Preparation Of SiO₂/MoS₂ Core-shell Catalyst And Evaluation Of Its Activity On The Slurry-Bed Hydrocraking For Heavy Oil

In this paper,with ammonium tetrathiomolybdate and hydroxylamine hydrochloride as raw materials,the synthesis of molybdenum disulfide has been optimized in liquid precipitation and hydrothermal systerm according to the conversion rate of molybdenum metal,and a new kind of core-shell structure catalyst with silica as the core and molybdenum disulfide as the shell was prepared.In the preparation process of core-shell structure catalyst,SDBS,CTAB,potassium oleate,PEG and PVP were respectly introduced as five kinds of modifiers in order to make molybdenum disulfide deposited well on the surface of silicon dioxide,SEM,TEM,IR,XRD,TG and other characterization methods were used to compare and analyze the synthetic products,a suitable core-shell structure catalyst was obtained.The effects of the amount of modifier and the ratio of raw materials on the structure of the product were also investigated.Taking Karamay atmospheric residue and Qingdao refinery catalytic cracking oil slurry as raw materials,the reactivity of the dispersed core-shell structure catalyst was investigated in autoclave.The preparation process of molybdenum disulfide showed that for the liquid phase precipitation method,when the reaction temperature is 80℃,the reaction time is 120min and the ratio of hydroxylamine hydrochloride to ATTM was 6:1,molybdenum conversion rate reached 83.10%;for the hydrothermal method,when the reaction temperature is 190℃,the reaction time is 24h,the ratio of hydroxylamine hydrochloride to ATTM was 3:1,molybdenum conversion rate reached 92.63%.In both liquid phase precipitation method and hydrothermal method,PVP has a promoting effect on the deposition of MoS₂ on the surface of silica to form a high degree of closure molybdenum disulfide shell,and the optimum addition amount of PVP was both 1.0%.For liquid phase precipitation method,the optimum ratio of ATTM and SiO₂ is 1:4.5.For hydrothermal method,the optimum ratio of ATTM and SiO₂ is 1:5.5.Under conditions above,SiO₂/MoS₂ core-shell structure catalyst with 10-20nm closure shell can be obtained.Other modifiers have little ability to promote deposition.Two products synthesized by liquid precipitation system and hydrothermal system can be used as catalysts in the slurry-bed hydrocracking process of heavy oil for fine performance of hydrogenation and coke inhibition.By comparing the hydrogenation activity of core-shell structure catalysts and previous molybdenum disulfide catalyst,core-shell structure catalysts showed a higher ability of hydrogenation inhibition and higher FCC oil slurry light capacity.