Coal-derived materials compounds

Later, D. W., Nitrogen Polycyclic Aromatic Compounds in Coal-Derived Materials, in Handbook of Polycyclic Aromatic Hydrocarbons (A. Bjprseth and T. Ramdahl, Eds.), Vol. 2, Dekker, New York, 1985. 

The results from the thermal cracking of unhydrogenated and hydrogenated coal-derived materials, a gas condensate, and model compounds led to the conclusions that ... 

The identification and quantitative determination of specific organic compounds in very complex samples is an area of intense current research activity in analytical chemistry Optical spectroscopy (particularly UV-visible and infrared absorption and molecular fluorescence and phosphorescence techniques) has been used widely in organic analysis. Any optical spectroscopic technique to be used for characterization of a very complex sample, such as a coal-derived material, should exhibit very high sensitivity (so that trace constituents can be determined) and extremely great selectivity (so that fractionation and separation steps prior to the actual analysis can be held to the minimum number and complexity). To achieve high analytical selectivity, an analytical spectroscopic technique should produce highly structured and specific spectra useful for "fingerprinting purposes," as well as to minimize the extent of overlap of spectral bands due to different constituents of complex samples. 

Preferred Annellated Structures of Polycyclic Aromatic Compounds in Coal-Derived Materials... 

In the study reported here, the abundances and structural characteristics of the numerous PACs identified in the SRC II heavy distillate and the coal tar were compiled and compared. The purpose of this comparison was to determine (1) if preferred aromatic structural features exist in the complex mixture of compounds present in a single coal-derived material and (2) to what extent these preferred structures are evident in different coal-derived materials produced from different feedstocks and under different conditions. Explanations for differences in the compositions and relative abundances of PACs in these materials are proposed. 

Very complex mixtures such as coal-derived materials often result in undesirably overlapping spectra for PAHs in Shpol skii matrices when a xenon lamp is used as the radiation source. In such cases, provided a sufficiently monochromatic source is used, the fluorescence may be selectively excited from one specific compound in a complex mixture of very similar PAHs. In practice, selective excitation usually entails using a laser for excitation. LIF in Shpol skii matrices has been used to identify and quantify individual PAHs in highly complex coal-derived materials. By way of example. Figure 2 shows the site-selective fluorescence of four individual PAHs in a solvent-retained coal liquid sample. The spectra were recorded following a 1000-fold dilution of the... 

Karaca, E, Millan, M., Behrouzi, M., Herod, A.A., Kandiyoti, R. (2005) The size exclusion chromatography calibration of mixed-A and mixed-D columns using various polymers and compounds an apphcation to coal derived materials. Anal. Chim. Acta. 547,78-82. 

With the demonstration of supercritical fluid extraction, an obvious extension would be to extract or dissolve the compounds of interest into the supercritical fluid before analysis with SFC.(6) This would be analogous to the case in HPLC, where the mobile phase solvent is commonly used for dissolving the sample. The work described here will employ a system capable of extracting materials with a supercritical fluid and introducing a known volume of this extract onto the column for analysis via SFC. Detection of the separated materials will be by on-line UV spectroscopy and infrared spectrometry. The optimized SFE/SFC system has been used to study selected nonvolatile coal-derived products. The work reported here involved the aliphatic and aromatic hydrocarbon fractions from this residuum material. Residua at several times were taken from the reactor and examined which provided some insight into the effects of catalyst decay on the products produced in a pilot plant operation. 

The PNA fraction of the shale oil was smaller (6%) than that fraction in the coal liquids (10- 29%). In shale oil, a larger fraction of the PNA compounds are alkylated than in coal-derived liquids. For example, C5 or higher-substituted aromatics were seen in shale oil but C3 substitution was rare in coal liquid. This characteristic difference in alkyl substitution was repeated also when the N-heterocyclic compounds were similarly compared. Few alkylated species were seen in the coal liquids but Ce and higher-substituted pyridines, quinolines, acridines, indoles, and carbazoles were detected in shale oil. For example, the PNA fraction of shale oil contained many indoles which can be seen in the gas chromatogram of this fraction see Figure 7). The different alkyl substitution patterns found in these two syncrude materials may well reflect the underlying structural differences in coal and kerogen. 

Experience in class separations and analyses of fossil-derived materials began with the petroleum industry. The literature in this area is far too extensive to review here. Furthermore, petroleum literature deals principally with physical and chemical analyses of distillate fractions which are important to product characteristics. Recently, asphalts have received increased attention since they contain a wide range of known hazardous compounds. Most methods applied to whole samples of petroleum crudes have proven inadequate when dealing with synthetic coal liquids or shale oils because of stable emulsion formation in separation steps caused by larger amounts of inorganic and hydrophilic compounds. 

This process will allow the recycling of solid waste to produce a useful product. High pressure and temperature combined with hydrogen can convert most types of domestic and industrial wastes back into products that are currently obtained from fossil coal and oil. No volatile polluting chemicals will be vented into the atmosphere. The metals can be recovered for further use and the ceramic materials will be converted into a product difficult to distinguish from natural rocks. This type of process will not solve all the solid waste disposal problems, but will provide a potential method for recovery of valuable products from waste. When implemented, it will dramatically reduce the amount of solid waste placed in landfills. This process also has the potential to reduce the amount of oil and coal mined to provide the carbon compounds needed to manufacture all petrochemical derived materials. This waste reduction process is a variation on the Fischer-Tropsch process, mentioned on page 101, in use commercially to produce hydrocarbon materials from coal. 

The chemical synonyms and identification numbers for wood creosote, coal tar creosote, and coal tar are listed in Tables 4-1 through 4-3. Coal tar pitch is similar in composition to coal tar creosote and is not presented separately. Coal tar pitch volatiles are compounds given off from coal tar pitch when it is heated. The volatile component is not shown separately because it varies with the composition of the pitch. Creosotes and coal tars are complex mixtures of variable composition containing primarily condensed aromatic ring compounds (coal-derived substances) or phenols (wood creosote). Therefore, it is not possible to represent these materials with a single chemical formula and structure. The sources, chemical properties, and composition of coal tar creosote, coal tar pitch, and coal tar justify treating these materials as a whole. Wood creosote is discussed separately because it is different in nature, use, and risk. 

Attention in fundamental and applied research on shape-selective catalysis has been largely focused on open-chain and monocyclic compounds. However, we have observed the rapid developments in polymer materials containing multi-ring aromatic units and the need to develop the monomers and other specialty chemicals from polyaromatic hydrocarbons that are rich in coal-derived liquids [Song and Schobert, 1993, 1996]. Scheme 1 shows the structures of some advanced polymer materials containing aromatic ring in the main-chain. 

In the selection of a raw material, availability and chemical nature are deciding factors. Olefinic and aliphatic chemicals such as ethylene, propylene and methanol are therefore produced from crude oil fractions and suitable natural gas, whereas polynuclear aromatics such as naphthalene, anthracene and pyrene are recovered almost exclusively from coal-derived raw materials. Mononuclear aromatics such as benzene, toluene and xylene occupy a medial position, being obtainable from both crude oil and coal feedstocks. Renewable raw materials are, owing to their chemical structure, particularly suitable for the production of compounds containing oxygen. 

The fourth group of papers (Chapters 25-28) describes pyrolyses of various compounds that are present in coal-derived liquids, oil shale, waste products, and miscellaneous organic materials. This particular type of pyrolysis will certainly increase in importance in the future, and the results of this section indicate that a good foundation is being established. 

The materials commonly used do not promote foaming and are not corrosive. The organic materials usually used for this purpose are alkaline tannin extracts, vegetable derivatives, polymeric compounds containing adjacent carboxy groups, such as a methylstyrenemaleic anhydride copolymer, carboxymethylcellulose, polyacrylates, n-nifrophenol dimers, colloidal peat, and a wood-fat-molasses—coal mixture. 

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