- Site-Selective Growth of AgPd Nanodendrite-Modified Au Nanoprisms: High Electrocatalytic Performance for CO2 Reduction
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Environmental impacts of continued CO2 production have led to an increased need for new methods of CO2 removal and energy development. Nanomaterials are of special interest for these applications, because of their unique chemical and physical properties that allow for highly active surfaces. Here, we successfully synthesize AgPd nanodendrite-modified Au nanoprisms in various shapes (nanoprisms, hexagonal nanoplates, and octahedral nanoparticles) by selective metal deposition. This strategy involves coupling galvanic replacement between Ag layers in Au@Ag core-shell nanoprisms and H2PdCl4 with a coreduction process of silver and palladium ions. Synthesis of AgPd nanodendrite-tipped (4.14-11.47 wt % Pd) and -edged (25.25-31.01 wt % Pd) Au nanoparticles can be controlled simply by tuning the concentration of H2PdCl4. More importantly, these multicomponent AgPd nanodendrite-modified Au nanoparticles show exceptional electrocatalytic performance for CO2 reduction. AgPd nanodendrite-edged Au nanoprisms show more favorable potentials (-0.18 V vs RHE) than previously reported nanocatalysts for the reduction of CO2 to formate, and exhibit higher faradaic efficiencies (49%) than Au, Au@Ag, and AgPd nanodendrite-tipped Au nanoprisms in aqueous electrolytes. Moreover, AgPd nanodendrite-modified Au nanoprisms show much higher selectivity and faradaic efficiency for CO2 reduction to CO (85-87%) than Au and Au@Ag nanoprisms (43-64%) in organic electrolytes. The high performance of these particles for CO2 reduction is attributed to the unique structure of AgPd nanodendrite-modified Au nanoprisms and the synergistic effect of Ag having an affinity for CO2, efficient binding of hydrogen at Pd, and Au as a stable, conductive support. In addition, AgPd nanodendrite-edged Au nanoprisms show highly stable catalytic activity during long-term electrolyses (up to 12 h) and repetitive use. These exciting results indicate that AgPd nanodendrite-modified Au nanoparticles are promising for application in CO2 conversion into useful fuels.
- Shan, Changsheng,Martin, Erin T.,Peters, Dennis G.,Zaleski, Jeffrey M.
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- The ozonization of model lignin compounds in aqueous solutions catalyzed by Mn(II) ions
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The influence of Mn(II) ions on the rate of the reaction between ozone and model lignin compounds, guaiacol and veratrole, was studied. The catalyst did not influence the rate of the destruction of the aromatic ring and intermediate ozonolysis products, compounds with conjugated double bonds, in acid media but substantially increased the rate of oxidation of saturated carboxylic acids, ketoacids, and aldehydes. Ozone consumption then increased from 2 to 5 moles per mole of the transformed substrate. A mechanism of the catalytic action of Mn(II) in reactions between ozone and the compounds studied was suggested.
- Mitrofanova,Khudoshin,Lunin
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- Electrochemical reduction of CO2 in a mixed supercritical fluid
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The electroreduction of CO2 in the liquid and supercritical states was studied on both Pt and Pb electrode surfaces using a mixture of 1,1,1,2-tetrafluoroethane (HFC 134a) and CO2 solvent. A decrease in the reduction potential on both electrode materials was observed in the supercritical state compared with the liquid state. Platinum was far better than lead as a cathode material on which to reduce CO2 in supercritical CO2/HFC 134a mixture by both voltametric and bulk electrolysis experiments. The use of the supercritical mixture, rather than an aprotic liquid as electrochemical solvent, significantly improved the faradaic efficiency of oxalate formation at a Pt electrode, which can be due to the high CO2 concentration at the electrode surface in the mixture.
- Abbott, Andrew P.,Eardley, Christopher A.
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- Studies on the oxygen atom transfer reactions of peroxomonosulfate: Oxidation of glycolic acid
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The kinetics of oxidation of glycolic acid, an α-hydroxy acid, by peroxomonosulfate (PMS) was studied in the presence of Ni(II) and Cu(II) ions and in acidic pH range 4.05-5.89. The metal glycolate, not the glycolic acid (GLYCA), is oxidized by PMS. The rate is first order in [PMS] and metal ion concentrations. The oxidation of nickel glycolate is zero-order in [GLYCA] and inverse first order in [H+]. The increase of [GLYCA] decreases the rate in copper glycolate, and the rate constants initially increase and then remain constant with pH. The results suggest that the metal glycolate ML + reacts with PMS through a metal-peroxide intermediate, which transforms slowly into a hydroperoxide intermediate by the oxygen atom transfer to hydroxyl group of the chelated GLYCA. The effect of hydrogen ion concentrations on kobs suggests that the structure of the metal-peroxide intermediates may be different in Ni(II) and Cu(II) glycolates.
- Shailaja,Ramachandran
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- Kinetics and mechanism of the degradation and mineralization of acetone in dilute aqueous solution sensitized by the UV photolysis of hydrogen peroxide
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Acetone is a significant pollutant in contaminated groundwaters and industrial effluents. It can be treated by the UV/H2O2 process but only slowly. This study aims to understand the degradation mechanism and hence the reasons for slow treatment. The degradation of acetone was carried out in a UV reactor in the presence of ~16 mM H2O2 such that most of the UV was absorbed by H2O2. The decay of acetone was followed by gas chromatography, and the generation of intermediates (identified as acetic, formic, and oxalic acids) was followed by ion chromatography. Measurement of the total organic carbon indicated a complete carbon balance throughout the reaction ending in mineralization. A kinetic model, based on an assumed mechanism, was developed that generated a profile of reactants and intermediates in agreement with the experimental data, including the pH profile. The initial concentrations of acetone and hydrogen peroxide strongly affect the initial rate of acetone degradation, but no pH effect was observed in the range of 2-7. It is concluded that acetone treats slowly because intermediates build up to such a concentration that they compete significantly for hydroxyl radicals and also because the mechanism appears to involve some degree of acetone recycling.
- Stefan, Mihaela I.,Hoy, Aitken R.,Bolton, James R.
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- Au-Pd/C catalysts for glyoxal and glucose selective oxidations
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A series of Au-Pd/C catalysts were prepared on an activated carbon named SX PLUS (SX+) by fixing the pH of impregnation in aqueous phase at an optimal value for maximizing the interactions between metals and surface. This bimetallic association leads to highly active catalysts in the oxidation of glyoxal into glyoxalic acid and of glucose into gluconic acid, with the activity correlated to high surface Pd/C ratios measured by XPS and the presence of small metallic Pd particles, even if gold was present as big crystallites. A cooperative effect between the two metals was evidenced on the yield in carboxylic acids in both reactions, which is believed to arise from an interface between the two metals even if they are mostly present as separated phases. The incorporation of Au on Pd rather than the opposite and the concomitant activation of both metals influence positively the catalytic performance. The use of NaBH4 as activating agent allowed the most active Au-Pd/C catalyst to be obtained, with similar performances to the best bimetallic Bi-Pd/C catalyst so far but without any metal leaching.
- Hermans, Sophie,Deffernez, Aurore,Devillers, Michel
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- Monitoring of β-blockers ozone degradation via electrospray ionization mass spectrometry
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The structures of intermediate products of ozone degradation of different pharmaceutical compounds have been studied. Under the conditions employed, complete ozone degradation of nadolol was achieved after 100 min. The degradation products obtained in aqueous solution were characterized by electrospray ionization mass (and tandem mass) spectrometry (ESI-MS and ESI-MS/MS). The proposed mechanism for degradation, ozone attacks at the aniline amino group giving rise to nitro compounds and further degradation occurs via a series of oxidative processes. Continuous online monitoring by ESI-MS(/MS) with high accuracy mass measurements showed that ozone degradation of atenolol (ATE) and acebutolol (ACE) occurs via mechanisms similar to that of nadolol.
- Quispe, Cristina,Nachtigall, Fabiane M.,Fonseca, Maria Francesca R.,Alberici, Rosana M.,Astudillo, Luis,Villasen?or, Jorge,Eberlin, Marcos N.,Santos, Leonardo S.
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- Improving the efficiency of Fenton reactions and their application in the degradation of benzimidazole in wastewater
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Reducing the quantity of sludge produced in Fenton reactions can be partly achieved by improving their efficiency. This paper firstly studies the effect of uniform deceleration feeding (ferrous iron and hydrogen peroxide) on the efficiency of a Fenton reaction by measuring the yield of hydroxyl radicals (OH) and chemical oxygen demand (COD) removal rate. The dynamic behavior of OH was also investigated. The results indicated that uniform deceleration feeding was the best feeding method compared with one-time feeding and uniform feeding methods when the same amount of Fenton reagents and the same reaction times were used. Besides, it was found the COD removal rate reached 79.3% when this method was applied to degrade 2-(a-hydroxyethyl)benzimidazole (HEBZ); this COD removal rate is larger than those when the other two modes were used (they reached 60.7% and 72.1%, respectively). The degradation pathway of HEBZ was determined using PL, UV-vis, FTIR, HPLC and GC-MS. Ultimately, HEBZ was decomposed into three small molecules (2-hydroxypropylamine, oxalic acid, and 2-hydroxypropamide). This research is of great significance for the application of Fenton reactions in wastewater treatment.
- Liu, Qinyao,Qian, Kun,Qi, Jinxu,Li, Chenru,Yao, Chen,Song, Wei,Wang, Yihong
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- Atomically mixed Fe-group nanoalloys: Catalyst design for the selective electrooxidation of ethylene glycol to oxalic acid
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We demonstrate electric power generation via the electrooxidation of ethylene glycol (EG) on a series of Fe-group nanoalloy (NA) catalysts in alkaline media. A series of Fe-group binary NA catalysts supported on carbon (FeCo/C, FeNi/C, and CoNi/C) and monometallic analogues (Fe/C, Co/C, and Ni/C) were synthesized. Catalytic activities and product distributions on the prepared Fe-group NA catalysts in the EG electrooxidation were investigated by cyclic voltammetry and chronoamperometry, and compared with those of the previously reported FeCoNi/C, which clarified the contributory factors of the metal components for the EG electrooxidation activity, C2 product selectivity, and catalyst durability. The Co-containing catalysts, such as Co/C, FeCo/C, and FeCoNi/C, exhibit relatively high catalytic activities for EG electrooxidation, whereas the catalytic performances of Ni-containing catalysts are relatively low. However, we found that the inclusion of Ni is a requisite for the prevention of rapid degradation due to surface modification of the catalyst. Notably, FeCoNi/C shows the highest selectivity for oxalic acid production without CO2 generation at 0.4 V vs. the reversible hydrogen electrode (RHE), resulting from the synergetic contribution of all of the component elements. Finally, we performed power generation using the direct EG alkaline fuel cell in the presence of the Fe-group catalysts. The power density obtained on each catalyst directly reflected the catalytic performances elucidated in the electrochemical experiments for the corresponding catalyst. The catalytic roles and alloying effects disclosed herein provide information on the design of highly efficient electrocatalysts containing Fe-group metals. This journal is
- Matsumoto, Takeshi,Sadakiyo, Masaaki,Ooi, Mei Lee,Yamamoto, Tomokazu,Matsumura, Syo,Kato, Kenichi,Takeguchi, Tatsuya,Ozawa, Nobuki,Kubo, Momoji,Yamauchi, Miho
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- Biocatalytic Production of Glyoxylic Acid
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The production of glyoxylic acid from glycolic (hydroxyacetic) acid has been demonstrated using the soluble enzymes glycolate oxidase and catalase as catalysts.Catalase was included as cocatalyst to decompose byproduct hydrogen peroxide, thus limiting peroxide-dependent formate production and glycolate oxidase deactivation.The addition to reaction mixtures of a primary amine capable of forming the hemiaminal or imine of glyoxylate resulted in an increase in the yield of glyoxylate; hemiaminal/imine mixtures of glyoxylate were not as readily oxidized to formate and carbon dioxide by hydrogen peroxide and also limited product inhibition of glycolate oxidase at high glyoxylate concentrations.A synergistic effect was observed when using Tris or ethylenediamine (EDA) with catalase, where increases in selectivity to glyoxylate were much greater than the sum of selectivities to glyoxylate obtained when using amine or catalase alone.The inclusion of EDA in reactions produced selectivities to glyoxylic acid in excess of 98-99percent at greater than 99percent conversion of 0.25M to 1.5M glycolic acid.The technical feasibility of a biocatalytic process for the production of glyoxylic acid was demonstrated by the preparation of ca. 0.50 kg of the acid in a series of 2.0-L batch reactions.
- Seip, John E.,Fager, Susan K.,Gavagan, John E.,Gosser, Lawrence W.,Anton, David L.,DiCosimo, Robert
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- Ozonation of azo dye Acid Black 1 under the suppression effect by chloride ion
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The aim of this study is to determine the kinetics of the Acid Black 1 dye by oxidizing action of ozone and to evaluate the influence of chloride ion contamination on the dye degradation. Pseudo-first order kinetics was observed for both decolorization (620 nm) and aromatic structure (321 nm) degradations. A complete color removal was verified in 25 min ([dye]0 = 1.8 × 10 -5 mol L-1), while aromatic structures degraded at slower rates. The presence of chloride ion, the principal impurity of the solid dye reagents, influences significantly the ozonation rate (-42percent), even at low chloride concentration (5.6 × 10-4 mol L-1). The most probable mechanism for the chloride suppression effect involves a direct reaction between O3 and Cl- generating HOCl, among other by-products. In despite of that, ozonation could be a competitive degradation process for this dye.
- Paprocki, Alexandre,Dos Santos, Heldiane S.,Hammerschitt, Marta E.,Pires, Marc?al,Azevedo, Carla M. N.
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- Real-Time FTIR Spectroscopy as a Quantitative Kinetic Probe of Competing Electrooxidation Pathways for Small Organic Molecules
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The application of real-time FTIR spectroscopy to probe quantitative kinetics and mechanisms of competing electrochemical patways on a voltammetric time scale is illustrated for the electrooxidation of ethanol, ethylene glycol, and glycolaldehyde in 0.1 M HClO4 at platinum.A simple procedure is outlined whereby the required ratio of molar absorptivities in the thin-layer cavity and bulk solution εeff/εb, can be evaluated.This approach enables the proportion of CO2 and partial oxidation products formed during voltammetric sweeps to be determined reliably and the role of adsorbed CO and other chemisorbed fragments in the electrocatalytic mechanisms to be evaluated.
- Leung, Lam-Wing H.,Weaver, Michael J.
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- THE STRUCTURE OF THEOBROMURIC ACID
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The structure of theobromuric acid was revised and the correct 8a-hydroxy-1,2,3,4,6,7,8,8a-octahydro-1,7-dimethyl-2,4,6,8-tetraoxoimidazo -1,3,5-triazine (5a) formula was assigned on the basis of chemical and spectroscopic evidence.
- Poje, M.,Palkovic, A.
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- Oxidation of coals in liquid phases. X. Mechanism of the cleavage of benzenecarboxylic acids to oxalic acid and carbon dioxide by the base-catalyzed oxygen-oxidation
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A kinetic study of the oxidation of benzenecarboxylic acids has been performed in order to clarify the mechanism. The reaction products were oxalic acid and carbon dioxide, along with a trace of acetic acid. The oxidation rate of phthalic acid was proportional to the first order of the molality of phthalic acid, the molality of NaOH, and partial oxygen pressure, respectively; the apparent activation energy was 126 kJ mol-1. These results show that the rate-determining step is a cleavage of the benzene ring proceeded by a base-catalyzed oxygen-oxidation mechanism in which a carbanion formed by hydrogen extraction from an aromatic ring is attacked by oxygen. In the cleavage of phthalic acid, NaOH increases the selectivity to form oxalic acid as well as the oxidation rate. In the oxidation of 1,2,3-benzentricarboxylic acid the same mechanism was recognized, but not for benzenehexacarboxylic acid which has no hydrogen on the benzene ring.
- Ichinose,Okuwaki
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- OZONIZATION OF ORGANIC COMPOUNDS - 5. AROMATIC COMPOUNDS.
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The ozonization of several aromatic compounds has been carried out at 30 degree C in carbon tetrachloride. It is found that three processes proceeded simultaneously; that is, normal and anomalous ozonolyses to give respectively alpha , beta -dicarbonyl and carboxylic compounds and polymerization. Carboxylic acids were the major products. Benzene and hexamethylbenzene gave formic acid and acetic acid respectively, while toluene and 1,3,5-trimethylbenzene gave mixtures of these acids. As the ozonization proceeded, white gummy polymers precipitated, the molecular weight ranged from several hundreds to a few thousands. They contained high concentrations of oxygen which was incorporated into polymer as carbonyl, carboxylic acid, peroxide and/or ether. The polymers were thermally stable below 150 degree C.
- Saito,Niki,Kamiya
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- Degradation of atrazine by Fenton and modified Fenton reactions
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For 50 years, farmers around the world have relied on the herbicide atrazine-one of the triazine family of herbicides-to fight weeds in corn, grain sorghum, sugar cane, and other crops. Although prohibited in the European Union because of widespread contamination of waterways and drinking water supplies, it is still one of the most widely used herbicides in the world. Atrazine and some of its degradation products are among the most commonly found xenobiotics in groundwater and soils in the world. It is also an endocrine disruptor that causes abnormal reproductive development and immune suppression in wildlife. The purpose of this study was to identify the degradation products of atrazine. Fenton reaction treatment, a hydroxyl radical oxidation process recently developed for the degradation of aqueous pesticide waste, was applied to the degradation of atrazine. Classical and modified Fenton reactions have been used as Advanced Oxidation Process treatment methods. A HPLC method was developed and optimized for the identification of resulting degradation products. In general, very good atrazine degradation efficiencies were achieved by both of the methods used. The degradation products, such as oxalic acid, urea, formic acid, acetic acid, and acetone, were identified by HPLC with a photodiode array detector.
- MacKul'Ak, Tomas,Prousek, Josef,Svorc, L'Ubomir
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- Oxidation of glyoxal initiated by ?OH in oxygenated aqueous solution
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The kinetics and mechanism of the oxidation of glyoxal, which is a constituent of cloud water, initiated by ?OH in oxygenated solution have been investigated using pulse radiolysis with optical and conductivity detection of the transient species, and steady-state radiolysis with spectrophotometric and ion chromatographic analysis of the permanent products. The data obtained are consistent with glyoxal being present in the form of the dihydrate [CH(OH)2]2 which is oxidised to glyoxylic acid (pK2 = 3.4) and hydrogen peroxide via a peroxyl radical ?O2C(OH)2CH(OH)2 that splits off HO2? in a non-rate determining step. The following rate constants have been determined: k{?OH + [CH(OH)2]2} = (1.10 + 0.04) × 109 dm3 mol-1 s-1 and k[?C(OH)2CH(OH)2 + O2] = (1.38 ± 0.11) × 109 dm3 mol-1 s-1. It is concluded that oxidation of glyoxal by ?OH in cloud water can proceed by a chain reaction involving H2O2.
- Buxton, George V.,Malone, Treena N.,Salmon, G. Arthur
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- Base-free selective oxidation of glycerol with 3% H2O 2 catalyzed by sulphonato-salen-chromium(III) intercalated LDH
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A MgAl layered-double hydroxides (LDH) intercalated by sulphonato-salen- chromium(III) complex was used to the selective oxidation of glycerol (GLY) using 3% H2O2 as oxidant. The results revealed that the LDH hosted chromium complex was effective heterogeneous catalyst. And the main product was the C3 oxygenated products of secondary alcohol-dihydroxyacetone (DHA). Under the optimal reaction conditions, the highest conversion of GLY reached 73.1% with 43.5% of the selectivity to DHA. Moreover, the catalytic performance remained after being recycled 6 times. In addition, the reaction probably involved an enzyme mimetic mechanism.
- Wang, Xiaoli,Wu, Gongde,Wang, Fang,Ding, Keqiang,Zhang, Fang,Liu, Xianfeng,Xue, Yunbo
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- Engaging thieno[2,3-b]indole-2,3-dione for the efficient synthesis of spiro[indoline-3,4′-thiopyrano[2,3-b]indole] by reaction with N-substituted isatilidenes
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A simple and efficient method, proceeding through a new mechanistic pathway, for the synthesis of spiro[indoline-3,4-thiopyrano[2.3-b]indole derivatives have been developed by exploiting the reaction of thieno[2,3-b]indole-2,3-dione with N-substituted isatilidenes. The compounds synthesized have been screened for antibacterial activity. The generality of the reaction and mechanistic rationale are presented.
- Thomas, Noble V.,Sathi, Vidya,Deepthi, Ani,Sudheendran Leena, Sruthi,Chopra, Sidharth
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- Catalytic ozonation of 4-chlorophenol and 4-phenolsulfonic acid by CeO2 films
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Ceria films (CeO2(f)) were deposited on glass substrate by a spray pyrolysis method. The catalytic oxidation performance of CeO2(f) was evaluated in the removal of 4-chlorophenol (4-CPh) and 4-phenolsulfonic acid (4-SPh). The catalytic oxidation reactions were carried out in water with ozone as an oxidant agent. Conventional and catalytic ozonation achieved complete removal of both compounds. Furthermore, TOC results showed higher catalytic activity with six CeO2(f) films in comparison with conventional ozonation after 120 min for the oxidation of both 4-CPh and 4-SPh. After five consecutive reuses of CeO2(f), the similar TOC removal for 4-CPh demonstrated the ceria films stability.
- Guzmán, Iveete C.,Rodríguez, Julia L.,Poznyak,Chairez, Isaac,Hernández, Isaías,Hernández, Roberto T.
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- Identification of 3,4-dihydroxy-2-oxo-butanal (L-threosone) as an intermediate compound in oxidative degradation of dehydro-L-ascorbic acid and 2,3-diketo-L-gulonic acid in a deuterium oxide phosphate buffer.
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Dehydro-L-ascorbic acid (DAA), an oxidation product of L-ascorbic acid (vitamin C), is unstable in the neutral and basic pH regions. When DAA was incubated in a phosphate buffer with deuterium oxide (pH 7.4), it was degraded to form the main degradation compound, which was identified as 3,4-dihydroxy-2-oxobutanal (L-threosone). This compound was also formed from diketo-L-gulonic acid (DKG) in a phosphate buffer with deuterium oxide. L-threosone had reducing activity, probably due to its enolization, and is likely to have been involved in the formation of the reducing activity that was observed in aqueous DAA and DKG solutions. As a reactive dicarbonyl compound, L-threosone might also take some role in the cross-linking of tissue proteins that are formed in vivo in the Maillard reaction.
- Nishikawa,Toyoshima,Kurata
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- VOLUBOLIN, A 4-PHENYL-2H-1-BENZOPYRAN-2ONE FROM DALBERGIA VOLUBILIS
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From the ether soluble portion of a methanolic extract of young non-green branches of Dalbergia volubilis, sitosterol, 7-hydroxy-4-methyl-2H-1-benzopyran-2-one, dalbergin, p-hydroxy cinnamic acid, biochanin-A and a new 4-phenylcoumarin, volubolin, have been isolated.The structure of volubolin as 7-hydroxy-4-(3-hydroxy-4-methoxy-phenyl)-2H-1-benzopyran-2-one has been established on the basis of spectral and chemical evidence.Cooccurrence of 4-methyl- and 4-phenyl-coumarins with isoflavones is of biogenetic interest. - Key Word Index: Dalbergia volubilis; Leguminosae; young branches; 7-hydroxy-4-methyl coumarin; dalbergin; biochanin-A; 7-hydroxy-4-(3-hydroxy-4-methoxyphenyl)-2H-1-benzopyran-2-one.
- Chawla, H. Mohindra,Mittal, Ram S.
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- Degradation and toxicity changes in aqueous solutions of chloroacetic acids by Fenton-like treatment using zero-valent iron
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Three priority pollutants, i.e. mono-, di-, and trichloroacetic acids, were degraded by the conventional Fenton AOP system (Fe2+ and H 2O2). The results obtained suggest that the degradation decreased in the order: monochl
- Macku'Ak, Tomas,Prousek, Josef,Smolinska, Miroslava,Olejnikova, Petra,Takacova, Alzbeta,Drtil, Miloslav
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- Molybdenum oxoanions as dispersing agents in the preparation of Pd/C catalysts for the selective oxidation of glyoxal
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Catalysts Pd/C were prepared in the presence of Mo oxoanions. The size of Mo precursor and the electrostatic interactions with the Pd precursor during the synthesis were found to be responsible for high Pd dispersions. These catalysts were very active for glyoxal oxidation into glyoxalic acid.
- Hermans,Thiltges,Deffernez,Devillers
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- Electrochemical Strategy for the Simultaneous Production of Cyclohexanone and Benzoquinone by the Reaction of Phenol and Water
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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
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p. 1556 - 1571
(2022/02/01)
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- Preparation method of aliphatic dicarboxylic acid
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The invention discloses a preparation method for aliphatic dicarboxylic acids. The preparation method mainly employs acetyl carboxylic acids and/or acetyl carboxylates as raw materials for preparing the aliphatic dicarboxylic acids in a high yield through a nonoxidation process. The preparation technology is simple, efficient, short in flow, less in by-product and suitable for large-scale industrialized production, and the obtained aliphatic dicarboxylic acids are high in purity, and are applicable to synthesize polyesters, polyamides, polyurethanes and other engineering plastic and are used as chemical engineering raw materials and medicine intermediates.
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Paragraph 0064-0065
(2021/03/17)
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- Electro-oxidation of glycerol into formic acid by nickel-copper electrocatalysts
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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
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- High-efficiency catalytic wet air oxidation of high salinity phenolic wastewater under atmospheric pressure in molten salt hydrate media
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An improved catalytic wet air oxidation (CWAO) process for high salinity phenolic wastewater is reported for the first time by using molten salt hydrates (MSHs) as reaction media. One feature of such a process is that it allows the operation to be conducted at atmospheric pressure owing to the temperature-increasing effect of MSHs. Another feature is that the inorganic salts in phenolic wastewater can be separated readily, taking advantage of the common-ion salting-out effect between inorganic salts and MSHs. Continuous catalytic oxidation degradation of the simulated high salinity phenolic wastewater demonstrated that more than 92% of phenol can be removed with chemical oxygen demand (COD) as high as 85% after reacting in CaCl2·3H2O medium at 150 °C with air as an oxidant. Meanwhile, the desalination efficiency of NaCl in continuous operation could reach up to 100%. It was found that CeCl3was an excellent catalyst for CWAO of phenol. XPS and UV-vis spectral characterization as well as radical scavenger experiments proved that [˙OH/Ce4+] was responsible for the synergistic catalytic degradation mechanism of phenol. Current work not only paves the way for developing a high-efficiency CWAO technology for concentrated organic wastewaters with high salinity, but also helps to better understand MSHs as reaction media.
- Tan, Hongzi,Wang, Shuai,Wang, Jinghua,Song, Feng,Sun, Xiuyu,Zhao, Rongrong,Zhang, Yuan,Cui, Hongyou
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supporting information
p. 2167 - 2174
(2021/02/06)
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- Influence of Pd and Au on electrochemical valorization of glycerol over Ni-rich surfaces
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Herein we synthesized bi-metallic Pd@Ni and Au@Ni core-shell-like nanoparticles (NPs) for glycerol electrooxidation reaction (GEOR) in alkaline media. The morphological, structural and surface properties of the NPs were evaluated using a range of physicochemical techniques. The catalytic activity and stability were studied using the three-electrode electrochemical cell and 25 cm2- continuous electrolysis cell. Among different atomic ratios, Ni80Pd20 and Ni90Au10 nanoparticles showed the highest current densities which are ~4.5 and 4.2 times higher than spherical Ni, respectively. The addition of Pd and Au (a remarkable glycerate selectivity of ~73.1% and 65.7% for Ni80Pd20 and Ni90Au10 catalysts at 1.3 V and 50 °C, respectively. Notably, after 6 h of electrolysis Pd@Ni and Au@Ni tend to suppress the C-C bond cleavage, compared to Ni at any applied potentials and temperatures. The DFT calculations predicted that the addition of Pd or Au to Ni reduces the work function of M@Ni NPs, which strengthens the OH adsorption and enhances the removal of GEOR intermediates.
- Houache, Mohamed S.E.,Shubair, Asma,Sandoval, Mario G.,Safari, Reza,Botton, Gianluigi A.,Jasen, Paula V.,González, Estela A.,Baranova, Elena A.
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- PROCESS FOR PRODUCTION OF FORMIC ACID AND ACETIC ACID BY ABSORBING CO2 VIA PHOTOCATALYTIC REDUCTION, IMPROVED CATALYST AND APPARATUS
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The present invention relates to a process for converting CO2 to short chain organic acids, which comprises the steps of: a) dissolution of silver containing fulvate chlatrate komplex catalyst in water to produce a catalyst solution; b) charging the catalyst solution into a pressure reactor; c) introducing a CO2 source into the reactor; d) exposing the reactor space with sunlight or artificial light, or electromagnetic wave while measuring the concentration of the produced organic acids; e) repeating the steps of c) and d) until the concentration of the produced organic acids reaches 2 to 5 % by weight in the reaction mixture; f) if the concentration of the produced organic acids reaches 2-5% by weight, collecting the aqueous solution from the, filtering and concentrating the same. The present invention also relates to a silver-containing fulvate-clathrate complex catalyst.
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Paragraph 0080
(2021/05/29)
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- Constructing an Acidic Microenvironment by MoS2 in Heterogeneous Fenton Reaction for Pollutant Control
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Although Fenton or Fenton-like reactions have been widely used in the environment, biology, life science, and other fields, the sharp decrease in their activity under macroneutral conditions is still a large problem. This study reports a MoS2 cocatalytic heterogeneous Fenton (CoFe2O4/MoS2) system capable of sustainably degrading organic pollutants, such as phenol, in a macroneutral buffer solution. An acidic microenvironment in the slipping plane of CoFe2O4 is successfully constructed by chemically bonding with MoS2. This microenvironment is not affected by the surrounding pH, which ensures the stable circulation of Fe3+/Fe2+ on the surface of CoFe2O4/MoS2 under neutral or even alkaline conditions. Additionally, CoFe2O4/MoS2 always exposes “fresh” active sites for the decomposition of H2O2 and the generation of 1O2, effectively inhibiting the production of iron sludge and enhancing the remediation of organic pollutants, even in actual wastewater. This work not only experimentally verifies the existence of an acidic microenvironment on the surface of heterogeneous catalysts for the first time, but also eliminates the pH limitation of the Fenton reaction for pollutant remediation, thereby expanding the applicability of Fenton technology.
- Huang, Kai,Lian, Cheng,Liang, Lihong,Xing, Mingyang,Yan, Qingyun,Yin, Pengcheng,Yu, Haoran,Zhang, Jinlong
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supporting information
p. 17155 - 17163
(2021/07/06)
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- Enhanced activation of persulfate by magnetic CuFe-layered double hydroxide nanocomposites under visible light irradiation for degradation of quinoline
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Magnetic CuFe-layered double hydroxide (Fe3O4@CuFe-LDH) nanocomposites were prepared with different Cu/Fe molar ratios for boosting the persulfate (Ps) activation under visible light irradiation. The LDH products were characterized in different ways. Recalcitrant quinoline (Qu) was the target pollutant in the experiments. It was found that the presence of the LDH photocatalyst caused significant enhancement in the Qu degradation so that the Vis/Ps/Fe3O4@LDH process could give 92.1% degradation and 70.5% mineralization efficiencies after 30?min operations at room temperature. The appropriate optimum conditions were Ps concentration of 450?mg/L, catalyst dosage of only 35?mg/L and the Cu/Fe molar ratio in the LDH structure of 3:1. The solution natural pH of about 6 provided the best performance. The LDH photocatalyst regeneration, in five cycles, each after a simple elution, exhibited good stability and reusability with an overall decrease of 4.9% in the activity. The presence of some co-existing anions of aqueous solutions causes diminishing the process efficiency. A pathway of Qu mineralization was proposed based on the identified intermediates. Taking into account the electrical energy and the consumed materials, an operating cost of $31.6/m3 was estimated for one order of magnitude reduction in the pollutant concentration.
- Nasri, M.,Pourehie, O.,Saien, J.
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- Degradation of minocycline by the adsorption–catalysis multifunctional PVDF–PVP–TiO2 membrane: Degradation kinetics, photocatalytic efficiency, and toxicity of products
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The photocatalytic degradation of minocycline was studied by using polyvinylidene fluoride–polyvinylpyrrolidone–TiO2 (PVDF–PVP–TiO2) fiber mats prepared by an electrospinning technology. The influences of the TiO2 dosage, minocycline concentrations, inorganic anions, pH values, and dissolved organic matter (DOM) concentrations on the degradation kinetics were investigated. A mass of 97% minocycline was degraded in 45 min at 5% TiO2 dosage. The corresponding decomposition rate constant was 0.069 min?1. The inorganic anions affected the minocycline decomposition in the order of HCO3? > Cl? > SO42? > NO3?, which was confirmed by the results of electron spin resonance (ESR) spectra. The lowest electrical energy per order (EEO) was 6.5 Wh/L. Over five cycles, there was no change in the photocatalytic performance of the degrading minocycline. Those investigations suggested that effective degradation of minocycline could be reached in the PVDF–PVP–TiO2 fiber mats with a low energy consumption, good separation and, good recovery. Three photocatalytic decomposition pathways of minocycline were proposed: (i) hydroxyl substitution of the acylamino group; (ii) hydroxyl substitution of the amide group, and (iii) a cleavage of the methyl groups and further oxidation of the amino group by OH. Potential risks caused by TP159 and TP99 should not be ignored, while the TP90 are nontoxic. Tests indicated that the toxicity of the photocatalytic process may be persistent if minocycline and its products were not mineralized completely.
- Zhou, Chengzhi,Sun, Yanlong,Zhang, Fan,Wu, Yuandong
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- Aromatic Ester-Functionalized Ionic Liquid for Highly Efficient CO2 Electrochemical Reduction to Oxalic Acid
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Electrochemical reduction of CO2 into valuable chemicals is a significant route to utilize CO2 resources. Among various electroreduction products, oxalic acid (H2C2O4) is an important chemical for pharmaceuticals, rare earth extraction, and metal processing. Here, an aprotic aromatic ester-functionalized ionic liquid (IL), 4-(methoxycarbonyl) phenol tetraethylammonium ([TEA][4-MF-PhO]), was designed as an electrolyte for CO2 electroreduction into oxalic acid. It exhibited a large oxalic acid partial current density of 9.03 mA cm?2 with a faradaic efficiency (FE) of 86 % at ?2.6 V (vs. Ag/Ag+), and the oxalic acid formation rate was as high as 168.4 μmol cm?2 h?1, which is the highest reported value to date. Moreover, the results of density functional theory calculations demonstrated that CO2 was efficiently activated to a ?COOH intermediate by bis-active sites of the aromatic ester anion via the formation of a [4-MF-PhO-COOH]? adduct, which finally dimerized into oxalic acid.
- Yang, Yingliang,Gao, Hongshuai,Feng, Jiaqi,Zeng, Shaojuan,Liu, Lei,Liu, Licheng,Ren, Baozeng,Li, Tao,Zhang, Suojiang,Zhang, Xiangping
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p. 4900 - 4905
(2020/08/19)
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- Dinitrosyl Iron Complex [K-18-crown-6-ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide
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Continued efforts are made for the utilization of CO2 as a C1 feedstock for regeneration of valuable chemicals and fuels. Mechanistic study of molecular (electro-/photo-)catalysts disclosed that initial step for CO2 activation involves either nucleophilic insertion or direct reduction of CO2. In this study, nucleophilic activation of CO2 by complex [(NO)2Fe(μ-MePyr)2Fe(NO)2]2? (2, MePyr=3-methylpyrazolate) results in the formation of CO2-captured complex [(NO)2Fe(MePyrCO2)]? (2-CO2, MePyrCO2=3-methyl-pyrazole-1-carboxylate). Single-crystal structure, spectroscopic, reactivity, and computational study unravels 2-CO2 as a unique intermediate for reductive transformation of CO2 promoted by Ca2+. Moreover, sequential reaction of 2 with CO2, Ca(OTf)2, and KC8 established a synthetic cycle, 2 → 2-CO2 → [(NO)2Fe(μ-MePyr)2Fe(NO)2] (1) → 2, for selective conversion of CO2 into oxalate. Presumably, characterization of the unprecedented intermediate 2-CO2 may open an avenue for systematic evaluation of the effects of alternative Lewis acids on reduction of CO2.
- Ching, Wei-Min,Liaw, Wen-Feng,Lu, Tsai-Te,Tseng, Yu-Ting
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supporting information
p. 11819 - 11823
(2020/05/26)
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- Carbon nanotubes as catalysts for wet peroxide oxidation: The effect of surface chemistry
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Three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (selectively N-doped), synthesized by catalytic chemical vapor deposition, were modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). Both treatments lead to higher specific surface areas. The acid treatment results in more acidic surfaces, with higher amounts of oxygenated species being introduced on N-doped surfaces. Heat-treated samples are less hydrophilic than those treated with nitric acid, heat treatment leading to neutral or basic surfaces, only N-quaternary and N-pyridinic species being found by XPS on N-doped surfaces. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L?1) at atmospheric pressure, T = 50 °C and pH = 3, using a catalyst load of 2.5 g L?1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. The high temperature treatment enhanced significantly the activity of the CNTs towards CWPO, evaluated in terms of 4-NP and total organic carbon conversion, due to the increased hydrophobicity of their surface. In particular, E30HT and E10A20HT were able to remove ca. 100% of 4-NP after 8 h of operation. On the other hand, by treating the CNTs with HNO3, the activity of the less hydrophilic samples decreased upon increasing the concentration of surface oxygen-containing functionalities, whilst the reactivity generated inside the opened nanotubes improved the activity of the highly hydrophilic A30 N.
- Martin-Martinez, Maria,Machado, Bruno F.,Serp, Philippe,Morales-Torres, Sergio,Silva, Adrián M.T.,Figueiredo, José L.,Faria, Joaquim L.,Gomes, Helder T.
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p. 332 - 340
(2019/03/17)
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- Electrochemical oxidation of amoxicillin on carbon nanotubes and carbon nanotube supported metal modified electrodes
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The electrolysis of amoxicillin (AMX) was carried out on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in 0.1 M NaOH, 0.1 M NaCl and 0.1 M Na2CO3/NaHCO3 buffer (pH 10) media with the aim of studying the significance of two factors, electrode material and pH, on the oxidative degradation and mineralization of AMX. For this purpose, the electrolysis products were identified by HPLC-MS and GC–MS, and quantified by HPLC-UV-RID and IC. The highest carbon mineralization efficiency, corresponding to 30% of the oxidized AMX, was found for Pt/CNT modified electrode in carbonate buffer medium. Regarding to the AMX conversion, the results show that the effect of pH is higher than that of the electrode material. Principal component analysis allowed to determine the experimental parameters vs. product distribution relationship and to elucidate the oxidation pathways for the studied electrodes. The results show that the hydroxylation of the aromatic ring and the nitrogen atom play an important role on the efficient degradation of AMX.
- Ferreira, Marta,Kuzniarska-Biernacka, Iwona,Fonseca, António M.,Neves, Isabel C.,Soares, Olívia S.G.P.,Pereira, Manuel F.R.,Figueiredo, José L.,Parpot, Pier
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p. 322 - 331
(2019/07/10)
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- In-situ fabrication of 0D/2D NiO/Bi12O17Cl2 heterojunction towards high-efficiency degrading 2, 4-dichlorophenol and mechanism insight
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2, 4-dichlorophenol (2, 4-DCP) as a persistent pollutant is frequently detected in water environments, complete eradication of trace which in water is an important task. Hence, a 0D/2D NiO/Bi12O17Cl2 heterojunction was achieved by in-situ fabrication of NiO nanodots on Bi12O17Cl2 nanosheets, which obviously improved the physical, optical and photoelectrochemical properties. The photocatalytic degradation activity of 0D/2D NiO/Bi12O17Cl2 heterojunction was boosted dramatically, which originated from the improved transfer and separation efficiency of charge carriers owing to the formation of Z-scheme heterostructure between NiO and Bi12O17Cl2. The possible photocatalytic reaction mechanism including migration behaviors of charge carriers, generation of reactive species and degradation intermediate products were revealed in depth. This work provides the valuable experiences for designing and fabricating otherwise 0D/2D heterojunction photocatalysts in the application of environmental treating fields.
- Song, Ning,Li, Jiaming,Li, Chunmei,Zhou, Pengjie,Jiang, Enhui,Zhang, Xiaoxu,Liu, Chunbo,Wu, Zhichen,Zheng, Hang,Che, Guangbo,Dong, Hongjun
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- Toward glucuronic acid through oxidation of methyl-glucoside using PdAu catalysts
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The production of glucuronic acid via enzyme catalysis from biomass is slow. Here we studied the oxidation of methoxy-protected glucose (MG) using Pd-on-Au nanoparticle model catalysts to generate methoxy-protected glucuronic acid (MGA), a precursor to glucuronic acid. Pd-on-Au showed volcano-shape activity dependence on calculated Pd surface coverage (sc). The 80 sc% Pd-on-Au catalyst composition showed maximum initial turnover frequency (413 mol-MG mol-surface-atom?1 h?1) that was 5× higher than that of Au/C, while Pd/C was inactive. This Pd-on-Au composition gave the highest MGA yield (46%), supporting a bimetallic approach to glucuronic acid production.
- Yin, Y. Ben,Chen, Li,Heck, Kimberly N.,Zhang, Z. Conrad,Wong, Michael S.
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- Mechanistic Studies on the Salicylate-Catalyzed Peroxyoxalate Chemiluminescence in Aqueous Medium
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The peroxyoxalate reaction is one of the most efficient chemiluminescence transformations known and the only system occurring by an intermolecular chemically initiated electron exchange luminescence (CIEEL) mechanism with confirmed high quantum yields. The peroxyoxalate chemiluminescence (PO-CL) is mainly studied in anhydrous organic medium; however, for bioanalytical application, it should be performed in aqueous media. In the present work, we study the peroxyoxalate system in a binary 1,2-dimethoxyethane/water mixture with bis(2,4,6-trichlorophenyl) oxalate (TCPO), bis(4-methylphenyl) oxalate (BMePO) and bis[2-(methoxycarbonyl)phenyl] oxalate (DMO), catalyzed by sodium salicylate, in the presence of rhodamine 6G as activator. Reproducible kinetic results are obtained for all systems; emission decay rate constants depend on the salicylate as well as hydrogen peroxide concentration, and the occurrence of a specific base catalysis is verified. Although singlet quantum yields determined are lower than in anhydrous media in comparable conditions, they are still considerably high and adequate for analytical applications. The highest singlet quantum yields are obtained for the “ecologically friendly” derivative DMO indicating that this derivative might be the most adequate substrate for the use of the peroxyoxalate system in bioanalytical applications.
- Cabello, Maidileyvis C.,Souza, Glalci A.,Bello, Liena V.,Baader, Wilhelm J.
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- Coupled heterogeneous photocatalysis using a P-TiO2-αFe2O3 catalyst and K2S2O8 for the efficient degradation of a sulfonamide mixture
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Phosphorous-doped Ti-Fe mixed oxide (P-TiO2-αFe2O3) catalysts were prepared by the microwave-assisted sol-gel route and characterized using XRD, SEM, N2 physisorption, UV–vis diffuse reflectance, FTIR, and XPS. P-TiO2-αFe2O3 was evaluated during the degradation of a sulfonamide mixture (5 mg/L, each) under visible light. The photocatalytic process was optimized with a face-centered central composite design. Under optimal conditions (0.5 wt% of αFe2O3, pH 10, and 0.75 g/L of catalyst loading), the sulfate radical advanced oxidation process was carried out using 5 mM K2S2O8 (PS). P doping shifted the light absorption of P-TiO2-αFe2O3 in the visible light range owing to substitutional doping, while the coupling of P-TiO2 with α-Fe2O3 enhanced the absorption in the visible range, which resulted in an increase in the lifetime of the charge carriers and in a superior photoactivity of the P-TiO2-αFe2O3 catalyst in comparison to that of TiO2. The mineralization yield of the sulfonamides (SNs) mixture was enhanced in the presence of an electron acceptor (SO4 ? [rad]), allowing nearly 69 % within 300 min with the P-TiO2-αFe2O3/PS system, while P-TiO2-αFe2O3 and K2S2O8 oxidation achieved only 27 % and 21 %, respectively. The biodegradability index was 0.48 using the P-TiO2-αFe2O3/PS system, indicating a less toxic effluent than the original compounds. Recycling tests demonstrated that P-TiO2-αFe2O3 exhibits good stability in activating PS for SNs degradation during three cycles. Two main intermediates (pyrimidine and hydroquinone) and their hydroxylated re-arrangements were detected during the degradation of the SNs by the coupled process. Oxalic, oxamic, sulfonic, and acetic acids were also identified as by-products from the degradation of the SNs.
- Guzmán-Mar, Jorge L.,Hernández-Ramírez, Aracely,Hinojosa-Reyes, Laura,Mendiola-Alvarez, Sandra Y.,Palomino-Cabello, Carlos,Turnes-Palomino, Gemma
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- CATALYST FOR SYNTHESIZING OXALATE BY CO COUPLING REACTION, PREPARATION AND USES
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The invention relates to a catalyst for synthesizing an oxalate by a CO coupling reaction. The catalyst comprises an active component, an auxiliary agent and hollow microspheres of α-Al2O3 as a carrier. The auxiliary agent may comprise an auxiliary element selected from the group consisting of nickel, cobalt, manganese, zirconium, cerium, lanthanum, molybdenum, barium, vanadium, titanium, iron, yttrium, niobium, tungsten, tin and bismuth. Also provided is a process for making the catalyst and a method for using the catalyst in synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN).
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Page/Page column 9
(2020/06/10)
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- Tetrachloromethane Hydrodechlorination over Palladium-Containing Nanodiamonds
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Abstract: Using nanodiamonds of the UDD-STP brand 1 wt % palladium-containing nanodiamonds are obtained and tested as catalysts of tetrachloromethane hydrodechlorination under mild conditions (solvents, ethanol and methanol; Т = 298–318 K; PH2 = 0.1 MPa). The catalytic properties of the obtained material and a palladium-containing analog based on activated carbon are compared. It is shown that the hydrodechlorination reaction occurs in a stepwise manner via two pathways: to form products with a smaller content of chlorine, for example, chloroform, and to yield oxygen-containing products, for example, diethyl carbonate. The qualitative and quantitative compositions of reaction products are determined by gas chromatography/mass spectrometry.
- Belkina, E. G.,Gruzdev, M. S.,Kalmykov, P. A.,Klyuev, M. V.,Lysenok, A. A.,Magdalinova, N. A.
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p. 1148 - 1153
(2020/10/14)
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- Electrogenerated Sm(II)-Catalyzed CO2 Activation for Carboxylation of Benzyl Halides
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Sm(II)-catalyzed carboxylation of benzyl halides is reported through the electrochemical reduction of CO2. The transformation proceeds under mild reaction conditions to afford the corresponding phenylacetic acids in good to excellent yields. This user-friendly and operationally simple protocol represents an alternative to traditional strategies, which usually proceeds through the C(sp3)-halide activation pathway.
- Bazzi, Sakna,Schulz, Emmanuelle,Mellah, Mohamed
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supporting information
p. 10033 - 10037
(2019/12/24)
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- Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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An efficient and environmentally friendly oxidation process for the one-pot preparation of oxime, imine and carbonyl compounds through alcohol oxidation in the presence of H2O2 and/or O2 have been developed by a melamine-Mn(III) Schiff base complex supported on Fe3O4@SiO2–Cl nanoparticles, named as Fe3O4@SiO2@Im[Cl]Mn(III)-complex nanocomposite, at room temperature. Direct oxidation of alcohol to carboxylic acid was performed using the catalyst in the presence of molecular O2 at room temperature in a different approach. The oxidation products were obtained with excellent yields and high TOFs. The properties of the catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis (C, H, N), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP), cyclic voltammetry (CV), nuclear magnetic resonance (1H & 13C NMR), vibration sample magnetometer (VSM), Brunauer– Emmett–Teller (BET) and differential pulse voltammetry (DPV) analyses. The mechanism of the oxidation processes was investigated for the both H2O2 and O2 oxidants. The role of the imidazolium moiety in the catalyst as a secondary functionality was investigated. Chemoselectivity behavior of the catalyst was studied by some combinations. The catalyst could be recycled from the reaction mixture by a simple external magnet and reused for several times without any considerable reactivity loss.
- Kazemnejadi, Milad,Alavi, Seyyedeh Ameneh,Rezazadeh, Zinat,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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p. 230 - 249
(2019/03/28)
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- Glycerol Partial Oxidation over Pt/Al2O3 Catalysts under Basic and Base-Free Conditions—Effect of the Particle Size
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The glycerol partial oxidation reaction over Pt/Al2O3 catalysts was studied under basic (NaOH/GLY molar ratio 4) and base-free conditions (NaOH/GLY molar ratio 0). Catalysts with small (2.95 nm) and large particle sizes (260.83 nm) were synthesized according to the use of different reducing agents, formaldehyde or sodium borohydride, and hydrazine, respectively. These different Pt particle sizes lead to a dramatic change in terms of activity, irrespective of the applied conditions. The biggest particles (i.e., 260 nm) seem to generate overoxidation products leading to a decrease in the carbon balance (to ~80%) while the smallest particles exhibit the highest initial glycerol transformation rate (i.e., ~10,000 mol h?1 molPt?1 under basic conditions at 60°C and ~2000 mol h?1 molPt?1 in the absence of a base at 100°C). In terms of selectivities, the main products are different as a function of the initial reaction conditions. For base-free conditions, the two main products are glyceraldehyde and glyceric acid with a sum of selectivities always larger than 80%. Under basic conditions, the major product is glyceric acid while no trace of glyceraldehyde is detected.
- Skrzyńska, El?bieta,El Roz, Ayman,Paul, Sébastien,Capron, Micka?l,Dumeignil, Franck
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- Selective oxidation of glycerol to tartronic acid over Pt/N-doped mesoporous carbon with extra framework magnesium catalysts under base-free conditions
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N-Doped mesoporous carbons (NMCs) with extra framework magnesium were prepared by a one-pot method and used as supports for Pt catalysts. The surface basicity of NMC improved in the presence of extra framework magnesium (e.g.,-Ph-O-Mg), meanwhile, the electron density of Pt was enriched by the electron transfer from graphitic N in NMC to Pt. As a result, the catalytic activity of the supported Pt catalyst was improved to be able to selectively oxidize glycerol (GLY) to tartronic acid (TA) under base-free conditions.
- Zhan, Tong,Liu, Weibing,Teng, Junjiang,Yue, Chaochao,Li, Dehao,Wang, Suhua,Tan, Hua
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supporting information
p. 2620 - 2623
(2019/03/05)
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- The Enhanced Catalytic Performance and Stability of Ordered Mesoporous Carbon Supported Nano-Gold with High Structural Integrity for Glycerol Oxidation
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Ordered mesoporous carbon (OMC) supported gold nanoparticles of size 3–4 nm having uniform dispersion were synthesized by sol-immobilization method. OMCs such as CMK-3 and NCCR-56 with high surface area and uniform pore size were obtained, respectively, using ordered mesoporous silicas such as SBA-15 and IITM-56 as hard templates, respectively. The resulting OMC supported monodispersed nano-gold, i. e., Au/CMK-3 and Au/NCCR-56, exhibited excellent performance as mild-oxidizing catalysts for oxidation of glycerol with high hydrothermal stability. Further, unlike activated carbon supported nano-gold catalysts (Au/AC), the OMC supported nano-gold catalysts, i. e., Au/CMK-3 and Au/NCCR-56, show no aggregation of active species even after recycling. Thus, in the case of Au/CMK-3 and Au/NCCR-56, both the fresh and regenerated catalysts showed excellent performane for the chosen reaction owing to an enhanced textural integrity of the catalysts and that with remarkable selectivity towards glyceric acid. The significance of the OMC supports in maintaining the dispersion of gold nanoparticles is explicit from this study, and that the activity of Au/AC catalyst is considerably decreased (～50 %) upon recycling as a result of agglomeration of the active gold nanoparticles over the disordered amorphous carbon matrix.
- Murthy, Palle R.,Selvam, Parasuraman
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p. 1913 - 1925
(2018/11/27)
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- Efficient and stable platinum nanocatalysts supported over Ca-doped ZnAl2O4 spinels for base-free selective oxidation of glycerol to glyceric acid
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In the work, highly dispersed platinum nanocatalysts supported over undoped and Ca-doped zinc aluminate spinels were developed and applied for aqueous-phase selective oxidation of glycerol to produce glyceric acid under base-free conditions. As-fabricated Pt-based catalyst with the incorporation of an appropriate Ca/(Ca + Zn) molar ratio of 0.1 into the spinel exhibited a higher catalytic activity, along with a selectivity to glyceric acid (>81%) and a high turnover frequency of 1160 h?1, compared with other supported Pt-based ones over zinc aluminates, as well as most of supported Pt catalysts previously reported. The structural characterizations and catalytic experiments showed that surface synergy between highly dispersed metallic Pt0 species and medium-strength basic sites mainly contributed to its enhanced catalytic efficiency for base-free glycerol oxidation. Moreover, the present Pt catalyst also presented high structural stability and good reusability. The work opens an alternative approach for constructing highly efficient and stable metal-base bifunctional catalysts for a wide range of heterogeneous oxidation processes without the addition of liquid alkalis.
- Han, Zhengya,Xie, Renfeng,Song, Yihui,Fan, Guoli,Yang, Lan,Li, Feng
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- Quantitative Determination of Pt- Catalyzed d -Glucose Oxidation Products Using 2D NMR
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Quantitative correlative 1H-13C NMR has long been discussed as a potential method for quantifying the components of complex reaction mixtures. Here, we show that quantitative HMBC NMR can be applied to understand the complexity of the catalytic oxidation of glucose to glucaric acid, which is a promising bio-derived precursor to adipic acid, under aqueous aerobic conditions. It is shown through 2D NMR analysis that the product streams of this increasingly studied reaction contain lactone and dilactone derivatives of acid products, including glucaric acid, which are not observable/quantifiable using traditional chromatographic techniques. At 98% glucose conversion, total C6 lactone yield reaches 44%. Furthermore, a study of catalyst stability shows that all Pt catalysts undergo product-mediated chemical leaching. Through catalyst development studies, it is shown that sequestration of leached Pt can be achieved through use of carbon supports.
- Armstrong,Hirayama,Knight,Hutchings
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p. 325 - 335
(2019/01/04)
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- Automated on-line monitoring of the TiO2-based photocatalytic degradation of dimethyl phthalate and diethyl phthalate
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A fully automated on-line system for monitoring the TiO2-based photocatalytic degradation of dimethyl phthalate (DMP) and diethyl phthalate (DEP) using sequential injection analysis (SIA) coupled to liquid chromatography (LC) with UV detection was proposed. The effects of the type of catalyst (sol-gel, Degussa P25 and Hombikat), the amount of catalyst (0.5, 1.0 and 1.5 g L-1), and the solution pH (4, 7 and 10) were evaluated through a three-level fractional factorial design (FFD) to verify the influence of the factors on the response variable (degradation efficiency, %). As a result of FFD evaluation, the main factor that influences the process is the type of catalyst. Degradation percentages close to 100% under UV-vis radiation were reached using the two commercial TiO2 materials, which present mixed phases (anatase/rutile), Degussa P25 (82%/18%) and Hombikat (76%/24%). 60% degradation was obtained using the laboratory-made pure anatase crystalline TiO2 phase. The pH and amount of catalyst showed minimum significant effect on the degradation efficiencies of DMP and DEP. Greater degradation efficiency was achieved using Degussa P25 at pH 10 with 1.5 g L-1 catalyst dosage. Under these conditions, complete degradation and 92% mineralization were achieved after 300 min of reaction. Additionally, a drastic decrease in the concentration of BOD5 and COD was observed, which results in significant enhancement of their biodegradability obtaining a BOD5/COD index of 0.66 after the photocatalytic treatment. The main intermediate products found were dimethyl 4-hydroxyphthalate, 4-hydroxy-diethyl phthalate, phthalic acid and phthalic anhydride indicating that the photocatalytic degradation pathway involved the hydrolysis reaction of the aliphatic chain and hydroxylation of the aromatic ring, obtaining products with lower toxicity than the initial molecules.
- Salazar-Beltrán, Daniel,Hinojosa-Reyes, Laura,Maya-Alejandro, Fernando,Turnes-Palomino, Gemma,Palomino-Cabello, Carlos,Hernández-Ramírez, Aracely,Guzmán-Mar, Jorge Luis
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p. 863 - 870
(2019/04/17)
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- Degradation of tri(2-chloroisopropyl) phosphate by the UV/H2O2 system: Kinetics, mechanisms and toxicity evaluation
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A photodegradation technology based on the combination of ultraviolet radiation with H2O2 (UV/H2O2) for degrading tri(chloroisopropyl) phosphate (TCPP) was developed. In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.0035 min?1 (R2 = 0.9871) for 5 mg L?1 TCPP using 250 W UV light irradiation with 50 mg L?1 H2O2. In detail, the yield rates of Cl? and PO43? reached 0.19 mg L?1 and 0.58 mg L?1, respectively. The total organic carbon (TOC) removal rate was 43.02%. The pH value of the TCPP solution after the reaction was 3.46. The mass spectrometric detection data showed a partial transformation of TCPP into a series of hydroxylated and dechlorinated products. Based on the luminescent bacteria experimental data, the toxicity of TCPP products increased obviously as the reaction proceeded. In conclusion, degradation of high concentration TCPP in UV/H2O2 systems may result in more toxic substances, but its potential application for real wastewater is promising in the future after appropriate optimization, domestication and evaluation.
- He, Huan,Ji, Qiuyi,Gao, Zhanqi,Yang, Shaogui,Sun, Cheng,Li, Shiyin,Zhang, Limin
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- Catalytic oxidative dehydrogenation of malic acid to oxaloacetic acid
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Here we report the oxidative dehydrogenation of malic acid to oxaloacetic acid, a key precursor in the fabrication of amino acids, over Pt-Bi/C catalysts. Under optimized conditions, we discovered that OAA was selectively produced with up to 60% conversion (i.e. 60% yield). The recurrent unwanted decarboxylation of OAA to pyruvic acid was circumvented by successfully conducting the catalytic reaction at 25 °C. A comparison with the classical Fenton oxidation reaction is discussed.
- Drif, Asmaa,Pineda, Antonio,Morvan, Didier,Belliere-Baca, Virginie,De Oliveira Vigier, Karine,Jér?me, Fran?ois
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supporting information
p. 4604 - 4608
(2019/09/09)
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- Template free mild hydrothermal synthesis of core-shell Cu2O(Cu)?CuO visible light photocatalysts for N-acetyl-para-aminophenol degradation
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Solar photocatalytic processes are a promising approach to environmental remediation, however their implementation requires improvements in visible light harvesting and conversion and a focus on low cost, Earth abundant materials. Semiconducting copper oxides are promising visible light photocatalysts for solar fuels and wastewater depollution. Here we report the mild, hydrothermal (template-free) synthesis of core-shell Cu2O(Cu)?CuO photocatalytic architectures for the visible light photocatalytic degradation of N-acetyl-para-aminophenol (APAP). Hollow and rattle-like core-shell nanosphere aggregates with diameters between 200 nm and 2.5 μm formed under different synthesis conditions; all comprised an inner Cu2O shell, formed of 10-50 nm nanoparticles, surrounded by a protective corona of CuO nanoparticles. High reductant and structure-directing agent concentrations promoted the formation of a yolk-like Cu2O/Cu core, associated with improved photophysical properties, notably a high oxidation potential and suppressed charge carrier recombination, that correlated with the highest apparent quantum efficiency (8%) and rate of APAP removal (7 μmol g-1 min-1). Trapping experiments demonstrated hydroxyl radicals were the primary active species responsible for APAP oxidation to quinones and short chain carboxylic acids. Rattle-like core-shell Cu2O/Cu?CuO nanospheres exhibited excellent physiochemical stability and recyclability for APAP photocatalytic degradation.
- Karthikeyan, Sekar,Chuaicham, Chitiphon,Pawar, Radheshyam R.,Sasaki, Keiko,Li, Wei,Lee, Adam F.,Wilson, Karen
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supporting information
p. 20767 - 20777
(2019/09/30)
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- Sustainable Synthesis of Oxalic and Succinic Acid through Aerobic Oxidation of C6 Polyols Under Mild Conditions
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The sustainable chemical industry encompasses a shift from the use of fossil carbon to renewable carbon. The synthesis of chemicals from nonedible biomass (cellulosic or oil) represents one of the key steps for “greening” the chemical industry. In this paper, we report the aerobic oxidative cleavage of C6 polyols (5-HMF, glucose, fructose and sucrose) to oxalic acid (OA) and succinic acid (SA) in water under mild conditions using M@CNT and M@NCNT (M=Fe, V; CNT=carbon nanotubes; NCNT=N-doped CNT), which, under suitable conditions, were recoverable and reusable without any loss of efficiency. The influence of the temperature, O2 pressure (P (Formula presented.)), reaction time and stirring rate are discussed and the best reaction conditions are determined for an almost complete conversion of the starting material and a good OA yield of 48 %. SA and formic acid were the only co-products. The former could be further converted into OA by oxidation in the presence of formic acid, resulting in an overall OA yield of >62 %. This process was clean and did not produce organic waste nor gas emissions.
- Ventura, Maria,Williamson, David,Lobefaro, Francesco,Jones, Matthew D.,Mattia, Davide,Nocito, Francesco,Aresta, Michele,Dibenedetto, Angela
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p. 1073 - 1081
(2018/02/28)
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- Electrochemical activation of CO2 by a di-Schiff base of N, N′-bis(2-hydroxy-1-naphthaldehyde)-m-phenylenediimine
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Electrochemical behavior of a di-Schiff base, N, N′-bis(2-hydroxy-1-naphthaldehyde)-m-phenylenediimine, NMPD, was investigated using cyclic voltammetry, chronoamperometry and controlled-potential coulometry in acetonitrile solution containing tetrabutylammonium perchlorate, as supporting electrolyte. The effect of different parameters such as potential scan rates, and time window of the chosen electrochemical method was examined in studying the electrochemical behavior of NMPD. According to the results of experiments, an EC2CE mechanism was proposed to electrochemical reduction of NMPD on the glassy carbon electrode surface. Furthermore, NMPD is an efficient electrocatalyst in reduction of CO2. This electrocatalytic activity is confirmed by 700 mV decreases in overpotential of CO2 reduction, significant increase in cathodic current of NMPD and also the spectrum characterization of the main product of the electrolysis process which is oxalic acid.
- Ghobadi, Kobra,Zare, Hamid R.,Gorji, Alireza,Benvidi, Ali
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- Catalytic conversion of glycerol to lactic acid over hydroxyapatite-supported metallic Ni0 nanoparticles
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Catalytic conversion of low-priced biomass glycerol to value-added lactic acid is an alternative route to the conventional fermentation process using sugar as the starting material. Nanosized hydroxyapatite-supported metallic Ni0 nanoparticles (Nix/HAP) prepared by the wetness chemical reduction method effectively catalyzed the conversion of high-concentrated glycerol (1.5-3 mol L-1) to lactic acid in a NaOH aqueous solution. The Nix/HAP catalysts exhibited higher catalytic activity for glycerol conversion to lactic acid than the sole metallic Ni0 nanoparticles.When the reaction was carried out over the Ni0.2/HAP catalyst with the initial glycerol and NaOH concentrations of 2.0 and 2.2 mol L-1 at 200 °C for 2 h, the selectivity of lactic acid reached 94.7% at the glycerol conversion of 92.1%.
- Qiu, Lang,Yin, Haixu,Yin, Hengbo,Wang, Aili
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p. 4734 - 4745
(2018/01/17)
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- Unraveling the mechanism of the oxidation of glycerol to dicarboxylic acids over a sonochemically synthesized copper oxide catalyst
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The utilization of low frequency ultrasound (US) offers a straightforward and powerful tool for the production of nanostructured materials, in particular for structurally stable, highly crystalline, and shape-controlled catalytic materials. Herein, we report an unconventional strategy for the synthesis of CuO nanoleaves within 5 min of US irradiation. The as-obtained CuO nanoleaves were found to be selective in the base-free aqueous oxidation of glycerol to dicarboxylic acids (78% yield of tartronic and oxalic acids), in the presence of hydrogen peroxide (H2O2) and under mild reaction conditions. Density Functional Theory (DFT) investigations revealed a synergy between the CuO catalyst and H2O2 in maintaining the structural integrity of the catalyst during the reaction, creating alternative efficient pathways for the selective formation of dicarboxylic acids. Isotope labeling experiments using H218O2 further confirmed that oxygen from hydrogen peroxide, not from CuO, was preferentially incorporated into the dicarboxylic acid, significantly preserving the monoclinic structure of the CuO catalyst.
- Amaniampong, Prince N.,Trinh, Quang Thang,Varghese, Jithin John,Behling, Ronan,Valange, Sabine,Mushrif, Samir H.,Jér?me, Francois
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supporting information
p. 2730 - 2741
(2018/06/29)
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- Silica Metal Oxide Vesicles Catalyze Comprehensive Prebiotic Chemistry
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It has recently been demonstrated that mineral self-assembled structures catalyzing prebiotic chemical reactions may form in natural waters derived from serpentinization, a geological process widespread in the early stages of Earth-like planets. We have s
- Mattia Bizzarri, Bruno,Botta, Lorenzo,Pérez-Valverde, Maritza Iveth,Saladino, Raffaele,Di Mauro, Ernesto,García-Ruiz, Juan Manuel
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p. 8126 - 8132
(2018/05/29)
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- Glycerol Oxidation Using MgO- and Al2O3-supported Gold and Gold–Palladium Nanoparticles Prepared in the Absence of Polymer Stabilizers
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Au and AuPd nanoparticles supported on MgO and Al2O3 were employed for the selective aqueous phase oxidation of glycerol under basic conditions. Catalysts were prepared by sol-immobilization without the addition of a stabilizing agent such as polyvinyl alcohol (PVA), which is generally added to stabilize the noble metal sol prior to immobilization. The obtained materials prepared with and without stabilizing agent were active for glycerol oxidation and showed similar catalytic performances—implying that the stabilizing polymer is not required to obtain active materials. Depending on the support used, it was possible to tailor the selectivity towards the desired oxidation products by using catalysts prepared with or without stabilizing agent. PVA-free Au/γ-Al2O3 exhibited a remarkably high selectivity towards tartronic acid (40 % at 97 % conversion), which was not observed for Au/γ-Al2O3 prepared with PVA (27 % at isoconversion). Selective glycerol oxidation performed under base-free conditions over AuPd/MgO catalysts also corroborated the previous results that the presence of a stabilizing polymer is not required to prepare active catalysts by sol-immobilization. Thus, a facile way to circumvent the inherent drawbacks encountered by the use of polymer stabilizers during catalyst preparation is presented herein. Experimental results suggest that the presence of the polymer stabilizers can affect the reaction pathways and control selectivity.
- Dodekatos, Georgios,Abis, Laura,Freakley, Simon J.,Tüysüz, Harun,Hutchings, Graham J.
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p. 1351 - 1359
(2018/03/30)
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- Gold-Doped Fe/TiO2 Catalysts: A Case of Extra-Low Gold Loading in Glycerol Oxidation
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Abstract: Au/Fe/TiO2 catalysts with a low Au content ( 16 000.
- Redina,Vikanova,Shesterkina,Kustov
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p. 2143 - 2147
(2018/10/24)
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- The Role of Mg(OH)2 in the So-Called “Base-Free” Oxidation of Glycerol with AuPd Catalysts
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Mg(OH)2- and Mg(OH)2-containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH)2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH)2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH)2 added under base-free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH)2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH)2, physically mixed (AuPd/C+Mg(OH)2) and (AuPd/C+NaHCO3) was obtained and compared. Furthermore, NaOH and Mg(OH)2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH)2 supported catalysts in base-free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction.
- Fu, Jile,He, Qian,Miedziak, Peter J.,Brett, Gemma L.,Huang, Xiaoyang,Pattisson, Samuel,Douthwaite, Mark,Hutchings, Graham J.
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supporting information
p. 2396 - 2402
(2018/02/06)
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- Promoting effect of solvent on Cu/CoO catalyst for selective glycerol oxidation under alkaline conditions
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Cu/CoO catalysts were employed for the selective oxidation of glycerol in the aqueous phase under basic conditions. The effect of the solvent on the catalytic performance was investigated and the impact on the catalyst was thoroughly elucidated. Detailed characterization of the catalysts by HR-TEM, XRD, and XPS analysis before and after the reaction revealed that the addition of co-solvents (ethanol, n-propanol, or tert-butanol) drastically altered the catalyst properties. In particular, the amount of the catalytically active CoO(OH) phase generated during the reaction depends on the co-solvent used. Generally, the co-solvent has a beneficial effect on the catalytic activity and improves the glycerol conversion by a factor of up to 1.8, which could be linearly correlated to the ET(30) solvent polarity.
- Dodekatos, Georgios,Ternieden, Jan,Schünemann, Stefan,Weidenthaler, Claudia,Tüysüz, Harun
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p. 4891 - 4899
(2018/10/24)
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- Study on the degradation mechanism and pathway of benzene dye intermediate 4-methoxy-2-nitroaniline: Via multiple methods in Fenton oxidation process
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Benzene dye intermediate (BDI) 4-methoxy-2-nitroaniline (4M2NA) wastewater has caused significant environmental concern due to its strong toxicity and potential carcinogenic effects. Reports concerning the degradation of 4M2NA by advanced oxidation process are limited. In this study, 4M2NA degradation by Fenton oxidation has been studied to obtain more insights into the reaction mechanism involved in the oxidation of 4M2NA. Results showed that when the 4M2NA (100 mg L-1) was completely decomposed, the TOC removal efficiency was only 30.70-31.54%, suggesting that some by-products highly recalcitrant to the Fenton oxidation were produced. UV-Vis spectra analysis based on Gauss peak fitting, HPLC analysis combined with two-dimensional correlation spectroscopy and GC-MS detection were carried out to clarify the degradation mechanism and pathway of 4M2NA. A total of nineteen reaction intermediates were identified and two possible degradation pathways were illustrated. Theoretical TOC calculated based on the concentration of oxalic acid, acetic acid, formic acid, and 4M2NA in the degradation process was nearly 94.41-97.11% of the measured TOC, indicating that the oxalic acid, acetic acid and formic acid were the main products. Finally, the predominant degradation pathway was proposed. These results could provide significant information to better understand the degradation mechanism of 4M2NA.
- Guo, Ying,Xue, Qiang,Cui, Kangping,Zhang, Jia,Wang, Hui,Zhang, Huanzhen,Yuan, Fang,Chen, Honghan
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p. 10764 - 10775
(2018/03/26)
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- Postsynthetic Selective Ligand Cleavage by Solid-Gas Phase Ozonolysis Fuses Micropores into Mesopores in Metal-Organic Frameworks
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Herein we report a novel, ozone-based method for postsynthetic generation of mesoporosity in metal-organic frameworks (MOFs). By carefully selecting mixed-ligand Zr-fcu-MOFs based on organic ligand pairs in which one ligand has ozone-cleavable olefin bonds and the other ligand is ozone-resistant, we were able to selectively break the cleavable ligand via ozonolysis to trigger fusion of micropores into mesopores within the MOF framework. This solid-gas phase method is performed at room-temperature, and, depending on the cleavable ligand used, the resultant ligand-fragments can be removed from the ozonated MOF by either washing or sublimation. Compared to the corresponding highly microporous starting MOFs, the highly mesoporous product MOFs exhibit radically distinct gas sorption properties.
- Guillerm, Vincent,Xu, Heng,Albalad, Jorge,Imaz, Inhar,Maspoch, Daniel
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p. 15022 - 15030
(2018/11/10)
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- Sphingobacterium sp. T2 Manganese Superoxide Dismutase Catalyzes the Oxidative Demethylation of Polymeric Lignin via Generation of Hydroxyl Radical
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Sphingobacterium sp. T2 contains two extracellular manganese superoxide dismutase enzymes which exhibit unprecedented activity for lignin oxidation but via an unknown mechanism. Enzymatic treatment of lignin model compounds gave products whose structures were indicative of aryl-Cα oxidative cleavage and demethylation, as well as alkene dihydroxylation and alcohol oxidation. 18O labeling studies on the SpMnSOD-catalyzed oxidation of lignin model compound guiaiacylglycerol-β-guaiacyl ether indicated that the an oxygen atom inserted by the enzyme is derived from superoxide or peroxide. Analysis of an alkali lignin treated by SpMnSOD1 by quantitative 31P NMR spectroscopy demonstrated 20-40% increases in phenolic and aliphatic OH content, consistent with lignin demethylation and some internal oxidative cleavage reactions. Assay for hydroxyl radical generation using a fluorometric hydroxyphenylfluorescein assay revealed the release of 4.1 molar equivalents of hydroxyl radical by SpMnSOD1. Four amino acid replacements in SpMnSOD1 were investigated, and A31H or Y27H site-directed mutant enzymes were found to show no lignin demethylation activity according to 31P NMR analysis. Structure determination of the A31H and Y27H mutant enzymes reveals the repositioning of an N-terminal protein loop, leading to widening of a solvent channel at the dimer interface, which would provide increased solvent access to the Mn center for hydroxyl radical generation.
- Rashid, Goran M. M.,Zhang, Xiaoyang,Wilkinson, Rachael C.,Fül?p, Vilmos,Cottyn, Betty,Baumberger, Stéphanie,Bugg, Timothy D. H.
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p. 2920 - 2929
(2018/10/20)
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- Oxygen-vacancy-promoted catalytic wet air oxidation of phenol from MnO: X-CeO2
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Catalytic oxidation can be effectively promoted by the presence of oxygen vacancies on the catalyst surface. In this study, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx-CeO2 as catalysts. CeO2 and MnOx-CeO2 catalysts with different amounts of oxygen vacancies were obtained via hydrothermal methods and applied for the CWAO of phenol. It was found that CeO2 and MnOx-CeO2 nanorods were much more active than the cubic nanorods. The physicochemical properties of the samples were characterized by TEM, XRD, BET, XPS, and H2-TPR techniques. The results revealed that the presence of oxygen vacancies in CeO2 and MnOx-CeO2 catalysts could increase the oxidizing ability of the catalysts surface. The addition of Mn could greatly improve the adsorption ability of CeO2 and more efficiently oxidize phenol and its intermediates. The synergy between Mn and Ce could further improve the catalyst redox properties and produce a larger amount of active oxygen species, which is the reason why MnOx-CeO2 nanorods are the most active catalysts among the catalysts investigated in this study.
- Ma, Changjian,Wen, Yaoyao,Yue, Qingqing,Li, Anqi,Fu, Jile,Zhang, Nouwei,Gai, Hengjun,Zheng, Jinbao,Chen, Bing H.
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p. 27079 - 27088
(2017/07/07)
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- Effect of Post-Treatment on Structure and Catalytic Activity of CuCo-based Materials for Glycerol Oxidation
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A series of CuCo-based materials prepared by co-precipitation with varied Co/Cu ratios and different post-treatments were applied in the selective oxidation of glycerol in the aqueous phase under basic conditions. The influence of the post-treatment on the structure of the materials and the catalytic performance was investigated in detail. As-prepared materials without calcination and materials calcined under air with subsequent reduction under ethanol/N2 gas stream showed higher conversion of glycerol compared to samples solely calcined under air or to samples calcined under air with subsequent reduction under H2/Ar gas stream. The main products identified in the liquid phase were glyceric, glycolic, and formic acids. Systematic catalytic studies for differently prepared samples with varied Cu content and subsequent characterization of the materials by N2 physisorption, XRD, TEM, and EDX allowed for the identification of CoO(OH) in contact with CuO as the potentially active phases.
- Dodekatos, Georgios,Tüysüz, Harun
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p. 610 - 619
(2017/02/26)
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- A switchable route to valuable commodity chemicals from glycerol via electrocatalytic oxidation with an earth abundant metal oxidation catalyst
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Electrocatalytic upgrading of glycerol to value-added commodity is demonstrated using an ultralow loading of a cobalt-based oxidation catalyst at 16 μg cm-2. Reactions take place under ambient conditions in an aqueous environment, while generating H2 as a byproduct. Selectivity towards two major products, lactic acid and glyceric acid, can be controlled via simple variation of reaction conditions. The system is scalable and functions well even in the presence of methanol, an impurity commonly found in the industrial bio-diesel waste stream. Industrial glycerol waste from a local bio-diesel plant was also shown to be upgradable after a simple aqueous pretreatment.
- Lam, Chun Ho,Bloomfield, Aaron J.,Anastas, Paul T.
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p. 1958 - 1968
(2017/06/09)
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- One-step synthesis of pyruvic acid from glycerol oxidation over Pb promoted Pt/activated carbon catalysts
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One-step production of pyruvic acid through selective oxidation of glycerol was investigated using lead promoted platinum/activated carbon (Pb-Pt/AC) catalysts under mild conditions. The results of N2 physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy revealed that the alloy phases of PtPb and PtxPb were favorable for pyruvic acid production from glycerol oxidation, whereas the Pb3(CO3)2(OH)2 and surface Pb0 species inhibited the glycerol conversion. The loading of Pb and the catalyst preparation method (including impregnation and deposition precipitation) affected the formation of different metal species. Pyruvic acid was obtained at a yield of 18.4% on a 5.0 wt% Pb-5.0 wt% Pt/AC catalyst prepared by co-deposition precipitation method and 500 °C argon treatment.
- Zhang, Chen,Wang, Tao,Ding, Yunjie
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p. 928 - 937
(2017/05/22)
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- Electrochemical production of lactic acid from glycerol oxidation catalyzed by AuPt nanoparticles
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The production of valuable chemicals from relatively inexpensive feedstocks utilizing electrochemical methods has been attracting widespread attention in recent years since it is highly efficient, decentralized, environmental-friendly and can operate in room temperature and pressure. Currently, the industrial production of lactic acid is mainly based on bio-fermentation, leading to drawbacks including severe conditions, unfriendliness to environment, low efficiency and requirement of expensive equipment, which can potentially overcome by electrochemical methods. Herein, we report for the first time the preparation of lactic acid at room temperature and pressure from the one-pot electro-oxidation of glycerol, a byproduct from biodiesel production. AuPt nanoparticles with different surface compositions were employed in this work to optimize the catalysis performance, and the glycerol oxidation was operated at a series of applied potentials, pH and glycerol concentration. The optimal lactic acid selectivity was 73%, obtained with Au-enriched surface at applied potential of 0.45 V vs. RHE.
- Dai, Chencheng,Sun, Libo,Liao, Hanbin,Khezri, Bahareh,Webster, Richard D.,Fisher, Adrian C.,Xu, Zhichuan J.
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