Synthesis Of Meso-microporous ZSM-5 By Soft Template Method And Its Adsorption Mechanism Analysis

ZSM-5 zeolites have been widely used in industrial adsorption due to their advantages including excellent shape-selective properties,high specific area and high hydrothermal stability.However,due to the existence of single pore structure（mainly micropores）,it is hard for larger molecules to enter the ZSM-5zeolites,which limits the adsorption capacity of ZSM-5 zeolites for the macromolecular pollutants.In order to improve the adsorption capactiy of ZSM-5 molecular sieves.The most common preparation process is prepared the meso-microporous ZSM-5 zeolites with the soft templates at present,it contains not only large and uniform mesopores but also certain amounts of micropores to overcome the restricted hydrothermal stabilities of mesoporous and the limited mass transfer of micropores.But the method of template has many disadvantages such as a hard synthesis process and the crystal cycle of templates is long.In this paper,the meso-microporous ZSM-5 zeolites were synthesized by two different synthesis routes（separation hydrolysis and co-hydrolysis）with hydrothermal method.The crystalinity and morphology of the fabricated samples were characterized by X-ray diffraction,scanning electron microscopy and transmission electron microscopy.Finally,on the basis of the optimal synthesis route,the effect of crystallization temperature and basicity of the meso-microporous ZSM-5 zeolites were characterized in detail and the optimum synthesis conditions were determined.Under the optimum synthesis route and the best experimental conditions:the separation hydrolysis was used to synthesis a simple and efficient meso-microporous ZSM-5 zeolite by soft template method,when the crystallization temperature at 170℃and the basicity of 0.2.The crystallinity,morphology,specific surface area and pore size were characterized in detail.The effect of organosilanes with different amount and different chain length on the channel regulation of the meso-microporous ZSM-5 were determined.When the amount of organosilane reached 1 Si O₂:0.05 Octyl trimethoxy silane,the crystallization process of meso-microporous ZSM-5 was verified by SEM and TEM images of meso-microporous ZSM-5 at different hydrothermal time.And the mechanism of mesopores pore formation in the hydrothermal synthesis of meso-microporous ZSM-5 was analyzed.In addition,according to the characteriztion results of ¹³C NMR spectra and infrared spectra of meso-microporous ZSM-5 in the range of hydroxyl stretching vibration.The reason for mesoporous channels of the meso-microporous ZSM-5 changed regularly with varying chain lengths was investigated.The adsorption and desorption properties of meso-microporous ZSM-5zeolite were explored by static adsorption experiments,dynamic adsorption experiments and cyclic adsorption experiments.The experimental results showed that the synthesized meso-microporous ZSM-5 combined the advantages of microporous zeolite and mesoporous zeolite.It guaranteed the framework structure of ZSM-5 zeolite and then added a second different type of channel structure,which made the volatile organic compounds（VOCs）were easy to enter the pore of the molecular sieve and adsorbed.Compared with the traditional ZSM-5 zeolite,it was found that the introduction of mesoporous greatly improved the mesoporous volume of ZSM-5 zeolite and enhanced the overall adsorption capacity of ZSM-5 zeolite.Based on these advantages,it was more practical and effcient to use meso-microporous ZSM-5 zeolite in the adsorption field of complex macromolecule industrial organic waste gas.