Kinetics of glycerol chlorination with hydrochloric acid:: A new route to α,γ-dichlorohydrin

The growing availability of glycerol, as a consequence of the increase in biodiesel production (for which glycerol is a byproduct), is rapidly saturating the market, and consequently, a great interest is now addressed to the development of new process routes for alternative uses of glycerol. Among the various possibilities, our attention has been focused on the glycerol chlorination reaction, with the aim to produce alpha,gamma-dichlorohydrin. This compound can then subsequently be converted into epichlorohydrin, which is an important intermediate in the production of epoxy resins. alpha,gamma-dicholorhydrin, together with alpha,beta-dichlorohydrin, is currently synthesized starting from propylene via allyl chloride. In the present paper, the kinetics of glycerol chlorination with gaseous hydrochloric acid, for the production of alpha,gamma-dichlorohydrin, has been investigated by means of a jacketed glass reactor operated in batch conditions for the substrate (glycerol) and continuously for the hydrochloric acid. Different organic acids have been tested as catalysts with good performances in terms of both activity and, in particular, selectivity toward the desired 1,3-dichlorinated product. A reaction mechanism has been proposed and a consequent kinetic model has been developed in order to quantitatively describe the experimental data collected at various temperatures (80-120 degrees C), and the kinetic parameters have been evaluated. A generally good agreement between the experimental data and the theoretical model has been found.