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Chinese Journal of Catalysis
2007, Vol. 28, No. 3
Online: 25 March 2007

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Synthesis of SAPO-11 and MgAPO-11 Molecular Sieves in Water-Butanol Biphase Media YANG Xiaomei;XU Zhusheng;MA Huaijun;XU Yunpeng;TIAN Zhijian;LIN Liwu 2007, 28 (3):  187-189.  Abstract ( 1940 )   [Full Text(HTML)] () PDF (235KB) ( 1026 )   SAPO-11 and MgAPO-11 molecular sieves were synthesized in water-butanol biphase media. The water-butanol biphase media favored the incorporation of Si into SAPO-11 and the formation of more acid sites. Therefore, the Pt catalyst supported on the SAPO-11 synthesized in the biphase medium exhibited much higher catalytic activity for the hydroisomerization of n-dodecane than that supported on the SAPO-11 synthesized in an aqueous medium. In contrast, the water-butanol biphase media were unfavorable for the Mg substitution into the framework, and thus the acid sites and the catalytic activity of Pt/MgAPO-11 decreased.

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V-Cu Composite Oxide Catalyst for Transesterification of Dimethyl Carbonate with Phenol to Diphenyl Carbonate TONG Dongshen;CHEN Tong;YAO Jie;WANG Yue;WANG Gongying;SHI Dachuan;LI Zheng;CHEN Zhiming 2007, 28 (3):  190-192.  Abstract ( 2184 )   [Full Text(HTML)] () PDF (181KB) ( 1045 )   The V-Cu composite oxide catalyst was prepared by coprecipitation and used for the synthesis of diphenyl carbonate (DPC) by transesterification of dimethyl carbonate (DMC) with phenol. The effect of the molar ratio of V/Cu and the reusability of the catalyst were investigated. The catalyst showed the highest activity with a V/Cu molar ratio of 4/1. Under the conditions of 150～180 ℃ and 9 h, the conversion of phenol and the transesterification selectivity over the V-Cu catalyst were 37.0% and 96.8%, respectively. According to the X-ray diffraction results, the V-Cu composite oxide was composed of crystalline V2O5 and CuV2O6 at V/Cu=4/1. Both crystalline V2O5 and CuV2O6 were the active phase. In addition, the activity of the catalyst was reduced from 37.0% to 23.7% after the catalyst was reused three times. However, the used catalyst could be easily regenerated by calcination at 550 ℃ in air for 5 h, and the catalytic activity of the regenerated catalyst was almost as high as that of the fresh sample.

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Effect of Supports on Catalytic Performance of Ni-Based Catalysts for Tri-reforming of Methane JIANG Hongtao;LI Huiquan*;ZHANG Yi 2007, 28 (3):  193-195.  Abstract ( 1938 )   [Full Text(HTML)] () PDF (211KB) ( 897 )   MgO, TiO2, and Mg0.5Ti0.5Ox composite oxides were prepared by the sol-gel technique. Ni was supported on these oxides by the wet impregnation method. No peak of free NiO was observed in all X-ray diffraction patterns of the catalysts. The addition of Ti to the NiO-MgO system prevents the formation of solid solution but does not decrease the dispersion of Ni particles. The catalytic performance of the catalysts for tri-reforming of methane was investigated in a fixed-bed flow reactor at 850 ℃ under 1.0 MPa with space velocity of 31 800 ml/(g·h) and feed composition of n(CH4)∶n(CO2)∶n(H2O)∶n(O2)=1∶0.48∶0.54∶0.1. The catalytic activity of Ni/TiO2 and Ni/MgO decreases during the reaction period. The Ni/Mg0.5Ti0.5Ox catalyst has a relatively high stability, which is mainly dependent on the moderate interaction between the metal and the support and the moderate ability to be reduced.

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Preparation of Graphitic Carbon as Support of Ru-Based Catalyst for Ammonia Synthesis ZHU Hong;HAN Wenfeng;CHAI Haifang;LIU Huazhang 2007, 28 (3):  196-200.  Abstract ( 1949 )   [Full Text(HTML)] () PDF (258KB) ( 1030 )   Activated carbon (AC)as a support of Ru-based catalyst for ammonia synthesis was graphitized at high temperature in argon and then oxidized with a O2-N2 mixture and HNO3. Its structure, texture, and surface oxygenous groups were investigated by N2-physisorption and temperature-programmed desorption. The results showed that the graphitization process could eliminate the carbon impurities and improve the support stability. However, after the thermal treatment, the specific surface area of AC decreased sharply, and its texture was destroyed. The surface area and porosity could be recovered partially by oxidation treatment with a O2-N2 mixture. In further treatment with HNO3, the amount of surface oxygenous groups was increased, and the surface polarity was transformed from hydrophobic to hydrophilic. HNO3 treatment led to a significant increase in the catalyst activity with an ammonia concentration in the exit being more than 19% (under the conditions of GHSV=10000 h-1, p=10 MPa, and θ=400 ℃). Thus, the AC graphitized at suitable temperature followed by oxidation with O2-N2 and HNO3 was a good support of Ru-based catalyst for ammonia synthesis.

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Alkylation of Propane with Benzene over Pt-Modified Zeolites HUANG Xueqing;;SUN Xinde;ZHU Shukui;LIU Zhongmin 2007, 28 (3):  201-204.  Abstract ( 2039 )   [Full Text(HTML)] () PDF (236KB) ( 721 )   The alkylation of propane with benzene over Pt catalysts supported on different zeolites was studied. Pt/HZSM-5 shows much higher selectivity for alkylbenzene than other catalysts. With increasing Pt loading from 0 to 0.3%, the conversion of propane and the selectivity for C9 and C10+ aromatics increase, whereas the selectivity for non-aromatics decreases. The effects of the reaction temperature, space velocity, and benzene/propane molar ratio on the alkylation of propane with benzene over Pt/HZSM-5 zeolite were investigated. Low reaction temperature, high space velocity, and high benzene/propane molar ratio favor the formation of alkylbenzene.

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Adsorption Performance of Zeolites for NO and NO2 XING Na;WANG Xinping*;YU Qing;GUO Xinwen 2007, 28 (3):  205-209.  Abstract ( 2672 )   [Full Text(HTML)] () PDF (355KB) ( 1342 )   The adsorption and desorption performance of different zeolites, such as ZSM-5, 13X, SAPO, Y, β, and A, for NO and NO2 at 40 ℃ was investigated in the absence and presence of 10%O2 in 0.02%NO/N2. The TPD results of NO and NO2 revealed that adsorption of NO on the zeolites, especially on sodium form ones, could be substantially increased by the presence of oxygen owing to the co-adsorption of NO and NO2. Among the zeolites tested, Hβ showed the largest capacity for NO adsorption under the conditions without oxygen, whereas 13X zeolite displayed outstanding behavior for NOx adsorption under the conditions with oxygen.

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Pt Catalyst Supported on Multiwalled Carbon Nanotubes for Hydrogenation-Dearomatization of Toluene ZHOU Min;LIN Guodong;ZHANG Hongbin* 2007, 28 (3):  210-216.  Abstract ( 1977 )   [Full Text(HTML)] () PDF (522KB) ( 1233 )   Using home-made multiwalled carbon nanotubes (CNTs) as the support, the Pt/CNTs catalyst was prepared by an incipient wetness method. Performance of the catalyst for hydrogenation-dearomatization (HDA) of toluene was evaluated and compared with the reference catalysts supported on γ-Al2O3 and activated carbon (AC). Over the 1.0%Pt/CNTs catalyst under the reaction conditions of 0.4 MPa, 373 K, PhCH3/H2=6/94 (mol/mol) and GHSV=120 L/(h·g), the observed conversion of toluene HDA reached 100%, and the corresponding specific reaction rate was 0.0523 mmol/(s·m2). This value was 1.17 and 1.18 times that of the 1.4%Pt/γ-Al2O3 and 2.4%Pt/AC catalysts with the respective optimal Pt loading, respectively. It was experimentally found that using CNTs in place of γ-Al2O3 or AC as the support of the catalyst did not cause a significant change in the apparent activation energy for the toluene HDA reaction but led to a slight increase in concentration of catalytically active Pt species (Pt0) at the surface of the functioning catalyst. In addition, the Pt/CNTs catalyst could reversibly adsorb a greater amount of hydrogen under atmospheric pressure at temperatures from room temperature to 573 K. This unique feature would help to generate a microenvironment with higher stationary state concentration of active hydrogen-adspecies at the surface of the functioning catalyst. These effects favored the toluene HDA reaction.

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Synthesis of Nanocrystalline MnCo2O4 by Microwave Treatment and Its Electrocatalytic Performance REN Zhiwei;ZHOU Debi*;TU Saiqi 2007, 28 (3):  217-221.  Abstract ( 2417 )   [Full Text(HTML)] () PDF (359KB) ( 1214 )   A composite oxide MnCo2O4 was prepared by microwave heating a precursor of oxalate mixture obtained by coprecipitation using manganese acetate and cobalt acetate as raw materials. X-ray diffraction and scanning electron microscopy results show that the MnCo2O4 is good nanocrystalline with high purity and 10-20 nm size. The catalytic activity of MnCo2O4 for oxygen reduction in a basic solution at room temperature was tested. The polarization curve reveals that the current density reaches 96 mA/cm2 at -0.2 V (vs Hg/HgO). In order to show the superiority of the microwave heating method, physical and chemical properties of the same product made by a conventional combustion method were also evaluated.

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Synthesis of Fe-MSU-1 and Its Catalytic Properties for Hydroxylation of Phenol LIU Hong*;WANG Zhigang;LI Hao 2007, 28 (3):  222-228.  Abstract ( 1971 )   [Full Text(HTML)] () PDF (423KB) ( 793 )   Iron-incorporated mesoporous silica material Fe-MSU-1 was successfully synthesized using lauryl alcohol-polyoxyethylene (23) ether as the templating agent under the neutral pH condition. The sample was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy, electron spin resonance, transmission electron microscopy, N2 adsorption, and inductively coupled plasma-atomic emission spectroscopy. Its catalytic performance for hydroxylation of phenol was studied. The effects of catalyst concentration, solvents, phenol/H2O2 molar ratio, reaction temperature, and reaction time on the hydroxylation of phenol over the Fe-MSU-1 catalyst were examined. The results showed that Fe3+ ions were successfully incorporated into the framework of MSU-1, and the Fe-MSU-1 material had a uniform worm-like mesoporous structure with about 2.9 nm pore diameter. After calcination, Fe3+ ions were mainly present in tetrahedral coordination, and no extraframework Fe2O3 was formed. Under the conditions of water solvent, n(phenol)/n(H2O2)=3, reaction temperature 353 K, and reaction time 7 h, the conversions of phenol and H2O2 and the selectivity for dihydroxybenzene reached 20.4%, 96.9%, and 99.6%, respectively.

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Preparation of Phthalocyanine-Modified Mesoporous Titania and Its Visible-Light Photocatalytic Activity LI Xiaopei;CHEN Feng*;ZHANG Jinlong 2007, 28 (3):  229-233.  Abstract ( 2246 )   [Full Text(HTML)] () PDF (312KB) ( 1147 )   Mesoporous titania was successfully prepared by the soft-template method. The low a ngle XRD pattern and BJH pore distribution indicated that the pores of mesoporou s titania were well ordered and had a average pore diameter of 4.75 nm. Cu( Ⅱ)-tetracarboxyphthalocyanine (CuPcTc)-sensitized mesoporous titania (CuPcTc -TiO2) photocatalyst samples were prepared by adsorption of CuPcTc on the surface of mesoporous titania. Under the irradiation of visible light (λ>5 50 nm), CuPcTc-TiO2 showed high photocatalytic activity for the degradat ion of fluorescein and had optimum visible-light activity when the CuPcTc ad sorption amount was 4% in mass fraction. In addition, CuPcTc-TiO2 exhibit ed higher visible-light photocatalytic activity than CuPcTc-sensitized P25 (CuP cTc-P25) for the degradation of fluorescein.

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Reduction of Pd/ZnO Catalyst and Its Catalytic Activity for Steam Reforming of Methanol WANG Yanhua*;ZHANG Jingchang;XU Hengyong;Bai Xuefeng 2007, 28 (3):  234-238.  Abstract ( 2259 )   [Full Text(HTML)] () PDF (336KB) ( 1027 )   The effect of reduction temperature of the coprecipitated 15.9%Pd/ZnO catalyst on the catalytic activity for steam reforming of methanol was investigated. The results showed that methanol conversion at 523 K reached a maximum of 41.6% with a CO2 selectivity of 94.6% and an outlet CO concentration of 1.26% over the catalyst reduced at 523-573 K. X-ray diffraction analysis revealed that a PdZn alloy began to form at a reduction temperature of 523 K. The improvement in activity at reduction temperature ranging from 523 to 573 K was attributed to the formation of the PdZn alloy with crystal size of 5-14 nm. The interaction between Pd and ZnO upon reduction was also explored by means of temperature-programmed reduction and X-ray diffraction. The results demonstrated that the reduction over Pd/ZnO might undergo a process PdO/ZnO→Pd/ZnO→PdZnO1-x/ZnO→PdZn alloy/ZnO. The PdZn alloy was found to be partially oxidized to PdZnO1-x again during the reaction. The PdZn alloy and PdZnO1-x species might be the real active species.

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Synthesis of Nanometer Au/ZSM-5 Catalyst and Its Catalytic Performance for Oxidation of β-Ionone with Molecular Oxygen PENG Zhiguang;L Gongxuan* 2007, 28 (3):  239-245.  Abstract ( 2493 )   [Full Text(HTML)] () PDF (462KB) ( 1119 )   Gold nanoparticles with different sizes were prepared by reducing HAuCl4 with nitromethane and were then supported on ZSM-5 zeolite by impregnation. The oxidation of β-ionone with molecular oxygen over Au/ZSM-5 was studied. The results indicated that β-ionone was catalytically oxidized to 5,6-epoxy-β-ionone, 4-oxo-β-ionone, 4-hydroxy-β-ionone, and a little dihydroactinidiolide. All the products were valuable flavors or their precursors. Compared with the traditional chromium catalyst, the Au/ZSM-5 catalyst could selectively catalyze the oxidation of β-ionone to epoxy compounds, and the catalyst could be easily separated after the reaction. The effects of the support, solvent, oxidant, reaction temperature, and time on the catalytic performance of Au/ZSM-5 were investigated. The catalytic activity of the Au/ZSM-5 catalyst decreased with increasing size of Au nanoparticles. In addition, the solvent played an important role in the performance of the catalyst. The catalytic activity of Au/ZSM-5 was maintained after repeated use five times.

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Synthesis of Cyclohexylbenzene by Hydroalkylation of Benzene over Pd/Hβ Binary Catalyst QIU Jun*;Kenichi KOMURA;Yoshihiro KUBOTA;Yoshihiro SUGI 2007, 28 (3):  246-250.  Abstract ( 2497 )   [Full Text(HTML)] () PDF (352KB) ( 843 )   The Pd/Hβ binary catalyst was prepared by the impregnation method and was used for the hydroalkylation of benzene to cyclohexylbenzene. The effects of reaction temperature, reaction time, hydrogen pressure, Hβ acidity, and metal loading were investigated. The results indicated that the conversion of benzene and the selectivity for cyclohexylbenzene approached 24.3% and 88.0%, respectively, under the conditions of 2.5 MPa H2, 200 ℃, and 3 h. The preferable balance between metal active sites and acidic sites in catalyst was the key to the hydroalkylation of benzene. Moreover, the mechanism of the reaction was discussed.

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Microemulsion Synthesis of Nanosized SiO2/TiO2 Particles and Their Photocatalytic Activity PU Yuying;FANG Jianzhang*;PENG Feng;LI Baojian;HUANG Lei 2007, 28 (3):  251-256.  Abstract ( 2502 )   [Full Text(HTML)] () PDF (484KB) ( 902 )   Nanosized TiO2 and SiO2/TiO2 particles were synthesized by hydrolysis of tetrabutyl titanate and tetraethyl orthosilicate in a Triton X-100/n-hexanol/cyclohexane/ammonia reverse microemulsion. The particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy. The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange under UV light irradiation. The effects of SiO2 content, crystal structure, and crystallite size on the photocatalytic activity were investigated. From FT-IR analysis, a new band at 950 cm-1 for Ti-O-Si vibration was observed. Ti-O-Si bond and amorphous SiO2 suppressed the phase transformation of titania from anatase to rutile, increased the stability of anatase TiO2, and inhibited the growth of crystallite. The average size of titania decreased from 38.4 nm in pure TiO2 to 3.9 nm in SiO2/TiO2 with a SiO2/TiO2 molar ratio of 2/1. In addition, the photocatalytic activity decreased with the increase of rutile content. SiO2/TiO2 particles with a SiO2/TiO2 molar ratio of 1/7 showed the highest photocatalytic activity for the photocatalytic degradation of methyl orange.

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Preparation of Pt-Pd/BaO/TiAlO Catalyst for NOx Storage-Reduction and Its Sulfur Resistance CHEN Ying*;HE Jun;MA Yugang;CHEN Xiaoping;WANG Lefu;LI Xuehui 2007, 28 (3):  257-263.  Abstract ( 2344 )   [Full Text(HTML)] () PDF (485KB) ( 969 )   NOx in exhaust gases from lean burn engines can be clarified over Toyota-type storage-reduction catalysts, but it is difficult for the catalyst to be applied in domestic automobiles due to deterioration caused by SO2 in the emission. A novel Pt-Pd/BaO/TiAlO catalyst for NOx storage-reduction (NSR) was prepared by coprecipitation-impregnation. The catalyst was evaluated by NOx storage in lean burn and by NOx storage-reduction in lean-rich cycles both in the absence and in the presence of SO2, respectively, using a series cyclic sequences of feed which changes from lean conditions (GHSV of 12000 h-1, 800 mg/m3 of NO, 4% of O2, 200 mg/m3 of SO2 for sulfur resistance test, remainder Ar, 350 ℃, and for 30 min) to rich conditions (GHSV of 12000 h-1, 4% of H2, remainder Ar, 350 ℃, and for 20 min). The TiAlO bi-oxide and the catalyst were characterized by temperature-programmed desorption, temperature-programmed reduction, N2 adsorption-desorption, and X-ray diffraction. The results showed that TiAlO bi-oxide in Pt-Pd/BaO/TiAlO catalyst acted as both a support and an adsorbent in the NOx storage-reduction process. The maximum capacity for NOx storage was obtained when the molar ratio of Ti/Al in TiAlO was 1∶2. BaO (4%) not only enhanced the thermal stability of catalyst but also increased NOx storage capacity. Pt-Pd/BaO/TiAlO had better sulfur resistance compared with the Toyota-type NSR catalyst Pt/BaO/γ-Al2O3. One of the reasons might be that sulfur compounds produced in NOx storage on the surface of the catalyst were unstable and easily to be removed by reduction.

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Synthesis and Characterization of Mesoporous TiO2-SO2-4 SHEN Jun;LUO Ni;ZHANG Mingjun;TIAN Congxue;ZHANG Zhao* 2007, 28 (3):  264-268.  Abstract ( 2074 )   [Full Text(HTML)] () PDF (407KB) ( 947 )   Mesoporous anatase TiO2-SO2-4 with high thermal stability was synthesized without organic templates. The sample was characterized using X-ray diffraction, N2 adsorption, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy, and its photocatalytic activity was tested. SO2-4 that is bonded to free -OH on pore walls of metatitanic acid during the calcination acts as the pore structure-directing agent and pore structure support. After calcination at 500 ℃, the mesoporous TiO2-SO2-4 has a surface area of 202.2 m2/g and an average pore diameter of 2.8 nm. The electron inductive effect of S=O in TiO2-SO2-4 not only makes adjacent Ti a superacidic center but also causes a red shift of the adsorption spectrum of the sample by 30 nm. Its photocatalytic activity is also enhanced obviously.

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Photocatalytic Performance of TiO2 Thin Films Deposited on Glass and Quartz Substrates ZHANG Wenjie;*;ZHU Shenglong;LI Ying;WANG Fuhui;HE Hongbo 2007, 28 (3):  269-273.  Abstract ( 2161 )   [Full Text(HTML)] () PDF (420KB) ( 1118 )   TiO2 thin films were deposited on glass and quartz substrates, respectively, using the direct current reactive magnetron sputtering method. When the oxygen flow rate exceeded its threshold, the average film deposition rate was 160 nm/h and uniform and transparent TiO2 films could be obtained. The films deposited on the two substrates were all composed of anatase crystals with a preferred orientation of (220) plane, and small holes were distributed among the crystalline particles. The absorption edges of the two films were nearly at the same position in the whole spectrum although quartz had higher transmittance than the glass substrate. The titanium in the films was in the oxidation state of Ti4+, and the oxygen was in the form of O2- in TiO2 and also in H2O which was chemically and physically adsorbed on the films. The photocatalytic activity of the TiO2 films for the degradation of methyl orange was evaluated under UV irradiation. There was little difference in the photocatalytic activity between the films deposited on the two substrates although sodium and calcium ions in the glass substrate might have negative effects.

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Effect of Surface Acid Amount of Y Zeolite on Activity and Sulfur Tolerance of Supported Pd-Pt Catalysts LIU Huiru;LI Jianrong;ZHAO Dishun;LI Yongdan* 2007, 28 (3):  274-280.  Abstract ( 2243 )   [Full Text(HTML)] () PDF (445KB) ( 985 )   USY zeolite supports with different acid amounts were obtained by steam dealumination. Dual metal catalysts with a total loading of Pd and Pt of 1.15% were prepared by the ion-exchange method. The supports and catalysts were characterized by temperature-programmed desorption of ammonia, X-ray diffraction, nitrogen adsorption, and X-ray photoelectron spectroscopy. The catalytic activity for the hydrogenation of tetralin was examined with a fixed-bed continuous-flow reactor operating at 4.0 MPa. The sulfur tolerance was tested with a feed of 200 μg/g sulfur in the form of 4,6-dimethyldibenzothiophene. The two catalysts supported on USY zeolites with surface acid amounts of 626 and 203 μmol/g, respectively, showed excellent sulfur tolerance, while the catalysts of higher and lower acid amount showed decreased sulfur tolerance. Energy dispersive spectroscopic analysis proved that the support with a large acid amount adsorbed more sulfur, which might lead to the lower sulfur tolerance of the catalyst. The low sulfur tolerance of the catalyst with a low acid amount was attributed to the insignificance of the electron deficiency of the metal particles.

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In-Situ Reduction of Acetophenone to α-Phenylethanol with Hydrogen Derived from Aqueous-Phase Reforming of Methanol JIANG Li;ZHU Yifeng;XIANG Yizhi;LI Xiaonian* 2007, 28 (3):  281-286.  Abstract ( 2435 )   [Full Text(HTML)] () PDF (293KB) ( 1232 )   Endothermic aqueous-phase reforming of methanol for hydrogen generation and exothermic hydrogenation of acetophenone to α-phenylethanol can be performed over the same type of catalyst under similar conditions (temperature and pressure). In the present work, a novel route for in-situ aqueous-phase hydrogenation of acetophenone to α-phenylethanol was proposed, in which active hydrogen was obtained directly from aqueous-phase reforming of methanol. The experimental results indicated that high selectivity for C=O bond hydrogenation (95% of α-phenylethanol selectivity) was reached. Furthermore, the conversion of methanol and the selectivity for hydrogen in the aqueous-phase reforming of methanol were significantly increased. Also, the optimization of reaction conditions, such as reaction temperature, reaction pressure, acetophenone concentration, and the ratio of raw materials, was performed to promote the selectivity for hydrogen in aqueous-phase reforming of methanol and for α-phenylethanol in acetophenone hydrogenation.