Yale team advances toward a one-pot oil extraction and transesterification process for algal biodiesel using a supercritical CO2 system
A team from Yale described advances toward achieving a single-step lipid extraction and transesterification process to produce algal biodiesel during the symposium “Biobased Feedstocks for Chemical and Fuel Production” at ACS’ 16th annual Green Chemistry & Engineering Conference. Such a one-pot process would have a significant impact on the lifecycle impact of algal biodiesel production.
Led by Dr. Julie Zimmerman, Associate Professor of Green Engineering, the researchers investigated the fundamental science necessary to achieve a one-pot approach that both extracts and transesterifies lipids from algae using supercritical carbon dioxide/methanol (scCO2/MeOH) and heterogeneous catalysts.
Zimmerman points out that supercritical carbon dioxide has long had a variety of commercial and industrial uses, ranging from a process used to decaffeinate coffee to a more environmentally friendly solvent for dry cleaning clothing. The process is nontoxic, which makes it an attractive alternative to some of the harsher, potentially toxic chemicals used in other algae-to-biofuel technology, she noted.
Lindsay Soh, a graduate student in Zimmerman’s lab, noted that similar approaches have been proposed for using supercritical methanol and ethanol; however, the use of supercritical carbon dioxide requires lower temperatures, making it easier to work with and less energy-intensive. Another advantage, Zimmerman noted, is that the supercritical carbon dioxide, which acts as a solvent for oil, can be tuned to extract only specific components from algae oils, saving time and resources. Such tuning is not possible with conventional solvents.
Zimmerman and Soh already have shown in previous research that supercritical carbon dioxide can extract lipids from algae (Soh and Zimmerman, 2011). Soh now is moving ahead with the next step, which involves converting the lipids to biodiesel, with the ultimate goal of performing the entire extraction and conversion in a single production chamber.
Soh is experimenting with a variety of both basic and acidic heterogeneous catalysts, focusing on commercially available catalysts that are insoluble in the supercritical carbon dioxide mixture so that they can be recovered after the reaction without additional steps, which take time, money and, frequently, potentially toxic chemicals.
The ACS Green Chemistry Institute (GCI) is an organization focused on catalyzing and enabling the implementation of green chemistry and engineering throughout the global chemical enterprise.
Lindsay Soh, 147 - One-pot algal biodiesel production in supercritical carbon dioxide
Lindsay Soh and Julie Zimmerman (2011) Biodiesel production: the potential of algal lipids extracted with supercritical carbon dioxide. Green Chem., 13, 1422-1429 doi: 10.1039/C1GC15068E