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Electrodeposited Pt and Pt-Sn nanoparticles on Ti as anodes for direct methanol fuel cells
Electro-oxidation of methanol was studied on titanium supported nanocrystallite Pt and Ptx-Sny catalysts prepared by electrodeposition techniques. Their electro-catalytic activities were studied in 0.5mol/L H2SO4 and compared to those of a smooth Pt, Pt/Pt and Pt-Sn/Pt electrodes. Platinum was deposited on Ti by galvanostatic and potentiostatic techniques. X-ray diffractometer (XRD) and energy dispersive X-ray (EDX) techniques were applied in order to investigate the chemical composition and the phase structure of the modified electrodes. Scanning electron microscopy (SEM) was used to characterize the surface morphology and to correlate the results obtained from the two electrochemical deposition methods. Results show that modified Pt/Ti electrodes prepared by the two methods have comparable performance and enhanced catalytic activity towards methanol electro-oxidation compared to Pt/Pt and smooth Pt electrodes. Steady state Tafel plots experiments show a higher rate of methanol oxidation on a Pt/Ti catalyst than that on a smooth Pt. Introduction of a small amount of Sn deposited with Pt improves the catalytic activity and the stability of prepared electrode with time as indicated from the cyclic votlammetry and the chronoamperometric experiments. The effect of variations in the composition for binary catalysts of the type Ptx-Sny/Ti towards the methanol oxidation reaction is reported. Consequently, the Ptx-Sny/Ti (x∶y (8∶1), molar ratio) catalyst is a very promising one for methanol oxidation....
2020-07-08 21:52:19浏览：62
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Effect of Lanthanum on Methanol Fuel Exhaust Deep Oxidation over Pall adium Catalyst
The performance of deep oxidation of methanol on supported Pd catalyst was examined by a chromatograph-micro-reactor. The results show that the addition of La into γ-Al2O3 support can affect greatly the performance of the Pd catalyst. In the absence of CO, La can decrease the content of oxygen-containing intermediate, although La can not lower the light-off temperature of methanol oxidation. In the presence of CO, La can lower the light-off temperature, decrease the amount of CO adsorption, and weaken evidently "CO inhibition" to the oxidation of methanol. By XPS technique, it is shown that La modifies the electronic structure of Pd, which attributes to the modifications of the catalytic performance....
2020-07-08 21:52:19浏览：70
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Novel methanol-tolerant Ir-S/C chalcogenide electrocatalysts for oxygen reduction in DMFC fuel cell
Novel methanol-tolerant oxygen-reduction catalysts, iridium-sulphur (Ir-S) chalcogenides with differ ent Ir/S atomic ratios, were synthesized via a precipitation method using H21rCI6 and Na2SO3 as the Ir and S precursors. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the IrxSl-x/C chalcogenide catalysts. Particle size ranging from 2.5 to 2.8 nm though obvious agglomeration was found on carbon support. However, these chalcogenide catalysts showed strong catalytic activity towards the oxygen reduction reaction (ORR) and high methanol tolerance, strongly suggesting these novel catalysts as promising candidates for direct methanol fuel cell (DMFC) cathode applications....
2020-07-08 21:52:19浏览：83
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A Novel Sulfided Mo/C Catalyst for Direct Vapor Phase Carbonylation of Methanol at Atmospheric Press
The direct carbonylation of methanol, without any halide in the feed as a promoter, ispresented. A series of Mo catalysts supported on activated carbon, γ-Al2O3 and SiO2 were prepared.The results show that the support greatly affects the Mo catalyst in the direct vapor-phase carbonylationof methanol, and activated carbon is the best supports of the investigated supports. In addition, therelationships between adsorptions of NH3 and CO and carbonylation of methanol were investigated. A novelsulfided Mo/C catalyst had high activity and selectivity for the vapor phase carbonylation of methanol tomethyl acetate without the addition ofa CH3I promoter to the feed. The reaction conditions were optimizedat a reaction temperature of 573 K, a methanol concentration of 23 mol% and a carbon monoxide spacevelocity of 3,000 L/(kg.h). Under these optimal conditions a methanol conversion of 50%, carbonylationselectivity of 80 mol%, and space-time yield of 8.0 mol/(kg.h) were obtained. The active phase of thisnovel sulfided Mo/C catalyst is the non-crystalline phase, and the active component is present as MoS2.5on the surface of the activated carbon....
2020-07-08 21:52:19浏览：68
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Effect of Rotation Rate on the Formation of Platinum-modified Polyaniline Film and Electrocatalytic
The oxidation of methanol was investigated on platinum-modified polyaniline electrode. Changes in the electrode rotation rates (Ω) during platinum electrodeposition remarkably affect the formation and distribution of platinum in the polymer matrix and consequently lead to different currents of methanol oxidation. The results show that platinum loading is proportional to rotation ratesΩ1/2....
2020-07-08 21:52:19浏览：40
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Preparation and characterization of SMA/S-POSS hybrid membranes for direct methanol fuel cell applic
A novel sulfonated polyhedral oligomeric silsesquioxane(S-POSS) monomer was synthesized successfully in this article. S-POSS acted as a donor of sulfonic acid group and reacted with poly(styrene-co-maleic anhydride) (SMA). FT-IR spectroscopy confirmed the modification through introduction of peaks characteristic of ester linkages and carboxylic groups. The SMA/S-POSS hybrid membranes were fabricated from different S-POSS contents. The proton conductivity and methanol permeability of the hybrid membranes were studied with changing S-POSS content from 5wt.% to 30wt.%. It was found that the proton conductivity and the methanol permeability were dependent on the S-POSS content. Both of proton conductivity and methanol permeability properties improve with increasing S-POSS content. The proton conductivities of the hybrid membranes are in the range of 10-3-10-2 S·cm-1,and the range of methanol permeabilities was between 10-8 and 10-7 cm2·s-1. The membranes show good thermal properties characterized by thermogravimetric analysis (TGA)....
2020-07-08 21:52:19浏览：61
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Direct Vapor Phase Carbonylation of Methanol over NiCl2/C Catalyst
Introduction
The carbonylation of alcohols via homogenous catalysis is important in manufacturing acetic acid and higher carboxylic acids and their esters[1,2]. The main route to produce acetic acid is to make methanol carbonylated by means of the Monsanto and BP process in which a homogeneous rhodium catalyst is used. Although the homogeneous carbonylation of methanol is a highly selective process, it is affected by the disadvantages associated with a highly corrosive reaction medium due to the use of methyl iodide as the promoter, and the difficulty of the product separation[3]. The use of a heterogeneous catalyst seems very interesting and attractive to us[4], especially the direct vapor phase carbonylation of methanol without a halide promoter is of considerable importance and is strong incentive economically. There has, however, been very little success in finding either heterogeneous or homogeneous catalysts that can catalyze the reaction effectively without the addition of a promoter[5,6]. According to the known carbonylation mechanism[7,8], the methyl iodide directly carbonylates with CO to from MeCOI which interacts with methanol(MeOH) to produce methyl acetate(MeCOOMe) and HI, and then MeOH reacts with HI to from CH3I. In fact, this carbonylation reaction is the indirect catalytic carbonylation of methanol[9]. In this work, a novel catalyst for the direct vapor phase carbonylation of methanol without the addition of any halide in the feed as a promoter was investigated. Compared to the known liquid phase methanol carbonylation process, some advantages of this vapor phase reaction are as follows:...2020-07-08 21:52:19浏览：58
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Toluene Alkylation with Methanol to p-Xylene over Heteropoly Acids Supported by Clay
The alkylation of toluene with methanol for the selective formation of p-xylene was systematically studied. Very few studies have been reported on the use of superacids such as heteropolyacids on cheap supports, such as clay. This article deals with the use of different heteropoly acids (HPAs),monium salt hydrate [H12Mo12N3O40P+aq] (DMAA), Dodeca-Molybdo Phosphoric acid (PMA) on clay (Montmorillonite, K-10) and as such plain clay. This comparative study reveals that 20%PMA/Clay shows 62% toluene conversion and 100% selectivity toward p-xylene....
2020-07-08 21:52:19浏览：34
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In-Situ FTIR Study on Effect of Lathanum on Oxidation Mechanism of Methanol Automobile Exhaust on Su
The performance of severe oxidation of methanol on 0.1%Pd supported on alumina was studied by a combined device of chromatograph-micro reactor. The results show that the addition of La into γ-Al2O3 as support can affect the performance of Pd catalyst greatly. By using Pd catalyst containing La in methanol oxidation, though, the ignition temperature is not lower than that by using Pd catalyst, the presence of La does suppress the formation of oxygenic intermediates. The results by in-situ FTIR show that the presence of La in the support affects the adsorbed species and hence the mechanism of severe oxidation of methanol on Pd catalyst....
2020-07-08 21:52:19浏览：55
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Purification Influence of Synthesis Gas Derived from Methanol Cracking on the Performance of Cobalt
Synthesis gas derived from methanol cracking (SGMC) was applied as simulating feedstock of Fischer-Tropsch synthesis (FTS) in laboratory. With MS and GC detector, a trifle of sulfur compounds,a small amount of oxygenates including H2O, CH3OH, DME and CO2 as well as a few of low carbon alkanes were found in the SGMC. After purification, the sulfur compounds, H2O, CH3OH and DME could be eliminated efficiently from the SGMC while CO2 and the low carbon alkanes were partly removed.When the unpurified SGMC, the desufurized SGMC and the totally purified SGMC were sequentially applied in cobalt-based FTS, the catalytic performance of Co/ZrO2/SiO2 catalyst was gradually improved corresponding to the degree of purification. The untreated SGMC led to the serious deactivation of the cobalt catalyst, the partially treated SGMC slowed down the deactivation rate and the totally purified SGMC resulted in little deactivation of the catalyst, which was similar to what the pure synthesis gas(the mixture of pure H2 and CO) did. The results indicated that the SGMC should be purified and the purification course used in this paper was effective for the SGMC. Furthermore, the totally purified SGMC could substitute for the pure synthesis gas in cobalt FTS....
2020-07-08 21:52:19浏览：75
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Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide Catalyzed by Potassium Hydroxide un
The synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide using potassium hydroxide as catalyst in the presence of CH3I and the effect of ionic liquid on the reaction were investigated. The results showed that KOH is an effective catalyst; the high selectivity and raised yield of DMC formation under mild conditions were achieved. However,the addition of the ionic liquid, 1-ethyl-3-methylimidazolium bromide (emimBr), can evidently accelerate the conversion of methanol and yield of the product....
2020-07-08 21:52:19浏览：45
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Study of CO2 Hydrogenation to Methanol over Cu-V/γ-Al2O3 Catalyst
The effect of vanadium addition to Cu/γ-Al2O3 catalyst used in the hydrogenation of CO2 to produce methanol was studied. It was found that the catalytic performance of the Cu-based catalyst improved after V addition. The influence of reaction temperature, space velocity and the molar ratio of H2 to CO2 on the performance of 12%Cu-6%V/γ-Al2Oa catalyst were also studied. The results indicated that the best conditions for reaction were as follows: 240 ℃, 3600 h-1 and a molar ratio of H2 to CO2 the dispersion of the supported CuO species, which resulted in the enhanced catalytic performance of Cu-V/γ-Al2O3 binary catalyst....
2020-07-08 21:52:19浏览：30
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Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO2
Direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated.The synthesized catalyst has been characterized by means of FTIR and XRD.Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC.However,DMC formation is limited by the reaction with co-produced water.DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2.As for the reactions in gas phase,it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature,owing to the decomposition of DMC at high temperatures.High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane (DMM) and methyl formate (MF)....
2020-07-08 21:52:19浏览：84
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Theoretical Study on the Adsorption and Decomposition of Methanol over the Pt-Mo(111)/C Surface
The density functional theory (DFT) and self-consistent periodic calculation were used to investigate the methanol adsorption on the Pt-Mo(111)/C surface. The adsorption energies,equilibrium geometries and vibration frequencies of CH3OH on nine types of sites on the Pt-Mo(111)/C surface were predicted and the favorite adsorption site for methanol is the top-Pt site.Both sites of valence and conduction bands of doped system have been broadened, which are favorable for electrons to transfer to the cavity. The possible decomposition pathway was investigated with transition state searching and the calculation results indicate that the O-H bond is first broken, and then the methanol decomposes into methoxy. The activation barrier of O-H bond breaking with Pt-Mo catalyst is only 104.8 kJ mol-1, showing that carbon supported Pt-Mo alloys have promoted the decomposition of methanol. Comparing with the adsorption energies of CH3OH on the Pt(111)/C surface and that of CO, the adsorption energies of CO are higher, and Pt(111)/C is liable to be oxidized and loses the activity, which suggests that the catalyst Pt-Mo(111)/C is in favor of decomposing methanol and has better anti-poisoning ability than Pt(111)/C....
2020-07-08 21:52:19浏览：72
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Treatment of methanol wastewater with two-stage and two-phase anaerobic process
The two-stage and two-phase anaerobic process (TSTP) composed of hydrolytic acidification reactor,first-order and second-order external circulation anaerobic reactors (EC) was taken to treat methanolwastewater. Test results show that TSTP process is quick start-up in 51 d, and the maximum VFA of hydrolytic acidification reactor effluent reaches 876 mg/L. Under the condition of volume loading of 6. 56 kgCOD/m~3·d,COD removal rate of the first-order EC reactor is about 85%, and under the condition of volume loading of 1.02 kgCOD/m~3·d, COD removal rate of the second-order EC reactor is about 50%. When the inflow COD of TSTP process is between 7000-11000 mg/L, its effluent COD is lower than 600 mg/L. In the biological conversion process of methanol into methane, the production of acetic acids as an intermediate product can be ignored and the direct production of methane from methanol is predominant....
2020-07-08 21:52:19浏览：40
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