CO2 reforming of methane to syngas over highly active and stable supported CoOx (accompanied with MgO, ZrO2 or CeO2) catalysts Original Research Article

Catalytically inactive CoOx–MgO (calcined at 900 °C) becomes highly active and selective in the CO2 reforming of methane to syngas when it is deposited on a commercial low surface-area macro-porous silica–alumina support (SA-5205) or when CoOx is deposited on the support precoated with MgO. Both the supported CoOx and MgO containing catalysts (CoOx–MgO/SA-5205 and CoOx/MgO/SA-5205) show high methane conversion (>98%) activity and H2 selectivity (>94%) and also high stability against carbon deposition [rate of carbon deposition ≤ 0.26 mg (C) g (catalyst)−1 h−1] in the CO2 reforming (at 850 °C, GHSV = 20,000 cm3 g−1 h−1). The CoOx/MgO/SA-5205 is, however, more active and stable than the CoOx–MgO/SA-5205. The supported catalyst prepared by depositing CoOx on SA-5205 precoated with ZrO2, CeO2, Y2O3 or ThO2 also shows very high stability against the carbon deposition [rate of carbon deposition < 0.1 mg(C) image h−1]. The choice of the metal oxide used for precoating the support for achieving better catalyst performance is in the following order: MgO > ZrO2 > CeO2 > Y2O3 > ThO2. The type of support (silica–alumina or zirconia–haffnia) also plays important role in deciding the catalyst performance; the catalysts with the commercial zirconia-haffnia support (SZ-5564) show, in general, poor activity with higher rates carbon deposition. In the absence of MgO or the other metal oxide, the catalyst (CoOx/SA-5205 or SZ-5564) shows very poor activity with higher carbon deposition rate.