Study On The Synthetic Technology Of SAPO-34 Molecular Sieve

The evolution process of molecular sieve were analyzed in this article, and it was reviewed that the current researching of SAPO-34 molecular sieve and Methanol-to-Olefins(MTO) at home and abroad. SAPO-5 molecular sieve samples have been synthesized by using Triethylamine as template and using hydrothermal method, while SAPO-34 molecular sieve samples have been synthesized by using Morpholine as template with hydrothermal method and vapour-phase crystallization method. The effect of various synthetic condition on the synthesis of SAPO-5 and SAPO-34 molecular sieve under every condition were investigated.SAPO-5 and SAPO-34 molecular sieve have been characterized by specific surface area, XRD, SEM and FT-IR techniques. The synthesis and catalytic performance of SAPO-34 molecular sieve synthesized by using different method were compared, so the optimum catalyst of MTO reaction was selected. The effect of process condition for MTO process catalyzed by SAPO-34 were studied.Under hydrothermal condition, the raw materials composition, SiO₂/Al₂O₃ ratio, template amount, the adding order of raw materials and water content have an important influence on the synthesis of SAPO-5 molecular sieve. n(SiO₂)/n(Al₂O₃)=0.8-2 is reasonable to the synthesis of SAPO-5. The composition of crystallization mixture, crystallization time, ageing process and stirring are important influencing factors on the hydrothermal synthesis of SAPO-34 molecular sieve. Ageing process and stirring are available to the synthesis of SAPO-34.The raw materials composition, SiO₂/Al₂O₃ ratio, and the template are primary factors that influence the synthesis of SAPO-34 molecular sieve with vapour-phase method. n(Si/Al₂O₃)=0.6-3 is reasonable to the vapour-phase synthesis of SAPO-34.In the part of catalyst's selection, the catalytic performance of SAPO-5 and SAPO-34 molecular sieve for methanol conversion reaction were investigated, the results show that SAPO-5 is unsuitable for MTO,but it can catalyze MTG process and 3,5-dimethylphenol amination reaction. The SAPO-34 molecular sieve synthesized by using hydrothermal method and vapour-phase crystallization method have excellent catalytic performance for MTO reaction, and nearly have the same results .In the investigation of process condition, the influence of reaction temperature, and composition of stuff on MTO reaction were investigated, using SAPO-34. synthesized by vapour-phase crystallization method as catalyst,the optimum process condition has been fixed.And the results indicated that the conversion of CH3OH exceeds 98%, the overall selection of ethylene and propylene is more than 84%.