Micro Kinetic Modeling of Catalytic Reaction Sequence by Drawing Analogous Electrical Analogy

MICRO KINETIC MODELING OF CATALYTIC REACTION SEQUENCE BY

DRAWING ANALOGOUS ELECTRICAL ANALOGY

Reduction of NO by CO

[pic 1]

[pic 2]

The catalytic reaction sequence for the reduction of NO by CO on Pt is as follows:

s1                        [pic 3]

s2                        [pic 4]

s3                              [pic 5]

s4                              [pic 6]

s5                              [pic 7]

s6                              [pic 8]

s7                              [pic 9]

s8                              [pic 10]

Number of elementary steps : p = 8

Number  of intermediate species : q = 6

Therefore, Number of independent pathways/routes = p-q = 2

The above reaction is not exactly a mechanism involving parallel pathway and obviously does not involve series pathway. Hence, drawing an electrical amalogy for such a typical reaction is the major challenge.

Electrical analogy for the above reaction sequence is as follows:

[pic 11]

[pic 12][pic 13][pic 14][pic 15][pic 16][pic 17][pic 18][pic 19][pic 20][pic 21][pic 22][pic 23][pic 24]

Conversion of wye network to delta network:

[pic 25]

Here,

Rj = (RARB+RBRC+RCRA)/RB

Ri = (RARB+RBRC+RCRA)/RC

Rk = (RARB+RBRC+RCRA)/RA

Where,

RA =  2R1+R2+R4+R5+R8

RB = R2+R3+R4+R5+R8

RC = R6+R7

Also,

rOR1 = (1-zOR1)/Rj

rOR2 = (1-zOR2)/Ri

where,

KOR1 = K12K2K4K5K6K7K8

KOR2 = (K1K2K4K5K8)2K3

zOR1 = (pN2pCO22)/( KOR1pNO2pCO2)

zOR2 = (pN2OpCO2)/( KOR2 pNO2pCO)

Given below are the rate equations for each reaction:

r1 = w1fƟo - w1bƟNO.S

r2 = w2fƟoƟNO.S – w2bƟN.SƟO.S

r3 = w3fƟN.S2 – w3bƟo2

r4 = w4fƟo – w4bƟCO.S

r5 = w5fƟCO.SƟO.S – w5bƟo2