cumene adsorption

7/23/2019 cumene adsorption

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ERT 208/4 REACTIONENGINEERING:Catalysis & Catalytic

Reaction MechanismPat !: The Rate

"imitin# $te%''!y( Ms )a*+a !inti $h

ERT 208/4 REACTION ENGINEERINGSEM 2 2009 2010


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Rate "imitin#

$te%..


hen heteo#eneo,s eactions ae caie o,t at$TEA1 $TATE'the ate o3 each o3 the eactionste% in seies 5aso%tion6 s,3ace eaction &eso%tion7 ae e,al to one anothe'

DsADA rrrr === '

only ONE %atic,la ste% in the seies is ,s,ally3o,n to 9e RATE "IMITING RATE CONTRO""ING

I3 ;e co,l ma-e this %atic,la ste% GO


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Rate "imitin# $te%..'''''cont'


A$$=MPTION''

All the ste%s ae e>esi9le eaction'

Acti>ity o3 the s,3ace to;as aso%tion6

eso%tion s,3ace eaction is IN1EPEN1ENT o3co>ea#e'

The s,3ace is essentially ,ni3om as 3a as the

>aio,s ste%s in the eaction ae concene'


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Rate "imitin# $te%..''''''cont


322 23 NHNH +

E?AMP"E @: A1$ORPTION "IMITE1 REACTION$ynthesis o3 Ammonia

Over an iron catal!t t"at #rocee$! % t"e &ollo'in

SHSH + 222

SNSSN

SNSN

++2

2

22

SNHSNH

SSNHSHSNH

SSNHSHSNH

SSHNSHSN

+++++ ++

33

32

2

Ra#i$

Rate"imitin#5aso%tion o3N2molec,les as

an N atom7

Ra#i$


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22

2

1NCONOCO

Cu

++

E?AMP"E 2: $=R


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( ) 63632356

HCHCCHCHHC +

$ynthesi+in# a Rate "a;6 Mechanism6 an Ra

E?AMP"E : 1ECOMPO$ITION O< C=MENE TO


7/33ERT 208/4 REACTION ENGINEERINGSEM 2 2009 2010

SCSC +

PSBSC +

SBSB +

Aso%tion

$,3ace Reaction

1eso%tion

A

Ac

kkK

=

S

S

Sk

kK

=

DB

BK

K 1=

SCAVCAAD CkCPkr =

SBPSSCSS CPkCkr =

VBDSBDD CPkPkr =

=

C

SCVCAAD

K

CCPkr

=

S

SBP

SCSSK

CPCkr

( )VBBSBDD

CPKCkr =

hich ste% is Rate "imitin# $te%...



SCSC +The ate o3 aso%tion :

=

C

SC

VCAADK

CCPkr

@7 Is theA1$ORPTION o3 c,mene is Rate "im

Ass,m%tion



The ate o3 aso%tion :

=

C

SC

VCAAD

K

CCPkr

Is theA1$ORPTION o3 c,mene is Rate "imiti


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The eso%tion ate eB%ession is :


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e -no; that 66

B

CS

PK

KKK ='5@07

=

C

SC

VCAADKCCPkr

P,t 57 in a9o>e

e,ation(

=

=

=

P

PB

CVAAD

CS

PBBCVAAD

CS

PVBB

VCAAD

K

PPPCkr

KK

PPKPCkr

KK

PCPKCPkr

hee

'5@@7

This tems is sim%ly theo>eall %atial %ess,ee,ili9i,m constant 3othis eaction'

PBC +


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To eliminate C>6 ;e ,se $ITE!A"ANCE6

P,t 587 an 57 in 5@27

''VBB

S

PVBB

Vt CPKK

PCPKCC ++=

$o '5@7

Total !ite! Ct5 C

v 6 CC7S7 6 C7S

acant

Site

Occ#ie$ Site(cene 3%enene

a$!or% on t"e!r&ace)

'5@27

$ol>in# 3o C>6

( )BB

S

PBB

Vt PKK

PPK

CC ++= 1

BB

S

PBB

t

V

PK

K

PPK

CC

++=

1


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No;6 ;e %,t 5@7 in5@07''

$o

'5@47

++=

=

P

PB

C

BB

S

PBB

t

AAD

P

PB

CVAAD

KPPP

PKK

PPKCkr

KPPPCkr

1

BBSPBB

PPSCtA

ADcPKKPPK

KPPPCkrr

++

==/1

)/('


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No;6 ;e ;ish to s-etch a %lot o3 the initial ate asa 3,nction o3 %atial %ess,e o3 c,mene6Pco

$othe initial ate6

I3 the c,mene

ecom%osition isA1$ORPTION"IMITE16 then theinitial ate ;ill 9e

linea ;ith theinitial atial

BBSPBB

PPSCtA

ADc

PKKPPK

KPPPCkrr

++

==

/1

)/('

0== Bp PPInitially6 no %o,ct ae %esent6 so

COCOtACO kPPCkr == '

'COrinitial ate6

initial %atial %ess,e o3 c,


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The ate o3 $=Rey $MA""

a oBimatel 0

PSBSC +

=

S

SBP

SCSSK

CPCkr '5@7

$ince ;e cannot eaily meas,e the conc o3 the aso9e s%ecies6;e m,st ,tili+e the aso%tion & eso%tion ste% to eliminate CC'$an C!'$ 3om this e,ation'


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The aso%tion ate eB%ession is :

=

C

SC

VCAAD

K

CCPkr

Is the$=R


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Is the$=R


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Is the$=R


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Is the$=R


20/33


Is the$=R


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Is the$=R


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Is the$=R


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Is the$=R


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The ate o3 1E$ORPTION:

7 Is the1E$ORPTIONo3 c,mene is Rate"imitin# $te%...

Ass,m%tion


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The aso%tion ate eB%ession is :

=

C

SC

VCAAD

K

CCPkr

Is the1E$ORPTIONo3 c,mene is Rate"imitin# $te%...''cont''


26/33


Is the1E$ORPTION o3 c,mene is Rate"imitin# $te%...''cont''The $=R


27/33


Is the1E$ORPTION o3 c,mene is Rate"imitin# $te%...''cont''No;6 %,t 547 an 5F7 in 5@7'

P

B

CS KK

KK=

e -no; that66

'587

Gas%hase

e,ili9i,mconstant

( )

V

P

B

P

c

CSDD

VBB

P

VcCS

DD

VBB

P

SCS

DD

VBBSBDD

CK

P

P

P

KKkr

CPKP

CPKKkr

CPKP

CKkr

CPKCkr

=

=

=

=

Is the 1E$ORPTION o3 c,mene is Rate


28/33


Is the1E$ORPTION o3 c,mene is Rate"imitin# $te%...''cont''

$ite !alance'

'57SCSBVt CCCC ++=

P

CCS

CC

t

V

P

CCS

CCVt

P

SCS

VccVt

P

PKKPK

CC

P

PKKPKCC

P

CK

CPKCC

++=

++=

++=

1

)1(

'5@07



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P,t 5@07 in 587'

CSCPCCP

P

PB

CSCtD

DC

P

CSC

CC

P

B

P

C

SCtDD

P

CSC

CC

t

P

B

P

C

SCDD

PKKPPKP

K

PPPKKCk

rr

P

PKKPK

K

P

P

PKKCkr

P

PKKPK

C

K

P

P

PKKkr

++

==

++

=

++

=

'

1/

1

'5@@7



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$othe initial ate6

0== Bp PPInitially6 no %o,ct ae %esent6 so

To etemine the e%enence o3 the initial ate on%atial %ess,e o3 c,mene6 ;e a#ain set:

Initial ateine%enent o3 theinitial %atial %ess,eo3 c,mene

CSCPCCP

P

PB

CSCtD

DCOPKKPPKP

K

PPPKKCk

rr++

== '

tDDCO Ckrr == 'initial ate6

initial %atial %ess,e o3 c,mene6Pco

'COr

$=MMAR O< T)E C=MENE


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$=MMAR O< T)E C=MENE1ECOMPO$ITIONThe eB%eimental o9se>ation o3 Hcoas a 3,nction

o3 Pcoae sho;n in *#,e''3om that6 ;e clealy can

see that eithe aso%tion no eso%tion is RATE"IMITINGinitial ate6

initial %atial %ess,e o3 c,mene6Pco

'COr

The ate la; ei>e 9y ass,min# that $=R


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A"GORIT)M


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cumene adsorption