In Situ Synthesis Of Low-dimensional Nano-zeolite Using Natural Clay As Raw Material And Template And Its Catalytic Performance

Compared with conventional zeolites,low-dimensional nanozeolites have smaller particle size,larger specific surface area,shorter material transmission path,and more acidic sites.Therefore,the catalytic performance is excellent,but its preparation requires the use of special and expensive template agents,which hinders its wide range of applications.In this paper,attapulgite,halloysite and kaolin are used as raw materials and templates to dissociate clay materials by heating,acidification,and organic intercalation,etc.,and then a layer of inert material is wrapped on the surface of the raw materials,in situ crystallization to synthesize low-dimensional nano zeolite.The thesis studies the dispersion,dissociation and coating of clay,and examines the effects of synthesis conditions,inert materials,raw material processing methods,etc.on the formation of zeolite.The zeolite was characterized by XRD,FT-IR,SEM and other characterization methods,and the mechanism of in situ conversion of clay to zeolite under inert materials restricted space was discussed.The catalytic properties of low-dimensional zeolite in the preparation of benzyl hexanoate and cyclohexane oxidation,as well as the structure-effect relationship of the materials were studied.The specific conclusions are as follows:(1)Being squeezed by the rollers,the dispersed attapulgite fibers were obtained;Kaolin was intercalated by urea,the expansion force generated by the urea dispersion could propagate the kaolin layers,and obtain kaolin nanosheets.Through the intercalation of dimethyl sulfoxide and the replacement of aniline,aniline can be introduced into the kaolin layer.(2)Using attapulgite fiber or halloysite fiber as raw materials,ZSM-5 zeolite and TS-1 zeolite nanofibers can be prepared.The attapulgite need only be acidified;for halloysite,the high temperature during carbonization and high concentration hydrochloric acid leaching treatment are beneficial to the leaching of aluminum inhalloysite and the subsequent formation of MFI zeolite.The crystallization law is as follows: Under alkaline conditions,the templating agent first forms crystal nuclei with the clay component and then absorbs the nearby silicon-aluminum component to transform into zeolite nanoparticles.The more the amount of template,the higher the crystallinity of zeolite;The mesopore pore volume is inversely proportional to the amount of ammonia and the crystallization temperature.When tetrabutyl titanate is introduced during synthesis,titanium atoms can enter the zeolite framework,thereby generating TS-1 zeolite.(3)Using kaolin as the raw material,carbon material and polyaniline as the inert material,ZSM-5 zeolite nanosheets can be prepared,and the kaolin component grows into zeolite nanoparticles and aggregates in the restricted space of the inert material under the action of the template agent.Compared with polyaniline,the carbon material is evenly distributed on the surface of kaolin,and the confinement effect is better.The many pores on the surface also make the template agent easier to enter.Therefore,the resulting nanozeolite has high crystallinity and smaller particle size.(4)The catalytic properties of the obtained zeolite nanosheets and nanofibers were studied.Due to the high specific surface area and large pore size,HZSM-5 zeolite nanofibers exhibit excellent catalytic performance,and the esterification rate of hexanoic acid and benzyl alcohol can reach 74.6%,after repeated use for 4 times,the esterification rate can still reach 49.8%,which has a good service life.The higher the Ti content in the obtained TS-1 zeolite nanofibers,the higher the conversion rate to cyclohexane,and the conversion rate can reach 50.7%.