Study On Low-cost Synthesis Of Beta Zeolite Without Ammonium Hydroxide

In 1967,Beta zeolite was first exploited by Wadlinger of Mobile in the United States,it is the only high silica zeolite with a three dimensional network of 12 ring pores straight channel system and is the only chiral hole in the aperture Network zeolite structure.Because of Beta zeolite with unique topology BEA,easily modulating in the ratio of Si/Al from a few dozen to several hundred of the framework,both acid selective catalytic activity and structure selective, high thermal stability(the lattice damage temperature is higher than 1200℃),hydrothermal stability and wear resistance,Beta zeolite shows an excellent performance in catalysis and adsorption,and rapidly become a new type of catalytic material in recent years and has been widely applicated with prospects.Beta zeolite is synthesized mainly by hydrothermal crystallization method,the cost is high,technology is complex,and causes serious environmental pollution,which greatly limits the applications in industry.Therefore,to reduce the cost of its synthesis,optimize the synthesis process and reduce the pollution to environment have an important practical significance.In this paper,cheap TEABr as template agent,without ammonium hydroxide as auxiliary, adding seed in the system,effects of synthetic materials,crystallization temperature, crystallization time,the amount of templating agent,the ratio of H₂O/SiO₂ and seed to the synthesis process were studied,and then the synthetic conditions were optimized;on this basis,Beta zeolite of relatively low ratio of Si/Al were synthesized;the catalytic properties of Beta zeolite synthesized with different amount of seed and low ratio of Si/Al under optimizing conditions were evaluated on the benzene/propylene alkylation.The results showed that using TEABr as template agent,without ammonium hydroxide as auxiliary,KOH and NaOH as alkali source,silica as silicon source,boehmite as aluminum source,the optimizing conditions for Beta zeolite synthesis is(Na₂O+K₂O):Al₂O₃: TEABr:H₂O:SiO₂=0.23:0.033:0.20:15:1,the adding volume of seed was 15%(SiO₂wt%), crystallization temperature was 145℃,the crystallization time was 5 days,Beta zeolite synthesized under these conditions with good shape had a high crystallinity and purity;under the optimizing conditions,Beta zeolite of low ratio of Si/Al from 10 to 20 were successfully synthesized by adjusting the system alkalinity and crystallization time.On the alkylation catalytic performance of benzene/propylene,Beta zeolite added seed 8%～30%(SiO₂ wt%) showed higher selectivity,in which the adding volume of seed 20%(SiO₂wt%) the showed a higher conversion rate,40%;Beta zeolite with low ratio of Si/Al from 10 to 20 showed the higher selectivity in the reaction,the ratio of Si/Al is 20 that showed a higher conversion rate of 37%,the stability declined with the decline of the ratio of Si/Al.