Thermodynamic And Kinetic Study Of Tert-amyl Methyl Ether (TAME) Synthesis

TAME is a blending ingredient of a kind of oxygen-containing gasoline with high octane number and the sourse to produce TAME is economical and convenient. The synthesis of TAME by which way olefins in the gasoline are converted to oxygen-containing compounds will greatly improve the quality of combustion. Under the condition that energy issue is severe at present, it is significant of TAME to the field of oil refining.The etherification of methanol (MeOH) with 2-methyl-1-butene (2M1B) and 2-methyl-2-butene (2M2B) catalyzed by the macroporous cation ion-exchange resin (D005II) was developed in a batch reactor. The optimum reaction conditions, the thermodynamic and kinetic data for the synthesis of TAME were studied in this paper. The yield of TAME along with time was obtained under different agitation speed, catalyst particle size, temperature and initial molar ratio. As the result shown, the 400 rpm agitation speed is sufficient to avoid external mass transfer resistances and the effectiveness factor of internal mass transfer is up to 0.95 when the particle size is lower than 0.50mm which means the intermal mass transfer is negelectable. Moreover, the optimum temperature of etherification reactions for TAME is a little lower than 80oC and the initial ratio of methanol versus isoamylene should be according to stoichiometric number.Then thermodynamic experiments were developed between 50 oC to 80 oC to calculate equilibrium constant. And the enthalpies, the entropies, the Gibbs free energies of the reactions were obtained by regressing equilibrium consant with temperature in the van't Hoff equation. The paramaters were in line with those published in the literature.Additionally, there were three mechanisms adopted for simulating reaction rate equations to explore the mechanism of the synthesis of TAME, containing homogeneous reaction mechanism, Langmuir-Hinshelwood (LH) type mechanism and Eley-Rideal (ER) type mechanism. The equations based on the LH type mechanism was found to get best fit with the experimental data with lowest WSAS, while the homogeneous model was the least appropriate model. Thus, the hypothesis of two activity sites on the catalyst is more reliable in the TAME synthesis. The activation energy evaluated by LH model was 88.1 kJ mol-1 and 102.1 kJ mol-1 for the etherification of 2M1B and 2M2B respectively.