Tungsten doped mesoporous SBA-16 as novel heterogeneous catalysts for oxidation of cyclopentene to glutaric acid

Article abstract of DOI:10.1002/aoc.4317

Novel heterogeneous tungsten species in mesoporous silica SBA-16 catalysts based on ship-in-a-bottle methodology are originally reported for oxidizing cyclopentene (CPE) to glutaric acid (GAC) using hydrogen peroxide (H₂O₂). For all W-SBA-16 catalysts, isolated tungsten species and octahedrally coordinated tungsten oxide species are observed while WO₃ crystallites are detected for the W-SBA-16 catalysts with Si/ W = 5, 10, and 20. The specific surface areas and the corresponding total pore volumes decrease significantly as increasing amounts of tungsten incorporated into the pores of SBA-16. Using tungsten-substituted mesoporous SBA-16 heterogeneous catalysts, high yield of GAC (55%) is achieved with low tungsten loading (for Si/W = 30, ~13?wt%) for oxidation of CPE. The W-SBA-16 catalysts with Si/W = 30 can be reused five times without dramatic deactivation. In fact, low catalytic activity provided by bulk WO₃ implies that the highly distributed tungsten species in SBA-16 and the steric confinement effect of SBA-16 are key elements for the outstanding catalytic performance.

Full text of DOI:10.1002/aoc.4317

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Received: 1 December 2017
DOI: 10.1002/aoc.4317
Revised: 17 January 2018
Accepted: 18 January 2018
F U L L P A P E R
Tungsten doped mesoporous SBA‐16 as novel heterogeneous
catalysts for oxidation of cyclopentene to glutaric acid
Manman Jin1 | Guodi Zhang1 | Zhenmei Guo2 | Zhiguo Lv1
1 College of Chemical Engineering,
Novel heterogeneous tungsten species in mesoporous silica SBA‐16 catalysts
Qingdao University of Science and
Technology, Qingdao 266042, PR China
2 College of Marine Science and Biological
based on ship‐in‐a‐bottle methodology are originally reported for oxidizing
cyclopentene (CPE) to glutaric acid (GAC) using hydrogen peroxide (H2O2).
Engineering, Qingdao University of
For all W‐SBA‐16 catalysts, isolated tungsten species and octahedrally coordi-
Science and Technology, Qingdao 266042,
PR China
nated tungsten oxide species are observed while WO3 crystallites are detected
for the W‐SBA‐16 catalysts with Si/ W = 5, 10, and 20. The specific surface areas
and the corresponding total pore volumes decrease significantly as increasing
amounts of tungsten incorporated into the pores of SBA‐16. Using tungsten‐
substituted mesoporous SBA‐16 heterogeneous catalysts, high yield of GAC
(55%) is achieved with low tungsten loading (for Si/W = 30, ~13 wt%) for oxida-
tion of CPE. The W‐SBA‐16 catalysts with Si/W = 30 can be reused five times
without dramatic deactivation. In fact, low catalytic activity provided by bulk
WO3 implies that the highly distributed tungsten species in SBA‐16 and the
steric confinement effect of SBA‐16 are key elements for the outstanding cata-
lytic performance.
Correspondence
Zhiguo Lv, College of Chemical
Engineering, Qingdao University of
Science and Technology, Qingdao, 266042,
PR China.
Email: lvzhiguo@qust.edu.cn
Funding information
Natural Research Major Foundation of
Shan Dong Province, Grant/Award Num-
ber: ZR2017ZC0632; National Natural Sci-
ence Foundation of China, Grant/Award
Number: NSFC21376128
KEYWORDS
cyclopentene, glutaric acid, heterogeneous catalysis, supported catalysts, W‐SBA‐16
1 | INTRODUCTION
and 1,3‐dicarbonyl derivatives[14] have also been reported
to manufacture carboxylic acids, but they are rarely used
Glutaric acid (GAC, dicarboxylic acid) has many compel-
ling physicochemical properties. One of the most impor-
tant applications of GAC and its derivatives is used for
the synthesis of liquid crystal materials (e.g., liquid crystal
displays).[1] GAC is an essential feedstock for the synthe-
sis of lubricating oil, polyester, synthetic rubber, and
polyamide.[2] It has also been reported in medicine that
GAC displays important physiological activity to reduce
glutamate uptake,[3] inhibit the energy metabolism,[4]
and induce oxidative stress in brain.[5] Several procedures
for synthesis of GAC have been described using
trimethylene cyanide,[6] methylene bis(malonic acid),[7]
and γ‐butyrolactone.[8] However, these methods are
inconvenient and unsuitable for large‐scale synthesis.
Amino acids,[9] alkanes,[10] ketones,[11,12] alcohols,[13]
or required complicated multi‐step to fabricate GAC.
Phase‐transfer catalysts W/[CH3(n‐C8H17)3N]HSO4 and
[π‐C5H5NC16H33]3[PW4O16] have been proposed for selec-
tive oxidation of olefins using H2O2 by Noyori et al.[15]
and Sun et al.,[16] repectively. However, the low recovery
rate of the phase‐transfer catalysts and the irreversible
structure of catalysts change after the reaction limit their
application. H2WO4 has also been used as a homogeneous
catalyst for oxidation of cyclopentene (CPE) to GAC,
but it is also difficult to recover.[17] A green synthesis
route for oxidizing reaction of CPE to GAC has been
suggested,[18] the catalyst needs to be further
explored. Vafaeezadeh et al.[19] have put forward the use
of bis (1‐butyl‐3‐methylimidazolium) tungstate for the
prepare of GAC through oxidative cleavage of CPE. A
Appl Organometal Chem. 2018;e4317.
wileyonlinelibrary.com/journal/aoc
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https://doi.org/10.1002/aoc.4317

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JIN ET AL.
desired yield of GAC can be obtained when p‐
toluenesulfonic acid or trifluoromethanesulfonic acid
was selected to provide acidic media. WO3/SiO2 synthe-
sized by ultrasound impregnation method has also been
used to catalyze the oxidation of CPE.[20] Heterogeneous
catalysts show distinct advantages for catalyst recovery
over homogeneous and phase‐transfer catalysts;
heterogenization of homogeneous catalysts has become
an important research direction.
the oxidation of CPE to GAC has not been catalyzed
by tungsten‐doped cage‐type mesoporous silica SBA‐16
heterogeneous catalysts.
Here, we first reported tungsten doped into the cages
of SBA‐16 catalysts for the oxidation of CPE to GAC and
compared the catalytic performance of tungsten
doped SBA‐16 catalysts with different tungsten loading.
Physicochemical properties of the synthesized catalysts
using one‐pot method[43] were characterized by X‐ray
diffraction (XRD), N2 adsorption‐desorption analysis,
diffuse‐reflectance ultraviolet‐visible light (DR‐UV‐Vis)
microscopy, fourier transform infrared spectroscopy (FT‐
IR), temperature programmed reduction for hydrogen
(H2‐TPR), and temperature programmed desorption of
ammonia (NH3‐TPD). This research produces an effective
and returnable catalyst for direct oxidation of CPE to GAC
and certifies the outstanding capacity of SBA‐16 as an
extremely efficient catalyst support.
Different approaches, such as chemical grafting,[21,22]
encapsulating in porous supports (ship‐in‐a‐bottle),[23,24]
using organic and inorganic hybrids,[25,26] intercalating
layered materials,[27,28] and forming ionic interac-
tions,[29,30] have been suggested to create heterogeneous
catalysts. The ship‐in‐a‐bottle method maintains the
chemical characteristics of the doped catalyst but not the
steric confinement of the multi‐hole carriers. It is a valid
method to imitate homogeneous catalysts. Sulikowski
et al.[31] proposed the ship‐in‐a‐bottle method and suc-
cessfully packaged phosphotungstic acid in the cage of a
Y zeolite; the encapsulated catalyst could be easily recov-
ered for reuse. However, the zeolite is only applicable for
small‐molecule reactions because of its pore size (<1 nm).
This makes it necessary to seek new materials with larger
pores to accelerate the appearance of ordered mesoporous
silicas (OMSs).
2 | EXPERIMENTAL
2.1 | Encapsulation of tungsten in the
nanocage of SBA‐16
Mesoporous W‐SBA‐16 catalysts were synthesized
according to a literature procedure with some adapta-
tions;[44,45] the samples are named based on their Si/W
mole ratio (i.e., W‐SBA‐16 (Si/W)). Typically, Triblock
OMSs initiated by Kresge et al.[32] have wide applica-
tions in many domains, such as catalysis,[33] separa-
tions,[34] and adsorption,[35] because of their superior and
adjustable specific surface areas, mesopore volumes, and
pore diameters. A tungsten complex, which is an efficient
catalyst for the oxidation of olefins, was immobilized on
silica to form metal‐incorporated mesoporous materials.
Different mesoporous silica materials (e.g., MCM‐41,
MCM‐48, HMS, SBA‐15, and KIT‐6) have been examined
for catalytic applications. W‐MCM‐41 was synthesized,
and its textural and structural properties were probed.[36]
Fan et al.[37–39] doped tungsten inside the pores of ordered
MCM‐48, HMS, and SBA‐15, which exhibited high
selectivity for the oxidation of CPE to glutaric dialdehyde.
Tungsten‐modified SBA‐15 and HMS were also detected
as carriers for Ni/W catalysts in the highly dispersible silica
reaction of thiophene by the Jiratova group.[40] Zhou
et al.[41] triumphantly immobilized tungsten into KIT‐6
under hydrothermal conditions. Nevertheless, 3D mesopo-
rous SBA‐16 has not attracted much attention. SBA‐16 is a
well‐ordered porous silica with large cage‐like mesopores
arranged in a cubic body‐centered Im‾3m symmetry,[42]
in which adjacent cages form a polydirectional system of
mesoporous reticulation via eight small pores; this struc-
ture facilitates mass transfer without blocking the pores.
The distinct structure of SBA‐16 is undoubtedly beneficial
to improve the activity of tungsten catalysts. Nevertheless,
copolymer Pluronic F127 (3.5 g, EO106PO70EO106
,
Macklin) was dissolved in a HCl solution (175 ml,
0.4 M) at 45 °C with vigorous stirring for 20 min. Then,
n‐butanol (10.5 g, Aladdin) was added and continuously
stirred for 1 h. Tetraethyl orthosilicate (16.7 g, Macklin)
and moderate amounts of sodium tungstate (Aladdin)
were added and continuously stirred for 24 h. The
resulting reaction mixture was treated at 100°C for
24 h under an idle state in a hydrothermal synthesis
reactor. After filtration, a white solid product was
obtained. Then, the product was dried at 100 °C for
12 h and calcined at 550 °C (temperature increase of
1 °C/min) for 6 h under air flow to remove the template.
2.2 | Characterization
Powder X‐ray diffraction (XRD) patterns were recorded
on a Rint 2000 vertical goniometer (Rigaku) equipped
with Cu Kα radiation (λ = 0.15418 nm) and operated at
40 kV and 100 mA with a scanning speed of 2°(2θ)/min.
N2 adsorption isotherms were measured at ‐196 °C on
an ASAP 2020 V4.01 (V 4.01 H; Micromeritics)
sorptometer. Before the physisorption measurement, all
samples were outgassed at 150 °C for 2 h. Diffuse reflec-
tance UV‐Vis (DR UV‐Vis) spectra were measured using

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JIN ET AL.
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a Cary 500 (8.01) spectrophotometer from 200‐800 nm at
25 °C. Fourier transform infrared (FT‐IR) spectra were
recorded on a HGCS20170343J spectrometer from 1400‐
400 cm‐1 using the KBr pellet technique. Temperature‐
programmed reduction (H2‐TPR) was performed using a
Micromeritics AutoChem II 2920 V 4.03 apparatus.
Temperature programmed desorption of ammonia (NH3‐
TPD) was recorded on Chembet Pulsar TPR/TPD instru-
ment. Typically, 100 mg sample was pretreated in He
(30 ml/min, 400 °C, 1 h). Subsequently, the sample was
exposed to 10%NH3/90% He at 80 °C for 1 h, then purged
with He for 0.5 h at 100 °C. The spectra of NH3‐TPD were
registered from 100 to 500 °C with a ramp of 10 °C/min.
The tungsten contents in W‐SBA‐16 and the reaction
liquids were measured by inductively coupled plasma‐
optical emission spectrometry (ICP‐OES, IRIS Intrepid,
Thermo Elemental Company) after solubilization of W‐
SBA‐16 in HF (40 wt% in water)/HNO3 (65 wt% in water)
solutions in which the volume ratio of HF to HNO3 is 3:7.
Liquid chromatography (LC, Agilent 1100) was carried
out using a Microsorb‐MV C18 (4.6 mm × 250 mm) ana-
lytical column with aqueous methanol (0.1‐0.3 volume
fraction) and aqueous KH2PO4 (5 mmol/l) as the mobile
phase with a flow rate of 1 ml/min. Gas chromatography
(GC, GC‐1102, Shanghai Analytical Instrument Factory)
was carried out using an SE‐30‐filled stainless steel
packed column (Φ 3 mm × 2 m).
until the solution became red from titration with trace
KMnO4 (0.005 mol/l) liquor. Then, it was concentrated
through vacuum distillation to remove part of the water,
refrigerated at 0 °C for 5 h, and filtered to form the
colorless GAC crystal.
LC and GC were used to analyze the purity of GAC.
Quantitative analysis by GC: A BF3‐ether solution (1 ml)
was added to absolute ethanol (5 ml) containing 0.1 g of
the solid sample. The mixture was esterified under sealed
conditions at 100 °C for 10 min. A solution of NaHCO3
and deionized water were added to the cooled esterifica-
tion reaction liquid to neutralize it and dissolve inorganic
substances, respectively. Then, the neutral solution was
extracted three times with anhydrous ether (3 ml), and
diethyl malonate (0.1 g) was added to the ether extract
to obtain an injection solution.
3 | RESULTS AND DISCUSSION
3.1 | Catalyst characterization
The mesoporosity of the W‐SBA‐16 catalysts were exam-
ined using small‐angle XRD measurement, and the
corresponding results are described in Figure 1. A well‐
resolved diffraction peak of the (110) reflection (2 θ =
0.84°), a small shoulder of the (200) reflection (2 θ =
1.01°), and another small shoulder of the (211) reflection
(2 θ = 1.25°) assigned to the cubic Im‾3m structure are
observed in SBA‐16.[45,47] The three diffraction peaks are
also detected in the W‐SBA‐16 catalysts; it indicates the
mesoporous structures still maintain after the immobili-
zation of tungsten species. The strength of the (110),
(200), and (211) reflection peaks gradually decreases in
W‐SBA‐16 catalysts with increasing amounts of tungsten.
When Si/W ≤ 20, the intensity of the (110) reflection peak
2.3 | Oxidation of CPE
A three‐neck round bottomed flask (25 ml), condensation
tube, balloon, and thermometer were used in this experi-
ment. The reaction process was violently exothermic;
therefore, a temperature‐controlled water bath was used
to easily control the temperature. An appropriate amount
of the catalyst (based on the tungsten content), H2O2
(50 wt%, 2.99 g), and CPE (0.68 g) were blended into the
flask. The mixture was heated at 50 °C with vigorous stir-
ring. CPE began to reflux when the temperature reached
45 °C. The temperature was set to 90 °C and maintained
for ~7 h until the reflux was complete.[46] The resulting
suspension was filtered to obtain the catalysts and a color-
less liquid (a colored liquid was obtained when WO3 was
used as the catalyst). The colorless liquid was divided into
four portions. One portion was titrated using NaOH
(0.487 mol/l) liquor to obtain the yield of organic acid.
Similarly, KMnO4 (0.005 mol/l) liquor was required to
titrate a second portion to determine the residual content
of H2O2. The third portion reacted for another 7 h at
90 °C. Then, the yield of organic acid and residual H2O2
content were re‐tested. The fourth portion was boiled to
disintegrate residual H2O2 under vacuum distillation to
avoid explosion. This process was repeated several times
FIGURE 1 Small‐angle XRD patterns of SBA‐16 and W‐SBA‐16
catalysts

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JIN ET AL.
decreases significantly and the characteristic peaks
ascribed to (200) and (211) reflection become less obvious;
those results suggest the long‐range ordering of the meso-
porous structure is destroyed partially. Furthermore, the
peak attributed to (110) in W‐SBA‐16(20, 10, and 5) is
broader than that in W‐SBA‐16(50, 40, and 30). It also
suggests partial disruption of the structural ordering at
Si/W≤ 20. As inferred from Table 1, the tungsten contents
measured in the W‐SBA‐16 catalysts from ICP test
are practically similar to the theoretical values with an
experimental error of a little bit less than 7 wt% for W‐
SBA‐16(10) and W‐SBA‐16(5) samples; this result indi-
cates that some tungsten is successfully incorporated
inside the SBA‐16.
Wide‐angle XRD images of SBA‐16 and the W‐SBA‐16
catalysts are shown in Figure 2. The characteristic diffrac-
tions of mesoporous silica (2 θ = 15°‐30°) are detected for
all the samples.[44] No bulk WO3 peaks are observed for
FIGURE 2 Wide‐angle XRD patterns of SBA‐16 and W‐SBA‐16
catalysts
the W‐SBA‐16 catalysts with tungsten loadings
≤
12.99 wt% (W‐SBA‐16(30)) (Table 1). WO3 crystal phase
characteristic reflections are not detected in the W‐SBA‐
16(30, 40, and 50) catalysts suggesting the presence of
highly dispersed tungsten species in SBA‐16.[44] However,
in W‐SBA‐16(5, 10, and 20) catalysts, characteristic peaks
corresponding to bulk WO3 are clearly observed and their
intensities increase with the increase of tungsten content.
The textural properties of all the samples are shown in
Figure 3. All samples reveal type‐IV isotherms with an
H2‐type hysteresis loop indicating typical cage‐like porous
structures according to the IUPAC classification.[45,48]
The sharp capillary condensation step of N2 (when P/P0
= 0.4‐0.8) indicates the uniform hole size of all samples.
For the W‐SBA‐16 materials, inflection is less sharp than
that of SBA‐16 and attenuated with increasing W content.
This phenomenon signifies the decrease of framework
mesoporosity. From Table 1, the value of BET surface area
(SBET) drastically decreases from 672 (W‐SBA‐16(50)) to
330 m2/g (W‐SBA‐16(5)); meanwhile a gradual decline
of the corresponding total pore volume (Vtot) is observed
from 0.61 to 0.34 cm3/g. The differences are caused by
the different amount of tungsten species encapsulated in
the skeleton of SBA‐16. A bimodal pore diameter distribu-
tion occurs from the pore diameter distributions of the
samples (Figure 4); the first peak reflects the size of the
mesopore entrance that interconnects the ordered
mesopores, and the second peak represents the pore
diameter of the ordered cage‐like pores.[48] With increased
tungsten loading up to 15.51 wt%, the SBET, Vtot, and pore
diameter decrease prominently suggesting some tungsten
species encapsulated in the nanocages of SBA‐16. How-
ever, for the W‐SBA‐16(10) and W‐SBA‐16(5) catalysts,
the pore diameters significantly increase to 6.42 and
6.52 nm, respectively; this can be assigned to massive
TABLE 1 Textural properities of SBA‐16 and the W‐SBA‐16 catalysts
d
e
Materials
Si/Wa Wb (wt%) Wc (wt%) SBET (m2/g) Vtot (cm3/g) Pore diameter (nm) Total acidity (mmol NH3/g)
SBA‐16
∞
50
40
30
20
10
5
0
9.97
0
9.68
689
672
669
638
632
500
330
0.63
0.61
0.56
0.54
0.53
0.44
0.34
5.54
5.42
4.93
4.86
4.84
6.42
6.52
‐
W‐SBA‐16(50)
W‐SBA‐16(40)
W‐SBA‐16(30)
W‐SBA‐16(20)
W‐SBA‐16(10)
W‐SBA‐16(5)
0.33
0.36
0.38
0.25
0.21
0.19
12.20
13.04
16.86
28.85
50.78
11.17
12.99
15.51
21.89
48.20
aMole ratio of Si and W.
bStoichiometric ratio in synthesis.
cDerived from ICP.
dSingle point adsorption total pore volume of pores at P/P0 = 0.99.
eBJH adsorption average pore size.