Role of Bronsted Acid Sites within 8-MR of Mordenite in the Deactivation Roadmap for Dimethyl Ether Carbonylation
Role of Bronsted Acid Sites within 8-MR of Mordenite in the Deactivation Roadmap for Dimethyl Ether Carbonylation
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DOI：
10.1021/acscatal.1c00159
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发表时间：
2021-04-23
期刊：
影响因子：
12.9
通讯作者：
Ma, Xinbin
中科院分区：
文献类型：
--
作者：
Cheng, Zaizhe;Huang, Shouying;Ma, Xinbin
丝光沸石具有良好的初活性和选择性，是目前最有前途的二甲醚羰基化合成乙酸甲酯催化剂，但其易失活。人们普遍认为，在12元环（B12-MR）中的布朗斯台德酸中心（BAS）处的焦化导致有限的催化寿命。然而，在某些情况下，矛盾的失活行为启发我们揭示二甲醚羰基化反应的失活机理，这是必要的，进一步工业化的重要过程。在此，我们主要集中于剖析八元环中的BAS（B8-MR）和B12-MR在失活中的作用。我们精确地调节了不同通道中BAS的浓度，并证实了B8-MR对焦炭形成的贡献。基于推测的失活机理，结合原位傅里叶变换红外光谱、气相色谱-质谱和程序升温氧化-质谱等技术，对DME羰基化反应早期的主要失活途径进行了动力学研究，并确定了BAS尤其是在8-MR中的具体作用。对失活机理的深入了解将为进一步设计和改性与羰基化反应相关的稳健沸石催化剂提供启示。
Mordenite zeolite is now the most promising catalyst for the carbonylation of dimethyl ether (DME) to methyl acetate because of the excellent initial activity and selectivity, but it suffers from rapid deactivation because of the carbonaceous deposits. It is generally accepted that coking at Bronsted acid sites (BASs) in the 12-membered ring (B12-MR) leads to the limited catalytic lifetime. However, contradictory deactivation behaviors in some cases inspire us to reveal the deactivation mechanism in DME carbonylation, which is essential for further industrialization of this important process. Herein, we mainly focus on dissecting the role of BASs in the 8-membered ring (B8-MR) and B12-MR in deactivation. We precisely modulated the concentration of BASs in different channels and confirmed the contribution of B8-MR to coke formation. Based on the speculated mechanism of deactivation, kinetic studies were performed together with in-situ Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and temperature programmed oxidation-mass spectroscopy to determine the predominant deactivation pathway during the early stage of DME carbonylation and the specific roles of BASs especially in 8-MR were identified. This insight into the deactivation mechanism will provide inspirations for further design and modification of robust zeolite catalysts associated with the carbonylation reaction.