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 Möller 1 , Jens Möllmer 2 , Marcus Lange 2 , Hannes Preißler 2 , Roger Gläser 2 , Matthias Thommes 3 1 3P INSTRUMENTS GmbH & Co. KG 2 INC Leipzig e.V. 3 Quantachrome Instruments 2018-05-08 CPM8 www.dynamicsorption.com 1
Accessible in a multigramm scale X-ray cri cristall llography 3 47 % porosity H 2 (Metrz-ia) cm 3 g -1 V Por ore,theor. = = 0.4 .42 cm CO CO 2 / / 273 K N 2 / / 77 K Loading n / mmol g -1 Loading n / mmol g -1 Desorption Adsorption V P, theor. = 0.42 cm 3 g -1 V P, theor. = 0.42 cm 3 g -1 V P, exp = 0.03 cm 3 g -1 V P, exp = 0.38 cm 3 g -1 Relative pressure p / p 0 Relative pressure p / p 0 J. Lincke, PhD-Thesis, Universität Leipzig, 20 2012. www.dynamicsorption.com 2 J. Lincke, D. Lässig, H. Krautscheid, Tetrahedron Letters 2010, 51, 653.
Reversible network collapse Type I 1. Generation Type III Guest-induced renewal 2. Generation Type II Guest-induced transformation 3. Generation loading gate opening pressure 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. www.dynamicsorption.com 3 S. Horike, S. Shimomura, S. Kitagawa, Nat. Chem. 2009 09, 1, 695-704.
1. Pure 2. In situ Component PXRD Sorption Interpretation of stepped Isotherms with C 4 -Hydrocarbons 3. Mixture Sorption Conclusions on Separation Effects and the Influence of the Structural Flexibility TCI Deutschland GmbH, http://www.tcichemicals.com/eshop/de/de/category_index/03900/. www.dynamicsorption.com 4 A. Schneemann, V. Bon, I. Schwedler, I. Senkovska, S. Kaskel, R. A. Fischer, Chem.Soc.Rev. 2014, 43, 6062.
n -Butane Isotherms Linear Logarithmic l g -1 l g -1 / mmol / mmol ing n / ing n / loadin loadin loa loa pressure p / kPa pressure p / / kPa • stepped isotherm with strong hysteresis in low pressure region (< 5 kPa) • hysteresis dependent on pressure and temperature Structural change? www.dynamicsorption.com 5
Comparison of n -Butane and Isobutane at 298 K Linear Logarithmic Isobutane Isob Isobutane Isob l g -1 l g -1 / mmol / mmol n -Butane n -Butane ing n / ing n / loadin loadin loa loa pressure p / kPa pressure p / / kPa • V P, exp = 0.31 cm 3 g -1 ( n -Butane) and 0.34 cm 3 g -1 (Isobutane) • Isobutane adsorption is much slower than n -Butane adsorption! www.dynamicsorption.com 6
Uptake Curves – an indication for the rate of adsorption n -But Butane, T T = = 298 K n -But Butane l g -1 / mmol ive uptake Isob obutane Phase 1, T = 298 K, ing n / P < 0.1 kPa elativ loadin rel loa Phase 1 pressure p / / kPa time t / tim / min in www.dynamicsorption.com 7
Uptake Curves – an indication for the rate of adsorption n -But Butane, T T = = 298 K n -But Butane Phase 2 l g -1 / mmol ive uptake Isob obutane Phase 2, T = 298 K, ing n / P ≥ 30 kPa elativ loadin rel loa pressure p / / kPa time t / tim / min in www.dynamicsorption.com 8
Uptake Curves – an indication for the rate of adsorption n -But Butane, T T = = 298 K n -But Butane l g -1 / mmol ive uptake gate opening , T = 298 K, gate opening ing n / 0.1 kPa < p < 1.1 kPa elativ loadin rel loa Isob obutane pressure p / / kPa tim ime t / / min in • gate opening has influence on rate of adsorption • Can this be utilized for a kinetic separation? www.dynamicsorption.com 9
Uptake Curves – an indication for the rate of adsorption n -But Butane, T T = = 298 K l g -1 / mmol ive uptake Isob obutane n -But Butane t 0. 0.5 = = 667 mi min gate opening t 0. 0.5 = = 14 mi min ing n / elativ loadin rel loa pressure p / / kPa time t / tim / min in • gate opening has influence on rate of adsorption • Can this be utilized for a kinetic separation? www.dynamicsorption.com 10
Experimental Setup Coupling of sorption experiments with powder x-ray diffractometry structural changes oberservable? Gas Supply X-ray source Detector Cu-K a www.dynamicsorption.com 11
Adsorption of n -Butane n -Bu Butane l g -1 / mmol ensity inten ing n / in loadin loa vacuum pressure p / / kPa • Structural Change observable during n -Butane adsorption www.dynamicsorption.com 12
Desorption of n -Butane n -Bu Butane l g -1 / mmol ensity inten ing n / loadin loa vacuum pressure p / / kPa • 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 www.dynamicsorption.com 13
Static Volumetric-Gravimetric Measurements with n -Butane/Isobutane Gas Mixtures in of n -Butane in total l g -1 adsorbate x n n -But Butane / mmol fraction of p total = 40 kPa ing n / loadin olar fr Isob obutane p total = 40 kPa loa mol mol olar fr fraction of of n -Butane in in gas phase y n mol olar fr fraction of of n -Butane in in gas phase y n 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 www.dynamicsorption.com 14
Static Volumetric-Gravimetric Measurements with n -Butane/Isobutane Gas Mixtures in adsorbate T = 313 K, p total = 40 kPa of n -Butane x n e Butane ivity for n -Bu Isobutane Isob so in Isobutane x iso fraction of n -Butane lectiv selec olar fr nd Isob se mol and time t / tim / min in time t / min tim in • faster adsorption of n -Butane opens pore structure • change in selectivity over time can be observed www.dynamicsorption.com 15
Static Volumetric-Gravimetric Measurement: Uptake Curves • Equilibrium times for different gas mixtures • Partial pressure of n -Butane determines ive uptake the time until equilibrium n: n:iso=7 =75:25 25 50: 50:50 50 25: 25:75 75 more n -Butane = faster equilibrium time t 0. 0.5 = = 14 mi min 55 mi min 391 mi min elativ rel time t / tim / min in www.dynamicsorption.com 16
Breakthrough Curve Experiment 100 rel. breakthrough / % • Sorption takes place in open system 80 60 • Pressure is constant 40 • Gas Mixtures only 20 • Outlet composition is recorded over 0 0.0 0.2 0.4 0.6 0.8 1.0 time time-on-stream / s • Fixed Bed Adsorber : Gas must not pass 𝑜 adsorbed = 𝑜 in (𝑢)d𝑢 − 𝑜 out (𝑢)d𝑢 without interaction 𝑜 adsorbed = 𝑊 in (𝑢) 𝑧 in (𝑢) d𝑢 − 𝑊 out (𝑢) 𝑧 out (𝑢) d𝑢 𝑊 𝑊 m m www.dynamicsorption.com 17
Breakthrough Curves n : : is iso = = 80:20 20 n : : is iso = = 50:50 50 n : : is iso = = 25:75 75 tot otal tot otal ion ion ion Isob sobutane n -Butane oncentratio oncentratio oncentratio otal tot ive con ive con ive con obutane Isobu n -Butane elativ elativ elativ n -Butane Isob sobutane Rela Rela rela spe pecif ific ic ti time t / m / min g -1 spe pecif ific ic ti time t / m / min g -1 spe pecif ific ic ti time t / m / min g -1 • BTC from n -Butane and Isobutane C 4 mixtures in N 2 : Combination of equilibrium and kinetic effects 313 K, Flow: 3 cm 3 min -1 • Adsorption of n -Butane is favored in the dynamic measurement p total = 100 kPa, p C4 = 40 kPa www.dynamicsorption.com 18
Comparison of Selectivities: Dynamic vs. Static 1.8 eff. selectivity b n/iso • Calculating the partial loadings by adsorbate x n (dynamic) 4.7 of integrating over the Breakthrough curves fraction of Determining effective selectivity β in ad • Values are very different from lar fr n -Butane in thermodynamic selectivity α ideal selectivity a n/iso mola 3.9 (equilibrium) ~0.5 • Gate opening influences selectivity in dynamic processes T = 313 K, p total = 40 kPa mola lar fr fraction of of n -Butane in in gas as phas ase y n www.dynamicsorption.com 19
• 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 www.dynamicsorption.com 20
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