Transesterification of phenol and dimethyl carbonate catalyzed by titanium oxide acetylacetonate catalyst

Article abstract of DOI:10.1016/S1872-2067(11)60381-1

Titanium oxide acetylacetonate (TiO(acac)₂) was found to be a novel and efficient heterogeneous catalyst for the transesterification of phenol and dimethyl carbonate (DMC) to diphenyl carbonate (DPC). The conversion of phenol was 45.8% on the TiO(acac)₂ pretreated at 180 °C, and the turnover number reached 96, which was better than the more common organic titanium catalyst. The effect of the amount of catalyst on the catalytic performance was investigated. The transesterification selectivity decreased with catalyst loadings over 0.2 g per 100 ml reactants. At the optimized amount of catalyst the conversion of phenol was 42.4%, and no anisole was detected. In particular, the TiO(acac)₂ catalyst proved reusable, and catalytic activity of the recovered TiO(acac)₂ was almost the same as that of the fresh catalyst. The conversion of phenol 40.0% was attained from TiO(acac)₂ recovered for the fifth time.

Full text of DOI:10.1016/S1872-2067(11)60381-1

CHINESE JOURNAL OF CATALYSIS
Volume 33, Issue 4, 2012
Online English edition of the Chinese language journal
Cite this article as: Chin. J. Catal., 2012, 33: 601–604.
COMMUNICATION
Transesterification of Phenol and Dimethyl Carbonate
Catalyzed by Titanium Oxide Acetylacetonate Catalyst
1
,2
1,2
1,
1
LI Bijing , TANG Rongzhi , CHEN Tong *, WANG Gongying
1
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, Sichuan, China
Graduate University of Chinese Academy of Sciences, Beijing 100049, China
2
2
Abstract: Titanium oxide acetylacetonate (TiO(acac) ) was found to be a novel and efficient heterogeneous catalyst for the transesterifi-
cation of phenol and dimethyl carbonate (DMC) to diphenyl carbonate (DPC). The conversion of phenol was 45.8% on the TiO(acac)
2
o
pretreated at 180 C, and the turnover number reached 96, which was better than the more common organic titanium catalyst. The effect of
the amount of catalyst on the catalytic performance was investigated. The transesterification selectivity decreased with catalyst loadings
over 0.2 g per 100 ml reactants. At the optimized amount of catalyst the conversion of phenol was 42.4%, and no anisole was detected. In
particular, the TiO(acac)
2
2
catalyst proved reusable, and catalytic activity of the recovered TiO(acac) was almost the same as that of the fresh
catalyst. The conversion of phenol 40.0% was attained from TiO(acac)
2
recovered for the fifth time.
Key words: titanium oxide acetylacetonate; diphenyl carbonate; transesterification; phenol; heterogeneous catalyst
Diphenyl carbonate (DPC) is an important chemical inter-
V-Cu complex oxide is better than other heterogeneous cata-
mediate and is used extensively for the preparation of many
organic compounds and polymer materials, especially for the
preparation of polycarbonates without the use of phosgene
bisphenol A in a melt transesterification. Transesterification of
phenol and dimethyl carbonate (DMC) is considered to be the
most promising method for the industrial production of DPC
because DMC is a relatively “green” raw material. The syn-
thesis of DPC via transesterification is usually carried out in the
liquid phase using homogeneous catalysts such as organic tin
or titanium compounds [1,2]. However, the titanium and tin
compounds are too poisonous to be considered environmen-
tally benign catalysts. Moreover, homogeneous catalysts are
generally difficult to separate from the final product. Solid
catalysts are generally the focus of current research. Until now,
several heterogeneous catalysts had been investigated for the
transesterification, such as complex metal oxides [3–6], het-
eropoly compounds [7,8], and molecular sieves [9,10].
Ti-HMS shows excellent transesterification selectivity, avoid-
ing the production of anisole and giving a 31.4% conversion of
phenol, but Ti-HMS cannot be reused. The stability of the
lysts, and the conversion of phenol was 37.0%. However, 3.2%
of the byproduct anisole was also produced.
In this work, TiO(acac) is the first heterogeneous catalyst
2
for the transesterification of DMC and phenol in the synthesis
of DPC to the best of our knowledge. It was found that
TiO(acac)2 is a highly efficient and stable heterogeneous
catalyst with greater than 99.9% transesterification selectivity.
The transesterification of phenol (AR, Guangdong
Guanghua Sci-Tech Co., Ltd., China) and DMC (ꢀ 99.9%,
Huasheng Co. Ltd., Shandong University of Petroleum, China)
was carried out in a 100 ml three-neck round-bottomed flask
under a nitrogen atmosphere. The mixture of phenol and
TiO(acac)2 (ꢀ 99.9%, Shanghai Dibo Chemical Co. Ltd.,
China) was stirred and heated to 175 °C. DMC was added
dropwise, and the reaction left for 9 h. TiO(acac) was used as a
2
heterogeneous catalyst, which is insoluble in the reaction sys-
tem. The products and the azeotrope of DMC with methanol
were analyzed by GC (Shimadzu, GC-12B).
Thermal analysis (Fig. 1) of the catalyst indicates that the
decomposition temperature of TiO(acac) is 238 °C. When
2
Received 9 January 2012. Accepted 27 February 2012.
*
Corresponding author. Tel: +86-28-85250005; Fax: +86-28-85220713; E-mail: chentongw@sina.com.cn
This work was supported by the Chinese Academy of Sciences “Western light” United Scholars Program.
Copyright © 2012, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier BV. All rights reserved.
DOI: 10.1016/S1872-2067(11)60381-1

LI Bijing et al. / Chinese Journal of Catalysis, 2012, 33: 601–604
0
1
00
Table 1 Reuse of TiO(acac)
2
in the transesterification of DMC and
Yield (%)
phenol
-10
9
8
7
6
5
0
0
0
0
0
Phenol conversion
%)
Run
-20
30
40
50
(
MPC
23.7
21.9
21.2
23.9
20.7
DPC
18.7
19.6
18.6
18.7
19.6
1
2
3
4
5
42.4
41.5
39.8
42.6
40.3
-
-
-
0
50 100 150 200 250 300 350
Reaction conditions: n(phenol) = n(DMC) = 160, m(catalyst) = 0.2 g,
o
Temperature ( C)
1
50~180°C, t = 9 h.
2
Fig. 1. TG-DTG curves of the TiO(acac) sample.
Table 1 shows that the catalytic activity of the recovered
TiO(acac)
2
was pretreated at 180 °C, the catalytic activity and
TiO(acac) was similar to the fresh catalyst. The conversion of
2
the transesterification selectivity increased significantly. The
conversion of phenol increased from 19.8% to 39.4%, and the
transesterification selectivity increased from 98.5% to 99.8%
with the use of 0.4 g of TiO(acac)2.
Figure 2 shows the effect of the amount of catalyst on the
transesterification. The conversion of phenol increased with
increasing catalyst amount up to 0.4 g, giving the highest
phenol conversion of 45.8% and transesterification selectivity
of 99.4%. Meanwhile, the turnover number (TON,
n(phenol)/n(Ti)) reached 96, which is superior to that of the
organic titanium homogeneous catalyst [2] (TON = 92).
However, the transesterification selectivity decreased as the
amount of catalyst increased. No anisole was produced using
phenol remained above 40.0%, and no anisole was detected.
For the transesterification of DMC and phenol, TiO(acac)2
has been found to be a novel and efficient heterogeneous
catalyst, with both high phenol conversion and good trans-
esterification selectivity. In particular, the selectivity and sta-
bility of TiO(acac) are superior to other heterogeneous cata-
2
lysts. Under the optimized reaction conditions, using 0.2 g
TiO(acac) , the conversion of phenol was 42.4% and the
2
transesterification selectivity was 100%. The TON reached 89,
which is similar to the best homogeneous catalyst. Therefore,
TiO(acac) is a highly efficient heterogeneous catalyst for the
2
transesterification of phenol and DMC to DPC.
less than 0.2 g of the catalyst. The weak acidity of TiO(acac) is
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