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Chinese Journal of Catalysis
2012, Vol. 33, No. 2
Online: 20 February 2012


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In their article on pages 230–236 Zheng et al. reported a highly efficient 1wt% Au/ZrO₂ low-temperature water-gas shift catalyst with hydrothermally synthesized ZrO₂ as a support. This catalyst shows better catalytic activity compared to Au/Fe₂O₃, Au/CeO₂, and Au/CeZrO₄ catalysts. The uniform nanodisk morphology and larger pore volume and pore size of ZrO₂ help to improve the catalyst performance.

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Table of Contents for Vol. 33 No. 2 2012, 33 (2):  0.  Abstract ( 1140 )   PDF (1536KB) ( 895 )

Summary

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Progress in the Catalysts for the Hydrodeoxygenation of Phenols in Bio-oil WANG Wei-Yan, ZHANG Xiao-Zhe, YANG Yun-Quan, YANG Yan-Song, PENG Hui-Zuo, LIU Wen-Ying 2012, 33 (2):  215-221.  DOI: 10.3724/SP.J.1088.2012.10922 Abstract ( 3074 )   [Full Text(HTML)] () PDF (469KB) ( 1737 )   With the declining of crude oil resources, the development of bio-oil from biomass into fast pyrolysis has attracted much attention. However, the bio-oil contains many oxygenic compounds such as phenols, funans, aldehyde, ketone, etc., and its oxygen content is high up to 50%, leading to its low heating value and thermal instability, which hinders its extensive application. It is necessary to remove the oxygen from bio-oil by a hydrodeoxygenation (HDO) process. Among many oxygenic compounds, phenolic hydroxyl oxygen is considered the most difficult one to be removed. The HDO of phenols was reviewed and the effective way for further improving the catalyst activity was proposed.

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Recent Development of Pt-Based Core-Shell Structured Electrocatalysts in Fuel Cells ZHANG Hai-Yan, CAO Chun-Hui, ZHAO Jian, LIN Rui, MA Jian-Xin 2012, 33 (2):  222-229.  DOI: 10.3724/SP.J.1088.2012.10947 Abstract ( 3217 )   [Full Text(HTML)] () PDF (468KB) ( 1879 )   Cost, durability, and fuel supply infrastructure remain the key problems barricading the successful commercialization of fuel cells. As for the proton exchange membrane fuel cells, the cost and durability of key materials come from Pt catalysts used in the fuel cells. Due to the various cost and resource issues regarding Pt, it is important for researchers to develop low-Pt fuel cell catalysts. Recently, core-shell structured electrocatalysts have attracted increasing attention because of their unique structure in reducing the amount of Pt. The recent de-velopment of the preparation methods and characterization techniques for core-shell structured catalysts are reviewed. First, an introduction to the preparation methods for the synthesis of core-shell structured electrocatalysts was presented, including the colloid method, electro-chemical method, and chemical reduction method. Among these methods, the colloid method is the most facile and controllable and has already been widely employed in the synthesis. Electrochemical and chemical reduction methods are the most promising methods that have been developed in the past several years. Then, the characterization techniques were discussed in details. Among these techniques, the high-angle annular dark field-scanning transmission electron microscopy developed during recent years is regarded as an effective way to characterize the core-shell structured catalysts. Finally, the application problems and some research trends were discussed and summarized.

Research Briefing

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Low-Temperature Water-Gas Shift Reaction over Au/ZrO2 Catalysts Using Hydrothermally Synthesized Zirconia as Supports ZHANG Yan-Jie, ZHAN Ying-Ying, CAO Yan-Ning, CHEN Chong-Qi, LIN Xing-Yi, ZHENG Qi 2012, 33 (2):  230-236.  DOI: 10.1016/S1872-2067(11)60327-6 Abstract ( 3106 )   [Full Text(HTML)] () PDF (989KB) ( 1192 )   Au/ZrO2 catalysts with a nominal gold loading of 1.0% were prepared by a deposition-precipitation method employing a series of ZrO2 samples synthesized by a convenient hydrothermal route as supports. These catalysts were evaluated for low-temperature water-gas shift reaction under a model reformed methanol gas atmosphere. The effect of the hydrothermal synthesis temperature of zirconia on the catalytic activity of Au/ZrO2 was investigated. The optimal hydrothermal synthesis temperature of ZrO2 was 150 °C. The corresponding catalyst offers a CO conversion of 87% at a reaction temperature of 240 °C, which is significantly higher than that of the previously reported Au/Fe2O3, Au/CeO2, and Au/CeZrO4 catalysts. The Au/ZrO2 catalysts were characterized by X-ray diffraction, atomic absorption spectrometry, N2-physisorption, and scanning electron microscopy. The results indicate that the catalytic performance of the Au/ZrO2 catalysts is mainly influenced by the morphology and pore structure of the ZrO2 that was hydrothermally synthesized at different temperatures. A uniform nanodisk morphology and increase in the pore volume and pore diameter of the ZrO2 particles lead to a higher catalytic activity of the Au/ZrO2 catalyst.

Research papers

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Nanocasting, Template Synthesis, and Structural Studies on Cesium Salt of Phosphotungstic Acid for the Synthesis of Novel 1,3,5-Triaryl-pyrazoline Derivatives Razieh FAZAELI, Hamid ALIYAN, Shahram TANGESTANINEJAD, Esmaeel MOHAMMADI, Maryam BORDBAR 2012, 33 (2):  237-246.  DOI: 10.1016/S1872-2067(11)60330-6 Abstract ( 2861 )   [Full Text(HTML)] () PDF (610KB) ( 1186 )   The elimination of the silica matrix of composites by HF occurred by a two-step reaction deposition of a Cs2.5H0.5PW12O40 (CsHPW) salt nanocrystal. We used 2D hexagonal SBA-15 silica as a template for the nanofabrication of CsHPW nanoparticles. Nanocast CsHPW materials are stable against leaching and colloidization in polar solvents. The catalytic performance of the nanocast CsHPW materials exceeded that of bulk Cs2.5H0.5PW12O40, which is the most active among the acidic HPW salts. A series of novel 1,3,5-triaryl-pyrazoline derivatives were synthesized by the reaction between chalcone and phenylhydrazine in high yield in the presence of CsHPW salt nanocrystals.

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H2 Production with Low CO Selectivity from Photocatalytic Reforming of Glucose on Ni/TiO2-SiO2 R. M. MOHAMED, Elham S. AAZAM 2012, 33 (2):  247-253.  DOI: 10.1016/S1872-2067(10)60276-8 Abstract ( 2885 )   [Full Text(HTML)] () PDF (516KB) ( 1034 )    Nano-sized Ni particles on TiO2-SiO2 were synthesized by the two methods of photo-assisted deposition (PAD) and impregnation. H2, which is a promising energy carrier, with a low CO concentration was produced by the photocatalytic reforming of glucose (a model biomass) on the Ni/TiO2-SiO2 catalyst. The supported Ni enhanced the rate of H2 production while it suppressed CO selectivity. The catalysts were characterized by X-ray diffraction, X-ray absorption fine structure, transmission electron microscope, and nitrogen adsorption analysis. Both H2 production and CO selectivity were strongly dependent on the preparation method, and PAD-Ni/TiO2-SiO2 was the better catalyst for H2 production with the lowest CO concentration.

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Hydrothermal Synthesis of Porous Ag2S Sensitized TiO2 Catalysts and Their Photocatalytic Activities in the Visible Light Range ZHU Lei, MENG Zeda, TRISHA Ghosh, OH Won-Chun 2012, 33 (2):  254-260.  DOI: 10.1016/S1872-2067(10)60296-3 Abstract ( 2521 )   [Full Text(HTML)] () PDF (738KB) ( 1642 )   Porous Ag2S sensitized TiO2 catalysts were synthesized by the hydrothermal process. The crystallization and porous structure of the Ag2S/TiO2 composite photocatalysts were investigated by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, UV-Vis diffuse reflectance spectroscopy, and N2 adsorption. The Ag2S/TiO2 composites were mainly composed of anatase TiO2 and acanthite Ag2S. The absorption edge wavelengths of TiO2 and the Ag2S/TiO2 composite prepared with 3 mmol Na2S·5H2O were 400 and 800 nm, respectively, that is, the absorption edge of the composite had a pronounced red shift. The photocatalytic activity under visible light was investigated by the degradation of methylene blue with a UV-Vis spectrophotometer. The photocatalytic activities under visible light of the Ag2S/TiO2 photocatalysts were much higher than that of TiO2.

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Photodegradation of Molasses by a MoO3-TiO2 Nanocrystalline Composite Material Madhukar NAVGIRE, Ajeet YELWANDE, Deepak TAYDE, Balasaheb ARBAD, Machhindra LANDE 2012, 33 (2):  261-266.  DOI: 10.1016/S1872-2067(10)60298-7 Abstract ( 2181 )   [Full Text(HTML)] () PDF (356KB) ( 1507 )   A MoO3-TiO2 nanocrystalline composite material was prepared by a simple sol-gel method. The synthesized material was characterized by X-ray diffraction, scanning electron microscopy with an electron dispersion spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water. This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water, soil, and air pollution. The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation. Analysis of treated and untreated molasses was carried out by measuring its color, chemical oxygen demand, biological oxygen demand, pH, and total dissolved solid. Results from these analyses indicate the effective photodegradation of the molasses. This methodology has several advantages such as high photocatalytic activity, non-toxicity, cleanliness, and reusability of the catalytic material.

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Polysulfide Poisoning of Ag Electrocatalyst during L-Ascorbate Ion Electro-oxidation in Alkaline Solution Fereydoon GOBAL, Laleh MAJARI KASMAEE 2012, 33 (2):  267-274.  DOI: 10.1016/S1872-2067(11)60331-8 Abstract ( 2362 )   [Full Text(HTML)] () PDF (403KB) ( 682 )   L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10–5 to 4.5 × 10–4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of –0.3 to –0.2 V/SCE. The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were, 10–3 to 1 × 10–2 s and 1 × 10–4 to 1 × 10–2 s, respectively depending on the potential used for the impedance analysis. Based on the cyclic voltammetry findings, a mechanism for L-ascorbate oxidation in the presence of polysulfide ions was proposed. Impedance calculations based on the kinetic analysis can account for the occurrence of a negative impedance in a potential region around –0.2 V/SCE in the Nyquist polts.

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Significantly Improved Equilibrium Yield of Long-Chain Alkyl Glucosides via Reverse Hydrolysis in a Water-Poor System Using Cross-Linked Almond Meal as a Cheap and Robust Biocatalyst WANG Qin-Qin, YU Hui-Lei, ZHAO Na, LI Chun-Xiu, SHANG Ya-Zhuo, LIU Hong-Lai, XU Jian-He 2012, 33 (2):  275-280.  DOI: 10.1016/S1872-2067(11)60333-1 Abstract ( 2851 )   [Full Text(HTML)] () PDF (450KB) ( 985 )   An array of ten β-D-glucopyranosides with varied alkyl chain lengths were enzymatically synthesized. It was found that for longer alkyl chains a lower initial rate and final yield of glucoside was obtained except for methyl glucoside because of the severe toxicity of methanol to the enzyme. From a thermodynamics point of view, the equilibrium constant and Gibbs free energy variation of the glucoside syntheses were systematically investigated. To improve the final yields of the glucosides containing long alkyl chains the equilibrium of the enzymatic glucoside synthesis was altered. The equilibrium yield of decyl β-D-glucoside increased from 1.9% to 6.1% when the water content was reduced from 10% to 5% (v/v) using tert-butanol as a cosolvent and 0.10 mol/L of glucose as a substrate. As for the other longer alkyl chain glucosides, heptyl β-D-glucoside was found to have significant surface activity as well.

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Co/CeO2 Catalysts Prepared Using Citric Acid Complexing for Ethanol Steam Reforming PANG Xiao-Jian, CHEN Ya-Zhong, DAI Rui-Qi, CUI Peng 2012, 33 (2):  281-289.  DOI: 10.1016/S1872-2067(11)60335-5 Abstract ( 3173 )   [Full Text(HTML)] () PDF (975KB) ( 984 )   Co/CeO2 catalysts with and without calcium doping were prepared by the citric acid complexing method, and characterized by N2 adsorption, X-ray diffraction, temperature-programmed reduction, Fourier transform infrared spectroscopy, and high resolution transmission electron microscope. Their catalytic performance measurement for ethanol steam reforming (ESR) at 400–650 oC and atmospheric pressure with a steam-to-carbon ratio of 3.0 and gas hourly space velocity of 50000 ml/(g·h) was measured. The citric acid complexing method enhanced metal-support interaction. The Co/CeO2 catalysts gave almost 100% ethanol conversion and good hydrogen yield at 500 oC. Calcium doping in the catalyst reduced the particle size of CeO2, but had little effect on the metallic cobalt size after reduction. Calcium doping higher than 5% deteriorated the redox properties and ESR catalytic performance, which was attributed to the fouling of CeO2 by CaO. Catalysts activated at 650 oC showed a better performance, which was due to a higher reduction degree of ceria and increase of the metal-oxide interface. Stability investigation of the catalysts suggested that 5% calcium doping enhanced carbon deposition resistance.

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Functionalized Carbon Nanotubes as Pt Catalyst Supports in Methanol Oxidation YIN Shi-Bin, ZHU Qiang-Qiang, QIANG Ying-Huai, LUO Lin 2012, 33 (2):  290-297.  DOI: 10.1016/S1872-2067(11)60332-X Abstract ( 2889 )   [Full Text(HTML)] () PDF (828KB) ( 982 )   An efficient method for the functionalization of carbon nanotubes (CNTs) is presented, which uses the HF corrosion and intermittent microwave heating (IMH) H2O2 solution. The Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy are used to investigate the physicochemical properties of the CNTs and the prepared catalysts thereof. Cyclic voltammetry, liner current sweeping measurements, chronoamperometry measurements are employed to study the performance of the prepared catalysts. CNTs further treated with IMH H2O2 solution (10s-on/20s-off, over five cycles) can be used as catalyst support, and exhibit significantly improved performance towards methanol oxidation in comparison with other modified CNTs. The results represent a novel approach to functionalize CNTs in a simple and economic way. The method can also be applied in the mass production of nanosized materials.

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Novel Approach to Benzimidazoles Using Fe3O4 Nanoparticles as a Magnetically Recoverable Catalyst Bahador KARAMI, Shaghayegh NIKOSERESHT, Saeed KHODABAKHSHI 2012, 33 (2):  298-301.  DOI: 10.1016/S1872-2067(11)60329-X Abstract ( 2810 )   [Full Text(HTML)] () PDF (243KB) ( 1320 )   Magnetically recoverable Fe3O4 nanoparticles have been synthesized as a catalyst for the cyclocondensation of 1,2- phenylenediamines with orthoesters under solvent-free conditions. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding benzimidazole derivative at 80 °C. This green method offers significant advantages in terms of its simplicity, low catalyst loadings, high product yields, and non-toxic nature. The Fe3O4 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy.

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Heterogeneous Expression of Epoxide Hydrolase Genes from Populus Tomentosa and Application of the Enzyme for Biocatalytic Resolution of Chiral Epoxides ZHAO Jing, JU Xin, PAN Jiang, LI Chun-Xiu, WANG Min-Jie, XU Jian-He 2012, 33 (2):  302-307.  DOI: 10.3724/SP.J.1088.2012.10832 Abstract ( 2078 )   [Full Text(HTML)] () PDF (739KB) ( 678 )   The genome of Populus tomentosa was the first to be reported in trees. Based on the mining results of the database, a gene pool encoding 24 potential soluble epoxide hydrolases was proposed. In which, 7 genes were selected in this study, and 5 genes were successfully cloned and sequenced. Sequence analysis showed that the cloned epoxide hydrolases had merely 24%–26% similarity to the newly cloned Bacillus megaterium epoxide hydrolase. Then the 5 genes were heterogeneously expressed in E. coli and used for hydrolytic reactions of two model substrates, phenyl glycidyl ether and p-nitrostyrene oxide. Epoxide hydrolysis activity was detected in 3 recombinant epoxide hydrolases, in which PTEH1 and PTEH2 showed (R)-selectivity in hydrolysis of phenyl glycidyl ether, while PTEH5 preferred to hydrolyze (S)-phenyl glycidyl ether. This work proves the diversity of epoxide hydrolases from P. tomentosa.

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Preparation of 2D Hexagonal p6mm Ordered Mesoporous WO3-TiO2 Composite Materials and Their Visible-Light Photocatalytic Activity HUANG Yan, LI Ke-Xin, YAN Liu-Shui, DAI Yu-Hua, HUANG Zhi-Min, XUE Kun-Peng, GUO Hui-Qin, XIONG Jing-Jing 2012, 33 (2):  308-316.  DOI: 10.3724/SP.J.1088.2011.10841 Abstract ( 3301 )   [Full Text(HTML)] () PDF (1829KB) ( 1188 )   A series of ordered mesoporous WO3-TiO2 composite materials with different WO3 loadings were prepared by using a single step nonionic-surfactant-templating combined with evaporation-induced self-assembly (EISA) technique. The mesostructure, morphology, porosity, optical property, and composition of as-prepared materials were characterized. The characterization results confirmed that the ordered composite materials exhibited 2D hexagonal p6mm symmetry and anatase phase structure with larger BET surface area (152–154 m2/g) and more uniform pore size (5.3 nm) compared with the disordered WO3-TiO2 composite material as well as narrow bandgap (3.0 eV) with respect to pure TiO2. Subsequently, the ordered mesoporous composite materials were successfully applied to the degradation of rhodamine B and 2,4-dichlorophenoxy acetic acid in the liquid phase under visible-light (l > 400 nm) irradiation, and enhanced photocatalytic activity compared with the disordered WO3-TiO2 composite material and pure TiO2 was obtained for the samples with suitable WO3 loadings.

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Effect of Calcination Temperature on the Structure and Catalytic Performance of K2WO4/Al2O3 Catalysts for Methanethiol Synthesis ZHANG Yuan-Hua, CHEN Shi-Ping, YUAN Cheng-Long, FANG Wei-Ping, YANG Yi-Quan 2012, 33 (2):  317-322.  DOI: 10.3724/SP.J.1088.2011.10870 Abstract ( 2898 )   [Full Text(HTML)] () PDF (546KB) ( 1104 )   The effect of calcination temperature on the surface morphology and catalytic performance of the K2WO4/Al2O3 catalyst prepared by the sol-gel method for the synthesis of methanethiol from methanol and hydrogen sulfide was investigated. Physicochemical characterization results of the catalyst showed that the K2WO4 is well dispersed on Al2O3, and the catalyst possesses uniform particle size after calcination at 450 or 550 oC. With increasing the calcination temperature, the specific surface area decreases, the interaction of W species with Al2O3 was weakened, but strengthened with basic species, leading to the decrease of surface acidity and basicity. No Brönsted acid was found on the catalyst surface. The catalytic activity of the catalyst is closely related with the specific surface area and the presence of conjugate acid-base pairs on the surface. Activity assay results show that the catalyst calcined at 550 oC exhibits the highest activity for the reaction.

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Preparation of AlCl3/γ-Al2O3 Catalyst and Its Performance for Removal of Thiophene from Coking Benzene WANG Wen-Bo, MA Lin, LIAO Jun-Jie, JIE Yuan-Yuan, CHANG Jin-Yu, CHANG Li-Ping 2012, 33 (2):  323-329.  DOI: 10.3724/SP.J.1088.2011.10845 Abstract ( 2887 )   [Full Text(HTML)] () PDF (554KB) ( 962 )   Thiophene and olefins are the main impurities influencing the grade and quality of coking benzene. The thiophene derivative, which can be formed by the alkylation of thiophene and olefins in benzene, is easy to be removed. A series of AlCl3/γ-Al2O3 catalyst samples were prepared by a gas loaded method and their catalytic activity for the alkylation of thiophene and olefins in benzene was measured. The effects of particle size of support, preparation temperature, preparation time, AlCl3 addition amount, and flow rate of carrier gas on the catalyst activity were investigated. Raman spectroscopy, X-ray diffraction, and N2 adsorption-desorption were used to characterize the samples, and gas chromatography-mass spectroscopy was used to analyze the reaction products. The results suggest that AlCl3 can be effectively loaded by reacting with the –OH group and the active component is uniformly distributed on the surface of γ-Al2O3. The catalytic effect of AlCl3/γ-Al2O3 for the alkylation of thiophene and 1-hexene is obvious and the main reaction product is alkylthiophene. Based on the evaluation results of the catalyst, the optimum preparation conditions of AlCl3/γ-Al2O3 are that 3 g of AlCl3 was loaded on 10 g of γ-Al2O3 with the γ-Al2O3 particle size of 0.198–0.246 mm under N2 atmosphere with a flow rate of 100 ml/min for 5 h at 200 °C, in which the removal efficiency of thiophene can reach 62.11% when the ratio of liquid to catalyst is 20 ml/g.

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Influence of Site-Directed Mutagenesis in Coenzyme-Binding Domain of Carbonyl Reductase on Its Catalytic Performance for Asymmetric Reduction GONG Xu-Min, NIE Yao, XU Yan, XIAO Rong, Gaetano T. MONTELIONE 2012, 33 (2):  330-335.  DOI: 10.3724/SP.J.1088.2011.10851 Abstract ( 2394 )   [Full Text(HTML)] () PDF (567KB) ( 1088 )   Based on homology modeling analysis, the sites, P124 and W125, in cofactor-binding domain of the carbonyl reductase SCR1 were found to have a steric effect on the binding of NADPH. The site-directed mutagenesis of these two sites using the amino acid residues with small side group showed that the substrate sepcificity and stereoselectivity of the enzyme were both changed in some level, indicating that these sites have a critical role in binding the cofactor, and the configuration of catalytic active center formed from enzyme/cofactor complex determines the recognition of the enzyme to substrate of different type and also the product of different stereo-configuration. Regarding the substrate specificity, the wild-type enzyme showed activity toward 2-hydroxyacetophenone, 2-bromoacetophenone and its derivatives, while the catalytic efficiency of mutants toward acetophenone and its derivatives and 2-octanone was enhanced. On the other hand, the stereospecificity of some mutants was even found to be inverted. The mutants P124A/W125A and P124G/W125G exhibited a shift of enantioselectivity toward 2-hydroxyacetophenone and ethyl 4-chloro-3-oxobutanoate to give the product in (R)-configuration.

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Preperation of High Performance Ce0.5Zr0.5O2 Rare Earth Oxygen Storage Material and Its Supported Pd-Only Three-Way Catalyst YAN Chao-Yang, LAN Li, CHEN Shan-Hu, ZHAO Ming, GONG Mao-Chu, CHEN Yao-Qiang-* 2012, 33 (2):  336-341.  DOI: 10.3724/SP.J.1088.2012.10933 Abstract ( 2768 )   [Full Text(HTML)] () PDF (514KB) ( 968 )   A series of Ce0.5Zr0.5O2 oxygen storage material samples were prepared by co-precipitation using ammonium carbonate as precipitant. The effect of the concentration of the salt solution on the performance of the target materials and its supported Pd-only catalyst was investigated. The samples were characterized by N2 adsorption, X-ray diffraction, oxygen storage capacity, and temperature-programmed reduction. The results showed that the prepared material exhibited high thermal stability and perfect redox properties. When the concentration of the salt solution was 0.3 mol/L, the obtained material presented the best textural properties with a surface area of 53.0 m2/g and pore volume of 0.17 cm3/g after calcination at 1000 oC for 5 h. The corresponding catalyst exhibited higher catalytic activity with relative low light-off and full conversion temperature, showing potential application in automotive catalysts.

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Mesoporous TiO2 Spheres Prepared by an Acid Catalyzed Hydrolysis Method Using Nanocrystalline Cellulose as Template LI Wei, ZHAO Ying, LIU Shou-Xin 2012, 33 (2):  342-347.  DOI: 10.3724/SP.J.1088.2011.10864 Abstract ( 2971 )   [Full Text(HTML)] () PDF (931KB) ( 1078 )   Mesoporous nanosize TiO2 spheres (SP-TiO2) were prepared using natural polymer nanocrystalline cellulose (NCC) as template. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, ultraviolet-visible diffuse reflection spectroscopy, and N2 adsorption-desorption were used for the characterization of the SP-TiO2 photocatalyst. The results showed that SP-TiO2 was uniform in size with a diameter of 100–200 nm. SP-TiO2 was composed of smaller crystal particles (10–20 nm). The average mesoporous pore diameter of SP-TiO2 was 8.2–13.5 nm, which increased with increasing calcination temperature. A nano-scale reactor that was formed by bonding between the hydroxyl groups of NCC long-chain can inhibit the growth and aggregation of the TiO2 precursor, promote its self-assembly into spherical structure, and inhibit the phase transformation from anatase to rutile. SP-TiO2 prepared at 600 ºC exhibited the highest activity with the phenol degradation percentage of 89%.

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Effects of Reduction Temperature on Selective Hydrogenation of Crotonaldehyde over Ir/ZrO2 Catalyst ZHU Lin, LU Ji-Qing, XIE Guan-Qun, CHEN Ping, LUO Meng-Fei 2012, 33 (2):  348-353.  DOI: 10.3724/SP.J.1088.2012.10919 Abstract ( 2964 )   [Full Text(HTML)] () PDF (537KB) ( 931 )   The Ir/ZrO2 catalyst was prepared by impregnation, and the effect of reduction temperature on its catalytic performance for hydrogenation of crotonaldehyde in gas phase was measured. With increasing reduction temperature, the crotonaldehyde conversion and selectivity for crotyl alcohol over the Ir/ZrO2 catalyst first increase and then decrease. The catalyst reduced at 400 oC exhibits the highest crotonaldehyde conversion, reaching a value as high as 32.2%, and the selectivity for ctotyl alcohol is 74.3%. The results of X-ray photoelectron spectroscopy indicated that both Ir0 and Ir3+ species coexist on the catalyst surface after reduction at 400 oC. With increasing reduction temperature, the ratio of Ir0/Ir3+ increases, and the surface Ir species exists mainly as Ir0 when the reduction temperature is 600 oC. Additionally, NH3 temperature-programmed desorption indicated that the amount and intensity of Lewis acid sites show a downward trend with increasing reduction temperature, which is attributed to the decline of Cl element in the catalyst. Therefore, it is concluded that the coexistence of Ir0 and Ir3+ and moderate-intensity of surface Lewis acid help improve the yield and selectivity of crotyl alcohol.

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Polyacrylamide Gel Synthesis of BaTiO3 Nanoparticles and Its Photocatalytic Properties for Methyl Red Degradation WANG Wei-Peng, YANG Hua, XIAN Tao, WEI Zhi-Qiang, MA Jin-Yuan, LI Rui-Shan, FENG Wang-Jun 2012, 33 (2):  354-359.  DOI: 10.3724/SP.J.1088.2011.10835 Abstract ( 2220 )   [Full Text(HTML)] () PDF (546KB) ( 1021 )   A polyacrylamide gel method was used to synthesize BaTiO3 nanoparticles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflectance spectroscopy were adopted to characterize the sample. The results demonstrate that single-phase BaTiO3 nanoparticles can be prepared at a calcination temperature of 700 oC when using citric acid as the chelating agent at pH = 2. The prepared particles are regularly shaped like spheres with an average particle size of ~55 nm and have an optical bandgap energy of 3.25 eV. The photocatalytic properties of BaTiO3 nanoparticles were investigated using the degradation of the azo dye methyl red. The experimental results reveal that the nanoparticles exhibit a pronounced photocatalytic activity for the methyl red degradation under ultraviolet light irradiation, and the direct oxidation by the hole is suggested to be the main mechanism responsible for the dye decomposition.

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Theoretical Study on the Mechanism of Benzyl Alcohol Oxidation to Benzaldehyde Catalyzed by Ti/SiO2 ZHANG Yan, HUANG Cui-Ying, WANG Jun-Fang, SUN Qi, WANG Chang-Sheng 2012, 33 (2):  360-366.  DOI: 10.3724/SP.J.1088.2012.10924 Abstract ( 2564 )   [Full Text(HTML)] () PDF (642KB) ( 1080 )   The mechanism of benzyl alcohol oxidation to benzaldehyde catalyzed by Ti/SiO2 in different solvents was studied by the density function theory B3LYP method. Total six possible reaction pathways and the corresponding optimal structures of reactants, transition states, intermediates, and products were located at the B3LYP/6-31G* level of theory. The reaction barriers were then calculated at the B3LYP/6–311++G(d,p) level of theory both in gas phase and in solvents. The calculation results show that a very high reaction barrier exists for the pathways where no catalyst is involved, suggesting that the oxidation cannot occur, while when Ti/SiO2 is involved, a reaction barrier about 123.8 kJ/mol is found for that in the acetonitrile solvent, indicating that the oxidation of benzyl alcohol by H2O2 to benzyl aldehyde can happen at about 353 K in the acetonitrile solvent. It is also found that the title reaction has a relative lower barrier in non-polar or low-polar solvent but relative higher barrier in a high-polar solvent.

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Temperature-Programmed Methanol Conversion and Coke Deposition on Fluidized-Bed Catalyst of SAPO-34 YUAN Cui-Yu, WEI Ying-Xu, LI Jin-Zhe, XU Shu-Tao, CHEN Jing-Run, ZHOU You, WANG Quan-Yi, XU Lei, LIU Zhong-Min 2012, 33 (2):  367-374.  DOI: 10.3724/SP.J.1088.2012.10838 Abstract ( 2634 )   [Full Text(HTML)] () PDF (432KB) ( 916 )   Temperature-programmed methanol conversion was performed in a microscale fluidized-bed reactor and the deposited coke species formed during the reaction at different temperature ranges was analyzed. By combining effluent detection and measurements of confined coke species evolution with thermal analysis and GC/MS, a particular phenomenon that appeared in the methanol conversion was explained. Among the coke products, besides aromatic coke species, a new kind of coke compounds, multi-ringed alkanes, mainly composed of methyladamantane hydrocarbons were found in the low temperature range. The generation and accommodation of these adamantane hydrocarbons on the SAPO-34 catalyst suppressed the successive formation of hydrocarbon pool species, polymethylbenzenes, as the reaction center of methanol conversion, and caused the low activity of the SAPO-34 catalyst at low reaction temperature. In the temperature range of 300–350 oC, methylbenzenes and methyladamantanes were the main coke materials and they were transformed to methylnaphthalenes and polycyclic aromatics at higher temperature. The evolution of the confined coke compounds corresponded to the initial reactivity enhancement of the catalyst at 300–325 oC, the lowered activity at 325–350 oC, and recovered methanol conversion at 350–400 oC. Based on the coke analysis and catalytic performance tests, a new deactivation mechanism was proposed for the methanol conversion with the consideration of the abundant formation of adamantane hydrocarbons as the confined materials at low temperature.