Heterogeneous-homogeneous catalytic oxide catalysts

E. Heterogeneous-Homogeneous Catalytic Reactions on Oxide Catalysts... 

Novel and innovative approaches for the selective catalytic homogeneous oxidation of alkanes and alkenes to produce industrially important alcohols, aldehydes, ketones, and epoxides aie still urgently needed. Homogeneous catalytic oxidation is a process that is more selective to products and, as well, the reactions aie carried out at lower temperatures in comparison to heterogeneous catalytic oxidation reactions. However, the separation of the homogeneous catalyst from the oxidation products is energy intensive for example, distillation, as well as possible thermal decomposition of the catalyst during distillation. We will discuss... 

Of course, selective heterogeneous oxidation catalysts will also possess many practical advantages. Active surfaces could avoid corrosion problems that plague some homogeneous catalyzed oxidations. In addition, continuous oxidation over a surface provides the opportunity to readily remove product as formed before it further oxidizes to an undesirable product. A major problem in homogeneous catalytic oxidation is that of oxidizability of ligand systems. Supports which are resistant to oxidation have an obvious advantage here. 

The reaction does not proceed in the absence of catalysts. As the contemporary Fischer-Tropsch catalysts were heterogeneous, the first hydroformylation catalyst was a solid (66% silica, 30% cobalt, 2% thorium oxide, and 2% magnesium oxide). Only later was the conclusion reached and proved (5) that the actual catalytic species is homogeneous. 

Catalytic oxidation is the most important technology for the conversion of hydrocarbon feedstocks (olefins, aromatics and alkanes) to a variety of bulk industrial chemicals.1 In general, two types of processes are used heterogeneous, gas phase oxidation and homogeneous liquid phase oxidation. The former tend to involve supported metal or metal oxide catalysts e.g. in tne manufacture of ethylene oxide, acrylonitrile and maleic anhydride whilst the latter generally employ dissolved metal salts, e.g. in the production of terephthalic acid, benzoic acid, acetic acid, phenol and propylene oxide. 

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