On the activity of copper chromite catalysts in ethyl acetate combustion in the presence and absence of oxygen

The catalytic combustion of ethyl acetate has been investigated using undoped and Mn- or Ba-doped copper chromite catalysts either in the presence or in the absence of molecular oxygen. The thermal reduction under hydrogen of undoped and Ba- or Mn-doped copper chromite system has been studied at different temperatures using the thermogravimetric technique. Evidences found by TG analyses (oxygen depletion rate) have shown a dependence on lattice oxygen mobility due to the crystal structure and the temperature. Relative to the undoped CuO-CuCr2O4, it has been found that the reduction rate is not significantly affected by the presence of BaO and MnO promoters but rather by the solid crystallinity, The catalytic results have shown that good conversions can be obtained even at low temperatures (180-240 degreesC). While in the presence of molecular oxygen the only product observed was CO2, when the reaction has been carried out in the absence of oxygen (with lattice oxygen alone) noticeable amounts of CO were also detected. These results are consistent with the hypothesis of two different mechanisms controlling the reaction in the presence or in the absence of molecular oxygen. Further it has been observed that the catalytic activity becomes stable only when a specific Cu2+/Cu+ ratio is obtained under typical reaction conditions. (C) 2003 Elsevier Science B.V. All rights reserved.