Lecture 10 Tuesday 2/5/08

Definition of Selectivety

Instantaneous SD/U = rD/rU

Overall = FD/FU

Semibatch Reactors

Read Problem P4-23 on page 246 before Lecture begins

Semibatch and Rate Law Intro

Semibatch reactors

example: A + B → C + D

A

B, v0

Initial V

tvVVvdt

dV

dt

dVV

Vmvmtvdt

dm

0000

00

1) Mole balances: A: in – out + gen = acc

0 - 0 + rAV = dNA/dt

B: FB – 0 + rBV = dNB/dt

dt

dVC

dt

dCV

dt

VCd

dt

dNA

AAA ][

tvVVV

Cvr

dt

dCV

Cvr

dt

dCV

CCvr

dt

dCV

Cvr

dt

dC

DD

D

CC

C

BBB

B

AA

A

00

0

0

00

0

5

4

3

)( 2

1

2) Rate Law:

3) Stoich:

4) Parameters:

VCN

VCN

N

NNX

rr

rr

rr

rrrr

CkCr

AA

AA

A

AA

AD

AC

AB

DCBA

BAA

12

11

10

9

8

71111

6

000

0

0

0000 , , , , BA CkvVC

example: A + B → C + D + CO2

1) Mole balances:

mass balances:

2) Rate law:

A

B, v0 CO2

MWVrv

dt

dV

dt

dVMWFv

MWFmvmVmdt

dmmm

FVr

Vrdt

dN

Vrdt

dN

FVrdt

dN

Vrdt

dN

CO

CO

CO

i

COCO

DD

CC

BBB

AA

2

2

2

22

0

0

00

0

0

6

0 5

4

3

2

1

BAA CkCr

3) Stoich:

4) Parameters:

0

0

CO

B

A

13

12

11

01

9

C 8

7

2

A

AA

A

AD

AC

A

BB

A

N

NNX

rr

rr

rr

rrV

NV

NC

, , , , , , ,0

000000 kMWC

FvFCCV

B

BBBA

Finding the Rate Law (Done in a batch reactor)

AA

AAA r

dt

dCVrVr

dt

dN 0

Assume power law relation:

Guess and check for α = 0, 1, 2 and check against experimental plot

AA

AA

kCdt

dC

kCr

ktCC

ktC

CktCr

AAA

AAA

0

00

11 ln

2 1 0

ttt

CA 1/CAln(CA0/CA)