Development of a sustainable process for the production of polymer grade lactic acid

Abstract

Lactic acid is a commonly occurring substance in nature, ranging from existence in micro-organisms to the human body. Traditionally, lactic acid has applications in industries such as food, chemicals, pharmaceuticals and textiles. In this work, a sustainable process for the production of polymer grade lactic acid (99 wt. % on dry basis) from crude lactic acid was simulated. The simulation was performed using Aspen Plus ® version 8.2. The thermodynamic model used for the process was NRTL – Hayden O’Connell due to the polar nature and non-ideal behavior of the species involved. The process was carried out in three stages. First, crude lactic acid was obtained by reacting calcium lactate with sulfuric acid. The second stage consisted of esterification of lactic acid by reactive distillation. A RadFrac column was used for this purpose which also facilitated easy separation of methyl lactate from methanol and water. Pure methyl lactate obtained from the second stage was then hydrolyzed in the third stage using pure lactic acid as an auto-catalyst to obtain the desired product. Use of pure lactic acid as an auto-catalyst helped to achieve the required purity as it minimized contamination. The process was optimized using sensitivity analysis in Aspen Plus ® .