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Design and Evaluation of Sustainable Lactide Production Process with an One-Step Gas Phase Synthesis Route

Heo, Seongmin, Park, Hyun Woo, Lee, Jay H., Chang, Yong Keun
ACS sustainable chemistry & engineering 2019 v.7 no.6 pp. 6178-6184
condensation reactions, depolymerization, economics, gases, global warming potential, lactic acid, life cycle assessment, process design
In this article, a conceptual process design for the production of lactide is proposed, where an one-step gas phase synthesis route is adopted. Then, the proposed process is evaluated and compared with the conventional two-step (polycondensation and depolymerization) lactide synthesis process. Specifically, techno-economic analysis and life cycle analysis are performed to compare both processes in terms of lactide conversion cost and global warming potential, respectively, to examine the sustainable production capability of the one-step lactide synthesis process. At the lactic acid feed supply rate of 20 ton/h, the lactide conversion cost was $37.57/ton and $70.82/ton for the one-step and two-step processes, respectively, showing that the one-step synthesis of lactide is economically more attractive than the conventional two-step approach. Also, the global warming potential was 0.11 and 0.22 kg CO₂ₑq/kg for the one-step and two-step processes, respectively, implying that the one-step process can produce lactide in a more sustainable way. Finally, sensitivity analysis is performed to identify important process operating conditions and parameters which affect the economics and sustainability significantly. It was shown that the operating variables of the reaction sections, which affect the purity of crude lactide, are the most important factors, and the one-step process is more sensitive to the changes in such variables than the conventional process.