Comparative study of the catalytic co-pyrolysis of microalgae (Chlorella Vulgaris) and polypropylene with acid and base catalysts toward valuable chemicals production

Abstract

The co-pyrolysis of microalgae with plastic for valuable chemical production is promising to address the inferiority of microalgae conversion while solving waste plastic problems. A deep understanding of the synergistic effects of different catalysts on the co-pyrolysis and reaction pathways could promote process intensification through interpreting the kinetics and product characterizations. The thermogravimetric analyzer (TGA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermal cracking-gas chromatography/mass spectrometer (py-GC/MS) facilitated the understanding of the process. The weight-loss rates of the catalytic co-pyrolysis showed a pattern of non-catalytic < CaO < ZSM-5. The experimental and theoretical values of the co-pyrolysis activation energy were 114.99 kJ/mol and 194.80 kJ/mol, respectively. ZSM-5 reduced the co-pyrolysis activation energy, while CaO had the opposite effects. Both CaO and ZSM-5 reduced the compositions of the oxygen- and nitrogen-containing groups in the pyrolysis product, but CaO preferred oxygen removal, and ZSM-5 favored the nitrogen removal. ZSM-5 was selective for aromatic hydrocarbons conversion (from 12.23% to 14.56%), while CaO was more inclined to aliphatic hydrocarbons formation (from 70.67% to 80.95%).