Synthesis of zeolite beta with pretreated rice husk silica and its transformation to ZSM-12

Silica with 98% purity was prepared from rice husk by acid leaching and used as a silica source for the syntheses of zeolite beta (Beta) under hydrothermal conditions with gel Si/Al ratios of 8, 13, 15, 20, 50, 100, 150, and 200. Based on powder X-ray diffraction patterns, samples with gel Si/Al ratios of 8–20 contained only the pure phase of Beta and the highest relative crystallinity was observed in the Beta with gel Si/Al ratio of 13. This sample was further characterized by scanning electron microscopy, particle size analyzer and N2 adsorption analysis. The Beta particles were sphere shaped with the average particle size of 1.5 μm and a surface area of 670 m2 g−1. The samples with gel Si/Al ratios ranging from 50 to 200 showed mixed phases of Beta and ZSM-12, and the latter phase was more dominant as the Si/Al ratio increased.