Session: 05-03: NOx Control for Alternative Fuels

Paper Number: 164377

164377 - An Investigation on Nitrous Oxide and Ammonia Formation of Lean NOx Trap 

Abstract: 

Automobiles are mandated to meet the increasingly stringent emission regulations as evident in EURO VII and EPA2027 requirements. Nitrogen oxides (NOx) are the major regulated emissions under these standards. For tailpipe NOx emissions control, the current single-stage catalytic solutions like selective catalytic reduction (SCR) and lean-NOx trap (LNT) catalyst have demonstrated reduction efficiency of 80% to 90%. While the LNT system, when paired with EGR, can achieve ultra-low tailpipe NOx emissions, partially mitigating the fuel efficiency penalty of regeneration, nitrous oxide (N₂O) and ammonia (NH₃) can be formed from NOx reduction, which need to be mitigated to align with the upcoming emission regulations. Renewable fuels, such as alcohols and ethers, are found to be highly effective as reductants in term of NOx conversion in LNT, while offering reasonable energy densities compared to conventional petroleum fuels and having no sulfur poisoning tendencies toward the catalyst.

This paper investigates the formation of NOx, N₂O, and NH₃ during the regeneration period on a commercially available lean NOx trap. Two reductant types are utilized, dimethyl ether and ethanol, to investigate the reductant reactivity effect. The effect of the catalyst temperature and reductant quantity on the performance and species selectivity of a lean NOx trap aftertreatment system are investigated on a heated flow bench platform. Relevant engine-out exhaust conditions from a CI engine running with respective fuels, including flow, temperature, and exhaust species are replicated on a heated aftertreatment flow bench. A comprehensive analysis of species before and after the catalyst is performed using Fourier-transformed infrared (FTIR) and mass spectrometers to study and quantify the conversion and formation of species, including ammonia, methane, and hydrogen, under different engine-out conditions. It is observed that, at high temperatures or reductant quantities, nitrate species on LNT become progressively unstable, and eventually cause the stored NOx released because of heat. This extra released NOx significantly influences the regeneration behavior of the LNT. 

Presenting Author: Xiao Yu University of Windsor

Presenting Author Biography: Dr. Yu is a senior research associate at Clean Combustion Engine Lab at the University of Windsor, specializing in clean combustion control and diagnostics, and advanced ignition system and strategy development.

Authors:

Chuankai Jiang University of Windsor
Navjot Sandhu University of Windsor
Xiao Yu University of Windsor
Ming Zheng University of Windsor