Alkylation: a beneficial pretreatment for coal liquefaction

Schlosberg, Richard H.; Neavel, Richard C.; Maa, Peter S.; Gorbaty, Martin L.

doi:10.1016/0016-2361(80)90009-5

Cited by 37 publications

(7 citation statements)

References 4 publications

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“…102 On the other hand, the oil yield was successfully increased by demineralization, 103 solvent swelling 101,104 or alkylation of coal. [105][106][107] These results suggest that the secondary interactions such as cation linkage and hydrogen bonding are related to the retrogressive reactions. Temperature programmed liquefaction studies done by Saini et al 108 and Song et al 109 concluded that benzyl-type radicals can lead to retrogressive reactions.…”

Section: Coal Dissolution Depolymerization and Retrogressive Reactionsmentioning

confidence: 90%

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Vasireddy

Morreale

Cugini

et al. 2011

Energy Environ. Sci.

334

209

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Increased demand for liquid transportation fuels coupled with gradual depletion of oil reserves and volatile petroleum prices have recently renewed interest in coal-to-liquids (CTL) technologies. Large recoverable global coal reserves can provide liquid fuels and significantly reduce dependence on oil imports. Direct coal liquefaction (DCL) converts solid coal (H/C ratio z 0.8) to liquid fuels (H/C ratio z 2) by adding hydrogen at high temperature and pressures in the presence or absence of catalyst. This review provides a comprehensive literature survey of the coal structure, chemistry and catalysis involved in direct liquefaction of coal. This report also touches briefly on the historical development and current status of DCL technologies. Key issues, challenges involved in DCL process and directions for the future research are also addressed.

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Section: Coal Dissolution Depolymerization and Retrogressive Reactionsmentioning

confidence: 90%

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Vasireddy

Morreale

Cugini

et al. 2011

Energy Environ. Sci.

334

209

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“…One way to improve the economics of direct liquefaction is to modify the coal feed before solubilization. Treatments such as alkylation, − acylation, partial oxidation, , and alkali hydrolysis , weaken and rupture the cross-linked bonds and result in a partially depolymerized coal. Although all of these methods of enhancing coal reactivity somewhat improve liquefaction yield, none has yet been employed as a process step in liquefaction.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Coal Direct Liquefaction by Steam Pretreatment

et al. 1997

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Pretreatment of coal by reaction with subcritical steam enhances its performance in direct liquefaction. Illinois No. 6 coal, first reacted with 51 atm of steam for 15 min at 340 °C, was liquefied in a coal injection autoclave to provide rapid heating. Liquefactions were carried out with raw and pretreated coal at high-severity (400 °C, 30 min) and low-severity (385 °C, 15 min) conditions under 1500 psia of hydrogen with tetralin as the donor solvent. Substantial improvement in product liquid quality is realized provided the pretreated coal is protected from oxygen and heated rapidly to liquefaction temperature. Under low-severity conditions, the oil yield is more than doubled, going from 12.5 to 29 wt %. Since previous work pointed to the destruction of ether cross-links by water as the dominant depolymerization mechanism during pretreatment, tests were conducted with several aromatic ethers as model compounds. These were exposed to steam and inert gas at pretreatment conditions and in some cases to liquid water at 315 °C. α-Benzylnaphthyl ether and α-naphthylmethyl phenyl ether show little difference in conversion and product distribution when the thermolysis atmosphere is changed from inert gas to steam. Hence, these compounds are poor models for coal in steam pretreatment. The otherwise thermally stable 9-phenoxyphenanthrene, on the other hand, is completely converted in 1 h by liquid water at 315 °C. At pretreatment conditions, however, mostly rearranged starting material is obtained. Therefore, 9-phenoxyphenanthrene, though less reactive, is a model for ether linkages in coal.

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“…Alkylation has been used with success to improve the dissolution of coal. − The objective of the coal alkylation was not to improve pentane solubility, but it indicated that Friedel–Crafts alkylation could potentially be a useful strategy. Although alkylation has never been industrially applied for the upgrading of asphaltenes, there are some studies that applied alkylation as a method to elucidate the molecular structure of asphaltenes as well as a method to increase the solubility of asphaltenes. − …”

Section: Introductionmentioning

confidence: 99%

Alkylation of Asphaltenes Using a FeCl₃Catalyst

Prado

Klerk

2015

Energy Fuels

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Friedel−Crafts alkylation as a strategy to convert asphaltenes to maltenes was investigated. It was postulated that conversion of polar hydroxyl groups in the asphaltenes would make the product more soluble in light hydrocarbons. Reactions were performed with oilsands bitumen-derived materials using FeCl 3 as a catalyst and o-xylene and methanol, separately. Only the reaction of o-xylene with asphaltenes was mildly beneficial; it resulted in 6% conversion of asphaltenes to maltenes and an increase of 9% in straight-run distillate and vacuum gas oil. The reactions of o-xylene with maltenes and bitumen were detrimental, as was all alkylation reactions with methanol. To better understand the nature of the conversion, the reactions were repeated with model compounds. With 2-naphthol, it was found that dimerization of 2-naphthol to produce (1,1′-binaphthalene)-2,2′-diol (BINOL) and the subsequent coordination with iron were the two dominant reactions. The adverse consequences of FeCl 3 -catalyzed conversion could be explained by such intermolecular addition reactions. The reaction of 2-naphthol with methanol and FeCl 3 also caused some chlorination of the product. The possibility that FeCl 3 as a catalyst affected ethers was explored by performing the reaction with dibenzyl ether as feed. It was found that the ether bonds were cleaved. In the presence of o-xylene, ether cleavage was followed by C-alkylation. The increase in maltenes after the reaction of o-xylene with asphaltenes was better explained by C-alkylation following ether cleavage than the reaction between o-xylene and the hydroxyl groups in the asphaltenes. The reaction of dibenzyl ether with methanol produced benzaldehyde, rearrangement products, and heavy gums.

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Alkylation: a beneficial pretreatment for coal liquefaction

Cited by 37 publications

References 4 publications

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Improvement of Coal Direct Liquefaction by Steam Pretreatment

Alkylation of Asphaltenes Using a FeCl₃Catalyst

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Alkylation: a beneficial pretreatment for coal liquefaction

Cited by 37 publications

References 4 publications

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Clean liquid fuels from direct coal liquefaction: chemistry, catalysis, technological status and challenges

Improvement of Coal Direct Liquefaction by Steam Pretreatment

Alkylation of Asphaltenes Using a FeCl3Catalyst

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Alkylation of Asphaltenes Using a FeCl₃Catalyst