Chinese Journal of Catalysis

Synthesis, Features, and Applications of Mesoporous Titania with TiO2(B)

CHEN Shanshan;ZHU Yinhua;LI Wei;LIU Weijia;LI Licheng;YANG Zhuhong;LIU Chang;YAO Wenjun;LU Xiaohua*;FENG Xin

2010, 31 (6): 605-614.

Abstract ( 4485 ) [Full Text(HTML)] ()

PDF (968KB) ( 1969 )

The mesoporous titania with TiO2(B) (mt-TiO2(B)), which has a lattice-matched core-shell crystalline structure with a thin TiO2(B) phase sheathing an anatase core, was synthesized from potassium titanate (K2Ti2O5) by hydration, ion exchange, and calcination. TiO2(B) is a crystalline form of titania with a looser structure than anatase and rutile. Its synthesis, structure, and functions are reviewed. It has all the features of a large specific surface area with a mesoporous architecture, pore wall of high crystallinity and high thermostability. Nanoparticles of noble metals in this mesoporous structured titania are stable. Its potential industrial applications include photocatalysis, oil hydrorefining, and use as a drug carrier, solid acid catalyst, and electrode material. A pilot plant to prepare this unique multifunctional titania material at low cost has been established with a production capacity of 20 tons per year.

Solvent-Free Oxidation of Alcohols Catalyzed by a Mn(III) Schiff-Base Complex Using Hydrogen Peroxide as an Oxidant

Hamid GOLCHOUBIAN;*;Seyyed Ebrahim BABAEI

2010, 31 (6): 615-618.

Abstract ( 2203 ) [Full Text(HTML)] ()

PDF (72KB) ( 1014 )

Aliphatic and aromatic alcohols are efficiently oxidized to ketones or carboxylic acids using aqueous hydrogen peroxide as an oxidant in the presence of a Mn(III) Schiff-base complex as a catalyst under solvent-free conditions. The oxidation of alcohols occurred at 50 °C to give the corresponding ketones or carboxylic acids with a yield higher than 60%.

Selective Catalytic Dehydration of 1,4-Butanediol to 3-Buten-1-ol over CeO2 with Different Morphology

HE Yongyi;LI Qibiao;WANG Yongzhao;ZHAO Yongxiang*

2010, 31 (6): 619-622.

Abstract ( 2219 ) [Full Text(HTML)] ()

PDF (411KB) ( 1576 )

CeO2 catalyst samples were prepared by the precipitation method using Ce(NO3)3•6H2O as a precursor. These samples were characterized by N2 adsorption-desorption, X-ray diffraction, high resolution transmission electron microscopy, and H2 temperature-programmed reduction. The catalytic performance of these samples for the selective dehydration of 1,4-butanediol to 3-buten-1-ol was investigated. The results show that the CeO2 catalyst samples that were prepared using different precipitants exhibited different morphology. The CeO2 sample precipitated by sodium carbonate showed regular rectangular morphology with clear edges, larger crystallite size, well-grown crystals and preferentially exposed (111) facets. It also had higher activity and higher selectivity in the selective dehydration of 1,4-butanediol to 3-buten-1-ol with yield as high as 59.7%.

Long Chain Aliphatic Amine-Modified Heteropolyacid Catalysts for Hydroxylation of Benzene to Phenol with Molecular Oxygen

ZHOU Changjiang;GE Hanqing;LENG Yan;WANG Jun儀

2010, 31 (6): 623-625.

Abstract ( 2262 ) [Full Text(HTML)] ()

PDF (308KB) ( 920 )

Organic-inorganic hybrid catalysts were prepared by combining laurylamine (or octadecylamine) and molybdovanadophosphoric acid, and their catalytic performance for the hydroxylation of benzene to phenol was evaluated using molecular oxygen as the oxidant in a pressured batch reactor. The laurylamine-modified heteropolyacid catalyst with a 4:1 molar ratio for the two moieties exhibited a much higher yield of phenol (11.5%) than that of the neat heteropolyacid H5PMo10V2O40 (3.9%). We discuss the promotional effect of the long chain aliphatic amines with regards to the interaction between the amine and the heteropolyacid framework, and we also discuss the ¨pseudo-liquid phase〃 behavior of the heteropolyacid.

Transfer Dehydrogenation of 1-Octanol to 1-Octanal over Cu/MgO Catalyst: Effect of Cu Particle Size

SHI Ruijuan;WANG Fei;MU Xiaoling;Ta Na;LI Yong;HUANG Xiumin;SHEN Wenjie儀*

2010, 31 (6): 626-630.

Abstract ( 2531 ) [Full Text(HTML)] ()

PDF (1561KB) ( 1168 )

Cu/MgO catalysts with different Cu particle sizes were prepared by a precipitation-deposition method and investigated for their activity in the transfer dehydrogenation of alcohols to carbonyl compounds. They were highly active for the conversion of primary aliphatic alcohols, e.g. 1-octanol. With increasing Cu particle size from 4.6 to 7.4 nm, the aldehyde yield decreased from 65% to 55%, which showed a size effect. The copper particle abstracted an -hydrogen from the reactive alkoxide intermediate formed on the surface of MgO and simul-taneously catalyzed the hydrogenation of styrene.

Preparation, Characterization, and Catalytic Application of a Nanosized Ce1MgxZr1-xO2 Solid Heterogeneous Catalyst for the Synthesis of Tetrahydrobenzo[b]pyran Derivatives

Sandip RATHOD;Balasaheb ARBAD;Machhindra LANDE

2010, 31 (6): 631-636.

Abstract ( 2215 ) [Full Text(HTML)] ()

PDF (280KB) ( 1876 )

A series of Ce1MgxZr1-xO2 mixed metal oxides with different molar ratios were prepared by simple co-precipitation and were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, temperature-pro- grammed desorption of CO2, and N2 adsorption techniques. The prepared materials were tested for catalytic activity by the synthesis of tet-rahydrobenzo[b]pyran derivatives using a three component reaction (aromatic aldehydes, malononitrile, and dimedone) in an ethanol me-dium. The best catalytic activity was obtained with Ce1Mg0.6Zr0.4O2. The particle size or crystallite size was estimated using the De-bye-Scherrer equation. The addition of magnesium oxide into the ceria-zirconia lattice resulted in the formation of nanosized particles rang-ing from 5.41 to 9.78 nm. This work describes the catalytic behavior of magnesium oxide in mixed metal oxide systems.

Preparation of SAPO-5 and Its Catalytic Synthesis of p-Aminophenol

WANG Shufang;WANG Yanji*;GAO Yang;ZHAO Xinqiang

2010, 31 (6): 637-644.

Abstract ( 2482 ) [Full Text(HTML)] ()

PDF (765KB) ( 1256 )

Silicoaluminophosphate molecular sieves (SAPO-5) were synthesized by hydrothermal crystallization using both a conventional aqueous medium and a HF medium. The SAPO-5 samples were characterized by X-ray diffraction, scanning electron microscopy, solid state NMR, Fourier transform infrared reflectance spectroscopy, and temperature-programmed desorption of adsorbed NH3. The effect of Si content and presence of HF in the initial gel on the structure of the SAPO-5 synthesized and the manner of Si incorporation into the framework were investigated. Their acidity and catalytic activity for phenylhydroxylamine (PHA) rearrangement in the synthesis of p-aminophenol (PAP) from nitrobenzene were studied. The incorporation of Si in the samples prepared in the presence of HF was mainly by the SM3 mechanism and patches of Si(4Si) were predominant. This resulted in a decrease in the acid amount and increase in acid strength. The presence of HF during synthesis increased the integrity of the SAPO-5 crystal and helped incorporate more Si in the SAPO-5 structure by inhibiting the polymerization of Si species to a reticulated silica gel. The samples prepared in the HF medium exhibited better catalytic performance for PHA rearrangement in the synthesis of PAP, and a PAP yield of 53.2% could be obtained.

Reaction Mechanism of Ethylene Aromatization over HZSM-5 Zeolite: From C4 to C6 Intermediates

CAO Liang;ZHOU Danhong;*;XING Shuangying;LI Xin

2010, 31 (6): 645-650.

Abstract ( 2746 ) [Full Text(HTML)] ()

PDF (536KB) ( 981 )

The ONIOM2 (B3LYP/6-31G(d,p):UFF) method based on the 78T cluster model was used to study the reaction mechanism of C4 to C6 intermediates during the ethylene aromatization over HZSM-5 zeolite. The catalytic mechanism of acidic zeolite and the effect of zeolite pore size on the shape selectivity for the products was discussed. The results indicated that the n-butoxide, which is the intermediate product of ethylene dimmerization, reacted with ethylene to form n-hexane alkoxide, but it was difficult to carry out further cyclization because of the restriction of the pore size of ZSM-5 zeolite. However, along the stepwise pathways, n-butoxide was transformed into n-butene through deprontonation and then reacted with ethylene to form 3-methylpentane alkoxide intermediate, which then formed methylcyclopentane through cyclization and deprotonation. The methylcyclopentane released a hydrogen molecule by the aid of zeolite acidic proton and formed the unstable methyl-cyclopentane carbonium, which then generated the cyclohexane carbonium through reconfiguration. The calculated activation energy was 158.42 kJ/mol for n-butoxide deprontonation, 130.71 kJ/mol for the oligomerization of 1-butene and ethylene, and 122.06 kJ/mol for the cyclization of 3-methylpentane alkoxide. As a result of the confinement of zeolite pore, the five-member ringed me-thylcyclopentane was formed as a crucial intermediate.

Enantioselective Synthesis of S-(+)-2,2-Dimethylcyclopropanecarboxylic Acid from Ethyl-2,2-dimethylcyclopropanecarboxylate Catalyzed by Lipase Novozyme 435

WANG Pu*;ZHU Jianan;HE Junyao

2010, 31 (6): 651-655.

Abstract ( 2708 ) [Full Text(HTML)] ()

PDF (368KB) ( 1687 )

S-(+)-2,2-dimethylcyclopropanecarboxylic acid (S-(+)-DMCPA) was synthesized by asymmetric hydrolysis of racemic ethyl-2,2- dimethylcyclopropane carboxylate (DMCPE) over different lipases. Among the five enzymes investigated, Novozyme 435 showed higher enantioselectivity and activity. The influence of reaction parameters, such as ionic strength, the ratio of lipase/DMCPE, buffer pH, reaction temperature, and reaction time, on the biosynthesis of S-(+)-DMCPA was investigated. The optimum DMCPE concentration, enzyme dosage, buffer pH, reaction temperature, and reaction time were 65 mmol/L, 16 g/L, 7.2, 30 oC, and 64 h, respectively. Under the optimal conditions, the higher yield of 45.6% and enantiomeric excess of 99.2% for S-(+)-DMCPA were obtained. The biocatalytic activity of Novozyme 435 was relatively stable, retaining 70.3% of the initial activity after reuse three times. The results demonstrated that lipase Novozyme 435 is a suitable biocatalyst for the synthesis of S-(+)-DMCPA and has great potential for industrial applications.

Selective Oxidation of Alcohols with Molecular Oxygen Catalyzed by RuCl3•3H2O in P- and N-Containing Ligand Functionalized Ionic Liquids

ZHOU Chengliang;LIU Ye*

2010, 31 (6): 656-660.

Abstract ( 2924 ) [Full Text(HTML)] ()

PDF (466KB) ( 885 )

The application of functionalized ionic liquids (ILs) in homogeneous catalysis facilitates the reaction efficiency in homogeneous phase, liquid-liquid separation, and IL solvent-catalyst recycling. In this work, a series of P- or N-containing ligand functionalized imida-zolium-based ILs were synthesized and used in conjunction with common ambient imidazolium-based ILs to afford the IL solution, which acted as both the ligand and the solvent. In such functionalized IL compositions, RuCl3•3H2O catalyzed oxidation of various alcohols using O2 to aldehydes and ketones was achieved with high selectivity (most above 95%) in the absence of co-oxidants. The catalytic performance of the RuCl3•3H2O catalyst was greatly influenced by the solvents and ligands. The N-containing ligand functionalized IL with weaker liga-tion to Ru center exhibited better activity and much higher selectivity. Whereas, the N,P-hybrid ligand functionalized IL with bidentate che-lating ability to Ru center showed relatively low activity. However, the recyclability of RuCl3•3H2O in such functionalized IL compositions was unavailable. The in situ 31P NMR spectroscopy study indicated that the oxidative degradation of the ligand itself was responsible for the deactivation of the Ru catalyst.

Selective Oxidation of Glucose in the Presence of PVP-Protected Colloidal Gold Solutions

SHI Lingling;LIU Kezeng;ZOU Xuhua;JIN Mingshan;SUO Zhanghuai*

2010, 31 (6): 661-665.

Abstract ( 2746 ) [Full Text(HTML)] ()

PDF (415KB) ( 1409 )

Colloidal metal gold catalysts were prepared by reducing a base solution of chlorauric acid in the presence of a polyvinylpyrrolidone (PVP) stabilizer. The selective oxidation of glucose to gluconic acid in aqueous solution using molecular oxygen as an oxidant at atmospheric pressure was studied. The activity of the colloidal gold was measured as a function of the PVP amount and various chlorauric acid concentrations. The highest activity with 54.4% conversion of glucose was obtained at a PVP/Au mass ratio of 40 and a 100 μg/ml chlorauric acid concentration. UV-Visible absorption spectroscopy and transmission electron microscopy results showed that the stable gold colloids contain smaller gold nanoparticles. Adjusting the PVP amount and chlorauric acid concentration in the preparation of colloidal gold nanoparticles can achieve high catalytic avtivity for glucose oxidation.

Preparation of ZnCl2-Modified Ion Exchange Resin and Its Catalytic Activity for Esterification of Ethanol and Acetic Acid under Microwave

ZHANG Feng;JIANG Xiaoyuan*;HONG Junjie;LOU Hui;ZHENG Xiaoming

2010, 31 (6): 666-670.

Abstract ( 2869 ) [Full Text(HTML)] ()

PDF (521KB) ( 1955 )

An ion-exchange method was used to prepare a ZnCl2-modified ion exchange resin. Several factors such as impregnation liquid con-centration, ion-exchange time, and solvent used in the preparation were examined. Optimal preparation conditions for the ZnCl2-modified ion exchange resin included the use of deionized water as solvent, 0.15% concentration (mass fraction) of the ZnCl2 solution, and ion-exchange time of 30 h. The H+ exchange capacity of the ZnCl2-modified ion exchange resin was investigated by acid-base titration. UV-Vis spectros-copy, Fourier transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption were used to characterize the catalyst. Gas chromatography was used to determine the catalyst activity for the esterification of ethanol and acetic acid under microwave. The acid strength and catalytic activity of the ion exchange resin were improved after being modified by ZnCl2, and the H+ exchange capacity of the modified catalyst is about 1.5 times that of the original one. Moreover, the skeleton structure of the modified resin has not changed. Only a small blue shift and reduction of the absorption intensity can be observed on the corresponding UV absorption peak, and the BET surface area decreases slightly. The ZnCl2-modified catalyst showed a higher reactivity in the water system and a better repeatability as compared to the unmodified one.

Effect of Alkali Metal Promoters on Water-Gas Shift Activity over Au-Pt/CeO2 Catalyst

YU Qiangqiang;LI Yang;ZOU Xuhua;ZHUO Hongying;YAO Yuanyuan;SUO Zhanghuai*

2010, 31 (6): 671-676.

Abstract ( 2614 ) [Full Text(HTML)] ()

PDF (463KB) ( 1193 )

Au-Pt/CeO2 catalyst samples modified with alkali metals M (M = Na, K, Rb, and Cs) were prepared and their catalytic activity for water-gas shift (WGS) was evaluated. The structure and surface properties of the Au-Pt/CeO2 catalyst promoted by potassium were investigated by X-ray powder diffraction, H2 temperature-programmed reduction, ultraviolet-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The higher activity obtained on the K-promoted Au-Pt/CeO2 sample was possibly due to the reduction of Au3+ species and the enrichment of Ce3+ on the catalyst surface, which generated more oxygen vacancies. The catalytic activity of Au-Pt/CeO2 was greatly influenced by the alkali metals. When the K content was 0.025%, the CO conversion achieved up to 95% at 250 oC.

Effect of Boron Nitride Support on Catalytic Activity of Ru-Ba/BN for Ammonia Synthesis

XU Chunfeng;OUYANG Liang;ZHANG Jia;ZHOU Bin;LI Ying*;LIU Huazhang

2010, 31 (6): 677-682.

Abstract ( 2481 ) [Full Text(HTML)] ()

PDF (777KB) ( 1248 )

Boron nitride (BN) nanoparticles with high surface area were prepared by temperature-programmed nitridation and temperature-programmed reduction methods. The catalytic activity of the Ru-Ba/BN ammonia synthesis catalyst was studied. Characterizations by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and Fourier transform infrared spectroscopy were performed to study the crystalline structure, pore structure, and surface properties of the BN material. The characterization results showed that using the above two methods can prepare hexagonal boron nitride with higher surface area, being 103 and 138 m2/g, respectively. The outlet ammonia concentration reached 7.3% under the conditions of 475 oC, 10 MPa, and 10 000 h–1 for the Ru-Ba/BN catalyst, and the activity was stable after thermal treatment at 550 oC for 30 h.

Structure of CuCl/SiO2-TiO2 Catalyst and Its Catalytic Properties for Oxidative Carbonylation of Methanol

LI Zhong;LIU Shusen;REN Jun*;NIU Yanyan;ZHENG Huayan;ZHAO Qiang;CUI Liping

2010, 31 (6): 683-688.

Abstract ( 2481 ) [Full Text(HTML)] ()

PDF (429KB) ( 995 )

Microwave heating for a mixture of CuCl and SiO2-TiO2 support was used to prepare a CuCl/SiO2-TiO2 catalyst with high dispersion of CuCl on the support surface in a short time. X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, thermal gravimetric analysis, H2 temperature-programmed reduction, and CO temperature-programmed desorption were carried out to examine the bulk and surface properties of the CuCl/SiO2-TiO2 catalyst. The characterization results showed that in the CuCl/SiO2-TiO2 catalyst prepared by microwave heating, a great amount of CuCl particles strongly attached to the SiO2-TiO2 support as compared with that prepared by con-ventional heating, resulting in a lower reduction temperature of copper species and a stronger adsorption to CO. Microwave heating also caused that the mass loss temperature of part CuCl was higher than 1 200 oC, which could be attributed to the formation of a strong Cu–O coordinate bond between CuCl and the SiO2-TiO2 support. Catalytic test results showed that the CuCl/SiO2-TiO2 catalyst prepared by mi-crowave heating exhibited methanol conversion of 11.7% and dimethyl carbonate selectivity of 96.5%, higher than that prepared by conven-tional heating in liquid-phase oxidative carbonylation of methanol.

Roles of Vanadium Substitution of Monoclinic TeMo5O16 Catalyst for Propane Selective Oxidation

DONG Xue;ZHU Yihan;LI Han;LU Weimin*

2010, 31 (6): 689-694.

Abstract ( 2209 ) [Full Text(HTML)] ()

PDF (394KB) ( 792 )

The vanadium-doped monoclinic TeMo5O16 catalysts were prepared and tested in the propane selective oxidation reaction. The doped catalysts showed high activity and high yield of propylene and acrolein. The catalysts were characterized by temperature-programmed surface reaction, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, H2 temperature-programmed reduction, and O2-thermogravity. The relationship between catalytic activity and catalyst properties on the surface and in the bulk was discussed. The results strongly suggested that the surface Mo–O bonds were changed by the V-doping. Thus the activity of surface redox sites was improved, and the amount of surface acid sites was increased, which promoted the activation and oxidation of propane. The bulk redox ability was further improved by a higher V-doping amount while the phase was unchanged basically.

Preparation of Highly Dispersed Ru/MMT Catalyst and Its Catalytic Activity for Quinoline Hydrogenation

ZHOU Limei;FU Haiyan;LI Qiang;CHEN Hua;*;LI Ruixiang;LI Xianjun

2010, 31 (6): 695-700.

Abstract ( 2307 ) [Full Text(HTML)] ()

PDF (510KB) ( 1088 )

A highly dispersed montmorillonite-supported Ru catalyst (Ru/MMT) was prepared by the ion-exchange method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, and high resolution transmission electron microscopy. The results showed that Ru was well dispersed on the montmorillonite interlayers, and the average size of Ru particles was about 2 nm. The catalyst exhibited high activity in the hydrogenation of quinoline under the mild reaction conditions (60 °C, 2 MPa H2, and H2O as solvent). The conversion of quinoline was 99.2% and the selectivity for 1,2,3,4-tetrahydroquinoline was 96.4%. When the temperature and hydrogen pressure were increased to 140 °C and 3 MPa, respectively, quinoline could be directly hydrogenated to decahydroquinoline with the selectivity up to 98.1%.

Ferrocene-Containing Hybrid Mesoporous Materials Prepared by Co-condensation and Grafting Methods and Their Catalytic Properties

ZHANG Tieming;GAO Pengfei;GAO Chunguang;YANG Hengquan;ZHAO Yongxiang*

2010, 31 (6): 701-704.

Abstract ( 2609 ) [Full Text(HTML)] ()

A new Ferrocene(Fc)-containing periodic mesoporous organosilica (PMO-Fc) was synthesized directly through co-condensation of 1,1'-bis[2-(triethoxylsilyl)ethyl]ferrocene and tetraethyl orthosilicate using supramolecular templates of cetyltrimethylammonium bromide as structure directing agents. A hybrid material, Fc-MCM-41, was also prepared by covalently anchoring ferrocene onto the mesoporous silica material MCM-41 using toluene as the dispersant. The prepared materials were characterized by nitrogen adsorption, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results showed that PMO-Fc had an ordered two-dimensional hexagonal mesostructure, higher BET surface area and pore volume. In the hydroxylation of benzene to phenol, PMO-Fc was highly active with 65.3% of phenol selectivity and 20.2% of phenol yield.

Synthesis, Characterization, and Catalytic Behavior of Biheteroatomic Fe-V-β Zeolite

XIAO Zhiwen;HE Hongyun*

2010, 31 (6): 705-710.

Abstract ( 2506 ) [Full Text(HTML)] ()

PDF (540KB) ( 840 )

The Fe-V-β zeolite was hydrothermally synthesized in a SiO2-Fe2O3-V2O5-(TEA)2O-H2O-NH4F system. The structure and chemical composition of the zeolite samples were characterized by X-ray diffraction, infrared spectroscopy, thermogravimetry-differential thermal analysis, inductively coupled plasma-atomic emission spetrometry, scanning electron microscopy-energy dispersive spectrometry, and ultra-violet-visual diffuse reflection spectroscopy. The factors that affected the synthesis of Fe-V-β zeolite were investigated. The results indicated that the well-crystallized Fe-V-β zeolite could be synthesized from the precursor with SiO2:Fe2O3:V2O5:(TEA)2O:H2O:NH4F molar ratio of 60:(0.1–0.75):(0.1–0.75):(17–18):(550–650):(30–50), and the Fe and V atoms entered the framework of the zeolite. The as-synthesized Fe-V-β zeolite with Si/(Fe+V) = 30 showed higher catalytic activity in the oxidation of styrene using H2O2 as the oxidant. The styrene con-version was 25.4%, and the selectivity was 69.1% for PhCHO, 22.5% for PhCH2CHO, and 4.1% for PhCOMe, respectively.

Characterization and Performance of High-Flux PdAu/Ceramic Composite Membranes

SHI Lei;;ZENG Gaofeng;;XU Hengyong;*

2010, 31 (6): 711-715.

Abstract ( 2228 ) [Full Text(HTML)] ()

PDF (506KB) ( 795 )

A PdAu membrane was prepared by sequential electroless plating of Pd and Au onto the outside surface of porous 冏-Al2O3 substrate followed by annealing and H2/N2 performance evaluation. X-ray diffraction was employed to study the PdAu alloy phase formation at 823 K under H2 and N2 atmospheres. Annealing experiments demonstrated that 200 h was needed to form a stoichiometrically homogeneous, 2-m thick Pd82.63Au17.37 membrane from sequentially deposited layers at 823 K and a noticeable particle agglomeration was observed under N2 atmosphere. The performance of the PdAu alloy membrane was evaluated with respect to the H2 flux and permselectivity between 823 and 423 K, which showed that the PdAu alloy membrane had higher H2 flux and lower activation energy than those of pure Pd membrane. The activation energy in the high temperature range is consistent with bulk diffusion-limited H2 transport, while the changes of these charac-teristics at lower temperatures below 573 K indicate desorption or surface limited H2 flux. After the conclusion of gas studies, the PdAu membrane was broken, the thickness and composition of the PdAu layers were determined by SEM and EDX completely.

List of Issues