KINETICS OF THE CATALYTIC DEHYDROGENATION OF ALCOHOLS AND GLYCOLS IN THE GASEOUS STATE

Abstract

The catalytic dehydrogenation of several alcohols and glycols, in the gaseous state, was found to be a first order process obeying the Arrhenius relation for variation of rate with temperature. Hence a large body of experimental data can be expressed by two constants that enable a ready comparison of different catalysts. A porous copper catalyst was found to be the most satisfactory. The fallacy of calculating the energy of activation from the temperature coefficient in this type of reaction is pointed out. Primary alcohols are dehydrogenated more slowly than secondary because the resulting aldehydes reversibly depress the activity of the catalyst, while methyl ketones have no measurable effect. Diacetyl acts as an aldehyde in this respect. The α-glycols form α-hydroxy aldehydes and ketones that depress the activity of the catalyst to a low but constant level. Rapid poisoning of the catalyst at constant temperature is a first order process. A regular relation exists between the temperature of reduction and the activity of the catalyst.Acetoin and diacetyl can be produced in almost quantitative yields by dehydrogenation of 2,3-butanediol vapour.