Interaction between PT catalyst and ozone for catalytic carbon monoxide oxidation

Both gasoline and diesel engines are trending toward highly fuel-efficient engines that produce lower exhaust gas temperature. Subsequently, emissions of hydrocarbons (HCs) and carbon monoxide (CO) have become severe issues, whereas the previous problem of NOx has become negligible. We show that the addition of O₃ generated by non-thermal plasmas can activate catalytic oxidation of CO in vehicle exhaust at the low temperatures typical of the cold-start problem in automobile engines. Our empirical results confirm that supplying a small amount of O₃ at low temperature results in a CO removal rate equivalent to that at double the operating temperature when using a catalyst alone. The removal rate of CO was found to be sensitive to the concentration of O₃; thus, by optimizing the concentration of O₃, catalytic CO oxidation could be achieved within 1 min. A possible reaction mechanism will be discussed in the paper¹ to explain how catalytic CO oxidation may be activated but subsequently becomes less effective at higher O₃ concentration. In our experiment, C₃H₈ and C₃H₆ were added to evaluate the effects of each gas on the enhancement of CO removal rate by O₃. Moreover, the rate of CO removal was evaluated with increasing O₃ concentration for practical applications such as the cold-start problem.