Effect of sulphur on coal liquefaction in the presence of dispersed iron or molybdenum catalysts

The effects of dispersed catalysts on coal liquefaction under hydrogen pressure were studied using small autoclaves. The catalysts were generated in situ by addition of elemental sulphur plus an oil-soluble carboxylic salt of either iron or molybdenum. Finely divided catalysts of relatively high activity were generated by this method. Residues isolated after liquefaction with added iron carboxylate and sulphur contained pyrrhotite, which is proposed to be the catalytically active species. The prime role of sulphur is to form pyrrhotite in combination with the iron. Addition of sulphur alone did not increase conversion. This method of catalyst preparation seems useful for further scientific study of the relationship between sulphur, metal sulphide catalysts and liquefaction activity.     

钼系催化剂对神东煤直接液化的影响

利用间歇式高压釜,采用钼系催化剂钼酸铵、三氧化钼和二硫化钼对神东煤进行煤直接液化性能的研究。研究表明,钼的添加量为0.1%时,钼酸铵的效果最好,转化率和油产率最高,分别为82.14%,39.47%。     

Catalysis of coal hydroliquefaction by synthetic iron catalysts

The following synthetic iron catalyst precursors were investigated: FeOOH and FeOOH-Al₂O₃ (90:10 wt%) co-precipitated by ammonia, washed and dried either in an oven or by spray-drying, and Fe₂O₃ prepared by flame decomposition of FeCl₃ in the gas phase. These catalyst precursors were sulphided in situ by CS₂ during the hydroliquefaction of a highly volatile bituminous coal. An increasing catalytic activity of the iron sulphide was observed as its particle size decreases down to a very low value (0.05 μm), compared to 2–3 μm and to ? 5 μm. Al₂O₃ did not act as an efficient promoter, even if it gives rise to a decrease of the iron sulphide crystallite size. Diffusional limitations and/or plugging by carbonaceous or mineral solids could result in a low efficiency of the iron sulphide crystallites which lie inside one iron catalyst particle. The above cited flame method, allowing the preparation of pure or doped Fe₂O₃ with particle size even less than 0.05 μm, is worthwhile for further work in coal hydroliquefaction catalysis, where the catalyst acts as Fe_1?xS.     

Dehydrogenation activities of coal liquefaction catalysts on various ranks of coals

The amount of hydrogen evolved from a coal during pyrolysis at atmospheric pressure in the presence of coal hydroliquefaction catalysts can be used to compare the activity of different catalysts for the highpressure hydrogenation of coals. This technique has now been used to compare the variation in the effectiveness of MoO₃-TiO₂, and Fe₂O₃-SO^2?₄, as hydroliquefaction catalysts with change in coal rank. It is indicated that coals with carbon contents of ≈ 82 wt% are the most amenable to hydroliquefaction at high pressure.     

Effects of solvent and iron-compounds on the liquefaction of brown coal

Hydrogen-donor solvents such as hydrophenanthrene are the most effective aromatic solvents for the liquefaction of brown coal. The hydrogen-donating ability of the solvent is more important for brown coals than for bituminous coals, because the thermal decomposition and subsequent recombination of the structure of the brown coals occurs rapidly. Three-ring aromatic hydrocarbons are more effective solvents than two-ring aromatics, and polar compounds are less effective solvents with brown coals than with bituminous coals. The thermal treatment of brown coal, accompanied by carbon dioxide evolution at temperatures > 300°C, in the presence of hydrogen-donating solvent did not affect the subsequent liquefaction reaction. However, thermal treatment in the absence of solvent strongly suppressed the liquefaction reaction, suggesting that the carbonization reaction occurred after the decarboxylation reaction in the absence of hydrogen donor. To study the effect of various iron compounds, brown coal and its THF-soluble fraction were hydrogenated at 450°C in the presence of ferrocene or iron oxide. The conversion of coal and the yield of degradation products are increased by the addition of the iron compounds, particularly ferrocene, and the yield of carbonaceous materials is decreased.     

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

Little is known about the hydrogenation and cracking 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 relationships between reactant structure and reactivity. Three-ring aromatic and hydroaromatic compounds were used to simulate some of the structural units present in coal. The catalysts examined were ZnCl₂ and AlCl₃. It has been established that the rates of both processes are strongly influenced by the Brönsted acidity of the active catalyst, e.g. H⁺ (MX_nY)^?, and the Brönsted basicity of the aromatic portions of the reactant. The source of the hydrogen used for 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, however, when hydrogenation is catalysed by ZnCl₂. The formation of reaction products and the trends in reactant reactivity are discussed on the basis of cationic mechanisms. The results of this study contribute to an understanding of the processes which occur during the liquefaction of coal using ZnCl₂ or AlCl₃.     

Bimetallic dispersed sulfide catalysts from organometallic clusters for coal liquefaction

Several heterometallic complexes consisting of Mo, Co and sulfur in a single molecule were synthesized and tested as precursors of dispersed catalysts for liquefaction of a subbituminous coal. The structure of the precursors, in particular the type of ligands to the metal species, significantly affects the activity of the bimetallic MoCo sulfide catalysts generated in situ. Among the M-M type precursors tested, Mo-Co thiocubane, Mo₂Co₂S₄(Cp)₂(CO)₂ (Cp = cyclopentadiene), produced the best catalyst.     

Hydrogenation of brown coal. 9. Physical characterization and liquefaction potential of australian coals

A detailed chemical study has been made on a suite of 27 Australian coals of varying rank. The coals had a wide range of H/C values and, in addition to chemical analysis, were examined by Fourier transform infrared spectroscopy and ¹³C solid state n.m.r. The coals were reacted with hydrogen in tetralin at 405°C and in decalin under nitrogen at 320°C. The products of these reactions were examined by a variety of spectroscopic and other analytical techniques. On the basis of the results it is proposed that brown coals consist of a polymeric lignin-based structure which traps varying amounts of smaller, more aliphatic, molecules. Black coals have more complex structures.     

Exfoliated MoS2 catalysts in coal liquefaction

A technique is described for the application of MoS₂ to coal particles. The method was used to determine the importance of several parameters to the performance of this direct coal liquefaction catalyst. Improved performance was obtained when MoS₂ was intercalated with lithium, then exfoliated in a mixture of tetrahydrofuran and water in the presence of coal. Performance was compared by subjecting dried coal/catalyst mixtures to uniform microautoclave liquefaction tests. Measurements of coal conversion and hydrogen consumption show that a combination of reduction of the MoS₂ stacking and improved coal/catalyst dispersion is beneficial.     

煤直接液化初始阶段反应特性的研究

以杨村煤为例,在490℃和2倍四氢萘溶剂的条件下,反应仅5min煤直接液化总转化率就达到84．47％,表明煤在直接液化的过程中具有初始高反应活性的特点。在纯氢气气氛下随着初始压力从1．5MPa增大到7MPa,转化率从66．38％上升为83．27％,表明压力大小对煤液化转化率有较大影响。1．5MPa下溶煤比提高到4：1以后,转化率增大到79．0％就不再增长,表明用添加过量供氢溶剂的方法弥补由于降低系统压力所带来的转化率损失不可行。     

Effects of catalyst and vehicle in coal liquefaction

Experiments have been carried out, using a semi-batch reactor equipped with a consecutive sampling device, to clarify the effects of catalysts and vehicles in the coal liquefaction process. The results show that a vehicle has a significant effect during preheating, unlike a catalyst which is not effective at this stage. A catalyst is more effective in promoting liquefaction under reaction conditions of 450°C and ≈ 20 MPa than is a vehicle. A vehicle higher in hydrogen donation increases the yield of oil even if a catalyst is present, providing a multiplier effect. In the development of a direct coal liquefaction process, therefore, selection of a vehicle is as important as that of a catalyst.     

Liquefaction of Yallourn brown coal at low pressures and rapid heating rates

Liquefaction of Yallourn brown coal in solvents at high temperature for short contact times and low pressures has been studied. Very high asphaltene yields are achieved with hydrogen-donating solvents (hydrogenated Ashland pitch A240, hydrogenated anthracene oil, and hydrogenated pyrene). For hydrogenated pyrene, yields of almost 90% were obtained during reaction at 450°C for 10 min or at 510°C for 1 min. The average molecular weight of the asphaltene found was 270, with 40 wt% being accounted for by three-and four-ring polynuclear hydrocarbons. The effect of liquefaction temperature, time, and solvents on the asphaltene yield have been examined to clarify the properties required for the solvent under the present conditions used. The behaviour of the asphaltene during pyrolysis and hydrotreatment has also been studied. Some mechanistic aspects of high-temperature, short contact time liquefaction are discussed with regard to the reactivities of the brown coal and the solvents.     

Structural study of hexane-soluble products from hydroliquefaction of three Yallourn brown coal lithotypes over molten salt catalysts

The hexane-soluble fractions of hydroliquefied products from three Yallourn brown coal lithotypes have been separated into five fractions by combined silica-alumina packed column chromatography. Analyses of various fractions by g.c.-m.s. permitted the identification of ≈50 components in the saturate fraction and 40 components in the diaromatic fraction, together with 30 components in the monoaromatics. The components identified were quite similar among hexane-soluble portions of all three lithotypes. A marked predominance of even carbon number alkane (C₂₃-C₂₉) was observed in the hydrocarbon fractions from pale lithotype over $\text{ZnCl}{}_2\text{KCl}$, and medium light lithotype over both pure ZnCl₂ and $\text{ZnCl}{}_2\text{KCl}$. However, medium dark lithotype over both melt catalysts produced a saturate fraction with an odd carbon number(C₂₂-C₂₈) preference. Based on spectral methods, Soxhlet extracts obtained from untreated lithotypes (hexane and benzene solubles) were characterized as complex mixtures of higher molecular weight(300–1000) aliphatic hydrocarbons, which were supposed to be a precursor of the saturates produced from the corresponding lithotype in the catalytic hydroliquefaction.     

The effect of alkali metal carbonate catalysts on the liquefaction of Victorian brown coal using carbon monoxide and steam

A study has been made of the use of the water-gas shift reaction as a source of hydrogen for the liquefaction of Victorian brown coal. At the comparatively low temperature of 350 °C liquefaction proceeds readily in the presence of alkali carbonate catalysts. Potassium and rubidium were found to be the most effective carbonate catalysts, giving the greatest oil yields. It was found that an essential requirement for the production of liquid products was close contact between coal and catalyst.     

胜利褐煤液化初期反应动力学研究

为研究胜利褐煤在初始阶段的煤液化反应动力学,在可快速升降温的微型高压釜中对胜利褐煤进行了加氢液化反应,得到了反应初期煤液化参数,并对胜利褐煤加氢液化反应初期的动力学行为进行分析。结果表明,虽然反应器升温速度较快,但到达反应温度时,仍有一定量的煤发生了转化,在反应温度440℃、反应时间为0时转化率达到28.12%;在较低温度下,胜利褐煤只发生了部分热解反应,反应后期几乎不再转化,在380℃、反应10 min后转化率已达28%,后续基本不变;随着反应温度的升高,反应转化率、油水产率、气产率等指标增大,反应前10 min增速较快,10~25 min时反应速率减缓,主要是沥青烯组分作为中间产物不断向油转化,速率较低。     

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.     

Reaction of catalysts with mineral matter during coal gasification

After a review of mineral matter of German hard coal, its reactions with catalysts during gasification with steam to form new crystalline phases are dealt with. Products of commercial plants and laboratory experiments were investigated by means of microscopy, XRD, XRF and microprobe analysis.     

Short contact time liquefaction of coal using hydrogen donor solvent

Liquefaction of coals to form benzene-soluble materials was studied at 400 °C under autogenous pressure conditions using tetrahydroquinoline (THQ), tetrahydroisoquinoline (THIQ) and tetralin (TL) as the hydrogen donating solvents. THQ was the best solvent with a conversion rate of 90% within 15 min for low rank coals (< 80% C). In contrast, it took 50 min to achieve a conversion of 80% when TL was used as the solvent, although both solvents could achieve almost complete conversion of coals into quinoline-soluble material within 10 min. THQ also showed excellent activity with blended coals. Some binary solvents exhibited activities which varied with the THQ content. A 1:3 by weight mixture of THQ and petroleum pitch produced the highest conversion of 100%.     

Alkanes and solvent dimers in successive extract fractions released from coal during liquefaction in a flowing-solvent reactor

Types of alkanes present in liquefaction product fractions released from coal during successive time—temperature intervals were examined by g.c.—m.s. Experiments were carried out in a flowing-solvent reactor where solubilized products are continuously removed from the reaction zone; tetralin, quinoline and hexadecane were used as the solvent. At 450°C (with 400 s holding) total conversions in tetralin, quinoline and hexadecane were 82.5, 74.7 and 24 wt% (daf), respectively. In tetralin, alkanes were released from coal more readily and at lower temperatures than in quinoline or hexadecane; m.s. signal intensities fell rapidly with increasing reaction temperature. In quinoline, lower intensities of alkane peaks were observed than in tetralin, although the trend with temperature was similar. In hexadecane however, the trend of intensity with temperature was reversed compared with liquefaction in tetralin or in quinoline; the range of alkanes detected was also smaller than in tetralin or in quinoline. The presence of alkenes in the hexadecane extracts suggested a pyrolytic mechanism for the thermal breakdown. Isoprenoid alkanes, pristane and phytane, were detected in the tetralin and quinoline extracts but not those prepared in hexadecane. Materials present in product mixtures and thought to originate with each solvent were briefly investigated: dimers were the most prominent species in tetralin extracts, with only low-intensity dimers being found in quinoline extracts and no apparent formation of higher homologues from hexadecane. These results were compared with the pattern of alkane release from coal during liquefaction in tetralin in a conventional minibomb reactor and in the pentane-soluble fraction of the total (unfractionated) extract from the F-S reactor.     

Interaction between coal and liquefaction catalysts studied by high temperature electron spin resonance

The high temperature electron spin resonance technique has been used to obtain in situ information on the behaviour of liquefaction catalysts during coal pyrolysis. The spin concentration in coal was induced in the presence of a catalyst at the pyrolysis temperature. ZnCl₂ drastically increased the spin concentration of coal. The order of activity of the catalysts with respect to the increase in spin concentration was: ZnCl₂ (impregnated) ?ZnCl₂ (dispersed) >ZnCl₂/KCl>SnCl₂ > SbCl₃≈AlCl₃ ≈CaCl₂ > coal alone.