Date of Award

Summer 2015

Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil & Environmental Engineering

Committee Director

Sandeep Kumar

Committee Member

Gary Schafran

Committee Member

Mujde Erten-Unal

Committee Member

James W. Lee


In recent years, sub- and supercritical water technologies received an increasing attention because of the numerous advantages they offer for biomass converting into biofuels. Water at elevated temperatures and pressures provides an ideal medium for chemical transformations. It serves as a reactant, reaction medium, and catalyst that helps biomass compounds undergo hydrolysis, depolymerization, dehydration, decarboxylation, and condensation/repolymerization reactions. Biomass is the fourth largest source of energy in the world after coal, oil, and natural gas that has the potential to provide the large scale substitution of hydrocarbon-based liquid transportation fuels and minimize the environmental issues. Biomass typically contains 40-60% oxygen. Maximal removal of oxygen from biomass is the main objective of biofuel production. In this work, several hydrothermal technologies of processing biomass to biofuels and valuable byproducts were investigated.

In Chapter 2, the reaction pathways of conversion of triacylglycerols into alkanes, influence on temperature, pressure, catalysts, and hydrogen on the hydrodeoxygenation process was reviewed in details.

In Chapter 3, the effects of reaction temperatures and catalysts on the degree of liquefaction, bio-oil yield, energy conversion ratio, and bio-oil composition were studied and the overall mass balance of the process was developed.

In Chapter 4, it was shown that the integrated process provides several major advantages over conventional processes: better extractability of oil, shorter extraction time, tolerance to high moisture content of the feedstock, avoiding preparation stages, and utilization of the extracted seedcake for biochar production.

In Chapter 5, it was demonstrated that the integration of hydrothermal liquefaction of algal biomass, extraction of bio-oil from the liquid phase, and gasification of the extracted aqueous phase can provide additional energy and a potential source of nutrients for fresh algae cultivation.

In Chapter 6, a novel approach to converting fatty acids into n-alkanes was investigated. Fuel range hydrocarbons were obtained in a continuous flow process within a short residence time from oleic acid using near- and supercritical water as reaction medium, granulated activated carbon as a catalyst, and ≤ 1% v/v formic acid as an in situ source of hydrogen.


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