Synthesis Of Meso-SAPO-11 Zeolite And Its Isomerization Performance Study

With the increasingly serious environmental problems and the enhancement of people's awareness of environmental protection,the demand for clean energy,especially high-quality gasoline and diesel oil,high-grade lubricants is increasing.Isomerization of n-alkanes plays an important role in improving the performance of petroleum products,such as increasing gasoline octane number.SAPO-11 zeolite has been widely used in the isomerization of n-alkanes due to its suitable acidity and shape-selectivity.However,SAPO-11 zeolite has a small pore size,and the long-chain alkane in the heavy oil has a large mass transfer resistance,so that the branching degree of intermediate is low and the product is difficult to escape,resulting in a low reactivity.Therefore,the synthesis of Meso-SAPO-11 zeolite with mesoporous structure is of great significance for enhancing the isomerization activity of n-alkanes.In this paper,according to the different degree of polymerization saccharides,glucose,sucrose,maltose,raffinose and cellulose were selected as mesoporous template to investigate the ability of saccharides to construct mesopores in the synthesis of SAPO-11 zeolite.Firstly,the crystallization temperature of the synthesis system with adding saccharides was researched.The results showed that the pore structure of the sample obtained at 200 C was optimal.In order to obtain SAPO-11 zeolite with high crystallinity,good pore structure and acid content,the effects of changing saccharides types and its'additions on the properties of SAPO-11 zeolite were further investigated.The results showed that the structure of Meso-SAPO-11 zeolite synthesized by using glucose as mesoporous template was optimal.Secondly,the samples were loaded with Ni metal.The changes of pore structure properties of the samples,the existence and distribution of Ni metal on SAPO-11 zeolite were investigated.The results showed that Ni metal was loaded onto the samples,and it occupied the surface and part of the pore channels,resulting in the decrease of surface area,pore volume and total acidity of the samples.Finally,Meso-SAPO-11 catalysts were prepared and applied to the isomerization of n-hexane.The relationship between the properties of samples and the activity of isomerization reaction was investigated.The results showed that the amount of Saccharide molecule added in the synthesis system was positively correlated with the ratio of B/L obtained by pyridine infrared spectroscopy.And the higher the amount of B acid in the sample,the stronger isomerization activity of n-hexane.From the results of NH₃-TPD test,it can be seen that the acid distribution of each sample was similar and weak acid was dominant,and the total acid content had no obvious difference.The introduction of saccharides increased the moderate acidity slightly.SAPO-11 zeolite synthesized with 15wt%glucose had the best acidity and reaction performance.The n-hexane isomerization performance of each sample was improved compared to commercial SAPO-11 zeolite.Therefore,the addition of saccharides as mesoporous template to synthesize SAPO-11 zeolite can enhance the yield and selectivity of n-alkanes in isomerization reaction.