Semester

Fall

Date of Graduation

1999

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Edwin L. Kugler.

Abstract

The storage stability of coal liquids is of great importance if coal liquefaction products are to replace petroleum products. It has been reported that gum formation occurs in coal-derived liquids during storage to a level at which it becomes a handling problem. The aging of coal hydropyrolysis liquids has been studied. Coal liquid products were placed in preweighed sample vials and stored under light, in the presence of air, at different storage temperatures (2, 21, and 32°C). The weight of gum formed was determined at specified sampling times. High performance liquid chromatography (HPLC) was used to monitor the changes in hydrocarbon class composition with storage time. The changes in boiling point distribution were also determined using simulated distillation with an evaporative light-scattering detector.;Results show that the rate of gum formation is fastest at the highest storage temperature and slowest at the lowest storage temperature. The gum formed increased significantly at the early stage of storage and then remained constant with time. It was found that the saturate compound class remained constant with time at all storage conditions. However, both the polar and aromatic compound classes decreased significantly at the early stage of storage and then remained constant with time. The polar compounds were separated from the aromatic and saturate compound classes using solid phase extraction. No gum formation was observed for both the polar compounds and the aromatic-saturate mixture. Results from HPLC and simulated distillation method show no signs of changes in their chemical composition and boiling point distribution. It was concluded that the main reactants in gum formation in coal liquids are the aromatic and polar compound classes. Results from GC/MS and FTIR show that the polar compounds consist mainly of phenols. The affects of inert gas on the stability of coal liquids were determined by storing coal liquid samples in the presence of argon gas. It was then concluded that the presence of inert gas does not prevent the formation gum; instead, it slows down the rate of gum formation. A kinetic model was developed that describes the experimental data.

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