Conversion in Chemical Reactors using Hollow Cylindrical Catalyst Pellet
Heterogeneous catalysis is vital for a number of
chemical, refinery and pollution control processes. The use of
catalyst pellets of hollow cylindrical shape provide several distinct
advantages over other common shapes, and can therefore help to
enhance conversion levels in reactors. A better utilization of the
catalytic material is probably most notable of these features due to
the absence of the pellet core, which helps to significantly lower the
effect of the internal transport resistance. This is reflected in the
enhancement of the effectiveness factor. For the case of the first order
irreversible kinetics, a substantial increase in the effectiveness factor
can be obtained by varying shape parameters. Important shape
parameters of a finite hollow cylinder are the ratio of the inside to the
outside radii (κ) and the height to the diameter ratio (γ). A high value
of κ the generally helps to enhance the effectiveness factor. On the
other hand, lower values of the effectiveness factors are obtained
when the dimension of the height and the diameter are comparable.
Thus, the departure of parameter γ from the unity favors higher
effectiveness factor. Since a higher effectiveness factor is a measure
of a greater utilization of the catalytic material, higher conversion
levels can be achieved using the hollow cylindrical pellets possessing
optimized shape parameters.
[1] Mars, P. and Gorgels, M. J., 1964, Hydrogenation of acetylene -a theory
of selectivity. In Chemical Reaction Engineering: Proceedings of the
Third European Symposium, Supplement to Chem. Eng. Sci., pp. 55-65.
Oxford: Pergamon Press.
[2] Michalko, E., 1966a, Method for oxidizing gaseous combustible waste
products, U.S. Patent 3,259,454.
[3] Michalko, E.,1966b, Preparation of catalyst for the treatment of
combustible waste products, U.S. Patent 3,259,589.
[4] Kasaoka, S. and Sakata, Y., 1968, Effectiveness factors for non-uniform
catalyst pellets, J. Chem. Eng. Japan 1: 138-142.
[5] Villadsen, J. and Michelsen, M.J., 1978, Solution of Differential
Equations Models by Polynomial Approximation, Prentice-Hall, New
Jersey
[6] Becker, E. R. and Wei, J., 1977, Non-uniform distribution of catalysts
on supports. Bimolecular Langmuir reactions, J. Catal. 46: 365-371.
[7] Juang, H.-D. and Weng, H.-S., 1983. Performance of catalysts with nonuniform
activity profiles 2. Theoretical analysis for non-isothermal
reactions. Ind. Eng. Chem. Fundam. 22: 224-230.
[8] Johnson, D. L., and Verykios, X. E., 1983, Selectivity enhancement in
ethylene oxidation employing partially impregnated catalysts, J. Catal.
79: 156-163.
[9] Johnson, D. L., and Verykios, X. E., 1984, Effects of radially nonuniform
distributions of catalytic activity on performance of spherical
catalyst pellets, AI.ChEJ. 30: 44-50.
[10] Morbidelli, M., Servida, A. and Varma, A., 1982, Optimal catalyst
activity profiles in pellets 1. The case of negligible external mass
transfer resistance, Ind. Eng. Chem. Fundam. 21: 278-284.
[11] Morbidelli, M., Gavriilidis, A. and Varma, A., 2001, Catalyst design,
Optimal distribution of catalyst in pellets, reactors and membranes,
Cambridge University Press, Cambridge, UK.
[12] Wu, H., Brunovska, A., Morbidelli, M. and Varma, A., 1990, Optimal
catalyst activity profiles in pellets VIII. General nonisothermal reacting
systems with arbitrary kinetics, Chem. Eng. Sci. 45: 1855-1862; 46:
3328-3329.
[13] Baratti, R., Gavriilidis, A., Morbidelli, M., and Varma, A., 1994,
Optimization of a non-isothermal non-adiabatic fixed-bed reactor using
Dirac-type silver catalysts for ethylene epoxidation, Chem. Eng. Sci. 49:
1925-1936
[14] Hwang, S., Linke, P. and Smith, R., 2004, Heterogeneous catalytic
reactor design with optimum temperature profile II: application o nonuniform
catalyst, Chem. Eng. Sci. 59: 4245-4260.
[15] Armor, J.N., 2005, Do you really have a better catalyst? Appl. Catal. A:
General 282: 1-4.
[16] Khanaev, V.M., Borisova, E.S. and Noskov, A.S., 2004, Optimization of
the active component through the catalyst bed, Chem. Eng. Sci. 59:
1213-1220.
[17] Macias, M.J. and Ancheyta, J., 2004, Simulation of an isotheral hydrodesulfurization
small reactor with different catalyst particle shapes,
Catalysis Today, 98: 243-252.
[18] Buffham, B.A., 2000a, Design relations for hollow catalyst pellets,
Chem. Eng. Res. Des. 78 Part A: 269-282.
[19] Buffham, B. A., 2000b, The size and compactness of particle of arbitrary
shape: application to catalyst effectiveness factor, Chem. Eng. Sci. 55:
5803- 5811.
[1] Mars, P. and Gorgels, M. J., 1964, Hydrogenation of acetylene -a theory
of selectivity. In Chemical Reaction Engineering: Proceedings of the
Third European Symposium, Supplement to Chem. Eng. Sci., pp. 55-65.
Oxford: Pergamon Press.
[2] Michalko, E., 1966a, Method for oxidizing gaseous combustible waste
products, U.S. Patent 3,259,454.
[3] Michalko, E.,1966b, Preparation of catalyst for the treatment of
combustible waste products, U.S. Patent 3,259,589.
[4] Kasaoka, S. and Sakata, Y., 1968, Effectiveness factors for non-uniform
catalyst pellets, J. Chem. Eng. Japan 1: 138-142.
[5] Villadsen, J. and Michelsen, M.J., 1978, Solution of Differential
Equations Models by Polynomial Approximation, Prentice-Hall, New
Jersey
[6] Becker, E. R. and Wei, J., 1977, Non-uniform distribution of catalysts
on supports. Bimolecular Langmuir reactions, J. Catal. 46: 365-371.
[7] Juang, H.-D. and Weng, H.-S., 1983. Performance of catalysts with nonuniform
activity profiles 2. Theoretical analysis for non-isothermal
reactions. Ind. Eng. Chem. Fundam. 22: 224-230.
[8] Johnson, D. L., and Verykios, X. E., 1983, Selectivity enhancement in
ethylene oxidation employing partially impregnated catalysts, J. Catal.
79: 156-163.
[9] Johnson, D. L., and Verykios, X. E., 1984, Effects of radially nonuniform
distributions of catalytic activity on performance of spherical
catalyst pellets, AI.ChEJ. 30: 44-50.
[10] Morbidelli, M., Servida, A. and Varma, A., 1982, Optimal catalyst
activity profiles in pellets 1. The case of negligible external mass
transfer resistance, Ind. Eng. Chem. Fundam. 21: 278-284.
[11] Morbidelli, M., Gavriilidis, A. and Varma, A., 2001, Catalyst design,
Optimal distribution of catalyst in pellets, reactors and membranes,
Cambridge University Press, Cambridge, UK.
[12] Wu, H., Brunovska, A., Morbidelli, M. and Varma, A., 1990, Optimal
catalyst activity profiles in pellets VIII. General nonisothermal reacting
systems with arbitrary kinetics, Chem. Eng. Sci. 45: 1855-1862; 46:
3328-3329.
[13] Baratti, R., Gavriilidis, A., Morbidelli, M., and Varma, A., 1994,
Optimization of a non-isothermal non-adiabatic fixed-bed reactor using
Dirac-type silver catalysts for ethylene epoxidation, Chem. Eng. Sci. 49:
1925-1936
[14] Hwang, S., Linke, P. and Smith, R., 2004, Heterogeneous catalytic
reactor design with optimum temperature profile II: application o nonuniform
catalyst, Chem. Eng. Sci. 59: 4245-4260.
[15] Armor, J.N., 2005, Do you really have a better catalyst? Appl. Catal. A:
General 282: 1-4.
[16] Khanaev, V.M., Borisova, E.S. and Noskov, A.S., 2004, Optimization of
the active component through the catalyst bed, Chem. Eng. Sci. 59:
1213-1220.
[17] Macias, M.J. and Ancheyta, J., 2004, Simulation of an isotheral hydrodesulfurization
small reactor with different catalyst particle shapes,
Catalysis Today, 98: 243-252.
[18] Buffham, B.A., 2000a, Design relations for hollow catalyst pellets,
Chem. Eng. Res. Des. 78 Part A: 269-282.
[19] Buffham, B. A., 2000b, The size and compactness of particle of arbitrary
shape: application to catalyst effectiveness factor, Chem. Eng. Sci. 55:
5803- 5811.
@article{"International Journal of Chemical, Materials and Biomolecular Sciences:55880", author = "Mohammad Asif", title = "Conversion in Chemical Reactors using Hollow Cylindrical Catalyst Pellet", abstract = "Heterogeneous catalysis is vital for a number of
chemical, refinery and pollution control processes. The use of
catalyst pellets of hollow cylindrical shape provide several distinct
advantages over other common shapes, and can therefore help to
enhance conversion levels in reactors. A better utilization of the
catalytic material is probably most notable of these features due to
the absence of the pellet core, which helps to significantly lower the
effect of the internal transport resistance. This is reflected in the
enhancement of the effectiveness factor. For the case of the first order
irreversible kinetics, a substantial increase in the effectiveness factor
can be obtained by varying shape parameters. Important shape
parameters of a finite hollow cylinder are the ratio of the inside to the
outside radii (κ) and the height to the diameter ratio (γ). A high value
of κ the generally helps to enhance the effectiveness factor. On the
other hand, lower values of the effectiveness factors are obtained
when the dimension of the height and the diameter are comparable.
Thus, the departure of parameter γ from the unity favors higher
effectiveness factor. Since a higher effectiveness factor is a measure
of a greater utilization of the catalytic material, higher conversion
levels can be achieved using the hollow cylindrical pellets possessing
optimized shape parameters.", keywords = "Finite hollow cylinder, Catalyst pellet, Effectiveness
factor, Thiele Modulus, Conversion", volume = "6", number = "2", pages = "161-6", }