Hydrogenation of brown coal. 3. Roles of hydrogen and hydrogen-donor solvents in systems catalysed by iron and tin compounds

The role of hydrogen and hydrogen-donor solvents in the liquefaction of a Victorian brown coal without added catalyst and in the presence of iron-and tin-based catalysts has been studied. Results of an investigation of the effect of temperature and pressure on the conversion parameters, of independent studies of asphaltene hydrogenation, and of work with model ethers are described. A mechanism is tentatively proposed to describe the role of iron, tin and iron-tin catalyst systems based upon these results.     

Formation of a new catalyst (Saechol) for coal hydrogenation on the surface of molybdenum alloys by catechol treatment

For the hydrogenation of Japanese Taiheiyo coal, a new catalyst, Saechol, formed on the surfaces of blades made from molybdenum-containing alloys such as SUS316, SCM3 and SKH9 showed significant activity. The activity survived in the flame but was lost easily by washing in 6N hydrochloric acid. The activity was easily regenerated. Several procedures for generation of activity are reported.     

Coal liquefaction model: microscopic examination of solids from metal halide catalysed coal hydrogenation experiments

Coal undergoes changes during the hydrogenation process which depend on the balance between carbonization and hydrogenation reactions, which in turn depend on various experimental conditions, i.e. hydrogen availability, heating rate etc. If carbonization conditions prevail, semicoke is formed, whereas liquid hydrocarbons are formed under hydrogenation conditions. This model is applicable to hydrogenation reactions carried out under a wide range of experimental conditions.     

Effects of Lewis acid catalysts on the hydrogenation and cracking of two-ring aromatic and hydroaromatic structures related to coal

Little is known about the hydrogenation of fused aromatic nuclei during the liquefaction of coal under the influence of Lewis acid catalysts. This study was conducted to establish the effects of catalyst acidity on the activity and selectivity of Lewis acid catalysts, the sources of hydrogen involved in hydrogenation and cracking, and the relations between reactant structure and reactivity. Two-ring aromatic and hydroaromatic compounds were used to simulate some of the structural units present in coal. The catalysts examined were ZnCl₂ and AlCl₃. ZnCl₂ is less active than AlCl₃ for both hydrogenation and cracking but it does not promote the formation of tars via Scholl condensation: Methyl or hydroxyl substitution of the reactants greatly enhances their reactivity towards hydrogenation and cracking. The source of hydrogen consumed during hydrogenation depends on the choice of catalyst. In the presence of AlCl₃, Scholl condensation of aromatic nuclei serves as the principal source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalysed by ZnCl₂. The formation of reaction products and the trends in reactant reactivity can be interpreted on the basis of carbonium ion mechanisms. The results of this study provide a basis for assessing the extent of hydrogenation occurring during the liquefaction of coal using ZnCl₂ or AlCl₃.     

Effect of air oxidation on coal hydrogenation

Japanese Taiheiyo coal (75.9%C) was oxidized with air at 250 °C for 3–40 h and at 300 °C for 3–10 h. The weight decreased from 16.3 to 46.5% at 250 °C and from 21.7 to 41.3% at 300 °C. Carbon loss and yield of NaOH soluble were obtained. The resultant oxidation products were hydrogenated at 370 °C for 1 h under 10 MPa hydrogen pressure using red mud with sulphur as catalyst and wash oil as solvent. Conversion to pyridine, benzene and n-hexane soluble fraction shows a minimum for the coal oxidized 10 h at 250 °C and for the coal oxidized for 3 h at 300 °C. Initial oxidation makes a network structure which contributes to a reduction in conversion, but in later stages of oxidation, splitting of bridge linkages and/or ring opening of aromatic structures, contribute to increases in conversion.     

Catalytic properties in hydrogenation and hydrodesulphurization reactions of ruthenium sulphide solid solutions containing iron,cobalt or nickel

Solid solutions M_xRu_1–xS₂ (M = Ni, Co, Fe) were prepared by sulphidation of mixtures of hydroxides at 673 K; their crystallographic properties were studied by X-ray diffraction. These new materials present interesting properties in biphenyl hydrogenation and in thiophene hydrodesulphurization. The catalytic properties are strongly dependent on the nature of the metal associated to ruthenium. Cobalt-ruthenium catalysts present a good activity for hydrodesulphurization but very low activity for hydrogenation, iron catalysts exhibit low activity for both reactions, and nickel catalysts possess remarkable properties in hydrogenation and hydrodesulphurization (twice the activity of pure ruthenium sulphide). A comparison has been established with the properties of molybdenum sulphide catalysts promoted by the same elements.     

Hydrogenation of brown coal: 6. Reactions of coal-derived products with hydrogen in the presence of metal-based catalysts

The product from the hydrogenation of an iron-tin treated Morwell, Victorian coal was separated into a number of fractions by solvent separation. Each of these fractions (tetrahydrofuran-insoluble materials, asphaltols, asphaltenes and oils) was reacted separately with hydrogen in tetralin both with and without added catalysts. The effect of added catalyst and of temperature, pressure, time and solvent on the hydrocracking and repolymerization reactions is discussed. The interconvertibility of the brown coal-derived products is clearly established, reinforcing the importance of incorporating reversibility of reactions in mechanistic models developed to describe coal hydroliquefaction.     

Evidence for direct interaction of hydrogen with brown coal in tin-catalysed reactions

Evidence is presented which shows that the major mechanism for the tin-catalysed hydrogenation of suspensions of brown coals in tetralin involves a direct interaction of hydrogen with the coal.     

Viscosity changes in coal paste during hydrogenation

Using a viscometer that operates up to a maximum pressure of 29.4 MPa and a maximum temperature of 550 °C, the viscosity of coal paste and its changes with temperature were investigated, and also some effects of: type of vehicle oil, coal to vehicle oil ratio, coal particle size, atmosphere, pressure, catalyst and coal rank. In the viscosity-temperature curve for the paste from high rank bituminous coals, a peak was observed near 300 °C, which is considered to be due to the extractive disintegration of the coal by the vehicle oil. Under hydrogenation with high pressure hydrogen and hydrogenation catalyst, the extractive disintegration of coal was promoted, and the viscosity was higher than that in nitrogen atmosphere. The viscosity behaviour of the coal paste from low rank coals was the same as that of the vehicle oil alone.     

Coal liquefaction by colloidal iron sulphide catalyst

Taiheiyo coal, which was treated with an aqueous solution of dodecyltrimethylammonium chloride, adsorbed colloidal iron sulphide prepared from FeS0₄ · 7H₂O and Na₂S · 9H₂O in aqueous media. The adsorbed colloidal iron sulphide was much more effective as a catalyst for the liquefaction of the coal itself than the usual powder-type iron sulphide. Thus in differential thermal analysis under hydrogen, the coal with 0.35wt% adsorbed colloidal iron sulphide gave an exothermic peak at 401 °C, which was ≈20 °C lower than when using the powder-type iron sulphide. The coal was smoothly hydrogenated at 450 °C to give a yield of ≈60% liquid products.     

Model for the coal hydrogenation process and its applications

A coal hydrogenation model has been formulated which incorporates both chemical and microscopic experimental data. In this generalized model, carbonization and hydrogenation are viewed as concurrent processes in the liquefaction of coal. Insufficient hydrogen availability, rapid heating rates and long reaction times at elevated temperatures can promote carbonization reactions. The model describes in detail the reaction pathways involved in the hydrogenation of both inertinite and vitrinite. When vitrinite is hydrogenated in the presence of a hydrogen donor solvent, a plastic material called vitroplast is formed. The vitroplast is either converted to liquid and gaseous products when hydrogen availability is high or becomes mesophase and then semicoke when hydrogen availability is low. Even under favourable hydrogenation conditions, the major reaction pathway in the hydrogenation of inertinite is one of initial mild carbonization followed by hydrogenation. It is evident that the difference in hydrogenation behaviour between vitrinite and inertinite is due, in part, to the ability of the hydrogen donor solvent to penetrate vitrinite but not inertinite particles. The hydrogenation model is useful for explaining various phenomena that occur during hydrogenation, such as the formation of mesophase and semicoke, and the blockage of reactors and preheaters.     

Mesophase formation and the degree of hydrogenation of coal

Samples of vitrinite and brown coal were heated in glass tubes under hydrogen pressure in the presence of metal chloride catalysts but without vehicle solvent. Highly hydrogenated coaly material near the surface of the samples gave a relatively small quantity of mesophase material. The least hydrogenated coaly material in the lowest portion of the samples did not change to mesophase. Mesophase material was formed only in the moderately hydrogenated zones.     

神府长焰煤加氢增黏反应中催化剂及氢传递机理

我国炼焦煤资源短缺且分布不均匀,而低阶煤储量丰富,价格低廉,具有低灰、低硫等特点,但其黏结性几近为零。催化加氢增黏是一种有效提高低阶煤黏结性的方法。本文通过对长焰煤进行催化加氢增黏,对原煤及增黏煤进行元素分析、红外分析、电子顺磁共振分析和反应中氢耗计算研究催化加氢增黏反应中催化剂及氢传递机理。结果表明：长焰煤黏结性显著增强,在炼焦过程中可部分替代炼焦煤使用;加氢增黏可以去除长焰煤中部分含氧官能团及烷基侧链,降低煤分子的交联程度;催化剂主要作用是活化氢气,其次可以促进煤分子解聚并且促进四氢萘到煤的氢传递。当催化剂存在时,催化加氢增黏反应氢传递路径主要是从氢气直接至煤分子,而不是通过供氢溶剂至煤分子。     

Reaction mechanism of coal hydrogenation. 3. Effect of coal type

Seven coals have been hydrogenated in naphthalene and phenanthrene under 10 MPa (initial pressure) of hydrogen with a stabilized niekel catalyst at 400°C for 15 min. Preasphaltene, asphaltene and oil conversions and solvent conversion were measured. The amounts of hydrogen absorbed by coal and by solvent were calculated. Coal conversion and the amount of hydrogen absorbed by coal decreased, while the amount of hydrogen absorbed by solvent increased, with increase in coal rank. The ratio of the amounts of hydrogen absorbed by coal and by solvent showed a good correlation with conversion to benzene- and n-hexanesoluble materials. Naphthalene and phenanthrene gave similar results, suggesting that the coal was hydrogenated directly by gaseous hydrogen.     

Catalytic hydrogenation of carbon monoxide to alkenes over partially degraded iron-cobalt complexes

Complex-derived iron–cobalt alloy catalysts have been studied under conditions similar to those normally prevailing in industry. Despite reports in the literature indicating unusual selectivities with iron–cobalt alloy catalysts under atmospheric pressure conditions, no deviations from normal selectivity behaviour have been observed when studied under steady-state conditions and pressures of 2.0 MPa. However, when promoted with manganous oxide or supported on silica-alumina, substantial deviations from Anderson-Schulz-Flory statistics occur during the first few days on stream. These deviations gradually disappear with increasing time on stream leading to normal selectivity behaviour. The unsupported catalysts displayed remarkably high activity and selectivity maintenance, in contrast to supported catalysts, which show substantial oscillations in the catalytic behaviour.     

对叔丁基苯酚催化加氢制备顺式对叔丁基环己醇

采用雷尼镍、Pd/C、Pt/C等为催化剂 ,由对叔丁基酚液相催化加氢合成顺式对叔丁基环己醇。在反应温度 110～ 130℃ ,反应压力 5MPa条件下 ,对叔丁基酚转化率 10 0 % ,对叔丁基环己醇收率 >98% ,顺式对叔丁基环己醇选择性 >75 %     

Hydrogenation of brown coal. 2. Iron-based catalysis

Some of the inherent cations of Victorian brown coals have been exchanged for iron by treatment with solutions of iron salts. Coals with various iron contents are obtained by variation of the pH of the solutions used. Hydrogenation of coals treated in this way at 395 °C, and an initial hydrogen pressure of 10 MPa, give product yields similar to those obtained using commercial cobalt molybdate on alumina catalysts, and greater than those obtained using red mud as a catalyst. The increase in yields compared with non-catalysed experiments results mainly from increased production of asphaltenes. The amount and composition of gas (80–90 wt% C0₂, resulting from decarboxylation) remains constant. Despite the similar conversions, the hydrogen consumption and tetralin/naphthalene ratios for iron-catalysed experiments are less than for cobalt—molybdate-catalysed experiments.     

Statistical and mathematical analysis of the catalytic hydrogenating depolymerization of benzene-insoluble coal extract fraction

This Paper presents a statistical and mathematical analysis of hypotheses concerning the autoclave hydrogenating depolymerization of coal extract fractions insoluble in benzene. From comparison of theoretical and experimental data the most probable reaction mechanism was selected.     

Variation in Victorian brown coal characteristics and hydrogenation potential

A detailed study of the variation of properties and characteristics of Victorian brown coal both within seams and between fields has been carried out. Within a seam, the organic coal properties are lithotype dependent whilst the exchangeable inorganic elements, Na, Mg, Ca and Fe, show no relation to lithotype and, hence, are believed to be of post-depositional origin. Considerable variation in coal properties between different brown coal fields has been demonstrated by analyses of 219 samples from 10 coal fields. The coal properties which correlate best with hydrogenation reactivity are primarily associated with the hydrogen content of the coal. The mineral matter also influences the hydrogenation reactivity, as demonstrated by the occurrence of the value for ash level in multiple linear regression equations.