Manganese-promoted Rh/Al2O3 for C2-oxygenates synthesis from syngas

• DOI: 10.1016/j.apcata.2003.10.033
• Publication Date: 2004-01-02T05:29:21Z
• Authors: Manuel Ojeda; Manuel López Gran...; Sergio Rojas; Pilar Terreros; F.Javier Garcı́a-...; José Luis G. Fierro
• Keywords: Oxygenate; Fischer–Tropsch process

The effect of manganese promoter loading on the catalytic properties of Rh/Al2O3 catalysts (Mn/Rh=0, 0.5, 1 and 2, atomic ratio) for the synthesis of oxygenated compounds from synthesis gas was investigated. Catalysts were characterized by means of TPR, XPS, H2 chemisorption, FT-IR, and TPSR of chemisorbed CO. It is suggested that manganese oxide promotes CO conversion as a result of the change in the relative surface coverage of H* and C* (θH/θC). The manganese oxide promoter also affected the selectivity to oxygenated compounds, mainly to ethanol. The manganese promoter behaved as an electron-withdrawing, partially oxidizing the rhodium atoms at the Rh–MnO interface and thus creating new sites for CO insertion. The amount of promoter seemed to be an important parameter to achieve the highest yield of the desired reaction products. For oxygenates formation, the optimum Mn/Rh atomic ratio was found to be around 1.<br/>One of us (M. Ojeda) acknowledges a fellowship from the Consejerı́a de Educación y Cultura (CAM). This work was partly supported by the Dirección General de Investigación, MCYT (Spain), under grant MAT2001-2215-C03-01. F.J.G.G. would like to thank the Swedish Research Council for economical support.<br/>