Effect of solvent on the kinetics of the hydration of 2-methylpropene catalyzed by strong acid ion exchangers

Abstract

The hydration of 2-methylpropene, catalyzed by strong acid ion exchange resins, was investigated in solvent mixtures of water and either 1,4 dioxan or sulfolane at 25.0 °C. A gel type, an intermediate type and a macroporous resin were all investigated. It appeared that the macroporous resin is the most active catalyst for almost all solvent compositions investigated. The influence of the solvent composition on the rate of the hydration reaction can be explained by the acidity of the acid groups of the resin and by the distribution coefficient, X, of the alkene defined as the concentration ratio at equilibrium between the resin phase and the liquid phase surrounding the catalyst particles. The solvent also determines the value of the distribution coefficient, λ, of the alkene between the resin phase and bulk liquid. For one resin this effect was determined quantitatively. A complicating effect is the difference in the composition of the solvent in the resin phase and in the bulk liquid. For mol fractions of the cosolvent above 40%, it appeared that the concentration of sulfolane in the resin phase is considerably larger than that of 1,4-dioxan. As a consequence, the distribution coefficient of the alkene over the resin phase and the surrounding liquid is much higher for mixtures of sulfolane and water than for mixtures of 1,4-dioxan and water. This results in considerably higher hydration rates for sulfolane-water than for the 1,4-dioxan-water mixtures of comparable compositions.