In-situ catalytic pyrolysis upgradation of microalgae into hydrocarbon rich bio-oil: Effects of nitrogen and carbon dioxide environment

Abstract

Pyrolysis of Spirulina Platensis (SP) microalgae was carried out under different reaction environment such as nitrogen (N₂) and carbon dioxide (CO₂) at different reaction temperatures of 300, 350, 400, 450 and 500 °C. Catalytic upgradations were examined over solid acid (ZSM-5) and solid base (MgO) catalyst, and with ZSM-5-MgO catalysts mixtures. Results showed, pyrolysis of non-catalytic biomass yielded maximum bio-oil of 43.6% under N₂. However catalytic upgradation in CO₂ environment produced lower bio-oil due to the coke formation. Maximum bio-oil (46.2 wt%) was obtained with basic metal MgO catalyst in N₂ environment compared to other catalyst and environments. Mixture of MgO-ZSM-5 catalyst improved the bio-oil yield (37.8-48.6 wt%) compared to individual catalytic reaction under N₂ and CO₂. Higher high heating value (HHV) was observed in catalytic bio-oil 36.8 MJ/Kg. Bio-oil (catalytic) analysis revealed that 64-70% of compounds are in hydrocarbon range. Bio-oil was rich in hydrocarbons of C₇-C₁₈ range with less oxygenated compounds.

Keywords: Acid-base catalyst; Catalytic pyrolysis; Environment effects; Fixed bed reactor; Hydrocarbons.