Preventing Loss of Selectivity during the Oxidative Dehydrogenation of Propane over Supported Vanadium Catalysts

IF 11.3 1区化学 Q1 CHEMISTRY, PHYSICAL

ACS Catalysis Pub Date : 2025-03-20 DOI:10.1021/acscatal.5c00720

Abdullah J. Al Abdulghani, Unni Kurumbail, Son Dong, Natalie R. Altvater, Rick W. Dorn, Melissa C. Cendejas, William P. McDermott, Theodore O. Agbi, Collin M. Queen, Matias Alvear, Ashley R. Head, Aaron J. Rossini, Ive Hermans

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Abstract

Supported vanadium materials are promising catalysts for the oxidative dehydrogenation of propane to propylene (ODHP), but a lack of mechanistic understanding limits the rational design of catalysts with improved propylene selectivity. Adding Ta to V/SiO₂ increases the propylene selectivity, as well as the activity, leading to superior performance compared to state-of-the-art boron-based systems. In this contribution, we utilize this surprising promotional effect of Ta to elucidate key elements of the mechanistic cycle. Through a combination of characterization techniques, computational modeling, and kinetic experiments, we show that the catalytic cycle over V/SiO₂ likely involves the formation of an isopropyl alcohol intermediate, the fate of which is in kinetic competition between subsequent dehydration to propylene or further oxidation. Furthermore, we show that the relatively facile propylene overoxidation observed for these materials occurs via the epoxidation of propylene by a proposed peroxovanadium intermediate, rather than the abstraction of propylene’s allylic C–H bond as previously assumed. Using these key mechanistic features, we rationalize the enhanced selectivity and activity of Ta promotion. Our mechanistic framework offers avenues for future catalyst development to improve supported vanadium materials for ODHP.

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支撑钒材料是丙烷氧化脱氢制丙烯（ODHP）的前景广阔的催化剂，但由于缺乏对机理的了解，限制了提高丙烯选择性催化剂的合理设计。在 V/SiO2 中添加 Ta 可以提高丙烯的选择性和活性，从而使催化剂的性能优于最先进的硼基体系。在这篇论文中，我们利用 Ta 的这种令人惊讶的促进作用来阐明机理循环的关键要素。通过结合表征技术、计算建模和动力学实验，我们发现 V/SiO2 催化循环很可能涉及异丙醇中间体的形成，而异丙醇中间体的命运则取决于后续脱水成丙烯或进一步氧化之间的动力学竞争。此外，我们还表明，在这些材料中观察到的相对容易的丙烯过氧化反应是通过一种拟过氧钒中间体对丙烯的环氧化作用而发生的，而不是像以前假设的那样是丙烯的烯丙基 C-H 键的抽离作用。利用这些关键的机理特征，我们合理地解释了 Ta 促进剂所增强的选择性和活性。我们的机理框架为未来催化剂的开发提供了途径，以改进用于 ODHP 的支撑钒材料。

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来源期刊

ACS Catalysis CHEMISTRY, PHYSICAL-

CiteScore

20.80

自引率

6.20%

发文量

1253

审稿时长

1.5 months

期刊介绍： ACS Catalysis is an esteemed journal that publishes original research in the fields of heterogeneous catalysis, molecular catalysis, and biocatalysis. It offers broad coverage across diverse areas such as life sciences, organometallics and synthesis, photochemistry and electrochemistry, drug discovery and synthesis, materials science, environmental protection, polymer discovery and synthesis, and energy and fuels. The scope of the journal is to showcase innovative work in various aspects of catalysis. This includes new reactions and novel synthetic approaches utilizing known catalysts, the discovery or modification of new catalysts, elucidation of catalytic mechanisms through cutting-edge investigations, practical enhancements of existing processes, as well as conceptual advances in the field. Contributions to ACS Catalysis can encompass both experimental and theoretical research focused on catalytic molecules, macromolecules, and materials that exhibit catalytic turnover.