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

Nanometer spinel-type Co/Mn oxides with different Co/Mn atomic ratios (Co3−xMnxO4, 0 < x ≤ 1.4), single phase composition and large specific surface area (> 70 m2/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 hydrogenation reaction tests. It was found that the complete formation temperature of nanometer spinel-type Co3−xMnxO4 (0 ≤ x ≤ 1.4) particles by sol-gel method was 350°C, much lower than that by using nitrate decomposition method (760°C) or solid-state reaction method (900°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 (0 < x ≤ 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.