• Naomi Kery García, Chemical Engineering, University of Delaware

• Dustin Kenefake, Chemical and Biomolecular Engineering, University of Delaware

Abstract: Simulation and Quantification of a Novel PU Recycling Process 

     This undergraduate research project investigates the crucial separation of components
from a polyurethane (PU) depolymerization reactor outlet, specifically addressing the
challenging triethylamine (TEA) and water azeotropic mixture. PUs are ubiquitous polymers, but
their widespread use generates significant waste, necessitating advanced chemical recycling
strategies to achieve material circularity. The broader goal of this research is to develop a
closed-loop recycling process that regenerates valuable PU monomers, such as isocyanates, and
recovers auxiliary components for reuse.
Following the organoboron Lewis acid-mediated depolymerization of PUs, the reactor
outlet stream undergoes neutralization of HCl with sodium hydroxide (NaOH), resulting in a
mixture containing TEA, water, and salts. The primary challenge for TEA recovery stems from
its azeotropic behavior with water. To overcome this, extractive distillation utilizing glycerol as a
separating agent was initially implemented. A key optimization involved precisely controlling
the distillate-to-feed (D/F) ratio at 0.6479 in a subsequent or refined distillation step. This
operational strategy allowed for the selective concentration of TEA in the column’s overhead
stream, effectively managing the azeotropic limitations by preventing the co-distillation of
excess water.

     This optimized separation process successfully yielded highly pure TEA, with the
azeotropic distillation step achieving a 99.1% mass fraction purity. Crucially, the process
demonstrated quantitative recovery of triethylamine, achieving 100% recovery in the simulation.
This highly efficient solvent recovery is a vital step for establishing a sustainable, circular
economy for PU materials, reducing the environmental impact, and minimizing the reliance on
virgin feedstocks.