Catalytic hydrodeoxygenation (HDO) of phenolics is a necessary step for upgrading bio-oils to transportation fuels. Bimetallic catalysts offer the potential of increased activities and selectivities for desired products. Adding non-metallic elements, such as phosphorous, allows for charge distribution between the metal and nonmetal atoms, which improves Lewis acid character of catalytic surfaces. This work utilizes experimental and density functional theory (DFT) based calculations to identify potential C–O bond cleavage pathways and product selectivities for HDO reactions on FeMoP, RuMoP, and NiMoP catalysts. Our work demonstrates that FeMoP catalyst favors direct deoxygenation pathway due to a lower activation energy barrier for C–O bond cleavage whereas RuMoP and NiMoP catalysts promote ring hydrogenation first, followed by the cleavage of C–O bond. The Bader charge analysis indicates that for these catalytic systems Mo^δ+ site bears a large positive charge which acts as a Lewis acid site for HDO reactions. Overall, we find that trends in the experimental product selectivities are in good agreement with that predicted with DFT calculations.

中文翻译：

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在双金属磷化物催化剂上对苯酚进行加氢脱氧的机理见解†

酚醛的催化加氢脱氧（HDO）是将生物油提质为运输燃料的必要步骤。双金属催化剂具有提高所需产物活性和选择性的潜力。添加非金属元素（例如磷）可实现金属和非金属原子之间的电荷分布，从而改善催化表面的路易斯酸特性。这项工作利用基于实验和密度泛函理论（DFT）的计算来确定在FeMoP，RuMoP和NiMoP催化剂上进行HDO反应的潜在C–O键裂解途径和产物选择性。我们的工作表明，由于FeMoP催化剂具有较低的C-O键裂解能垒，而MoMoP和NiMoP催化剂则首先促进环加氢，因此倾向于直接脱氧途径。接着是C–O键的断裂。Bader电荷分析表明，对于这些催化体系，Mo^{δ +}位带有大的正电荷，可作为HDO反应的路易斯酸位。总体而言，我们发现实验产品选择性的趋势与DFT计算所预测的趋势非常吻合。