High temperature hydrothermal crystallization, morphology and yield control of zeolite type K-LTL

Abstract K-LTL zeolite was prepared by hydrothermal crystallization at 443 K from gels having molar composition x K 2 O: y SiO 2 :Al 2 O 3 : z H 2 O, where 2 ⩽  x  ⩽ 8, 8 ⩽  y  ⩽ 20 and 80 ⩽  z  ⩽ 200. The influence of various synthesis variables such as SiO 2 /Al 2 O 3 , K 2 O/SiO 2 , H 2 O/SiO 2 molar ratios in the initial gel mixture and the nature of source materials used on crystallization kinetics, product composition, morphology and yield was investigated. The samples were characterized by powder XRD, FT-IR, XRF and SEM techniques. High rates of nucleation and crystallization of the most siliceous gel system resulted in the formation of more siliceous K-LTL zeolite with less yield and clam shaped agglomerates. Because of poor nucleation ability, dilute system comprising of lower molar ratios of SiO 2 /Al 2 O 3 and K 2 O/SiO 2 yielded cylindrical K-LTL crystals with higher Si/Al ratio. In more aluminous system the particle size, Si/Al ratio and the yield of the product were found to increase with decrease in molar K 2 O/SiO 2 ratio. In present studies, silica sol and pseudoboehmite were found to be better raw materials for optimal preparation of K-LTL zeolite with desired characteristics and better yield.