Pyrolysis behaviour of the main carbohydrates of brown macro-algae

The pyrolysis characteristics of the four main carbohydrates (alginic acid, mannitol, laminarin and fucoidan) of brown macro-algae were investigated using py-GC/MS over a wide temperature range (200–800 °C) and thermogravimetric analysis (TGA). The initial pyrolysis kinetic parameters have been calculated by using the Senum and Yang integral approximation. Py-GC/MS indicated that each of the model compounds produces a characteristic fingerprint. The volatile fragment for alginic acid was found to be predominantly furfural. For fucoidan the main fragments were found to be 5-methyl 2-furancarboxaldehyde and 2-methoxy-5-methyl thiophene. For mannitol the main fragments were found to be 1-(2-furanyl) ethanone and dianhydromannitol and finally for laminarin 1,2-cyclopentanedione, 2-hydroxy-3-methyl 2-cyclopenten-1-one and acetic acid. TGA analysis has revealed the different degradation pathways of the carbohydrates. Laminarin and alginic acid were found to have lower activation energies than mannitol and fucoidan. Activation energy for fucoidan was high for biomass samples (247.2 kJ/mol). An attempt to correlate the biochemical composition of brown macro-algae with TGA data was also made.