synthesis.
- Cheng, Tao,Gao, Chuanbo,Jiang, Yilan,Liu, Kai,Liu, Moxuan,Liu, Zhaojun,Lu, Yiming,Wang, Xiaoxiao,Xie, Miao,Zhang, Qing,Zhang, Shumeng,Zhang, Zhixue
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supporting information
p. 15373 - 15380
(2021/07/21)
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- PROCESS FOR PRODUCTION OF FORMIC ACID AND ACETIC ACID BY ABSORBING CO2 VIA PHOTOCATALYTIC REDUCTION, IMPROVED CATALYST AND APPARATUS
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The present invention relates to a process for converting CO2 to short chain organic acids, which comprises the steps of: a) dissolution of silver containing fulvate chlatrate komplex catalyst in water to produce a catalyst solution; b) charging the catalyst solution into a pressure reactor; c) introducing a CO2 source into the reactor; d) exposing the reactor space with sunlight or artificial light, or electromagnetic wave while measuring the concentration of the produced organic acids; e) repeating the steps of c) and d) until the concentration of the produced organic acids reaches 2 to 5 % by weight in the reaction mixture; f) if the concentration of the produced organic acids reaches 2-5% by weight, collecting the aqueous solution from the, filtering and concentrating the same. The present invention also relates to a silver-containing fulvate-clathrate complex catalyst.
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Paragraph 0078-0079
(2021/05/29)
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- Method for preparing acetic acid from halomethane
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The invention provides a method for preparing acetic acid from halomethane. The method at least comprises the following steps: contacting and reacting feed gas containing halomethane and carbon monoxide with a solid acid catalyst to obtain acetic acid, wherein the solid acid catalyst includes an acidic zeolite molecular sieve. The halomethane is used as a raw material, the acid-catalyzed halomethane is directionally converted to generate the acetic acid under the gas-solid phase condition for the first time, and a new path for preparing high-added-value chemicals through methane conversion is opened up.
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-
Paragraph 0101-0105
(2021/06/12)
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- The selective oxidation of glycerol over metal-free photocatalysts: insights into the solvent effect on catalytic efficiency and product distribution
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Selective oxidation of glycerol to high value-added derivatives is a promising biomass conversion pathway, but the related reaction mechanism, in particular the solvent effect, is rarely studied. In this work, O-doped g-C3N4was used as a metal-free catalyst to catalyze the selective oxidation of glycerol in different solvents. It was found that solvents can affect both catalytic efficiency and product distribution. A series of controlled experiments and theoretical calculation were applied to attest that the difference in interaction between glycerol and catalysts in different solvents is the main factor: competitive adsorption and hydrogen bond network from water inhibit the adsorption and activation of glycerol on the catalyst surface and reduce the conversion efficiency, while in acetonitrile, the stronger adsorption makes the oxidation reaction continue to yield esters. Two reaction routes in different solvents over O-doped g-C3N4are proposed for the first time, which is helpful for people to better understand the related reaction mechanism.
- Fan, Mingming,Haryonob, Agus,Jiang, Pingping,Leng, Yan,Yue, Chengguang,Zhang, Pingbo
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p. 3385 - 3392
(2021/06/06)
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- Transformation of biomass derivatives in aqueous medium: Oxidation of ethanol from sugarcane and acetol from biodiesel glycerol catalyzed by Fe3+- H2O2
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Ethanol obtained from sugarcane is an interesting biomass feedstock that is widely used as fuel and fuel additive. Another relevant biomass feedstock is acetol obtained from glycerol, the major byproduct of biodiesel manufacturing. Ethanol and acetol were oxidized by the Fe(ClO4)3-HClO4-H2O2 system in water at 60 °C with full conversions. Ethanol (0.1 M) oxidation yielded 0.058 M formic acid (HFO) and 0.085 M acetic acid (HAC), whereas acetol (0.1 M) oxidation provided 0.059 M HFO and 0.1 M HAC. On the basis of kinetic studies, the oxidation of these feedstocks followed different mechanisms. Ethanol oxidation followed a chain mechanism induced by hydroxyl radicals generated during the catalytic decomposition of H2O2 by Fe3+. Acetol oxidation, on the other hand, followed a non-chain process in which the complex formed between acetol (as substrate) and the catalyst played a decisive role, and interaction between this complex and H2O2 was the limiting stage. The activation energies for ethanol and acetol oxidation were 24.1 and 14.8 kcal/mol, respectively.
- Carvalho, Wagner Alves,Correia, Gilvan Aguiar,Kozlov, Yuriy Nikitovich,Mandelli, Dalmo,Shul'pin, Georgiy Borisovich,Shul'pina, Lidia Sergeevna,de Araújo, Marcos Lopes
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- Hierarchically Porous Metal–Organic Framework/MoS2 Interface for Selective Photocatalytic Conversion of CO2 with H2O into CH3COOH
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Metal–organic frameworks (MOFs) provide a platform to design new heterogeneous catalysts for catalytic CO2 reduction, but selective formation of C2 valuable liquid fuel products remains a challenge. Herein, we propose a strategy to synthesize composites by integrating MoS2 nanosheets into hierarchically porous defective UiO-66 (d-UiO-66) to form Mo-O-Zr bimetallic sites on the interfaces between UiO-66 and MoS2. The active interfaces are favorable for the efficient transfer of photo-generated charge carriers and for promoting the activity, whereas, the synergy of the components at the interfaces achieves selectivity for C2 production. The d-UiO-66/MoS2 composite facilitates the photo-catalytic conversion of gas phase CO2 and H2O to CH3COOH under visible light irradiation without any other adducts. The evolution rate and selectivity of CH3COOH reached 39.0 μmol g?1 h?1 and 94 %, respectively, without any C1 products, suggesting a new approach for the design of highly efficient photocatalysts of CO2 for C2 production. Theoretical calculations demonstrate the charge-polarized Zr-O-Mo aided the C?C coupling process with the largely reduced energy barrier.
- Yu, Fengyang,Jing, Xu,Wang, Yao,Sun, Mingyang,Duan, Chunying
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supporting information
p. 24849 - 24853
(2021/09/20)
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- Sustainable production of propionic acid: catalytic deoxygenation of lactic acid over MoOx/Fe
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The synergistic effect between Mo and Fe on deoxygenation of lactic acid to propionic acid was studied in this work. The catalyst structure and its chemical composites were characterized by XRD, FT-IR and EDS, respectively. The morphology of the catalyst was observed by SEM, and the reducibility was evaluated by H2-TPR. According to its structure characterization, Mo species were coated on the surface of iron powders as MoO3, and the interactions between Mo and Fe species were investigated by H2-TPR under calcination at high temperatures. A reduction peak at 650 °C moved toward low temperatures with the addition of an iron component, suggesting that iron promoted the reduction of Mo species. Due to this reason, catalytic performances are rapidly enhanced, being far more superior to any one of the Mo-Fe components. However, an excess of Fe content,ca.Fe/Mo molar ratios >0.908, decreases the activity on lactic acid deoxygenation, suggesting that the redox property of the catalyst is a major factor. Catalysts with Co and Ni substituting for Fe displayed lower selectivity to propionic acid, demonstrating that regulating appropriately the redox properties is a key to improve lactic acid deoxygenation again. The hydrothermal temperature and calcination temperature have an important influence on the formation of MoO3and its decomposition, which then affects its activity. Inspiringly, the catalyst with a Fe/Mo molar ratio of 0.908 offered an excellent stability, which proceeded efficiently for 120 h on stream under a high LHSV of 37 h?1at 390 °C.
- Chen, Zhi,Dai, Yunsheng,Li, Xinli,Pang, Jun,Tang, Congming,Wang, Hongqin,Yang, Chenglong
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p. 15831 - 15839
(2021/09/22)
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- Cooperative Co-Activation of Water and Hypochlorite by a Non-Heme Diiron(III) Complex
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Aqueous solutions of the iron(III) complex ofN,N,N′-tris(2-pyridylmethyl)ethylenediamine-N′-acetate (tpena) react with hypochlorite (ClO-) to produce the reactive high-valent [FeIV(O)(tpena)]+. Under catalytic conditions, in bicarbonate-buffered media (pH 8) with a set ionic strength (10 mM NaCl), kinetic analysis shows that two equivalents of [FeIV(O)(tpena)]+per one ClO-are produced, with benign chloride ions the only byproduct. An unprecedented supramolecular activation of ClO-by {(HCO3)?[(tpena)FeIII(μ-O)FeIII(Htpena)]}2+is proposed. This mode of activation has great advantage for use in the catalytic oxidation of C-H bonds in water since: (i) the catalyst scaffold is protected from oxidative degradation and (ii) undesirable radical side reactions which produce toxic chlorinated compounds are circumvented by this novel coactivation of water and ClO-. The unique activation mechanism by the Fe-tpena system makes possible the destruction of organic contaminants as an add-on technology to water disinfection by chlorination, demonstrated here through (i) the catalytic oxidation of micropollutant metaldehyde, and (ii) mineralization of the model substrate formate. The resting-state speciation at pH 3, 5, 7, and 9, as well as the catalytically active iron speciation are characterized with Mo?ssbauer and EPR spectroscopy and supported by DFT calculations. Our study provides fundamentally new insights into the design and activation mode of iron-based catalysts relevant to applications in water remediation.
- Bill, Eckhard,Chang, Yingyue,Hedeg?rd, Erik Donovan,McKenzie, Christine J.,McPherson, James N.,Miller, Christopher J.,Waite, T. David,Wegeberg, Christina
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supporting information
p. 15400 - 15412
(2021/09/30)
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- AN IMPROVED PROCESS FOR PHOTOCATALYTIC HYDROCARBOXYLATION OF METHANOL WITH CO2 TO PRODUCE ACETIC ACID
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An improved process for photocatalytic hydrocarboxylation of methanol with CO2 to produce acetic acid The present invention discloses a photocatalytic process and methodology for the preparation of acetic acid by a hydrocarboxylation reaction of methanol using carbon dioxide under visible light irradiation. Importantly, the reaction occurred under ambient temperature and pressure condition using a readily available household LED lamp in the presence of a transition metal based molecular photocatalyst, homogeneous as well as supported to semiconductor support and a CO2-philic solvent without adding any external electron and proton donors.
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Paragraph 0079-0082
(2021/09/26)
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- An innovative light assisted production of acetic acid from CO2and methanol: A first photocatalytic approach using a reusable cobalt(ii) molecular hybrid at atmospheric pressure
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Acetic acid is an important commodity chemical that is produced either by fermentation processes, or more commonly, through chemical routes such as methanol carbonylation with CO and H2, acetaldehyde oxidation, or hydrocarbon oxidation. More recently, methanol hydrocarboxylation with CO2 and H2 under thermal catalytic conditions has attracted interest. The synthesis of acetic acid from easily available CO2 is of great significance yet rarely reported. The present paper describes the first photocatalytic approach for the synthesis of acetic acid from methanol and CO2 under ambient reaction conditions without using molecular hydrogen. The maximum conversion of methanol achieved is 60% with a selectivity of 81% towards acetic acid using an octa-sulfur bound cobalt phthalocyanine (CoPc/S8) photocatalyst without an additional sacrificial electron donor. Product analysis, controlled experiments and DFT calculations suggest the formation of methylene carbene as a reactive intermediate. The developed methodology represents a potentially exciting approach for synthesizing acetic acid utilizing CO2 in a sustainable manner.
- Jain, Suman L.,Krishnamurty, Sailaja,Ray, Anjan,Saini, Sandhya,Samal, Pragnya Paramita
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p. 9048 - 9060
(2021/11/30)
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- Machine-Learning-Guided Discovery and Optimization of Additives in Preparing Cu Catalysts for CO2Reduction
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Discovery and optimization of new catalysts can be potentially accelerated by efficient data analysis using machine-learning (ML). In this paper, we record the process of searching for additives in the electrochemical deposition of Cu catalysts for CO2 reduction (CO2RR) using ML, which includes three iterative cycles: "experimental test; ML analysis; prediction and redesign". Cu catalysts are known for CO2RR to obtain a range of products including C1 (CO, HCOOH, CH4, CH3OH) and C2+ (C2H4, C2H6, C2H5OH, C3H7OH). Subtle changes in morphology and surface structure of the catalysts caused by additives in catalyst preparation can lead to dramatic shifts in CO2RR selectivity. After several ML cycles, we obtained catalysts selective for CO, HCOOH, and C2+ products. This catalyst discovery process highlights the potential of ML to accelerate material development by efficiently extracting information from a limited number of experimental data.
- Guo, Ying,He, Xinru,Su, Yuming,Dai, Yiheng,Xie, Mingcan,Yang, Shuangli,Chen, Jiawei,Wang, Kun,Zhou, Da,Wang, Cheng
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supporting information
p. 5755 - 5762
(2021/05/07)
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- Preparation of acetylcholine biosensor for the diagnosis of Alzheimer's disease
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We report herein the design of a novel biosensor sensing strategy for sensitive detection of acetylcholine based on PAMAM-Sal dendrimer. PAMAM-Sal, salicylaldehyde and PAMAM dendrimer have been synthesized by means of condensation. It has been determined that PAMAM-Sal dendrimer was formed by the formation of Schiff base with FT-IR, 1H NMR and UV spectra. In addition, the structure has been supported by elemental analysis. Later, a bienzymatic biosensor system has been developed. The bienzymatic biosensor system with acetylcholine esterase (AChE) and choline oxidase (ChO) was prepared with carbon paste electrode modified with PAMAM-Sal for determination of the amount of acetylcholine. Acetylcholine esterase and choline oxidase enzymes were immobilized onto modified carbon paste electrode by cross-linking with glutaraldehyde. Determination of acetylcholine was carried out by the oxidation of enzymatically produced H2O2 at +0.4 V vs. Ag/AgCl. The linear working range for acetylcholine determination of biosensor was identified. The effects of pH and temperature on the response of the biosensor were examined. Reusability and storage stability of the biosensor were determined. Interference effects of interferants which might be in biologic media on the response of the biosensor were also studied.
- ?olak, ?zlem,Arslan, Fatma,Arslan, Halit,Bodur, Onur Can,Di?li, Ali,Hasano?lu ?zkan, Elvan,Sar?, Nur?en
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- Modified bile acids and androstanes—Novel promising inhibitors of human cytochrome P450 17A1
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Cytochromes P450 are key enzymes for steroid hormone biosynthesis in human body. They are considered as targets for the screening of novel high efficient drugs. The results of screening of bile acids and androstane derivatives toward human recombinant steroid 17α-hydroxylase/17,20-lyase (CYP17A1) are presented in this paper. A group of steroids, binding with micromolar or submicromolar affinity (in a range from 9 μM – less than 0.1 μM), was identified. Results presented here showed that these steroidal compounds are able to decrease rate of hydroxylation of essential CYP17A1 substrate – progesterone, while some compounds completely inhibited enzyme activity. Structure-activity relationship (SAR) analysis based on in vitro and in silico studies showed that high affinity of the enzyme to bile acids derivatives is correlated with side chain hydrophobicity and presence of hydroxyl or keto group at C3 position. From the other side, bile acid-derived compounds with more polar side chain or substituents at C7 and C12 positions possess higher Kd values. Among androstane-derived steroids couple of Δ5-steroids with hydroxyl group at C3 position, as well as 16,17-secosteroids, were found to be high affinity ligands of this enzyme. The data obtained could be useful for the design of novel highly efficient inhibitors of CYP17A1, since the bile acids-derived compounds are for first time recognized as effective CYP17A1 inhibitors.
- Dzichenka, Yaraslau,Shapira, Michail,Yantsevich, Aliaksei,Cherkesova, Tatsiana,Grbovi?, Ljubica,Savi?, Marina,Usanov, Sergey,Jovanovi?-?anta, Suzana
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- Vanadium oxide integrated on hierarchically nanoporous copper for efficient electroreduction of CO2to ethanol
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The electrochemical reduction of CO2to an ethanol product is regarded as a highly promising route for CO2utilization. However, the poor selectivity is still a critical challenge for increasing the yield of the specific ethanol. As a CO2reduction catalyst, the hierarchically nanoporous copper integrated with vanadium oxide can achieve a 30.1% faradaic efficiency for CO2-to-ethanol production and an ethanol partial current density of ?16 mA cm?2at ?0.62 Vvs.RHE, corresponding to a 4-fold increase in activity compared to bare nanoporous Cu. It even delivers an ethanol partial current density that exceeds ?39 mA cm?2at ?0.8 Vvs.RHE in a flow-cell reactor. The hierarchically nanoporous Cu skeleton not only facilitates both electron and electrolyte transport but also provides a large specific surface area for high active site density. Density functional theory reveals that the vanadium oxide decorated Cu surface can facilitate water dissociation and optimize the hydrogen adsorption energy on Cu, lowering the energy barrier for the protonation of carbon dioxide and C-C coupling. Meanwhile, it can increase hydrogen proton coverage on the catalyst surface and inhibit dehydration, which are beneficial for breaking the C=C bond of the *HCCOH intermediate, thus enhancing the faradaic efficiency of ethanol significantly. The highly efficient conversion of CO2to ethanol demonstrates that the hybrid electrocatalyst is considered as a promising candidate for practical electrocatalytic CO2RR applications.
- Yang, Qingcheng,Liu, Xunlin,Peng, Wei,Zhao, Yang,Liu, Zhixiao,Peng, Ming,Lu, Ying-Rui,Chan, Ting-Shan,Xu, Xiandong,Tan, Yongwen
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supporting information
p. 3044 - 3051
(2021/02/16)
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- High-efficiency catalytic wet air oxidation of high salinity phenolic wastewater under atmospheric pressure in molten salt hydrate media
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An improved catalytic wet air oxidation (CWAO) process for high salinity phenolic wastewater is reported for the first time by using molten salt hydrates (MSHs) as reaction media. One feature of such a process is that it allows the operation to be conducted at atmospheric pressure owing to the temperature-increasing effect of MSHs. Another feature is that the inorganic salts in phenolic wastewater can be separated readily, taking advantage of the common-ion salting-out effect between inorganic salts and MSHs. Continuous catalytic oxidation degradation of the simulated high salinity phenolic wastewater demonstrated that more than 92% of phenol can be removed with chemical oxygen demand (COD) as high as 85% after reacting in CaCl2·3H2O medium at 150 °C with air as an oxidant. Meanwhile, the desalination efficiency of NaCl in continuous operation could reach up to 100%. It was found that CeCl3was an excellent catalyst for CWAO of phenol. XPS and UV-vis spectral characterization as well as radical scavenger experiments proved that [˙OH/Ce4+] was responsible for the synergistic catalytic degradation mechanism of phenol. Current work not only paves the way for developing a high-efficiency CWAO technology for concentrated organic wastewaters with high salinity, but also helps to better understand MSHs as reaction media.
- Tan, Hongzi,Wang, Shuai,Wang, Jinghua,Song, Feng,Sun, Xiuyu,Zhao, Rongrong,Zhang, Yuan,Cui, Hongyou
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supporting information
p. 2167 - 2174
(2021/02/06)
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- B-Cu-Zn Gas Diffusion Electrodes for CO2 Electroreduction to C2+ Products at High Current Densities
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Electroreduction of CO2 to multi-carbon products has attracted considerable attention as it provides an avenue to high-density renewable energy storage. However, the selectivity and stability under high current densities are rarely reported. Herein, B-doped Cu (B-Cu) and B-Cu-Zn gas diffusion electrodes (GDE) were developed for highly selective and stable CO2 conversion to C2+ products at industrially relevant current densities. The B-Cu GDE exhibited a high Faradaic efficiency of 79 % for C2+ products formation at a current density of ?200 mA cm?2 and a potential of ?0.45 V vs. RHE. The long-term stability for C2+ formation was substantially improved by incorporating an optimal amount of Zn. Operando Raman spectra confirm the retained Cu+ species under CO2 reduction conditions and the lower overpotential for *OCO formation upon incorporation of Zn, which lead to the excellent conversion of CO2 to C2+ products on B-Cu-Zn GDEs.
- Song, Yanfang,Junqueira, Jo?o R. C.,Sikdar, Nivedita,?hl, Denis,Dieckh?fer, Stefan,Quast, Thomas,Seisel, Sabine,Masa, Justus,Andronescu, Corina,Schuhmann, Wolfgang
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supporting information
p. 9135 - 9141
(2021/03/16)
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- Fe-O Clusters Anchored on Nodes of Metal–Organic Frameworks for Direct Methane Oxidation
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Direct methane oxidation into value-added organic oxygenates with high productivity under mild condition remains a great challenge. We show Fe-O clusters on nodes of metal–organic frameworks (MOFs) with tunable electronic state for direct methane oxidation into C1 organic oxygenates at 50 °C. The Fe-O clusters are grafted onto inorganic Zr6 nodes of UiO-66, while the organic terephthalic acid (H2BDC) ligands of UiO-66 are partially substituted with monocarboxylic modulators of acetic acid (AA) or trifluoroacetic acid (TFA). Experiments and theoretical calculation disclose that the TFA group coordinated with Zr6 node of UiO-66 enhances the oxidation state of adjacent Fe-O cluster due to its electron-withdrawing ability, promotes the activation of C?H bond of methane, and increases its selective conversion, thus leading to the extraordinarily high C1 oxygenate yield of 4799 μmol gcat?1 h?1 with 97.9 % selectivity, circa 8 times higher than those modulated with AA.
- Zhao, Wenshi,Shi, Yanan,Jiang, Yuheng,Zhang, Xiaofei,Long, Chang,An, Pengfei,Zhu, Yanfei,Shao, Shengxian,Yan, Zhuang,Li, Guodong,Tang, Zhiyong
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supporting information
p. 5811 - 5815
(2021/02/06)
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- Electrochemical oxidation of diclofenac on CNT and M/CNT modified electrodes
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The electrochemical oxidation of diclofenac (DCF), a non-steroidal anti-inflammatory drug considered as an emerging pollutant (frequently detected in wastewater), was investigated on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in aqueous media. The electroreactivity of DCF on these modified electrodes was studied using cyclic voltammetry and the kinetic parameters were calculated from the scan rate study. Cyclic voltammograms show several oxidation processes, which confirm the interaction between DCF and the catalyst surface necessary for direct oxidation processes. Constant potential electrolysis of DCF was carried out on carbon nanotubes (CNT) and metal supported CNT (M/CNT) modified electrodes, in 0.1 M NaOH and 0.1 M Na2CO3/NaHCO3buffer media. The highest DCF conversion (88% after 8 h of electrolysis) was found in carbonate buffer medium, for Ru/CNT, while the best carbon mineralization efficiency (corresponding to 48% of the oxidized DCF) was obtained on Pt/CNT modified electrode in 0.1 M NaOH medium. The products of the electrolyses were identified and quantified by HPLC-MS, GC-MS, HPLC-UV-RID and IC. The results show the presence of some low molecular weight carboxylic acids, confirming the cleavage of the aromatic rings during the oxidation process.
- Ferreira, M.,Figueiredo, J. L.,Fonseca, A. M.,Güney, S.,Ku?niarska-Biernacka, I.,Neves, I. C.,Parpot, P.,Pereira, M. F. R.,Soares, O. S. G. P.
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p. 12622 - 12633
(2021/07/25)
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- METHOD FOR PREPARING ACRYLIC ACID AND METHYL ACRYLATE
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The present invention provides a method for preparing acrylic acid and methyl acrylate. The method comprises passing the feed gas containing dimethoxymethane and carbon monoxide through a solid acid catalyst to generate acrylic acid and methyl acrylate with a high conversion rate and selectivity at a reaction temperature in a range from 180 to 400 and a reaction pressure in a range from 0.1 MPa to 15.0 MPa, the mass space velocity of dimethoxymethane in the feed gas is in a range from 0.05 h?1 to 10.0 h?1, and the volume percentage of dimethoxymethane in the feed gas is in a range from 0.1% to 95%.
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Paragraph 0082; 0083
(2021/04/23)
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- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Oxidative dehydrogenation of ethyl lactate to ethyl pyruvate over vanadium and iron antimonates catalysts
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The oxidative dehydrogenation of ethyl lactate to ethyl pyruvate, corresponding to the first step of a new process in the industrial production of methionine, has been investigated. Iron and vanadium antimonates were developed as catalysts, and were optimized to reach 87 % conversion of ethyl lactate, with 88 % selectivity to ethyl pyruvate, at only 275 °C. The catalysts were characterized before and after catalytic testing, and in situ using various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and XANES spectroscopy. The results show that neither the Sb3+/Sb5+ nor the Fe2+/Fe3+ redox couple were involved in the dehydrogenation of ethyl lactate, or in the catalysts re-oxidation. The active and selective catalytic sites correspond to surface V5+ species. These species should not be considered as part of the bulk oxide, but as supra-surface species whose surface content is monitored with the bulk composition.
- Huchede,Morvan,Vera,Bellière-Baca,Millet
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- Synthesis of acetic acid from CO2, CH3I and H2using a water-soluble electron storage catalyst
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This paper reports a possible mechanism of acetic acid formation from CO2, CH3I and H2in aqueous media and the central role played by a water-soluble Rh-based electron storage catalyst. In addition to water-solubility, we also report the crystal structures of two presumed intermediates. These findings together reveal (1) the advantage of water, not only as a green solvent, but also as a reactive Lewis base to extract H+from H2, (2) the role of the metal (Rh) centre as a point for storing electrons from H2and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage.
- Yatabe, Takeshi,Kamitakahara, Kazuki,Higashijima, Kaede,Ando, Tatsuya,Matsumoto, Takahiro,Yoon, Ki-Seok,Enomoto, Takao,Ogo, Seiji
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supporting information
p. 4772 - 4774
(2021/05/25)
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- AEROBIC ELECTROCATALYTIC OXIDATION OF HYDROCARBONS
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This invention is directed to a method of oxygenating hydrocarbons with molecular oxygen, O2, as oxidant under electrochemical reducing conditions, using polyoxometalate compounds containing copper such as Q10 [Gu4(H2O)2(B-α-PW9O)2] or Q12{ [Cu(H2O)]3[(A-α- PW9O34)2(NO3)-] } or solvates thereof as catalysts, wherein Q are each independently selected from alkali metal cations, alkaline earth metal cations, transition metal cations, NH4+,H+ or any combination thereof.
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Paragraph 0074
(2022/01/04)
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- Alcohol-Activated Vanadium-Containing Polyoxometalate Complexes in Homogeneous Glucose Oxidation Identified with 51V-NMR and EPR Spectroscopy
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Alcoholic solvents, especially methanol, show an activating affect for heteropolyacids in homogenously catalysed glucose transformation reactions. In detail, they manipulate the polyoxometalate-based catalyst in a way that thermodynamically favoured total oxidation to CO2 can be completely supressed. This allows a nearly 100 % carbon efficiency in the transformation reaction of glucose to methyl formate in methanolic solution at mild reaction conditions of 90 °C and 20 bar oxygen pressure. By using powerful spectroscopic tools like 51V-NMR and continuous wave EPR we could unambiguously prove that the vanadate-methanol-complex[VO(OMe)3]n is responsible for the selectivity shift in methanolic solution compared to the aqueous reference system.
- Wesinger, Stefanie,Mendt, Matthias,Albert, Jakob
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p. 3662 - 3670
(2021/06/18)
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