Direct liquefaction of hydrolytic eucalyptus lignin in the presence of sulphided iron catalysts

The liquefaction of hydrolytic eucalyptus lignin has been studied in hydrogen donor and non-donor solvents in the presence of ferrocene and of ferrocene associated with sulphur or carbon disulphide. With the exception of tetralin, all reactions were carried out at supercritical conditions of the solvent. It was found that the yields of heavy oils increase significantly with the increase in hydrogen pressure in the non-donor solvents. The oil yields also increase with the density of the solvent but level out at densities higher than 0.30 g/ml. The consumption of molecular hydrogen is significant in the non-donor solvents; in the donor solvents the hydrogen is mostly transferred from the solvent itself. In the non-donor solvents, the oil yields depend strongly on the efficiency of the catalyst, but not in the donor solvents.     

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.     

Coal liquefaction mechanism using a tritium tracer method

To determine the behavior of hydrogen in tetralin, the reaction of tetralin with tritiated gaseous hydrogen was studied in a flow reactor at 400–450°C, 2.5–9.8 MPa for various residence times. The amount of hydrogen exchange between tetralin and tritiated hydrogen was estimated from the balance of hydrogen and tritium. Although yields of methylindan and naphthalene, and the hydrogen-exchange ratio (HER) of tetralin increased monotonously with residence time, these values were scarcely influenced by the reaction pressure at every temperature. It was thought that the formation of tetralyl radicals in this system would be the rate-determining step for both the conversions of tetralin into methylindan and naphthalene, and the hydrogen exchange of tetralin. Conversions of tetralin into methylindan and naphthalene, and the hydrogen-exchange reaction using the autoclave were very close to those using the flow reactor.     

Catalytic effects of MoCl3- and NiCl2-containing molten salts in hydroliquefaction of Akabira bituminous coal with and without hydrogen-donor vehicle

Catalytic effects of MoCl₃-LiCl-KCl and NiCl₂-LiCl-KCl molten salts in hydroliquefaction of Akabira bituminous coal were studied. In the absence of solvent, both catalysts showed high coal conversion activity and high selectivity for the formation of hexane-soluble oil product. Oil yields from the catalytic runs were 3.4–3.0 times that from a non-catalytic run. Addition of hydrogen-donor tetralin considerably increased the oil yield and conversion and reduced the total hydrogen consumption. About 95 and 91 wt% daf coal was converted into pyridine-solubles and 59 and 54 wt% into oil with relatively low total hydrogen consumption (3.5 and 3.1 wt% daf coal) with the MoCl₃ and NiCl₂ catalysts respectively, in the presence of tetralin. Thermogravimetric analysis indicated that these catalysts enhanced the depolymerization of the coal organic matrix. Analysis of the liquefaction products suggested that the catalysts effectively catalysed the hydrocracking of polyaromatic structures contained in heavy products to hydroaromatics with relatively small ring sizes, explaining the high oil selectivity.     

Hydrogenation and rearrangement of coal-related aromatic and hydroaromatic molecules promoted under mild conditions by aluminium trichloride

The action of AlCl₃ on representative polyaromatic (naphthalene, anthracene, phenanthrene) and hydroaromatic (tetralin, dodecahydrotriphenylene) molecules under inert atmosphere conditions at 20 °C (hexane solution) or 70 °C (heptane solution) has been investigated. Even at these low temperatures conversion to hydrogenated and rearranged structures is significant, giving product distributions resembling those obtained from corresponding reactions conducted at 300–400 °C under hydrogen pressure.     

Liquefaction mechanism of Wandoan coal using tritium and 14C tracer methods: 2. Liquefaction using 3H labelled gaseous hydrogen

Tritium labelled gaseous hydrogen was used to clarify the role of gaseous hydrogen in coal liquefaction. Wandoan coal was hydrogenated under 5.9 MPa (initial pressure) of ³H-labelled hydrogen and in unlabelled solvents such as tetralin, naphthalene and decalin at 400 °C and for 30 min in the presence or absence of NiMoAl₂O₃ catalyst. Without a catalyst, liquefaction proceeded by addition of the hydrogen from donor solvent. The NiMoAl₂O₃ catalyst enhanced both hydrogen transfer from gas phase to coal and hydrocracking of coal-derived liquids. With NiMoAl₂O₃ catalyst, liquefaction in naphthalene solvent proceeded through the hydrogen-donation cycle: naphthalene → tetralin → naphthalene. The amount of residues showed that this cycle was more effective for coal liquefaction than the direct addition of hydrogen from gas phase to coal in decalin solvent. The ³H incorporated in the coal-derived liquids from gas phase was found to increase in the following order: oil < asphaltenes < preasphaltenes < residue.     

Reactivity and structure of two coals containing significant methoxy group concentrations

Two coals (Beulah, PSOC-1483, and a Thai coal, TH23) of unusually high reactivity with hydrogen and tetralin were shown to contain significant methoxy group contents. The fate of the methoxy groups when these coals were reacted under N₂ at 320°C (with and without added decalin) and with H₂—tetralin and H₂---SnO₂ at 405°C was studied. The reactions of TH23 coal gave unexpectedly high water yields. Reactions of model compounds containing methoxy groups under similar conditions also gave high water yields. Proton magnetic resonance thermal analysis (PMRTA) confirmed that TH23 host and guest coal components are structurally distinct from those of Loy Yang (Victoria) run-of-mine coal.     

Relationship between solids formation,residuum conversion,liquid yields and losses during athabasca bitumen processing in the presence of a variety of chemicals

Conditions were chosen for the batch processing of Athabasca bitumen such that approximately 8% of the feed was converted to solids under an atmosphere of nitrogen. When hydrogen or tetralin was used, the amount of solids formed was cut in half. The combination of hydrogen and tetralin decreased the amount of solids formed by one-half again. These conditions were used to study radical trapping reactions and hydrogen transfer under a variety of conditions using solids formation as a measure of reaction. None of the reagents used decreased solids formation significantly, and many increased the retrograde reaction. Correlations between solids formation (2–25% of feed) and yields and conversions showed that CCR conversion and sulfur conversion were not correlated with solids formation but nitrogen and vanadium conversions were. Most significant was the finding that losses (yields of gases) were constant for the 29 runs, at constant residuum conversion. Gases must be formed as a result of the initial thermally induced carbon-to-carbon bond breaking step in order for the yield to be independent of solids formation. Distillate yields decreased as solids formation increased.     

Solubilization of bituminous coal in aromatic and hydroaromatic solvents

The Solubilization of a bituminous coal (Ruhr District) in aromatic and the corresponding hydroaromatic compounds was compared at temperatures from 250–450°C. The solvent pair naphthalene and tetralin exhibit marked differences in solvent power as only tetralin is a ‘true’ hydrogen donor and, thus, an excellent solvent for coal. In the series of quinolines, however, the difference in solvent efficiency became significant only at temperatures ?350°C. The high solvent power of anthracene oil is explained on the basis of transferable hydrogen and the presence of N-heterocyclic compounds. Inference is drawn as to the optimum constitution of a vehicle oil.     

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.     

Microscopic investigation of agglomeration of coal hydrogenation residues by secondary vitroplast

The agglomeration of coal hydrogenation residues by secondary vitroplast was investigated using both optical and scanning electron microscopy (SEM). Hydrogenation reactions were performed in a stirred batch autoclave at five temperatures between 375 and 475 °C for 1 h using tetralin as hydrogen donor solvent. Agglomeration was found to depend on the amount of secondary vitroplast present in the slurry and was most effective at 400 °C under the experimental conditions used. Both optical and SEM techniques have been found to be useful for investigation of the agglomeration of residues by secondary vitroplast.     

The influence of hydrogen donors on the pyrolysis of a bituminous coal as studied by in situ e.s.r. spectroscopy

The effect of hydrogen gas, a hydrogen donor solvent (tetralin) and a non-donor solvent (decane) on the pyrolysis (to 500 °C) of a bituminous coal, before and after extraction with chloroform, has been studied by in situ e.s.r. in a flowing gas cell at atmospheric pressure. It was found that hydrogen gas at 1 bar had an insignificant effect on the course of the reaction, as determined by free radical population measurements, compared with nitrogen gas. In contrast, both tetralin and decane change the free radical populations developed during pyrolysis, and the extent of the induced change varies upon chloroform extraction of the coal. These results are discussed with reference to current coal liquefaction models, and are interpreted in terms of the chemical and physical interactions of the solvent with the coal.     

Liquefaction of subbituminous coals with a basic nitrogenous model process solvent

Liquefaction reactions in a tubing-bomb reactor have been carried out as a function of coal, coal sampling source, reaction time, atmosphere, temperature, coal pre-treatment, SRC post-treatment and process solvent. Pyridine as well as toluene conversions ranging from 70 to > 90 wt% involving both eastern bituminous and western subbituminous coals are obtained. 1,2,3,4-Tetrahydroquinoline (THQ) has been extensively used as a process solvent under optimized liquefaction conditions of 2:1 solvent: coal, 7.5 MPa H₂, 691 K and 30 min reaction time. Comparisons of THQ with other model process solvents such as methylnaphthalene and tetralin are described. Liquefaction product yield for conversion of subbituminous coal is markedly decreased when surface water is removed from the coal by drying in vacuo at room temperature prior to liquefaction. The effect of mixing THQ with Wilsonville hydrogenated process solvent in the liquefaction of Wyodak and Indiana V coals is described.     

Analysis of solvent extracts from coal liquefaction in a flowing solvent reactor

Point of Ayr coal has been extracted using three solvents, tetralin, quinoline and 1-methyl-2-pyrrolidinone (NMP) at two temperatures 350 and 450 °C, corresponding approximately to before and after the onset of massive covalent bond scission by pyrolysis. The three solvents differ in solvent power and the ability to donate hydrogen atoms to stabilise free radicals produced by pyrolysis of the coal. The extracts were prepared in a flowing solvent reactor to minimise secondary thermal degradation of the primary extracts. Analysis of the pentane-insoluble fractions of the extracts was achieved by size exclusion chromatography, UV-fluorescence spectroscopy in NMP solvent and probe mass. With increasing extraction temperature, the ratio of the amount having big molecular weight to that having small molecular weight in tetralin extracts was increased; the tetralin extract yield increased from 12.8% to 75.9%; in quinoline, increasing extraction temperature didn't have an effect on the molecular weight of products but there was a big increase in extract yield. The extracts in NMP showed the enhanced solvent extraction power at both temperatures, with a shift in the ratio of larger molecules to smaller molecules with increasing extraction temperature and with the highest conversion of Point of Ayr coal among these three solvents at both temperatures. Solvent adducts were detected in the tetralin and quinoline extracts by probe mass spectrometry; solvent products were formed from NMP at both temperatures.     

Effect of solvent on molecular composition in coal liquefaction

The product from uncatalysed liquefaction of lignite using synthesis gas (CO-Steam process) was examined by column chromatography, high-resolution mass spectrometry, gas chromatography-mass spectrometry, and low-voltage mass spectrometry. The nature of the vehicle solvent affected the type and distribution of compounds in the product oil. Anthracene oil and recycle oil as solvents gave mainly aromatics and phenols. When tetralin was used as solvent, the product showed larger amounts of oxygen compounds, more hydroaromatic compounds, and a greater degree of alkylation in high-molecular-weight aromatics. Tetralin, therefore, appears to be a more powerful hydrogen donor than anthracene oil or recycle oil in stabilizing intermediate fragments that would otherwise repolymerize. Carbon-number analysis data for liquids prepared using three different solvents are presented.     

Liquefaction of coal using supercritical fluid mixtures

Powhatan No. 5 and Bruceton coals were liquefied for 15–60 min at 653 K and 30 MPa in supercritical aqueous mixtures containing 10–20 wt% tetrahydroquinoline (THQ), quinoline or tetralin. The THQ-water mixtures produced the highest conversion to tetrahydrofuran (THF) soluble products (up to 74%). Tetralin-water, quinoline-water and pure water solvents gave increasingly lower yields of THF solubles. Addition of hydrogen to the quinoline-water solvent mixture increased yields slightly, but not to the level obtained using the THQ-water mixture.The yields of THF solubles in all instances depended upon the concentration of solvent in the mixture, with the 10 wt% THQ and 10 wt% tetralin (in water) giving higher yields than either 0 or 20 wt% concentrations. The nitrogen-containing solvents were chemically bonded to the THF-soluble product, as observed by g.p.c.     

Pyrolysis of hydrocarbon mixtures characteristic of coal: Application to dibenzyl mixture

Thermal cracking of dibenzyl dissolved in two solvents, tetralin and decalin, has been studied in a flow reactor, in the presence of steam, under atmospheric pressure and at temperatures between 600 and 750 °C. The nature of the products obtained depends upon the structure of the hydrogen-donor agent, but is independent of the structure of dibenzyl. Valuable products such as ethylene and a benzene, toluene and xylene (BTX) mixture, obtained by a β-scission reaction with a monomolecular mechanism, are predominant when decalin is used as solvent. The dehydrogenation of tetralin to naphthalene precedes cracking reactions of the bimolecular type, which lead to significant production of hydroaromatics such as indene. Cracking of dibenzyl, followed by hydrogen transfer from the solvent to the radicals formed, leads to toluene irrespective of the chemical nature of the hydrogen donor.     

超细FeS对五彩湾煤直接液化性能的影响

以硫酸亚铁为铁源,硫化钠为沉淀剂,采用液相沉淀法合成了超细FeS催化剂。以四氢萘为溶剂,反应温度430℃、氢初压6.0 MPa、反应时间60 min、溶煤比2∶1条件下,探讨超细FeS催化剂对五彩湾煤直接液化性能的影响。结果表明：硫酸亚铁基超细FeS粒子形貌均一,呈细棒状;五彩湾煤直接液化实验的油产率、液化率和转化率,以2.0%（wt,以活性金属元素计,相对于干燥无灰煤,下同）超细FeS为催化剂的实验分别达到56.15、73.29和81.21%（wt,相对于干燥无灰煤,下同）,高于相同条件下,以3.0%分析纯Fe2O3为催化剂的实验产率（分别是44.00、49.33和62.05%）。     

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.     

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%.