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Integrated In Situ Characterization of a Molten Salt Catalyst Surface: Evidence of Sodium Peroxide and Hydroxyl Radical Formation
Author(s) -
Takanabe Kazuhiro,
Khan Abdulaziz M.,
Tang Yu,
Nguyen Luan,
Ziani Ahmed,
Jacobs Benjamin W.,
Elbaz Ayman M.,
Sarathy S. Mani,
Tao Franklin Feng
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201704758
Subject(s) - catalysis , chemistry , x ray photoelectron spectroscopy , radical , molten salt , melting point , peroxide , inorganic chemistry , hydrocarbon , methane , salt (chemistry) , in situ , photochemistry , organic chemistry , chemical engineering , engineering
Sodium‐based catalysts (such as Na 2 WO 4 ) were proposed to selectively catalyze OH radical formation from H 2 O and O 2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na 2 WO 4 , which can form OH radicals, using in situ techniques including X‐ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient‐pressure X‐ray photoelectron spectroscopy (AP‐XPS). As a result, Na 2 O 2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800 °C, and these species are useful for various gas‐phase hydrocarbon reactions, including the selective transformation of methane to ethane.