Research On The Preparation And Catalytic Performance Of Mesoporous Magnesium Silica Molecular Sieve Catalyst

In petroleum refining industry, hydroisomerization reaction is related to the production of green fuel oil and high quality lube oils, and plays an important role in the process of improving the gasoline octane number. Meanwhile bifunctional catalyst with hydrogenation-dehydrogenation and acid active ingredient is the primary catalyst of hydroisomerization reaction.Mesoporous molecular sieve MCM-48 with three-dimensional spiral channel structure is conducive to material transfer, high specific surface area is conducive to the dispersion of active components. However, the catalytic activity of pure silica mesoporous molecular sieve MCM-48 is poor. Therefore, it has great potential and vast development prospects to introduce active component to mesoporous materials to synthesize mesoporous catalyst with stable catalytic activity. In this paper, magnesium modified Mg-MCM-48 catalyst is used as a carrier to prepared bifunctional catalysts. By means of XRD, N2 adsorption-desorption, FT-IR,SEM and NH3-TPD techniques, the influences of Mg on the structure, morphology, acidity and stability were studied. The catalytic performance of Ni/Mg-MCM-48 for n-heptane isomerization was also studied. The central content in this paper were discussed as follows:1. Mg modified mesoporous silica MCM-48 was prepared by in-situ doping hydrothermal synthesis. The influences of different preparation conditions on the structure of mesoporous silica MCM-48 were discussed. The results reveal that mesoporous silica MCM-48 with better long-range order was prepared at the conditions of 0.02 Mg/Si,crystallization temperature 110 o C, crystallization time 72 h, calcination temperature 550 o C and calcination time 5h.2. The metal Ni is used as active components, magnesium modified Mg-MCM-48 catalyst is used as a carrier to prepare Ni/Mg-MCM-48 bifunctional catalysts by step impregnation method. The influences of preparation conditions, reduction conditions and reaction conditions on catalytic performance of rare earth modified MCM-48 catalysts were studied. The results showed that the conversion and the selectivity reached 44.7% and 90.3%respectively at the preparation conditions of 3%Ni, molar ratio of Mg to Si is 0.02, calcination time 4 hand calcination temperature 400 o C and the reduction conditions of reduction time 4h,reduction temperature 400 o C, and the reaction conditions of reaction temperature 250 o C,WHSV 6.8 h-1 and flow rate of H2 is 40ml/min.