Synthesis of ZSM-5 zeolite from lignite fly ash and rice husk ash

The lignite fly ash from the Mae-Moh power plant, Thailand, and lice husk ash were used as raw materials for ZSM-5 zeolite synthesis. Factors affecting the yield of ZSM-5 zeolite synthesized from fly ash, i.e., the SiO2/Al2O3 mole ratio, the presence of tetrapropyl ammonium bromide (TPABr, the structure-directing material for ZSM-5 zeolite synthesis), the holding temperature and time, and the initial pressure were investigated. It was found that without TPABr only zeolite P could be synthesized at SiO2/Al2O3 mole ratios of 2.8-200. In order to synthesize ZSM-5 zeolite, sodium silicate solution was added to adjust the SiO2/Al2O3 mole ratio in raw ash. The yield of ZSM-5 zeolite was as high as 59 wt.% when following conditions were used: SiO2/Al2O3 mole ratio, 40; the holding temperature, 210 degreesC; the holding time, 4 h and the initial pressure, 4 bar. The catalytic performance for CO2 hydrogenation reaction of the ZSM-5 zeolite was preliminary tested and compared with that of commercial one. It was observed that there was no significant difference in the catalytic performance between these two catalysts. (C) 2004 Elsevier B.V. All rights reserved.