Understanding the Role of SnO2 Support in Water‐Tolerant Methane Combustion: In situ Observation of Pd(OH)2 and Comparison with Pd/Al2O3. Issue 3 (11th December 2019)

• Record Type: Journal Article
• Authors: Barrett, William; Shen, Jing; Hu, Yongfeng; Hayes, Robert E.; Scott, Robert W. J.; Semagina, Natalia
• Is Part Of: ChemCatChem. Volume 12:Issue 3(2020)
• Page Start: 944
• Page End: 952
• Publication Date: 2019-12-11
• Subjects: heterogeneous catalysis -- methane combustion -- tin oxide -- palladium -- X-ray absorption spectroscopy; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201901744
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Quantitative analysis of poisonous Pd hydroxide phase formation during methane combustion in the presence of water is performed via in situ X‐ray absorption spectroscopy from 200 to 500 deg C for palladium catalysts supported on tin and aluminum oxides. Water presence inhibits oxidation of the metallic Pd; for the Pd/Al2 O3 catalyst the major oxidation product is Pd(OH)2, with PdO being the dominant phase on the Pd/SnO2 system. Tin dioxide is reduced during methane oxidation in the presence of water, regardless of the excess oxygen in the feed. Temperature‐programmed surface reactions at anaerobic and low‐oxygen conditions revealed that the Pd/SnO2 catalyst has an inability to catalyze methane steam reforming, as opposed to Pd/Al2 O3 . We suggest that tin oxide extracts hydroxyls from the PdO surface, which makes the latter more active in methane combustion in the presence of water but inactive in methane steam reforming. Abstract : Hydroxyls away ! Tin oxide extracts hydroxyls from Pd and liberates it for methane combustion but renders Pd inactive for methane steam reforming, as opposed to Pd/Al2 O3 . Quantitative analysis of metallic Pd, PdO, and Pd(OH)2 is presented for Pd/Al2 O3 and Pd/SnO2 catalysts as a function of temperature during methane‐lean combustion in the presence of water, as found by in situ X‐ray absorption spectroscopy.