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

The co-pyrolysis of microalgae with plastic for valuable chemical production is promising to address the infe-riority 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 composi-tions 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%).

Automated summary

The co-pyrolysis of microalgae with plastic shows promise for producing valuable chemicals and addressing waste plastic problems. Understanding the effects of different catalysts on the co-pyrolysis and reaction pathways can help intensify the process. Experimental results showed that ZSM-5 reduced the activation energy of co-pyrolysis, while CaO had the opposite effect. Both catalysts reduced the oxygen and nitrogen content in the pyrolysis product, but CaO preferred oxygen removal and ZSM-5 favored nitrogen removal. ZSM-5 was more selective for aromatic hydrocarbon conversion, while CaO favored the formation of aliphatic hydrocarbons.