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 2 R. Staudt, A. Möller

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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