Selective catalytic reduction of nitrogen oxides with methanol over the (cobalt-molybdenum)/alumina dual catalysts under the diesel methanol dual fuel exhaust conditions

Abstract

The (cobalt-molybdenum)/alumina ((Co-Mo)/Al2O3) dual catalysts have an excellent performance on the selective catalytic reduction (SCR) of nitric oxide with methanol (methanol-SCR) on the synthetic gas test bench. The catalytic performance of (Co-Mo)/Al2O3 needs to be studied on the engine test bench due to the complicated emissions of engines. Tests were carried out on the diesel methanol dual fuel (DMDF) engine. The effect of methanol supply methods, methanol dosing, injection timings of diesel fuel and exhaust gas recirculation (EGR) ratios on the performance of methanol-SCR was investigated. Results show that the performance of methanol-SCR on the engine test bench slightly deteriorates compared with that on the synthetic gas test bench. The performance of methanol-SCR on the active methanol supply mode is superior to that on the passive methanol supply mode. The low nitrogen oxides (NOX) conversion with passive methanol supply mode suggests that the ratio of carbon monoxide to hydrocarbons (more than 1) and the ratio of nitrogen dioxide to NOX are the critical factors on NOX conversion during the catalyst selection. However, the passive methanol supply mode has less effect on the fuel consumption. The catalytic efficiency of methanol-SCR is improved by the increased methanol dosing and EGR ratios and the retarded injection timings. The methanol dosing increases the particulate emissions and the fuel consumption. Increasing EGR ratios is less bad for the fuel consumption than retarding injection timings. A combination of the DMDF engine and the methanol-SCR realizes the ultra-low NOX emissions.