Synthesis And Application Of Hierarchical Shape-selective Zeolite

ZSM-5,which is a typical shape-selective zeolite plays an important role in petroleum processing such as catalytic cracking.However,the smaller pore size limited its application in macromolecular catalytic conversion.Therefore,the obtaining of ZSM-5 with hierarchical pores is of great significance.Hydrothermal treatment strategy is the most common method to introducing mesopores.However,this method suffers from decreased crystallinity and low reproducibility.In this paper,the synthesis of hierarchical ZSM-5 was systematically investigated in view of the shortcomings of the present process:1.The hierarchical ZSM-5 was synthesized by S-1 nanocrystal seed modified with cationic surfactant CTA+ denoted as "CTA+@S-1" seed.In this novel strategy,combination of CTAB and S-1 seeds are obtained by charge matching,in which embedding of CTA+improves the dispersibility of S-1 seeds and avoids dense agglomeration of crystal nuclei,thus leading to the formation of intercrystalline mesopores.The effects of CTAB/TPABr ratio on the properties of the products were investigated.It was found that intercrystalline mesopores predominated with lower CTAB amount,and the intracrystalline mesopores predominated with high amount of CTAB.2.Using the amphiphilic silicon-based surfactant MT synthesized by our research group as a mesoporous template,the hydrophobic group was introduced into walls of zeolites by the hydrolysis of MT.As the consequence of this,mesopores were obtained by in-situ crystallization.In this process,tetra-propylammonium bromide(TPABr)was used as the microporous template.The competition balance between the two templates was investigated.It was found that intracrystalline mesopores predominate with low amount of MT,and the intracrystalline and intercrystalline mesopores were obtained with high amount of MT.Moreover,modulation of mesoporous pore size could be achieved by changing the amount of MT.The amount of templating agent was 0.22 g TPABr/g zeolite and 0.15 g MT/g zeolite.The total surface area of the product was 344.3 m2/g,and the mesoporous ratio was 149.0 m2/g.Amplification synthesis of a 20 L crystallizer was carried out,and the total product specific surface area was 401.6 m2/g,and the mesoporous ratio surface was 180.5 m2/g.3.The calcined activated kaolin fine powder was used as raw material,and crystal seeds was used as the directing agent to obtain kaolin/ZSM-5 composites.In this process,the kaolin/ZSM-5 composite material was synthesized by in-situ,crystallization composites with graded pores ware obtained by using the inherent macropores in kaolin.The crystallinity of composite is greater than 80%and the total surface area is 336.5 m2/g.The amplification synthesis was carried out in 2 L and 20 L autoclaves,and the results shed a light on the industrial application of the hierarchical zeolites.