Preparation Of Spherical ZSM-5 Zeolite Catalyst And Its MTO Catalytic Performance

In this paper,a new method for the preparation of spherical as a whole ZSM-5 was developed.Aiming at solving the problem that the selectivity of the ZSM-5 molecular in the process of preparing low-carbon olefins in methanol(MTO reaction)is relatively low,on the basis of spherical monolithic molecular sieves,the modification of the metal element Fe and the non-metallic element P doping was applied to improve the selectivity during the MTO reaction.Meanwhile,based on the preliminary work in our laboratory,the composite molecular sieves of the spherical monolithic ZSM-5 coated with AlPO4-5 were also prepared to further improve the selectivity.The details as follows:First of all,through new method for making spherical integral ZSM-5 molecular sieve by one step,a spherical monolithic ZSM-5 molecular sieve was successfully-prepared.And the preparation path was investigated to obtain the following conclusions:The prepared pellets showed scarcely catalytic activity and still exhibited poor MTO catalytic activity even after calcinations.But it was found that the spherical monolithic molecular sieves treated with ammonium nitrate showed good catalytic activity.So the effect of calcination temperature on its catalytic effect was futher investigated,and the resulted when the sample was calcined at 550?,the ZSM-5 molecular sieve displayed the best MTO catalytic performance.Finally,the effects of different ZSM-5 additions were investigated,the results show:The prepared spherical ZSM-5 spherical monolithic molecular sieves exhibited good catalytic activity and met the requirements of the monolithic molecular sieve in the fixed bed reactor.The selectivity of the lower olefins is 69.1%,the ethylene selectivity is 25.9%,and the selectivity of propylene is 33%.Secondly,on the basis of the optimal preparation path of the spherical ZSM-5 molecular sieve,we further researched the modification effect of different content of Fe element doping on its properties.The results showed that the selectivity of 3%Fe element modified spherical monolithic molecular sieve was 75.2%,while the selectivity of ethylene and propylene were 38.2%and 29.4%,respectively.In order to further improve the selectivity of propylene and lower olefins,the modification method of doping with different amounts of non-metallic P element was also investigated.The results showed that the selectivity of 1%P modified spherical monolithic zeolite was 76.7%,the selectivity of ethylene was 25.2%,and the selectivity of propylene was 38.9%.Finally,ZSM-5/AlPO4-5 composite molecular sieves were prepared by different synthetic methods and applied to MTO reaction.the selectivity of ZSM-5/AlPO4-5 composite zeolite which was prepared by using SAPO-5 molecular sieve as seed crystal at 150? with the speed of 2r/min showed good catalytic performance.The selectivity of low olefins was 74.7%,the selectivity of propylene was 34.9%,and the selectivity of ethylene was 28.2%.