Date of Award

Summer 8-2023

Document Type


Degree Name

Master of Science (MS)


Civil & Environmental Engineering


Environmental Engineering

Committee Director

Sandeep Kumar

Committee Member

Mujde Erten-Unal

Committee Member

James W. Lee


This study aims to address knowledge gaps in the production of valuable products from waste streams generated during lignocellulosic biofuel production. The primary objective is to develop a process that converts lignin, a byproduct of bioethanol refineries, into a sustainable biolubricant.

The first chapter examines recent advancements in synthesizing biolubricants and investigates their scalability. It explores innovative materials, catalysts, chemical modification approaches, and additives that have emerged in the field. A particular hurdle is the oxidative stability of biolubricants derived from plant oils, which are prone to autooxidation due to their C=C bonds. To overcome this, the study aims to use a three-step approach to produce biolubricant enhancer: hydrothermal liquefaction of lignin, hydrodeoxygenation, and aromatic alkylation. The focus is to economically and efficiently utilize lignin obtained from bioethanol refineries and transform these compounds into high value lubricant improvers.

In the second chapter, the study focuses on the first step, the hydrothermal liquefaction of lignin, with an emphasis on increasing the yield of aromatic hydrocarbons using subcritical water. A new lab-scale batch reactor with an induction heating system is designed. This system enables rapid heating rates of around 100 °C/min, while a conventional electrical heater employs slower heating rates at approximately 5.3 °C/min. The study investigates the influence of heating rate and short residence time on the process. Detailed analysis of the resulting biocrude reveals hat the rapid heating rate improves the selectivity of specific compounds, such as phenol, while the slower heating rate yields a broader range of compounds including anisole and alkyl phenol.

Overall, the developed processes provide an improved conversion rate into value-added products generated from lignin, contributing to greater financial and environmental sustainability


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