SYNTHESIS OF ZEOLITE-BETA AND CATALYTIC ISOMERIZATION OF NORMAL-HEXANE OVER PT/H-BETA CATALYSTS

Zeolite beta was synthesized from aluminosilicate gels in the presence of tetraethylammonium hydroxide (TEAOH) under hydrothermal conditions. The effects of silica/alumina ratio, water content, TEA+ cation, crystallization temperature and time on the synthesis were investigated. The best synthesis conditions found were: SiO2/Al2O3 = 26-70, H2O/Al2O3<800, (TEA)2O/Al2O3>2.0, crystallization temperature 403-443 K, and crystallization time 50-270 h. The activation energies of crystallization and nucleation were calculated to be E(c) = 15.2 kcal/mol (1 cal = 4.1868 J) and E(n) = 7.0 kcal/mol. Techniques including XRD, ICP, DTA, FTIR and TPD have been used for the characterization of zeolite beta. Catalytic activities and product distribution for n-hexane isomerization over platinum-loaded zeolite catalysts, Pt/H-mordenite, Pt/HY and Pt/H-ZSM-5, were compared. Platinum-loaded zeolite beta was found to show high activity and high selectivity for dimethylbutane. The best composition of the catalyst was zeolite beta with Si/Al = 6.7, loaded with 0.1-0.3 wt.-% of platinum. The best reaction temperature was 513-533 K.