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Preparation and Characterization of Zeolite-KL with High Silica Alumina Ratio

Author: ShiXiaoHong
Tutor: ChenYi
School: Zhengzhou University
Course: Industrial Catalysis
Keywords: Zeolite L Preparation Characterization Dealumination Water vapor roasting Al ratio
CLC: O643.36
Type: Master's thesis
Year: 2008
Downloads: 30
Quote: 0
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Abstract


Zeolite L is a date in nature yet found equivalent synthetic zeolite pore hexagonal prism cage by the cancrinite the cage (CAN cage) alternating and overlapping composition (D6R) in the c-axis direction, and then the six-fold axis rotation generated one-dimensional 12-membered ring channels, kinetic diameter of 0.71nm. Due to its excellent adsorption and catalytic properties of petroleum cracking, catalytic reforming, aromatization such broad application prospects. However, due to its special crystallization environment and crystal structure of the constraints, generally obtained higher levels of alkaline cations Al ratio is relatively low. High and low aluminosilicate nature of this base cation content of the zeolite L unfavorable to its application to the FCC. FCC, the FCC is acid-catalyzed reaction, L zeolite application requires a certain number of acid sites. Al ratio of zeolite and its catalytic properties are closely related surface acidic centers increased with the raise of the zeolite framework zeolites, acid distribution broadens, improved the stability of the skeleton. In practical applications, the high silica to alumina ratio of the L-zeolite catalyst can be effectively suppressed hydrogen transfer reaction and the condensation reaction between the molecules in the catalytic cracking process, thereby reducing the olefin content in gasoline. FCC hydrocarbon oil hydrotreating, catalytic reaction High-SiO2/Al2O3 L zeolite catalyst has better catalytic performance, so the research the High-SiO2/Al2O3 the synthesis of zeolite L and modified to reduce its potassium content, improve its Al ratio is of great significance. See literature, mainly from two aspects of the synthesis and modification to start preparation High-SiO2/Al2O3 L zeolite. Research in of High-SiO2/Al2O3 zeolite L improvement. Synthesis paper is mainly based in hydrothermal synthesis method by changing the silicon source feeding sequence and experimental conditions High-SiO2/Al2O3 preparation of zeolite L, and also study the feeding the aluminosilicate relatively high KNa Preparation of zeolite L. Modified aspects of the self-made K-type zeolite L ion exchange reduce potassium content based on chemical dealumination and hydrothermal roasting off Aluminum complement silicon method of combining preparation the High-SiO2/Al2O3 zeolite L. XRD, IR, SEM, TGA-DTA characterized samples prepared. The experimental results show that the hydrothermal synthesis by changing the experimental conditions, the zeolite L prepared the silicoaluminophosphate has significantly improved. Dealumination and steam roasting off Aluminum complement silicon by chemical method of combining modified zeolite L better experimental results, the modified zeolite L Al ratio increasing more obvious, and the relative degree of crystallinity reserved than high. Drawn in the study of a variety of modified zeolite L, the preparation of high silicon aluminum is a better route than the zeolite L is a combination of ion exchange and calcination processing its potassium content fell to a range of catalytic cracking requirements of L zeolite , and then by the acid treatment to wash away its channels of amorphous aluminum and its skeleton Al ratio to meet its practical application in the petrochemical extraction framework aluminum. In this experiment, the degree of crystallinity of the zeolite L obtained by the synthesis system, wherein silicoaluminophosphate highest ratio reached 3.70, increased by about 25% than the laboratory in the past synthesized L zeolite silica to alumina ratio (2.76). The modified better sample prepared silica to alumina ratio of up to 21.9, and the relative degree of crystallinity higher than 80%. The potassium content of the sample fell 1.7%, to the lattice collapse temperature of 989 ° C.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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