Supporting Information

Transcription

1 ACS Catalysis Supporting Information Cooperative Catalysis for Multistep Biomass Conversion with Sn/Al Beta Zeolite Jan Dijkmans a, Michiel Dusselier a, Dries Gabriëls a, Kristof Houthoofd a, Pieter C.M.M. Magusin a, Shuigen Huang b, Yiannis Pontikes b, Maarten Trekels c, André Vantomme c, Lars Giebeler d, Steffen Oswald d, Bert F. Sels a *. a Center for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium. E- mail: Bert.Sels@biw.kuleuven.be. b Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium. c Nuclear and Radiation Physics Section, KU Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium. d Institute for Complex Materials, Leibniz-Institute for Solid State and Material Research, Helmholtzstraβe 20, Dresden, Germany. S1

2 X-ray Analysis Figure S1: Diffraction patterns for a. SnO 2 b. Alβ c. Sn/14.4pDeAlβ d. Sn/7.2pDeAlβ e. Sn/3.6pDeAlβ f. Sn/2.88pDeAlβ g. Sn/1.44pDeAlβ and h. hydrothermally synthesized Snβ as measured with Cu K α1 radiation (λ = Å) Determination of XRD SnO 2 detection limit Physical mixtures of CP814E beta zeolite with different concentrations (5, 1, 0.5 and 0.25wt%) of SnO 2 oxide (Alfa Aesar, < 10 μm powder, 6 m 2.g -1 ) were made and measured using the same equipment and methods as were used for the grafted samples. The most prominent reflections at 34 (d 101 ) and 52 (d 211 ) were visible clearly for the 5wt% sample, and weakly for the 1 and 0.5 wt% sample. No reflections of the oxide could be detected at concentrations of the oxide lower than 0.5wt% with the used method, indicating a detection limit of 0.5wt%. The diffraction patterns of the physical mixtures are shown in Figure S2. S2

3 Figure S2: Diffraction patterns for a. SnO 2 b. CP814E c. 5 wt% SnO 2 d. 1 wt% SnO 2 e. 0.5 wt% SnO 2 f wt% SnO 2 as measured with Cu K α1 radiation (λ = Å). The inset shows the 25 to 60 region into more detail. SEM-analysis Figure S3: SEM images of (a) conventional Snβ and (b) Sn/deAl-β (scale bars 5 μm and 200 nm, respectively). S3

4 119 Sn Mössbauer Spectroscopy Figure S4: 119 Sn Mossbauer spectrum of a. Sn/7,2pDeAlβ sample, b. SnO 2 and c. SnCl 4.5H 2 O. The circles are the experimental data, the lines are the fitted data. Determination of possible contamination of the sample with SnCl 4 or SnO 2 with 119 Sn Mössbauer Spectroscopy The sensitivity of the Mossbauer fit of the data is tested by adding a component to the fit with the hyperfine parameters of SnO 2 or SnCl 4. The hyperfine parameters of these two chemical states of Sn were determined using commercial reference materials. Figure S5 shows our fit to the data, including an additional SnCl 4 component. The red line corresponds to the total fit, the blue line is a site with the hyperfine parameters of the sample and the green line the site with the hyperfine parameters of the possible contaminating species. The amount of SnCl 4 was gradually increased until a clear deviation of the total fit from the data was observed. In the case of SnCl 4, this resulted in an upper limit of the order of 7at%. The deviation of the fit with respect to the data is mostly seen in the edges of the absorption peak. The same procedure was used to make a similar estimate for SnO 2 (Figure S6). Since the hyperfine parameters of SnO 2 deviate less from the sample, the sensitivity to SnO 2 is lower. An upper limit of the order of 17at% SnO 2 was determined. The Sn/7,2pDeAlβ sample contains 1.57wt% Sn, of which 17 and 7at% could be present as SnO 2 and SnCl 4 respectively, corresponding to a detection limit of 0.27 and 0.11wt% (measured as Sn) for SnO 2 and SnCl 4 respectively. The obtained sensitivities are within the expected values for Mossbauer spectroscopy. It is clear that sensitivity will drop when the hyperfine parameters of two compounds become more similar. Neutral Sn and Sn in the 2+ state can be excluded on the less than 1at% level, since these components have isomer shifts that are well separated from the one obtained for the measured sample. S4

5 Figure S5: 119 Sn Mossbauer spectrum of Sn/7,2pDeAlβ sample with SnCl 4 contamination Figure S6: 119 Sn Mossbauer spectrum of Sn/7,2pDeAlβ sample with SnO 2 contamination Determination of SnO 2 detection limit for 119 Sn MAS NMR In an effort to determine the sensitivity of the 119 Sn MAS NMR analysis, a series measurements on pure SnO 2 were performed. Measurement conditions were identical to those used for the samples as was described in the experimental part of the manuscript, but the number of scans was varied. Figure S7 plots the spectra of the measurements with 8, 16, 32, 64, 256 and 512 scans for 30.1mg of SnO 2. A signal at -604 ppm was found, sidebands are visible and denoted with an asterisk. Figure S8 shows a plot of the Signal-to-Noise (S/N) ratio in function of the number of scans. The intensity of the signal is linearly correlated to the amount of scans, indicating that no saturation of the NMR-signal was present with the used measurement conditions. Using the linear correlation between S/N and the amount of scans, a theoretical exercise was performed to find a detection limit of SnO scans were used in the measurement of the Sn/7.2pDeAlβ sample. For SnO 2, this would correspond to a S/N of Assuming a minimal S/N of 2 for a detectable signal, the minimal detectable amount of SnO 2 is 0.011mg corresponding to mg of Sn per rotor. The rotor for the Sn/7.2pDeAlβ measurements was S5

6 filled with 61.5mg of powder, resulting in a detection limit for SnO 2 of wt%. This corresponds to 0.9 at% of the Sn present in the Sn/7.2pDeAlβ sample (1.57 wt% of Sn). This exercise was performed with bulk SnO 2 (Alfa Aesar, < 10 μm powder, 6 m 2.g -1 ). If SnO 2 is formed in the synthesis of the grafted materials, it is possible that the formed SnO 2 clusters are much smaller, less crystalline and therefore less chemically identical (broader 119 Sn MAS NMR signals) in comparison with the used bulk SnO 2. The results of this exercise should therefore be handled with care and are just an indication of the sensitivity of the analysis. Figure S7: 119 Sn MAS NMR spectra of SnO 2 with 8 (red), 16 (orange), 32 (yellow), 64 (green), 256 (blue) and 512 (purple) scans. Spinning sidebands are denoted with an asterisk (*). S6

7 Figure S8: Plot of the Signal/Noise ratio of the -604 ppm signal of bulk SnO 2 in function of the amount of scans in the 119 Sn MAS NMR analysis. A linear correlation was found for measurements with >8 scans. Information on the linear correlation are displayed in the inset. CD 3 CN-FTIR spectroscopy Figure S9: FTIR spectra of hydrothermally synthesized Snβ (dotted line) and adsorbed deuterated acetonitrille (full lines) at different stages of desorbing in vacuo. DR UV-vis spectroscopy Determination of the UV-vis SnO 2 detection limit Physical mixtures of CP814E beta zeolite with different concentrations (5, 1, 0.5, 0.25, 0.1 and 0.05 wt%) of SnO 2 oxide (Alfa Aesar, < 10 μm powder, 6 m 2.g -1 ) were made and its absorption S7

8 spectra were measured using the same equipment and methods as were used for the grafted samples. SnO 2 shows a broad absorption with maxima at 253 and 298 nm. Similar absorption signals are found in physical mixtures with 5, 1, 0.5 and 0.25wt% SnO 2. The signal at 253 nm is no longer visible in the 0.10wt% sample, yet a weak absorption 298 nm was still observed. For the 0.05wt% sample, no more SnO 2 -related signals were observed. Therefore, a detection limit of 0.10wt% for SnO 2 in beta zeolites was established with the used equipment. 0.10wt% SnO 2 corresponds to 0.079wt% Sn. According to the Kubelka-Munk model, a linear relationship between peak height and concentration of the sample (at low concentrations) is expected. 1 Such a linear relationship was found between the 298 nm peak height and the concentration of SnO 2 in the sample and is shown in Figure S9. Figure S10: DR UV-vis spectra of a. beta zeolite(black), b. 0.05wt% SnO 2 (brown), c. 0.1 wt% SnO 2 (purple), d wt% SnO 2 (blue), e. 0.5 wt% SnO 2 (green), f. 1 wt% SnO 2 (yellow), g. 5 wt% SnO 2 (orange) and h. SnO 2 (red). Samples b. to g. are physical mixtures of SnO 2 and beta zeolite. All samples are corrected with a beta zeolite to single out the signals originating from SnO 2. The graph on the right-hand-side shows the detailed spectra for samples a. to e. S8

9 Figure S11: Height of the 298nm reflection signal from the detection limit tests with DR UV-vis plotted against the concentration of SnO 2 present in the sample. The colors of the data squares match these of Figure S8. The table shows info on the linear fit of the data points. Figure S12: DR-UV spectrum of samples a. Sn/1.44pDeAlβ b. Sn/2.88pDeAlβ, c. Sn/3.6pDeAlβ, d. Sn/7.2pDeAlβ, e. Sn/14.4pDeAlβ, f. 2xSn/2.16pDeAlβ and g. hydrothermally synthesized Snβ. All samples were dried at 573K in O2. Spectra were corrected with the corresponding spectra of pdealβ (a white standard was used for hydrothermally synthesized Snβ) to better identify the absorption signals related to Sn. 29 Si MAS NMR S9

10 Figure S13: 29 Si MAS NMR of a. Alβ, b. 7.2pDeAlβ, c. Sn/7.2pDeAlβ and d. hydrothermal Snβ. Al IVa vs. Al IVb Figure S14: 27 Al MAS NMR of the materials (a.) Alβ, (b.) Sn/1.44pDeAlβ, (c.) Sn/1.8pDeAlβ, (d.) Sn/2.88pDeAlβ, (e.) Sn/3.6pDeAlβ, (f.) Sn/7.2pDeAlβ and (g.) Sn/14.4pDeAlβ. The table shows the Al IVa /(Al IVa +Al IVb )-ratio of the samples, as was determined by deconvolution of the signals. Signals are scaled to weigth. The Al IV -signal of the spectra of the 27 Al MAS NMR analysis were empirically deconvoluted by fitting the signal with two Gaussian curves at 56.9 and 53.9 ppm, designated by Al IVa and Al IVb respectively. To obtain the ratio of the Al IV species, the area of the fitted signals was integrated. The Al IVa /(Al IVa +Al IVb )-ratio of the samples is displayed in a Table in Figure S14. Absolute concentration of each of the Al IV species was calculated by multiplying the relative ratio of each of the species with the total concentration of Al which was determined with ICP-analysis. S10

11 Plots of Brønsted acidity versus Al-content The Brønsted acidity measured with pyridine probed FTIR, was plotted against the total Al-content (Al IVa + Al IVb), the Al IVa -content and the Al IVb -content. Lineair trendlines were fitted through the points. If every Alatom is a Brønsted acid site, and is probed with one molecule of pyridine, a slope of 1 will be present. We assumed one pyridine molecule per Al-atom. For the plot with Al IVa + Al IVb a slope of 0.40 was found (R 2 =0.98), indicating that the measured acidity accords to 40% of the total Al-content. When plotted against Al IVa, a slope of 1.39 was found ((R 2 =0.99), indicating that more mole of acidity is measured than moles of Al IVa is present in the sample, which in impossible. For Al IVb, a slope of 0.56 (R 2 =0.96) was found, indicating a Brønsted acid site for 56% of the Al IVb sites. This value is similar to the ratio of Lewis acidity to Sn-content. Incomplete pyridine probing of acid sites is often described in zeolites, see article. 2 S11

12 Figure S15:Plots of a. Al IVa+IVb -species, b. Al IVa -species and c. Al IVb -species (obtained from 27 Al MAS NMR and ICP) vs. Brønsted acidity (obtained from pyridine probed FTIR) S12

13 References: (1) Nishikida, K.; Nishio, E.; Hannah, R. W. Selected Applications of Modern FT-IR Techniques; Kodansha Ltd: Tokyo, 1995, (2) Nesterenko, N. S.; Thibault-Starzyk, F.; Montouilliout, V.; Yushchenko, V. V.; Fernandez, C.; Gilson, J. P.; Fajula, F.; Ivanova, I. I. Kinet. Catal. 2006, 47, S13