Synthesis of tertiary amyl methyl ether (TAME): Equilibrium of the multiple reactions

Abstract

The octane enhancer tertiary amyl methyl ether (TAME) is produced by liquid phase synthesis from methanol and a mixture of isoamylenes, namely 2‐methyl‐1‐butene and 2‐methyl‐2‐butene, using a sulfonic acid ion exchange resin as catalyst. Three reactions take place simultaneously in TAME synthesis: etherification of the two methylbutenes and their isomerisation. In order to study the equilibrium of the multiple reactions in TAME synthesis, the thermodynamic properties of the compounds in the liquid phase and equilibrium constants were calculated using a modified UNIFAC method to describe the nonideality of the system. Four parameters influencing the equilibrium conversion were derived and discussed in detail. Supplemental experiments were performed at three temperatures in the range from 303 to 343 K and at different initial molar ratios of educts. Equilibrium conversions of methanol were determined from these experiments and compared with calculated values. At 298 K the predicted activity based equilibrium constant was 22.9 for TAME synthesis from 2‐methyl‐1‐butene and 1.6 for TAME synthesis from 2‐methyl‐2‐butene; for isomerisation of 2‐methyl‐1‐butene to 2‐methyl‐2‐butene a value of 14.3 was obtained.