Catalytic Coal Gasification: An Emerging Technology

Hirsch, Robert; Gallagher, Julie; Lessard, Richard R.; Wesslhoft, Robert D.

doi:10.1126/science.215.4529.121

Cited by 82 publications

(39 citation statements)

References 3 publications

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“…It has been proposed that coke is removed in a reaction cycle in which oxidic K and H 2 O form KOH which reacts further with carbon to form K 2 CO 3 . The carbonate decomposes, releases CO 2 and leaves K-oxides behind [7,8,11,12]. …”

Section: Dehydrogenation On α-Fementioning

confidence: 99%

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Styrene synthesis: in situ characterization and reactivity studies of unpromoted and potassium-promoted iron oxide model catalysts

Shekhah

Ranke

Schlögl

2004

Journal of Catalysis

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Abstract:Styrene synthesis over iron oxide model catalysts was studied by combining UHV characterization methods with in-situ conversion measurements in a micro-flow reactor under realistic reaction conditions. Both unpromoted Fe 2 O 3 and K-promoted model catalysts show a similar high starting activity while that of Fe 3 O 4 is clearly lower. Water limits and Kpromotion slows down deactivation by coking and oxide reduction. The deactivation can be prevented and the high initial yield preserved by adding a small amount of oxygen to the feed. Both the presence of Fe 3+ and intermediate adsorption strength for ethylbenzene and styrene are essential for high conversion yields.

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Section: Dehydrogenation On α-Fementioning

confidence: 99%

“…Potassium stabilizes the catalyst against reduction [10] and supports the removal of coke. K 2 CO 3 is believed to represent the active center for carbon gasification [5,11,12]. Benzene and toluene as the main side products may be formed at different sites [5,6,13].…”

Section: Introductionmentioning

confidence: 99%

Styrene synthesis: in situ characterization and reactivity studies of unpromoted and potassium-promoted iron oxide model catalysts

Shekhah

Ranke

Schlögl

2004

Journal of Catalysis

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“…This agrees also with the prior observations that the time of the catalyst treatment has no effect on the catalyst uptake, and that the internal pore structures of chars were not affected by the catalyst impregnation. This finding also helps explain why the method of impregnation, whether by bulk mixing, ball milling, solution soaking, or ion exchange, is sometimes reported to have little effect on gasification rate (Hirsch et al, 1982).…”

Section: Catalyst Penetratlonmentioning

confidence: 88%

Porosity effects on catalytic char oxidation. Part I: A catalyst deposition model

Perlmutter

1985

AIChE Journal

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Six char samples generated from two coals were impregnated by solutions with different concentrations of NazC03 and/or KzCO3. The catalyst solution penetration was studied, the catalyst uptake was measured, and the effects of impregnation on the char pore structure were determined experimentally. The results indicate that the impregnated catalysts reside only on particle exteriors without significant penetration. The overall rate of reaction is therefore the combination of catalytic reaction on particle exteriors and noncatalytic reaction on the pore surfaces inside the particle. A kinetic model is presented that takes these findings into account. J. L. SU and D. D. PERLMUllER Department of Chemical EngineeringUniversity of Pennsylvania Philadelphia, PA 19104 SCOPESix char samples generated from two coals were impregnated by solutions containing different concentrations of NazC03 and/or KzCO3. The effects of catalyst impregnation on the char pore structure were examined by COz adsorption and mercury porosimetry. The catalyst uptakes were determined by atomic absorption. Pycnometry tests were also conducted to determine the degree of catalyst penetration during impregnation. Catalyzed and uncatalyzed samples were examined under a scanning electron microscope at both unreacted and partially reacted stages. The experimental results were used to formulate a kinetic model that accounts for the several findings. CONCLUSIONS AND SIGNIFICANCEThe experimental work of this study focused on the degree of catalyst solution penetration that occurs during impregnation of chars. The catalyst uptake was determined as well as the effects of impregnation on the char pore structure. The impregnating solution was found unable to penetrate into the interior pore structure of a char. The deposited catalysts resided mainly on particle exteriors without affecting the pore structure. As a consequence, rapid catalytic reaction occurs on a char's exterior surfaces, reducing particle size, while a slower noncatalytic reaction occurs simultaneously inside the pore structures. The observed reaction rate is then the combination of the contributions from catalytic and noncatalytic mechanisms.From such a physical picture a model was developed for reaction kinetics of catalytic gasification. The model produces an expectation that the enhanced reactivity would be more significant at low levels of conversion, and predicts that the overall rate would decrease to that of the noncatalytic reaction at high conversion. The contributions to the overall reaction rate of catalytic and noncatalytic steps are discussed.

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“…Alas, all these gasification processes are largely noncatalytic [4] and one-quarter of a century later catalytic coal gasification is still ''an emerging technology'' [5]. The most popular entrained-flow Texaco and Shell gasifiers operate at high temperature (>1400 • C) to produce mostly CO and H 2 .…”

Section: Processesmentioning

confidence: 99%

“…A large number of authoritative reviews on the various aspects of catalysis of coal and carbon gasification have been published, especially during the 1980s [1,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The Exxon Catalytic Coal Gasification process [7,26] is a good point of departure both for its practical aspects -it was (and still appears to be) the closest to commercial development [27] -and as a basis for a more fundamental discussion.…”

Section: Processesmentioning

confidence: 99%