Effect of the silica sources on the crystallinity of nanosized ZSM-5 zeolite

Silica sources can influence different aspects of ZSM-5 crystallization and it leads to change in the properties of the final product. The crystallinity of nanosized ZSM-5 zeolite from precursors mixtures containing different silica sources, e.g. tetraethylorthosilicate (TEOS), colloidal silica (Ludox LS 30), sodium metasilicate and fumed silica have been studied. The produced samples are investigated using XRD, SEM, and carbon % in the samples after calcination in air and BET surface area. The product obtained by TEOS, fumed silica and colloidal silica is ZSM-5 phase, but the product obtained by sodium metasilicate is the quartz phase. The crystallinity, and % of the nanosized ZSM-5 zeolite increased in the following order: sodium metasilicate < colloidal silica < TEOS < fumed silica. The average crystal size increased in the following order: fumed silica < TEOS < colloidal silica < sodium metasilicate. The surface area increased in the following order: sodium metasilicate < colloidal silica < TEOS < fumed silica. The template was almost completely removed from the ZSM-5 by calcination at 550 degrees C for 8 h in air. (c) 2004 Elsevier Inc. All rights reserved.