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Identification of Active Sites in the Catalytic Oxidation of 2‐Propanol over Co 1+x Fe 2–x O 4 Spinel Oxides at Solid/Liquid and Solid/Gas Interfaces
Author(s) -
Falk Tobias,
Budiyanto Eko,
Dreyer Maik,
Pflieger Christin,
Waffel Daniel,
Büker Julia,
Weidenthaler Claudia,
Ortega Klaus Friedel,
Behrens Malte,
Tüysüz Harun,
Muhler Martin,
Peng Baoxiang
Publication year - 2021
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.202100352
Subject(s) - catalysis , spinel , aqueous solution , chemistry , x ray photoelectron spectroscopy , propanol , activation energy , inorganic chemistry , phase (matter) , analytical chemistry (journal) , materials science , methanol , chemical engineering , organic chemistry , engineering , metallurgy
A series of Co 1+x Fe 2–x O 4 (0≤x≤2) spinel nanowires was synthesized by nanocasting using SBA‐15 silica as hard template, which was characterized by X‐ray powder diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy. The Co 1+x Fe 2–x O 4 spinels were applied in the aerobic oxidation of aqueous 2‐propanol solutions to systematically study the influence of exposed Co and Fe cations on the catalytic properties. The activity of the catalysts was found to depend strongly on the Co content, showing an exponential increase of the reaction rate with increasing Co content. Ensembles of Co 3+ cus (coordinatively unsaturated) sites were identified as the active sites for selective 2‐propanol oxidation, which are assumed to consist of more than six Co ions. In addition, gas‐phase oxidation with and without water vapor co‐feeding was performed to achieve a comparison with liquid‐phase oxidation kinetics. An apparent activation energy of 94 kJ mol −1 was determined for 2‐propanol oxidation over Co 3 O 4 in the liquid phase, which is in good agreement with the gas‐phase oxidation in the presence of water vapor. In contrast to gas‐phase conditions, the catalysts showed high stability and reusability in the aqueous phase with constant conversion in three consecutive runs.