Recent advancement in homogeneous functionalizations of methane

Hu, Anhua; Chang, Liang; Zuo, Zhiwei

doi:10.1360/n972019-00115

Cited by 3 publications

(2 citation statements)

References 15 publications

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“…Engineering catalysts with a high affinity toward C–H bond activation to selectively produce value-added products is an active area of research that can solve major energy and global warming-related issues. Several catalytic systems composed of the metal complexes such as Hg, Pt, Pd, Au, Ru, Rh, and V have been explored, but low catalytic activity, the requirement of corrosive acids, unselective oxidation, and difficult/nonfeasible separation remain an obstacle. − Other components such as molecular sieves, ZSM-5, metal–organic frameworks (MOFs), etc., have also been investigated for the direct methane conversion. − The large energy gap between the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), weak polarizability (2.84 × 10–40 C 2 m 2 J –1 ) with identical electronics environment, high ionization energy (≈12.6 eV), low proton affinity (543.9 kJ mol –1 ) and weak acidity (p K a ≈ 48) make CH 4 activation via the first C–H bond cleavage a highly unfavorable reaction . Despite the inactivity of the CH 4 molecule, it can be activated due to the fractional contribution of the ionic resonance structure.…”

Section: Introductionmentioning

confidence: 99%

Single Atom Catalysts for Selective Methane Oxidation to Oxygenates

Kumar

Al‐Attas

et al. 2022

ACS Nano

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Direct conversion of methane (CH 4 ) to C 1−2 liquid oxygenates is a captivating approach to lock carbons in transportable value-added chemicals, while reducing global warming. Existing approaches utilizing the transformation of CH 4 to liquid fuel via tandemized steam methane reforming and the Fischer−Tropsch synthesis are energy and capital intensive. Chemocatalytic partial oxidation of methane remains challenging due to the negligible electron affinity, poor C−H bond polarizability, and high activation energy barrier. Transition-metal and stoichiometric catalysts utilizing harsh oxidants and reaction conditions perform poorly with randomized product distribution. Paradoxically, the catalysts which are active enough to break C−H also promote overoxidation, resulting in CO 2 generation and reduced carbon balance. Developing catalysts which can break C−H bonds of methane to selectively make useful chemicals at mild conditions is vital to commercialization. Single atom catalysts (SACs) with specifically coordinated metal centers on active support have displayed intrigued reactivity and selectivity for methane oxidation. SACs can significantly reduce the activation energy due to induced electrostatic polarization of the C−H bond to facilitate the accelerated reaction rate at the low reaction temperature. The distinct metal−support interaction can stabilize the intermediate and prevent the overoxidation of the reaction products. The present review accounts for recent progress in the field of SACs for the selective oxidation of CH 4 to C 1−2 oxygenates. The chemical nature of catalytic sites, effects of metal−support interaction, and stabilization of intermediate species on catalysts to minimize overoxidation are thoroughly discussed with a forward-looking perspective to improve the catalytic performance.

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Section: Introductionmentioning

confidence: 99%

Single Atom Catalysts for Selective Methane Oxidation to Oxygenates

Kumar

Al‐Attas

et al. 2022

ACS Nano

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“…Due to the inert chemical properties of CH 4 , the functionalization of CH 4 into intermediate chemicals is required for the further transformation into high-value-added products. − Various reaction systems have been developed for methane functionalization under both homogeneous , and heterogeneous conditions. ,, Catalytic methane halogenation, especially chlorination and bromination, is an effective way to increase the utilization value of methane . Methyl chloride (CH 3 Cl) is an important chemical intermediate in the organic chemical industry .…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic Chlorination of Methane Using Alkali Chloride Solution

Shen

Zhang

et al. 2022

ACS Catal.

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The development of direct conversion for selective functionalization of inert methane plays an important role in the chemical sciences. Here, we report a photocatalytic approach to successfully convert methane into methyl chloride over NaTaO3 photocatalyst using an alkali chloride solution as the chlorine source under ambient conditions, which can overcome disadvantages of toxicity and corrosiveness in the traditional chlorination of methane. Various noble metals and oxide cocatalysts (Pt, Pd, Au, Ag, and Ag2O) and different chloride ion solutions (NaCl, KCl, LiCl, MgCl2, BaCl2, CaCl2, CuCl2, FeCl3, ZnCl2, etc.) are investigated to optimize the photocatalytic chlorination processes. Ag2O/NaTaO3 is the best photocatalyst, giving the maximum CH3Cl yield of 152 μmol g–1 h–1 in aqueous NaCl solutions and an apparent quantum yield of 7.2% under 254 nm monochromatic light irradiation. The target product CH3Cl is verified to be formed by a direct combination of the photoinduced species •CH3 and •Cl on the Ag2O surface. This work provides a meaningful approach for the conversion of methane into chloromethane under normal conditions.

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