The hydroxyalkylation of phenol with formaldehyde over mesoporous M(Al, Zr, Al-Zr)-SBA-15 catalysts: The effect on the isomer distribution of bisphenol F

Article abstract of DOI:10.1016/j.catcom.2015.03.019

Mesoporous M(Al, Zr, Al-Zr)-SBA-15 catalysts prepared by a direct method were used for the hydroxyalkylation of phenol with formaldehyde to bisphenol F in the presence of water. The results showed that M(20)-SBA-15 with the Si/M molar ratio of 20 exhibited higher catalytic activity. The isomer distribution of bisphenol F could be regulated in the hydroxyalkylation of phenol with formaldehyde by changing the Al/Zr ratio in M(20)-SBA-15 catalysts. Al(20)-SBA-15 was in favor of the formation of 4,4′-isomer, whereas Zr(20)-SBA-15 was in favor of the formation of 2,4′- and 2,2′-isomers.

Full text of DOI:10.1016/j.catcom.2015.03.019

Catalysis Communications 67 (2015) 21–25
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Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
The hydroxyalkylation of phenol with formaldehyde over mesoporous
M(Al, Zr, Al–Zr)-SBA-15 catalysts: The effect on the isomer distribution
of bisphenol F
⁎
⁎
Ying Tan, Yongfei Li , Yuanfeng Wei, Zhimin Wu, Jiaqi Yan, Langsheng Pan, Yuejin Liu
School of Chemical Engineering, Xiangtan University, Xiangtan 411105, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Mesoporous M(Al, Zr, Al–Zr)-SBA-15 catalysts prepared by a direct method were used for the hydroxyalkylation
of phenol with formaldehyde to bisphenol F in the presence of water. The results showed that M(20)-SBA-15
with the Si/M molar ratio of 20 exhibited higher catalytic activity. The isomer distribution of bisphenol F could
be regulated in the hydroxyalkylation of phenol with formaldehyde by changing the Al/Zr ratio in M(20)-SBA-
15 catalysts. Al(20)-SBA-15 was in favor of the formation of 4,4′-isomer, whereas Zr(20)-SBA-15 was in favor
of the formation of 2,4′- and 2,2′-isomers.
Received 24 January 2015
Received in revised form 16 March 2015
Accepted 18 March 2015
Available online 28 March 2015
Keywords:
M-SBA-15
© 2015 Elsevier B.V. All rights reserved.
Hydroxyalkylation
Bisphenol F
Isomer distribution
Regulation
1. Introduction
method to regulate the isomer distribution of bisphenol F in the
hydroxyalkylation of phenol with formaldehyde.
The hydroxyalkylation of phenol with formaldehyde to bisphenol F
(a mixture of 4,4′-, 2,4′- and 2,2′-isomers) is commercially important
[1], which usually occurs in the presence of acid. Both homogeneous liq-
uid acid such as hydrochloric acid, phosphoric acid, oxalic acid [2–4],
and heterogeneous solid acid such as mesoporous aluminosilicate
MCM-41 [5,6], zeolites [7], and dodecatungstophosphoric acid impreg-
nated on SiO2 [8] were used for this reaction. The results showed that
the hydroxyalkylation of phenol with formaldehyde to bisphenol F
could be efficiently catalyzed in a moderate acidic environment. How-
ever, the isomer distribution of bisphenol F was always similar in the
hydroxyalkylation of phenol with formaldehyde over the above-
mentioned homogeneous and heterogeneous acid catalysts. Therefore,
it is difficult to make different isomer distributions of bisphenol F
to meet the need for industrial applications [9,10].
To the best of our knowledge, there are few reports related to the
regulation of the isomer distribution of bisphenol F. Therefore, in this
paper, mesoporous M(Al, Zr, Al–Zr)-SBA-15 catalysts prepared by a
direct method were used for the hydroxyalkylation of phenol with
formaldehyde to bisphenol F. The results demonstrated that M(20)-
SBA-15 with the Si/M molar ratio of 20 exhibited higher catalytic activ-
ity, and the isomer distribution of bisphenol F could be regulated by
changing the Al/Zr ratio in M(20)-SBA-15 catalysts.
2. Experimental
2.1. Preparation of M-SBA-15
It is known that in the hydroxyalkylation of phenol with acetone to
bisphenol A, a high selectivity of 4,4′-bisphenol A was obtained because
of the steric hindrance [11]. However, in the hydroxyalkylation of
phenol with formaldehyde to bisphenol F, the situation is different.
Compared with acetone, the formaldehyde molecule is more active
and smaller. It is easy to make formaldehyde molecules simultaneously
attack the para- and ortho-positions of phenol to form 4,4′-, 2,4′- and
2,2′-bisphenol F. Therefore, it is a challenge to find an effective catalytic
SBA-15 and M-SBA-15 were synthesized according to the proce-
dures reported previously [12,13]. Typically, 4 g of Pluronic P123 and
130 ml of HCl aqueous solution (pH = 1.5) were stirred at 40 °C until
dissolved completely, and then 9 g TEOS together with a required
amount of Al(NO)3·9H2O and ZrO(NO3)2·xH2O was added into the
mixture to obtain different Si/M molar ratios of gel, followed by mag-
netic stirring for 24 h at 40 °C. Then the mixture was introduced into a
250 ml Teflon lined stainless steel autoclave and crystallized for 24 h at
100 °C. After the mixture was cooled down to room temperature, the
precipitate was filtered, washed with deionized water, dried overnight
at 60 °C and calcined at 550 °C for 8 h. Finally, M(X)-SBA-15 catalysts
⁎
Corresponding authors.
E-mail addresses: liyongfei98@163.com (Y. Li), xdlyj@163.com (Y. Liu).
http://dx.doi.org/10.1016/j.catcom.2015.03.019
1566-7367/© 2015 Elsevier B.V. All rights reserved.

22
Y. Tan et al. / Catalysis Communications 67 (2015) 21–25
with different Si/M ratios were prepared, where M stands for Al, Zr or
3.2. Characterization of M(20)-SBA-15 with different Al/Zr ratios
Al–Zr, and X stands for the Si/M ratio.
The small-angle X-ray diffraction patterns of pure siliceous SBA-15
and M(20)-SBA-15 with different Al/Zr ratios are shown in Fig. 2. All
the samples including pure siliceous SBA-15 present three diffraction
peaks that can be indexed as (100), (110) and (200) reflections of 2-D
hexagonal lattice symmetry [16], indicating that well ordered
mesostructures were obtained. Compared with SBA-15, the three dif-
fraction peaks of M(20)-SBA-15 samples are slightly shifted to the left.
This was because the ionic radii of Al3+ and Zr4+ are larger than that
of Si4+, so the lattice of M(20)-SBA-15 slightly changed after the incor-
poration of metal ions into SBA-15 mesopore frameworks [17]. Their
textural properties are listed in Table. 1. Compared with SBA-15, the
pore volume of M(20)-SBA-15 slightly increases with the incorporation
of metal ions into SBA-15, which might be associated with the expan-
sion of the aluminosilicate framework caused by the incorporation of
Al in SBA-15 [17]. However, the changing trend of both BET surface
area and pore size is not regular. This is because SBA-15 has an amor-
phous structure [15].
2.2. Characterization of M-SBA-15
The powder XRD patterns were recorded with a Japan Rigaku D/Max
2550 VB+ 18 kW X-ray diffractometer with Cu-Ka (λ = 1.5418 Å). The
specific surface area, pore diameter and pore volume were determined
by N2 adsorption at 77 K using a Nove-2200e automated gas sorption
system. The pyridine FT-IR adsorption spectra were collected on a Nico-
let 380 spectrometer.
2.3. Hydroxyalkylation of phenol with formaldehyde
The hydroxyalkylation of phenol with formaldehyde to bisphenol F
was carried out in a 100 ml magnetically stirred glass reactor equipped
with a reflux condenser. Typically, 9.4 g of phenol, 0.2703 g of 37% aque-
ous formaldehyde and 0.1 g of the M-SBA-15 catalyst were added into
the reactor which then was heated to 80 °C keeping for 4 h. The reaction
products were analyzed by an Agilent 7890A GC with the internal stan-
dard method. The yield and selectivity of bisphenol F were calculated on
consumed formaldehyde [14].
The adsorption–desorption isotherms and the BJH pore size distribu-
tions of M(20)-SBA-15 with different Al/Zr ratios are depicted in Fig. 3.
All the isotherms display type IV with H1 hysteresis loops at a high rel-
ative pressure, suggesting a typical mesoporous structure in these sam-
ples. The ordered mesostructure can also be reflected by the narrow
pore size distribution [18,19].
3. Results and discussion
3.1. Catalytic activity comparison of M-SBA-15 with different Si/M ratios
The pyridine FT-IR spectra of M(20)-SBA-15 catalysts with different
Al/Zr ratios are shown in Fig. 4. The IR bands at 1596 and 1598 cm−1 are
assigned to Brønsted (B) acid sites due to the formation of bridged
hydroxyl groups [20], and the band at 1490 cm−1 [21] is the interaction
of B and Lewis (L) acid sites. The bands at 1445 and 1446 cm−1 are
assigned to L acid sites [22,23]. The results of pyridine FT-IR spectra in-
dicate that there are both B and L acid sites in M(20)-SBA-15 catalysts. It
is noted that with the increment of Zr content, the band at 1490 cm−1
becomes more obvious, and this is because the strength of B and L
acid sites increases.
As shown in Fig. 1, the pure siliceous SBA-15 has almost no catalytic
activity in the hydroxyalkylation of phenol with formaldehyde to
bisphenol F; however, M-SBA-15 catalysts exhibit high catalytic activity
after metal ions were incorporated into SBA-15. The catalytic activity
comparison of M(Al, Zr, Al/Zr = 1)-SBA-15 with different Si/M ratios
of 10, 20, 30 and 50 is illustrated in Fig. 1. Among them, M(20)-SBA-
15 catalysts exhibit higher catalytic activity and high selectivity for
bisphenol F, respectively. This is because the extra-framework metal
oxide particles formed in the mesoporous walls could decrease the
number of accessible catalytic sites at low Si/M ratios. At high Si/M
ratios, however, there were not enough catalytic sites formed in the
framework of SBA-15 [15]. M(20)-SBA-15, the most reactive among
the studied catalysts, was chosen for further investigations on the
hydroxyalkylation of phenol with formaldehyde to bisphenol F.
3.3. The isomer distribution of bisphenol F
The isomer distributions of bisphenol F in the hydroxyalkylation of
phenol with formaldehyde over M(20)-SBA-15 catalysts with different
Al/Zr ratios are listed in Table 2.
From Table 2, it can be seen that although there are somewhat irreg-
ular fluctuated changes for the yield and selectivity of bisphenol F that
range from 79% to 87.9% and 92.4% to 94.6% with the changing of Al/Zr
Yield(%)
Selectivity(%)
100
80
60
40
20
100
110
200
Zr(20)-SBA-15
Al-Zr(20)-SBA-15(Al/Zr=0.5)
Al-Zr(20)-SBA-15(Al/Zr=1)
Al-Zr(20)-SBA-15(Al/Zr=2)
0
)
-15
A
-15
r=1)
r=1)
r=1)
A-15
A-15
A-15
Z
Z
Z
/
l/Zr=1
SBA-15
Al
-SBA
-SB
)
)
)-SB
Al(20)-SBA-15
SBA-15
0
(30)-SB
Al(10)-SBAA-1l5(20)-SBAA-1l5
r(30)-SB
A-15(Al/
Zr(1
Zr(20
Z
Zr(50
Al(50)-SBA-15
SB
r(50)-
-Z
Al-Z15r((3A0)-SBAAl -15(
Al-Zr(10)-SBAl--1Z5r((A20l/)-SB
A
1
2
3
4
5
2
θ
Fig. 1. Catalytic activity comparison of M(Al, Zr, Al/Zr = 1)-SBA-15 with different Si/M
ratios. Reaction conditions: phenol/formaldehyde molar ratio of 30, catalyst/formaldehyde
mass ratio of 1, reaction temperature of 80 °C and reaction time of 4 h.
Fig. 2. The small-angle XRD patterns of M(20)-SBA-15 with different Al/Zr ratios.

Y. Tan et al. / Catalysis Communications 67 (2015) 21–25
23
Table 1
The textural properties of M(20)-SBA-15 catalysts with different Al/Zr ratios.
1446
1446
Samples
Surface
area
Pore
Pore
volume
a0
(nm)
1596
1596
diameter
1490
1490
Zr(20)-SBA-15
(m2g−1
)
Dv(d) (nm) (cm3g−1
)
SBA-15
Al(20)-SBA-15
Al–Zr(20)-SBA-15 (Al/Zr = 2)
Al–Zr(20)-SBA-15 (Al/Zr = 1)
Al–Zr(20)-SBA-15 (Al/Zr = 0.5) 800.784
Zr(20)-SBA-15 777.739
816.548
879.094
819.993
726.980
6.654
7.865
6.579
6.628
6.591
6.642
0.814
1.149
1.055
0.921
0.893
0.819
12.015
12.081
12.217
12.593
11.524
11.674
Al-Zr(20)-SBA-15(Al/Zr=0.5)
1446
1446
1598
Al-Zr(20)-SBA-15(Al/Zr=1)
1596
Pore diameter calculated from N2 desorption data based on the BJH method, and a0
¼
pffiffiffi
Al-Zr(20)-SBA-15(Al/Zr=2)
2d100= 3.
1596
1445
Al(20)-SBA-15
ratios, respectively, there is a regular change in the isomer distribution
of bisphenol F with the changing of Al/Zr ratio in M(20)-SBA-15 cata-
lysts. With the decreasing of the Al/Zr ratio from pure Al to pure Zr,
2,4′- and 2,2′-isomers gradually increased from 44.5% to 61.1% and
16% to 31%, respectively, whereas 4,4′-isomer gradually decreased
from 39.5% to 7.9%.
1700
1650
1600
1550
1500
1450
Wavenumber
(
cm-1
)
Fig. 4. Pyridine FTIR spectra of M(20)-SBA-15 catalysts after pyridine desorption at 150 °C
To explain the above regular change of the isomer distribution of
bisphenol F, the difference in the acidic property of M(20)-SBA-15 cat-
alysts is firstly considered. It was reported that Al-SBA-15 and Zr-SBA-
15 mainly exhibit B acid [20,23] and L acid [24,25] properties, respec-
tively. When the Al/Zr ratio in M(20)-SBA-15 catalysts is different,
there exists a different ratio of B/L acid sites. With the increment of Zr
content in M(20)-SBA-15, the ratio of L/B acid sites increases (Fig. 4).
Therefore, it seems that B acid is in favor of the formation of 4,4′-isomer,
whereas L acid is in favor of the formation of 2,4′- and 2,2′-isomers.
for 0.5 h.
ratio may prefer the ortho rearrangement to form more stable 2,4′- and
2,2′-isomers. As a result, the regulative isomer distribution of bisphenol
F appeared with the changing of the Al/Zr ratio in M-SBA-15 catalysts.
4. Conclusion
Pure siliceous SBA-15 has almost no catalytic activity in the
hydroxyalkylation of phenol with formaldehyde to bisphenol F. Howev-
er, M-SBA-15 exhibited high catalytic activity after metal ions are incor-
porated into SBA-15. Among them, M(20)-SBA-15 with the Si/M ratio of
20 exhibited higher catalytic activity. With the increment of the Al/Zr
ratio in M(20)-SBA-15 catalysts, the ratio of B/L acid sites increases.
Al(20)-SBA-15 is in favor of the formation of 4,4′-isomer, whereas
Zr(20)-SBA-15 is in favor of the formation of 2,4′- and 2,2′-isomers.
The isomer distribution of bisphenol F in the hydroxyalkylation of phe-
nol with formaldehyde can be regulated by changing the Al/Zr ratio in
M(20)-SBA-15 catalysts.
3.4. Plausible mechanistic pathway
Based on the results discussed above, a plausible mechanistic path-
way for the isomer distribution of bisphenol F in the hydroxyalkylation
of phenol with formaldehyde over M-SBA-15 is proposed in Scheme 1.
Firstly, the protonation of formaldehyde with M-SBA-15 occurs to
form the hydroxymethyl carbocation CH2OH+. Then, the hydroxymeth-
yl carbocation CH2OH+ attacks phenol mainly to form O-alkylated in-
termediate A and part of C-alkylated intermediate B and intermediate
C, respectively [26,27]. Then the O-alkylated intermediate A rearranges
to C-alkylated intermediate B and intermediate C, and both of them con-
tinue to attack another phenol to form O-alkylated intermediate D and
intermediate E, respectively. Finally, the O-alkylated intermediate D
and intermediate E continue to rearrange to form C-alkylated 4,4′-,
2,4′- and 2,4′-,2,2′-isomers, respectively. In general, because of the steric
hindrance and the effect of B acid, the C-alkylated 4,4′-isomer is more
likely to form. However, the nature of Zr with the higher L/B acid site
Acknowledgments
This work is supported by the National Natural Science Foundation
of China (No. 21276217), Hunan Provincial Natural Science Foundation
of China (No. 13JJ6039) and Graduate Innovation Fund of Hunan prov-
ince (No. CX2012B254).
a
b
Zr(20)-SBA-15
Zr(20)-SBA-15
Al-Zr(20)-SBA-15(Al/Zr=0.5)
Al-Zr(20)-SBA-15(Al/Zr=1)
Al-Zr(20)-SBA-15(Al/Zr=0.5)
Al-Zr(20)-SBA-15(Al/Zr=1)
Al-Zr(20)-SBA-15(Al/Zr=2)
Al-Zr(20)-SBA-15(Al/Zr=2)
Al(20)-SBA-15
Al(20)-SBA-15
SBA-15
SBA-15
0.0
0.2
0.4
0.6
0.8
1.0
10
100
Relative pressure (P/P0)
Pore Diameter(nm)
Fig. 3. (a) Nitrogen absorption isotherms (b) and BJH pore size distributions of M(20)-SBA-15 catalysts with different Al/Zr ratios.

24
Y. Tan et al. / Catalysis Communications 67 (2015) 21–25
Table 2
Results on bisphenol F synthesis over M(20)-SBA-15 catalysts with different Al/Zr ratios.
Catalysts
Bisphenol F yield (%)
Bisphenol F selectivity (%)
Bisphenol F isomer distribution (%) after 4 h of reaction
4,4′-Isomer
2,4′-Isomer
2,2′-Isomer
Al(20)-SBA-15
79.0
87.9
82.4
84.6
82.7
93.0
94.6
92.4
93.8
93.7
39.5
34.6
23.6
19.0
7.9
44.5
46.2
53.2
53.8
61.1
16.0
19.2
23.2
27.2
31.0
Al-Zr(20)-SBA-15(Al/Zr = 2)
Al-Zr(20)-SBA-15(Al/Zr = 1)
Al-Zr(20)-SBA-15(Al/Zr = 0.5)
Zr(20)-SBA-15
Reaction conditions: phenol/formaldehyde molar ratio of 30, catalyst/formaldehyde mass ratio of 1, reaction temperature of 90 °C and reaction time of 4 h.
Scheme 1. The plausible mechanistic pathway for the isomer distribution of bisphenol F.
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