Silver-Decorated Hafnium Metal-Organic Framework for. Ethylene/Ethane Separation

Transcription

1 Supporting Information Silver-Decorated Hafnium Metal-Organic Framework for Ethylene/Ethane Separation Yuxiang Wang, Zhigang Hu, Youdong Cheng, and Dan Zhao * Department of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore Correspondence and requests for materials should be addressed to D.Z. ( chezhao@nus.edu.sg). S1

2 Calculation of Modified Auger Parameter The Auger parameter ( ) is the difference between the kinetic energy of an Auger electron minus the kinetic energy of a photoelectron. Modified Auger parameter ( h ) was defined by Gaarenstroom and Winograd as follows, 1-2 h E Auger ) E (PE) (1) ( B where E Auger is the kinetic energy of Auger electrons and E PE is the binding energy of photon electrons. B h is the photon energy, Calculation of Isosteric Heat of Adsorption (Q st ) The gas adsorption isotherms measured at 283 K and 298 K were firstly fitted to a virial equation (Equation 2). The fitting parameters were then used to calculate the isosteric heat of adsorption (Q st ) using Equation 3, 1 ln P ln N a N b N m m n i i i T i i i i Qst R ain i (3) where P is pressure (mmhg), N is adsorbed quantity (mmol g -1 ), T is temperature (K), R is gas constant (8.314 J K -1 mol -1 ), a i and b i are virial coefficients, m and n represent the number of coefficients required to adequately describe the isotherms (herein, m = 5, n = 2). Calculation of Gas Selectivity based on Ideal Adsorption Solution Theory (IAST) 3 The gas adsorption isotherms were firstly fitted to a dual-site Langmuir-Freundlich (DSLF) model (Equation 4), q b p q b p q 1 1 A B sat, A A sat, B B A B bap bbp where q is the amount of adsorbed gas (mmol g -1 ), p is the bulk gas phase pressure (bar), q sat is the saturation amount (mmol g -1 ), b is the Langmuir-Freundlich parameter (bar -α ), α is the Langmuir-Freundlich exponent (dimensionless) for two adsorption sites A and B indicating the presence of weak and strong adsorption sites. IAST starts from the Raoults Law type of relationship between fluid and adsorbed phase, P Py P x o i i i i (2) (4) (5) P n n i xi i 1 i 1 Pi 1 (6) where P i is partial pressure of component i (bar), P is total pressure (bar), y i and x i represent mole fractions of component i in gas and adsorbed phase (dimensionless). P i is equilibrium vapour pressure (bar). In IAST, P i is defined by relating to spreading pressure π, S P i qi( Pi) dp (Constant) i RT Pi (7) where π is spreading pressure, S is specific surface area of adsorbent (m 2 g -1 ), R is gas constant S2

3 (8.314 J K -1 mol -1 ), T is temperature (K), q i (P i ) is the single component equilibrium obtained from isotherm (mmol g -1 ). For a dual-site Langmuir-Freundlich (DSLF) model, we have an analytical expression for the integral, Pi qi( P) q q dp b P b P P i,, (Constant) sat A A sat B ln[1 ( ) ] ln[1 ( B i A i B i ) ] i A B (8) The isotherm parameters will be known from the previous fitting. For a binary component system the unknowns will be П, P 1, and P 2 which can be obtained by simultaneously solving Equations 5 and 7. The adsorbed amount for each component in a mixture is q x q mix i i T (9) 1 q x ( ) n i o T i 1 qi Pi (1) where q mix i is the adsorbed amount of component i (mmol g -1 ), q T is the total adsorbed amount (mmol g -1 ). The adsorption selectivities S ads were calculated using Equation 1. S ads q1/ q2 p / p 1 2 In this study, IAST calculations were carried out assuming C 2 H 4 /C 2 H 6 (5/5) binary mixed gases at 298 K and pressures up to 1 bar. (11) S3

4 Scheme S1. The scheme of a home-built breakthrough set up used in this study. S4

5 Intensity (a.u.) NUS-6(Hf) NUS-6(Hf)-Ag O 1s C 1s Ag 3d 5/2 Hf 4f Hf 4d 5/2 4d 3/2 Hf 4p 3/2 3d 3/2 S 2p Binding Energy (ev) Figure S1. XPS survey of NUS-6(Hf) and NUS-6(Hf)-Ag. S5

6 Intensity (a.u.) Intensity (a.u.) Intensity (a.u.) (a) Theta (degree) (b) Ag 3d Binding Energy (ev) (c) Ag MNN Binding Energy (ev) Figure S2. (a) XPS survey of UiO-66(Hf)-Ag. (b) XPS detailed spectrum of Ag 3d of UiO-66(Hf)-Ag. (c) XPS detailed spectrum of Ag auger lines of UiO-66(Hf)-Ag. S6

7 (a) (b) Figure S3. SEM images with 5 k (a) and 25 k (b) magnification of NUS-6(Hf) treated with HBF 4 aqueous solution of the ph value similar to that of the mother solution in PSIE process. The surface morphology of these crystals resembled that of NUS-6(Hf)-Ag, suggesting that the rugged surface of the NUS-6(Hf)-Ag crystals may originate from the etching of HBF 4 generated in situ during the ion-exchange process. S7

8 Figure S4. EDS spectrum of NUS-6(Hf)-Ag. S8

9 Gas Uptake (mmol g -1 ) Absolute Pressure (kpa) Figure S5. C 2 H 4 (circle) and C 2 H 6 (square) sorption isotherms of UiO-66(Hf)-Ag (red) and UiO-66(Hf) (blue) at 298 K (filled, adsorption; open, desorption). S9

10 Gas Uptake (mmol g -1 ) C 2 H 4 sorption, NUS-6(Hf)-Ag C 2 H 4 sorption, NUS-6(Hf) C 2 H 6 sorption, NUS-6(Hf)-Ag C 2 H 6 sorption, NUS-6(Hf) Absolute Pressure (kpa) Figure S6. C 2 H 4 and C 2 H 6 sorption isotherms of NUS-6(Hf) and NUS-6(Hf)-Ag at 283 K (filled, adsorption; open, desorption). S1

11 Q st / kj mol Q st of C 2 H 4 adsorption Q st of C 2 H 6 adsorption Gas Uptake / mmol g -1 Figure S7. Q st of C 2 H 4 and C 2 H 6 in NUS-6(Hf). S11

12 Intensity (a.u.) V ads (cm stp g -1 ) (a) (b) Relative Pressure (P/P ) Theta (degree) Figure S8. (a) N 2 sorption isotherm at 77 K of NUS-6(Hf)-Ag after 8 cycles of C 2 H 4 sorption tests (filled, adsorption; open, desorption). (b) XRD pattern of NUS-6(Hf)-Ag after 8 cycles of C 2 H 4 sorption tests. S12

13 F F Ethane Ethylene Time / s Figure S9. Breakthrough curves of C 2 H 4 and C 2 H 6 running through a bypass gas line. The dead volume time of the gas mixture was hence calculated to be s. S13

14 Composition (%) 6 5 Ethane Ethylene Time (s) Figure S1. Typical desorption curves of NUS-6(Hf)-Ag under the condition of 2 sccm He flow at room temperature. S14

15 F F -1 F F -1 (a) Ethane Ethylene (b) Ethane Ethylene Time / s Time / s Figure S11. 2 nd (a) and 3 rd (b) breakthrough curves obtained by passing an equimolar C 2 H 4 /C 2 H 6 mixture gas through a column packed with NUS-6(Hf)-Ag at 1 atm, room temperature. S15

16 Intensity (a.u.) Intensity (a.u.) Intensity (a.u.) (a) (b) 2 Theta (degree) Ag 3d 5/2 Ag 3d 3/ (c) Binding Energy (ev) Binding Energy (ev) Figure S12. (a) XRD pattern of NUS-6(Hf)-Ag after breakthrough experiment. (b) XPS detailed spectra of Ag 3d. (c) Auger spectrum of Ag of NUS-6(Hf)-Ag after breakthrough experiment. The M 4 N 5 N 5 line was located at ev and 3d 5/2 was located at ev, leading to a modified auger parameter equal to ev. S16

17 Entry Table S1. Calculation results of three breakthrough runs. C 2 H 6 residence time / s C 2 H 6 corrected residence time * / s C 2 H 4 residence time / s C 2 H 4 corrected residence time * / * Corrected residence time is equal to corresponding residence time minus dead volume time. s C 2 H 6 uptake C 2 H 4 uptake / / mmol g -1 mmol g -1 selectivity S17

18 References (1) Gaarenstroom, S. W.; Winograd, N. Initial and final state effects in the ESCA spectra of cadmium and silver oxides. J. Chem. Phys. 1977, 67, (2) Wagner, C. D.; Joshi, A. The auger parameter, its utility and advantages: a review. J. Electron. Spectrosc. Relat. Phenom. 1988, 47, (3) Myers, A. L.; Prausnitz, J. M. Thermodynamics of mixed-gas adsorption. AIChE J. 1965, 11, S18