Synthesis And Adsorption Properties Of Beta Molecular Sieves

Beta molecular sieve is widely used in industrial production due to its unique three-dimensional 12-membered ring structure,which has moderate acidity,good hydrothermal stability and good adsorption performance.In this paper,the single template tempering method TEAOH+ seeding method and single/double template method for synthesizing Beta molecular sieve were studied respectively,and a preparation condition with high product stability,reasonable cost and high benzene adsorption amount was explored.The Beta molecular sieves were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),nitrogen adsorption desorption,and scanning electron microscopy(SEM).The adsorption capacity of Beta molecular sieves was studied by testing benzene adsorption.The main research work is as follows:1.Single template TEAOH+seed crystal synthesized Beta molecular sieve: The aluminum source was pseudo-boehmite,sodium metaaluminate,and the silicon source was silica sol,white carbon black,fumed silica,Beta Molecular Sieve were synthesized at 160?for 24 hours,28 hours and 30 hours.The aluminum source was studied as a sample of pseudo-boehmite:when the silicon source was white carbon black or fumed silica,the product was relatively stable and all were pure phase Beta molecular sieves.When the silicon source was a silica sol,the sample synthesized by crystallization for 28 hours and it exhibited a peak of mordenite.The aluminum source was studied as a sample synthesized by sodium metaaluminate: when the silicon source was white carbon black or fumed silica,the products were pure phase Beta molecular sieves.When the silicon source was a silica sol,the sample were Beta molecular sieves by crystallization for 24 hours.but it did not appear the small molecular peak of the Beta sieve at21.2°.However,as the crystallization time prolonged,the small peak appeared and the product was a pure phase Beta molecular sieve.According to experimental analysis,it is understood that the synthesized product is relatively stable compared with the silica sol when the silicon source is white carbon black or fumed silica.The specific surface area of the sample prepared by the aluminum source of sodium metaaluminate is substantially higher than that of the sample prepared by the pseudo-boehmite.Therefore,the aluminum source is sodium metaaluminate,the silicon source is white carbon black and fumed silica to prepare samples.According to the benzene experimental data,it is not the larger the specific surface area of the sample,the largerthe amount of benzene adsorbed.The amount of benzene adsorbed is not positively correlated with the specific surface area and is also related to the aluminum source and the silicon source.2.Single/double template method synthesized Beta molecular sieve: single element template TEAOH and double template agent TEAOH+TEABr were studied.The silicon sources were fumed silica,silica sol and silica,Beta Molecular Sieve were synthesized at 160?,170?,175?for 24 hours.The single template was studied as a sample synthesized by TEAOH: when the crystallization temperature was 160?,only the silicon source was fumed silica,the product was a pure phase of the Beta molecular sieve,and the other silicon sources were amorphous products.As the crystallization temperature increases,the degree of crystallization of the product gradually increases.The samples synthesized by the double template TEAOH and TEABr were studied: At different crystallization temperatures,the product of the silicon source being fumed silica is relatively stable,followed by silica.As the crystallization temperature increases,the degree of crystallization of the product gradually increases.When the silicon source is a silica sol,the samples are all amorphous products.The comparison of the experimental data of single template and double template showed that the single template synthesis sample is more stable than the double template synthesis sample,indicating that TEAOH played a leading role in the crystallization process of molecular sieve compared with TEABr,and the crystallization product is relatively stable.Whether using a single templating agent or a double templating agent to synthesize a sample,the product is the best,which was fumed silica at 160?.According to the benzene adsorption amount and specific surface area data,the specific surface area affects the benzene adsorption amount,but the benzene adsorption amount does not have a simple positive correlation with the specific surface area.