Selective Reduction of NO_x over Co-Alumina Catalyst by Japan Diesel 13-Mode Cycle

摘要

Selective catalytic reduction of NO_x was performed under the condition of Japan diesel 13-mode cycle over a Co-alumina catalyst using a light oil as reducing agent. The reaction temperature of the NO_x reduction in each mode was sat at that of the exhaust gas. The adsorption of NO_x on Co-alumina was observed under low load conditions, that is, NO_x was adsorbed on Co-alumina when the exhaust gas temperature was below 250 deg C. However, when the temperature was above 300 deg C, NO_x conversion increased with increased intensity of reaction, and at near 550 deg C, it attained its maximum value. The decrease in NO_x conversion was observed at 90% oxidation of the light oil. The result of such temperature dependence of NO_x conversion was compatible with our previous result. The NO_x mass emission from the diesel engine tested was 6.5 g·kW~(-1)w#·h~(-1) under Japan diesel 13-mode cycle, assuming that all NO_x in the exhaust was NO_2. The NO_x mass emission was 4.4 g·kW~(-1)·h~(-1) when the Co-alumina catalyst was used. The decrease in NO_x mass emission by use of the catalyst resulted in NO_x reduction at medium to high load modes and NO_x adsorption at low load modes. When the NO_x conversion was assumed to 0% at low load modes (1-5 and 13 modes) over the Co-alumina catalyst saturated with adsorption of NO_x, the NO_x mass emission was 4.7 g·kW~(-1)~·h(-1).