Transition-metal-catalyzed heterogeneous hydrogenation

Scheme 3.20 Process flow scheme for the combined continuous flow reactors for transition-metal-catalyzed heterogeneous hydrogenation and ion-exchange-polymer-catalyzed epimerization and the subsequent batch biotransformations.

The hydrogenation reactions occurring on heterogeneous basic catalysts have characteristic features, which distinguish heterogeneous basic catalysts from transition metal catalysts.44 The key features of the base-catalyzed hydrogenation reactions are as follows ... 

In fluid-solution systems, the plain hydrogenation of thiophenes to thioether products has been found to be catalyzed by various transition metal complexes surprisingly, none of these catalysts contains either molybdenum or tungsten, which are essential components of heterogeneous HDS catalysts [1 b]. Unpromoted M0S2, on the other hand, is quite active for the HDS of thioethers with no need of assistance by a late transition metal promoter [lb]. 

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