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.

The Thermal Decomposition of Thorium Oxalate

“…I t is possible that the loss of catalytic activity above 450 "0. (Winfield 1950) is due to structural changes which accompany loss of this water.…”

Conversion of 2,3-butanediol to butenes over bifunctional catalysts in a single reactor

“…Duan et al [18] investigated the dehydration of 2,3-BDO over monoclinic ZrO 2 and the result showed that 3-buten-2-ol was produced with a maximum selectivity of 59.0% along with major byproducts such as MEK and 3-hydroxy-2-butanone. In addition, further dehydration of 2,3-BDO yields 1,3-butadiene [19], which can be dimerized to produce the aromatic intermediate styrene (Diels-Alder reaction) [20] and hydrogenated to butene. Sato and coworkers investigated dehydration of 2,3-BDO to 1,3-butadiene over Sc 2 O 3 [21], and dehydration of other diols, such as 1,3-butanediol and 1,4-butanediol over rare earth oxides [22,23], ZrO 2 [24] and Cu-based catalysts [25].…”

Drying characteristics of thorium fuel corrosion products

“…Surface hydroxyl groups are probably not removed at outgassing temperatures below 250°C, even under vacuum conditions of 10 À7 kPa [38,56]. Anecdotal evidence indicates temperatures of at least 800-1000°C are necessary to remove all chemisorbed water from the ThO 2 surface [57][58][59]. Outgassing at temperatures as high as 1300°C may be necessary to reduce the surface hydroxyl content of thorium oxide below levels detectable by infrared spectroscopy [36,38].…”

“…Generally, the literature sources give nonequilibrium isotherms [59,64] indicative of the problems associated with rehydrating this material. The only data for reversible equilibrium water vapor pressure isotherms at moderate temperatures are given for 25, 100, 200, 300, 400, and 500°C and were composed over a period of two years [50].…”