Production of light bio-aromatics from co-catalytic fast pyrolysis of torrefied bamboo and high-density polyethylene

Light aromatics are extremely important building blocks in the chemical industry which can be produced from the co-catalytic fast pyrolysis (Co-CFP) of biomass and waste plastics. In this work, torrefaction pretreatment was first employed to remove the oxygen element from bamboo for improving the the quality of bamboo. Then, the hierarchical HZSM-5 was prepared by alkali pretreatment of HZSM-5 using Na₂CO₃ solution. At last, the optimal operation condition was investigated during Co-CFP of bamboo and high-density polyethylene (HDPE). Results showed that during torrefaction pretreatment process, the carbon content of bamboo gradually increased with the increase of torrefaction temperature, while the oxygen content decreased. The oxygen removal rate and HHV reached their maximum value of 40.3% and 25.64 MJ/kg at 300 ℃, respectively. The specific surface area, pore volume of mesopore, and average pore size of HZSM-5 increased after alkali pretreatment, indicating the development of the micro-mesoporous hierarchical structure in HZSM-5. The Diels-Alder reaction between the furans from pyrolysis of bamboo and the light olefins from pyrolysis of HDPE was the most important synergistic catalytic reaction which could highly promote the formation of light aromatics. The maximum yield of BTX (benzene, toluene, and xylene) was 3.05×10⁸ p.a./mg when the torrefaction temperature, the concentration of Na₂CO₃, the mass ratio of torrefied bamboo and HDPE, and the pyrolysis temperature were 250 ℃, 0.6 mol/L, 1∶2, and 800 ℃, respectively.