Titanium Nitride-Nickel Nanocomposite as Heterogeneous Catalyst for the Hydrogenolysis of Aryl Ethers Valerio Molinari, Cristina Giordano, Markus Antonietti and Davide Esposito* Max-Planck-Institute of Colloids and Interfaces, 14424 Potsdam (Germany) Supporting Information Table of Contents 1 MATERIALS AND METHODS S1 2 CHARACTERIZATION OF THE COMPOSITES S2 2.1 PICTURES OF THE POWDERS S2 2.2 INFRARED SPECTROSCOPY OF METAL PRECURSORS AND POWDERS S2 2.3 EELS SPECTROSCOPY ON TiN NANOPARTICLES S3 2.4 XRD AND SEM PICTURES OF TiO2-Ni S4 2.5 XRD PATTERN OF TiN-Ni S5 2.6 TiN THERMAL STABILITY AFTER REHEATING TREATMENT S5 2.7 SIZE OF NANOPARTICLES CALCULATED BY SCHERRER EQUATION S6 2.8 ELEMENTAL ANALYSIS S6 2.9 TEM AND EDX ANALYSIS S7-8 2.10 SEM ANALYSIS S9 2.11 NITROGEN ABSORPTION ANALYSIS S10 2.12 XRD OF ALL THE RECOVERED CATALYSTS S10 2.13 CATALYTIC ACTIVITY ON THE HYDROGENATION OF NITROBENZENE S11 2.14 REPRODUCIBILITY EXPERIMENTS FOR THE HYDROGENOLYSIS OF NITROBENZENE AND PHENYL BENZYL ETHER S11 2.15 COMPARISON OF SELECTIVITY BETWEEN TiN-Ni, RANEY NICKEL AND Pd/C S11 2.16 QUALITATIVE DEPOLYMERIZATION OF LIGNIN S12
Materials: Urea, nickel(ii) acetate tetrahydrate, titanium tetrachloride, diphenyl ether, benzyl phenyl ether (98%), phenol (99%), nitrobenzene (99%), 4-phenoxyphenol were purchased from Sigma Aldrich. 2-phenylethyl phenyl ether was bought from Frinton Laboratories (>99%). All chemicals were used without further purification. Characterization: Nitrogen sorption experiments were performed using Quantachrome Quadrasorb at the temperature of liquid nitrogen. All the samples were degassed at 150 C for 20 hours before measurements and analyzed with a QuadraWin software (version 5.05). SEM images were performed on a LEO 1550 Gemini instrument. The samples were loaded on carbon coated aluminium holder and measured without any additional coating. TEM images were recorded using a Zeiss EM 912Ω microscope operated at an acceleration voltage of 120 kv. High resolution TEM and EELS measurements were recorded on a CM200FEG (Philips) microscope, operated at 200 kv and equipped with a field emission gun and a post column EELS spectrometer (GATAN Tridiem). FT-IR spectras were recorded on a Varian1000 FT-IR spectrometer. XRD measurements were performed on a Bruker D8 diffractometer using Cu-Kα radiation (λ = 0.154 nm) and a scintillation counter (KeveX Detector). Reference patterns were obtained from the ICDD PDF-4+ database (2011 edition). Elemental analysis was performed as combustion analysis using a Vario Micro device. GC-MS analysis was performed using an Agilent Technologies 5975 gas chromatograph equipped with a MS detector and a capillary column (HP-5MS, 30 m, 0.25 mm, 0.25 micron). The temperature program used to monitor the reaction on model compounds started with an isothermal step at 50 C for 2 min, the temperature was then increased to 300 C with a rate of 30 C/min and maintained for 1 min. The temperature program used for the experiments of lignin conversion started with an isothermal step at 50 C for 2 min, the temperature was then increased to 300 C with a rate of 30 C/min and maintained for 15 min. Qualitative analysis was performed with MS library NIST 08 database with a retention index allowance of ± 100. Quantification was performed by external standard method. Calibration curves were prepared using solution of the analytes at different concentrations. The curves showed linearity in the range of concentrations of interest (correlation coefficient R 2 0.998). Reactions were carried out multiple times and showed good reproducibility. TiN preparation: Titanium tetrachloride (1156 µl, 10.53 mmol) was added dropwise to ethanol (5 ml), until a yellowish solution was obtained. Urea (2.61 g, 42.11 mmol) was added slowly to the solution forming a homogeneous yellow gel. The gel was then heated under nitrogen flow (heating ramp of 2 K min -1 ) up to 750 C holding the final temperature (750 C) for an additional 3 hours. The resulting bronze powder was analyzed by XRD (compared to 00-038-1420, PDF4 database) and used as such. TiN-Ni preparation: Nickel acetate tetrahydrate (1.66 g, 6.66 mmol) was dissolved in ethanol (15 ml) and added drop wise to titanium nitride (0.864 g, 13.32 mmol). The suspension was stirred overnight, thus the solvent was slowly evaporated under nitrogen flow yielding a homogeneous bronze powder. The powder was heated under nitrogen flow (heating ramp of 2 K min -1 ) holding the final temperature (500, 600 or 700 C) for 3 hours. The resulting magnetic powders were analyzed by XRD (TiO 2 pattern was compared to 04-014-5762, the Ni pattern to 00-004-0850, PDF4 database) and used as such. Ni preparation: Nickel acetate tetrahydrate (1.66 g, 6.66 mmol) was heated under nitrogen flow (heating ramp of 2 K min -1 ) holding the final temperature (600 C) for 3 hours. The resulting magnetic powder was analyzed by XRD and used without purification. Catalytic tests: All the reactions were performed using a H-Cube Pro reactor [1] equipped with a hydrogen feed (generated in situ) and a liquid feed. Solutions of the starting materials at the desired concentration were pumped through a 70mm column packed with TiN (0.85 g, 7.3 mmol), Ni (0.6 g, 9.7 mmol) or TiN-Ni (0.8 g, 4.6 mmol of Ni) using a HPLC pump. Commercial CatCarts (30 mm) filled with Pd/C and Raney Nickel have been used for the comparison of the catalytic activity of TiN-Ni with conventional catalyts. The residence time was controlled by adjusting the flow rate. The hydrogen produced in situ is mixed with the eluent at 12 bars before reaching the packed cartridge. After equilibrating the system at the desired temperature over a period of 20 minutes, samples from the eluate were collected and analyzed by GC-MS. S1
Figure S1. Macroscopic images of the TiN, TiN-Ni 500 C and Ni powders after calcination under nitrogen. Figure S2. Overlaid infrared spectra of Ni(OAc) 2 4H 2 O and Ni(OAc) 2 4H 2 O@TiN (A); Overlaid infrared spectra of TiN and TiN-Ni prepared at 500 C (B). S2
Figure S3. Electron energy loss spectroscopy performed on TiN. Table S1. Numerical values for electron energy loss spectroscopy performed on TiN. Signal Reference [2] Compound (ev) (ev) 398.4-406.1 400 c.ca N 428.2-438.8 N 457.8 457.60 Ti (nitride) 461.2 460.9 Ti (nitride) 486.4 Ti (nitride) 506 Ti (nitride) 531.4-541.8 531.8 O S3
Figure S4. XRD pattern of TiN compared to the TiO 2 -Ni obtained by calcination in one step. Figure S5. SEM pictures of TiO2-Ni obtained by calcination in one step. S4
Figure S6. XRD patterns of pure TiN, TiN-Ni and TiO 2 -Ni nanocomposites. The expected XRD pattern of TiN, TiC, TiON and TiO 2 are reported for comparison. Figure S7. XRD pattern of TiN and TiN subjected to re-heating process at 500 C. S5
Table S2. Size of TiN nanoparticles calculated using the Debye-Scherrer equation. Material Size of TiN Phase(nm) (Debye-Scherrer equation) TiN 11.1 TiN-Ni 500 C 9.6 TiN-Ni 600 C 12.3 TiN-Ni 700 C 14.0 Table S3. Elemental analysis for TiN, Nickel and TiN-Ni nanocomposites prepared at 500, 600 and 700 C respectively. Sample N (% m/m) C (%m/m) TiN 14.21 5.46 Ni (600 C) 0.06 7.32 TiN-Ni (500 C) 6.60 10.2 TiN-Ni (600 C) 7.01 5.85 TiN-Ni (700 C) 6.8 5.43 S6
Figure S8. TEM pictures of different areas in the TiN-Ni nanocomposites with the corresponding EDX analysis (A, B). TEM overview of the nanocomposite (C). S7
Figure S9. Enlarged TEM pictures of TiN (A), Nickel (B), TiN-Ni prepared at 500 C (C) and 600 C (D) with SAED analysis. S8
Figure S10. SEM images of TiN prepared via urea route (A), Nickel (B), TiN-Ni prepared at 500 C (C) and 600 C (D). S9
Figure S11. Nitrogen absorption analysis of TiN, Ni and TiN-Ni prepared at 500, 600 and 700 C respectively. Figure S12. XRD pattern of TiN, TiN-Ni and Ni catalysts as synthesized and recovered (rec.) after several hours of reaction. S10
Table S4. Catalytic hydrogenation of nitrobenzene using Ni, TiN and TiN-Ni. Conditions: 0,5 ml min -1, 0,05 M nitrobenzene in EtOH, 12 bar. Conversion (X) and selectivity (S) were determined by GC-MS. Entry cat T ( C) X (%) S (%) 1 TiN 100 0 2 Ni 50 51 100 3 Ni 75 80 100 4 Ni 100 >99 100 5 TiN-Ni 25 >99 100 A B Figure S13. GC chromatograms for the conversion of nitrobenzene (a) and phenyl-benzyl ether (b) showing the reproducibility of the reaction performed with different catalyst batches or different time on stream. Table S5. Comparison of selectivity between Pd/C, RaNi and TiN-Ni for the hydrogenolysis of 8 at full conversion. Entry Cat. Substrate T Conversion (c) Selectivity (%) (c) ( C) (%) 10 11 12 13 14 15 16 17 18 19 1 (a) Pd/C 8 150 >99 - - - - - - 16 75 16-2 (a) RaNi 8 150 >99 7 - - 35 - - 49 - - 9 3 (b) TiN-Ni 8 150 >99 5 - - 46 - - 49 - - - Conditions: (a) 0.01 M in EtOH, 0.3 ml min -1, 12 bar. (b) 0.025 M in EtOH, 0.3 ml min -1. (c) Determined by GC-MS analysis. S11
Qualitative catalytic depolymerization of lignin. Alkali lignin (purchased from Sigma Aldrich) was dissolved in MeOH and reacted using TiN-Ni as the catalysts, following the procedure described in the paragraph Catalytic tests, page S1. The non-optimized conversion of lignin at different temperature and the simultaneous generation of small molecular weight aliphatic and aromatic products were qualitatively monitored by GC experiments (figure S14). The change of M n and M w indexes measured by gel permeation chromatography in DMSO using polymethylmethacrylate standards (starting lignin: M n 2970 Da, M w 1840 Da; reacted lignin: M n 2660 Da, M w 1545) additionally confirmed the occurrence of hydrogenolysis. Figure S14. GC chromatograms for the non-optimized hydrogenolysis of lignin (12 bars, 0.1 ml min -1 ) in the presence of TiN-Ni at 135 C and 150 C, compared to the chromatogram of the lignin starting material. (1) http://www.thalesnano.com/products/h-cube%20pro. (2) X-ray Photoelectrical Spectroscopy Database, Vol. 4.1, National Institute of Standards and Technology, Gaithersburg, 2012. S12