CO hydrogenation over nanometer spinel-type Co/Mn complex oxides prepared by sol-gel method

Nanometer spinel-type Co/Mn oxides with different Co/Mn atomic ratios (Co3-xMnxO4, 0<x less than or equal to 1.4), single phase composition and large specific surface area (> 70 m(2)/g) were prepared by the sol-gel method. The formation process, structure and catalytic properties of these Co/Mn oxides were studied by XRD, TEM, FTIR, TPR, XPS and CO hydro enation reaction tests. It was found that the complete formation temperature of nanometer spinel-type Co3-xMnxO4 (0 less than or equal to x less than or equal to 1.4) particles by sol-gel method was 350 degrees C, much lower than that by using nitrate decomposition method (760 degrees C) or solid-state reaction method (900 degrees C). CO hydrogenation reaction tests indicated that the nanometer Co/Mn oxide catalysts had much higher selectivity to light olefins and a lower catalytic activity and methane formation than the corresponding coprecipitated catalysts with the same composition. Different heat treatments of the nanometer Co/Mn oxide catalyst could also influence the catalytic properties. With the increase of the calcination temperature, the catalytic activity decreased, while the selectivity of light olefins increased. For nanometer spinel type Co3-xMnxO4 (O less than or equal to x less than or equal to 1.4) catalysts with different Co/Mn ratios, with the increase of the Mn content, both the catalytic activity and methane formation were decreased, but the formation of light olefins was enhanced. (C) 1998 Elsevier Science B.V.