PREPARATION OF MICRO-MESOPOROUS COMPOSITE SIEVES CATALYST AND ITS CATALYTIC CRACKING PERFORMANCE OF COAL TAR

摘要

At present, China's large amount of coal tar is relatively crude and its low processing and conversion capacity is low. Catalytic pyrolysis is an effective way to improve the quality of the coal tar, heavy components in tar to be divided into BTX, PCX, and other light aromatics components, in order to improve the quality of the tar. In this paper, SBA-15 mesoporous molecular sieves were prepared mainly by hydrothermal synthesis and microwave hydrothermal synthesis. The main use of triblock copolymer P123 as template, tetraethyl orthosilicate as silicon source, and the synthesis conditions were studied under the condition of acid, the influence of the crystallization time on the synthesis effect was discussed. The synthesis conditions under acidic conditions were carried out to explore the influence of the synthesis effect by using different crystallization time. The traditional hydrothermal method was optimized by ultrasonic dissolving, the temperature water bath was 40°C, the crystallization temperature was 90°C, and the crystallization time was 24h. The microwave hydrothermal method can improve the crystallization efficiency, and shorten the crystallization time to 2h. The micro-mesoporous molecular sieves were obtained by mechanical mixing microporous molecular sieve ZSM-5. The SBA-15 prepared by hydrothermal synthesis has a hexagonal column structure with moderate pore size, thicker pore walls, and higher hydrothermal stability. In addition, the isothermal adsorption curve and pore size distribution of N_2 adsorption-desorption also verified that SBA-15 indeed has the structural properties of mesoporous materials. Finally, the catalytic cracking experiment was used to study the application of ZSM-5/SBA-15 composite molecular seive in the catalysis of coal tar cracking. It was found that the ZSM-5/SBA-15 has a good catalytic effect.