450
LAMBERT, DEROUANE, AND KOZHEVNIKOV
4
3
2
1
0
double-bond migration to form 2-butene, apparently pro-
ceeding through relatively stable π-allyl Pd(II) complexes.
This complicates the kinetics of 1-butene oxidation. Some
overoxidation of reaction products takes place in the semi-
continuous reactor. Use of a flow reactor with continuous
removal of the products from the catalyst solution could
reduce their overoxidation.
ethene
propene
1-butene
ACKNOWLEDGMENTS
The authors thank Dr. A. Lapkin, Dr. P. Plucinski, and Dr. B.-G. Park
(University of Bath) for valuable discussion and the EPSRC, U.K. for
support (grant GR/N06762).
0
0.5
1
1.5
2
O2 Absorption Rate, mmol/dm3 min
REFERENCES
FIG. 8. Olefin absorption rate versus O2 absorption rate (50 mM
HPA-3, 0.10 mM Pd(II), 5.0 mM Cl−, 20–50◦C, 4.0 cm3/min oxygen,
8.0 cm3/min olefin). The straight line corresponds to 2 : 1 stoichiometry.
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Kinet. Katal. 18, 320 (1977).
ethene ≥ 1-butene > propene, which correlates with the
oxidisibility of the corresponding products (acetaldehyde
≥ MEK > acetone). This may be explained by the co-
oxidation of HPA-3 blue and the products by O2, leading
to overoxidation of products. Indeed, some acetic acid was
found among the products by GC analysis. It was shown
that the oxidation of HPA-n blues with a low average de-
gree of reduction (<1 e− per Keggin anion) occurs through
the formation of free radicals (HO•) that can initiate the
aerobic oxidation of organic compounds if they are present
in the system (13, 20). Use of a flow reactor with continuous
removal of the products could reduce their overoxidation.
7. Matveev, K. I., Kinet. Katal. 18, 716 (1977).
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A. V., Shadrin, L. P., and Dzhalalova, M. M., U.K. Patent No. 1,508,331
(1977).
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Trans. 1223 (1984).
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Reactions” (J. R. Kosak and T. A. Johnson, Eds.), p. 213. Dekker,
New York, 1994.
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(M. T. Pope and A. A. Mu¨ller, Eds.), p. 281. Kluwer Academic,
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CONCLUSIONS
The steady-state kinetics of the one-stage Wacker oxi-
dation of gaseous olefins such as ethene, propene, and
1-butene by oxygen catalysed by the Pd(II)/HPA-3 redox
system to form, respectively, acetaldehyde, acetone, and
MEK in aqueous solution has been studied in a semicon-
tinuous reactor by reacting a stoichiometric 1 : 2 mixture of
O2 and olefin at 20–50◦C. The chosen catalyst composition
matches Catalytica’s system and involves Pd(II) chloride
(0.05–2 mM Pd(II), [Pd(II)]/[Cl−] = 1 : 50) and Keggin-type
heteropoly anions [PMo9V3O40]6− (50 mM) at pH 1.3. Un-
der these conditions in a steady state, the reactivity of
olefins increases in the following order: ethene ≤ 1-butene
< propene; but the total range is only a factor of 3. The
oxidation of ethene and propene occurs without any com-
plication. The oxidation of 1-butene is accompanied by