Variables affecting activity of molybdena-alumina hydroforming catalyst in aromatization of cyclohexane

Rudershausen, C.G.; Watson, C. C.

doi:10.1016/0009-2509(54)80016-9

Cited by 33 publications

(8 citation statements)

References 4 publications

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“…Since catalyst decay is largely a result of the carbon formation, it is strongly related to catalyst-to-oil contact time. Voorhies' basic conclusions were subsequently verified by Rudershausen and Watson (1954) and Prater and Lago (1956) in studies of cyclohexane and cumene cracking, respectively. Appelby (1962) studied the chemistry of coke formation for a variety of aromatic, naphthenic, and paraffinic hydrocarbons and showed that carbon formation resulted primarily from aromatic condensation and hydrogen elimination reactions.…”

Section: Scopementioning

confidence: 81%

A lumping and reaction scheme for catalytic cracking

et al. 1976

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A predictive kinetic model has been developed for fluid catalytic cracking (FCC). The kinetic scheme involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions. The kinetic model also incorporates the effect of nitrogen poisoning, aromatic ring adsorption, and time dependent catalyst decay. The rate constants for these lumped species are invariant with respect to charge stock composition. The predictive capabilities of the model have been verified for wide ranges of charge stocks and process conditions.In this work, a wide variety of charge stocks were cracked in a fluidized dense-bed reactor. Detailed analysis of the molecular compositions of the charge stocks and products provided the necessary data to develop a predictive kinetic model. Rate constants and activation energies were calculated for lumped species including paraffins, naphthenes, aromatic rings, and aromatic substituent groups. The reliability of the kinetic predictions for various charge stocks over a wide range of process conditions has been shown. CONCLUSIONS AND SIGNIFICANCEThe reaction kinetics of catalytic cracking is presented, based on a reaction scheme that includes paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions. The kinetic model also accounts for nitrogen poisoning, aromatic adsorption, and time dependent catalyst decay. The conversion of Gross.Correspondence concerning this paper should be addressed to Benjamin these lumped species to gasoline, light products, coke, heavy fuel oil, and light fuel oil can be readily calculated by these kinetics. In addition, the detailed composition of the heavy and light fuel oil fractions can be tracked, increasing the utility of the model for predicting recycle behavior and physical properties of the products. The invariant kinetic parameters (rate constants and activation energies) allow the conversion and product selectiv-dimensions and operating conditions for maximum thermal efficiency and/or McGill University minimum operating cost. Application of these basic principles is illustrated Montreal, Quebec by the design of an industrial size, spray drying chamber for a specific feed solution and production rate. SCOPEThe growing importance of spray drying is abundantly evident from the ever increasing number of industrial applications in the production of pharmaceuticals, detergents, food products, pigments, ceramics, and a large number of organic and inorganic chemical compounds. In sylvania.

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Section: Scopementioning

confidence: 81%

A lumping and reaction scheme for catalytic cracking

et al. 1976

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“…A similar mechanism for coke deposition during the aromatization of cyclohexane on a molybdena-alumina catalyst has also been suggested by Rudershausen and Watson. 23 Trimm" has mentioned also that hydrocarbons tend to split out hydrogen over nickel and unsaturated hydrocarbons are likely intermediates for coke formation. Another possibility is that benzene increases the deactivation rate by affecting the concentration of other coke precursors such as cyclohexadiene which has been postulated as an intermediate in this reaction.21 Since the rate of deactivation was virtually independent of the cyclohexane partial pressure, the deactivation rate data were modelled using the following expression da k,, exp( -Ed/RT)pFad _--dt + KHdpk Initially, KHd was assumed to vary exponentially with temperature; however, the calculated activation energy was not significant at the 95 % confidence level and therefore KH, was assumed to be independent of temperature.…”

Section: Kinetics Of Deactivationmentioning

confidence: 99%

Cyclohexane dehydrogenation on a nickel catalyst: Kinetics and catalyst fouling

Al-Ayed

Kunzru

1988

J of Chemical Tech & Biotech

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The main reaction and deactivation kinetics of cyclohexane dehydrogenation in the presence of hydrogen has been investigated at atmospheric pressure over a nickel kieselguhr catalyst in the temperature range 583–623 K. The rate of reaction for the fresh catalyst increased with increasing temperature, cyclohexane and hydrogen partial pressures whereas it decreased with an increase in the benzene partial pressure. The experimental data could be adequately modelled by a power law rate expression. The catalyst activity decreased with run time due to catalyst fouling by coke deposition. The rate of deactivation was independent of cyclohexane partial pressure, increased with increasing benzene concentration and decreased with increasing hydrogen partial pressure. It is postulated that coke is most likely formed by the successive dehydrogenation of benzene.

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“…Over the years, Voorhies's work gained increasing support as evidenced by the number of investigators that have reported a good agreement between (1) and experimentally measured coke deposition rates (e.g., Rudershausen and Watson, 1954;Prater and Lago, 1956;Wilson and Den Herder, 1958;Andrews, 1959;Butt et al, 1975). Over the years, Voorhies's work gained increasing support as evidenced by the number of investigators that have reported a good agreement between (1) and experimentally measured coke deposition rates (e.g., Rudershausen and Watson, 1954;Prater and Lago, 1956;Wilson and Den Herder, 1958;Andrews, 1959;Butt et al, 1975).…”

Section: Introductionmentioning

confidence: 95%

Analysis of zeolite catalyst deactivation during catalytic cracking reactions

Reyes¹,

Scriven²

1991

Ind. Eng. Chem. Res.

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Herman, R. G.; Klier, K. Reaction Kinetics of the Higher Alcohol and Oxygenate Synthesis over Cesium Doped Cu/ZnO Catalysta. Znd. Eng. Chem. Res. 1990, to be submitted. Tronconi, E.; Ferlazzo, N.; Forzatti, P.; Pasquon, I. Synthesis ofCatalyst deactivation during cracking reactions is analyzed in terms of the physical, chemical, and transport processes taking place within zeolite crystals. Special attention is given to the interactions of zeolite morphology and the wide range of components present in a typical cracking feed. By analyzing the functional form of activity decays, obtained via a detailed model of adsorption, diffusion, and reaction, it is possible to identify three regimes of deactivation. These can be classified as dynamical, chemical, and structural. They dominate the shape of the activity decay curves at short, intermediate, and longer times, and are related to competitive adsorption, site coverage, and pore blockage phenomena, respectively. The model predicts the correct activity patterns under a wide variety of reaction conditions, closely mimics those observed experimentally, and spans those obtained from available empirical correlations.0888.58851 91 / 2630-0071$02.50/0 -0 1991 American Chemical Societv

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Variables affecting activity of molybdena-alumina hydroforming catalyst in aromatization of cyclohexane

Cited by 33 publications

References 4 publications

A lumping and reaction scheme for catalytic cracking

A lumping and reaction scheme for catalytic cracking

Cyclohexane dehydrogenation on a nickel catalyst: Kinetics and catalyst fouling

Analysis of zeolite catalyst deactivation during catalytic cracking reactions

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