Effect of Oxygen Containing Biofuels on the Emissions with ExhaustGas Catalysts

One of the first alternative fuels have been fossil crude oil based containing a small amount of biomass derived compounds (bioethanol or biodiesel). Biofuels usually contain oxygenated hydrocarbons such as alcohols or esters. The increasing use of alternative fuels will occur at the same time when various after-treatment systems (oxidation catalysts, filters, SCR catalysts) will be commercialized world-widely between 2010 and 2020. The effects of biofuels on emissions and emission catalysts were reviewed widely in this study. The change in raw emissions has effects on the selection, performance and durability of catalytic systems.

Bioethanol has been used widely with emission catalysts since 1990's in Brazil. The results with three-way catalysts (TWC) were analyzed in those conditions. PtRh catalysts showed the better performance and durability than Pd containing TWCs.

The effect of noble metal type (Pt, Pd, PtPd), loading and space velocity was studied with aged diesel oxidation catalyst samples under laboratory conditions. Ethanol and acetaldehyde were used to simulate biofuel compounds and derivates formed in engine. The formation of acetaldehyde is higher with ethanol than with diesel fuels. The ethanol reactions on oxidation catalysts was experimentally simulated over European Driving Cycle (EDC) in comparison to diesel exhaust gases. The formation and oxidation of acetaldehyde were detected on Pd-containing oxidation catalysts but Pt-only catalyst showed the lowest acetaldehyde formation ability. The net effect is clearly positive to reduce acetaldehyde emissions with efficient oxidation catalyst.