The Catalytic Dehydration of 2,3-Butanediol to Butadiene. II. Adsorption Equilibria

Abstract

Further understanding of the reaction in which 2,3-butanediol is dehydrated over thorium oxide to methyl vinyl carbinol and butadiene has been gained by measuring the adsorption on thoria of water, methyl ethyl ketone and the above-mentioned diol, carbinol, and diene, at temperatures up to 200 °C. In some instances satisfactory isotherms could not be obtained because sufficient chemisorption occurred, followed by polymerization or dehydration reactions, to reduce seriously the area of thoria surface available for adsorption. There was evidence to suggest that water, alone of the vapours concerned, was taken up in greater amount than could be accounted for by adsorption. The bearing of this on the dehydration and its relation to the structure of the catalyst is briefly discussed. A suggestion in a previous paper(1) that water is the product which retards the catalytic dehydration is confirmed. At temperatures little above 50 °C, methyl vinyl carbinol is dehydrated by thoria to butadiene, while methyl ethyl ketone at room temperature undergoes self-condensation on thoria to yield a methyl heptenone. Also at quite low temperatures dimerization of butadiene brings about appreciable reduction of available surface. Some loss of activity on this account must therefore be expected when thoria is used to dehydrate 2,3-butanediol, even though butadiene is adsorbed only weakly.