Co-pyrolysis of biomass and polyethylene terephthalate (PET) is an alternative to produce chemical and energy products

Abstract

Polyethylene terephthalate (PET) plastics are valuable materials for packaging and various consumer items, but poorly managed PET waste constitutes a serious environmental issue. In order to solve this problem, the process of copyrolysis of PET and biomass has been an alternative for reuse of this material and generation of solid and liquid products of industrial interest. Therefore, the main objective of this study was to evaluate the effect of different heating rates (1, 3 and 5 ºC.min-1 ) and the addition of PET in different proportions (0, 15 and 25%, weight basis) on the co-pyrolytic charcoal and wood vinegar from the copyrolysis of biomass and PET. Subsequently, the co-pyrolysis products (copyrolytic charcoal, pyroligneous liquid and non-condensable gases) were calculated. Co-pyrolytic charcoal was evaluated for its physical (bulk density, apparent density, and moisture), chemical (Fourier-transform infrared spectroscopy) and energy (higher, lower, and net heating values) properties. For purification of the pyroligneous liquid, double-distillation was carried out at 100 °C to eliminate the toxic fraction of the material and obtain the fraction of interest, called wood vinegar. Purification yields were calculated. Subsequently, the pH, density and viscosity of wood vinegar were analyzed. The chemical evaluation of wood vinegar was performed using GC-MS analysis. The addition of PET reduced by 7% the yield of co-pyrolytic charcoal and by 20% the yield of pyroligneous liquid, products of the co-pyrolysis. Higher PET additions (25%) associated with lower heating rates (1 ºC.min-1 ) were responsible for a maximum energy density of 4.7 Gcal.m-3 of the co-pyrolytic charcoal. Regarding wood vinegar, lower heating rates (1 ºC.min-1 ) favored the formation of more chemical compounds (ketones, hydrocarbons, furans and pyrans). However, ketones were still the major compounds. In short, the co-pyrolysis of biomass and PET can be a sustainable and innovative strategy for generating solid and liquid products of commercial value.