Grantee Research Project Results
Final Report: Low Cost NOx Abatement in Off-Road Sources
EPA Contract Number: EPD08030Title: Low Cost NOx Abatement in Off-Road Sources
Investigators: White, James H.
Small Business: Eltron Research & Development Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2008 through August 31, 2008
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2008) RFA Text | Recipients Lists
Research Category: SBIR - Emission Reductions and Biofuels , Small Business Innovation Research (SBIR)
Description:
This Phase I program addressed the design, selection, and employment of a heterogeneous catalyst for promoting the post-combustion removal of NOx and incompletely oxidized species (CO2 unburned hydrocarbons, and TAPs) from diesel sources without the use of supplemental fuel, ammonia, or urea. This approach is advantageous when compared to selective catalytic reduction (SCR) in that atom economy is improved (stoichiometric ammonia or other reagents are unnecessary) and the costs of reagents eliminated. Additionally, application to area (mobile or small, widespread) sources is far more attractive than the alternative SCR, SNCR, and NSR processes. It was anticipated that the proposed approach would achieve project objectives by utilizing selected metal nitrides as supports for metals and/or metal oxides. Heterogeneous catalyst candidates for this application were selected on the basis of previous results that were, in turn, identified on the basis of optimal oxygen and NOx binding as well as combustion activity or efficient reagent (i.e., CO or hydrocarbons for passive catalytic reduction) utilization for application under net oxidizing conditions, which is appropriate for effectively promoting NOx reduction in the exhausts of real combustion sources. Phase I identified novel catalyst materials which, when used in monolithic form, demonstrated useful activity in real diesel exhaust and were estimated to be more cost effective than existing approaches for retrofit applications in non-highway (off-road) diesel sources.
Summary/Accomplishments (Outputs/Outcomes):
Key Phase I findings were as follows:
- Validated previous bench (simulated exhaust) results obtained with silicon nitride supported metal.
- Synthesized existing Eltron catalyst compositions and derivatives of these compositions using wetness impregnation, ion exchange, or coprecipitation methods.
- By screening catalyst candidates in simulated exhaust (400ppm NO, 400–600ppm ethylene, 8% O2, and 3% H2O at 250°C and 112,500 h-1), identified preferred materials. A main group nitride material proved to be the best catalyst support.
- Preferred supported metal catalyst materials gave up to 44 percent conversion of NOx under the above conditions. Preferred metal oxide materials gave up to approximately 40 percent NOx conversion under the same conditions.
- Temperature dependence of catalyst activity investigated was between 100 and 500°C. Supported metal generally gave a narrow temperature window. Supported metal oxides gave a much wider temperature window. For example, the best supported metal oxide gave a maximum conversion at approximately 350°C of approximately 41 percent and a minimum of 29 percent at only 100°C.
- Dependence of catalyst performance on space velocity and ethylene concentration was also investigated. Both increased ethylene/NOx ratio and increased space velocity.
- Lead candidate catalyst materials were coarse optimized for activity. All of the lead candidates displayed activity (in simulated exhaust) that was greater than that of a baseline Pt-β catalyst.
- Best catalyst materials were incorporated onto metal (fecralloy) honeycomb monoliths.
- Monoliths were tested under fixed conditions (i.e., fixed load of 1,000 W) in the exhaust of a single cylinder, four stroke diesel engine. Preferred candidates identified on the basis of activity exhibited and catalyst adherence to monolith.
- Preferred candidate monoliths were evaluated as a function of engine load, temperature, and time on-line. The best candidate monolith identified incorporated a supported metal oxide catalyst and displayed NOx conversion of more than 37 percent. One monolith was cumulatively used in diesel exhaust for up to 10.5 hours without major activity loss.
- At loads greater than 40 percent of the rated engine power, NOx emissions were less than 3 g/bhp•h and as little as 1.8 g/bhp•h.
- Cost of monolith catalyst was estimated to be only approximately one-fifth of existing diesel NOx abatement approaches.
The most significant observations of Phase I were the identification of several supported metal and metal oxide materials possessing activity exceeding that of a baseline catalyst. Equally important is the observation that some of the supported metal oxide materials displayed wide temperature windows. Additionally, reduction of NOx emissions from a real non-highway diesel source to within some U.S. Environmental Protection Agency (EPA) standards (Tier 3) was realized.
Conclusions:
Results of Phase I strongly support the concept proposed (i.e., metal nitride supported metals and metal oxides, as passive NOx catalysts for non-highway diesel applications). Activity obtained and reasonable cost suggests that further development is warranted.
Supplemental Keywords:
small business, SBIR, EPA, ozone, aerosols, acid rain, engine emissions reduction, vehicle emissions reduction, emissions standards, diesel engine, nitrogen oxide, NOx, nitrogen oxide emissions, catalytic technology, nitrogen oxide abatement, direct decomposition, passive lean reduction activity, diesel exhaust, urea reduction, hydrocarbon reduction, selective catalyst reduction, SCR, zero ammonia diesel exhaust, lean burn gasoline engines, natural gas-fired boilers, turbines, coal-fired combustion, sustainable industry/business, scientific discipline, RFA, technology for sustainable environment, sustainable environment, environmental engineering, environmental chemistry, diesel exhaust, automobile engine exhausts, air pollutants,, RFA, Scientific Discipline, Sustainable Industry/Business, Environmental Chemistry, Sustainable Environment, Technology for Sustainable Environment, Environmental Engineering, air pollutants, nitrogren oxides (NOx), automobile engine exhausts, diesel exhaustThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.