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 formatio n temperature of nanometer spinel-type Co3-xMnxO4 (0 less than or equa l 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 hyd rogenation reaction tests indicated that the nanometer Co/Mn oxide cat alysts had much higher selectivity to light olefins and a lower cataly tic activity and methane formation than the corresponding coprecipitat ed catalysts with the same composition. Different heat treatments of t he nanometer Co/Mn oxide catalyst could also influence the catalytic p roperties. With the increase of the calcination temperature, the catal ytic activity decreased, while the selectivity of light olefins increa sed. For nanometer spinel type Co3-xMnxO4 (O less than or equal to x l ess than or equal to 1.4) catalysts with different Co/Mn ratios, with the increase of the Mn content, both the catalytic activity and methan e formation were decreased, but the formation of light olefins was enh anced. (C) 1998 Elsevier Science B.V.