M.D. Guillén

Characterization of coal tar pitches with different softening points by 1H NMR: Role of the different kinds of protons in the thermal process

Abstract Optimum experimental conditions for a quantitative 1 H Nuclear Magnetic Resonance ( 1 H NMR) analysis of coal tar pitches are given. From the variety of sample concentrations studied, it was found that 3% in weight was the most suitable concentration for 1 H NMR experiments. The cut-off points were adjusted and the different types of hydrogen in the resultant regions were identified. The patterns used for both purposes were prepared according to the quali- and quantitative information given by Gas Chromatography (gc). Using these conditions, four coal tar pitches with different softening point were characterized. Some new parameters were defined with the aim of obtaining an important amount of more reliable information.

Polynuclear aromatic hydrocarbon retention indices on SE-54 stationary phase of the volatile components of a coal tar pitch: Relationships between chromatographic retention and thermal reactivity

Abstract The components of the volatile fraction of a coal tar pitch were studied by capillary gas chromatography and combined gas chromatography-mass spectrometry using the stationary phase SE-54 in both instances. The molecular weight and the retention indices of each identified compound are given. These values are compared with those determined on the stationary phase OV-1701. Relationships between information from the gas chromatography study and from the thermal reactivity of coal tar pitch components are discussed.

Fourier transform infrared study of coal tar pitches

Abstract Semiquantitative analysis of the infrared spectra from 650 to 4000 cm −1 of nine coal tar pitches supplies excellent information on the concentrations of several functionalities. Relations have been found between the infrared data and the solubility, coke yield and composition of the volatile fraction of these pitches. The results contribute to a better understanding of pitch structure.

Capillary gas chromatographic and combined gas chromatography—mass spectrometric study of the volatile fraction of a coal tar pitch using OV-1701 stationary phase

Abstract The components of the volatile fraction of a coal tar pitch were studied by capillary gas chromatography and combined gas chromatography—mass spectrometry using the OV-1701 stationary phase in both instances. The temperature-programmed retention indices and the molecular weight of each identified compound are given. It is shown that the volatile fraction of the coal tar pitch is composed of a group of homologous series of polycyclic aromatic compounds.

Flame ionization detection relative response factors of some polycyclic aromatic compounds: Determination of the main components of the coal tar pitch volatile fraction

Abstract The flame ionization detection (FID) relative response factors of some commercially available polycyclic aromatic compounds using split injection were determined and compared with other published FID relative response factors obtained using splitless and cold on-column injection technique. From these data FID relative response factors of some non-available polycyclic aromatic compounds were calculated in an approximate way. These factors were used in a quantitative study of the main components of a coal tar pitch volatile fraction. For this quantification the internal standard method and the absolute calibration with separate standard method were employed. Good reproducibility of the determinations using both methods was found.

Analysis of coal tar pitch : relations between thermal behaviour and composition

This paper discusses the influence of pitch composition on its thermal behaviour. The value of the approach consisting in the characterization of these materials by analysis of their volatile fraction is demonstrated. The pyrolysis of nine coal tar pitches was studied by thermogravimetric analysis (t.g.a.) and derivative thermogravimetry (d.t.g.). The coke yield was closely related to both the rate of weight loss and the temperatures at which the d.t.g. curve reached maxima. To obtain information about the influence of the structures present in pitches on their thermal behaviour, the composition of the volatile fraction (evaluated by gas chromatography) was considered. The degree of condensation and the relative proportions of the different kinds of polycyclic aromatic hydrocarbons in this fraction were related to important thermal parameters deduced through t.g.a. and d.t.g. High coke yields are associated with a highly condensed volatile fraction in which alternant peri-condensed polycyclic aromatic hydrocarbons predominate over non-alternant systems.

Preliminary results of extraction experiments in an oil shale

Abstract Soxhlet versus ultrasonic extraction efficiency on the immature Puertollano oil shale has been tested. The yields from the two methods are compared. The extracts were compared by gas chromatography and geochemical parameters such as CPI and pristine/phytane ratio calculated. The ultrasonic extraction procedure is an effective, quick and easy method which does not change the biomarker ratios of the bitumen. Minor efficiency differences can be observed among the solvents allowing a choice on the basis of handling properties. Carbon disulfide and chloroform are easiest to eliminate from the extract.

Gas chromatography of deuterated and protiated chloro derivatives of 1,4-dimethylbenzene

Abstract Eighteen compounds obtained from the chlorinationof mixtures of 1,4-dimethylbenzene and [2H10]-1,4-dimethylbenzene in the ring and methyl groups were separated by capillary gas chromatography on four stationary phases of different polarities (from 0 to ca. 1420 on the McReynolds scale). Light isoemrs were eluted later than their heavy analogues, in accordance with the higher vapour pressures of the latter. Relative retention times and Kovats retentionindices on the four stationary phases are given and approximate boiling points are calculated from empirical relationships among the Kovats indices, boiling points and Van der Waals volumes of the solutes.

Semiquantitative gas chromatographic analysis of the volatile fraction in several extracts obtained by treatment of coal tar pitches with different organic solvents

Abstract The solubility of four coal tar pitches in several organic solvents and the semiquantitative gas chromatographic analysis of the corresponding volatile fraction extracts are discussed. Close relationships between the extraction yield and the chromatographic material concentration of the several extracts studied are found. These correlations show that the increase in extraction ability from one solvent to another is basically due to the solvents ability to extract unchromatographed compounds of high molecular weight. In general, hexane (pentane) and methanol extract chromatographic fractions have a smaller concentration of compounds of high molecular weight. No solvent selectivity towards polycyclic aromatic hydrocarbons, oxygenated compounds and thiophene derivatives is found. Nevertheless, methanol shows greater tendency to extract pyrrole benzoderivatives than other groups of compounds, but the extractive ability of methanol towards this group of compounds is not the highest. It is observed that solvents with medium extractive ability are able to extract the same amount of chromatographed compounds present in a pitch as solvents with high effectiveness. Furthermore, a comparison between semiquantification by means of gas chromatography and infrared spectroscopy is made in order to test the scope of the volatile fraction approach in pitch characterization. This comparison shows that the proportion of polycyclic aromatic hydrocarbons in chromatographic and non-chromatographic fractions is fairly close.

Comparative petrographic and geochemical study of the Puertollano oil shale kerogens

The bituminous series in the Puertollano oil shale field (central Spain) consists of three oil shale beds named PA, PB and PC from top to bottom. The kerogens from the three oil shales have been studied by microscopy, thermogravimetric analysis, Rock-Eval pyrolysis and Fourier transform infrared (FT-ir) spectroscopy. The shale oils have also been studied by FT-ir, nuclear magnetic resonance spectroscopy and gas chromatography and the results interpreted in terms of variations in palaeoenvironmental conditions and maturity. The three oil shales are dominated by autochthonous algal material (lamalginite and telalginite) in different proportions. The elemental composition of the kerogens and their thermal behaviour are, however, very similar, indicating that both telalginite and lamalginite may represent different growing states of the same algae, Botryococcus. The shale oils show that the kerogens are made up of highly aliphatic, weakly branched macromolecules typical of rocks rich in Botryococcus. Some differences in the chemical composition of shale oils are attributable to the absorptive and catalytic effect of the mineral matter. Some other differences such as the higher carbonyl/carboxyl to aliphatic ratio and the higher degree of substitution of aromatic structures found in the upper oil shale would indicate a slightly lower degree of thermal evolution of this oil shale. This is confirmed by the fluorescence parameters of lamalginite which showed a greenish-yellow hue in the lamalginite from the upper band and a yellow hue in the lamalginite from the two lower beds.