Solid State Synthesis Of Hierarchical Y/ZSM-5 Composite Zeolite Via Inter-zeolite Conversion From USY

Zeolite is an important inorganic porous crystal material with unique pore structure and adjustable acid properties.It is widely used in many fields such as petroleum refining,shape selective catalysis,adsorption separation and biomass conversion.Y zeolite is the main active component of FCC catalyst.ZSM-5 zeolite has unique cross pore structure and good shape selective catalytic performance.It is often used as an olefin production promoter and high octane number promoter in FCC catalyst to improve the selectivity of low carbon olefins in FCC process.At present,Y and ZSM-5 zeolites are mechanically mixed and added to FCC catalyst in FCC industry.These two zeolites need to be prepared and modified separately,and then added separately.This mixing method can not give full play to the synergistic catalytic effect of the two zeolites.Therefore,the research of Y/ZSM-5 composite zeolite is of great significance in petroleum refining industry.In this paper,Y/ZSM-5 composite zeolite with industrial application prospect was prepared by improving the traditional preparation method,and the crystallization mechanism of composite zeolite was explored.In this paper,an innovative preparation method of Y/ZSM-5 composite zeolites,solid phase conversion method,was used.Using USY as a single raw material,framework silicon and part of framework aluminum were selectively removed by solid-phase alkali treatment to obtain silicon aluminum source.Mesoporous silica was introduced into USY zeolites,and then under high temperature and alkaline conditions,This part of silicon aluminum source was transformed into ZSM-5 zeolite under the action of TPA~+,thus the hierarchical pore USY/ZSM-5 composite zeolite was successfully synthesized.On this basis,we investigated the effects of different synthesis factors on the solid phase conversion process of USY zeolites,and synthesized hierarchical pore USY/nano ZSM-5composite zeolites by low-temperature crystallization and variable temperature crystallization(The maximum mesoporous volume is 0.67 cm~3/g;The size of ZSM-5 zeolite is about hundreds of nanometers).Subsequently,a batch of USY/ZSM-5 composite zeolites with phase ratio(mass ratio)less than 20%were successfully prepared,and samples with excellent catalytic performance were found.Through the above research on the preparation of USY/ZSM-5 composite zeolites by solid-phase conversion method,the composite zeolites with excellent catalytic performance were successfully prepared,and the morphology and structure of the composite zeolites were successfully controlled to a certain extent,which proved that the solid-phase conversion method was not only simple to operate,but also had great potential for industrialization.This synthesis method provides an important idea for the green synthesis of composite zeolites,and has a certain reference value for the control of the morphology,structure and particle size of composite zeolites.