Synthesis Of B-Oriented Silicalite-1 Zeolite Membranes And Structure-directing Agents Removal From Silicalite-1 Zeolite

MFI zeolite films have shown to have interesting properties as membranes and membrane reactors,chemical sensors,heat pumps,catalytic coating reactors and corrosion resistant coatings;thus there has been growing attention on the preparation of zeolite films in various fields.Due to the anisotropic pore structure of MFI zeolites,the orientation of constituent micro-crystals in a MFI zeolite membrane can significantly affect its molecular sieving effect and especially the highly b-oriented MFI films show superior separation performance.In terms of synthesis of b-oriented MFI membranes,this article reported on the synthesis of silicalite-1 zeolite-GO(graphene oxide)composites by introducing GO nanosheets(5,10,22%wt)into a silicalite-1 synthesis system.The growth of b-oriented silicalite-1 nanosheets has been confined in 2D space of GO nanosheets and its threedimensional intergrowth has been repressed.In the meantime,silicalite-1 crystals grown in the presence of GO exhibited looser and larger lateral plates with reduced intergrowth.In this dissertation,only water and a little TPAOH were applied without gel preparation step and a simple method was proposed based on confined space dissolution and recrystallization(CSDR),in which pre-coated as-synthesized silicalite-1/GO microcrystal monolayers are transformed into continuous zeolite thin films after steaming under saturated conditions omitting the gel aging process.It was found that the micro-crystal layer could be convert to b-oriented continuous zeolite MFI thin 600-nm thick films at 185 ? for 40 h with water content of 190 ?L.This article also researched on the methods of dielectric-barrier discharge plasma technique under air atmosphere to remove the structure-directing agent of silicalite-1-GO zeolite crystals in order to release pores.The highest temperature of DBD is below 140 ?.The dissertation achieved synthesis of uniform b-oriented continuous zeolite MFI thin films using looser silicalite-1/GO zeolite crystals with high aspect ratio.In the meantime,the highest temperature during DBD plasma was far below thermal calcination,which led to less effect on zeolite framework shrinking than thermal calcination.