Chemical looping beyond combustion – a perspective

Energy & Environmental Science, Journal Year: 2020, Volume and Issue: 13(3), P. 772 - 804

Published: Jan. 1, 2020

Facilitated by redox catalysts capable of catalytic reactions and reactive separation, chemical looping offers exciting opportunities for intensified production.

Language: Английский

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Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Chemical Reviews, Journal Year: 2022, Volume and Issue: 123(9), P. 6039 - 6106

Published: Sept. 1, 2022

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, nanoparticles in the framework-associated sites extra-framework positions, thus affording metal-in-zeolite catalysts outstanding activity, unique shape selectivity, enhanced recyclability processes of Brønsted acid-, Lewis metal-catalyzed reactions. Especially, thanks to advances zeolite synthesis characterization techniques recent years, zeolite-confined (denoted as metal@zeolite composites) have experienced rapid development heterogeneous catalysis, owing combination merits both intrinsic properties. In this review, we will present developments strategies incorporating tailoring zeolites advanced identification location, distribution, coordination environment species zeolites. Furthermore, catalytic applications demonstrated, emphasis on composites hydrogenation, dehydrogenation, oxidation Finally, point out current challenges future perspectives precise synthesis, atomic level identification, practical application catalyst system.

Language: Английский

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Continuous Partial Oxidation of Methane to Methanol Catalyzed by Diffusion-Paired Copper Dimers in Copper-Exchanged Zeolites

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(29), P. 11641 - 11650

Published: June 21, 2019

Copper-exchanged zeolites can continuously and selectively catalyze the partial oxidation of methane to methanol using only oxygen water at low temperatures, but genesis nature active sites are currently unknown. Herein, we demonstrate that this reaction is catalyzed by a [Cu–O–Cu]2+ motif forms via hypothesized proton-aided diffusion hydrated Cu ions within cages SSZ-13 zeolites. While various configurations may be present for oxidation, dimeric primary site selective oxidation. Mechanistically, CH4 activation proceeds rate-determining C–H scission form surface-bound C1 intermediate either desorbed as in presence H2O/H+ or completely oxidized CO2 gas-phase O2. High selectivity obtained with (i) high pressures (ii) maximizing dimer formation Al content loadings.

Language: Английский

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Misconceptions and challenges in methane-to-methanol over transition-metal-exchanged zeolites

Nature Catalysis, Journal Year: 2019, Volume and Issue: 2(6), P. 485 - 494

Published: May 20, 2019

Language: Английский

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Binary Au–Cu Reaction Sites Decorated ZnO for Selective Methane Oxidation to C1 Oxygenates with Nearly 100% Selectivity at Room Temperature

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 144(2), P. 740 - 750

Published: Dec. 20, 2021

Direct and efficient oxidation of methane to methanol the related liquid oxygenates provides a promising pathway for sustainable chemical industry, while still remaining an ongoing challenge owing dilemma between activation overoxidation. Here, ZnO with highly dispersed dual Au Cu species as cocatalysts enables selective photocatalytic conversion one-carbon (C1) using O2 oxidant operated at ambient temperature. The optimized AuCu-ZnO photocatalyst achieves up 11225 μmol·g-1·h-1 primary products (CH3OH CH3OOH) HCHO nearly 100% selectivity, resulting in 14.1% apparent quantum yield 365 nm, much higher than previous best photocatalysts reported oxygenates. In situ EPR XPS disclose that serve photoinduced electron mediators promote •OOH, simultaneously is hole acceptor enhance H2O •OH, thus synergistically promoting charge separation transformation. This work highlights significances co-modification suitable on simultaneous regulation activity selectivity.

Language: Английский

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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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Methane selective oxidation to methanol by metal-exchanged zeolites: a review of active sites and their reactivity

Catalysis Science & Technology, Journal Year: 2019, Volume and Issue: 9(8), P. 1744 - 1768

Published: Jan. 1, 2019

A review of the recent progress in revealing structures, formation, and reactivity active sites Fe-, Co-, Ni- Cu-exchanged zeolites as well outlooks on future research challenges opportunities is presented.

Language: Английский

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Selective Photo-oxidation of Methane to Methanol with Oxygen over Dual-Cocatalyst-Modified Titanium Dioxide

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(23), P. 14318 - 14326

Published: Nov. 23, 2020

Direct and selective oxidation of CH4 with dioxygen to methanol is a "dream reaction" in modern catalysis yet remains great challenge. Here, we report that TiO2 loaded dual cocatalysts, is, nanometals cobalt oxide (CoOx) nanoclusters, capable selectively catalyzing CH3OH at room temperature under photoexcitation using abundant inexpensive O2 as an oxidant. The best activity for the formation primary products, CH3OOH CH3OH, up 50.8 μmol 2 h 95% selectivity. Mechanistic studies elucidate superior selectivity result from synergistic effect CoOx. Nanometals enhance conversion by promoting separation photoexcited electron reduction O2. CoOx mediates mild process suppressing highly oxidative •OH radicals can further oxidize HCHO CO2, thereby preserving high toward oxygenated products. This work provides prototype designing efficient photocatalysts conditions.

Language: Английский

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Structure–Activity Relationships That Identify Metal–Organic Framework Catalysts for Methane Activation

ACS Catalysis, Journal Year: 2019, Volume and Issue: 9(4), P. 3576 - 3587

Published: March 8, 2019

In this work, we leverage advances in computational screening based on periodic density functional theory (DFT) to study a diverse set of experimentally derived metal–organic frameworks (MOFs) with accessible metal sites for the oxidative activation methane. We find that thermodynamic favorability forming metal-oxo active site has strong, inverse correlation reactivity toward C–H bond wide range MOFs. This scaling relationship is found hold over MOFs varying coordination environments and compositions, provided bonds framework atoms are conserved. The need conserve an important constraint correlations but also demonstrates route intentionally break generate novel catalytic reactivity. Periodic trends observed across data screened MOFs, later transition metals less stable more reactive sites. Collectively, results work provide robust rules-of-thumb choosing investigate methane at moderate reaction conditions.

Language: Английский

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Activation and conversion of alkanes in the confined space of zeolite-type materials

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(15), P. 8511 - 8595

Published: Jan. 1, 2021

Microporous zeolite-type materials are able to activate and efficiently convert stable C₁⁺alkanes. This review analyzes, at the molecular level, role of active sites contribution diffusion, shape-selectivity confinement effects.

Language: Английский

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