Showing papers on "Carbochemistry published in 1989"
TL;DR: In this paper, the authors measured the low-temperature (25-140°C) oxidation rate of a single coal sample in a well-insulated vessel, while at the same time performing gas analyses.
125 citations
64 citations
TL;DR: In this paper, the results of catalytic hydropyrolysis experiments in which greater than 60% daf coal basis yields of tar are produced with weight ratios of tar to gases up to 80% higher than observed in an uncatalyzed reaction were reported.
Abstract: In this paper the authors report the results of catalytic hydropyrolysis experiments in which greater than 60% daf coal basis yields of tar are produced with weight ratios of tar to gases up to 80% higher than observed in an uncatalyzed reaction. The work has also shown that dispersed sulfided molybdenum and hydrous titanium oxide (HTO) catalysts coated directly on the coal are superior to Lewis acids and alumina supported hydrogenation catalysts in terms of tar yields achieved and reduction of the amount of light hydrocarbon gases produced. In addition, they have performed two-stage hydropyrolysis tests which demonstrate that the tar produced is readily upgraded.
62 citations
TL;DR: The authors showed that a significant amount of bond scission under pyrolysis cannot be due to simple thermolysis and must be induced by some other means, such as free H-atoms or cyclohexadienyl radicals.
47 citations
TL;DR: In this paper, the rate and extent of direct coal hydroliquefaction for 5 bituminous coals from the Argonne Premium Sample Bank have been measured and data were obtained in batch microautoclave tubing bomb reactors at three temperatures (375, 400, 425/degree/C) and 5 residence times (3, 5, 10, 15, 40 minutes) in 1-methylnaphthalene vehicle under a hydrogen blanket.
Abstract: The rate and extent of direct coal hydroliquefaction for 5 bituminous coals from the Argonne Premium Sample Bank have been measured. Data were obtained in batch microautoclave tubing bomb reactors at three temperatures (375, 400, 425/degree/C) and 5 residence times (3, 5, 10, 15, 40 minutes) in 1-methylnaphthalene vehicle under a hydrogen blanket. Data on rate of conversion of coal to THF and toluene solubles were modeled with a simple reversible rate expression, and activation energies for conversion to each solvent solubility class determined. Data on carbon and proton distribution in the coals were obtained by /sup 1/H-NMR (Combined Rotational and Multiple Pulse Spectroscopy) and /sup 13/C-NMR (CPMAS/Dipolar Dephasing). A strong correlation of activation energy with the aliphatic hydrogen content of the coal was found for conversion to THF solubles. Toluene solubles activation energies were found to be highly correlated (R/sup 2/ > 90%) with total oxygen, and protonated aliphatic carbon. /sup 13/C-NMR data indicated a high degree of correlation between protonated aliphatic carbon and total oxygen for only the bituminous coals from the Argonne suite, suggesting the importance of etheric oxygen in crosslinking structures for determination of bituminous coal reactivity.
42 citations
TL;DR: In this paper, the naphthalene-steam reaction was studied as a model reaction for homogeneous gas/gas reactions in coal gasification, and the experiments were performed in an isothermal flow tube reactor.
41 citations
TL;DR: In this article, it was shown that steam reacts with the ether linkages in coal, forming hydroxyl groups and thereby substantially reducing the presence of an important covalent cross-link in the coal structure.
Abstract: Steam-treated coal swells considerably more than the raw coal in water. This implies that the steam-treated coal is more hydrophilic. It exhibits a lower degree of hydrogen bonding and has an IR spectrum different from that of raw coal. Elemental analysis of treated coal shows a significant decrease in organic oxygen content. A mild O-alkylation of treated coal with labeled methyl iodide, however, introduces twice the enrichment by 13 C as does the same procedure carried out on raw coal. It may be concluded that steam-modified coal contains twice as many hydroxyl groups as raw coal. It is postulated that steam reacts with the ether linkages in coal, forming hydroxyl groups and thereby substantially reducing the presence of an important covalent cross-link in the coal structure
39 citations
38 citations
TL;DR: In this article, a 0.30 m diameter atmospheric pressure gasifier operated as either a fluidized or a spouted bed was used to extract coke from two Alberta oil sands operations.
36 citations
TL;DR: In this article, the importance of cations in the organic structure of coal and suggest that metal complexation and removal is another mechanism used by microorganisms to solubilize low-rank coals.
Abstract: Microorganisms are able to solubilize low-rank coals using the mechanism of base solubilization, but a pH values of ≤8. Pretreatment of coals with HCl under nonoxidizing conditions removes organically bound multivalent cations and results in an increase in the amounts of coal solubilized either by microorganisms or in alkaline buffers. These results indicate the importance of cations in the organic structure of coal and suggest that metal complexation and removal is another mechanism used by microorganisms to solubilize low-rank coals
35 citations
TL;DR: In this paper, the effects of four metal oxides (SiO2, Al2O3, CaO and FeO3) and quartz beads on the secondary reactions of volatiles from coal pyrolysis have been investigated by using a two-stage reactor.
TL;DR: In this article, high fluid fresh bituminous coals were oxidised and four techniques (cross-link measurement, chloroform extraction, proton magnetic resonance thermal analysis (PMRTA) and FT-i.r. diffuse reflectance spectroscopy) were used to correlate Gieseler fluidity changes with chemical differences between the fresh and oxidised samples.
TL;DR: In this article, the authors performed differential scanning calorimetry, thermogravimetry and differential thermograimetry studies on 10 different coals: four lignite, four subbituminous and two bituminous coals.
TL;DR: In this paper, a dry phase oxidation of a subbituminous coal with air was carried out in a fluidized bed reactor at 175, 200, 250 and 275 °C, where coal samples were withdrawn during the reaction at fixed intervals up to 12 hours.
TL;DR: In this paper, the authors investigated the catalytic properties of various iron and molybdenum catalysts for coal liquefaction and showed that the high catalytic activity of Fe(CO) 5 and Fe( CO) 6 -S was correlated with the hydrogenation of dibenzyl ether and benzyl phenyl ether.
Abstract: In order to understand differences in the catalytic activities of various iron and molybdenum catalysts for coal liquefaction, model reactions such as hydrogenation of phenanthrene and pyrene and hydrogenolysis of diphenylmethane, dibenzyl ether, and benzyl phenyl ether were investigated. The high catalytic activities of Fe(CO) 5 of Fe(CO) 5 -S in coal liquefaction were closely correlated to the higher activity of the catalyst for the hydrogenation of phenanthrene and pyrene. Mo(CO) 6 -S strongly promoted hydrogenation of polycyclic aromatic compounds. Only Mo(CO) 6 -S exhibited high catalytic activity for the hydrogenolysis of dibenzyl ether and benzyl phenyl ether
TL;DR: In this article, the authors quantified the oxidation kinetics of Illinois No. 6 bituminous coal between 295 and 398 K using X-ray photoelectron spectroscopy (XPS) to determine the changes in the amount of surface organic oxygen and provide an oxygen functional group distribution.
Abstract: We have quantified the oxidation kinetics of Illinois No. 6 bituminous coal between 295 and 398 K. X-ray photoelectron spectroscopy (XPS) was used to determine the changes in the amount of surface organic oxygen and provide an oxygen functional group distribution. GC analysis of the gas-phase products and weight changes from TGA experiments were used to place the XPS results in the context of bulk oxidation
TL;DR: Differential scanning calorimetry (d.s.c) was used in this article to study the heat effects associated with pyrolysis of 17 different coals, ranging in rank from anthracite to lignite.
TL;DR: In this article, a coprocessing study of coal and petroleum resid combinations to processing under thermal hydrotreatment conditions, the means of increasing the conversion of coal, and the nature of resid demetalation effects are described.
Abstract: Initial coprocessing studies, performed to provide a basis for larger scale tests of coprocessing options using batch one-liter autoclave and continuous hydrotreater facilities at PETC, are described. Areas investigated included the response of coal and petroleum resid combinations to processing under thermal hydrotreatment conditions, the means of increasing the conversion of coal, and the nature of resid demetalation effects. The petroleum resids possessed rather low donable-hydrogen capacities, and the interactions between the resids and coals are weak with respect to promoting formation of liquid products under thermal conditions. Maya ATB was superior to Boscan ATB or North Slope VTB for the conversion of Illinois No. 6 coal to liquid or soluble products. The Maya ATB/Illinois No. 6 coal system responded favorably to the addition of low concentrations of a highly dispersed, unsupported molybdenum catalyst. Extensive demetalation of the liquid product was observed and was a function of the amount of coal added. Results obtained using different coal and resid combinations, under thermal and catalytic conditions, and in the presence of various additives, imply that an absorptive mechanism is operative. The primary interactions leading to demetalation appear to be between the metal complexes of the resid and the insoluble carbonaceous coal-derivedmore » material. Demetalation of the liquid product was not observed to be dependent on conversion of the organically complexed metal in the resids to inorganic form.« less
TL;DR: In this article, the effects of coal oxidation on thermoplastic properties and on the conversion of coals to liquids are related to the formation of cross-links in the coal structure through the thermally induced reactions of oxygen-containing functional groups.
Abstract: Certain aspects of the chemical and physical changes that occur during coal processing are reviewed and discussed in relation to the influences of coal oxidation and catalytic hydrogenation under low-severity conditions. The adverse effects of oxidation on thermoplastic properties and on the conversion of coals to liquids are related to the formation of cross-links in the coal structure through the thermally induced reactions of oxygen-containing functional groups. Microscopic techniques and, in particular, fluorescence microscopy can be usefully applied to studying the structural changes caused by reaction under hydrogenating and non-hydrogenating conditions
TL;DR: In this article, Australian coals of varying rank from a well characterized suite and with a wide range of atomic H C ratios have been reacted with hydrogen in tetralin at 405 °C both in the presence and absence of a tin promoter, and with both hydrogen and tin without solvent at 320 °C.
TL;DR: In this article, the temperature dependence of coal pyrolysis in a sealed tube was investigated and it was found that the temperature-dependent behavior was not consistent with the simple Curie law temperature dependence usually assumed in calculating the spin population at elevated temperature.
TL;DR: In this paper, the authors investigated the effect of low molecular weight extractable substances on the plasticity of coal residues after their extraction with mixed solvents and found that coal resolidification temperature and the plastic range decreased with an increase in extraction yield.
TL;DR: A suite of coals from several continents has been characterized and reacted under conditions similar to those used by us for a suite of Australian coals. as mentioned in this paper showed that the reactivity of these coals with hydrogen in tetralin at 405 °C correlated well with the atomic HC ratios of the coals and the correlation curve was similar to that for Australian COals.
TL;DR: In this paper, coal was successively extracted in anthracene oil, quinoline, and liquid paraffin solvents, and the combined total extractability of coal in all the solvent systems increased with an increase in the extraction time in successive extractions.
Abstract: Assam coal was successively extracted in anthracene oil, quinoline, and liquid paraffin. About 68% of the coal was rendered extractable through successive extraction in anthracene oil followed by quinoline and then finally in liquid paraffin. The combined total extractability of coal in all the solvent systems increased with an increase in the extraction time in successive extractions. Assam, Talcher, and Raniganj coals and Neyveli lignite gave more than 50% extraction yields through the successive extractive disintegration using an anthracene oil-quinoline-liquid paraffin solvent system. Possible explanations for successive extractive disintegration of coal in anthracene oil-quinoline-liquid paraffin solvents are given
TL;DR: In this article, supercritical gas extractions of 15 UK coal samples of rank CRC 500-900 were carried out in a 500 ml batch autoclave fitted with a condenser and a siphon arrangement.
TL;DR: In this paper, the conversion of bituminous coals to solvent solubles (coal dissolution) was carried out in tetralin and naphthalene at 300-450 o C for 1 h under N 2 atmosphere to investigate coal dissolution behavior in the initial stage of coal liquefaction.
Abstract: Conversion of three bituminous coals to solvent solubles (coal dissolution) was carried out in tetralin and naphthalene at 300-450 o C for 1 h under N 2 atmosphere to investigate coal dissolution behavior in the initial stage of coal liquefaction. The products were extracted with an effective extraction solvent, a CS 2 -N-methyl-2-pyrrolidinone (NMP) mixed solvent (1:1 by volume), and conversions were determined from the quantity of its residue (MI fraction). The extracts obtained were further fractionated into a THF-insoluble and mixed-solvent-soluble fraction (TIMS), preasphaltene, asphaltene, and oil by using THF, benzene, and n-hexane. The effect of extractable substances in coals on coal dissolution and its retrogressive reaction was discussed
TL;DR: Pulsed H2O gasification of Yallourn coal char (prepared at 1073 K for 30 min under argon) loaded with Na2CO3 or Fe(NO3)3 revealed that reaction of H 2O with metallic Na or Fe, formed during preheat treatment of the char at 1273 K under flowing helium, occurred at a temperature as low as 873 K to give H2 and metal oxides as mentioned in this paper.
TL;DR: In this paper, the effects of Fe + Ca and Ni + Ca dual catalysts on hydrogasification of coal char were studied between 1 and 30 atm and between 750 and 900 C. The results are discussed in comparison with the authors previous study using model carbons.
Abstract: The effects of Fe + Ca and Ni + Ca dual catalysts on hydrogasification of coal char were studied between 1 and 30 atm and between 750 and 900{degrees}C. Promotions of Fe- and Ni-catalyzed reactions by added Ca were observed in the reactions of all coal chars used. The degree of promotion increased with increases in the amount of added Ca, temperature, and pressure. The initial surface area of coal char was found to greatly affect the activities of dual catalysts, probably due to different dispersions of catalyst particles at the stage of impregnation. The rate of Ni-catalyzed gasification increased with time during the isothermal mode, and the added Ca accelerated the rate increase. The results are discussed in comparison with the authors previous study using model carbons.
TL;DR: In this paper, the rates of evolution of hydrogen sulfide have been measured for the steam/oxygen gasification of a devolatilized Western Kentucky bituminous coal, a New Mexico subbituminous co-product, and a Texas lignite in a pilot-scale fluidized bed reactor and a phenomenological model has been formulated to correlate the results.
Abstract: The rates of evolution of hydrogen sulfide have been measured for the steam/oxygen gasification of a devolatilized Western Kentucky bituminous coal, a New Mexico subbituminous coal, and a Texas lignite in a pilot-scale fluidized bed reactor, and a phenomenological model has been formulated to correlate the results. The model assumes instantaneous devolatilization and partial combustion of the coal followed by rate-limited gasification of the char in a single well-mixed stage and includes kinetic correlations for the water gas shift reaction and char hydrodesulfurization. Estimated char reactivities agree well with results obtained in other studies, and the model predictions are generally satisfactory, especially considering the relative simplicity of the model. The results indicate that sulfur present in the coal as pyrite, mercaptans, aliphatic sulfides, and disulfides is converted completely, while sulfur in aryl sulfides and thiophenes is only partially converted. A substantial fraction of the sulfur converted during gasification is released in pyrolysis - 50-70% for the subbituminous coal and 35-45% for the lignite.
TL;DR: In this paper, several ion ores for possible use as disposable catalysts for direct coal liquefaction were pretreated to enhance their catalytic activity, which resulted in significant changes in the specific surface area and pore volume distribution of the ores.