Preparation Of SSZ-13 Molecular Sieve And Its Catalytic Performance On MTO

As the basic organic chemical materials,ethylene and propylene play an important role in modern chemical industry.With the increasing scarcity of petroleum resources and the increasing demand for downstream chemical products such as ethylene and propylene,people gradually shift their focus to non-petroleum routes,where coal,natural gas,or biomass is used to obtain olefins（MTO）via methanol.MTO Process is the most promising route at present.The key technology in the MTO process lies in the selection,preparation,and modification of highly active and highly selective catalysts.In this paper,SSZ-13 molecular sieves were synthesized by hydrothermal crystallization method using template method（choline chloride,N,N,N-trimethyladamantyl ammonium hydroxide as template）and no template method.The effects of different aluminum sources,crystallization time and other factors on the synthesis of SSZ-13 molecular sieves were investigated,and the synthesis conditions of synthetic SSZ-13 molecular sieves were optimized.The prepared samples were analyzed by XRD,BET,SEM,TEM,NH₃-TPD,TG and other characterization methods.The catalytic performance of SSZ-13 was determined by the conversion of methanol in the MTO reaction and the selectivity of ethylene and propylene.Inspection.The main research content is as follows:（1）Preparation of porous SSZ-13 molecular sieve microspheres with high silica-alumina ratio.The hydrothermal crystallization synthesis method was used to synthesize SSZ-13 molecular sieve microspheres with multiple pores using aluminum isopropoxide as the aluminum source,ultrafine silica as the silicon source and choline chloride as the template.The result of scanning electron microscopy showed that microspheres with a diameter of about 10μm were obtained.Based on this,the effects of crystallization time,aluminum source and other factors on the synthesis of molecular sieves were explored.Finally,the catalytic performance of MTO catalysts for different synthetic aluminum zeolite catalysts was analyzed.（2）Template-free induction of synthesis of SSZ-13 molecular sieve.The SSZ-13molecular sieve was successfully synthesized by using organic template-free method,using isopropanol as aluminum source and SSZ-13 molecular sieve as seed,and compared with the template SSZ-13 molecular sieve,the catalytic performance of MTO was investigated.（3）Preparation of SSZ-13 molecular sieve nanocrystals.Using aluminum isopropoxide as the aluminum source,fumed silica as the silicon source and TMAdaOH as the template,SSZ-13 nanoparticles were synthesized.Characterization by scanning electron microscopy and the like indicate that the resulting molecular sieve is a nanoscale small particle.The catalytic performance of nano-SSZ-13 was investigated under different process conditions.Nano-SSZ-13 molecular sieve has good MTO catalytic activity due to the existence of multi-order pore structure and small crystal size.