CC Bond Cleavage Research Articles

The effect of metal properties on the reaction routes of glycerol hydrogenolysis over platinum and ruthenium catalysts

The CC bond and CO bond cleavages in glycerol hydrogenolysis were compared over Pt and Ru supported on ZrO2 and WO3/ZrO2 (ZrW). The prepared catalysts were characterized by nitrogen adsorption/desorption, X-ray powder diffraction, transmission electron microscopy, CO and H2 chemisorption, O2 titration, H2-temperature programmed reduction, diffuse reflectance infrared Fourier transform spectra of adsorbed CO and Fourier transform infrared spectra of pyridine adsorption. The electron density of metal on ZrO2 was different from that on ZrW, resulting in the different ability on CC bond cleavage in glycerol hydrogenolysis. Pt/ZrW exhibited a better hydrogen activation and spillover capacity than Ru/ZrW, leading to a higher selectivity of 1,3-propanediol. The effect of H2 pressure was also studied and reaction routes of glycerol hydrogenolysis to propanediols were discussed.

Conversion of n-hexane and n-dodecane over H-ZSM-5, H-Y and Al-MCM-41 at supercritical conditions

Catalytic reactions of supercritical n-hexane and n-dodecane were studied over H-ZSM-5, H-Y and Al-MCM-41 at pressures between 4 and 6MPa and temperatures between 558 and 748K, using a combination of experimental and theoretical approaches. The primary reaction for n-hexane conversion over H-ZSM-5 was cracking, whereas the primary reaction over H-Y and Al-MCM-41 was isomerization. In contrast, cracking was the primary reaction of n-dodecane over all of the aluminosilicates. Turnover frequencies (TOFs) for n-hexane and n-dodecane conversion over H-ZSM-5 were much greater than for H-Y and Al-MCM-41 under all tested reaction conditions. The invariance of TOFs for n-hexane conversion over H-ZSM-5 and H-Y over the pressure range studied indicated that the reaction was nearly zero-order in hydrocarbon at the supercritical conditions used here. Configurational-bias Monte Carlo simulations indicate that the loadings of reactant molecules reached only about half of their saturation values at the experimental conditions, but plateaus in the adsorption isotherms of n-hexane in H-ZSM-5 and of n-dodecane in both H-ZSM-5 and H-Y zeolites account for the nearly zero-order kinetics. At supercritical conditions, the apparent activation energy of n-dodecane cracking over H-ZSM-5, H-Y and Al-MCM-41 as well as that for n-hexane cracking over H-ZSM-5 was associated with the rate constant for CC bond cleavage (156–200kJmol−1). Density-functional theory calculations show that for n-hexane conversion over H-ZSM-5, β-scission from the bound alkoxide possesses the highest barriers, ranging from 167–177kJmol−1 depending on the mode of cracking. The intrinsic activation barriers for isomerization and hydride transfer reactions were calculated to be significantly lower, at 94 and 96–124kJmol−1, respectively, although still higher than the experimentally observed value of 74±6kJmol−1 for n-hexane conversion over H-Y. Rate expressions derived for monomolecular cracking, bimolecular cracking, and isomerization reactions suggest that the differences between the apparent barriers determined experimentally and the intrinsic barriers calculated theoretically are likely due to the competing hydrocarbon adsorption or quasi-equilibrated exothermic reaction steps. The increased selectivity to cracking over isomerization for n-hexane in H-ZSM-5 was attributed to the difficulty of product removal from the zeolite and, for n-dodecane, to the greatly reduced β-scission barriers and the much stronger product adsorption.

A water-assisted nucleophilic mechanism utilized by BphD, the meta-cleavage product hydrolase in biphenyl degradation

As members of the α/β-hydrolase superfamily, Meta-cleavage product (MCP) hydrolases generally utilize a Ser-His-Asp catalytic triad to hydrolyze the cleavage of CC bond during the aerobic catabolism of aromatic compounds by bacteria. BphD is one kind of MCP hydrolase that catalyzes the hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) to 2-hydroxypenta-2,4-dienoic acid (HPD) and benzoate. In this article, a combined quantum mechanics and molecule mechanics (QM/MM) approach has been employed to explore the reaction mechanism of BphD from Burkholderia xenovorans LB400. On the basis of the recently resolved crystal structures, three computational models have been constructed. Our calculation results reveal that BphD utilizes a water-assisted nucleophilic mechanism, which contains acylation and deacylation stages. In acylation reaction, an active site water molecule assists the proton transfer from Ser112 to the carbanion intermediate (substrate) by forming hydrogen bonds with Ser112 and His265, and this proton transfer is in concert with the nucleophilic attack of deprotonated Ser112 on the C6-carbonyl of substrate to form the acylated intermediate. In deacylation, the Asp237-His265 dyad acts as a general base to activate the hydrolytic water, whose nucleophilic attack leads to the collapses of acyl-enzyme intermediate. The acylation and deacylation process correspond to the highest energy barriers of 21.0 and 23.9kcal/mol, respectively. During the catalytic reaction, the active site water and Asp237-His265 dyad play an important role for each elementary steps.

Highly efficient C[sbnd]Cl bond cleavage and unprecedented C[sbnd]C bond cleavage of environmentally toxic DDT through molecular electrochemical catalysis

The electrocatalytic properties of a Co(II)octaalkoxyphthalocyanine complex (Co(II)Pc) with eight strongly electron-donating substituents provide the first example of the complete dechlorination of DDT through molecular electrocatalysis, rather than the use of metal electrodes which had been achieved previously. Interaction with a highly nucleophilic [Co(I)Pc]2− species results in rapid cleavage of the C(sp3)Cl, C(sp2)Cl and aromatic C(sp2)Cl bonds. Bis(p-chlorophenyl)methanone (BPCl2) is detected in high yield along with its full dechlorination product, diphenylmethanone (BP) and the conventional CCl bond cleavage products, due to an unprecedented CC bond cleavage reaction that is followed by the formation of a C−O bond. Theoretical calculations are used to analyze trends in the electronic structure of the Co(II)octaalkoxyphthalocyanine complex that account for the efficiency of the CCl bond cleavage reactions, and the reaction process and mechanism are analyzed in depth.

An oxidovanadium(IV) complex having a perrhenato ligand: An efficient catalyst for aerobic oxidation reactions of benzylic and propargylic alcohols

An oxidovanadium(IV) complex having a perrhenato ligand [VO(ReO4)(4,4′-tBubpy)2][0.25SO4·0.5ReO4] (4,4′-tBubpy=4,4′-di-tert-butyl-2,2′-bipyridine) efficiently catalyzes not only dehydrogenative oxidation of benzylic and propargylic mono-alcohols but also oxidative CC bond cleavage of meso-1,2-diaryl-1,2-ethanediols under atmospheric molecular oxygen, affording the corresponding carbonyl compounds in good yield.

Study of thermal maturation processes of sulfur-rich source rock using compound specific sulfur isotope analysis

Semi-open pyrolysis experiments were conducted on a thermally immature, organic and sulfur-rich source rock (Ghareb Formation, Israel). Structural and sulfur isotope ratio (34S/32S) changes in specific organic sulfur compounds were studied along with bulk sulfur phases (H2S, kerogen, oil) during thermal maturation and oil formation. Oil, gas and rock samples were collected sequentially at several points along the maturation path and were analyzed. In addition, four natural crude oils from Israel were analyzed and the results were compared to the pyrolytic oils.The results showed relatively large δ34S variability (∼10‰) of the organic sulfur compounds (OSCs) in the bitumen of the unheated rock and first pyrolytic oil. This variability was probably a remnant of the original sulfur isotopic signature acquired during the sulfurization of the organic matter in the early diagenetic process. At later stages of thermal maturation, the variability of the sulfur isotopic values in the kerogen gradually decreased to ∼2‰. Three mechanisms were suggested to explain the structural changes and isotopic fractionations of OSCs in the kerogen and generated oils: (A) Cleavage of weak SS and CS bonds leading to the release of large amounts of H2S and to cyclization of the precursors in the kerogen with small fractionations. Thus, the OSCs released by this mechanism preserved their distinct δ34S values. (B) Re-reaction of the released S species with hydrocarbons and generation of new OSCs within the kerogen (or bitumen) matrix. (C) Cleavage of stronger CC bonds and transformation of OSCs to create more stable compounds (e.g. dibenzothiophenes) from multiple sulfur sources. Mechanisms (B) and (C) homogenized the δ34S values of the different OSCs which reflected that of the bulk kerogen.The bulk organic sulfur phases (bitumen, oil, kerogen) were 34S enriched by<1‰ despite large amounts of 34S-depleted H2S (53% of total S) that was released continuously (“open system”). Therefore, the preferential loss of H2S during thermal maturation may not be responsible to the 34S enrichment of oils as reported in some petroleum basins. The overall outcome of the maturation process yields OSCs with δ34S values that closely reflect the kerogen and can be used as a fingerprint for oil-oil and oil-source rock correlation over wide ranges of thermal maturity. The applicability of such correlation is demonstrated by the very good correlation of δ34S values of specific OSCs between artificial and natural oil samples.

Transformation of biomass polyol into hydrocarbon fuels in aqueous medium over Ru-Mo/CNT catalyst

The hydrodeoxygenation (HDO) of sorbitol in aqueous medium was performed over CNT supported Ru-Mo bimetallic catalyst. Compared with Ru-Mo/AC, Ru-Mo/CNT showed higher yield and selectivity towards C5/C6 alkanes due to the higher relative rate of CO vs. CC bond cleavage of sorbitol. Based on TEM, XPS and H2-TPR characterizations, the role of CNT in HDO reaction was studied to clarify the likely reasons for the selective CO vs. CC bond cleavage. It is suggested that an increase concentration of MoOx (x<3) species and a smaller metal particle size in the Ru-Mo/CNT catalyst are key factors for the improvement of HDO performance.

Hydrogen from glycerol steam reforming with a platinum catalyst supported on a SiO2-C composite

This work studies 2 wt% Pt catalysts. The support is a SiO2-C composite whose main features are a high specific surface due to its mesoporosity, a higher thermal stability than the C support, and the absence of surface acid sites which could promote the dehydration reactions that produce coke precursors. The Pt/SiO2-C catalyst has very small metallic particles (dva = 1.37 nm) that favor the CC bond cleavage reactions which allow obtaining total gas conversion at 450 °C. With this catalyst, it is possible to obtain high yields to H2, between 4 and 5, which indicates that the active sites promote the WGS reaction, even with glycerol concentrations of 30 and 50%. Pt/SiO2-C is a very stable catalyst since it loses only 10% of its initial activity after 66 h on stream and is resistant to sintering and coke deposition.

Steam reforming of acetic acid over MgAl2O4-supported Co and Ni catalysts: Effect of the composition of Ni/Co and reactants on reaction pathways

The steam reforming of acetic acid (AcH), a model compound of pyrolysis-oil, was studied over MgAl2O4-supported Co-Ni catalysts with different Co/Ni ratios, prepared by impregnation using the incipient wetness method. The catalysts were characterized by X-ray powder diffraction, temperature programmed reduction, temperature programmed desorption, and thermogravimetry. In the steam reforming reaction of AcH, both Ni and Co catalysts suffered partial oxidation due to contact with the reaction mixture. The ketonization reaction occurred on the MgAl2O4 support and the presence of Co or Ni changed the reaction pathway of species adsorbed on the support, which suppressed the formation of acetone. The cleavage of CC bonds was favored on the Ni surface, resulting in CHx species, which in the presence of H2 were preferentially hydrogenated to CH4 at low temperatures. On the other hand, on the Co surface the CHx species were decomposed to C* and H* as the temperature increased. The addition of Co to Ni catalysts inhibited CH4 formation and carbon accumulation.

Structure, activity, and selectivity of bimetallic Pd-Fe/SiO2 and Pd-Fe/γ-Al2O3 catalysts for the conversion of furfural

The conversion of furfural has been investigated in vapor and liquid phases over a series of supported monometallic Pd and bimetallic Pd-Fe catalysts. Over the monometallic Pd/SiO2 catalyst, the decarbonylation reaction dominates, yielding furan as the main product. By contrast, over the bimetallic Pd-Fe/SiO2 catalyst a high yield of 2-methylfuran is obtained with much lower yield to furan. Interestingly, changing the catalyst support affects the product distribution. For instance, using γ-Al2O3 instead of SiO2 as support of the bimetallic catalyst changed the dominant product from 2-methylfuran to furan. That is, Pd-Fe/γ-Al2O3 behaves more like monometallic Pd/SiO2 than bimetallic Pd-Fe/SiO2. A detailed characterization of the catalysts via XPS, XRD, and TEM indicated that a Pd-Fe alloy is formed on the SiO2 support but not on the γ-Al2O3 support. Theoretical density functional theory calculations suggest that on the Pd-Fe alloy binding of the furan ring to the surface is weakened compared to on pure Pd. This weakening disfavors the ring hydrogenation and decarbonylation paths, while the oxophilic nature of Fe atoms enhances the interaction of the CO and the OH groups with the metal surface, which favors the CO hydrogenation and CO bond cleavage paths. The presence of the solvent has a less pronounced effect, but clearly has a stronger inhibition on CC bond cleavage (decarbonylation to furan) than on CO bond cleavage (hydrogenolysis to methylfuran).

Oxidative C(OH)[sbnd]C bond cleavage of secondary alcohols to acids over a copper catalyst with molecular oxygen as the oxidant

Selective oxidative cleavage of CC bond is pivotal for producing functionalized molecules, useful for organic synthesis and biomass utilization. We herein report the oxidative C(OH)C bond cleavage of secondary alcohols to acids over a copper/1, 10-phenanthroline complex with molecular oxygen as the oxidant. A wide range of secondary alcohols are converted into acids with up to 98% yields. More interestingly, it is effective for breaking up lignin model systems into acids, which is rarely achieved in previous studies. Density functional theory (DFT) calculations indicate a copper-oxo-bridged oxygen dimer is the active species for the CH bond cleavage which is the rate-determining step for CC bond.

Use of chemical descriptors approach and DFT to analyze the C[sbnd]C bond cleavage on Pt3Re1 alloy in the ethanol oxidation reaction for fuel cells

Design of selective catalysts able to cleave CC bond in ethanol oxidation reaction at low temperatures is primordial for improving the direct ethanol proton exchange membrane fuel cells (DEFCs). PtRe mixture could be an appropriate alloy for the CC bond cleavage in ethanol decomposition, but yet, it has not been studied in detail the reactivity of this alloy for this step. In this work, the reactivity of Pt3Re1 surface for the CC bond cleavage is studied and compared with pure metal surfaces Pt and Re, using chemical descriptors through density functional theory (DFT) calculations. The adsorption energies of CHCO, CO and CH molecules are the chemical descriptors investigated and the results are analyzed with respect to the electronic structure of the surface in order to understand the nature of the active sites. It is found that the addition of Re to Pt leads to form an active site with a Re atom, which is more reactive for the CC bond cleavage in CHCO, but the sites without Re become less reactive for this step. Then the addition of Re to Pt has not a significant effect on the promotion of full oxidation of ethanol, since not all sites at the Pt3Re1 surface are more active towards CC bond cleavage.

Carbon nanotube supported PdAg nanoparticles for electrocatalytic oxidation of glycerol in anion exchange membrane fuel cells

Electro-oxidation of alcohol is the key reaction occurring at the anode of a direct alcohol fuel cell (DAFC), in which both reaction kinetics (rate) and selectivity (to deep oxidation products) need improvement to obtain higher power density and fuel utilization for a more efficient DAFC. We recently found that a PdAg bimetallic nanoparticle catalyst is more efficient than Pd for alcohol oxidation: Pd can facilitate deprotonation of alcohol in a base electrolyte, while Ag can promote intermediate aldehyde oxidation and cleavage of CC bond of C3 species to C2 species. Therefore, a combination of the two active sites (Pd and Ag) with two different functions, can simultaneously improve the reaction rates and deeper oxidation products of alcohols (Applied Catalysis B, 2016, 199, 494). In this continuing work, Pd, Ag mono, and bimetallic nanoparticles supported on carbon nanotubes (Ag/CNT, Pd/CNT, Pd1Ag1/CNT, and Pd1Ag3/CNT) were prepared using an aqueous-phase reduction method; they served as working catalysts for studying electrocatalytic oxidation of glycerol in an anion-exchange membrane-based direct glycerol fuel cell. Combined XRD, TEM, and HAADF-STEM analyses performed to fully characterize as-prepared catalysts suggested that they have small particle sizes: 2.0nm for Pd/CNT, 2.3nm for PdAg/CNT, 2.4nm for PdAg3/CNT, and 13.9nm for Ag/CNT. XPS further shows that alloying with Ag results in more metal state Pd presented on the surface, and this may be related to their higher direct glycerol fuel cell (DGFC) performances. Single DGFC performance and product analysis results show that PdAg bimetallic nanoparticles can not only improve the glycerol reaction rate so that higher power output can be achieved, but also facilitate deep oxidation of glycerol so that a higher faradaic efficiency and fuel utilization can be achieved along with optimal reaction conditions (increased base-to-fuel ratio). Half-cell electrocatalytic activity measurement and single fuel cell product analysis of different glycerol oxidation intermediates, including C3: glycerate, tartronate, mesoxalate, and lactate; C2: glycolate and oxalate, over PdAg/CNT catalyst was further conducted and produced deeper insight into the synergistic effects and reaction pathways of bimetallic PdAg catalysts in glycerol electrocatalytic oxidation.

Degradation of lignin in NaVO3-H2SO4 aqueous solution with oxygen

Catalytic oxidation of lignocellulose in hydrothermal condition catalyzed by vanadium-containing homogeneous catalysts is a promising method to prepare formic acid (FA), a potential material in emerging field of clean energy technologies. The FA production from polysaccharides components of lignocellulose has already been well studied. However, the conversion of lignin component, which quite differs in structure from polysaccharides, has not been studied systematically. In this work, the lignin degradation was studied in NaVO3-H2SO4 aqueous solution with O2 as oxidant. The degradation mechanism was studied in detail. Compared with polysaccharides, lignin can produce a much lower yield of FA with a formation of a larger amount of CO2. H2SO4 can catalyze highly-polymerized lignin to segments by CO bond hydrolytic cleavage, but the conversion is limited. NaVO3 and O2 can accelerate the lignin degradation by weakening the CO bond. In liquid phase, NaVO3 and O2, with a low selectivity on products, lead to different kinds of reactions, mainly including phenolic hydroxyl oxidation to quinone, aliphatic hydroxyl oxidation to ketone/aldehyde, aliphatic CC bond cleavage, intramolecular dehydration and decarboxylation. This study gives a deep understanding of lignin transformation during catalytic oxidation, and provides guidance to the further application of FA production from natural lignocellulose.

Reactivity of lignin model compounds through hydrogen transfer catalysis in ethanol/water mixtures

The conversion of lignin into useful bio-based chemicals and fuels requires a fundamental understanding of the reaction mechanisms involved in the cleavage of the specific chemical bonds that constitute its polymeric structure. The catalytic conversion of eight lignin model compounds emulating various CO and CC bond of lignin was explored in a batch reactor with a Pt/C catalyst in ethanol/water mixtures, using ethanol as both H-donor and solvent. The order of reactivity for hydrogenolysis of CO model bonds was found: βO4>αO4>>4O5, the 4O5 bond exhibiting a very low reactivity. Phenolic hydroxyl and methoxyl groups were unreactive, whereas aliphatic hydroxyl groups could be eliminated by dehydration, leading to an overall partial deoxygenation. α-1 model CC bonds were also cleaved by hydrogenolysis, but β-1 model CC bonds were not. The cleavage of CO and CC bonds obtained by H-transfer catalysis in water-ethanol mixtures was very selective, intermediate products were sometimes detected before full reaction completion but no decomposition or degradation products.

Oxidative Recyclization of 1H-Indoles for Synthesis of 2-Indolylbenzoxazinones via Cleavage of the C2-C3 Bond with AIBN under Air.

A novel and concise method for the oxidation of unprotected indole derivatives to synthesize 2-indolylbenzoxazinones in the presence of AIBN under open air has been successfully demonstrated. This metal-free reaction is both atom- and step-efficient and is applicable to a broad scope of substrates. This new methodology provides a facile pathway for oxidative C2-C3 bond cleavage and recyclization of 1H-indoles.

Hydroconversion of methyl laurate on bifunctional Ni2P/AlMCM-41 catalyst prepared via in situ phosphorization using triphenylphosphine

A series of Ni2P/AlMCM-41-x bifunctional catalysts with different Si/Al ratios (x) were synthesized by in situ phosphorization of Ni/AlMCM-41-x with triphenylphosphine (nominal Ni/P ratio of 0.75) at 300°C on a fixed-bed reactor. For comparison, NiP/AlMCM-41-5-TPR was also prepared by the TPR method from the supported nickel phosphate with the Ni/P ratio of 1.0, during which metallic Ni rather than Ni2P formed. TEM images show that Ni and Ni2P particles uniformly distributed in Ni2P/AlMCM-41-x and NiP/AlMCM-41-5-TPR. The Ni2P/AlMCM-41-x acidity increased with decreasing the Si/Al ratio. In the hydroconversion of methyl laurate, the conversions were close to 100% on all catalysts at 360°C, 3.0MPa, methyl laurate WHSV of 2h−1 and H2/methyl laurate ratio of 25. As to Ni2P/AlMCM-41-x, with decreasing the Si/Al ratio, the total selectivity to C11 and C12 hydrocarbons decreased, while the total selectivity to isoundecane and isododecane (Si-C11+i-C12) firstly increased and then decreased. Ni2P/AlMCM-41-5 gave the largest Si-C11+i-C12 of 43.2%. While NiP/AlMCM-41-5-TPR gave higher Si-C11+i-C12 than Ni2P/AlMCM-41-5, it was more active for the undesired CC bond cleavage and methanation. We propose that the in-situ phosphorization adopted here is a promising approach to preparing Ni2P-based bifunctional catalysts.

Structural features and thermal degradation behaviors of extracts obtained by heat reflux extraction of low rank coals with cyclohexanone

Investigation on the properties of mobile phase in low rank coals and its pyrolysis characteristics is an alternative approach for understanding the pyrolysis mechanism and structure features of these coals. In this work, heat reflux extraction with cyclohexanone (CYC) was developed to dissolve the mobile phases in two low rank coals and afford one extract from Chifeng coal (ECF) and another extract from Hami coal (EHM). The structural features of the extracts were investigated using multiple analytical techniques first. Then, thermal reactivity and gaseous product evolution of the extracts, residues, and raw coals were evaluated by TG–FTIR. Detailed volatile specie composition during fast pyrolysis of extracts were further detected on the pyrolysis gas chromatography/time of flight mass spectrometer (Py–GC/TOF–MS). The results suggest that heat reflux extraction with CYC is an effective method for dissolving a fairly high fraction of the organic matters in low rank coals. Two low rank coals mainly showed one mass loss stage of devolatilization of the organic matters near 430°C and large numbers of gaseous products were released such as hydrocarbons (CH4, C2H4, C2+ aliphatics, and arenes), CO2, CO and CO bonds containing species, which were the result of the cracking and cleavage of the alkyl sides, strongly bonded functional groups, and bridged bonds, respectively. Forming of CO during pyrolysis of low rank coals was mainly derived from the cracking of the O-containing primary tar fragment and the condensation reactions of the aromatic clusters above 600°C rather than from the initial cleavage of the organic structures in low rank coals. Thermal dissolution effect of CYC can depolymerize the macromolecular structure of raw coals and thereby the dissociated coal structures (residues) are beneficial to crack the alkyl side chains and break the O-containing structures at lower temperatures. Two extracts can be pyrolyzed at temperatures lower than that of their parent coals and large quantities of O-containing gaseous products and C2+ aliphatics release during pyrolysis process. Furthermore, aliphatic hydrocarbons, arenes, ketones, phenols, and benzofurans are the most abundant species in the products during fast pyrolysis of both two extracts. Notably, the cleavage of CC bonds near the aromatic rings in longer-chain alkylbenzenes is a crucial reaction during fast pyrolysis of ECF and EHM.

New protocol of copper-catalyzed oxidative C(CO)[sbnd]C bond cleavage of aryl and aliphatic ketones to organic acids using O2 as the terminal oxidant

Catalytic oxidation of CC bond is a key technology to transform petroleum-based as well as sustainable biomass feedstock into more valuable oxygenates. We herein describe a convenient and useful oxidation strategy of converting ketones into carboxylic acids using homogeneous copper catalyst without additives and with O2 as the terminal oxidant. A wide range of aryl and aliphatic ketones as well as β–O–4 lignin models were selectively oxidized to acids via CC bond cleavage. Mechanism studies by EPR and in situ NMR elucidate the principles of Cu/O2 reactivity that involves CH bond and O2 activation via a peroxide species. This provides an important foundation for expanding the scope of useful aerobic oxidation reactions using copper catalysts.

Pt20RuxSny nanoparticles dispersed on mesoporous carbon CMK-3 and their application in the oxidation of 2-carbon alcohols and fermentation effluent

We report the synthesis of Pt-Sn binary and Pt-Ru-Sn ternary alloy nanoparticles (NPs) dispersed on mesoporous carbon CMK-3 for bioalcohol fuel cell applications where ethanol, ethylene glycol, and fermentative hydrogen production effluent were used as the fuels. The proposed alloy electrocatalysts, denoted as Pt20RuxSny@C (where 20, x, and y represent the weight fractions of Pt, Ru, and Sn, respectively), were examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction analysis, and electrochemical measurements, in order to determine their morphologies, microstructures, compositions, phase structures, and electrochemical characteristics. The effects of the Sn content on the following factors were examined: 1) average particle size of the alloy NPs, 2) mesoporosity, 3) electrochemically active surfaces of Pt20RuxSny@C, and 4) ethanol oxidation reaction and ethylene glycol oxidation reaction activities. Higher Sn contents improved the catalytic efficiency of Pt20RuxSny when x=0 or x=10, with the optimized compositions being Pt20Sn30 and Pt20Ru10Sn15 for the binary and ternary alloys, respectively. Based on the ethanol and ethylene glycol oxidation reactions, we explain the role of Sn in promoting CC bond cleavage and in improving catalyst tolerance against poisoning. Overall, for both the ethanol system and the ethylene glycol system, the catalytic activities could be arranged as follows: Pt20Ru10Sn15@C>Pt20Sn30@C>Pt20Ru10@C>Pt20@C. The chronoamperometric measurement shows that Pt20Ru10Sn15@C is more stable than commercial E-TEK Pt/C catalyst under ethanol environment. Finally, the catalyst Pt20Ru10Sn15 was used successfully to demonstrate the feasibility of using the bioalcohol from a fermentation effluent as a fuel.