Heterogenization of homogeneous catalytic systems

This type of catalytic material and mode of use provided the basis for the Shell process, the first direct hydration route to ethanol. The approach remains the basis for the manufacture of all synthetic ethanol and most of the isopropanol (2-propanol) produced today. 

A similar approach has been adopted in a number of other reaction systems. A common example is the use of supported melts of copper chloride (with possibly other metal chlorides incorporated to reduce volatility or provide a 

The maintenance of a supported liquid layer in gas-phase reactions is also important in other heterogeneous catalytic applications, such as the Bayer/Hoechst process for vinyl acetate manufacture. However, in these systems, the catalytic metal is reduced to the metallic state, leading to significant mechanistic differences from the formally related homogeneous Wacker-type alkene oxidation/acetoxylation processes (section 11.7.7.3). 

A heterogeneous-catalyst is a solid composition which can effect or accelerate reaction by contact between its surface and either a liquid-phase reaction mixture (in which the catalytic material must be essentially insoluble) or gaseous reactants. In liquid-phase systems, one or more of the reactants may be introduced as a gas, but access of such reactants to the (fully wetted) surface of the catalyst is almost invariably by dissolution in the reaction medium and subsequent diffusion. 

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