Showing papers on "Carbochemistry published in 1984"
TL;DR: In this paper, a detailed chemical analysis of coal and products from various liquefaction schemes is presented to show the steps in the conversion process, and the nature of the products.
331 citations
TL;DR: The literature on the potassium catalysed gasification of carbon in CO2 is critically reviewed with respect to the mechanism and the experimental "facts" relevant to the mechanistic considerations as mentioned in this paper.
124 citations
01 Jan 1984
Abstract: Publisher Summary It is the geoscience of coals, that is, their geochemistry of origin and postburial geological history, that suggests that coals are a very diverse set of materials. This chapter discusses the relations between the chemistry of coal macerals and reviews the biochemistry of their precursors and the biological markers in coals that are indicative of their origins. The content of carboxyl groups in coals is commonly determined by an ion-exchange reaction with barium acetate. Values of 1–4 milliequivalents per gram have been found for lignites and lower-rank subbituminous coals—decreasing with increasing rank and essentially zero for coals of higher rank—except that HVC coals of the Rocky Mountain province may contain some carboxyl. The cations in the carboxylates of low-rank coals can give rise to calcite deposits in liquefaction reactors, can promote liquefaction, and can give rise to catalysts for the gasification of lignite chars.
122 citations
TL;DR: In this paper, coal particles with diameters of 3-11 mm were injected into a small, hot bed of sand fluidized by nitrogen and their evolution was followed by sampling the exit gas stream and subsequent analysis by gas chromatography, concluding that heat transfer is the main process controlling the volatilization time in fluidized bed combustors.
82 citations
TL;DR: In this paper, a set of coal extracts have been characterized by FT-i.m. spectroscopy and proton n.r. bands were used to test the absorption coefficients of the coal extracts.
73 citations
TL;DR: In this article, the thermal decomposition of pyrite crystals in coal from the Prince Colliery, Cape Breton, Nova Scotia, has been studied to determine both the temperature of decomposition and the distribution of the sulphur liberated into the coal matrix.
73 citations
TL;DR: In this article, a review of R and D in catalytic direct liquefaction has shown that catalyst lifetime is more important than initial activity, and that contamination by 20-30 wt% carbonaceous material and 2-8 wt % inorganics results in deactivation best described by the shell progressive deactivation mechanism.
Abstract: A review of R and D in catalytic direct liquefaction has shown that catalyst lifetime is more important than initial activity. Deactivation studies indicate that contamination by 20-30 wt% carbonaceous material and 2-8 wt% inorganics results in deactivation best described by the shell progressive deactivation mechanism. Metals contamination is confined to the outer several hundred microns of the catalyst and pore volume distributions show a marked change towards higher average pore size in support of this mechanism. The indication is that the primary function of catalysts in direct liquefaction is hydrogenation of solvents.
60 citations
TL;DR: In this article, the authors investigated the devolatilisation behavior of Yallourn brown coal under rapid heating conditions using two different flash pyrolysers: a fluid-bed reactor giving coal particle heating rates of 104 °C−1 with a gas residence time of about 0.5 s and a shock tube which generated heating rates in the order of 107 °Cs−1 and a 1 ms reaction time.
54 citations
TL;DR: In this paper, the dissolution behavior of brown coal (67-75% C, daf) in pyridine, primary amines and aqueous KOH has been studied, and it is concluded that ester-bond breaking is necessary before extensive dissolution can take place.
54 citations
TL;DR: In this paper, a detailed mechanism for the action of the inorganic catalyst in char gasification is proposed based on results from a variety of experimental measurements, and it is shown that a catalyst such as potassium carbonate in contact with char undergoes a chemical and physical transformation to form a molten potassium oxide film that covers the char surface.
53 citations
TL;DR: In this article, the effect of impregnating ZnCI2 is to increase the char yield and to suppress tar production, and it was found that this trend can be reversed by flash-pyrolysing the Znci2-impregnated samples.
TL;DR: In this article, the catalytic effects of Na2CO3, NaHCO3 and NaCl on steam gasification of coal chars have been studied by gravimetric measurements at temperatures ranging from 600 to 750 °C and at atmospheric pressure.
TL;DR: Pyridine disrupts the non-covalent crosslinks in coal, so the addition of very small amounts of pyridine leads to an enormous increase in the uptake of chlorobenzene by the coal as discussed by the authors.
TL;DR: In this article, an Illinois No. 6 coal, PSOC-26, was converted to a fully pyridine-soluble product, with benzene and hexane solubilities of 50% and 18%, respectively.
TL;DR: In this paper, a superacidic system was used for low temperature coal depolymerization and hydroliquefaction and was found to be extremely effective for low-temperature liquefaction of coal.
TL;DR: In this article, the effects of dispersed catalysts on coal liquefaction under hydrogen pressure were studied using small autoclaves, where the catalysts were generated in situ by adding of elemental sulphur plus an oil-soluble carboxylic salt of either iron or molybdenum.
TL;DR: In this article, it was shown that the low molecular weight olefins (ethylene, propylene and butadiene) derived from the same precursors in coal, whereas methane, benzene and other pyrolysis products are mainly formed from different components in coal.
TL;DR: In this paper, brown coal samples in tetralin (1:3) were reacted with hydrogen in a continuous reactor system with and without the addition of iron and iron-tin-based catalysts.
TL;DR: In this paper, it was shown that pyrolysis of the methane quite independently of the coal, except with the possible catalysis by coal, coke or mineral matter in the coal ash.
TL;DR: In this paper, a simple particle model is used to interpret differential thermogravimetric data taken on the gasification of coal/char with CO2, H2 and H2O.
Abstract: A simple particle model is used to interpret differential thermogravimetric data taken on the gasification of coal/char with CO2, H2 and H2O. The model takes into account the major physical factors which influence the gasification rate, viz., the changing magnitudes of surface area, porosity, activation energy and effective diffusivity during gasification. Specific reaction rate constants based on surface area and activation energies are extracted from the data. Practical criteria for regimes of reaction rate and diffusion control and for particle isothermality are developed. For isothermal particles at low classical Thiele moduli, the data can be correlated with only one parameter, which has a simple physical interpretation.
TL;DR: In this article, selected model compounds representing coal structural entities were studied under the conditions of HF-BF 3 -H 2 catalysed mild coal liquefaction and showed that the formation of condensation products in these conversion processes could be suppressed by the use of a good hydrogen donor, such as isopentane.
TL;DR: In this article, the authors investigated the effect of tetralin in the solvent used for supercritical gas extraction and found that the improvement in conversion was due to hydrogen donation rather than to a change in the physical properties of the solvent.
TL;DR: In this article, the coal was smoothly hydrogenated at 450 °C to give a yield of ≈60% liquid products, which was ≈20 °C lower than when using the powder-type iron sulphide.
TL;DR: The role of low-rank coal in the United States energy system increased dramatically in the 1970s due to a combination of factors, including the escalating prices of oil and natural gas, the possibility of using lowrank coal to comply with clean-air regulations in some regions, the development of improved combustion technology, and the increased wheeling of power from region to region as mentioned in this paper.
Abstract: Resources of low-rank coals in the United States are comparable in quantity to available resources of bituminous coals but are found primarily in the western part of the country. With the exception of the Gulf region lignites, these coals are generally remote from major energy-consuming areas. In most cases, the relatively thick seams of low-rank coal found close to the surface can be strip-mined at a fraction of the cost required to produce US bituminous coals. The importance of low-rank coal in the US energy system increased dramatically in the 1970s. This increase resulted from a combination of factors, including the escalating prices of oil and natural gas, the possibility of using low-rank coal to comply with clean-air regulations in some regions, the development of improved combustion technology, and the increased wheeling of power from region to region. Low-rank coals are noted for causing ash-related problems during combustion. However, the high alkali and low sulfur contents of many lowrank coals make them attractive for reducing sulfur emissions without much addition of limestone or lime. Some low-rank coals are especially attractive for gasification and liquefaction and are likely to dominate the early development of synthetic fuels plants and coal gasification/combined-cycle utilitymore » power plants. With all these factors considered, the role of low-rank coals in the United States is likely to continue growing as process improvements are made.« less
TL;DR: In this article, a coal liquid extract was examined for partially hydrogenated nitrogen-containing polynuclear aromatic hydrocarbons using mass spectrometry/mass spectrometric analysis.
Abstract: A nitrogen-base extract of a coal liquid has been examined for partially hydrogenated nitrogen-containing polynuclear aromatic hydrocarbons using mass spectrometry/mass spectrometry. Four different partially hydrogenated nitrogen-containing PAH structures were detected, together with a number of other nitrogen-containing constituents. Parent scanning was used to show that benzylamino-containing compounds were not present at a detectable level.
TL;DR: In this article, the role of the support in the hydrotreatment of a solvent refined coal was studied to find a catalyst which can upgrade selectively its heavier component, comparing a natural clay and a titania as the support for the nickel-molybdenum with alumina of a commercial one.
Abstract: Roles of the support in the hydrotreatment of a solvent refined coal were studied to find a catalyst which can upgrade selectively its heavier component, comparing a natural clay and a titania as the support for the nickel-molybdenum with alumina of a commercial one. The two trial catalysts, using titania and sepiolite as the support converted more preferentially the heavier fractions of a coal liquid with higher durability at lower hydrogen consumptions as compared with the commercial catalyst.
TL;DR: In this paper, the liquefaction kinetics of Powhatan No. 5 mine coal (Pittsburgh Seam) in the presence of SRC-II recycle solvent at short contact times (<10 min) and temperature and pressure ranges of 573-723 K and 10.3-13.8 MPa are examined in a well-mixed reactor.
Abstract: The liquefaction kinetics of Powhatan No. 5 mine coal (Pittsburgh Seam) in the presence of SRC-II recycle solvent at short contact times (<10 min) and temperature and pressure ranges of 573-723 K and 10.3-13.8 MPa is examined in a well-mixed reactor. In the initial stages of liquefaction, while overall coal conversion (tetrahydrofuran solubles) increases with temperature, oil (pentane solubles) is lost with an increase in temperature. An increase in solvent-to-coal ratio results in an increase of conversion. The initial coal particle size distribution, total pressure, and nature of gas phase (nitrogen or hydrogen) have no significant effect on the production of any of the product of liquefaction for contact times up to 10 min. A lumped kinetic model is presented to describe the product distribution.
TL;DR: In this paper, the authors performed EPR studies on coal and the products of its extraction with ethylenediamine, pyridine and tetrahydrofuran and found that the concentration of paramagnetic centres in the residue and extracts is lower than in the coal.
TL;DR: In this article, the authors used iron pentacarbonyl(Fe(CO) 5 ) at 425-460°C under a hydrogen pressure of 4.9MPa in a non-hydrogen donating solvent, 1-methylnaphthalene.
TL;DR: In this paper, it has been shown that the use of 1.4% aqueous sodium hydroxide was capable of rendering about 40-50% coal extractable in ethylene diamine in two alkali treatments followed by extractions.