Low temperature complete combustion of a lean mixture of LPG emissions over cobaltite catalysts

Abstract

LPG is used as a cleaner substitute for gasoline and diesel for automobiles. However, it is a source of hydrocarbon (HC) emissions, causing adverse effects on living beings and the environment. Therefore, to reduce tailpipe HC emissions, this work aims to develop cobaltite spinel catalysts for the oxidation of a lean mixture of LPG. Cobaltite spinel catalysts i.e. MCo₂O₄ (M = Ni, Cu, Zn) were synthesized by a coprecipitation method and characterized by FTIR, N₂ adsorption and XRD. The XRD/FTIR of the prepared cobaltite catalysts showed the formation of the corresponding MCo₂O₄ spinels. Among the studied catalysts, NiCo₂O₄ showed the highest activity with total oxidation of LPG below 200 °C. When CO was also added into the feed, a synergistic effect was observed for the simultaneous oxidation of LPG and CO at lower temperature. The total conversion was obtained at a temperature 10 °C less than that for the oxidation of LPG alone over NiCo₂O₄. The order of activity of the catalysts calcined at 300 °C was as follows: NiCo₂O₄ > CuCo₂O₄ > ZnCo₂O₄. With calcination of NiCo₂O₄ at higher temperatures of 400 and 500 °C, total LPG conversion was obtained at higher temperatures of 228 °C and 265 °C respectively. However, it maintained 100% LPG conversion over a 50 h continuous run at a constant temperature of 265 °C. Thus, NiCo₂O₄ is suitable for low temperature (>300 °C) complete combustion of a lean mixture of LPG emissions.