Study On The Catalyst For Catalytic Conversion Of Methanol To Propene And Clean Gasoline

Propene and gasoline are essential for meeting global material and energy demands.The methanol-to-hydrocarbon technology has been regarded as a competitive route to upgrade any gasifiable carbon-rich feedstock to olefins and clean oil.Currently,the low utilization of CH₂in methanol and severe side reactions in methanol conversion limit its further application.To solve this problem,this thesis focused on improving the one-pass selectivity to propene and P/E,and increasing the olefins content in gasoline,which can produce clean oil through etherification and alkylation.Systematic studies have been conducted on the role of pore structures and acid properties.Based on this,fixed-bed Silicalite-1 catalyst and fluidized-bed hierarchical ZSM-11 catalyst have been utilized to produce propene and gasoline.The nature of the active sites over different zeolites has been studied through micro-activity evaluation and detailed characterization techniques.The role of silanols distribution in methanol conversion and deactivation via coking was proposed.Meanwhile,the composition of two catalysts above has been further explored to meet the requirements of industrial application.Pore structure and acid property determined the reaction extent and formation of light olefins.Nano-structure and low sinuosity were found to promote methanol to light olefins and tune the ratio of olefins-and aromatic-based cycle effectively.Hierarchical ZSM-11 with intergrowth morphology exhibited optimal catalytic performance.Small crystal size and moderate Si/Al ratio were essential to further reduce the hydrogen transfer and dealkylation activity,and the light olefins were enhanced subsequently.Silicalite-2 zeolite exhibited a higher propene yield and showed a much lower deactivation rate than H-ZSM-11?Si/Al=26?.The H-bonded silanol groups in Silicalite-2 and bridging Si-OH-Al groups in H-ZSM-11 determined the formation of Br?nsted acid sites and reaction performance.The consumption or deposition of H-bonded silanols was related to the initial conversion,while the reduction of the isolated silanols was accompanied by deactivation.The external surface area determined the tolerance for coke deposition on the external.The internal isolated silanol groups can promote the deposition of hydrocarbon fragments inside the zeolite channels.Thus,after acidization,the increased internal isolated silanol groups and decreased external surface resulted in low capacity of external and internal coke;the increased external surface area and decreased internal isolated silanols contributed to a long catalytic regeneration time for desilicated samples.No direct relations were found between the deactivation behaviors and production of ethene and propene with the crystallite size and porous sinuosity.The direct effect of the hydroxyl distribution on the location of coke and deactivation behaviors was also evidenced as above.Silicalite-1 zeolite displayed a longer catalytic regeneration time than Silicalite-2zeolite.Ethene was formed in the channels and its production was subjected to the restriction of aromatic-based intermediate species in the pores.However,propene can be formed both in the pores and on the external surface?and in pore mouth?,and it mainly depended on the amount of Bronsted acid sites.To prepare the fixed bed Silicalite-1 catalyst,binder suitable was particularly important.The introduction of alumina increased the methane yield substantially and led to a fast deactivation.The addition of basic sites and a certain amunt of Bronsted acid sites in the binder can modulate its product distribution effectively.Compared with current MTP processes,the Silicalite-1 catalyst prepared has advantage in product distribution and regeneration cycle and exhibits promising applications.In the preparation of fluidized-bed ZSM-11 catalyst,the aluminum in the carrier or binder can accelerate the deactivation and promote methanol decomposition.The addition of phosphorus can modulate the Al-OH,and thus improved the hydrothermal stability of catalyst,slowed down the catalyst deactivation,and reduced the side effects.Optimal catalyst composition was ZSM-11/Kaolin/silica sol/P₂O₅:30.0/52.5/30.0/52.5.High gas-solid contact efficiency and low solid back-mixing were necessary to promote methanol conversion and inhibit side reactions.Thus,a novel multi-regime reactor with dense-phase reaction section and dilute-phase conveying region was designed,in which the propene yield can reach to16.0 wt%.In addition,etherification or alkylation of the C₄ olefins and olefins in gasoline were also proposed for maximizing propene and clean gasoline production.