sorption measurements on zeolites under equilibrium and...
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Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Sorption Measurements on Zeolites under Equilibrium and
Non-Equilibrium
Project 2R. Staudt, A. Möller
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Aim of Project 2
• macroscopic measurement of transport diffusivities in adsorption/desorptionexperiments
• comparison of the obtained results with other techniques (NMR, QENS, ZLC etc.)
• supplying equilibrium data (isothermes)
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Systems under Investigation - period 1
methane, i-butane on ZSM-5 and silicalite-1
n-butane, n-hexane, n-octane and n-decane on zeolite A (XY-155 NaCa 76A)
propane, n-butane on zeolite A XY-293 NaCaA
propane, n-butane on modified zeolite A XY-293 TEOS-NaCaA
Equilibrium data for:
Transport diffusivities for:propane, n-butane on zeolite A (XY-155 NaCa76A, XY-293 NaCaA, and XY-293 TEOS-NaCaA)
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Instrumental Setup
Stocking volume
Magnetic suspension balance
Sample holder for thin layers of zeolite
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
• msample about 300 mg• evacuating of samples• heating of samples
– heating-rate 100 K/h– max. temperature 400 °C
• cooling down of sample0 100 200 300 400 500
-0,030
-0,025
-0,020
-0,015
-0,010
-0,005
0,000
0,005
measurement change temperature
time [min]
mea
sure
men
t cha
nge
[g]
0
100
200
300
temperature [°C
]
• Weight of silicalite-1 and ZSM-50 is constant above 200 °C.• A-Zeolite were heated up to 380 °C.
Preparation of the Samples
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Isotherms
, , • i-butane at 30°C, x, i-butane at 60°C
+ i-butane at 120°C, sun et al.
Isotherms on silicalite-1
0,00
0,40
0,80
1,20
1,60
2,00
0,0001 0,001 0,01 0,1 1 10
pressure [bar]
amou
nt a
dsor
bed
[mm
ol/g
]
0,00
0,50
1,00
1,50
2,00
0,0001 0,001 0,01 0,1 1 10
pressure [bar]
amou
nt a
dsor
bed
[mm
ol/g
]
•, , n-butane at 98°C, 151°C, 208°C
, , n-hexane at 104°C, 153°C, 195°C
Isotherms on zeolite A
Ref : M. S. Sun, D. B. Shah, H.H.Xu, O. Talu Adsorption Equilibira of C1 to C4 Alkanes, CO2 and SF6 on Silicalite, J. Phys. Chem. B, 1998, 102, S. 1466-1473,
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Adsorption-Desorption curve• Curve of an adsorption step and a desorption
step of n-butane on XY-155 NaCa76A at 200°C
adsorption from 4,6 mbar to 10,6 mbar
desorption from 10,6 mbar to 2,6 mbar
1,0
2,0
3,0
-100 900 1900 2900 3900
time [s]
mas
s ch
ange
[mg]
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Kinetic Behavior of n-butane
mass change for an adsorption step
(n-butane on XY-155 NaCa76A; 200 °C; p0=Vacuum, pE=16 mbar)
mass change for a desorption step
(n-butane on XY-155 NaCa76A; 200 °C; p0=10 mbar, pE=3 mbar)
-3,00
-2,00
-1,00
0,00
0 25 50 75 100
time [s]
mas
s ch
ange
[mg]
0,00
1,00
2,00
3,00
4,00
5,00
6,00
0 25 50 75 100
time [s]
mas
s ch
ange
[mg]
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Reproducibility of kinetics
Plot of relative uptakes for adsorption and desorption steps for n-butane on XY-293 NaCaA at 100 °C p0=2 mbar, pEnd=10 mbar
0
0,2
0,4
0,6
0,8
1
0 100 200 300 400 500time [s]
rela
tive
upta
ke
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Influence of a Surface barrier
relative Uptakes for a untreated and a modified zeolite material for propane at 100 °C: untreated NaCaA p0=3,1 mbar pEq= 14,5 mbar, TEOS modified p0=2,5 mbar pEq=
21,4 mbar, fitted with Nonisothermal and isothermal model, respectively
0
0,2
0,4
0,6
0,8
1
0 500 1000 1500 2000 2500 3000
time [s]
rela
tive
Upt
ake
Ψ(t)
Calculated Transport diffusivities: 4*10-13 m2/s, 3*10-14 m2/s
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Results of kinetic measurements
(7±2)*10-13145
(6±4)*10-13101propane(2,5±1,2)*10-12145(4,5±0,6)*10-12200(2,7±0,3)*10-13101n-butane
XY-293-2-CaA(7±5)*10-13200n-butane
(3,2±0,9)*10-12200
(1,6±0,6)*10-12200propane
XY-155-NaCaA
Diffusivities [m2/s]temperature [°C]alkane
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Comparison with other Data
Ref : J. Kärger et al.,Diffusion Fundamentals I, Leipzig 2005
Diffusivities of propane, n-butane and n-hexane on zeolite A (XY-155 NaCa76A); 200 °C
0,001
0,01
0,1
1
10
100
0 2 4 6 8 10 12 14 16 18
Carbon Number
Dx1
012
(m2 /s
) at 2
00°C
PFG NMR 473 K
PFG NMR 473 K
PFG NMR 473 K
NSE 473 K
ZLC 473 K
ZLC 473 K
XY 155nonisothermal
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Non-Isothermal Model
• Non-isothermal model was developed and published by D.M. Ruthven, L.K. Lee and H. Yucel.– Assumptions:
• sample consists of uniform spherical particles,• significant heat transfer resistance can only be
observed at the external surface of the sample,• intraparticle diffusion is significant resistance to mass
transfer,• the diffusivity is assumed constant (isotherms in Henry
regime).
Ref : D.M. Ruthven, L.K. Lee, H. Yucel, Kinetics of Non-Isothermal Sorption in Molecular Sieve Crystals, AiChE, Vol. 26, No. 1 (1980)
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Equations of the Model• solution of the Non-Isothermal model:
( )(1)
11cotcot231
1cot91
12
22
2
2
∑∞
=∞⎥⎦
⎤⎢⎣
⎡+
−+
⎟⎠⎞
⎜⎝⎛ ⋅⋅−⋅⎥
⎦
⎤⎢⎣
⎡ −
−=n
n
nnnn
nn
nn
t
qqqqq
trDqEXP
qqq
mm
β
( ) (2) 1cot3 2 αβ −=− nnn qqq
(3) 11
1 ⎟⎟⎠
⎞⎜⎜⎝
⎛+⋅
−⋅+
−=∞ β
αβ
β tEXPmmt
• calculation of α and β from the long time region with equation (3)
• numerical determination of qn for n=[1..10] as roots of equation (2)
• insertion of the qn values in equation (1) and applying them to exp. data
Ref : D.M. Ruthven, L.K. Lee, H. Yucel, Kinetics of Non-Isothermal Sorption in Molecular Sieve Crystals, AiChE, Vol. 26, No. 1 (1980)
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Long time region
estimation of slope and intercept for the non-isoth. model(n-butane on XY-155 NaCa76A; 200 °C;p0=10 mbar, pE=3 mbar)
estimation of slope and intercept for the non-isoth. model (n-butane on XY-155 NaCa76A; 200 °C;p0=Vacuum, pE=16 mbar)
y = -0,0145x - 2,2138R2 = 0,9088
-5,0
-4,0
-3,0
-2,0
-1,0
0,0
0 25 50 75 100
time [s]
ln(r
elat
ive
Upt
ake)
y = -0,0051x - 3,4164R2 = 0,8984
-5,0
-4,0
-3,0
-2,0
-1,0
0,0
0 50 100 150 200
time [s]
ln(1
-rel
ativ
e U
ptak
e)
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Fit on Experimental Data
D/r2= 9,6*10-3 s-1
r=9,3*10-6 mD=8*10-13 m2/s (n-butane on XY-155 NaCa76A; 200 °C;p0= 10 mbar, pE= 3 mbar)
0,0
0,2
0,4
0,6
0,8
1,0
0 25 50 75 100
time [s]
rela
tive
Upt
ake
D/r2=5,8*10-3 s-1
r=9,3*10-6 mD=5*10-13 m2/s(n-butane on XY-155 NaCa76A; 200 °C;p0= Vacuum, pE= 16 mbar)
0,0
0,2
0,4
0,6
0,8
1,0
0 25 50 75 100
time [s]
rela
tive
Upt
ake
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Half time for the fractional uptake• t0,5 is the time to reach the half of relative uptake • for linear isotherms should be the same for adsorption and
desorption steps
• t0,5 experimental 5,5 sRef : D. D. Do ,Adsorption Analysis: Equilibria and Kinetics, (1998)
0,00
0,20
0,40
0,60
0,80
1,00
0 25 50 75 100
time [s]
rela
tive
Upt
ake
Adsorption: n-butane on XY 155 NaCa76A at 200°C; p0=vacuum;pE=10,9 mbar
Desorption: n-butane on XY 155 NaCa76A at 200°C; p0=10 mbar; pE=3 mbar
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
94,22547 g
T
T p
gas supply
vacuum pump
gas circulationpump
storagevessel 1
storagevessel 2
microbalance
sample
T
gaschromatograph
magneticcoupling
IS 1
IS 2
injectionsystems
Calibration:Volume of vessel & sample holder, GC ...
Volume-Gravimetry:
Measurement: p, T, m
Calculation: mfl
1, mfl2, m1, m2
Volumetry with GC:
Measurement: p, T, c
Calculation: mfl
1, mfl2, m1, m2
Volume-Gravimetry & Volumetry with GC
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Adsorption Kinetics of binary mixture on Activated Carbon
t [h]0 5 10 15 20 25 30 35 40 45
∆m [g
]
46
47
48
49
50
51
CO2, p = 0,086 MPa
CH4, p = 0,045 MPa
CO2 + CH4, p = 0,101 MPa
CH4 + CO2, p = 0,113 MPa
t [h]
0 5 10 15 20
y CH
4(t)
und
x CH
4,ex
(t)
0,0
0,2
0,4
0,6
0,8
1,0
yCH4(t)
xCH4,ex(t)
Microbalance signal CH4/CO2 on AC Norit R1, T = 298 K, P = 0,113 MPaand P = 0,101 MPa.
Molar concentration of methane in the adsorptive (yCH4(t)) and in the adsorbate (xCH4(t)) for the adsorption of CH4/CO2 mixture on preloaded AC Norit R1
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Kinetics of CO2, CH4 and a mixture on 4A pellets
0
0,1
0,2
0,3
0,4
0 50 100 150
time [min]
wei
ght o
f sam
ple
[g]
0
0,2
0,4
0,6
0,8
1
0 50 100 150
time [min]
rela
tive
Upt
ake
Ψ(t)
weight of a 4A zeolite sample during an adsorptionstep for CO2 (30°C; pEq,CO2=0,22 bar), CH4+CO2(30°C; pEq,CH4+CO2=5,07 bar) und CH4 (30°C; pEq,CH4=1,02 bar)
relative Uptake of a 4A zeolite sample during an adsorption step for CO2 (30°C; pEq,CO2=0,22 bar), CH4+CO2 (30°C; pEq,CH4+CO2=5,07 bar) und CH4(30°C; pEq,CH4=1,02 bar)
Used Model : ( ) 22
3-1-1 ⎟⎟
⎠
⎞⎜⎜⎝
⎛ Ψ⋅⋅
⋅=
tt
rDEffπ
πRef : F. Dreisbach, Fortschritt-Berichte, VDI, 3, 547, 1998, 131; W. Kast, Adsorption aus der Gasphase, VCH-Verlag, Weinheim, 1988
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Kinetics of CO2, CH4 and a mixture on 4A pellets
effektive transport coefficients as a function of loadingfor CO2 (30°C; pEq,CO2=0,22 bar), ∆ CH4+CO2
(30°C; pEq,CH4+CO2=5,07 bar) und • CH4 (30°C; pEq,CH4=1,02 bar)
0,0
0,2
0,4
0,6
0,8
1,0
0 50 100 150
time [min]
rela
tive
Upt
ake
Ψ(t)
relative Uptake of a 4A zeolite sample during an adsorption step for CO2 (30°C; pEq,CO2=0,22 bar), CH4+CO2 (30°C; pEq,CH4+CO2=5,07 bar) und CH4
(30°C; pEq,CH4=1,02 bar); Fit of experimental data
0,0E+00
1,0E-09
2,0E-09
3,0E-09
0 0,2 0,4 0,6 0,8 1
loading of sample
DEf
f (m
2 /s]
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Kinetics of CO2, CH4 and a mixture on 4A pellets
relative amount of sorbate in 4A zeolite pellets during a desorptionstep at 30°C CO2, CH4+CO2 and CH4
0
0,2
0,4
0,6
0,8
1
0 50 100 150
time [min]
rela
tive
amou
nt o
f sor
bate
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Work Programm
• Completion of the transient sorption device • Measurements of binary adsorption equilibria• Studies of existence and quantification of possible surface
barriers• Two component diffusion in one dimensional channels• Compare and discuss results from other techniques in this
project
Institut für Nichtklassische Chemie e.V. an der Universität Leipzig
Requested Financial Support
Personnel• 1 PhD student BAT IIa/2, for performing and analysing the gravimetric and
volume-gravimetric experiments• 1 Research Assistant (80 h/month), for the routine measurement of adsorption
isotherms
Durable Equipments• Pressure sensors (ultrahigh precision), € 2,500.-• Data acquisition system, € 2,500.-• Gas circulator pump, € 800.-• Gas storage vessel for volumetric part of apparatus, € 1200.-
Consumables• Sorptive gases (ultra-high purity), € 6,000.-• Delivery and handling of gas steel bottles, € 1,500.-• Valves, Sealings etc., € 3,500.-• Computer & Printer Supply, € 1,000.-
Travelling 2000 € per year