Conversion and rate behavior of brown macroalgae in pyrolysis: Detailed effects of operating parameters.

Non-catalytic pyrolysis of brown macroalgae (Padina sp.) was studied in a batch reactor at temperature ranges of 400-600 °C and 10-90 min reaction times on the product distribution and conversion rate behavior. The highest pyro-oil and pyro-gas yields were obtained at 600 °C, which reached 67 wt% and 27 wt%, respectively, when the reaction times were prolonged (30-90 min). In addition, the high reaction temperature resulted in more generations of heavy tar and a considerable enhancement in aromatization degree. N-aromatic groups and phenol were observed from pyro-oil at 500 °C and 600 °C, respectively. Tar yield increased with reaction temperature, reflecting an order of reaction greater than one for tar production. The rate constant of tar formation was found to be 0.0013/s at 400 °C; 0.0023/s at 500 °C; and 0.0033/s at 600 °C, respectively, with the reaction order being higher than one (1.25). These findings highlighted that the proposed model could be used to accurately predict the pyrolysis process's behavior.