(390g) Technoeconomic Analysis and Life Cycle Assessment of Bio-Based Non-Isocyanate Polyhydroxyurethane and Polythiourethane Production with Monomer Recovery

Background: In 2016, 2900 kt (kilotonnes) of polyurethane (PU) were produced in the United States at the expense of 1100 kt of crude oil and 1100 kt of natural gas.¹ With a 5.5% of end-of-life recycling rate, polyurethanes are recycled at less than the average recycling rate of U.S. plastics in 2015.^1,2 The use of fossil fuel and natural gas reserves depletes nonrenewable resources while releasing emissions that directly contribute to global warming. To mitigate issues with sustainability, it is necessary to advance technologies for bio-based PU synthesis and to expand methods for recycling PU monomers. To alleviate issues with safety, the U.S. Environmental Protection Agency (EPA) has begun to phase out the use of isocyanates in the synthesis of PU.³ Polyhydroxyurethane (PHU) and polythiourethane (PTU) can be synthesized and reprocessed from biomass using isocyanate-free methods. Catalytic coupling of epoxide residues with either carbon dioxide or carbon disulfide affords 5-membered cyclic carbonates or 5-membered cyclic dithiocarbonates, respectively. Subsequent ring opening polyaddition with a diamine can afford PHU from the cyclic carbonates or PTU from the cyclic dithiocarbonates. Chemicals that can be derived from biomass, including 1,3-butadiene or 1,4-butanediol,⁴ are readily epoxidized via a reaction with hydrogen peroxide or an S_N2 substitution with epichlorohydrin. Cyclic carbonate and dithiocarbonate moieties have also previously been derived from epoxidized plant seed oils for PU biosynthesis.^5,6

Results: We examine case studies for phasing out non-renewables and shifting toward a more circular economy. To boost the bio-based content of PU consumption in the United States, it is proposed to substitute with non-isocyanate polyurethanes (NIPU), PHU and PTU, synthesized using bio-based monomers. Production processes with monomer recovery for PHU and PTU, modeled using AspenPlus, inform the results of a life cycle assessment (LCA) and technoeconomic analysis (TEA). The LCA component of the study discusses the environmental impacts of PHU and PTU synthesis in terms of energy usage, emissions, and water usage. The TEA component of the study discusses the profitability of selling PHU and PTU and breaks down the major components of their production costs. Preliminary results indicate raw materials drive cost and GHG emissions of PHU and PTU production from bio-based intermediates. Monomer recovery costs are predominantly affected by the depolymerization yield and the cost of solvent.

¹Liang, C., Gracida-Alvarez, U.R., Gallant, E.T., Gillis, P.A., Marques, Y.A., Abramo, G.P., Hawkins, T.R. and Dunn, J.B. "Material flows of polyurethane in the United States." Environmental Science & Technology 55.20 (2021): 14215-14224.

²Di, J., Reck, B.K., Miatto, A. and Graedel, T.E. "United States plastics: Large flows, short lifetimes, and negligible recycling." Resources, Conservation and Recycling 167 (2021): 105440.

³US Environmental Protection Agency. "Methylene Diphenyl Diisocyanate (MDI) And Related Compounds Action Plan." (2011).

⁴Biddy, M.J., Scarlata, C. and Kinchin, C. “Chemicals from biomass: a market assessment of bioproducts with near-term potential.” No. NREL/TP-5100-65509. National Renewable Energy Lab.(NREL), Golden, CO (United States), 2016.

⁵Hu, S., Chen, X. and Torkelson, J.M. "Biobased reprocessable polyhydroxyurethane networks: Full recovery of crosslink density with three concurrent dynamic chemistries." ACS Sustainable Chemistry & Engineering 7.11 (2019): 10025-10034.

⁶Vanbiervliet, E., Fouquay, S., Michaud, G., Simon, F., Carpentier, J.F. and Guillaume, S.M. "Non-isocyanate polythiourethanes (NIPTUs) from cyclodithiocarbonate telechelic polyethers." Macromolecules 52.15 (2019): 5838-5849.