Emission Reduction of NOx, CO, HC, PM2.5, and PAHs by Using a Catalyst in a Diesel Engine

Pollutants derived from diesel exhaust gases are considered harmful to human health. In 2021, 23 million motor vehicles were in use, and diesel cars accounted for 4.07% of them. Strategies involving after-treatment technologies, with exhaust gas processing incorporating a selective catalytic reaction (EGP-SCR system) for diesel engines, are considered in this study. By conducting a World Harmonized Transient Cycle (WHTC) under cold start driving test, this study measured pollutant emissions upstream and downstream of the after-treatment system. Our results indicate that equipped with EGP-SCR catalysts as after treatment device can eliminate particles and regulated pollutants from the engine out emissions. LMW g-PAHs (two- and three-ring PAHs) provided the largest contribution to exhaust emissions, accounting for more than 90% of total PAHs. After the EGP-SCR treatment was applied, LMW g-PAHs were identified the highest reduction followed by MMW g-PAHs and HMW g-PAHs. It is noteworthy that, the reduction of p-PAHs was related to the decrease of total particulate matter (PM2.5) when the SCR device was applied, and the reduction rate of 56.7% can be observed. However, low exhaust temperature of the diesel engine leads to the activity of the SCR catalyst being reduced, and it was thus not capable of decomposing PAHs effectively. The ILCR values for g-PAHs were 1.93 x 10(-3) and 1.45 x 10(-3) in adults and children, respectively, indicating potential health risk in this study. The data reveal that the EGP-SCR system can effectively decline regulated and help avoid inhalation of carcinogenic substances (PM2.5). Moreover, g-PAHs create serious carcinogenic hazards, cannot be suppressed by the EGP-SCR after-treatment system under cold start condition.