Preparation Of Mesoporous TiO₂-Al₂O₃ Composites And Study Of Their Hydrotreating Performance

As the crude oil becomes more inferior and sticker,heavy oil hydrotreating has become one of the main methods for the production of clean oil and the key of hydrotreating process is the development of catalyst.In this thesis,aluminum-isopropoxide and titanium isopropoxide were used as raw materials.Titanium-aluminum composite support（EISA-n,n is the atomic ratio of Ti/Al）was prepared by solvent evaporation sel-assembly method.Based on optimization of the specific surface area,pore volume and pore size,it’s concluded that the optimal preparation conditions are reactant mole ratio ethanol:H₂O:HNO₃:（Ti+Al）:P123=9000:460:270:115:1.Under the optimal conditions,the specific surface area of EISA supports is larger than 330 m²·g^-1,the pore volume is between 0.75 and 0.90 mL·g^-1 and the average pore size is between 7 and 11 nm.The pore structure,crystalline characteristics,surface morphology and acidity of the prepared composite supports and the corresponding catalysts were characterized by means of BET,XRD,TEM,NH₃-TPD and Py-IR.It is found that all the composite supports have an ordered mesoporous structure,just like a kind of regular honeycomb.The thermal stability of TiO₂ can be improved effectively by the combination of titanium and aluminum.The directional control of the acid strength and distribution of the support and its catalyst can be realized by adjusting the atomic ratio of Ti/Al.Compared with alumina based catalyst,the introduction of TiO₂ can change the existing state of active metals and further improve its reduction and vulcanization properties.Through the study of the hydrodenitrogenation reaction of indole and quinoline on NiMo/EISA-0.4 catalyst.It is found that indole is usually converted to indoline（2H-IND）,which will quickly reach equilibrium and be restricted by thermodynamics.After indole is converted into 2H-IND,one-step cleavage of the C-N bond and the second cleavage of the C-N bond can be successively performed.The control step of the hydrodenitrogenation of indole can be considered as the cleavage of the C-N bond.When quinoline is reacted on this catalyst,it is usually first saturated with1,2,3,4-tetrahydroquinoline（THQ-1）.While THQ-1 is hard to directly break C-N bond and needs to be saturated into decahydroquinoline（DHQ）,then followed by the C-N bond cleavage.In this process,there is also a side reaction of dehydrogenation of DHQ to 5,6,7,8-tetrahydroquinoline（THQ-5）.The main control step of the quinoline hydrodenitrogenation reaction can be considered as the process of DHQ or the THQ-1hydrogenation saturation.The hydrogenation reaction performance of the catalysts was also evaluated with the Liaohe coked gas oil as raw material.The results showed that the NiMo/EISA-0.3catalyst shows the highest reactive activity.The HDS and HDN rate can reach 98.1%and 88.6%under the reaction condition of 380°C,8 MPa,1 h^-1 and 1000（H₂/Oil）.Through comparison with alumina based catalyst,the HDS and HDN rate were respectively increased by more than 10 percent and 30 percent.