Transcript Folie 1 - uni

Adsorption hysteresis in mesopores.
Remarks on the thermodynamic nature of the states within the hysteresis loop
exp. adsoption isotherm, Ar / SBA-15, 77.35K
6.E-09
adsorption [mol/cm^2]
5.E-09
R.Rockmann,
PhD Thesis 2007,
U Leipzig
4.E-09
3.E-09
2.E-09
1.E-09
0.E+00
0
0.2
0.4
0.6
P/P0
0.8
1
Simulation Method: convolution function method, f(r)  V(r) * g(r)
physical concept akin to DFT
3 parameters for EOS of fluid
1 parameter for range of fluid/fluid interaction
2 parameters for range and strength of fluid / wall interaction
adsorption isotherm, model calculation
pore size distribution
7.E-09
0.35
0.3
6.E-09
probability
adsorption [mol/cm^2]
0.25
5.E-09
0.2
0.15
0.1
4.E-09
0.05
0
3.E-09
0
2
4
6
8
diameter [nm]
2.E-09
adsorption
desorption
low pressure
1.E-09
0.E+00
0
0.1
0.2
0.3
0.4
0.5
P/P0
0.6
0.7
0.8
0.9
1
Thermodynamics
vdW EOS.
Fit to waterstates
at 493K
EOS
+ equilibrium
-150000
+ metastable state
chem. Pot.
tie line
equilibrium
Chem.Pot. m
lowering grand potential W
lowering free energy A
-250000
coexistence
of two
phases
-350000
10
100
1000
molar volume [cm^3]
10000
Simulation: cylindrical pore in physical contact with gas reservoir
adsorption
isotherm finite pore length
desorption
adsorption [mol/cm^2]
5.E-09
gas
phase
4.E-09
3.E-09
2.E-09
1.E-09
-66000
-65000
-64000
-63000
chem. pot.
-62000
-61000
-60000
gas
phase
Simulation: adsorption in cylindrical pore of infinite length  EOS
infinite pore length vs. finite pore length
6.E-09
gas
phas
e
load [mol/cm^2]
5.E-09
4.E-09
infinite pore (EOS)
adsorption
3.E-09
desorption
controlled volume increase
controlled volume decrease
2.E-09
1.E-09
0.E+00
-72000
-70000
-68000
-66000
-64000
chem. potential [bar*cm^3/mol]
-62000
-60000
Simulation: finite pore length, isotherm
isotherm finite pore length
5.E-09
adsorption [mol/cm^2]
adsorption
desorption
4.E-09
3.E-09
2.E-09
1.E-09
-66000
-65000
-64000
-63000
chem. pot.
-62000
-61000
-60000
Simulation: finite pore length, isotherm (desorption, volume controlled)
isotherm finite pore length
adsorption[mol/cm^2]
[mol/cm^2]
adsorption
adsorption
[mol/cm^2]
5.E-09
5.E-09
5.E-09
4.E-09
4.E-09
4.E-09
adsorption
adsorption
adsorption
desorption
desorption(vol. contr.)
desorption
desorption
adsorption
desorption(vol.
(vol.contr.)
contr.)
desorption
(vol.
contr.)
3.E-09
3.E-09
3.E-09
2.E-09
2.E-09
2.E-09
1.E-09
1.E-09
-63800 -63700
-63600 -63500
-63400 -63000
-63300
-63100
-62800
-63350
-63345
-63340
-63335
-63325 -63200
-63320-62000
-63315 -63000
-63310
-63305 -60000
-63300
-66000
-65000
-64000-63330
-61000-62900
chem. pot.
Simulation: finite pore length, isotherm (adsorption, volume controlled)
isotherm finite pore length
4.E-09
3.E-09
2.E-09
1.E-09
-66000
2.84E-09
adsorption
desorption
desorption (vol. contr.)
adsorption (vol. contr.)
adsorption [mol/cm^2]
adsorption [mol/cm^2]
5.E-09
one IF
-65000
2.83E-09
2.82E-09
2.81E-09
2.8E-09
2.79E-09
-64000
-61763
-63000
-61762pot.
chem.
-62000
-61000
-60000
-61761
-61760
-61759
chem. pot.
-61758
Simulation: finite pore length, isotherm, dynamics of pressure jump
isotherm finite pore length
adsorption [mol/cm^2]
5.E-09
4.E-09
adsorption
adsorption
desorption
desorption
desorption
desorption(vol.
(vol.contr.)
contr.)
adsorption
(vol.
adsorption (vol.contr.)
contr.)
dynamic, min[chem.pot.]
dynamic, max[chem.pot.]
3.E-09
2.E-09
1.E-09
-66000
-65000
-64000
-63000
chem. pot.
-62000
-61000
-60000
Simulation: finite pore length, isotherm, 2 states of different topology
isotherm finite pore length
5.E-09
adsorption [mol/cm^2]
contr. chem. pot.
4.E-09
two IF
contr. volume
3.E-09
one IF
contr. amount
2.E-09
1.E-09
-66000
-65000
-64000
-63000
chem. pot.
-62000
-61000
-60000