Synthesis And Pore Structure Of Low-silica Mesozeolite

Zeolites are crystalline aluminosilicate materials with large surface areas,intricate pore and channel systems,well stability,tunable surface property,strong acidic property,immensely used in separations,ion exchange industry and catalysis.But the innate small micropores(usually 0.3?0.7nm)of zeolite strongly limit the diffusion of reagents and reaction products,especially once the adsorption or reaction process refers to relative large molecules.The limited pore size of zeolite imposes large diffusion and spatial resistance,greatly reduces the accessibility of active sites,resulting in the maximal availiablity of zeolite difficult to be implemented in industry.Therefore,it's of great importance to increase the transport efficiency and the availability of active sites in zeolites.Mesozeolite can be used to solve the problems of zeolite.Mesozeolite not only retains the microporous properties of zeolite,but also introduces mesopores or macropores in the materials,which largely shorten the diffusion path,reduce the diffusion residence,speed up the diffusion of molecular,enhance the accessibility and availability of active sites.The appearance of mesozeolite widely broadens the field of application.Herein,through "Templating methods”and "Bond-Blocking Principle"we successfully synthesized three low-silica mesozeolites:mesoporous zeolite A,X and Y.1.Mesoporous zeolites A were hydrothermally synthesized from silica source Si-MCM-41 organic functioned by henylaminopropyl-trimethoxysilane(Y-5669).The results showed that zeolte A synthesized has abundant intracrystal mesopores.And it has much higher surface area,external surface area and mesopore volume than that of the compared mesoporous zeolite A.2.Mesoporous zeolites Y were hydrothermally synthesized using an organosilane surfactant TPOAC,which as mesopore-generating agent was added into the conventional synthesis system of the crystalline microporous aluminosilicates.The results showed that the presence of TPOAC led to the introduction of abundant intracrystal mesopores and formation of assemblies of nanoscale zeolite crystals,thus obtaining the meso-zeolites Y with micropores,intra-,and inter-mesopore.3.Mesoporous zeolites X were hydrothermally synthesized using two organosilane surfactants Y-5669 and TPOAC,which as mesopore-generating agent were added into the conventional synthesis system of the crystalline microporous aluminosilicates.The results showed that zeolite X synthesized with Y-5669 had none of mesopore.But the presence of TPOAC led to the introduction of abundant intracrystal mesopores and formation of assemblies of nanoscale zeolite crystals,thus obtaining the meso-zeolites X with micropores,intra-,and inter-mesopore.4.Mesoporous zeolites X were hydrothermally synthesized from silica source Si-MCM-41 organic functioned by Y-5669 and TPOAC.The results showed that zeolite X synthesized from silica source Si-MCM-41 organic functioned by Y-5669 has abundant mesopores.But the presence of silica source Si-MCM-41 organic functioned by TPOAC led to the introduction of abundant intracrystal mesopores and formation of assemblies of nanoscale zeolite crystals,thus obtaining the meso-zeolites X with micropores,intra-,and inter-mesopore.And TPOAC is a better candidate to creat intracrystal mesoporous in zeolite X by“Bond-Blocking Principle".These mesoporous zeolites X have higher external surface area than others,so "Bond-Blocking Principle" is much better than "Templating methods" to synthesize mesoporous zeloite X.