(88c) Reactive Distillation Process of Methyl Acetate Hydrolysis Directly Intensified by Auxiliary Reaction of Methanol Dehydration

The green novel technology reactive distillation (RD) has provided with great potentials. However, it is limited due to physical properties of the reaction system, such as multiple liquid phases restricting solubility of catalyst and miscibility of reactants, and formulation of azeotropic mixtures entraining reactant or product and making downstream separation very difficult. Typical industrial examples include complete recovery of methyl acetate (MeOAc) from waste of polyvinyl alcohol processes. For MeOAc hydrolysis, the chemical equilibrium constant is very low. In order to reach high conversion, excessive water is needed which causes high energy consumption in downstream separation.

In order to make use of the advantages of reactive distillation, process intensification by auxiliary reactions is proposed in this contribution. Methanol is introduced as subsidiary reactant and provides water by its dehydration reaction. Water is supplied for hydrolysis reaction of MeOAc, which produces methanol and product acetic acid (HOAc). Since methanol is lighter and water is heavier, they are moved by distillation effect to their reactive zones respectively once formed. As a result, extra water is not needed and methanol is in-situ transferred to product dimethyl ether (DME). The reaction of methyl acetate hydrolysis is thus directly intensified by methanol dehydration.

A residue curve maps (RCMs) is developed to analyze the mechanism of intensification for the case with two reactions and multiple components. The analysis of thermodynamics and RCMs reveals that the reaction of MeOH dehydration is the controlling step which limits the conversion of MeOAc. Based on the chemical equilibrium and kinetically controlled design, a novel process is developed to hydrolyze MeOAc and MeOH in the process of polyvinyl alcohol. Compared to traditional processes, no additional water is required to feed into the RD column and the process is significantly simplified. With equal mole of MeOAc and MeOH as feed and a set of pre-reactor, closely 100% conversion of MeOAc and MeOH can be achieved and high purity dimethyl ether and acetic acid are the products in the RD column.