Consequences of exchange-site heterogeneity and dynamics on the UV-visible spectrum of Cu-exchanged SSZ-13

Chemical Science, Journal Year: 2018, Volume and Issue: 10(8), P. 2373 - 2384

Published: Dec. 28, 2018

Theory and experiment reveal relationships between observed UV-visible spectra ion exchange site types, nuclearity, finite-temperature dynamics in Cu exchanged chabazite (SSZ-13) zeolites.

Language: Английский

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Quantum Chemical Characterization of Structural Single Fe(II) Sites in MIL-Type Metal–Organic Frameworks for the Oxidation of Methane to Methanol and Ethane to Ethanol

ACS Catalysis, Journal Year: 2019, Volume and Issue: 9(4), P. 2870 - 2879

Published: Jan. 10, 2019

Single non-heme Fe(II) ions present as structural moieties in several metal–organic frameworks (e.g., MIL-100, MIL-101, and MIL-808, where MIL indicates Materials of Institute Lavoisier) are identified by Kohn–Sham density functional calculations promising catalysts for C–H bond activation, with energetic barriers low 40 kJ mol–1 ethane 60 methane following the oxidative activation iron. The rate-determining step is N2O has a barrier 140 mol–1. Through consideration full reaction profile leading to corresponding alcohols, ethanol methanol, we have key changes chemical composition node that would modulate catalytic activity. thermal stabilities these materials, together scalability their syntheses, make them attractive selective low-temperature conversion light alkanes higher-value oxygenates.

Language: Английский

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Structure, Dynamics, and Reactivity for Light Alkane Oxidation of Fe(II) Sites Situated in the Nodes of a Metal–Organic Framework

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(45), P. 18142 - 18151

Published: Oct. 31, 2019

Metal organic frameworks (MOFs), with their crystalline, porous structures, can be synthesized to incorporate a wide range of catalytically active metals in tailored surroundings. These materials have potential as catalysts for conversion light alkanes, feedstocks available large quantities from shale gas that are changing the economics manufacturing commodity chemicals. Mononuclear high-spin (S = 2) Fe(II) sites situated nodes MOF MIL-100(Fe) convert propane via dehydrogenation, hydroxylation, and overoxidation pathways reactions atomic oxidant N2O. Pair distribution function analysis, N2 adsorption isotherms, X-ray diffraction patterns, infrared Raman spectra confirm single-phase crystallinity stability under reaction conditions (523 K vacuo, 378-408 C3H8 + N2O). Density functional theory (DFT) calculations illustrate mechanism formation 2-propanol, propylene, 1-propanol involving oxidation Fe(III) Fe(IV)═O intermediate. The speciation dynamic interchange was characterized by situ absorption spectroscopy ex Mössbauer spectroscopy. catalytic relevance number such were determined using chemical titrations NO. C3H6 production rates found first-order N2O partial pressure zero-order pressure, consistent DFT predict rate determining. broken symmetry method show Fe-trimer affecting contain antiferromagnetically coupled iron species, highlight importance stabilizing species effecting alkane at low temperatures (<408 K).

Language: Английский

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Recent Progress in Direct Conversion of Methane to Methanol Over Copper-Exchanged Zeolites

Frontiers in Chemistry, Journal Year: 2019, Volume and Issue: 7

Published: July 17, 2019

The conversion of methane into an easily transportable liquid fuel or chemicals has become a highly sought-after goal spurred by the increasing availability cheap and abundant natural gas. While utilization for production syngas its subsequent via indirect route is typical, it cost-intensive, alternative direct routes have been investigated actively. One most promising directions among these low-temperature partial oxidation to methanol over metal-loaded zeolite, which mimics facile enzymatic chemistry oxidation. Thus mono-, bi-, trinuclear oxide compounds iron copper stabilized on ZSM-5 mordenite, are structurally analogous those found in monooxygenases, demonstrated catalytic performances. two major problems theses zeolites low yield batch-like non-catalytic reaction systems challenging extend industrial scale. In this mini-review, attention was given copper-loaded zeolite systems. A brief introduction current status applied metal-containing including ones with ions given. Next, analyzing extensive experimental theoretical data available, consensus researchers achieve target high discussed terms topology, active species, parameters. Finally, recent efforts continuous from aiming process summarized.

Language: Английский

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Water Is the Oxygen Source for Methanol Produced in Partial Oxidation of Methane in a Flow Reactor over Cu-SSZ-13

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(28), P. 11962 - 11966

Published: June 29, 2020

Direct oxidation of methane to methanol is a long-standing challenge in the heterogeneous catalysis community. This Communication demonstrates that water, not dioxygen, main source oxygen present produced partial over Cu-SSZ-13 continuous-flow reactor. confirmed by experiments performed absence molecular and with use 18O-labeled water. These findings should lead new approaches for improving properties copper zeolites.

Language: Английский

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