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

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+ andmore » Cu3O3 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:
Grant/Contract Number:
AC02-76SF00515
Type:
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)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; density functional theory; methanol; partial methane oxidation; zeolites; [CuOH]+
OSTI Identifier:
1348922