Hydrothermal liquefaction of microalgae with metal halides for bio-crude production

In this study, the microalgae Spirulina was converted into bio-crudes under hydrothermal conditions. In the first part (non-additive experiments), the effects of different hydrothermal processing temperatures (ranged from 250 to 375 degrees C), different initial pressures (ranged from 1 to 4 MPa) and residence times (ranged from 30 to 120 min) on the bio-crude and solid residue yields were investigated. The highest bio-crude yield was about 36wt% and obtained at 350 degrees C with a residence time of 30 min and an initial pressure of 1 MPa. In second part (experiments with metal halide additives), the effect of metal halides (CsCl, CsCl-KCl, CsCl-NaCl, CsCl-ZnCl2, and CsCl-SnCl2) on the bio-crude yields and compositions were investigated. The metal halides used in the experiments were ineffective on bio-crude yields. The highest diesel fuel content of the bio-crude was 78wt% and obtained from the run with CsCl-NaCl. The use of catalysts slightly increased the carbon content and slightly decreased the oxygen content in bio-crudes in comparison with the run without a catalyst. The key compounds in bio-crudes were nitrogen containing compounds including amines, amides, pyrrolidines, indoles, and pyrazines. The highest heating value of the bio-crude was about 33 MJ/kg and obtained in the runs with CsCl and CsCl-SnCl2.