Study On Gas Separation And Shape-selective Catalysis Performance Of Oriented Zeolite MFI Membrane

Separation is an important industrial process with energy consumption for 40%?60%of the total.Membrane separation plays a significant role in modern industrial process due to its low energy consumption and high separation efficiency.Membrane reactor is an emerging technology which has simple equipment,low energy consumption,high reaction conversion and selectivity by taking advantages of both separation and catalytic properties.MFI type zeolite membrane has large application prospect in the field of membrane reactor because of its unique molecular sieving function,excellent thermal stability and adjustable acidity.Oriented MFI type membrane is the most beneficial to separation and catalytic applications base on minimum mass transfer resistance.Secondary growth is a common method for oriented MFI type membrane preparation,and oriented seed layer assembly is the key step.As a new single molecular sieve assembly technique,Langmuir-Blodget(LB)technology has great potential for oriented membrane preparation and always been the focus of our research team.In this research,potential of LB assembly technology in oriented membrane preparation and application field will be further explored and promoted.Main work includes the following aspects.1.On the basis of previous studies,LB technology continue to be used in pure silicon MFI type membrane,zeolite silicalite-1 membrane preparation videlicet,and further research the impact of density and orientation of membrane gas separation performance systematically.The results confirme that CO2/H2 separation mechanism of silicalite-1 membrane base on molecular sieve model.The permeance of H2 is larger than CO2 as well as the value of H2/CO2 ideal selectivity is higher than Knudsen constant and the actual separation factor is 10.31 under 0.1 MPa.It indicates that gas separation performance of oriented silicalite-1 membrane is very well.This research promotes oriented MFI type membrane prepared by LB technology to separate application field creatively.2.LB technology is popularized to prepare oriented zeolite TS-1 membrane as titanium skeleton replaced MFI type membrane.Experimental result confirmes that precursor pretreatment method is more effective approach of preparing defect-free and highly oriented TS-1 membrane and the CPO(0k0)value of this membrane prepared at 170? for 6 h is as high as 0.884.CO2/H2 separation mechanism of TS-1 membrane base on adsorption separation model.The permeance of CO2 is larger than H2 as well as the value of CO2/H2 ideal selectivity is higher than Knudsen constant and the actual separation factor is 2.29 under 0.1 MPa.It indicate that gas separation performance of oriented TS-1 membrane is well either.As a novel method to synthesize compact,highly oriented and rich skeleton titanium content TS-1 membrane,LB method has solved the difficult problem of zeolite TS-1 membrane preparation and laid the foundation for the further research of membrane efficient separation and green shape-selective catalysis industry.3.Further LB technology is popularized to aluminium skeleton replaced MFI type membrane,namely orientation zeolite ZSM-5 membrane preparation.Dual-core quaternary ammonium salt is synthesized and tested as structure-directing agent to improve the membrane orientation.Compact and oriented ZSM-5 membrane getted under the reaction time of 48 h,after template agent removing and defects,compactness and the gas separation performance of the membrane have been improved.The results confirme that Si/Al ratio of ZSM-5 membrane affects gas separation performance significantly.CO2/H2 separation mechanism of ZSM-5 membrane transforms from molecular sieve to adsorption separation with Si/Al ratio decreasing and than 80 is the critical point for this transformation.The permeance of CO2 and H2 reverse periodically as Gate Opening Effect.0.1 MPa,500 0C,shape-selective catalysis performance of ZSM-5 membrane with 160 Si/Al ratio is the best for toluene alkylation with methanol reaction by 81.08%toluene conversion and 37.56%p-xylene selectivity.This study further develop the application of LB zeolite membrane preparing technology,as a new starting point of shape-selective catalytic membrane reactor integration process.