An Investigation on the Regeneration of Lean NOx Trap using Ethanol and n-Butanol 2019-01-0737

The negative impacts of automotive pollutants on local air quality, human health, and climate change are a major concern worldwide. Therefore, internal combustion engine (ICE) powered automobiles are expected to be able to meet increasingly stringent emission and fuel efficiency standards. The use of alternative fuels such as ethanol and n-butanol in a compression ignition engine together with the application of moderate Exhaust Gas Recirculation (EGR) can produce low engine-out NOx and soot emissions. However, to meet current and forthcoming real driving NOx emission legislation, the use of both alternative fuels and advanced after-treatment technology may be required. This study is an investigation on NOx reduction and by-product formation over lean NOx trap (LNT) with diesel, ethanol, and n-butanol as the reductant. Engine tests are conducted using alternative fuels to determine the engine exhaust conditions and a long breathing LNT strategy is examined on a separate offline flow bench under simulated exhaust conditions. To analyze the effectiveness of the reductant in lowering NOx, the inlet gas composition and temperature during adsorption are kept similar but the reductant concentration and type are varied during regeneration. Two oxygen concentrations 8.5% and 3% are used for experiments. Apart from NOx release, the other major products formed during regeneration such as ammonia (NH3), and nitrous oxide (N2O) are analyzed based on Fourier-Transform Infrared spectrometer (FT-IR) measurements. Ethanol and n-butanol shows higher NOx conversion efficiency and regeneration effectiveness compare to diesel. As the quantity of ethanol and n-butanol increases, NH3 formation also increases but N2O formation decreases. Hydrogen (H2) measurement is also conducted which shows higher H2 release using ethanol during regeneration. Hydrocarbon speciation downstream of LNT is investigated based on FT-IR data to understand the conversion of ethanol, n-butanol and diesel over the catalyst during regeneration.