This dissertation focuses on eliminating plastic waste through the chemical upcycling of poly(ethylene terephthalate) (PET) via ammonolysis. Model studies on dimethyl terephthalate (DMT) and bis(2-hydroxyethyl) terephthalate (BHET) establish kinetic parameters, with pseudo-first-order rate constants of k1′ = 0.25 ± 0.02 h−1 and k2′ = 0.11 ± 0.02 h−1 for DMT at 100 °C, and k1′ = 0.958 ± 0.076 h−1 and k2′ = 0.359 ± 0.034 h−1 for BHET. Activation energies for ammonolysis are determined as Ea1 = 27.9 ± 2.2 kJ/mol and Ea2 = 37.3 ± 3.3 kJ/mol for DMT and Ea1 = 7.01 ± 0.65 kJ/mol and Ea2 = 13.74 ± 0.66 kJ/mol for BHET. The reaction is autocatalyzed by ethylene glycol (EG), with a 22-fold rate enhancement when EG is present in a 3:1 excess.Ammonolysis of waste PET thermoforms is conducted in methanol and ethylene glycol, with diffusion limitations quantified using particle sizes of 150–250 μm, 250–600 μm, and 1800–2500 μm. The estimated ammonia diffusivity in PET at 100 °C is 1.37 ± 0.48 × 10−7 cm2/s, and diffusion effects reduce the reaction rate by an order of magnitude for millimeter-scale particles. To enhance profitability, the resulting terephthalamide (TPD) undergoes Hofmann rearrangement to produce p-phenylenediamine (PPD) and 1,4-diisocyanatobenzene (DCB). PPD serves as a precursor for Kevlar® synthesis from 100% recycled PET, while DCB reacts with polyols to produce phosgene-free polyurethanes, aligning with Green Chemistry principles. To test economic viability, a large-scale process of upcycling PET to PPD is modeled using ASPEN Plus. Two potential designs are discussed at three different scales of PET processed per day: 1 ton, 30 tons, and 100 tons. Preliminary design results for the 100 ton per day process show high profitability with internal rate of return of 51.5%! These findings enhance our understanding of PET ammonolysis, addressing diffusion barriers, optimizing reaction conditions, and developing scalable pathways for sustainable plastic recycling within a circular materials economy.
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