Preparation Of Micromesoporous Composite Molecular Sieve Catalyst And Its Application Study On Catalytic Cracking Performance Of C4 Hydrocarbon

Propylene is an important industrial chemical raw material,and its downstream products,such as polypropylene and acrylonitrile,play an important role in industrial production.Therefore,improving the yield of propylene has become a current research focus.At present,the industrial production of propylene in China mainly adopts catalytic cracking,propane dehydrogenation（PDH）,methanol to olefin（MTO）,coal to olefin（CTO）and other methods.Among them,C4 olefins catalytic cracking technology has become the main way of propylene production because of its abundant raw materials.Catalytic cracking reaction is easy to generate carbon deposition,then the microporous zeolite is easy to be blocked by the carbon blockage caused by catalyst inactivation.In order to solve these problems,scholars try to form multistage porous zeolite catalytic materials by forming macropores or mesopores in existing zeolite catalytic materials.Based on the above research status,this paper carries out the following two aspects:Zeolite SAPO-18 with AEI topology shows high propene selectivity in the cracking reaction of butene due to its unique pear-shaped cage cavity.Mesoporous zeolite SAPO-18 catalysts with different Si/Al and P/Al ratios have been synthesized by in-situ synthesis and post-treatment.The SAPO-18 catalyst was used for the catalytic cracking of 1-butene.The optimal catalytic conditions were determined by adjusting the reaction temperature and reaction time,and the influence of SAPO-18 catalyst on the catalytic cracking performance of 1-butene was investigated.The results showed that when the reaction temperature was 450 ℃,Si/Al was 0.6and P/Al was 0.86,the conversion rate of 1-butene was 85.8%,the selectivity of propylene was46.8% and the selectivity of ethylene was 5.7%,indicating that the catalyst had a high P/E（Propylene / ethylene）value.Zeolite SAPO-18 has certain advantages in propylene selectivity.Zeolite ECR-1 with EON-type structure is a aluminosilicate material that have twelve-ring channels.In the traditional synthesis methods,the crystallization time of zeolite ECR-1 is generally long,which limits its industrial production and application.In this work,several different types of crystal seeds were introduced into the synthesis of zeolite ECR-1 without adding organic templates.A free radical seed assisted method for rapid synthesis of zeolite ECR-1 without the presence of organic templates was demonstrated.Zeolite ECR-1 seed after ball milling can be radicalized and accelerate the induction and growth stages of crystallization process,simultaneously.Zeolite ECR-1 products were characterized by X-ray diffraction,scanning electron microscopy,X-ray fluorescence and nitrogen adsorption-desorption.Zeolite ECR-1 was used for the catalytic cracking reaction of 1-butene.The results show that when the reaction temperature is 500 ℃,the raw material conversion is higher,the conversion of iso-butane is 83.0%.Compared with the traditional synthesis method,the crystallization time of the radicalized seed-assist route is obviously shortened,which has potential significance for its industrial application.