Study on synergistic mechanism of Co-hydrothermal liquefaction of microalgae and macroalgae

The mechanism of Co-hydrothermal liquefaction (Co-HTL) between microalgae (Chlorella vulgaris) and macroalgae (Enteromorpha clathrata) was studied, and the effects of different mass ratios of microalgae and macroalgae on the yield of Co-HTL products and the distribution of nitrogen-contained compounds were discussed. The study found that Co-HTL has a positive effect on the increase of bio-oil yield, with a maximum increase of 15.0 wt%. The ultimate analysis, FTIR, GC-MS and other means were carried out to investigate the composition liquefied oil products. Compared with the bio-oil obtained from Enteromorpha, the nitrogen compounds content of amides in the bio-oil prepared by mixed sample increased significantly, and maximum yield increased from 0.9% to 13.6%, while pyrazine and piperazine significantly decreased by 5.1% and 11.0%, respectively. This could be due to the intensification of the amidation reaction in the Co-HTL, and consequently interfering with the Maillard pathway. Except for at the ratio of 1/1, the content of nitrogen compounds in the oil phase at all ratios was lower than the theoretical value. At the ratio of 3/1, the content of nitrogen compounds decreased the most compared with the theoretical value, which is reduced by 7.5%, and the content was 41.0%. When the mixing ratio was 1/3, the nitrogen content of aqueous phase was the highest (85.7%), and the total nitrogen content in aqueous phase was 2669.2 mg/L.