| Low temperature Hydrodesulfurization catalysts can compensate the disadvantages of high investment?high operating costs and high energy consumption for SCOT technology.Development the catalyst supports is an effective method to develop hydrodesulfurization catalysts,and it has been the current hotspot.The different kinds of TiO2/?-Al2O3 composite supports were prepared by impregnation, co-precipitation, and sol-gel methods. Loaded 12wt% NiO and 5wt% MoO3 to prepare the catalysts. The activity of the catalysts was evaluated in terms of simulative claus tail gas. Explore the best preparation method, optimize the formulation and preparation process of the preparation method.XRD?TPR?SEM?and BET were used to characterise these optimal materials.To explore the interaction between TiO2 and ?-Al2O3 and the dispersed state of active substances on composite supports.The main work and conclusions are as follows:(1)Tetrabutyl titanate as precursor. The TiO2/?-Al2O3 composite supports prepared by impregnation with TiO2 loadings of 10% have high surface area(245.74m2/g) and pore volume(0.39cm3/g),which are higher than those of ?-Al2O3(126.44m2/g, 0.33cm3/g).The dispersion threshold of TiO2 is 0.079 g TiO2/100m2 ?-A12O3.TiO2 disperses onto the surface of ?-A12O3 to from a monolayer or submonolayer when the content is less than this value,and then the catalyst has the highest catalytic activity with conversion of 100% and selectivity of 50% at 190 ?;crystalline TiO2 appears when this value is exceeded.Incorporation of TiO2 into ?-Al2O3 support can adjust the interaction of support and active metal, and thus improve the reducibility of molybdenum on TiO2 /?-A12O3 support.TiS2 is generated during the presulfurization process of Ni-Mo/(TiO2/?-Al2O3) catalyst.After that,TiS2 is converted to TiO2 in the catalytic reaction.So that the conversion of H2 S is higher than 100%.(2) Tetrabutyl titanate and aluminium isopropoxide as precursor. The TiO2/?-Al2O3 composite supports prepared by co-precipitation with TiO2 loadings of 20% have high surface area(241.95m2/g) and pore volume(0.31cm3/g).The dispersion threshold of TiO2 is 20wt%.Ti O2 disperses onto the surface of ?-A12O3 to from a monolayer or submonolayer when the content is less than this value,and then the catalyst has the highest catalytic activity with conversion of 100% and selectivity of 40% at 200?;crystalline Ti O2 appears when this value is exceeded.(3)The TiO2/?-Al2O3 composite supports prepared by co-precipitation with tetrabutyl titanate,aluminium isopropoxide and aluminium nitrate.Using CTAB as template can significantly improve the activity of the composite supports,but Using PS microspheres as template reduces the activity of the composite carrier. When the molar ratio of CTAB is 0.4 the catalyst has the highest catalytic activity,with conversion of 100% and selectivity of 61% at 200?.Then,the surface area of the composite support is as high as 392.37m2/g, the pore volume is as high as 0.49 cm3/g, and the composite support has two-stage mesoporous structure.(4)All of The TiO2/?-Al2O3 composite supports prepared by three different methods have very high catalytic activity(?200?).The properties of composite supports prepared by impregnation are limited by the properties of ?-Al2O3,and strength worse than coprecipitation.The composite supports prepared by sol-gel have the highest surface area and pore volume,however the strength is also worse. The co-precipitation method not only has simple process, short production cycle, The TiO2/?-Al2O3 composite supports slao have high strength, this prepare methods has a significant industrial value. |
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