The decomposition of NO into N2 and O2 occurs via elementary steps consisting of: (1) quasi-equilibrated molecular adsorption of NO; (2) irreversible dissociation of adsorbed NO by interaction with a neighboring free site; (3) irreversible recombination of adsorbed N atoms to form N2; and (4) quasi-equilibrated desorption of adsorbed O atoms to form 02. The reaction is catalyzed within porous catalytic pellets of slab geometry (thickness = 2L). a) Write the mechanism of the reaction with the stoichiometric number of each step. b) Derive the rate expression in terms of constants and measurable quantities, assuming O* is the MARI/MASI. c) The steady-state condition for the porous slab is shown below (A=NO): Саб Bulk BL CATALYS SLAB BL Bulk CAB2 САБ At high oxygen pressures, the concentration of oxygen can be assumed as constant and lumped into the rate constant, leaving the reaction rate as first order in (NO). Assume that the internal effectiveness factor in the catalyst slab is 0.2. There is an external film boundary layer and the concentration of NO at the surface of the slab (CAb/2) is half of the bulk NO concentration (CAb). If the ratio of the mass transfer coefficient in the external boundary layer (kc) to the effective first-order rate constant (keff) is 0.01 cm, what is the thickness (2L) of the slab?
The decomposition of NO into N2 and O2 occurs via elementary steps consisting of: (1) quasi-equilibrated molecular adsorption of NO; (2) irreversible dissociation of adsorbed NO by interaction with a neighboring free site; (3) irreversible recombination of adsorbed N atoms to form N2; and (4) quasi-equilibrated desorption of adsorbed O atoms to form 02. The reaction is catalyzed within porous catalytic pellets of slab geometry (thickness = 2L). a) Write the mechanism of the reaction with the stoichiometric number of each step. b) Derive the rate expression in terms of constants and measurable quantities, assuming O* is the MARI/MASI. c) The steady-state condition for the porous slab is shown below (A=NO): Саб Bulk BL CATALYS SLAB BL Bulk CAB2 САБ At high oxygen pressures, the concentration of oxygen can be assumed as constant and lumped into the rate constant, leaving the reaction rate as first order in (NO). Assume that the internal effectiveness factor in the catalyst slab is 0.2. There is an external film boundary layer and the concentration of NO at the surface of the slab (CAb/2) is half of the bulk NO concentration (CAb). If the ratio of the mass transfer coefficient in the external boundary layer (kc) to the effective first-order rate constant (keff) is 0.01 cm, what is the thickness (2L) of the slab?
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:The decomposition of NO into N2 and O2 occurs via elementary steps consisting of: (1)
quasi-equilibrated molecular adsorption of NO; (2) irreversible dissociation of adsorbed NO by
interaction with a neighboring free site; (3) irreversible recombination of adsorbed N atoms to
form N2; and (4) quasi-equilibrated desorption of adsorbed O atoms to form 02. The reaction is
catalyzed within porous catalytic pellets of slab geometry (thickness = 2L).
a) Write the mechanism of the reaction with the stoichiometric number of each step.
b) Derive the rate expression in terms of constants and measurable quantities, assuming
O* is the MARI/MASI.
c) The steady-state condition for the porous slab is shown below (A=NO):
Саб
Bulk BL
CATALYS
SLAB
BL
Bulk
CAB2
САБ
At high oxygen pressures, the concentration of oxygen can be assumed as constant and
lumped into the rate constant, leaving the reaction rate as first order in (NO). Assume that the
internal effectiveness factor in the catalyst slab is 0.2. There is an external film boundary layer
and the concentration of NO at the surface of the slab (CAb/2) is half of the bulk NO
concentration (CAb). If the ratio of the mass transfer coefficient in the external boundary layer
(kc) to the effective first-order rate constant (keff) is 0.01 cm, what is the thickness (2L) of the
slab?
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