A shrinking core model for the alkaline hydrolysis of PET assisted by tributylhexadecylphosphonium bromide

The kinetics of the alkaline hydrolysis of PET in an aqueous slurry assisted by tributylhexadecylphosphonium bromide as suitable phase transfer catalyst was studied at temperatures ranging from 60 to 80 °C. The results were adequately described by an unreacted shrinking core model that was first order with respect to sodium hydroxide concentration, quaternary salt concentration, and particle surface area and, hence, to the remaining particle mass raised to the 2/3 power. Temperature effects for both catalytic and non-catalytic steps were modelled with an Arrhenius equation resulting in activation energy values of 61–63 kJ mol−1, thereby suggesting a similar mechanism for the alkaline hydrolysis with or without phase transfer catalyst. Hence, the notable enhancement in reaction rate observed when using the selected quaternary salt was mainly attributed to an increase in the concentration of the reactive hydroxide anion in the liquid–solid boundary layer.