Researcher(s)
- Keira Auchenbach, Chemical Engineering, University of Delaware
Faculty Mentor(s)
- Dion Vlachos, Chemical & Biomolecular Engineering, University of Delaware
Abstract
Traditional methods of confronting plastic waste lack proper sustainability, but the Center for Plastics Innovation (CPI) aims to solve this issue through hydrocracking: a catalytic deconstruction of plastic polymers into chemicals for fuels and other platform chemicals. Recent studies have shown that real commercial plastics carry nitrogen-containing additives that hinder the hydrocracking process by poisoning the hydrocracking catalyst, reducing the efficiency of polymer conversion. As a solution to this problem, microwave-assisted solvent extraction is a promising pre-treatment step to selectively remove these problematic additives before plastic waste encounters the hydrocracking catalyst.
The work begins by fabricating single-layer LDPE films to contain a known concentration of oleamide, which was chosen as a model nitrogen-containing additive. Various solvents were screened to test their additive-extraction efficiency from the LDPE matrix; toluene and hexanes proved the best performance. The role of polymer swelling in promoting additive diffusion was also investigated. The effect of temperature was explored; higher temperatures increase the rate of diffusion, yet too high temperatures result in undesired LDPE dissolution. Extending time results in a higher degree of extraction by allowing deeply entrained additives with long diffusion paths to reach the film surface. Current data shows 90% extraction is achieved with toluene at 60 °C for 15 minutes. However, toluene is a poor microwave susceptor, so future work will investigate the usage of binary solvent mixtures to reduce heating requirements. Methods to increase polymer swelling will also be investigated to further improve additive diffusion. Finally, catalytic tests will be ran to prove the stripped LDPE is more easily deconstructed compared to non-stripped LDPE. Overall, microwave-assisted solvent extraction of problematic polymer additives is a promising process to enable the low-temperature hydrocracking of plastic waste into valuable chemicals.