EPOXIDATION OF ALLYL ALCOHOL TO GLYCIDOL WITH HYDROGEN PEROXIDE AT TITANIUM SILICALITE

Abstract

It was studied the epoxidation mechanism of allyl alcohol using titanosilicate zeolite (TS-1) at 40°C by means of procedures for the nomination and discrimination of mechanism hypotheses. The hypotheses was carried out using the literature data and the preliminary experiment results. Discrimination hypothetical mechanisms implemented on the basis of the univariate results of the kinetic experiment, varying concentrations of allyl alcohol, hydrogen peroxide and glycidol. The most probable mechanism involves the hydrogen peroxide and allyl alcohol adsorption at the catalyst active centers and the glycidol formation at a reversible stage in the interaction of the adsorbed molecules of the reactants. Considered hypotheses include a different sequence of interaction of the reactants with active catalyst centre. In addition, hypotheses take into account the formation of intermediate compounds as well as inactive products of the interaction of substances present in the reaction system, with the active centers on the silicalite surface. For each hypothesis, it was formulated the corresponding system of differential equations and carried out the estimation of the rate constants. The quality of the experimental data description was judged by the residual sums of squared deviations and correlation coefficients. The best results are obtained for the hypothesis involving the hydrogen peroxide and allyl alcohol adsorption at the two active catalyst centers with subsequent interaction of the resultant intermediates between them, with the formation of glycidol adsorbed on one center, free catalyst centre and molecule of water. Formation of free glycidol occurs at a reversible stage. A significant part of the active centers of the catalyst increasing the concentration of glycidol is associated with it. This is the main reason for the decrease of the reaction rate, apart from reducing the concentration of the reactants.