Organic Process Research & Development 2004, 8, 131−132
Table 1. Effect of different volume ratios of TBP/toluenea
Letters to the Editor
TBP/toluene yield conversion selectivity recovery yield
volume ratio) (%)b
(%)
c
(%)d
(wt %)
(
toluene
18.1
68.6
82.0
90.4
85.8
56.3
33.5
31.5
66.9
84.5
98.4
98.2
97.7
72.2
46.4
39.8
27.0
80.9
83.3
92.0
87.8
78.0
72.2
79.6
70.4
86.8
86.2
94.0
85.8
27.7
59.1
66.0
Ep o x id a t io n o f P ro p yle n e w it h Aq u e o u s
Hyd ro g e n P e ro x id e o n a
Re a c t io n -Co n t ro lle d P h a s e -Tra n s fe r
Ca t a lys t
1
1
:3
:2
3:4
1:1
2
3
:1
:1
TBP
To the Editor:
Sir: The better result (the selectivity for propylene oxide
a
Reaction conditions: solvent volume was kept at 70 mL, others were the
b
c
same as the experimental section. Yield of PO was based on H
of propylene was based on H
2
O
2
Conversion
based on propylene is 92.0%, and the yield based on H
2 2
O
O
2
. d Selectivity for PO was based on propylene.
2
is 90.9%) was obtained for homogeneous catalytic epoxi-
dation of propylene with aqueous H
controlled phase-transfer catalyst.
2 2
O on a reaction-
capacity. In a typical experiment, toluene (40 mL), tributyl
phosphate (30 mL), 52% H (1.74 g), catalyst (0.253 g),
2
O
2
Propylene oxide (PO) is one of the most important
chemical feedstocks. Current commercial productions usually
employ the chlorohydrin process and the Halcon process,
which give rise to serious environmental pollution as well
as a large amount of coproducts. As a result of increasingly
stringent environmental legislation, there is currently much
interest in the substitution of enviromentally friendly oxidants
in processes involving pollutant oxidants. Selective epoxi-
dation of propylene with molecular oxygen is a great
challenge to chemists for both academic and industrial
interest. Unfortunately, direct epoxidation of propylene with
dioxygen is difficult because of the poor selectivity under
and benzene (0.7 g, as internal standard) were added. The
weight of gaseous propylene fed into the autoclave was
measured by an electronic balance of 6 kg capacity and 0.01
g sensitivity. The reaction was maintained at 65 °C with
vigorous stirring for 4.5 h. After the reaction, the autoclave
was cooled to 25 °C, and then the gas in the autoclave was
discharged. The solution was analyzed by gas chromatog-
raphy (GC, Agilent 4890D, equipped with a flame ionization
detector and a packed column (2.4 m × 2 mm) containing
PEG 20M as the stationary phase). The propylene oxide in
the gas was ignored. The propylene in the gas was figured
by weight.
The tributyl phosphate (TBP)/toluene volume ratio has a
great influence on the epoxidation of propylene. The changes
of the reaction results with the TBP/toluene volume ratio
are listed in Table 1. In this table, the yield of PO, the
selectivity for propylene, and the recovered yield of the
catalyst all increase with the increase of the TBP/toluene
volume ratio and decrease after the volume ratio of TBP/
toluene reaches 3:4. It is considered that the water phase is
unfavorable to the epoxidation reaction due to the solubility
in water and the hydrolysis of PO to propylene glycol. When
only toluene was used as the solvent, the yield of PO based
the conventional severe conditions. H
oxidant, and the TS-1 zeolite catalyst for propylene epoxi-
dation with aqueous H in methanol solution has high
2 2
O is also a clean
2
O
2
1
catalytic activity and selectivity. Moreover, the TS-1 zeolite
can be regenerated by calcination or washing with the
solvent. However, this method has not yet been commercial-
ized because of economic reasons. Since PO is water soluble,
2 2
a few homogeneous catalytic systems with aqueous H O
2
as oxidant have been reported. Recently, we have reported
a reaction-controlled phase-transfer catalytic system for
3
2 2
propylene epoxidation with in situ formed H O .
Herein we disclose a better result on the homogeneous
catalytic epoxidation of propylene by 52% H to propylene
2 2
on H O and the selectivity for PO based on propylene were
2 2
O
1
8.1% and 27.0%, respectively. With the amount of TBP
oxide using the same reaction-controlled phase-transfer
catalyst. The catalyst is easily recovered with 94% recovery
yield (by weight). The selectivity for propylene oxide is
increasing, the yield and the selectivity became much better.
When the volume ratio of TBP/toluene reaches 3:4, the
polarity of TBP makes the aqueous/oil biphasic system
remain in the same phase, and no aqueous phase dissociates
from the oil phase. Thus, the epoxidation reaction cannot
be affected by water produced from added 52% H O
2 2.
Interestingly, higher amounts of TBP had the opposite effect
and decreased the propylene oxide yield. As we know, the
92.0% based on propylene, and the yield is 90.9% based on
2 2
H O .
5 5 33 3 4
The catalyst, [π-C H NC16H ] [PW O16], was prepared
according to ref 4.
The catalytic epoxidation reactions were carried out in a
stainless steel autoclave with a glass liner of 250 mL
5 5 33 3 4
catalyst, [π-C H NC16H ] [PW O16], consists of two parts
*
Author for correspondence. E-mail: sgao@dicp.ac.cn. Telephone: 86-411-
heteropolyoxotungstate anion and quaternary ammonium
cation which have nearly opposite effects on catalyst
solubility. When the amount of TBP was in excess, the
catalyst could not dissolve completely in the reaction system
4
379248.
(
(
1) Clerici, M. G.; Bellussi, G.; Romano, U. J. Catal. 1991, 129, 159.
2) (a) Venturello, C.; Alneri, E.; Ricci, M. J. Org. Chem. 1983, 48, 3831. (b)
Kamata, K.; Yonehara, K.; Sumida, Y.; Yamaguchi, K.; Hukichi, S.; Mizuno,
N. Science 2003, 300, 5621.
3) Zuwei, X.; Ning, Z.; Yu, S.; Kunlan, L. Science 2001, 292, 1139.
4) Sun, Y.; Xi, Z.; Cao, G. J. Mol. Catal. A: Chem. 2001, 166, 219.
2 2
even under the action of H O , and the catalytic activity
(
(
became lower.
1
0.1021/op0341014 CCC: $27.50 © 2004 American Chemical Society
Vol. 8, No. 1, 2004 / Organic Process Research & Development
•
131
Published on Web 11/20/2003
Gao, Shuang
