volume fraction plays an important role in final porosity,
hence in accessibility to active functional sites and in reaction
conversions. Very good conversions were reached for materials
with the highest porosity. Further work is in progress to
maximize accessible functional sites on the surface, and are
being investigated for other catalytic applications.
Notes and references
Fig. 3 Conversion of MPS (after 50 min, a) and DBT (after 2 h, b) as
a function of fPOR (the dashed line is a guideline).
z Silica–titania materials were prepared by mixing a siloxane solution
ꢂ1
ꢂ1
(
3
mmol g
)
with Ti(OiPr)
2
(acac)
2
and the chitin suspension
2
BET = 795 m g , Si/Ti = 112) gave a conversion of 36%
ꢂ1
(
S
(0.03 mmol l ). The reactant proportions are set to reach the
water–ethanol azeotrope composition (ca. 96 wt% ethanol) and a
given chitin volume fraction fCHI in the final nano-composites. After
spray-drying (393 K), powders are further dried (333 K, 72 h) and
calcined under air (8 h, 823 K).
after 60 min of reaction, a SiO –TiO non-hydrolytic sol–gel
2
2
2
ꢂ1
material (SBET = 1215 m
g
, Si/Ti = 22) yielded full
conversion after 45 min. A similar remarkable catalytic
performance was obtained in the present study with full
y Catalytic sulfoxidation reactions were carried out with 50 mg of the
catalyst suspended under stirring in a mixture containing 1.5 mmol
of the organic substrate and 15 ml of solvent. The adequate volume of
hydrogen peroxide (50 wt% aqueous) was added at the beginning of
experiments.
oxidation of MPS in 50 minutes for the sample with fPOR
0
=
2
.44 (SBET = 445 m g , Si/Ti = 19). The catalyst presented here
ꢂ1
has thus a three times higher activity with respect to surface area.
This result points out the efficiency of the obtained material for
mild sulfoxidation which can be ascribed to the unique network of
isolated and interconnected mesopores (Fig. 1d and Fig. S1, ESIw
for fCHI=0.65) facilitating mass transfer and suggesting that the
Ti species are well distributed in the material.
1
2
3
(a) D. R. C. Huybrechts, L. De Bruycher and P. A. Jacobs, Nature,
990, 345, 240; (b) R. S. Reddy, J. Sudhakar Reddy, R. Kumar and
P. Kumar, Chem. Commun., 1992, 84; (c) T. Blasco, A. Corma,
M. T. Navarro and J. Perez Pariente, J. Catal., 1995, 156, 65.
(a) P. T. Tanev, M. Chibwe and T. J. Pinnavaia, Nature, 1994,
85, 321; (b) A. Corma, M. Domine, J. A. Gaona, J. L. Jorda
´
M. T. Navarro, F. Rey, J. Perez-Pariente, J. Tsuji, B. McCulloch
and L. T. Nemeth, Chem. Commun., 1998, 2211.
(a) N. Ravasio, F. Zaccheria, M. Guidotti and R. Psaro, Top.
Catal., 2004, 27, 157; (b) M. Guidotti, C. Pirovano, N. Ravasio,
B. Lazaro, J. M. Fraile, J. A. Mayoral, B. Coq and A. Galarneau,
´
1
´
3
´
,
For the materials with maximal porosity, and thus maximal
Ti accessibility (fPOR = 0.44), the amount of Ti was varied
between 1.4 and 5 mol% (Si/Ti = 19 and above), to assess the
effect of total titanium content on the accessibility of the Ti
sites in the appropriate tetrahedral coordination. It should be
noted that identical textural properties were obtained for all Ti
contents. These materials were tested for the MPS oxidation, and
conversions after 50 min were monitored. A ratio of Si/Ti = 38
yielded conversion of 94%, thus only slightly lower than with
Si/Ti = 19 achieving 99% conversion. That is a significant point
if we think of lowering the amount of necessary Ti and assessing
the optimal Ti/Si ratio. The material containing less Ti (Si/Ti = 68)
showed a limited conversion of 36%, while the blank experiment
showed 4% conversion.
Green Chem., 2009, 11, 1421.
4
5
R. Huttler, T. Mallat and A. Baiker, J. Catal., 1995, 153, 177.
M. Andrianainarivelo, R. Corriu, D. Leclercq, P. H. Mutin and
A. Vioux, J. Mater. Chem., 1996, 6, 1665.
6
(a) A. M. Cojocariu, P. H. Mutin, E. Dumitriu, F. Fajula, A. Vioux
and V. Hulea, Chem. Commun., 2008, 5357; (b) A. M. Cojocariu,
P. H. Mutin, E. Dumitriu, F. Fajula, A. Vioux and V. Hulea, Appl.
Catal. B, 2010, 97, 407.
7 L. Yu, K. Dean and L. Li, Prog. Polym. Sci., 2006, 31, 576.
8 P. Tundo, P. Anastas, D. S. Black, J. Breen, T. Collins, S. Memoli,
J. Miyamoto, M. Polyakoff and W. Tumas, Pure Appl. Chem.,
2
000, 72, 1207.
(a) C. Sanchez, H. Arribart and M. M. G. Guille, Nat. Mater.,
005, 4, 277; (b) S. Mann, Nat. Mater., 2009, 8, 781; (c) G. A. Ozin,
9
The recycling behaviour of the catalyst was investigated
for the MPS oxidation with one of the catalysts (Si/Ti = 19,
2
K. Hou, B. V. Lotsch, L. Cademartiri, D. P. Puzzo, F. Scotognella,
A. Ghadimi and J. Thomson, Mater. Today, 2009, 12, 12.
f
POR = 0.24, 2 h). The conversion of MPS for the first five
1
0 B. Alonso and E. Belamie, Angew. Chem., Int. Ed., 2010, 49,
201.
11 E. Belamie, M. Y. Boltoeva, K. Yang, T. Cacciaguerra and
runs was 88, 77, 75, 72 and 69%, showing thus only slight
deactivation. Leaching tests were performed by filtering off
the catalyst after 10 min. The solution was further reacted for
8
B. Alonso, J. Mater. Chem., 2011, 21, 16997.
1
2 (a) S. Pega, C. Boissie
Surf. Sci. Catal., 2008, 174, 471; (b) S. Pega, C. Boissi, D. Grosso,
T. Azaıs, A. Chaumonnot and C. Sanchez, Angew. Chem., Int. Ed.,
2009, 48, 2784.
3 (a) M. Fatnassi, C. Tourne
J.-M. Devoisselle and B. Alonso, New J. Chem., 2010, 34, 607;
b) B. Alonso, E. Veron, D. Durand, D. Massiot and C. Clinard,
Microporous Mesoporous Mater., 2007, 106, 76.
`
re, A. Chaumonnot and C. Sanchez, Stud.
60 min at 333 K and no significant increase (from 42 to 45%) in
conversion was observed. DR UV-vis spectra were recorded
before and after catalytic tests (Fig. S7, ESIw) and only a slight
alteration in adsorption was detected. The slight shift of the lower
energy band towards higher wavelengths indicates a minor change
in the coordination environment. We are currently studying in
more detail the modification of Ti sites during reactions and
the improvement of the catalytic performances.
¨
1
´
-Peteilh, T. Cacciaguerra, P. Dieudonne,
´ ´
(
´
14 E. Belamie, P. Davidson and M. M. Giraud-Guille, J. Phys. Chem.
B, 2004, 108, 14991.
1
5 P. H. Mutin, V. Lafond, A. F. Popa, M. Granier, L. Markey and
A. Dereux, Chem. Mater., 2004, 16, 567.
In conclusion, we have presented a new route for the prepara-
tion of titania–silica mesoporous catalysts based on spray-drying
and colloidal self-assembly involving a-chitin nano-rods. This
route is simple and yields materials with tunable properties
16 M. R. Boccuti, K. M. Rao, A. Zecchina, G. Leofanti and
G. Petrini, Stud. Surf. Sci. Catal., 1989, 48, 133.
17 R. J. Davis and Z. Liu, Chem. Mater., 1997, 9, 2311.
18 G. N. Vayssilov, Catal. Rev. Sci. Eng., 1997, 39, 209.
19 E. Ito and J. A. R. Van Veen, Catal. Today, 2006, 116, 446.
(composition, texture) which are active and efficient catalysts for
the oxidation of bulky sulphur-containing compounds. The chitin
20 I. Fernandez and N. Khiar, Chem. Rev., 2003, 103, 3651.
1
0650 Chem. Commun., 2012, 48, 10648–10650
This journal is c The Royal Society of Chemistry 2012