Nature and origin of asphaltenes in processed coals. Annual report. [55 references]

Whitehurst, D.D.; Farcasiu, M.; Mitchell, T.O.

doi:10.2172/5153104

Cited by 26 publications

(35 citation statements)

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“…Our results show that the temperature has a strong positive effect on the production of THF solubles (see Table 10). Whitehurst et al (1977), Longanbach et al (1978), and Traeger et al (1979) have also reported a very fast increase in the formation of THF solubles for times u p to 4 min.…”

Section: A Effect Of Temperaturementioning

confidence: 89%

“…Various studies (Curran et al, 1966;Whitehurst et al, 1977) have shown that the size of the coal in the normal range of interest (1 to 1,200 pm) has a very small effect on the yields of coal liquefaction. However, in all of these studies the maceral and mineral compositions may have changed with the particle size, and hence the results obtained were not conclusive.…”

Section: Effect Of Initial Coal Particle Sizementioning

confidence: 99%

“…It is, therefore, necessary to quantitatively evaluate the chemical changes occurring in the preheater. Studies on short contact time coal liquefaction have shown that coal undergoes initial reactions in the preheater, involving both chemical and physical property changes (Whitehurst et al, 1977;Wen and Han, 1978). For good design and scale-up of coal liquefaction units it is essential to obtain reliable kinetic data under conditions existing both in preheater and reactor.…”

Section: Introductionmentioning

confidence: 99%

“…Most kinetic studies reported in literature haye been carried out at high temperatures (>673 K) and at long residence times (10-60 min) (Cronauer et al, 1978;Shalabi et al, 1979). Studies in short contact time coal liquefaction have shown that coal is thermally fragmented into smaller molecules which are soluble in pyridine (Neavel, 1976;Whitehurst et al, 1977). In the initial stages of reaction, it is believed that a large number of free radicals are produced which are then stabilized by hydrogen abstraction from hydrogen-rich portions of coal or solvent (Curran et al, 1966;Collins et al, 1978;Petrakis and Grandy, 1980;Larsen et al, 1981), very little molecular hydrogen is consumed in this stage.…”

Section: Introductionmentioning

confidence: 99%

“…The oil fraction increases after certain reaction times, indicating that the intermediates are eventually converted to oils. Whitehurst et al (1977) have reported that a certain amount of initially pyridine-soluble coal was converted to pyridine insolubles when liquefied at high temperatures (>673 K). This was attributed to the repolymerization of preasphaltenes at this temperature, giving char which no longer reacts.…”

mentioning

confidence: 99%

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Kinetics of short contact time coal liquefaction. Part I: Effect of operating variables

et al. 1984

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Section: A Effect Of Temperaturementioning

confidence: 89%

Section: Effect Of Initial Coal Particle Sizementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Kinetics of short contact time coal liquefaction. Part I: Effect of operating variables

et al. 1984

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Energy‐Related Catalysis: Sections 3.12.5 – 3.19.8

Sie¹,

Maxwell²,

Minderhoud³

et al. 1997

Handbook of Heterogeneous Catalysis

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Kinetics of short contact time coal liquefaction. Part II: Effect of nature of coal and solvent

et al. 1984

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A bituminous coal (Powhatan No. 5 ) and a subbituminous coal (Belle Ayr) were liquefied in the presence of hydrogen donor solvents. Statistical analyses of the data showed that for contact times up to 10 min, the coal conversion, measured in terms of tetrahydrofuran solubles, was not significantly different for the two coals. However, the subbituminous coal gave more asphaltenes than the bituminous coal.The hydrogen-donating capacity of the solvent was varied by the addition of hydrogenated phenanthrene to SRC-I1 recycle solvent. The results indicated that there are two routes for the formation of oils from coal. One is by adduct formation giving asphaltenes and preasphaltenes, which in turn gives oils, and the other is direct oil formation from coal. The preferred route depends on the hydrogendonating capacity of the solvent, The kinetic model, proposed in Part I of this paper, is extended to account for the change in the donor capacity of the solvent. SCOPECoal liquefaction can be characterized as occurring in three stages, namely dissolution, hydrogen transfer, and hydrogenation. In each of these stages the nature of the solvent can affect the rate of reaction and the selectivity of the products. Solvent components which affect the behavior of coal liquefaction processes can be classified as hydrogen donors, hydrogen shuttlers, and components that aid in solubilization. Recent studies have shown that poor bydrogendonating solvents form adducts with coal to give insoluble products. This appears to occur to a lesser extent with good donor solvents. It is likely that for the case of good hydrogen donor solvents the formation of soluble products compensate for the adduct formation. Kinetic measurements at short contact times (up to 10 min) with solvents of varying hydrogen donor capacity have been made to provide a better understanding of the processes of liquefaction and adduct formation. CONCLUSIONS AND SIGNIFICANCEIn a stirred tank batch reactor, there appears to be no significant difference in the conversion of Powhatan No. 5 bituminous and Belle Ayr subbituminous coal to pentane and tetrahydrofuran (THF) solubles for contact times up to 10 min. More asphaltenes are recovered from the liquefaction of Belle Ayr coal than from that of Powhatan coal. Both the coals, when contacted with SRC-I1 recycle solvent, show an initial effective loss of solvent.The initial depletion of oils progressively decreases with an increase in the hydrogen-donating capacity of the solvent, indicating that the initial loss of solvent is independent of the nature of coal, but it is dependent on the hydrogen-donating capacity of the solvent. Oils can be formed either directly from coal or by an indirect route via asphaltenes and preasphaltenes through adduct formation. The latter results in an initial loss of solvent. The former route gains preference over the latter as the hydrogen-donating capacity of the solvent is increased. A single kinetic model entailing both direct and indirect routes is shown to adequately represent the data o...

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Nature and origin of asphaltenes in processed coals. Annual report. [55 references]

Cited by 26 publications

References 0 publications

Kinetics of short contact time coal liquefaction. Part I: Effect of operating variables

Kinetics of short contact time coal liquefaction. Part I: Effect of operating variables

Energy‐Related Catalysis: Sections 3.12.5 – 3.19.8

Kinetics of short contact time coal liquefaction. Part II: Effect of nature of coal and solvent

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