Chemical Reaction Engineering (CRE) is the field that
studies the rates and mechanisms of chemical reactions and
the design of the reactors in which they take place.
TODAY’S LECTURE
Introduction
Definitions
General Mole Balance Equation
Batch
CSTR
PFR
PBR

Chemical Reaction Engineering
Chemical reaction engineering is at the heart of virtually
every chemical process. It separates the chemical engineer
from other engineers.
Industries that Draw Heavily on Chemical Reaction
Engineering (CRE) are:
CPI (Chemical Process Industries)
Dow, DuPont, Amoco, Chevron

Materials on the Web and CDROM
http://www.engin.umich.edu/~cre/

Developing Critical Thinking Skills
Socratic Questioning
is the
Heart of Critical Thinking
R. W. Paul’s Nine Types of Socratic
Questions

Let’s Begin CRE
Chemical Reaction Engineering (CRE) is
the field that studies the rates and
mechanisms of chemical reactions and the
design of the reactors in which they take
place.

• A chemical species is said to have reacted
when it has lost its chemical identity.
Chemical Identity

• A chemical species is said to have reacted
when it has lost its chemical identity.
• The identity of a chemical species is
determined by the kind, number, and
configuration of that species’ atoms.
Chemical Identity

• A chemical species is said to have reacted
when it has lost its chemical identity.
1. Decomposition
Chemical Identity

• A chemical species is said to have reacted
when it has lost its chemical identity.
1. Decomposition
2. Combination
Chemical Identity

• A chemical species is said to have reacted
when it has lost its chemical identity.
1. Decomposition
2. Combination
3. Isomerization
Chemical Identity

• The reaction rate is the rate at which a
species looses its chemical identity per unit
volume.
Reaction Rate

• The reaction rate is the rate at which a
species looses its chemical identity per unit
volume.
• The rate of a reaction (mol/dm3/s) can be
expressed as either
the rate of Disappearance: -rA
or as
the rate of Formation (Generation): rA
Reaction Rate

Reaction Rate
Consider the isomerization AB
rA = the rate of formation of species A per unit volume
-rA = the rate of a disappearance of species A per unit volume
rB = the rate of formation of species B per unit volume

Reaction Rate
• EXAMPLE: AB
If Species B is being formed at a rate of
0.2 moles per decimeter cubed per second, ie,
rB = 0.2 mole/dm3/s

Reaction Rate
• EXAMPLE: AB
rB = 0.2 mole/dm3/s
Then A is disappearing at the same rate:
-rA= 0.2 mole/dm3/s

Reaction Rate
• EXAMPLE: AB
rB = 0.2 mole/dm3/s
Then A is disappearing at the same rate:
-rA= 0.2 mole/dm3/s
The rate of formation (generation of A) is
rA= -0.2 mole/dm3/s

Reaction Rate
• For a catalytic reaction, we refer to -rA',
which is the rate of disappearance of
species A on a per mass of catalyst basis.
(mol/gcat/s)
NOTE: dCA/dt is not the rate of reaction

Reaction Rate
Consider species j:
• rj is the rate of formation of species j per
unit volume [e.g. mol/dm3/s]

Reaction Rate
• rj is the rate of formation of species j per
unit volume [e.g. mol/dm3*s]
• rj is a function of concentration,
temperature, pressure, and the type of
catalyst (if any)

Reaction Rate
• rj is the rate of formation of species j per unit
volume [e.g. mol/dm3/s]
• rj is a function of concentration, temperature,
pressure, and the type of catalyst (if any)
• rj is independent of the type of reaction system
(batch reactor, plug flow reactor, etc.)

Reaction Rate
• rj is the rate of formation of species j per
unit volume [e.g. mol/dm3/s]
• rj is a function of concentration,
temperature, pressure, and the type of
catalyst (if any)
• rj is independent of the type of reaction
system (batch, plug flow, etc.)
• rj is an algebraic equation, not a
differential equation

General Mole Balance

General Mole Balance

Batch Reactor Mole Balance

CSTR
Mole Balance

Plug Flow Reactor

Plug Flow Reactor Mole Balance
PFR:
The integral form is: V
dFA
rA
FA 0
FA

This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA0 to the
exit molar flow rate of FA.

Packed Bed Reactor
Mole Balance
PBR
The integral form to find the catalyst weight is: W 
dFA

rA
FA 0
FA

FA0 FA  
rAdW 
dNA
dt


Reactor Mole Balance Summary

Fast Forward to the Future
Thursday March 20th, 2008
Reactors with Heat Effects

Production of Propylene Glycol in an Adiabatic
CSTR

What are the exit conversion X and exit temperature T?
Solution
Let the reaction be represented by

KEEPING UP

Separations
These topics do not build upon one another
Filtration Distillation Adsorption

Reaction Engineering
These topics build upon one another
Mole Balance Rate Laws Stoichiometry

Mole Balance
Rate Laws
Stoichiometry
Isothermal Design
Heat Effects

Mole Balance Rate Laws

Mole Balance
Rate Laws
Stoichiometry
Isothermal Design
Heat Effects

Batch Reactor Mole Balance

Batch Reactor Mole Balance

Batch Reactor Mole Balance

Batch Reactor Mole Balance

Batch Reactor Mole Balance

Continuously Stirred Tank Reactor
Mole Balance

Continuously Stirred Tank Reactor
Mole Balance

Continuously Stirred Tank Reactor
Mole Balance

C S T R
Mole Balance

CSTR
Mole Balance

Plug Flow Reactor

Plug Flow Reactor Mole Balance
PFR:

Plug Flow Reactor Mole Balance
PFR:

Plug Flow Reactor Mole Balance
PFR:

Plug Flow Reactor Mole Balance
PFR:

Plug Flow Reactor Mole Balance
PFR:

Plug Flow Reactor Mole Balance
PFR:
The integral form is: V
dFA
rA
FA 0
FA


Plug Flow Reactor Mole Balance
PFR:
The integral form is: V
dFA
rA
FA 0
FA

This is the volume necessary to reduce the entering molar flow rate (mol/s) from FA0 to the
exit molar flow rate of FA.

Packed Bed Reactor Mole
Balance
PBR

Packed Bed Reactor Mole
Balance
PBR
FA0 FA  
rAdW 
dNA
dt


Packed Bed Reactor Mole
Balance
PBR
FA0 FA  
rAdW 
dNA
dt


Packed Bed Reactor Mole
Balance
PBR
FA0 FA  
rAdW 
dNA
dt


Packed Bed Reactor Mole
Balance
PBR
The integral form to find the catalyst weight is: W 
dFA

rA
FA 0
FA

FA0 FA  
rAdW 
dNA
dt


Reactor Mole Balance Summary

Reactor Mole Balance Summary

Reactor Mole Balance Summary

Reactor Mole Balance Summary

Chemical Reaction Engineering
Asynchronous Video Series
Chapter 1:
General Mole Balance Equation
Applied to
Batch Reactors, CSTRs, PFRs,
and PBRs

http://www.engin.umich.edu/~cre

Chemical Reaction Engineering
Chemical reaction engineering is at the heart of virtually
every chemical process. It separates the chemical engineer
from other engineers.
Industries that Draw Heavily on Chemical Reaction
Engineering (CRE) are:
CPI (Chemical Process Industries)
Dow, DuPont, Amoco, Chevron
Pharmaceutical – Antivenom, Drug Delivery
Medicine – Tissue Engineering, Drinking and Driving

Compartments for perfusion
Perfusion interactions between
compartments are shown by arrows.
VG, VL, VC, and VM are -tissue water
volumes for the gastrointestinal,
liver, central and muscle
compartments, respectively.
VS is the stomach contents volume.
Stomach
VG = 2.4 l
Gastrointestinal
VG = 2.4 l
tG = 2.67 min
Liver
Alcohol
VL = 2.4 l
tL = 2.4 min
Central
VC = 15.3 l
tC = 0.9 min
Muscle & Fat
VM = 22.0 l
tM = 27 min

Chemical Reaction Engineering
Chemical reaction engineering is at the heart of virtually
every chemical process. It separates the chemical engineer
from other engineers.
Industries that Draw Heavily on Chemical Reaction
Engineering (CRE) are:
CPI (Chemical Process Industries)
Dow, DuPont, Amoco, Chevron
Pharmaceutical – Antivenom, Drug Delivery
Medicine –Pharmacokinetics, Drinking and Driving
Microelectronics – CVD

Reaction Rate
Consider the isomerization AB
rA = the rate of formation of species A per unit volume

Reaction Rate
Consider the isomerization AB
rA = the rate of formation of species A per unit volume
-rA = the rate of a disappearance of species A per unit volume

Reactor Mole Balance Summary