Synthesis of ZSM-5 Zeolite from Silica Stone Occurred in Ioh Island, Kagoshima Prefecture, Japan

Abstract

ZSM-5 zeolite with the molar ratios SiO2/Al2O3=61-75 was synthesized hydrothermally at 220°C from silica stone containing Al2O3 component of 1.40wt% (occurred in Ioh island, Kagoshima Prefecture, Japan), with tetra-n-propylammonium bromide (TPABr) and NaOH solution. The formation ratio, yield, and morphology of ZSM-5 were strongly affected by the concentration of NaOH solution. Increasing NaOH concentration decreased the yield and SiO2/Al2O3 ratio of ZSM-5. ZSM-5 zeolite formed from the silica stone smaller than 44μm in NaOH solutions of concentrations higher than 1.0mol/l consisted of rectangular particles of about 5μm. The Al2O3 and Fe2O3 components in the silica stone remained in the formed ZSM-5. It was possible to control the SiO2/Al2O3 ratio of ZSM-5 from 44 to 431 by adding NaAlO2 or amorphous SiO2 to the Ioh island stone. Roles of Na and TPA ions in the formation of ZSM-5 were also discussed.