Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation
Previously tested 2 wt % palladium-platinum catalysts supported on Norit activated carbon preheated to 1600 °C have been reinvestigated in CHFCl<sub>2</sub> hydrodechlorination. An additionally adopted catalyst oxidation at 350–400 °C produced nearly an order of magnitude increase in the...
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MDPI AG
2021-04-01
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| author | Monika Radlik Wojciech Juszczyk Wioletta Raróg-Pilecka Magdalena Zybert Zbigniew Karpiński |
| author_facet | Monika Radlik Wojciech Juszczyk Wioletta Raróg-Pilecka Magdalena Zybert Zbigniew Karpiński |
| author_sort | Monika Radlik |
| collection | DOAJ |
| description | Previously tested 2 wt % palladium-platinum catalysts supported on Norit activated carbon preheated to 1600 °C have been reinvestigated in CHFCl<sub>2</sub> hydrodechlorination. An additionally adopted catalyst oxidation at 350–400 °C produced nearly an order of magnitude increase in the turnover frequency of Pd/C, from 4.1 × 10<sup>−4</sup> to 2.63 × 10<sup>−3</sup> s<sup>−1</sup>. This increase is not caused by changes in metal dispersion or possible decontamination of the Pd surface from superficial carbon, but rather by unlocking the active surface, originally inaccessible in metal particles tightly packed in the pores of carbon. Burning carbon from the pore walls attached to the metal changes the pore structure, providing easier access for the reactants to the entire palladium surface. Calcination of Pt/C and Pd-Pt/C catalysts results in much smaller evolution of catalytic activity than that observed for Pd/C. This shapes the relationship between turnover frequency (TOF) and alloy composition, which now does not confirm the Pd-Pt synergy invoked in the previous work. The absence of this synergy is confirmed by gradual regular changes in product selectivity, from 70 to 80% towards CH<sub>2</sub>F<sub>2</sub> for Pd/C to almost 60% towards CH<sub>4</sub> for Pt/C. The use of even higher-preheated carbon (1800 °C), completely free of micropores, results in a Pd/C catalyst that does not need to be oxidized to achieve high activity and excellent selectivity to CH<sub>2</sub>F<sub>2</sub> (>90%). |
| first_indexed | 2024-03-10T12:07:18Z |
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| issn | 2073-4344 |
| language | English |
| last_indexed | 2024-03-10T12:07:18Z |
| publishDate | 2021-04-01 |
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| series | Catalysts |
| spelling | doaj.art-0745306df0084d8b987738086f6f60e22023-11-21T16:26:41ZengMDPI AGCatalysts2073-43442021-04-0111552510.3390/catal11050525Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst OxidationMonika Radlik0Wojciech Juszczyk1Wioletta Raróg-Pilecka2Magdalena Zybert3Zbigniew Karpiński4Faculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszyński University in Warsaw, ul. Wóycickiego 1/3, PL-01938 Warszawa, PolandInstitute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01224 Warszawa, PolandFaculty of Chemistry, Warsaw University of Technology, ul. Noakowskiego 3, PL-00664 Warszawa, PolandFaculty of Chemistry, Warsaw University of Technology, ul. Noakowskiego 3, PL-00664 Warszawa, PolandFaculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszyński University in Warsaw, ul. Wóycickiego 1/3, PL-01938 Warszawa, PolandPreviously tested 2 wt % palladium-platinum catalysts supported on Norit activated carbon preheated to 1600 °C have been reinvestigated in CHFCl<sub>2</sub> hydrodechlorination. An additionally adopted catalyst oxidation at 350–400 °C produced nearly an order of magnitude increase in the turnover frequency of Pd/C, from 4.1 × 10<sup>−4</sup> to 2.63 × 10<sup>−3</sup> s<sup>−1</sup>. This increase is not caused by changes in metal dispersion or possible decontamination of the Pd surface from superficial carbon, but rather by unlocking the active surface, originally inaccessible in metal particles tightly packed in the pores of carbon. Burning carbon from the pore walls attached to the metal changes the pore structure, providing easier access for the reactants to the entire palladium surface. Calcination of Pt/C and Pd-Pt/C catalysts results in much smaller evolution of catalytic activity than that observed for Pd/C. This shapes the relationship between turnover frequency (TOF) and alloy composition, which now does not confirm the Pd-Pt synergy invoked in the previous work. The absence of this synergy is confirmed by gradual regular changes in product selectivity, from 70 to 80% towards CH<sub>2</sub>F<sub>2</sub> for Pd/C to almost 60% towards CH<sub>4</sub> for Pt/C. The use of even higher-preheated carbon (1800 °C), completely free of micropores, results in a Pd/C catalyst that does not need to be oxidized to achieve high activity and excellent selectivity to CH<sub>2</sub>F<sub>2</sub> (>90%).https://www.mdpi.com/2073-4344/11/5/525CHClF<sub>2</sub> hydrodechlorinationPd-Pt/Cthermally modified activated carbonbeneficial effect of catalyst oxidationpore structure changes |
| spellingShingle | Monika Radlik Wojciech Juszczyk Wioletta Raróg-Pilecka Magdalena Zybert Zbigniew Karpiński Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation Catalysts CHClF<sub>2</sub> hydrodechlorination Pd-Pt/C thermally modified activated carbon beneficial effect of catalyst oxidation pore structure changes |
| title | Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation |
| title_full | Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation |
| title_fullStr | Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation |
| title_full_unstemmed | Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation |
| title_short | Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation |
| title_sort | chlorodifluoromethane hydrodechlorination on carbon supported pd pt catalysts beneficial effect of catalyst oxidation |
| topic | CHClF<sub>2</sub> hydrodechlorination Pd-Pt/C thermally modified activated carbon beneficial effect of catalyst oxidation pore structure changes |
| url | https://www.mdpi.com/2073-4344/11/5/525 |
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