Hydrogenation of the inertinite macerals of Bayswater coal

Yields of products from the hydrogenation of the inertinite and vitrinite+exinite macerals of the Bayswater (New South Wales, Australia) coal in a batch autoclave were investigated. Samples were hydrogenated for 1 h at 400 and 450 °C with tetralin as vehicle, hydrogen as charge gas and no added catalyst. The results show that the inertinite macerals contributed significantly to the liquid hydrogenation products, in particular to the oil yield obtained at 450 °C.     

Influence of temperature on the hydrogenation of Australian Loy-Yang brown coal. 1. Oxygen removal from coal and product distribution

A study is made of the composition of the solid, liquid and gaseous fractions produced by hydrogenation of Australian Loy-Yang brown coal at temperatures ranging from 300 to 500 °C. The high oxygen content of the coal (25.5 wt%) is not found to result in a proportionally higher hydrogen consumption when compared to previously published results for a coal with approximately half the oxygen content. Oxygen is found to be removed from the coal mainly as carbon dioxide and water, most probably by decarboxylation and dehydration reactions. At temperatures up to ≈400 °C hydrogen is consumed almost solely by transference from the solvent tetralin to the coal. By this temperature both the maximum degree of conversion and the maximum oil yield are reached. The heavy oil fraction at 400 °C is composed mainly of asphaltenes and preasphaltenes. Above 400 °C hydrogen is consumed from both solvent and gas. A major part of this appears to be involved in the stabilization of decomposition products from the tetralin. The yield of pentane-soluble material is relatively constant up to 450 °C, however, at higher temperatures conversion of asphaltenes and preasphaltenes to pentane-solubles occurs in conjunction with gasification to C₁–C₃ hydrocarbons. Despite the fact hydrogen consumption and oxygen removal both increase with rising hydrogenation temperature, the H/C atomic ratio for the three heavy oil fractions decreases over the same range.     

Hydrogenation of Liddell coal. Yields and mean chemical structures of the products

The products from the hydrogenation of an Australian medium-volatile bituminous coal (Liddell) in batch autoclaves have been investigated. Tetralin was used as a vehicle and Cyanamid HDS-3A as catalyst. The influences of temperature (315–400 °C), hydrogen pressure (3.4–17.2 MPa) and reaction time (0–4 h) on the yields of pre-asphaltene, asphaltene, oil and pitch were studied. The chemical compositions of these materials were investigated by nuclear magnetic resonance and infrared spectrometry, and high-pressure liquid chromatography. Higher temperatures (400 °C) and pressures (17.2 MPa) favour the formation of products with lower average molecular size, lower aromatic carbon and aromatic proton contents and smaller average aromatic fused-ring number. N.m.r. evidence is presented which shows that increasing the temperature from 370 °C to 400 °C or pressure to 17.2 MPa assists reactions which bring about hydrogenation and cleavage of aryl rings. Longer reaction times (4 h) promote reactions by which the oxygen content of the product is decreased and by which polymethylene becomes cleaved from other functional groups. The results show that asphaltenes are true intermediates in the formation of oil from coal.     

Hydrogenation of anthracene over active carbon-supported nickel catalyst

Hydrogen transfer behavior over active carbon and carbon-supported Ni catalyst was examined in the hydrogenation of anthracene with three kinds of hydrogen sources: hydrogen gas, hydrogen-donor tetralin and the combination of both. In tetralin, active carbon itself provided higher conversions of anthracene in the temperature range of 350–400°C than Ni/C catalyst, while under the pressure of hydrogen gas, the addition of Ni metal onto active carbon remarkably promoted the hydrogenation of anthracene, providing a complete conversion at 300°C. When both tetralin and hydrogen gas were used together, an apparent improvement in both conversion and product distribution was observed with active carbon, whereas with Ni/C catalyst, the rate of hydrogen consumed in the hydrogenation was apparently low in the temperature range of 300–320°C, compared to that observed at the same temperatures using hydrogen gas alone.     

Reaction mechanism of coal hydrogenation: 1. Two-ring solvent system

Taiheiyo coal was hydrogenated in naphthalene, tetralin and decalin under 10 MPa (initial pressure) of hydrogen or nitrogen with stabilized nickel as catalyst at 400 °C for 15 min. Preasphaltene, asphaltene and oil conversions and the conversion of the solvents were measured. The hydrogen absorbed by coal from molecular hydrogen and from the donor solvent was calculated. The main reaction route appears to be the direct hydrogenation of coal by molecular hydrogen, with the side reaction via solvent by molecular hydrogen occurring only slightly, when an active catalyst such as stabilized nickel is present.     

Deuterium as a tracer in coal liquefaction Part 2. Non-catalytic studies

A bituminous Australian coal (Liddell) was liquefied in the absence of catalyst using tetralin as vehicle, and molecular deuterium and hydrogen—deuterium gas mixtures. The structures of the liquid and gaseous products were investigated by mass spectroscopy, ¹H-and ²H-NMR spectroscopy and gel permeation chromatography (GPC). The proportion of ²H to ¹H in the liquid products was found to be higher at 425°C than at 400°C because deuterium preferentially enters more aromatic rings at the higher temperature.The distributions of deuterium in the deuteromethanes formed during liquefaction show that deuterium randomly enters the structural groups in the coal which produce methane before the methane is released to the gas phase. This illustrates the extreme mobility of hydrogen, including the hydrogen that originates from the coal. As a consequence, it is proposed that hydrogen released as methane arises from a pool in which memory of the original bonding is lost.     

Chemistry of Texas lignite liquefaction in a hydrogen-donor solvent system

To study the nature of chemical cleavage and resultant product transfer from solid lignite phase to liquid phase, autoclave (300 cm³) experiments have been carried out at pressures ranging up to 34 MPa and temperatures of 380–390 °C. The charge to the autoclave was freshly mined wet lignite, tetralin and hydrogen or helium. To obtain an indication of the reaction mechanisms underlying the liquefaction process, liquid and gas samples from the reactor at different time intervals were analysed. The gas samples were analysed by use of a multi-column, multi-valve automated gas Chromatograph, a system specially fabricated for coal-derived gas analysis. The liquid sample was filtered through Millipore filters and separate into three fractions by gel permeation chromatography. Fraction 1 is mostly colloidal carbon and high-molecular-weight species which cannot be separated on a g.c. Fractions 2 and 3 were analysed by gas chromatography — mass spectrometry (g.c.-m.s.). Fraction 2 represents the liquid products released from lignite and fraction 3 is mostly the tetralin and tetralin-derived products. Gel permeation chromatography (g.p.c.) followed by gas chromatography (g.c.) was used to devise a method for monitoring the extent of liquefaction. The production of carbon dioxide is at a maximum before the liquefaction reactions are at a significant rate. The source of carbon dioxide appears to be the carboxylic groups in lignite. The liquefaction reactions consume hydrogen from tetralin which undergoes dehydrogenation to form naphthalene. Once the lignite has undergone depolymerization, the tetralin to naphthalene conversion slows down. The continued heating of lignite conversion products in excess of tetralin does not appear to alter the molecular size distribution of the liquid product. The distillable fraction of lignite-derived liquid is composed of various alkylated phenols and aromatics and alkanes, and they are formed simultaneously.     

Structures of the distillates obtained from hydrogenation and pyrolysis of Liddell coal

The structures of the distillable fractions (oils, b.p. >200 °C and volatile fractions, b.p. <200 °C) of the products from hydrogenation and pyrolysis of an Australian bituminous coal (Liddell) were investigated by gas chromatography-mass spectrometry (g.c.-m.s.) and nuclear magnetic resonance spectroscopy (n.m.r.). The distillable oil generated from hydrogenation of Liddell coal at 400 °C, using nickel molybdenum ortin (II) chloride as catalyst and tetralin or recycle oil as vehicle, consisted of a wide range of compounds. Long straight-chain alkanes were important components together with alkyl-substituted benzenes and tetralins, phenols and polycyclic material. When yields were low, as in the case of catalytic experiments with nickel molybdenum catalysts and no vehicle, isoprenoids could be identified. When a substantial proportion of the coal was converted to oil, branched-chain alkanes were not important components of the product. The replacement of tetralin and nickel molybdenum catalyst with stannous chloride reduced the amounts of methyl tetralins in the product. When tetralin was replaced by recycle oil, alkanes were more important components of the liquid products. Although alkenes were absent in oils generated by hydrogenation, they were important components of oils generated by pyrolysis. The highly volatile fractions (b.p. <200 °C) produced during hydrogenation consisted of alkyl-substituted benzenes, decalins, methylindan and straight-chain alkanes. Straight-chain alkanes were more abundant in those volatile fractions generated by hydrogenation with recycle vehicle than with tetralin. The Brown-Ladner method of estimating the fraction of aromatic carbon in distillable oils was adequate for less volatile fractions but was inadequate for the highly volatile fractions because of the large amounts of α-CH₃ and β-CH₃ alkyl groups present.     

高温下工业NiW/Al2O3催化剂上萘的加氢饱和反应

在中压固定床中,高温条件下研究了工业NiW/Al2O3催化剂上硫化氢气氛中反应温度、反应压力和空速对萘加氢饱和反应过程的影响。实验结果表明,在液时空速为10—30 h-1,氢油体积比为800,高反应温度区320—380℃的实验条件下,萘加氢主要生成四氢萘和十氢萘,而进一步加氢裂化产物较少;提高反应温度,萘转化率和四氢萘的收率下降,加氢裂化产物略有升高,表明高温不利于芳环的加氢饱和;提高加氢反应压力,萘的转化率和四氢萘的芳环加氢程度提高;综合反应结果,提出了高温条件下萘加氢的简化可逆连串反应途径。     

Relative reactivity of hydrogen donor solvent in coal liquefaction

Hydrogen transfer from donor solvent to coal must involve reactions such as hydrogen donation to free radicals and hydrogenation of aromatic structures. The relative reactivities of five typical hydrogen donor solvents, more reactive than tetralin, were determined using a competing elimination reaction in the liquefaction of a bituminous coal at 400 °C and a brown coal at 350 °C. 9,10-Dihydroanthracene, 9,10-dihydrophenanthrene and 1,2,3,4-tetrahydroquinoline exhibited outstanding hydrogen donating ability. Further, the relative reactivities of five mild hydrogen donor solvents such as acenaphthene and indan were determined by a similar elimination reaction using a bituminous coal at 450 °C.     

Hydrogenation of liddell vitrinite: Effects of metal halide catalysts in the temperature range 200–480°C

A vitrinite concentrate prepared from the Liddell Seam (high volatile bituminous coal, NSW, Australia) has been hydrogenated in an unstirred 50 cm³, batch autoclave at reaction temperatures between 200 and 480°C in the presence of metal halides (SnCl₁ or ZnCl₁) and/or alumina (α-Al₁O₃). A vehicle was not used. The influence of reaction temperature, metal halide and alumina on the composition of the products was studied by gas chromatography (GC), gel permeation chromatography (gpc), ¹H solution and ¹³C solid-state cross polarization (CP) nuclear magnetic resonance (nmr) spectroscopy and optical microscopy.The metal halides lower the temperature at which softening and agglomeration of vitrinite takes place. The resultant plastic isotropic material forms mesophase at temperatures above 400°C unless an inert diluent, i.e. alumina, is added. The alumina inhibits reactions involved in the formation of mesophase which would otherwise compete with hydrogenation reactions that yield hexane soluble material (oil).Above 400°C carbon monoxide, carbon dioxide and C₁-C₅ alkanes are the principal gaseous products. At lower temperatures, in the presence of alumina, ethylene is formed in the catalysed experiments; the ethylene is converted to ethane at higher temperatures. The structure of the hexane soluble products derived from vitrinite is also temperature dependent. Above 420°C much of the aliphatic component decomposes to yield further quantities of hydrocarbon gases. Tin(II) chloride and zinc chloride produce hexane soluble products of similar molecular composition, which suggests that they operate through a similar mechanism.The addition of alumina to the reaction mixture results in a more aromatic liquid product with shorter aliphatic carbon chains. Whether or not alumina is present, the aromaticity of the solid residues increases with increase in hydrogenation temperature. Thus the increased aromaticity of the liquid products is not caused by the extraction of a greater proportion of aromatic material from the coal with increase in the hydrogenation temperature. It follows that with increase in hydrogenation temperature an increasing proportion of the aliphatic material becomes transformed into aromatic compounds and/or gas.In summary, the results show that over a wide range of temperatures (200–480°C) the structure of the hexane soluble product depends on the thermal stability of the products and the degree of competition from reactions leading to mesophase formation, and not on the nature of the halide catalyst.     

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.     

The chemical and physical structure of hydrogenation residues of maceral concentrates

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. It is shown that even before coal morphology is modified, aromatic substitution reactions result in loss of ether and/or phenolic groups from the coal. The results also demonstrate that the structure of residues depends markedly on the hydrogen source available for reaction. Tetralin, 1-methylnaphthalene and molecular hydrogen provide hydrogen to cap radicals, the order of efficiency being tetralin > molecular hydrogen > 1-methylnaphthalene. Although molecular hydrogen and 1-methylnaphthalene are insufficiently reactive to cause liquefaction, they reduce the degree of cross-linking of aromatic rings, thereby enhancing the plasticity of the residues.     

Additive effect of tyre constituents on the hydrogenolyses of coal liquefaction residue

A numerous amount of waste tyre is landfilled or dumped all over the world, which causes environmental problems. The coal liquefaction residue (CLR) produced in 30% yield through the process supporting unit of the NEDOL coal liquefaction process. As one of the effective method for processing both CLR and waste tyre, simultaneous hydrogenolyses of these materials was carried out. The synergistic effects to upgrading, such as the increase of oil yield and the decrease of asphaltene yield, were appeared on the hydrogenolyses. However, the interaction between tyre and CLR to synergistic effects was not clarified. In this study, the effects of hydrogen donatable solvent (tetralin) and pressurized gas on the hydrogenolyses of CLR and tyre constituents are discussed. As a result, it was clarified that both tetralin and the pressurized H₂ gas were necessary for the simultaneous hydrogenolyses of CLR and tyre. The hydrogen shuttling from H₂ gas and tetralin was enhanced by the aromatic compounds derived from tyre rubber constituents (styrene-butadiene rubber and natural rubber). The hydrogenation of the heavy oil constituent in CLR was enhanced by carbon black and the inorganic constituents in tyre, such as zinc oxide and sulfur. Accordingly, the synergistic effects on the simultaneous hydrogenolyses of CLR and tyre were appeared because the hydrogen shuttling occurred by the aromatics from tyre rubber constituents, and the hydrogenation was enhanced by carbon black and the inorganic constituents in tyre.     

Review of the kinetics of pyrolysis and hydropyrolysis in relation to the chemical constitution of coal

Kinetic data show that the pyrolysis reactions of hard coal may be interpreted in terms of parallel first order reactions, relating to the coal functional groups which can be considered as predecessors of the pyrolysis products. This relation is confirmed by C-, H- and O-balances of pyrolysis products and those of the corresponding predecessor structural groups of the coal. The activation energies measured are of the same order of magnitude as the bonding energies of bridge CC bonds between the aromatic ring-systems in the coal molecule. These observations suggest a mechanism of coal pyrolysis, consisting of the following steps: rupture of CC bridges; formation of radical groups; and recombination of radicals to stable molecules part of which, i.e., those of low molecular weight, diffuse out of the solid matter whereas the rest (whose diffusion in the pore system of the solid is prevented due to their higher molecular weight) react with each other at higher temperatures to give coke, releasing elementary hydrogen. In the presence of hydrogen > 500 °C, additional reactions of partial hydrogenation of polynuclear aromatics with subsequent hydrocracking will occur, leading to increased formation of highly aromatic tar, BTX, CH₄ and H₂O.     

Process effects on the nature of coal liquefaction products

The products obtained by liquefaction of the same coal using four different processes are compared. The processes were dry hydrogenation (hydropyrolysis) in a short residence time semi-continuous reactor and in a rotating autoclave, and supercritical gas extraction using toluene with and without hydrogen assistance using an autoclave and a short residence time reactor. The temperature and pressure were the same for all the experiments and runs were carried out with and without catalysts. The liquid product from the rotating autoclave was more aromatic and contained less polar compounds than the product from the semi-continuous reactor. The asphaltenes from supercritical gas extraction were more aliphatic and of higher molecular weight than those obtained on dry hydrogenation. Solvent breakdown products had a considerable effect on the composition of the oil from supercritical gas extraction, and this breakdown was affected by the time that the solvent was maintained at temperature.     

真菌降解光-氧氧化内蒙古胜利褐煤产物分析

为掌握黄孢原毛平革菌降解光-氧氧化内蒙古胜利褐煤固体残渣的成分、结构和热稳定性的变化规律,以及降解液的主要物质构成,为降解工艺的改进以及降解产物的分离和利用提供参考,对降解所得的固体和液体产物进行了检测分析.结果表明:光-氧氧化煤被黄孢原毛平革菌作用后,煤残渣的水分、灰分和挥发分的质量分数均增加,固定碳的质量分数降低,...     

Reactivity of some organic compounds with supercritical water

This study was initiated to determine some of the chemical reactions that occur during the supercritical fluid extraction of coal, using model compounds to simulate molecular structures found in coal. Water was chosen as the fluid because of its unique chemical and physical properties at critical conditions. Two primary functions of coal processing are the removal of heteroatoms and the depolymerization of larger molecules, thus the reactions of quinoline and isoquinoline were extensively examined, with very brief studies made of benzonitrile, aniline, tetralin, dihydroanthracene and ethylbenzene. In addition, since ZnCl₂ has been used as a hydrogenation catalyst and in the hydrocracking of aromatics, it was added in some experiments to increase the reactivity of some of the compounds. It was found that the compounds studied were more reactive and reached by different mechanisms in the presence of supercritical water than when undergoing inert pyrolysis. The product distributions from the two quinolines indicated that they reacted by very different mechanisms; possible reaction schemes for these are discussed. In addition, it was found that about 70% of the nitrogen from the consumed quinolines and aniline was removed in the water layer as ammonia, that alkyl sidechains on aromatics were somewhat reactive and that some carbon atoms are oxidized by the water thus providing a source of hydrogen for the formation of other products.     

Thermal dissociation of tetralin between 300 and 450 °C

Most studies of the hydrogenation of coal in hydrogen-donor solvents involve the reaction of hydrogen with coal slurried in tetralin, with or without catalysts. Reaction schemes proposed usually ignore the possibility of the contribution of products of the thermal breakdown of tetralin itself. In the work presented below tetralin was heated for various periods at temperatures between 300 and 450 °C without hydrogen or coal, and the products were analysed by capillary chromatography. The main products formed were naphthalene and the tetralin isomer 1-methyl indan. Tetralin did not disproportionate to naphthalene and decalin, although this has been suggested in the literature as a mechanism for the formation of the naphthalene usually observed. Naphthalene was produced, at temperatures as low as 350 to 400 °C, by dehydrogenation of the saturated ring. This ring also rearranged to give 1-methyl indan, and at higher temperatures broke open to yield alkyl benzenes. This cracking of the saturated ring was found to enhance the naphthalene formation.     

Free radical chemistry of coal liquefaction: role of molecular hydrogen

Model compounds containing the types of carboncarbon bonds thought to be present in coal were pyrolyzed in the presence of tetralin and molecular hydrogen at 450 °C. The relative rates of conversion of the model structures are predictable from the bond dissociation energies of the compounds. Conversion of dibenzyl in the presence of both tetralin and molecular hydrogen or in the presence of hydrogen alone proceeds along two parallel reaction paths. Toluene is produced by a thermal cracking reaction in which the rate-controlling step is the thermal cleavage of the β-bond in dibenzyl. Benzene and ethylbenzene are produced by a hydrocracking reaction. The rate of the hydrocracking reaction is directly proportional to the hydrogen pressure. The strong bond in diphenyl is hydrocracked in a system containing both molecular hydrogen and a source of free radicals. These studies on model coal structures offer firm evidence that molecular hydrogen can participate directly in free radical reactions under coal liquefaction conditions. Under some conditions molecular hydrogen can compete with a good donor solvent to stabilize the thermally produced free radicals. Molecular hydrogen can also promote some hydrocracking reactions in coal liquefaction that do not occur to an appreciable extent in the presence of only donor.