The influence of acid strength and pore size effect on propene elimination reaction over zeolites: A theoretical study
The influence of acid strength and pore size effect on propene elimination reaction over zeolites: A theoretical study
复制标题
酸强度和孔径效应对沸石上丙烯消除反应的影响：理论研究
DOI：
10.1016/j.micromeso.2018.11.026
复制
发表时间：
2019
影响因子：
5.2
通讯作者：
Zheng Anmin
中科院分区：
文献类型：
--
作者：
Li Xin;Shen Wanling;Zheng Anmin
甲醇制烯烃（MTO）反应在分子筛催化剂上的应用研究具有重要的理论意义和工业应用价值。采用密度泛函理论（DFT）方法，系统研究了分子筛上质子酸强度和孔径效应对“烃池”（HCP）过程中丙烯消除反应的影响。考虑了丙烯消除反应的直接机理和以水为质子转移剂的间接螺环机理。在直接反应机理中，反应活性可以通过增加酸强度来提高。而在间接机理中，适度的酸度更好。间接机制具有比直接机制低的活化势垒，因此更优选。由于孔径效应，在间接机理中，孔径最大的SSZ-13分子筛的催化活性最高。下面是ZSM-5沸石。而在孔径最小的ZSM-22分子筛中，由于空间位阻严重，反应很难进行。
The methanol-to-olefins (MTO) reaction over zeolite catalysts is very important for both fundamental research and industrial application to produce light olefins. In this study, the influences of the BrØnsted acid strength and pore size effect on the propene elimination in “hydrocarbon pool” (HCP) process over a series of zeolites are systematically investigated by density functional theory (DFT) calculations. The direct mechanism and indirect spiro mechanism with water as the proton transfer reagent in the propene elimination are considered. In the direct mechanism, the reactivity can be enhanced by increasing the acid strength. While, in the indirect mechanism, a moderate acidity is better. The indirect mechanism has a lower activation barrier than the direct one and thus is much more preferable. Because of the pore size effect, the SSZ-13 zeolite with the largest pore has the highest catalytic activity in the indirect mechanism. Following is the ZSM-5 zeolite. While, due to the serious steric hindrance, the reaction is hard to occur in the ZSM-22 zeolite with the smallest pore size.