Date of Award

May 2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

First Advisor

Wayne Seames

Abstract

The global demand for carbon fibers has experienced exponential growth over the last decade, driven by the desire for materials with high strength and low density for applications in aerospace, automotive, wind energy, and specialty industrial markets. Currently, carbon fibers are almost exclusively produced from petroleum-based precursors, most commonly polyacrylonitrile (PAN) and petroleum-derived pitch. The high production costs associated with these fossil-based precursors limit the broader adoption of carbon fibers and represent a significant barrier to market expansion. The development of a bio-based carbon fiber precursor derived from renewable feedstocks would help transition this market away from fossil carbon sources while providing an economically valuable co-product to the renewable fuels industry.The research presented herein documents the production of mesophase pitch from bio-tars derived from the non-catalytic thermal cracking of food-grade corn oil to demonstrate the technical feasibility of corn oil bio-tars as a renewable precursor for carbon fiber production. Two corn oil feedstocks were evaluated: commercial food-grade corn oil and distillers grain corn oil (DGO), a co-product of the corn ethanol fermentation process. A multi-stage distillation system was employed to prepare bio-tar feedstocks from corn oil crackates through sequential atmospheric and vacuum distillation steps, recovering approximately 22 wt% of the original crackate as tar feedstock. The prepared bio-tars were subsequently processed in a continuous pitching reactor at temperatures of 430, 440, 450, and 470°C to evaluate the effect of operating temperature on mesophase pitch formation and quality.

It was observed that increasing pitching temperature led to increased volatilization of heavy distillate components and decreased pitch yield, with an overall mass recovery of approximately 3.3 wt% of the corn oil crackate as solid pitch product at 470°C. Visual inspection confirmed that glassy, hard, solid pitch products characteristic of mesophase pitch formation were obtained only at operating temperatures of 450 and 470°C. Differential scanning calorimetry (DSC) analysis determined glass transition temperatures of 233 ± 10°C and 258 ± 10°C for the 450 and 470°C food-grade corn oil pitch products, respectively, with the DGO-derived pitch at 470 °C yielding a glass transition temperature of 241 ± 10°C. Polarized light microscopy (PLM) analysis confirmed anisotropic mesophase contents of 8.13%, 21.08%, and 19.55% for the food-grade corn oil 450°C, food-grade corn oil 470°C, and DGO 470°C pitch products, respectively. These results demonstrate that corn oil bio-tars are a technically feasible feedstock for mesophase pitch production and that distillers grain corn oil is a viable alternative to food-grade corn oil. Continued development toward higher anisotropic content, elevated glass transition temperatures, and optimization of pitching reactor conditions is recommended to achieve pitch properties suitable for continuous carbon fiber production.

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