Effect of promoters on the selective hydrogenolysis of glycerol over Pt/W-containing catalysts

Article abstract of DOI:10.1016/S1872-2067(16)62479-8

Diverse promoters, including noble metals (such as Ru, Ir and Rh) and transition metal oxides (such as Re, La, Fe, Zr, Sn and Ce oxides) were introduced into Pt/WO_x and Pt/WO_x/Al₂O₃ catalysts to investigate the ability of these promoters to modify activity and selectivity during glycerol hydrogenolysis to 1,3-propanediol. Among these, La exhibited the greatest promotional effect; the introduction of 0.1% La to the Pt/WO_x improved activity, selectivity and stability, although the significant increase in selectivity came at the cost of a slight activity loss in the case of the Pt/WO_x/Al₂O₃ catalyst. Transmission electron microscopy, high angle annular dark field scanning tunneling electron microscopy and NH₃-temperature programmed desorption all demonstrated that the introduction of La generates a greater quantity of acidic sites on the catalyst surface, and that the majority of the La species are associated with Pt particles. Most of the other additives resulted in only minimal improvements or even detrimental effects with regard to both activity and selectivity, although some appear to improve the stability of the catalyst.

Full text of DOI:10.1016/S1872-2067(16)62479-8

Chinese Journal of Catalysis 37 (2016) 1513–1519
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
Effect of promoters on the selective hydrogenolysis of glycerol over
Pt/W‐containing catalysts
Jia Wanga,b,†, Nian Leia,b,†, Chaojun Yanga,b, Yang Sua, Xiaochen Zhaoa,*, Aiqin Wanga,#
a State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
b University of Chinese Academy of Sciences, Beijing 100049, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Diverse promoters, including noble metals (such as Ru, Ir and Rh) and transition metal oxides (such
as Re, La, Fe, Zr, Sn and Ce oxides) were introduced into Pt/WOx and Pt/WOx/Al2O3 catalysts to
investigate the ability of these promoters to modify activity and selectivity during glycerol hydro‐
genolysis to 1,3‐propanediol. Among these, La exhibited the greatest promotional effect; the intro‐
duction of 0.1% La to the Pt/WOx improved activity, selectivity and stability, although the significant
increase in selectivity came at the cost of a slight activity loss in the case of the Pt/WOx/Al2O3 cata‐
lyst. Transmission electron microscopy, high angle annular dark field scanning tunneling electron
microscopy and NH3‐temperature programmed desorption all demonstrated that the introduction
of La generates a greater quantity of acidic sites on the catalyst surface, and that the majority of the
La species are associated with Pt particles. Most of the other additives resulted in only minimal
improvements or even detrimental effects with regard to both activity and selectivity, although
some appear to improve the stability of the catalyst.
Received 5 April 2016
Accepted 26 May 2016
Published 5 September 2016
Keywords:
Glycerol
Hydrogenolysis
1,3‐propanediol
Tungsten oxide
Promoter
© 2016, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1. Introduction
complished with a wide range of catalysts, only Pt‐W catalysts
[11–13] and Ir‐Re catalysts [14–16] can selectively cleave the
Advances in the biodiesel industry have resulted in the
production of large amounts of glycerol as a byproduct of the
transesterification of vegetable oils. Adding value to surplus
glycerol by chemical transformations has attracted significant
attention in recent decades [1]. Among the various transfor‐
mation routes such as dehydration [2–4], oxidation [5,6], and
reforming [7,8], the selective hydrogenolysis of glycerol to
1,3‐propanediol (1,3‐PD) is highly desirable, owing to the
widespread use of 1,3‐PD in the polyester industry for the
production of polytrimethylene terephthalate (PTT) [9,10].
Whereas the synthesis of 1,2‐propanediol (1,2‐PD) can be ac‐
secondary –OH group of the glycerol molecule to obtain high
yields of 1,3‐PD. Very recently, our group developed a novel Pt
single/pseudo‐single atom catalyst deposited on a mesoporous
tungsten oxide [17]. The optimized interface between the Pt
and the WOx, as well as the mesoporous structure of the mate‐
rial, result in outstanding activity by this catalyst under rela‐
tively low H2 pressures (i.e. 1MPa), as well as a high space‐time
yield of 1,3‐PD. Even under mild reaction conditions, however,
the undesirable formation of 1‐propanol as a result of
over‐hydrogenolysis is still the dominant reaction, with ap‐
proximately 50% selectivity for this product. Therefore, there
* Corresponding author. Tel: +86‐411‐84379416; E‐mail: zxc@dicp.ac.cn
# Corresponding author. Tel: +86‐411‐84379348; Fax: +86‐411‐84685940; E‐mail: aqwang@dicp.ac.cn
† These authors contributed equally to this work.
This work was supported by the National Natural Science Foundation of China (21176235, 21373206, 21303187).
DOI: 10.1016/S1872‐2067(16)62479‐8 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 37, No. 9, September 2016

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Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
is a requirement to further enhance the selectivity for 1,3‐PD
by suppressing the formation of 1‐propanol, and the addition of
small amounts of promoters to the present Pt/WOx catalyst
appears promising in this regard.
Transition metal promoted catalysts were prepared using
the incipient wetness impregnation method. The metal pre‐
cursors
used
included
NH4ReO4,
La(NO3)3·6H2O,
Zr(NO3)2·5H2O, Al(NO3)3·9H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O,
Ce(NO3)3·6H2O, SnCl4·5H2O, Ga(NO3)3·4.5H2O, and ammonium
paratungstate (APT). After impregnation, the samples were
dried at 383 K for 12 h and then calcined at 673 K for 1 h at a
heating rate of 2 K /min. These materials are denoted as
M/Pt/WOx. The M loading was fixed at 0.1 wt% and was calcu‐
lated based on the mass of the mother catalyst. All the catalysts
were reduced in H2 at 573 K prior to reaction trials.
The introduction of a promoter is generally used to improve
catalyst performance and stability via controlling and/or mod‐
ulating the electronic structure of the noble metal [18], cover‐
ing unfavorable sites [19], or modifying the surface chemistry
of the support and its consequent interaction with the noble
metal [20,21]. Because the selective hydrogenolysis of glycerol
to 1,3‐PD is a synergistic process based on concerted dehydra‐
tion and hydrogenation, modification of the catalyst with a
promoter could definitely tune both the catalytic performance
and the distribution of products. Therefore, an investigation of
promoter effects on Pt‐W catalysts will be crucial to future
breakthroughs in catalyst design. In previous studies, AlOx
promoters [22] and Al2O3 supports [11] have both demon‐
strated promising promotional effects during the selective hy‐
drogenolysis of glycerol to 1,3‐PD (90% and 100% glycerol
conversions with 44% and 66% 1,3‐PD selectivities, respec‐
tively). It is likely that the AlOx support inhibits the
over‐hydrogenolysis reaction, although the mechanism is still
unclear. Moreover, in contrast to Pt/WOx, supported catalysts
are more desirable in practical applications owing to their fa‐
vorable mechanical and shaping properties. Despite this, posi‐
tive promoters that work for Pt/WOx might not function with
supported catalysts, because the different chemical properties
of Al2O3 and WOx may affect the action of the promoters. To
examine such effects, the present work employed both Pt/WOx
and Pt/WOx/Al2O3 as the mother catalysts, and introduced
transition metal (such as Re, La, Fe, Zr, Sn and Ce) oxides and
noble metals (such as Ru, Ir and Rh) as promoters, and investi‐
gated the role of the promoters in modifying the hydrogenoly‐
sis reactivity. Among these catalysts, La and Fe showed positive
promotional effects on Pt/WOx, while Re showed a similar ef‐
fect on Pt/WOx/Al2O3.
2.1.2. Preparation of the promoted Pt/WOx/Al2O3 catalyst
The Pt/WOx/Al2O3 catalyst was prepared using a sequential
impregnation method. WOx/Al2O3 was initially synthesized
according to a previously published procedure [11]. In this
process, 1.248 g of APT was dissolved in distilled water at
363 K. The solution was then cooled to room temperature, after
which 10 g of Al2O3 was added, followed by additional stirring
at room temperature for 16 h. The solid was subsequently fil‐
tered off, dried at 383 K for 12 h, and calcined at 1073 K for 3 h
to obtain WOx/Al2O3. This material was then impregnated with
an aqueous solution of H2PtCl6·6H2O, followed by drying at 383
K for 12 h and calcination at 573 K for 3 h to obtain the
Pt/WOx/Al2O3 catalyst. Analysis by inductively coupled plas‐
ma‐atomic emission spectroscopy showed that the catalyst
contained 7.0 wt% tungsten and 2.0 wt% platinum.
The introduction of promotors to the Pt/WOx/Al2O3 catalyst
was performed in a manner similar to that applied in the case
of the Pt/WOx, except for the use of a calcination temperature
of 573 K. The promoted catalysts are referred to herein as
M/Pt/WOx/Al2O3, where the M loading was fixed at 0.1 wt% as
calculated based on the mother catalyst.
For comparison purposes, M‐Pt/WOx/Al2O3 catalysts were
also prepared by co‐impregnation of WOx/Al2O3 using a solu‐
tion of H2PtCl6·6H2O and the corresponding metal precursor.
The resulting solids were dried at 383 K and calcined at 573 K
for 3 h. In addition, Pt/M/WOx/Al2O3 catalysts were prepared
by sequential incipient wetness impregnation of WOx/Al2O3
with solutions of the corresponding metal precursor and
H2PtCl6·6H2O.
2. Experimental
2.1. Catalyst preparation
2.1.1. Preparation of a promoted Pt/WOx catalyst
The WOx/Pt/Al2O3 catalyst was prepared via a sequential
impregnation method. The initial Pt/Al2O3 catalyst was pre‐
pared by impregnation of Al2O3 samples with an aqueous solu‐
tion of H2PtCl6·6H2O, after which the impregnated sample was
dried at 383K for 12 h and subsequently calcined at 673K for 3
h. WOx/Pt/Al2O3 was prepared by impregnation of Pt/Al2O3
samples with an aqueous solution of ammonium metatungstate
(AMT). Impregnated samples were dried at 383K for 12 h and
subsequently calcined at 823 K for 3 h. The platinum content
was fixed at 2 wt%, while the tungsten content was varied be‐
tween (0.1 and 8) wt%.
The Pt/WOx was prepared according to a previously re‐
ported method [17]. Briefly, 3 g of WCl6 was added to 100 mL
of ethanol with stirring at 500 r/min for 20 min, and then
transferred to a Teflon‐lined autoclave and heated in an oven at
433 K for 36 h. After cooling to room temperature, the solution
was filtered and the recovered WOx was washed with ethanol
and water, then dried at 323 K for 6 h under vacuum. This ma‐
terial is denoted simply as WOx herein. Pt/WOx was prepared
by impregnating this material with an aqueous solution of
H2PtCl6, followed by drying at 323 K for 6 h under vacuum.
Noble metal promoted catalysts were prepared by impreg‐
nating the Pt/WOx in RhCl3·3H2O, RuCl3·3H2O, or H2IrCl6 solu‐
tions overnight, with subsequent drying at 383 K for 12 h. The
as‐prepared catalysts were calcined at 673 K for 1 h at a heat‐
ing rate of 2 K/min.
2.2. Catalytic reactions and product analysis
Glycerol hydrogenolysis trials over Pt/WOx were conducted
in a 75‐mL autoclave with a Teflon lining. Typically, 0.3 g of

Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
1515
catalyst and 12 g of an aqueous glycerol solution (5 wt%) were
transferred into the autoclave, after which the chamber was
flushed several times with H2 and then filled with H2 to a pres‐
sure of 1.0 MPa. The reactor was subsequently sealed and
heated to 413 K and the reaction proceeded at a stirring speed
of 800 r/min for 12 h. The same conditions were applied in the
performance tests over Pt/WOx/Al2O3, except using a 3 wt%
glycerol solution, an initial H2 pressure of 5.0 MPa and a reac‐
tion temperature of 453 K.
and then cooled to 373 K prior to pulse adsorption trials. After
adsorption saturation, the amount of NH3 adsorption was cal‐
culated accordingly.
H2 adsorption trials were conducted with the same instru‐
ment to measure the H2 uptake of catalysts. The samples were
reduced in H2 flow at 573 K for 1 h after being degassed in Ar
flow at 583 K for 30 min, then cooled to 323 K in preparation
for pulsed adsorption. After adsorption saturation, the amount
of H2 adsorption was calculated accordingly.
After each reaction, the gaseous and liquid products were
collected separately. The liquid phase products were analyzed
with an Agilent 7890B gas chromatograph with an
HP‐INNOWAX capillary column (30 m × 0.32 mm × 0.5 µm,
flame ionization detector) using n‐butanol as the internal
standard, while the gaseous products were analyzed online
using the same instrument with a HayeSep Q packed column (3
m × 1/8", thermal conductivity detector). The conversion of
glycerol and the selectivity for each liquid product were calcu‐
lated using the following equations.
3. Results and discussion
3.1. The effects of transition metal promoters
As noted, transition metal promoters can drastically change
the activity and selectivity of noble metal supported catalysts.
Thus the effects of transition metal promoters during the hy‐
drogenolysis of glycerol were examined in the present work,
with the results shown in Table 1. In the case of Pt/WOx, the
additions of Re, Sn, Zn, and Ga (Entries 5–8) decreased glycerol
conversion but increased 1,3‐PD selectivity, while Zr (Entry 4)
had the opposite effect. During the sequential glycerol hydro‐
genolysis reaction, it is usually difficult to simultaneously en‐
hance both glycerol conversion and selectivity for 1,3‐PD, be‐
Conversion of glycerol (%) = (moles of glycerol con‐
sumed)/(moles of glycerol initially added) × 100.
Selectivity (%) = (moles of carbon in a given prod‐
uct)/(moles of carbon in glycerol consumed) × 100
Deactivation rate (% h–1) = (Conv.max  Conv.final) × 100 / ( t ×
Conv.max
)
cause
a
highly
active
catalyst
often
generates
2.3. Catalyst characterization
over‐hydrogenolysis, thus decreasing the selectivity, and vice
versa. However, when promoted by La or Fe (Entries 2 and 3),
the glycerol conversion was increased from 37.4% to 39.9% or
41.6%, respectively, while the 1,3‐PD selectivity was improved
from 35.1% to 41.3% or 37.8%. These slight enhancements
resulted in a higher yield of 1,3‐PD compared with that ob‐
tained with Pt/WOx. Moreover, the incorporation of La obvi‐
ously improved the stability of the mother catalyst. The
0.1La/Pt/WOx had an average 0.13% activity loss per hour
during an 85‐h stability test (Fig. 1), while the activity loss of
the Pt/WOx was 0.33% per hour over a 70‐h stability test [17].
In the case of the Pt/WOx/Al2O3, the addition of La or Fe also
High resolution transmission electron microscopy (HRTEM)
and high angle annular dark field scanning tunneling electron
microscopy (HAADF‐STEM) images were obtained on a
JEM‐2100F instrument operating at 200 kV. The samples were
prepared by ultrasonically dispersing the finely powdered cat‐
alysts in ethanol and the dropping each solution onto a C/Cu
TEM grid.
NH3‐adsorption data were obtained using a Micromeritics
AutoChem II 2920 chemisorber to measure the acidity of cata‐
lysts. The samples were degassed in He flow at 393 K for 1 h
Table 1
Results obtained with transition metal promoters on Pt‐W catalysts during the hydrogenolysis of glycerol.
Conv.
(%)
Selectivity ( % )
Yield
(%)
13.1
16.5
15.8
13.4
7.0
11.8
7.2
9.1
Entry
Catalyst
2‐PO
5.1
4.80
6.1
5.7
5.2
5.8
4.7
6.1
6.6
7.4
9.5
6.2
7.1
10.6
9.7
9.4
1‐PO
50.3
44.7
50.5
46.9
46.1
40.8
40.0
44.0
54.4
23.2
24.1
21.8
26.4
29.6
32.4
16.5
1,2‐PD
2.3
2.8
2.4
4.5
4.0
8.5
6.3
6.1
4.8
7.2
12.5
12.2
5.8
8.7
16.0
19.2
1,3‐PD
35.1
41.3
37.8
33.3
38.4
39.6
44.2
36.5
24.6
48.2
56.9
57.0
49.1
49.0
32.6
51.5
Others a
7.2
6.4
3.2
9.6
6.3
5.3
4.8
7.3
9.6
14.0
1.3
2.8
11.6
2.1
1
2
3
4
5
6
7
8
Pt/WOx
0.1La/Pt/WOx
0.1Fe/Pt/WOx
0.1Zr/Pt/WOx
0.1Re/Pt/WOx
0.1Sn/Pt/WOx
0.1Zn/Pt/WOx
0.1Ga/Pt/WOx
37.4
39.9
41.6
40.2
18.1
29.8
16.2
25.0
4.0
65.4
47.4
38.3
55.9
67.9
21.0
32.7
9
0.1Ce/Pt/WOx
Pt/WOx/Al2O3
1.0
10
11
12
13
14
15
16
31.5
27.0
21.8
27.4
33.3
6.8
0.1La/Pt/WOx/Al2O3
0.1Fe/Pt/WOx/Al2O3
0.1Zr/Pt/WOx/Al2O3
0.1Re/Pt/WOx/Al2O3
0.1Sn/Pt/WOx/Al2O3
0.1Ce/Pt/WOx/Al2O3
9.3
3.4
16.8
a This category included propane, ethylene glycol, ethanol, methanol, methane and ethane.

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Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
Table 2
Textural parameters and acid properties of La‐promoted catalysts and
reference catalysts.
60
50
40
30
20
10
0
60
50
40
30
20
10
0
Conversion
Acid content
(mmol/g)
BET
(m2/g)
Dp
(nm)
Catalyst
1-PO
Pt/WOx
0.65
0.86
0.40
0.50
82
62
105
101
6.5
5.0
9.0
9.3
1,3-PD
0.1La/Pt/WOx
Pt/WOx/Al2O3
0.1La/Pt/WOx/Al2O3
Yield
glycerol conversion and product selectivity [23, 24]. According
to the NH3 adsorption results (Table 2), the addition of La did
indeed generate a greater quantity of acidic sites on both the
0.1La/Pt/WOx and 0.1La/Pt/WOx/Al2O3. In addition to these
surface acid sites, as determined by NH3 adsorption, we pro‐
pose that acid sites could also have originated from Brønsted
acid sites generated in situ by the heterolytic dissociation of H2
on metal sites with subsequent spillover to the support [17]. In
addition to the increased acid site concentration, the Brunau‐
er‐Emmett‐Teller (BET) surface area and pore structure of the
original Pt/WOx were both greatly decreased after the intro‐
duction of La, possibly due to partial collapse of the mesopo‐
rous WOx structure during calcination. In the case of the
Pt/WOx/Al2O3, however, the BET surface area and pore struc‐
ture were almost unchanged after La introduction, indicating
the superior mechanical strength of the Al2O3 support com‐
pared to the WOx.
1,2-PD
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
Time (h)
Fig. 1. Stability of 0.1La/Pt/WOx over time. Conditions: fixed‐bed reac‐
tor at 413 K, 1.0 MPa, gas hourly space velocity of 1000 h−1, liquid
hourly space velocity of 1 h−1, 5 wt% glycerol.
remarkably enhanced the 1,3‐PD selectivity (from 48.2% to
57.0%) although the glycerol conversion decreased to some
extent. We assume that the inherently higher activity of the
Pt/WOx/Al2O3 was responsible for the lesser extent of activity
enhancement on adding the promoters. It should be noted that
improved selectivity at the cost of a slight loss of activity is the
most acceptable scenario with regard to practical applications.
In this regard, La is the better promoter.
TEM and HAADF‐STEM images demonstrated aggregations
of Pt single/pseudo‐single atoms after La introduction (Fig. 2),
which may have been caused by the high temperature calcina‐
tion following impregnation. In contrast, EDS results showed
that Pt species were only partially aggregated, and that there
were still a large number of single/pseudo‐single Pt atoms
highly dispersed on the W species. In addition, the majority of
the La species were found to be associated with Pt species, in
To illustrate the effects of promoters on hydrogenolysis
performance with or without the Al2O3 support, further inves‐
tigations were performed, using La as a model promoter.
In principle, hydrogenolysis requires acidic sites for dehy‐
dration and metallic sites for hydrogenation, and the selective
hydrogenolysis of glycerol to 1,3‐PD involves the concerted
functioning of these two types of sites. For this reason, the acid‐
ity of a catalyst is widely accepted as playing a crucial role in
(a)
(c)
Position 1
0.3
Position 2
0
Element (%)
La
Pt
2.4
24.3
72.1
W
93.9
(d)
(b)
Position 1
0.71
Position 2
0
Element (%)
La
Pt
21.4
0.7
W
22.2
16.2
Fig. 2. TEM images of (a) 0.1La/Pt/WOx and (b) 0.1La/Pt/WOx/Al2O3, and HAADF‐STEM images of (c) 0.1La/Pt/WOx and (d) 0.1La/Pt/WOx/Al2O3.
The tables present STEM‐EDS elemental analysis data for positions 1 and 2.

Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
1517
accordance with the deposition sequence of each component.
It has been reported that La possesses unique properties for
catalytic cellulose conversion [25]. In the present study, La also
exhibited a superior promotional effect for Pt‐W catalysts dur‐
ing the selective hydrogenolysis of glycerol to 1,3‐PD, thus it
was thought that optimization of the La content might provide
opportunities to further improve the hydrogenolysis perfor‐
mance. However, additional evaluation (Table 3) demonstrated
that the use of a greater quantity of La both lowered glycerol
conversion and decreased 1,3‐PD selectivity, likely due to
over‐coverage of the active Pt sites by La species. Further in‐
vestigation of the deposition sequence of La relative to Pt on
the WOx/Al2O3 sample showed that La must be introduced after
Pt loading, otherwise the activity is greatly decreased upon
introduction of the La. This result suggests that the coverage of
the highly active Pt sites by a very small amount of La tends to
enhance selectivity without much activity loss.
Ru/Pt/WOx/Al2O3, indicating that Ru has the same function
with and without a support. In contrast, the negative effect of
Rh was eliminated when employing Al2O3 as the support, and
the yield of 1,3‐PD returned to 32.4%. In addition, introducing
Ir to the Pt/WOx/Al2O3 decreased not only the glycerol conver‐
sion but also the 1,3‐PD selectivity, indicating the negative ef‐
fects were more pronounced on supported catalysts. Chemical
adsorption results demonstrated that variation in the initial
acid amounts over the Al2O3 supported catalysts (from 0.40 to
0.39 mmol/g) was less than that over the Pt/WOx (from 0.65 to
0.55 mmol/g) after Ir introduction, suggesting that the hydro‐
genolysis reactivity is not highly correlated with the initial acid
amount. As well, compared with the transition metal promoted
catalysts, that decreased the H2 uptake from 0.067 to the range
of 0.046 to 0.049 mmol/g, the use of Ir greatly decreased the H2
uptake, from 0.067 to 0.024 mmol/g. This effect most likely
was responsible for the inferior performance of this catalyst
during the hydrogenolysis of glycerol to 1,3‐PD.
3.2. The effects of noble metal promoters
Electron microscopy (Fig. 3) shows significant aggregation
of Pt on the Pt/WOx after Ir introduction, consistent with the H2
adsorption results, and presumably responsible for the low
activity of this material during the hydrogenolysis reaction. The
Pt particle sizes were maintained over the supported catalysts,
indicating that the presence of an Al2O3 support may facilitate
the stabilization of these particles. Taking the chemical H2 ad‐
sorption results into account, the significant decrease in the H2
uptake over the Ir promoted Pt/WOx/Al2O3 is attributed to the
change in electronic structure, rather than particle size, of the
active Pt species, which greatly influenced the performance of
this material during the selective hydrogenolysis of glycerol.
Ru, Ir, and Rh were introduced to Pt/WOx and Pt/WOx/Al2O3
with a loading of 0.1 wt %, respectively, and the promotional
effects were examined during the hydrogenolysis of glycerol
under optimized reaction conditions (Table 4). In the case of
the Pt/WOx, the Ru promoted material showed similar perfor‐
mance to the mother catalyst (Entry 2), while Ir and Rh pro‐
moters significantly decreased the glycerol conversion (from
37.4% to approximately 26.3%) but maintained the 1,3‐PD
selectivity at approximately 35.0% (Entries 3 and 4). Similarly,
no obvious effect was identified when using the
Table 3
The effects of La on Pt‐W catalysts during hydrogenolysis of glycerol.
Selectivity ( % )
Conv.
Yield
(%)
Entry
Catalyst
2‐PO
5.1
4.8
5.9
5.9
6.1
7.4
9.5
4.2
7.3
1‐PO
50.3
44.7
45.2
47.1
45.4
23.2
24.1
12.2
17.2
1,2‐PD
2.3
1,3‐PD
35.1
41.3
38.5
37.3
37.7
48.2
56.9
51.1
50.0
Others a
7.2
6.4
4.7
5.6
6.8
14.0
1.3
18.5
10.6
(%)
37.4
39.9
28.6
17.0
14.8
65.4
47.4
37.5
32.9
1
2
3
4
5
6
7
8
9
Pt/WOx
0.1La/Pt/WOx
0.2LaPt/WOx
0.4LaPt/WOx
0.5LaPt/WOx
Pt/WOx/Al2O3
13.1
16.5
11.0
6.3
2.8
5.7
4.1
4.0
7.2
5.6
31.5
27.0
19.2
16.4
0.1La/Pt/WOx/Al2O3
Pt/0.1La/WOx/Al2O3
Pt‐0.1La/WOx/Al2O3
12.5
14.0
14.9
a This category included propane, ethylene glycol, ethanol, methanol, methane and ethane.
Table 4
The effects of noble metal promoters on Pt‐W catalysts during hydrogenolysis of glycerol.
Selectivity ( % )
Conv.
Yield
(%)
Entry
Catalyst
2‐PO
5.1
5.1
5.6
5.9
7.4
7.7
6.4
5.2
1‐PO
50.3
49.9
53.0
50.2
23.2
26.2
33.1
19.8
1,2‐PD
2.3
1,3‐PD
35.1
35.5
34.4
33.1
48.2
50.0
41.1
47.8
Others a
7.2
6.9
2.5
6.8
14.0
6.9
13.3
17.9
(%)
37.4
33.6
25.6
26.3
65.4
58.1
55.7
67.7
1
2
3
4
5
6
7
8
Pt/WOx
0.1Ru/Pt/WOx
0.1Ir/Pt/WOx
0.1Rh/Pt/WOx
13.1
12.0
8.8
2.6
4.5
4.0
7.2
8.7
Pt/WOx/Al2O3
31.5
29.1
22.9
32.4
0.1Ru/Pt/WOx/Al2O3
0.1Ir/Pt/WOx/Al2O3
0.1Rh/Pt/WOx/Al2O3
9.2
6.1
9.3
a This category included propane, ethylene glycol, ethanol, methanol, methane and ethane.

1518
Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
product from glycerol hydrogenolysis was 1,2‐PD rather than
(c)
(a)
1,3‐PD. However, further increasing the amount of WOx (En‐
tries 8 and 9) led to more 1,3‐PD and less 1,2‐PD, akin to the
results obtained from a typical Pt/WOx/Al2O3 catalyst. These
results strongly suggest that the interface between the Pt and
WOx determines the selective hydrogenolysis of glycerol to give
1,3‐PD, irrespective of their deposition sequence. Therefore,
future work may focus on the design of more selective catalysts
by maximizing the Pt/WOx interface.
(b) (d)
4. Conclusions
In summary, a diverse range of promoters, including transi‐
tion and noble metals, was introduced to Pt/WOx and
Pt/WOx/Al2O3. La was the most effective promoter, and the
introduction of 0.1% La improved catalytic activity and selec‐
tivity for 1,3‐PD, as well as the stability of Pt/WOx. However,
the significant increase in 1,3‐PD selectivity came at the cost of
a slight activity loss in the case of the Pt/WOx/Al2O3. In some
instances, the same promoter exhibited different effects with or
without an Al2O3 support. Fe promoted Pt/WOx and Re pro‐
moted Pt/WOx/Al2O3 both demonstrated superior 1,3‐PD
productivity relative to the unpromoted catalysts, while the
opposite effect was observed when varying the mother cata‐
lysts. In addition, some other promoted catalysts, such as Zr
and Sn promoted Pt/WOx and Fe and Zr promoted
Pt/WOx/Al2O3, showed slightly decreased production of 1,3‐PD
but still have significant potential in practical applications. This
is because the introduction of promoters sometimes enhances
the stability of the catalysts, which might be even more signifi‐
cant than the reactivity itself. Characterization of selected cata‐
lysts implied that the promotion mechanism likely results from
modifying the electronic structure of the active Pt species. Hy‐
drogenolysis performance is not highly correlated with original
acid amounts, and therefore measurements of acidic sites gen‐
erated in situ will be of great importance in future work to pro‐
vide insight into the reaction mechanism and allow the rational
design of such catalysts.
Fig. 3. TEM images of (a) 0.1Ir/Pt/WOx and (b) 0.1Ir/Pt/WOx/Al2O3,
and HAADF‐STEM images of (c) 0.1Ir/Pt/WOx and (d) 0.1Ir/Pt/WOx/
Al2O3.
3.3. The effect of impregnation sequence
Previous studies have demonstrated that the addition se‐
quence of the AlOx promoter strongly influences the hydrogen‐
olysis reactivity and the product selectivities [22]. Therefore,
taking Pt/WOx and Pt/WOx/Al2O3 as reference catalysts, the
effects of varying the Al and W impregnation sequence were
investigated (Table 5). The introduction of either W or Al spe‐
cies to the Pt/WOx resulted in lower reactivity (glycerol con‐
version decreased from 37.4% to 27.1 % or 17.0%, respective‐
ly), owing to the coverage of active sites, while no significant
improvements were identified in the selectivity for 1,3‐PD.
Similar effects were observed when introducing W to the
Pt/WOx/Al2O3 catalyst. These results imply that merely cover‐
ing the active Pt sites by other species cannot enhance the se‐
lectivity for 1,3‐PD, although it does decrease the glycerol con‐
version. To probe the interactions between Pt and WOx, we
deposited a small amount of WOx species on the Pt/Al2O3
mother catalyst (Entries 6 and 7). In this case, the predominant
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Jia Wang et al. / Chinese Journal of Catalysis 37 (2016) 1513–1519
1519
Graphical Abstract
Chin. J. Catal., 2016, 37: 1513–1519 doi: 10.1016/S1872‐2067(16)62479‐8
Effect of promoters on the selective hydrogenolysis of glycerol over Pt/W‐containing catalysts
Jia Wang, Nian Lei, Chaojun Yang, Yang Su, Xiaochen Zhao*,
Aiqin Wang*
Dalian Institute of Chemical Physics, Chinese Academy of Sciences
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