Improving algal biocrude from hydrothermal liquefaction

[USA] Biocrude oil obtained from hydrothermal liquefaction (HTL) of algae can be an energy-efficient replacement for the fossil crude oil normally used in the production of fuels. HTL is a high-pressure, high-temperature process that allows scientists to mimic, in a matter of minutes, the natural geological processes considered responsible for the production of fossil fuels.

HTL does not require drying of the algal biomass (an energy-consuming step) and enables conversion of full algae cells to fuels. However, crude oils from traditional HTL processes have a high content of nitrogen-rich aromatic heteroatoms – a major hurdle in the upgrading of crude oil to fuels using existing refinery infrastructures.

To address this challenge, researchers in SRI’s Chemistry and Materials Laboratory are improving a novel process that separates the nitrogen-rich compounds that come from proteins. The resulting side stream can be recycled back into the algae production process.

The nitrogen removal process reduces the amount of aromatic heterocycles in the biocrude oil, which can help meet environmental requirements and extend the lifetime of catalysts used during the upgrading to fuels.

The SRI-led team is conducting this work for the Department of Energy’s Carbon Hydrogen and Separations Efficiency (CHASE) program. They are studying chemical pathways in the hydrothermal process, analyzing products, evaluating upgrading potential of biocrude oils, executing continuous operation tests, studying scale-up, and carrying out lifecycle analysis.

After in-depth evaluation of the different scenarios, SRI will select operating conditions that optimize carbon and energy efficiencies while maintaining product composition within industrial specifications.

This material is based upon work supported by the Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), under Award Number DE-EE0000635/0000.


Photo: High-pressure reactor for hydrothermal liquefaction

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