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

초록

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 degrees C) and fluidization velocity (2.0-3.0 x Umf) 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 degrees C and 2.5 x Umf, 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.

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