Date of Graduation

2001

Document Type

Thesis

Degree Type

MS

Committee Chair

Peter G. Stansberry

Abstract

There is a renewed interest in using direct coal liquefaction as an alternate route to produce precursors for value-added carbon products. Research conducted by the Chemical Engineering Department at West Virginia University has shown that β-resins of direct coal liquefaction products can serve as a precursor for pitches with exceptional properties in applications related to carbon fibers. The objective of this research was to evaluate the effects of the hydrogenation solvent composition and different catalysts on the resulting pitch and its β-resins. Tetralin, an excellent hydrogen donor solvent, and a mixture of tetralin and creosote oil (CTM) were used as the hydrogenation solvents in the coal liquefaction. Catalytic additives were used to study their effects on the product distribution and properties. Tin chloride, iron sulfate, and ammonium molybdate were chosen based on their ability to affect the coal liquefaction products. Based on previous work at West Virginia University, the 1-gallon bolted closure autoclave reactors were pressurized to 400 psig (cold) and then heated to 450°C for 1 hour. The reaction products were separated by filtration, rotary evaporation, and vacuum distillation. Characterization tests on the products included helium pycnomety (density), elemental analysis (C/H ratio), FTIR (aromaticity), viscosity at different shear rates and temperatures, differential scanning calorimetry (glass transition temperature), β-resins content (toluene insolubility), ash content, and coking value. The β-resins were isolated by a toluene extraction and subjected to a second hydrogenation. The conditions (solvent type and ratio, hydrogen pressure, temperature, etc.) of this β-resins hydrogenation were held constant. Theses products were processed and characterized. The coal liquefaction solvent composition and the catalytic additives had profound effects on the liquefaction products. The CTM allowed for the elimination of the N-methyl pyrrolidone (NMP) extraction, which was essential when tetralin was the hydrogenation solvent. However, when the CTM solvent was used varying amounts (depending upon the liquefaction catalyst) of creosote oil remained in the pitch. It is unclear exactly how the remaining creosote affected the liquefaction products, although it increased the aromaticity, C/H atomic ratio, and density of the pitch product. One possibility is the creosote oil reacted with itself, the coal, or the tetralin causing this increase in aromaticity. Another explanation maybe that the CTM solvent supplied enough hydrogen to form large stable (aromatic) molecules, but deprived the molecules of the needed hydrogen to progress toward the smaller more aliphatic molecules. The catalysts influenced the extraction yield, coke yield, C/H atomic ratio, aromaticity, and βresins content of the liquefaction products, but to a lesser degree than the hydrogenation solvent.

Download

Share

COinS