Application of equilibrium analysis to a Fischer-Tropsch product

Norval, Graeme W.; Phillips, M. J.

doi:10.1016/0021-9517(90)90048-o

Cited by 15 publications

(25 citation statements)

References 7 publications

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“…The Fischer-Tropsch process is usually defined by chemical equations such as Norval and Phillips (1990), demonstrated that an equilibrium approach gave the equations: (Alberty, 1983;Alberty and Gehrig, 1984;Alberty et al, 1987). There is no requirement that the components of a system be the chemical elements; the sole requirement is that the components be linearly independent and satisfy the material balance requirements of the formula matrix (Smith and Missen, 1982).…”

Section: Derivationmentioning

confidence: 99%

“…In essence, this approach implies a stoichiometric restriction to an equilibrium system (Norval et al, 1992). Norval and Phillips (1990) demonstrated that an equation relating equilibrium concentration and carbon number could be derived from thermodynamics. The equation has the same form as that of the Anderson-Schultz-Flory (ASF) product distribution, albeit with a two parameter model-the two parameters being the chemical potentials of C and H in the system.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Derivationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Norval

2008

Can J Chem Eng

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“…Norval and Phillips (1990), demonstrated that an equilibrium approach gave the equations: where $\Psi _{{\rm Cp}}$ , $\Psi _{{\rm Hp}}$ , $\Psi _{{\rm Co}}$ , $\Psi _{{\rm Ho}}$ are the Lagrange multipliers for carbon and hydrogen in the paraffin, alkene and alcohol series, respectively. The constants $A'_{\rm p}$ , $B'_{\rm p}$ , $A'_{\rm o}$ , $B'_{\rm o}$ , $A'_{\rm a}$ , and $B'_{\rm a}$ are the values of the constants for the free energies of formations of the alkane, alkene, and alcohol homologous series (Alberty, 1983; Alberty and Gehrig, 1984; Alberty et al, 1987).…”

Section: Derivationmentioning

confidence: 99%

“…Norval and Phillips (1990) demonstrated that an equation relating equilibrium concentration and carbon number could be derived from thermodynamics. The equation has the same form as that of the Anderson–Schultz–Flory (ASF) product distribution, albeit with a two parameter model—the two parameters being the chemical potentials of C and H in the system.…”

Section: Introductionmentioning

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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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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“…Typical high of CH 4 --+ (C) in methane and low ethane mole functions are correctly predicted. Similar calculations have been recently given by Norval [6]. These calculations do not represent equilibrium, since the interaction of the hydrocarbons with the CO, COb H 2 and H 2 0 in Most attempts to explain Fischer-Tropsch synthesis have con-the gas phase are deliberately avoided.…”

Section: Symbolsmentioning

confidence: 91%

Thermodynamically Controlled Catalysis: Equilibria in Fischer-Tropsch Synthesis

Bell¹

1995

Canadian Metallurgical Quarterly

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Previous treatments of the thermodynamic equilibria in Fischer-Tropsch synthesis have ignored the thermodynamic properties of the catalyst. When the assumption is made that the metal is the catalyst, the oxidation state of the gas is fixed at the Pco)Pco ratio, at which the metal catalyst oxidizes. Thermodynamic equilibria show that only cobalt and iron have P CO 2 to P CO ratios, required to maintain the catalyst element as metal, that permit longer chain hydrocarbons to form. Nickel has a higher Peo)P co ratio, so that only methane is a stable synthesis product, and nickel is therefore only a methanation catalyst. Thermodynamic equilibria predict the correct operating temperatures and pressures for Fischer-Tropsch synthesis on cobalt and iron catalysts. Thermodynamic equilibria also predict linear ASF plots with characteristic high methane and low ethane values. All of the extensive database of Sarup and W ojciechowski for synthesis on a cobalt catalyst is predicted by thermodynamic equilibria with a L\Ffor formation of hydrogen in cobalt being a simple linear function of the square root of the final hydrogen pressure. X t1F* t1F**

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Application of equilibrium analysis to a Fischer-Tropsch product

Cited by 15 publications

References 7 publications

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

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

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

Thermodynamically Controlled Catalysis: Equilibria in Fischer-Tropsch Synthesis

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