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Gas-phase epoxidation of propylene by molecular oxygen over Ag-Cu-Cl/BaCO_3 catalyst:Effects of Cu and Cl loadings

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Chinese Journal of Catalysis 2017年第1期38卷 65-72页

作者： Qing Zhang Yanglong Guo Wangcheng Zhan Yun Guo Li Wang Yunsong Wang Guanzhong Lu Key Laboratory for Advanced Materials Research Institute of Industrial Catalysis School of Chemistry and Molecular Engineering East China University of Science and Technology Shanghai 200237 China

Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.

关键词： epoxidation of propylene propylene oxide Molecular oxygen Ag‐based catalyst Copper Chlorine

Direct gas-phase epoxidation of propylene to propylene oxide using air as oxidant on supported gold catalyst

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Journal of Natural Gas Chemistry 2008年第2期17卷 184-190页

作者： Zhanghuai Suo Mingshan Jin Jiqing Lu Zhaobin Wei Can Li Institute of Applied Catalysis Yantai University Yantai 264005 Shandong China State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 Liaoning China

Gold catalysts supported on SiO2, TiO2, TiO2-SiO2, and ZrO2-SiO2 supports were prepared by impregnating each support with a basic solution of tetrachloroauric acid. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and X-ray photoelectron spectroscopy （XPS） techniques were used to characterize their structure and surface composition. The results indicated that the size of gold particles could be controlled to below 10 nm by this method of preparation. Washing gold catalysts with water could markedly enhance the dispersion of metallic gold particles on the surface, but it could not completely remove the chloride ions left on the surface. The catalytic performance of direct vapor-phase epoxidation of propylene using air as an oxidant over these catalysts was evaluated at atmospheric pressure. The selectivity to propylene oxide （PO） was found to vary with reaction time on the stream. At the reaction conditions of atmosphere pressure, temperature 325 ℃, feed gas ratio V（C3H6）/V（O2）= 1/2, and GHSV =6000h^-1, 17.9% PO selectivity with 0.9% propylene conversion were obtained at initial 10 min for Au/SiO2 catalyst. After reacting 60 min only 8.9% PO selectivity were detected, but the propylene conversion rises to 1.4% and the main product is transferred to acrolein （72% selectivity）. Washing Au/TiO2-SiO2 and Aa/ZrO2-SiO2 samples with magnesium citrate solution could markedly enhance the activity and PO selectivity because smaller gold particles were obtained.

关键词： gold catalyst support modified impregnation method epoxidation of propylene molecular oxygen

Deactivation and regeneration of TS-1/SiO2 catalyst for epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor

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Frontiers of Chemical Science and Engineering 2013年第2期7卷 202-209页

作者： Hainan SHI Yaquan WANG Guoqiang WU Wenping FENG Yi Lin Teng ZHANG Xing JIN Shuhai WANG Xiaoxue WU Pengxu YAO Key Laboratory for Green Chemical Technology of the Ministry of Education School of Chemical Engineering & Technology Yianjin University Tianjin 300072 China

TS-1/SiO2 catalyst for the epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor has been investigated. The catalyst activity decreases gradually with the online reaction time, but the selectivity of propylene epoxide is kept at about 93%. The fresh, deactivated and regenerated catalysts were characterized with X-ray diffraction, Fourier transform infrared spectro- scopy, ultra-violet-visible diffuse reflectance, Brunner- Emmett-TeUer method and thermogravimetric analysis, and the deactivated catalyst was regenerated with H2O2/ methanol solution. Compared with the fresh catalyst, both the framework structure and the content of titanium in the framework of the deactivated and regenerated TS-1/SiO2 catalysts were not changed. The major reason of the catalyst deactivation was the blockage of the channels of the catalyst by bulky organic by-products, which covered the active centers of titanium in TS-1. The deposited materials on the deactivated TS-1/SiO2 catalyst could be removed by treatment with hydrogen peroxide/methanol solution or pure methanol; the higher the treatment temperature and the higher the concentration of H2O2 in methanol, the higher the extent of the regeneration. The regeneration treatment did not influence the product selectivity in the propylene epoxidation.

关键词： TS-1/SiO2 epoxidation of propylene fixed-bed reactor deactivation regeneration

Effect of triethylamine treatment of titanium silicalite-1 on propylene epoxidation

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Frontiers of Chemical Science and Engineering 2014年第4期8卷 478-487页

作者： Juan XU Yaquan WANG Wenping FENG Yi LIN Shuhai WANG Key Laboratory for Green Chemical Technology of the Ministry of Education School of Chemical Engineering & Technology Tianjin University Tianjin 300072 China

Titanium silicalite- 1 （TS- 1） treated with triethy- lamine （TEA） solution under different conditions was characterized by X-ray powder diffraction （XRD）, Fourier- transform infrared spectrum （FTIR）, ultraviolet-visible diffuse reflectance spectrum （UV-Vis）, nitrogen physical adsorption and desorption, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA con- centration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.

关键词： titanium silicalite-1 triethylamine hollowcavity epoxidation of propylene catalyst life