Showing papers on "Carbochemistry published in 1983"

Electrochemistry of Coal Slurries II . Studies on Various Experimental Parameters Affecting Oxidation of Coal Slurries

Abstract: The anodic oxidation of coal slurries has been studied under various experimental conditions. Results obtained from various experiments support the mechanism of the catalytic oxidation of coal slurries by iron (III in solution, followed by the oxidation of reduced iron (II) to iron (III) at the electrode. The oxidation of coal slurries by iron (III) in solution is found to be a first-order process with respect to both reactants, i.e., coal and iron (III), from concentration dependency studies, indicating that the overall reaction may consist of a sequence of one-election transfers. It may also be concluded from various experimental results that the electrolysis reaction proceeds through the sequential formation, first of carbon oxides on the coal surface, and then of carbon dioxide as a final product. Of various catalyst oxidants studied, bromine and cerium (IV) appear to have the largest pseudo first-order catalytic rate constants with 1.1 X 10/sup -3/sec/sup -1/ and 4.1 X 10/sup -4/sec/sup -1/, respectively. Redox potentials of the catalyst pairs appear to be the most important parameter in determining catalytic reaction rates.

Isothermal studies of the liquefaction of Liddell coal

Abstract: The liquefaction of an Australian bituminous coal (Liddell) was studied under isothermal conditions with tetralin as solvent. The influences of reaction temperature and reaction time on the yields and nature of the products were determined. Particular emphasis was placed on short contact times (0-20 min). The high average molecular weights of the product fractions at very short reaction times (<5 min) have not been observed in studies with conventional autoclaves. The total aromaticity of the products and residues from coal liquefaction were determined. At 450/sup 0/C, significant increases in the aromaticities of the products and residue occurred in the first 2.5 min of reaction, and a large proportion of the aliphatic components of the coal was rapidly converted to gas.

Hydrogenation reactions of model titanium compounds under coal liquefaction conditions

Abstract: Used catalyst and reactor deposits from a fixed-bed coal liquefaction unit show high concentrations of titanium and boron. The titanium was present as anatase, a titania polymorph. Hydrogenation reactions with and without catalyst were performed with model titanium and boron compounds under liquefaction conditions. The catalyst used was Harshaw 0402T 3% CoO - 15% MoO/sub 3/ on an alumina-silica support. Rutile remained unchanged by reactor conditions. In all other runs the titanium starting material, whether organic or inorganic in nature, converted to anatase. When the deposition of the reaction products was monitored, only that anatase derived from organic titanium compounds accumulated on and in the catalyst pellets to an appreciable extent.

Comparison of normal and rapid heat-up modes in a batch screening test for coal liquefaction catalysts

Abstract: A comparison was made between normal and rapid heat-up modes of testing for a batch screening test to determine the initial activity of coal liquefaction catalysts. Some effects of choice of solvent, temperature, oil/coal ratio, catalyst/coal ratio, and coal batch on the test results are given. The results indicate that only minor differences in conversions of coal to soluble products are obtained by using the two different tests. No differences in hydrodesulphurisation were observed. Neither test is capable of causing nitrogen removal at the chosen test conditions.

Large block experiments in underground coal gasification

Abstract: The process of in-situ coal gasification, while extremely simple in concept, is complicated in practice because, as the burn proceeds, the reacting volume is constantly changing geometry. In addition, the process takes place underground where it is extremely difficult to observe in detail. The five large block experiments described here were planned as a series of gasification experiments each of which was to be terminated at a fairly early stage of cavity development and examined by postburn excavation. The experiments included 1:1 and 3:1 steam:oxygen injection at two different flow-rate schedules, an air-injection burn, and a test of the controlled retracting injection point (CRIP) system. The results indicate that the underground coal gasification process at this location is insensitive to changes in steam:oxygen ratios or flow rate over the range used. The burn cavities were all mostly filled with rubble and thermally altered coal.

Catalytic activities of iron ores in direct liquefaction of coal

Abstract: Catalytic activities of various iron ores, hematite, limonite and magnetite, mixed with sulfur were examined in order to develop a disposable catalyst in direct liquefaction of coal. The catalytic mechanism was investigated with differential thermal analysis and X-ray diffraction analysis. The following results were obtained: Most of the iron ores mixed with sulfur were as active as or more active than red mud mixed with sulfur, which has been regarded as a catalyst, even under relatively mild liquefaction conditions. The resulting liquefaction products were rich in middle and light oils. Thus, they are expected to become one of the catalysts; the catalytic mechanism in the presence of these iron ores plus sulfur, except for magnetite, was found to be similar to that of Fe/sub 2/O/sub 3/ mixed with sulfur.

Aromatics production from coal syncrudes

Abstract: The properties of syncrudes obtained from the H-Coal, SRC-II and Exxon Donor Solvent processes are compared with those of a typical petroleum crude. The results are then presented of the hydroprocessing and reforming of representative coal naphthas made by these processes. The objective was to utilise the high cyclic content of these naphthas to produce high yields of aromatics or, alternatively, gasoline blend stock.

Novel kinetic analysis of coal liquefaction

Abstract: The application of a non-isothermal method of kinetic analysis to the study of coal hydrogenation is described. Kinetic parameters obtained by this technique compare favourably with those obtained with a conventional approach. The non-isothermal method is convenient and provides a means of obtaining reaction rate data for the complex initial stages of the coal liquefaction process.

MoO3-SILICATE SLUDGE CATALYST FOR COAL LIQUEFACTION

Abstract: Silicate sludge obtained from a geothermal power generation plant was applied to prepare the catalyst for coal liquefaction. The sludge has a very high surface area, a large pore volume, and a wide-range pore size distribution. It was found that the activity of the catalyst prepared by supporting MoO3 on the sludge is superior to commercially available Ni–Mo/Al2O3 catalyst.

Yubari Coal Depolymerization and Catalysis of ZnCl2-containing Melt for Hydrocracking of the Coal Extract

Abstract: In the depolymerization of Yubari coal in the presence of tetralin, reaction time did not alter the average molecular weight of the coal extract but it effected deoxygenation and hydrogenation in which its nitrogen content remained constant. These effects are explained by referring to the average structure's change of two coal extracts. The coal extract from the depolymerization was hydrocracked over ZnCl2 or over ZnCl2-CuCl melt at 400°C for 3hr with an initial hydrogen pressure of 100kg/cm2. Analysis of PSH (higher boiling portion of pentane soluble) and of BS (benzene soluble) revealed that ZnCl2-CuCl was superior to ZnCl2 in removing the heteroatoms. The effectiveness of ZnCl2-containing melts for denitrogenation of coal and coal related materials was discussed on the basis of hydrocracking of quinoline over ZnCl2 and over quinoline-ZnCl2 complex. The close similarity of these products strongly suggests that denitrogenation of the basic fraction of the coal extract proceeds via the complex formation of nitrogen atoms with ZnCl2.

Enhancement of catalyst performance in upgrading liquefied coal

Abstract: A small amount of water added to light-ends column feed from the SRC-II coal liquefaction process enhances the denitrogenation capability of Co, Mo, Ni and W catalysts.

Alkali treatment of coal

Abstract: Alkali fusion was examined for 3 Japanese coals without any solvents (320-440C) and the alkali-treated coals were extracted with solvents (benzene, methanol and pyridine). Extract yields, especially the yield of pyridine extract, were greatly affected by the reaction temperature and time, and the best yield (about 85%) was achieved under mild conditions (320-350 C for 1h). The characteristics and the decomposition process of this procedure are discussed in comparison with other methods.

Investigation of low-rank coal hydropyrolysis

Abstract: Laboratory microscale studies have demonstrated that the coal pyrolysis in a hydrogen atmosphere gave higher degree of devolatilization in low-rank coals than pyrolysis in an inert atmosphere. In hydrogen atmosphere two distinct steps in coal devolatilization were observed as shown by the double peak of the devolatilization rate. Only one step was observed under nitrogen atmosphere. In a comparison of kinetic parameters, a high reaction order and a low activation energy were also obtained in the coal hydropyrolysis. Application of data and observations from this study could lead to a better understanding of chemical and physical changes during the coal hydropyrolysis and alternative coal conversion routes. (JMT)