Siliceous Fly Ash Utilization Conditions for Zeolite Synthesis

Fly ash is a coal combustion product partly disposed of in landfills since it finds no other application. Recycling this solid is of great benefit in terms of quality, cost effectiveness and the environment. The chemical and mineralogical composition of siliceous fly ash makes it an attractive and economic raw material for the synthesis of zeolites. Zeolites are microporous, aluminosilicate minerals characterized by a three-dimensional network of tetrahedral units produced industrially on a large scale. In this work, synthetic X and A-type zeolite with high crystallinity and high value of surface area were synthesized by a pre-fusion method followed by a hydrothermal treatment under various conditions. The data indicate that zeolitic products were obtained using NaOH while no zeolitic material was crystallized using KOH and LiOH. Pre-treatment of fly ash with acid before being used in the synthesis of artificial zeolites is considered an important parameter for the purity phase of zeolites. Without sodium aluminate additions, synthetic zeolite A was not formed. The results confirm that temperature, crystallization time, SiO2/Al2O3 ratio and type of water (distilled water and seawater) are also important parameters influencing type of zeolite synthesized. Zeolite X was used as a novel catalyst for the alkylation of phenol using diethyl carbonate.