(637d) Isolation of High Grade Methyl Acetate Via Pervaporation

T. Winkler, S. Lux, M. Siebenhofer

Graz University of Technology, Institute of Chemical Engineering and Environmental Technology, Graz/Austria

Aim of process intensification is to overcome limitations of mass and heat transfer, product yield and selectivity of chemical reactions, through new or different combination of technologies and/or process steps. Thermodynamic limitations and challenges in purification of the desired product are unavoidable when dealing with esterification reactions. Speeding up reaction kinetics of equilibrium reactions and elimination of azeotropes by adaptive configuration of reaction and separation steps was the basic strategy of this research activity.                                              

The synthesis of methyl acetate via esterification of acetic acid with methanol served as a welcome model process, as the basic type of reaction is applicable to a variety of esterification reactions.  Methyl acetate forms low boiling azeotropes with methanol and with water. The bulk product methyl acetate is produced in large quantities based on the established Eastman Kodak process.

This project deals with the investigation of alternative paths in the synthesis and purification of methyl acetate. Selective permeation is a promising route of azeotrope breaking. This unit operation can handle higher water contents than reactive distillation technology. Side reactions can be suppressed since operation temperatures are moderate.

Esterification is carried out under acid limiting conditions. When using a hydrophilic membrane methanol and water can pass the membrane, whereas methyl acetate is kept in the retentate phase. In case of hydrophobic membranes methyl acetate is transferred into the permeate phase.

Separation selectivity and permeate flux of several membranes of hydrophilic and hydrophobic surface properties were investigated. The influence of the operation parameters on the membrane performance was quantified and modeled. Permeate flux was determined based on a solution-diffusion model. Process schemes for the acid limited reaction route were designed and validation experiments were conducted.