ETHERS FROM ETHANOL .1. EQUILIBRIUM THERMODYNAMIC ANALYSIS OF THE LIQUID-PHASE ETHYL TERT-BUTYL ETHER REACTION

The equilibrium-limited liquid-phase synthesis of ethyl tert-butyl eth er (ETBE) from the combination of ethanol and isobutylene over an ion- exchange resin catalyst, typically Amberlyst 15, is a reaction of cons iderable industrial importance now. An equilibrium constant relationsh ip is developed here for the liquid-phase ETBE reaction by following t hree alternative thermodynamic pathways and critically evaluating the resulting expressions. The final theoretical expression is compared ag ainst experimental data obtained in this study from the decomposition of ETBE over Amberlyst 15, as well as that reported in the literature for ETBE synthesis. It can thus be used with reasonable confidence for the calculation of the equilibrium constant, despite a dearth of ther modynamic data yet available in the literature far ETBE. In addition, an expression is derived for the gas-phase equilibrium constant and co mpared to experimental data from the literature. The thermodynamic app roach utilized here should also be useful for other liquid-phase react ion systems.