ACTIVITY SCREENING OF DIVERSE CATALYSTS FOR THE ALKALINE HYDROLYSIS OF PET

This thesis investigated the catalytic alkaline hydrolysis of post-consumer poly(ethylene terephthalate) (PET) tray material using selected quaternary ammonium and phosphonium phase-transfer catalysts (PTCs). The work aimed to establish an experimental and analytical basis for developing recoverable allyl-functional PTC systems through preliminary catalyst evaluation and a ¹H-NMR-based monitoring approach to track hydrolysis progress. The experimental programme screened candidate catalysts and examined the effect of NaOH/repeat-unit molar ratio, succinic acid addition timing, N-Allyl-N,N-dimethylhexadecan-1-aminium chloride (ADMHACl) loading, and oil-bath temperature; it further included differential scanning calorimetry (DSC) of the initial feedstock and dynamic light scattering (DLS) of PET-free water/NaOH/ADMHACl model formulations. Hydrolysis yield was principally estimated from ethylene glycol formation via ¹H-NMR quantification setting succinic acid as internal standard, and this metric was benchmarked against gravimetric residual-solid conversion for selected matched conditions. After PTCs screening, ADMHACl was selected for the parameter studies. Nominal hydroxide availability and internal standard addition timing both strongly influenced the outcome, whereas ADMHACl loading showed a pronounced response at low concentrations followed by an apparent plateau near 1.20 wt% relative to initial PET mass under the sealed-vial conditions tested. Raising the oil-bath temperature from 50 to 120 °C correspondingly lifted the endpoint conversion value from 8.0% to 73.5%. The matched comparison yielded mean ¹H-NMR-based and gravimetric values of "71.3 ± 2.7" % and "75.8 ± 1.2" %, respectively. DLS, by contrast, offered only comparative scattering information; it did not resolve the dispersion state of ADMHACl or account for the observed hydrolysis behaviour. Collectively, these results lay the experimental and analytical groundwork needed for future work on catalyst recovery, reuse, time-resolved monitoring, and polymer-supported catalyst design.