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Problem 4: The importance of diffusion in catalyst particles is often determined by measuring the effect of pellet size on the observed reaction rate. In this problem, consider an irreversible first order reaction occurring in catalyst pellets where the surface concentration of reactant A is kept at Cas 0.15 M in a spinning basket reactor. The results that are obtained from 16 experiments at 2 different temperatures, where the observed reaction rate per volume of catalyst (foes) is obtained as a function of the catalyst particle diameter (D) and temperature, is given in TableP4. Assume that spherical particles were used. Table P4: Observed reaction rate as function of catalyst diameter and temperature T-500K Experiment D. (cm) Foes (mol h cm Experiment T-530K D(cm) (mol hcm) 1 10.0 1.1 9 10.0 3.7 2 5.0 2.1 10 5.0 7.2 3 1.0 8.3 11 1.0 32 4 0.50 10.9 12 5 0.20 12.5 6 0.10 12.8 14 7 0.0020 12.9 15 8 0.0010 13.0 16 23355 0.50 56 13 0.20 86 0.10 96 0.0020 99 0.0010 100 (3) a) Motivate which experiments are affected by internal diffusion limitations. b) At T 500 K, determine the volumetric intrinsic rate constant (ks in s) and the effective diffusivity (De in m2 s). Also prepare a figure (Excel) of the observed reaction rate as a function of the particle diameter, where the experimental data is compared to your modelled data using the obtained values for ki and De. (14) c) At T 500K, if internal diffusion was not affecting the reaction rate, what reaction rate would have been obtained in Experiment 1? d) Determine the activation energy of the reaction. (3) (5)

Problem 4: The importance of diffusion in catalyst particles is often determined by measuring the effect of pellet size on the observed reaction rate. In this problem, consider an irreversible first order reaction occurring in catalyst pellets where the surface concentration of reactant A is kept at Cas 0.15 M in a spinning basket reactor. The results that are obtained from 16 experiments at 2 different temperatures, where the observed reaction rate per volume of catalyst (foes) is obtained as a function of the catalyst particle diameter (D) and temperature, is given in TableP4. Assume that spherical particles were used. Table P4: Observed reaction rate as function of catalyst diameter and temperature T-500K Experiment D. (cm) Foes (mol h cm Experiment T-530K D(cm) (mol hcm) 1 10.0 1.1 9 10.0 3.7 2 5.0 2.1 10 5.0 7.2 3 1.0 8.3 11 1.0 32 4 0.50 10.9 12 5 0.20 12.5 6 0.10 12.8 14 7 0.0020 12.9 15 8 0.0010 13.0 16 23355 0.50 56 13 0.20 86 0.10 96 0.0020 99 0.0010 100 (3) a) Motivate which experiments are affected by internal diffusion limitations. b) At T 500 K, determine the volumetric intrinsic rate constant (ks in s) and the effective diffusivity (De in m2 s). Also prepare a figure (Excel) of the observed reaction rate as a function of the particle diameter, where the experimental data is compared to your modelled data using the obtained values for ki and De. (14) c) At T 500K, if internal diffusion was not affecting the reaction rate, what reaction rate would have been obtained in Experiment 1? d) Determine the activation energy of the reaction. (3) (5)

Introduction to Chemical Engineering Thermodynamics
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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Problem 4: The importance of diffusion in catalyst particles is often determined by measuring the effect of pellet size on the observed reaction rate. In this problem, consider an irreversible first order reaction occurring in catalyst pellets where the surface concentration of reactant A is kept at Cas 0.15 M in a spinning basket reactor. The results that are obtained from 16 experiments at 2 different temperatures, where the observed reaction rate per volume of catalyst (foes) is obtained as a function of the catalyst particle diameter (D) and temperature, is given in TableP4. Assume that spherical particles were used. Table P4: Observed reaction rate as function of catalyst diameter and temperature T-500K Experiment D. (cm) Foes (mol h cm Experiment T-530K D(cm) (mol hcm) 1 10.0 1.1 9 10.0 3.7 2 5.0 2.1 10 5.0 7.2 3 1.0 8.3 11 1.0 32 4 0.50 10.9 12 5 0.20 12.5 6 0.10 12.8 14 7 0.0020 12.9 15 8 0.0010 13.0 16 23355 0.50 56 13 0.20 86 0.10 96 0.0020 99 0.0010 100 (3) a) Motivate which experiments are affected by internal diffusion limitations. b) At T 500 K, determine the volumetric intrinsic rate constant (ks in s) and the effective diffusivity (De in m2 s). Also prepare a figure (Excel) of the observed reaction rate as a function of the particle diameter, where the experimental data is compared to your modelled data using the obtained values for ki and De. (14) c) At T 500K, if internal diffusion was not affecting the reaction rate, what reaction rate would have been obtained in Experiment 1? d) Determine the activation energy of the reaction. (3) (5)
Transcribed Image Text:Problem 4: The importance of diffusion in catalyst particles is often determined by measuring the effect of pellet size on the observed reaction rate. In this problem, consider an irreversible first order reaction occurring in catalyst pellets where the surface concentration of reactant A is kept at Cas 0.15 M in a spinning basket reactor. The results that are obtained from 16 experiments at 2 different temperatures, where the observed reaction rate per volume of catalyst (foes) is obtained as a function of the catalyst particle diameter (D) and temperature, is given in TableP4. Assume that spherical particles were used. Table P4: Observed reaction rate as function of catalyst diameter and temperature T-500K Experiment D. (cm) Foes (mol h cm Experiment T-530K D(cm) (mol hcm) 1 10.0 1.1 9 10.0 3.7 2 5.0 2.1 10 5.0 7.2 3 1.0 8.3 11 1.0 32 4 0.50 10.9 12 5 0.20 12.5 6 0.10 12.8 14 7 0.0020 12.9 15 8 0.0010 13.0 16 23355 0.50 56 13 0.20 86 0.10 96 0.0020 99 0.0010 100 (3) a) Motivate which experiments are affected by internal diffusion limitations. b) At T 500 K, determine the volumetric intrinsic rate constant (ks in s) and the effective diffusivity (De in m2 s). Also prepare a figure (Excel) of the observed reaction rate as a function of the particle diameter, where the experimental data is compared to your modelled data using the obtained values for ki and De. (14) c) At T 500K, if internal diffusion was not affecting the reaction rate, what reaction rate would have been obtained in Experiment 1? d) Determine the activation energy of the reaction. (3) (5)
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