Tuning the ethylene-to-propylene ratio in methanol-to-olefins catalysis on window-cage type zeolites
Tuning the ethylene-to-propylene ratio in methanol-to-olefins catalysis on window-cage type zeolites
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DOI：
10.1016/j.jcat.2021.01.015
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发表时间：
2021-03
影响因子：
7.3
通讯作者：
Zhichen Shi;A. Bhan
中科院分区：
文献类型：
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作者：
Zhichen Shi;A. Bhan
在HSAPO-34、HSSZ-13和HSSZ-39上的甲醇制烯烃（MTO）催化过程中，降低入口甲醇分压和甲醇空速分别使累积乙烯与丙烯比增加约2.3倍、约2.4倍和约2.2倍。当在MTO期间以类似的周转数进行比较时，在催化剂中闭塞的烃的组合物表明，降低催化剂床中的甲醇浓度降低了夹带芳烃的池内的甲苯同系化的程度，导致相对于丙烯的芳烃前体的浓度增加到乙烯。在一次催化剂转换中，乙烯与丙烯的比例变化了约1.3倍，并且在入口甲醇压力阶跃变化后<10 s运行;在此期间，夹带的甲苯的形态没有变化，因为小于1 molCmolH+− 1转化为烃，表明瞬时乙烯和丙烯选择性敏感地取决于局部甲醇浓度。这些机制的见解，确定局部甲醇浓度的显着参数，在调制产品的选择性在MTO窗口笼型材料。
Decreasing inlet methanol partial pressure and methanol space velocity during methanol-to-olefins (MTO) catalysis on HSAPO-34, HSSZ-13, and HSSZ-39 increases cumulative ethylene-to-propylene ratio by a factor of ~2.3x, ~2.4x, and ~2.2x, respectively. The composition of hydrocarbons occluded in the catalyst when compared at a similar turnover number during MTO suggests that decreasing methanol concentration in the catalyst bed decreases the extent of methylbenzene homologation within the pool of entrained aromatics, resulting in increments in the concentration of aromatic precursors to ethylene relative to those for propylene. Ethylene-to-propylene ratio changed by a factor of ~1.3x within one catalyst turnover and <10 s on-stream after a step-change in the inlet methanol pressure; in this duration the speciation of entrained methylbenzenes is unchanged as less than 1 molCmolH+−1was converted to hydrocarbons, revealing that instantaneous ethylene and propylene selectivity depends sensitively on local methanol concentration. These mechanistic insights identify local methanol concentration as the salient parameter in modulating product selectivity during MTO on window-cage type materials.