Reactivity of Novel High-performance fuels on Three-way Catalysts for Control of SI Engine Emissions
Sreshtha Sinha Majumdar, Oak Ridge National Laboratory
In order to reduce petroleum consumption, novel high-performance fuels are being developed simultaneously with the design of highly efficient engines. Commercial three-way catalysts (TWC) are very effective at meeting the stringent emissions regulations on pollutants such as nitrogen oxides (NOx), non-methane organic gases (NMOG) and carbon monoxide (CO) from gasoline fueled spark-ignition (SI) engines operating under stoichiometric conditions. TWCs, however, are only active above a critical temperature known as the catalyst light-off temperature. Until the TWC is sufficiently heated, during cold-start, the criteria pollutants are likely to escape into the environment, which is highly undesirable. Thus, a novel fuel component under consideration must be evaluated in terms of its light-off characteristics on the TWC to ensure that these deleterious pollutants do not slip out of the exhaust under vehicle operating conditions.
In the current study, prior to performance evaluation, a commercial three-way catalyst has been hydrothermally aged as per industry guidelines. The light-off behavior of the novel fuel components, down-selected based on their compatibility with existing engine architecture, on the aged TWC has been investigated. A LabVIEW controlled automated reactor fitted with a vapor delivery module, Fourier transform infra-red (FTIR), flame ionization detector (FID) and a mass spectrometer (MS) has been used to conduct and analyze these experiments as per protocol set by industry. The influence of functional groups of the fuels such as alkanes, alkenes, alcohols, ketones, esters, aromatic ethers, and non-oxygenated aromatic hydrocarbons, on the catalyst light-off temperature has been investigated. Furthermore, we have also examined the effect of the chemical structure of these hydrocarbons, whether straight-chained, branched or cyclic, on their light-off profile. Additionally, we have investigated the light-off of fuel blends of the most promising high-performance fuel candidates as real-world fuels are multi-component blends. The impact on the CO and NOx conversions based on the specific fuel light-off characteristics has also been studied.