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Abstract Direct synthesis of CH3COOH from CH4and CO2is an appealing approach for the utilization of two potent greenhouse gases that are notoriously difficult to activate. In thisCommunication, we report an integrated route to enable this reaction. Recognizing the thermodynamic stability of CO2, our strategy sought to first activate CO2to produce CO (through electrochemical CO2reduction) and O2(through water oxidation), followed by oxidative CH4carbonylation catalyzed by Rh single atom catalysts supported on zeolite. The net result was CH4carboxylation with 100 % atom economy. CH3COOH was obtained at a high selectivity (>80 %) and good yield (ca. 3.2 mmol g−1catin 3 h). Isotope labelling experiments confirmed that CH3COOH is produced through the coupling of CH4and CO2. This work represents the first successful integration of CO/O2production with oxidative carbonylation reaction. The result is expected to inspire more carboxylation reactions utilizing preactivated CO2that take advantage of both products from the reduction and oxidation processes, thus achieving high atom efficiency in the synthesis.
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Ozonolysis can produce long-lived greenhouse gases from commercial refrigerants
Hydrofluoroolefins are being adopted as sustainable alternatives to long-lived fluorine- and chlorine-containing gases and are finding current or potential mass-market applications as refrigerants, among a myriad of other uses. Their olefinic bond affords relatively rapid reaction with hydroxyl radicals present in the atmosphere, leading to short lifetimes and proportionally small global warming potentials. However, this type of functionality also allows reaction with ozone, and whilst these reactions are slow, we show that the products of these reactions can be extremely long-lived. Our chamber measurements show that several industrially important hydrofluoroolefins produce CHF3(fluoroform, HFC-23), a potent, long-lived greenhouse gas. When this process is accounted for in atmospheric chemical and transport modeling simulations, we find that the total radiative effect of certain compounds can be several times that of the direct radiative effect currently recommended by the World Meteorological Organization. Our supporting quantum chemical calculations indicate that a large range of exothermicity is exhibited in the initial stages of ozonolysis, which has a powerful influence on the CHF3yield. Furthermore, we identify certain molecular configurations that preclude the formation of long-lived greenhouse gases. This demonstrates the importance of product quantification and ozonolysis kinetics in determining the overall environmental impact of hydrofluoroolefin emissions.
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- Award ID(s):
- 2108202
- PAR ID:
- 10517062
- Publisher / Repository:
- National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 51
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2312714120
