Mass transfer effects in surface catalysis

Ford, F. E.; Perlmutter, David D.

doi:10.1002/aic.690090319

Cited by 11 publications

(5 citation statements)

References 14 publications

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“…The initial portions of the plots show appreciable dependence of conversion on stirrer speed due to imperfect mixing and/or interfacial mass transfer resistances between the gas and catalyst phases, which is considered in the next section. It can be seen that the minimum speed required to eliminate mass transfer resistance (homogeneous and heterogeneous) is higher at higher temperatures, which is in agreement with the observation of Ford (1963). From Figure 2 the mass transfer resistances appear to be negligible above 1500 rpm.…”

Section: Mass (And Heat) Transfersupporting

confidence: 86%

“…However, none of these methods can be considered as conclusively indicative of the absence of the mass transfer effect. A yes-or-no decision based on the flatness of the conversion-stirrer speed curve is questionable, as pointed out by Ford and Perlmutter (1963), who observed that mass transfer effects which have been found negligible by these two methods could lead to values of Ap/pg as high as 150% (as against zero in the absence of mass transfer), when this effect is computed by a more rigorous proce- Plots of log r' (where r' has units of w') vs. log w' were prepared at different temperatures; the slope d log r'/d log w' (and therefore the ratio Ap/pg) approaches zero asymptotically as the stirrer speed is increased. Ap/pg was calculated from eq 4 for a series of stirrer speeds and plots were prepared to show the variation of this ratio with the stirrer speed.…”

Section: Mass (And Heat) Transfermentioning

confidence: 99%

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A Kinetic Model for the Isomerization of n-Butene to Isobutene

Choudhary¹,

Doraiswamy²

1975

Ind. Eng. Chem. Proc. Des. Dev.

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Section: Mass (And Heat) Transfersupporting

confidence: 86%

Section: Mass (And Heat) Transfermentioning

confidence: 99%

A Kinetic Model for the Isomerization of n-Butene to Isobutene

Choudhary¹,

Doraiswamy²

1975

Ind. Eng. Chem. Proc. Des. Dev.

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“…Runs with three different catalyst sizes (-70 to +80, -80 to +100, -100 to +120 mesh) under identical conditions yielded only marginal differences in overall conversion, and thus it was established that for the particle size (-70 to +80 mesh) employed in the kinetic runs pore diffusion effects were not prevalent. The method of Ford and Perlmutter (1963) was employed to check the partial pressure gradient AP/Pg and establish that for the runs in the present study AP/Pg was not appreciable, thus showing the absence of external mass transfer effects.…”

Section: Reaction Systemmentioning

confidence: 85%

Dilution of catalyst in a fluidized bed. Dehydration of ethanol

Irani¹,

Kulkarni²,

Doraiswamy³

et al. 1982

Ind. Eng. Chem. Proc. Des. Dev.

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I 5 6 7 3 9 1 0 1 1 !2 Catalyst loaalng x 10' 4 gm mi-' Figure 3. Effect of catalyst loading on reaction rate. expression (Table 111). A few experiments were also done varying the initial concentration of o-nitroaniline and the values of the specific reaction rate were observed to be essentially constant. Thus it appears that the kinetic data could be correlated by an empirical rate expression: r = Effect of Temperature. The temperature of the reaction was varied from 47 to 74 "C. The rate of the reaction increased significantly with the increase in temperature. The apparent activation energy was found to be 13.0 kcal/mol (Figure 2). kCN COMMUNICATIONSEffect of Catalyst Loading. The catalyst loading was varied from 0.484 to 1.21 g/L at 69 "C, keeping the initial concentration of o-nitroaniline and hydrogen partial pressure at 0.701 M and 961.1 kN/m2, respectively ( Figure 3). As expected, the reaction rate was found to increase linearly with the catalyst loading. AcknowledgmentOne of the authors (P.B.K) would like to thank University Grants Commission for award of a research fellowship. Nomenclature CN = concentration of o-nitroaniline, mol/mL k = rate constant, s-l r = rate of reaction, mol/mL s I = fraction of o-nitroaniline converted into o-phenylenedi- Literature CitedAcres, G. The dehydration of ethanol over alumina is studied in an integral(plug flow) and undiluted and diluted fluid bed reactors. At any given conversion level the Selectivity of the intermediate (ether) is always higher for the plug flow reactor than for the fluid bed reactor. Catalyst dilution in the fluid bed keeping residence time unaltered is seen to result in an increase in the formation of intermediate ether without a majar fall in overall conversion. Thus dilution of catalyst results in an improvement in the selectivity of intermediate without affecting the other useful features of fluid bed operation. An optimum catalyst dilution R' (mass of catalyst in the undiluted bed/mass of catalyst in the diluted bed) = 3.67 is shown to exist for the parameter values employed, such that intermediate formation at the bed exit is maximum.

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“…However, none of these methods can be considered conclusively indicative of the absence of the mass transfer effect. A yes-or-no decision based on the flatness of the conversion-velocity curve is questionable, as pointed out by Ford and Perlmutter (1963), who observed that mass 150£7 (as against zero in the absence of mass transfer), when this effect is computed by a more rigorous procedure. By equating the rates of mass transfer and chemical reaction under conditions of steady state, they derived the equation…”

Section: Diffusional Resistancesmentioning

confidence: 99%