Synthesis And Properties Of Modified Al-SBA-16 Mesoporous Molecular Sieve

SBA-16 mesoporous molecular sieve has a cubic symmetrical structure,a wide range of adjustable pore size,a highly ordered pore structure,a high specific surface area,and good thermal stability.It is widely used in catalysis,adsorption,and biological transportation,Environment and other fields.However,the pure SBA-16mesoporous molecular sieve lacks active centers,and is subject to many restrictions in practical applications.The loading of heteroatoms on the molecular sieve is an effective method to increase activity and improve application conditions.In this paper,polyether（F127）is used as a template,ethyl orthosilicate is used as a silicon source,and aluminum chloride hexahydrate is used as an aluminum source.The acid generated in the hydrolysis of aluminum chloride is used to provide the acidity of the synthesis system.The hydrothermal synthesis method is used.The Al-SBA-16 mesoporous molecular sieve was synthesized and its structure was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N₂ isothermal adsorption-desorption and Fourier transform infrared spectroscopy;its catalytic cracking of waste plastics was studied performance.The control variable method was used to study the synthesis conditions of Al-SBA-16.The results show that when the molar ratio of Si to Al is 30,the ratio of template to silicon is 0.45,hydrothermal crystallization reaction is carried out at120℃for 48 h,and high temperature calcination is performed at 550℃to synthesize Al-SBA-16 mesoporous molecular sieve has the best morphology and structure,its specific surface area is up to 694 m²/g,pore size and pore volume are 11.6 nm and 2.0cm³/g respectively.Al-SBA-16 with the best morphology and structure is used as a catalyst to catalytically crack polyethylene and polypropylene.The results show that,compared with thermal cracking,the conversion rate of polyethylene catalytic cracking increased from 80.1 wt%to 99.5 wt%;the liquid yield increased from 42.0 wt%to75.2 wt%;the conversion rate of polypropylene catalytic cracking increased from91.8 wt%to 99.0 wt%;liquid yield increased from 65.5 wt%to 80.1 wt%.Comparing the distribution of carbon atoms in the liquid product,it can be seen that catalytic cracking has better selectivity than thermal cracking.The cycle experiment shows that the prepared catalyst has a longer catalytic life.