Catalytic upgrading of crude algal oil using platinum/gamma alumina in supercritical water

We report herein on the catalytic upgrading of crude oil, produced from the hydrothermal liquefaction of Chlorella pyrenoidosa over platinum on gamma alumina (Pt/γ-Al2O3) in supercritical water (SCW) at 400 °C for 1 h. We determined the influence of catalyst loading (varied from 0 to 40 wt.%), water density (varied from 0 to 0.1 g/cm3), and formic acid (HCOOH) loading (varied from 2 to 37 mmol) on the product yields and properties of the treated oil. The product yields and properties of the treated oil were largely insensitive to the catalyst loading and sensitive to water density and HCOOH loading. Increasing the catalyst loading or decreasing the water density and formic acid loading produced a lower yield but higher quality treated oil. Moreover, including the Pt/γ-Al2O3 in the reactor led to a product oil that was a freely flowing liquid, as opposed to being the viscous, sticky, and tar-like crude oil material. Compared to SCW + H2, the presence of SCW + HCOOH effectively controls the coke formation. The catalyst experienced a reduction in surface area and micropore volume when used for hydrothermal upgrading. These changes did not influence the catalyst activity, however. Unreacted H2 was the main gaseous product, together with lower yields of CO2 and C1C5 hydrocarbon.