Decomposition of gaseous terephthalic acid in the presence of CaO

The decomposition of PET during thermal treatment of municipal waste results in the formation of sublimating substances such as terephthalic acid (TPA) and benzoic acid, causing blockage and corrosion of pipes in the treatment facilities. To prevent these effects, TPA can be decarboxylated in the presence of calcium oxide (CaO) to obtain benzene as the main product. However, high concentrations of TPA cause the formation of large char fractions, reducing the yield of desired products. In this investigation, TPA was decarboxylated using a fixed-bed reactor filled with CaO. To increase the yield of benzene and reduce the carbonaceous residue, the effects of pyrolysis temperature and TPA feed rate were investigated. The best results were achieved at 500 °C and a TPA feed rate of 51 mg L¹, yielding 67% benzene with a purity of 99.2% and a carbonaceous residue containing 18% of the initial carbon.