BIO-OIL PRODUCTION FROM ALGAE BY TWO-STEP HYDROTHERMAL LIQUEFACTION PROCESS

Abstract

Microalgae is biomass which can be used as an alternative energy source since it has high performance to produce high content of liquid fuel and it also has high growth rate. This research work presents the method to convert microalgae as the liquid fuel via hydrothermal liquefaction in semi-continuous reactor under high temperature and pressure to degrade microalgae as organic compounds with smaller molecules. The objective of this research was to study the production and quality improvement of bio-oil derived from two-step hydrothermal liquefaction and compared to one-step hydrothermal liquefaction operated at 280 to 360 oC, water pressure of 12 to 20 MPa and water flow rate of 0.25 to 1.00 mL/min. The result showed that this process carried out at 320 oC, 20 MPa and a water flow rate of 0.50 mL/min provided 29.5 wt% of bio-oil containing a large amount of nitrogen compounds (8.7 wt%). Thus, the two-step hydrothermal liquefaction was applied. In the first step, the temperature was controlled in the range of 150 to 225 oC and the temperature used in the second step was 280 to 360 oC. All process was under a pressure of 12 to 20 MPa with a water flow rate of 0.25 to 1.00 mL/min. It was found that the two-step hydrothermal liquefaction decreased the amount of nitrogen compounds to 4.8 wt% with high bio-oil yield (32.0 wt%). When the continuous phase was changed from water to basic solutions containing sodium carbonate or potassium hydroxide (10 wt% of solvent), the amount of nitrogen compounds in the obtained bio-oil decreased to 3.1 wt% with a lower bio-oil yield (22.4 wt%).