Date of Award
Doctor of Philosophy (PhD)
Chemistry and Biochemistry
Patrick G. Hatcher
The use of algae as a feedstock for hydrous pyrolysis has a high potential for producing biofuels. The non-food nature of algae in addition to the various advantages associated with the hydrous pyrolysis process makes this combination for the production of biofuels of high interest. However, current results from algae processing have alluded to some challenges: byproducts arising from the thermal transformation of carbohydrates and proteins, which become incorporated in the oil fraction, result in high oxygen and nitrogen contents of the oil. Accordingly, this produces an oil of low quality for refineries. This dissertation investigates use of a pretreatment approach where only the energy-rich component of algae, called algaenan, is used as feedstock for hydrous pyrolysis, thus removing the carbohydrate and proteinaceous components prior to hydrous pyrolysis. This leads to the production of a higher quality oil with less oxygen and nitrogen content.
Algaenan from Scenedesmus spp. was isolated using the three most common chemical isolation protocols followed in the literature to investigate their effects on the algaenan structure. A new isolation protocol was proposed based on selecting the most effective chemical treatments, from each of the three procedures, which had the least effect on the algaenan structure. Algaenan isolated by an abbreviated isolation approach was then subjected to hydrous pyrolysis to investigate its potential to produce a hydrocarbon-rich oil. Detailed analysis of the oil by advanced analytical techniques, including two dimensional gas chromatography coupled to time-of-flight mass spectrometry and electrospray ionization coupled to Fourier transform ion cyclotron mass spectrometry, revealed it to have hydrocarbon-rich and heteroatom-poor qualities similar to many Type I kerogen derived crude oils.
Results also showed that hydrous pyrolysis treatment can be used to effectively concentrate algaenan from algal cells by finding the optimum temperature and time parameters. A protocol is presented which outlines a stepwise process to reach the optimum algaenan isolation parameters. Such a need can be envisioned if one is to eventually commercialize the process.
From the results, a new two-step strategy is proposed to 1) isolate algaenan, by low temperature hydrous pyrolysis followed by 2) produce high quality oils from the isolated algaenan by high temperature hydrous pyrolysis. This strategy aimed to minimize the incorporation of heteroatoms into the oils by using hydrous pyrolysis to remove the carbohydrates and proteins prior to producing oils from algaenan. Detailed analysis of the produced oil with this approach shows that it is hydrocarbon-rich, heteroatom-poor and similar to that produced from the hydrous pyrolysis of the chemically isolated algaenan.
Obeid, Wassim A..
"Investigation of the Potential for Algaenan to Produce Hydrocarbon Based Fuels From Algae by Hydrous Pyrolysis"
(2015). Doctor of Philosophy (PhD), Dissertation, Chemistry and Biochemistry, Old Dominion University, DOI: 10.25777/v08w-g828