Copper supported on Co substituted hydroxyapatite for complete oxidation of diesel engine exhaust and VOC

Abstract

The Co substituted HAp catalysts were prepared by co-precipitation method followed by the deposition of Cu and used for complete oxidation of CO, propene, as the model component of diesel engine exhaust and toluene as VOC. The activity of Co substituted Cu/HAp was compared with Cu/HAp. The Cu/Co0.4HAp showed 100% CO conversion at 157 °C whereas Cu/HAp at 376 °C. Furthermore, Cu/CoxHAp showed propene and toluene conversion at 310 and 315 °C respectively, whereas Cu/HAp showed 100% conversion at 400 and 340 °C respectively. The PXRD, ATR-FTIR, H2-TPR, XPS, EDS, HRTEM techniques were used for characterization of catalysts. The Cu/Co0.4HAp showed improved sulfur tolerance compared to the Cu/Hap. The characterization demonstrates that the Co substituted HAp improved the surface redox properties of CuOx species and preserver hydrotalcite structure. The spherical shape of smaller Cu species was observed at CoxHAp surface. However, Cu/HAp showed formation of quasi spherical Cu on HAp surface. Co and HAp interaction could improve the activation of hydrocarbon at a lower temperature compared to the Cu/HAp. The weakly bound oxygen on the Cu/CoxHAp surface could be responsible for the facile activation of CO and hydrocarbon at lower temperature which further oxidized into CO2. The Co doped Cu/HAp catalyst showed higher and stable activity at lower and higher temperature window respectively. The kinetic and mechanistic aspects of Cu/Hap and Cu/CoxHap for oxidation has been explained in detail.