Catalytic Pyrolysis of Spirulina platensis Residue (SPR): Thermochemical Behavior and Kinetics

Abstract

Abstract. The pyrolysis characteristics of Spirulina platensis residue (SPR) with silica–alumina catalysts were investigated using thermogravimetric analysis (TGA). The effects of differing amounts of catalysts on thermochemical behavior and kinetics parameters (pre-exponential factor in Arrhenius equation [A] and activation energy [Ea]) were studied. The experiment was carried out from 30 to 1000°C at a heating rate of 20°C/min for the case of non-catalytic and catalytic pyrolysis (silica–alumina). For the catalytic pyrolysis, also of interest were the catalyst-to-SPR weight ratios of 1:1 and 1:2. The TGA curve and differential thermogravimetric peak analysis results suggest that the use of catalysts in pyrolysis (particularly at a catalyst-to-SPR weight ratio of 1:1) reduces both pyrolysis time and temperature range to 14.68 min and 230–555°C, respectively. The kinetic parameters were then calculated in a one-step global non-isothermal model and solved using a least squares method in MATLAB. The presence of catalyst was able to reduce Ea to the lowest value from 41.10 kJ/mol (without catalyst) to 40.77 kJ/mol (weight ratio of 1:2) and 39.46 kJ/mol (weight ratio of 1:1) in Zone 1. However, the increase of catalyst quantity was not in line with the increase of reaction rate constant (k) and resulted in reasonably low A of, respectively, 593.30, 406.31, and 266.37.