Doctor of Philosophy
Chemical and Biochemical Engineering
Prof. Paul Charpentier and Prof. Mita Ray
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.
Ogbeide, Osariemen, "Supercritical Fluid Extraction of Valuable Chemicals: Application of Microalgae and Pyrolysis Oil as Feedstocks" (2017). Electronic Thesis and Dissertation Repository. 4518.
Available for download on Sunday, December 30, 2018