Effect of Wyodak coal properties on hydroliquefaction reactivity

The effect of Wyodak coal properties on liquefaction reactivity as measured by distillate yield and cyclohexane conversion has been investigated. Spot samples of four Wyodak subbituminous coals from the Anderson and Canyon coal seams in the Powder River Basin of NE Wyoming were liquefied in microautoclave and batch reactor experiments. Runs were made using two different Wyodak coal-derived solvents. Emphasis in this work was directed toward correlation of C₄-700 K distillate yield and cyclohexane conversion as functions of measurable physical, chemical and petrographic properties of the feed coal. Reactivity rankings were found to be the same using either measure of coal reactivity. However, the data indicated that distillate yields were a function of both solvent quality and feed coal properties. For each solvent studied, selected coal properties, including carbon content, total and organic sulphur content, vitrinite content and total reactive maceral (vitrinite plus exinite) content, were found to give statistically significant correlations with distillate production and cyclohexane conversion. Pyritic and sulphate sulphur contents did not appear to enhance liquefaction yield or conversion at the reaction conditions studied. However, any catalytic effects due to pyrite or sulphate sulphur may have been masked by the use of two high quality liquefaction solvents.     

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.     

Effects of petrographic constituents in three Yallourn brown coal lithotypes on hydroliquefaction processes

Pale, medium-light and medium-dark lithotypes of Yallourn coal were hydrogenated with and without ZnCl₂-containing catalysts (400 °C, 9.8 MPa H₂ and 3 h). The degree of hydroliquefaction was examined petrographically. Without catalyst, the amounts of water produced can be correlated with the amounts of humodetrinite; whereas with catalyst, either humotelinite or humocollinite may contribute to coal liquefaction in addition to humodetrinite; with pale lithotypes in the presence of catalyst, three submaceral groups may be converted.     

Liquefaction of blended coal

The effect on liquefaction of the blending of two coals of different rank has been evaluated in a conventional autoclave experiment at ≈400 °C by the solvent-refined coal (SRC) method as well as by short-contact-time hydrogenation at temperatures up to 550 °C without solvent and using a specially designed cylindrical autoclave. Using the latter method, higher conversions of coal to gas and liquid, than those calculated by the additivity rule, were observed.     

Superacid coal chemistry: 1. HF:BF3 catalysed depolymerization—ionic hydroliquefaction of coals under mild conditions

HF:BF₃:H₂ catalysed depolymerization and hydroliquefaction of coal was studied. This superacidic system was found to be extremely effective for low temperature liquefaction of coal. Illinois No. 6 coal could be solubilized in pyridine to the extent of > 90% by treating it at ≈ 105 °C for 4 h. Under somewhat more elevated temperature (150–170 °C) cyclohexane extractabilities of up to 22% and distillability of up to 28% is achieved. A hydrogen donor solvent such as isopentane is shown to improve the efficiency of the superacidic catalyst for the conversion of coal to cyclohexane soluble products.     

Optimal batch hydroliquefaction of sulcis coal

The hydroliquefaction of a high-sulphur, high-ash Italian coal (Sulcis, Sardinia) was studied in a 1.5 dm³ batch autoclave at different levels of coal size (89–664μm), catalyst/coal ratio (0–24 mg g⁻¹) and temperature (300–400 °C), by using a factorial technique. The yields of this process were found to be mainly dependent on temperature and, to a minor extent on catalyst/coal ratio. By using the only statistically significant factors, it was possible not only to express the observations with a mean standard error < 13% by means of quadratic equations but also to determine a set of alternative conditions yielding 90% coal liquefaction with 50% oil yield and 30–40% asphaltene yields; sulphur removal as H₂S > 80% and sulphur residua in the asphaltene and liquid fractions virtually zero.     

Effects of brown coal quality and process parameters on the hydroliquefaction of brown coal

During the development of the HVB process the influence of different parameters on the process have been investigated. In this Paper the influence of the properties of the brown coal on the process is reported. It is shown that: (1) the petrographical composition of Rhenish brown coal has virtually no effect on the HVB process; (2) the problems of sedimentation caused by the ash composition of the brown coal can be overcome by a particular thermal pretreatment of the coal; and (3) the moisture content of the brown coal is of minor importance for the technical realization of the HVB process.     

Kinetic studies on Victorian brown coal hydroliquefaction

Reaction kinetics of the liquefaction of Victorian brown coal in a process development unit (PDU) having three reactors in series have been studied at temperatures of 430–470°C, and pressures of 15–25 MPa. It is shown that the rate of hydrogen consumption can be expressed as a function of the concentrations of coal and catalyst, hydrogen partial pressure, reaction temperature and residence time, and is controlled by the rates of hydrogenation of polynuclear aromatic components, and the rates of formation and stabilization of radicals. The relative contribution of these reactions, at any temperature, determine the influence of the hydrogen partial pressure on the rate of the hydrogen consumption. The kinetics of the decomposition reactions of brown coal to preasphaltene, asphaltene and to oil also have been studied. The apparent activation energies determined are 25 kJ mol^?1 for the brown coal to preasphaltene, 50 kJ mol^?1 for preasphaltene to asphaltene, 76 kJ mol^?1 for asphaltene to oil, and 184 kJ mole^?1 for oil to gases.     

煤质特性与煤直接液化关系分析

简要讨论了原料煤特性对煤直接液化的影响,在煤的组成和物理性质等与煤液化关系之间建立良好的对应关系并总结了适合直接液化用煤种的一些特性。     

神东煤与煤液化残渣共热解研究

为实现煤液化残渣的资源化利用,采用神东煤与液化残渣进行共热解试验,研究了神东煤粒度、残渣粒度、残渣比例对热解产物分布及热解半焦强度的影响,建立了热解半焦强度测试方法。结果表明,共热解后焦油干基收率随着液化残渣加入量的增多而增大,液化残渣的加入对焦油的生成有正协同作用。1 mm液化残渣添加量由10%增加到30%,3~6 mm神东煤共热解半焦转鼓强度增大29.3%,易碎性F值降低22.8%;同样条件下,液化残渣添加量对3~6 mm神东煤共热解半焦转鼓强度的影响更大,1 mm的液化残渣添加量对神东煤共热解半焦易碎性F值影响更大,3 mm神东煤和1 mm的液化残渣共热解半焦转鼓强度小,易碎性F值高,因此热解过程原料煤应当设置粒度下限。     

Dependence of coal liquefaction behaviour on coal characteristics. 8. Aspects of the phenomenology of the liquefaction of some coal

Steps are now being taken to define in more detail the phenomenology of coal liquefaction and to provide a scientific basis for empirical correlations previously established between liquefaction conversion and basic compositional characteristics of coals. The rates of production of oils, asphaltenes and preaphaltenes have been determined at four temperatures for three coals, two of Carboniferous and one of Creaceousage. Products are formed more slowly from the younger coal (which is of slightly lower rank) than from the others, but oxygen, partly as OH but probably mostly in a type of ether, is lost more rapidly. It is estimated that the maximum content of O as cleavable ether is 7.7 atoms/100 C atoms for the younger coal (from Wyoming) and 4.1 and 5.1 for the other two (from Oklahoma and Ohio, respectively). Until ≈ 50% of the amount present in the Oklahoma coal is lost, the rates of removal of oxygen and organic sulphur are approximately equal; beyond this level, the removal of S is more rapid. The loss of organic sulphur from the Ohio coal is slightly faster. Even so, the data do not support the idea that cleavage of thioethers is more rapid than that of ethers and that this is the basic reason why a high organic sulphur content tends to promote liquefaction. Conversion of the pyrite in the Ohio coal to pyrrhotite occurs considerably more rapidly than the pyrite in the Oklahoma coal. In preliminary experiments, it is shown that a curve-resolving programme allows two aromatic and five aliphatic C-H stretching vibrations to be distinguished in FTIR spectra of the hexane-insoluble products, and the distribution changes with degree of conversion. In particular, there is evidence that new aryl methyl are generated during liquefaction, in agreement with evidence from oxidation studies.     

The effects of iron sulphide surface area variations on coal liquefaction

The purpose of this work was to determine the effects of surface area variations of iron sulphides on coal liquefaction. Several iron sulphides were synthesized including pyrites (FeS₂) with 46.6 wt% Fe, pyrrhotites (Fe_1?xS) with ~ 60 wt% Fe and iron-sulphur compounds of unknown composition. Surface areas of the synthetic pyrites varied from 2 to ? 10 m² g^?1, pyrrhotite surface areas were 6 and 10 m² g^?1, and the surface areas of the iron-sulphur compounds were 40 and 80 m² g^?1. These iron sulphides were tested for catalytic activity in tubing reactor runs with West Virginia Blacksville no. 2 coal and SRC-II heavy distillate. All these sulphides showed catalytic effects as compared to runs with only coal and solvent, although the effects were not as large as those obtained with a cobalt-molybdenum on alumina catalyst. Large differences in surface areas before reactor testing did not cause any significant differences in conversion. The results from an additional series of tubing reactor runs, which was carried out to determine how iron sulphide surface areas change during liquefaction, showed that the surface areas were drastically changed during the two-minute heat-up of the reactor. Robena pyrite with a surface area of 2.0 m² g^?1 and the iron-sulphur compound with a surface area of 80 m² g^?1 yielded iron sulphides with surface areas of 5.2 and 10.8 m² g^?1 after a two-minute heat-up to 425°C and subsequent one-minute quench.     

Hydrogen mass transfer and mixing energy effects in SRC-II coal liquefaction reactors

This paper summarizes the experimental work performed on a bench-scale pre-pilot unit for investigating hydrogen mass transfer and mixing energy effects in SRC-II coal liquefaction reactors. Experiments were carried out with an Ireland Mine coal where the effects of mixing energy level (150–1000 rpm), method of hydrogen introduction (preheater flow and direct reactor sparging) and hydrogen treat rate (4 to 6 g of hydrogen/100 g of feed slurry) were investigated. Several runs using Powhatan No. 6 coal were also carried out where the effect of mixing energy level (200–1000 rpm) was investigated. Other run conditions were fixed to correspond to those likely to be used in commercial operation. The experimental results clearly indicated that below a mixing energy level corresponding to 400 rpm a significant cement-like solid deposition within the reactor (hydrogen mass transfer limitation) occurred. Below this mixing energy level the C₅+ liquid yield decreases, and the selectivity of the reaction changes, resulting in an increase in the C₁C₄ yield. This critical mechanical mixing level corresponds to a mixing energy per unit of reactor volume of ≈3500 ergs/cm³ s (350 watts m^?3). For the run conditions employed, increasing the preheater hydrogen flow from 4 to 6 g of $\text{H}{}_2\text{100 g}$ of slurry prevented the formation of solid deposits at a mechanical mixing energy level as low as that corresponding to 200 rpm. Furthermore, the highest C₅+ yield in the entire data set occurred when the preheater hydrogen flow was at the higher level.     

Effects of coal cleaning on the short contact time liquefaction of Illinois No. 6 coal

This study was carried out to determine the effect of coal cleaning by oil agglomeration and sink-float methods on yields from short contact time liquefaction of Illinois No. 6 coal. The runs were made in a continuous unit using SRC-II distillates as process solvent. Measured yields included hydrogen (consumption), hydrocarbon gas, distillate oil, SRC (the pyridine-soluble portion of the residue) and insoluble organic matter, the pyridine-insoluble organic residue. The solubility of product SRC in hexane, toluene and pyridine was also determined. The principal finding was that coal cleaning by density methods reduced the yield of IOM obtained in subsequent liquefaction and this is attributed to the removal of inert components from the feed coal. In addition, cleaning which significantly reduced pyrite content of the feed coal also reduced the yield of distillate oil and tended to give a less soluble SRC during liquefaction. Deep cleaning by gravity methods gave the lowest IOM, but reduced pyrite content to the point where distillate oil was consumed rather than produced. Oil agglomeration reduced total ash to 50% of that in the run-of-mine coal, but left the pyrite level in the coal high. The relevance of these results to two-stage liquefaction is discussed.     

Short contact-time liquefaction of subbituminous coal: Directions for improving coal conversion

This study was undertaken to find ways to solubilize subbituminous coal in high yield at short contact times. Short contact-time hydroliquefaction runs were carried out in a continuous unit using Belle Ayr subbituminous coal with a solvent rich in hydrogen-donor molecules derived from the Lummus ITSL process, and also with solvents lower in donor concentration derived from the SRC processes. Catalysis by pyrite, molybdenum and supported cobalt-molybdenum was also studied. It was found that pyrite and other hydrogenation catalysts enhanced solubilization and also increased production of distillate oil. Solvent quality seemed to have no effect on the solubilization of Belle Ayr coal. The availability of H₂S also appeared to have no effect. Provided that pyrite was present, reaction could be carried out at severities high enough to give insoluble organic matter yields equivalent to those obtained with bituminous coals (5–10 wt% daf coal). At equivalent levels of solubilization, however, hydrocarbon gas and distillate yields were invariably higher for the subbituminous coal. Implications for two-stage processing of Belle Ayr coal are discussed.     

Comparison of coal hydroliquefaction catalysed by ZnCl2-MCln (CuCl,CrCl3 and MoCl5) and ZnCl2 melts

Hydrogenation of four bituminous coals impregnated with 5 wt% of either mixtures of ZnCl₂-MCl_n (CuCl, CrCl₃ and MoCl₅) systems or ZnCl₂ was carried out using a batch autoclave system at 400° for 3 h at 9.8 MPa of initial hydrogen pressure. The ZnCl₂-MoCl₅ system showed the highest yield of the hexane-soluble (HS) fraction compared with the other systems irrespective of the coal used. The difference between the yields of HS fractions using the ZnCl₂-MoCl₅ and other systems was most marked for coals of fairly low volatile matter content, though the conversion was relatively low (47–66%), whilst for coals of high volatile matter content HS yields with the binary melt systems were high (86–91% conversion). Elemental analyses of the HS fractions indicated that the ZnCl₂-MoCl₅ system is most favourable in decreasing the average molecular weight and the heteroatom content of HS, this characteristic trend being confirmed also with five HS fractions separated by Chromatographic techniques. Both elemental analyses and molecular weights of asphaltene (benzene-soluble materials, BS) indicated that the ZnCl₂-MoCl₅ system is also most effective in cracking coal structure.     

Synergistic effects between light and heavy solvent components during coal liquefaction

As part of research to examine coal conversion in solvents containing high-boiling-point components, experimental studies were carried out with model compound solvents. The dissolution of bituminous and subbituminous coals was investigated in pyrene-tetralin and 2-methylnaphthalene-tetralin mixtures. The effects of donor level, gas atmosphere, hydrogen pressure and conversion temperature were determined. At 400 °C, in the presence of hydrogen gas, pyrene-tetralin solvent mixtures show synergism in coal conversion. At donor concentrations as low at 15 wt%, the degree of conversion was almost as high as in pure tetralin. This phenomenon was not apparent in 2-methylnaphthalene-tetralin mixtures. The relative ease of reduction of pyrene and its ability to shuttle hydrogen is considered to be a principal reason for this difference in behaviour. Conversion in pure pyrene and in pyrene-tetralin mixtures at low donor concentrations increased with increasing hydrogen pressure. At 427 °C, bituminous coal conversion was higher in a 30 wt% tetralin-70 wt% pyrene mixture than in either pure compound. It was found that in the absence of coal pyrene can be hydrogenated by H-transfer from tetralin as well as by reaction with hydrogen gas. This can provide a means to increase the rate of transfer of hydrogen to the dissolving coal through the formation of a very active donor (dihydropyrene). During coal liquefaction, several pathways appear to be available for hydrogen transfer for a given coal, the optimal route being dependent upon the solvent composition and the conditions of reaction.     

由煤制取芳烃化合物的研究进展

综述了国内外由煤制取芳烃化合物的三种思路：一是通过将煤直接进行液化获取,或者先将煤液化再从产物中获得芳烃化合物;二是先对煤进行溶剂抽提,然后对产物分类加工制取芳烃化合物;三是将煤进行氧化处理来获得高价值的芳烃化合物。分析了由煤制取芳烃化合物的所面临的产物分离困难、污染环境等问题,并指出了今后需要在分离工艺和催化剂以及如何实现煤的定向转化等方面进行重点研究。     

煤的结构对直接液化反应性影响的分析

系统地分析了煤的组成结构及液化前的预处理对直接液化反应性的影响，包括煤阶、岩相组成、各种矿物质及酸洗脱除、水分及烘干、孔隙性、物理结构及预溶胀、H／C比等，指出不同的工艺条件下它们对直接液化的影响是不同的。     

Two-stage liquefaction of a subbituminous coal

The two-stage conversion of a subbituminous coal has been investigated using an autoclave reactor system. The overall performance of the reaction is found to be determined by the effectiveness of the first-stage operation and by the method of sequencing of the stages. The initial thermal products can undergo condensation reactions which render them unresponsive to subsequent catalytic conversion and which increase the light gas yield. This can occur during the first stage reaction, if there is limited capacity for free-radical stabilization, and upon storage and/or thermal cycling between stages. The latter effects are circumvented by operating the two stages in immediate sequence. Condensation is also reduced by increasing the solvent quality and the solvent:coal ratio. The presence of a catalyst during thermal decomposition of coal can greatly improve conversion and product stability even at short reaction time and can reduce constraints on solvent quality. The more feasible approaches to improving first-stage operation appear to be in controlling the solvent composition and in employing hydrogenation catalysts.