PET waste to terephthalic acid, biphenyl, and benzoic acid via dolomite catalytic fast pyrolysis in fluidized-bed reactor: Experimental and techno-economic analysis

The rapid accumulation of polyethylene terephthalate (PET) waste has emerged as a serious environmental problem, highlighting the need for sustainable valorization pathways. This study investigates the catalytic fast pyrolysis of PET using calcined dolomite in a bubbling fluidized-bed reactor to recover valuable aromatic compounds. The operating conditions were systematically varied to evaluate the effect of temperature (475–550 °C) and fluidization velocity (2.0–3.0 × Uₘ_f) on product distribution. Gas chromatography–mass spectrometry (GC–MS) analysis of the pyrolysis oil showed that dolomite catalysis significantly increased the formation of biphenyl and benzoic acid compared to the non-catalytic process. Optimal yields (5.53 wt% biphenyl, 10.65 wt% recycled terephthalic acid (rTPA), and 18.46 wt% benzoic acid) were achieved at 500 °C and 2.5 × Uₘ_f, demonstrating the catalyst's effectiveness in promoting selective bond cleavage and stabilizing oxygenated intermediates. The recovered rTPA was structurally confirmed using FTIR and UV–Vis spectroscopy and found to be suitable for potential reutilization. A comprehensive techno-economic analysis further validated the process's scalability and economic feasibility, attributed to the abundance and reusability of dolomite. These results highlight the promise of dolomite-catalyzed pyrolysis as a circular-economy strategy for PET waste valorization, advancing thermochemical recycling by integrating process optimization, product recovery, and economic assessment.