Preparation And Isomerization Performance Of MCM-48 Molecular Sieves

As one of the main routes to produce high-octane gasoline blending components in the crude oil refining industry, alkanes isomerization has drawn much attention throughout the world because it can greatly improve the gasoline quality. For alkanes isomerization, one of the key issues is to develop catalysts with higher activity and higher stability, which has been widely pursued due to its importance both in academic research and in industrial utilization.We synthesized MCM-48 mesoporous sieves using water-heat synthesis, prepared Ni and heteropolyacid loaded on MCM-48 bifunctional catalysts, investigated isomerization of n-heptane on these catalysts, discussed the effect of different preparation conditions, reduction conditions and reaction conditions on the conversion and isomerization selectivity of n-heptane. The main contents of the thesis were discussed as follows:The effect of calcination temperature, crystallization time, crystallization temperature, for synthesis of MCM-48 was researched. The results showed that, When MCM-48 was synthesized at the conditions of crystallized at 110℃for 3d, roasted at 550℃, the 211 diffraction peak of MCM-48 is the strongest, and the 220 diffraction peak were obtained, characteristic peak at 2θ=4°~5°can still identified. MCM-48 samples have a regular channel structure.The isomerization of n-heptane on Ni/ MCM-48 catalysts was investigated. The result showed that the conversion of n-heptane and isomerization selectivity to i-heptane can reach 14.2% and 65.6% on Ni-PMo12/MCM-48 catalyst when calcination temperature is 550℃, H2 reduction temperature is 400℃, reducted for 4h, flow rate of H2 is 30mL/min, content of Ni and PMo12 is 3% and 30%, and reaction temperature is 300℃.Ni-SiW12/MCM-48 catalyst has a good performance for n-heptane isomerization. The conversion of n-heptane and isomerization selectivity to i-heptane can reach 10.5% and 70.6% on Ni-SiW12/MCM-48 catalyst when the content of Ni and SiW12 is 3% and 30%, and reaction temperature is 300℃.