Effect of additive mixture on microwave-assisted catalysis pyrolysis of microalgae

Abstract

In this paper, the microwave-assisted pyrolysis characteristics of Dunaliella Salina under compound additive (the mixture of graphite and Fe2O3) was studied. Different addition amounts (5% and 10%) and varying mixing ratios (graphite/Fe2O3 = 0:10, 3:7, 4:6, 5:5, 6:4, 7:3, and 10:0) of compound additive were studied by thermogravimetric analysis (TGA). The results revealed that the addition of compound additive increased the microwave heating rate considerably. With the increase of the proportion of graphite, the comprehensive pyrolysis characteristic index (S) increased, while the initial pyrolysis temperature (Ti) and peak temperature (Tp) decreased. When the additive amount was 5%, the G3Fe7 (graphite/Fe2O3 = 3:7) group had synergistic effect on the average weight loss rate (Ra), the maximum heating rate (Hm) and average heating rate (Ha). When 10% compound additive was added, graphite and Fe2O3 (GFe) inhibited all the temperature characteristic parameters. At the same mixing ratio, when the compound additive amount increased from 5% to 10%, Ti and Tp decreased, pyrolysis residue mass (M) increased, and reaction rate at the peak (Rp) showed a downward trend. Kinetic analysis showed that additives could reduce the apparent activation energy (E) of D. salina, and the E of G7Fe3 group with 10% addition amount was lowest (28.26 kJ/mol).