Study on Preparation of P-Phenylenediamine from Wasted Polyester

Abstract

The important fine chemical intermediate p-phenylenediamine (PPA) was prepared by a two-step process of catalytic ammonolysis and Hoffmann rearrangement from polyester fiber waste (WP) as raw material. The catalysts, solvents, water, solvent dosage, reaction temperature and other factors in the ammonolysis process were investigated respectively. As well as the solvents, reaction temperature, sodium hydroxide dosage, sodium hypochlorite dosage, residence time and other factors in the rearrangement process. The optimum process condition was obtained as follows: the ratio of m(WP):m(nano-copper oxide, N-Cu):m(NH₃)=1:0.1:11 for catalytic ammonolysis, reaction temperature of 150°C, reaction time of 24 h, and anhydrous environment; the reaction temperature of microchannel rearrangement was 60°C, residence time of 300 s, and the ratio of n(terephthalamide, DMA):n( NaOH):n(NaClO)=1:3.2:2.1. The conversion of polyester fiber waste yarn was 71.2% and the yield of p-phenylenediamine was 58.2%.