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

Abstract

Catalytically inactive CoO_x-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 CoO_x is deposited on the support precoated with MgO. Both the supported CoO_x and MgO containing catalysts (CoO_x-MgO/SA-5205 and CoO_x/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 CoO_x/MgO/SA-5205 is, however, more active and stable than the CoO_x-MgO/SA-5205. The supported catalyst prepared by depositing CoO_x 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) g^-1 _(catalyst)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 (CoO_x/SA-5205 or SZ-5564) shows very poor activity with higher carbon deposition rate.