Date of Award

December 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Computing

Committee Member

Mark C Thies

Committee Member

David A Bruce

Committee Member

Amod A Ogale

Committee Member

Wesley P Hoffman

Committee Member

Srikanth Pilla

Abstract

Carbonaceous pitches derived from pure polycyclic aromatic hydrocarbons (PAHs) are oligomeric materials that have been shown to be useful precursors for advanced carbon materials in which thermal management plays a large role. Examples include, but are not limited to, heat dissipation in electric and hybrid vehicles and heat dispersion on the leading edges of aircraft and spacecraft. Although the final properties of these products are clearly impacted by the bulk properties of the precursors, the effect of oligomeric composition on the bulk properties of the pitch is still poorly understood.Pyrene was chosen as the model PAH monomer for this work because the oligomerization process to produce pitch occurs with minimal disruption of the polycyclic aromatic rings, producing intact dimers, trimers, and higher oligomers. The kinetics of the catalytic polymerization of pyrene monomer to oligomeric pitch in the presence of aluminum trichloride (AlCl3) were studied at temperatures between 200 and 370 °C. Semi-batch supercritical extraction (SCE) (also called dense-gas extraction (DGE)) with toluene proved to be indispensable for isolating the pure oligomers in the pitch products, so that concentrations of monomer and oligomers could be determined and the mass balance closed. Using the above information, a microkinetic model for describing the consumption and production of the monomer, dimer, and trimer components of the pyrene pitch was developed. The model was then used to predict compositions at different reaction times and temperatures, enabling pitch generation to be tailored to maximize the oligomer(s) of interest for further study. To determine the effect of oligomeric composition on the bulk properties of pyrene pitch, a continuous-flow SCE apparatus was constructed for generating oligomeric mixtures rich in particular “mers”. By using one-stage, continuous DGE with toluene at 330 °C and 330 psig, monomer content was lowered from 30 to 10 wt % in the bottom pitch product, resulting in a monomer-depleted pitch with a softening point of 185 °C and char yield of nearly 70%. In another experiment, a two-stage configuration of SCE/DGE with toluene was used to extract monomer through trimer in the first stage at 330 °C and 700 psig; the second stage at 330 °C and 330 psig was then used to strip monomer out as the top product, resulting in a dimer- and trimer-rich bottoms product having a softening point of 278 °C and char yield of 47%.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.