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Title: Lean NO x reduction over Ag/alumina catalysts via ethanol-SCR using ethanol/gasoline blends

Abstract

This paper focuses on the activity for lean NO x reduction over sol-gel synthesized silver alumina (Ag/Al 2O 3) catalysts, with and without platinum doping, using ethanol (EtOH), EtOH/C 3H 6 and EtOH/gasoline blends as reducing agents. The effect of ethanol concentration, both by varying the hydrocarbon-to-NO x ratio and by alternating the gasoline concentration in the EtOH/gasoline mixture, is investigated. High activity for NO x reduction is demonstrated for powder catalysts for EtOH and EtOH/C 3H 6 as well as for monolith coated catalysts (EtOH and EtOH/gasoline). The results show that pure Ag/Al 2O 3 catalysts display higher NO x reduction and lower light-off temperature as compared to the platinum doped samples. The 4 wt.% Ag/Al 2O 3 catalyst displays 100% reduction in the range 340–425 °C, with up to 37% selectivity towards NH 3. These results are also supported by DRIFTS (Diffuse reflection infrared Fourier transform spectroscopy) experiments. Finally, the high ammonia formation could, in combination with an NH 3-SCR catalyst, be utilized to construct a NO x reduction system with lower fuel penalty cf. stand alone HC-SCR. In addition, it would result in an overall decrease in CO 2 emissions.

Authors:
 [1];  [2];  [2];  [1]; ORCiD logo [1]
  1. Chalmers Univ. of Technology, Gothenburg (Sweden). Dept. of Chemistry and Chemical Engineering. Competence Centre for Catalysis
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fuels, Engines, and Emissions Research Center
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chalmers Univ. of Technology, Gothenburg (Sweden)
Sponsoring Org.:
USDOE; Swedish Energy Agency (Sweden); Knut and Alice Wallenberg Foundation (Sweden)
OSTI Identifier:
1327667
Grant/Contract Number:
AC05-00OR22725; Dnr KAW 2005.0055
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Catalysis. B, Environmental
Additional Journal Information:
Journal Volume: 202; Journal ID: ISSN 0926-3373
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Silver-alumina; Ag/Al2O3; HC-SCR; Platinum doping; Lean NOx reduction

Citation Formats

Gunnarsson, Fredrik, Pihl, Josh A., Toops, Todd J., Skoglundh, Magnus, and Härelind, Hanna. Lean NOx reduction over Ag/alumina catalysts via ethanol-SCR using ethanol/gasoline blends. United States: N. p., 2016. Web. doi:10.1016/j.apcatb.2016.09.009.
Gunnarsson, Fredrik, Pihl, Josh A., Toops, Todd J., Skoglundh, Magnus, & Härelind, Hanna. Lean NOx reduction over Ag/alumina catalysts via ethanol-SCR using ethanol/gasoline blends. United States. doi:10.1016/j.apcatb.2016.09.009.
Gunnarsson, Fredrik, Pihl, Josh A., Toops, Todd J., Skoglundh, Magnus, and Härelind, Hanna. 2016. "Lean NOx reduction over Ag/alumina catalysts via ethanol-SCR using ethanol/gasoline blends". United States. doi:10.1016/j.apcatb.2016.09.009. https://www.osti.gov/servlets/purl/1327667.
@article{osti_1327667,
title = {Lean NOx reduction over Ag/alumina catalysts via ethanol-SCR using ethanol/gasoline blends},
author = {Gunnarsson, Fredrik and Pihl, Josh A. and Toops, Todd J. and Skoglundh, Magnus and Härelind, Hanna},
abstractNote = {This paper focuses on the activity for lean NOx reduction over sol-gel synthesized silver alumina (Ag/Al2O3) catalysts, with and without platinum doping, using ethanol (EtOH), EtOH/C3H6 and EtOH/gasoline blends as reducing agents. The effect of ethanol concentration, both by varying the hydrocarbon-to-NOx ratio and by alternating the gasoline concentration in the EtOH/gasoline mixture, is investigated. High activity for NOx reduction is demonstrated for powder catalysts for EtOH and EtOH/C3H6 as well as for monolith coated catalysts (EtOH and EtOH/gasoline). The results show that pure Ag/Al2O3 catalysts display higher NOx reduction and lower light-off temperature as compared to the platinum doped samples. The 4 wt.% Ag/Al2O3 catalyst displays 100% reduction in the range 340–425 °C, with up to 37% selectivity towards NH3. These results are also supported by DRIFTS (Diffuse reflection infrared Fourier transform spectroscopy) experiments. Finally, the high ammonia formation could, in combination with an NH3-SCR catalyst, be utilized to construct a NOx reduction system with lower fuel penalty cf. stand alone HC-SCR. In addition, it would result in an overall decrease in CO2 emissions.},
doi = {10.1016/j.apcatb.2016.09.009},
journal = {Applied Catalysis. B, Environmental},
number = ,
volume = 202,
place = {United States},
year = 2016,
month = 9
}

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  • Ethanol is a very effective reductant of nitrogen oxides (NOX) over silver/alumina (Ag/Al2O3) catalysts in lean exhaust environment. With the widespread availability of ethanol/gasoline-blended fuel in the USA, lean gasoline engines equipped with an Ag/Al2O3 catalyst have the potential to deliver higher fuel economy than stoichiometric gasoline engines and to increase biofuel utilization while meeting exhaust emissions regulations. In this work a pre-commercial 2 wt% Ag/Al2O3 catalyst was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine for the selective catalytic reduction (SCR) of NOX with ethanol/gasoline blends. The ethanol/gasoline blends were delivered via in-pipe injection upstream ofmore » the Ag/Al2O3 catalyst with the engine operating under lean conditions. A number of engine conditions were chosen to provide a range of temperatures and space velocities for the catalyst performance evaluations. High NOX conversions were achieved with ethanol/gasoline blends containing at least 50% ethanol; however, higher C1/N ratio was needed to achieve greater than 90% NOX conversion, which also resulted in significant HC slip. Temperature and HC dosing were important in controlling selectivity to NH3 and N2O. At high temperatures, NH3 and N2O yields increased with increased HC dosing. At low temperatures, NH3 yield was very low, however, N2O levels became significant. The ability to generate NH3 under lean conditions has potential for application of a dual SCR approach (HC SCR + NH3 SCR) to reduce fuel consumption needed for NOX reduction and/or increased NOX conversion, which is discussed in this work.« less
  • Lean gasoline engines running on ethanol/gasoline blends and equipped with a silver/alumina catalyst for selective catalytic reduction (SCR) of NO by ethanol provide a pathway to reduced petroleum consumption through both increased biofuel utilization and improved engine efficiency relative to the current stoichiometric gasoline engines that dominate the U.S. light duty vehicle fleet. A pre-commercial silver/alumina catalyst demonstrated high NO x conversions over a moderate temperature window with both neat ethanol and ethanol/gasoline blends containing at least 50% ethanol. Selectivity to NH 3 increases with HC dosing and ethanol content in gasoline blends, but appears to saturate at around 45%.more » NO 2 and acetaldehyde behave like intermediates in the ethanol SCR of NO. NH 3 SCR of NO x does not appear to play a major role in the ethanol SCR reaction mechanism. Ethanol is responsible for the low temperature SCR activity observed with the ethanol/gasoline blends. In conclusion, the gasoline HCs do not deactivate the catalyst ethanol SCR activity, but they also do not appear to be significantly activated by the presence of ethanol.« less
  • The role of plasma processing on NOx reduction over gammma-alumina and a basic zeolite, NaY was examined. During the plasma treatment NO is oxidized to NO2 and propylene is partially oxidized to CO, CO2, acetaldehyde, and formaldehyde. With plasma treatment, NO as the NOx gas, and a NaY catalyst, the maximum NOx conversion was 70% between 180 and 230?C. The activity decreased at higher and lower temperatures. As high as 80% NOx removal over gamma alumina was measured by a chemiluminescent NOx meter with plasma treatment and NO as the NOx gas. For both catalysts a simultaneous decrease in NOxmore » and aldehydes concentrations was observed, which suggests that aldehyde may be important components for NOx reduction in plasma-treated exhaust.« less
  • NOx reduction with NO2 as the NOx gas in the absence of plasma was compared to plasma treated lean NOx exhaust where NO is converted to NO2 in the plasma. Product nitrogen was measured to prove true chemical reduction of NOx to N2. With plasma treatment, NO as the NOx gas, and a NaY catalyst, the maximum conversion to nitrogen was 50% between 180-230?C. The activity decreased at higher and lower temperatures. At 130?C a complete nitrogen balance could be obtained, however between 164-227?C less than 20% of the NOx is converted to a nitrogen-containing compound or compounds not readilymore » detected by GC or FTIR analysis. With plasma treatment, NO2 as the NOx gas, and a NaY catalyst, a complete nitrogen balance is obtained with a maximum conversion to nitrogen of 55% at 225?C. For gamma alumina, with plasma treatment and NO2 as the NOx gas, 59% of the NOx is converted to nitrogen at 340?C. A complete nitrogen balance was obtained at these conditions. As high as 80% NOx removal over gamma alumina was measured by a chemiluminescent NOx meter with plasma treatment and NO as the NOx gas. When NO is replaced with NO2 and the simulated exhaust gases are not plasma treated, the maximum NOx reduction activity of NaY and gamma alumina decreases to 26% and 10%, respectively. This is a large reduction in activity compared to similar conditions where the simulated exhaust was plasma treated. Therefore, in addition to NO2, other plasma-generated species are required to maximize NOx reduction.« less
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