Researcher(s)
- Ashley Tolocka, Chemical Engineering, University of Delaware
Faculty Mentor(s)
- Pedro Moura, Vlachos Group, University of Delaware
Abstract
Chemical upcycling of polyolefins through hydroconversion presents a promising solution for managing polyolefinic plastic waste. However, the hydroconversion of mixed plastic waste containing polyamide 6 (PA6) remains challenging due to PA6 poisoning of catalyst sites (1) and poor product selectivity (2), resulting in the devalorization of PA6. To address these issues, we aimed to valorize a commercial two-layer PA6 film [25% PA6, 75% polyethylene (PE)] by hydrolyzing the PA6 to caprolactam (CL) using a recyclable HT-TiO₂ catalyst, followed by hydrocracking of the remaining PE into naphtha.
We examined the time-dependent hydrolysis of a PA6 film and observed a 20% lower CL yield compared to pure PA6 resin at the same reaction time, with the film requiring up to 2 hours to reach CL equilibrium. ATR-FTIR analysis of the feedstock revealed that the PE layer contains a fatty acid amide slip agent, indicated by NH₂ stretching bands at 3190 and 3395 cm⁻¹ (3), which is known to poison hydrocracking catalysts (1). DSC and ATR-FTIR confirmed the degradation of PA6 over time, with the melting peak (~210 °C) fading after 0.5 hours and disappearing by 2 hours. A gradual reduction in the amide band (1500–1700 cm⁻¹) showed only trace amounts of PA6 at 2 hours and negligible levels after 6 hours. The absence of fatty acid amide bands after 0.5 hours suggests effective slip agent removal. TGA detected inorganic content in the PA6 film, which may influence analysis accuracy. Overall, the 6-hour hydrolysis residue appears suitable for hydrocracking, though further elemental analysis and HPLC-MS of PA6 oligomers are ongoing to close the nitrogen balance and confirm complete polymer breakdown.