Intermediates and Dominating Reaction Mechanism During the Early Period of the Methanol-to-Olefin Conversion on SAPO-41
Intermediates and Dominating Reaction Mechanism During the Early Period of the Methanol-to-Olefin Conversion on SAPO-41
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SAPO-41甲醇制烯烃早期中间体及主要反应机理
DOI：
10.1021/jp5118757
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发表时间：
2015-02-05
影响因子：
3.7
通讯作者：
Hunger, Michael
中科院分区：
文献类型：
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作者：
Dai, Weili;Dyballa, Michael;Hunger, Michael
阐明了一维十环孔系硅铝磷酸盐SAPO-41甲醇转化初期反应中间体的形成和演化以及反应机理。根据原位紫外可见光谱，监测了甲醇转化过程中催化剂上形成的中间体的形成和性质。通过非原位 UVvis、1H MAS NMR 和 C-13 MAS NMR 光谱测定了甲醇转化淬灭后残留在催化剂上的中间体，并通过氨吸附和随后的固态 NMR 光谱研究了这些物质的反应性。上述光谱研究对 SAPO-41 上甲醇转化的诱导期提供了详细的机制了解。单烯基碳正离子是甲醇转化初期的主要物种，迅速形成，并逐渐转变为二烯基碳正离子、苯基碳正离子和三烯基碳正离子，此外还有三环化合物和不同链长的二烯。基于这些光谱观察和催化结果，基于烯烃的反应循环被揭示为 SAPO-41 甲醇转化初期的主要反应机制。
The formation and evolution of initial reaction intermediates as well as the reaction mechanism during the early period of the methanol conversion on the silicoaluminophosphate SAPO-41 with one-dimensional and 10-numbered ring pore system was elucidated. According to in situ UVvis spectroscopy, the formation and nature of intermediates formed on the catalysts in the methanol conversion process were monitored. The intermediates remaining on the catalysts after quenching the methanol conversion were determined by ex situ UVvis, 1H MAS NMR, and C-13 MAS NMR spectroscopy, and the reactivity of these species was investigated by adsorption of ammonia and subsequent solid-state NMR spectroscopy. The above-mentioned spectroscopic studies gave a detailed mechanistic insight into the induction period of the methanol conversion on SAPO-41. Monoenylic carbenium ions, being the dominating species during the initial period of the methanol conversion, were rapidly formed and gradually transferred to dienylic carbenium ions, benzene-based carbenium ions, and trienylic carbenium ions, in addition to three-ring compounds and dienes with different chain lengths. On the basis of these spectroscopic observations and the catalytic results, the olefin-based reaction cycle is disclosed to be the dominating reaction mechanism in the initial period of the methanol conversion on SAPO-41.