Kinetic study of glycerol etherification with isobutene

The etherification of biodiesel based glycerol with isobutene catalyzed by an ion-exchange resin (NKC-9) was studied in a stirred batch reactor. The effects of temperature, catalyst loading, and feed composition on the product distribution were investigated. A kinetic model based on Eley-Rideal mechanism was developed according to the experimental results. In this model, three consecutive etherifications and a dimerization of isobutene were taken into account; isomers in the product were lumped as monoethers (ME), diethers (DE), and dimers of isobutene (DIB); glycerol and isobutene were thought to be adsorbed on the active sites of catalyst and the surface reactions were treated as the rate determine step; the acceleration function of ME to the reactions was also considered. The activities of components were employed in rate equations with the activity coefficients calculated by UNIFAC. Model parameters including reaction and adsorption equilibrium constants as well as rate constants were estimated. The model reliability was validated through the prediction of glycerol conversion and ether yields under different conditions.