Abstract:

Small grained hierarchical pore ZSM-11 zeolites were synthesized by dynamic crystallization using conventional hydrothermal synthesis with polyacrylamide (PAM) as the mesoporous template agent. In order to reduce the amount of organic template agent and the synthesis cost, ZSM-11 zeolite was synthesized by a pre-crystallization liquid method. A variety of techniques including XRD, cryogenic N₂ physisorption, SEM, and NH₃-TPD were used to characterize the synthesized samples. The relation of PAM with zeolite particle size and catalytic cracking reaction performance was investigated. It was found that the addition of PMA to the synthesis gel did not change the topology of ZSM-11 zeolites but significantly affected the morphology, pore structure, and acidity of the zeolites. The particle size of ZSM-11 zeolites would be greatly reduced, with the formation of mesoporous structure, and the amount of acid and acid strength of the sample were increased. In the evaluation of n-octane catalytic cracking reaction, the small crystal sized ZSM-11 gave higher reactivity, less hydrogen transfer reaction, and higher yield of propene.

Key words: ZSM-11 zeolite, small grains, catalytic cracking, propene

摘要：

采用传统水热合成法，以聚丙烯酰胺（PAM）为介孔模板剂，动态晶化合成小晶粒多级孔ZSM-11分子筛。并采用预晶化液法以减少有机模板剂的用量，降低合成成本。通过X射线衍射仪、低温N₂物理吸附、扫描电子显微镜和化学吸附仪等多种手段对合成样品进行了系统表征。考察了介孔模板剂的用量对合成小晶粒ZSM-11分子筛颗粒尺寸的影响及其催化裂化反应性能的影响。研究发现，在合成凝胶中加入聚丙烯酰胺并不会改变ZSM-11的拓扑结构，但会显著影响分子筛的形貌、孔结构及分子筛的酸性。合成的ZSM-11晶粒尺寸大幅度减小，同时出现介孔结构，样品的酸量和酸强度均增加。在正辛烷催化裂化微反评价中小晶粒ZSM-11分子筛表现出更高的活性稳定性、更少的氢转移反应和更高的丙烯收率。

关键词: ZSM-11分子筛, 小晶粒, 催化裂化, 丙烯