Thermal Treatment of Crude Algae Oils Prepared Under Hydrothermal Extraction Conditions

Abstract

We demonstrate that removal of oxygen and metals from crude algae oils produced by hydrothermal treatment processes is possible by thermal means alone and without the use of catalysts or hydrogen. Thermal treatment can reduce the total amounts of acids in the crude algae oil and thus decrease the total acidity of the oil. Thermal treatment also reduces the boiling point range of crude algae oils, making them more volatile and less viscous, benefitting shipping and upgrading. Trace metals are significantly reduced as the thermal treatment temperature increases. The results obtained in this study are consistent with existing theories of the formation of petroleum crude oils and create a link between the upgrading of crude algae oils and the mechanisms involved in the formation of conventional fossil fuels. The results and possible pathways of the reaction mechanisms are presented.

Process application of Subcritical Water Extraction (SWE) for algal bio-products and biofuels production

“…Roussis et al [78] demonstrated a thermal treatment process to remove oxygen and metals from fresh algal oils. They found that the thermal treatment improves oil fluidity characteristics by increasing volatility and decreasing viscosity thus reducing their boiling point.…”

Thermogravimetric and kinetic analysis of bio-crude from hydrothermal liquefaction of Enteromorpha prolifera

“…The total mass loss increased slightly from 78.5% to 79.5% as β increased from 5 to 40 K/min, indicating that the thermal decomposition reaction resulted in coke and char yields of approximate 21.0%. Roussis et al [12] reported that the solid yield was 19.3% after thermal treatment of bio-crude at 723 K for 60 min. In the range of 513-603 K, the maximum mass loss rate gradually decreased and the corresponding temperature increased with increasing β possibly due to thermal hysteresis effect.…”

“…(7), (11), (12) and (13), plots of ln[β(dα / dT)], lgβ, ln(β / T 2 ) and ln[β / T 2 (1 − 2RT / E)] versus 1/T yields straight lines, and the slope corresponds to − E/R or − 0.4567E/R. Because the left-hand side of Eq.…”

“…Thermal upgrading operated at lower pressures does not require novel metal catalysts nor high pressure hydrogen, thus the equipment investment and operating cost can be greatly reduced. Roussis et al [12] proposed a thermal treatment process of bio-crude. After thermal treatment at 673 K for 60 min, the density, acidity and boiling range distribution of bio-crude were all improved, the oxygen content was reduced to 0.2%, and the higher heat value (HHV) was elevated to 45 MJ/kg.…”

Hydrothermal Disintegration and Extraction of Different Microalgae Species

“…As only little information on this topic can be found in literature [11,12,15,16] the aim of this work was to study the described effect for several different algae species, as the morphologic variation between different microalgae species and strains can be great. In order to evaluate if the extraction of hydrothermal treated algae is efficient the obtained results are compared with yields and qualities of conventional extraction methods.…”