Recent development of methanol electrooxidation catalysts for directmethanol fuel cell

Direct methanol fuel cells （DMFCs） are very promising power source for stationary and portable miniatureelectric appliances due to its high efficiency and low emissions of pollutants. As the key material, cata-lysts for both cathode and anode face several problems which hinder the commercialization of DMFCs.In this review, we mainly focus on anode catalysts of DMFCs. The process and mechanism of methanolelectrooxidation on Pt and Pt-based catalysts in acidic medium have been introduced. The influences ofsize effect and morphology on electrocatalytic activity are discussed though whether there is a size effectin MOP, catalyst is under debate. Besides, the non Pt catalysts are also listed to emphasize though Pt isstill deemed as the indispensable element in anode catalyst of DMFCs in acidic medium. Different cata-lyst systems are compared to illustrate the level of research at present. ome debates need to be verifiedwith experimental evidences.

Optimum Operating and Regeneration Parameters of ZnI2 Catalyst for Converting Methanol to Triptane:An Ideal Component of Unleaded Aviation Gasoline

Conversion of methanol(MeOH) to 2,2,3-trimethylbutane(triptane) over zinc iodide(ZnI_2)catalyst was investigated in a closed batch reactor.Optimum operating parameters were searched and catalyst deactivation and regeneration behaviors were discussed.The fresh,spent and regenerated catalysts were characterized by XRD,TG and XRF measurements to elucidate the related mechanism.The experimental results showed that the triptane yield reached up to 12.2% under the process conditions,including a reaction temperature of 200℃,an initial pressure of 0.35 MPa,a reaction time of 2 h,and a Me OH to ZnI_2 molar ratio of 2.The catalyst was gradually deactivated after several run cycles.A small amount of iodine was lost and a certain amount of ZnO was formed on the deactivated ZnI_2 catalyst.Deactivation of the catalyst could be attributed to the reduction of ZnI_2 amount,resulted from iodine loss and formation of Zn O.It was firstly pointed out from our work that the deactivated catalyst could be well regenerated by the hydrogen iodide(HI) and the tert-butanol compensation method,wherein the latter was added as an initiator into the reaction system.The activity recovery of the deactivated(spent) catalyst might be related to the reformation of ZnI_2 and acceleration of the initiation step of this reaction.

Introduction of table sugar as a soft second template in ZSM-5 nanocatalyst and its effect on product distribution and catalyst lifetime in methanol to gasoline conversion

Methanol to gasoline reaction was investigated on two prepared ZSM-5 catalysts. The first one was a conventional catalyst denoted as ZSM-5（C） and the other was a hierarchical catalyst-ZSM-5（S） which was prepared by incorporation of table sugar in catalyst gel during the synthesis procedure. The catalysts were characterized by FTIR, XRD, FE-SEM, N2 adsorption-desorption, NH3-TPD and TGA analytical technics. The proposed material showed pore modification as well as acidity moderating properties in ZSM-5 catalyst. The methanol to gasoline reaction was conducted in a fixed bed reactor with a WHSV of 1.5 h-1.Methanol conversions, gasoline yield and selectivity in production for the synthesized catalysts were determined by gas chromatography method. The sugar modified catalyst converted more methanol than the conventional one and an enhancement in catalyst’s life time was observed. The selectivity to aromatics and durene were reduced compared to the conventional catalyst, so the gasoline quality was also further improved. The coking rate of catalysts was calculated employing TGA method. A reduction in coking rate and an increase in coke capacity of the modified catalyst were observed.

Synthesis and study of λ-MnO_2 supported Pt nanocatalyst for methanol electro-oxidation

A λ-MnO2 supported Pt nanocatalyst（5 wt.% Pt/λ-MnO2） was synthesized using a facile approach.X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, scanning electronic microscope（SEM）, transmission electron microscopy（TEM）, and energy disperse spectroscopy（EDS） were used for catalyst structure and morphology characterization, which showed that the metallic Pt particles were attached on a λ-MnO2 surface through the interaction between Pt and λ-MnO2.Cyclic voltammetry（CV） was used to test the catalytic activity of Pt/λ-MnO2 toward methanol oxidation, which showed that Pt/λ-MnO2 catalyst has much higher catalytic activity than baseline Pt/C catalyst.

Methanol Synthesis from CO2 Hydrogenation with a Cu/Zn/Al/Zr Fibrous Catalyst

A highly active Cu/Zn/Al/Zr fibrous catalyst was developed for methanol synthesis from CO2 hydrogenation.Various factors that affect the activity of the catalyst,including the reaction temperature,pressure and space velocity,were investigated.The kinetic parameters in Graaf's kinetic model for methanol synthesis were obtained.A quasistable economical process for CO2 hydrogenation through CO circulation was simulated and higher methanol yield was obtained.

A sulfur-tolerant Pd/CeO_2 catalyst for methanol synthesis from syngas

The catalytic activity of ceria-supported Pd for selective hydrogenation of CO is well preserved in the presence of 30 ppm H2S due to the parallel oxidation of sulfur by CeO2 under standard methanol synthesis conditions. The bifunctional nature of this catalyst opens a route for the conversion of sulfur-contaminated gas streams such as the integrated gasification combined cycle syngas or biogas into liquid fuels if desulfurization by conventional means is not practical.

Studies on Catalyst Deactivation Rate and Byproducts Yield during Conversion of Methanol to Olefins

The conversion of methanol to olefins (MTO) over the SAPO-34 catalyst in fixed-bed microreactor was studied. The effect of reaction temperatures for methanol conversion to olefins and byproducts was investigated. A temperature of 425 ℃ appeared to be the optimum one suitable for conversion of methanol to olefins. Since the presence of water could increase the olefins selectivity, the methanol conversion reactions with mixed water/methanol feed were also studied. The effect of weight hourly space velocity on conversion of methanol was also studied. The results indicated that the olefins selectivity was significantly increased as WHSV increased till approximately 7.69 h-1 then it began to level off. Different factors affecting the catalyst deactivation rate was studied, showing that the catalyst deactivation time was dependent on reaction conditions, and temperatures higher and lower than the optimal one made the catalyst deactivation faster. Adding water to methanol could slow down the catalyst deactivation rate.

Effect of preparation methods of aluminum emulsions on catalytic performance of copper-based catalysts for methanol synthesis from syngas

Various Cu/ZnO/Al2O3 catalysts have been synthesized by different aluminum emulsions as aluminum sources and their pertormances tor methanol synthesis from syngas have been investigated. The influences of preparation methods of aluminum emulsions on physicochemical and catalytic properties of catalysts were studied by XRD, SEM, XPS,N2 adsorption-desorption techniques and methanol synthesis from syngas. The preparation methods of aluminum emulsions were found to influence the catalytic activity, CuO crystallite size, surface area and Cu0 surface area and reduction process. The results show that the catalyst CN using the aluminum source prepared by addition the ammonia into the aluminum nitrate （NP） exhibited the best catalytic performance for methanol synthesis from syngas.

Synthesis of dimethyl carbonate by gas-phase oxidative carbonylation of methanol in the presence of solid catalyst I. Catalyst preparation and catalytic Properties

The gas-phase synthesis of dimethyl carbonate (DMC) from methanol, carbon monoxide and oXygen has here Studied in a flow system at atomspheric Pressure. A series of Catalyst used in this reaCtion have been prepared and evaluated. The influence of trivared carbon supporters, alkaline metal Promoters and operation conditions on DMC opthesis reaction has been discussed. Under the conditions of 130℃, CO/O2=1 .96, SV=3340h-1, the space-time yield (STY) of DMC over PdCl2-CuCl2-CH3COOK/ac. catalyst is 217g/l-cat h,which is higher than what is published in the literatUre so far.

Stabilization of Cu/ZnO Based Catalysts by Nickel Additive in Methanol Decomposstion

A series of Cu/Zn based catalysts with and without Ni, prepared by the co-precipitation method, has been studied for methanol decomposition. CO and H2 are the major products. The Cu/Zn catalysts show a low initial activity and a poor stability. The formation of the CuZn alloys was observed in the deactivated Cu/Zn catalysts which were used for methanol decomposition at 250 . When small amounts of Ni were added in the catalyst, the Cu/Zn/Ni(molar ratio 5/4/ x) catalysts showed a high activity at a low temperature. The activity and the stability of the catalyst depend on the nickel content. The activity of the Cu/Zn/Ni catalysts was maintained at a. relatively stable value of 78% conversion of methanol with 95% selectivity of H2, 93% selectivity of CO, and a more than 70% yield of hydrogen was obtained at 250 C when x >1. The stability of the Cu/Zn/Ni (molar ratio 5/4/x) catalysts showed the maximum (ca 88%) when x=1. The stabilization effect of nickel on the Cu/Zn based catalysts may lead to the increasin

Fabrication of C@MoxTi1-xO2-δ nanocrystalline with functionalized interface as efficient and robust PtRu catalyst support for methanol electrooxidation

A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.

Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

Carbon nanotubes-Nafion （CNTs-Nation） composites were prepared by impregnated CNTs with Nation in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, CO stripping voltammetry, cyclic voltammetry （CV） and chronoamperometry （CA）. The results showed that the Nation incorporation in CNTs-Nation composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Naton showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

In-Situ FTIR Study on Effect of Lathanum on Oxidation Mechanism of Methanol Automobile Exhaust on Supported Palladium Catalyst

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-Al 2O 3 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.

A Novel Sulfided Mo/C Catalyst for Direct Vapor Phase Carbonylation of Methanol at Atmospheric Pressure

The direct carbonylation of methanol, without any halide in the feed as apromoter, is presented. A series of Mo catalysts supported on activated carbon, γ-Al_2O_3 and SiO_2were prepared. The results show that the support greatly affects the Mo catalyst in the directvapor-phase carbonylation of methanol, and activated carbon is the best supports of the investigatedsupports. In addition, the relationships between adsorptions of NH_3 and CO and carbonylation ofmethanol were investigated. A novel sulfided Mo/C catalyst had high activity and selectivity for thevapor phase carbonylation of methanol to methyl acetate without the addition of a CH_3I promoter tothe feed. The reaction conditions were optimized at a reaction temperature of 573 K, a methanolconcentration of 23 mol% and a carbon monoxide space velocity of 3,000 L/(kg·h). Under theseoptimal conditions a methanol conversion of 50%, carbonylation selectivity of 80 rnol%, andspace-time yield of 8.0 mol/(kg·h) were obtained. The active phase of this novel sulfided Mo/Ccatalyst is the non-crystalline phase, and the active component is present as MoS_(2.5) on thesurface of the activated carbon.

Study on Highly Active Catalysts and a Once-Through Process for Methanol Synthesis from Syngas

Highly active CNT-promoted co-precipitated Cu-ZnO-Al_2O_3 catalysts,symbolized as Cu_iZn_jAl_k-x%CNTs, were prepared, and their catalytic activity for once-throughmethanol synthesis from syngas was investigated. The results illustrated that, under the reactionconditions (at 493 K, 5.0 MPa, the volume ratio of H_2/CO/CO_2/N_2= 62/30/5/3, GHSV= 4000 h^(-1),the observed single-pass CO-conversion and methanol-STY over a Cu_6Zn_3Al_1-12.5%CNTs catalystreached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h·g))over the corresponding CNT-free catalyst, Cu-6Zn_3Al_1, respectively. The characteristic studies ofthe catalysts revealed that appropriate incorporation of a minor amount of the CNTs into theCu_iZn_jAl_k brought about little change in the apparent activation energy of the methanol synthesisreaction, however, led to a considerable increase in the catalyst's active Cu surface area andpronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on the surfaceof the functioning catalyst, which would be favorable to increasing the rate of the COhydro-genation reactions. Moreover, the operation temperature for methanol synthesis over theCNT-promoted catalysts can be 10-20 degrees lower than that over the corresponding CNT-free contrastsystem, which would contribute considerably to an increase in equilibrium CO-conversion andCH_3OH-yield.

Characterization and performance of Cu/ZnO/Al_2O_3 catalysts prepared via decomposition of M(Cu,Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H_2 and CO_2

Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M（Cu,Zn）-ammonia complexes （DMAC） at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol （212 g/（Lcat·h）;T=513 K,p=3MPa,SV=12000 h-1）.

Direct partial oxidation of methane to methanol:Reaction zones and role of catalyst location

Direct partial oxidation of methane to methanol was investigated in a specially designed reactor. Methanol yield of about 7%-8% was obtained in gas phase partial oxidation. It was proposed that the reactor could be divided into three reaction zones, namely pre-reaction zone, fierce reaction zone, and post-reaction zone, when the temperature was high enough to initiate a reaction. The oxidation of methane proceeded and was completed mostly in the fierce reaction zone. When the reactant mixture entered the post-reaction zone, only a small amount of produced methanol would bring about secondary reactions, because molecular oxygen had been exhausted in the fierce reaction zone. A catalyst, if necessary, should be placed either in the pre-reaction zone, to initiate a partial oxidation reaction at a lower temperature, or in the fierce reaction zone to control the homogeneous free radical reaction.

The Effect of Rare Earth on the Activity of Methanol Synthesis Catalyst

In this paper several rare earth oxides were added into methanol synthesis catalyst by solid-mixing method to improve the activity of methanol synthesis catalyst. Nd2O3, CeO2, La2O3 and Sm2O3 decrease the catalyst activity, while Pr2O3, Gd2O3 and Eu2O3 increase the methanol yield.

Simultaneous operation of dibenzothiophene hydrodesulfurization and methanol reforming reactions over Pd promoted alumina based catalysts

In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic(Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method.In situ hydrogen utilization and low Pd loadings were the major targets of this study.For comparison purpose,catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well.Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e.Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380 ℃ and 12 h reaction time.Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature.Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.

Progress in the Field of Converting Methanol into Light Olefins over the ZSM-5 Zeolite Catalyst

Technical progress in the field of conversion of methanol into ethylene and propylene over the ZSM-5 catalyst was summarized. The economical analysis of the technology, the mechanism of chemical reaction and reaction kinetics were introduced. The factors including the effect of the operating conditions,the influence of catalyst preparation conditions and modification of ZSM-5 zeolite on the reaction and coke formation were also discussed.