Reaction-assisted separation of acetone from the azeotrope of methanol and acetone

Abstract

The separation of methanol–acetone azeotrope has been a challenging issue. Methanol in the azeotrope was selectively transformed and removed in this paper. Under mild conditions, 95.5% of methanol was transformed into methyl phenylcarbonate (MPC), phenol and dimethyl carbonate (DMC), while acetone was not converted. The separation process of reaction products was simulated, and 99% of acetone with purity of 99.3 wt% was recovered. The byproducts phenol and DMC were also recovered with purity of 93 and 76 wt%, respectively. Compared to the typical pressure-swing and extractive-distillation schemes, the total number of theoretical stages and heat duty could be reduced by 27.7–38.3% and 48.6–58.4%, approximately. The results of thermodynamic experiments showed that the apparent equilibrium constant (124.4 at 23.1 °C) in the first step was much larger than that (12.9) in the second step, indicating that the intermediate MPC was very stable, and thermodynamic factors originating from the specific coplanar structure of substrate contributed to the high methanol conversion. The transesterification reactions were endothermic and spontaneous due to the positive ΔH and negative ΔG values. The spontaneity of reactions was attributed to the increase of entropy, for which the reason was the more possible spatial distributions of atoms in the products. This paper is beneficial for the separation of alcohols from various aprotic solvents.