Dehydration of glycerin to acrolein over H3PW12O40 catalyst supported on mesoporous titania

Article abstract of DOI:10.1166/jnn.2016.13248

H₃PW₁₂O₄₀ catalysts supported on mesoporous titania (XH₃PW₁₂O₄₀/MT (X = 5, 10, 15, 20, 25, and 30)) were prepared with a variation of H₃PW₁₂O₄₀ content (X, wt%), and they were applied to the dehydration of glycerin to acrolein. The prepared catalysts were characterized by FT-IR spectroscopy, X-ray diffraction, N₂ adsorption-desorption, and pyridine-adsorbed in-situ FT-IR spectroscopy analyses. The effect of H₃PW₁₂O₄₀ content on the physicochemical properties and catalytic activities of XH₃PW₁₂O₄₀/MT catalysts was investigated. It was found that surface area and pore volume of XH₃PW₁₂O₄₀/MT catalysts decreased with increasing H₃PW₁₂O₄₀ content. Br?nsted acidity of XH₃PW₁₂O₄₀/MT catalysts showed a volcano-shaped trend with respect to H₃PW₁₂O₄₀ content. The catalytic performance of XH₃PW₁₂O₄₀/MT catalysts was closely related to the Br?nsted acidity of the catalysts. It was revealed that yield for acrolein over XH₃PW₁₂O₄₀/MT catalysts increased with increasing Br?nsted acidity of the catalysts. Among the catalysts tested, 20H₃PW₁₂O₄₀/MT catalyst with the largest Br?nsted acidity showed the highest yield for acrolein.

Full text of DOI:10.1166/jnn.2016.13248

Article
Journal of
Nanoscience and Nanotechnology
Vol. 16, 10829–10834, 2016
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Copyright © 2016 American Scientific Publishers
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Dehydration of Glycerin to Acrolein Over H3PW12O40
Catalyst Supported on Mesoporous Titania
Tae Hun Kang1, Jung Ho Choi1, Min Yeong Gim1, Jun Seon Choi2, Wangrae Joe2, and In Kyu Song1ꢀ∗
1School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University,
Shinlim-dong, Kwanak-ku, Seoul 151-744, South Korea
2LG Chem. Ltd., Moonji-dong, Yuseong-Gu, Daejeon 305-380, South Korea
H3PW12O40 catalysts supported on mesoporous titania (XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ
and 30)) were prepared with a variation of H3PW12O40 content (X, wt%), and they were applied
to the dehydration of glycerin to acrolein. The prepared catalysts were characterized by FT-IR
spectroscopy, X-ray diffraction, N2 adsorption–desorption, and pyridine-adsorbed in-situ FT-IR spec-
troscopy analyses. The effect of H3PW12O40 content on the physicochemical properties and catalytic
activities of XH3PW12O40/MT catalysts was investigated. It was found that surface area and pore vol-
ume of XH3PW12O40/MT catalysts decreased with increasing H3PW12O40 content. Brønsted acidity
of XH3PW12O40/MT catalysts showed a volcano-shaped trend with respect to H3PW12O40 content.
The catalytic performance of XH3PW12O40/MT catalysts was closely related to the Brønsted acidity
of the catalysts. It was revealed that yield for acrolein over XH PW O /MT catalysts increased
Delivered by Ingenta to: State University of New3Yor1k2 a4t0Binghamton
with increasing Brønsted acidity of the catalysts. Among the catalysts tested, 20H3PW12O40/MT
IP: 37.9.41.147 On: Wed, 08 Mar 2017 14:16:41
catalyst with the largest Brønsted acidity showed the highest yield for acrolein.
Copyright: American Scientific Publishers
Keywords: Heteropolyacid, Mesoporous Titania, Dehydration of Glycerin, Acrolein, Brønsted
Acidity.
1. INTRODUCTION
comparison with the petroleum-based process.1ꢀ2 Several
solid acid catalysts including zeolites,10 metal oxides,11
and phosphates12 have been investigated as catalysts for
gas-phase dehydration of glycerin. However, a previous
work showed that the acid-catalyzed dehydration of glyc-
erin suffered from catalyst deactivation and low catalytic
activity due to coke formation and considerable activation
energy, respectively.7
It has been reported that Brønsted acid strength of het-
eropolyacids (HPAs) is stronger than that of conventional
solid acid.13ꢀ14 For this reason, HPAs have been utilized
as benign solid acid catalysts in several acid-catalyzed
reactions. However, one of the disadvantages of HPA cat-
alysts is their low surface area (<10 m2/g), leading to
fast catalyst deactivation during a long-time reaction. To
overcome this problem, HPAs supported on mesoporous
materials with high surface area such as silica, alumina,
and activated carbon have been investigated as catalysts
for acid-catalyzed reactions. Among them, titania has been
widely used as a support because of its outstanding textu-
ral properties.15ꢀ16
Due to fossil fuel depletion and new energy policy,
biomass has attracted much attention as a clean energy
resource.1–3 In the production of biodiesel from biomass
resource, a considerable amount of glycerin is formed as
a by-product (10% by weight).1ꢀ2 Therefore, a number of
researches have been conducted to find new applications
to convert low-value glycerin feedstock into value-added
chemicals.4–6 Among the catalytic processes for glycerin
conversion, catalytic dehydration of glycerin to acrolein
is one of the most promising research areas due to ver-
satile applicability of acrolein as a chemical intermediate
for the synthesis of acrylic acid, methionine, and super-
absorbent polymers.7ꢀ8 Acrolein has been conventionally
produced by partial oxidation process of petroleum-based
propylene over multi-component metal oxide catalysts.9
However, the catalytic dehydration of glycerin to acrolein
has recently become a promising route for acrolein produc-
tion due to economical and environmental advantages in
∗Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2016, Vol. 16, No. 10
1533-4880/2016/16/10829/006
doi:10.1166/jnn.2016.13248 10829

Dehydration of Glycerin Over H3PW12O40/TiO2
Kang et al.
In this work, a series of H3PW12O40 catalysts sup-
ported on mesoporous titania (XH3PW12O40/MT (X =
5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30)) were prepared with a vari-
ation of H3PW12O40 content (X, wt%) to investigate
the effect of H3PW12O40 content on the physicochem-
ical properties and catalytic activities in the dehydra-
tion of glycerin to acrolein. The prepared catalysts were
characterized by ICP-AES, FT-IR, XRD, and nitrogen
adsorption–desorption analyses. Pyridine-adsorbed in-situ
FT-IR spectroscopy analyses were also conducted to exam-
ine the acid properties of XH3PW12O40/MT catalysts.
A correlation between acid properties and catalytic activ-
ities in the dehydration of glycerin to acrolein was then
established and discussed.
of the catalysts were determined by BJH (Barret-Joyner-
Hallender) method.
Acid properties of XH3PW12O40/MT catalysts were
determined by pyridine-adsorbed in-situ FT-IR spec-
troscopy measurements. Each catalyst (0.04 g) was pressed
into a pellet with a radius of 0.65 cm. The pellet was pre-
ꢀ
heated at 200 C for 1 h with a stream of He (40 ml/min)
ꢀ
in a tubular quartz cell. After cooling the pellet to 50 C,
pyridine vapor (5 ml) was pulsed into the reactor with a
stream of He (40 ml/min) until the acid sites were satu-
ꢀ
rated with pyridine. The reactor was evacuated at 50 C
ꢀ
for 1 h. IR spectra were then recorded at 50 C within the
spectral range of 1600–1400 cm−1
.
2.3. Gas-Phase Dehydration of Glycerin
Gas-phase dehydration of glycerin was carried out at
275 C under atmospheric pressure in a continuous flow
2. EXPERIMENTAL DETAILS
2.1. Preparation of Catalysts
ꢀ
fixed-bed reactor. The tubular pyrex reactor was packed
with a catalyst (0.1 g), and it was preheated with a stream
Mesoporous titania support was prepared by a sol–gel
method according to the procedures in the literature.17
Titanium butoxide (TB, Sigma-Aldrich) was dissolved in
absolute ethanol, and it was stirred for 30 min to obtain
a homogeneous solution. Hydrochloric acid (HCl, Sigma-
Aldrich) was added into the TB solution at a constant rate
for 2 h to form an alcogel. The alcogel was further aged
ꢀ
of nitrogen carrier gas (30 ml/min) at 275 C for 0.5 h
to achieve steady-state operation. Glycerin feed (7 mol%
aqueous solution, 1.0 mmol/h) was sufficiently vaporized
by passing through a pre-heating zone, and it was con-
tinuously fed into the reactor together with nitrogen car-
ꢀ
rier (30 ml/min). The reaction was carried out at 275 C
ꢀ
at room temperature for 48 h and it was dried at 100 C
for 5 h. The reaction products were analyzed using a gas
for 24 h. The resulting yellow solid was finally calcined at
chromatograph equipped with a flame ionization detec-
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ꢀ
400 C for 5 h. The prepared mesoporous titania support
IP: 37.9.41.147 On: Wed, 0to8r M(Yaoru2ng0l1in7, 1Y4L:16610:401GC) and a capillary column (Agi-
was denoted as MT. XH PW O /MT catalysts with dif-
Copyright: American Scientific Publishers
3
12 40
lent, DB-5MS, 60 m × 0.32 mm). 1,4-Dioxane (Samchun
Chem.) was used as an internal standard for quantitative
calculation. Conversion of glycerin, selectivity for prod-
uct, and yield for product were calculated according to the
following equations.
ferent H3PW12O40 content (X, wt%) were then prepared
by an incipient wetness impregnation method. For this,
a known amount of tungstophosphoric acid (H3PW12O40ꢁ
was dissolved in distilled water, and pH of the solution
was adjusted to be 1.0 using hydrochloric acid. The solu-
tion containing H3PW12O40 was then added into MT sup-
port. The mixture was stirred and evaporated at 80 ꢀC. The
Conversion of glycerin (%)
mole of glycerin inlet−mole of glycerin outlet
ꢀ
=
×100
impregnated catalyst was dried at 100 C for 12 h, and
mole of glycerin inlet
ꢀ
it was calcined at 300 C for 5 h. The prepared catalysts
(1)
were denoted as XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ
and 30), where X represented the weight percentage of
H3PW12O40.
Selectivity for product (%)
mole of product outlet
=
×100
mole of glycerin inlet−mole of glycerin outlet
2.2. Characterization of Catalysts
(2)
H3PW12O40 contents in the XH3PW12O40/MT catalysts
were determined by inductively coupled plasma-atomic
emission spectrometry (ICP-AES) analyses (Shimadzu,
ICP-1000IV). Infrared spectra of the catalysts were
obtained with a Fourier transform infrared (FT-IR) spec-
trometer (Thermo Scientific, Nicolet 6700). X-ray diffrac-
tion (XRD) patterns of the catalysts were obtained by
XRD measurements (Rigaku, D-MAX2500-PC) using
Cu-Kꢂ radiation operated at 50 kV and 100 mA.
Nitrogen adsorption–desorption experiments (BEL Japan,
BELSORP-mini II) were conducted to examine the tex-
tural properties of the catalysts. Pore size distributions
mole of product outlet
Yield for product (%) =
×100
mole of glycerin inlet
(3)
3. RESULTS AND DISCUSSION
3.1. Characterization of XH3PW12O40/MT Catalysts
Figure 1 shows the FT-IR spectra of MT, H3PW12O40,
and XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) cat-
alysts. IR spectrum of MT was well consistent with
the result in the previous literature.18 H3PW12O40 exhib-
ited four characteristic IR bands appearing at 1080 cm−1
10830
J. Nanosci. Nanotechnol. 16, 10829–10834, 2016

Kang et al.
Dehydration of Glycerin Over H3PW12O40/TiO2
MT
MT
5H3PW12O40/MT
10H3PW12O40/MT
15H3PW12O40/MT
20H3PW12O40/MT
25H3PW12O40/MT
5H3PW12O40/MT
10H3PW12O40/MT
15H3PW12O40/MT
20H3PW12O40/MT
25H3PW12O40/MT
30H3PW12O40/MT
30H3PW12O40/MT
H3PW12O40
(x1/2)
(x1/6)
10
20
30
40
50
60
70
80
H3PW12O40
2 Theta (degree)
Figure 2. XRD patterns of MT, H3PW12O40, and XH3PW12O40/MT
(X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts.
2000 1800 1600 1400 1200 1000
800
exhibited type-IV isotherm with H2 hysteresis loop.
Nitrogen adsorption–desorption isotherms and pore size
distributions of XH3PW12O40/MT catalysts were similar to
those of MT support (not shown here), indicating that pore
structure of support was maintained even after the impreg-
nation of H3PW12O40 on the support. Surface area, pore
Wavenumber (cm–1
)
Figure 1. FT-IR spectra of MT, H3PW12O40, and XH3PW12O40/MT
(X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts.
(P–O band), 983 cm−1 (W
O
band), 890 cm−1
(W–Oc–W band), and 812 cm−1 (W–Oe–W band), cor-
responding to the primary structure of H3PW12O40.19
These four characteristic IR bands were not clearly
(a)
120
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3
IP: 37.9.41.147 On: Wed, 08 Mar 2017 14:16:41
20H3PW12O40/MT
observed in the 5H3PW12O40/MT and 10H3PW O40/MT
Copyright1:2American Scientific Publishers
30H3PW12O40/MT
90
60
30
0
catalysts because of low H3PW12O40 content. However,
the four characteristic IR bands were observed in the
15H3PW12O40/MT, 20H3PW12O40/MT, 25H3PW12O40/MT,
and 30H3PW12O40/MT catalysts. Moreover, peak inten-
sities of characteristic IR bands corresponding to
H3PW12O40 increased with increasing H3PW12O40 con-
tent. This result indicates that the primary structure of
H3PW12O40 was still maintained even after the impregna-
tion of H3PW12O40 on MT.
Figure 2 shows the XRD patterns of MT, H3PW12O40,
and XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30)
catalysts. The diffraction patterns of MT indicates that
MT retained an anatase structure.20 It was observed that
XH3PW12O40/MT catalysts with low H3PW12O40 load-
ing (X = 5ꢀ10ꢀ15ꢀ and 20) did not show character-
istic diffraction peaks for H3PW12O40, indicating that
H3PW12O40 was finely dispersed on the support. On the
other hand, XRD peaks for H3PW12O40 were observed
in the XH3PW12O40/MT catalysts with high H3PW12O40
loading (X = 25 and 30) due to aggregation of H3PW12O40.
Furthermore, intensity of XRD peaks for H3PW12O40
increased with increasing H3PW12O40 content, indicat-
ing that aggregation of H3PW12O40 was dominant with
increasing H3PW12O40 content.
0
0.2 0.4 0.6 0.8 1.0
Relative pressure(P/P0)
(b) 0.4
10H3PW12O40/MT
20H3PW12O40/MT
30H3PW12O40/MT
0.3
0.2
0.1
0
0
10
20
30
40
50
Pore size (nm)
Figure 3 shows the nitrogen adsorption–desorption
isotherms and pore size distributions of XH3PW12O40/MT
(X = 10ꢀ20ꢀ and 30) catalysts. XH3PW12O40/MT catalysts
Figure 3. (a) Nitrogen adsorption–desorption isotherms and (b) pore
size distributions of XH3PW12O40/MT (X = 10ꢀ20ꢀ and 30) catalysts.
J. Nanosci. Nanotechnol. 16, 10829–10834, 2016
10831

Dehydration of Glycerin Over H3PW12O40/TiO2
Kang et al.
Table I. Physicochemical properties of XH3PW12O40/MT catalysts.
H3PW12O40
Surface area
(m2/g)b
Pore volume
(cm3/g)c
Average pore
Brønsted acidity
(mmol-pyridine/g-cat.)
Lewis acidity
(mmol-pyridine/g-cat.)
Catalyst
content (wt%)a
diameter (nm)d
5H3PW12O40/MT
10H3PW12O40/MT
15H3PW12O40/MT
20H3PW12O40/MT
25H3PW12O40/MT
30H3PW12O40/MT
4ꢃ8
9ꢃ4
14ꢃ5
19ꢃ1
23ꢃ8
28ꢃ6
120ꢃ3
105ꢃ8
97ꢃ2
91ꢃ6
84ꢃ3
78ꢃ0
0ꢃ187
0ꢃ172
0ꢃ159
0ꢃ148
0ꢃ131
0ꢃ123
8ꢃ3
8ꢃ2
8ꢃ1
8ꢃ2
8ꢃ2
8ꢃ2
0ꢃ346
0ꢃ512
0ꢃ569
0ꢃ762
0ꢃ726
0ꢃ665
0ꢃ734
0ꢃ692
0ꢃ673
0ꢃ584
0ꢃ541
0ꢃ503
Notes: aDetermined by ICP-AES measurement; bCalculated by BET equation; cBJH desorption pore volume; dBJH desorption average pore diameter.
volume, and average pore diameter of H3PW12O40/MT
catalysts are summarized in Table I. It was found that sur-
face area and pore volume of XH3PW12O40/MT catalysts
decreased with increasing H3PW12O40 content. However,
average pore diameter of XH3PW12O40/MT catalysts was
almost the same. It was also observed that H3PW12O40
contents in the XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ
and 30) catalysts were well consistent with the designed
values, indicating that all the catalysts were successfully
prepared in this work.
It was found that Brønsted acidity of the catalysts
showed a volcano-shaped trend with respect to H3PW12O40
content. Among the catalysts tested, 20H3PW12O40/MT
retained the largest Brønsted acidity. It has been reported
in the previous literature23 that acidity of H3PW12O40
impregnated on silica support did not increase in propor-
tion to H3PW12O40 which possessed pure Brønsted acid
sites. It has also been reported that acidity of impregnated
catalysts with high H3PW12O40 content decreased, because
H3PW12O40 agglomerates were caged in the pore walls
and blocked the pores, leading to a decreased amount of
H3PW12O40 exposed on the surface and leading to poor
diffusion of reactant onto the acid sites.23ꢀ24 In this work,
formation of H3PW12O40 aggregates was also observed
in the XH3PW12O40/MT catalysts with high H3PW12O40
3.2. Acid Properties of XH3PW12O40/MT Catalysts
In order to investigate the acid properties of
XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts,
pyridine-adsorbed in-situ FT-IR spectroscopy measure-
Delivered by Ingenta to: State University of New York at Binghamton
loading. Therefore, it can be inferred that Brønsted acidity
IP: 37.9.41.147 On: Wed, 08 Mar 2017 14:16:41
of XH3PW12O40/MT catalysts exhibited a volcano-shaped
adsorbed in-situ FT-IR spectra ofCoXpHyrigPWht: AOme/MricTan Scientific Publishers
ments were carried out. Figure 4 shows the pyridine-
3
12 40
trend with respect to H3PW12O40 content due to restricted
exposure of H3PW12O40 and diffusional restraint of pyri-
dine. Moreover, it was also found that Lewis acidity of
the catalysts decreased with increasing H3PW12O40 con-
tent. It is believed that surface Ti4+ cations, which served
as Lewis acid sites, were blocked by the impregnated
H3PW12O40 species.
catalysts. IR bands were assigned according to the previ-
ous study.21 All the XH3PW12O40/MT catalysts exhibited
IR bands due to Lewis acid-bound pyridine (1450 and
1490 cm−1ꢁ and Brønsted acid-bound pyridinium ion (1490
and 1545 cm−1ꢁ. Brønsted acidity and Lewis acidity of
XH3PW12O40/MT catalysts were quantitatively measured
according to the method in the literature22 as summarized
in Table I.
3.3. Catalytic Performance of XH3PW12O40/MT
Catalysts
L
Figure 5 shows the conversion of glycerin and yield for
acrolein over XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and
30) catalysts with time on stream in the dehydration of
B+L
5H3PW12O40/MT
10H3PW12O40/MT
B
L
L
B+L
ꢀ
B
B
glycerin at 275 C. Conversion of glycerin, selectivity for
product, and yield for acrolein after a 5 h-reaction are
summarized in Table II. According to the literature,10 cat-
alytic dehydration of glycerin follows consecutive reaction
pathways. Acid catalyst initiates the formation of primary
and secondary carbocations, and the secondary carboca-
tion is more stable than primary carbocation due to the
thermodynamic effect. Thus, acrolein formed through two-
step dehydration via secondary carbocation was a main
product, while hydroxyacetone formed from primary car-
bocation was a major by-product. Other compounds such
as allyl alcohol, acetaldehyde, acetic acid, and acetone
were produced as minor by-products in the dehydration of
glycerin.7ꢀ8
B+L
B+L
15H3PW12O40/MT
20H3PW12O40/MT
25H3PW12O40/MT
B
B
L
B+L
B+L
L
L
B
30H3PW12O40/MT
1600
1550
1500
1450
1400
Wavenumber (cm–1
)
Figure 4. Pyridine-adsorbed in-situ FT-IR spectra of XH3PW12O40/MT
(X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts.
10832
J. Nanosci. Nanotechnol. 16, 10829–10834, 2016

Kang et al.
Dehydration of Glycerin Over H3PW12O40/TiO2
(a)
70
65
60
55
50
45
100
20H3PW12O40/MT
95
90
85
80
75
70
25H3PW12O40/MT
30H3PW12O40/MT
15H3PW12O40/MT
5H3PW12O40/MT
10H3PW12O40/MT
10H3PW12O40/MT
15H3PW12 40
20H3PW12 40
25H3PW12 40
30H3PW12 40
O
O
O
O
/MT
/MT
/MT
/MT
5H3PW12O40/MT
60
120
180
240
300
Time on stream (min)
0.3
0.4
0.5
0.6
0.7
0.8
(b)
100
90
80
70
60
50
40
Brønsted acidity (mmol-pyridine/g-cat.)
5H3PW12O40/MT
10H3PW12O40/MT
15H3PW12 40
20H3PW12 40
25H3PW12 40
30H3PW12 40
Figure 6. A correlation between yield for acrolein after a 5 h-reaction
over XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts and
Brønsted acidity of the catalysts.
O
O
O
O
/MT
/MT
/MT
/MT
stream. Furthermore, the calculated carbon balance after
the 5 h-reaction (Table II) was less than 100% due to
carbon deposition derived from polymerization of acrolein
and oligomerization of glycerin.25ꢀ26
It was revealed that yield for acrolein increased in
the order of 5H3PW12O40/MT < 10H3PW12O40/MT <
60
120
180
240
300
15H3PW12O40/MT
<
30H3PW12O40/MT
<
Time on stream (min)
Delivered by Ingenta to: State University of New York at Binghamton
25H3PW12O40/MT < 20H3PW12O40/MT. This trend
of yield for acrolein over XH3PW12O40/MT (X =
5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts was closely related
to the Brønsted acidity of the catalysts. Figure 6 shows
the correlation between yield for acrolein after a 5 h-
reaction over XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ
and 30) catalysts and Brønsted acidity of the catalysts.
It is interesting to note that yield for acrolein increased
with increasing Brønsted acidity of the catalysts, in
good agreement with the previous works.27ꢀ28 In case of
Brønsted acid sites, proton can be easily transferred to
internal oxygen of glycerin due to the absence of steric
hindrance. Therefore, Brønsted acid sites mainly protonate
the internal oxygen of glycerin, leading to the formation of
acrolein via secondary carbocation. However, interaction
IP: 37.9.41.147 On: Wed, 08 Mar 2017 14:16:41
Figure 5. (a) Conversion of glycerin and (b) yield for acrolein over
Copyright: American Scientific Publishers
XH3PW12O40/MT (X = 5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts with time on
stream in the dehydration of glycerin at 275 ꢀC.
It was observed that the catalytic performance of
XH3PW12O40/MT catalysts gradually decreased with
time on stream during the 5 h-reaction. The spent
XH3PW12O40/MT catalysts were collected after the 5 h-
reaction and investigated by CNHS analyses. The amount
of carbon deposition in the spent XH3PW12O40/MT cat-
alysts determined by CHNS analyses is summarized in
Table II. It is believed that carbonaceous materials formed
during the dehydration reaction blocked the active sites of
the catalysts, resulting in catalyst deactivation with time on
Table II. Conversion of glycerin, selectivity for product, yield for acrolein, carbon balance, and amount of carbon deposition over XH3PW12O40/MT
catalysts after a 5 h-reaction.
Selectivity for product (%)
Conversion of
glycerin (%) Acrolein
Hydroxy-
acetone
Acetal-
Yield for
Carbon balance
(%)
Amount of
carbon deposition (%)
Catalyst
Ally alcohol dehyde Othersa acrolein (%)
5H3PW12O40/MT
10H3PW12O40/MT
15H3PW12O40/MT
20H3PW12O40/MT
25H3PW12O40/MT
30H3PW12O40/MT
83ꢃ4
85ꢃ4
88ꢃ7
91ꢃ7
87ꢃ3
86ꢃ1
59ꢃ7
63ꢃ5
66ꢃ1
71ꢃ3
71ꢃ9
70ꢃ4
8ꢃ3
8ꢃ2
7ꢃ4
6ꢃ5
5ꢃ8
5ꢃ9
2ꢃ5
3ꢃ1
3ꢃ4
3ꢃ0
2ꢃ6
2ꢃ8
1ꢃ6
1ꢃ4
1ꢃ9
1ꢃ8
2ꢃ3
2ꢃ1
19ꢃ3
16ꢃ9
16ꢃ6
12ꢃ9
11ꢃ6
12ꢃ6
49ꢃ8
54ꢃ2
58ꢃ7
65ꢃ4
62ꢃ8
60ꢃ7
91ꢃ4
93ꢃ1
95ꢃ4
95ꢃ5
94ꢃ2
93ꢃ8
3ꢃ7
4ꢃ3
4ꢃ5
5ꢃ3
5ꢃ0
4ꢃ6
Note: aOthers contain acetic acid, acetone, and several unidentified products.
J. Nanosci. Nanotechnol. 16, 10829–10834, 2016
10833

Dehydration of Glycerin Over H3PW12O40/TiO2
Kang et al.
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20H3PW12O40/MT catalyst with largest Brønsted acidity
showed the highest yield for acrolein. Thus, Brønsted
acidity of the catalysts played an important role in the
catalytic dehydration of glycerin to acrolein.
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4. CONCLUSIONS
Gas-phase dehydration of glycerin to acrolein was carried
out over H3PW12O40 catalysts supported on mesoporous
titania (XH3PW12O40/MT) with different H3PW12O40 con-
tent (X, wt%). Yield for acrolein over XH3PW12O40/MT
catalysts showed a volcano-shaped trend with respect
to H3PW12O40 content. Brønsted acidity of the cata-
lysts determined from pyridine-adsorbed in-situ FT-IR
spectroscopy also exhibited a volcano-shaped trend with
respect to H3PW12O40 content. It was revealed that
the catalytic performance of XH3PW12O40/MT (X =
5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts in the dehydration of
glycerin was closely related to the Brønsted acidity of the
catalysts. Yield for acrolein over XH3PW12O40/MT (X =
5ꢀ10ꢀ15ꢀ20ꢀ25ꢀ and 30) catalysts increased with increas-
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IP: 37.9.41.147 On: Wed, 08 Mar 2017 14:16:41
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Brønsted acidity of the catalysts served as a key factor
determining the catalytic performance in the dehydration
of glycerin to acrolein.
Copyright: American Scientific Publishers
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Received: 9 July 2015. Accepted: 17 February 2016.
10834
J. Nanosci. Nanotechnol. 16, 10829–10834, 2016