A review on the active sites for direct oxidation of methane to methanol by copper-zeolites: Coordination structure, formation and activity

Coordination Chemistry Reviews, Journal Year: 2024, Volume and Issue: 503, P. 215637 - 215637

Published: Jan. 10, 2024

Language: Английский

---

Structure and Reactivity of Binuclear Cu Active Sites in Cu-CHA Zeolites for Stoichiometric Partial Methane Oxidation to Methanol

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(5), P. 3647 - 3663

Published: Feb. 21, 2024

Aluminosilicate zeolites exchanged with copper ions facilitate partial methane oxidation (PMO) to methanol in stoichiometric and reduction cycles, yet the identities of active Cu sites details reaction mechanism remain debated. Here, we use high-symmetry chabazite (CHA) zeolite framework as a model support probe relationship between bulk composition, speciation, response various oxidizing reducing treatments. Density functional theory first-principles thermodynamics combined statistical models reveal that speciation composition depend strongly on Al configuration external gas conditions. Cu-CHA samples were synthesized survey broad regions Si/Al Cu/Al space proximity. Characterization by situ X-ray absorption UV–visible spectroscopy during exposure different conditions extent is sensitive activation thus both kinetic thermodynamic factors influence oxidizability given material. Similar characterizations CO titrates Cu2+ amounts suggesting presence O- O2-bridged species. In contrast, CH4 autoreduction (He) treatments reduce similar but smaller numbers than CO, implicating dimers potential common intermediate former pathways. A systematic increase yields (per Cu) PMO cycles fraction binuclear Ox-bridged suggests these species sites, depicted an updated mechanism.

Language: Английский

---

Copper–oxygen adducts: new trends in characterization and properties towards C–H activation

Chemical Science, Journal Year: 2024, Volume and Issue: 15(27), P. 10308 - 10349

Published: Jan. 1, 2024

Recent progresses in Cu–oxygen adducts towards recalcitrant C–H activation are reviewed with focus on Cu metalloenzymes and bioinspired synthetic models, mono- to polynuclear complexes, working under homogeneous heterogeneous catalytic conditions.

Language: Английский

---

Tuning the Ni/Co Ratios and Surface Concentration of Reduced Molybdenum States for Enhanced Electrocatalytic Performance in Trimetallic Molybdates: OER, HER, and MOR Activity

ACS Applied Energy Materials, Journal Year: 2022, Volume and Issue: 5(11), P. 14059 - 14070

Published: Oct. 18, 2022

The heterogeneous nature of trimetallic catalyst systems comes with beneficial synergy for catalytic applications. Nonetheless, the challenges associated to validate and control critical characteristics enhanced electrocatalytic efficiencies are yet be known. Herein, a genre catalysts were synthesized Ni, Co, Mo metals, whose morphological, structural, electronic, interface properties depend on Ni/Co Mo+4/Mo+5 ratios dominant element surface catalyst. results suggest that introduction third metal, is, Mo, is only when ratio optimally maintained. By combining electronic structural analyses such as electron energy loss spectroscopy, X-ray photoelectron line scan, Raman spectra, electrochemical data, it was realized metallic Ni favor oxygen evolution reaction (OER), methanol oxidation (MOR) activity, respectively. Interestingly, adsorbed water molecules found vital higher performance in both OER MOR processes. chronopotentiometry tests performed optimized Ni56Co7Mo37 showed an overpotential around ca. 309 mV at 720 mA·cm–2 even after 17 h (and also Tafel slope 60 mV·dec–1 10 mA·cm–2). peak current density (from cyclic voltammetry tests) catalyst, Ni66Co31Mo3 (for MOR), almost 300-fold activity 1 M KOH + CH3OH solution compared KOH. Further, comparative studies conducted bimetallic understand better combinations promoting OER, hydrogen reaction, efficiencies. This work highlights importance maintaining elemental composition bulk lead active environment processes thereby opening gateways rational design electrocatalysts.

Language: Английский

---

Investigation of the Active-Site Structure of Cu-CHA Catalysts for the Direct Oxidation of Methane to Methanol Using In Situ UV–Vis Spectroscopy

Energy & Fuels, Journal Year: 2023, Volume and Issue: 37(13), P. 9411 - 9418

Published: June 13, 2023

Among Cu-containing zeolites, Cu-CHA exhibits relatively high catalytic performance in direct oxidation of CH4 to CH3OH a continuous-flow reaction CH4–O2–H2O gas mixture. The activity varies with its composition, e.g., Cu loading and Si/Al ratio, suggesting formation different active-site structures depending on the composition. In present study, identify catalytically active species, 18 catalysts having three ratios six loadings at each ratio were prepared, their was evaluated. Based performance, species categorized into groups: those selectivity but low formed Cu/Al (group A); for production medium B); complete CO2 C). Thus, representative corresponding groups selected analyzed using situ UV–vis spectroscopy, from which spectral features involved extracted difference between spectra under reduction conditions conditions. comparison simulated various literature, main suggested: Cu2+ six-membered ring SSZ-13 zeolites water-coordinated CuOH+ eight-membered zeolite group A; mono-(μ-oxo) di-Cu B; μ-η2:η2 peroxide di-Cu, trans-μ-1,2-peroxo and/or mono-/bis-(μ-hydroxo) C. Therefore, is proposed as CH3OH.

Language: Английский

---

Effect of Framework Composition and NH₃ on the Diffusion of Cu⁺ in Cu-CHA Catalysts Predicted by Machine-Learning Accelerated Molecular Dynamics

ACS Central Science, Journal Year: 2023, Volume and Issue: 9(11), P. 2044 - 2056

Published: Oct. 18, 2023

Cu-exchanged zeolites rely on mobile solvated Cu+ cations for their catalytic activity, but the role of framework composition in transport is not fully understood. Ab initio molecular dynamics simulations can provide quantitative atomistic insight are too computationally expensive to explore large length and time scales or diverse compositions. We report a machine-learning interatomic potential that accurately reproduces ab results effectively generalizes allow multinanosecond supercells chemical Biased unbiased [Cu(NH3)2]+ mobility show aluminum pairing eight-membered rings accelerates local hopping demonstrate increased NH3 concentration enhances long-range diffusion. The probability finding two complexes same cage, which key SCR-NOx reaction, increases with Cu content Al does correlate Cu+. Supporting experimental evidence was obtained from reactivity tests Cu-CHA catalysts controlled composition.

Language: Английский

---

Correlative In Situ Spectro-Microscopy of Supported Single CuO Nanoparticles: Unveiling the Relationships between Morphology and Chemical State during Thermal Reduction

ACS Nano, Journal Year: 2024, Volume and Issue: 18(21), P. 13714 - 13725

Published: May 14, 2024

The activity, selectivity, and lifetime of nanocatalysts critically depend on parameters such as their morphology, support, chemical composition, oxidation state. Thus, correlating these with final catalytic properties is essential. However, heterogeneity across nanoparticles (NPs) generally expected. Moreover, nature can also change during reactions. Therefore, investigating catalysts in situ at the single-particle level provides insights into how tunable affect efficiency. To unravel this question, we applied spectro-microscopy to investigate thermal reduction SiO2-supported copper oxide NPs ultrahigh vacuum. Copper was selected since its state morphological transformations strongly impact product selectivity many Here, evolution NPs' monitored annealing correlated morphology situ. A reaction front observed CuO Cu2O. From temperature dependence front, activation energy extracted. Two were found influence NP reduction: initial nanoparticle size SiO2. substrate. CuOx be completed first smaller favored over partially reduced SiOx regions that resulted from X-ray beam irradiation. This methodology resolution a way isolating diverse morphologic, electronic, influences reaction. knowledge gained crucial for future design more complex multimetallic systems.

Language: Английский

---

Direct oxidation of methane to methanol using CuMoO₄

RSC Advances, Journal Year: 2023, Volume and Issue: 13(8), P. 5393 - 5404

Published: Jan. 1, 2023

Upgrading methane into methanol or other high value-added chemicals is not only beneficial to mitigate the greenhouse effect, but also provides basic raw materials for industrial production. Nowadays, most research limited zeolite systems, and it a considerable challenge extend support metal oxides while achieving yield of methanol. In this paper, we take advantage impregnation methods synthesise novel Cu/MoO

Language: Английский

---

Formation of HCHO, CO and H₂ by methane oxidation with O₂ over Cu catalysts stabilized in silicoaluminophosphates

Catalysis Science & Technology, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

The catalytic performance of Cu catalysts supported on SAPO34 (denoted as Cu/SAPO) for methane oxidation with O 2 has been investigated in detail.

Language: Английский

---

Catalytic oxidation of methane for methanol production over copper sepiolite: Effect of noble metals

Chinese Journal of Chemical Engineering, Journal Year: 2025, Volume and Issue: unknown

Published: March 1, 2025

Language: Английский

---