Structural transformations of CuMoO4 in the catalytic oxidation of carbon

The catalytic combustion of carbon black at 350–420°C in the presence of CuMoO₄ has been investigated. The separate catalyst reduction and reoxidation stages make nonadditive contributions to the overall heat of the process. This indicates the formation of catalytically intermediate compounds during the redox reactions. The reduction of the catalyst with carbon yields the copper(I) molybdates Cu₆Mo₅O₁₈ and Cu₄Mo₅O₁₇ on its surface. The reoxidation of the reduced phases is accompanied by the release of Cu₂O and MoO₃ followed by the formation of the active phase Cu_{4 ? x} Mo₃O₁₂, which is capable of activating carbon black combustion.