Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate

In ongoing attempts to efficiently utilize abundant natural gas, there has been steady scientific and industrial interest in using an environmentally benign and inexpensive oxidant (dioxygen O<sub>2</sub>) for the direct catalytic oxidation of methane to oxygenate products under mild con...

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Main Authors: Huyen Tran Dang, Seokhyeon Cheong, Jiyun Kim, Ngoc Tuan Tran, Honggon Kim, Hyunjoo Lee
Format: Article
Language:English
Published: MDPI AG 2022-11-01
Series:Catalysts
Subjects:
Online Access:https://www.mdpi.com/2073-4344/12/11/1419
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author Huyen Tran Dang
Seokhyeon Cheong
Jiyun Kim
Ngoc Tuan Tran
Honggon Kim
Hyunjoo Lee
author_facet Huyen Tran Dang
Seokhyeon Cheong
Jiyun Kim
Ngoc Tuan Tran
Honggon Kim
Hyunjoo Lee
author_sort Huyen Tran Dang
collection DOAJ
description In ongoing attempts to efficiently utilize abundant natural gas, there has been steady scientific and industrial interest in using an environmentally benign and inexpensive oxidant (dioxygen O<sub>2</sub>) for the direct catalytic oxidation of methane to oxygenate products under mild conditions. Here, we report the homogeneous bis(tetramethylammonium) tetrachlorocobaltate ([Me<sub>4</sub>N]<sub>2</sub>CoCl<sub>4</sub>)-catalyzed methane oxidation to methyl trifluoroacetate (MeTFA) with dioxygen O<sub>2</sub> in trifluoroacetic acid (HTFA) media. [Me<sub>4</sub>N]<sub>2</sub>CoCl<sub>4</sub> had the highest catalytic activity among previously reported homogeneous cobalt-based catalyst systems; the turnover of methane to MeTFA reached 8.26 mol<sub>ester</sub> mol<sub>metal</sub><sup>−1</sup>h<sup>−1</sup> at 180 °C. Results suggest that the ionic form of the catalyst makes the Co species more soluble in the HTFA media; consequently, an active catalyst form, [CoTFA<sub>x</sub>Cl<sub>y</sub>]<sup>2−</sup>, can form very rapidly. Furthermore, chloride anions dissociated from CoCl<sub>4</sub><sup>2−</sup> appear to suppress oxidation of the solvent HTFA, thereby driving the reaction toward methane oxidation. The effects of reaction time, catalyst concentration, O<sub>2</sub> and methane pressure, and reaction temperature on MeTFA production were also investigated.
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spelling doaj.art-ad21cd4dc4a84ae6b2627c5e5ceb79ca2023-11-24T07:55:47ZengMDPI AGCatalysts2073-43442022-11-011211141910.3390/catal12111419Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl TrifluoroacetateHuyen Tran Dang0Seokhyeon Cheong1Jiyun Kim2Ngoc Tuan Tran3Honggon Kim4Hyunjoo Lee5Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, KoreaClean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, KoreaDivision of Energy & Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, KoreaClean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, KoreaDivision of Energy & Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, KoreaClean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, KoreaIn ongoing attempts to efficiently utilize abundant natural gas, there has been steady scientific and industrial interest in using an environmentally benign and inexpensive oxidant (dioxygen O<sub>2</sub>) for the direct catalytic oxidation of methane to oxygenate products under mild conditions. Here, we report the homogeneous bis(tetramethylammonium) tetrachlorocobaltate ([Me<sub>4</sub>N]<sub>2</sub>CoCl<sub>4</sub>)-catalyzed methane oxidation to methyl trifluoroacetate (MeTFA) with dioxygen O<sub>2</sub> in trifluoroacetic acid (HTFA) media. [Me<sub>4</sub>N]<sub>2</sub>CoCl<sub>4</sub> had the highest catalytic activity among previously reported homogeneous cobalt-based catalyst systems; the turnover of methane to MeTFA reached 8.26 mol<sub>ester</sub> mol<sub>metal</sub><sup>−1</sup>h<sup>−1</sup> at 180 °C. Results suggest that the ionic form of the catalyst makes the Co species more soluble in the HTFA media; consequently, an active catalyst form, [CoTFA<sub>x</sub>Cl<sub>y</sub>]<sup>2−</sup>, can form very rapidly. Furthermore, chloride anions dissociated from CoCl<sub>4</sub><sup>2−</sup> appear to suppress oxidation of the solvent HTFA, thereby driving the reaction toward methane oxidation. The effects of reaction time, catalyst concentration, O<sub>2</sub> and methane pressure, and reaction temperature on MeTFA production were also investigated.https://www.mdpi.com/2073-4344/12/11/1419methaneoxidationairmethyl trifluoroacetatecobalt catalyst
spellingShingle Huyen Tran Dang
Seokhyeon Cheong
Jiyun Kim
Ngoc Tuan Tran
Honggon Kim
Hyunjoo Lee
Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
Catalysts
methane
oxidation
air
methyl trifluoroacetate
cobalt catalyst
title Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
title_full Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
title_fullStr Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
title_full_unstemmed Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
title_short Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate
title_sort tetrachlorocobaltate catalyzed methane oxidation to methyl trifluoroacetate
topic methane
oxidation
air
methyl trifluoroacetate
cobalt catalyst
url https://www.mdpi.com/2073-4344/12/11/1419
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AT ngoctuantran tetrachlorocobaltatecatalyzedmethaneoxidationtomethyltrifluoroacetate
AT honggonkim tetrachlorocobaltatecatalyzedmethaneoxidationtomethyltrifluoroacetate
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