Combustion of carbonaceous materials by Cu-K-V based catalysts .1. Role of copper and potassium vanadates

Several formulations of a Cu-K-V catalyst supported on alpha-Al2O3 with different Cu:K:V atomic ratios and with different loadings of the active components on the support were prepared by impregnation with aqueous solutions of KCl, CuCl2 . H2O and NH4VO3, drying and calcination. The composition of these catalysts, suitable for greatly accelerating the combustion of carbonaceous materials, was investigated by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Their activity in the combustion of amorphous carbon was assessed by differential scanning calorimetry (DSC). The latter showed that the combustion peak temperature can be decreased from 617 degrees C (uncatalysed oxidation) down to 382 degrees C for the best prepared Cu-K-V catalyst (atomic ratio: Cu:K:V = 2:2:1). The results of activity tests and the identification of the compounds present in the catalyst samples suggested that the catalyst activity is mainly due to the synergic action of some vanadates (Cu-3(VO4)(2), KVO3, K0.7Cu0.3VO3, CuVO2) and chlorides (KCl, Cu-2(OH)(3)Cl). Other catalysts based on each of these vanadates + KCl were prepared, characterised and tested, getting slightly lower activities than that of the best Cu-K-V catalyst.