Supercritical Fluid Extraction of Valuable Chemicals: Application of Microalgae and Pyrolysis Oil as Feedstocks

Author

Osariemen Ogbeide, The University of Western OntarioFollow

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Prof. Paul Charpentier

2nd Supervisor

Prof. Mita Ray

Joint Supervisor

Abstract

In this dissertation, pure and modified carbon dioxide were used as non-conventional solvents for the investigation of lutein, chlorophyll a, chlorophyll b extraction from microalgae and for caffeine extraction from the pyrolysis oil of spent coffee grounds. The use of toxic organic solvents in supercritical fluid extraction has propelled research efforts to develop new solvents that are environmentally friendly and provide faster extraction compared to conventional extraction processes. For this reason, phosphatidylethanolamine (PE), a major phospholipid consisting of 14% of the entire soybean lecithin was acetylated with acetic anhydride, providing a surfactant (N-A-PE).

Then, the synthesized N-A-PE was employed as a co-solvent with CO₂ for valorization of compounds from microalgae. Among all the solvent mixtures tested containing N-A-PE, a maximum oil yield of 52 wt. % was obtained when using 5% EtOH/95% CO₂, N-A-PE:algae mass ratio of 0.6, 338 K, 40 MPa and 2 mL/min. Then, algae oil was transesterified with methanolic KOH to produce biodiesel. The biodiesel content was analyzed by GC-FID providing palmitic acid (C16:0), oleic acid (C18:1), linoleic (C18:2) and arachidic acid (C20:4) yields of 27, 17, 18 and 4 mg/g dry algae, respectively. The best extraction yield of lutein (416 µg/g dry algae) was obtained at 338 K, 40 MPa and 2 mL/min while that of chlorophyll a was 532 µg/g dry algae found at 338 K, 40 MPa, 1.3 mL/min using 7.5% ETOH/92.5% CO₂ at N-A-PE:algae mass ratio of 0.35. Chlorophyll b was better extracted using 10% ETOH/90% CO₂ without N-A-PE resulted to 2760 µg/g dry algae using 338 K, 40 MPa, 1.3 mL/min.

Pyrolysis oil of spent coffee grounds was used as a resource for caffeine extraction using pure and modified CO₂ methods. The SFE extraction results showed that a maximum of 90 % of caffeine was extracted from this pyrolysis oil using 10% EtOH/90% CO₂ at 35.2 MPa, 333 K and 1 mL/min at extraction time of 20 min. Later, purification of 99.9 % of caffeine was attainable from the extract stream by supercritical fluid chromatography at 14.5 MPa, 333 K and 2 mL/min, using 10-30% ethanol gradient as a co-solvent in CO₂.

Recommended Citation

Ogbeide, Osariemen, "Supercritical Fluid Extraction of Valuable Chemicals: Application of Microalgae and Pyrolysis Oil as Feedstocks" (2017). Electronic Thesis and Dissertation Repository. 4518.
https://ir.lib.uwo.ca/etd/4518