Zeolite X crystals were synthesized by hydrothermal crystallization from gels with different compositions. The syntheses were performed at 95 degrees C using different silica sources such as sodium metasilicate anhydrous, sodium metasilicate pentahydrate, silicate solution and Cab-O-Sil. Triethanolamine was used in some syntheses in order to grow large crystals. Zeolite X crystals with diameters in the range of 1-220 mu m were obtained, and Cab-O-Sil in concert with triethanolamine yielded the largest crystals. (C) 2014 Elsevier B.V. All rights reserved.