On the Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane

Transcription

1 Supporting Information: On the Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane D. Delgado a, B. Solsona b,*, A. Ykrelef b, e, A. Rodríguez-Gómez c, A. Caballero c, E. Rodríguez-Aguado d, E. Rodríguez-Castellón d, J.M. López Nieto a,* a) Instituto de Tecnología Química, Universitat Politècnica de València- Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, Valencia, Spain. b) Department of Chemical Engineering, Universitat de València, Av. Universitat s/n, Burjassot-Valencia, Spain. c) Instituto de Ciencia de Materiales de Sevilla (CSIC-University of Seville) and Departamento de Quimica Inorganica, University of Seville. Avda. Américo Vespucio, Seville, Spain. d) Departamento de Química Inorgánica, Universidad de Málaga, Málaga, Spain e) On leave from Université de Blida 1, Faculté de Technologie, Blida, Argelie. S1

2 Ethane conversion, % Selectivity, % A W/F = methane and begin to be formed Time on line, h Ethylene B C W/F = Methane Time on line, h Carbon balance, % C H2 yield W/F = C-balance Time on line, h Yield, % Figure S1. Evolution of the ethane conversion (A), selectivity to reaction products (B) and yield and carbon balance (C) with the time on line for Sn-NiO catalyst. Reaction conditions: / : 30/0/70 (molar ratio), T=475ºC, contact time, W/F, from 2.7 to 20 g cat h (mol C2 ) -1. S2

3 Table S1. Bulk and surface average composition of fresh Sn- and Nb- promoted NiO catalysts Sample Composition (at. %) Bulk a Surface b Ni Promoter Ni Promoter Sn-NiO Nb-NiO a) Obtained by EDX; b) Calculated by XPS S3

4 c Nb-NiO Sn-NiO NiO Ni-O Vibrational modes Nb-O Vibrational modes Intensity (u.a.) b 494 a Wavenumber (cm -1 ) Figure S2. Raman spectra of fresh NiO-based catalysts. a) Un-NiO b) Sn-NiO c) Nb- NiO. S4

5 A B Ni-Kα Sn-Kα Figure S3. HAADF-STEM images and EDX maps of Nb-NiO (A) and Sn-NiO (B) catalysts. S5

6 A Image Spectrum At. % B Spec.1 At. % Spec.2 At. % Image Spec. At. % Ni 94.6 Ni Nb 5.9 Sn A B Figure S4. HAADF-STEM images and the corresponding atomic compositions obtained by EDX of Nb-NiO (A) and Sn-NiO (B) catalysts. The data of image spectra for both catalysts correspond to the catalyst average composition (see table S1). S6

7 Ni 2p3/2 O 1s c CPS c CPS b b a a Binding energy (ev) Binding energy (ev) Figure S5. Ni 2p3/2 and O1s core level XPS spectra of NiO based catalysts: a) Un-NiO b) Sn-NiO c) Nb-NiO. S7

8 Fit Experimental A 81 min B 114 min Normalized XANES 51 min 45 min 0 min Normalized XANES 81 min 42 min 0 min Normalized XANES Energy (ev) D 75 min 48 min 12 min 0 min Normalized XANES Energy (ev) C 126 min 81 min 27 min 0 min Energy (ev) Energy (ev) Figure S6. Ni K-edge XANES spectra of NiO-based during reduction-reoxidationreduction experiments at 450ºC*, recorded at times when the highest degree of reduction or oxidation is achieved. Linear combination fits are also depicted. A)Nb-NiO B) Sn- NiO C) La-NiO and D) Un-NiO. * Reduction in :, 25/25 (ml/min). Reoxidation:, 5/25 (ml/min). Reduction in :, 5/25 (ml/min) S8

9 Table S2. Summarized results of linear combination fitting of normalized XANES spectra during reduction-reoxidation-reduction under, and mixtures, respectively. Sample Treatment t i (min) t f (min) % NiO % Ni R-factor x * * * Nb-NiO x x x x x 10-4 Sn-NiO x x ** x x x 10-4 NiO-ox x 10-4 La-NiO x x x x x x x 10-5 t i : initial time of treatment t f : time of the maximum degree of oxidation/reduction S9

10 a / c Energy (ev) Energy (ev) b d Reduction degree / Reduction degree Time (min) Time (min) Figure S7. Time-resolved Ni K-edge XANES spectra (a, c), and the corresponding kinetic curves calculated by LCF from the time-resolved Ni K-edge XANES spectra (b, d), during in situ treatment in the presence of ethane, with and without oxygen in the feed, at 450ºC* for un-nio (a,b) or Sn-NiO (c and d). Feed:, 5/25 (ml/min); or / = 5/5/20 S10

11 Table S3. Summarized results of linear combination fitting of normalized XANES spectra of NiNbO catalyst at different temperatures during reduction-reoxidationreduction under, and mixtures, respectively. Sample (Reaction temperature) Nb-NiO (400ºC) Nb-NiO (450 ºC) Nb-NiO (500 ºC) Treatment t i (min) t f (min) % NiO % Ni R-factor x x x * * * x x * * * x x x x * * * x x x 10-5 t i : initial time of treatment t f : time of the maximum degree of oxidation/reduction S11

12 Table S4. Summarized results of linear combination fitting of normalized XANES spectra of NiSnO catalyst at different temperatures during reduction-reoxidationreduction under, and mixtures, respectively. sample (Reaction temperature) Sn-NiO (400ºC) Sn-NiO (450 ºC) Sn-NiO (500 ºC) Treatment t i (min) t f (min) % NiO % Ni R-factor x x x x * x x x x x * x x x x x * x 10-4 t i : initial time of treatment t f : time of the maximum degree of oxidation/reduction S12

13 A theta B C C-Kα Figure S8. XRD pattern (A) and BF-STEM image with its corresponding C-Kα EDX map (B) of reduced (ethane) Sn-NiO catalyst. S13

14 Table S5. Surface composition of reduced Sn- and Nb- promoted NiO catalysts Sample surface composition (at. %) a Ni Promoter C O Sn-NiO Nb-Ni a) Calculated by XPS S14