An Investigation of Catalytic Hydrothermal Liquification of Chlorella

Document Type


Degree Name

Master of Science (MS)



Date of Award

Summer 2021


The development of third generation biofuels from microalgae has seen extensive research over the last few years. The hydrothermal liquefaction (HTL) is the promising route for the production of bio-oils. The major drawback in HTL is the high temperature and high pressure which result in high capital cost of equipment. To make HTL an economical process for bio-oil production, the temperature and pressure should be reduced and can be achieved by adding alcohol to water for HTL. The efficiency of the HTL process can also be improved by using a suitable heterogeneous catalyst with additional modifications. In this project, we investigated the effect of dielectric barrier discharge (DBD) plasma (argon and hydrogen plasma) modified zeolite Y as catalysts on the yield and quality of bio-oils produced in hydrogen atmosphere at different reaction times (0 min and 15 min) and temperatures (240 °C and 250 °C). The mixture of solvents (50 vol. % water & 50 vol. % ethanol) was used in HTL to increase the yield of bio-oils. Two sequential extractions were used to extract bio-oils from HTL products using dichloromethane. Different analytical techniques, such as thermal gravimetric analysis, elemental analysis, and gas chromatography-mass spectrometry, used to understand the physicochemical properties of the bio-oils and for the determination of higher heating value (HHV). The introduction of DBD plasma to modify zeolite Y improved the bio-oil quality and yield from HTL processes. H2 plasma catalyst enhanced the bio-oil yield from 46.83±1.48 (240-0-H2-ZY) to 50.04±0.88 (240-0-H2-ZY-HP) and from 50.24±1.96 (250-0-H2-ZY) to 53.01±0.73 (250-0-H2-ZY-HP). Argon plasma catalyst reduced N-containing compounds from 29.42 % (240-0-H2-ZY) to 2.94 % (240-0-H2-ZY-AP) and decreased O-containing compounds from 4.02 % (240-0-H2-ZY) to 1.38 % (240-0-H2-ZY-AP). Overall, the introduction of H2 atmosphere, zeolite Y and plasma zeolite Y in the HTL of Chlorella increased the bio-oil yield, reduced the N-containing compounds and O-containing compounds, enhanced the content of hydrocarbons, alcohols, and esters, and increased the 110-300 ° C fraction of bio-oils.


Ben Jang

Subject Categories

Chemistry | Physical Sciences and Mathematics