Etherification of glycerol and ethylene glycol by isobutylene

The influence of catalyst, solvent and temperature on the etherification of glycerol and ethylene glycol with isobutylene in the liquid phase catalysed by strong acid ion-exchange resins of Amberlyst type (Amberlyst 15 and 35), p-toluenesulfonic acid and by two large-pore zeolites H-Y and H-Beta was studied. Reactions were carried out in the temperature range from 50 to 90 degrees C at autogenous pressure in solvent (dioxane, dimethyl sulfoxide and sulfolane). The basic kinetic parameters for complex of I I equilibrium reactions for glycerol and 5 equilibrium reactions for ethylene glycol were estimated. The highest conversion of glycerol was achieved on H-Beta, but on this catalyst the formation of tri-tert-butyl glycerol was sterically hindered. The highest amount of di- and tri-ethers was formed over Amberlyst 35. Over H-Y the reaction was slower due to its lower acidity, and final concentration of di- and tri-ethers was not achieved in monitored reaction time. p-Toluenesulfonic acid provides satisfactory results only when sulfolane was used as a solvent. The solvent plays an essential role because it can affect the investigated etherification reaction with its polarity and homogenization of reaction mixture. The concentration of glycerol and ethylene glycol higher ethers in end product can decrease as temperature increases showing that the side reaction of isobutylene dimerisation is more sensitive to temperature. (c) 2007 Elsevier B.V. All rights reserved.