Catalytic Hydration of Alkenes

Alkene hydration to alcohols is a reaction of some industrial importance, although there have been few fundamental investigations in recent years. Beranek and Kraus have pointed out that the reaction equilibrium for the vapour phase process, though more favoured by low temperatures, still favours dehydration even at room temperature. Consequently, when high temperatures are employed to give more rapid reaction, high pressures must also be employed and even then the maximum attainable conversion may be low. Matters are improved somewhat by use of a three phase system (solid catalyst, liquid water, and gaseous alkene), for which conversion is improved by virtue of the alcohol solubility in water. 

It was also pointed out that good dehydration catalysts are not necessarily good hydration catalysts and the important factor appears to be the presence of sites of the correct acid strength. Thus, for ethylene hydration, sites with acid strengths in the range — 8.2 —3.0 are 

Relatively few kinetic studies have been carried out, but Beranek and Kraus have reported that many catalysts give rise to data which satisfy Langmuir-Hinshelwood expressions of the form (equation 9)  

The advantages of the ion-exchange resins, a common one being a sulphon-ated styrene-divinyl benzene cross-linked polymer, were claimed to be as follows  

The process can be operated under relatively mild conditions i.e., 130-150 °C and 60-100 atmospheres. 

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