Preparation Of MFI Type Zeolite Films Based On The Space Limitation Of Graphene Oxide

The separation process is always an indispensable and important unit in the industrial field.Membrane separation has attracted extensive attention due to its advantages such as high separation efficiency and low cost.MFI molecular sieve membrane is stable and has uniform pore sizes,so it is widely used in the industry of membrane reactors and separation.Therefore,it is of great significance to study the synthesis and separation performance.In recent years,in the synthesis methods of molecular sieve membranes,researchers mostly adopt the secondary growth method.In order to reduce the mass transfer resistance,they focus on the synthesis of b-axis oriented ultra-thin molecular sieve membranes without twin crystals.The key to the synthesis of molecular sieve membrane by secondary growth method is the preparation of high-quality crystal seed layer.Langmuir-Blodgett(LB)technology has a good effect for assembling oriented monolayer seed layer.It is a novel technology used to assemble single molecular layer and the focus of this group.This study will continue to use LB technology to assemble the seed layer,and the main research work include:1.The synthesis and assembling by LB technology of GO and the synthesis of molecular sieve nano-crystals and nano-sheets.FT-IR and SEM show that GO is synthesized successfully.The thin film of GO deposited by LB technology is observed through AFM.The results show that a single layer and tightly arranged GO film is assembled successfully and the average thickness is about 2 nm.FT-IR and XRD are used to characterize the synthesized molecular sieve nano-crystals and show that there are characteristic peaks of MFI structure.The particle size analysis result shows that the particle size is around 140 nm,which indicates that silicalite-1 nano-crystals have been synthesized successfully.The synthesis of nano-sheets is studied.Through the study on the molar ratio and synthesis time,when the molar ratio of water is 1000 and the synthesis time is 12 h,the molecular sieve nano-sheets with the thickness of less than 10 nm are successfully prepared,which has a very broad prospect for the synthesis of ultra-thin oriented molecular sieve membranes.3.The seed layer was prepared by LB technology.Then the synthesis of the ultra-thin molecular sieve film and the separation properties of H2/CO2 were studied.The results showed that the assembled seed layer was arranged in a tight monolayer when the concentration of seed dispersion solution was 0.1%and the film pressure was 30 mN/m.The ultrathin oriented molecular sieve films were synthesized using the preparation sequence of substrate-seed layer-GO overlay on stainless steel.The research results showed that the thickness of the synthesized films decreased with the decrease of the concentration of the synthetic solution,when the synthesis time was 4 h.When the molar ratio of water was 2000,the synthesized film was the thinnest with a thickness of 200-300 nm.Under this ratio,the influence of growth time on the synthesis of molecular sieve films was studied.When the growth time was 24 h,the film was b-oriented and the thickness was about 500 nm,indicating that the ultrathin oriented molecular sieve film was synthesized successfully.The results of H2/CO2 separation by molecular sieve membranes synthesized on porous alumina showed that the ideal selectivity of the membranes repaired by APTES were greatly improved,showing better gas separation performance.The ideal selectivity of the membrane reached a maximum of 15.83,when the growth time was 24 h.