Susumu Yokoyama

Combination of 13C- and 1H-n.m.r. spectroscopy for structural analyses of neutral, acidic and basic heteroatom compounds in products from coal hydrogenation

Abstract Polar compounds consisting of acidic, basic and neutral nonhydrocarbons were separated from the oil portion derived from coal hydrogenation by means of liquid chromatography. These polar compounds comprised a substantial amount of the oil portion, up to ≈ 60 wt%. Acidic and basic compounds were extracted subsequently by chemical methods, leaving the neutral nonhydrocarbons. The neutral nonhydrocarbons were derived further into eight subfractions, Fr-PP n -1 to-8, using gel permeation chromatography. The fractions were analysed quantitatively using 13 C- and 1 H-n.m.r.. Information on the distribution of functional groups containing heteroatoms, especially oxygen, which were present as phenolic, phenylether or heteroaromatic rings, was provided indirectly by 13 C-n.m.r. spectra, utilizing the chemical shift of the carbon which can be distinguished by an adjacent oxygen. Simultaneous application of 13 C-n.m.r. with 1 H-n.m.r. reduced considerably the number of assumptions required for estimating the average molecular structure of polar compounds.

Analysis of a coal-derived liquid using highpressure liquid chromatography and synchronous fluorescence spectrometry

Abstract Synchronous fluorescence spectra of model polycondensed aromatic hydrocarbon molecules were recorded and used to identify the number of condensed rings in the aromatic molecules. A coal-derived liquid from Yubarishinko coal was initially separated into fractions having different number of condensed aromatic rings, and each fraction was further divided into narrow fractions having different numbers of carbon atoms. These fractions were studied using synchronous fluorescence spectroscopy. Results indicate the potential usefulness of synchronous fluorescence spectroscopy as a method of analysis of complex mixtures as coal-derived liquids despite the limitation of the method that some molecules give only weak peaks. Several components in some fractions were identified by a combination of synchronous fluorescence spectra and conventional excitation and emission fluorescence spectra.

Structural characterization of coal-hydrogenation products by proton and carbon-13 nuclear magnetic resonance

Heavy oil derived from coal hydrogenation was separated into saturated fractions, neutral aromatic oil, and asphaltene, and these materials were subsequently fractionated according to the magnitude of their respective molecular sizes by gel-permeation chromatography. These GPC subfractions were analysed by proton and carbon-13 n.m.r. spectroscopy and by an additional procedure using gas chromatography for the paraffinic GPC subfractions. 13C-n.m.r. spectra for the GPC subfraction of saturated material showed typical long straight-chain paraffin spectral patterns accompanied by iso-and cycloparaffinic carbon signals. The results from gas-chromatographic measurement for the paraffinic GPC subfractions agree fairly well with the trends of average carbon numbers and contents of straight-chain paraffins obtained by varying the fraction numbers, estimated from 13C-n.m.r. analyses. The ratios of aromatic carbon to total carbon (fa) for aromatic oil and asphaltene GPC subfractions obtained directly from 13C-n.m.r. spectra are slightly lower than the results from the 1H-n.m.r. method assuming x = y = 2 in the Brown—Ladner equation. Peak intensities of the respective carbon species in 13C-n.m.r. spectra were compared with the peak intensities of correspondingly bonded species obtained from 1H-n.m.r. measurement. Some inadequacy was recognized in both measurements. It is assumed that there are two reasons for the discrepancy, one of which is the inaccuracy of 13C-n.m.r. results owing to the long relaxation times and the effect of Nuclear Overhauser Enhancement, and another is the application of unsuitable values of x and y for calculations from the Brown—Ladner equation. New analytical treatments for 13C-n.m.r. results in combination with 1H-n.m.r. analyses are suggested in this study to avoid these uncertainties in structural analyses. From this procedure, it is believed that the actual contents of aromatic and aliphatic carbon and appropriate values of x and y can be derived.

An h.p.l.e. and m.s. analysis of distillate fractions of neutral oil from hydrogenated Akabira coal to elucidate chemical structures

Abstract Akabira coal-derived neutral oil was separated into 25 narrow boiling range fractions covering 183–423 °C, and subsequently separated into compound class fractions : alkanes, monoaromatics, naphthalene-type diaromatics, fluorene-type diaromatics and tri- and/or tetraaromatics, by high performance liquid chromatography (h.p.l.c.). The compound type analyses of the distillate/h.p.l.c. fractions were performed using electron impact mass spectroscopy (e.i.m.s.) or field ionization mass spectroscopy (f.i.m.s.). Aromatic/hydroaromatic compound types and the alkyl side-chain carbon distribution of the distillate/h.p.l.c. fractions were clarified, based on the separation behaviour of h.p.l.c. and the type analyses according to Z value by m.s. By the distillation/h.p.l.c./m.s. method, coal-derived oil was characterized in terms of the distribution of the numbers of aromatic rings, naphthenic rings and carbons of alkyl groups attached to these rings. The variations in chemical structure in a compound class with distillation temperature are discussed in terms of these chemical structural factors.

Effect of SO42− on catalytic activity of Fe2O3 for hydrocracking of coal

Abstract The catalytic activity of Fe 2 O 3 for the hydrocracking of a bituminous coal at 673K increases when a small amount of SO 4 2− is included in the catalyst. The effect of SO 4 2− is marked in the formation of resins, stronger polar compounds and asphaltenes.

Structural analysis and estimation of boiling point of hydrocarbons in a coal-derived liquid by a group contribution method

Abstract The relationship between chemical structure and boiling point of hydrocarbons in a heavy oil has been proposed based upon systematic structural analyses using high performance liquid chromatography (h.p.l.c.) and gas chromatography-mass spectroscopy (g.c.-m.s.). The boiling point of a compound in a coal-derived liquid was converted from the retention time in g.c.-m.s. by calibration using a series of aromatic hydrocarbon standards. The chemical structures of the aromatic hydrocarbon compound types are characterized by five atomic groups: numbers of total carbons, aromatic rings, naphthenic rings, aromatic conjunction carbons and aromatic inner carbons. At a total carbon number in a given compound, the group contributions to the boiling point, rendered as deviations from the boiling point of an n-paraffin with the same carbon number, were determined by regression analysis. They are as follows: 29.7 K per aromatic ring, 10.4 K per naphthenic ring, 1.7 K per aromatic conjunction carbon and −4.6 K per aromatic inner carbon. A simple equation for calculating boiling points of hydrocarbons is proposed, which requires only chemical structure information.

Distribution in coal-derived oil of aromatic hydrocarbon compound types grouped according to boiling point by high performance liquid chromatography-gas chromatography/mass spectrometry

Abstract Yubarishinko coal-derived neutral oil was separated into compound class fractions, alkanes (Fr-P), monoaromatics (Fr-M), diaromatics (Fr-D) and tri- and/or tetra-aromatics (Fr-T), by high performance liquid chromatography (h.p.l.c.). The compound type analyses of aromatic compound class fractions were performed using a gas chromatograph/mass spectrometer. Based on h.p.l.c. separation behaviour and the compound type analyses according to Z number by mass spectroscopy (m.s.), aromatic fractions in a neutral oil were characterized in terms of three chemical structural parameters: the number of aromatic rings; the number of naphthenic rings; and the number of alkyl side chain carbons attached to these rings. Converting gas chromatography (g.c.) retention time into boiling point, the boiling point distributions of aromatic hydrocarbon compound types were clarified and the variations in chemical structure with boiling point are discussed in terms of their chemical structural parameters.

Catalytic activities and selectivities of complex metal oxides for hydrocracking of bituminous coal

The activities and selectivities of ten complex metal oxides for hydrocracking of Akabira coal were examined at 400°C under 200 kg/cm2 of hydrogen pressure. The best three catalysts which showed high percentage conversion were found to be Fe2O3 + SO42− (75.0%) MoO3TiO2 (71.7%), and MoO3Fe2O3SnO2 (68.4%), while those which gave high selectivity for the formation of oil were MoO3Fe2O3SnO2 (33.0%), Fe2O3 + SO42− (31.0%), and MoO3TiO2 (28.6%). The reason for the high activities and selectivities of these catalysts is discussed briefly.

Estimation of compound classes in coal hydrogenation liquids by thin-layer chromatography

Abstract Compound classes in coal liquids were investigated by thin-layer chromatography coupled with a flame ionization detector (t.l.c.-f.i.d.). Individual t.l.c. peaks for coal liquids were identified as paraffins, aromatics, polar compounds and more strongly polar compounds or asphaltenes in order of increasing Rf values by comparison with specific compounds separated previously by conventional liquid chromatography. Concentrations of compound classes for a series of samples obtained by varying the hydrogenation time were estimated and good agreement was found with the results obtained by the USBM-API 60 liquid chromatography procedure. By using the t.l.c.-f.i.d. method, the relation of distribution of compound classes to the reaction conditions of coal hydrogenation could be derived quantitatively with relative ease.

Chemical structure of coal-derived oil. Structural changes of each compound type with severity of hydrogenation

Abstract The chemical structure of the oil from hydrogenation of Miike caking coal using red-mud and sulphur in a batch autoclave has been investigated. The oil was separated into compound-type concentrates in a silica-alumina dual-packed liquid-solid chromatographie column. The effects of reaction temperature (400 and 450 °C), and nominal reaction time (0–120 min) on the chemical composition of each compound-type of oil were studied. The chemical compositions of these compound types were investigated by means of 1 H-n.m.r. spectroscopy, elemental analysis and molecular weight measurement. Under mild reaction conditions (400 °C) there were slight changes in the yield and composition of the oil with the reaction time. Under more severe conditions (450 °C) short alkyl-substituted aromatics and cycloalkyl aromatics in each compound-type of the oil were observed. The oil may be produced by splitting of the bridges connecting unit structures.