Jaroslav Černý

Compound-class fractionation of coal-derived liquids by extrography

Abstract An extrographic procedure for compound-class fractionation of coal-derived liquids and related materials is presented. The fractionation column consists of one extrographic separation section (silica gel) and two filter sections (silica gel and basic alumina). The fractions obtained are: saturates, aromatics free of nitrogen, neutral heterocompounds with pyrrolic nitrogen, monohydric phenols, dihydric phenols, and highly polar compounds. From preliminary analyses it can be predicted that the fractionation selectivity of extrography is very close to that of chromatography.

Structural dependence of CH bond absorptivities and consequences for FT-i.r. analysis of coals

Nine liquid products from processing of high- and low-rank coals, oil shale and crude oil were analysed by quantitative FT-i.r. spectroscopy to understand the effect of sample structure on the absorptivities for aliphatic and aromatic CH bonds. Variation in the structure of samples was additionally enlarged by comprehensive fractionation of the products by liquid chromatography. 1H n.m.r. spectroscopy was used as a reference analytical tool for the determination of the absorptivities. Absorptivity for aliphatic CH bond stretching modes was found to depend linearly on hydrogen aromaticity of the hydrocarbon-type samples with heteroatom content ≲2 wt%. The absorptivities of heteroatom-rich fractions were lower than those of hydrocarbons and did not show any dependence on hydrogen aromaticity. Their values were rather random in a broad interval, thus showing high but not predictable influence of molecular structure. Absorptivities for aromatic CH bond stretching and out-of-plane bending modes were found to be independent of structure. As a consequence for structural analysis of coal, the structural independence of absorptivity for aromatic CH bonds allows a relatively reliable assessment of aromatic hydrogen content in coals. On the other hand, evaluation of aliphatic hydrogen content can be greatly affected by the amount of chloroform-extractables in a coal, which contain a highly aliphatic material with a high absorptivity of aliphatic CH bonds, especially those in long methylene chains. For reliable structural analysis by FT-i.r., extraction of coal with chloroform is recommended to analyse the bulk of the coal substance.

Comparison of the selectivity of extrographic and chromatographic fractionations

Abstract In order to study fractionation selectivity, chromatography of shale oil on silica gel was used as a reference for comparison with the extrographic fractionation previously described. The overlapping effects between the adjacent fractions were evaluated using i.r., 1 H n.m.r. and mass spectrometry. It was found that extrographic fractionation produced better separation than chromatography. In both cases, subsequent separation of the n -hexane fractions on silica gel/silver nitrate columns into saturates and olefin/monoaromatic fractions was needed.

ALIPHATIC C-H BOND RESPONSES IN THE 900-700 cm−1 REGION OF THE FTIR SPECTRA OF COAL TARS

ABSTRACT Four bituminous coals were comprehensively separated by column chromatography into a number of fractions. Four aromatic hydrocarbon fractions of each tar were analyzed by FTIR spectroscopy, and the 900-700 cm−1 spectral region was evaluated. This spectral region was found to be composed of at least 14 separate bands, which were resolved by using self-deconvolution and curve-fitting procedures. The bands near 821 cm−1, 791 cm−1, and 784 cm−1 were proposed to originate from rocking vibrations of aliphatic C-H bonds. For the tar samples with a proton aromaticity between 0.21 and 0.37, these bands account for on average 12% of the total integral intensity of the 900-700 cm−1 region. This percentage cannot likely be neglected in a correct quantitative evaluation of the region and calculation of the aromatic hydrogen concentration. However, a correct resolution of the bands can be very difficult in the FTIR spectra of a complex material, such as coal.

Relationship between properties and conversions of North Bohemian coals during coal/oil coprocessing

Abstract Eleven low rank coals from North Bohemian mines were comprehensively characterized by using a number of analytical methods. Along with common proximate and ultimate analysis, spectroscopic techniques, porosity measurement, extractability and swelling in organic solvents were used. Although coals were of similar geological origin, some of their characteristics largely differed from one coal to another. Coals were coprocessed with petroleum vacuum residue at 440°C for 1 h and yields of reaction products and coal conversions were determined. Despite the differences in composition and properties, the coals provided similar conversions and yields of distillable reaction products. A small positive effect on coal conversion was found for ash content and microporosity of coals. However, a small negative effect was found for carbon content, optical reflectance and solvent extractability of coals.

Composition and properties of North Bohemian coals

Abstract This work presents the mean chemical, micropetrographic, surface and other characteristics of coal seams from western, central, and eastern parts of the North Bohemian brown coal basin. Attention was especially paid to the elemental composition, ash content, content and forms of sulphur, occurrence of syngenetic and epigenetic sulphides, maceral composition, and degree of gelification and decomposition of components in the huminite maceral group. Some other coal characteristics were also assessed, such as pore texture, extractability and solvent swelling of the coals. The coals examined were huminitic with a variable xylite and detrite content. Huminite reflectance varied between 0.33 and 0.39%. Substantial differences in pore texture of the coals were found in the range of meso- and macropores. These differences largely affected the extractability of the North Bohemian coals. The coals also exhibited extremely high swelling ratios in basic solvents, such as pyridine.

Use of basic alumina in fractionation of fossil fuels

Abstract The use and efficiency of extrographic fractionation are reported for a number of fossil fuels and their processing products. The influence of basic alumina, which is a constituent of the column packing, on the fractionation selectivity is discussed. This fractionation is capable of an efficient separation of non-polar hydrocarbons, pyrrolic-type nitrogen compounds, and phenolic compounds. The hydrocarbon fraction also includes highly condensed polyaromatics. In the chromatographic fractionation these polyaromatics are eluted along with heteroatom-rich compounds. The extrographic fractionation has been found to be independent of column loading on going from a sample-to-sorbent ratio of 1:15 to 1:8 (w/w). However, it is not possible to separate aromatic hydrocarbons according to the ring number, and therefore the extrography is a suitable method for the fractionation of coal-derived liquids containing large amounts of heteroatom compounds of different polarity.

Chemical changes of coal matter after treatment with ethylenediamine

Abstract A severe chemical reaction of ethylenediamine (EDA) with subbituminous coal was found to proceed during Soxhlet extraction. The significant structural changes of coal matter after extraction at approximately 117°C are discussed based on results from thermogravimetry, IR and 1 H NMR spectroscopy measurements. Possible reaction paths are the following: reaction of EDA with carboxyls and esters to yield amides; cleavage of weak ether linkages in the coal structure. The EDA extract does not reflect the chemical composition and structure of coal due to the high content of nitrogen that is built into coal matter.