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Title: Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites

Abstract

Direct conversion of methane to methanol using oxygen is experiencing renewed interest owing to the availability of new natural gas resources. Copper-exchanged zeolites such as mordenite and ZSM-5 have shown encouraging results, and di- and tri-copper species have been suggested as active sites. Recently, small eight-membered ring (8MR) zeolites including SSZ-13, -16, and -39 have been shown to be active for methane oxidation, but the active sites and reaction mechanisms in these 8MR zeolites are not known. In this work, we use density functional theory (DFT) calculations to systematically evaluate monocopper species as active sites for the partial methane oxidation reaction in Cu-exchanged SSZ-13. On the basis of kinetic and thermodynamic arguments, we suggest that [Cu IIOH] + species in the 8MR are responsible for the experimentally observed activity. Furthermore, our results successfully explain the available spectroscopic data and experimental observations including (i) the necessity of water for methanol extraction and (ii) the effect of Si/Al ratio on the catalyst activity. Monocopper species have not yet been suggested as an active site for the partial methane oxidation reaction, and our results suggest that [Cu IIOH] + active site may provide complementary routes for methane activation in zeolites in addition tomore » the known [Cu–O–Cu] 2+ and Cu 3O 3 motifs.« less

Authors:
 [1];  [2];  [3];  [1];  [4]
  1. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Tianjin Univ. (People's Republic of China)
  3. Stanford Univ., Stanford, CA (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States); Karlsruhe Institute of Technology (Germany)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1348922
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 6; Journal Issue: 10; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; density functional theory; methanol; partial methane oxidation; zeolites; [CuOH]+

Citation Formats

Kulkarni, Ambarish R., Zhao, Zhi -Jian, Siahrostami, Samira, Nørskov, Jens K., and Studt, Felix. Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites. United States: N. p., 2016. Web. doi:10.1021/acscatal.6b01895.
Kulkarni, Ambarish R., Zhao, Zhi -Jian, Siahrostami, Samira, Nørskov, Jens K., & Studt, Felix. Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites. United States. doi:10.1021/acscatal.6b01895.
Kulkarni, Ambarish R., Zhao, Zhi -Jian, Siahrostami, Samira, Nørskov, Jens K., and Studt, Felix. 2016. "Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites". United States. doi:10.1021/acscatal.6b01895. https://www.osti.gov/servlets/purl/1348922.
@article{osti_1348922,
title = {Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites},
author = {Kulkarni, Ambarish R. and Zhao, Zhi -Jian and Siahrostami, Samira and Nørskov, Jens K. and Studt, Felix},
abstractNote = {Direct conversion of methane to methanol using oxygen is experiencing renewed interest owing to the availability of new natural gas resources. Copper-exchanged zeolites such as mordenite and ZSM-5 have shown encouraging results, and di- and tri-copper species have been suggested as active sites. Recently, small eight-membered ring (8MR) zeolites including SSZ-13, -16, and -39 have been shown to be active for methane oxidation, but the active sites and reaction mechanisms in these 8MR zeolites are not known. In this work, we use density functional theory (DFT) calculations to systematically evaluate monocopper species as active sites for the partial methane oxidation reaction in Cu-exchanged SSZ-13. On the basis of kinetic and thermodynamic arguments, we suggest that [CuIIOH]+ species in the 8MR are responsible for the experimentally observed activity. Furthermore, our results successfully explain the available spectroscopic data and experimental observations including (i) the necessity of water for methanol extraction and (ii) the effect of Si/Al ratio on the catalyst activity. Monocopper species have not yet been suggested as an active site for the partial methane oxidation reaction, and our results suggest that [CuIIOH]+ active site may provide complementary routes for methane activation in zeolites in addition to the known [Cu–O–Cu]2+ and Cu3O3 motifs.},
doi = {10.1021/acscatal.6b01895},
journal = {ACS Catalysis},
number = 10,
volume = 6,
place = {United States},
year = 2016,
month = 8
}

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Cited by: 6works
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  • Rare-earth metal ions have proven to be particularly useful in zeolite catalysis, both as stabilizing ions and by virtue of their redox chemistry. In the research reported here, the europium Moessbauer spectra of hydrated and dehydrated euorpium-exchanged zeolites A, Y, and ZSM-5 have been studied. Eu(OH)/sub 2/.H/sub 2/O, used to ion exchange Eu/sup 2 +/ into the zeolites, immediately oxidizes to an Eu/sup 3 +/ complex in a deoxygenated aqueous solution. This same reaction occurs in the solid state for Eu(OH)/sub 2/.H/sub 2/O. An investigation into the role of europium in the thermolytic decomposition of water has been made, andmore » the redox changes from the 3+ to the 2+ oxidation states of europium in zeolites Y and ZSM-5 have been confirmed by EPR. The Moessbauer isomer shifts are sufficiently sensitive to detect the difference in the chemical environment of Eu/sup 3 +/ as a consequence of oxidation by chlorine and oxygen. No evidence of Eu/sup 4 +/ has been found in an isomer shift range of +- 35 mm/s. Metal ions produced by dissolving europium metal in liquid ammonia can be exchanged into the zeolites to give an Eu/sup 2 +/ species as indicated by Moessbauer spectroscopy.« less
  • The study deals with the identification of the active nickel phase as a function of the oxygen conversion during the partial oxidation of methane to synthesis gas by means of in situ high-temperature X-ray diffraction (HTXRD), semi-in situ X-ray photoelectron spectroscopy (XPS) on a nonporous model catalyst (wafer), activity measurements, and temperature-programmed surface reaction (TPSR) experiments. The results demonstrate that the combustion of methane partly proceeds on bulk nickel oxide. A highly active phase, which is associated with partially oxidized nickel, is suggested to account for the major part of the combustion reaction. Finally, the reforming of methane to synthesismore » gas calls for the presence of metallic nickel sites. Evidently, the nature of the active phase is not uniform along the catalyst bed under reaction conditions. This highly complicating factor should be taken into account when investigating the mechanism of the partial oxidation of methane to synthesis gas. It is concluded that the results of mechanistic studies conducted at high oxygen conversion levels using either a fluidized bed reactor or a pulse apparatus should be considered with care. 58 refs., 6 figs.« less
  • The syntheses of biomimetic complexes that mimic the major structural features of the hydroxylase component of methane monooxygenase enzyme (MMO) and, more importantly, that provide similar alkane functionalization activity, in the presence of an oxidant, have been of great interest to the discipline of bioinorganic chemistry. In this communication, we will demonstrate the feasibility of conducting biomimetic oxidation studies in H{sub 2}O with soluble substrates, i.e., alcohols (cyclohexanol, benzyl alcohol), using H{sub 2}O-stable MMO mimics at pH 4.2, and the oxidant, tert-butyl hydroperoxide (TBHP). Both the Mitusunobu procedure and the mesylate displacement reaction proceeded with complete inversion of the stereo-centermore » and provided optically pure penultimate intermediate (>99.9% ee). The synthesis was completed by reduction of the nitro group under standard conditions to deliver LY300164 in 87%. In summary, we have developed an efficient and environmentally benign synthesis of the 5H-2,3-benzodiazepine LY300164 that provides the optically pure compound in 51% overall yield. Intramolecular hydrazone alkylation led to a remarkably facile and selective formation of the benzodiazepine. Furthermore, the application of resins to whole-cell-based biotransformations should find general utility for similar reactions that are complicated by component inhibition and product isolation. 11 refs., 1 fig.« less
  • Pd was introduced by exchange in non-dealuminated and dealuminated mordenites. After activation under oxygen at 500 C, NO adsorption revealed the presence of isolated Pd{sup 2} ions and Pd/PdO particles. Two types of Pd ions were shown: the first one would be located in the small cavities and leads to the formation of dinitrosyl complexes, whereas the second one, probably sitting in the main channels, is responsible for the obtainment of mononitrosyl complexes. Pd/PdO particles are active in the direct combustion of CH{sub 4} by oxygen and poorly active in the selective reduction (SCR) of NO. Pd ions are activemore » for the NO SCR; the ions in the small cavities for accessibility reasons. In the case of the non-dealuminated mordenite catalyst, an activation under reactants is observed. Moreover, the activity is increased by the addition of 10 vol% water which is the opposite of the classical behavior of metal-loaded zeolites. Both phenomena are attributed to a migration of Pd ions from hidden to accessible sites. For the dealuminated sample, the observed deactivation seems to be due to a migration of isolated Pd ions into PdO particles located outside the zeolite matrix.« less
  • This paper reports selectivity in the products during single oxygen mediated oxidation of olefins included within dye-exchanged X and Y zeolites. Singlet oxygen is generated within a zeolite by irradiating a thiazine dye exchanged into zeolites. Oxazine and thiazine dye molecules can be readily exchanged for alkali cations present in the interior of faujasite (X and Y) zeolites. Depending on the status of hydration, these dye molecules exist either in monomeric or dimeric forms. We show here that when a thiazine dye molecule is present in its monomeric form within a zeolite, it serves as an excellent singlet oxygen sensitizer.more » Utilizing zeolite supercages as `active reaction cavities`, we have directed the reactive oxygen toward a particular face of the olefin and obtained a high selectivity in the products of oxidation. 18 refs., 4 figs.« less