Ethanol method boosts low temperature NOx cleanup catalysts

by Riko Seibo
Los Angeles CA (SPX) Mar 11, 2026
A research team has reported a simple new preparation strategy that sharply improves the low temperature performance of carbon based catalysts used to remove nitrogen oxides from industrial exhaust. The work focuses on ammonia selective catalytic reduction, a widely used process that converts nitrogen oxides into nitrogen and water, and demonstrates that replacing water with ethanol during catalyst impregnation can deliver much higher activity at temperatures where many flue gases actually operate.

Nitrogen oxides, often grouped as NOx, are harmful air pollutants generated during the combustion of fossil fuels in power plants and heavy industry. They contribute to smog, acid rain, and a range of environmental and health impacts, so many facilities use ammonia selective catalytic reduction systems to limit emissions before release to the atmosphere. Conventional catalysts in these systems typically work best between about 300 and 400 degrees Celsius, which creates a mismatch for sectors such as steel, cement, and glass production where exhaust streams are substantially cooler and often would need reheating to meet the catalyst operating window.

To overcome that limitation, the researchers developed a manganese oxide catalyst supported on activated carbon, a material chosen for its high surface area and strong adsorption capabilities. The key change in their approach was to use ethanol instead of water as the solvent during the impregnation step that deposits manganese precursor onto the carbon support. In their tests, ethanol altered how the liquid phase interacted with the porous carbon and led to a more favorable distribution of the active component.

Because ethanol has lower polarity and surface tension than water, it can wet the carbon surface more effectively, spread across it more uniformly, and infiltrate the pores more completely. As a result, the active manganese oxide species formed during subsequent processing disperse more evenly throughout the catalyst structure rather than aggregating in localized regions. Lead researcher Donghong Nan explained that the team aimed to improve how catalytic components spread across the carbon and found that ethanol impregnation delivered a much more uniform distribution, which is essential for achieving high catalytic performance.

The preparation route combines ethanol assisted impregnation with carefully controlled low temperature calcination. This thermal treatment increases the fraction of manganese present as Mn4+, an oxidation state known to play a critical role in the catalytic reduction of nitrogen oxides under ammonia selective catalytic reduction conditions. By adjusting the calcination temperature and atmosphere, the team was able to tune the surface chemistry to favor both active Mn4+ species and reactive surface oxygen that participate directly in the redox steps of the reaction.

Laboratory measurements showed that the optimized catalyst performed strongly at only 150 degrees Celsius, a temperature far below that of typical high temperature commercial systems. At this temperature and a gas hourly space velocity of 20,000 per hour, the manganese on carbon catalyst prepared with ethanol reached a nitrogen oxide conversion efficiency of 96.3 percent. For comparison, a similar catalyst prepared with water as the impregnation solvent achieved 82.9 percent conversion under the same conditions, highlighting the performance gain from the solvent switch alone.

Corresponding author Kai Li described the improvement as striking, noting that simply changing the solvent used during the preparation step led to a substantial jump in catalytic activity at low temperature. The team also mapped out the best preparation parameters, finding that an eight percent manganese loading combined with calcination in air at 200 degrees Celsius produced the highest performance. Under those conditions, the material exhibited a high proportion of Mn4+ and robust surface oxygen activity, both seen as crucial for driving the ammonia selective catalytic reduction reaction efficiently.

Beyond the performance metrics, the authors emphasized that the ethanol assisted route does not require complex new equipment or exotic processing steps. The method can be integrated into existing catalyst production lines with only minor modifications, which could lower barriers to adoption in commercial settings. That practicality, combined with lower temperature operation, suggests potential energy savings because exhaust streams may not need as much additional heating to reach effective reaction temperatures.

For industrial users dealing with relatively cool exhaust gases, such as certain segments of the steel, cement, and glass industries, the new catalyst design could offer a more efficient option for cutting nitrogen oxide emissions. Higher activity at lower temperatures can translate into improved removal efficiency and reduced operating costs in systems where reheating flue gas is currently necessary. The researchers argue that this kind of incremental process change in catalyst preparation can deliver notable environmental benefits without requiring a complete redesign of existing pollution control infrastructure.

The team further suggests that tailoring solvent properties during catalyst preparation may be a broadly useful lever for designing next generation environmental catalysts. By selecting solvents with specific polarity, surface tension, and wetting behavior, it may be possible to engineer more uniform distributions of active components and favorable surface chemistries across different catalytic systems. Nan noted that the study shows how relatively subtle changes in the manufacturing process can open new pathways for more efficient low temperature pollution control technologies.

Research Report:Preparation and performance evaluation of a novel ethanol-enhanced Mn-modified carbon-based deNOx catalyst