adsorption of polar and nonpolar vapors on selected ......1 adsorption of polar and nonpolar vapors...
TRANSCRIPT
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Adsorption of Polar and Nonpolar Vapors
on Selected Adsorbents: Breakthrough Curves and their Simulation
Dr. Robert EschrichQuantachrome GmbH & Co. KG
2018-04-17
Leipziger Symposium on Dynamic Sorption 2018 sorption heat and energy storage
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1. Breakthrough Curve Introduction
2. The mixSorb L with Vapor Option
3. Breakthrough Curves of Vapors
I. Water Breakthrough Curves on Zeolite, Silica Gel Regenerability and Heat Output
II. Toluene Breakthrough Curveon Activates Carbon
III. Ethanol/water Mixture Adsorptionon Activates Carbon
4. Modelling
I. Simulating Water Breakthrough Curves
II. Simulating Ethanol Breakthrough Curves
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𝑛ads,𝑖 = 𝑛dosed,𝑖 − 𝑛free,𝑖
𝑛free,𝑖 =𝑝Cell,𝑖 𝑉Dose + 𝑉Cell
𝑅𝑇
𝑛dosed,𝑖 =𝑝Dose,𝑖 𝑉Dose
𝑅𝑇
𝑛ads =
0
𝑖
𝑛ads,𝑖
Static Volumetric Measurements• Sorption takes place in enclosed chamber• Pressure is recorded over time• Pure Gases only
Breakthrough Experiment• Sorption takes place in open system• Pressure is constant• Gas Mixtures only• Outlet composition is recorded over time
𝑛adsorbed = 𝑛in(𝑡)d𝑡 − 𝑛out(𝑡)d𝑡
𝑛adsorbed = 𝑉in(𝑡)𝑦in(𝑡)
𝑉md𝑡 − 𝑉out(𝑡)
𝑦out(𝑡)
𝑉md𝑡
0.0 0.2 0.4 0.6 0.8 1.00
1
2
3
4
loadin
g m
mol g
-1
p/p0
0.0 0.2 0.4 0.6 0.8 1.00
20
40
60
80
100
rel. b
reakth
rough /
%
time-on-stream / s
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• Not all Gas Flow Experiments are Breakthrough Experiments!
• Requirement: Fixed Adsorber Bed gas must not pass the sample without interaction!
• What is the result of a breakthrough experiment?
Breakthrough Curves
T
T
T
T
gas inlet
gas outlet detection
adsorber
cin uin
cout uout
axial dispersion
adsorbent
adsorptive
heat of adsorption
transport into particle
adsorption
Time until 5 %, 50 % ,… of breakthrough is the cycle or production time
Integration of the full curve gives saturation capacity of a gas on the adsorbent (equilibrium)
Integration until cycle time gives technically usable sorption capacity
Shape of the curve contains information about kinetics/mass transfer
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T
T
T
T
gas inlet
gas outlet detection
adsorber
cin uin
cout uout
axial dispersion
adsorbent
adsorptive
heat of adsorption
transport into particle
adsorption
Macroscopic
• Size of Adsorber
• Shape of Adsorber
Mesoscopic
• Nature of the Fixed Bed
• Bed Porosity
• Shape of Particles
Microscopic
• Textural Properties
• Surface Characteristics
• Accessibility
Different Scales
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Resulting Curves
• 40 °C, 2 L min-1
• 5 bar (pressurization with N2)
• Inlet compositions: 5 % CO2 in N2
• Temperature Maxima Decrease in Flow Direction Increasing Dispersion
• Area under Temperature Curves increases in Flow Direction Transfer of heat through gas flow
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Calculating Loadings
Saturation Capacitydq = 0.611 mmol g-1
Technically Usable Sorption Capacitydq = 0.445 mmol g-1
Integrating over the full Curve Integrating over the Curve to e.g. 1 % Breakthrough
𝑛adsorbed = 𝑛in(𝑡)d𝑡 − 𝑛out(𝑡)d𝑡
𝑛adsorbed = 𝑉in(𝑡)𝑦in(𝑡)
𝑉md𝑡 − 𝑉out(𝑡)
𝑦out(𝑡)
𝑉md𝑡
8 www.dynamicsorption.com
mixSorb L
• Fully automated Breakthrough Analyzer
• Integrated Gas Mixing – Including Vapors
• Up to 40 L/min Gas Flow, up to 10 bar
• Up to 4 mass flow controllers (MFCs)
• Up to 2 Evaporators, each capable to supply vapor mixtures
• Monitoring of gas composition by TCD at the Outlet or Bypass
• You can attach any additional Analytical Device (e.g. Mass Spec) at the sample port
• 3P-SIM Simulation Software
9 www.dynamicsorption.com
I. Breakthrough Curves of H2O
• Drying of process gases
Important to remove Water and CO2 in Air before Cryogenic Air Separation
Water would plug the piping by freezing.
Air separation with Pressure Swing Adsorption (PSA) on Zeolites
Water has strong affinity to surface
• Energy Storage
Adsorption of water vapor releasing heat of adsorption. Control heat output with dosing of water
Regeneration with e.g. thermal solar energy
Can be used for cooling as well
Adsorber
Δp%
RH
% RH
Cooling/Condensation
Heating/Evaporation
Condensate
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• Experimental conditions of a simple breakthrough experiment after Activation at 400 °C for 4 h
• 25 °C, Flow rate 4 L min-1
• Pressure: 1 bar
• Standard Adsorber with 80 g of sample
• Inlet composition: 5 g h-1 H2O in N2
(volume fraction y(H2O) = 2.59 %, Relative humidity approx. 80 % @ 25 °C)
High temperatures during adsorption
Loading: 18.9 mmol g-1
Regeneration at 130 °C for 3.5 h
Breakthrough Curve of H2O / N2 on Zeolite 13X
0 50 100 150 200 250 300 350 4000.0
0.5
1.0
1.5
2.0
2.5
3.0
y(H2O)
T4T3
T2
T1
volu
me fra
ction
y(H
2O
) / %
time-on-stream t / min
20
30
40
50
60
70
80
be
d tem
pe
ratu
re T
/ °
C
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0 50 100 150 200 250 300 350 4000.0
0.5
1.0
1.5
2.0
2.5
3.0
y(H2O)
T4
T3T2
T1
volu
me fra
ction
y(H
2O
) / %
time-on-stream t / min
20
30
40
50
60
70
80
be
d tem
pe
ratu
re T
/ °
C
Breakthrough Curve of H2O / N2 on Zeolite 13X• Sample regenerated at 130 °C for 3.5 h
• Same experimental conditions
• Inlet composition: 5 g h-1 H2O in N2
(volume fraction y(H2O) = 2.59 %, Relative humidity approx. 80 % @ 25 °C)
Loading: 15.4 mmol g-1 lower
Unsymmetrical temperature profiles
Residual loading before experiment not equally distributed
Overlay
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0 50 100 150 200 250 300 350 4000.0
0.5
1.0
1.5
2.0
2.5
3.0
regenerated 130 °C
regenerated
400 °C
vo
lum
e fra
ction
y(H
2O
) / %
time-on-stream t / min
Breakthrough Curve of H2O / N2 on Zeolite 13X• Loadings:
18.9 mmol g-1 (activated at 400 °C) vs.15.4 mmol g-1 (regenerated at 130 °C)
• Breakthrough Curve shifted to the left
• Breakthrough curves still have similar shapes
Zeolite requires harsh regeneration
High temperatures
Steep Breakthrough Curves indicate steep isotherms
High affinity to water
13 www.dynamicsorption.com
Breakthrough Curve of H2O / N2 on Silica Gel
0 100 200 300 400 500 600 700 800 900 1000 11000.0
0.5
1.0
1.5
2.0
2.5
3.0
y(H2O)
T4T3T2
T1
volu
me fra
ction
y(H
2O
) / %
time-on-stream t / min
20
30
40
50
60
70
80
be
d tem
pe
ratu
re T
/ °
C
• Experimental conditions of a simple breakthrough experiment after Activation at 350 °C for 4 h
• 25 °C, Flow rate 4 L min-1
• Pressure: 1 bar
• Standard Adsorber with 80 g of sample
• Inlet composition: 5 g h-1 H2O in N2
(volume fraction y(H2O) = 2.59 %, Relative humidity approx. 80 % @ 25 °C)
Smaller temperatures peaks
Much longer measurement
Loading: 25.9 mmol g-1
Regeneration at 130 °C for 3.5 h
14 www.dynamicsorption.com
Breakthrough Curve of H2O / N2 on Silica Gel
0 100 200 300 400 500 600 700 800 900 1000 11000.0
0.5
1.0
1.5
2.0
2.5
3.0
y(H2O)
T4T3T2
T1
volu
me fra
ction
y(H
2O
) / %
time-on-stream t / min
20
30
40
50
60
70
80
be
d tem
pe
ratu
re T
/ °
C
• Sample regenerated at 130 °C for 3.5 h
• Same experimental conditions
• Inlet composition: 5 g h-1 H2O in N2
(volume fraction y(H2O) = 2.59 %, Relative humidity approx. 80 % @ 25 °C)
Loading: 25.1 mmol g-1
almost identical
Overlay
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Breakthrough Curve of H2O / N2 on Silica Gel
0 200 400 600 800 10000.0
0.5
1.0
1.5
2.0
2.5
3.0
regenerated 130 °C
regenerated
400 °C
vo
lum
e fra
ction
y(H
2O
) / %
time-on-stream t / min
• Loadings:25.9 mmol g-1 (activated at 350 °C) vs.25.1 mmol g-1 (regenerated at 130 °C)
• Breakthrough Curve changed slope
• Changing surface chemistry until stable in cycles
Regeneration much easier, efficient
No high temperature required
Regeneration possible by Pressure Reduction
But: Breakthrough occurs earlier!
16 www.dynamicsorption.com
Breakthrough Curve of H2O / N2 on Zeolite 13X and Silica Gel
0 1 2 3 4 5 6 7 8
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Zeolite activated
Zeolite regenerated
Silica activated
Silica regenerated
vo
lum
e f
ractio
n y
(H2O
) / %
time per volume tV / min cm
-3
• Materials behave differently in Adsorption/Desorption Cycles
• Good Agreement with Isotherm data (right hand side)
Can we use these curves to get information about stored energy and heating power?
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
5
10
15
20
25
30
Zeolite 13X
Silica
loa
din
g q
(H2O
) /
mm
ol g
-1
p / p0
17 www.dynamicsorption.com
Immersion Calorimetry
• Determining the Heat of Adsorption in Liquid Phase
0 5 10 15 200
5
10
15
20
25
30
35
40
Zeolite 13X
Silica
he
at flow
/ m
W
time t / min
Enthalpy of wettingZeolite: 550 J g-1 (g of Adsorbent)Silica Gel: 140 J g-1(g of Adsorbent)
Zeolite: 1600 J g-1 (g of water)Silica Gel: 300 J g-1 (g of water)(re-calculated according to water isotherms)
Zeolite 13X Silica Gel
hW / J g-1 (H2O) 1600 300
hC / J g-1 (H2O) 2500 2500
hA / J g-1 (H2O) 4100 2800
»Enthalpy of Adsorption = Wetting + Condensation«hA = hW + hC
18 www.dynamicsorption.com
0 200 400 600 800 1000 12000.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Silica Gel
Zeolite
Hea
t P
ow
er
P / W
att
time-on-stream t / min
Heat Power Comparison
• Comparing the Heating Power during Adsorption
𝑃 = (1 − rel. Breakthrough) ×5gh
3600sh
× ℎ𝐴
• Zeolite: More Heating Power, but over short duration abrupt drop
• Silica Gel: Less Heating Power, continuously decreasing longer duration
19 www.dynamicsorption.com
• 25 °C, 4 L min-1
• 1 bar
• Inlet composition: 5 g h-1 H2O in N2
(volume fraction y(H2O) = 2.59 %, RH approx. 80%)
• Loading: 10.0 mmol g-1
• Shape of curves can be explained by adsorption and condensationin the pores.
• Fast breakthrough due to hydrophobic surface
• Similar to Silica Gel, but Condensation is more pronounced
Breakthrough Curve of H2O / N2 on Activated Carbon
0 50 100 150 200 250 300 350 400 4500.0
0.5
1.0
1.5
2.0
2.5
3.0
y(H2O)
T4T3
T2
T1
volu
me fra
ction
y(H
2O
) / %
time-on-stream t / min
24
26
28
30
32
34
36
38
40
42
44
be
d tem
pe
ratu
re T
/ K
20 www.dynamicsorption.com
• Activated Carbon D55/1.5
• 25 °C, 4 L min-1
• Inlet composition: 20 g h-1 Toluene in N2
(volume fraction y(Toluene) = 2.0 %, p/p0= 0.53 (@ 25 °C)
Large temperature peaks
Steep Breakthrough Curve
Loading: 2.1 mmol g-1
More similar to H2O/Zeolite than H2O/Activated Carbon
0 10 20 30 40 50 60 70 800.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
y(Toluene)
T4T3
T2
T1
volu
me fra
ction y
(Tolu
en
e)
/ %
time-on-stream t / min
20
25
30
35
40
45
50
55
60
bed
tem
pera
ture
T / °
C
II. Breakthrough Curve of Toluene/N2
21 www.dynamicsorption.com2.5 % H2O, 1 % EtOH in N2, Total Flow: 4 Nl min-1 T = 25 °C
III. Breakthrough Curves of a EtOH/H2O Mixture in N2 on Activated Carbon
0 50 100 150 200 25020
22
24
26
28
30
32
34
36
Temperature T4 (250 mm)
tem
pera
ture
/ °
C
time-on-stream / min
0 50 100 150 200 2500.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
H2O
EtOH
time-on-stream / min
volu
me fra
ction / %
• complex breakthrough due to Type-V/Type-I isotherms
• roll-up effect for H2O due to replacement by EtOH
22 www.dynamicsorption.com
1. Measuring Breakthrough Curve
2. Measuring Pure Component Isotherms: 1 of each adsorptive for isothermal simulations 3 of each adsorptive for non-isothermal simulations
3. Predict Mixture Adsorption with IAST or Multi-Component Models
4. Predict Breakthrough Curves based on Mass- and Energy Balances
5. Evaluate mass transfer by varying kLDF to fit the predicted to the experimental Breakthrough Curves
Procedure
23 www.dynamicsorption.com
con
cen
trat
ion
c lo
adin
gq
distance r
Mass Transfer coefficient kLDF
Adsorptive
Adsorbent
Adsorbate
Convection, Diffusion
Film Diffusion
Pore Diffusion
Pore
Free Diffusion
KNUDSEN
Diffusion
Surface Diffusion
Film Diffusion
Adsorption
Convection, Diffusion
Effective InnerMass Transfer,
Linear Driving Force
(LDF)
Adsorption
Convection, Diffusion
W. Kast, Adsorption aus der Gasphase: Ingenieurwissenschaftliche Grundlagen und technische Verfahren, 1.Aufl., VCH Wiley Verlag, Weinheim, 1988.
Simplification
LDF
24 www.dynamicsorption.com
0 5 10 15 20 250
1
2
3
4
5
6
7
8
vo
lum
e f
ractio
n y
(CO
2)
/ %
time-on-stream t / min
34
36
38
40
42
44
46
48
50
Te
mp
era
ture
/
°C
0 5 10 15 20 250
1
2
3
4
5
6
7
8
vo
lum
e f
ractio
n y
(CO
2)
/ %
time-on-stream t / min
34
36
38
40
42
44
46
48
50
Te
mp
era
ture
/
°C
T1T2
T4T3
y(CO2)
T1T2 T4T3
y(CO2)
Fitting of Breakthrough Curves + TemperaturesExperiment Simulation
• After fitting the kLDF Mass Transfer Coefficient Good Agreement of Experiment and Simulation in a Standard Breakthrough Experiment (5% CO2 in N2)
• Course of Volume Fraction and Temperatures is depicted correctly
25 www.dynamicsorption.com
0 5 10 15 20 250
1
2
3
4
5
6
7
8
vo
lum
e f
ractio
n y
(CO
2)
/ %
time-on-stream t / min
34
36
38
40
42
44
46
48
50
Te
mp
era
ture
/
°C
Fitting of Breakthrough Curves + Temperatures
• After fitting the kLDF Mass Transfer Coefficient Good Agreement of Experiment and Simulation in a Standard Breakthrough Experiment (5% CO2 in N2)
• Course of Volume Fraction and Temperatures is depicted correctly
Overlay of Experiment (Points) and Simulation (Line)T4
y(CO2)
26 www.dynamicsorption.com
• Good correlation between experiment and simulation for Type I isotherms
• Heat effects can be simulated by using non-isothermal models
• Future Improvements: Using 2D, instead of 1D models (radial discretization)
Sample: 13XBFK, conditions: 2.5 % H2O in N2, 4 NL min-1, 25 °C (80 % RH)
𝑞eq = 𝑞max
𝐾1 ∙ 𝑝
1 + 𝐾1 ∙ 𝑝+
𝐾2 ∙ 𝑝𝑡
1 + 𝐾2 ∙ 𝑝𝑡
H2O on 13XBFK – Modeling with Dual-site Langmuir Sips isotherm model (DSLAI-SIPS)
0 100 200 300 400 500 6000.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Experiment
non-isothermal SIM
time-on-stream / min
vo
lum
e f
ractio
n H
2O
/ %
0 100 200 300 400 500 60025
30
35
40
45
50
55
60
65
T (150 mm)
non-isothermal SIM
tem
pe
ratu
re /
°C
time-on-stream / min
27 www.dynamicsorption.com
H2O on Silica Gel – Modeling with DSLAI-SIPSUsing heat of adsorption Q1, determined by fitting 3 isotherms
And Q2 = QEvap
Using heats of adsorption Q1, Q2, determined by fitting 3 isotherms
0 200 400 600 800 1000 12000.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Exp. y and T
SIM y and T
time-on-stream / min
volu
me fra
ction H
2O
/ %
24
26
28
30
32
34
36
38
40
tem
pera
ture
/ °
C
0 200 400 600 800 1000 12000.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Exp. y and T
SIM y and T
time-on-stream / min
volu
me fra
ction H
2O
/ %
24
26
28
30
32
34
36
38
40
tem
pera
ture
/ °
C
• Good correlation between experiment and simulation• Better prediction of breakthrough curve with Q2 = Qevap
• Better description of temperature curves with Q1, Q2 = heats of adsorption (1=LANGMUIR, 2=SIPS)
28 www.dynamicsorption.com
0 100 200 300 400 500 6000.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Experiment
isothermal SIM
non-isothermal SIM
time-on-stream / min
vo
lum
e f
ractio
n H
2O
/ %
0 100 200 300 400 500 60024
25
26
27
28
29
30
31
32
T (150 mm)
non-isothermal SIM
tem
pe
ratu
re /
°C
time-on-stream / min
Sample: Activated Carbon, conditions: 2.5 % H2O in N2, 4 NL min-1, 25 °C (80 % RH)Crank J.; The Mathematics of Diffusion, Oxford University Press, 1975.
H2O on Activated Carbon (Type V Isotherm) – Modeling with DSLAI-SIPS
• Good correlation between experiment and Simulation for with non-isothermal model• Poor Correlation for isothermal models
• Improvement of Breakthrough fit by using loading-dependent kLDF adsorption + pore filling by condensation But: prediction of temperatures gets worse
29 www.dynamicsorption.com
EtOH on Activated Carbon – Modeling with DSLAI-SIPS
0 10 20 30 40 50 60 70 80 90 1000.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Experiment
non-isothermal SIM
time-on-stream / min
vo
lum
e f
ractio
n E
tOH
/ %
0 10 20 30 40 50 60 70 80 90 10010
15
20
25
30
35
40
45
50
T
non-isothermal SIM
tem
pe
ratu
re /
°C
time-on-stream / min
• Good correlation between experiment and simulation
• Future Improvements: Using 2D, instead of 1D models (radial discretization)
Using Isosteric heat instead of heat of adsorption
30 www.dynamicsorption.com
• mixSorb L is very versatile instrument for application-related studies
Vapor Sorption, determine Isotherms, Mixture Isotherms
Breakthrough curves of other Adsorptivesin the Presence of Water
Adsorption Studies of Organic Vapors: VOC adsorption
• 3P-SIM is a powerful simulation tool for Breakthrough Prediction
• Future steps:
Simulation of vapor mixture adsorption
Implementing 2D, instead of 1D models (radial discretization)
Implementing isosteric heat into non-isothermal models, where possible
Characterization under application-related conditions!
31 www.dynamicsorption.com
Thank you for your attention!
Dr. Robert Eschrich, Leipziger Symposium on Dynamic Sorption, 2018-04-17