Thermal Cracking of Isobutane. Kinetics and Product Distributions

Buekens, Alfons; Froment, Gilbert F.

doi:10.1021/i260039a005

Cited by 15 publications

(5 citation statements)

References 7 publications

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“…Sulfided MoO 3 , in particular, was demonstrated to be catalytically active for isobutane dehydrogenation at 560 °C. However, the reported conversion approached equilibrium values (75%) and may also have been influenced by acid-catalyzed or thermal cracking at these conditions. ,− Therefore, it was not clear from that study whether the high conversions were due to high rates or simply from long reactor contact times. Additionally, the sulfided metal oxide catalysts rapidly deactivated within 1 h on stream, which was ascribed to sulfur loss at these high conversions, making it further challenging to compare these catalysts to others on a rate basis.…”

Section: Introductionmentioning

confidence: 92%

“…This temperature requirement for isobutane decreases even further to 384 °C, owing to its weak, tertiary C–H bond. In undesired side reactions, isobutane can also crack down to propane/propylene and methane . Thus, in addition to its industrial relevance, isobutane is a good probe molecule for investigating activity and selectivity in light alkane dehydrogenation catalysis under relatively accessible conditions.…”

Section: Introductionmentioning

confidence: 99%

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Isobutane Dehydrogenation over Bulk and Supported Molybdenum Sulfide Catalysts

Cheng

McCullough

Noh³

et al. 2019

Ind. Eng. Chem. Res.

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Bulk and supported MoS x materials have gained interest as alternative catalysts for light alkane dehydrogenation, but there is little kinetic data published with which rigorous comparisons can be made to other catalysts. Here, rates, selectivities, and activation barriers are collected under conditions of differential conversion for the dehydrogenation of isobutane over various morphologies of molybdenum sulfide. We find that a "rag-like" MoS 2 composed of small, disordered crystallites exhibits higher catalytic rates than layered, highly crystalline MoS 2 (52 vs 2.7 μmol ks −1 g cat −1 at 360 °C). This is in part not only due to increased surface area but also due to intrinsically more active edge and defect sites exposed by the rag-like structure, as shown by a decrease in apparent activation energy from 61 to 43 kJ mol −1 . Supporting MoS x on metal oxides or metal organic frameworks gives small MoS x clusters that have up to 7-fold higher rates per mass of MoS 2 than even the rag-like MoS 2 . Rates are support-dependent, with the highest rates per mass of MoS 2 observed over MoS x /TiO 2 . Pt/Al 2 O 3 has a ∼50-fold higher rate than the best MoS 2 catalysts (2700 μmol ks −1 g cat −1 at 360 °C), but it has an apparent activation energy of 41 kJ mol −1 , similar to that of the rag-like MoS 2 . Therefore, the rates over MoS 2 appear to be limited by a small number of active sites on the surface, rather than intrinsically poor activity. Given the data provided in this manuscript and the enormous phase space available to metal sulfides, these materials warrant further investigation as alternative light alkane dehydrogenation catalysts, especially for use under conditions that would deactivate a precious metal catalyst.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Isobutane Dehydrogenation over Bulk and Supported Molybdenum Sulfide Catalysts

Cheng

McCullough

Noh³

et al. 2019

Ind. Eng. Chem. Res.

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“…The simplest method would be to use some global criteria based on the observation that the rate of disappearance of reactant tends to be independent of both pressure and surface'to-volume rate of the reactor (Zdonik and Green, 1967;Buekens and Froment, 1971). This can be expressed as depending on a reaction rate which is directly proportional to the concentration of hydrocarbon feed and referred to as first-order kinetics.…”

Section: Kinetics Of the Thermal Crackingmentioning

confidence: 99%

Dynamic model of a pyrolysis furnace

McGreavy

Odloak

1986

Transactions of the Institute of Measurement and Control

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A dynamic model of a pyrolysis furnace is developed which takes account of the lags arising from the reactor coils, the radiation and convection combustion zones and the furnace refractories. The physical problem is analysed to find computational strategies for the numerical solution which overcome the inherent stiffness of the overall system equations. In order to be able to predict the product distribution during transient operation, it is essential to have a mechanistic-type kinetic model for the reactions, and the thermal processes must be capable of predicting the spatial distribution of temperature at any time. An examintion of the minimum level of detail to do this provides valuable insight as to how the observed dynamic responses can be explained in terms of the interaction of the characteristic fundamental processes. From this, it is possible to identify modes of operation which will not result in design limitations being exceeded, and enable safe procedures to be established for start-up and shutdown which can be interpreted in terms of the physicochemical processes.

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“…Isobutane Cracking Buekens and Froment (1971) have proposed a reaction mechanism for isobutane cracking. Recently Bradley (1974) Figure 6.…”

Section: Propane Crackingmentioning

confidence: 99%

“…Reactions leading to the primary products have been discussed by Buekens and Froment (1971). Although small amounts of both propadiene and methyl acetylene are observed, the latter is the more stable compound.…”

Section: Propane Crackingmentioning

confidence: 99%

Modeling of Thermal Cracking Kinetics. 3. Radical Mechanisms for the Pyrolysis of Simple Paraffins, Olefins, and Their Mixtures

Sundaram¹,

Froment²

1978

Ind. Eng. Chem. Fund.

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190

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Radical reaction schemes for the cracking of ethane, propane, normal and isobutane, ethylene, and propylene were set up. The kinetic parameters of these schemes were determined by fitting experimental data obtained under nonisothermal and nonisobaric conditions In a pilot plant. The set of continuity equations for both molecular and radical species was Integrated using Gear's algorithm for stiff differential equations. The reliability of the parameters was tested by simulating the cracking of binary and ternary paraffinic mixtures. A satisfactory fit of the results of mixtures cracking was obtained with a reaction scheme derived from the superposition of the schemes for single-component cracking.

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Thermal Cracking of Isobutane. Kinetics and Product Distributions

Cited by 15 publications

References 7 publications

Isobutane Dehydrogenation over Bulk and Supported Molybdenum Sulfide Catalysts

Isobutane Dehydrogenation over Bulk and Supported Molybdenum Sulfide Catalysts

Dynamic model of a pyrolysis furnace

Modeling of Thermal Cracking Kinetics. 3. Radical Mechanisms for the Pyrolysis of Simple Paraffins, Olefins, and Their Mixtures

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