Post on 05-Jan-2016
Chemical Reaction Engineering
Asynchronous Video Series
Chapter 3, Part 4:
Reaction Stoichiometry
Measures Other Than Conversion
H. Scott Fogler, Ph.D.
Measures Other Than Conversion
Uses: A. Membrane reactors
B. Multiple reaction
Liquids: Use concentrations, i.e., CA
€
C A =FA
υ0
Measures Other Than Conversion
Uses: A. Membrane reactors
B. Multiple reaction
Liquids: Use concentrations, i.e., CA
1. For the elementary liquid phase reaction carried out in a CSTR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the combined
mole balance, rate laws, and stoichiometry are:
€
C A =FA
υ0
€
A ⇔ B
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
Uses: A. Membrane reactors
B. Multiple reaction
Liquids: Use concentrations, i.e., CA
1. For the elementary liquid phase reaction carried out in a CSTR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the
combined mole balance, rate laws, and stoichiometry are:
€
C A =FA
υ0
€
A ⇔ B
€
C A0 − CA
−rA=
€
V =FA0 − FA
−rA=
υ 0 C A 0 −C A[ ]
−rA
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
Uses: A. Membrane reactors
B. Multiple reaction
Liquids: Use concentrations, i.e., CA
1. For the elementary liquid phase reaction carried out in a CSTR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the
combined mole balance, rate laws, and stoichiometry are:
€
C A =FA
υ0
€
A ⇔ B
€
C A0 − CA
−rA=
€
V =FA0 − FA
−rA=
υ 0 C A 0 −C A[ ]
−rA
€
τ =CA 0 − C A
k CA −CB
K C
⎡
⎣ ⎢
⎤
⎦ ⎥
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
Uses: A. Membrane reactors
B. Multiple reaction
Liquids: Use concentrations, i.e., CA
1. For the elementary liquid phase reaction carried out in a CSTR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the
combined mole balance, rate laws, and stoichiometry are:
€
C A =FA
υ0
€
A ⇔ B
€
C A0 − CA
−rA=
€
V =FA0 − FA
−rA=
υ 0 C A 0 −C A[ ]
−rA
€
τ =CA 0 − C A
k CA −CB
K C
⎡
⎣ ⎢
⎤
⎦ ⎥
€
V =FB 0 − FB
−rB
=υ 0 C B 0 − C B[ ]
−rB
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
€
τ =3s, C A 0 = 2 mol dm3 , K C =10, k = 0.1s −1
Measures Other Than Conversion
€
τ=C B0 − CB
−rB=
0− CB
−rB=
−C B
rA=
C B
−rA=
C B
k CA −C B
KC
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
€
τ =C B
k CA −CB
K C
⎡
⎣ ⎢
⎤
⎦ ⎥
€
τ =3s, C A 0 = 2 mol dm3 , K C =10, k = 0.1s −1
Measures Other Than Conversion
€
τ=C B0 − CB
−rB=
0− CB
−rB=
−C B
rA=
C B
−rA=
C B
k CA −C B
KC
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
2. There are two equations, two unknowns, CA and CB
€
τ =3s, C A 0 = 2 mol dm3 , K C =10, k = 0.1s −1
€
τ =C B
k CA −CB
K C
⎡
⎣ ⎢
⎤
⎦ ⎥
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
€
C A = C T0
FA
FT
⎛
⎝ ⎜
⎞
⎠ ⎟PP0
T0
T , CT 0 =P0
RT0
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
If the above reaction, ,carried out in the gas phase in a PFR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the combined
mole balance, rate laws, and stoichiometry yield, for isothermal operation (T=To) and no pressure drop (P=0) are:
€
C A = C T0
FA
FT
⎛
⎝ ⎜
⎞
⎠ ⎟PP0
T0
T , CT 0 =P0
RT0
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
If the above reaction, ,carried out in the gas phase in a PFR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the combined
mole balance, rate laws, and stoichiometry yield, for isothermal operation (T=To) and no pressure drop (P=0) are:
€
C A = C T0
FA
FT
⎛
⎝ ⎜
⎞
⎠ ⎟PP0
T0
T , CT 0 =P0
RT0
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
• Gases: Use molar flow rates, i.e., FI
If the above reaction, ,carried out in the gas phase in a PFR, where V, vo,CAo,k, and Kc are given and the feed is pure A, the combined mole
balance, rate laws, and stoichiometry yield, for isothermal operation (T=To) and no pressure drop (P=0) are:
€
C A = C T0
FA
FT
⎛
⎝ ⎜
⎞
⎠ ⎟PP0
T0
T , CT 0 =P0
RT0
€
C T =FT
υ=
PRT
, CT 0 =FT 0
υ 0
=P
RT0
Use Polymath to plot FA and FB down the length of the reactor.
€
−rA = k C A −CB
K C
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Measures Other Than Conversion
Use Polymath to plot FA and FB down the length of the reactor.
Given:
€
V0 = 30 dm 3 , υ 0 = 10 dm 3 s, K C = 10, k = 0.1s −1
Measures Other Than Conversion
Use Polymath to plot FA and FB down the length of the reactor.
Given:
€
V0 = 30 dm 3 , υ 0 = 10 dm 3 s, K C = 10, k = 0.1s −1
V
FA
FB
Summary
At the start of the chapter we saw we needed -rA=f(X). This result is achieved in two steps.
Summary
At the start of the chapter we saw we needed -rA=f(X). This result is achieved in two steps.
1. Rate Laws
– -rA=k f(Ci)
– 1st order A--> B or 1st order
-rA=kCA
€
−rA = k C A −C B
KC
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
Summary
At the start of the chapter we saw we needed -rA=f(X). This result is achieved in two steps.
1. Rate Laws
– -rA=k f(Ci)
– 1st order A--> B or 1st order
– 2nd order A+B --> C
– Rate laws are found by experiment
-rA=kCA
€
−rA = k C A −C B
KC
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
-rA=kACACB
Summary
At the start of the chapter we saw we needed -rA=f(X). This result is achieved in two steps.
1. Rate Laws
– -rA=k f(Ci)
– 1st order A--> B or 1st order
– 2nd order A+B --> C
– Rate laws are found by experiment
2. Stoichiometry
– Liquid:
– Gas:
-rA=kCA
€
−rA = k C A −C B
KC
⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
-rA=kACACB
€
C A = CA 0 1− X( )
€
C A =CA 0 1− X( )
1+ εX( )PP0
T0
T
€
C A = CT 0
FA
FT
PP0
T0
T