Comprehending the role of water in the methanol-to-olefins (MTO) reaction is of utmost importance. Herein, we report an unprecedented ethene selectivity of approximately 58% with water assistance during the MTO reaction over SAPO-34, along with an extension of catalyst lifespan. The in situ spectroscopic observations and isotope switching experiments revealed that naphthyl species with higher concentration were retained in SAPO-34 and exhibited higher reactivity when cofeeding water with methanol. The density functional theory calculations suggested that the water-mediated microenvironment not only activates the methanol molecules but also serves as a proton transfer reagent between the zeolite framework and the organic intermediates, contributing to a lower reaction energy barrier for ethene formation. A strategy of cofeeding water with methanol over a naphthyl-species pre-accommodated SAPO-34 catalyst is proposed, achieving an enhanced ethene selectivity up to 67.5%. The mechanistic insights and strategy development deepen the understanding of the role of water in zeolite catalysis and offer optimizations for MTO industrial applications.

了解水在甲醇制烯烃 (MTO) 反应中的作用至关重要。在此，我们报道了在 SAPO-34 的 MTO 反应过程中，在水的辅助下，乙烯选择性达到前所未有的约 58%，同时催化剂寿命也得到延长。原位光谱观察和同位素转换实验表明，SAPO-34 中保留了较高浓度的萘基物质，并且当水与甲醇共进料时表现出较高的反应活性。密度泛函理论计算表明，水介导的微环境不仅激活甲醇分子，而且还充当沸石骨架和有机中间体之间的质子转移试剂，有助于降低乙烯形成的反应能垒。提出了在萘基预容纳 SAPO-34 催化剂上共进水和甲醇的策略，将乙烯选择性提高至 67.5%。机理见解和策略开发加深了对水在沸石催化中的作用的理解，并为 MTO 工业应用提供了优化。