Co-liquefaction of microalgae and polypropylene in sub-/super-critical water

In the current study, Dunaliella tertiolecta (D. tertiolecta) and polypropylene (PP) were chosen to investigate the co-liquefaction process of microalgae and plastic. The results show that a maximum synergistic effect was found when the mass ratio of D. tertiolecta to PP was 8 : 2. The addition of PP mainly impacts the composition of the bio-oil products, particularly reducing the acid content. When D. tertiolecta was liquefied individually, the relative content of acid in bio-oil could reach 18.73%, while for D. tertiolecta and PP co-liquefaction in a ratio of 8 : 2, the acid content of bio-oil was lower than the detection limit of GC-MS (lower than 100 ppm). The reaction mechanism for the co-liquefaction process of PP and the main components of microalgae has also been studied. The addition of PP has a significant effect on the transformation pathways of carbohydrates in microalgae, and this also promotes the Maillard reaction between carbohydrates and proteins or their hydrolysates.