Synthesis And Properties Of Mesoporous ZSM-5 By Organosilanized Doubleterminal Amino Polyetheramine Template Method

The ZSM-5 molecular sieve with the advantages of regular pore structure,adjustable acid distribution,high thermal stability and high selectivity is favored in the field of shape-selective catalysis.However,because the traditional ZSM-5molecular sieve structure contains only micropores,its The characteristics of narrow pore size and long pores will restrict the entry and exit of macromolecules,and it is easy to deposit carbon during the catalytic reaction of macromolecules to reduce the conversion rate of the reaction.Molecular sieve can effectively overcome the above disadvantages.The mesoporous zeolite molecular sieve combines the advantages of both zeolite molecular sieve material and mesoporous material.It not only has good hydrothermal stability but also allows the increased mesoporous to play the role of expanding the mass transfer efficiency.There are many methods for preparing mesoporous molecular sieves,but new mesoporous template agents designed and synthesized using template method organosilane coupling agent and polyetheramine as precursors are rarely reported.In this paper,organosilane and various double-ended amino polyetheramines are used.Bridged into excellent mesoporous template agents KH560-D400,KH560-13-W,KH560-D2000,mesoporous ZSM-5 zeolite molecular sieve was successfully prepared by hydrothermal synthesis.The structure and morphology of the mesoporous ZSM-5 zeolite molecular sieve synthesized were characterized by XRD,N₂adsorption-desorption,infrared,NH₃-TPD,SEM electron microscopy,etc.During the hydrothermal synthesis of mesoporous ZSM-5,the crystallization temperature,crystallization time,silicon-aluminum ratio,TPAOH and the amount of templating agent are all influencing factors:too low crystallization temperature will lead to a slow crystallization rate and cannot be synthesized.When the crystallization time is too short,the crystallization reaction will not proceed sufficiently,and if the crystallization time is too long,the specific surface area of the micropores will be reduced;if the ratio of silicon to aluminum is too low,it will reach the limit of gel crystallization and cannot be synthesized.Pore ZSM-5 zeolite molecular sieve,too high silica-aluminum ratio is not necessary;the increase of TPAOH amount can accelerate the decomposition of silicon source aluminum source and accelerate crystallization,but too high will cause the molecular sieve to produce amorphous substances;The pore growth is not obvious,on the contrary,adding too much template agent will self-assemble.Therefore,we must strictly control the influencing factors.The thiophene alkylation desulfurization reaction was selected as the catalytic probe reaction in this study.The mesoporous ZSM-5 synthesized by the self-made organosilanated double-terminal amino polyetheramine molecules KH560-D400 and KH560-13-W as mesoporous pore-forming agents was used as a catalyst for thiophene alkylation.After determining the optimal conditions for the thiophene alkylation reaction.In this experiment,the ZSM-5 molecular sieve with n(SiO₂)/n(Al₂O₃)=75 has a high acid content and the best catalytic effect.Within the scope of KH560-D400,the thiophene conversion of the sample with 5ml of template added amount reached 81.81%,and the selectivity reached 86.14%,which is the highest in the system;When the amount of template added in the range of KH560-13-W is 3ml,the thiophene conversion rate X%reaches 79.81%and the selectivity S%reaches 82.30%.Compared with traditional ZSM-5 molecular sieve,the catalytic effect of mesoporous ZSM-5molecular sieve is significantly improved.