弱酸强度对二甲醚羰基化反应的积极影响及其性质——以掺铁MOR沸石为例

IF 4.8 2区化学 Q2 CHEMISTRY, PHYSICAL

Applied Catalysis A: General Pub Date : 2025-09-27 DOI:10.1016/j.apcata.2025.120609

Li-Yun Zhang , Xiao-Bo Feng , Pan Deng , Feng Chen , Jia-Pei Guo , Yu-Hui Wang , Kang-Zhou Wang , Jing-Pei Cao

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引用次数: 0

摘要

同形取代是提高沸石在碳-碳偶联反应中催化性能的一种很有前途的策略。选择性地将Fe原子掺入MOR沸石的12元环（12-MR）中，显著富集了8-MR （B8-MR）中的Brønsted酸位，同时降低了它们的酸强度，大大提高了二甲醚（DME）羰基化反应的活性、醋酸甲酯（MA）选择性和催化剂稳定性。实验和理论结果表明，减弱的B8-MR抑制了甲氧基和乙酰基碳正离子的形成，导致诱导期延长。此外，将弱酸强度的O-H去质子化后形成的带负电荷的亲核性较强的沸石对乙酰碳正离子具有较高的吸附稳定性，显著抑制了其快速重构为烯酮。然而，从烯酮到乙酰基的进化路径受减弱的B8-MR影响较小。因此，烯酮在减弱的B8-MR上形成缓慢但转化率不变，意外地促进了烯酮在8-MR内原位转化为乙酰基，而不是扩散到12-MR生成焦炭，从而提高了MA选择性和催化剂寿命。弱酸强度对铁掺杂MOR沸石上二甲醚羰基化的积极影响的新范式将为酸催化反应提供有意义的指导。

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The positive effect and the nature of weakened acid strength on DME carbonylation: A case study of Fe-doped MOR zeolite

Isomorphous substitution is a promising strategy for improving the catalytic performance of zeolites in C-C coupling reactions. Selectively incorporating Fe atoms into the 12-membered ring (12-MR) of MOR zeolite significantly enriches Brønsted acid sites in the 8-MR (B_8-MR) and simultaneously reduces their acid strength, greatly improving activity, methyl acetate (MA) selectivity, and catalyst stability during dimethyl ether (DME) carbonylation. Experimental and theoretical results reveal that the weakened B_8-MR suppresses methoxy and acetyl carbocation formation due to the increased energy barriers, causing a prolonged induction period. Moreover, the negatively charged zeolite with stronger nucleophilicity formed after deprotonation of weaker acid strength of O–H exhibits higher adsorption stability of acetyl carbocation that significantly inhibits its rapid reconstruction into ketene. However, the evolution path from ketene to acetyl group is less affected by the weakened B_8-MR. Therefore, the slow formation but unchanged conversion rate of ketene on the weakened B_8-MR unexpectedly facilitates the in-situ conversion of ketene into acetyl group within 8-MR rather than diffusing into 12-MR to generate coke, thereby increasing MA selectivity and catalyst lifespan. The new paradigm regarding the positive effect of weakened acid strength on DME carbonylation over Fe-doped MOR zeolite will provide meaningful guidance for acid-catalyzed reaction.

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来源期刊

Applied Catalysis A: General 化学-环境科学

CiteScore

9.00

自引率

5.50%

发文量

415

审稿时长

24 days

期刊介绍： Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications. Papers that report results of a thorough study or optimization of systems or processes that are well understood, widely studied, or minor variations of known ones are discouraged. Authors should include statements in a separate section "Justification for Publication" of how the manuscript fits the scope of the journal in the cover letter to the editors. Submissions without such justification will be rejected without review.