Howard F. Silver

Relationship between solvent-derived and compound-class fractions in coal-derived distillates and vacuum still bottoms

Abstract High-boiling SRC-1 process-derived distillable liquids and nondistillable vacuum still bottoms (VSB) from Wyodak and Kentucky 9/14 coals were separated into solvent-derived and compound-class fractions using Chromatographic techniques. The fractions were characterized using infrared spectrometry, proton nuclear magnetic resonance spectrometry, field ionization mass spectrometry, and elemental analysis. Emphasis was placed on the determination of the composition of oils and asphaltenes. Results showed that oils and asphaltenes consist of the same compound classes: hydrocarbons, nitrogen compounds, and hydroxyl aromatics. The main differences between the oil and asphaltene fractions are in concentrations of compound classes. It was found that oils are rich in hydrocarbons while asphaltenes are rich in hydroxyl aromatics. Also, oils and asphaltenes contain compounds of the same homologous series, and molecular weight is not a factor which differentiates oils and asphaltenes. Components in VSB oils have higher molecular weights than components in distillate asphaltenes. Molecular structure rather than molecular weight is a major parameter that determines solubility of coal-derived liquids.

Solvent composition effects with a cyano and a silica gel stationary phase in normal-phase liquid chromatography of alkylphenols and naphthols

Abstract Several liquid chromatographic models were investigated with μBondapak CN and μPorasil stationary phases. n-Heptane—2 propanol and n-heptane—ethyl acetate mobile phases of different composition were used, and alkylphenols and naphthols were employed as model compounds. The linear relationships obtained from graphs of k′ vs. log mole fraction of the strong solvent were found useful in understanding the retention behavior of the solutes.

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.

Hydroliquefaction of Wyodak coal using bottoms recycle

Abstract Wyodak coal has been liquefied using recycle solvents consisting of blends of Wyodak coal-derived distillates and SRC or SRC oils, asphaltenes and oils plus asphaltenes. Whilst the quality of the distillate portion of the bottoms recycle is maintained by hydrogenation and distillation in the Exxon Donor Solvent (EDS) process, no reported efforts have been made to hydrogenate the nondistillable portion of the EDS bottoms recycle solvent nor the bottoms recycle solvent in the SRC-II process. As hydrogenation of the distillate portion of the recycle solvent in the EDS process increased Wyodak coal distillate yields, this study was initiated to determine whether hydrogenation of the nondistillable portions of Wyodak coal-derived bottoms recycle solvent would show similar beneficial effects. Results suggest that distillable liquid yields in the range of 55–60 wt% of dry Wyodak coal can be obtained using mildly hydrogenated SRC or SRC oils plus asphaltenes as a bottoms recycle solvent component. This result can be compared to distillable liquid yields of 40 wt% of dry, Wyodak coal obtained from the EDS process using bottoms recycle. Further, the unhydrogenated, SRC-derived oil and asphaltene portions of the recycle solvent also appear to be effective solvent components. However, the most effective solvents were obtained using hydrogenated SRC or SRC-derived oils plus asphaltenes.

Separation and characterization of nitrogen heterocycle and hydroxyl aromatic compounds in non-distillable coal-derived liquids

Abstract The extent of compound class overlap for a previously developed fluorocarbon/basic alumina chromatographic method was investigated. It was found that the extent of hydroxyl aromatic and nitrogen aromatic compound overlap was minimal for the chromatographic method with oils and asphaltenes isolated from a Wyodak coal-derived liquid. A high-performance liquid chromatographic method was developed which very effectively grouped nitrogen aromatic compounds and hydroxyl aromatic compounds isolated from oils and asphaltenes with the fluorocarbon/basic alumina chromatographic approach. The high-performance liquid chromatographic method consisted of silica and various dimethyl sulfoxide—carbon tetrachloride mobile phases. Accurate elemental analysis data could not be obtained from the high-performance liquid chromatography subfractions because inorganic material was removed from the silica stationary phase with the dimethyl sulfoxide—carbon tetrachloride mobile phases. The hydroxyl aromatic and nitrogen aromatic compound fractions from the high-performance liquid chromatographic steps were characterized by proton nuclear magnetic resonance, infrared, and field-ionization mass spectrometry. The combination of the fluorocarbon/basic alumina and high-performance liquid chromatography steps with the field-ionization with the field-ionization mass spectrometry and infrared spectrometry permitted a high degree of compound-class separation and general spectral characterization of coal-liquid fractions.

Dissolution of subbituminous coal in tetrahydroquinoline

Two different samples of Wyodak subbituminous coal from the Powder River Basin in Wyoming were liquefied in a two dm3 batch reactor using 1,2,3,4 tetrahydroquinoline, THQ, as a solvent. Sufficient sample was produced to determine product boiling ranges by distillation and to measure THQ distribution in the product. Product distillation showed that even at cyclohexane conversions greater than 50%, net distillate yields produced using THQ as a solvent were negative. In some cases, high boiling, coal-derived resid yields were greater than the dry coal charged to the reactor. These observations have been attributed to THQ losses resulting from dimerization of the THQ and reactions between THQ and coal derived components.

Effect of iron and sulphur compounds on liquefaction of Wyoming subbituminous coal

The effects of Fe2O3, sulphided Fe2O3, CS2 and sulphur on the liquefaction of Clovis Point subbituminous coal (Powder River Basin, Wyoming) in a 2dm3 autoclave Magnedrive II batch reactor have been evaluated. All these additives increased the distillate yields and, with the exception of elemental sulphur, decreased the pyridine-insoluble, unconverted coal yields. In the batch reactor, CS2 was the most effective in increasing distillate yields and decreasing gas yields, while Fe2O3 was the most effective in decreasing unconverted coal yields.

Separation and characterization of large-ring number polycyclic aromatic hydrocarbons in non-distillable, pyridine soluble coal-liquids

Low-pressure liquid chromatography, high-performance liquid chromatography, and field ionization mass spectrometry (f.i.m.s.) were used to obtain compositional information on large-ring number polycyclic aromatic hydrocarbon (PAH) present in a non-distillable coal liquid sample. A highly selective h.p.l.c. method for the separation of (PAH) from polar compounds was applied to nitrogen-compound fractions derived from a Wyodak non-distillable (> 427 °C) coal-liquid sample. F.i.m.s. analyses revealed that the PAH subfractions isolated by the h.p.l.c. procedure contained large-ring number PAH and relatively few nitrogen compounds. The methods developed can generally be applied to the analyses of complex organic mixtures, and in conjunction with other methods, can yield detailed polycyclic aromatic hydrocarbon compositional information.

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.