Sustainable production of chemical intermediates for nylon manufacture: A techno-economic analysis for renewable production of caprolactone

Caprolactone is a precursor for the synthesis of caprolactam, the key monomer for nylon-6 which is produced globally at a scale of 4 million tonnes per annum. This work describes and assesses a bio-based production route to caprolactone from an agricultural residue, specifically corn stover, via glucose, fructose, 5-hydroxymethyl furfural (HMF) and 1,6-hexanediol. The material and energy balances, the cost efficiency, as well as on the potential reduction of greenhouse gas (GHG) emissions are reported and discussed. The developed process model was simulated in Aspen Plus™ with the optimization and energy integration performed for the entire process from corn stover to caprolactone. A sensitivity analysis was performed with consideration of various economic factors to explore the process economics. The results of the techno-economic and environmental assessment show that a bio-based caprolactone production process via glucose and HMF could be competitive with conventional hydrocarbon-based processes when major by-products are valorised and has a lower environmental impact. Areas where further investigation is needed to improve sustainable caprolactone production are identified and discussed.