The effect of the nature of the lanthanide (Ln = La, Ce, Pr, Sm, Gd) on the structure and reactivity of Co/SiO₂ catalysts for CO hydrogenation (i.e., Fischer Trospch synthesis) was investigated. In-situ temperature programmed reduction with extended x-ray absorption fine structure and x-ray absorption near edge spectroscopy (TPR-EXAFS/XANES) of the structure of both Co and Ln containing phases under activation and CO hydrogenation conditions were performed. Concerning catalyst selectivity (made at comparable conversion levels), while methane selectivity was higher for the Gd-doped catalyst (∼100%, relative) compared to the unpromoted catalyst, the selectivity to olefins plus alcohols and C₂-C₄ products was higher (∼35%, relative), compared to the unpromoted catalyst. The Ce-promoted Co/SiO₂ catalyst presented the highest oxygenate/olefin selectivity (∼40%), among the promoted catalysts tested at a similar conversion level of ∼20%. Under reactive conditions (both following H₂ activation and during CO+H₂ flow), a mixture containing small LnO_X/CoO/Co° nanocrystallites likely constitute the active sites during reaction. These results imply that the presence of the lanthanide likely introduces surface defects in the oxides (LnO_X and/or CoO) located at the metallic cobalt nanoparticle rim which may serve as active sites for active O-containing species (e.g., mobile Type II OH groups) that may either serve as chain termination species, or generate chain terminating species such as formates (i.e., essentially molecularly adsorbed CO) upon CO adsorption.

研究了镧系元素的性质（Ln = La，Ce，Pr，Sm，Gd）对Co / SiO ₂催化剂用于CO加氢（即Fischer Trospch合成）的结构和反应活性的影响。在活化和CO加氢条件下，对含有Co和Ln的相的结构进行了扩展的x射线吸收精细结构和x射线吸收近边缘光谱（TPR-EXAFS / XANES）的原位温度程序控制还原。关于催化剂的选择性（在相当的转化水平下制备），与未助催化的催化剂相比，Gd掺杂的催化剂的甲烷选择性更高（约100％，相对），但对烯烃，醇和C ₂ -C ₄的选择性与未助催化剂相比，产物更高（相对值约35％）。在以约20％的相似转化率进行测试的促进催化剂中，铈促进的Co / SiO ₂催化剂具有最高的含氧化合物/烯烃选择性（约40％）。在反应条件下（在H ₂活化之后和在CO + H ₂流动期间），包含小LnO _X / CoO / Co°纳米微晶的混合物很可能在反应过程中构成活性位点。这些结果表明，镧系元素的存在可能会在氧化物（LnO _X 和/或CoO）位于金属钴纳米粒子的边缘，可以用作含活性O的物种（例如，流动的II型OH基团）的活性位点，该物种既可以用作链终止物种，也可以生成链终止物种，例如甲酸酯（即，基本上是分子吸附的CO）在CO吸附时。