Selective Cleavage of Chemical Bonds in Targeted Intermediates for Highly Selective Photooxidation of Methane to Methanol

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(15), P. 8609 - 8620

Published: April 6, 2023

Restrained by the uncontrollable cleavage process of chemical bonds in methane molecules and corresponding formed intermediates, target product reaction selective oxidation to methanol would suffer from an inevitable overoxidation process, which is considered be one most challenging issues field catalysis. Herein, we report a conceptually different method for modulating conversion pathway through key intermediates suppress generation peroxidation products. Taking metal oxides, typical semiconductors as model catalysts, confirm that CH3O* could greatly affect methane, has vital role selectivity. Specifically, it revealed formation products significantly prevented C-O instead metal-O bonds, proved combination density functional theory calculations situ infrared spectroscopy based on isotope labeling. By manipulating lattice oxygen mobility electrons transferring surface directionally inject into antibonding orbitals bond, resulting its cleavage. As result, gallium oxide with low shows 3.8% rate high (∼325.4 μmol g-1 h-1) selectivity (∼87.0%) under room temperature atmospheric pressure absence extra oxidants, superior among reported studies (reaction pressure: <20 bar).

Language: Английский

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Electro-assisted methane oxidation to formic acid via in-situ cathodically generated H2O2 under ambient conditions

Nature Communications, Journal Year: 2023, Volume and Issue: 14(1)

Published: Aug. 5, 2023

Direct partial oxidation of methane to liquid oxygenates has been regarded as a potential route valorize methane. However, CH4 activation usually requires high temperature and pressure, which lowers the feasibility reaction. Here, we propose an electro-assisted approach for methane, using in-situ cathodically generated reactive oxygen species, at ambient pressure. Upon acid-treated carbon electrocatalyst, system enables in acidic electrolyte produce oxygenated products. We also demonstrate production rate (18.9 μmol h-1) with selective HCOOH production. Mechanistic analysis reveals that species such ∙OH ∙OOH radicals are produced activate CH3OH. In addition, unstable CH3OOH from can be additionally reduced CH3OH on cathode, so-produced is further oxidized HCOOH, allowing oxidation.

Language: Английский

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Synergy of Ag and AgBr in a Pressurized Flow Reactor for Selective Photocatalytic Oxidative Coupling of Methane

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(6), P. 3768 - 3774

Published: March 2, 2023

Oxidation of methane into valuable chemicals, such as C2+ molecules, has been long sought after but the dilemma between high yield and selectivity desired products remains. Herein, is upgraded through photocatalytic oxidative coupling (OCM) over a ternary Ag–AgBr/TiO2 catalyst in pressurized flow reactor. The ethane 35.4 μmol/h with 79% obtained under 6 bar pressure. These are much better than most previous benchmark performance OCM processes. results attributed to synergy Ag AgBr, where serves an electron acceptor promotes charge transfer AgBr forms heterostructure TiO2 not only facilitate separation also avoid overoxidation process. This work thus demonstrates efficient strategy for conversion by both rational design reactor engineering conversion.

Language: Английский

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Water Microdroplets-Initiated Methane Oxidation

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(50), P. 27198 - 27204

Published: Dec. 6, 2023

The special redox reactivity of water microdroplets causes "mild ignition" methane gas to form oxygenates. C(sp3)–H bond can be activated by the hydroxyl radical (OH·) or hydrogen (H·) across air–water interface (AWI) generate methyl (CH3·). Once CH3· is formed, it undergoes free-radical reactions with O2 in air, excessive OH· and H· AWI, H2O2 present at AWI generated itself produce methanol other species. Production oxygenates was confirmed chromatography, mass spectrometry, 1H- 13C-nuclear magnetic resonance. Formic acid, acetic ethanol, carbon dioxide, peroxide were also detected as oxidation byproducts. This microdroplet-initiated process further enhanced under ultrasonication yield 2.66 ± 0.77 mM conversion from a single spray run for 30 min, selectivity 19.2% compared all oxygenated

Language: Английский

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Highly Selective Conversion of CH₄ to High Value‐Added C₁ Oxygenates over Pd Loaded ZnTi‐LDH

Advanced Energy Materials, Journal Year: 2023, Volume and Issue: 13(29)

Published: June 19, 2023

Abstract The selective oxidation of methane to high value‐added liquid oxygenated compounds under mild conditions is great significance promote the efficient utilization carbon source, but it also faces dilemma low activity and over‐oxidation. Here, ZnTi‐layered double hydroxides (LDH)‐A200 photocatalysts with Pd loading are prepared achieve methane, O 2 as an oxidant ambient condition. highest generation rate C 1 products (methanol formaldehyde) reaches 4924.47 µmol g −1 h a selectivity close 100% over 0.5Pd‐ZnTi‐LDH‐A200, which 20 times higher than that bare ZnTi‐LDH‐A200. photochemical results show modified present much separation efficiency electron‐hole pairs. In situ X–ray photoelectron spectroscopy indicates nanoparticles hole acceptor, beneficial charge in photocatalysis. Furthermore, electron spinresonance temperature–programmed–desorption analysis prove helpful adsorption oxygen on surface ZnTi‐LDH‐A200, promoting production reactive species activation methane. All these factors work together conversion CH 4 oxygenates.

Language: Английский

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