Catalytic behavior and phase composition change of iron catalyst in hydrogenation of carbon dioxide.

Lee, Min-Dar; Lee, Jyh‐Fu; Chang, Chau-Shang

doi:10.1252/jcej.23.130

Cited by 46 publications

(27 citation statements)

References 13 publications

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“…Iron catalysts are a mixture of magnetite and iron carbide. The results of Lee et al (1990) demonstrated that the reaction rate, product distribution and catalyst change as a function of temperature, pressure and H 2 /CO 2 ratio. Increased pressures lead to increased fractions of Fe 3 O 4 and decreased fractions of Fe 5 C 2 .…”

Section: Discussionmentioning

confidence: 99%

“…The one unresolved issue relates to why alcohol products are formed in greater amounts at elevated pressures. Higher system pressures will change the balance of phases on the catalyst surface (Lee et al, 1990). Equilibrium theory is able to determine the stable phases of a catalyst in equilibrium with a gas of a CHO composition, and it is able to determine the equilibrium composition of a reacting gas mixture.…”

Section: Discussionmentioning

confidence: 99%

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Increased prevalence of semaphorin 3C, a repellent of sympathetic nerve fibers, in the synovial tissue of patients with rheumatoid arthritis

Miller¹,

Weidler²,

Falk³

et al. 2004

Arthritis & Rheumatism

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ObjectiveThe presence of selective sympathetic nerve repellents, i.e., semaphorins, may be responsible for the observed reduction of sympathetic innervation in the synovial tissue of patients with rheumatoid arthritis (RA). This study was undertaken to investigate the presence of different semaphorins in synovial tissue of patients with RA, patients with osteoarthritis (OA), and control subjects without inflammation.MethodsIn situ hybridizations with digoxigenin‐labeled RNA probes directed against different semaphorins were performed. The presence of semaphorin 3C (S3C) in the synovial tissue of 10 RA, 10 OA, and 5 control subjects was investigated using a polyclonal antiserum directed against S3C.ResultsAll in situ hybridizations revealed the presence of S3C messenger RNA, but no other investigated semaphorin (i.e., against primary afferent sensory nerve fibers), in the synovial tissue of RA and OA patients. Immunohistologic double staining demonstrated that macrophages and fibroblasts were positive for S3C protein. Quantitative analysis of S3C protein staining showed an increased density of S3C‐positive cells in the synovial tissue of RA patients (mean ± SEM 339 ± 65 cells/mm2) in comparison with OA patients (168 ± 27/mm2; P = 0.031 versus RA) and controls (126 ± 26/mm2; P = 0.027 versus RA). Studies of the relationship between sympathetic nerve fiber density and S3C‐positive cell density in the tissue of all patients showed that RA patients generally had lower densities of sympathetic nerve fibers and higher densities of S3C‐positive cells than OA patients and control subjects.ConclusionThese findings suggest that S3C from macrophages and fibroblasts, which is selectively directed against sympathetic nerve fibers, could be one element responsible for reduced sympathetic innervation in RA tissue. The inability of sympathetic nerve fibers to reinnervate synovial tissue could contribute to the chronic nature of RA.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Increased prevalence of semaphorin 3C, a repellent of sympathetic nerve fibers, in the synovial tissue of patients with rheumatoid arthritis

Miller¹,

Weidler²,

Falk³

et al. 2004

Arthritis & Rheumatism

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“…The results of Lee et al (1990) demonstrated that the reaction rate, product distribution and catalyst change as a function of temperature, pressure and H 2 /CO 2 ratio. Increased pressures lead to increased fractions of Fe 3 O 4 and decreased fractions of Fe 5 C 2 .…”

Section: Iron-based Catalystsmentioning

confidence: 95%

“…Higher system pressures will change the balance of phases on the catalyst surface (Lee et al, 1990). Equilibrium theory is able to determine the stable phases of a catalyst in equilibrium with a gas of a CHO composition, and it is able to determine the equilibrium composition of a reacting gas mixture.…”

Section: Limitations On the Equilibrium Approachmentioning

confidence: 99%

Notes on the issues of equilibrium in the Fischer–Tropsch synthesis

Norval

2008

Can J Chem Eng

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The product distribution for the Fischer-Tropsch synthesis is normally described using the kinetically derived (Anderson-Schultz-Flory) ASF model. Variations of the kinetic model have been proposed to explain deviations from the ASF distribution. The Fischer-Tropsch system can be equally well described using a pseudo-element (CH 2 , H 2 , O) equilibrium approach. A one-parameter equilibrium model is derived for the product distributions for alkenes, alkanes and alcohols.The Fischer-Tropsch system should be considered as three separate partial equilibria systems: the product homologous series; the water gas shift system, and the redox behaviour of the catalyst with the H 2 /O ratio of the gas. This approach correctly predicts the impacts of changes in a variety of parameters (temperature pressure, feed composition) on the ASF product distribution. In addition, the catalyst phase changes with gas composition and pressure, indicative of an equilibrium response. Equilibrium is of much greater importance to the Fischer-Tropsch system than previously thought, and the decision to use a complex kinetics-based model rather than a simpler equilibrium based model should be taken with care.La distribution de produits dans la synthèse Fischer-Tropsch est normalement décrite par le modèle ASF (Anderson-Schultz-Flory)établi par la cinétique. Des variations du modèle cinétique sont proposées pour expliquer lesécarts par rapportà la distribution de l'ASF. Le système FischerTropsch peutêtre aussi bien décrit par la méthode deséquilibres de pseudo-éléments (CH 2 , H 2 , O). Un modèle d'équilibreà un paramètre est etabli pour la distribution des alcènes, alcanes et alcools. Le système Fischer-Tropsch devraitêtre considéré comme 3 systèmes d'équilibres partiels séparés: la série homologue de produits, le système de conversion eau-gaz et le comportement redox du catalyseur avec le rapport H 2 :O du gaz. Cette approche prédit correctement l'impact des changements sur plusieurs paramètres (température, pression, composition de l'alimentation) sur la distribution de produits de l'ASF. En outre, la phase du catalyseur change avec la composition du gaz et la pression, indiquant une réactioǹ a l'équilibre. L'équilibre est d'une importance beaucoup plus grande pour le modèle Fischer-Tropsch que ce qu'on pensait, et la décision d'utiliser un modèle complexe basé sur la cinétique plutôt que basé sur deséquilibres plus simple devraitêtre soigneusement pesée.

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“…In addition, the olefin/paraffin ratio in the C2-C4 fraction decreased, indicating the conversion dependence of selectivity over all catalysts (Amelse et a]., 198 1 ;Novak et al, 1982;Arcuri et al, 1984;Lee et al 1990). In addition, the olefin/paraffin ratio in the C2-C4 fraction decreased, indicating the conversion dependence of selectivity over all catalysts (Amelse et a]., 198 1 ;Novak et al, 1982;Arcuri et al, 1984;Lee et al 1990).…”

Section: Reductionmentioning

confidence: 96%

Hydrogenation of carbon dioxide on iron catalysts doubly promoted with manganese and potassium

et al. 1992

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The effect of addition of manganese and potassium promoters onto iron catalysts for hydrogenation of carbon dioxide was investigated. Catalyst characterizations were performed using BET surface area measurement, carbon monoxide chemisorption, temperature-programmed reduction and Mossbauer spectroscopy. It was noted that metallic iron catalysts were carburized to 0-Fe,C and x-FeSC, as well as oxidized to Fe30, during the course of reaction. The promotional effect of manganese was reflected in stabilization of catalytic behavior owing to a higher resistance to bulk oxidation.However, the distribution of hydrocarbon products did not change significantly in the presence of manganese promoter.With further addition of potassium promoter, the bulk phase was more likely to transform to carbides, and the selectivity toward olefins and long-chain hydrocarbons was remarkably enhanced.On a itudik I'effet de I'ajout de promoteurs au manganbse et potassium sur des catalyseurs de fer pour I'hydrogination du gaz carbonique. La caractkrisation des catalyseurs a etk realiske par une mesure BET de la zone de surface, la chimisorption de I'oxyde de carbone, une reduction i tempkrature programmke et la spectroscopie Mossbauer. On a remarquk que les catalyseurs de fer mttallique sont ckmentks en 0-Fe,C et X-Fe,C2 et qu'ils sont oxydes en Fe,O, lors de la rkaction. L'effet promotionnel du manganbse se reflkte dans la stabilisation du comportement catalytique en raison d'une plus haute rksistance B I'oxydation en masse. Cependant, la distribution des hydrocarbures ne change pas de facon significative en prksence du promoteur au manganbse. Avec un nouvel ajout de promoteur de potassium. la phase principale est plus susceptible de se transformer en carbures, et la selectivitk vers les olefines et les hydrocarbures de chaines longues est remarquablement amkliorke.

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Catalytic behavior and phase composition change of iron catalyst in hydrogenation of carbon dioxide.

Cited by 46 publications

References 13 publications

Increased prevalence of semaphorin 3C, a repellent of sympathetic nerve fibers, in the synovial tissue of patients with rheumatoid arthritis

Increased prevalence of semaphorin 3C, a repellent of sympathetic nerve fibers, in the synovial tissue of patients with rheumatoid arthritis

Notes on the issues of equilibrium in the Fischer–Tropsch synthesis

Hydrogenation of carbon dioxide on iron catalysts doubly promoted with manganese and potassium

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