a
Table 1 Oxidation of dodecane in air: comparison of catalysts
b
Product distribution/mmol
Catalyst
Conv./mmol
C
1
-ol
C
1
-al Lauric acid C
2
-ol
C
2
-one
C
3
-ol
C
3
-one
C
4
-ol
C
4
-one
C
5
-ol
C
5
-one Othersc
Mn-ALPO-18 (0.04) 16.08
Mn-ALPO-36 (0.04) 15.20
1.27
0.47
—
4.71 1.65
4.47
0.95
—
3.25
1.27
—
—
—
—
—
—
— 0.73
—
—
—
0.55
—
—
1.37
2.28
0.75
1.45
1.97
1.19
2.63 2.07
2.07 2.83
0.58 1.03
1.65 1.89
1.59 2.46
0.43 0.91
0.90
0.55
0.25
Mn-ALPO-5 (0.04)
Mn-ALPO-11 (0.04)
13.75
6.82
0.24
0.91
0.53
a
Dodecane = 49.7 g; catalyst = 0.5 g; air = 1.5 MPa; temp. = 373 K; time = 24 h. b
-one = dodecan-2-one; C -ol = dodecan-3-ol; C -one = dodecan-3-one; C -ol = dodecan-4-ol; C
dodecan-5-one. Others = mainly CO , CO, water and lower olefins/hydrocarbons in the gas phase.
C
1
-ol = dodecan-1-ol; C
1
-al = dodecanal; C
2
-ol = dodecan-2-ol;
-one
C
=
2
3
3
4
4
-one = dodecan-4-one; C
5
-ol = dodecan-5-ol; C
5
c
2
framework of the microporous host favours the regeneration of
the catalyst’s activity. Its selectivity, however, is solely due to
the pore size dimensions that govern access of the hydrocarbon.
It should be mentioned that, after the reaction, the catalyst
(
MnAlPO-18) was washed thoroughly with methanol and
activated at 550 °C for 12 h in the presence of dry air. It was then
recycled twice without significant loss in catalytic activity
(
conv. = 15.65 mmol) and selectivity (C
7.6%).
We thank EPSRC, UK for financial support (rolling grant to
1 2
= 48% and C =
4
J. M. T.), the Royal Commission for the Exhibition of 1851 for
a Research Fellowship to R. R., Dr G. Sankar for help in sample
preparation and useful discussions and Dr R. G. Bell for
computer guidance.
Notes and references
Fig. 3 Typical kinetic plots for the oxidation of dodecane over MnAlPO-18
catalyst under the conditions given in Table 1
†
E-mail: robert@ri.ac.uk, jmt@ri.ac.uk
1
C. L. Hill, in Activation and functionalisation of alkanes, Wiley,
Chichester, 1989; see also J. M. Thomas, Nature, 1985, 314, 669 and
references therein.
oxidation of the dodecane (total conversion = 5.5 wt.%) only at
1 2
C and C , whereas in MnAlPO-36 (possessing essentially the
2
Dioxygen Reactions, ed. I. Bertini, H. B. Grey, S. J. Lippard and J. S.
Valentine, Mill Valley, CA, 1994.
N. Herron and C. A. Tolman, J. Am. Chem. Soc., 1987, 109, 2837.
K. Sauer, V. K. Yachandra, R. D. Britt and M. P. Klein, in Manganese
Redox Enzymes, ed. V. L. Pecoraro, VCH Publishers, New York,
1992.
same concentration of the active site) (total conversion = 5.2
wt.%) the oxyfunctionalization occurs at essentially all the
carbon atoms of the dodecane backbone, and more predom-
3
4
4 5
inantly at the C and C positions. The kinetics of oxidation of
dodecane using MnAlPO-18 was studied in detail (Fig. 3), and
after an initial period of induction (4 h), dodecan-1-ol and
dodecan-2-ol were formed simultaneously, and were subse-
quently oxidised to dodecanal, lauric acid and dodecan-2-one at
prolonged contact times. In an identical experiment, the solid
catalyst was filtered off (when hot) after 8 h (conversion = 2.4
wt.%) and the reaction was continued for a further 16 h. But, no
5 J. M. Thomas, G. N. Greaves, G. Sankar, P. A. Wright, J. Chen, A. J.
Dent and L. Marchese, Angew. Chem., 1994, 33, 1871.
6
7
8
9
J. Chen and J. M. Thomas, J. Chem. Soc., Chem. Commun., 1994,
03.
6
P. A. Barrett, G. Sankar, C. R. A. Catlow and J. M. Thomas, J. Phys.
Chem., 1996, 100, 8977.
A. Simmen, L. B. McCusker, Ch. Baerlocher and W. M. Meier, Zeolites,
III
further conversion was observed, showing that the Mn ions in
1
991, 11, 654.
the framework of the molecular sieve are solely responsible for
the catalysis. (The reaction mixture was independently analysed
by ICP analysis and no detectable quantities of Mn or Co were
observed.) MnAlPO-18 and CoAlPO-18 (and possibly other
transition-metal ion substituted AlPO-18) are therefore good
candidates for suitable catalysts in the production of function-
alised hydrocarbons required as surfactants and detergents. We
know from parallel work14 that a CoAlPO-18 (total conversion
J. Chen, P. A. Wright, J. M. Thomas, S. Natarajan, L. Marchese, S. M.
Bradley, G. Sankar, C. R. A. Catlow, P. L. Gai-Boyes, R. P. Townsend
and C. M. Lok, J. Phys. Chem., 1994, 98, 10216.
10 J. M. Thomas and G. N. Greaves, Science, 1994, 265, 1675.
1
1 G. Sankar, J. M. Thomas, G. N. Greaves and A. J. Dent, J. Phys. IV.
France), 1997, 7, C2, 871.
(
1
2 R. Raja and P. Ratnasamy, Catal. Lett., 1997, 48, 1.
1
3 P. A. Wright, S. Natarajan, J. M. Thomas, R. G. Bell, P. L. Gai-Boyes,
R. H. Jones and J. S. Chen, Angew. Chem., Int. Ed. Engl., 1992, 31,
=
7.1 wt.%) catalyst preferentially activates the terminal and
1
472.
secondary methyl groups of n-hexane.
1
4 R. Raja, J. M. Thomas, G. Sankar and R. G. Bell, in preparation.
We believe that the key to the catalytic activity is the
15 C. Lamberti, S. Bordiga, A. Zecchina, G. Vlaic, G. Tozzola, G. Petrini
and A. Carati, J. Phys. IV. (France), 1997, 7, C2, 851.
16 G. Sankar, F. Rey, J. M. Thomas, G. N. Greaves, A. Corma, B. R.
Dobson and A. J. Dent, J. Chem. Soc., Chem. Commun., 1994, 2279.
17 T. Maschmeyer, F. Rey, G. Sankar and J. M. Thomas, Nature, 1995,
III
coordinatively unsaturated Mn ion. Just as with the tetra-
IV
15
hedrally coordinated Ti ions in TS-1, metallocene derived
16,17
III
Ti—MCM-41
and especially the Co ions in CoAlPO-
8, expansion of the coordination shell in the transition state
14
1
3
78, 159.
is likely to be facile. Moreover, after the departure of the
products, the retention of the isolated MnIII ions in the
Received in Liverpool, UK, 27th May 1998; 8/03984D
1842
Chem. Commun., 1998