钴-钼氧化物用于乙烷活化和二氧化碳还原催化的有效耦合,ACS Catalysis

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钴-钼氧化物用于乙烷活化和二氧化碳还原催化的有效耦合
ACS Catalysis ( IF 11.3 ) Pub Date : 2022-09-26 , DOI: 10.1021/acscatal.2c02525
Rui Yao _{1,

2,

3} , Jayson Pinals ₄ , Roham Dorakhan ₁ , José E. Herrera ₅ , Minhua Zhang ₂ , Prashant Deshlahra ₄ , Ya-Huei Cathy Chin ₁

Affiliation

本研究报告了在 C ₂ H ₆ –CO ₂催化中具有协同催化作用的 CoMoO _x部分的发现。C ₂ H ₆ -CO ₂催化通过多个伴随的催化循环发生，由C ₂ H ₆活化和CO ₂活化的双循环以及不希望的焦炭沉积循环引发。C ₂ H ₆活化需要活性氧，以协助动力学相关的 C-H 键活化；这些氧是由 CO _2产生的逆水煤气变换 (RWGS) 反应中的活化循环。在 RWGS 反应中有效的 CO _{2活化将在 CoMoO}_x部分中保留更高的 O 含量，从而导致 C ₂ H ₆的更有效的动力学相关 C-H 键活化和焦炭前体的氧化，从而在减轻失活的同时增加周转率。这种机制洞察力使我们设计了 CoMoO _x部分，其中 Co 阳离子充当路易斯酸。与邻位氧空位一起，Co 阳离子通过空位途径激活 CO ₂，形成动力学相关的 [Co···C(O) ═ O··· □_空位···Mo] ^‡过渡态，此时Co与C相互作用，氧空位（□_空位）提取CO ₂的离去O。动力学耦合循环导致脱氢和重整反应中的乙烷转化率都直接取决于 RWGS 反应速率。这种对速率耦合的机理理解导致设计了具有双重功能的 CoMoO _x_{部分，以实现有效的 C 2} H ₆ -CO ₂催化。

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Cobalt-Molybdenum Oxides for Effective Coupling of Ethane Activation and Carbon Dioxide Reduction Catalysis

This study reports the discovery of CoMoO_x moieties with synergistic catalytic roles in C₂H₆–CO₂ catalysis. C₂H₆–CO₂ catalysis occurs through multiple, concomitant catalytic cycles, initiated by the dual cycles of C₂H₆ activation and CO₂ activation, together with an undesired coke deposition cycle. C₂H₆ activation requires reactive oxygen species that assist with the kinetically relevant C–H bond activation; these oxygen species are generated from the CO₂ activation cycle within the reverse water-gas shift (RWGS) reaction. An efficient CO₂ activation in the RWGS reaction would retain higher O contents in CoMoO_x moieties, leading to more effective kinetically relevant C–H bond activation of C₂H₆ and oxidation of coke precursors and thus increasing turnovers while mitigating deactivation. This mechanistic insight led us to design CoMoO_x moieties, where the Co cation acts as a Lewis acid. Together with a vicinal oxygen vacancy, the Co cation activates CO₂ via a Vacancy route through the formation of a kinetically relevant [Co···C(O) ═ O··· □_vacancy···Mo]^‡ transition state, at which the Co interacts with the C and the oxygen vacancy (□_vacancy) abstracts the leaving O of CO₂. The kinetically coupled cycles lead the ethane conversion rates in dehydrogenation and reforming reactions to both depend directly on the RWGS reaction rates. This mechanistic understanding of rate coupling has led to the design of CoMoO_x moieties with dual functionality for effective C₂H₆–CO₂ catalysis.

更新日期：2022-09-26

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