Activity of LaMO3 (M=Mn, Fe, CO, and Ni) perovskite catalysts for Oxidation of exhaust gas pollutants of natural gas vehicles

فاقد چكيده

Different LaMO3 (M= Mn, Fe, Co and Ni) perovskite-type catalysts were prepared via solution combustion method, calcined at 700oC for 5 h and were characterized by X-ray diffraction method (XRD), BET specific surface area and H2 temperature programmed reduction (TPR). The catalysts activity for the abatement of pollutants (i.e. CO and CH4) emitted from natural-gas (NG) fuelled vehicles were investigated using a synthetic exhaust conditions. A gas mixture of 2 vol% CO and 2000 ppm CH4 in Ar together with proper flow of air (SN=1.1) was used as the synthetic exhaust gas of NG engines. LaCoO3 presents the best performance for CO oxidation among other catalysts examined. The 90% conversion temperature of CO is 235oC over LaCoO3 that is 113oC lower than LaMnO3 (i.e. the least active catalyst for CO oxidation). On the other hand, LaFeO3 is found to be the most active catalyst for CH4 oxidation. The half-conversion temperature of CH4 is 553oC over LaFeO3 which is 82oC lower than LaNiO3- that shows the least activity in CH4 oxidation. TPR results reveal that perovskites which reduce at moderate temperatures show higher activity for CO oxidation, while catalysts that are more stable at higher temperatures, show better performance for CH4 oxidation.