Highly efficient and stable PbO-ZrO2 catalyst for the disproportionation of methyl phenyl carbonate to synthesize diphenyl carbonate

Article abstract of DOI:10.1016/j.molcata.2016.04.002

Heterogeneous PbO-ZrO₂ catalysts (PbZr) were first prepared by coprecipitation method, and used to catalyze the liquid-phase disproportionation reaction of methyl phenyl carbonate (MPC) to synthesize diphenyl carbonate (DPC). PbZr with PbO loading of 15.2 wt% (15.2PbZr) exhibited the best catalytic performance. Under the optimal conditions (200 °C, 2.5 h, and 1.2 g catalyst), the conversion of MPC reached 76.6% and the selectivity of DPC was 99.3%, respectively, which were significantly higher than those of heterogeneous catalysts reported before. The characterization results of XPS, H₂-TPR, XRD and BET analyses showed that 15.2PbZr gave the strongest interaction between Pb and Zr, the highest dispersion of PbO as well as the largest surface area and pore volume. Moreover, for 15.2PbZr, though reused for five recycles, the conversion of MPC still reached 75% and the selectivity of DPC was kept at 99.0%, implying that 15.2PbZr represented superior reusability. Besides, the structure of the 15.2PbZr after five times reaction was almost identical to that of the fresh, and Pb was almost not leached out of the catalyst, indicating that the stability of Pb species was improved, due to the existence of favorable interaction between Pb and Zr as well as part of the Pb entering into ZrO₂ structure. Thus, 15.2PbZr may serve as a promising catalyst for MPC disproportionation.

Full text of DOI:10.1016/j.molcata.2016.04.002

Accepted Manuscript
Title: Highly efficient and stable PbO–ZrO2 catalyst for the
disproportionation of methyl phenyl carbonate to synthesize
diphenyl carbonate
Author: Songlin Wang Changgong Li Zhongliang Xiao Tong
Chen Gongying Wang
PII:
S1381-1169(16)30124-8
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.04.002
MOLCAA 9846
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
26-1-2016
1-4-2016
2-4-2016
Please cite this article as: Songlin Wang, Changgong Li, Zhongliang Xiao, Tong
Chen, Gongying Wang, Highly efficient and stable PbOndashZrO2 catalyst for the
disproportionationofmethylphenylcarbonatetosynthesizediphenylcarbonate, Journal
of Molecular Catalysis A: Chemical http://dx.doi.org/10.1016/j.molcata.2016.04.002
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Highly efficient and stable PbO–ZrO2 catalyst for the
disproportionation of methyl phenyl carbonate to synthesize diphenyl
carbonate
Songlin Wang a, b, Changgong Li a, Zhongliang Xiao b, Tong Chen b, * and Gongying Wang b
a School of Chemistry and Chemical Engineering, Henan Institute of Science and Technology,
Xinxiang 453003, PR China;
b
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041,
PR China;
Corresponding author. Tel.: +86 028 85250005; fax: +86 028 85220713.
E–mail: chentongw@sina.com.cn (Tong Chen)
Graphical Abstract
Highlights
 Heterogeneous PbO–ZrO2 composite oxide is first prepared by coprecipitation
method.
 PbO–ZrO2 exhibits excellent catalytic activity and reusability for MPC
disproportionation.
 Pb2+ could insert into the ZrO2 structure.
1

 Strong interactions between Pb and Zr causing the high dispersion of Pb species
improve the catalytic performance.
Abstract: Heterogeneous PbO−ZrO2 catalysts (PbZr) were first prepared by coprecipitation
method, and used to catalyze the liquid–phase disproportionation reaction of methyl phenyl
carbonate (MPC) to synthesize diphenyl carbonate (DPC). PbZr with PbO loading of 15.2
wt% (15.2PbZr) exhibited the best catalytic performance. Under the optimal conditions (200
oC, 2.5 h, and 1.2 g catalyst), the conversion of MPC reached 76.6% and the selectivity of
DPC was 99.3%, respectively, which were significantly higher than those of heterogeneous
catalysts reported before. The characterization results of XPS, H2–TPR, XRD and BET
analyses showed that 15.2PbZr gave the strongest interaction between Pb and Zr, the highest
dispersion of PbO as well as the largest surface area and pore volume. Moreover, for
15.2PbZr, though reused for five recycles, the conversion of MPC still reached 75% and the
selectivity of DPC was kept at 99.0%, implying that 15.2PbZr represented superior
reusability. Besides, the structure of the 15.2PbZr after five times reaction was almost
identical to that of the fresh, and Pb was almost not leached out of the catalyst, indicating that
the stability of Pb species was improved, due to the existence of favorable interaction
between Pb and Zr as well as part of the Pb entering into ZrO2 structure. Thus, 15.2PbZr may
serve as a promising catalyst for MPC disproportionation.
Keywords: diphenyl carbonate; disproportionaton; methyl phenyl carbonate; PbO–ZrO2;
heterogeneous catalyst
1. Introduction
Diphenyl carbonate (DPC) is extensively employed to produce various organic compounds
and polymer materials, especially utilized as an important precursor for the synthesis of
polycarbonate to substitute phosgene [1–3]. The transesterification of dimethyl carbonate
(DMC) and phenol is the most prospective route to synthesize DPC without using phosgene
2

[4, 5]. This route is a two-step process [6, 7]. In the first step, intermediate methyl phenyl
carbonate (MPC) is formed by the transesterification of phenol and DMC (Scheme 1, Eq.
(1)), and in the second step, MPC is converted into DPC by the further transesterification of
MPC with phenol (Scheme 1, Eq. (2)) or the disproportionation of MPC (Scheme 1, Eq. (3)).
o
o
The equilibrium constants K2 (1.2×10–5, 25 C) and K3 (0.19, 25 C) showed that DPC was
mainly generated by the disproportionation of MPC rather than the further transesterification
of MPC. The first step is the rate–controlling step, since the equilibrium constant K1
o
(6.3×10–5, 25 C) is much smaller than K3 even at elevated temperatures [8, 9]. Thus,
strenuous efforts have been devoted to the first-step transesterification of phenol and DMC
[10–17], while the independent disproportionation of MPC is rarely reported [18–20]. To
maximize the yield of DPC, the research concentrated on the disproportionation to improve
the conversion of MPC is also very important.
Some homogeneous catalytic processes have been researched using Bu2SnO, BuSnO(OH),
Bu2Sn(OCOC11H23)2 and Bu3SnOSnBu3 in the disproportionation of MPC [18], but these
catalysts are complicated to be separated from the products and recovered for the reuse.
Therefore, several heterogeneous catalysts have been explored using various metal oxides
like PbO, CuO, TiO2, V2O5, MoO3 and SnO2, and PbO presents outstanding catalytic
performance with MPC conversion of 58.2% and DPC selectivity of 99.2% [20]. However,
the dissolution of PbO still leads to difficulty for the separation of the product and the catalyst,
as well as the loss of Pb and residual contamination [21]. Thus, it is quite demanded to
further develop highly efficient catalysts for catalyzing MPC disproportionation.
In recent years, ZrO2 as catalyst support with high thermal stability, chemical durability
and large surface area have attracted a great deal of attention. Several ZrO2−based composite
metal oxides such as MoO3−ZrO2 [22], Cr2O3−ZrO2 [23] and BiCl3−ZrO2 [24] have already
been reported, which are highly active and recyclable in many important liquid–phase
reactions including acetalization of 1, 3-propanediol, ethanol dehydration/dehydrogenation
and synthesis of pyrazolyl chalcones [22−24]. Therefore, in this paper, ZrO2 is selected as the
support to disperse the Pb species and stabilize the active Pb components in order to promote
the catalytic activity of PbO. Heterogeneous PbO−ZrO2 catalysts are firstly prepared by
3

coprecipitation method, and used to catalyze the disproportionation of MPC. To investigate
the relationship of structure and the catalytic property, catalysts are characterized by XRD,
XPS, H2–TPR, FT–IR and BET experiment. Additionally, the influence of the structural
property on the stability of the catalyst is also researched.
2. Experimental
2.1 Materials preparation
The PbO–ZrO2 catalysts were prepared by coprecipitation method [22, 25]. Zirconyl
chloride octahydrate (ZrOCl2·8H2O, ≥99%), lead nitrate (Pb(NO3)2, ≥99%) and ammonia
hydroxide (28–30%) were purchased from Sigma-Aldrich. A detailed process was as follows:
11.0 g ZrOCl2·8H2O and desirable amount of Pb(NO3)2 were added into 100 mL deionized
water, and then the mixture was heated to 90 °C to completely dissolve the solids. Afterwards,
ammonium hydroxide was added dropwise into the above solution with rigorous stirring until
the final solution pH was 9.3. The resulting solids were aged at 60 °C for 24 h, followed by
filtration and washed with distilled water. The obtained samples were then dried at 110 °C
overnight and calcined at 600 °C in air for 5 h. The mixed oxides are denoted as xPbZr,
where x is the loading amount of PbO (wt %) (calculated by the atom molar ratio of Pb to Zr).
For comparison, pure ZrO2 and PbO were prepared by the same method.
Supported PbO/ZrO2 catalysts were prepared with mechanical milling method and
impregnation method, respectively. For the mechanical milling method, ZrO2 and Pb(NO3)2
were mixed and ground uniformly, and then the mixture was calcined at 600 oC for 5 h. As to
the impregnation method, ZrO2 was impregnated by appropriate amount of Pb(NO3)2 solution
at ambient temperature for 24 h. The sample was dried at 110 °C overnight, and then calcined
o
at 600 C for 5 h. Other supported PbO catalysts using different supports, including SiO2,
TiO2, MgO and Al2O3, were also prepared by the impregnation method described above.
2.2 Materials characterization
Powder X–ray diffraction (XRD) measurement was performed using a X’pert PRO MPD
diffractometer (Philip) with Cu Kα (λ=1.54056 Å) radiation at 40 kV and 45 mA in the 2
theta range from 5 to 90°. The diffraction line positions were determined with a scanning rate
4

of 1.2°/min.
Temperature–programmed reduction (H2–TPR) was carried out using automatic
multi–purpose adsorption instrument (Micro TP–5080, Tianjin Xianquan Industry and Trade
Development Co., Ltd.). Samples (50 mg) were pretreated with flowing N2 (99.999%, 20
mL/min) at 400 °C for 1 h. Before testing, the baseline was stabilized at 30 °C in the flowing
gas. A 10% (volume fraction) H2 in N2 mixture was used as the reducing gas. The reactor was
heated in a temperature-programmed range from 30 to 800 °C (10 °C/min). The H2
consumption as a function of the reduction temperature was continuously detected by TCD.
X–ray photoelectron spectroscopy (XPS) was detected on a Kratos Model XSAM 800
apparatus with an Al Kα=1486.6 eV exciting X–rays source (15 kV, 12 mA). The lines were
recorded with a narrow sweep width in the range of 5–7 eV and an energy pass of 50 eV. The
binding energies were calibrated by reference of the C1s peak (284.6 eV) as internal standard
to reduce the charge effect of samples.
The textural properties of samples were measured by N2 adsorption/desorption at –196 °C
using automatic NOVA Win2200E adsorption analyzer (Quantanchrome, USA). Before
measurement, samples were treated under high vacuum at 300 °C for 3 h. The total specific
surface area was calculated by multi-point Brunauer–Emmett–Teller (BET) method, and the
porous distribution was determined by Barrett–Joyner–Hallenda (BJH) method.
IR spectra were recorded using Nicolet 560 Fourier transform infrared (FT–IR) spectra at
room temperature (25 °C) with KBr pellets in the range of 4000–400 cm–1 and the resolution
was 4 cm-1.
The element contents were determined by inductively coupled plasma–atomic emission
spectrometry (ICP–AES) using an IRIS 1000 instrument (Thermo Electron, USA).
2.3 Catalytic performance tests
MPC was synthesized and purified in the laboratory, and its purity was 99.8% determined
by high performance liquid chromatography.
The disproportionation of MPC was performed in a round-bottomed flask (100 mL) with a
5

fractionating column connected to a liquid dividing head. In a typical procedure, MPC (150
mmol) and a certain amount of catalyst were added into the reactor under nitrogen
atmosphere. The mixture was gradually heated to desired temperature under rigorous stirring,
and then the temperature was kept at desired temperature. During the reaction, DMC was
continuously distilled out to shift the equilibrium towards DPC.
The reaction mixture was quantified by GC–MS on a HP–6890/5973 system. The products
were quantitatively analyzed by GC system (Agilent Technologies 7820A) with a flame
ionization detector (FID) and a DB–35 capillary column (30 m × 320 μm × 0.25 μm). The
conversion of MPC and selectivity of DPC were calculated by GC results using a correction
factor normalization method.
3. Results and discussion
3.1 Materials Characterization
3.1.1 XRD analysis
Generally, ZrO2 mainly exists in the monoclinic, tetragonal and cubic phases, and the
tetragonal phase is of importance for catalytic applications due to the high mechanical
strength and interesting physicochemical properties [26−28]. The XRD patterns of the
samples prepared by coprecipitation method are shown in Fig. 1(a), and pure ZrO2 exhibits
the only monoclinic (2θ=24.8o, 28.2o, 31.5o, 34.1o and 50.4o, JCPDS No. 37−1484)
crystalline phases. PbZr with PbO loading of 1.9−15.2% exhibits the coexistence of
monoclinic and tetragonal (2θ=30.2o, 35.1o, 50.2o and 60.2o, JCPDS No. 27−997) ZrO2
phases, but the monoclinic structure decreases and the tetragonal structure increases with the
increasing of PbO loading. When PbO loading increases to 22.8%, the monoclinic structure
almost disappears. The results suggest that Pb promotes the crystalline transformation of
zirconia from monoclinic to tetragonal phases. Additionally, as the PbO content increases,
the peak positions gradually shift to lower angle (for a clear observation, for example, the
peak positions of 2θ=28.2, 30.2 and 31.5o are magnified in Fig. 1(b).), and when the PbO
content increases to 30.4%, the peak positions do not shift. This is mainly attributed to the
incorporation of Pb ions into the ZrO2 crystal lattice because Pb2+ (1.2 nm) is larger than
6

Zr4+ (0.8 nm). Significantly, for PbZr samples, no diffraction peaks ascribed to PbO phases
can be observed even when the PbO loading is up to 30.4%, indicating that PbO is highly
dispersed. However, weak crystalline PbO phase appears when the content is 47.5%.
3.1.2 H2–TPR analysis
H2–TPR profiles of PbZr samples are shown in Fig. 2. The reduction temperature of ZrO2
appears around 625 oC, and the reduction temperature of PbO appears at 615 oC. Interestingly,
the reduction temperature of PbZr is lower than those of PbO and ZrO2. Meanwhile, as PbO
loading increasing from 1.9% to 22.8%, the reduction temperature shifts to low temperature,
related to the strengthened interaction between Pb and Zr [29, 30]. It is noteworthy that the
reduction temperatures of PbO loading with 22.8% and 30.4% are basically identical. The
reason is probably that the formation of Pb−Zr solid solution leading to the unchanged
interaction between Pb and Zr [31−33], which is agreed with the XRD result of the
appreciable shifts to low angle of 2θ=30.2o for 22.8PbZr and 30.4PbZr (seen in Fig. 1(b)).
However, further increasing the PbO loading to 47.5%, the reduction temperature inversely
shifts to high value, trending to that of bulk PbO, which can be attributed to the formation of
crystalline PbO. This is also in agreement with the result of XRD analysis. Thus, 15.2% PbO
is the appropriate loading before the Pb−Zr solid solution is formed.
3.1.3 XPS analysis
XPS spectra of PbZr samples are shown in Fig. 3. The binding energy of Zr 3d5/2 in ZrO2 is
179 eV. As shown in Fig. 3(a), the introduction of Pb increases the binding energy of Zr 3d5/2
to 181.2 eV, and with the increase of PbO loading from 3.8% to 22.8%, the binding energy of
Zr 3d5/2 further shifts to high value from 181.2 eV to 181.8 eV. The binding energy of Pb 4f7/2
in PbO is 137 eV. As shown in Fig. 3(b), the introduction of Pb also increases the binding
energy of Pb 4f7/2, but the variation is less than that of Zr 3d5/2. The binding energies of O 1s
in ZrO2 and PbO are 530.2 eV and 531.3 eV. As shown in Fig. 3(c), the introduction of Pb
decreases the binding energy of O 1s. For a clear observation, the deconvolution of O 1s is
divided into two Gaussian component peaks of 531.3 eV and 529.8 eV, which are assigned to
the surface absorbed oxygen and lattice oxygen, respectively [34, 35]. The binding energy for
7

lattice oxygen shifts to lower value.
These phenomena are ascribed to the variation of the electron density around the central
atom by the formation of Pb−O−Zr bond [36, 37]. Owing to much higher electronegativity of
O (3.44) than those of Zr (1.33) and Pb (1.54), partial electrons could transfer from Zr and Pb
to O through the Pb−O−Zr bond, resulting in a rich electron state of O and a deficient
electron state of Zr and Pb species. Therefore, the binding energies of Zr 3d5/2 and Pb 4f7/2
rise and the O 1s binding energies reduce. Besides, the electronegativity of Zr and Pb
indicates that Zr is easier to lose electron than Pb, thus causing the bigger variation of Zr 3d5/2
binding energy compared to that of Pb 4f7/2. These changes of binding energies further testify
that the interaction between Zr and Pb is formed by Pb−O−Zr and strengthened with the
increasing PbO content. When PbO loading increases to 30.4%, the binding energy slightly
changes, suggesting that the interaction between Pb and Zr is close for 22.8PbZr and
30.4PbZr, verifying that the analysis is in good accordance with XRD and H2–TPR results.
As PbO loading further increasing to 47.5%, the binding energies of Zr 3d5/2 and Pb 4f7/2
decrease, since the surface is covered by crystalline PbO which reduces the interaction of Zr
and Pb [29, 30]. Apparently, for PbZr samples, the binding energies of 15.2PbZr have the
most remarkable shifts, illustrating the strongest interaction between Zr and Pb.
Table 1 displays that the surface atomic ratio of Pb/Zr is far higher than the bulk atomic
ratio from the theoretical calculation. This means that more active Pb species migrate from
the bulk to the surface, which may be ascribed to the surface segregation of PbO due to the
lower melting point of PbO than ZrO2 (melting point 880 °C versus 2700 °C). The PbO
enrichment on the surface would be favorable to improving the catalytic performances of the
PbZr.
3.1.4 BET analysis
N2 adsorption–desorption isotherm and pore diameter distribution of PbZr samples are
shown in Fig. 4. Fig. 4(a) shows all the isotherms of PbZr (except 47.5PbZr) are typical
mesoporous materials. Fig. 4(b) shows the isotherm of 47.5PbZr with little adsorption
8

capacity is similar to that of PbO, due to the formation of crystalline PbO covering the
surface of ZrO2. Fig. 4(c) shows that the pore size distribution of ZrO2 is broad, giving an
average pore diameter of 8.3 nm. However, the pore size distributions of PbZr exhibit
relatively homogeneity with the average pore diameter of less than 8.3 nm, indicating that the
channel change shifts the pore to the small distribution. Nevertheless, the shift is much larger
when the PbO loading is greater than 15.2%, because partial channel is blocked by excessive
PbO [38]. Clearly, 15.2PbZr displays the highest pore homogeneity, suggesting that 15.2PbZr
possesses the largest channel change which benefits to increase the surface area and pore
volume.
Table 1 lists the textural parameters of these PbZr samples. The introduction of Pb could
change the channel, create the new pores, decrease the pore size and enlarge the surface area
and pore volume [38]. As PbO loading exceeds 15.2%, the pore could not continue to be
created, and further increasing PbO loading blocks up the original pores. Therefore, the
surface area and pore volume drop. The results indicate that the PbO loading significantly
affects the textural properties of PbZr. Among them, 15.2PbZr owns the largest surface area
and pore volume. Additionally, it may be inferred that the formation of Pb−Zr solid solution
is not beneficial to the dispersion of PbO, because of the decrease in the surface area and pore
volume.
3.2 Results of catalytic performance test
3.2.1 Effect of catalyst support
In previous work, different metal oxide catalysts have been explored for MPC
disproportionation, and PbO presents high catalytic activity with MPC conversion of 58.2%
[20]. Nevertheless, the dissolution of PbO in the reaction is fairly unsatisfactory for its
application. As a preliminary exploration of heterogeneous catalysts, supported PbO catalysts
with PbO loading of 15.2% on different supports are prepared by impregnation method, and
the catalytic activity for MPC disproportionation is listed in Table 2. Among them, MgO and
ZrO2 are suitable supports for the disproportionation of MPC, and more than 60% MPC
conversion is attained over PbO/MgO or PbO/ZrO2. However, more byproduct anisole is
9

formed over PbO/MgO, due to the higher basic sites of MgO resulting in the decarboxylation
of MPC [39–41]. Accordingly, ZrO2 is selected to use as the support for MPC
disproportionation, since DPC selectivity is up to 98.7% over PbO/ZrO2.
3.2.2 Effect of preparation method
The effect of preparation methods on the catalytic activity of PbO/ZrO2 is also listed in
Table 2. As seen in Table 2, the PbZr prepared by coprecipitation method displays the
outstanding disproportionate performance with MPC conversion of 76.6% along with DPC
selectivity of 99.3%. Therefore, the coprecipitation method is appropriate to prepare PbZr for
MPC disproportionation.
3.2.3 Effect of PbO loading
Effect of PbO loading on catalytic performance of PbZr is carefully studied. As can be seen
in Table 3, ZrO2 has almost no catalytic activity. For supported PbO catalysts, the conversion
of MPC distinctly increases with PbO loading increase and reaches the maximum of 76.6% at
15.2% loading. However, further increasing PbO loading, MPC conversion maintains at
63−66%, which is close to the conversion value by the catalysts prepared with impregnation
method and mechanical milling method. As revealed in the characterization results of XRD,
H2–TPR and XPS, when PbO loading is 22.8−30.4%, the Pb−Zr solid solution is formed, and
further increasing PbO loading to 47.5%, the dispersion of PbO decreases. As a result, the
efficient active sites of PbO do not increase despite the loading is above 15.2%. Therefore,
the interaction of Pb and Zr and the surface area are important factors for that 15.2PbZr
exhibits higher catalytic activity than others. From the results of XRD, H2–TPR, XPS and
BET measurements, 15.2PbZr provides the strongest interaction between Zr and Pb and the
maximum surface area, which enables to highly disperse the PbO and afford more efficient
exposure of active sites [42–44]. Additionally, this result also suggests that the coprecipitation
method dispersing PbO is better than impregnation and mechanical milling method so that
the catalyst prepared by coprecipitation method exhibits higher catalytic activity than the
other two methods.
10

3.2.4 Effect of calcination temperature
Effect of calcination temperature on the catalytic behavior of 15.2PbZr is shown in Fig. 5.
o
Below 600 C, the catalytic activity increases with increasing of calcination temperature.
When the calcination temperature is 600 oC, the conversion of MPC reaches the maximum of
73.3%, and the selectivity of DPC is 99.7%. As calcination temperature further increases, the
conversion conversely decreases. From XRD results (Fig. S1, see Supplementary Material),
o
at higher than 700 C, the PbO crystalline phases appear [45], implying that PbO is poorly
dispersed. Simultaneously, the obvious monoclinic zirconia phases are also observed. Thus,
the optimum calcination temperature is 600 °C.
In order to systematically understand the catalytic reaction, the effect of catalyst amount,
reaction temperature as well as the reaction time on the catalytic performance of 15.2PbZr is
also optimized (Fig. S2, S3 and S4, see Supplementary Material). With a catalyst amount of
o
1.2 g, a reaction temperature of 200 C and a reaction time of 2.5 h, MPC conversion of
76.6% and DPC selectivity of 99.3% are obtained, respectively. Previous studies have
reported that MoO3/SiO2 catalyst exhibits MPC conversion of 72.8% and DPC selectivity of
98.1% under optimum conditions, and it was easily deactivated by the adsorption of
carbonate species on the catalyst surface [19]. For comparison, 15.2PbZr reveals superior
catalytic activity comparing with PbO and MoO3/SiO2, and has the potential application in
industry.
3.3 Reusability of 15.2PbZr
The heterogeneity of 15.2PbZr is investigated by a hot leaching test [46, 47], and the
results are given in Fig. 6. The catalyst is removed by filtration after the reaction proceeds for
1 h, and then the reaction is continued by using the filtrate under the same condition. It is
found that the yield of DPC increases as the prolonged time and reaches the highest at 3 h,
while it keeps almost unchanged in the filtrate without catalyst even prolonging the reaction
time to 4 h. The leaching test suggests that 15.2PbZr is an efficient and stable heterogeneous
catalyst.
11

.
The reusability of 15.2PbZr is tested by five consecutive runs and the result is illustrated in
Fig. 7. After each reaction, the catalyst is facilely recovered by filtration. As shown in Fig. 8,
the catalyst is reused for five recycles without substantial decrease of activity. Elemental
analysis of the filtrate presents that little Pb is leached out of the catalyst after each run (Table
S1, see Supplementary Material). Besides, as shown in Fig. 8, XRD pattern and FT–IR
spectrum show that the crystal phase structures and group compositions of the used 15.2PbZr
after five times are identical to those of the fresh 15.2PbZr. Therefore, 15.2PbZr may serve as
a highly stable catalyst for MPC disproportionation. Its good stability is mainly attributed to
the existence of favorable interaction between Pb and Zr.
4. Conclusions
PbZr catalysts with different methods are prepared, and used to catalyze the
disproportionation reaction of MPC. 15.2PbZr (PbO loading of 15.2 wt% on ZrO2) prepared
by coprecipitation method exhibits the best catalytic performance, due to the high dispersion
of PbO, the strong interaction between Pb and Zr as well as the large surface area and pore
volume. The introduction of Pb promotes the structural transformation of zirconia from
monoclinic to tetragonal phases, and part of Pb entering into ZrO2 structure is in favor of
improving the stability of Pb species. The formation of Pb−Zr solid solution at PbO loading
of 22.8−30.4% decreases the PbO dispersion, which are not beneficial to improve the
catalytic activity. Under the optimized conditions (PbO loading of 15.2 wt%, calcination
o
temperature of 600 C, catalyst amount of 1.2 g, reaction temperature of 200 oC and reaction
time of 2.5 h), MPC conversion of 76.6% and DPC selectivity of 99.3% over 15.2PbZr are
attained. Besides, 15.2PbZr after simple separation by filtration could be reused for five
recycles without remarkable loss of activity. Also its structural features are maintained well
after recycling use. The construction of strong interaction between Pb and Zr (promoting the
high dispersion of PbO on ZrO2) plays an important role for fabricating the highly active and
stable catalyst. The excellent catalytic performance, easy separation and superior stability
12

indicate that PbZr catalysts deserve more attention and have the potential application in
industry.
Acknowledgements
We acknowledge gratefully the National High Technology Research and Development
Program of China (863 program, No. 2013AA031703), the Science and Technology Support
Program of Sichuan Province (No. 2013GZX0135), the Science and Technology Innovation
Program for Youth Team of Sichuan Province (No. 2013TD0010) and the National Natural
Science Foundation of China (No. 21072046) for financial support of this research.
References
[1] J. Andraos, Pure Appl. Chem. 84 (2012) 827.
[2] S.L. Wang, R.Z. Tang, Y.Z. Zhang, T. Chen, G.Y. Wang, Chem. Eng. Sci. 138 (2015) 93.
[3] R. Kanega, Top. Catal. 57 (2014) 995.
[4] S.J. Park, I.C. Hwang, S.H. Shin, J. Chem. Eng. Data 59 (2014) 323.
[5] S. Fukuoka, M. Kawamura, K. Komiya, M. Tojo, H. Hachiya, K. Hasegawa, M. Aminaka,
H. Okamoto, I. Fukawa, S. Konno, Green Chem. 5 (2003) 497.
[6] J.L. Gong, X.B. Ma, S.P. Wang, Appl. Catal. A: Gen. 316 (2007) 1.
[7] W.B. Kim, U.A. Joshi, J.S. Lee, Ind. Eng. Chem. Res. 43 (2004) 1897.
[8] J. Haubrock, M. Raspe, G.F. Versteeg, H.A. Kooijman, R. Taylor, J.A. Hogendoorn, Ind.
Eng. Chem. Res. 47 (2008) 9854.
[9] J. Haubrock, W. Wermink, G.F. Versteeg, H.A. Kooijman, R. Taylor, M.V. Annaland, J.A.
Hogendoorn, Ind. Eng. Chem. Res. 47 (2008) 9862.
[10]A. Dibenedetto, A. Angelini, L. di Bitonto, E. De Giglio, S. Cometa, M. Aresta,
ChemSusChem 7 (2014) 1155.
[11]K.M. Deshmukh, Z.S. Qureshi, K.P. Dhake, B.M. Bhanage, Catal. Commun. 12 (2010)
207.
[12]Y.T. Kim, E.D. Park, Appl. Catal. A: Gen. 361 (2009) 26.
13

[13]T. Kotbagi, D.L. Nguyen, C. Lancelot, C. Lamonier, K.A. Thavornprasert, W.L. Zhu, M.
Capron, L.J. Duhamel, S. Umbarkar, M. Dongare, F. Dumeignil, ChemSusChem 5 (2012)
1467.
[14]S. Han, M. Luo, X.L. Zhou, Z. He, L.P. Xiong, Ind. Eng. Chem. Res. 51 (2012) 5433.
[15]K. Cheng, S.J. Wang, D.S.H. Wong, Comput. Chem. Eng. 52 (2013) 262.
[16]S. Wang, R.X. Bai, F.M. Mei, G.X. Li, Catal. Commun. 11 (2009) 201.
[17]S.J. Luo, Y.N. Chi, L.N. Sun, Q. Wang, C.W. Hu, Catal. Commun. 9 (2008) 2560.
[18]S.L. Wang, Y.Z. Zhang, Y. Chen, R.Z. Tang, T. Chen, G.Y. Wang, Chem. J. Chinese U. 35
(2014) 2177.
[19]S.L. Wang, Y.Z. Zhang, T. Chen, G.Y. Wang, J. Mol. Catal. A: Chem. 398 (2015) 248.
[20]Z. Luo, Y. Wang, Y. Zhang, D. Wei, J. Jiang, G.Y. Wang, Fine Chemicals (Chinese) 25
(2008) 813.
[21]S.L. Wang, F. Ma, J.G. Li, G. Zhai, T. Chen, G.Y. Wang, Petrochemical Technology
(Chinese) 42 (2013) 928.
[22]M. Wu, C.L. Li, J. Zhang, C.C. Miao, Y.P. Zheng, Y.M. Sun, Ind. Eng. Chem. Res. 51
(2012) 6304.
[23]H.R. Mahmoud, J. Mol. Catal. A: Chem. 392 (2014) 216.
[24]S. Tarannum, Z.N. Siddiqui, J. Mol. Catal. A: Chem. 394 (2014) 262.
[25]H. Song, N. Wang, H.L. Song, F. Li, Catal. Commun. 59 (2015) 61.
[26]K.G. Li, J. Wang, Y.C. Zou, X.J. Song, H.C. Gao, W.C. Zhu, W.X. Zhang, J.H. Yu, M.J.
Jia, Appl. Catal. A: Gen. 482 (2014) 84.
[27]S.R. Ginjupalli, S. Mugawar, N.P. Rajan, P.K. Balla, V.R.C. Komandur, Appl. Surf. Sci.
309 (2014) 153.
[28]Z.H. Li, K.M. Su, J. Mol. Catal. A: Chem. 277 (2007) 180.
[29]W.Q. Zhou, X.Q. Zhao, Y.J. Wang, J.Y. Zhang, Appl. Catal. A: Gen. 260 (2004) 19.
[30]B. de Rivas, R. Lopez-Fonseca, C. Sampedro, J.I. Gutierrez-Ortiz, Appl. Catal. B:
Environ. 90 (2009) 545.
[31]X.Y. Pang, H.C. Zeng, J.C. Wu, K. Li, Appl. Catal. B: Environ. 9 (1996) 149.
[32]C.M. Lu, Y.M. Lin, I. Wang, Appl. Catal. A: Gen. 198 (2000) 223.
[33]A.M. Ruppert, T. Paryjczak, Appl. Catal. A: Gen. 320 (2007) 80.
14

[34]H. Peng, J. Cui, H.J. Zhan, X. Zhang, Chem. Eng. J. 264 (2015) 316.
[35]P. Yang, Z.H. Meng, S.S. Yang, Z.N. Shi, R.X. Zhou, J. Mol. Catal. A: Chem. 393 (2014)
75.
[36]H.T. Wu, Y. Yang, H.Y. Suo, M. Qing, L. Yan, B.S. Wu, J. Xu, H.W. Xiang, Y.W. Li, J.
Mol. Catal. A: Chem. 396 (2015) 108.
[37]H.B. Zhu, D.H. Anjum, Q.X. Wang, E. Abou-Hamad, L. Emsley, H. Dong, P. Laveille,
L.D. Li, A.K. Samal, J.M. Basset, J. Catal. 320 (2014) 52.
[38]A. Calafat, L. Avilan, J. Aldana, Appl. Catal. A: Gen. 201 (2000) 215.
[39]W.B. Kim, Y.G. Kim, J.S. Lee, Appl. Catal. A: Gen. 194/195 (2000) 403.
[40]M. Cao, Y.Z. Meng, Y.X. Lu, Catal. Commun. 6 (2005) 802.
[41]J. ten Dam, K. Djanashvili, F. Kapteijn, U. Hanefeld, ChemCatChem 5 (2013) 497.
[42]M. Kuzminska, T.V. Kovalchuk, R. Backov, E.M, Gaigneaux, J. Catal. 320 (2014) 1.
[43]F. Jiang, L. Zeng, S.R. Li, G. Liu, S.P. Wang, J.L. Gong, ACS Catal. 5 (2015) 438.
[44]P Yang, S.S. Yang, Z.N. Shi, F. Tao, X.L. Guo, R.X. Zhou, Chem. Eng. J. 285 (2016)
544.
[45]A.R. Rautioa, P. Maki-Arvelab, A. Ahob, K. Eranenb, K. Kordas, Catal. Today 241 (2015)
170.
[46]F. Adam, J. Andas, I. Ab Rahman, Chem. Eng. J. 165 (2010) 658.
[47]F. Adam, J.T. Wong, E.P. Ng, Chem. Eng. J. 214 (2013) 63.
15

Fig. 1. XRD patterns (a) and enlarged peaks at 2θ=28.2, 30.2 and 31.5o (b) of the samples.
Fig. 2. H2–TPR profiles of the samples.
16

17

Fig. 3. Binding energies of Zr 3d5/2 (a), Pb 4f7/2 (b) and O 1s (c) of the samples.
18

Fig. 4. N2 adsorption–desorption isotherms (a), (b) and pore diameter distributions (c) of the samples.
19

Fig. 5. Effect of calcination temperature. Reaction conditions: 200 ºC, 3 h, 1.0 g catalyst.
Fig. 6. Leaching test of 15.2PbZr in the disproportionation of MPC (■ with 15.2PbZr, ● filtrate
without 15.2PbZr). Reaction conditions: 200 ºC, 1.0 g catalyst
20

Fig. 7. Reusability of 15.2PbZr. Reaction conditions: 200 ºC, 2.5 h, 1.2 g catalyst.
Fig. 8. XRD pattern (a) and FT–IR spectra (b) of fresh and used 15.2PbZr.
21

Scheme 1. Transesterification of phenol with DMC to synthesize DPC.
22

Table 1 The textural properties of the samples.
BET surface Pore volume Mean pore
Catalyst
Pb/Zra Pb/Zrb
area (m2·g–1) (cm3·g–1)
diameter (nm)
ZrO2
40
50
0.080
0.100
0.127
0.061
0.058
−
8.3
7.8
7.0
6.0
4.6
−
3.8PbZr
0.022 0.056
0.099 0.209
0.158 0.270
0.241 0.327
0.500 0.611
15.2PbZr 70
22.8PbZr 37
30.4PbZr 35
47.5PbZr
PbO
1
0.6
−
−
a Pb/Zr atomic ratio estimated by theoretical calculation.
b Pb/Zr atom ratio estimated from XPS.
Table 2 Catalytic performances of the catalysts for MPC disproportionation
Yield (%)
MPC
DPC
Catalyst
conversion (%)
selectivity (%)
DPC Anisole
32.9 1.3
43.1 4.2
55.1 1.5
62.1 5.4
62.3 0.8
64.6 0.7
76.1 0.5
PbO/TiO2
34.2
96.2
91.1
97.3
92
PbO/Al2O3 47.3
PbO/SiO2 56.6
PbO/MgO 67.5
a
PbO/ZrO2
PbO/ZrO2
PbZr c
63.1
65.3
76.6
98.7
98.9
99.3
b
Reaction conditions: 200 ºC, 2.5 h, 1.2 g catalyst with PbO loading of 15.2%.
Anisole was detected as the only byproduct.
a Impregnation method.
b Mechanical milling method.
c Coprecipitation method.
23

Table 3 Effect of PbO loading on ZrO2 for MPC disproportionation
Yields (%)
DPC
3.5
MPC
conversion (%)
3.7
DPC
Catalyst
selectivity (%)
94.6
Anisole
0.2
ZrO2
1.9PbZr
3.8PbZr
7.6PbZr
15.2PbZr
22.8PbZr
30.4PbZr
47.5PbZr
21.3
20.8
29.7
54
0.5
97.7
30.1
0.4
98.7
54.7
0.7
98.7
76.6
76.1
65.5
63.7
61.9
0.5
99.3
66.3
0.8
98.8
64.5
0.8
98.8
63.2
1.3
97.9
Reaction conditions: 200 ºC, 2.5 h, 1.2 g catalyst.
24