Todd W. Allen

Changes in composition of solvent-refined coal with severity of hydrogenation

The effects of mild and severe hydrogenation on the chemical composition of solvent-refined coal (SRC) produced from Wyodak subbituminous coal in the direct coal liquefaction SRC-I process were investigated. The yields of solvent-derived fractions of ‘oils’ and ‘asphaltenes’ increased with increasing severity of hydrogenation at the expense of ‘preasphaltenes’. Further separation of ‘oils’ and ‘asphaltenes’, each into three compound-class fractions, revealed more compositional changes. Concentrations of hydrocarbons, nitrogen compounds and hydroxyl aromatics in ‘oils’ increased with increasing severity of hydrogenation. ‘Asphaltenes’, containing nitrogen compounds and hydroxyl aromatic fractions but almost no hydrocarbons, showed an increase in nitrogen-compound concentration with increasing severity of hydrogenation. Hydroxyl aromatic concentration in ‘asphaltenes’ increased under mild but decreased under severe hydrogenation conditions. High-performance liquid chromatography followed by field-ionization mass spectrometry analysis of the hydrocarbon subfractions revealed a complex picture of structural transformations. Over fifty homologous series of aromatic and hydroaromatic hydrocarbons covering a carbon number range from about C12 to C50 were identified and approximate concentrations obtained. Small amounts of partly aromatized pentacyclic triterpane ‘biomarkers’ and their hydrogenation products were found.

Compositions of distillate recycle solvents derived from direct coal liquefaction in the SRC-I process: 1. Hydrocarbons

Abstract The qualitative and quantitative compositions of 260–427 °C distillate recycle solvents derived from direct liquefaction of subbituminous Wyodak coal and bituminous Kentucky 9 14 coal in the SRC-I process are discussed. A liquid chromatography method which involves a column switching technique was used to provide solubility characteristics and compound-class compositions. The hydrocarbon compounds, which accountfor> 60 wt% of the distillate recycle solvents, were further analysed using a unique combination of high-performance liquid chromatography (h.p.l.c.) and field ionization mass spectrometry (f.i.m.s.). Thirty homologous series were identified. Carbon number and distribution and concentration of the homologous series were determined. The h.p.l.c./f.i.m.s. method unravelled various hydroaromatic types which otherwise would be very difficult or impossible to determine.

Estimation of alkylphenol content in coal recycle solvents

Alkylphenols from coal recycle solvents were separated into mono-ortho and non-ortho substituted alkylphenol fractions. Each fraction was further separated with a high-performance liquid chromatographic μ-Bondapak NH2 column and straight-chain heptane:isopropanol (99:1) mobile phase. The areas under the chromatographic peaks corresponding to the mono-ortho and non-ortho substituted phenols were determined and the percentages of these alkylphenols were calculated. The method yielded a pooled standard deviation of 0.76% for the mono-ortho determinations and 0.61% for the non-ortho determinations. Thirty-three recycle solvents were investigated.

Characterization of polycyclic aromatic hydrocarbons and hydroaromatics in a distillable coal-derived solvent by chromatographic and corrected fluorescence methods

Abstract Polycyclic aromatic hydrocarbons and hydroaromatics were separated from a coal-derived distillate by dry-column chromatography and high-performance liquid chromatography. Individual components in the isolated fractions were characterized by corrected excitation fluorescence spectrometry. With the chromatographic data and the fluorescence data, compound identification was possible in some cases.

Standardization of aluminum oxide and detection of polycyclic aromatic hydrocarbons on aluminum oxide

Abstract Luminescence methods are described for detecting polycyclic aromatic hydrocarbons (6-, 5-, 4-, and 3-ring) on aluminum oxide after separation by dry-column chromatography. A method is reported for standardizing the water content in the aluminum oxide used for dry-column chromatography. A water content of 4.74% was chosen to define the activity of aluminum oxide because there was minimum overlap among the PAH bands.

Predicting the migration characteristics of polynuclear aromatic hydrocarbons and hydroaromatics in dry-column chromatography

Abstract An approach developed by Snyder to predict Rf values in thin-layer chromatography was used to predict the migration properties of twenty-one polynuclear aromatic hydrocarbons and hydroaromatics. Dry-column chromatography was employed as a separation step with aluminum oxide as the stationary phase and n-hexane—ether (19:1 v v ) as the mobile phase. When a correction factor was used, very good correspondence was achieved between the calculated and experimental Rf values.