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Sourav S, Wang Y, Kiani D, Baltrusaitis J, Fushimi RR, Wachs IE. New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na 2 WO 4 /SiO 2 Catalysts. Angew Chem Int Ed Engl 2021; 60:21502-21511. [PMID: 34339591 DOI: 10.1002/anie.202108201] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Indexed: 12/14/2022]
Abstract
The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na2 WO4 /SiO2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H2 -TPR, TAP and steady-state kinetics) experiments, that the long speculated crystalline Na2 WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2 Hx and over-oxidizing CHy to CO and (ii) molten Na2 WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2 H6 to C2 H4 . These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2 WO4 /SiO2 catalysts.
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Affiliation(s)
- Sagar Sourav
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA.,Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Yixiao Wang
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA
| | - Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Rebecca R Fushimi
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA
| | - Israel E Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
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