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

Susmit S Bapat,Clint P Aichele,Karen A High

doi:10.1186/2043-7129-2-3

Abstract

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®.

Highlights

Lactic acid was first isolated in 1780 by Swedish scientist Carl Wilhelm Scheele by crystallizing its calcium salt [1]
Lactic acid with a purity of about 85 wt. % is used to induce a sour taste in food products, for example in pickles and sauerkraut
There has been an increased focus on manufacturing lactic acid of high purity (99 wt. % on dry basis) which can be used as the monomer for producing poly-lactic acid (PLA)

Summary

Introduction

Lactic acid was first isolated in 1780 by Swedish scientist Carl Wilhelm Scheele by crystallizing its calcium salt [1]. It is a weak organic acid with a hydroxyl group and a carboxylic group present on adjacent carbon atoms in the carbon chain. % is used to induce a sour taste in food products, for example in pickles and sauerkraut. Lactic acid with a purity of about 85 wt. It is used as an acidulant in the food industry [2]. PLA can be obtained from lactic acid via two different mechanisms – 1) direct polymerization of lactic acid by poly-condensation or 2)

Methods

Results

Conclusion