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Direct conversion of methane to oxygenates catalyzed by iron( III ) chloride in water at near ambient temperature
Author(s) -
Zhang Li,
Sun Zhuxing,
Lang Junyu,
Hu Yun Hang
Publication year - 2021
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.5948
Subject(s) - chemistry , methane , catalysis , formic acid , methanol , inorganic chemistry , anaerobic oxidation of methane , hydrogen peroxide , oxygenate , chloride , gibbs free energy , ion , density functional theory , radical , photochemistry , organic chemistry , computational chemistry , thermodynamics , physics
Summary The conversion of natural gas (mainly methane) to more valuable compounds is an attractive topic in energy field. While heterogeneously catalytic conversion of methane with hydrogen peroxide (H 2 O 2 ) has been extensively studied, in‐depth study on similar homogeneous systems is lacking. In this work, FeCl 3 was demonstrated as an excellent homogeneous catalyst for direct oxidation of methane in the presence of H 2 O 2 at near ambient temperature (50°C) in water, with significant yields of methanol (1972.2 μmol/g cat ) and formic acid (33 273.5 μmol/g cat ) and a high turnover frequency (TOF) of 5.7 hours −1 . The superiorities of both the cation (Fe 3+ ) and the anion (Cl − ) were revealed by studying the cation and anion effects in comparison with CoCl 2 and NiCl 2 (TOF of 0.035 and 0 hour −1 , respectively) as well as Fe(NO 3 ) 3 and FeBr 3 (TOF of 3.3 and 0.73 hour −1 , respectively). Furthermore, it was found that the hydrated ferryl ion [(H 2 O) 5 Fe IV O] 2+ could be the major active species for the activation of CH 4 and the formation of CH 3 OH, whereas the hydroxyl radicals (·OH) were responsible for the formation of HCOOH, CO and CO 2 . Moreover, theoretical study based on density function theory (DFT) suggested that the cation effect could be related to the Gibbs free energies for CH 4 activation on their corresponding active species. Meanwhile, the anions affect the performance mainly by the structural features.