Showing papers on "Carbochemistry published in 1986"
TL;DR: In this paper, an investigation has been made of the liquefaction of a bituminous and a subbituminous coal under conditions where reaction is conducted in successive stages of increasing temperature and in the presence of a dispersed sulphided Mo catalyst.
49 citations
TL;DR: In this article, a new mechanism of water vapour gasification of coal, coke or carbon is proposed, which assumes condention of hydroxyl groups formed by dissociation of water at active sites.
48 citations
TL;DR: The authors showed that using lignin to a reaction mixture of coal plus hydrogen-donor solvent promoted more extensive depolymerization of the coal at lower temperatures, and that using guaiacol as solvent further increased coal conversion.
40 citations
TL;DR: In this paper, a bench-scale fluidized bed reactor was used for the gasification of coal with steam as the fluidizing medium, and the gas composition and yield of the hydrogen-rich product gas were studied as a function of temperature.
Abstract: Thermal gasification has been proposed as one technical option for the conversion of coal to gaseous fuels and/or chemicals to supplement supplies presently derived from petroleum and natural gas. In the present study, a bench-scale fluidized bed reactor was used for the gasification of coal with steam as the fluidizing medium. A mixture of sand and limestone used as the bed material made it possible to gasify a caking coal without the problem of agglomeration. The gas composition and yield of the hydrogen-rich product gas were studied as a function of temperature.
To study the heterogeneous reactions taking place in the reactor and also the transient behavior of the system, a mathematical model was developed. The model assumed a reaction mechanism that accounted for the devolatilization of coal, cracking of volatiles, char gasification, and the water-gas shift reaction. Both the dynamic behavior and steady state performance of the gasifier were simulated based on the model. The steady state results of the simulation were compared with the experimental data. This comparison enabled us to ascertain that the proposed reaction mechanism and dynamic model predicted the correct trends.
35 citations
TL;DR: In this paper, the extraction of five Victorian brown coals with supercritical water in a semi-continuous reactor was investigated, and the extracts were separated into oils, asphaltenes and pre-asphaltene and these were studied by NMR spectroscopy combined with elemental, OH and molecular weight analyses.
31 citations
TL;DR: In this article, the catalytic activity of cobalt molybdenum sulphide, cobalt oxide, iron sulfate, iron acetate dibasic and H 2 S during the reaction between supercritical CO and water, and during liquefaction of coal using supercritical water-water-solvent mixtures was studied.
31 citations
TL;DR: In this paper, gasification reactivities of raw and acid-washed coal chars obtained from the three most important coal-bearing regions in Chile have been determined in 0.1 MPa of oxygen using a thermobalance.
30 citations
TL;DR: In this paper, the authors found that the promoters which are active in dry hydrogenation reactions (Co, Ni, Cu, Zn, Mo, Sn and Pb) lost some activity for conversion to oil when water was added to the reactions.
30 citations
TL;DR: In the absence of poisons such as sulphur, arsenic, phosphorous, and heavy metals, the major way in which the catalyst loses activity is due to accumulation of carbonaceous residues on its surface as mentioned in this paper.
Abstract: One of the most interesting and intriguing topics in the field of heterogeneous catalysis is the mechanism by which metallic particles influence the gasification of graphite. The gasification of carbon by oxidizing gases is often the limiting factor in the performance of graphite structures at high temperatures. Currently, one of the most important areas involves the function of metals in the removal of carbonaceous deposits from spent catalysts and steam cracker tubes. Supported metal catalysts are employed in a variety of commercial hydrocarbon conversion processes. Such catalysts consist, in general, of small metal crystallites (0.5 to 2.5 nm diameter) dispersed on nonmetallic oxide supports. In the absence of such poisons as sulphur, arsenic, phosphorous, and heavy metals, the major way in which the catalyst loses activity is due to accumulation of carbonaceous residues on its surface. Catalyst regeneration is usually achieved by gasification of the deposit in an oxidizing environment at about 500°C. The efficiency of this process is variable and so there is an increasing demand to learn more about the process so that gasification can be optimized.
26 citations
TL;DR: The world coal reserves constitute an important source of energy and base chemicals after the 1973 oil crisis and warning reports of the Club of Rome for the limited world supplies of oil and natural gas as discussed by the authors.
Abstract: The world coal reserves constitute an important source of energy and base chemicals After the 1973 oil crisis and warning reports of the Club of Rome for the limited world supplies of oil and natural gas the importance of coal for political, economical and energy preservation reasons was acknowledged again Increasing efforts in coal research could be observed from that time
24 citations
TL;DR: In this article, a non-isothermal experimental technique is presented to study the mechanism of coal extraction with solvents at sub- and supercritical temperatures between 20 °C and 550 °C, and pressures up to 15 MPa.
TL;DR: In this article, the contents of oxygen-containing functional groups were determined in Czech coal and carbonization residues and the dependence of the oxygen functions and the phenol yield on temperature and coal rank was discussed.
TL;DR: In this paper, the interaction of barium carbonate with carbon black was studied to understand catalysed CO2 gasification of carbon, and it was shown that carbon dramatically accelerated the rate of BaCO3 decomposition to form BaO and CO2, which rapidly gasified carbon to form CO.
TL;DR: In this paper, a mathematical model based on the concept of reactions in a continuum is developed to simulate coal liquefaction kinetics, where the rate-limiting reactions are irreversible cracking reactions involving cleavage of carbon and oxygen linkages.
Abstract: Based on the concept of reactions in a continuum, a mathematical model has been developed to simulate coal liquefaction kinetics. In an excess hydrogen donor environment, the rate-limiting reactions are considered to be irreversible cracking reactions involving cleavage of carbon and oxygen linkages. Concurrent evolution of a wide spectrum of products, with an initial rapid formation of species of high carbon and oxygen contents, followed by progressively slower reactions leading to lower carbon and oxygen content species is predicted. Simple lumping functions are employed to obtain conventional lumped pseudocomponents (preasphaltenes, asphaltenes, and oils). Parameter analysis has been carried out.
TL;DR: Petroleum heavy oil and anthracene oil were used as hydrogen donor solvents in a coal liquefaction test as mentioned in this paper, and a positive synergistic effect was obtained when mixed (petroleum heavy oils; anthrasene oil) solvent was employed.
TL;DR: In this article, the effect of added catalysts and of temperature, pressure, time and solvent on the hydrocracking and repolymerization reactions of brown coal-derived products is discussed.
TL;DR: In this article, the estimation of primary aromatic amines (PAA) and other basic nitrogen compounds in coal liquefaction products is described, where aqueous acid extraction was used to isolate basic nitrogen fractions which were analyzed by gas chromatography (GC) and mass spectrometry (MS).
Abstract: The estimation of primary aromatic amines (PAA) and other basic nitrogen compounds in coal liquefaction products is described. Aqueous acid extraction was used to isolate basic nitrogen fractions which were analyzed by gas chromatography (GC) and mass spectrometry (MS). Selective chemical derivatization in conjunction with single-ion GC-MS was used to distinguish between the PAA and the isomeric aza heterocycles. The relative merits of the proprietary methylating reagent ‘Methyl-8’ (dimethylformamide dimethylacetal) and a more conventional fluoroacylating reagent for the selective derivatization of PAA are evaluated. Quantitative aspects of the analyses are discussed.
TL;DR: In this paper, the results of catalytic hyroliquefaction under batch conditions depend on a large number of variables, such as the influence of the catalyst concentration, the mode of sulfidation or the introduction of the catalysts in the coal/solvent mixture, and the nature of the model compound solvent.
TL;DR: In this paper, the influence of digestion and filtration conditions in a coal liquefaction process have been investigated to determine their effect on ash levels and trace elements in the extract solution.
TL;DR: In this article, the effects of reaction time and temperature are coupled via a severity index that arises in the model as a dimensionless reaction time, and it is shown that the product distribution for a particular coal seems to be a function only of the conversion even in the presence of catalysts.
Abstract: Experimental kinetic data for three Australian coals compared with predictions from the mathematical model developed. For these coals, as well as data reported for North American coals, the model is found to show good agreement, using the characteristic molecular weight as the only parameter. The effects of reaction time and temperature are coupled via a severity index that arises in the model as a dimensionless reaction time. The model is also shown to be applicable when catalysts are present. The product distribution for a particular coal seems to be a function only of the conversion even in the presence of catalysts, as long as the chemical reaction controls the rate of liquefaction.
TL;DR: In this article, the effect of temperature and gaseous compositions on the reactivities of coal derived chars is studied and a first order expression is used to correlate the reaction rate data during gasification with O2.
Abstract: The effect of temperature and gaseous compositions on the reactivities of coal derived chars is studied. Experimental data for gasification with CO2 are correlated with a Langmuir-Hinselwood type kinetic expression, the inhibition effects of CO are quantified and the temperature dependence of all kinetic constants is presented. A first order expression is used to correlate the reaction rate data during gasification with O2. Preexponential factors and activation energies for this reaction are also reported.
TL;DR: In this article, the effects of temperature, catalyst surface area and decay were studied for continuous steam reforming of rice hull in a fluidized bed reactor containing Ni catalyst. But the authors focused on the degradation of the Ni surface and reaction temperature.
TL;DR: In this article, the low temperature oxidation of a Montana subbituminous coal was investigated using round bottom 100 ml flasks in constant temperature baths with particle sizes ranging from 4 mesh to 100 mesh.
Abstract: The low temperature oxidation of a Montana subbituminous coal was investigated using round bottom 100 ml flasks in constant temperature baths. The experiments were carried out in normal and oxygen enriched air at 30°C, 45°C and 70°C with particle sizes ranging from 4 mesh to 100 mesh. Periodic analysis of gas samples from the flasks provided the rate data. The reactivity of the as received coal was compared with that of the same coal dried (i) in high pressure steam and (ii) in hot water A rate equation has been proposed incorporating the effects of oxygen diffusion and surface reaction. For higher oxygen concentration and smaller particle sizes, the zero order surface reaction was found to be controlling. The temperature dependency of the reaction rate was found to be well represented by the Arrhenius equation. The activation energy varied slightly under various conditions between 15 to 20 kca)/g mole The reactivity of the hot water dried coal was found to be similar to that of the as received coal. Stea...
TL;DR: In this article, the initial stages of coal liquefaction have been investigated in small batch autoclaves at moderate to low liquidation temperatures, and it was shown that ammonium molybdate had a beneficial effect on conversion at lower temperatures as revealed by a decrease in the demands placed on the liquidation solvent.
TL;DR: In this article, a comparative study of coal carbonization samples under various conditions of hydroliquefaction was performed for tars and pitches with different separation, fractionation and identification schemes.
TL;DR: In this paper, the chemical structure of the residues from hydrogenation of maceral concentrates of an Australian bituminous coal have been investigated using nuclear magnetic resonance and infrared spectroscopic techniques and microscopy.
TL;DR: In this article, two samples of Teruel (Spain) subbituminous coals were liquefied in batch type autoclave experiments with reaction temperature in the range 400 to 440°C, initial hydrogen pressure 80 kg/cm 2, reaction time 60 min, anthracene oil as slurry vehicle agent and pyrite, CoMo and NiCo catalysts.
TL;DR: In this paper, a rheometer has been used to measure the apparent viscosity of coal paste from room temperature up to 653 K. This study was performed with two coals of different natures at several different shear rates.
TL;DR: In this paper, the catalytic effects of MoCl3 and NiCl2 for the hydroliquefaction of Morwell brown and Taiheiyo subbituminous coals at 400 °C for 1 h in a batch reactor with an initial hydrogen pressure of 9.8 MPa.
Abstract: The catalytic effects of MoCl3–LiCl–KCl and NiCl2–LiCl–KCl molten salts were studied for the hydroliquefaction of Morwell brown and Taiheiyo subbituminous coals at 400 °C for 1 h in a batch reactor with an initial hydrogen pressure of 9.8 MPa. The conversion to pyridine-soluble materials and the yield of hexane-soluble materials (HS) with the MoCl3 catalyst were 82 and 42% for Morwell coal, and 84 and 61% for Taiheiyo coal, respectively. The conversion and HS yield with the NiCl2 catalyst were 87 and 43% for Morwell coal, and 82 and 56% for Taiheiyo coal, respectively. The HS yield of the catalytic runs was about 2.6–3.2 times higher than that of noncatalytic runs. This finding established the effectiveness of the two new catalysts for the hydroliquefaction of brown and subbituminous coals. Detailed analyses of the reaction products have revealed that these catalysts promoted a depolymerization of the coals and strongly catalyzed the hydrocracking of polynuclear aromatic structures of heavy products into ...