After-Treatment Technologies for Emissions of Low-Carbon Fuel Internal Combustion Engines: Current Status and Prospects

Najunzhe Jin, Wuqiang Long, Chunyang Xie and Hua Tian ()
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Najunzhe Jin: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Wuqiang Long: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Chunyang Xie: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Hua Tian: School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China

Energies, 2025, vol. 18, issue 15, 1-24

Abstract: In response to increasingly stringent emission regulations, low-carbon fuels have received significant attention as sustainable energy sources for internal combustion engines. This study investigates four representative low-carbon fuels, methane, methanol, hydrogen, and ammonia, by systematically summarizing their combustion characteristics and emission profiles, along with a review of existing after-treatment technologies tailored to each fuel type. For methane engines, unburned hydrocarbon (UHC) produced during low-temperature combustion exhibits poor oxidation reactivity, necessitating integration of oxidation strategies such as diesel oxidation catalyst (DOC), particulate oxidation catalyst (POC), ozone-assisted oxidation, and zoned catalyst coatings to improve purification efficiency. Methanol combustion under low-temperature conditions tends to produce formaldehyde and other UHCs. Due to the lack of dedicated after-treatment systems, pollutant control currently relies on general-purpose catalysts such as three-way catalyst (TWC), DOC, and POC. Although hydrogen combustion is carbon-free, its high combustion temperature often leads to elevated nitrogen oxide (NO x ) emissions, requiring a combination of optimized hydrogen supply strategies and selective catalytic reduction (SCR)-based denitrification systems. Similarly, while ammonia offers carbon-free combustion and benefits from easier storage and transportation, its practical application is hindered by several challenges, including low ignitability, high toxicity, and notable NO x emissions compared to conventional fuels. Current exhaust treatment for ammonia-fueled engines primarily depends on SCR, selective catalytic reduction-coated diesel particulate filter (SDPF). Emerging NO x purification technologies, such as integrated NO x reduction via hydrogen or ammonia fuel utilization, still face challenges of stability and narrow effective temperatures.

Keywords: low-carbon fuels; internal combustion engines; unburned hydrocarbons; nitrogen oxides; emissions after-treatment (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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