Experimental investigation on the influence of the presence of alkali compounds on the performance of a commercial Pt–Pd/Al2O3 diesel oxidation catalyst

Experimental investigation was conducted on the influence of the presence of alkali compounds such as K and Na present in biofuels on catalytic behaviors of a commercial diesel oxidation catalyst (Pt/Pd/Al2O3) in the monolith form. Doping of different alkali metal components on carrots of monolith was performed. These carrots were physicochemically characterized, and the catalytic tests consisted of series of temperature-programmed surface reactions with representative exhaust gas mixtures from diesel combustion. The aim of the present study is to reveal the effect of the alkali metal on overall catalytic activity of diesel oxidation catalyst (DOC) and more particularly to show their influence on the reactions involving CO, hydrocarbons, NO, and NO2. Potassium and sodium lead to different catalytic properties. A promotion effect was found in the presence of K, whereas an inhibiting effect was evidenced in the presence of Na or when both Na and K were doped onto the DOC.