Aromatic-rich oil production from catalytic co-pyrolysis of pine sawdust and LDPE with bifunctional biochar by different preparation methods

Background

Catalytic co-pyrolysis of biomass with waste plastics can produce high-quality chemicals, making it a potential alternative to fossil fuels. The production of aromatic-rich oil was achieved in this work by the catalytic co-pyrolysis of pine sawdust and low-density polyethylene (LDPE) using a series of biochar (BC) made using different preparation methods. Zinc chloride (ZnCl₂) was employed to activate the BC during the preparation process, owing to its optimal activity for the co-pyrolysis intermediates. The study compared the effects of BCs activated using different treatment methods on the yield and fractions of pine sawdust and LDPE co-pyrolysis in a fast pyrolysis tube furnace at 650 °C.

Results

The study indicates that the ZnCl₂ BC, prepared from pine sawdust by fast pyrolysis (F-AC), exhibited the best aromatic catalytic activity. The selectivity to aromatic hydrocarbons was 72.53%, and the content of BTEX (benzene, toluene, ethylbenzene, and xylene) was 32.17%.

Conclusion

The Diels–Alder reaction and aromatization were made more effective due to the Zn sites and large pore structure in F-AC. Using Fourier transform infrared, scanning electron microscopy and X-ray photoelectron spectroscopy analysis, it was found that F-AC contained more oxygen (O)-containing groups in abundance, which improved its adsorption capacity for reaction intermediates. At the same time, the porous structure and high SSA of BC provided a region for the reaction intermediate to interact with the active center containing O-containing groups. This enhanced the synergy between biomass and plastics and raised the selectivity of aromatic hydrocarbons. It provides a reference for the application of carbon-based materials in the co-pyrolysis of biomass and waste plastics. © 2024 Society of Chemical Industry (SCI).