Multiscale Modelling in Computational Heterogeneous Catalysis - Multiscale Molecular Methods in Applied Chemistry - page 94

One-step alkylation of benzene:

H 2 C

CH 2

H
O

H
O

O O

CH 2

Si Al Si + + H 2 C Si co-adsorption

Al Si

ZOH ZOH(C 2 H 4 ,C 6 H 6 )

H 2 C

2

H
O

H
O

k 1
k -1

O O

reaction

Si

Si Al Si Al Si

ZOH (C 8 H 10 )

H
O

H
O O O

desorption

Si

Si Al Si Al Si +

Two-step alkylation of benzene:

H 2 C CH 2

H
O

H
O

O

O

CH 2

Si Al Si + H 2 C Si Al Si adsorption

ZOH

H 2 C

CH 2 CH 3

H

H
O

CH

k 1
k -1

O O O

Si

Al Si Si Al Si

reaction 1

CH 3 CH 3

H

H

CH CH

O O

O O

Si Al Si + Si Al Si adsorption

ZOH 2 H 5 (C 6 H 6 )

CH 3

H

H
O

C H

O O O

reaction 2

Si Si

Al Si Al Si

ZOH(C 8 H 10 )

H
O

H
O

O

O

Si Al Si Si Al Si +

desorption

Fig. 6 Elementary steps involved in the alkylation of benzene

This is caused by dispersion interaction between the carbon atoms of the reactant
and the oxygen atoms of the zeolite framework. Interaction of the reactants with the
Brønsted acid site further reduces the potential. The intrinsic energy barrier for
the forward reaction is the difference between the bottom of the well for the co-
adsorption of A and B at the active site and the top of the transition state. First, the