Photocatalytic synthesis of oxygenated hydrocarbons from diesel fuel for mobile deNOx application

Photocatalytic partial oxidation of dodecane has been studied as a model reaction of diesel fuel conversion to oxygenated hydrocarbons (OHCs) as an effective nitrogen oxide (NOx) reductant in selective catalytic reduction (SCR) systems. Thus, TiO2-based photocatalysts produced OHCs composed mainly of C1–C6 aldehydes under UV irradiation, and TiO2–SiO2 mixed oxide photocatalysts showed higher selectivity and yield to OHCs than pristine TiO2 by diluting contiguous Ti sites and suppressing complete oxidation to CO2. The effects of reaction variables were studied in detail. A novel scheme of NOx after-treatment system for diesel engine exhaust line was proposed involving the new photocatalytic reaction, where on-board photocatalytic partial oxidation of a small amount of diesel fuel produced OHCs that were supplied to the deNOx system as NOx reductant. Although further improvement is needed in the selectivity for OHCs as well as the system operability, the proposed scheme could be a more environment-friendly option than the reduction by urea, currently considered the most promising technology.