Premium
Structural characterization of alumina‐supported nickel molybdena catalysts
Author(s) -
Sarbak Z.
Publication year - 1990
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170250614
Subject(s) - catalysis , hydrogen , chemistry , hydrogen sulfide , nickel , oxide , sulfur , oxygen , inorganic chemistry , sulfide , ion , hydrogen sulphide , ion exchange , organic chemistry
The object of our studies was a NiMo/Al 2 O 3 catalyst thermally activated in oxygen, hydrogen, and in a mixture of hydrogen and hydrogen sulfide. On the surface of the oxide form of the catalyst there are different species, among them dimeric and polymeric octahedrally coordinated Mo 6+ ions containing oxygen bridges are found. The presence of structures resembling α‐ and β‐NiMoO 4 and 6‐heteropolymolybdenates was determined. Reduction with hydrogen leads to formation of two nuclear structures with single and double bridges of [Mo 2 5+ O 3 ] and [Mo 5+ O 4 ] type, respectively, and partially reduced 6‐heteropolymolybdenates. On the other hand, when the reduction and sulfiding take place at the same time, then terminal oxide ions are partially replaced by sulfide ones. The presence of [MoO 2 S 2 ] 2− species has been observed, however, there is no evidence of the exchange —OH groups for —SH ones and exchange of oxygen bridged ions for sulfur ions. It has been also noted that the subsurface structures remained intact after reduction and sulfiding.