Enhanced recovery of PGME and PGMEA from waste photoresistor thinners by heterogeneous azeotropic dividing-wall column

Propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA) are representative photoresistor thinners used extensively and generated as waste during the display and semiconductor material manufacturing processes. Although the waste thinner is normally retrieved by distillation, the azeotropes of these two thinner components with water limit the distillation performance. In this paper, an extensive design study of enhanced distillation processes was carried out to determine a favorable path for waste thinner recovery. Appropriate thermodynamic models for the design of a waste thinner recovery process were obtained through the regression and validation of experimental vapor-liquid-liquid equilibrium data. An optimal direct sequence using three conventional distillation columns with a decanter was introduced as a base design to overcome the distillation boundary by azeotropes. Several advanced distillation configurations were examined to further improve the energy efficiency of the conventional recovery process. A novel heterogeneous azeotropic dividing-wall column was developed based on process intensification and integration. The proposed enhanced recovery process reduced the energy requirement for waste thinner recovery significantly by 33.1%. The advanced distillation configuration can be an attractive option for improving the economic and environmental efficiency of the commercial waste thinner recovery and recycling processes. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.