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Molecular Models for Bi/Mo Oxidation Catalysts
John H. Thurston, Department of Chemistry, The College of Idaho
The SOHIO oxidation process describes the conversion of propene into acrolein or acrylonitrile over a multicomponent Bi2O3∙MoO3 catalyst. The process continues to be of considerable industrial importance due to the
heavy demand for both acrolein or acrylonitrile worldwide. It is therefore interesting to note that the exact
mechanism by which the catalyst is able to facilitate the observed chemical transformations remains unclear. It
is possible that additional insight into the mechanism of functioning of Bi2O3∙MoO3 based oxidation catalysts
could be gained through the investigation of molecular complexes whose composition, geometry and bonding
arrangements mimic what is seen in the bulk material. Unfortunately, literature reports of molecular Bi/Mo
complexes are scarce, with species that contain structural features associated with the bulk oxidation catalyst
(including Bi-OH, Bi-O-Bi, Mo-O-Bi and Mo=O moieties) being particularly elusive.
Our group has developed a “bottom-up” synthetic approach to heterobimetallic Bi/Mo coordination complexes
in which a structurally robust polynuclear bismuth core is functionalized with preformed transition metal
fragments. Using this method, we have recently successfully prepared a series of molecular coordination
complexes that contain functional groups associated with the SOHIO oxidation catalyst, one of which is pictured
below. A significant outcome of this study, which sets it apart from previously reported work, is the apparent
generality of our synthetic method for the production of a range of bismuth-based heterobimetallic complexes
from a common set of reaction conditions and the potential control over composition and geometry that can be
realized through control of the reaction stoichiometry and the steric requirements of the two metal species.
Bi8
W1
O3
Bi4
W2
Bi1
Bi6 Bi5
O4
Bi3
Bi9
Bi2
Bi7