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The Effects of Platinum Dispersion and Pt State on Catalytic Properties of Pt/Al 2 O 3 in NH 3 Oxidation
Author(s) -
Slavinskaya Elena M.,
Kibis Lidiya S.,
Stonkus Olga A.,
Svintsitskiy Dmitry A.,
Stadnichenko Andrei I.,
Fedorova Elizaveta A.,
Romanenko Anatolii V.,
Marchuk Vasyl,
Doronkin Dmitry E.,
Boronin Andrei I.
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.202001320
Subject(s) - catalysis , platinum , dispersion (optics) , selectivity , particle size , oxidation state , chemistry , ionic bonding , partial oxidation , inorganic chemistry , materials science , ion , organic chemistry , physics , optics
Dependence of NH 3 oxidation on the state and dispersion of Pt species in Pt/γ‐Al 2 O 3 catalysts was investigated. Prereduced Pt/γ‐Al 2 O 3 catalysts containing Pt 0 nanoparticles exhibited significantly higher activity than preoxidized ones with the same Pt dispersion. The most significant improvement of the catalytic activity (TOF increased by 30 times) was observed when the size of Pt 0 particles increased from ∼1 to ∼8 nm. N 2 selectivity was found to be mainly determined by the reaction temperature, with a minor influence of Pt particle size. Preoxidized catalysts containing ionic Pt were activated by the reaction medium, while partial deactivation was observed for the prereduced ones. The activity improvement was associated with the presence of Pt 4+ /Pt 2+ species on the surface of preoxidized catalysts. The activity decrease of the prereduced catalysts was due to the partial oxidation and subsequent redispersion of Pt particles. Introduction of H 2 O and CO 2 to the reaction mixture only moderately influenced NH 3 oxidation activity shifting NH 3 conversion curves by about +15 °C.