The investigation examined woody biomass vacuum pyrolysis to understand the yield and quality of the resulting py-oil. The product characteristics and chemical composition were evaluated at varying pyrolysis temperatures and with different carbonate catalysts, including CaCO3, K2CO3, Na2CO3, MgCO3, and NaHCO3. In the absence of catalysts, the highest biomass yield was 48.58 wt.% at 500 °C. The use of carbonate catalysts has been proven to have a notable impact on py-oil yield and its elemental composition under thermal conditions. Notably, the heating value for non-catalytic py-oil was computed at 20.11 MJ/kg, with heating values of 22.49, 22.82, 23.00, 23.83, and 24.17 MJ/kg obtained upon upgrading with CaCO3, NaHCO3, MgCO3, Na2CO3, and K2CO3, respectively. Deoxygenation is the main reaction promoted by K2CO3, during which the oxygen content decreased from 32.64 % to 23.30 %. In addition, the catalyst level was strongly related to the catalyst pH and the increase in py-oil heating value (HHV). GC/MS analysis demonstrated that phenolic compounds can be significantly elevated in the py-oil due to K2CO3 and Na2CO3, indicating that this fuel is of high quality and has potential as a chemical resource. In this work, carbonate-based catalysts for the transformation of wood waste into phenolic-enriched py-oil are proposed to minimise environmental impact and possibly enhance py-oil quality in a vacuum pyrolysis process.
