Study On Synthesis Of L Zeolite And T-L Composite Zeolite Based On Hemamethonium Bromide

Hexamethonium bromide?HMBr₂?is the template reagent of quaternary ammonium salt with rich structure and high charge density of the skeleton,which shows distinctive advantage in the synthesis of zeolites.Zeolite L belongs to the hexagonal system with the structure of one dimensional 12-membered ring channel along[001]direction and it is widely used in the field of reforming,aromatization,isomerization,chlorinated aromatic hydrocarbons,catalytic cracking,et al.At present,most of zeolites are synthesized by hydrothermal method,involving the use of long crystallization time,high crystallization temperature and tedious process,which lead to a serious waste of energy and the high cost.It is urgent to explore the methods of low energy consumption and high efficiency for the preparation of zeolite L.The zeolite L in the study was synthesized through a moderate amount of hexamethonium bromide template approach by hydrothermal method in a low tempreture of 373K and characterized by means of XRD,N₂ adsorption-desorption,SEM-EDX,TEM,FT-IR,electrophoresis,TG-DTG,et al.Then,nickel-containing zeolite L was prepared by a direct hydrothermal method and characterized by above testing technologies.The results showed that highly crystalline zeolite L could be produced with material ratios of n?K₂O?/n?SiO₂?=0.37⁰.39,n?HMBr₂?/n?Al₂O₃?=0.4¹.2 and with appropriate crystallization time?40⁴8h?.The synthesized zeolite is a well crystallized spherical particle containing mesoporous,and the particle size increased with the increasing amount of the nickel.Zeolite T and zeolite L both have similar channel structures and hole crystal silicate belong to the hexagonal system.Their skeletons both are composed of cancrinite cage and the double six-membered rings.Combining the high selectivity of zeolite L to aromatic hydrocarbons and the high activity of zeolite T to lower alkane will be conducive to achieve the synergy.The T-L composite zeolite with the binary structures of zeolite T and zeolite L was synthesized rapidly in the system of Na₂O-K₂O-Al₂O₃-SiO₂-HMBr₂-H₂O by a direct approach under hydrothermal conditions and characterized by above testing technologies.The results showed that the synthetic samples possessed a composite phase with the mosaic morphology about 1²?m of zeolite L growing on one side of zeolite T particle.The promotion effect is attributed to complex pore channel structure in the T-L composite zeolite:the composite sample has hierarchical structure and the size of the hysteresis loops are proportional to the zeolite L content which is controlled by the atomic ratio of R=K₂O/?K₂O+Na₂O?in the composite material.For the preparation of T-L composite zeolite,the optimum atomic ratio of R ranges from 0.3 to 0.5.Zeolite L consisting of agglomerates of nanoparticles can prevent the filter paper from being clogged,which is conducive to the large-scale industrialized production.The study adopted dry gel method to investigate the synthesis of zeolite L.The reaction conditions and properties of products were discussed systematically.Exploring the technological conditions and physico-chemical properties of the samples,the results revealed that the as-synthesized sample containing micropore and mesoporous was agglomerates about 0.3¹?m of nanoparticles,which facilitated filtration and had better thermal stability.For the preparation of zeolite L,the optimum atomic ratio of R ranges from 0.7 to 1.