- Synergistic activating effect of promoter and oxidant in single step conversion of methane into methanol over a tailored polymer-Ag coordination complex
-
Single-step conversion of methane to its oxygenated derivatives, such as methanol, is a challenging topic in C1 chemistry. The presence of Br?nsted-acidic sites, N- and O-type chelating ligands, and noble metals are demonstrated to be essential criteria for effective catalysis of this reaction. Considering these criteria, a catalytic complex was tailored herein. Poly-d-glucosamine (Ch) was used as chelating ligand for Ag, to incorporate the robust redox properties of Ag(i). The prepared AgCh complex was characterized by techniques including solid-state 1H-NMR, FE-TEM, XANES, and XPS. Besides highlighting the utility of chelate complexation for providing new materials, this study elucidates the effects of the oxidant and promoters on the methane oxidation. The catalytic activity was tested for different oxidant combinations, including hydrogen peroxide, oxygen, and carbon dioxide. Of all of them, a mixture of hydrogen peroxide and oxygen showed the highest selectivity for oxidation of methane to methanol. Further, it was observed that the addition of 1-butyl-3-methylimidazolium chloride [BMIM]+Cl- as a promoter to the hydrogen peroxide and oxygen-containing AgCh system could enhance methanol production. The methanol yield reached up to 3166 μmol, representing an 18-fold yield increase and an 8-fold methane conversion increase when compared to the results (175 μmol) without a promoter.
- Shavi, Raghavendra,Hiremath, Vishwanath,Sharma, Aditya,Won, Sung Ok,Seo, Jeong Gil
-
-
Read Online
- Mechanism of the Photooxidation of Formaldehyde Studied by Flash Photolysis of CH2O-O2-NO Mixtures
-
The mechanism of the chain process leading to formic acid in the photooxidation of CH2O has been studied with the flash photolysis technique.Mixtures of CH2O, O2, and NO were photolyzed and the rate of appearance and yield of NO2 were monitored.Kinetic simulations of both sets of data allowed the determination of the rate constants for the main reactions HO2 + CH2O -> O2CH2OH (6), OCH2OH + O2 -> HO2 + HCO2H (8), OCH2OH + NO -> products (9) (k6=(7.5 +/-3.5)E-14; k8=(3.5 +/-1.6)E-14; k9=(4.0 +/-1.9)E-11 cm3molecule-1s-1).Quantum calculations provided estimates of the heats of formation for the radicals involved.The effect of temperature was investigated, suggesting the importance of the decomposition of the radical HOCH2O into H atom and formic acid.The validity of the global scheme is discussed along with its importance for the removal of CH2O and the production of formic acid in the athmosphere.
- Veyret, Bernard,Rayez, Jean-Claude,Lesclaux, Robert
-
-
Read Online
- Photo-reduction of CO2 by vis light on polythiophene-ZSM-5 zeolite hybrid photo-catalyst
-
A new hybrid photo-catalyst based on ZSM-5 zeolite suitable for reduction of carbon dioxide was synthesized. The photo-catalyst was prepared by oxidative polymerization of thiophene with FeCl3 in the presence of ZSM-5 with participation of ultrasound. The synthesized photo-catalyst strongly absorbs light radiation up to approx. 650 nm, with the absorption edge in the NIR region. Reactive radicals were generated by VIS light irradiation in an aqueous suspension consisting of the photo-catalyst with CO2. Formic acid and acetic acid were generated as the main products of the CO2 reduction. EPR spin trapping technique was applied to identify the reactive radical intermediates. In this work, the mechanism of product formation is also discussed.
- Kiani?ka, Jana,?ík, Gabriel,?er?eň, Franti?ek,?pánik, Ivan,Sokolík, Robert,Filo, Juraj
-
-
Read Online
- Drastically enhanced visible-light photocatalytic degradation of colorless aromatic pollutants over TiO2 via a charge-transfer-complex path: A correlation between chemical structure and degradation rate of the pollutants
-
Photocatalytic degradation of colorless aniline and phenolic pollutants was investigated over TiO2 under visible-light irradiation, which was confirmed to proceed via a charge-transfer-complex (CTC)-mediated pathway. The correlation between the chemical structure and the degradation rate of these pollutants was established experimentally and theoretically. It was found that an electron-donating substituent in benzene ring, which raises the highest occupied molecular orbital and lowers the ionization potential of the organic compound, is favorable to the CTC-mediated photodegradation of the pollutant, but an electron- withdrawing substituent has a reversed effect. The addition of sacrificial electron acceptors was adopted to enhance the degradation and mineralization of the aromatic pollutants. The increased degradation rate by 3 to 10 times suggests that the CTC-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants in the presence of sacrificial electron acceptors.
- Wang, Nan,Zhu, Lihua,Huang, Yingping,She, Yuanbin,Yu, Yanmin,Tang, Heqing
-
-
Read Online
- MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-Durable Hydrogen and Chemical Productions in Acidic Solutions
-
Electrocatalytic hydrogen production under acidic conditions is of great importance for industrialization in comparison to that in alkaline media, which, unfortunately, still remains challenging due to the lack of earth-abundant, cost-effective and highly active anodic electrocatalysts that can be used durably under strongly acidic conditions. Here we report an unexpected finding that manganese oxide, a kind of common non-noble catalysts easily soluble in acidic solutions, can be applied as a highly efficient and extremely durable anodic electrocatalyst for hydrogen production from an acidic aqueous solution of alcohols. Particularly in a glycerol solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA cm?2, which is 270 mV lower than that of oxygen evolution reaction (OER), to oxidize glycerol into value-added chemicals such as formic acid, without oxygen production. To our surprise, the manganese oxide exhibits extremely high stability for electrocatalytic hydrogen production in coupling with glycerol oxidation for longer than 865 hours compared to shorter than 10 h for OER. Moreover, the effect of the addition of glycerol on the electrochemical durability has been probed via in situ Raman spectroscopic analysis and density functional theory (DFT) calculations. This work demonstrates that acid-unstable metal oxide electrocatalysts can be used robustly in acidic media under the presence of certain substances for electrochemical purposes, such as hydrogen production.
- Chen, Lisong,Han, Shuhe,Li, Yan,Shi, Jianlin,Wei, Xinfa
-
-
Read Online
- Use of Bifurcation Diagrams as Fingerprints of Chemical Mechanisms
-
Various chemical reagents were fed continuously into a continuously stirred tank reactor to perturb the Belousov-Zhabotinskii system.The resulting bifurcation diagrams each contain multiple curves separating regions with different types of dynamical behav
- Noszticzius, Zoltan,McCormick, William D.,Swinney, Harry L.
-
-
Read Online
- SYNTHESIS OF D-RIBO-C-NUCLEOSIDE ANALOGUES BY DEHYDRATION OF NEW D-ALLO-PENTITOL-1-YL HETEROCYCLES
-
The reaction of 2-amino-2-deoxy-D-glycero-D-altro-heptose hydrochloride with acyclic and cyclic 1,3-dicarbonyl compounds gives, respectively, (D-allo-pentitol-1-yl)-pyrroles and -tetrahydroindoles that can be dehydrated to yield D-ribo-C-glycosyl heterocycles having furanoid or pyranoid structures, depending on the reaction conditions.Thus, when the reactions were kinetically controlled, α- and β-D-ribofuranosyl heterocycles were obtained, but α- and β-D-ribopyranosyl heterocycles were formed under conditions of thermodynamic control.A criterion is proposed to differentiate between both structures on the basis of the mass spectra of their triacetates.
- Perez, Juan A. Galbis,Caballero, Reyes Babiano,Ventula, Arturo Cert
-
-
Read Online
- Formate ester Norrish Type II elimination: Diode laser probing of gas-phase yields
-
Time-resolved infrared absorption spectroscopy was utilized to monitor the production of HCOOH, CO2, and CO following ultraviolet laser excitation of gas-phase formate esters. Excitation of ethyl formate at 227.5 nm resulted in formation of HCOOH and CO2. The CO2 quantum yield was estimated to be 0.5 ± 0.1. No evidence for CO formation was obtained at this wavelength. Relative quantum yields for the Norrish Type II elimination of HCOOH from ethyl, n-propyl, n-butyl, isopropyl, isobutyl, and tert-butyl formate were obtained at 227.5 and 222 nm. Normalization of the observed HCOOH yields with respect to the number of γ-hydrogen atoms resulted in reactivity trends at 227.5 nm of 1:3:9 for the abstraction of primary, secondary, and tertiary hydrogen atoms, respectively. At 222 nm, a similar reactivity trend was observed with yields per available γ-hydrogen of 1:3:7 for abstraction of primary, secondary, and tertiary hydrogen atoms. Yields were found to be independent of ester pressure over the range 100-550 mTorr. Semiempirical and ab initio calculations of the excited state hydrogen abstraction step were performed and enthalpies of activation of 8-12 kcal/mol were obtained using AM1 with configuration interaction.
- Niu, Yuping,Christophy, Elizabeth,Pisano, Patrick J.,Zhang, Ying,Hossenlopp, Jeanne M.
-
-
Read Online
- Radical-initiated oxidative conversion of methane to methanol over metallic iron and copper catalysts
-
Oxidative conversion of methane gas into value-added chemicals such as methanol is of great interest due to high economic feasibility of liquid fuel molecules for storage and transportation purpose. Activation and conversion of methane occur at very high temperatures due to its strong C–H bonding and hence the process is highly energy intensive. Therefore, homolytic cleavage of methane to produce CH3 and H radicals and subsequent conversion to methanol could be an alternative way to catalyze the reaction through a less energy-intensive process. In this work, radical-based conversion of methane to methanol was conducted in water-diluted 1-butyl-3-methylimidazolium chloride ionic liquid (IL) using metallic iron and copper as catalysts. The acidic IL, besides producing the high oxidation potential radicals from K2S2O8, enhanced their longevity. ZV Cu was found to be highly active in the reaction catalyzing with steady rate at a lower activation energy (Ea = 31.5 kJ/mol) and retains its oxidation state even after the reaction. On the other hand, ZV Fe, catalyzed the reaction with slightly slow initial rate ultimately resulting in moderate activation energy (40.77 kJ/mol). However, it was observed that ZV Fe fails to retain its oxidation state after reaction.
- Shavi, Raghavendra,Hiremath, Vishwanath,Seo, Jeong Gil
-
-
Read Online
- Cerium Doped Pt/TiO2 for Catalytic Oxidation of Low Concentration Formaldehyde at Room Temperature
-
Abstract: Formaldehyde is a carcinogenic and teratogenic toxic gas. With the extensive use of a variety of building materials, indoor formaldehyde has seriously threatened human health and environment. The catalytic oxidation is considered the most promising method for the removal of formaldehyde from air. In this work, we report a Pt/TiO2 catalyst with Ce modification, and investigate its activity of catalytic oxidation of low concentration formaldehyde at room temperature. The experimental results show that the trace formaldehyde (20?mg/m3) could be completely degraded at 55?min by using Pt–Ce/TiO2 catalyst. In view of multiple characterizations, such as BET, XRD, TEM, STEM, XPS and CO adsorption, it is indicated that the modification of Ce can effectively improve the dispersion of Pt particles in the surface and reduction of Pt particle size from 2.9 to 2.2?nm. Moreover, XPS results show that the Ce in the catalyst could enhance the binding energies of Pt, provide abundant oxygen vacancies, and could increase the ratio of adsorbed oxygen atoms to lattice oxygen atoms, which is conducive to the adsorption of oxygen, leading to the improvement of catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].
- Shi, Yuanyuan,Qiao, Zhiwei,Liu, Zili,Zuo, Jianliang
-
-
Read Online
- Facile synthesis of Au-Pt bimetallic nanocomplexes for direct oxidation of methanol and formic acid
-
Au-Pt bimetallic nanocomplexes were synthesized and the composition and morphology of the nanocomplexes could be easily controlled by a facile synthesis method. The eletrochemical activity and stability of the nanocomplexes can be optimized by tuning their Au-to-Pt molar ratio. The efficient electrocatalytic performance is confirmed by direct oxidation of methanol and formic acid.
- Xie, Ruigang,Chen, Muzi,Wang, Jiaqing,Mei, Sujuan,Pan, Yue,Gu, Hongwei
-
-
Read Online
- Micellar effect on the reaction of chromium(VI) oxidation of L-sorbose in the presence and absence of picolinic acid in aqueous acid media: A kinetic study
-
The kinetics and mechanism of chromic acid oxidation of L-sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L-sorbose]T >> [PA]T >> [Cr(VI)]T, at different temperatures. In the absence of PA, the monomeric
- Saha, Bidyut,Das, Mahua,Mohanty, Rajani K.,Das, Asim K.
-
-
Read Online
- Immobilizing AgPd alloy on Vulcan XC-72 carbon: a novel catalyst for highly efficient hydrogen generation from formaldehyde aqueous solution
-
A novel bimetallic catalyst, AgPd nanoalloy supported on Vulcan XC-72 carbon (AgPd@C-72), has been successfully fabricated and used for catalyzing H2 generation from formaldehyde aqueous solution at room temperature for the first time. The catalyst exhibits high catalytic activity and good stability, and the hydrogen generation rates could reach up to 237.4 mL min?1 g?1, which could be attributed to the high dispersion of metal nanoparticles, the synergistic effect of bimetal AgPd, and distinct interaction between the bimetal and the support. The excellent performance of the new catalytic system renders it quite attractive as a superior competitor for efficient hydrogen production from formaldehyde at room temperature. This work might open up a new way to further develop cost-effective and highly efficient bimetallic catalysts for the generation of H2 from formaldehyde aqueous solution.
- Gao, Shutao,Feng, Tao,Wu, Qiuhua,Feng, Cheng,Shang, Ningzhao,Wang, Chun
-
p. 105638 - 105643
(2016)
-
Read Online
- Oxidation of aldehydes with permanganate in acidic and alkaline media
-
The oxidation mechanism of aldehydes with permanganate was studied in acidic and alkaline media on acetaldehyde, propionaldehyde, pivalaldehyde (2,2′-dimethylpropanal) and chloral substrates. On addition of water to acetaldehyde dissolved in organic solvents the rate increased, and therefore it may be stated that the hydrate form is more reactive than the aldehyde form. Acid-catalysed nucleophilic addition of permanganate is suggested. In alkaline medium a mechanism based on electron abstraction from the alkoxy anion of the hydrate is proposed. Deprotonation constants of hydrate could be calculated..
- Jaky,Szammer
-
-
Read Online
- Proton inventory study of the base-catalyzed hydrolysis of formamide. Consideration of the nucleophilic and general base mechanisms
-
An NMR study of the rates of hydroxide-promoted hydrolysis of formamide in aqueous media of varying mole fraction D2O (n) was performed at [LO-] = 1.42 M, T = 25 °C, to shed light on whether the mechanism involves a nucleophilic attack of HO- on the C = O or HO- acting as a general base to remove a proton from an attacking water. The solvent deuterium kinetic isotope effect under these conditions is inverse, kOH/kOD = 0.77 ± 0.02 or kOD/kOH = 1.30 ± 0.03. Proton inventory analysis of the kn versus n data was undertaken through NLLSQ fits to equations representing four possible mechanisms encompassing nucleophilic and general base ones with waters of solvation on the attacking hydroxide, and with or without waters of solvation on the developing amide hydrate oxyanion. Both nucleophilic and general base mechanisms can be accommodated, but there are restraints on each that are discussed. The preferred mechanism is a nucleophilic one proceeding through a transition state having two solvating waters remaining on the attacking hydroxide and three additional waters attached to the developing amide hydrate oxyanion.
- Slebocka-Tilk,Neverov, Alexei A.,Brown
-
-
Read Online
- Photocatalytic degradation of chlorinated ethanes in the gas phase on the porous TiO2 pellets: Effect of surface acidity
-
The photocatalytic degradation of chlorinated ethanes was studied in a tubular photoreactor packed with TiO2 pellets prepared by sol-gel method. The steady-state condition was not obtained, but the deterioration in the photocatalytic activity was observed during the irradiation. Effects of mole fractions of water vapor, O2, and C2H5Cl or C2H4Cl2 and reaction temperature on the photodegradation of C2H5Cl or C2H 4Cl2 were examined, and these data were compared with those obtained by the photodegradation of chlorinated ethylenes. On the basis of the products detected with and without oxygen in the reactant's gas stream, we proposed the degradation mechanism. Measurement of diffuse reflectance infrared Fourier transform spectroscopy of pyridine adsorbed on the catalysts showed that decrease in the conversion for the photodegradation of C2H 5Cl was attributable to the formation of Bronsted acid sites. Comparison of the data obtained with the TiO2 and the sulfated TiO2 (SO42-/TiO2) pellets indicated that the photodegradation of C2H5Cl was suppressed by the presence of the Bronsted sites, but that of trichloroethylene was not affected. Such a difference is attributable to the adsorption process of these reactants on the acid sites on the catalyst surface.
- Yamazaki, Suzuko,Ichikawa, Keiko,Saeki, Atsue,Tanimura, Toshifumi,Adachi, Kenta
-
-
Read Online
- A halide perovskite as a catalyst to simultaneously achieve efficient photocatalytic CO2 reduction and methanol oxidation
-
A halide perovskite based photocatalyst has been demonstrated for the first time to simultaneously achieve efficient photocatalytic CO2 reduction and methanol oxidation, exhibiting an exciting yield of 1835 μmol g-1 for photocatalytic CO2-to-CO conversion. Moreover, almost stoichiometric value-added formic acid can be produced from methanol oxidation.
- Dong, Guang-Xing,Zhang, Wen,Mu, Yan-Fei,Su, Ke,Zhang, Min,Lu, Tong-Bu
-
-
Read Online
- Catalytic conversion of biomass-derived carbohydrates to formic acid using molecular oxygen
-
Here we report a catalytic process for the efficient production of formic acid (FA) from common carbohydrates via VO2+ formed by dissolving sodium metavanadate in acidic water. The polysaccharides undergo a hydrolysis reaction and an immediate oxidation reaction successively to produce FA in the same reaction system. The hydrolysis reaction decomposes the polymerized structures to produce monosaccharides, which are readily oxidized to FA under catalysis of VO2+. Typically, formic acid mole yields are 64.9% from cellulose and 63.5% from xylan (hemicellulose). The separation of FA from the catalytic system and recycling of the catalyst are demonstrated. the Partner Organisations 2014.
- Wang, Wenhua,Niu, Muge,Hou, Yucui,Wu, Weize,Liu, Zhenyu,Liu, Qingya,Ren, Shuhang,Marsh, Kenneth N.
-
-
Read Online
- WET OXIDATION OF MODEL CARBOHYDRATE COMPOUNDS
-
The major product formed by wet oxidation of a series of model compounds: D-xylose, D-glucose, D-glucitol, cellulose, and dextran, was formic acid.Its yield varied according to the structure of the carbohydrate, oxygen pressure, temperature, and the presence or absence of ferric sulfate.Acetic acid was also formed; its yield was much less dependent on the structure of carbohydrate.Other products formed include methanol, acetaldehyde, acetone, and a series of hydroxylated acids.
- McGinnis, Gary D.,Prince, Shawn E.,Biermann, Chris J.,Lowrimore, James T.
-
-
Read Online
- Bacteria-Like Fixation of Carbon Dioxide under UV-Light Irradiation with Defect-Free ZnS Quantum Crystallites
-
Photoreduction of CO2 to formic acid and a small quantity of CO can be achieved effectively in water by using defect-free ZnS quantum crystallites and their aggregates as catalysts and S(2-) and H2PO2(1-) ions as sacrificial electron donors under more tha
- Kanemoto, Masashi,Shiragami, Tsutomu,Pac, Chyongjin,Yanagida, Shozo
-
-
Read Online
- Efficient Electrochemical Reduction of Carbon Dioxide to Acetate on Nitrogen-Doped Nanodiamond
-
Electrochemical reduction of CO2 is an attractive technique for reducing CO2 emission and converting it into useful chemicals, but it suffers from high overpotential, low efficiency or poor product selectivity. Here, N-doped nanodiam
- Liu, Yanming,Chen, Shuo,Quan, Xie,Yu, Hongtao
-
-
Read Online
- Direct synthesis of formic acid by partial oxidation of methane on H-ZSM-5 solid acid catalyst
-
The direct synthesis of formic acid by partial oxidation of methane was studied using hydrogen peroxide (H2O2) as oxidant with keeping reaction temperature of 373 K and a pressure of 2.6 MPa. High yield (13.0%) and selectivity (66.8%
- Rahman, Abul Kalam Md. Lutfor,Kumashiro, Masako,Ishihara, Tatsumi
-
-
Read Online
- Mechanism of C-C bond formation in the electrocatalytic reduction of CO2 to acetic acid. A challenging reaction to use renewable energy with chemistry
-
Copper nanoparticles on carbon nanotubes are used in the reduction of CO2 to acetic acid (with simultaneous water electrolysis) in a flow electrocatalytic reactor operating at room temperature and atmospheric pressure. A turnover frequency of about 7000 h-1 and a carbon-based Faradaic selectivity to acetic acid of about 56% were observed, indicating potential interest in this approach for using renewable energy. The only other products of reaction detected were formic acid and methanol (the latter in some cases), besides H2. The reaction mechanism, particularly the critical step of C-C bond formation, was studied by comparing the reactivity in tests with CO2 or CO, where formic acid or formaldehyde where initially added. The results indicate the need for having dissolved CO2 to form acetic acid, likely via the reaction of CO2?- with surface adsorbed -CH3 like species. The pathway towards formic acid is instead different from the route of the formation of acetic acid.
- Genovese, Chiara,Ampelli, Claudio,Perathoner, Siglinda,Centi, Gabriele
-
-
Read Online
- Kinetics and mechanism of the Ir(III)-catalyzed oxidation of xylose and maltose by potassium iodate in aqueous alkaline medium
-
For the first time, the Ir(III) catalysis of the iodate oxidation of xylose and maltose in aqueous alkaline medium has been investigated. The reactions exhibit first-order kinetics with respect to lower [IO3-] and [OH-] and show zero-order kinetics at their higher concentrations. Unity order at low concentrations of maltose becomes zero order at its higher concentrations, whereas zero-order kinetics with respect to [xylose] was observed throughout its variation. The reaction rate is found to be directly proportional to [Ir(III)] in the oxidation of both reducing sugars. Negligible effect of [Cl-] and nil effect of ionic strength (μ) on the rate of oxidation have also been noted. The species, [IrCl3(H2O)2OH]- was ascertained as the reactive species of Ir(III) chloride for both the redox systems. Various activation parameters have been calculated. Formic acid and arabinonic acid for maltose and formic acid and threonic acid for xylose were identified as the main oxidation products of the reactions. Mechanisms consistent with the observed kinetic data and spectral evidence have been proposed for the oxidation of xylose and maltose.
- Singh, Ashok Kumar,Srivastava, Shalini,Srivastava, Jaya,Singh, Reena
-
-
Read Online
- Mechanism of methylphosphonic acid photo-degradation based on phosphate oxygen isotopes and density functional theory
-
Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerve agents, such as sarin and VX, and a biosynthesis product of marine microbes with ramifications to global climate change and eutrophication. Here, we applied the multi-labeled water isotope probing (MLWIP) approach to investigate the C-P bond cleavage mechanism of MPn under UV irradiation and density functional theory (DFT) to simulate the photo-oxidation reaction process involving reactive oxygen species (ROS). The results contrasted with those of the addition of the ROS-quenching compounds, 2-propanol and NaN3. The degradation kinetics results indicated that the extent of MPn degradation was more under alkaline conditions and that the degradation process was more rapid at the initial stage of the reaction. The phosphate oxygen isotope data confirmed that one exogenous oxygen atom was incorporated into the product orthophosphate (PO4) following the C-P bond cleavage, and the oxygen isotopic composition of this free PO4 was found to vary with pH. The combined results of the ROS-quenching experiments and DFT indicate that the C-P bond was cleaved by OH-/OH and not by other reactive oxygen species. Based on these results, we have established a mechanistic model for the photolysis of MPn, which provides new insights into the fate of MPn and other phosphonate/organophosphate compounds in the environment.
- Xia, Congcong,Geng, Huanhuan,Li, Xiaobao,Zhang, Yiyue,Wang, Fei,Tang, Xiaowen,Blake,Li, Hui,Chang, Sae Jung,Yu, Chan
-
-
Read Online
- Oxidation of aci-nitromethane by singlet oxygen in aqueous solution
-
In alkaline solution nitromethane (NM) forms a stable act tautomer (H2C=NO2-) which may be used as a spin trap for radicals, including NO? and NO2?. We have noticed previously that in aerated photochemical systems NM can undergo photosensitized degradation (Bilski et al., J. Am. Chem. Soc. 1992, 114, 549), possibly via singlet oxygen (1O2). We have now confirmed that aci-NM does indeed quench 1O2 phosphorescence (kq = 2.4 × 107 M-1 s-1), and that the addition of 1O2 to aci-NM is solely responsible for this chemical quenching, as confirmed by the high quantum yield of O2 photoconsumption (φ = 0.65 for [NM] = 35 mM). To obtain "labeled" fragments from the decomposition of the resultant aci-NM-O2 peroxy species we have applied another spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), in a novel way: we used an EPR silent hydroxylamine adduct (DMPOH/CH=NO2-) formed by nucleophilic addition of aci-NM to DMPO. Reaction of DMPOH/CH=NO2- with 1O2 resulted in the generation of the DMPO/CO2?- radical, suggesting that in the absence of DMPO the following mechanism may occur: 1O2 + CH2=NO2- → NO2- + HCOOH. We have found that nitrite and formate production accounts for most of the oxygen consumed. This suggests that 1O2 reacts mainly with the carbon atom of NM producing a biradical transient which decomposes yielding thermodynamically stable products nitrite and formate. A minor product is peroxynitrite (OONO-) which must be produced via an ozonide-type intermediate formed by intramolecular recombination of the biradical. Prolonged irradiation of Rose Bengal and aci-NM resulted in accumulation of nitrite which was then photooxidized to NO2?, trapped by unreacted aci-NM and identified as the NM/NO2? spin adduct.
- Bilski, Piotr,Reszka, Krzysztof,Chignell, Colin F.
-
-
Read Online
- Kinetics of the Ru(III) Catalyzed Oxidation of Formaldehyde and Acetaldehyde by Alkaline Hexacyanoferrate(III)
-
The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically.The rate of oxidation of formaldehyde is directly proportional to while that of acetaldehyde is proportional to k/>, where k, k' and k" are rate constants.The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0.The rate of reaction is proportional to T in each case.A suitable mechanism is proposed are discussed. -Keywords: Kinetics; Mechanism; Oxidation; Ru(III) catalyzed
- Awasthi, Anil K.,Upadhyay, Santosh K.
-
-
Read Online
- Room-Temperature Activation of the C-H Bond in Methane over Terminal ZnII-Oxyl Species in an MFI Zeolite: A Combined Spectroscopic and Computational Study of the Reactive Frontier Molecular Orbitals and Their Origins
-
Oxygenase reactivity toward selective partial oxidation of CH4 to CH3OH requires an atomic oxygen-radical bound to metal (M-O?: oxyl intermediate) that is capable of abstracting an H atom from the significantly strong C-H bond in CH4. Because such a reaction is frequently observed in metal-doped zeolites, it has been recognized that the zeolite provides an environment that stabilizes the M-O? intermediate. However, no experimental data of M-O? have so far been discovered in the zeolite; thus, little is known about the correlation among the state of M-O?, its reactivity for CH4, and the nature of the zeolite environment. Here, we report a combined spectroscopic and computational study of the room-temperature activation of CH4 over ZnII-O? in the MFI zeolite. One ZnII-O? species does perform H-abstraction from CH4 at room temperature. The resultant CH3? species reacts with the other ZnII-O? site to form the ZnII-OCH3 species. The H2O-assisted extraction of surface methoxide yields 29 μmol g-1 of CH3OH with a 94% selectivity. The quantum mechanics (QM)/molecular mechanics (MM) calculation determined the central step as the oxyl-mediated hydrogen atom transfer which requires an activation energy of only 10 kJ mol-1. On the basis of the findings in gas-phase experiments regarding the CH4 activation by the free [M-O?]+ species, the remarkable H-abstraction reactivity of the ZnII-O? species in zeolites was totally rationalized. Additionally, the experimentally validated QM/MM calculation revealed that the zeolite lattice has potential as the ligand to enhance the polarization of the M-O? bond and thereby enables to create effectively the highly reactive M-O? bond required for low-temperature activation of CH4. The present study proposes that tuning of the polarization effect of the anchoring site over heterogeneous catalysts is the valuable way to create the oxyl-based functionality on the heterogeneous catalyst.
- Oda, Akira,Ohkubo, Takahiro,Yumura, Takashi,Kobayashi, Hisayoshi,Kuroda, Yasushige
-
-
Read Online
- CO2 hydrogenation to formic acid over heterogenized ruthenium catalysts using a fixed bed reactor with separation units
-
Along with the mitigation of CO2 emission, recently, the CO2-derived formic acid process has drawn attention as a promising platform for the renewable-energy-derived hydrogen storage cycle by using formic acid as a liquid organic hydrogen carrier (LOHC). Here, a heterogenized Ru molecular catalyst on a bpyTN-30-CTF support is prepared and successfully implemented in an integrated trickle-bed reactor system for continuous CO2 hydrogenation to produce formic acid. The bpyTN-30-CTF support with an alternative structure of the bpy and TN motif increases the porosity and metal anchoring sites. The Ru/bpyTN-30-CTF catalyst prepared using the bpyTN-30-CTF support displays sufficient catalytic activity for commercialization. Under the continuous process, the catalyst exhibits substantial catalytic performance with the highest productivity of 669.0 gform. gcat-1 d-1 with CO2 conversion of 44.8% for a superficial gas velocity of 72 cm s-1. Furthermore, the catalyst shows excellent stability in the continuous hydrogenation process with a trickle-bed reactor over 30 days of operation, reaching a total turnover number of 524?000 without any significant deactivation. Based on kinetic data, a new process to produce formic acid by CO2 hydrogenation has thus been proposed here.
- Park, Kwangho,Gunasekar, Gunniya Hariyanandam,Kim, Seong-Hoon,Park, Hongjin,Kim, Samhwan,Park, Kiyoung,Jung, Kwang-Deog,Yoon, Sungho
-
-
Read Online
- Conversion of saccharides into formic acid using hydrogen peroxide and a recyclable palladium(ii) catalyst in aqueous alkaline media at ambient temperatures
-
We have developed an effective method that converts a variety of mono- and disaccharides into formic acid predominantly. Our recyclable NHC-amidate palladium(ii) catalyst facilitated oxidative degradation of carbohydrates without using excess oxidant. Stoichiometric amounts of hydrogen peroxide and sodium hydroxide were employed at ambient temperatures.
- Zargari,Kim,Jung
-
-
Read Online
- Aspects of the hydrolysis of formamide: Revisitation of the water reaction and determination of the solvent deuterium kinetic isotope effect in base
-
A study of the hydrolysis of formamide is reported with the aims of isolating the water reaction for hydrolysis from the acid and base hydrolysis terms and determining the solvent deuterium kinetic isotope effect (dkie) on base-catalyzed hydrolysis. Respective activation parameters (ΔH? and ΔS?) of (17.0 ± 0.4) kcal mol-1 and (-18.8 ± 1.3) cal mol-1 K-1 for the acid reaction and (17.9 ± 0.2) kcal mol-1 and (-11.1 ± 0.5) cal mol-1 K-1 for the base reaction were determined from Eyring plots of the second-order rate constants over the range of 27-120°C. Kinetic studies at the minima of the pH/rate profiles in the pH range from 5.6 to 6.2 in MES buffers at 56°C, and in the pH range of 4.25-6.87 in acetate and phosphate buffers at 120°C are reported. At 56°C the available data fit the expression kobs56 = 0.00303[H3O+] + 0.032[HO-] + (3.6 ± 0.1) × 10-9, while at 120°C the data fit kobs120 = (0.15 ± 0.02)[H3O+] + (3.20 ± 0.24)[HO-] + (1.09 ± 0.29) × 10-6. Preliminary experimental estimates of Ea (ln A) of 22.5 kcal mol-1 (15.03) for the water rate constant (kw) are calculated from an Arrhenius plot of the 56 and 120°C data giving an estimated kw of 1.1 × 10-10 s-1 (t1/2 = 199 years) at 25°C. Solvent dkie values of kOH/kOD = 1.15 and 0.77 ± 0.06 were determined at [OL-] = 0.075 and 1.47 M, respectively. The inverse value is determined under conditions where the the first step of the reaction dominates and is analyzed in terms of a rate-limiting attack of OL-.
- Slebocka-Tilk,Sauriol,Monette, Martine,Brown
-
-
Read Online
- In situ infrared study of photoreaction of ethanol on Au and Ag/TiO2
-
An in situ IR technique was used to study the role of Au and Ag additives on photocatalytic reaction of ethanol on TiO2 at 300 K. Au and Ag additives increased water/ethanol coverage and decreased the rate of ethanol's C-H scission, a step involving in scavenging photogenerated holes. Au and Ag promoted adsorption of ethanol as monodentate ethoxy, accelerated its conversion to formate (HCOO-ad) and acetate (CH3COO-ad). In contrast, adsorbed ethanol on TiO2 did not produce IR-observable products and exhibited a Stark effect with a decreased C-H intensity upon accumulation of photogenerated electrons.
- Rismanchian, Azadeh,Chen, Yu-Wen,Chuang, Steven S.C.
-
-
Read Online
- Oxidation of formaldehyde by chlorite in basic and slightly acidic media
-
The reaction of chlorite and formaldehyde was studied in basic and slightly acidic media. Though the expected product was CO2, the oxidation of HCHO, however, gave nearly quantitative formation of ClO2, the oxidation product of ClO2-. In excess HCHO the stoichiometry of the reaction was deduced as 3ClO2-+HCHO+2H+→HCOOH +2ClO2(aq)+Cl-+2H2O; but in high excess of ClO2- the stoichiometry was 6ClO2-+HCHO +4H+→CO2(g)+4ClO2(aq)+3H2 O+2Cl-. The reaction is autocatalytic in HOCl. The first step of the reaction produces HOCl, which catalyzes the formation of ClO2 and further oxidation of HCOOH to CO2. ClO2 was found to be relatively unreactive toward HCHO and HCOOH, and hence it accumulated rapidly.
- Chinake,Olojo,Simoyi
-
-
Read Online
- KINETICS AND MECHANISM OF OXIDATION OF SOME ALCOHOLS BY OSMIUM TETROXIDE
-
Spectrophotometric studies of the kinetics of oxidation of 2-methylpropan-1-ol and 2-butanol by an alkaline solution of osmium tetroxide have been reported.A first-order dependence to osmium tetroxide was observed.A first-order dependence to both 2-methylpropan-1-ol and alkali at low concentration tends to zero order at higher concentrations.In the case of 2-butanol, first-order kinetics is exhibited with respect to 2-butanol but first-order kinetics observed at lower concentrations of alkali decrease at higher concentrations.A negligible ionic strength effect of the medium was observed.Activation parameters have been computed.A suitable mechanism in conformity with our kinetic observations has been suggested.
- Singh, Bharat,Singh, A. K.,Singh, M. B.,Singh, A. P.
-
-
Read Online
- Structural Optimization of Metal Oxyhalide for CO2 Reduction with High Selectivity and Current Density
-
Electrochemical CO2 reduction into value-added liquid fuels using CO2 neutral renewable energy sources is very promising to solve climatic issues. In order to realize their practical applications, highly active and inexpensive electr
- Duan, Yan-Xin,Liu, Kai-Hua,Meng, Fan-Lu,Zhang, Qi,Zhang, Xin-Bo
-
-
Read Online
- Multiple isotope effect study of the acid-catalyzed hydrolysis of formamide
-
Multiple isotope effects were measured at the reactive center of formamide during acid-catalyzed hydrolysis in water at 25 °C. The mechanism involves a rapid pre-equilibrium protonation of the carbonyl oxygen, followed by the formation of at least one tetrahedral intermediate, which does not appreciably exchange its carbonyl oxygen with the solvent (kh/kcx = 55). The pKa for formamide was determined by 15N NMR and found to be about -2.0. The formyl-hydrogen kinetic isotope effect (KIE) is indicative of a transition state that is highly tetrahedral (Dk obs = 0.79); the carbonyl-carbon KIE (13kobs = 1.031) is in agreement with this conclusion. The small leaving-nitrogen KIE (15kobs = 1.0050) is consistent with some step prior to breaking the C-N bond as rate-determining. The carbonyl-oxygen KIE ( 18kobs = 0.996) points to attack of water as the rate-determining step. On the basis of these results, a mechanism is proposed in which attachment of the nucleophile to a protonated formamide molecule is rate determining.
- Marlier, John F.,Campbell, Erica,Lai, Catherine,Weber, Michael,Reinhardt, Laurie A.,Cleland
-
-
Read Online
- Solar-assisted co-electrolysis of glycerol and water for concurrent production of formic acid and hydrogen
-
Renewable electricity-driven water splitting provides a pathway to manufacturing hydrogen as a promising alternative to fossil fuels. A typical water electrolysis device is comprised of a cathodic hydrogen evolution reaction (HER) and an anodic oxygen evolution reaction (OER). Unfortunately, the OER consumes most of the overall electricity supply while generating negligible economic value, which inhibits the large-scale deployment of the water electrolysis technology. Here, we explored alternatives to the OER and demonstrated that electrooxidation of glycerol (a cheap byproduct of biodiesel and soap production) could lower anodic electricity consumption by up to 0.27 V while producing high-value formic acid with 96.2% faradaic efficiency (FE). Further, glycerol electrooxidation was combined with the photoelectrochemical HER to diminish the electricity requirement to 1.15 V, reducing the electricity consumption by ~30% relative to typical water electrolysis. This study suggests that solar-assisted co-electrolysis of high-volume block chemicals and water may be an energy efficient and economically viable strategy to realize the sustainable production of value-added chemicals and hydrogen energy.
- Gu, Jing,He, Dong,Ke, Zunjian,Pan, Xiaoqing,Song, Xianyin,Williams, Nicholas,Xiao, Xiangheng,Yan, Xingxu,Younan, Sabrina
-
-
Read Online
- Spectroscopic and electrochemical characterization of heteropoly acids for their optimized application in selective biomass oxidation to formic acid
-
Different Keggin-type polyoxometalates have been synthesized and characterized in order to identify optimized homogeneous catalysts for the selective oxidation of biomass to formic acid (FA) using oxygen as an oxidant and p-toluenesulfonic acid as an additive. Applying the optimized polyoxometalate catalyst system H8[PV5Mo7O 40] (HPA-5), a total FA-yield (with respect to carbon in the biogenic feedstock) of 60% for glucose within 8 h reaction time and 28% for cellulose within 24 h reaction time could be achieved. The transformation is characterized by its mild reaction temperature, its excellent selectivity to FA in the liquid product phase and its applicability to a very wide range of biogenic raw materials including non-edible biopolymers and complex biogenic mixtures.
- Albert, Jakob,Lueders, Daniela,Boesmann, Andreas,Guldi, Dirk M.,Wasserscheid, Peter
-
-
Read Online
- Kinetics and Mechanism of Oxidation of L-Arabinose by Vanadium(V)
-
Vanadium(V) oxidation of L-arabinose has been found to be first order with respect to oxidant and substrate concentrations.It has been found that the order with respect to changes from one in 2.5M-4.5M acid concentration range to two in 5.0M-6.5M acid concentration range.The oxidation rate has been found to increase with ionic strength and decrease with dielectric constant of the medium.Thermodynamic parameters ΔE, ΔS(excit.) and ΔG(excit.) have been evaluated as 22.63+/- 0.19 kcal/mol,-3.00+/- 0.65 e.u. and 23.59+/- 0.05 kcal/mol respectively.The reaction has been found to be initiated by the formation of free radical in a slow rate determining step. - Keywords: Kinetics of L-arabinose oxidation; Oxidation by vanadium(V)
- Bhatnagar, R.P.,Fadnis, A.G.
-
-
Read Online
- Nonuniform Electric Field-Enhanced In-Source Declustering in High-Pressure Photoionization/Photoionization-Induced Chemical Ionization Mass Spectrometry for Operando Catalytic Reaction Monitoring
-
Photoionization mass spectrometry (PI-MS) is a powerful and highly sensitive analytical technique for online monitoring of volatile organic compounds (VOCs). However, due to the large difference of PI cross sections for different compounds and the limitation of photon energy, the ability of lamp-based PI-MS for detection of compounds with low PI cross sections and high ionization energies (IEs) is insufficient. Although the ion production rate can be improved by elevating the ion source pressure, the problem of generating plenty of cluster ions, such as [MH]+·(H2O)n (n = 1 and 2) and [M2]+, needs be solved. In this work, we developed a new nonuniform electric field high-pressure photoionization/photoionization-induced chemical ionization (NEF-HPPI/PICI) source with the abilities of both HPPI and PICI, which was accomplished through ion-molecule reactions with high-intensity H3O+ reactant ions generated by photoelectron ionization (PEI) of water molecules. By establishing a nonuniform electric field in a three-zone ionization region to enhance in-source declustering and using 99.999% helium as the carrier gas, not only the formation of cluster ions was significantly diminished, but the ion transmission efficiency was also improved. Consequently, the main characteristic ion for each analyte both in HPPI and PICI occupied more than 80%, especially [HCOOH·H]+ with a yield ratio of 99.2% for formic acid. The analytical capacity of this system was demonstrated by operando monitoring the hydrocarbons and oxygenated VOC products during the methanol-to-olefins and methane conversion catalytic reaction processes, exhibiting wide potential applications in process monitoring, reaction mechanism research, and online quality control.
- Wan, Ningbo,Jiang, Jichun,Hu, Fan,Chen, Ping,Zhu, Kaixin,Deng, Dehui,Xie, Yuanyuan,Wu, Chenxin,Hua, Lei,Li, Haiyang
-
-
Read Online
- Catalytic oxidative conversion of cellulosic biomass to formic acid and acetic acid with exceptionally high yields
-
Direct conversion of raw biomass materials to fine chemicals is of great significance from both economic and ecological perspectives. In this paper, we report that a Keggin-type vanadium-substituted phosphomolybdic acid catalyst, namely H4PVMo11O40, is capable of converting various biomass-derived substrates to formic acid and acetic acid with high selectivity in a water medium and oxygen atmosphere. Under optimized reaction conditions, H4PVMo11O40 gave an exceptionally high yield of formic acid (67.8%) from cellulose, far exceeding the values achieved in previous catalytic systems. Our study demonstrates that heteropoly acids are generally effective catalysts for biomass conversion due to their strong acidities, whereas the composition of metal addenda atoms in the catalysts has crucial influence on the reaction pathway and the product selectivity.
- Zhang, Jizhe,Sun, Miao,Liu, Xin,Han, Yu
-
-
Read Online
- The Promotion Effect of NaCl on the Conversion of Xylose to Furfural?
-
In this work, the promotion effect of NaCl on the conversion of xylose to furfural in H2O was studied. It was found that xylose conversion and furfural yield increased with NaCl concentration. NaCl decreased the pH of the solution providing H+ for the acid catalytic dehydration of xylose. The formation of oligomers was determined by GPC and ESI-MS in the initial stage of reaction, especially at low temperature. Excess NaCl promoted the formation of humins in the late stage of the reaction. NaCl could also change the decomposition route of formic acid. Meanwhile, NaCl had the ability of phase separation. Combining these effects with organic solvent during the reaction could inhibit the formation of humins and increase the yield of furfural. In NaCl-H2O-THF biphasic system without other catalyst, the optimal furfural yield of 76.7% and selectivity of 77.6% were achieved at 463 K in 2 h.
- Fang, Qianying,Hu, Changwei,Jiang, Zhicheng,Li, Zheng,Luo, Yiping
-
-
Read Online
- Crystal structure of an S-formylglutathione hydrolase from pseudoalteromonas haloplanktis TAC125
-
S-formylglutathione hydrolases (FGHs) constitute a family of ubiquitous enzymes which play a key role in formaldehyde detoxification both in prokaryotes and eukaryotes, catalyzing the hydrolysis of S-formylglutathione to formic acid and glutathione. While a large number of functional studies have been reported on these enzymes, few structural studies have so far been carried out. In this article we report on the functional and structural characterization of PhEst, a FGH isolated from the psychrophilic bacterium Pseudoalteromonas haloplanktis. According to our functional studies, this enzyme is able to efficiently hydrolyze several thioester substrates with very small acyl moieties. By contrast, the enzyme shows no activity toward substrates with bulky acyl groups. These data are in line with structural studies which highlight for this enzyme a very narrow acyl-binding pocket in a typical α/β-hydrolase fold. PhEst represents the first cold-adapted FGH structurally characterized to date; comparison with its mesophilic counterparts of known three-dimensional structure allowed to obtain useful insights into molecular determinants responsible for the ability of this psychrophilic enzyme to work at low temperature.
- Alterio, Vincenzo,Aurilia, Vincenzo,Romanelli, Alessandra,Parracino, Antonietta,Saviano, Michele,D'Auria, Sabato,de Simone, Giuseppina
-
-
Read Online
- Autocatalytic Waves in the Nitric Acid - Formaldehyde System
-
Propagating reaction fronts generated in the autocatalytic oxidation of formaldehyde by nitric acid have been investigated.The experimental values of the wave velocity ν and those of the maximal reaction rate rm at a given spatial coordinate have been described by the formulae ν = 2(Dk0)1/2 and rm = 0.247 x k02, respectively, (D and k are constants).Similarities and differences to other nitric acid oxidations have been discussed.
- Komlosi, Andrea,Pota, Gyoergy,Stedman, Geoffrey
-
-
Read Online
- 3D structured TiO2-based aerogel photocatalyst for the high-efficiency degradation of toluene gas
-
Photocatalytic technology is a green , environmentally friendly, energy-saving technology, which is considered to be an ideal method for removing volatile organic compounds (VOCs). At present, photocatalytic technology mostly uses powdered catalysts, which is not conducive to recycling and restricts the contact between the gas and catalyst. In this work, a three-dimensional (3D)-structured TiO2-based aerogel with TiO2 as the main body and all the components beneficial to photocatalysis was prepared for the first time. Under simulated sunlight irradiation, the toluene-removal rate of the Pt-loaded TiO2 and reduced graphene oxide (RGO) composite aerogel (denoted as Pt-TiO2/RGO aerogel, or PTA thereafter) was 60.47% higher than that of the pure RGO aerogel, and 56.03% higher than that of the bare TiO2 nanofibers. The block-shaped composite aerogel could be easily recycled, and the C/C0 of toluene using the recycled sample decreased by only 5.31% in the 5th run. The Pt-TiO2/RGO composite aerogel had the highest photocatalytic degradation rate of toluene with a relative humidity (RH) of 60-80%, which is conducive to the purification of VOCs in high-humidity areas. The 3D aerogel enriches the contact between the solid photocatalyst and the toluene molecules, and also solves the problem of low adhesion between the catalyst and the carrier. This work provides a new perspective for the efficient removal of toluene gas by constructing a highly active 3D TiO2 aerogel with an increased gas-solid reaction rate.
- Dai, Li,Guan, Jie,Li, Shijie,Li, Xueying,Yu, Wei,Zhang, Li
-
p. 2272 - 2281
(2022/02/16)
-
- Manganese oxide as an alternative to vanadium-based catalysts for effective conversion of glucose to formic acid in water
-
MnOx catalysts were synthesized under hydrothermal conditions for conversion of glucose into formic acid (FA) in water with the objective to develop vanadium-free reaction systems. An FA yield of 81.1% was obtained with a MnOx catalyst and glucose substrate in water at 160 °C and is almost twice the value obtained with vanadium-based heterogeneous catalysts. MnOx materials prepared hydrothermally at 100 °C had higher Mn2+/Mn3+ ratios and adsorbed oxygen species than those prepared at higher temperatures and gave the highest FA yields among the catalysts evaluated. Mechanistic studies of glucose–MnOx–water reaction systems revealed that two parallel reactions existed with arabinose being the intermediate in the α-scission route and glyoxylic acid being the intermediate in the β-scission route where CO2 co-forms with FA. Small water-soluble carbohydrates (glucose, sucrose, cellobiose, maltose, xylose) afforded FA yields greater than 50%, while starch afforded FA yields greater than 20%, thus demonstrating the potential of MnOx catalysts for converting biomass into FA.
- Li, Jialu,Smith, Richard Lee,Xu, Siyu,Li, De,Yang, Jirui,Zhang, Keqiang,Shen, Feng
-
p. 315 - 324
(2022/01/19)
-
- Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation
-
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.
-
p. 626 - 639
(2022/01/22)
-
- Electrochemical Strategy for the Simultaneous Production of Cyclohexanone and Benzoquinone by the Reaction of Phenol and Water
-
Cyclohexanone and benzoquinone are important chemicals in chemical and manufacturing industries. The simultaneous production of cyclohexanone and benzoquinone by the reaction of phenol and water is an ideal route for the economical production of the two c
- Wu, Ruizhi,Meng, Qinglei,Yan, Jiang,Liu, Huizhen,Zhu, Qinggong,Zheng, Lirong,Zhang, Jing,Han, Buxing
-
p. 1556 - 1571
(2022/02/01)
-
- Direct catalytic benzene hydroxylation under mild reaction conditions by using a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups
-
Direct catalytic hydroxylation of benzene under mild reaction conditions proceeded efficiently in the presence of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups in an acetonitrile solution with excess H2O2. Mechanistic studies suggested that the reaction was catalyzed by a high-valent iron-oxo species generated in situ. Moreover, the peripheral methyl groups of the catalyst were presumed to have enhanced the production rate of the iron-oxo species.
- Tanaka, Kentaro,Teoh, Chee-Ming,Toyoda, Yuka,Yamada, Yasuyuki
-
supporting information
p. 955 - 958
(2022/02/07)
-
- 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
-
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
-
p. 813 - 822
(2022/02/09)
-
- Method for preparing formic acid from biomass polyol
-
The invention relates to a method for preparing formic acid through photo-thermal catalysis of oxidative cleavage of a C-C bond of biomass polyol by using a cerium dioxide-based catalyst. According to the method, glycerol, xylose, glucose, fructose, cane sugar, cellobiose or starch are used as reaction substrates, oxygen is used as an oxidizing agent, cerium dioxide or loaded cerium dioxide is used as a catalyst, and the reaction substrates are selectively oxidized into formic acid at a certain temperature under irradiation of visible light of 400-650 nm; and the method comprises the following reaction processes: dissolving a substrate in a solvent, adding a catalyst, sealing a reactor, replacing with oxygen three times, keeping a certain pressure, and irradiating with 400-650 nm visible light at a temperature of 40-150 DEG C for reaction to generate formic acid. The synthesis method possibly plays an important role in preparation of formic acid through high-selectivity oxidation of biomass polyol.
- -
-
Paragraph 0023-0024; 0025-0026; 0027-0028; 0029-0030; ...
(2021/06/26)
-
- Electro-oxidation of glycerol into formic acid by nickel-copper electrocatalysts
-
Herein, non-precious metallic nickel-copper electrocatalysts were synthesized for electro-oxidation of glycerol in alkaline electrolytes. Activated carbon felt (ACF) is used as a supporting material because of its good conductivity, chemical inertness, and porous structure which is conducive to the transport of the reactants/electrons. The structural features of the catalysts were characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical activity of the catalysts was revealed by cyclic voltammetry, linear sweeping voltammetry, and chronoamperometry. The electrochemical results show that the Cu1Ni1@ACF catalyst possesses the highest current density of 1.31 mA cm-2 at 1.895 V. High-performance liquid chromatography results show that the as-prepared catalysts have high selectivities for formic acid (FA). Especially, the Cu1Ni1@ACF catalyst yields a selectivity of 97.4% for FA, which has so far been the largest value reported in the literature. Additionally, the effects of applied potentials and reaction time on product selectivity were studied.
- Shen, Yi,Zhang, Jiali
-
-
- Synthesis of Core@Shell Cu-Ni@Pt-Cu Nano-Octahedra and Their Improved MOR Activity
-
Fabrication of 3d metal-based core@shell nanocatalysts with engineered Pt-surfaces provides an effective approach for improving the catalytic performance. The challenges in such preparation include shape control of the 3d metallic cores and thickness control of the Pt-based shells. Herein, we report a colloidal seed-mediated method to prepare octahedral CuNi@Pt-Cu core@shell nanocrystals using CuNi octahedral cores as the template. By precisely controlling the synthesis conditions including the deposition rate and diffusion rate of the shell-formation through tuning the capping ligand, reaction temperature, and heating rate, uniform Pt-based shells can be achieved with a thickness of 1 nm. The resultant carbon-supported CuNi@Pt-Cu core@shell nano-octahedra showed superior activity in electrochemical methanol oxidation reaction (MOR) compared with the commercial Pt/C catalysts and carbon-supported CuNi@Pt-Cu nano-polyhedron counterparts.
- Li, Can,Chen, Xiaobo,Zhang, Lihua,Yan, Shaohui,Sharma, Anju,Zhao, Bo,Kumbhar, Amar,Zhou, Guangwen,Fang, Jiye
-
supporting information
p. 7675 - 7680
(2021/03/01)
-
- Unprecedentedly high efficiency for photocatalytic conversion of methane to methanol over Au-Pd/TiO2-what is the role of each component in the system?
-
Direct and highly efficient conversion of methane to methanol under mild conditions still remains a great challenge. Here, we report that Au-Pd/TiO2 could directly catalyze the conversion of methane to methanol with an unprecedentedly high methanol yield of 12.6 mmol gcat-1 in a one-hour photocatalytic reaction in the presence of oxygen and water. Such an impressive efficiency is contributed by several factors, including the affinity between Au-Pd nanoparticles and intermediate species, the photothermal effect induced by visible light absorption of Au-Pd nanoparticles, the employment of O2 as a mild oxidant, and the effective dissolution of methanol in water. More importantly, for the first time, thermo-photo catalysis is demonstrated by the distinct roles of light. Namely, UV light is absorbed by TiO2 to excite charge carriers, while visible light is absorbed by Au-Pd nanoparticles to increase the temperature of the catalyst, which further enhances the driving force of corresponding redox reactions. These results not only provide a valuable guide for designing a photocatalytic system to realize highly efficient production of methanol, but also, highlight the great promise of thermo-photo catalysis. This journal is
- Cai, Xiaojiao,Fang, Siyuan,Hu, Yun Hang
-
supporting information
p. 10796 - 10802
(2021/05/14)
-
- High catalytic methane oxidation activity of monocationic μ-nitrido-bridged iron phthalocyanine dimer with sixteen methyl groups
-
Herein, we report the highly potent catalytic methane oxidation activity of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups. It was confirmed that this complex oxidized methane stably into MeOH, HCHO, and HCOOH in a catalytic manner in an acidic aqueous solution containing excess H2O2 at 60 °C. The total turnover number of the reaction reached 135 after 12 h, which is almost seven times higher than that of a monocatinoic μ-nitrido-bridged iron phthalocyanine dimer with no peripheral substituents. This suggests that the increased number of peripheral electron-donating substituents could have facilitated the generation of a reactive high-valent iron-oxo species as well as hydrogen abstraction from methane by the reactive iron-oxo species.
- Kura, Jyunichi,Tanaka, Kentaro,Toyoda, Yuka,Yamada, Yasuyuki
-
supporting information
p. 6718 - 6724
(2021/05/26)
-
- Formic acid disproportionation into formaldehyde triggered by vanadium complexes with iridium catalysis under mild conditions inN-methylation
-
Formaldehyde (CH2O) has been used as a key platform reagent in the chemical industry for many decades. Currently, the industrial production of CH2O mainly depends on fossil resources, involving a highly energetic three-step process (200-1100 °C). Herein, we describe renewable formic acid (HCO2H) disproportionation into CH2O triggered by vanadium complexes with iridium catalysis under mild conditions at 30-50 °C inN-methylation. The gram-scale application ofin situgenerated CH2O by HCO2H disproportionation is demonstrated.
- Guo, Yan-Jun,Li, Yang,Zhang, Ping,Zhao, Yu-Rou,Zhou, Chao-Zheng
-
supporting information
p. 2918 - 2924
(2021/05/05)
-
- Alcohol-Activated Vanadium-Containing Polyoxometalate Complexes in Homogeneous Glucose Oxidation Identified with 51V-NMR and EPR Spectroscopy
-
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
-
p. 3662 - 3670
(2021/06/18)
-
- Electro- and Photochemical Reduction of CO2 by Molecular Manganese Catalysts: Exploring the Positional Effect of Second-Sphere Hydrogen-Bond Donors
-
A series of molecular Mn catalysts featuring aniline groups in the second-coordination sphere has been developed for electrochemical and photochemical CO2 reduction. The arylamine moieties were installed at the 6 position of 2,2’-bipyridine (bpy) to generate a family of isomers in which the primary amine is located at the ortho- (1-Mn), meta- (2-Mn), or para-site (3-Mn) of the aniline ring. The proximity of the second-sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst 1-Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9-fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)3Br (901 vs. 102 s?1, respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration-dependent shift in product selectivity from CO (at high [catalyst]) to HCO2H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.
- Roy, Sayontani Sinha,Talukdar, Kallol,Jurss, Jonah W.
-
p. 662 - 670
(2020/11/30)
-
- Investigation of Cyclam Based Re-Complexes as Potential Electrocatalysts for the CO2 Reduction Reaction
-
Among the various homogenous electrocatalysts, especially Re(bpy)(CO)3Cl and [Ni(cyclam)]2+ were shown to be highly efficient for the selective conversion of CO2 to CO at moderate potentials. However, a purposeful combination of a ReI tricarbonyl unit with a cyclam ligand hitherto received no attention. Herein, we report on a series of cyclam based Re complexes comprising the original {N4} as well as heteroatom-altered ligand frameworks, describe their synthesis, reveal their coordination behavior and furthermore investigate their performance towards the electrochemical CO2 reduction.
- Gerschel, Philipp,Cordes, Anna L.,Bimmermann, Sarah,Siegmund, Daniel,Metzler-Nolte, Nils,Apfel, Ulf-Peter
-
p. 968 - 977
(2021/04/09)
-
- Engineering Bismuth–Tin Interface in Bimetallic Aerogel with a 3D Porous Structure for Highly Selective Electrocatalytic CO2 Reduction to HCOOH
-
Electrochemical reduction of CO2 (CO2RR) into valuable hydrocarbons is appealing in alleviating the excessive CO2 level. We present the very first utilization of metallic bismuth–tin (Bi-Sn) aerogel for CO2RR with selective HCOOH production. A non-precious bimetallic aerogel of Bi-Sn is readily prepared at ambient temperature, which exhibits 3D morphology with interconnected channels, abundant interfaces and a hydrophilic surface. Superior to Bi and Sn, the Bi-Sn aerogel exposes more active sites and it has favorable mass transfer properties, which endow it with a high FEHCOOH of 93.9 %. Moreover, the Bi-Sn aerogel achieves a FEHCOOH of ca. 90 % that was maintained for 10 h in a flow battery. In situ ATR-FTIR measurements confirmed that the formation of *HCOO is the rate-determining step toward formic acid generation. DFT demonstrated the coexistence of Bi and Sn optimized the energy barrier for the production of HCOOH, thereby improving the catalytic activity.
- Wu, Zexing,Wu, Hengbo,Cai, Weiquan,Wen, Zhenhai,Jia, Baohua,Wang, Lei,Jin, Wei,Ma, Tianyi
-
supporting information
p. 12554 - 12559
(2021/04/30)
-
- Transition-Metal-Modified Vanadoborate Clusters as Stable and Efficient Photocatalysts for CO2Reduction
-
Photocatalytic carbon dioxide reduction (CO2RR) is considered to be a promising sustainable and clean approach to solve environmental issues. Polyoxometalates (POMs), with advantages in fast, reversible, and stepwise multiple-electron transfer without changing their structures, have been promising catalysts in various redox reactions. However, their performance is often restricted by poor thermal or chemical stability. In this work, two transition-metal-modified vanadoborate clusters, [Co(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Co) and [Ni(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Ni), are reported for photocatalytic CO2 reduction. V12B18-Co and V12B18-Ni can preserve their structures to 200 and 250 °C, respectively, and remain stable in polar organic solvents and a wide range of pH solutions. Under visible-light irradiation, CO2 can be converted into syngas and HCOO- with V12B18-Co or V12B18-Ni as catalysts. The total amount of gaseous products and liquid products for V12B18-Co is up to 9.5 and 0.168 mmol g-1 h-1. Comparing with V12B18-Co, the yield of CO for V12B18-Ni declines by 1.8-fold, while that of HCOO- increases by 35%. The AQY of V12B18-Co and V12B18-Ni is 1.1% and 0.93%, respectively. These values are higher than most of the reported POM materials under similar conditions. The density functional theory (DFT) calculations illuminate the active site of CO2RR and the reduction mechanism. This work provides new insights into the design of stable, high-performance, and low-cost photocatalysts for CO2 reduction.
- Yu, Xiang,Zhao, Cong-Cong,Gu, Jian-Xia,Sun, Chun-Yi,Zheng, Hai-Yan,Yan, Li-Kai,Sun, Min,Wang, Xin-Long,Su, Zhong-Min
-
supporting information
p. 7364 - 7371
(2021/05/31)
-
- Enhanced Ethylene Formation from Carbon Dioxide Reduction through Sequential Catalysis on Au Decorated Cubic Cu2O Electrocatalyst
-
Electrochemical reduction of carbon dioxide to fuels has been recognized as a perspective way to address the environmental and energy issues. Herein, the novel Au decorated Cu2O electrocatalysts were synthesized via the galvanic replacement reaction and the successive pre-reduction by linear voltammetry (LSV) method. In contrast to Cu2O, CO formation became dominant over HCOOH and H2 on AuxCu2O, and a remarkably enhanced selectivity of C2H4 was obtained beyond ?1.1 V vs. RHE. Among them, Au0.02Cu2O exhibited the highest Faraday efficiency (FE) of C2H4 of 24.4 % at ?1.3 V vs. RHE, which was as high as 2~2.5 and 5 times of those on other two AuxCu2O and bare Cu2O, respectively. Meanwhile, it is demonstrated that the optimal ratio of Au/Cu was essential for effective sequential catalysis between Au and Cu2O to enhance C?C coupling. Furthermore, the effect of copper states resulting from different pre-reduction methods on the selectivity of C2H4 was explored. A half decrease of C2H4 FE was observed on HPR-Au0.02Cu2O (high potential reduced) relative to the LSV reduced Au0.02Cu2O, which was ascribed to the different content of Cu0 and residual Cu+ in two catalysts. Our results demonstrate an effective approach to construct Cu2O based bimetallic catalysts for ethylene formation from CO2.
- Cao, Xuerui,Cao, Guangwei,Li, Mei,Zhu, Xinli,Han, Jinyu,Ge, Qingfeng,Wang, Hua
-
p. 2353 - 2364
(2021/06/17)
-
- Machine-Learning-Guided Discovery and Optimization of Additives in Preparing Cu Catalysts for CO2Reduction
-
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
-
supporting information
p. 5755 - 5762
(2021/05/07)
-
- (1,2-Azole)bis(bipyridyl)ruthenium(II) Complexes: Electrochemistry, Luminescent Properties, and Electro- And Photocatalysts for CO2Reduction
-
New cis-(1,2-azole)-aquo bis(2,2′-bipyridyl)ruthenium(II) (1,2-azole (az*H) = pzH (pyrazole), dmpzH (3,5-dimethylpyrazole), and indzH (indazole)) complexes are synthesized via chlorido abstraction from cis-[Ru(bipy)2Cl(az*H)]OTf. The latter are obtained from cis-[Ru(bipy)2Cl2] after the subsequent coordination of the 1,2-azole. All the compounds are characterized by 1H, 13C, 15N NMR spectroscopy as well as IR spectroscopy. Two chlorido complexes (pzH and indzH) and two aquo complexes (indzH and dmpzH) are also characterized by X-ray diffraction. Photophysical and electrochemical studies were carried out on all the complexes. The photophysical data support the phosphorescence of the complexes. The electrochemical behavior of all the complexes in an Ar atmosphere indicate that the oxidation processes assigned to Ru(II) → Ru(III) occurs at higher potentials in the aquo complexes. The reduction processes under Ar lead to several waves, indicating that the complexes undergo successive electron-transfer reductions that are centered in the bipy ligands. The first electron reduction is reversible. The electrochemical behavior in CO2 media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [icat(CO2)/ip(Ar)] ranged from 2.9 to 10.8. Controlled potential electrolysis of the chlorido and aquo complexes affords CO and formic acid, with the latter as the major product after 2 h. Photocatalytic experiments in MeCN with [Ru(bipy)3]Cl2 as the photosensitizer and TEOA as the electron donor, which were irradiated with >300 nm light for 24 h, led to CO and HCOOH as the main reduction products, achieving a combined turnover number (TONCO+HCOO-) as high as 107 for 2c after 24 h of irradiation.
- Angeles-Boza, Alfredo M.,Cuéllar, Elena,Diez-Varga, Alberto,García-Herbosa, Gabriel,Martín-Alvarez, Jose M.,Miguel, Daniel,Nganga, John,Pastor, Laura,Torroba, Tomás,Villafa?e, Fernando
-
p. 692 - 704
(2021/01/13)
-
- Defect evolution of hierarchical SnO2aggregates for boosting CO2electrocatalytic reduction
-
To efficiently convert CO2into high-value added productsviathe electrocatalytic reduction, the rational regulation of surface defects (e.g., oxygen vacancies) and the interfacial structure of electrocatalysts are crucial but still challenging. Herein, a feasible strategy is presented to manipulate oxygen vacancies and interfacial boundaries on hierarchical tin oxide aggregatesviaa thermal reduction process. The optimized Sn/SnO2-2h electrocatalyst exhibited the maximum faradaic efficiencies (FEs) of 92.5 and 96.4% for C1 products (FEC1) in the H-type cell and the flow cell, respectively. Online differential electrochemical mass spectrometry confirmed the lower onset potential for the electrocatalytic CO2reduction reaction (ECRR) in comparison with the pristine SnO2. With the defect evolution from oxygen vacancies (Ovacs), the formation of Sn/SnO2with favorable interfacial features is crucial to achieve an enhanced performance. More importantly, thein situcharacterization studies and density functional theory (DFT) calculations revealed that the synergistic effect of both residual Ovacsand the interfacial structure is responsible for the energy favorable reduction of carbon dioxideviaproton-coupled electron transfer, thus improving the selectivity for formate generation. This facile strategy for modulating surface defects provides an ideal approach to guide the future designs of ECRR catalysts.
- Cao, Xueying,Tan, Dongxing,Wulan, Bari,Zhang, Baohua,Zhang, Jintao
-
supporting information
p. 14741 - 14751
(2021/07/12)
-
- Sn(101) Derived from Metal-Organic Frameworks for Efficient Electrocatalytic Reduction of CO2
-
The synthesis of a specific Sn plane as an efficient electrocatalyst for CO2 electrochemical reduction to generate fuels and chemicals is still a huge challenge. Density functional theory (DFT) calculations first reveal that the Sn(101) crystal plane is more advantageous for CO2 electroreduction. A metal-organic framework (MOF) precursor Sn-MOF has been carbonized and then etched to successfully fabricate Sn(101)/SnO2/C composites with good control of the carbonization time and the concentration of hydrochloric acid. The Sn(101) crystal plane of the catalyst could enhance the faradaic efficiency of formate to as high as 93.3% and catalytic stability up to 20 h. The promotion of the selectivity and activity by Sn(101) advances new possibilities for the rational design of high-activity Sn catalysts derived from MOFs.
- Wu, Jian-Xiang,Zhu, Xiao-Rong,Liang, Ting,Zhang, Xiang-Da,Hou, Shu-Zhen,Xu, Ming,Li, Ya-Fei,Gu, Zhi-Yuan
-
supporting information
p. 9653 - 9659
(2021/07/19)
-
- Binuclear rhenium complex taking dipyridyl xanthene as ligand as well as synthesis method and application of binuclear rhenium complex
-
The invention discloses a binuclear rhenium complex taking dipyridyl xanthene as a ligand as well as a synthesis method and application of the binuclear rhenium complex. The invention aims to provide a catalyst which has good catalytic activity on photocatalytic carbon dioxide reduction under the conditions of normal temperature and normal pressure in an air atmosphere. According to the technical scheme, the preparation method comprises the following steps: putting a 4-bibpy ligand and a pentacarbonyl chloride rhenium solid in a Schracker bottle according to a substance amount ratio of 1: 1.5-2.5, vacuumizing and filling argon for three times; bubbling by using an inert gas for 15-25 minutes, injecting into a bottle, sealing, stirring and heating to 70-90 DEG C under the inert gas component, carrying out condensation reflux reaction for 10-16 hours, and washing the obtained yellow precipitate solid by using a detergent for multiple times; and carrying out alumina column chromatography purification analysis to obtain a trans product of the binuclear rhenium complex trans-bibpyRe2 (CO) 6Cl2 and a cis product of the binuclear rhenium complex cis-bibpyRe2 (CO) 6Cl2. The method belongs to the technical field of catalysts.
- -
-
Paragraph 0038-0039; 0043-0044; 0048-0049
(2021/07/21)
-
- Selectivity Switching of CO2Hydrogenation from HCOOH to CO with an in Situ Formed Ru-Li Complex
-
Herein, we report the role of alkali halide salt in regulating the pathway of CO2 hydrogenation in the presence of Shvo's complex. Particularly, the collaboration of Shvo's complex with LiCl exhibited as a highly efficient catalyst for CO2 hydrogenation to CO instead of the kinetically favorable product HCOOH under mild conditions. The reaction can be initiated at 45 °C with CO as the dominant product, and the rate of CO formation was almost 80 times to that in the absence of LiCl at 60 °C. Under optimized conditions, the TONCO could reach 1555 at 160 °C, much higher than the reported results of the most efficient Ru-based homogeneous catalyst. Density functional theory calculations demonstrated that the cooperation of the alkali cation and chloride anion contributed to reducing the energy barrier of CO2 activation to form the key Ru-CO2H intermediate. An in situ formed mixed Ru-Li complex (5) has been characterized by X-ray crystallography, highlighting the indispensability of electrostatic interactions between LiCl and Shvo's complex for enhanced reactivity and altered selectivity.
- Chen, Qiongyao,Shen, Chaoren,Zhu, Gangli,Zhang, Xuehua,Lv, Chun-Lin,Zeng, Bo,Wang, Sen,Li, Junfen,Fan, Weibin,He, Lin
-
p. 9390 - 9396
(2021/07/31)
-
- Homogeneous electrocatalytic CO2 reduction by hexacarbonyl diiron dithiolate complex bearing hydroquinone
-
Recently, the hexacarbonyl diiron dithiolate complex ((bdt)Fe2(CO)6, bdt = benzene-1,2-dithiolate) was reported for electrochemical CO2 reduction in CH3OH/CH3CN solution. To further simulate the [NiFe] carbon monoxide dehydrogenase (CODH) active center, another diiron dithiolate complex (1) with phenolic hydroxyl as second coordination sphere group was introduced to catalyze CO2 reduction electrochemically. Cyclic voltammetry measurements revealed that the phenolic hydroxyl group of 1 could lower the onset potential of electrochemical CO2 reduction. Under the best conditions, the maximum turnover frequency (TOFmax) of about 35 s?1 and an almost equal amount of HCOOH, CO, and H2 were obtained. Fourier transform infrared reflectance spectroelectrochemistry (IR-SEC) experiments illuminated the intermediate with terminal coordinated –COOH and the changes of intermolecular hydrogen bonds during the catalytic cycle.
- Cheng, Minglun,Fan, Fenglan,Liu, Jinyu,Wang, Lingjuan
-
-
- Mild selective oxidative cleavage of lignin C-C bonds over a copper catalyst in water
-
The conversion of lignin into aromatics as commodity chemicals and high-quality fuels is a highly desirable goal for biorefineries. However, the presence of robust inter-unit carbon-carbon (C-C) bonds in natural lignin seriously impedes this process. Herein, for the first time, we report the selective cleavage of C-C bonds in β-O-4 and β-1 linkages catalyzed by cheap copper and a base to yield aromatic acids and phenols in excellent yields in water at 30 °C under air without the need for additional complex ligands. Isotope-labeling experiments show that a base-mediated Cβ-H bond cleavage is the rate-determining step for Cα-Cβ bond cleavage. Density functional theory (DFT) calculations suggest that the oxidation of β-O-4 ketone to a key intermediate, i.e., a peroxide, by copper and O2 lowers the Cα-Cβ bond dissociation energy and facilitates its subsequent cleavage. In addition, the catalytic system could be successfully applied to the depolymerization of various authentic lignin feedstocks, affording excellent yields of aromatic compounds and high selectivity of a single monomer. This study offers the potential to economically produce aromatic chemicals from biomass.
- Hu, Yuzhen,Li, Song,Ma, Longlong,Wang, Chenguang,Yan, Long,Zhang, Qi,Zhang, Xinghua,Zhao, Xuelai
-
p. 7030 - 7040
(2021/09/28)
-
- Direct Partial Oxidation of Methane Catalyzed by an in Situ Generated Active Au(III) Complex at Low Temperature in Ionic Liquids
-
An in situ generated AuIII catalyst is found to catalyze the direct oxidation of CH4 to C1 oxygenates in 1-ethylimidazolium bis-(trifluoromethylsulfonyl)amide ([Eim][NTf2]) at 90 °C. The formation of 13CH3OH and H13COOH from 13CH4 as a feed verifies the CH4 oxidation to CH3OH and HCOOH. Ionic liquids (ILs) with a wide range of structural types as potential reaction media and a number of solid, liquid, and gaseous oxidants are screened in a temperature range of 90-200 °C. Among the ILs and the oxidants, [Eim][NTf2] and hydrogen peroxide (H2O2) are identified to be compatible as the stable solvent and the most efficient oxidant, respectively, for the selective oxidation of CH4 to C1 oxygenates, with CH3OH as the primary product. An AuIII-CH4 H-bonding structure, produced in situ by adding two molar equivalent of silver trifluoromethanesulfonate (AgOTf) to the AuCl3(phen) (phen=phenanthroline) precursor under high CH4 pressure, forms a resting state of the AuIII catalyst, which produces CH3OH in the presence of H2O. After each catalytic turnover, AuI is oxidized by H2O2 to regenerate the active AuIII state. In the absence of CH4, unstable AuCl(OTf)2(phen) rapidly forms an orange-colored precipitate that shows no activity in CH4 activation. CH3OH overoxidation to HCOOH was dominantly catalyzed by potent Au0 species as a result of AuI disproportionation, which is the detrimental catalyst deactivation mechanism. Increasing CH4 pressure and H2O2 concentration successfully enhances the catalyst lifetime and significantly improves the CH4 oxidation efficiency with the improved CH3OH/HCOOH ratio. Density functional theory (DFT) calculations showed that (1) a C-H bond in CH4 was activated by forming AuIII-CH3 with a free energy barrier of 26.7 kcal/mol in a six-membered ring transition state and (2) AuIII-CH3 was functionalized to CH3OH by nucleophilic H2O with a free energy barrier of 29.1 kcal/mol or by MeOTf reductive elimination with a free energy barrier of 21.1 kcal/mol.
- Huang, Tingyu,Xu, Zhanwei,Yan, Peifang,Liu, Xiumei,Fan, Hongjun,Zhang, Z. Conrad
-
p. 370 - 382
(2021/02/27)
-
- Chromium-Catalyzed Production of Diols From Olefins
-
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.
- -
-
Paragraph 0111
(2021/03/19)
-
- Oxidative Conversion of Glucose to Formic Acid as a Renewable Hydrogen Source Using an Abundant Solid Base Catalyst
-
Formic acid is one of the most desirable liquid hydrogen carriers. The selective production of formic acid from monosaccharides in water under mild reaction conditions using solid catalysts was investigated. Calcium oxide, an abundant solid base catalyst available from seashell or limestone by thermal decomposition, was found to be the most active of the simple oxides tested, with formic acid yields of 50 % and 66 % from glucose and xylose, respectively, in 1.4 % H2O2 aqueous solution at 343 K for 30 min. The main reaction pathway is a sequential formation of formic acid from glucose by C?C bond cleavage involving aldehyde groups in the acyclic form. The reaction also involves base-catalyzed aldose-ketose isomerization and retroaldol reaction, resulting in the formation of fructose and trioses including glyceraldehyde and dihydroxyacetone. These intermediates were further decomposed into formic acid or glycolic acid. The catalytic activity remained unchanged for further reuse by a simple post-calcination.
- Takagaki, Atsushi,Obata, Wataru,Ishihara, Tatsumi
-
p. 954 - 959
(2021/07/14)
-
- Supported CuII Single-Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass-Based Platform Molecules in the N-Formylation of Amines
-
The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value-added formamides were synthesized in good yields by the reaction of amines with C2 and C3 biomass-based platform molecules such as glycolic acid, 1,3-dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu-containing zeolite 5A through the in situ formation of carbonyl-containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass-based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single CuII sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin-trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH-like intermediate and .NHPh radicals, in which the selective formation of .OOH radicals might play a key role.
- Brückner, Angelika,Dai, Xingchao,Kreyenschulte, Carsten,Rabeah, Jabor,Shi, Feng,Wang, Xinzhi
-
p. 16889 - 16895
(2021/09/25)
-
- CuAg nanoparticle/carbon aerogel for electrochemical CO2reduction
-
The electrochemical carbon dioxide reduction reaction (eCO2RR) is a promising technology that uses electrical energy to catalytically reduce greenhouse gas-CO2, converting CO2into high value-added products such as hydrocarbons and alcohols. However, due to the complexity of the eCO2RR, the activity and selectivity of the eCO2RR is highly dependent on the intrinsic catalytic activity of a catalyst with mass transportation-favorable morphology. Herein, silk fibroin-derived carbon aerogels (CAs) loaded with small amounts of Cu and Ag nanoparticles were synthesized. Based on the molar content of Cu, the catalysts were labeled SF-CuAg/CA-N(N= 20%, 40%, 60%, 80%). Among them, SF-CuAg/CA-40% showed a good FECOof 71% at ?1.26 Vvs.a reversible hydrogen electrode (RHE), and a significant current density of ?15.77 mA cm?2towards CO at ?1.06 Vvs.RHE, which is close to 2.6, 2.53 and 2.71 times those of SF-CuAg/CA-20% (?6.02 mA cm?2), SF-CuAg/CA-60% (?6.24 mA cm?2) and SF-CuAg/CA-80% (?5.82 mA cm?2). The SF-CuAg/CA-Ncomposite materials prepared in this study provide new ideas for the design of highly efficient electrocatalysts for the eCO2RR.
- Gong, Shanhe,Liu, Bin,Lu, Runqing,Lv, Xiaomeng,Sam, Daniel Kobina,Wang, Wenbo,Xiao, Xinxin
-
p. 18290 - 18295
(2021/10/19)
-
- 5-(Chloromethyl)furfural production from glucose: A pioneer kinetic model development exploring the mechanism
-
Conversion of glucose to 5-(chloromethyl)furfural (CMF) is one of the well-known high yield unit processes in lignocellulosic biomass valorization. A kinetic modeling study was not reported for the reaction, owing to the complexity in quantification of CMF. Herein we have successfully developed a rapid, sensitive, and specific HPLC method (reverse phase) to quantify the generated CMF (range: 10–650?μg/mL) in a dichloroethane solvent. The Box–Behnken design of experiment method employed for the statistical optimization. A kinetic model was developed based on the homogeneous first-order kinetic model, and the results are in good agreement with the experiment data. The formation of CMF, 5-(hydroxymethyl)furfural, formic acid, levulinic acid, and humins from glucose and HCl were modeled using a serial parallel reaction mechanism. The apparent activation energy (Ea) for glucose decomposition and CMF formation is 99 and 31 kJ/mol.
- Antonyraj, Churchil A.,Chennattussery, Amal J.,Haridas, Ajit
-
p. 825 - 833
(2021/03/18)
-
- Facile synthesis of N-doped carbon supported iron species for highly efficient methane conversion with H2O2 at ambient temperature
-
A series of N-doped carbon supported highly-dispersed Fe catalysts are prepared, and their catalytic performances for the direct conversion of methane to CH3OH and HCOOH with by-product CO2 are tested at ambient temperature. The nitrogen doping can greatly improve the metal-support interaction, and anchor the Fe species on the support. The catalytic activity of the catalyst is further enhanced by the modification of hydroxylamine hydrochloride. The optimized 2.5 wt%Fe/NC?HH catalyst shows 475 μmol/gcat for CH3OH and 832 μmol/gcat for HCOOH after 1 h reaction. The effect of the type of nitrogen species on the catalytic performance of the catalyst has been studied in detail. In addition, other transition metals (Ni, Co, Cu and Mn) as active centers have been also studied, and none of them is effective for the conversion of methane. Additionally, it is found that the methane conversion over the prepared catalysts proceed via a radical mechanism.
- Zhang, Li,Lin, Yan
-
-
- Lanthanum modified Fe-ZSM-5 zeolites for selective methane oxidation with H2O2
-
Selective partial oxidation of methane to methanol under ambient conditions is a great challenge in chemistry. Iron modified ZSM-5 catalysts are shown to be effective for this reaction using H2O2as the oxidant. However, the high consumption of H2O2over this catalyst presents a major disadvantage. Here we report a lanthanum modified Fe-ZSM-5 (LaFe-ZSM-5) catalyst for enhanced selective methane oxidation with suppressed H2O2consumption. Using 0.5 wt% LaFe-ZSM-5 pretreated with H2the productivity of primary oxygenated products (CH3OH, CH3OOH, HCOOH) is 3200 mol kgLaFe?1h?1in 0.1 M H2O2, with a selectivity of 98.9% to primary oxygenated products. The productivity is increased to 11?460 mol kgLaFe?1h?1in 0.5 M H2O2. Compared with Fe-ZSM-5, LaFe-ZSM-5 uses 31% less H2O2for obtaining per mol of product under the same conditions.In situDRIFT spectroscopy and solid state MAS NMR revealed the high H2O2consumption in ZSM-5 based catalyst maybe closely related to the acidity of strong Br?nsted acid sites (Si(OH)Al). The La modified ZSM-5 catalyst can decrease the acidity of the strong Br?nsted acid sites and this suppresses the decomposition of H2O2
- Barnes, Alexandra J.,Bere, Takudzwa,Dummer, Nicholas F.,Gong, Xiaoxiao,Hutchings, Graham J.,Lewis, Richard J.,Morgan, David J.,Richards, Nia,Shaw, Greg,Sun, Songmei
-
p. 8052 - 8064
(2021/12/27)
-
- PREPARATION OF HMF CATALYZED BY A MIXTURE OF SALT AND ACID
-
The present invention relates to a method for the production of 5-hydroxymethylfurfural (HMF), which converts a fructose-containing component using a catalyst system comprising a solution of a salt and acid mixture at a temperature of 90 to 200° C. and leads to obtaining an HMF-containing product mixture, wherein advantageously a high HMF selectivity with significantly lower by-product formation is achieved at the same time.
- -
-
Paragraph 0174-0194
(2021/07/17)
-
- Photoelectrochemical reduction of dissolved carbon dioxide over Ni(OH)2 into organic oxygenates
-
Abstract: The hydrothermal method has been used to prepare Ni(OH)2 photocathode. The photoelectrochemical (PEC) reduction of CO2 over Ni(OH)2 has been conducted in 0.2?M LiClO4 in aqueous and N,N-dimethylformamide (DMF) medium under visible light irradiation. The thin film was characterized by XRD, UV–Vis, FTIR, FESEM-EDX, BET analysis, and electrochemical method for the determination of phases, bandgap energy, chemical bonding, surface morphology, elemental compositions, surface area, and electrochemical properties, respectively. Based on UV–Vis spectroscopy, the bandgap energy of Ni(OH)2 was 1.8?eV which enabled efficient visible light absorption for the photoreaction. The photocurrent density in aqueous and DMF solution at 0.2?V (vs. Ag/AgCl) was 24?mA?cm?2 and 5?mA?cm?2, respectively. Acetaldehyde and methanol are the products in aqueous solution, while formic acid and methanol are the products in DMF, after 6?h of photoelectrolysis. The product formations from the photoelectrochemical reduction of dissolved CO2 were 612 and 854?ppm in aqueous and DMF, respectively, where the Faradaic efficiency in aqueous and DMF is 24 and 33%, respectively. Furthermore, throughout the PEC study, the transformation of Ni(OH)2 to NiO plays a significant role in the formation of organic oxygenates from the reduction reaction of CO2. Graphic abstract: [Figure not available: see fulltext.]
- Che Mat, Ahmad Nazeer,Basirun, Wan Jefrey,Shahid, Muhammad Mehmood
-
p. 1363 - 1372
(2021/01/07)
-
- Catalytic Hydrogenation of CO2to Methanol Using Multinuclear Iridium Complexes in a Gas-Solid Phase Reaction
-
We report a novel approach toward the catalytic hydrogenation of CO2 to methanol performed in the gas-solid phase using multinuclear iridium complexes at low temperature (30-80 °C). Although homogeneous CO2 hydrogenation in water catalyzed by amide-based iridium catalysts provided only a negligible amount of methanol, the combination of a multinuclear catalyst and gas-solid phase reaction conditions led to the effective production of methanol from CO2. The catalytic activities of the multinuclear catalyst were dependent on the relative configuration of each active species. Conveniently, methanol obtained from the gas phase could be easily isolated from the catalyst without contamination with CO, CH4, or formic acid (FA). The catalyst can be recycled in a batchwise manner via gas release and filling. A final turnover number of 113 was obtained upon reusing the catalyst at 60 °C and 4 MPa of H2/CO2 (3:1). The high reactivity of this system has been attributed to hydride complex formation upon exposure to H2 gas, suppression of the liberation of FA under gas-solid phase reaction conditions, and intramolecular multiple hydride transfer to CO2 by the multinuclear catalyst.
- Kanega, Ryoichi,Onishi, Naoya,Tanaka, Shinji,Kishimoto, Haruo,Himeda, Yuichiro
-
supporting information
p. 1570 - 1576
(2021/02/01)
-
- Highly Efficient CO2 Electroreduction to Methanol through Atomically Dispersed Sn Coupled with Defective CuO Catalysts
-
Using renewable electricity to drive CO2 electroreduction is an attractive way to achieve carbon-neutral energy cycle and produce value-added chemicals and fuels. As an important platform molecule and clean fuel, methanol requires 6-electron transfer in the process of CO2 reduction. Currently, CO2 electroreduction to methanol suffers from poor efficiency and low selectivity. Herein, we report the first work to design atomically dispersed Sn site anchored on defective CuO catalysts for CO2 electroreduction to methanol. It exhibits high methanol Faradaic efficiency (FE) of 88.6 % with a current density of 67.0 mA cm?2 and remarkable stability in a H-cell, which is the highest FE(methanol) with such high current density compared with the results reported to date. The atomic Sn site, adjacent oxygen vacancy and CuO support cooperate very well, leading to higher double-layer capacitance, larger CO2 adsorption capacity and lower interfacial charge transfer resistance. Operando experiments and density functional theory calculations demonstrate that the catalyst is beneficial for CO2 activation via decreasing the energy barrier of *COOH dissociation to form *CO. The obtained key intermediate *CO is then bound to the Cu species for further reduction, leading to high selectivity toward methanol.
- Chen, Chunjun,Guo, Weiwei,Han, Buxing,Huang, Yuying,Liu, Shoujie,Ma, Jingyuan,Sun, Xiaofu,Tan, Xingxing,Wu, Ruizhi,Yan, Xupeng,Zhang, Jing,Zheng, Lirong,Zhu, Qinggong
-
supporting information
p. 21979 - 21987
(2021/08/30)
-
- PROCESS FOR PRODUCTION OF FORMIC ACID AND ACETIC ACID BY ABSORBING CO2 VIA PHOTOCATALYTIC REDUCTION, IMPROVED CATALYST AND APPARATUS
-
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.
- -
-
Paragraph 0078-0079
(2021/05/29)
-
- Selective oxidation of methane to methanol using AuPd@ZIF-8
-
Selective methane conversion to alcohol derivatives remains an open challenge. Here, bimetallic catalyst, AuPd@ZIF-8, has been synthesized and demonstrated as an excellent catalyst in the presence of H2O2 and O2 under mild
- Sun, Chenghua,Xu, Guowang,Xu, Yongjun,Yu, Aimin
-
-
- Ternary ZnO/CuO/Zeolite composite obtained from volcanic ash for photocatalytic CO2 reduction and H2O decomposition
-
An n-p heterojunction based on ZnO/CuO supported in a zeolitic framework (ZF) was designed to produce solar fuels from H2O decomposition and CO2 conversion. ZF was synthesized from volcanic ashes by an alternative microwave-hydrothermal method using a biodegradable template for its formation. The framework resulted in NaAlSiO4 (NAS) with a high surface area and a morphology composed of circular channels of 50 nm. Incorporating the ZnO/CuO heterostructure in the NAS channels resulted in an improved light-absorption, more efficient charge transfer, nanostructure morphology, and more active sites available for the CO2 adsorption and photocatalytic reactions. The activities for H2 and light-hydrocarbons (HCOOH, HCOH, and CH3OH) evolution were evaluated in the photocatalytic water-splitting and CO2 reduction under UVA irradiation, respectively. The ZnO/CuO/NAS composite exhibited a remarkably higher H2 (187 μmol/g) and HCOOH (2721 μmol/g) evolution after 3 h of irradiation. These results were related to the synergistic effect among ZnO, CuO, and NAS framework. A mechanism of the photocatalytic reaction was proposed.
- Luévano-Hipólito,Torres-Martínez, Leticia M.,Fernández-Trujillo
-
-
- The selective oxidation of glycerol over metal-free photocatalysts: insights into the solvent effect on catalytic efficiency and product distribution
-
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
-
p. 3385 - 3392
(2021/06/06)
-
- Earth-abundant manganese oxide nanoneedle as highly efficient electrocatalyst for selective glycerol electro-oxidation to dihydroxyacetone
-
In this study, earth-abundant manganese oxide (MnO2) was used as a catalyst for the electrocatalytic glycerol oxidation with a satisfactory yield and high selectivity under mild pH media; that is, the high current density of 6.0 mA cm?2 and selectivity of ca. 46% for dihydroxyacetone (DHA). MnO2 also exhibited reasonable durability without considerable changes for 3 h. More importantly, by combination of operando Raman and electrochemical studies, a tentative reaction pathway was also proposed. It is found that high selectivity of formic acid at low potential was due to predominant coverage of α-MnO2 on catalyst surface. Meanwhile, at high applied potential, partial transformation of α-MnO2 to δ-MnO2 causes decreasing C-C bond cleavage, leading to high DHA selectivity. The results of this work not only demonstrate that MnO2 holds promise as an efficient electrocatalyst for selectively producing DHA but also provides realistic details on electrochemically generated species under working condition.
- Chiang, Chia-Ying,Tran, Giang-Son,Vo, Truong-Giang
-
p. 139 - 148
(2021/10/07)
-
- In Situ Phase Separation into Coupled Interfaces for Promoting CO2 Electroreduction to Formate over a Wide Potential Window
-
Bimetallic sulfides are expected to realize efficient CO2 electroreduction into formate over a wide potential window, however, they will undergo in situ structural evolution under the reaction conditions. Therefore, clarifying the structural evolution process, the real active site and the catalytic mechanism is significant. Here, taking Cu2SnS3 as an example, we unveiled that Cu2SnS3 occurred self-adapted phase separation toward forming the stable SnO2@CuS and SnO2@Cu2O heterojunction during the electrochemical process. Calculations illustrated that the strongly coupled interfaces as real active sites driven the electron self-flow from Sn4+ to Cu+, thereby promoting the delocalized Sn sites to combine HCOO* with H*. Cu2SnS3 nanosheets achieve over 83.4 % formate selectivity in a wide potential range from ?0.6 V to ?1.1 V. Our findings provide insight into the structural evolution process and performance-enhanced origin of ternary sulfides under the CO2 electroreduction.
- Duan, Junyuan,Li, Huiqiao,Liu, Youwen,Nie, Anmin,Wang, Wenbin,Wang, Zhitong,Xia, Bao Yu,Yang, Ruoou,Zhai, Tianyou
-
supporting information
p. 22940 - 22947
(2021/09/14)
-
- Transformation of biomass derivatives in aqueous medium: Oxidation of ethanol from sugarcane and acetol from biodiesel glycerol catalyzed by Fe3+- H2O2
-
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
-
-
- The site pair matching of a tandem Au/CuO-CuO nanocatalyst for promoting the selective electrolysis of CO2to C2products
-
Tandem catalysis, in which a CO2-to-C2 process is divided into a CO2-to-CO/?CO step and a CO/?CO-to-C2 step, is promising for enhancing the C2 product selectivity when using Cu-based electrochemical CO2 reduction catalysts. In this work, a nanoporous hollow Au/CuO-CuO tandem catalyst was used for catalyzing the eCO2RR, which exhibited a C2 product FE of 52.8% at -1.0 V vs. RHE and a C2 product partial current density of 78.77 mA cm-2 at -1.5 V vs. RHE. In addition, the C2 product FE stably remained at over 40% over a wide potential range, from -1.0 V to -1.5 V. This superior performance was attributed to good matching in terms of the optimal working potential and charge-transfer resistance between CO/?CO-production sites (Au/CuO) and CO/?CO-reduction sites (CuO). This site pair matching effect ensured sufficient supplies of CO/?CO and electrons at CuO sites at the working potentials, thus dramatically enhancing the formation rate of C2 products. This journal is
- Sun, Xiao-Chen,Yin, Hai-Jing,Yuan, Chen-Yue,Yuan, Kun,Zhang, Ya-Wen,Zheng, Ya-Li,Zhou, Jun-Hao
-
p. 38486 - 38494
(2021/12/20)
-
- Method for synergistically preparing formic acid and glycollic acid by catalyzing 1, 3-dihydroxyacetone with bimetallic catalyst
-
The invention discloses a method for synergistically preparing formic acid and glycollic acid by catalyzing 1, 3-dihydroxyacetone with a bimetallic catalyst, and belongs to the technical field of chemical synthesis and biomass heterogeneous catalytic conversion. The preparation method comprises the following specific steps: putting a bimetallic catalyst, 1, 3-dihydroxyacetone and a solvent into a reaction container, finally adding an oxidant, sealing the reaction container, and starting a reaction to prepare formic acid and glycollic acid compounds, wherein the initial concentration of 1, 3-dihydroxyacetone is not lower than 0.1 mol/L, the initial reaction pH is 0.5-9, the reaction temperature is 20-100 DEG C, and the reaction time is 1-72 hours. According to the invention, the efficient synergistic production of formic acid and glycollic acid can be realized, wherein the yield of formic acid is 91.06%, the yield of glycollic acid is 82.46%, the utilization rate of carbon atoms is 85.33%, and the carbon atom utilization rate is extremely high; and the method has the advantages of mild reaction conditions, no alkali, cheap catalyst, simple preparation and wide application prospect.
- -
-
Paragraph 0043-0053
(2021/05/29)
-