Mo oxide modified catalysts for direct methanol, formaldehyde and formic acid fuel cells

Pt black and PtRu black fuel cell anodes have been modified with Mo oxide and evaluated in direct methanol, formaldehyde and formic acid fuel cells. Mo oxide deposition by reductive electrodeposition from sodium molybdate or by spraying of the fuel cell anode with aqueous sodium molybdate resulted in similar performance gains in formaldehyde cells. At current densities below ca. 20 mA cm⁻², cell voltages were 350–450 mV higher when the Pt catalyst was modified with Mo oxide, but these performance gains decreased sharply at higher current densities. For PtRu, voltage gains of up to 125 mV were observed. Modification of Pt and PtRu back catalysts with Mo oxide also significantly improved their activities in direct formic acid cells, but performances in direct methanol fuel cells were decreased.     

Oxidation of methanol at copper surfaces

The role of preadsorbed oxygen present at Cu(111), Cu(110) and polycrystalline surfaces in the oxidation of methanol has been investigated by X-ray and electron energy loss spectroscopies. In addition to the well established formation of methoxy species and its subsequent decomposition and desorption as formaldehyde, a second reaction pathway to surface formate is present. The latter is temperature dependent being undetectable at 260 K at a polycrystalline surface but occurs at a significant rate at 295 K and above. The limitations of experimental data for methanol oxidation by temperature programmed desorption and molecular beam techniques are discussed.     

甲酸甲酯水解法制甲酸装置技术经济分析

介绍了从CO和甲醇合成甲酸甲酯,再经甲酸甲酯水解制甲酸的工艺方法,并就该工艺的国内外技术进展和市场前景做了阐述。对2万t／a甲酸装置进行初步经济分析,表明此生产方法具有良好的经济效益和应用前景。     

Linear free energy relationships for C1-oxygenate decomposition on transition metal surfaces

Linear free energy relationships for the decomposition of formate and methoxide intermediates on metal surfaces have been developed. These demonstrate that Group VIII and Group IB metals do not obey the same correlations. Implications of these observations include the potential for misinterpretation of classical Balandin volcano plots.     

Role of ZnO in methanol synthesis on copper catalysts

The varied results obtained by different groups concerning synergy between ZnO and Cu metal in methanol synthesis catalysts are shown to be a result of different experimental test conditions. It is suggested that synergy, when it occurs, arises from H spillover from ZnO to Cu metal. This revised version was published online in July 2006 with corrections to the Cover Date.     

甲酸催化玉米芯水解生成木糖的动力学

玉米芯是一种价格低廉、可再生的资源,其可以被用来生产高附加值的化工产品。本文主要研究在甲酸质量分数3%、液固比为10mL/g、反应温度（120～150℃）、反应时间（0～240min）条件下玉米芯中半纤维素水解过程。采用两相模型对玉米芯水解过程中木糖浓度进行拟合并得到反应过程的动力学参数。木糖降解反应的活化能大于其生成反应的活化能,这表明高温不利于木糖的生产。对得到动力学方程进行分析,获得最佳的反应条件：甲酸质量分数3%、液固比10mL/g、反应温度140℃、反应时间180min。最佳反应条件下得到的木糖浓度为26.9 g/L。     

甲酸生产的技术经济评选

介绍了甲酸的国内外市场状况及甲酸甲酯法生产甲酸的技术进展，对１万ｔ／ａ甲酸生产装置进行了经济评价。     

Selective conversion of glucose into lactic acid and acetic acid with copper oxide under hydrothermal conditions

Biomass as a source for chemicals production attracts growing attention due to the decreasing storage of fossil fuels and global warming caused by emission of CO₂. In this study, conversion of glucose with copper oxide (CuO) was studied under alkaline hydrothermal conditions using a batch reactor and continuous flow reactor. CuO, as an oxidant, greatly improves the yields of lactic acid (LA) and acetic acid from glucose and was reduced into Cu₂O and Cu. Selective production of LA with the highest yield of 59% and acetic acid with the highest yield of 32% can be achieved by controlling reaction time, temperature, and addition of CuO. A possible mechanism of conversion of glucose with CuO was proposed. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2096–2104, 2013     

Catalytic performance of sulfate-grafted graphene oxide for esterification of acetic acid with methanol

Graphene oxide possesses tremendous mechanical and electronic properties in combination with large surface area and accessible active sites leading to the development of novel innovative heterogeneous catalysts. The present study elaborates the catalytic activity of graphene oxide, enhanced by grafting active sulfate groups on its surface to result as a superior catalyst. The catalyst was evaluated in the model acetic acid esterification reaction with methanol in terms of acid conversion. Catalysts consisting of varied sulfate concentrations and calcination time were synthesized and optimized for its best catalytic activity. The prepared catalysts (GO-SO₄) were characterized using XRD, FT-IR, SEM-EDS, XPS, and BET. A 44% enhancement in catalyst activity was observed using sulfate-grafted graphene oxide (GO-SO₄) catalyst over bare GO due to the synergistic effect of sulfate ions. The catalyst can be separated out by simple filtration. Further, the influence of operating process parameters including catalyst loading, and the reaction temperature was evaluated toward the maximum acid conversion. In addition, the detailed kinetic study was also done in this system using Pseudo-homogeneous model.     

碳载PdCo合金催化剂对甲酸的电催化氧化

用间歇式微波法制备了不同Pt：Co原子比的碳载PdCo合金催化剂（PdCo／C）,发现在酸性溶液中Pd：Co原子比2：1催化剂对甲酸的电氧化有良好的催化活性和稳定性。从H在电极表面的吸脱附峰计算出来的结果表明,催化剂中加入一定比例的金属Co能够增加催化剂的电化学比表面。     

The conversion of polysaccharides to hydrogen gas. Part I: The palladium catalysed decomposition of formic acid/sodium formate solutions

The palladium catalysed decomposition, to H₂+CO₂, of solutions containing formic acid and sodium formate, in various proportions, has been studied in a stirred reactor in the temperature range 60–90°C. The production of hydrogen gas was at its optimum in the pH range 3.8–6.5 and the order of reaction varied with the solution composition from 0.33 (100 mol % formic acid) to 1.07 (100 mol% formate ion). Energies of activation lay in the range 20±9.5 kJ mol^?1–41.8±7 kJ mol^?1, the larger values occurring at the ends of the composition range. Electrode potential measurements were also performed and these were helpful in explaining the (i) cessation of hydrogen production at low HCOO^? ion concentrations before completion of reaction and (ii) the possible nature of catalyst poisons. In no case was the theoretical quantity of hydrogen obtained, although yields >90% can be achieved. It is proposed that reaction proceeds via a surface formate intermediate with different rate determining steps operating at high and low HCOO^? ion concentrations. A number of reversible catalyst poisons are discussed including carbon monoxide and methyl formate, which appear to be the most likely.     

络合萃取法分离甲酸稀溶液的研究

以三辛胺TOA为络合萃取剂,正辛醇稀释改质剂,对甲酸稀溶液进行络合萃取研究.讨论了萃取剂在有机相中的浓度、萃取平衡温度和盐析效应对萃取过程的影响,并对萃取剂进行再生利用;实验结果表明在室温条件下,萃取剂采取37％TOA+ 63％正辛醇有较好的萃取效果,加入盐析剂后萃取率达到99％以上;并利用红外光谱法对萃取特征和机理进行进一步探讨.     

Kinetic studies of alkyl formate hydrolysis using formic acid as a catalyst

BACKGROUND: The hydrolysis of methyl formate is the major industrial process for the production of formic acid. The aim of the work is to determine the reaction kinetics quantitatively in the presence of formic acid catalyst, develop a mathematical model for the reaction system and estimate the kinetic parameters for the purpose of optimization. RESULTS: Liquid phase hydrolysis kinetics of alkyl formates (ethyl and methyl formate) was studied in an isothermal batch reactor at 80–110 °C and 20 bar nitrogen pressure. The catalyst of choice was formic acid. The reaction rate was enhanced but the formic acid product yield was slightly suppressed relative to the uncatalysed system. A kinetic model comprising mass balances and rate equations was developed and the kinetic and equilibrium parameters included in the rate equations were estimated from the experimental data with non‐linear regression analysis. CONCLUSION: The model was able to predict the experimental results successfully. The results obtained were compared quantitatively with an earlier model involving alkyl formate hydrolysis in a neutral aqueous solution. Copyright © 2011 Society of Chemical Industry     

Improvements of electrocatalytic activity of PtRu nanoparticles on multi-walled carbon nanotubes by a H2 plasma treatment in methanol and formic acid oxidation

A H₂ plasma has been used to treat the PtRu nanoparticles supported on the plasma functionalized multi-walled carbon nanotubes (PtRu/PS-MWCNTs). The plasma treatment does not change the size and crystalline structure of PtRu nanoparticles, but reduces the fraction of the oxidized species at the outermost perimeter of particles. The electrochemical results show that these plasma treated PtRu/PS-MWCNTs exhibit increased electrochemically active surface area, improved electrocatalytic activity and long term stability toward methanol and formic acid oxidation, and enhanced tolerance to carbonaceous species relative to the sample untreated with the H₂ plasma. The electrocatalytic activities of the plasma treated PtRu/PS-MWCNTs are found to be dependent upon the Pt:Ru atomic ratios of PtRu nanoparticles. The catalysts with a Pt:Ru atomic ratio close to 1:1 show superior properties in the electrooxidation of methanol and formic acid at room temperature and better tolerance to carbonaceous species.     

甲酸生产工艺技术及应用

甲酸是甲醇深加工的重要下游产品之一。本文对甲酸钠法、丁烷液相氧化法、甲酰胺法、甲酸甲酯水解法制甲酸生产工艺进行了对比分析,同时简要介绍了甲酸生产与消费情况。     

活性炭改性对用于甲酸分解的Pd/活性炭催化剂的影响

采用磁力搅拌法和水浴振荡法制备应用于甲酸分解的Pd/活性炭(AC)催化剂,研究了活性炭载体改性和制备方法对催化剂分解甲酸性能的影响。采用恒温水浴振荡装置,在80℃水浴中进行甲酸催化分解反应,以甲酸的催化分解率评价催化剂催化活性。结果表明,以经过不同的酸、碱、盐溶液改性后的活性炭为载体采用不同方法制备的Pd/AC催化剂对甲酸的催化分解效果不同,以Na2CO3改性的活性炭为载体采用磁力搅拌法制备的催化剂活性最好,甲酸水溶液的分解率达85%以上,含甲酸的工业废水的分解率达70%。     

Selective kinetic deactivation model for methanol synthesis from simultaneous reaction of CO2 and CO with H2 on a commercial copper/zinc oxide catalyst

A kinetic model for the deactivation of copper/zinc oxide catalyst during the methanol synthesis has been developed. This model is of the Langmuir-Hinshelwood-Hougen-Watson type and considers two types of active sites for the deactivation of catalyst. One of the site types on copper is allocated for the deactivation of the catalyst due to carbon dioxide while another type is assigned for the deactivation of the catalyst due to carbon monoxide. The parameters of the deactivation rate equations based on the above concept have been determined using the experimental data of Hoffmann (1993). The validity of the deactivation model has been checked by comparing the results predicted by the model with experimental data different than of those used to evaluate the parameters of the model. The good agreement that noticed in this comparison confirmed the idea that CO and CO₂ are responsible at different extent for the deactivation of Cu/ZnO catalyst during methanol synthesis.     

Electro-oxidation mechanisms of methanol and formic acid on Pt-Ru alloy surfaces

Voltammetry combined with single-potential alteration infrared spectroscopy (SPAIRS) were used to study the extent of adsorbed CO produced at Pt, Ru and Pt-Ru alloy electrodes during methanol and formic acid oxidation in acidic supporting electrolyte. The addition of even small atomic fractions of Ru to Pt surfaces caused a decrease in the quasi-steady-state level of CO on the surface for both reactions. This result is consistent with the bifunctional mechanism proposed previously: Ru sites nucleate oxygen containing species at ≈0.2-0.3 V lower potential than on the pure Pt surface; the adsorption of methanol occurs on Pt ensembles producing adsorbed CO; in the case of formic acid, adsorption is equally facile at Pt-Pt, Pt-Ru and Ru-Ru sites, with dehydration producing adsorbed CO; the further electro-oxidation of CO is catalyzed by oxygen-containing species nucleated onto nearby by Ru atoms. The improved efficiency of the alloy surfaces for oxidation of adsorbed CO at low potential shifts the rate limiting step to the adsorption step, which results in very low coverages of the surfaces by adsorbed CO.     

Transient measurements of lattice oxygen in photocatalytic decomposition of formic acid on TiO2

In the absence of gas-phase O₂, formic acid extracted lattice oxygen from TiO₂ during photocatalytic decomposition (PCD) at room temperature. The amount of oxygen extracted was determined by interrupting PCD of a monolayer of formic acid after various reaction times and measuring O₂ uptake in the dark. After surface oxygen was depleted by PCD, oxygen diffused from the bulk to replenish the surface oxygen vacancies. The rate of oxygen diffusion to the surface was determined by measuring O₂ uptake after various dark times. A small fraction of the CO₂ that formed during PCD remained on the reduced sites of the TiO₂ surface, but this CO₂ was displaced by O₂ adsorption at room temperature.