“…Nitrogen oxides (NOx), besides CO2, are key pollutants in the flue gas emitted from the fossil fuel combustion process, and are very hazardous, having harmful effects on the human and global environment, such as damage to the ozone layer, greenhouse effects, formation of acid rain and photochemical smog (Wang et al, 2012;Wang et al, 2014;Zhang et al, 2014;Bueno-López et al, 2016;Ahmad et al, 2017;Yu et al, 2017;Cheng et al, 2018;Nimcharoen et al, 2018). Diesel engines are among the main contributors of NOx emissions into the atmosphere (Zhu et al, 2008;Choi & Lee, 2014;Cheng et al, 2018). Demand for diesel-engined vehicles is steadily growing due to an increase in their fuel consumption efficiency of 2030% over gasoline vehicles (Li et al, 2009;Choi & Lee, 2014).…”