Cai Wenjin, Wang Chao, Chu Yueying, Hu Min, Wang Qiang, Xu Jun, Deng Feng
National Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Nat Commun. 2024 Oct 9;15(1):8736. doi: 10.1038/s41467-024-52999-8.
The conversion of methanol over zeolites offers a sustainable alternative for fuels and chemicals production. However, a complete understanding of the competing reaction pathways, particularly those leading to C-C bond formation, remains elusive. This work presents a novel mechanism for selective methanol conversion in ZSM-5 zeolites, involving a Brønsted acid site (BAS)-mediated Meerwein-Ponndorf-Verley (MPV) reduction pathway. Employing a multidimensional solid-state NMR spectroscopy combined with isotopic labeling and theoretical calculations, we identify this pathway for acetaldehyde reduction with methanol, directly contributing to ethene formation. This mechanism, involving carbenium ion intermediates like 1-hydroxyethane or 1-methoxyethane ions, contrasts with the well-established Lewis acid-catalyzed MPV process. Based on reactant adsorption modes, we propose two distinct reaction routes for BAS-MPV reduction, bridging the gap between direct and hydrocarbon pool mechanisms in methanol conversion. We further demonstrate the applicability of this pathway to acetone, highlighting its broader role in the early stages of the reaction.
沸石上甲醇的转化为燃料和化学品生产提供了一种可持续的替代方案。然而，对竞争反应途径，特别是那些导致碳-碳键形成的途径的全面理解仍然难以捉摸。这项工作提出了一种在ZSM-5沸石中选择性甲醇转化的新机制，涉及布朗斯特酸位点（BAS）介导的迈尔外因-庞多夫-韦利（MPV）还原途径。利用多维固态核磁共振光谱结合同位素标记和理论计算，我们确定了甲醇还原乙醛生成乙烯的这一途径。这种机制涉及碳正离子中间体，如1-羟基乙烷或1-甲氧基乙烷离子，与成熟的路易斯酸催化的MPV过程不同。基于反应物的吸附模式，我们提出了BAS-MPV还原的两种不同反应路线，弥合了甲醇转化中直接机制和烃池机制之间的差距。我们进一步证明了该途径对丙酮的适用性，突出了其在反应早期更广泛的作用。
