Understanding the deactivation behavior of Pt/WO3/Al2O3 catalyst in the glycerol hydrogenolysis reaction

Article abstract of DOI:10.1016/S1872-2067(20)63549-5

The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both improving the profitability of biodiesel and valorization of biomass. While intensive research efforts have been devoted to enhancing the catalytic activity and selectivity, little is focused on the stability although the latter is of paramount importance to practical applications. In this work, we investigated the stability of Pt/WO₃/Al₂O₃ and observed a continuous deactivation trend during a 700 h time-on-stream run. Neither the leaching of active W nor the coking was responsible for the deactivation. Instead, XRD, HAADF-STEM and CO chemisorption results clearly showed the occurrence of significant aggregation of Pt particles, which caused a remarkable decrease of Pt-WO_x interfacial sites. As a consequence, strong Br?nsted acid sites which were in situ formed by H₂ dissociation at the Pt-WO_x interfacial sites were reduced, leading to the deactivation of the catalyst.

Full text of DOI:10.1016/S1872-2067(20)63549-5

Chinese Journal of Catalysis 41 (2020) 1261–1267
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Understanding the deactivation behavior of Pt/WO
in the glycerol hydrogenolysis reaction
3
/Al
2
O catalyst
3
a,b
a
a
a
a
a,
a
Nian Lei , Zhili Miao , Fei Liu , Hua Wang , Xiaoli Pan , Aiqin Wang *, Tao Zhang
a
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
University of Chinese Academy of Sciences, Beijing 100049, PR China
b
A R T I C L E I N F O
A B S T R A C T
Article history:
The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both
improving the profitability of biodiesel and valorization of biomass. While intensive research efforts
have been devoted to enhancing the catalytic activity and selectivity, little is focused on the stability
although the latter is of paramount importance to practical applications. In this work, we investi-
Received 15 November 2019
Accepted 19 December 2019
Published 5 August 2020
gated the stability of Pt/WO
3
/Al
2
O and observed a continuous deactivation trend during a 700 h
3
time-on-stream run. Neither the leaching of active W nor the coking was responsible for the deacti-
vation. Instead, XRD, HAADF-STEM and CO chemisorption results clearly showed the occurrence of
Keywords:
Glycerol
Hydrogenolysis
significant aggregation of Pt particles, which caused a remarkable decrease of Pt-WO
sites. As a consequence, strong Brönsted acid sites which were in situ formed by H dissociation at
the Pt-WO interfacial sites were reduced, leading to the deactivation of the catalyst.
x
interfacial
2
1,3-propanediol
x
Deactivation
Aggregation/agglomeration
©
2020, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1
.
Introduction
Glycerol, as a byproduct in the production of biodiesel, is
ondary C–O bond of glycerol, bi-functional catalysts which are
comprised of a noble metal like Pt, Ir, Rh and an acidic metal
oxide such as WO
example, Ir-ReO /SiO
Tomishige and coworkers, could afford 1,3-PDO yield of 38% at
81% glycerol conversion at 120 °C and 8 MPa H . Nevertheless,
x
and ReO
x
have been developed [6–40]. For
being considered as an ideal renewable feedstock for produc-
tion of high-value important chemicals due to its availability at
large volume and low cost [1,2]. Among various potential
products from glycerol, 1,3-propanediol (1,3-PDO) is the most
important one as it has been widely used as the monomer for
x
2
catalyst, which was first reported by
2
such a good performance was only achieved with the promo-
+
tion of liquid sulfuric acid (H /Re = 1) [6,7], which would cause
production of polytrimethylene terephthalate (PTT),
a
equipment corrosion and environmental problems. Compared
high-performance polyester [3,4]. For glycerol transformation
into 1,3-PDO, it is required to selectively cleave the secondary
C–O bond. The steric hindrance, however, along with the simi-
lar reactivities between primary and secondary –OH groups,
poses a significant challenge for the selective hydrogenolysis of
glycerol to 1,3-PDO [5]. In order to selectively cleave the sec-
with Ir-ReO
x
system [6–16], Pt-WO based catalysts have
x
shown a greater potential for practical applications because
they could give promising 1,3-PDO selectivity (40%‒70%) at
moderate glycerol conversions without addition of any pro-
moters [19–34]. Moreover, the activity and selectivity of the
Pt-WO combination can be tuned by interaction with the oxide
x
*
Corresponding author. Tel: +86-411-84379348; Fax: +86-411-84685940; E-mail: aqwang@dicp.ac.cn
This work was supported by the National Key Projects for Fundamental Research and Development of China (2018YFB1501600), the National Natu-
ral Science Foundation of China (21690080, 21690084, 21721004, 21673228), the Strategic Priority Research Program of the Chinese Academy of
Sciences (XDB17020100), DNL Cooperation Fund (DNL180303), CAS and DICP ZZBS 201612.
DOI: 10.1016/S1872-2067(20)63549-5 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 41, No. 8, August 2020

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Nian Lei et al. / Chinese Journal of Catalysis 41 (2020) 1261–1267
support as well as the preparation procedures. For example,
Pt/WO /ZrO catalyst was reported in 2008 to show 1,3-PDO
yield up to 24% in DMI (1,3-dimethyl-2-imidazolidinone) sol-
vent at 170 °C [19]. Quite different from this early report, later
studies revealed that water was the best solvent, and
liquid pump, affording a liquid-hour space velocity (LHSV) of 1
‒1
3
2
h , while H was co-fed at a flow rate of 33 mL/min, corre-
2
‒1
sponding to a gas-hour space velocity (GHSV) of 1000 h . The
effluent gas and liquid were separated by a condenser, and the
liquid product was sampled at a certain interval and then ana-
lyzed on a gas chromatograph (Agilent 7890B) equipped with
an HP-INNO WAX capillary column (30 m × 0.32 mm × 0.5 µm)
and FID detector using n-butanol as internal standard. The
conversion of glycerol and the selectivity of products were cal-
culated based on the following equations:
Pt/WO
tion was conducted in water at 130 °C and 4 MPa H
doping a suitable amount of Mn, the turnover frequency of
,3-PDO could be increased by 2.6 times than the non-doped
Pt/WO /ZrO catalyst [21]. In addition to Pt/WO /ZrO system,
other catalysts systems have also been investigated for the
reaction, including Pt/WO /TiO /SiO [22,23], Pt/WO /Al
24–26], Pt/W-SBA-15 [27], Pt-WO /SAPO-34 [28], and even
system [30–33]. Among them,
3
/ZrO
2
could gave 1,3-PDO yield of 32% when the reac-
2
[20]. By
1
3
2
3
2
Conversion of glycerol (%) = (mole of glycerol in – mole of
glycerol out) / (mole of glycerol in)  100%.
Selectivity (%) = (mole of carbon in specific product) /
(mole of carbon in consumed glycerol)  100%.
3
2
2
3
O
2 3
[
x
non-supported Pt-WO
x
Pt/WO
yield of 66% after reaction at 180 °C and 5 MPa H
34].
Although intensive efforts have been invested towards en-
hancing the catalytic activity and 1,3-PDO selectivity, little at-
tention has been paid to the catalyst stability. In fact, catalyst
durability is a paramount factor to be considered for practical
applications. In this work, we investigated the stability of
3
/AlOOH showed the best performance, giving 1,3-PDO
2
for 12 h
2.3. Characterization
[
Nitrogen adsorption-desorption measurements were con-
ducted at −196 °C on a Micromeritics ASAP 2460 instrument.
Before the measurements, the sample was firstly dehydrated at
110 °C for 1 h and then degassed at 300 °C for at least 4 h. The
specific surface areas (ABET) were calculated from the N
ad-
2
Pt/WO
3
/Al
2
O
3
catalyst during the long-term continuous reac-
sorption isotherm with BET equation, and the pore size distri-
butions were obtained using desorption branch of the iso-
therms and BJH method.
tion, and observed a clear deactivation trend. By characteriza-
tion of both fresh and spent catalysts using X-ray diffraction
(
XRD), chemical adsorption, High-angle annular dark-field
Powder XRD patterns of the reduced samples were acquired
on a PW3040/60 X’Pert PRO (PANalytical) diffractometer
scanning transmission electron microscopy (HAADF-STEM),
thermogravimetric (TG), as well as 2-butanol dehydra-
tion/dehydrogenation as the probe reaction, we are able to
provide an insightful understanding of the deactivation behav-
ior.
equipped with a Cu K radiation source (λ = 0.15432 nm) oper-
α
ated at 40 kV and 40 mA, in the 2θ range from 10° to 80°.
HAADF-STEM images were obtained on a JEM-2100F
transmission electron microscope operated at 200 kV and
equipped with EDS microanalysis system. The reduced powder
sample was ultrasonically dispersed into ethanol solvent and
deposited on a holey carbon/copper TEM grid prior to the ob-
servations.
2
.
Experimental
2
.1. Catalyst preparation
CO chemisorption and temperature-programmed oxidation
(TPO) were conducted on a Micromeritics AutoChem II 2920
chemisorber. In CO chemisorption measurements, the samples
The Pt/WO
3
/Al
2
O
3
catalyst was prepared by a sequential
impregnation method according to our previous report [26]. In
brief, WO
3
was first supported on a home-made alumina (ABET
=
were first pre-reduced at 300 °C under a stream of pure H
for
2
2
151 m /g) with ammonium metatungstate (AMT) as the pre-
1 h, and then purged under He gas flow for 30 min at 310 °C.
After being cooled down to 50 °C, pulses of 5% CO/He were
introduced to the reactor for CO chemisorption until saturation
was reached.
In TPO measurements, the spent catalyst was first treated at
150 °C under He for 1 h. After being cooled down to 40 °C, the
cursor followed by calcination at 700 °C for 3 h. Then, Pt was
loaded onto the as-prepared WO /Al by using hydrochloro-
platinic acid (H PtCl ·6H O) as the precursor. After drying at
10 °C for 12 h and calcination in air at 300 °C for 3 h, the
Pt/WO /Al catalyst was obtained. ICP analysis showed the
loadings of W and Pt were 9.1 wt% and 4.6 wt%, respectively.
3
O
2 3
2
6
2
1
3
O
2 3
2
sample was heated from 40 to 800 °C in 2% O /He at ramp of
1
0 °C/min, while the consumed O and the oxidative products
2
2
.2. Reaction test
were online monitored by a mass spectrometer system.
Thermogravimetric (TG) analysis was performed on a SDT
Q600 analyser in a flowing air (100 mL/min) at a heating rate
of 10 °C/min up to 900 °C.
The reaction for glycerol hydrogenolysis was conducted in a
fixed-bed reaction system at 180 °C and 5 MPa H . Prior to the
2
reaction, the catalyst sample (2.0 mL, 20–40 mesh) was loaded
into a stainless steel reactor (400 mm  9 mm) at the center
position between two beds of quartz sands, and then was in
The dehydration/dehydrogenation of 2-butanol was used as
a model reaction to probe the acid sites of the catalysts, which
was carried out at 140 °C in a quartz flow reactor. Prior to the
situ reduced in flowing H
desired temperature (180 °C), an aqueous solution of glycerol
50 wt%) was fed into the reactor through a high-pressure
2
at 300 °C for 1 h. After cooling to the
reaction test, the sample (0.030 g) was reduced in flowing H
(20 mL/min) at 300 °C for 1 h. After being cooled down to the
reaction temperature, liquid 2-butanol was bubbled with flow-
2
(

Nian Lei et al. / Chinese Journal of Catalysis 41 (2020) 1261–1267
1263
ing N
0 °C. Reactant and product concentrations were measured by
Agilent 7890B GC with a HP-INNO WAX capillary column (30 m
0.32 mm × 0.5 µm, FID detector). The conversion of 2-butanol
and the selectivity of products were calculated based on the
following equations:
2
or H
2
(20 mL/min) into the reaction system at 1 bar and
This result suggests that the activity for cleaving the secondary
C–O bond had a gradual decrease, if it is assumed that at least a
part of 1-PO results from cleavage of the secondary C–O bond
of 1,2-PDO [41]. Overall, the glycerol conversion dropped by
more than half in the whole process, from the initial 57.5% to
25.1% at 700 h.
6
×
Conversion of 2-butanol (%) = (mole of 2-butanol in – mole
of 2-butanol out) / (mole of 2-butanol in)  100.
Selectivity (%) = (mole of specific product) / (mole of con-
sumed 2-butanol)  100.
In order to understand the mechanism for the deactivation
behavior, both the fresh and spent catalysts were character-
ized. First, the textural properties of the catalysts were ana-
lyzed. As shown in Fig. 2 and Table 1, the adsorp-
tion-desorption isotherms of the spent catalyst are almost
identical to the fresh one; the BET surface area, the pore vol-
ume, and the pore size distribution kept essentially unchanged
after the long-term reaction. This result clearly indicated that
the deactivation was not caused by the textural change of the
3.
Results and discussion
To better assess the potential for practical applications, we
here evaluated the catalyst using a relatively high concentra-
tion of glycerol solution, which is distinct from most of the pre-
vious reports where an extreme dilute glycerol solution was
used as the feedstock [34–40]. Fig. 1(a) shows the glycerol
conversion and product selectivity with time on stream for a
continuous running of 700 h. The catalyst exhibited a high ini-
tial activity and promising 1,3-PDO selectivity, with glycerol
conversion of 57.5% and 1,3-PDO selectivity of 40.4%, which
was similar to our previous reports [26]. Besides the target
product 1,3-PDO, there were also 1,2-PDO, 1-propanol (1-PO)
and 2-propanol (2-PO) whose initial selectivities were 6.3%,
support, confirming that the WO
endure the hydrothermal conditions. It was reported that the
doping of WO or TiO on the alumina supports can greatly
3
/Al
2
O was robust enough to
3
3
2
improve their hydrothermal stability [42–45], in agreement
with our present finding.
Subsequently, elemental analysis was performed to check
whether the active components were leached out during the
long-term reaction. As shown in Table 1, both the Pt and the W
contents had a slight decrease after the long-term reaction. In
particular, the W content dropped more obviously, from 9.1 to
7.8 wt%, a decrease by 14%. The reason of W leaching is not
3
1
6.7%, and 11.5%, respectively. The much higher selectivity of
,3-PDO than 1,2-PDO suggests that the catalyst possesses the
clear yet, it might be related with the ligating interaction of WO
x
higher intrinsic activity for cleaving the secondary C–O bond
than the primary C–O bond. However, the glycerol conversion
declined remarkably with the time on stream, from the initial
with glycerol [24]. In order to figure out if the leaching of W
component was responsible for the deactivation of the catalyst,
we further analyzed the W concentration in the liquid product
at various reaction time. As shown in Table 2, the deactivation
rate could be hardly correlated with the W leaching, suggesting
that the loss of W during the reaction was not the dominant
57.5% to 44.9% at 100 h. The deactivation rate can be further
estimated by fitting the data with three-stage lines (Fig. 1(b)).
The first-stage line fits to the initial reaction time of 100 h,
which has the highest slope, corresponding to a deactivation
rate of 0.111 %/h. After that, the catalyst began to deactivate at
a slower rate, 0.037 %/h, until the time on stream for 600 h. In
the last stage from 600 to 700 h, the glycerol conversion ap-
peared stable. Contrary to the obvious drop of glycerol conver-
sion in the initial stage, the 1,3-PDO selectivity kept rather sta-
ble over the whole reaction duration. Interestingly, the selec-
tivity of 1,2-PDO had a gradual increase with the reaction time,
and as a consequence, the selectivity of 1-PO decreased slightly.
reason for the deactivation of the Pt/WO
ertheless, the continuous leaching of W might cause the aggre-
gation of Pt nanoparticles due to the destruction of Pt-WO
3
/Al
2
O catalyst. Nev-
3
x
interaction to some extent. It should also be noted that we did
not detect any Pt species in the liquid product, indicating that
Pt was not leached out during the reaction.
The XRD patterns of the fresh and spent catalysts are shown
in Fig. 3. In addition to the three peaks assigned to reflections of
o
γ-Al
2
O
3
, a new peak at 2θ = 39.8 assignable to reflection of Pt
(
a) 60
(b) 60
Regeneration
(
1)
Conv.
5
4
3
2
1
0
0
0
0
0
0
50
1
,3-PDO Sel.
40
30
20
10
0
(2)
(
1) y = -0.111x + 57.5
(3)
1
-PO Sel.
2
R = 0.90
1
,3-PDO Yield
(2) y = -0.037x + 49.8
2
R = 0.96
2
-PO Sel.
(3) y = -0.002x + 26.9
2
R = 0.09
1
,2-PDO Sel.
0
100
200
300
400
500
600
700
0
100
200
300
400
500
600
700
Time on stream (h)
Time on stream (h)
Fig. 1. Stability test of Pt/WO
Fitting of the deactivation curve with three-stage lines. Reaction conditions: 180 °C, 5.0 MPa H
LHSV = 1.0 h‒1
3
/Al
2
O catalyst for glycerol hydrogenolysis. (a) Glycerol conversion and products selectivity with time on stream; (b)
3
‒1
2
, 50 wt% glycerol aqueous solution, GHSV = 1000 h ,
.

1264
Nian Lei et al. / Chinese Journal of Catalysis 41 (2020) 1261–1267
1
1
50
20
(
a)
(b)
Fresh
Spent
Fresh
Spent
9
6
3
0
0
0
0
.0
0.2
0.4
0.6
0.8
1.0
0
10
20
30
40
50
Relative pressure (P/P0)
Pore diameter (nm)
Fig. 2. Adsorption-desorption isotherms (a) and BJH pore size distributions (b) of fresh and spent Pt/WO
3
/Al
2
O catalysts.
3
Table 1
Physical and chemical properties of the fresh and spent Pt/WO
/Al O
3 2 3
catalysts.
2
3
a
c
Sample
Fresh
Spent
A
BET (m /g) Pore volume (cm /g) Pore size (nm) Pt content a (wt%) W content (wt%) CO uptake b (μmol/g) Dispersion (%)
127
139
0.21
0.21
5.4
5.1
4.6
4.2
9.1
7.8
68.6
21.7
29.1
10.1
a
Detected by ICP-AES. b Detected by CO chemisorption. c Determined by CO uptake based on CO/Pt = 1.
(
111) appeared in the spent catalyst whereas it was absent in
that the images of Pt and W were well overlapped (Fig. 4(e) and
(f)), suggesting that most of the Pt species were still dispersed
the fresh catalyst. The emergence of this peak in the spent cat-
alyst suggested the occurrence of aggregation/agglomeration
of Pt particles during the long-term reaction. The HAADF-STEM
images in Fig. 4 further confirmed this point. In accordance
with our previous report [26], the Pt nanoparticles were finely
on the WO after the long-term reaction.
x
Chemisorption of CO is very useful to quantitatively meas-
ure the change of Pt dispersion. The data in Table 1 revealed
that the fresh catalyst had a CO uptake of 68.6 μmol/g, corre-
sponding to the Pt dispersion of 29.1% if assuming CO/Pt mo-
lar ratio of 1/1 [46]. After the reaction it dropped down to 21.7
dispersed onto the WO
3
/Al
2
O support, with a mean size of 1.9
3
nm (Fig. 4(a) and (b)). After the reaction, the growth of Pt par-
ticles are prominent, with the formation of some irregu-
lar-shaped large particles (Fig. 4(c) and (d)). The mean particle
size of the spent catalyst is 3.1 nm. Since Pt and W have close
atomic number, it is difficult to distinguish Pt and W from
HAADF-STEM images. Then we conducted elemental mapping
of Pt and W in the spent catalyst using EDS. The result showed
Table 2
W concentration in the liquid product at various time as well as the
deactivation rate.
Sample
W concentration (10‒6
)
Deactivation rate (%/h)
100 h
200 h
300 h
400 h
0.54
0.71
0.85
0.94
0.111
0.037
0.037
0.037
.

Pt
Al O
.
2
3
Spent
Fresh



1
0
20
30
40
50
60
70
80
Fig. 4. HAADF-STEM images and Pt particle size distributions of
2 (degree)
Pt/WO /Al O
3 2 3
catalyst before (a, b) and after (c, d) stability test, as well
/Al catalyst after stability test (e, f).
as EDS analysis of Pt/WO
3
O
2 3
Fig. 3. XRD patterns of the fresh and spent Pt/WO
3
/Al
O
2 3
catalysts.

Nian Lei et al. / Chinese Journal of Catalysis 41 (2020) 1261–1267
1265
0.05
(b)
1
00 (a)
Weight (%)
Deriv. Weight (%/ C)
o
9
9
0.04
9
8
Mass 18
Mass 44
Mass 32
0.03
97
3.6%
96
0.02
95
0.01
94
93
0.00
00 200 300 400 500 600 700 800 900
1
100
200
300
400
500
600
700
800
Temperature (°C)
Temperature (°C)
Fig. 5. TG (a) and TPO (MS signal) (b) profiles of the spent Pt/WO
3
/Al catalyst.
2
O
3
μmol/g and the Pt dispersion decreased to 10.1%. This result is
in good agreement with the HAADF-STEM, pointing to the oc-
currence of significant aggregation/agglomeration of Pt nano-
particles. Consequently, the surface Pt sites decreased, result-
ing in the activity decline.
above characterizations that neither the W leaching nor the
coking could be responsible for the continuous deactivation of
the Pt/WO
tion/agglomeration of Pt nanoparticles decreased the interfa-
cial sites between Pt and WO , which most likely decreased the
/Al O
3 2 3
catalyst; instead, the aggrega-
x
In addition to the aggregation of Pt particles, coking is an-
other possible reason for deactivation. To address this issue,
we performed TG analysis and TPO for the spent catalyst. As
shown in Fig. 5(a), there are two weight-loss stages in the TG
profile. The first weight loss (1.5 wt%) occurred below 150 °C
due to the evaporation of physically adsorbed water on the
surface. The second weight loss (3.6 wt%) occurred between
number of the strong Brönsted acid sites. In order to prove this
point, we subsequently used 2-butanol dehydration and dehy-
drogenation as the probe reaction to study the change of strong
Brönsted acid sites before and after the reaction [49,50]. As
shown in Fig. 6, in N atmosphere, the 2-butanol mainly un-
2
derwent dehydrogenation reaction to form 2-butanal, and de-
hydration reaction occurred only to a minor extent. Compared
to the fresh catalyst on which dehydrogenation/dehydration
ratio was about 4/1, the spent catalyst led to a greater dehy-
drogenation/dehydration ratio (10/1), indicating the growth of
Pt particles caused the decrease of Brönsted acid sites and thus
decreased the dehydration activity. When the reaction pro-
200–500 °C, which can be ascribed to combustion of coke on
the surface. Benjamin et al. studied the chemical nature of the
coke which was formed in the glycerol dehydration, and found
that the coke was aromatic and aliphatic C
The TPO profile of the spent catalyst (Fig. 5(b)) showed that
both H O and CO were formed at 320 °C, confirming that the
coke contained both C and H. Nevertheless, after removing the
coke by feeding 3% O /He to the spent catalyst at 500 °C for 3
h, the activity was not recovered; instead, it dropped further
Fig. 1(a)). This result suggests that coking is not the major
H O
x y z
species [47].
2
2
ceeded in H
dominated, indicating that new strong Brönsted acid sites were
created in H . Moreover, compared with the fresh catalyst, the
2
, dehydration, instead of dehydrogenation, became
2
2
dehydration activity of the spent catalyst decreased almost by
50%, showing a strong implication that the growth of Pt parti-
cles brought about a sharp decrease of the in situ formed
strong Brönsted acid sites. As a consequence, the activity for
cleaving the second C–O bond decreased. This result demon-
strated that the reaction for glycerol hydrogenolysis to 1,3-PDO
is structure-sensitive, and the high dispersion of Pt is a prereq-
uisite for obtaining the high 1,3-PDO yield.
(
reason for the catalyst deactivation, in agreement with the lit-
erature reports [37,48].
Based on the mechanism understanding of the glycerol hy-
drogenolysis, the formation of 1,3-PDO is closely related to the
strong Brönsted acid, which is in situ formed via hydrogen dis-
sociation at Pt-WO interface [26,32]. We have known from the
x
100
N2 metal
N2 acid
H2 metal
H2 acid
80
60
40
20
0
Fresh
Spent
Fresh
Spent
Fig. 6. The performance of 2-butanol dehydration/dehydrogenation in the presence of N
2
or H
2
over both fresh and spent Pt/WO
3
/Al
2
O catalysts.
3

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Nian Lei et al. / Chinese Journal of Catalysis 41 (2020) 1261–1267
4
.
Conclusions
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1
[
[
[
[
In summary, long-term stability is of paramount importance
for practical applications of glycerol hydrogenolysis into
,3-PDO. Pt/WO /Al is one of the most active and selective
1
3
O
2 3
2
015, 410, 81–88.
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750–1758.
catalysts for this reaction, however, its long-term stability is not
satisfactory. By using various techniques, we for the first time
revealed that the aggregation/agglomeration of Pt nanoparti-
cles took place with time on stream, and it caused significant
decrease of Pt dispersion. As a result, the interfacial sites be-
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Graphical Abstract
Chin. J. Catal., 2020, 41: 1261–1267 doi: 10.1016/S1872-2067(20)63549-5
Understanding the deactivation behavior of Pt/WO
catalyst in the glycerol hydrogenolysis reaction
/Al O
3 2 3
Nian Lei, Zhili Miao, Fei Liu, Hua Wang, Xiaoli Pan, Aiqin Wang *,
Tao Zhang
Dalian Institute of Chemical Physics, Chinese Academy of Sciences;
University of Chinese Academy of Sciences
A continuous deactivation trend was observed during the stability
test of glycerol hydrogenolysis over Pt/WO
/Al O
3 2 3
catalyst. Char-
acterization results suggested that the aggregation of Pt particles
and decrease of Pt-WO
deactivation.
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interfacial sites were responsible for the

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[
甘油氢解反应中Pt/WO /Al O 催化剂的失活行为
3
2
3
a,b
a
a
a
a
a,*
a
雷 念 , 苗治理 , 刘 菲 , 王 华 , 潘晓丽 , 王爱琴 , 张 涛
a
中国科学院大连化学物理研究所, 催化基础国家重点实验室, 辽宁大连116023
b
中国科学院大学, 北京100049
摘要: 随着生物柴油产业的高速发展, 其副产物甘油大量过剩, 亟需寻找高效的甘油高值化利用途径来提高整个生物柴油
产业链的经济性. 在各种甘油转化路线中, 甘油选择性氢解制备1,3-丙二醇可用作高端聚酯PTT的单体, 因而成为最具应用
潜力的高质化路线之一. 同时, 该反应涉及到仲羟基的选择性脱除, 对其它生物质加氢脱氧反应也具有普遍意义. 目前, 在
提高甘油氢解反应活性和1,3-丙二醇选择性方面已经做了大量的研究工作, 但是关于催化剂稳定性的研究却鲜有报道, 而
3 2 3
后者对于整个过程的工业应用是必不可少的. 鉴于此, 我们以Pt/WO /Al O 为催化剂, 在连续运行的固定床反应器上对其
甘油氢解反应的长期稳定性以及其失活的机理进行了详细的考察.
Pt/WO
3
/Al
2
O
3
催化剂表现出较高的初始活性: 甘油的转化率为57.5%, 目标产物1,3-丙二醇的选择性可达40.4%, 主要
/Al 催化
副产物1,2-丙二醇、正丙醇和异丙醇的选择性分别为6.3%, 37.3%和11.5%. 在长达700 h的稳定性测试中, Pt/WO
3
2 3
O
剂呈现缓慢失活的趋势: 甘油转化率从57.5%下降到25.1%, 而1,3-丙二醇选择性基本不变. 通过对失活曲线进行拟合可以
得出催化剂的失活呈现三个阶段: 第一阶段内(0100 h)催化剂的失活速率最快, 甘油转化率由57.5%降至44.9%, 失活速率
为0.111%/h; 第二阶段内(100600 h)催化剂的失活明显变缓, 失活速率降至0.037%/h; 第三阶段内(600700 h)甘油转化率
基本保持不变.
N
2
物理吸附、电感耦合等离子体原子发射光谱、热重和程序升温氧化等表征结果显示, 活性组分(铂, 氧化钨)的流失或
积炭都不是催化剂失活的主要原因. 同时X射线衍射、高角环形暗场扫描透射电子显微镜和CO化学吸附等表征结果表明,
反应过程中Pt/WO /Al 催化剂上Pt颗粒发生了明显的聚集长大, 使得Pt的分散度由29.1%降至10.1%. 仲丁醇脱水/脱氢探
针反应的结果显示, 稳定性测试后催化剂在氢气气氛下产生原位B酸的能力显著降低. 由此可以得出, 反应过程中
Pt/WO /Al 催化剂失活的主要原因是催化剂表面Pt颗粒的聚集长大, 因而引起催化剂加氢能力的降低, 同时Pt-WO 界面
3
2 3
O
3
2
O
3
x
位点的数量下降, 使得在氢气气氛下催化剂产生原位B酸的能力大大降低, 从而导致了催化剂的失活.
关键词: 甘油; 氢解; 1,3-丙二醇; 失活; 聚集
收稿日期: 2019-11-15. 接受日期: 2019-12-19. 出版日期: 2020-08-05.
*
通讯联系人. 电话: (0411)84379348; 传真: (0411)84685940; 电子信箱: aqwang@dicp.ac.cn
基金来源: 国家重点基础研究发展计划(2018YFB1501600); 国家自然科学基金(21690080, 21690084, 21721004, 21673228); 中国
科学院战略性先导科技专项(XDB17020100); 中国科学院洁净能源创新研究院合作基金(DNL180303); 中国科学院大连化学物理
研究所自主部署青年基金(DICP ZZBS 201612).
本文的电子版全文由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).