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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Insights into the Mechanism of Olefin Elimination in the Methanol-to-Olefin Process over HZSM-5, HMOR, HBEA, and HMCM-22 Zeolites
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Theoretical Insights into the Mechanism of Olefin Elimination in the Methanol-to-Olefin Process over HZSM-5, HMOR, HBEA, and HMCM-22 Zeolites

机译：HZSM-5，HMOR，HBEA和HMCM-22沸石在甲醇制烯烃过程中消除烯烃机理的理论研究

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摘要

The mechanism of olefin elimination in the process of methanol-to-olefins (MTO) over a series of zeolites like HZSM-5, HMOR, HBEA, and HMCM-22 was investigated by DFT-D calculations, which is a crucial step that controls the MTO product distribution. The results demonstrate that the manners of olefin elimination are related to the pore structure of zeolite catalyst and the interaction between proton transfer reagent (water or methanol) and zeolite acidic framework. The indirect spiro mechanism is preferable to the direct mechanism over HMOR, HBEA, and HMCM-22 zeolites with large pores, as suggested by the energy barrier of rate-determining step and the potential energy surface (PES), but is unfavorable over HZSM-5 with medium-sized pores due to the steric hindrance of spiro intermediates. Over various zeolites, water and methanol perform differently in proton transfer to form the spiro intermediates; over HMOR and HBEA with strong acidity, water is superior to methanol in promoting propene elimination, whereas over HMCM-22 with relatively weaker acidity, methanol is more favorable as a proton transfer reagent.
机译：通过DFT-D计算研究了在HZSM-5，HMOR，HBEA和HMCM-22等一系列沸石上甲醇制烯烃（MTO）过程中烯烃消除的机理，这是控制反应的关键步骤MTO产品分销。结果表明，烯烃的脱除方式与沸石催化剂的孔结构以及质子转移剂（水或甲醇）与沸石酸性骨架的相互作用有关。速率决定步骤和势能面（PES）的能垒表明，间接螺线机理优于具有大孔的HMOR，HBEA和HMCM-22沸石的直接机理，但比HZSM-不利。 5由于螺旋中间体的空间位阻，具有中等大小的孔。在各种沸石上，水和甲醇在质子转移中的性能不同，从而形成螺环中间体。与具有强酸性的HMOR和HBEA相比，水在促进丙烯消除方面优于甲醇，而与具有相对弱酸性的HMCM-22相比，甲醇更适合作为质子转移试剂。

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