(403e) Catalytic Hydrothermal Liquefaction of a Microalgae in a Two-Chamber Reactor

We carried out catalytic hydrothermal liquefaction of Nannochloropsis sp. in a novel two-chamber reactor, which physically separates algae and catalyst by a porous metal frit. The experiments were carried out at 350 ^oC for 1h. Algae was loaded in one chamber and catalyst was loaded in another chamber. Water was loaded in both chambers. We explored the effect of different headspace gases and pressure, catalyst loading, and reaction time on the reaction. GC-FID, FC-TCD, GC-MS, ¹³C NMR, and elemental analysis were applied to analyze the products. We determined the biocrude yields and elemental composition, heavy vs. light biocrude fractions, and gas distribution.

The two-chamber reactor produced higher oil yields, a higher light biocrude fraction, a more hydrocarbon-rich gas and more light compounds than did a single-chamber reactor.  The initial addition of catalyst promoted formation of hydrocarbon gases and light liquid-phase compounds compared to runs with no catalyst. The further increase of catalyst loading in the two-chamber reactor decreased the biocrude yield, which may be caused by cracking of hydrocarbons to gas products. More catalyst had the desirable effect of giving a higher light biocrude fraction at a low H₂ pressure.  Using a longer reaction time of 4 hr in the two-chamber reactor decreased oil yield and light compounds but doubled the hydrocarbon percentage in the gas phase. After catalytic hydrothermal liquefaction for 1 h with 10 bar H₂, the carbon and hydrogen content in the light biocrude increased to 75.8 and 9.9%, respectively, compared to 52.6 and 7.4% in the dry algae.  Longer reaction time and higher H₂ loading led to further increases in the carbon and hydrogen content.