Upgrading of hydrothermal liquefaction biocrude from algae grown in municipal wastewater

Algae biocrude was treated with hydrogen using metal catalysts supported on activated carbon for the production of biofuel. The biocrude was produced using hydrothermal liquefaction of microalgae (Scenedesmus-dominated polyculture) grown in municipal wastewater. Four metal catalysts (platinum, ruthenium, nickel and cobalt) were tested at 350 degrees C under the presence of high pressure hydrogen, and all the experiments were conducted at a weight hourly space velocity of 0.51 g/g(cat).h. Hydrotreating with all the catalysts increased higher heating value, while reducing viscosity and total acid number (TAN) of the biocrude. For example, biocrude upgraded using platinum catalyst increased the heating value from 45.9 to 47.0 MJ/Icg and reduced the TAN from 11.56 to 0.1 mg KOH/g. In addition, the liquid produced was colorless. Furthermore, the use of ruthenium and platinum catalysts greatly enhanced the yield of hexadecane and octadecane in the hydrogen-treated liquids whereas heptadecane was less favored. Overall, hydrogen treatment of biocrude was effective in improving the quality of biocrude produced from algae grown in wastewater. The BET surface area was reduced for all the spent catalysts. An SEM-EDS analysis revealed that some liquid products and sulfur were deposited in the spent catalysts. (C) 2015 Elsevier B.V. All rights reserved.