Active sites and mechanisms in the direct conversion of methane to methanol using Cu in zeolitic hosts: a critical examination

Mark A. Newton; Amy J. Knorpp; Vitaly L. Sushkevich; Dennis Palagin; Jeroen A. van Bokhoven

doi:10.1039/c7cs00709d

CH4-to-CH3OH on Mononuclear Cu(II) Sites Supported on Al2O3: Structure of Active Sites from Electron Paramagnetic Resonance

10.26434/chemrxiv.13295879.v2 ◽

2021 ◽

Author(s):

Jordan Meyet ◽

Anton Ashuiev ◽

Gina Noh ◽

Mark Newton ◽

Daniel Klose ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Organometallic Chemistry ◽

Active Sites ◽

Spectroscopic Characterization ◽

Paramagnetic Resonance ◽

Transition Alumina ◽

Selective Conversion ◽

Conversion Of Methane ◽

Electron Paramagnetic ◽

Alumina Supports

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown to selectively convert methane to methanol under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric Cu(II). Herein, we report the formation of well-dispersed monomeric Cu(II) species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in gamma- and eta-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al2O)CuIIO(OH)]-,T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involve two of these isolated monomeric Cu(II) sites that play in concert.

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CH4-to-CH3OH on Mononuclear Cu(II) Sites Supported on Al2O3: Structure of Active Sites from Electron Paramagnetic Resonance

10.26434/chemrxiv.13295879.v1 ◽

2020 ◽

Author(s):

Jordan Meyet ◽

Anton Ashuiev ◽

Gina Noh ◽

Mark Newton ◽

Daniel Klose ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Organometallic Chemistry ◽

Active Sites ◽

Spectroscopic Characterization ◽

Paramagnetic Resonance ◽

Transition Alumina ◽

Selective Conversion ◽

Conversion Of Methane ◽

Electron Paramagnetic ◽

Alumina Supports

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown to selectively convert methane to methanol under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric Cu(II). Herein, we report the formation of well-dispersed monomeric Cu(II) species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in gamma- and eta-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al2O)CuIIO(OH)]-,T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involve two of these isolated monomeric Cu(II) sites that play in concert.

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Effects of single and double active sites of Cu oxide clusters over MFI zeolite for direct conversion of methane to methanol: DFT calculations

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05435f ◽

2021 ◽

Author(s):

Watinee Nunthakitgoson ◽

Anawat Thivasasith ◽

Thana Maihom ◽

Chularat Wattanakit

Keyword(s):

Dft Calculations ◽

Active Sites ◽

Direct Conversion ◽

Mfi Zeolite ◽

Zeolite Framework ◽

Conversion Of Methane

In this context, we investigate the effect of the single and double active sites of Cu oxide clusters over the MFI zeolite framework for direct conversion of methane to methanol....

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Active sites and mechanism of the direct conversion of methane and carbon dioxide to acetic acid over the zinc-modified H-ZSM-5 zeolite

Catalysis Science & Technology ◽

10.1039/c9cy01749f ◽

2019 ◽

Vol 9 (22) ◽

pp. 6297-6307 ◽

Cited By ~ 1

Author(s):

Peng Zhang ◽

Xuejing Yang ◽

Xiuli Hou ◽

Jianli Mi ◽

Zhizhong Yuan ◽

...

Keyword(s):

Carbon Dioxide ◽

Acetic Acid ◽

Catalytic Activity ◽

Active Sites ◽

Direct Conversion ◽

Conversion Of Methane ◽

Zeolite P

The catalytic activity of the conversion of CH4 and CO2 on zinc modified H-ZSM-5 is strongly dependent on the structure of the active sites.

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Comparing the Nature of Active Sites in Cu-loaded SAPO-34 and SSZ-13 for the Direct Conversion of Methane to Methanol

Catalysts ◽

10.3390/catal10020191 ◽

2020 ◽

Vol 10 (2) ◽

pp. 191 ◽

Cited By ~ 1

Author(s):

Karoline Kvande ◽

Dimitrios K. Pappas ◽

Michael Dyballa ◽

Carlo Buono ◽

Matteo Signorile ◽

...

Keyword(s):

Active Sites ◽

Co Adsorption ◽

Direct Conversion ◽

Active Species ◽

Ch4 Oxidation ◽

Structure Activity ◽

Conversion Of Methane ◽

Higher Temperature ◽

X Ray Absorption ◽

Better Than

On our route towards a more sustainable future, the use of stranded and underutilized natural gas to produce chemicals would be a great aid in mitigating climate change, due to the reduced CO2 emissions in comparison to using petroleum. In this study, we investigate the performance of Cu-exchanged SSZ-13 and SAPO-34 microporous materials in the stepwise, direct conversion of methane to methanol. With the use of X-ray absorption spectroscopy, infrared (in combination with CO adsorption) and Raman spectroscopy, we compared the structure–activity relationships for the two materials. We found that SSZ-13 performed significantly better than SAPO-34 at the standard conditions. From CH4-TPR, it is evident that SAPO-34 requires a higher temperature for CH4 oxidation, and by changing the CH4 loading temperature from 200 to 300 °C, the yield (μmol/g) of SAPO-34 was increased tenfold. As observed from spectroscopy, both three- and four-fold coordinated Cu-species were formed after O2-activation; among them, the active species for methane activation. The Cu speciation in SAPO-34 is distinct from that in SSZ-13. These deviations can be attributed to several factors, including the different framework polarities, and the amount and distribution of ion exchange sites.

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Copper-Modified Zeolites and Silica for Conversion of Methane to Methanol

Catalysts ◽

10.3390/catal8110545 ◽

2018 ◽

Vol 8 (11) ◽

pp. 545 ◽

Cited By ~ 14

Author(s):

Xueting Wang ◽

Natalia Martin ◽

Johan Nilsson ◽

Stefan Carlson ◽

Johan Gustafson ◽

...

Keyword(s):

Active Sites ◽

Copper Ions ◽

Ambient Pressure ◽

Direct Conversion ◽

Minor Amount ◽

Powder Materials ◽

Methanol Production ◽

Conversion Of Methane ◽

First Time

Powder materials containing copper ions supported on ZSM-5 (Cu-Zeolite Socony Mobil-5) and SSZ-13 (Cu-Standard Oil synthesised zeolite-13), and predominantly CuO nanoparticles on amorphous SiO 2 were synthesised, characterised, wash-coated onto ceramic monoliths and, for the first time, compared as catalysts for direct conversion of methane to methanol (DCMM) at ambient pressure (1 atm) using O 2 , N 2 O and NO as oxidants. Methanol production was monitored and quantified using Fourier transform infrared spectroscopy. Methanol is formed over all monolith samples, though the formation is considerably higher for the copper-exchanged zeolites. Hence, copper ions are the main active sites for DCMM. The minor amount of methanol produced over the Cu/SiO 2 sample, however, suggests that zeolites are not the sole substrate that can host those active copper sites but also silica. Further, we present the first ambient pressure in situ infrared spectroscopic measurements revealing the formation and consumption of surface methoxy species, which are considered to be key intermediates in the DCMM reaction.

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CH4-to-CH3OH on Mononuclear Cu(II) Sites Supported on Al2O3: Structure of Active Sites from Electron Paramagnetic Resonance

10.26434/chemrxiv.13295879 ◽

2020 ◽

Author(s):

Jordan Meyet ◽

Anton Ashuiev ◽

Gina Noh ◽

Mark Newton ◽

Daniel Klose ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Organometallic Chemistry ◽

Active Sites ◽

Spectroscopic Characterization ◽

Paramagnetic Resonance ◽

Transition Alumina ◽

Selective Conversion ◽

Conversion Of Methane ◽

Electron Paramagnetic ◽

Alumina Supports

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown to selectively convert methane to methanol under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric Cu(II). Herein, we report the formation of well-dispersed monomeric Cu(II) species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in gamma- and eta-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al2O)CuIIO(OH)]-,T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involve two of these isolated monomeric Cu(II) sites that play in concert.

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