◦
functionalised molecules of interest in the synthesis of fine
chemicals.
The reaction mixture was heated and stirred at 85 C in a
closed glass reactor, and a solution of H
2
O (30% aqueous
2
solution; Riedel-de-Haen) in anhydrous solvent (2.5 mmol H
2
O
2
1
-
in 1.8 mL of solution) was added dropwise (0.01 mL min
Experimental
-
1
-1
over 3 h corresponding to 4.17 mmol H
2
O
2
h
gcat ) with
Catalysts and materials
an automatic dosimetric apparatus. Decane with tert-butanol
or mesitylene for acetonitrile was added as internal standard.
Yields were computed according to the relation:
Titanocene-grafted catalysts were prepared by grafting ti-
tanocene dichloride onto the surface of the mesoporous silica
materials as reported previously. Ti(Cp)
4
,7
2
Cl
2
was dissolved in
Y epox = [mol (obtained epoxide)/mol (H O )] ¥ 100
2
2
chloroform and allowed to diffuse into silica. The solid was
then exposed in situ to triethylamine to activate the nucleophilic
substitution of surface silanols onto titanocene. After filtering,
Ti(IV) active centres were obtained after calcination under dry
using pure standards to evaluate the GC response factors. Over
the three systems, routine heterogeneity tests were performed
(
hot filtration and separation of the solid catalysts) to ascertain
◦
the heterogeneous character of the catalysts.
oxygen at 550 C for 3 h.
During recycling tests, the catalyst was filtered off, washed
Three silica materials were used as supports for grafting: SiO ,
2
◦
with fresh solvent, calcined at 500 C for 1 h under dry air, cooled
a commercial mesoporous non-ordered silica purchased from
Davison Grace (Davisil). MCM-41 and MCM-48 were prepared
using Aerosil 200 (Degussa) as silica source and cetyltrimethyl
ammonium bromide (CTAB) as surfactant. For MCM-41 the
under vacuum and reused under the same conditions. Catalytic
performance was determined on GC analysis (HP6890; HP-5
3
0m-column; FID detector). The final conversion of H
2
2
O and
oxidant efficiency was confirmed by iodometric titration of the
final solution.
mixture molar ratio was: 1 SiO
2
/0.1 CTAB, 0.25 NaOH, 20
◦
H
2
O. The slurry was maintained at 115 C for 24 h before
◦
◦
being filtered, washed, dried at 80 C and calcined at 550 C
for 8 h. MCM-48 was prepared as reported previously. For
29
Acknowledgements
MCM-48 the mixture molar ratio was: 1 SiO
.38 NaOH, 120 H
2
, 0.175 CTAB,
◦
The financial support of IDECAT NoE is greatly acknowledged.
The research has also received funding from the European
Community’s Seventh Framework Programme through the
Marie Curie Initial Training Network NANO-HOST, under
grant agreement no. 215193. The authors thank Dr Daniel
Brunel for the fruitful discussions.
0
2
O. The slurry was maintained at 150
C
for 4 h. The solid precipitate was filtered and subjected to two
successive post-synthesis treatments in water at 130 C for 2 h.
◦
The as-synthesized MCM-48 was then filtered, washed, dried
◦
◦
at 80 C and calcined at 550 C for 8 h. Textural properties
of starting SiO , calcined MCM-41 and MCM-48, as well as
their titanocene-grafted equivalents and their calcined forms
named Ti/SiO , Ti/MCM-41 and Ti/MCM-48, respectively,
2
2
Notes and references
are summarised in Table 1. Textural properties of titanium-
containing catalysts after one run as catalyst are also reported
in Table 1.
Powder X-ray diffraction (XRD) data of materials were
obtained on a Bruker AXS D8 diffractometer using Cu Ka
radiation and Ni filter.
1
2
3
R. Anwander, Chem. Mater., 2001, 13, 4419; T. Maschmeyer and
L. M. van de Water, in Catalysts for Fine Chemical Synthesis, ed.
E. G. Derouane, Wiley, 2006, p. 39.
O. A. Kholdeeva and N. N. Trukhan, Russ. Chem. Rev., 2006, 75,
4
2
11; N. Ravasio, F. Zaccheria, M. Guidotti and R. Psaro, Top. Catal.,
004, 27(1–4), 157.
J. M. Fraile, J. I. Garc ´ı a, J. A. Mayoral, L. C. de Menorval and F.
Rachdi, J. Chem. Soc., Chem. Commun., 1995, 539; C. Cativiela, J. M.
Fraile, J. I. Garc ´ı a and J. A. Mayoral, J. Mol. Catal. A: Chem., 1996,
Nitrogen adsorption/desorption isotherms of materials were
measured using a Micromeritics ASAP 2010 instrument. The
1
12, 259; J. M. Fraile, J. Garc ´ı a, J. A. Mayoral, M. G. Proietti and
◦
◦
calcined samples were outgassed at 250 C, or 120 C for
titanocene-containing samples, until a stable static vacuum of
M. C. S a´ nchez, J. Phys. Chem., 1996, 100, 19484; J. M. Fraile, J. I.
Garc ´ı a, J. A. Mayoral and E. Vispe, J. Catal., 2000, 189, 40.
4 T. Maschmeyer, F. Rey, G. Sankar and J. M. Thomas, Nature, 1995,
-
3
3
¥ 10 Torr was reached. Mesopore diameters were calculated
3
78, 159.
from the desorption branch of the nitrogen isotherms by the
Broekhoff and de Boer (BdB) method, which has been shown
5
R. D. Oldroyd, J. M. Thomas, T. Maschmeyer, P. A. MacFaul, D. W.
Snelgrove, K. U. Ingold and D. D. M. Wayner, Angew. Chem., Int.
Ed. Engl., 1996, 35, 2787.
C. Berlini, M. Guidotti, G. Moretti, R. Psaro and N. Ravasio, Catal.
Today, 2000, 60, 219.
M. Guidotti, N. Ravasio, R. Psaro, G. Ferraris and G. Moretti,
J. Catal., 2003, 214(2), 242.
30
31
to provide reliable results for MCM-41 materials.
UV-Vis diffuse reflectance spectra were obtained in a Varian
Cary 05 E UV-Vis-NIR spectrophotometer using BaSO as
background standard. Ti content was determined by ICP-AES
on an Intrepid Iris instrument (Thermo Elemental). The content
of organic compounds after catalytic tests was evaluated by
thermogravimetric analysis (TGA; Pyris 7HT Perkin Elmer).
6
7
4
8 M. Guidotti, N. Ravasio, R. Psaro, E. Gianotti, L. Marchese and
S. Coluccia, Green Chem., 2003, 5, 421; M. Guidotti, R. Psaro, N.
Ravasio, M. Sgobba, E. Gianotti and S. Grinberg, Catal. Lett., 2008,
1
22, 53.
9
E. Jorda, A. Tuel, R. Teissier and J. Kervennal, J. Catal., 1998, 175,
Catalytic experiments
93.
1
0 H. Kochkar and F. Figueras, J. Catal., 1997, 171, 420.
◦
All the catalysts were dried at 140 C under vacuum for 12 h
11 M. A. Camblor, A. Corma, P. Esteve, A. Martinez and S. Valencia,
Chem. Commun., 1997, 795.
prior to use. The catalyst (200 mg) was added to a solution
of cyclohexene (12.5 mmol; Aldrich) in 5 mL of anhydrous
solvent (tert-butanol or acetonitrile; dried over 3A zeolites).
1
1
2 L. Y. Chen, G. K. Chuah and S. Jaenicke, Catal. Lett., 1998, 50, 107.
3 F. Chiker, F. Launay, J. P. Nogier and J. L. Bonardet, Green Chem.,
2003, 5, 318.
1
426 | Green Chem., 2009, 11, 1421–1427
This journal is © The Royal Society of Chemistry 2009
Guidotti, Matteo
