Control Of Local Environment And Hierarchical Structure Of Zeolite Nanopores

Zeolites,a kind of porous materials with unique structure such as multidimensional channels and large specific surface area,have important application in volatile organic compounds(VOC)treatment due to their high adsorption capacity.There are a large number of silicon hydroxyls existing in pores and external surface of zeolites,which result in their sharp decrease in adsorption ability in wet environment.In addition,the size of aperture in microporous zeolites is usually less than 2 nm,which is too small for mass transfer and diffusion of large molecules.Therefore,how to control the local environment and hierarchical structure of zeolite nanopores is of great importance.One of the modified methods of silicon hydroxyls is to introduce organic groups in order to increase the hydrophobicity of zeolites.Various organic-functionalized molecular sieves(OFMS)have been synthesized,like phenyl and vinyl functionalized ZSM-5,Y,Beta,etc.There are mainly two ways to synthesize OFMS:the in situ synthesis and the post-processing method.However,most of in situ synthetic methods need organic template agents,high temperature and long crystallization time.The post-processing method which is complicated will lead to the unexpected distribution of organic groups as well as the sacrifice of crystallinity.Therefore,we propose an in situ template-free synthesis of OFMS in mild conditions.As for the low efficiency in mass transfer and diffusion of large molecules,the commonly effective solution is to synthesize hierarchical zeolites by introducing the mesoporous channels.However,extra mesoporous organic template agent is needed in the synthesis of hierarchical zeolites,which highly increase the cost and will be unfriendly to environment.Hence,we come up with an in situ self-assembly synthesis of hierarchical AlPO4-5 without mesoporous template.Therefore,this paper mainly focuses on the in situ synthesis of OFMS and hierarchical zeolites to control the local environment and hierarchical structure of zeolite nanopores.First of all,phenyl and methyl functionalized Beta zeolites were synthesized with seeds.Then,phenyl functionalized ZSM-5 zeolites were synthesized by a template-free and solvent-free method.A series of techniques were employed to confirm the successful introduction of organic groups in zeolites.To evaluate the adsorption capability of toluene on OFMS,the breakthrough curves of toluene on various samples under the condition of 1000 ppm in dry(RH=0)and wet(RH?80%)air were drawn.The results showed that the adsorption capability of toluene on conventional zeolites dropped greatly while it almost remained no decrease on OFMS in the high humidity environment.Finally,hierarchical AlPO4-5 zeolite was in situ self-assembly synthesized only with the microporous templates by the solvent-free method.The N2 sorption isotherms proved the successful introduction of mesopores.The crystallization process was studied by TGA,NMR and so on.