Methane Oxidation to Methanol

Chemical Reviews, Journal Year: 2022, Volume and Issue: 123(9), P. 6359 - 6411

Published: Dec. 2, 2022

The direct transformation of methane to methanol remains a significant challenge for operation at larger scale. Central this is the low reactivity conditions that can facilitate product recovery. This review discusses issue through examination several promising routes and an evaluation performance targets are required develop process We explore methods currently used, emergence active heterogeneous catalysts their design reaction mechanisms provide critical perspective on future operation. Initial experiments discussed where identification gas phase radical chemistry limited further development by approach. Subsequently, new class catalytic materials based natural systems such as iron or copper containing zeolites were explored milder conditions. key issues these technologies conversion often overoxidation products. Despite this, interest high in wider appeal effective route products from C–H activation, particularly with need transition net carbon zero renewable sources exciting.

Language: Английский

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Atomic Insights into the Cu Species Supported on Zeolite for Direct Oxidation of Methane to Methanol via Low‐Damage HAADF‐STEM

Advanced Materials, Journal Year: 2023, Volume and Issue: 35(25)

Published: April 4, 2023

Precise determination of the structure-property relationship zeolite-based metal catalysts is critical for development toward practical applications. However, scarcity real-space imaging low-atomic-number (LAN) materials due to electron-beam sensitivity zeolites has led continuous debates regarding exact LAN configurations. Here, a low-damage high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) technique employed direct visualization and (Cu) species in ZSM-5 zeolite frameworks. The structures Cu are revealed based on evidence also proved by complementary spectroscopy results. correlation between characteristic size Cu/ZSM-5 their oxidation methane methanol reaction properties unveiled. As result, mono-Cu stably anchored Al pairs inside channels identified as key structure higher C1 oxygenates yield selectivity methane. Meanwhile, local topological flexibility rigid frameworks induced agglomeration revealed. This work exemplifies combination characterization serves complete arsenal revealing relationships supported metal-zeolite catalysts.

Language: Английский

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Maximizing Active Fe Species in ZSM-5 Zeolite Using Organic-Template-Free Synthesis for Efficient Selective Methane Oxidation

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(10), P. 5888 - 5898

Published: Feb. 14, 2023

The selective oxidation of CH4 in the aqueous phase to produce valuable chemicals has attracted considerable attention due its mild reaction conditions and simple process. As most widely studied catalyst for this reaction, Fe-ZSM-5 demonstrates high intrinsic activity selectivity; however, prepared using conventional methods a limited number active Fe sites, resulting low conversion per unit mass catalyst. This study reports facile organic-template-free synthesis strategy that enables incorporation more into zeolite framework with higher dispersion degree compared methods. Because incorporated way is readily transformed isolated extra-framework species under thermal treatment, overall effect method (Fe-HZ5-TF) 3 times as many catalytically sites Fe-ZSM-5. When used 0.5 M H2O2 at 75 °C, Fe-HZ5-TF produced C1 oxygenate yield 109.4 mmol gcat-1 h-1 (a HCOOH selectivity 91.1%), surpassing other catalysts reported date. Spectroscopic characterization density functional theory calculations revealed are mononuclear form [(H2O)3Fe(IV)═O]2+ bound Al pairs framework. differs from Fe-ZSM-5, where binuclear acts site. Analysis product evolution during suggests radical-driven pathway explain activation site subsequent oxygenates.

Language: Английский

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In Situ UV–Vis–NIR Absorption Spectroscopy and Catalysis

Chemical Reviews, Journal Year: 2024, Volume and Issue: 124(5), P. 2352 - 2418

Published: Feb. 26, 2024

This review highlights

Language: Английский

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Competition between Mononuclear and Binuclear Copper Sites across Different Zeolite Topologies

JACS Au, Journal Year: 2024, Volume and Issue: 4(1), P. 197 - 215

Published: Jan. 4, 2024

A key challenge for metal-exchanged zeolites is the determination of metal cation speciation and nuclearity under synthesis reaction conditions. Copper-exchanged zeolites, which are widely used in automotive emissions control potential catalysts partial methane oxidation, have particular evidenced a wide variety Cu structures that observed to change with exposure conditions, zeolite composition, topology. Here, we develop predictive models CHA, MOR, BEA, AFX, FER topologies using interatomic potentials, quantum chemical calculations, Monte Carlo simulations interrogate this vast configurational compositional space. Model predictions rationalize experimentally differences between Cu-zeolites wide-body literature, including populations, structural variations, methanol per yields. Our results show both topological features commonly Al-siting biases MOR increase population binuclear sites, explaining small mononuclear sites these materials relative other such as CHA BEA. Finally, machine learning classification model determine preference form or at different Al configurations 200 international database. reveal several extreme ends vs spectrum, highlighting synthetic options realization strong preferences.

Language: Английский

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Direct Methane to Methanol Conversion: An Overview of Non‐Syn Gas Catalytic Strategies

The Chemical Record, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 16, 2025

Abstract Direct methane to methanol conversion is a dream reaction in industrial chemistry, which takes inspiration from the biological production catalysed by monooxygenase enzymes (MMOs). Over years, extensive studies have been conducted on this topic bioengineering MMOs, and tailoring methods isolate MMOs active form. Similarly, remarkable achievements noted other activation strategies such as use of heterogeneous catalysts or molecular catalysts. In review, we outline metabolism performed methanotrophs detail latest advancements site structures catalytic mechanisms both types MMOs. Also, recent progress bioinspired approaches using various catalysts, especially first‐row transition metal zeolites mechanistic insights are discussed. addition, complexes “Periana catalyst” for through methyl ester formation presence strong acids also detailed. Compared zeolites‐mediated field, utilisation application still its nascent phase further research required overcome limitations these effectively.

Language: Английский

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Selective Catalytic Oxidation of Methane to Methanol in Aqueous Medium over Copper Cations Promoted by Atomically Dispersed Rhodium on TiO₂

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(18)

Published: Feb. 24, 2022

Direct conversion of methane into value-added chemicals, such as methanol under mild conditions, is a promising route for industrial applications. In this work, atomically dispersed Rh on TiO2 suspended in an aqueous solution was used the oxidation to methanol. Promoted by copper cations (as co-catalyst) solution, catalysts exhibited high activity and selectivity production using molecular oxygen with presence carbon monoxide at 150 °C reaction pressure 31 bar. Millimole level yields were reached higher than 99 % Rh/TiO2 promotion cation. CO reductive agent generate H2 from O, which led formation O2 through . Atomically activated C-H bond CH4 catalyzed Copper maintained low-valence state Rh. Moreover, acted scavenger suppressing overoxidation, thus leading

Language: Английский

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Exploring the Impact of Active Site Structure on the Conversion of Methane to Methanol in Cu‐Exchanged Zeolites

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(23)

Published: April 4, 2024

Abstract In the past, Cu‐oxo or ‐hydroxy clusters hosted in zeolites have been suggested to enable selective conversion of methane methanol, but impact active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling conjunction with experiments study these two factors partial oxidation Cu‐exchanged zeolite SSZ‐13. Phase diagrams developed from first‐principles suggest that Cu‐hydroxy dimers are stabilized when O 2 N used activate catalyst, respectively. We confirm predictions experimentally determine a stepwise process, can convert twice as much compared Cu‐hydroxyl dimers. Our models rationalize how Cu‐di‐oxo up molecules while Cu‐di‐hydroxyl only one molecule per catalytic cycle. These findings imply Cu clusters, at least oxo group hydroxyl groups needed This simple structure–activity relationship allows intuitively understand potential small oxygenated hydroxylated transition metal methanol.

Language: Английский

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Magnetic Exchange Coupling in Zeolite Copper Dimers and Its Contribution to Methane Activation

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(9), P. 6061 - 6071

Published: Feb. 22, 2024

The highly reactive binuclear [Cu2O]2+ active site in copper zeolites activates the inert C–H bond of methane at low temperatures, offering a potential solution to reduce flaring and mitigate atmospheric levels. While substantial progress has been made understanding activation by this core, one critical aspect, site's spin, remained undetermined. In study, we use variable-temperature, variable-field magnetic circular dichroism spectroscopy define ground state spin sites Cu-CHA Cu-MFI. This novel approach allows for site-selective determination exchange coupling between two centers specific cores heterogeneous mixture, circumventing drawbacks bulk techniques. These experimental findings are coupled density functional theory calculations elucidate magnetostructural correlations that different from those homogeneous Cu(II) complexes. states have reactivities governed how approaches site. introduces new zeolite topological control on reactivity.

Language: Английский

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Homolytic versus Heterolytic Methane Hydroxylation in Copper Zeolites

ACS Catalysis, Journal Year: 2025, Volume and Issue: unknown, P. 1249 - 1264

Published: Jan. 7, 2025

Oxygen-activated copper zeolites are capable of selectively converting methane to methanol at mild conditions, using a mono-oxygen bridged Cu(II) site [CuOCu]2+ as the active core. Based on previous DFT reports + CH4 reaction general consensus was reached concerning oxidation mechanism, where rate-limiting step involves homolytic C–H bond cleavage form [Cu(OH)Cu]2+ with physisorbed •CH3. An alternative possibility, i.e. heterolytic H-abstraction passing through four-center transition state give an intermediate Cu–CH3 bond, given consideration only in few recent studies, but found less favorable than radical activation. In this contribution methane-to-methanol conversion by Cu–CHA is investigated large cluster models and employing either DFT, extensive list 97 functionals, or high-level correlated DMRG/cu(4)-CASPT2 method. all cases dissociation most favorably proceeds via (S = 1) TS1r, whereas H-abstraction, TS1n, has 0) ground state. The results convincingly point route, calculated activation enthalpy 12.3 kcal/mol, compared 21.1 kcal/mol for dissociation. contrast, obtained strongly functional dependent. Conform preferred B3LYP (almost exclusively used model studies). However, many other hybrid meta-GGA functionals particular, agree present reopen debate validity rebound mechanism hydroxylation core also highlight need caution when relying specific elucidate mechanisms metal-based catalytic systems.

Language: Английский

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