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Dynamic Sorp rption Experiments Dr. Robert Eschrich 1 Christian - - PowerPoint PPT Presentation

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Fle lexible MOFs for Gas Separation A Case Study Based on Static and Dynamic Sorp rption Experiments Dr. Robert Eschrich 1 Christian Reichenbach 1 , Andreas Mller 1 , Jens Mllmer 2 , Marcus Lange 2 , Hannes Preiler 2 , Roger Glser 2 ,

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www.dynamicsorption.com

Fle lexible MOFs for Gas Separation ‒ A Case Study Based on Static and Dynamic Sorp rption Experiments

  • Dr. Robert Eschrich1

Christian Reichenbach1, Andreas Möller1, Jens Möllmer2, Marcus Lange2, Hannes Preißler2, Roger Gläser2, Matthias Thommes3

1 3P INSTRUMENTS GmbH & Co. KG 2 INC Leipzig e.V. 3 Quantachrome Instruments

2018-05-08 CPM8

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N2 / / 77 K

VP, theor. = 0.42 cm3 g-1 VP, exp = 0.03 cm3 g-1

3

CO CO2 / / 273 K

VP, theor. = 0.42 cm3 g-1 VP, exp = 0.38 cm3 g-1 Desorption Adsorption

  • J. Lincke, PhD-Thesis, Universität Leipzig, 20

2012.

  • J. Lincke, D. Lässig, H. Krautscheid, Tetrahedron Letters 2010, 51, 653.

H2(Metrz-ia)

Accessible in a multigramm scale X-ray cri cristall llography 47 % porosity VPor

  • re,theor. =

= 0.4 .42 cm cm3 g-1

Relative pressure p / p0 Loading n / mmol g-1 Relative pressure p / p0 Loading n / mmol g-1

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  • S. Kitagawa, K. Uemura, Chem. Soc. Rev. 2005

05, 34, 109, S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. 2004 04, 116, 2388-2430; Angew. Chem. Int. Ed. 2004 04, 43, 2334-2375.

  • S. Horike, S. Shimomura, S. Kitagawa, Nat. Chem. 2009

09, 1, 695-704.

  • 1. Generation
  • 2. Generation

Type I Type II Type III

Reversible network collapse Guest-induced renewal Guest-induced transformation

gate opening

pressure loading

  • 3. Generation
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  • 1. Pure

Component Sorption

  • 2. In situ

PXRD Conclusions on Separation Effects and the Influence of the Structural Flexibility

  • 3. Mixture Sorption

Interpretation of stepped Isotherms with C4-Hydrocarbons

TCI Deutschland GmbH, http://www.tcichemicals.com/eshop/de/de/category_index/03900/.

  • A. Schneemann, V. Bon, I. Schwedler, I. Senkovska, S. Kaskel, R. A. Fischer, Chem.Soc.Rev. 2014, 43, 6062.
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pressure p / kPa pressure p / / kPa loa loadin ing n / / mmol l g-1 loa loadin ing n / / mmol l g-1

n-Butane Isotherms

  • stepped isotherm with strong hysteresis in low pressure region (< 5 kPa)
  • hysteresis dependent on pressure and temperature

 Structural change?

Linear Logarithmic

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  • VP, exp = 0.31 cm3 g-1 (n-Butane) and 0.34 cm3 g-1 (Isobutane)
  • Isobutane adsorption is much slower than n-Butane adsorption!

pressure p / kPa pressure p / / kPa loa loadin ing n / / mmol l g-1 loa loadin ing n / / mmol l g-1

n-Butane n-Butane Isob Isobutane Isob Isobutane

Comparison of n-Butane and Isobutane at 298 K

Linear Logarithmic

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Phase 1 pressure p / / kPa loa loadin ing n / / mmol l g-1

Uptake Curves – an indication for the rate of adsorption

tim time t / / min in rel elativ ive uptake

n-But Butane Isob

  • butane

n-But Butane, T T = = 298 K Phase 1, T = 298 K, P < 0.1 kPa

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Phase 2 pressure p / / kPa loa loadin ing n / / mmol l g-1

Uptake Curves – an indication for the rate of adsorption

tim time t / / min in rel elativ ive uptake

n-But Butane Isob

  • butane

n-But Butane, T T = = 298 K Phase 2, T = 298 K, P ≥ 30 kPa

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gate opening

  • gate opening has influence on rate of adsorption
  • Can this be utilized for a kinetic separation?

pressure p / / kPa loa loadin ing n / / mmol l g-1

Uptake Curves – an indication for the rate of adsorption

tim ime t / / min in rel elativ ive uptake

n-But Butane Isob

  • butane

n-But Butane, T T = = 298 K gate opening, T = 298 K, 0.1 kPa < p < 1.1 kPa

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gate opening

  • gate opening has influence on rate of adsorption
  • Can this be utilized for a kinetic separation?

pressure p / / kPa loa loadin ing n / / mmol l g-1

Uptake Curves – an indication for the rate of adsorption

tim time t / / min in rel elativ ive uptake

Isob

  • butane

n-But Butane t0.

0.5 =

= 14 mi min n-But Butane, T T = = 298 K t0.

0.5 =

= 667 mi min

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Coupling of sorption experiments with powder x-ray diffractometry  structural changes oberservable?

Gas Supply Detector X-ray source Cu-Ka

Experimental Setup

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in inten ensity pressure p / / kPa loa loadin ing n / / mmol l g-1 n-Bu Butane

Adsorption of n-Butane

  • Structural Change observable during n-Butane adsorption

vacuum

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pressure p / / kPa loa loadin ing n / / mmol l g-1 n-Bu Butane

Desorption of n-Butane

  • Closed structure is retained after desorption. Open structure is retained after resolvatization
  • Monoclinic crystal structure before and after gate-opening
  • With n-Butane  Guest-induced transformation  3. Generation – Type II

inten ensity

vacuum

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  • High experimental effort – continous mixing of the gas phase
  • GC analysis before and after each experiment  partial loadings
  • Calculation of the mixture isotherm with the IAST

 thermodynamically ideal behaviour

mol

  • lar fr

fraction of

  • f n-Butane in

in gas phase yn mol

  • lar fr

fraction of

  • f n-Butane in

in adsorbate xn loa loadin ing n / / mmol l g-1 mol

  • lar fr

fraction of

  • f n-Butane in

in gas phase yn

Static Volumetric-Gravimetric Measurements with n-Butane/Isobutane Gas Mixtures

ptotal= 40 kPa ptotal= 40 kPa total

n-But Butane Isob

  • butane
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  • faster adsorption of n-Butane opens pore structure
  • change in selectivity over time can be observed

tim time t / / min in tim time t / min in mol

  • lar fr

fraction of

  • f n-Butane xn

and nd Isob Isobutane xiso

so in

in adsorbate se selec lectiv ivity for n-Bu Butane e

Static Volumetric-Gravimetric Measurements with n-Butane/Isobutane Gas Mixtures

n-Butane Isob Isobutane T = 313 K, ptotal= 40 kPa

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  • Equilibrium times for different

gas mixtures

  • Partial pressure of n-Butane determines

the time until equilibrium  more n-Butane = faster equilibrium time

n: n:iso=7 =75:25 25 50: 50:50 50 25: 25:75 75 t0.

0.5 =

= 14 mi min 55 mi min 391 mi min

tim time t / / min in rel elativ ive uptake

Static Volumetric-Gravimetric Measurement: Uptake Curves

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  • Sorption takes place in open system
  • Pressure is constant
  • Gas Mixtures only
  • Outlet composition is recorded over

time

  • Fixed Bed Adsorber: Gas must not pass

without interaction

𝑜adsorbed = 𝑜 in(𝑢)d𝑢 − 𝑜 out(𝑢)d𝑢 𝑜adsorbed = 𝑊 in(𝑢) 𝑧in(𝑢) 𝑊

m

d𝑢 − 𝑊 out(𝑢) 𝑧out(𝑢) 𝑊

m

d𝑢

0.0 0.2 0.4 0.6 0.8 1.0 20 40 60 80 100

  • rel. breakthrough / %

time-on-stream / s

Breakthrough Curve Experiment

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  • BTC from n-Butane and Isobutane

 Combination of equilibrium and kinetic effects

  • Adsorption of n-Butane is favored in the dynamic measurement

n : : is iso = = 25:75 75 n : : is iso = = 50:50 50 n : : is iso = = 80:20 20 C4 mixtures in N2: 313 K, Flow: 3 cm3 min-1 ptotal = 100 kPa, pC4 = 40 kPa

spe pecif ific ic ti time t / m / min g-1 rela elativ ive con

  • ncentratio

ion

Breakthrough Curves

Rela elativ ive con

  • ncentratio

ion Rela elativ ive con

  • ncentratio

ion spe pecif ific ic ti time t / m / min g-1 spe pecif ific ic ti time t / m / min g-1

tot

  • tal

tot

  • tal

tot

  • tal

n-Butane n-Butane n-Butane Isob sobutane Isob sobutane

Isobu

  • butane
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  • eff. selectivity bn/iso

(dynamic) 3.9 4.7 1.8

  • Calculating the partial loadings by

integrating over the Breakthrough curves  Determining effective selectivity β

  • Values are very different from

thermodynamic selectivity α

  • Gate opening influences

selectivity in dynamic processes

~0.5 ideal selectivity an/iso (equilibrium)

mola lar fr fraction of

  • f

n-Butane in in ad adsorbate xn mola lar fr fraction of

  • f n-Butane in

in gas as phas ase yn Comparison of Selectivities: Dynamic vs. Static

T = 313 K, ptotal= 40 kPa

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  • Enrichment of Isobutane on the surface in equilibrium
  • Sorption-induced structural changes determined with XRD
  • gate opening dependent on n-Butane partial pressure
  • Stepwise breakthrough curves for n-Butane; spontaneous

Breakthrough for Isobutane

  • Enrichment of n-Butane on the surface in dynamic

measurements

  • Kinetics of gate-opening determine selectivities

 interesting for gas separation applications

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