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Chinese Journal of Catalysis
2007, Vol. 28, No. 9
Online: 25 September 2007

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A Direct Ammonia Tubular Solid Oxide Fuel Cell ZHANG Limin;CONG You;YANG Weishen*;LIN Liwu 2007, 28 (9):  749-751.  Abstract ( 2220 )   [Full Text(HTML)] () PDF (257KB) ( 1290 )   A Ni-anode-supported tubular solid oxide fuel cell (SOFC) with a dense yttria-stabilized zirconia (YSZ) thin film was fabricated. The YSZ film was prepared using the vacuum-assisted dip-coating method. The performance of the single SOFC-based system running on ammonia was compared with that running on hydrogen. At 800 ℃, the peak power densities were 202 and 200 mW/cm2 with hydrogen and ammonia as the fuel, respectively. A GC analysis of the effluent from the anode showed considerable amounts of nitrogen and hydrogen, but no trace of NOx, when using ammonia as the fuel. The ammonia performance is comparable to hydrogen, suggesting that ammonia can be an attractive alternative fuel.

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Thermodynamic and Kinetic Considerations for Ethanol Electrooxidation in Direct Ethanol Fuel Cells SONG Shuqin*;WANG Yi;SHEN Peikang 2007, 28 (9):  752-754.  Abstract ( 2170 )   [Full Text(HTML)] () PDF (218KB) ( 1644 )   Thermodynamic and kinetic considerations for the ethanol electrooxidation in a proton exchange membrane fuel cell (PEMFC) were discussed. Theoretical calculations show that direct ethanol fuel cells (DEFCs) exhibit better exergic efficiency than ethanol reforming PEMFC. The thermodynamic analysis show that when temperature is lower than 100 ℃, the conversion of ethanol steam reforming is less than 14% for ethanol complete oxidation. The kinetic study shows that PtSn/C anodes have a relatively high activity for ethanol electrooxidation, but such activity is not high enough for ethanol complete electrooxidation. The thermodynamic and kinetic analyses suggest that the cell temperature is one of the key factors for the DEFC development.

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Catalyst-Enhanced Chemical Vapor Deposition of Palladium-Platinum Bilayer Nano-Films on Polysulfone ZHENG Jianhua;ZHOU Jinlan;TIAN Xike;FENG Wenfang;YU Kaichao* 2007, 28 (9):  755-757.  Abstract ( 1925 )   [Full Text(HTML)] () PDF (225KB) ( 1062 )   Catalyst-enhanced chemical vapour deposition of Pt and Pd-Pt bilayer films on polysulfone using N2 and O2 as the carrier gas was investigated. Only Pt was deposited when the mixture of complexes Pt(COD)Me2 and Pd(hfac)2 was used as precursors in the same chamber. Sequential deposition of two metals formed Pd-Pt bilayer films. The particle size of Pd and Pt on polysulfone is 15-30 nm, and the thickness of the bilayer is 120-180 nm.

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Preparation and Catalytic Performance of Zeolite Layer in Microchannels of a Microreactor by an on-Site Flow Synthesis Method CAI Hongli;ZHANG Xiongfu*;LIU Haiou;YEUNG King Lun 2007, 28 (9):  758-760.  Abstract ( 2186 )   [Full Text(HTML)] () PDF (251KB) ( 1057 )   A zeolite-based microreactor was fabricated and tested for Knoevenagel condensation between benzaldehyde and ethylcyanoacetate with a continuous CsNaX zeolite layer as the catalyst, which was prepared within the microreactor channel using a novel flow method. The method involved two-step procedures in which NaX zeolite seeds for the growth of zeolite layer were introduced onto the internal surface of the microchannel by using a seeding technique and then grew into a zeolite layer by an on-site flow hydrothermal treatment followed by ion-exchange with 0.5 mol/L CsNO3 solution. The zeolite-based microreactor showed higher catalytic activity for the reaction compared with the conventional batch reactor.

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Direct Synthesis of NaY Zeolite with Small Crystal Size via Hydrothermal Method without Seed Gel HU Linyan;XIE Sujuan;WANG Qingxia;LIU Shenglin;XU Longya* 2007, 28 (9):  761-765.  Abstract ( 2112 )   [Full Text(HTML)] () PDF (303KB) ( 1053 )   The NaY zeolite with small crystal size between 0.30 and 0.35 μm could be directly synthesized by the hydrothermal method, using sodium aluminate and silica sol as the main raw materials without seed gel or organic additives under hydrothermal conditions. The molar composition of reactants was 5.1 Na2O•Al2O3•10 SiO2•(140-220) H2O, and the reaction system was aged at room temperature for 3 d and was then crystallized at 100 ℃ for 9 h). The NaY zeolite samples were characterized by XRD, SEM, XRF, and DLS techniques. The samples have uniform granularity and good dispersibility. The catalytic performance of two La/Y catalyst samples with different crystal sizes for 1-butene pulse aromatization was measured. The La/Y catalyst sample with smaller crystal size has better aromatization stability, coke accommodation capability, and resistance ability to coke deposition.

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Effect of Na Addition on Iron-Based Catalyst for Fischer-Tropsch Synthesis AN Xia;WU Baoshan*;WAN Haijun;LI Tingzhen;TAO Zhichao;XIANG Hongwei;LI Yongwang 2007, 28 (9):  766-772.  Abstract ( 2102 )   [Full Text(HTML)] () PDF (503KB) ( 1114 )   A series of Fe-based catalysts for Fischer-Tropsch synthesis (FTS) were prepared by impregnation of the FeCuK/SiO2 precursor with different amounts of sodium acetate. The catalysts were characterized by atomic emission spectroscopy, N2 adsorption, temperature-programmed reduction, and Mssbauer effect spectroscopy. The catalytic performance for FTS was investigated in a continuous stirred tank slurry reactor under reaction conditions of H2/CO=0.67, WHSV=2000h-1, 1.5 MPa, and 250 ℃. A low level of Na loading increases the surface area of the catalyst and enhances the dispersion of iron species in the catalyst, but excessive addition of Na decreases the surface area. Incorporation of Na in the catalyst inhibits the first step reduction in H2 and promotes carburization in CO or syngas. The catalysts with different Na loadings display various FTS activity and are deactivated after 500 h on stream to some extent. Moreover, the reaction results indicate that the addition of Na slightly affects water-gas shift activity, suppresses methane selectivity, and promotes light alkene selectivity.

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Influence of Preparation Methods on Properties of Nanosized ZrO2/Al2O3 Composite Supports LI Ning*;LUO Laitao 2007, 28 (9):  773-778.  Abstract ( 1978 )   [Full Text(HTML)] () PDF (378KB) ( 978 )   The impregnation-precipitation method was adopted to prepare the nano-sized ZrO2/Al2O3 composite supports. The effects of impregnation and drying methods on the surface properties, thermal stability, and crystal structure of composite supports were characterized byX-raydiffraction, N2 physical adsorption, differential scanning calorimetry (DSC), and temperature-programmed desorption. The results showed that there was no ZrO2-Al2O3 mixture or solid solution formed in the composite, and the nano-ZrO2 was only loaded on the surface of Al2O3. The specific surface area of ZrO2/Al2O3 dried under microwave (158.7 m2/g) was large with the most probable pore size of 19.4 nm, and the particle size of ZrO2 was about 4.2 nm with a tetragonal phase. Microwave induced the formation of new acid-base centers and enhanced the interaction between ZrO2 particles and Al2O3. The ZrO2/Al2O3 composite support prepared by microwave drying had better thermal stability, and there was no absorption peak in the range of 873-1073K in the DSC curves. The ZrO2/Al2O3 composite supports prepared by other methods have an obvious endothermic peak in the range of 903-1023K, indicating that some of the tetragonal ZrO2 crystals on the composite support surface transformed into monoclinic ZrO2. Microwave drying could enhance the interaction between the nano-ZrO2 particles and Al2O3 of the ZrO2/Al2O3 composite support prepared using the ultrasonic method and make the ZrO2 particle size (3.4 nm) smaller, without changing the crystal structure of ZrO2.

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Removal of Organic Pollutants from Raw Water by Combined Process of TiO2-Photocatalytic Ozonation and Biologically Activated Carbon LI Laisheng*;ZHU Wanpeng;ZHANG Pengyi;ZHANG Qiuyun 2007, 28 (9):  779-782.  Abstract ( 1992 )   [Full Text(HTML)] () PDF (230KB) ( 1037 )   Removal of organic pollutants from raw water by a combined process of TiO2-photocatalytic ozonation and biologically activated carbon (TiO2/UV/O3-BAC) was investigated. The TiO2/UV/O3 process decomposed macromolecule organic compounds into small molecules and increased their biodegradability. Under the optimum conditions, the dissolved organic carbon (DOC) was removed by 46.5% in the TiO2/UV/O3-BAC process, but the DOC was removed by only 41.6% in the UV/O3-BAC process. Compared with the UV/O3-BAC process, the synergetic effect of the TiO2/UV/O3-BAC process was stronger. The TiO2/UV/O3-BAC process was effective in removing phthalate esters, and their removal ratio reached more than 94% but decreased with the increase in the length of the alkyl side chains and the alkyl branch chains. The TiO2/UV/O3-BAC process was also very effective in removing polybromobiphenyls, and their removal ratio reached more than 89% but decreased with the increase in substitutional bromine atoms except for 2,2′,5,5′-tetrabromobiphenyl, which could be completely removed.

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Catalytic Combustion of Methane on CaxLa1-xMnAl11O19Hexaaluminates LI Tong;ZHANG Ke;LIU Shuo;DOU Lixin;LI Yongdan* 2007, 28 (9):  783-788.  Abstract ( 2128 )   [Full Text(HTML)] () PDF (469KB) ( 821 )   The effects of calcium substitution for lanthanum on the catalytic activity and stability of CaxLa1-x-MnAl11O19hexaaluminate catalyst prepared by co-precipitation were investigated. The samples were characterized byX-raydiffraction, N2 adsorption, temperature-programmed reduction, and transmission electron microscopy (TEM). It was observed that Ca could not be totally incorporated into the hexaaluminate lattice for a high doping amount (x=0.8). In this case, a separate CaAl4O7 phase was formed. Ca0.2La0.8MnAl11O19possessed the best catalytic activity with light-off temperature of 723 K and the highest BET surface area of 26.1 m2/g after calcination at1373K. The TEM results revealed that the substitution of La3+by Ca2+led to a thinner hexaaluminate planer crystal, which improved the sintering resistance, increased the surface area, and raised the amount of reactive Mn3+species and the reducibility of the hexaaluminate. The enhanced catalytic activity was attributed to the combined effect of higher specific surface area and Mn3+content. Compared to Sr2+- and K+-substituted La-hexaaluminates, the Ca2+-substituted samples demonstrated the lowest light-off temperature in methane combustion.

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In Situ Infrared Spectroscopy of Active Oxygen Species for Oxidative Coupling of Methane over BaF2/La2O3 Catalyst WANG Lihua;YI Xiaodong;WENG Weizheng*;WAN Huilin* 2007, 28 (9):  789-793.  Abstract ( 2149 )   [Full Text(HTML)] () PDF (359KB) ( 1042 )   In situ IR spectroscopy was used to study the superoxide species (O-2) for oxidative coupling of methane (OCM) over the BaF2/La2O3 catalyst. After the pretreatment of the catalyst with O2, the IR peak at 1108-1118 cm-1appeared, which was assigned toO-Obond stretching vibration in O-2 species. After the introduction of18O2isotope, the IR peak at 1108-1118 cm-1was weakened, and the absorption peaks appeared at1086and1051cm-1, which was consistent with the assignment of theO-18Obond and18O-18Obond stretching vibrations in the superoxide species, respectively. At 700 ℃, the superoxide species could react with CH4, accompanied by the formation of gas phase C2H4. A good correlation between the rate of O-2 consumption and the rate of C2H4 formation was observed, so the superoxide species was believed to be responsible for the OCM reaction over the BaF2/La2O3 catalyst.

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Preparation of Pd/Al2O3 Membrane and Its Catalytic Performance for Hydrogenation of1,5-Cyclooctadiene ZHOU Yonghua*;YE Hongqi;Reinhard SCHOMCKER 2007, 28 (9):  794-798.  Abstract ( 2226 )   [Full Text(HTML)] () PDF (380KB) ( 875 )   The supported Pd/Al2O3 membrane samples with controllable Pd loading were prepared by impregnation with Pd-containing microemulsion. Pd nanoparticles in the microemulsion and in the pore structure of Al2O3 membrane were characterized by scanning electron microscopy and atomic absorption spectroscopy. The catalytic performance of the Pd/Al2O3 membrane samples for the hydrogenation of1,5-cyclooctadiene over a catalytic contactor membrane reactor was measured. The results showed that the Pd loading amount, impregnation methods, calcination temperature, and pore size of the Al2O3 support affected the activity and selectivity of the Pd/Al2O3 membrane samples. The optimal preparation conditions for Pd/Al2O3 membrane with high activity and higher selectivity for cyclooctene were that the Pd nano-particles were slowly deposited from Pd-containing microemulsion while the Al2O3 membrane support was circularly impregnated with Pd-containing microemulsion, the calcination temperature was 300 ℃, and the pore size of the Al2O3 support was 1.9 μm.

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Vinyl Chloride Production by Oxychlorination of Ethane over CuCl2-KCl Catalysts Supported on MgO-Modified γ-Al2O3 LIU Jie;ZHOU Guangdong;L Xueju;ZHEN Kaiji;ZHANG Wenxiang;CHENG Tiexin* 2007, 28 (9):  799-804.  Abstract ( 2177 )   [Full Text(HTML)] () PDF (468KB) ( 939 )   A series of CuCl2-KCl catalysts supported on MgO-modified γ-Al2O3 were prepared by the impregnation method.X-raypowder diffraction (XRD), N2 physical adsorption, NH3-temperature-programmed desorption (TPD), and temperature-programmed reduction (TPR) techniques were employed to characterize the structure, the acidity, the reduction and oxidation properties of the catalysts, respectively. The catalytic performance of CuCl2-KCl/MgO-Al2O3 catalysts was evaluated for the oxychlorination of ethane to produce vinyl chloride. XRD results indicate that impregnation of γ-Al2O3 with Mg(NO3)2 forms surface MgAl2O4 spinel on the support. TPR results show that the formation of MgAl2O4 strengthens the interaction between Cu species and the support and promotes the reduction of CuⅡto CuⅠ. The catalytic results reveal that the conversion of ethane and the selectivity for vinyl chloride increase with increasing MgO content, and the highest vinyl chloride selectivity (49.1%) is obtained over the CuCl2-KCl/MgO-Al2O3 catalyst with 10% MgO loading. NH3-TPD results indicate that the surface MgAl2O4 neutralizes strong acid sites of the γ-Al2O3 support and increases the number of weak acid sites, and this is the main reason for the increase of vinyl chloride selectivity.

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CO2 Adsorption on SBA-15 Modified by Aminosilane WANG Linfang;MA Lei*;WANG Aiqin;LIU Qian;ZHANG Tao* 2007, 28 (9):  805-810.  Abstract ( 2065 )   [Full Text(HTML)] () PDF (367KB) ( 1020 )   By grafting amines onto the mesoporous support SBA-15, a highly efficient adsorbent has been obtained. This material shows potential applications in the removal of CO2 from enclosed areas such as space shuttles and submarines. SBA-15 was modified with 3-aminopropyl-triethoxysilane (APTES) by post-synthesis silylation and one-step silylation methods using ethanol as the solvent. The physical properties of these adsorbents were characterized byX-raypowder diffraction and N2 adsorption-desorption. The ordered hexagonal mesoporous structure of SBA-15 is well preserved after the modification. CO2 adsorption was tested using a static adsorption equipment. Adsorption isotherms demonstrate that the one-step silylation method is better than the post-synthesis silylation method. SBA-15 that was modified with APTES through one-step silylation can adsorb 34.2 mg/g of CO2 at room temperature when the partial pressure of CO2 is 0.005 MPa. Active carbon, the traditional adsorbent of CO2, was also tested. At room temperature, modified SBA-15 shows better performance than active carbon when the partial pressure of CO2 is lower than 0.02 MPa.

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Optimized Preparation and Characterization of Copper-Based Catalyst by Acid-Alkali Alternate Precipitation Method for Methanol Synthesis WU Zaiguo;CEN Yaqing;LIU Huazhang* 2007, 28 (9):  811-816.  Abstract ( 2026 )   [Full Text(HTML)] () PDF (464KB) ( 1126 )   The Cu-based catalyst (500 g) for methanol synthesis was prepared by an acid-alkali alternate precipitation method. The catalyst samples were characterized by means ofX-raydiffraction, N2 adsorption, scanning electron microscopy, oxygen chemisorption, and H2 temperature-programmed reduction. The effects of the stirring speed, the trickle speed of solution, and the concentration of alkali and metal salt solution on the catalytic performance of the Cu-based catalyst for methanol synthesis were studied. The amorphous CuO-ZnO solid solution was formed in the catalyst, and itsX-raydiffraction was weakened and broadened, indicating the lower crystallization degree. The size of CuO and ZnO crystallites was decreased, the catalyst grains became smaller, and its particle size distribution was more homogeneous. The existence of amorphous CuO-ZnO solid solution could increase the BET surface area of the catalyst. The catalyst prepared by the acid-alkali alternate precipitation method showed higher Cu dispersion and bigger Cu surface area. Under the optimized preparation conditions, the Cu-based catalyst prepared in this work was higher than other domestic and foreign industrial catalysts in activity and thermal stability.

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Synthesis of ZSM-34 and Its Catalytic Properties in Methanol-to-Olefins Reaction ZHOU Fan;TIAN Peng;LIU Zhongmin*;LIU Guangyu;CHANG Fuxiang;LI Jinzhe; 2007, 28 (9):  817-822.  Abstract ( 2014 )   [Full Text(HTML)] () PDF (434KB) ( 689 )   ZSM-34 (OFF/ERI intergrowth) was synthesized using choline chloride as the template in a shorter crystallization time under hydrothermal conditions. Many factors that may influence the synthesis were investigated. The ERI content in ZSM-34 could be adjusted by selecting different synthesis conditions. The synthesized products were characterized byX-raydiffraction, scanning electron microscopy, andX-rayfluorescence spectroscopy. Adsorption experiments showed that ZSM-34 possessed high pore volume, and the adsorption amount of n-hexane reached 11.4%. In the methanol-to-olefins reaction, HZSM-34 exhibited high selectivity for ethylene. The maximum selectivity for total olefins (C2H4+C3H6) over HZSM-34 was 86.0%, and it nearly did not change even when the methanol conversion decreased. High-temperature steam treatment increased the framework Si/Al ratio and thus decreased the acidity of HZSM-34, which led to the obvious decrease in propane selectivity and the increase in initial olefins selectivity.

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Selective Hydrodesulfurization of Full-Range FCC Gasoline over ZnO/θ-Al2O3 Catalyst WEN Guangming;WANG Wenshou;CHEN Lixing;GUO Hongchen*;WANG Xiangsheng 2007, 28 (9):  823-828.  Abstract ( 2157 )   [Full Text(HTML)] () PDF (462KB) ( 883 )   The selective hydrodesulfurization performance of three kinds of aluminas and the ZnO/θ-Al2O3 catalyst was studied with full-range FCC gasoline as the feedstock. The selective factor of θ-Al2O3 for the hydrodesulfurization of the full-range fluidized catalytic cracking gasoline is much higher than those of γ-Al2O3 and γ-Al2O3 calcined at 900 ℃. Impregnation of θ-Al2O3 with ZnO can further enhance the hydrodesulfurization activity and selectivity of θ-Al2O3. The characterization results of pyridine adsorption Fourier transform infrared spectroscopy (FT-IR), H2 temperature-programmed reduction (H2-TPR), andX-raydiffraction indicate that there is only weak Lewis acidity on the surface of θ-Al2O3, and the FT-IR spectrum of pyridine adsorption on θ-Al2O3 is quite different from the other two aluminas. The loading of ZnO onto the surface of θ-Al2O3 results in the formation of Zn(AlO2)2 spinel structure and the shift of the high-temperature H2-TPR peak of the catalyst toward lower temperature.

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Preparation of Ultrafine Ni-Cu-Co-La Catalysts for Hydrogenation of Acetonitrile REN Fei;LI Qiuxiao* 2007, 28 (9):  829-834.  Abstract ( 1967 )   [Full Text(HTML)] () PDF (466KB) ( 807 )   The ultrafine Ni-Cu-Co-La, being employed as an efficient catalyst for hydrogenation of acetonitrile to ethylamine, was prepared by co-reduction of the mixed solution of NiCl2•6H2O, CuSO4•5H2O, CoCl2•6H2O, and LaCl3•7H2O using hydrazine hydrate and potassium borohydride.X-raydiffraction,X-rayphotoelectron spectroscopy, transmission electron microscopy, and temperature-programmed desorption were used for the characterization of the catalyst. It was found that Cu, Co, and La showed the positive effects on acetonitrile conversion and ethylamine yield. Under the conditions of 1.8 MPa, 120 ℃, and1 h, the conversion of acetonitrile and the selectivity for ethylamine reached 100% and 98.24%, respectively. For the hydrogenation of acetonitrile to ethylamine, the ultrafine Ni-Cu-Co-La catalyst exhibited higher activity and selectivity than other types of catalysts, such as Ni-B amorphous alloy, Co-B amorphous alloy, and Raney Ni catalyst.

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Effect of Support on Close Coupled Supported Palladium Catalysts LI Xiang;MENG Ming*;LIU Yong;LUO Jinyong 2007, 28 (9):  835-840.  Abstract ( 2263 )   [Full Text(HTML)] () PDF (409KB) ( 1023 )   The ZrO2, SnO2, and SnO2-ZrO2 oxides were prepared by the urea-hydrolysis method, and the SnO2-Al2O3 was prepared by the adsorption-precipitation method. A series of catalysts with 0.5% Pd supported on these oxides were prepared by the impregnation method.X-rayphotoelectron spectroscopy, in-situ diffuse reflectance FT-IR (DRIFTS), laser Raman spectroscopy, and temperature-programmed reduction were employed to characterize the catalysts. The effect of support on the chemisorption and redox ability of the supported palladium oxide species (PdOx) was investigated and correlated with the C3H8 oxidation performance of the catalyst. The DRIFTS results indicate that the dilution effect of Pd cluster on Al2O3 by Sn in Pd/SnO2-Al2O3 catalyst increases both the dispersion of Pd and the intensity of linear CO adsorption. However, the dilution effect probably decreases the amount of Pd-PdO active site pairs and inhibits the condensation of palladium hydroxides (Pd-OH), which blocks the active sites and thus decreases the catalytic activity. In Sn0.4Zr0.6O2 support, SnO2 prevents the transformation of tetragonal phase ZrO2, and the surface area of Sn0.4Zr0.6O2 binary oxide is larger than that of SnO2 and ZrO2. As a result, the PdOx crystallites possess a moderate dispersion on Sn0.4Zr0.6O2 support. Additionally, the interaction between Pd and Sn0.4Zr0.6O2 support leads to the oxidation state of Pd between Pd0 and PdO, making the PdOx more favorable to activatingC-Hbonds. The results of activity evaluation reveal that Pd/Sn0.4Zr0.6O2 with lower surface area shows the best C3H8 oxidation activity, whereas Pd/SnO2-Al2O3 with higher surface area gives very low oxidation activity. This indicates that the highly dispersed PdOx species appear to be responsible for the detrimental effect on the C3H8 oxidation process, whereas the PdOx (x<1) crystalline with moderate dispersion and low oxidation state is the main active component.