Cobalt carbide (Co₂C) has recently been reported to be efficient for the conversion of syngas (CO+H₂) to lower olefins (C₂–C₄) and higher alcohols (C₂₊ alcohols); however, its properties and formation conditions remain ambiguous. On the basis of our previous investigations concerning the formation of Co₂C, the work herein was aimed at defining the mechanism by which the manganese promoter functions in the Co-based catalysts supported on activated carbon (CoxMn/AC). Experimental studies validated that Mn facilitates the dissociation and disproportionation of CO on the surface of catalyst and prohibits H₂ adsorption to some extent, creating a relative C-rich and H-lean surface chemical environment. We advocate that the surface conditions result in the transformation from metallic Co to Co₂C phase under realistic reaction conditions to form [email protected]₂C nanoparticles, in which residual small Co⁰ ensembles (<6 nm) distribute on the surface of Co₂C nanoparticles (∼20 nm). Compared with the Co/AC catalyst, where the active site is composed of Co₂C phase on the surface of Co⁰ nanoparticles (Co₂[email protected]), the Mn-promoted catalysts ([email protected]₂C) displayed much higher olefin selectivity (10% versus 40%), while the selectivity to alcohols over the two catalysts are similar (∼20%). The rationale behind the strong structure–performance relationship is twofold. On the one hand, Co–Co₂C interfaces exist universally in the catalysts, where synergistic effects between metallic Co and Co₂C phase occur and are responsible for the formation of alcohols. On the other hand, the relative C-rich and H-lean surface chemical environment created by Mn on the [email protected]₂C catalysts facilitates the formation of olefins.

中文翻译：

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从合成气直接合成高级醇和烯烃的[受电子邮件保护的] ₂ C催化剂形成的见解

最近有报道称，碳化钴（Co ₂ C）可有效地将合成气（CO + H ₂）转化为低级烯烃（C ₂ -C ₄）和高级醇（C ₂₊醇）。但是，其性质和形成条件仍然不明确。基于我们先前关于Co ₂ C形成的研究，本文的工作旨在确定锰助催化剂在活性炭负载的Co基催化剂（CoxMn / AC）中所起作用的机理。实验研究证实，Mn促进了催化剂表面CO的解离和歧化，并阻止了H _{2的生成。}在一定程度上吸附，创造了一个相对富碳和贫氢的表面化学环境。我们主张表面条件导致在实际反应条件下从金属Co转变为Co ₂ C相，形成[受电子邮件保护的] ₂ C纳米颗粒，其中残留的小Co ⁰团簇（<6 nm）分布在Co的表面上₂ C纳米粒子（〜20 nm）。与Co / AC催化剂（其中活性位点由Co ⁰纳米颗粒的表面上的Co ₂ C相组成（Co ₂ [受电子邮件保护]）相比，Mn促进的催化剂（[受电子邮件保护] ₂C）显示出更高的烯烃选择性（10％对40％），而在两种催化剂上对醇的选择性相似（〜20％）。强大的结构与绩效关系背后的理由是双重的。一方面，Co-Co ₂ C界面普遍存在于催化剂中，其中金属Co和Co ₂ C相之间会发生协同作用，并负责形成醇。另一方面，由Mn在[受电子邮件保护的] ₂ C催化剂上产生的相对富C和贫H的表面化学环境促进了烯烃的形成。