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Study on the properties of iron–cobalt alumina supported catalyst for ammonia
Author(s) -
Kaleńczuk Ryszard J.
Publication year - 1994
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280590112
Subject(s) - cobalt , catalysis , ammonia , ammonia production , chemistry , chemical engineering , inorganic chemistry , materials science , organic chemistry , engineering
The addition of Co to Fe/Al 2 O 3 increases the catalytic activity in NH 3 synthesis. The maximum effect is observed for 20% by weight of Co in the metallic phase. Bivalent cobalt atoms replace bivalent iron atoms (a similar ionic radius) in the crystal lattice. This process changes the reducibility of the samples. The Fe‐Co compound and its formation results in the fairly high temperature of reduction (873 K) which is needed to prepare the most active catalyst. Changing the reactor atmosphere from reducing to inert causes the disappearance of free iron (escape of Fe to the crystal lattice of support with formation of a new compound with a spinel character). This is the effect of the iron‐hydrogen interaction. The formation of an intermetallic iron‐cobalt compound is crucial to the catalyst activity. This might be due to the surface restructuring by exposing the most active iron surface, Fe(111). The potassium addition in the form of KOH causes an increase in the catalytic activity. The increase is not as high as for a ‘super basic’ Fe‐Co magnesium hydroxide carbonate supported catalyst studied earlier. A part of the potassium hydroxide is used to neutralize the acid sites on the surface of alumina.