Green Glycol: A Novel 2-Step Process
Ethylene glycol demand is growing rapidly, particularly in the global polyethylene terephthalate markets.¹ Traditional production of non-renewable ethylene glycol involves steam cracking of ethane or the methanol-to-olefin process to obtain ethylene.6 In response to environmental movements, Coca-Cola® began creating ethylene glycol from renewably sourced ethanol, by producing the ethylene oxide intermediate in a two-step reaction process.² Novel research at Leiden University, entitled Direct conversion of ethanol into ethylene oxide on gold based catalysts, explores a catalyst which produces ethylene oxide in one step, showing potential for a more efficient renewable process.³ This project explores the scaling of the Leiden research to an industrial level. The makeup raw material flows accounting for the recycle streams in the process are 237,000 MT fuel-grade ethanol per year, 81,000 MT oxygen per year, and 26,000 MT carbon dioxide diluent per year. The design first reacts ethanol and low concentration oxygen feeds to form an ethylene oxide intermediate, as well as undesired byproducts. A series of separations isolate ethylene oxide for further reaction, while recycling unconverted feeds and diluents. EO is then hydrolyzed to form mono-, di-, tri-, and higher order glycols. The following separation series removes water for recycle, then isolates fiber grade (99.9 wt%) monoethylene glycol as the main product. The bottoms of this separation results in an ethylene glycol mixture that is sold as a slurry for additional revenue. A financial analysis of the process over a 15 year period shows that the process does not directly compete with the existing monoethylene glycol market. However, a 14.5% green premium on the selling price of monoethylene glycol would reach a 15% IRR and achieve profitability. Future work should be focused on investigating catalyst performance and reproducing similar reaction behavior in industrial-scale conditions.