Preparation And Modification Of MOR-based Hierarchical Zeolite And Its Application In Hydroisomerization

In order to meet the standards of automobile exhaust,the National VI gasoline standard will lead to further decrease high octane components,such as olefins,benzene and aromatics,and the gasoline's Octane number can't meet the requirements.Nowadays,the main method of solving this problem is producing gasoline with high content of isoalkane,and hydroisomerization reaction is an important way to produce the gasoline.The catalyst of this reaction is a bifunctional catalyst with hydrogenation/dehydrogenation and isomerization functions,and the catalyst is very important.MOR zeolite is an excellent acid carrier due to its special pore structure,adjustable acidity and excellent isomerization performance.However,the narrow pore channel of traditional MOR increases the diffusion resistance of molecules,and its strong acidity can contribute to many side reactions.Moreover,it is important to evaluate the synergistic effect of the acid carrier and the metal active center.In the thesis,commercial MOR zeolite was used as a raw material to prepare hierarchical MOR via desilication.The effects of temperature,time,concentration and liquid-solid ratio on the pore structure were investigated.Then,the acidity of MOR was tuned by dealumination,aiming to strengthen the isomerization performance.After that,the obtained samples were used to test the performance.At last,zeolite of core-shell structured MOR@MCM-41 was prepared to research the synergistic effect of catalyst.It can adjust the distance between metal and acid sites,affecting the reaction of hydroisomerization.The results are as follows:(1)Compared with commercial microporous MOR zeolite,the hierarchical MOR can improve the conversion and yield,and the two-branched chain products are the main increasing part.(2)The conditions play a significant role influence on the reaction.5 wt.%nickel load,275?temperature,3.6 h^-1 hexane airspeed and 35 sccm hydrogen flow rate are the most suitable conditions.(3)Hierarchical MOR with rich mesoporosity and better connectivity can be prepared by acid treatment,and it can decrease the strong acid concentration to reduce side reactions,improving the selectivity.(4)The core-shell structured MOR@MCM-41 zeolite can improve the yield and selectivity,and suitable distance between metal and acid sites can improve the reaction performance of hydroisomerization.