Graduation Semester and Year
Spring 2026
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Chemistry
Department
Chemistry and Biochemistry
First Advisor
Kevin A. Schug
Second Advisor
Saiful Chowdhury
Third Advisor
Krishnan Rajeshwar
Fourth Advisor
Jongyun Heo
Abstract
Petroleum is a foundational material in modern industry, used in a wide range of products from fuels to pharmaceuticals. However, its status as a non-renewable resource and the subsequent environmental crisis caused by its use have necessitated a shift towards examining alternatives to petroleum. One promising solution is plastic waste pyrolysis, a thermochemical process that decomposes plastic waste, a petroleum derivative, in an oxygen-free environment. This process produces gases, liquid oils, and char, which can serve as substitutes for petroleum in future fuels and as chemical feedstocks in industrial processes. However, the resulting oils are chemically complex and require a deeper understanding of their composition before they can be adapted and refined as petroleum substitutes. Traditionally, this requires advanced analytical techniques due to the sheer complexity of these products. This work examines the use of supercritical fluid chromatography, gas chromatography, and vacuum ultraviolet spectroscopy to provide a simpler methodology for analyzing complex plastic waste pyrolysis oils.
Three studies were performed to attempt to simplify the analysis of plastic waste
pyrolysis oils. The first utilized supercritical fluid chromatography with ultraviolet spectroscopy. The core of the study involved differentiating oils derived from polyethylene versus polypropylene feedstocks. Using serially coupled columns, two distinct fingerprint regions were formed, which were able to discriminate between feedstocks that produced the different plastic waste pyrolysis oils. Principal component analysis was then used, which showed that the method could differentiate between the oil types and a mixture formed by mixing two oils, each from a different plastic type. A limitation of the study was the detector used, as ultraviolet spectroscopy can only identify aromatic components; alkane, alkene, and cyclo-/branched-alkane species are invisible at those wavelengths.
To gain deeper insights, the research transitioned to an offline two-dimensional analysis, the first to use supercritical fluid chromatography with gas chromatography–vacuum ultraviolet spectroscopy. Fractions were collected from each fingerprint region identified in the previous study at an analytical scale, then analyzed using gas chromatography-vacuum ultraviolet spectroscopy and a proprietary software that can examine the paraffin, isoparaffin, olefin, naphthene, and aromatic (PIONA) content. Analysis revealed that the initial fractions contained higher levels of paraffins and isoparaffins than the oils themselves, which were more olefin-rich. However, the sensitivity limits of the vacuum ultraviolet detector limited the approach.
The final study marked the first reported use of supercritical fluid chromatography–vacuum ultraviolet spectroscopy for examining waste plastic pyrolysis oils. This setup enabled the detection of olefins directly within the supercritical fluid chromatography workflow, using a state-of-the-art vacuum ultraviolet detector that could be coupled to the system. The results demonstrated that even when oils are derived from the same plastic type, their chemical profiles in the aforementioned fingerprint regions can vary significantly. The application of supercritical fluid chromatography to examine these oils can potentially be adapted to simplify analysis and increase the adoption of plastic waste pyrolysis technology.
Keywords
Supercritical Fluid Chromatography, Vacuum Ultraviolet Spectroscopy, Plastic Waste Pyrolysis Oil, Gas Chromatography, Two-Dimensional Chromatography, Chemical Recyling
Disciplines
Analytical Chemistry
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Kaplitz, Alexander S., "ANALYSIS OF PLASTIC WASTE PYROLYSIS OILS USING CHROMATOGRAPHIC METHODS" (2026). Chemistry & Biochemistry Dissertations. 5.
https://mavmatrix.uta.edu/chemistry_dissertations2/5