Slow Pyrolysis of Quercus cerris Cork: Characterization of Biochars and Pyrolysis Volatiles

Abstract

Waste cork granules of Quercus cerris bark were subjected to isothermal and non-isothermal slow pyrolysis. The heat of the reaction, as well as the yields and properties of biochar, bio-oil, and pyrolysis gas were investigated by thermogravimetric analysis, FT-IR, CHN elemental analysis, higher heating value (HHV) determinations, scanning electron microscopy (SEM), and gas chromatography (GC). The slow pyrolysis was carried out in a semi-batch reactor using an isothermal or a non-isothermal dynamic approach. The results demonstrated that isothermal or non-isothermal slow pyrolysis of cork is a slightly exothermic reaction that produces biochars. The elemental analysis results indicated that non-isothermally produced chars have similar fuel properties compared to isothermally produced chars. The FT-IR results showed that cork suberin undergoes a higher degree of degradation in isothermal chars and aromatization begins in the char structure. Bio-oils are also produced and they consist of C5–C12 hydrocarbons with C8 carbon compounds making up the main fraction. Lighter components, mainly C1–C2 hydrocarbons are collected in the gas phase. The overall results indicate a possible reduced-cost route for the production of cork-based biochars by using non-isothermal slow pyrolysis.