Study Of The Relationship Betweem The Pore Structure Of Ten-membered Rings Zeolites And The Performance Of Methyl Halide To Propene

With the increasing demand of propylene,the oil as raw materials is non-renewable resources,and will take all exhausted one day,So the development economic efficient of oil-base propylene production line is imperative.Unconventional gas is rich in natural resources,from the perspective of economic and the raw material,using natural gas as raw materials via halogen methane for intermediate route for propylene production,is a more ideal path.The preparation of low carbon olefin by halogenated methane is an important part of the reaction route,and the design and development of high efficiency catalyst is the key.For Me XTO reaction,most of the research work at present is mainly to improve the performance of the catalyst.But the nature of the role of the research has not been given,there are many issues need to be explored.Among them,a facial point is the relation between the properties of molecular sieve catalyst and the catalytic performance.As the goal reaction of methyl halide to propylene,we choose a series of molecular sieve material with typical channel structure.Based on the similarities and differences of product distribution and methyl halide conversion ability,in order to gain the association rule of molecular sieve pore structure and catalytic performance,revealing the influence of channel structure to the generation and out of the produc,to complete the investigation of the relationship between structure and catalytic properties of molecular sieve hole.Specific research work is as follows:Firstly,silica sol is used as the source of silica,and sodium sulphate and sodium metaluminate are aluminum sources.The series molecular sieve H-ZSM-22,H-ZSM-35 and H-ZSM-35,which have typical pore structure,are synthesized by adding base source and template agent.Secondly,the relationship between the number of channels and the catalytic performance is investigated.The properties of ZSM-5,ZSM-35 and ZSM-22 based on acid and other properties were detected,and the catalytic performance under the same reaction conditions was compared.It was found that the conversion rate of methyl halide was the highest with the dimensional of three,the yield of propylene was the highest,and inactivation was the slowest,but the high carbon products were more.The conversion and propylene yield of methyl halide on ZSM-35 catalyst were secondary,and the catalyst life was also between ZSM-5 and ZSM-22,with the least high carbon products.The conversion rate of methyl halide on the one-dimensional ZSM-22 catalyst and the yield of propylene are the lowest,with the fastest inactivation and high carbon products.The results show that the more the number of channels,the better the conversion of methyl halide.Thirdly,The effects of F modification on the catalytic performance of ZSM-5,ZSM-35 and ZSM-22 were investigated separately.It was found that the modification of F made three kinds of molecular sieves dealuminized and the skeleton aluminum decreased,resulting in the non-skeleton aluminum,which led to the sharp decrease of the catalyst acid,especially the B acid.For ZSM-5 and ZSM-35,with the increase of fluorine concentration,the conversion rate of methyl halide,the selectivity of propylene and the yield of propylene were both increased and then decreased.For ZSM-22,F modification can only reduce its catalytic performance.Therefore,acidity is an important factor affecting the catalytic performance of molecular sieve.However,vertical Comparison of ZSM-5,ZSM-35 and ZSM-22 with different acid,found that ZSM-22 and ZSM-35 catalysts were more acidic,but the catalytic performance was far less than that of the less acidic ZSM-5.This indicates that acidity is not a determinant factor of catalytic performance.Fourthly,the status of Al species in different catalysts was obtained by ²⁷ Al MAS NMR,and the content of different Al species was calculated.The relationship between the content of different aluminum species and the catalytic performance was compared.Results show that,for molecular sieves with one dimension,the content of the skeleton aluminum is similar to that of the catalytic performance.There is no significant correlation between the distribution of the aluminum species and the catalytic performance of the molecular sieve of different dimensions,indicating that there are other factors that affect the catalytic performance in addition to the distribution of the aluminum species.We explores the transforming ability of molecular sieve pore structure of reactants,the influence factors of target product selectivity and stability of catalyst,in order to analyze hydrocarbon pool species on the catalyst,which further reveals the nature impact of molecular sieve pore structure to the catalytic performance.