Synthesis Of Hierarchical Zeolite Y By Using Rice Husk As Raw Material

zeolite Y is the active components of catalytic cracking catalysts.The active centers are mainly distributed on the inner surfaces of zeolite.As crude oil becomes more and more heavy,heavy oil macromolecules can not diffuse efficient in the zeolite micropore,and the utilization of zeolite is low,which can seriously deactivate the catalyst due to coking.Although the mesoporous SiO₂ materials have large pore sizes,their pore walls ar amorpous with poor hydrothermal stability.Therefore,more and more researches ture their focus on the preparation of hierarchical zeolite.Rice husk is a by-production of rice production,with high yields and low prices.At the same time,rice husk is rich in silica and organic components.If it can be used as a raw material to synthesize hierarchical zeolite,it will be able to realize“turning waste into treasure”,which has very important economic and academic value.In this paper,the influencing factors of silica extraction rate in rice husk carbon were studied first,and the effects of extraction temperature and time on the extraction rate were investigated..The optimunm extraction conditions were as follows:extraction temperatures of90 ?,and extraction times of 5 hours.The extraction rate of silica was achieved up to 96.69%.The activation process of rice husk included carbonization and NaOH activation.The carbonization process is the decomposition of volatiles.The effects of carbonization atmosphere,carbonization time,and carbonization temperature on carbonization were investigated.The activation process uses alkali to activate silicon and carbon compounds in rice husks..The effects of activation temperature and activation time on the activation were investigated.The optimum conditions were as follows:carbonization at 400 ? for 3 hours in air atmosphere,and then activation at 800 ? for 0.5 hour.The specific surface area of rice huak carbon was 969.71 m²/g,with a mesopore volume of 0.89 cm³/g.At the same time,the silicon in the rice husk was used as the silicon source,and the carbon in the rice husk was used as the hard templating agent to synthesize hierarchical zeolite Y by hydrothermal synthesis.The effects of alkalinity,crystallization time and crystallization temperatures on the synthesis are investigated.The crystalline structure,morphology and pore structure of zeolite Y were characterized by X-ray powder diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,N₂adsorption-desorption techniques Under the optimum synthesis conditionsbasicity of 6.66,crystallization temperature of 90 ? and crystallization time of 16 h,,the zeolite Y contained less impurity crystalline phase.Compared with the conventional zeolite Y,the obtained zeolite Y has smaller crystallite size and a significant increase in mesopore volume.The specific surface area of the synthesized sample is 499.8m²/g with a mesopore volume of 0.092cm³/g.