Preparation And Characterization Of Zeolite-kl With High Silica Alumina Ratio

L zeolite is a synthetic zeolite, without any known natural equivalent.The crystalline frame is composed of cancrinite cages and hexagonal prisms arrangements which provide in the structure a lattice of unidimensional channels, parallel to c axis, having a twelve oxygen atoms opening and whose diameter is close to 0.71 nm. It has the wide foreground of use in the processes of petroleum cracking,catalyse reforming and aromatization etc., because of its excellent adsorption and catalyse performance. But under the restrict of its crystallizing conditions and crystalline frame,the products have higher content of alkali cations and lower silica alumina ratio .The kind of property of L zeolite with higher content of alkali cations and lower silica alumina ratio is disadvantageous for its use in the FCC. In FCC, the reaction is acid catalysis. Some acid sites were needed in the use of L zeolite. At the same time, the silica alumina ratio of zeolite relate to its catalytic properties intimately. With the silica alumina ratio of zeolite increasing, the acid sites increased, the acid distribution extended and the frame stability of zeolite improved. The high silicon L zeolite is used in catalytic cracking,hydrogen refining for its better catalyse performance.So,it is important to research the preparation of high silicon L zeolite and the reduction of the potassium oxide content of L zeolite .In this study,synthesis and modification as two mostly ways were used to prepare high silicon L zeolite. Some advancements were wished to obtain. In synthesis, improving the conditions and the ways were researched to acquire high silicon L zeolite. At the same time,KNa-L zeolite with stuff of high silica alumina ratio was investigated,too. In modification, the influence of ion exchange on the reduction of the potassium oxide content of L zeolite and the influence of dealumination by hydrothermal and chemical methods on the increasing silica alumina ratio were investigated. The samples were characterized by XRD,IR,SEM and TGA-DTA etc. The results showed that the silica alumina ratio of L zeolite which was prepared by hydrothermal synthesis with the modification of experimental materials and conditions was increased evidently. The good modified results were obtained by the combination of hydrothermal and chemical methods.The modified L zeolite has high silica alumina ratio and relative crystallinity. We finded that the good way of preparing high silicon L zeolite was to reduce the potassium oxide content of L zeolite with the combination of ion exchange and hydrothermal firstly.And then through chemical dealumination to increase its silica alumina ratio.L zeolite can satisfy the use in petrochemical after modification.In this study,the silica alumina ratio of L zeolite with higher silica alumina ratio which was prepared by synthesis is 3.70.This samples have very high crystallinity.Its silica alumina ratio was compare with the prevenient sample's increased about25%.The silica alumina ratio of the modified L zeolite is 21.9 .Its relative crystallinity was higher than 80% .The potassium oxide content of the modified zeolite reduced to 1.7% and its crystal lattice landslip temperature is989℃.