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The Effect of Transition Alumina (γ‐, η‐, χ‐Al 2 O 3 ) on the Activity and Stability of Chromia/Alumina Catalysts. Part I: Model Catalysts and Aging Conditions
Author(s) -
Nazimov Daniil A.,
Klimov Oleg V.,
Trukhan Sergey N.,
Cherepanova Svetlana V.,
Prosvirin Igor P.,
Noskov Aleksandr S.
Publication year - 2019
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201800735
Subject(s) - chromia , catalysis , dehydrogenation , sintering , calcination , x ray photoelectron spectroscopy , materials science , isobutane , inorganic chemistry , chemical engineering , chemistry , metallurgy , organic chemistry , engineering
The effect of transition alumina (γ‐, η‐, χ‐Al 2 O 3 ) on the activity and stability of model chromia/alumina catalysts with 4 wt% Cr in isobutane dehydrogenation is studied. It is shown that a fresh catalyst with η‐Al 2 O 3 as a support has the highest activity, while with χ‐Al 2 O 3 has the lowest one. The characterization of the catalysts by N 2 adsorption, X‐ray diffraction (XRD), electron spin resonance (ESR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS) is used to describe changes in the catalysts induced by high‐temperature treatment at 800, 1000, and 1200 °C in air. It is shown that sintering of the alumina support and formation of chromia‐alumina solid solutions are the reasons of irreversible decline in the catalytic activity. Cr/γ‐Al 2 O 3 is found to be the most stable to sintering and phase transformation, whereas Cr/χ‐Al 2 O 3 is found to be the least stable. Due to its highest initial activity, the η‐Al 2 O 3 ‐supported catalyst loses its dehydrogenation activity most rapidly as the calcination temperature is raised. The segregation of sodium impurities is observed in the course of heat treatment, which may be an additional cause of deactivation.