article · American Journal of Applied Chemistry
Recycling Polyethylene terephthalate (PET) by hydrolysis using excess citric acid molecules as catalysts to generate H<sup>+</sup> protonic acid sites had been undertaken. The products of this recycling process are PolyEster Citric Acid (PEAc), formed by the polyesterification of two citric acid molecules, Ethane Diol (ED) or ethylene glycol, and a new solid material called PAT-Ac, whose molecular formula is made up of one molecule of pure terephthalic acid (PAT) and two molecules of citric acid. Two procedures had been established, one for extracting the PEAc solution and the Ethane diol in acetone solution (AED-solution) using the usual organic solvents dichloromethane and acetone, and the second for extracting pure Ethane diol (ED) by vacuum evaporation using a rotavapor. This recycling was carried out in a laboratory glassware reactor, in a 1000ml cylindrical beaker covered by a funnel with a conical lid, capped but non-watertight, and therefore under atmospheric pressure at a temperature of 150°C. A kinetic study of this recycling process was carried out, using an acid-base assay with HF-0.0026N to follow the progress of the recycled TAP and deduce the evolution of PET conversion with reaction time; and an acid-base titration with NaOH-0.05N to quantify the H<sup>+</sup> protonic acid sites coming from the acid catalysts of the citric acid molecules and deduce the evolution of the citric acid quantity in the reaction medium. This latter assay also enabled the determination of the PAT-Ac molecular structure. A reaction mechanism for this recycling of PET by hydrolysis, using excess citric acid molecules as a catalyst source of H<sup>+</sup> proton active sites, is proposed and validated by the kinetic data collected during the various acid-base assays mentioned above. The maximum conversion of PET to PAT and ED recorded during the kinetic study is 34.49% after 20mn reaction time or 1.5114×10<sup>-3</sup> [moles of PAT regenerated per Gram of PET load], or 7.5572×10<sup>-5</sup> [moles of PAT regenerated per Gram of PET and per Minute]. In addition, the volume of ED collected is 17ml and the mass of PAT-Ac synthesized is 2.6 [g].
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DOI: 10.11648/j.ajac.20251303.13
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