Hydrothermal Synthesis Of Nano Zeolite ZSM-5 With Premixing In A Rotating Packed Bed

Zeolite ZSM-5,a kind of aluminosilicate crystal material,with unique pore structure,stable crystal structure,good thermal stability,good ion exchange performance,strong acidity,and good shape-selective catalytic properties,has been widely used in industrial catalysis process.ZSM-5 is mainly prepared by the combination method of pre-mixing and hydrothermal method.While there has crystal nucleus formation during the pre-mixing process,and the quantity and uniformity of this process will greatly affect the particle size distribution(PSD)of hydrothermal products,furthermore,it will influence the catalytic performance of the zeolite.Previous studies on the preparation of ZSM-5 mainly focused on the hydrothermal process,and there is few studies on the influence of the premixing on product physicochemical properties.Therefore,the preparation of zeolite ZSM-5 by premixing in stirred reactor(STR)and rotating packed bed(RPB)was proposed.The influence of various operating conditions in STR or RPB on the average particle size of zeolite ZSM-5 was studied systematically.The main research contents and conclusions are as follows:1.Study on the preparation of zeolite ZSM-5 by premixing in STR and hydrothermal method.The effects of premixing time,raw material ratio,reaction temperature,reaction time and other factors on the average particle size of zeolite ZSM-5 were investigated.The optimal operating conditions were obtained:template agent tetrapropylammonium hydroxide(TPAOH)content of 3.5 mol/L,alkali metal salt NaCl content of 0.3 mol/L,reaction temperature of 130?,reaction time of 24 h,and premixing time of 8 h.Under this conditions,the prepared product with an ellipsoidal morphology,a specific surface area of 314 m2/g,an average particle size of 400 nm and a PSD of 0.17-0.9?m was prepared.2.Study on the preparation of zeolite ZSM-5 by premixing in RPB and hydrothermal method.Based on the above study,the effects of operation mode,flow rate,rotation speed and premixing time in RPB on the average particle size of zeolite ZSM-5 were studied.The optimal operating conditions were obtained:operating mode of an equal-proportional cycle flow,rotation speed of 2850 rpm,silicon source flow rate of 114 mL/s,aluminum source flow rate of 311 mL/s,and premixing time of 30 min.Under the optimal conditions,the prepared ZSM-5 with specific surface area of 382 m2/g,and average particle size of 300 nm,and PSD of 0.15-0.45 ?m,good thermos ability can be prepared.From the comparative experiments,it was found that the average size of product and PSD of the products prepared by RPB premixing-hydrothermal method are smaller and narrower than the product prepared by STR premixing-hydrothermal method and commercial product.In addition,the premixing time in the RPB of 30 min is much shorter than that in STR of 8 h.This topic focuses on the preparation of ZSM-5 process by premixing hydrothermal method in STR and RPB.It was found that the premixing process has an important influence on the average particle size of the prepared zeolite ZSM-5.Process optimization was performed and the optimal operating conditions were obtained.The research provides a novel route for the preparation of zeolite ZSM-5 by hydrothermal method.