Conversion of rice husk ash to zeolite beta

White rice husk ash (RHA), an agriculture waste containing crystalline tridymite and alpha-cristobalite, was used as a silica source for zeolite Beta synthesis. The crystallization of zeolite Beta from RHA at 150 degrees C in the presence of tetraethylammonium hydroxide was monitored by XRD, FTIR and Si-29 MAS NMR techniques. It was found that zeolite Beta started to form after 12 h and the complete crystallization of zeolite Beta phase was achieved after 2 d. XRD, Si-29 MAS NMR and solid yield studies indicate that the transformation mechanism of silica present in RHA to zeolite Beta involves dissolution of the ash, formation of an amorphous aluminosilicate after 6 h of crystallization, followed by dissolution in the mother liquor and final transformation to pure zeolite Beta crystals. (c) 2005 Elsevier Ltd. All rights reserved.