Dehydration of the alcohol in the etherification of isoamylenes with methanol and ethanol

The kinetics of the dehydration of methanol and ethanol, which is a side reaction in the synthesis of tertiary ethers (TAME, 2-methoxy-2-methylbutane; TAEE, 2-ethoxy-2-methylbutane), were investigated in a continuous stirred tank reactor, with a commercial ion-exchange resin (Amberlyst 16) used as the catalyst. The effect of the alcohol concentration on the formation rates of dimethyl ether (DME) and diethyl ether (DEE) was measured between 323 and 363 K. The formation of the dialkyl ethers was favored by high temperatures and high-alcohol concentrations. At higher temperatures DME formed at a faster rate than DEE. The experimental results were best described with a model where one alcohol molecule is adsorbed and the other reacts from the liquid phase. Kinetic models for the synthesis of TAME and TAEE expanded with the dehydration reactions and written in terms of component activities, are presented. The UNIFAC method was applied for the calculation of activity coefficients. The activation energy was determined to be 102.6 kJ/mol for methanol dehydration to yield DME and 90.5 kJ/mol for ethanol dehydration to yield DEE.