Combustion of carbon particulate catalysed by mixed potassium vanadates and KI

A K-V-I-containing catalyst for low-temperature combustion of carbonaceous materials was studied so as to check its potential in diesel particulate removal. X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS) showed that its main constituting compounds are KVO3, KI and K4O7. Differential scanning calorimetry (DSC) and temperature-programmed oxidation (TPO) tests enlightened that the catalyst is active well below 400°C (peak combustion temperature: Tp = 380°C). Thermal treatments carried out at this temperature with dry or humid air did not entail detrimental effects on the catalyst performance. Similar treatments at higher temperatures (600 and 750°C) resulted in a modification of the catalyst composition and in a slight decrease of its activity (Tp increases of about 60°C). These last treatments caused the progressive loss of active components due to either evaporation of eutectic liquid formed at about 450°C or production of gaseous iodine through a reaction between KI and KVO3, which also gave rise to the formation of K4V2O7. However, the consequent deactivation was moderate owing to the high intrinsic activity displayed by the formed potassium pyrovanadate.