Catalytic fast pyrolysis of Arthrospira platensis (spirulina) algae using zeolites

• Fast pyrolysis of A. platensis (spirulina) algae was carried out using Py–GC/MS.
• Effects of temperature, different zeolites, algae:zeolite on products were evaluated.
• Production of long chain organics (>C10) decreased with increase in temperature.
• Zeolites promoted the formation of nitriles, aromatics and cyclic hydrocarbons.
• Benzene, toluene, xylene, cyclobutane and acetonitrile were the major organics obtained using zeolites.

This study is aimed at characterizing the thermal stability and evaluating the conversion of Arthrospira platensis (Spirulina platensis), a species of microalgae, to various chemicals and intermediates via non-catalytic and catalytic fast pyrolysis using different zeolites. Thermogravimetric analysis was performed to evaluate the kinetics of decomposition of the algae using integral isoconversional method of Vyazovkin, and fast pyrolysis experiments were performed in a micropyrolyzer and the relative composition of the pyrolysates was analyzed in a gas chromatograph/mass spectrometer. The effects of (i) temperature during non-catalytic fast pyrolysis, and (ii) zeolite type, zeolite:algae mass ratio and temperature during catalytic fast pyrolysis on pyrolysate composition were analyzed. The formation of long chain organics like alkanes, alkenes, carboxylic acids and nitriles decreased, while that of CO2 increased with increase in pyrolysis temperature from 350 to 800 °C. The addition of ZSM5, zeolite-β and zeolite-Y catalysts at 10:1 wt./wt. loading to algae at 600 °C significantly altered the product spectrum involving the formation of nitriles, aromatics, and cycloalkanes. Acetonitrile, benzene, toluene, xylene, cyclobutane and dimethyl cyclopropane were the major organics. Calorific value of the organic components in the pyrolysate (>30 MJ kg−1) was significantly higher than that of the raw algae (20.75 MJ kg−1). Increase in catalyst loading (from 2:1 to 50:1 wt./wt.) and temperature (from 350 to 600 °C) resulted in significant increase in production of monoaromatics, polyaromatics and cycloalkanes, whereas the formation of nitriles increased and decreased with catalyst loading and temperature, respectively. Plausible reactions leading to the observed product distribution are discussed. This study shows that useful organic intermediates can be obtained via catalytic fast pyrolysis of spirulina.