Mechanisms leading to process improvements in lignite liquefaction using CO and H2S☆

Sondreal, E.A.; Wilson, W.G.; Stenberg, Virgil I.

doi:10.1016/0016-2361(82)90091-6

Cited by 36 publications

(9 citation statements)

References 13 publications

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“…In our results, at 400 °C for 600 min, the HER of tetralin in the presence of H 2 S reached 71%. This value shows that not only α-hydrogen in a naphthene ring but also hydrogen in an aromatic ring and β-hydrogen in a naphthene ring become more exchangeable in the presence of H 2 S. Stenberg et al reported that hydrogen donor ability of H 2 S was indicated by the stoichiometry of the bibenzyl conversion and the favorably low bond dissociation energies of H 2 S compared with H 2 . The bond energy of H 2 is greater than that of most C−H bonds, whereas that for H 2 S is not.…”

Section: Resultsmentioning

confidence: 96%

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

et al. 1997

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To elucidate the effect of H2S and H2O on hydrogen exchange reactions between tetralin and gaseous hydrogen, the reactions of tetralin with tritiated hydrogen in the presence of H2S or H2O were performed under practical coal liquefaction conditions. The amounts of hydrogen exchange between tetralin and tritiated hydrogen were estimated from hydrogen and tritium balance. The conversions of tetralin in the presence and absence of H2S at 400 °C for 300 min were 4.1 and 3.9%, respectively, while the hydrogen exchange ratio (HER) of tetralin remarkably increased from 4.6% to 40.4% in the presence of H2S and reached 71% at 400 °C for 600 min. It was suggested that the hydrogen exchange mechanism of tetralin with hydrogen in the presence of H2S would include a different mechanism from that in the absence of H2S. It was considered that the H2S molecule acted as both an initiating species and an HS• radical and rapidly abstracted and added hydrogen atom reversibly, promoting the hydrogen exchange in both an aromatic ring and a naphthene ring. In addition to the radical mechanism, the electrophilic exchange with a proton formed from hydrogen sulfide was proposed for the hydrogen exchange mechanism. On the other hand, the conversion and HER of tetralin in the presence of H2O at 400 °C for 300 min were 1.7 and 1.3%, respectively. These values were smaller than those in the absence of H2O. It was considered that H2O inhibited the formation of tetralyl radicals and the hydrogen transfer from tritiated hydrogen to tetralyl radicals. The tritium distribution in H2S reached equilibrium at the initial stage of the reaction, and the hydrogen exchange reaction between gaseous hydrogen and H2S rapidly occurred. However, it was estimated that the hydrogen exchange reaction between gaseous hydrogen and H2O was slower than that with H2S.

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Section: Resultsmentioning

confidence: 96%

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

et al. 1997

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“…Other activities include using isotopic tracers ( 13 C and Z H) to follow Reactions were carried out in the 54 kg/day (120 lb/day) GFETC CPU (tubular reactor) on as received and slurry-dried lignite using either H2 or syngas. Benefits were more pronounced with syngas and water than with hydrogen (40).…”

Section: Liquefaction Of Low-rank Coalmentioning

confidence: 93%

“…Direct liquefaction processes react coal with a process-derived solvent and a reducing gas. Three processes aimed at distillate production have Optimum distillate yields from US lignites (40) have been shown to be as high on a dry, ash-free basis as those obtained from bituminous coals, but only if the vacuum bottoms are recycled. Lignites are more readily liquefield if the reducing gas contains some carbon monoxide and water, which together with recycling the bottoms yields the highest conversions and the best bench-unit operability.…”

Section: Liquefaction Of Low-rank Coalmentioning

confidence: 99%

“…The beneficial effect of HzS compensates for a low hydrogen-donor solvent quality. The superiority of HzS as a liquefaction promoter for lignite over iron compounds and sulfur is illustrated in Figure 8 (40), which graphs total conversion at 460°C. Even more significantly, the total oil yield from one Texas lignite in recycle liquefaction using syngas was shown to be higher at 400°C with H 2S added than at 460DC without HzS, and both gas production and reductant consumption were reduced by two thirds.…”

Section: Liquefaction Of Low-rank Coalmentioning

confidence: 99%

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Low-Rank Coal: Its Present and Future Role in the United States

Sondreal¹,

Wiltsee²

1984

Annu. Rev. Energy.

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Low-rank coals-lignite and subbituminous coal-are those that have been subjected to the least metamorphic change during the coal-forming process. As such, they retain greater fractions of moisture and volatile matter and contain less fixed carbon than the high-rank coals-bituminous and anthracite. The primary measure used to classify the lower ranks of coal is the heating value. Lignite is defined by the American Society for Testing and Materials (standard D-388) as coal with a heating value less than 8300 Btujlb, on a moist, mineral-matter-free basis (m,mmf). Subbituminous coal ranges in heating value from 8300 to 11,500 Btujlb (m,mmf). Bituminous coal and anthracite range from 10,500 to over 15,000 Btu/lb (m,mmf). Low-rank coals represent a major but largely untapped energy resource in the United States. Very extensive deposits of lignite and subbituminous coal exist in the western states, the Gulf Coast, and Alaska (Figure 1). Major deposits of low-rank coal are also found in many other countries, most

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“…Addition of hydrogen atoms to the ipso-position of DNM should be the crucial step for DNM hydrocracking . Under elevated temperatures, sulfur added easily reacts with H 2 to afford H 2 S. − Relatively weaker H−SH bond (389 kJ/mol) than H−H bond (427 kJ/mol) makes hydrogen atoms form easier from H 2 S than from H 2 . As Table shows, sulfur addition did not lead to DNM hydrocracking without H 2 .…”

mentioning

confidence: 99%

Synergic Effect of Sulfur on Activated Carbon-Catalyzed Hydrocracking of Di(1-naphthyl)methane

Zong

Zhang

et al. 2002

Energy Fuels

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As a model reaction for coal liquefaction, the hydrocracking of di(1-naphthyl)methane (DNM) was investigated under different reaction conditions. The results show that activated carbon selectively catalyzes DNM hydrocracking and that sulfur has a synergic effect on the activated carbon-catalyzed hydrocracking of DNM. The synergic effect can be ascribed to the catalysis of the activated carbon in H2S dissociation.

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Mechanisms leading to process improvements in lignite liquefaction using CO and H2S☆

Cited by 36 publications

References 13 publications

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Low-Rank Coal: Its Present and Future Role in the United States

Synergic Effect of Sulfur on Activated Carbon-Catalyzed Hydrocracking of Di(1-naphthyl)methane

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Mechanisms leading to process improvements in lignite liquefaction using CO and H2S☆

Cited by 36 publications

References 13 publications

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H2S and H2O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H2S and H2O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Low-Rank Coal: Its Present and Future Role in the United States

Synergic Effect of Sulfur on Activated Carbon-Catalyzed Hydrocracking of Di(1-naphthyl)methane

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Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen