The hydrocarbon pool (HP) species in methanol-to-olefins (MTO) reactions over zeolite H-ZSM-5 were investigated by solid-state NMR spectroscopy and GC–MS. The distribution and reactivity of retained HP species such as carbocations and methylbenzenes (MBs) were found to evolve with reaction time and their positions in the catalyst bed. The underlying mechanism of the typical S-shaped methanol conversion curve was revealed, in which the dominating reaction route was found to be dependent on the formation and reactivity of different HP species that were varied at different reaction time. During the induction period, cyclopentenyl cations served as the precursor to MBs and exhibited higher reactivity than the latter. The reaction was accelerated by the accumulation of alkenes and further enhanced by consequent involvement of the cyclopentenyl cations and aromatics, which eventually led to a steady state reaction. The interconversions of the reaction cycles based on alkenes, cyclopentenyl cations, and MBs were proposed for the formation of light olefins. The co-catalysis of HP species in the MTO reactions showed that the cyclopentenyl cations and alkenes favored propene formation, while the light MBs such as xylene and triMB facilitated ethene formation. Within the catalyst bed, both cyclopentenyl cations and MBs were dominantly formed in the upper catalyst layers. The experiments indicated that both cyclopentenyl cations and alkenes maintained high reactivity throughout the catalytic bed, while MBs exhibited high reactivity only in the upper catalyst position.

通过固态NMR光谱和GC-MS研究了H-ZSM-5沸石在甲醇到烯烃（MTO）反应中的烃库（HP）种类。发现保留的HP物质（例如碳阳离子和甲基苯（MBs））的分布和反应性随反应时间及其在催化剂床中的位置而变化。揭示了典型的S形甲醇转化曲线的潜在机理，其中主要的反应路线取决于在不同反应时间变化的不同HP物种的形成和反应性。在诱导期间，环戊烯基阳离子充当MBs的前体，并显示出比后者更高的反应性。该反应通过烯烃的积累而加速，并且由于环戊烯基阳离子和芳族化合物的随后参与而进一步增强，最终导致稳态反应。为了形成轻烯烃，提出了基于烯烃，环戊烯基阳离子和MBs的反应循环的相互转化。HP物种在MTO反应中的共催化表明，环戊烯基阳离子和烯烃有利于丙烯的形成，而轻质MB（如二甲苯和triMB）则有助于乙烯的形成。在催化剂床层中，上部催化剂层中主要形成环戊烯基阳离子和MBs。实验表明，环戊烯基阳离子和烯烃在整个催化床中均保持高反应性，而MBs仅在较高的催化剂位置上才显示高反应性。