Hydroprocessing of stuart a (Australian) oil shale

Research on production of shale oil by direct hydrogenation of oil shale has been conducted in batch stirred autoclave reactors. The objective of the work has been to elucidate the effect of operating variables on conversion of organic carbon, and the resulting product yield structure (oil/gas). Yields of oil and gas (hydrocarbon and carbon oxide) have been quantified for hydroprocessing under a wide range of operating conditions using both hydrogen donor and pyrolysis oil (non-donor) solvents. The effects of temperature, reaction time, pressure, hydrogen partial pressure, and solvent characteristics on yield structure are described.     

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.     

Petroleum heavy oil mixtures as a source of hydrogen in the liquefaction of Cerrejon coal

Petroleum heavy oil and anthracene oil were used as hydrogen donor solvents in a coal liquefaction test. A positive synergistic effect was obtained when mixed (petroleum heavy oil; anthracene oil) solvent was employed. The temperature of maximum conversion was also lower for this mixed solvent than for any of the solvents alone. It is shown from the ¹ H n.m.r. spectral data that petroleum heavy oil acts as a hydrogen donor to anthracene oil resulting in hydroaromatic derivatives. These hydroaromatic species donate hydrogen to the coal fragments. The ¹ H n.m.r. spectral data allow monitoring of the temperature at which the petroleum heavy oils have maximum donor capacity and consequently the temperature for coal liquefaction in this process.     

Experimental study on the coal tar hydrocracking process in supercritical solvents

In order to find the optimal operating parameters in high-temperature and low-temperature coal tar hydrocracking processes and to maximize the light oil yields, experimental studies have been carried out in a one-stage reactor in supercritical solvents. Xylene and gasoline were used as supercritical solvents to investigate their effects on the light oil yields. The results show that gasoline was more suitable as a supercritical solvent and that a suitable ratio of gasoline solvent to coal tar could result in higher light oil yields in both high- and low-temperature coal tar hydrocracking processes. The effects of different operating parameters, including temperature, hydrogen pressure, catalyst, and residence time, on light oil yield were tested. It was found that the yields of light oil from the two coal tar hydrocracking processes varied with the operating parameters in a similar manner. However, different values of the operating parameters gave rise to the maximum yields of light oil from the respective processes.     

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.     

Reaction mechanism of coal hydrogenation: 2. Three rings solvent system

Taiheiyo coal was hydrogenated in phenanthrene, 9,10-dihydrophenanthrene, 1,2,3,4,5,6,7,8-octahydrophenanthrene and perhydrophenanthrene under 10 MPa (initial pressure) of hydrogen or nitrogen with or without stabilized nickel as catalyst at 400 °C for 15 min. Preasphaltene, asphaltene and oil conversions and the conversion of solvents were measured, and the amounts of hydrogen absorbed by coal from molecular hydrogen and from donor solvent were calculated. The main route of reaction appears to be the direct hydrogenation of coal by molecular hydrogen and the contribution of hydrogenation via the solvent was greater than in the case of the two rings solvent system.     

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.     

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.     

Coal hydrogenation: Quality of start-up solvents and partially process-derived recycle solvents

The performance of three sets of start-up solvents and one set of partially process-derived recycle solvents was studied in small autoclave coal hydrogenation tests. The start-up solvents were obtained by catalytically hydrotreating anthracene oils or creosote oils. It is shown that this preparation procedure converts polynuclear aromatics and two-ring aromatics to hydroaromatics and, ultimately, to alicyclics. Coal conversions using start-up solvents are found to reach a maximum at intermediate degrees of solvent hydrogenation which is believed to correspond to a maximal abundance of hydroaromatic solvent hydrogen donors. A solvent hydrogen donor index (SHDI), simply derived from ¹H n.m.r. spectral data, was devised and is found to successfully correlate coal conversions obtained using different start-up solvents, especially where N₂ gas rather than H₂ gas is employed in the autoclave tests. A set of partially process-derived recycle solvents were produced in multiple cycle continuous coal hydrogenation experiments. These were tested under relatively severe hydrogenation conditions in the presence of hydrogen gas, using the small autoclave unit. Substantial donation of solvent hydrogen was found to occur and coal conversions to hexane — and toluene-soluble products are found to be a smooth function of the solvent hydrogen donor index. It is concluded that the hydrogen donor capacity of a solvent is a major factor governing coal conversion, especially when the demand for solvent hydrogen is high. The SHDI parameter is useful in rationalizing the behaviour of start-up solvents. Also, at least in the first few cycles of a continuous two stage coal hydrogenation process, the SHDI parameter allows solvent quality to be monitored, and consequently optimized.     

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.     

Hydroliquefaction of Victorian brown coal in a continuous reactor : 2. Comparison of tetralin and a coal-derived oil as hydrogen donor solvents

Slurries of Victorian brown coal in either tetralin (1:3) or a hydrogenated creosote oil (HKC 300) (1:3) were reacted with hydrogen in a continuous reactor system both with and without the addition of iron/tin based catalysts. The product yields and distributions from reactions using HKC 300 oil as a solvent are different from those obtained using tetralin. Under similar operating conditions, conversions are slightly lower and the asphaltene yields are higher for reactions in HKC 300 relative to those in tetralin. These differences are presumably due to the poorer hydrogen donor ability of the HKC 300. The yields of asphaltols, asphaltenes and oils for reactions in both solvent systems under a wide range of conditions are discussed as a function of overall conversion.     

Copolymerization of ethylene with vinyl acetate. II. Effect of solvent on polymer yield and molecular weight

In the free-radical solution copolymerization of ethylene and vinyl acetate, polymer yield and molecular weight were found to vary considerably with the solvent used. Solvents were toluene, benzene, hexane, heptane, and cyclohexane. Molecular weights were highest in benzene and lowest in toluene and were readily explained by different solvent chain-transfer constants. Polymer yields were highest in aliphatic solvents and lowest in aromatic solvents including benzene. This was attributed to different types of interactions of the solvents with radical species. The saturated aliphatic solvents undergo hydrogen abstraction reactions, but these give reactive alkyl radicals which reinitiate polymer growth. Toluene also undergoes hydrogen abstraction reactions, but the resultant benzyl radical is resonance stabilized and does not readily reinitiate polymerization. Benzene does not undergo hydrogen abstraction reactions. The low yields are attributed to complex formation. A consideration of kinetic theory indicates that complex formation with both initiator and growing polymer radicals is involved. Differences in viscosity, ethylene solubility, and initiator half-life in the different solvents, as well as induced decomposition of the initiator, were not determining factors.     

Unusually high extraction yield from the liquefaction of an Egyptian coal from Al Maghara coalfield

Liquefaction of an Egyptian coal collected from Al Maghara coalfield in the northern Sinai has been carried out using hydrogenated anthracene oil in a stirred autoclave. The solvent, coal solution and light distillate product were characterized by gas chromatography, including simulated distillation. The extraction yield from the coal was 98.9% (dmmf), indicating that the organic matter was almost entirely soluble in the hydrogen donor solvents. The proportion of desirable light distillates in the extract was much higher than average, and the upgrading potential of the heavier components is likely to be good, with a small hydrogen demand. The sulphur content of the extract was very low. Pyrite in the coal is considered to have a beneficial catalytic effect on extraction.     

Performance indices for coal liquefaction solvents

Most coal liquefaction processes are based on the thermal cleavage of activated bonds giving reactive carbon and oxygen radicals which abstract hydrogen atoms from the donor solvent. The role of oil is approximated in this study by using a simple standard reaction. A series of five representative solvents react with phenyl and phenyloxy radicals generated by thermolysis of benzoyl peroxide at 87 °C in tetrachloroethylene. The n.m.r. analysis of the reacting mixture defines four performance indices, i.e. the hydrogen-donor, the efficiency, the recycle and the scavenger indices, which characterize the ability of these solvents as efficient recycle oils in coal liquefaction processes. 9,10-dihydrophenanthrene proves to be by far the most appropriate solvent for this purpose.     

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.     

Effect of pre-swelling of coal on its solvent extraction and liquefaction properties

Effects of pre-swelling of coal on solvent extraction and liquefaction properties were studied with Shenhua coal. It was found that pre-swelling treatments of the coal in three solvents, i.e., toluene (TOL), N-methyl-2-pyrrolidinone (NMP) and tetralin (THN) increased its extraction yield and liquefaction conversion, and differed the liquefied product distributions. The pre-swollen coals after removing the swelling solvents showed increased conversion in liquefaction compared with that of the swollen coals in the presence of swelling solvents. It was also found that the yields of (oil + gas) in liquefaction of the pre-swollen coals with NMP and TOL dramatically decreased in the presence of swelling solvent. TG and FTIR analyses of the raw coal, the swollen coals and the liquefied products were carried out in order to investigate the mechanism governing the effects of pre-swelling treatment on coal extraction and liquefaction. The results showed that the swelling pre-treatment could disrupt some non-covalent interactions of the coal molecules, relax its network structure and loosened the coal structure. It would thus benefit diffusion of a hydrogen donor solvent into the coal structure during liquefaction, and also enhance the hydrogen donating ability of the hydrogen-rich species derived from the coal.     

Investigation of free radicals produced during coal liquefaction using ESR

Coal liquefaction experiments are described which were carried out to dissolve a subbituminous coal in low and high hydrogen content solvents, in which liquid samples were periodically withdrawn and examined by electron spin resonance spectroscopy. The objectives of this study were to gain information on the free radical processes involved in coal liquefaction, to determine the relative effectiveness of two solvents (H-donor and non-donor) in influencing the radical processes involved in coal liquefaction and to investigate changes in radical concentration on storage.     

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.     

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.     

Amines from aldehydes derived from the ozonization of soybean esters

Investigations were carried out on reductive amination of caproaldehyde, pelargonaldehyde and azelaaldehydate esters, obtainable from ozonolysis of soybean oil products, with ammonia and hydrogen in the presence of nickel catalyst. A solvent system giving good yields of primary amine while suppressing amide formation was devised. Excess ammonia and homogeneous solutions suppressed secondary amine formation. Nonpolar solvents suppressed ammonolysis. Optimum conditions for reaction varied with the aldehyde. Excellent yields of hexylamine (91%), nonylamine (90%), methyl 9-aminononanoate (92%) and butyl 9-aminononanoate (93%) were obtained from caproaldehyde, pelargonaldehyde, methyl azelaaldehydate and butyl azelaaldehydate, respectively, when aminated in anhydrous ammonia and either cyclohexane or methyl cyclohexane. Presented at the AOCS meeting, Chicago, 1964. A laboratory of the No. Utiliz. Res. and Dev. Div., ARS, USDA.