Aqueous phase reforming of alcohols over Pt has been discussed to operate along two pathways, decarbonylation and decarboxylation. To gain a better understanding of the activity of various catalysts for decarboxylation, we examined computationally a key step of this mechanism on the 12 transition metals of groups 8 to 11, namely the formation of a carboxylic acid intermediate via metal-mediated insertion of OH into an acyl group. The trend of the calculated barriers of OH insertion parallels the oxophilicity of the metals. A separation of the reaction into two formal steps isolates OH activation as a major contribution to the barrier and, not unexpectedly, indicates a strong dependence on the OH adsorption energy. A decomposition analysis of the activation energy reveals that weaker OH adsorption also correlates with the interaction energy between the adsorbed fragments in the transition state, thus indirectly lowering the barrier for OH insertion. Metals in the bottom right-hand corner of the transition metal block studied –Pt, Au, and Ag– bind OH relatively weakly, hence feature a high OH insertion activity. We applied these findings to rationalize various experimental results and suggest catalysts for decarboxylation.

中文翻译：

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通过羟基插入后期过渡金属上的酰基部分形成羧酸

已经讨论了在Pt上进行醇的水相重整可通过两个途径进行：脱羰和脱羧。为了更好地了解各种脱羧催化剂的活性，我们通过计算方法研究了第8至11组12种过渡金属上该机理的关键步骤，即通过金属介导的OH插入酰基。计算得出的OH插入势垒的趋势与金属的亲氧性平行。将反应分为两个正式步骤可将OH活化分离为对屏障的主要贡献，并且不出所料地表明强烈依赖OH吸附能。活化能的分解分析表明，较弱的OH吸附作用还与过渡态吸附片段之间的相互作用能相关，因此间接降低了OH插入的势垒。研究的过渡金属块右下角的金属-Pt，Au和Ag-与OH的结合相对较弱，因此具有较高的OH插入活性。我们应用这些发现合理化了各种实验结果，并提出了用于脱羧的催化剂。