Heterogeneous catalytic reactors undergoing chemical deactivation. Part I: Deactivation kinetics and pellet effectiveness

Lee, H. H.; Butt, John

doi:10.1002/aic.690280307

AIChE Journal

1982

DOI: 10.1002/aic.690280307

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Heterogeneous catalytic reactors undergoing chemical deactivation. Part I: Deactivation kinetics and pellet effectiveness

H. H. Lee

John Butt

Abstract: Greek Letters= pressure drop across a screen layer = pressure drop across a clean screen layer = density of gas = density of particle = initial single fiber efficiency = single fiber efficiency for the k-th layer screen = time = gas viscosity LITERATURE CITED Davies, C. N., "Air Filtration," Academic Press (1973). Dyment, J., "Theory and Practice in Air Filtration," Depositton and Fdtration of

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Cited by 12 publications

References 10 publications

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Approximate global rates: Reactions affected by diffusion and chemical deactivation

Lee¹

1983

AIChE Journal

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atoms is relatively hindered due to stenc reasons. One would expect that 0 2 develops a rounded pit in the early stage which leads to a circular pit. When tungsten carbide is present on the surface, 0 atoms are expected to be present near the surface because tungsten carbide is effective in dissociating 0 2 . It might involve an oxygen spillover process similar to the hydrogen spillover phenomenon (Levy and Boudart, 1974). With 0 atoms the steric factor should not be important and indeed hexagonal pits are formed by 0 atoms from the gas phase (Wong et al., 1983). A spillover mechanism was earlier proposed for chrornia catalyzed carbon oxidation (McKee, 1970 Baker, 1981. A further for the tungsten being in the form of tungsten carbide is that any metallic tungsten would have been oxidized, at least on the surface layers, under our conditions, and tungsten oxide behaves very differently in its catalytic activity. Our results on WOs catalyzed carbon oxidation will be reported shortly.The orientation of the hexagonal etch pits has been determined by in situ 4ectron diffraction using TEM. All sides of the pits are in the (1,010) direction i.e., they are zigzag surfaces, which is the orientation shown in Figure 4, as well as the orientation of the hexagonal pits etched by 0 atoms (Wong et al., 1983). Deep pits created by catalyst particles are mostly circular, but in a few cases hexagonal, e.g., by Fez03 (Thomas, 1965;McKee, 1970). The mechanism proposed here may also be operative in deep pits formation.

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Approximate global rates: Reactions affected by diffusion and chemical deactivation

Lee¹

1983

AIChE Journal

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Fixed bed with catalyst deactivation: On‐line estimation of deactivation, control, and design

Hong

Lee

1985

AIChE Journal

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On-line measurements of temperature and concentration and the global rate for fresh catalyst can be used to estimate a measure of catalyst deactivation. A feedback control policy is obtained from this ineasure of catalyst deactivation for maintaining the reactor outlet conversion constant with time at a desired level. This feedback control enables one to maintain the desired conversion without any knowledge of deactivation kinetics. 'These results are applicable to any type of deactivation. The optimal control can easily be taken into consideration for reactor design. This combination of process design and control with due consideration of catalyst deactivation for both is shown to result in a substantial improvement of the reactor performance.

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Catalyst pellet with unsymmetrical shell-progressive deactivation

Cho

Lee

1992

Chemical Engineering Science

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Heterogeneous catalytic reactors undergoing chemical deactivation. Part I: Deactivation kinetics and pellet effectiveness

Cited by 12 publications

References 10 publications

Approximate global rates: Reactions affected by diffusion and chemical deactivation

Approximate global rates: Reactions affected by diffusion and chemical deactivation

Fixed bed with catalyst deactivation: On‐line estimation of deactivation, control, and design

Catalyst pellet with unsymmetrical shell-progressive deactivation

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