Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap
Hydrocarbon traps for exhaust emissions control adsorb hydrocarbons in low temperature exhaust and release them as the exhaust warms up. In this work, a Pd/BEA hydrocarbon trap was tested under lean exhaust conditions using ethylene and dodecane as model hydrocarbons. Ethylene uptake was partially i...
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| Format: | Article |
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MDPI AG
2021-03-01
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| Series: | Catalysts |
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| Online Access: | https://www.mdpi.com/2073-4344/11/3/348 |
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| author | Ryan Zelinsky William S. Epling |
| author_facet | Ryan Zelinsky William S. Epling |
| author_sort | Ryan Zelinsky |
| collection | DOAJ |
| description | Hydrocarbon traps for exhaust emissions control adsorb hydrocarbons in low temperature exhaust and release them as the exhaust warms up. In this work, a Pd/BEA hydrocarbon trap was tested under lean exhaust conditions using ethylene and dodecane as model hydrocarbons. Ethylene uptake was partially inhibited by CO and H<sub>2</sub>O when fed separately. When both were added, the loss in ethylene uptake was 90% relative to the condition with no H<sub>2</sub>O or CO. Dodecane uptake was unchanged under all conditions tested. During a temperature ramp, ethylene desorbed and was combusted to CO<sub>2</sub> and H<sub>2</sub>O over active Pd centers. Further, oxidation light-off of dodecane generated an exotherm which caused rapid desorption of the remaining hydrocarbon species from the zeolite. For both hydrocarbons, CO co-feed led to a decreased oxidation light-off temperature, and therefore lower desorption temperature. By pretreating the catalyst in CO and H<sub>2</sub>O at 80 °C, and even after removing CO from the feed, the enhanced oxidation light-off behavior was observed. DRIFTS characterization shows that some form of oxidized Pd was reducible to Pd<sup>0</sup> by CO at 80 °C only in the presence of H<sub>2</sub>O. Further, this reduction appears reversible by high temperature oxygen treatment. We speculate that this reduced Pd phase serves as the active site for low temperature hydrocarbon oxidation. |
| first_indexed | 2024-03-09T04:59:48Z |
| format | Article |
| id | doaj.art-36b68b1be94d44a993c051208559feef |
| institution | Directory Open Access Journal |
| issn | 2073-4344 |
| language | English |
| last_indexed | 2024-03-09T04:59:48Z |
| publishDate | 2021-03-01 |
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| spelling | doaj.art-36b68b1be94d44a993c051208559feef2023-12-03T13:01:09ZengMDPI AGCatalysts2073-43442021-03-0111334810.3390/catal11030348Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon TrapRyan Zelinsky0William S. Epling1Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, USADepartment of Chemical Engineering, University of Virginia, Charlottesville, VA 22904, USAHydrocarbon traps for exhaust emissions control adsorb hydrocarbons in low temperature exhaust and release them as the exhaust warms up. In this work, a Pd/BEA hydrocarbon trap was tested under lean exhaust conditions using ethylene and dodecane as model hydrocarbons. Ethylene uptake was partially inhibited by CO and H<sub>2</sub>O when fed separately. When both were added, the loss in ethylene uptake was 90% relative to the condition with no H<sub>2</sub>O or CO. Dodecane uptake was unchanged under all conditions tested. During a temperature ramp, ethylene desorbed and was combusted to CO<sub>2</sub> and H<sub>2</sub>O over active Pd centers. Further, oxidation light-off of dodecane generated an exotherm which caused rapid desorption of the remaining hydrocarbon species from the zeolite. For both hydrocarbons, CO co-feed led to a decreased oxidation light-off temperature, and therefore lower desorption temperature. By pretreating the catalyst in CO and H<sub>2</sub>O at 80 °C, and even after removing CO from the feed, the enhanced oxidation light-off behavior was observed. DRIFTS characterization shows that some form of oxidized Pd was reducible to Pd<sup>0</sup> by CO at 80 °C only in the presence of H<sub>2</sub>O. Further, this reduction appears reversible by high temperature oxygen treatment. We speculate that this reduced Pd phase serves as the active site for low temperature hydrocarbon oxidation.https://www.mdpi.com/2073-4344/11/3/348palladium zeolitehydrocarbon trapemissions controlcold start emissions |
| spellingShingle | Ryan Zelinsky William S. Epling Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap Catalysts palladium zeolite hydrocarbon trap emissions control cold start emissions |
| title | Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap |
| title_full | Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap |
| title_fullStr | Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap |
| title_full_unstemmed | Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap |
| title_short | Effects of CO and H<sub>2</sub>O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap |
| title_sort | effects of co and h sub 2 sub o co feed on the adsorption and oxidation properties of a pd bea hydrocarbon trap |
| topic | palladium zeolite hydrocarbon trap emissions control cold start emissions |
| url | https://www.mdpi.com/2073-4344/11/3/348 |
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