Effects of bio-derived oxygenated fuel molecules on emission reduction by a three-way catalyst during combustion in a direct-injection spark ignition engine

The displacement of fossil fuel use for transport with sustainable alternatives is urgently required to reduce greenhouse gas emissions and address global climate change. Advanced biofuels from renewable feedstocks, for example waste biomass, present an opportunity to decarbonise the use of combustion for propulsion however sustainable utilisation of these fuels also requires consideration of impacts on other exhaust pollutants that negatively affect the environment and human health. Therefore, while exhaust after-treatment systems are an established and effective means of emission reduction during combustion of hydrocarbon fuels, there is a need to understand impacts of biofuel use on the performance of devices including three-way catalysts (TWC) for simultaneous reduction of nitrogen oxides (NOx), carbon monoxide (CO) and unburnt hydrocarbons (THC). This experimental study therefore investigates the effects of four potential biofuel molecules, 2-methylfuran (MF), 2-methyltetrahydrofuran (MTHF), gamma valerolactone (GVL) and linalool (LNL), on combustion, engine-out exhaust emissions and pollutant conversion across a three-way catalyst (TWC) in a gasoline direct-injection engine. The potential biofuel molecules were blended with reference gasoline (RGL) at 20% wt/wt and supplied to a light-duty direct-injection spark ignition engine operated at constant conditions, with gaseous and particulate exhaust emissions measured pre- and post- TWC during catalyst warm-up during engine cold-start and at steady state. While the biofuel blends displayed similar rates of heat release rate relative to gasoline combustion, the MF blend significantly increased CO and NOx engine-out emissions both during cold-start and at steady state. The use of GVL reduced NOx, while hydrogen (H 2 ) emissions correlated with blend hydrogen carbon ratio. All of the biofuel blends increased the TWC inlet temperature required for pollutant conversion, while MF, LNL and GVL increased H 2 levels post-TWC at higher temperatures. LNL exhibited higher particulate levels post-TWC than gasoline only, despite lower engine-out emissions during combustion of the biofuel blend.