Supporting Information. High Selectivity of Supported Ru Catalysts in the Selective. CO Methanation - Water Makes the Difference

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1 S1 Supporting Information High Selectivity of Supported Ru Catalysts in the Selective CO Methanation - Water Makes the Difference Ali M. Abdel-Mageed,, Stephan Eckle, and R. Ju rgen Behm *, Institute of Surface Chemistry and Catalysis, Ulm University, D-8969 Ulm, Germany Clariant Produkte (Deutschland) GmbH / Clariant SE, Lenbachplatz 6, D-8333 München, Germany Experimental: Catalysts and catalyst properties: The two supported Ru catalysts used in the study included a commercial. wt % Ru/Al 2 O 3 catalyst (Johnson Matthey) and a 2.2 wt % Ru/zeolite catalyst prepared by Clariant Produkte (Deutschland) GmbH. The surface areas were determined by N 2 adsorption (BET) and are and 4 m 2 g -1 for the Ru/Al 2 O 3 and the Ru/zeolite catalyst, respectively. Kinetic measurements: The kinetic measurements were performed at atmospheric pressure in a quartz tube micro reactor using the as received catalysts. Catalysts were diluted with varying amounts of SiO 2 (inactive under present reaction conditions) to maintain differential reaction conditions (conversion of the reactants < 2%). In total, about 2 mg of diluted catalyst was used, resulting in a catalyst bed of about 1 cm length. The dilution of the catalyst with SiO 2 depended on the catalyst and on the reaction atmosphere (dry / wet) (Ru/zeolite catalyst: 1:2 (wet) 1:4 (dry); Ru/Al 2 O 3 catalyst (wet and dry): 1:1). In experiments performed in wet gas atmospheres the gas flow was corrected for the amount of gas displaced by the water vapour introduced to keep the total CO flow (mole min -1 ) unchanged (see Table S1). Water was introduced by saturating the dry gas mixture using a humidifier which was kept at a constant temperature. All measurements were performed at

2 S2 19 C, following the reaction over minutes. The gas mixtures were prepared using mass flow controllers from Hastings (HFC-22). Influent and effluent gases were analyzed by on-line gas chromatography with a CO detection limit of ca. ppm (DANI 86.), using H 2 as carrier gas and thermal conductivity detectors. XAS measurements: In situ EXAFS experiments were performed at the X1 beamline at HASYSLAB and at the XAFS beamline at Elettra Synchrotron, using a Si-311 double crystal monochromator. The estimated beam dimensions are roughly 6 mm vertical and 2 mm horizontal. A specially designed stainless steel tube reactor was used for the measurements, with a cylindrical channel (i.d. 2 mm) along the axis of the tube, which contained the catalyst bed (length ca. mm, ca. 2 mg undiluted catalyst) and allowed the gases to pass through. A slit along the central axis of the tube (width about 2 mm x mm) allowed the X-ray beam to pass through the catalyst bed. Under reaction conditions, the reaction cell is closed off by two catalytically inactive kapton windows. Heating of the cell was achieved by heating wires inside two ceramic rods, which were placed in bore holes in the reactor body close to the catalyst bed. All gas lines were heated to C to avoid water condensation during the process. The spectra (Ru k-edge, ev) were collected in transmission mode using two Ar/N 2 filled ionization chambers. A ruthenium metal foil placed in between the second and an additional ionization chamber allowed for internal and simultaneous calibration during all measurements. The pre-edge region was measured in the energy range of ev with a step size of ev. For the XANES region ( ev) and EXAFS region ( ev), step widths of. and.98 ev, respectively, were used. The in situ XAS measurements were performed with high purity gases (99.999%), passed through the reaction cell at a gas flow depending on the water content (see Table S1). The gas flow of each species was adjusted via mass flow controllers (Bronkhorst F21C-FA-88V). Prior to the in situ experiments, the catalyst was heated up to 1 C in a N 2 flow and kept for 3 min in N 2 at that temperature. Afterwards the catalyst was heated up within minutes to the reaction temperature of 19 C in the reactive gas atmosphere. All EXAFS measurements

3 S3 were performed in idealized reformate (.6% CO, 3% N 2, balance H 2 ) at atmospheric pressure. This gas mixture was saturated with varying amounts of water (see Table S1). For technical reasons a water concentration of 3% was not possible during the EXAFS experiments. The evaluation of EXAFS spectra was carried out using the program XDAP with standard procedures described elsewhere. 1 Theoretical references were calculated by FEFF 8. 2 and calibrated against spectra of a Ru foil and of RuO 2 powder as experimental references to determine the damping factor S 2 o, the phase shift F and the mean free path of the electrons δ. 1 The coordination number (CN) of the Ru-Ru shell for different samples was obtained by fitting the EXAFS data of the first Ru-Ru shell at 2.67 Å to the calibrated Ru foil reference (See Tables S2 and S3). In situ IR spectroscopy measurements: In situ diffuse reflectance FTIR spectroscopy (DRIFTS) measurements were performed using a commercial in situ reaction cell (Harricks HV-DR2). The spectra were recorded in a Magna 67 spectrometer (Thermo), equipped with a MCT narrow-band detector. Gas mixtures were prepared as described above, and identical gas flows were used (see Table S1). Prior to the experiments, the catalysts were heated up within min in a N 2 stream to 1 C, then water vapor was introduced by passing pure N 2 through a water bath, and the background spectra were recorded in the presence of water. Afterwards the catalysts were heated within 2 sec to the reaction temperature (19 C) in reaction atmosphere. Spectra were collected in the different reformate gases described in Table 1. The reaction was followed over 8 min with spectra recorded in situ (4 scans collected per one spectrum). The intensities were evaluated in Kubelka-Munk units, which are linearly related to the adsorbate coverage. 3 The background subtraction and normalization of the spectra were performed by dividing the measured absorption by the absorption obtained in spectra recorded in a flow of N 2 directly after heating the catalyst to 1 C.

4 S4 Table S1 Amount of water added to the reaction gas mixture and corresponding gas flow (Nml min -1 ). Water content in reformate / % Corrected gas flow / Nml min Table S2 Fit data used for the evaluation of the EXAFS measurements and structural parameters of Ru/Al 2 O 3 in reaction gas mixtures containing different amounts of water under steady-state conditions in idealized reaction reformate (.6% CO, 3% N 2, balance H 2 ) at a reaction temperature of 19 C. Water / % CN DW / -3 Å 2 r / Å E / ev Dispersion / % Particle size / nm Table S3 Fit data used for the evaluation of the EXAFS measurements and structural parameters of Ru/zeolite in reaction gas mixtures containing different amounts of water under steady-state conditions in idealized reaction reformate (.6% CO, 3% N 2, balance H 2 ) at a reaction temperature of 19 C. Water / % CN DW/ -3 Å 2 r / Å E / ev Dispersion / % Particle size / nm

5 k 3 x(k) FT (Å 3 ) S Figure S1 (a,c) k 3 weighted chi function and (b, d) corresponding Fourier transforms ( Å -1 ) on a 2.2 wt % Ru/zeolite catalyst during reaction in an idealized reformate gas mixture (.6 % CO, 3% N 2, balance H 2 ) containing % water (upper panels) or % water (lower panels). Solid lines are EXAFS data, and dashed lines are fits. - - a) c) k / Å b) d) r / Å - - References (1) Koningsberger, D. C.; Mojet, B. L.; van Dorssen, G. E.; Ramaker, D. E. Top. Catal. 2,, 143. (2) Ankudinov, A. L.; Ravel, B.; Rehr, J. J.; Conradson, S. D. Phys. Rev. B 1998, 8, 76. (3) Hamadeh, I. M.; Griffiths, P. R. Appl. Spectrosc. 1987, 41, 682.