STUDIES ON THE PRODUCTION OF P-PHENYLENEDIAMINE FROM PET WASTE BASED ON AN EFFICIENT METHOD AND INCREASING THE REACTION YIELD

Abstract. This study focuses on the synthesis of p-phenylenediamine using polyethylene terephthalate (PET) waste as a raw material. Initially, terephthalic acid was recovered from PET waste via an alkaline hydrolysis method. The obtained terephthalic acid was then amidated with urea under high pressure in the presence of a catalyst. Subsequent chlorination was carried out under controlled neutral conditions. In the following step, an alkali treatment based on the Hofmann rearrangement was applied, and the resulting product was filtered and purified from salts through extraction with organic solvents. Throughout the process, key parameters such as catalyst type, temperature, pH, chlorine flow rate, and pressure were systematically varied to maximize the reaction yield. The composition and properties of the synthesized p-phenylenediamine were characterized using IR spectroscopy, SEM, TG, and DTA analyses. Optimal conditions were established for the amidation step, with a mass ratio of terephthalic acid to urea of 1:1.4. The reaction temperature was 185 ºC, the pressure was 6 atm, 1.6% (K1) catalyst was used, and the reaction took 3 hours. For the chlorination process, the reaction took 3.5 hours, 5ºC, pH 7, and a chlorine flow rate of 4 g/min were considered the most optimal options, and the reaction yield of p-phenylenediamine was 95%.