Reaction Calorimetry Study of the Liquid-Phase Synthesis of tert-Butyl Methyl Ether

The liquid-phase addition of methanol to isobutene to give tert-butyl methyl ether (MTBE) on the ion-exchange resin Lewatit K2631 has been studied in a calorimetric reactor. Heat capacity of MTBE and enthalpy of the MTBE synthesis reaction in the temperature range 312--333 K have been determined. MTBE heat capacity in the liquid phase has been found to obey the equation c[sub P] (J/mol[center dot]K) = 472.34 [minus] 2.468(T/K) + 0.005071(T/K)[sup 2]. At 298 K the standard molar reaction enthalpy is [Delta]H[degree] = [minus]33.8 kJ/mol. A method to estimate apparent activation energies from heat flow rate in a given reaction has been developed and proved to be valid for the MTBE synthesis. Using this method, an apparent activation energy of 91.1--95.2 kJ/mol is calculated. A [minus]3.8 kJ/mol value has been found for the adsorption enthalpy of methanol on the ion-exchange resin Lewatit K2631 by a combination of reaction calorimetry and thermogravimetry. This allows the calculation of an activation energy on the gel phase of the resin of 91 kJ/mol.