Promotion of organotin modified SBA-15 in the selective carboxylation of BPA with DMC

Article abstract of DOI:10.1016/j.catcom.2011.02.015

Two-methylcarbonate-ended-BPA (DmC(1)) was selectively synthesized from dimethyl carbonate (DMC) and bisphenol A (BPA) over organotin modified SBA-15. Organotin modified samples were characterized by XRD, FT-IR, BET and TG, and the relations between catalytic performance and catalyst properties were discussed. When heterogeneous SBA-15(CH₂)₃SnOC₄H ₉ was used as catalyst, DmC(1) achieved better yield and higher selectivity than that obtained over homogeneous (C₄H ₉)₂SnO. The confined region effect of SBA-15(CH ₂)₃SnOC₄H₉ was the main reason to promote the reaction between one-methylcarbonate-ended-BPA (MmC(1)) and DMC.

Full text of DOI:10.1016/j.catcom.2011.02.015

Catalysis Communications 12 (2011) 932–935
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Promotion of organotin modified SBA-15 in the selective carboxylation of BPA
with DMC
b
a,
a
a
b
Zhenhuan Li a, , Kunmei Su , Bowen Cheng , Jun Ming , Lei Zhang , Yongchao Xu
⁎
⁎
a
School of Materials Science and Engineering, and Tianjin Key Lab of Fiber Modification & Functional Fiber, Tianjin Polytechnic University, 300160 Tianjin, China
School of environment Science and Chemisty Engineering, and Tianjin Key Lab of Fiber Modification & Functional Fiber, Tianjin Polytechnic University, 300160 Tianjin, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 January 2011
Received in revised form 17 February 2011
Accepted 20 February 2011
Available online 26 February 2011
Two-methylcarbonate-ended-BPA (DmC(1)) was selectively synthesized from dimethyl carbonate (DMC)
and bisphenol A (BPA) over organotin modified SBA-15. Organotin modified samples were characterized by
XRD, FT-IR, BET and TG, and the relations between catalytic performance and catalyst properties were
discussed. When heterogeneous SBA-15(CH2)3SnOC4H9 was used as catalyst, DmC(1) achieved better yield
and higher selectivity than that obtained over homogeneous (C4H9)2SnO. The confined region effect of SBA-15
(CH2)3SnOC4H9 was the main reason to promote the reaction between one-methylcarbonate-ended-BPA
(MmC(1)) and DMC.
Keywords:
Organotin
SBA-15
Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.
Carboxymethylation
Dimethyl carbonate
Bisphenol A
1. Introduction
synthesis, however, the separation of homogeneous organotin
catalyst from products was complicated. The development of
Poly (bisphenol A carbonate) (PC) is an important thermoplastic
which is often produced by the interfacial polycondensation of
bisphenol A (BPA) and phosgene. In an attempt to devise a phosgene-
free PC synthesis process, diphenyl carbonate (DPC) [1–6], CO [7–13]
and DMC [14–18] were used as carbonylating agents to replace
phosgene. The direct synthesis of PC from BPA and DMC is an attractive
and challenging subject. Shaikh et al. [14] and Haba et al. [18] reported
that both methylcarbonate-ended oligomers were most reactive in
producing high molecular weight polymers compared with hydroxyl-
ended oligomers. Therefore, the selective synthesis of methylcarbonate-
ended oligomers from BPA and DMC has become particularly important.
The presence of two nonequivalent electrophilic centers in DMC
(the carbonyl and methyl moieties) make it possible for BPA to
undergo methylation and carboxylation [19]. However, the carboxyl-
ation reaction between BPA and DMC to synthesize DmC(1) suffers
from low yield and selectivity even at elevated temperature, and
reaction rate is somewhat slow. Therefore, the design of new active
catalytic systems are prerequisite to promote DmC(1) synthesis. The
carboxylation of BPA with DMC was often catalyzed by Lewis acid
catalysts, for example, TiO2/SBA-15[20], TiO2/SiO2 [21], (Bu2SnCl)2O
[18], Bu2SnO and titanium alkoxides. Haba et al. [18] reported that
organotin was the best catalyst for methylcarbonate-ended oligomer
heterogeneous catalysts with better performance was highly desir-
able in view of regeneration and separation. The carboxylation of BPA
with DMC can be promoted by TiO2/SBA-15 (see Scheme 1) [22],
however, the yield and selectivity of DmC(1)) over TiO2/SBA-15 were
still far from satisfaction in comparation with those over homoge-
neous organotin catalyst.
In this work, we have found that SBA-15(CH2)3SnOC4H9 displays a
better performance than organotin in DmC(1) synthesis, and that
organotin modified SBA-15 could be easily regenerated and separated.
2. Experiments
2.1. Chemical Reagents
P123 [(EO)20(PO)70(EO)20]) and CPTMS (3-chloropropyltriethox-
ysilane) (purity 97%) were purchase from Sigma-Aldrich Company
Ltd. DMC (Tianjin Chemical Reagent Research Institute) was fraction-
ally distilled and stored over molecular sieve (4 Å). Tetrabutoxy
titanium (TBOT), tetraethylorthosilicate (TEOS, 98%) and BPA was of
analytic reagent (AR) grade and used without further purification.
2.2. Sample Preparation
SBA-15 was synthesized in accordance with the published
procedure [23]. To prepare TiO2/SBA-15 catalysts, SBA-15 was
impregnated in ethanol solution of TBOT at room temperature for
24 h, and then dried in an oven at 80 °C for 8 h to remove ethanol. The
⁎
Corresponding authors at: School of Materials and Engineering, Tianjin Polytechnic
University, Tianjin 300160, China. Fax: +86 222452 8055.
E-mail addresses: Zhenhuanli1975@yahoo.com.cn (Z. Li), bowen15@tjpu.edu.con
(B. Cheng).
1566-7367/$ – see front matter. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2011.02.015

Z. Li et al. / Catalysis Communications 12 (2011) 932–935
933
CH3
C
CH3
C
O
O
O
DMC
BPA
HO
OCOCH3
+ H3COCO
OCOCH3
TiO2/SBA-15
CH3
CH3
MmC(1)
DmC(1)
Scheme 1. The main products of reaction between BPA and DMC.
TBOT-impregnated silica was calcined with an air stream at 550 °C for
3 h. The organotin modified SBA-15 was synthesized in accordance
with the following procedure. CPTMS reacted with Mg in distilled
toluene to give (CH3O)3Si(CH2)3MgCl, which further reacted with
SnCl4 to produce (CH3O)3Si(CH2)3SnCl3. C4H9Cl and PhCH2Cl reacted
with Mg in distilled THF to give C4H9MgCl and PhCH2MgCl which
reacted with (CH3O)3Si(CH2)3SnCl3 to give (CH3O)3Si(CH2)3SnCl2C4H9
and (CH3O)3Si(CH2)3SnCl2CH2Ph. (CH3O)3Si(CH2)3SnCl3, (CH3O)3Si
(CH2)3SnCl2C4H9 and (CH3O)3Si(CH2)3SnCl2CH2Ph were anchored
onto SBA-15 surface, and the grafted samples were dipped in NaOH
solution for 24 h at R.T. The finally obtained solid dried at 120 °C, and the
obtained samples were referred as SBA-15(CH2)3SnO(OH), SBA-15
(CH2)3SnOC4H9 and SBA-15(CH2)3SnOCH2Ph.
tion was in good agreement with the XRD pattern of pure hexagonally
ordered SBA-15 material [24–26]. The characterized results indicated
that SBA-15(CH2)3SnOCH2Ph had a well-ordered two-dimensional
mesoporous structure with a hexagonal porous network. Nearly no
(110) and (200) peaks appeared in the XRD pattern of SBA-15
(CH2)3SnO(OH) and SBA-15(CH2)3SnOC4H9, due to much more
organotin being impregnated into the channels of SBA-15 support.
However, the presence of intensive 100 reflections indicated that SBA-
15(CH2)3SnO(OH) and SBA-15(CH2)3SnOC4H9 still retained a well-
ordered structure.
3.2. FT-IR of Samples
2.3. Characterization
FT-IR spectra of the samples are presented in Fig. 2. The
characteristic vibration bands at around 1101, 791 and 493 cm−1
were caused by the stretching, bending and out of plane deformation
vibrations of Si–O–Si bonds, respectively [27,28]. By analyzing the
spectra of SBA-15 and organotin modified SBA-15, CH2 pattern was
observed [25]. A very broad absorption band centered at 3450 cm−1
was assigned to the hydrogen bond of surface Si–OH groups [29]. The
spectra of the organotin modified SBA-15 showed less silanol species
than the spectrum of the no-functionalized material SBA-15, which
suggested that the organotin was immobilized onto SBA-15.
XRD patterns were measured on a Bruker AXS (Germany) using Cu
Kα radiation. The date was recorded from 1° to 80° (2θ). FT-IR
spectrum was obtained on a Nicolet Nexus 470 FT-IR analyzer using
the KBr method. The porosity of all samples is measured by adsorption
and desorption of nitrogen at −196 °C using a Micromeritics Tristar
3000 surface analyzer. Before plotting the isotherms, the samples are
treated in vacuum (10−6 mmHg) at 100 °C and maintained overnight
at that value. The specific surface areas of the samples were calculated
using the multiple-point Brunauer–Emmett–Teller (BET) method. The
pore size distribution was calculated from the adsorption branch of
the isotherms using the Barrett–Joyner–Halenda (BJH) method.
Thermogravimetric analysis (TGA) was performed on a Setaram TGA-
92 thermogravimetric analyzer with a heating speed of 10 °C/min under
air with a flow rate of 100 mL/min.
Reaction products were analyzed by HPLC and GC-MS (HP5972)
(capillary column: 30 m SE-30, 0.25 mm ID, and 0.25 μm film thickness)
to identify products and polycarbonate precursors. Quantitative analysis
was carried on a gas chromatograph (Agilent 6890 N GC with an FID
detector, HP-5/DB-5 capillary column) with cetane as interior standard.
The HPLC analyses were carried out by a reverse-phase method on a
Waters 2690 separation module (Waters Associates, Milford, MA). The
reverse-phase LC column was Waters Lichrosorb RP18 analytical
column.
3.3. Nitrogen Adsorption–desorption
The characterization of samples was summarized in Table 1. The
organotin modified SBA-15 samples displayed the type IV isotherms
with a hysteresis loop (Fig. 3), which is characteristic of mesos-
tructured solids. The BJH pore diameter distribution is also shown in
Fig. 3. All samples had a tightly controlled pore size distribution in the
mesoporous range, and organotin modified SBA-15 displayed smaller
pore size than SBA-15 support. The graft of organotin onto SBA-15
resulted in smaller pore size, and organotin dispersed well on the
internal surface of their parent support.
2.4. Reaction Procedure
Ph
Reactions were carried out in a four neck flask which was equipped
with a thermometer, a nitrogen inlet, a dropping funnel and a
fractionating column connected to a liquid dividing head. BPA and
catalyst were charged into a flask under nitrogen atmosphere. During
the reaction, a distillate of DMC and methanol was collected slowly in
a receiver flask. After the reaction finished, the mixture was cooled
and analyzed. The yield of DmC(1) and DmC(1) was based on initial
BPA.
OH
SBA-15
C4
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2 Theta degree
Ph
OH
SBA-15
C4
3. Results and Discussion
3.1. XRD Characterization
1
2
3
4
5
6
The XRD pattern of the samples is depicted in Fig. 1. The low-angle
XRD measurement showed that SBA-15 and SBA-15(CH2)3SnOCH2Ph
exhibited three peaks which could be indexed to (100), (110), and
(200) reflections of the hexagonal p6mm space group. The observa-
2 Theta degree
Fig. 1. Low-angle XRD patterns of organotin-SBA-15 (Ph=SBA-15(CH2)3SnOCH2Ph,
C4=SBA-15(CH2)3SnOC4H9, OH=SBA-15(CH2)3SnO(OH)).

934
Z. Li et al. / Catalysis Communications 12 (2011) 932–935
949oC
100
98
96
94
92
90
88
86
84
82
80
OH
C4
SBA-15
96.8 wt%
Ph
SBA-15
OH
85.7 wt%
84.4 wt%
Ph
C4
80.4 wt%
0
100 200 300 400 500 600 700 800 900 1000
TemperatureoC
3500
3000
2500
2000
1500
1000
500
Wavenumber cm-1
Fig. 2. FT-IR spectra of samples (Ph=SBA-15(CH2)3SnOCH2Ph, C4=SBA-15
Fig. 4. Thermogravimetric analysis results of organotin-SBA-15 (Ph=SBA-15
(CH2)3SnOC4H9, OH=SBA-15(CH2)3SnO(OH)).
(CH2)3SnOCH2Ph, C4=SBA-15(CH2)3SnOC4H9, OH=SBA-15(CH2)3SnO(OH)).
1.63 mmol/g, respectively. The variety of organotin loading amount
was caused by the different volume of graft organic group.
3.4. Thermogravimetric Analysis
Thermogravimetric analysis results of the samples are shown in
Fig. 4. At the temperature range of room temperature to 950 °C, SBA-
15, SBA-15(CH2)3SnO(OH), SBA-15(CH2)3SnOC4H9 and SBA-15
(CH2)3SnOCH2Ph exhibited 96.8%, 84.4%, 85.7% and 80.4% weight
loss. A major weight loss was observed up to temperature 550 °C,
which was mainly attributed to the decomposition of loaded
organotin. Organotin loading amount over SBA-15 was calculated
from thermogravimetric analysis results and summarized in Table 1.
The organotin loading amount of SBA-15(CH2)3SnO(OH), SBA-15
(CH2)3SnOC4H9 and SBA-15(CH2)3SnOCH2Ph was 7.24, 4.42 and
3.5. The Promotion of Organotin Modified SBA-15 in the Carboxylation of
BPA with DMC
As shown in Table 2, SBA-15(CH2)3SnOC4H9 showed the better
performance for DmC(1) synthesis. DmC(1) could be produced with
10.6% yield, and the selectivity to DmC(1) achieved 26.1% (entry 3).
Organotin was the best catalyst for the carboxylation of BPA with DMC
into methylcarbonate-ended oligomers, but the yield and selectivity
of DmC(1) over (C4H9)2SnO were 10.0% and 18.1% (entry 2). However,
when SBA-15(CH2)3SnOCH2Ph was used as catalyst, DmC(1) yields
declined to 1.0%, and DmC(1) selectivity decreased to 3.3% (entry 4).
SBA-15(CH2)3SnO(OH) had no activity in DmC(1) synthesis because
the hydroxyl of SnO(OH) could resulted in DMC decomposition (entry
5). The lower activity of SBA-15(CH2)3SnOCH2Ph in DmC(1) synthesis
was caused by its higher steric hindrance which came from the phenyl
group. The higher activity showed by SBA-15(CH2)3SnOC4H9 may be
due to its confined region effects. More specifically, the high MmC(1)
concentration in the mesopore of SBA-15(CH2)3SnOC4H9 may
increase the reaction rate between MmC(1) and DMC.
Table 1
Texture and properties of samples.
Catalyst
Surface area
Pore volume
Pore diameter
(nm)
Loading
(mmol/g)
Loading
(wt.%)
(m2 g−1
)
(cm3 g−1
)
C4
Ph
OH
SBA-15
178.5
391.8
337.7
457.9
0.20
0.74
0.49
0.86
5.70
5.50
5.55
8.11
4.42
1.63
7.24
0
55.3
35.4
64.4
0
Ph=SBA-15(CH2)3SnOCH2Ph, C4=SBA-15(CH2)3SnOC4H9, OH=SBA-15(CH2)3SnO(OH).
3.6. Suggested Mechanism
We suggest the following mechanism for our process (Scheme 2).
Coordination of the carbonyl oxygen to tin increases the positive
character of the carbon atom. At the same time, the hydroxyl of BPA
can also be activated by the hydrogen bonding with the oxygen of
SBA-15(CH2)3SnOC4H9, which increases the nucleophilicity of oxy-
gen. Therefore, the latter may easily attack carbonyl carbon of DMC to
form MmC(1).
140
Ph
600
C4
120
OH
SBA-15
100
80
60
40
20
0
500
400
300
200
100
0
-20
2
4
6
8
10 12 14 16 18 20
Ph
C4
OH
SBA-15
Pore size distribution(log)
Table 2
The effects of catalyst on the selective carboxylation of BPA with DMC.
Ent. Catalyst
Product distribution (mol.%)
YMmC(1) YDPC(1)
(mol.%)
(mol.%)
MmC(1) DmC(1) Methylation
1
2
3
4
5
TiO2/SBA-15 83.4
11.7
18.1
26.1
3.3
4.9
1.4
6.8
46.9
20.1
25.3
44.3
27.2
14.5
4.3
3.6
10.0
10.6
1.0
(C4H9)2SnO
80.5
67.1
49.8
79.2
C4
Ph
OH
0.0
0.2
0.4
0.6
0.8
1.0
0.7
0.04
Ralative pressure (P/P0)
Condition: BPA 11.4 g, DMC 18 g, catalyst 5 g, temperature 170–180 °C, 10 h, BPA/
DMC = 1:4 (mol). Ph = SBA-15(CH2)3SnOCH2Ph, C4 = SBA-15(CH2)3SnOC4H9,
OH=SBA-15(CH2)3SnO(OH).
Fig. 3. Nitrogen adsorption analysis for organotin modified SBA-15 material (Ph=SBA-
15(CH2)3SnOCH2Ph, C4=SBA-15(CH2)3SnOC4H9, OH=SBA-15(CH2)3SnO(OH)).

Z. Li et al. / Catalysis Communications 12 (2011) 932–935
935
O
O
O
O
H3C
H3C
CH3
CH3
C
H
C
CH3OH
CH3OH
O
DmC(1)
O
CH3
C
CH3
C
O
O
O
O
OH
O
OCOCH3
H
CH3
CH3
Scheme 2. The suggested mechanism for SBA-15(CH2)3SnOC4H9 having better DMC(1) yield and higher DMC(1) selectivity.
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concentration in the mesopore of SBA-15(CH2)3SnOC4H9, resulting in
higher DmC(1) selectivity. SBA-15(CH2)3SnO(OH) caused DMC
decomposition, while the low activity of SBA-15(CH2)3SnOCH2Ph
may be attributed to steric hindrance.
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Acknowledgments
The authors are grateful for the financial support of the National
and Tianjin Natural Science Foundation of China (Nos. 21006071 and
09JCYBJC03000) and the Natural Science Foundation of Tianjin
Education Committee (20070607).
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