多级孔ZSM-5分子筛中油酸甲酯催化裂解吸附和扩散行为模拟研究  

Theoretical study on the adsorption and diffusion behavior of methyl oleate catalytic cracking in hierarchical ZSM-5 zeolite

作　　者：秦晗淞 李国梁[2] 闫昊[2] 冯翔[2] 刘熠斌[2] 陈小博[2] 杨朝合[2] QIN Hansong;LI Guoliang;YAN Hao;FENG Xiang;LIU Yibin;CHEN Xiaobo;YANG Chaohe(Sinopec Research Institute of Petroleum Processing Co.,Ltd.,Beijing 100083,China;State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Qingdao 266580,Shandong,China)

机构地区：[1]中石化石油化工科学研究院有限公司,北京100083 [2]中国石油大学(华东)重质油国家重点实验室,山东青岛266580

出　　处：《化工学报》2024年第5期1870-1881,共12页CIESC Journal

基　　金：国家自然科学基金项目(2207080344)。

摘　　要：多级孔ZSM-5分子筛具有丰富的孔道结构,其独特的微-介复合孔道结构可显著促进油酸甲酯(OAME)等大分子反应的发生,但其在分子层面上的促进机制及构-效关系仍不明晰。本工作采用Monte Carlo模拟(MC)结合分子动力学(MD)方法,研究了OAME催化裂解反应中反应物和5种产物分子(丙烯、丁烯、苯、甲苯和二甲苯)在多级孔分子筛上的吸附和扩散行为。通过分析吸附等温线、吸附密度图和反应物种的扩散系数,发现升温不利于OAME的吸附,从而抑制了反应的发生,这与实验结果一致。同时,直孔道和多级孔道这两种吸附位点在催化裂解反应中起到的作用截然不同:直孔道提供芳构化反应活性中心,而多级孔道则主要促进BTX主产物分子的传质扩散。这种多孔道的协同催化作用使得多级孔分子筛相较于微孔分子筛展现出优异的催化性能。此外,发现多级孔ZSM-5分子筛能提高芳烃收率的主要原因是其能够加速BTX向介孔的快速扩散。以上模拟结果不仅有助于从微观角度优化脂肪酸酯催化裂解反应的实验条件,同时也丰富了对多级孔分子筛能多产芳烃微观机制的理解。The hierarchical ZSM-5 zeolite has abundant pore structure,and its unique micro-mesopic pore structure can significantly promote the occurrence of macromolecular reactions such as methyl oleate(OAME),while the promotion mechanism and structure-activity relationship at the molecular level are still unclear.In this work,we studied the adsorption and diffusion behavior of the reactants and five product molecules(C3H6,C4H8 and BTX)in the catalytic cracking reaction of OAME via Monte Carlo simulation(MC)combined with molecular dynamics(MD).By analyzing the adsorption isotherms,adsorption density maps and diffusion coefficients of the reacting species,we found that rising temperature was detrimental to the adsorption of OAME,thus inhibiting the reaction,which is consistent with the experimental results.At the same time,the two adsorption sites in the zeolite play significantly different roles.The straight channel provides the aromatization active center in the catalytic creaking reaction,while the role of the hierarchical channel is reflected in promoting the mass transfer and diffusion of the main product molecules of BTX.Such synergistic catalysis effect of hierarchical ZSM-5 zeolite channel increases the BTX yield compared to microporous.In addition,it was found that the main reason why the hierarchical pore ZSM-5 molecular sieve can improve the aromatic yield is that it can accelerate the rapid diffusion of BTX into the mesopores.The above simulation results not only help to determine the experimental conditions of the fatty acid ester catalytic cracking reaction from the microscopic point of view,but also could enrich our understanding of the microcosmic mechanism of hierarchical zeolites for prolific aromatics.

关 键 词：多级孔分子筛 扩散 吸附 分子模拟 

分 类 号：TE624.4[石油与天然气工程—油气加工工程]