Number of actives sites in TAME synthesis: Mechanism and kinetic modeling

The kinetics and thermodynamic equilibrium of tert-amyl methyl ether (TAME) liquid-phase synthesis from the reactions between methanol and the isoamylenes 2-methyl-1-butene (2M1B) and 2-methyl-2-butene (2M2B) were studied in a batch reactor in the temperature range 324362 K at 10 bar using Amberlyst 15Wet as catalyst. A kinetic model based on a Langmuir-Hinshelwood-type mechanism was developed assuming methanol as the most abundant surface species. To ensure model applicability for a large range of species activities, the fraction of vacant sites was not neglected. The reaction rates were written in terms of activities, and the liquid-phase activity coefficients were calculated by the modified UNIFAC method of Dortmund. The number of active sites involved in TAME synthesis was also investigated by using a partially deactivated catalyst. The results showed that the etherification reaction rates are proportional to the square of the concentration of active sites of the catalyst, i.e., there are two active sites involved in each etherification reaction, which indicates that a two-site Langmuir-Hinshelwood mechanism is the most adequate for the description of the TAME catalytic synthesis in the liquid phase.