Research On The Ultrasonic-assisted Synthesis Of SAPO-34 Molecular Sieve And Its Catalytic Performance Of Methanol To Olefin Reaction

The methanol to olefin?MTO?process is one of the new processes for the production of light olefins.SAPO-34 molecular sieves are considered to be the most efficient molecular sieve catalysts in the methanol to olefins process.In this paper,SAPO-34 molecular sieves with different ratios of silicon to aluminum,different crystallization time,different different templates,templating agents and different ratios of water to aluminum were synthesized by ultrasonic assisted synthesis.XRD,SEM,N₂ physical adsorption-desorption,NH₃-TPD,ICP-AES and other methods to characterize the structure and acidity of molecular sieve samples,and evaluate the reaction of molecular sieves by methanol to olefin reaction.The ultrasonic assisted synthesis method and different preparation conditions for catalyst structure,acidity and catalytic performance were studied.The results show that when the ratio of silicon to aluminum is 0.4,the prepared molecular sieve has the highest micropore surface area and micropore volume.When the ratio of silicon to aluminum is 0.6,the sample has the highest acid amount;the relative value of the sample crystallized for 48 hours.The crystallinity is the highest;in the absence of a templating agent,a mixture of SAPO-34and SAPO-5 can be formed;the lower the water to aluminum ratio,the smaller the particle size of the sample.Sample with an ultrasonic pretreatment of SiO₂/Al₂O₃=0.2had the highest stability?12%reduction in olefin yield in the 2 hour reaction?,sample with an ultrasonic pretreatment of SiO₂/Al₂O₃=0.4 had the highestthe highest olefin selectivity?91.4%?.