Wei Zhou and Dehua He*

Transcription

1 Lengthen alkyl spacer to increase SBA-15-anchored Rh-P complex activities in 1-octene hydroformylation Wei Zhou and Dehua He* Innovative Catalysis Program, Key Lab of Organoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing , People s Republic of China *Corresponding author. Professor Dehua He, hedeh@mail.tsinghua.edu.cn; Tel & Fax: +86(10) CONTENTS 1. Preparation of SARC catalysts Characterization of SARC catalysts Transmission electron microscopy (TEM) Powder X-ray diffraction (XRD) Isothermal N 2 sorption analysis Octene hydroformylation Reaction operation Rh loss in catalytic 1-octene hydroformylation Other rhodium precursors C CP-MAS NMR spectroscopy References Preparation of SARC catalysts Please refer to Scheme 1 in the manuscript for sample correspondence.

2 Ordered silica-based mesoporous molecular sieve SBA-15 was synthesized in a three-necked flask 1. P123 (PEO 20 PPO 70 PEO 20, M n = 5800, Aldrich) was dissolved in HCl (2 mol L -1 ). Tetraethyl orthosilicate (TEOS, Acrös) was added dropwise. The mixture was stirred for 20 h under 308 K. The flask was then sealed and kept under 353 K for 24 h. Molar ratio of the initial gel was 0.017P123:aH 2 O:4.78HCl:1TEOS. The resultant solid was recovered and washed. As-synthesized SBA-15 was calcined at 773 K for 6 h. To preserve as much as possible sufficient hydroxyls on the SBA-15 surface and consequently to achieve better grafting, the following calcination program with a ramp of 1 K min -1 is recommended 2 : Temperature (K) Time (min) Fig. E1 Recommended calcination program for P123-bearing SBA-15. Three steps lasted for 60 mins, 60 mins, and 360 mins, respectively. The following experiments were carried out under Schlenk operation. Solvents (toluene, THF, and ether) were in advance refluxed with sodium under nitrogen. Haloalkylation was finished by the grafting method 3. Parent SBA-15 was suspended in toluene and excessive silane X(CH 2 ) n Si(OCH 3 ) 3 was added (silanes with n = 1, 3, and 11 were purchased from ABCR GmbH & Co. KG; silanes with n = 5 and 8 were prepared according to the literatures 4,5. For n = 11, X = Br, others X = Cl). The mixture was refluxed for 24 h. The resulting solid was recovered and washed by CH 2 Cl 2 in a Soxhlet s extractor for 12 h to remove physisorbed species. Phosphine ligand preparation and connection: PPh 3 (Ph = phenyl, Fluka) was dissolved in THF. Li meanings (Sinopharm Chemical Reagent Co., Ltd) were added. The mixture was stirred at room temperature and in dry nitrogen s atmosphere for 3 h. After removing the surplus metal, t-c 4 H 9 Cl (Sinopharm Chemical Reagent Co., Ltd) was added at 273 K to decompose LiPh. Stir was held at 273 K for 1 h and then at room 1

3 temperature for 2 h. Haloalkylated SBA-15 (S-C n -X) was afterwards mixed with the red LiPPh 2 solution and the continuous stir was held for 16 h under room temperature. Molar ratio of LiPPh 2 and silane was 4. The resulting solid was recovered, and then washed by CH 2 Cl 2 in a Soxhlet s extractor and in N 2 for 12 h. Rhodium anchor: S-C n -PPh 2 was mixed with RhCl 3 (6 w.t.% of S-C n -PPh 2, Aldrich) in ethanol. The mixture was refluxed under syngas (H 2 /CO = 1) for 6 h. The successful formation of Rh-P complex was evidenced by the observation that the mixture turned from red to brown in several minutes. Resultant SARC catalyst (S-C n -PPh 2 -Rh) was washed with ethanol by an ultra-sonic device 6 to free uncoordinated ions. Owing to raw materials limit, the preparation of 8-chlorooctyltrimethoxylane started from the reaction of 8-chloro-1-octanol (98%, Acrös) with PBr 3 (99%, Acrös) in toluene. α-br, ω-cl alkane and Mg were of the same molar. Scheme E1 showed the preparation of silanes with spacer n = 5 and 8. Pyridine was in advance dried by calcined (573 K for 3 h) 4A molecular sieves overnight and was employed for the absorption of acid. 1-bromo-5-chloropentane, Mg, SiCl 4, and NaOCH 3 were purchased form Alfa Aesar. Detailed preparation could be acquired from literatures 4,5. Scheme E1 Preparation of 5-chloropentyltrimethoxysilane and 8-chlorooctyltrimethoxysilane. 2. Characterization of SARC catalysts 2.1 Transmission electron microscopy (TEM) TEM measurements were performed with a PHILIP EM400ST electron microscope operated at 100 kv. Sample material was mounted on a holey carbon film supported on a Cu grid by drying a droplet of a suspension of ground sample in ethanol on the grid. 2

4 Fig. E2 TEM micrographs of parent SBA-15 at different focuses. Fig. E2 showed TEM micrographs of parent SBA-15. Very ordered and regular honeycomb-like hexagonal mesopores (ca. 5-6 nm in pore size) were clearly observed. The particle size of SBA-15 at lower focus revealed ca. 0.5 μm 0.8 μm. 2.2 Powder X-ray diffraction (XRD) XRD data at low angles were collected on a Rigaku D/max-RB diffractometer at a scan solution of 2 min -1 with CuKα radiation (λ = nm). XRD characterization was powered at 40 kv and 100 ma. Fig. E3 shows XRD patterns of SARC catalysts with different alkyl spacers. The well-resolved d 100 reflection at ca. 2Theta = 1 indicated all SARC catalysts preserved typical hexagonal symmetry 2 from the support. Unit cell parameter a 0 of hexagonal structure (see Table 1 in the manuscript) was calculated by the equation 7 : a = 0 2 d

5 Fig. E3 Powder XRD patterns of SARC catalysts S-C n -PPh 2 -Rh. 2.3 Isothermal N 2 sorption analysis Isothermal nitrogen sorption at 77 K was performed on a Micromeritics ASAP 2010 analysis system. The BET (Brunauer-Emmett-Teller) and the BJH (Barrett- Joyner-Halenda) methods were applied for the specific surface area and pore size distribution calculations, respectively. Fig. E4 (on next page) shows the isotherms of parent SBA-15 and SARC catalysts. Inserts are corresponding pore size distribution plot. Type IV according to the IUPAC classification and narrow pore size distribution are shown (see corresponding inserts), indicating the ordered regular mesopores were preserved during the Rh-P complex anchor. N 2 sorption analysis results are in accordance with XRD characterization Octene hydroformylation 3.1 Reaction operation Hydroformylation of 1-octene was carried out as follows. 5 ml 1-octene (Acrös, 99%) was mixed with 15 ml toluene (as solvent, sodium-refluxed, A.R.) in a 100 ml autoclave and the SARC catalyst was added. The autoclave was then firmly sealed 4

6 and syngas (H 2 /CO = 1) was injected at lower than 278 K to replace the air inside the autoclave (3 ). The autoclave was heated to 393 K and the syngas was injected to 5 MPa. The electromagnetic stir was started and lasted for 2.5 h. At the end of the reaction, the autoclave was cooled to lower than 278 K and the pressure was released. 1 ml isopropyl alcohol (A.R.) was added as internal standard. The resulting mixture was analyzed by a GC equipped with an SE-30 capillary column (0.32 mm 0.25 μm 30 m). In the recycle experiments, the separated catalysts were above all washed by toluene under ultrasonic washing. Parent SBA-15 Fig. E4 Isotherms of parent SBA-15 and SARC catalysts; Inserts: corresponding pore size distribution plot. 5

7 3.2 Rh loss in catalytic 1-octene hydroformylation Fig. E5 Rh leaching during the recycle of SARC catalysts S-C n -PPh 2 -Rh. The percentage in the insert is the sum of Rh leaching from SARC catalyst recycles. Immobilized Rh contents of SARC catalysts were received by an IRIS Intrepid II ICP-AES spectrometer. Leached Rh contents in reaction liquids were analyzed by an X series In 20000CPS/ppb (1.5%RSD) ICP-MS spectrometer. 2 ml reaction liquid was calcined at 573 K to evaporate all liquids. 0.5 ml concentrated H 2 SO 4 (98%) was added to the residue and heated for eliminating residue organics. Then, 1 ml HNO 3 (63%) was added. The resulting acidic liquid mixture was then diluted to 25 ml for ICP-MS analysis. Rh loss % equals to the ratio of Rh in reaction liquids (sum of recycles) and immobilized Rh of the SARC catalyst. Fig. E5 reveals the leaching of Rh from SARC catalysts gradually decreases along with catalyst runs. The leaching of Rh of the several beginning recycles might be original from the external surface of SBA Other rhodium precursors Table E1 shows 1-octene hydroformylation over SBA-15 anchored Rh catalyst with spacer C 11. Four rhodium precursors were employed, including rhodium acetate dimer, rhodium chloride, a rhodium complex, and Wilkinson s catalyst. It is obvious the immobilized catalyst shows higher activity if more active rhodium precursor was used. All four heterogeneous catalysts showed comparable activity to corresponding homogeneous counterpart, but they gave higher selectivity of nonyl aldehydes. This indicates the absolute activity of SARC catalyst could be promoted by using more active rhodium precursor, which evidenced the general preparative strategy to 6

8 increase immobilized catalyst activity adopting more efficient ligands 8. Noticeably, the molar ratio of normal and branched nonyl aldehyde is increased if the rhodium precursor has more PPh 3 ligands. This is in accordance with previous researches in homogeneous process 9. The preparation of S-C 11 -PPh 2 -anchored RhCl(CO)(PPh 3 ) 2 or RhCl(PPh 3 ) 3 catalyst was carried out by stirring S-C 11 -PPh 2 with rhodium complex (Strem) in CH 2 Cl 2 for 24 h at room temperature (N 2 atmosphere). The resulting catalyst was washed by CH 2 Cl 2 under ultra-sonic for removing physisorbed species. Table E1 1-Octene hydroformylation over S-C 11 -PPh 2 -anchored Rh catalysts: a comparison among four rhodium precursors. [Rh(CH 3 COO) 2 ] 2 (Rh = 1.8 w.t.%) RhCl 3 (Rh = 1.5 w.t.%) Rhodium precursors RhCl(CO)(PPh 3 ) 2 (Rh = 0.35 w.t.%) RhCl(PPh 3 ) 3 (Rh = 0.28 w.t.%) TON Sel. n/i TON Sel. n/i TON Sel. n/i TON Sel. n/i Homogeneous % % % % 2.5 S-C 11 -PPh 2 -Rh % % % % 2.2 a Reaction temperature 393 K, reaction time 2.5 h, initial syngas pressure 5 MPa (see section 3.1). b TON = 1-octene turnover number (molar ratio of converted 1-octene and immobilized rhodium). Sel. = selectivity of nonyl aldehydes. n/i = ratio of linear and branched nonyl aldehyde. c Data from the heterogenized catalysts refer to the first catalyst cycle C CP-MAS NMR spectroscopy 13 C{ 1 H} cross polarization-magic angle spinning (CP-MAS) NMR spectroscopy was applied to fresh and recycled SARC catalysts on a Bruker 300 MHz spectrometer. The 5 mm probe was set to 5.5 KHz. Fig. E6 is the NMR spectra of fresh (a) and recycled (b) SARC catalyst with spacer C 3 as example. In the spectrum of fresh S-C 3 -PPh 2 -Rh (a), the coordinated carbonyl showed a signal at ppm. The phenyl rings gave a signal at ppm, original from C=C bond. These resonances were broadened by the influences of coordinated Rh. The propyl spacer showed peaks 10 at 21.6, 14.9, and 8.3 ppm. The peaks at 57.3 and 44.6 ppm might be original from the hydrogen-bonded solvent ethanol or non-bonded methoxyls of the silane 10. In the spectrum of recycled S-C 3 -PPh 2 -Rh catalyst (b), a broadened resonance was found at ppm. Since no coordinated carbonyl could observed in the IR spectrum of the recycled catalyst, this peak can be accordingly assigned to the carbonyl in the (C=O)-(C=C)- structure of the alfa,beta-unsaturated aldehyde. The resonance from C=C carbon was slightly shifted to ppm. This is might because the influence of the C=C bond in the alfa,beta-unsaturated aldehyde, which cannot be distinguished from the phenyl resonance in the NMR spectrum. Noticeably, the 7

9 recycled S-C 3 -PPh 2 -Rh catalyst spectrum gave more signals of alkyl carbon in the range 50 0 ppm, indicating the dehydrated product of the aldol condensation of nonyl aldehyde, an 18-carbon alfa,beta-unsaturated aldehyde. However the alkyl carbons of the by-product cannot be finely resolved owing to the similar chemical surroundings of the carbons. Similar conclusions can be received from 13 C CP-MAS NMR spectra of SARC catalysts with other spacers. 8

10 Fig. E6 13 C Cross Polarization-Magic Angle Spinning NMR spectra of fresh S-C 3 -PPh 2 -Rh (a) and recycled S-C 3 -PPh 2 -Rh (b) catalyst. 9

11 4. References 1. X.-Y. Hao, W. Zhou, J.-W. Wang, Y.-Q. Zhang, S. Liu, Chem. Lett., 2005, 34, D. Zhao, Q. Huo, J. Feng, B. F. Chmelka and G. D. Stucky, J. Am. Chem. Soc., 1998, 120, C. Zhang, W. Zhou and S. Liu, J. Phys. Chem. B, 2005, 109, R. A. Benkeser, S. D. Smith, J. L. Noe, J. Org. Chem., 1968, 33, C. S. Marvel, W. E. Garrison, Jr, J. Am. Chem. Soc., 1959, 81, X.-Y. Hao, Y.-Q. Zhang, J.-W. Wang, W. Zhou, C. Zhang, S. Liu, Micropor. Mesopor. Mater., 2006, 88, J. S. Beck, J. C. Vartuli, W. J. Roth, M. E. Leonowicz, C. T. Kresge, K. D. Schmitt, C. T. W. Chu, D. H. Olson, E. W. Sheppard, S. B. McCullen, J. B. Higgins, J. L. Schlenke, J. Am. Chem. Soc., 1992, 114, A. J. Sandee, L. A. van der Veen, J. N. H. Reek, P. C. J. Kamer, M. Lutz, A. L. Spek, P. W. N. M. van Leeuwen, Angew. Chem. Int. Ed., 1999, 38, D. Evans, J. A. Osborn, G. Wilkinson, J. Chem. Soc. (A), 1968, J. Kramer, E. Nöllen, W. Buijs, W. L. Driessen, J. Reedijk, React. Funct. Polym., 2003, 57, 1. 10