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Batch Stoichiometric Table
Species Symbol Initial Change Remaining
D D
________ ____________
C C
B B
A A
Inert I -------
where and
B N B 0
N A 0
Concentration: Batch Systems
Constant Volume Batch:
Note: if the reaction occurs in the liquid phase
or
if a gas phase reaction occurs in a rigid (e.g., steel) batch reactor
Then
etc.
If then
And we have –rA=f(X)
Flow System Stoichiometric Table
Species Symbol Initial Change Remaining
________ ____________
A
B B
A
C C
D D
Inert I
where and
B FB 0
FA 0
Concentration: Liquid Flow System
• Flow Stystem:
• Liquid Phase Flow System:
etc.
If the rate of reaction were
then we would have
This gives us -rA = f(X). Consequently, we can use the methods discussed in
Chapter 2 to size a large number of reactors, either alone or in series.
Concentration: Gas Flow System
0
FT
FT0
P0
PTT0
FT
FT 0
FT 0 FA 0X
FT 0
1 y A 0 X 1X
FT C T and FT 0 C T 00 C T 0
CT
0
C T PRT
and C T 0 P0
RT0
with
C A FA 0 1 X
THEN
Note that the reaction is: A + (b/a)B - (c/a)C + (d/a)D
THEN
IF the reaction rate is given by -rA = k CA2 CB
Multiple ReactionsUse molar flow rates and concentrations; DO NOT use conversion!
Types of Multiple Reactions
1. Series Reactions
2. Parallel Reactions
3. Complex Reactions: Series and Parallel
4. Independent
Selectivity and Yield
Instantaneous Overall
Selectivity
Yield:
Example: (1) desired product , rD=k1CA2CB
(2) undesired product , rU=k2CACB
A Bk 2 U1
Another example about Selectivity and Yield
(1) desired product , rD=k1CA2CB
(2) undesired product , rU=k2CACB
(3)
A Bk
2 U1
A Bk
3 U2
rU 2k 3C BC A
3
SD/U1 /U 2
k1CA2 CB
k 2CACB k 3CBCA3then
k1CA
k 2 k 3CA2
CA
SD/U1/U2
Algorithm for Multiple Reactions
Mole Balances
Net Rate of Reaction for Species A
Series Reactions
, t=0 CA=CA0
Series Reactions
dCC
dtk 2CB , t 0 CC 0
Elementary Multiple Reactions
1 A2B C
2 3C+ 2A D
r1A k1A CA CB2
r2C k2CCA2 CC
3
rA r1A r2 A
rA k1 ACACB2 2
3k 2CCA
2 CC3
r1A k 1A CA CB2
r2A
2 r2C
3
r2A 23
r2 C 23
k 2CCA2 CC
3
rD 0 r2D r2C
3
rD 13
k2CCC3 CA
2
rB r1B 0 2r1A
rB 2k1ACACB2
r1B
2
r1A
1r1B 2r1A
r2B 0
rC r1C r2C r1A r2C
rC k1ACACB2 k2 CCA
2 CC3
r1A
1
r1C
1r1C r1A
r2C k 2 CC A2 CC
3
r1D 0r2C
3
r2 D
1
Case 1:Liquid Phase Reaction in a CSTR
Case 1:Liquid Phase Reaction in a CSTR
Case 1:Liquid Phase Reaction in a CSTR
Polymath Solution
Polymath Solution
Polymath Solution
Elementary Multiple Reactions
1 A2B C
2 3C+ 2A D
r1A k1A CA CB2
r2C k2CCA2 CC
3
rA r1A r2 A
rA k1 ACACB2 2
3k 2CCA
2 CC3
r1A k 1A CA CB2
r2A
2 r2C
3
r2A 23
r2 C 23
k 2CCA2 CC
3
rD 0 r2D r2C
3
rD 13
k2CCC3 CA
2
rB r1B 0 2r1A
rB 2k1ACACB2
r1B
2
r1A
1r1B 2r1A
r2B 0
rC r1C r2C r1A r2C
rC k1ACACB2 k2 CCA
2 CC3
r1A
1
r1C
1r1C r1A
r2C k 2 CC A2 CC
3
r1D 0r2C
3
r2 D
1
Example: Liquid Phase Reaction
Example: Liquid Phase Reaction
Example: Liquid Phase Reaction
Example: Liquid Phase Reaction
Multiple Reactions — Gas Phase
Use Molar Flow Rates!!!
The Algorithm
The Algorithm
(given)
The Algorithm
Heterogeneous Catalytic Reaction
1-External diffusion of reactants towards the external surface of the catalyst pellet
2-Internal diffusion of reactants into the pores of the catalyst pellet
3- Adsorption of reactants on the active sites
4- Surface reaction
5- Desorption of products from active sites into the pore volume of the catalyst pellet
6- Internal diffusion of products through the pores of the catalyst pellet towards the external surface of the catalyst pellet
7- External diffusion of products to the bulk of the fluid
Molecular Adsorption
Molecular Adsorption
CA•S KAPA
1KAPA
Steps of Catalytic Reaction
B B
Steps of Catalytic Reaction
B B
B DA
A B
C
C D
AB
C+ D
C
D
+ C
+ D
Example: Catalytic Reaction to Improve the Octane Number of Gasoline
Focusing on the second reaction:
Example: Catalytic Reaction to Improve the Octane Number of Gasoline
Example: Catalytic Reaction to Improve the Octane Number of Gasoline
rN rS kS C N,S C I•S
KS
CV CT
1 KNPN KIPI
Different Surface Mechanisms
