Janusz Pajak

Application of Fourier self-deconvolution to the FT-i.r. characterization of coals and their N-methyl 2-pyrrolidinone extraction products

Abstract Analysis by Fourier transform infrared (FT-i.r.) spectroscopy of coals and their extraction products, i.e. extracts and residues, gives an insight into the chemical structure of the initial material and changes due to the separation procedure. High quality spectra are obtained for solids by diffuse reflectance FT-i.r. spectroscopy. They also provide rather broad overlapping bands which have to be manipulated to supply useful information. It is shown that Fourier self-deconvolution improves the qualitative and semi quantitative analysis of FT-i.r. spectra of the coals and their N -methyl 2-pyrrolidinone (NMP) extraction products. Several samples of coals (rank ranging from C (wt%, daf) 85.6 to 92.4) were studied. Four spectral regions were selected for discussion: 3100-2800 cm −1 ν(CH ar ), ν(CH ali ); 1750-1600 cm −1 ν(CO), ν(CC ar ); 1260-1034 cm −1 ν(CO); 900-650 cm −1 γ(CH ar ). Several ratios were calculated, including: [ν(CH ar )/ν(CH 2 ,CH 3 )], [ν(CO)/ν(CC)], [ν(CO)/ν(CC)], [γ(CH)(1H)/Σγ(CH)], [γ(CH)(2,3H)/Σγ(CH)] and [γ(CH)(4H)/Σγ(CH)]. These data led to a comparison of the structural characteristics of the coals and of their extraction products. In each case the results are discussed in relation to the various trends observed in the samples, the possible relations with Gieseler fluidity of coals and the sizes of molecular orientations in the relevant cokes obtained by pyrolysis at 1000°C.

A physicochemical study of carbonization phases. Part I. Tars migration and coking pressure

During the coking process, the production of volatile matters, in the plastic phase of the coking charge, leads to the development of dangerous internal pressures if hindrance is encountered in the gas release. By withdrawing and quenching coking coal charges at a given temperature in the course of heating, several phases of carbonization were isolated and submitted to physicochemical analyses: diffuse reflectance infrared spectroscopy (DRIFT), proximate and ultimate analysis, N-methyl-2-pyrrolidinone (NMP) extraction and hydrogen transfer (HT). By these means, two distinct ways of migration of volatile matters through coking material were evidenced. For ‘dangerous coals’ (including excessive coking pressure) the volatile materials migrate mainly from the plastic layer to the cold side of the oven, giving rise to impregnation of the remaining coal. On the contrary, a large part of volatile components of ‘safe’ coals migrate towards the hot side of the oven through semi-coke and coke. These results are in agreement with our preliminary study on the variations of the permeability of the different phases of carbonization.

Compositions of solvent-extracts of a Polish bituminous coal

Abstract The compositions of acetone, tetrahydrofuran and pyridine extracts from a bituminous coal were studied using mass spectrometry and the main components were identified. The compositions of the extracts were similar, as predicted by the electron-donor-acceptor mechanism of coal extraction. Different extract yields are due mainly to differences in the fraction of high molecular weight components in the extracts.

Influence of pre-swelling on extraction of coal

Abstract Swelling of hvB coal by vapour of the solvents pyridine, tetrahedrofuran, dimethylformamide and methanol was carried out. Vapour-saturated coals were extracted using selected solvents and extract yields for swollen and fresh coals were compared. It is found that some solvents can block pathways to some, but not all, sites that were accessible to other solvents when they were interacting singly with fresh coal.

Hydrogen transfer from tetralin to coal macerals. Reactivity of macerals

Abstract The kinetics of the transfer of hydrogen from tetralin to a Polish bituminous coal and maceral groups separated from it have been examined. The total yield of transferred hydrogen, second-order rate constants and Arrhenius parameters have been compared. The balance of hydrogen transfer indicates that coal/tetralin reaction can be considered as a set of parallel maceral/tetralin reactions. The differences in maceral reactivity may indicate differences in reaction mechanisms.

Application of ultrasonic measurements to the determination of concentration of coal extracts

Abstract The velocities of ultrasonic wave propagation in tetrahydrofuran solutions of coal extracts from various coals (within the range 64.9–85.6% carbon) have been measured. Linear correlations between extract concentrations and ultrasonic wave velocities have been found.

Effects of pressure on the rate of hydrogen transfer from tetralin to different rank coals

Abstract Four coals have been tested to study the influence of pressure on their reaction with tetralin at the temperature of 300–320 °C. The coals differ strongly in reactivity with tetralin and in pressure effects. The coals with high oxygen content are the most reactive and their reaction rate was accelerated with the increase of pressure. The molar activation volume for the reaction of subbituminous coal and low-rank bituminous coal with tetralin at 300 °C is about −20 and −15 cm 3 /mol, respectively. Such results support bimolecular transition state. For high-rank bituminous coals, the reaction rate is not affected by pressure.

Pyrolysis of coal tar pitch mixed in the presence of a graphite intercalation compound : a kinetic study

Abstract A kinetic study has been carried out to determine the influence of the addition of first stage FeCl 3 -graphite intercalation compound (GIC) to coal tar pitch (CTP) on the formation and the development of the mesophase. The mesophase formation was followed by the determination of the tetrahydrofuran insoluble fraction (THFI) of the solid residues, which were further characterized by polarized light microscopy. The presence of the Lewis acid (desorbed from the graphite layers) has a great influence during the mesophase spherule formation and development. The activation energy of the formation and the development of the mesophase (E a ) is equal to 159 and 204 kJ/mol in the case of the CTP-GIC 8% mixture and the CTP respectively. This corresponds to a decrease of 22% of E a when the CTP is mixed with the GIC. The authors want to highlight the difficulties and mainly the limitations of the method used to calculate this activation energy by THFI measurements. However, we assume that the mesophase formation and growth rates are accelerated in the presence of compounds such as GIC for two reasons: the absence of QI particles on the surface of the mesophase spherules and the catalytic activity of the Lewis acid.

DRIFT spectroscopic characterization of coal samples modified by chemical treatments

The modifications afforded by several chemical treatments to the main functional groups of a bituminous coal were characterized by diffuse reflectance infrared spectroscopy. The starting materials were the polyanions and potassium coal adducts obtained from the parent coal, treated with potassium according to the Sternberg and Lazarov reactions. The results show the differences in the reactive sites involved in these reactions and in the behaviour of these sites during protonation or alkylation. Some of the typical functional groups introduced (or modified) can be active acceptor sites during hydrogen transfer from tetralin at low temperature (315°C) in conditions avoiding thermal bond cleavage. Taking into account the semiquantitative results of the i.r. analysis, the participation of several active sites in the total hydrogen transfer was estimated, indicating the role of quinonic, aromatic and alkyl groups.

Hydrogen transfer from tetralin and decalin to high-temperature coal tars. Relation with carbon deposit formation

Studies of pyrolysis of a coal charge containing various quantities of water from 0.8 to 15 wt.% in a two-stage reactor were performed. The rate of formation of solid carbon deposits was followed and some properties of high-temperature tars were investigated. These tars differ in elemental composition and hexane solubility. Hydrogen acceptor abilities were evaluated by reaction with tetralin at 320°C and with decalin at 400°C. Hydrogen transfer from decalin to several model organic compounds was also studied. The rate of carbon deposit formation and hydrogen acceptor abilities of tars are different for various quantities of water in the starting coal charge. The relation between the hydrogen transfer properties of tars expressed as the ratio of decalin hydrogen transfer (DHT) to tetralin hydrogen transfer (THT) and the rate of carbon deposit formation seems to indicate the importance of hydrogen transfer during secondary pyrolysis.