Adsorption Isotherms of Ethylene in NaX (Zeolite Structure FAU)

temperature in °C

0

This Demonstration plots adsorbtion versus pressure,

P

, at various temperatures for ethylene (

C

2

H

4

) in NaX, known as faujasite zeolite structure (FAU). The amount adsorbed,

n

(expressed in mol/kg), increases at low temperatures and high pressures. The adsorption isotherm, shown in red, is given by the following relation:

P(n)=

nm

K

0

(m-n)

exp

C

1

n+

C

2

n

+

C

3

n

exp

(

D

0

+

D

1

n)

R

1

T

-

1

T

0

,

where

K

0

is Henry's constant at

T=

T

0

, expressed in mol/(kg kPa),

m

is the saturation capacity, equal to 2.9997 mol/kg, and

C

i

, for

i

=1 to 3, are the virial coefficients. If these coefficients are set equal to zero, one recovers the well-known Langmuir equation (the blue curve). The term

(

D

0

+

D

1

n)

is the differential enthalpy of adsorption.