a
.
a
Zeolites are hydrated alumino
−
-
silicates which have a three
−
-
dimenstional network structure containing water molecules in their pores. ltbr.
b
.
b
To use them as catalysts, they are heated so that the water of hydration present in the pores is lost and the pores become vacant.
c
.
c
The size of the pores varies from 260 to
740
±
.
740
Thus, only those molecules can be adsorbed in these pores and catalyzed whose size is small enought to enter these pores. Hence, they act as molecular sieves or shape
−
-
selective catalysts. ,brgt An important catalyst used in petroleum industry is
Z
S
M
−
5
(
Z
zeolite sieve of molecular porosity
5
)
5
. It converts alcohols into petrol by first dehydrating them to form a mixture of hydrocarbons.
Alcohols
Z
S
M
−
5
−−−−−−−→
D
e
h
y
d
r
a
t
i
o
n
H
y
d
r
o
c
a
r
b
o
n
s
→
