Isomerization of n-pentane over platinum promoted tungstated zirconia supported on mesoporous SBA-15 prepared by supercritical impregnation

Article abstract of DOI:10.1002/jccs.202000473

Tungstated zirconia was supported on mesoporous SBA-15 by impregnation in supercritical ethanol. The resultant catalyst promoted with 1 wt% of Pt shows 100% selectivity of iso-pentane and two times higher conversion in n-pentane isomerization than the one prepared by conventional impregnation. Supercritical impregnation exerts no destruction of the porous silica and offers better dispersion of tungstated zirconia than conventional impregnation. Optimized loading of WO₃/ZrO₂/SBA-15 is 20/40/40 wt%, which infers to 2.4 W-atoms/nm² and 8.9 Zr-atoms/nm² dispersed on the SBA-15 support. Moreover, introducing a proper mole fraction of hydrogen in the reactants markedly improves the catalytic activity in n-pentane isomerization. The role of hydrogen was not only served as the reactants, it also acted to regenerate Br?nsted acid sites during n-pentane isomerization. However, overdose of hydrogen leaded to a leveling-off in the rate of isomerization and enhanced hydrogenolysis reaction. The in situ IR spectroscopic studies suggested that Br?nsted acid sites were the active centers for the isomerization. A reaction mechanism was, therefore, proposed that heterolytic fission of hydrogen and dehydrogenation of n-pentane took place over Pt. The secondary carbocation formed over Br?nsted acid sites was rearranged to a tertiary carbocation by methyl migration, followed by reacting with a hydride to generate iso-pentane.

Full text of DOI:10.1002/jccs.202000473

Received: 26 October 2020
DOI: 10.1002/jccs.202000473
Revised: 1 December 2020
Accepted: 2 December 2020
S P E C I A L I S S U E P A P E R
Isomerization of n-pentane over platinum promoted
tungstated zirconia supported on mesoporous SBA-15
prepared by supercritical impregnation
Wenchao Lee | Chieh-Chao Yang | Soofin Cheng
Department of Chemistry, National
Abstract
Taiwan University, Taipei, Taiwan
Tungstated zirconia was supported on mesoporous SBA-15 by impregnation in
Correspondence
Soofin Cheng, Department of Chemistry,
supercritical ethanol. The resultant catalyst promoted with 1 wt% of Pt shows
100% selectivity of iso-pentane and two times higher conversion in n-pentane
National Taiwan University,
No. 1, Roosevelt Rd. Sec. 4, Taipei 10617,
isomerization than the one prepared by conventional impregnation. Supercriti-
Taiwan.
cal impregnation exerts no destruction of the porous silica and offers better dis-
Email: chem1031@ntu.edu.tw
persion of tungstated zirconia than conventional impregnation. Optimized
Funding information
Ministry of Science and Technology,
loading of WO3/ZrO2/SBA-15 is 20/40/40 wt%, which infers to 2.4 W-atoms/
nm2 and 8.9 Zr-atoms/nm2 dispersed on the SBA-15 support. Moreover, intro-
Taiwan
ducing a proper mole fraction of hydrogen in the reactants markedly improves
the catalytic activity in n-pentane isomerization. The role of hydrogen was not
only served as the reactants, it also acted to regenerate Brønsted acid sites dur-
ing n-pentane isomerization. However, overdose of hydrogen leaded to a
leveling-off in the rate of isomerization and enhanced hydrogenolysis reaction.
The in situ IR spectroscopic studies suggested that Brønsted acid sites were the
active centers for the isomerization. A reaction mechanism was, therefore, pro-
posed that heterolytic fission of hydrogen and dehydrogenation of n-pentane
took place over Pt. The secondary carbocation formed over Brønsted acid sites
was rearranged to a tertiary carbocation by methyl migration, followed by
reacting with a hydride to generate iso-pentane.
K E Y W O R D S
acid catalyst, n-pentane isomerization, Pt, SBA-15, supercritical fluid, tungstated zirconia
1 | INTRODUCTION
process to produce high-octane gasoline components
from low-octane light naphtha fractions. However, coke
formation and retention of heavy side products on solid
catalysts in the pores are the most frequent causes of cat-
alyst deactivation in industrial processes.[2]
Sulfated zirconia and tungstated zirconia have been
studied as strong solid acid catalysts because they show
high catalytic activities in skeletal isomerization of
alkanes at relatively low temperatures.[2,3] Arata and
Hino classified the sulfated and tungstated zirconia
Strong mineral acids, such as HF and H2SO4, are com-
monly used in current petrochemical industries. Such
catalytic processes generate a large amount of non-
recyclable acid wastes, which are hazardous to the envi-
ronment. Great efforts have been made in seeking the
alternative acids, especially the solid acids, in order to
replace the strong mineral acids.[1] Solid acid catalysts
have been used in modern refiners in isomerization
J Chin Chem Soc. 2021;68:409–420.
http://www.jccs.wiley-vch.de
© 2020 The Chemical Society Located in Taipei & Wiley-VCH GmbH
409

410
LEE ET AL.
materials to be superacid catalysts.[4,5] However, acidity
measurements have shown that their acid strengths are
merely in medium to strong range.[6] The catalytic activi-
ties decayed markedly with time-on-stream as the active
acid sites were covered by coke during alkane isomeriza-
tion. Moreover, the loss of sulfur species during the cata-
lytic reactions also contributed to the deactivation of
sulfated zirconia catalysts. As to tungstated zirconia, the
low surface areas (around 50 m2/g) may also contribute
to the fast deactivation.
materials were characterized by ammonia temperature-
programmed desorption (TPD) and pyridine sorption,
Isomerization of n-pentane was studied to evaluate the
catalytic performance of the prepared samples. Several
factors were examined to obtain the optimization condi-
tion of the catalytic system—the weight ratios of WO3,
ZrO2, and SBA-15, the introduction of hydrogen into the
reactants, and the promotion effect of Pt. Moreover, a
reaction mechanism of n-pentane isomerization over the
Pt-promoted WZ catalysts was proposed.
Mesoporous siliceous materials, which contain high sur-
face areas (600–1,000 m2/g) and tunable ordered large pores
(2–10 nm) have been considered to be potential supports to
increase the dispersion of solid acid catalysts.[6–9] Sulfated
zirconia supported on siliceous Mobil Composition of Mat-
ter No. 41 (MCM-41) has been reported to enhance the cat-
alytic activities in n-butane isomerization.[7–9] Mixed
tungstate-zirconia has been supported on various porous sil-
ica materials, such as Santa Barbara Amorphous-15 (SBA-
15), MCM-41 and silica gel,[6] and their catalytic activities
in n-pentane isomerization were compared. SBA-15
supported tungstate-zirconia has shown better conversion
and iso-pentane selectivity than MCM-41 support, attribut-
ing to that SBA-15 could maintain the ordered porous struc-
ture after loading with W/Zr mixed oxides whereas MCM-
41 and silica gel could not.
Supercritical (SC) fluids own characteristics of low
viscosity, high diffusivity, and extremely low surface ten-
sion, which reduce the mass transfer restriction of the
dissolved solutes.[10] Several research groups have applied
SC media to synthesize small crystalline metal oxides by
thermal decomposition of the metal precursors dissolved
in SC fluids. Chhor and his coworkers[11] investigated the
synthesis of submicron TiO2 powders by thermal decom-
position of the metal alkoxide in a SC ethanol at 350ꢀC.
The as-prepared TiO2 particles in 30–60 nm were well
crystallized in anatase phase, and no further thermal
treatment was needed. Hayashi et al.[12] prepared titania
nanoparticles (20–115 nm) with mesoporosity (4–25 nm)
by hydrothermal treatment under various subcritical and
SC water conditions. The pore size and crystallinity of
TiO2 can be tuned by changing the hydrothermal temper-
ature between 100 and 400ꢀC. Morère et al.[13] reported
the deposition of Pd onto SBA-15 silica using SC CO2 at a
mild condition of 40ꢀC and 85 bar. Nano-sized Pt parti-
cles (6–9 nm) were found to uniformly disperse over
SBA-15.
2 | RESULTS AND DISCUSSION
2.1 | Characterization of WO3-ZrO2/SBA-
15 catalysts
Figure 1 shows the X-ray diffraction (XRD) patterns of
Pt-promoted WZ supported on SBA-15 prepared by con-
ventional and SC impregnation. A WZ sample without
SBA-15 support (named WZ(SC)) is also shown as a refer-
ence catalyst. The triplet diffraction peaks at 2θ = 23.1ꢀ,
23.6ꢀ, and 24.4ꢀ and duplet peaks at 2θ = 34.8ꢀ and 35.1ꢀ
are the characteristic peaks of monoclinic WO3,[14] while
the strong diffraction at 30.5ꢀ corresponds to tetrahedral
ZrO2 phase. For tungsten oxide deposited sample, Pt/W
(SC)/SBA-15, only WO3 phase was observed accordingly.
For SBA-15 supported WZ prepared by conventional
impregnation, Pt/WZ(IM)/SBA-15 shows stronger diffrac-
tion peaks of WO3 than Pt/WZ(SC)/SBA-15, indicating
that smaller particle size of WO3 is formed by SC impreg-
nation. Moreover, tungsten oxide deposited sample Pt/W
(SC)/SBA-15 has more intense diffraction peaks of WO3
W : WO3
Z : ZrO2
Z
W
W
Pt/WZ(SC)
SBA-15
Pt/WZ(I)/SBA-15
Pt/WZ(SC)/SBA-15
Pt/W(SC)/SBA-15
1
2
20
30
40
50
60
70
80
In the present study, tungstated zirconia (WZ) cata-
lysts supported on mesoporous SBA-15 were prepared by
conventional and SC impregnation. SC ethanol is consid-
ered a proper solvent to use because it is a polar solvent
and the critical temperature at 241ꢀC is much lower than
that of water (373ꢀC). The acidities of the resultant
2θ
FIGURE 1 XRD patterns of SBA-15 and various Pt/WO3/ZrO2
loading samples. For Pt/WZ/SBABA-15 materials, Pt/WO3/ZrO2
loadings = 1/20/40 wt%. For WZ(SC), WO3/ZrO2 = 20 wt%

LEE ET AL.
411
than WZ deposited sample Pt/WZ(SC)/SBA-15. It implies
that ZrO2 may improve the dispersion of WO3 during cat-
alyst preparation.
by SC impregnation shows a less decrease in surface area
and pore volume (219 m2/g and 0.50 cm3/g) albeit still
lower compared with pure SBA-15. It suggests a better
dispersion of WZ on SBA-15 by SC than conventional
impregnation. That is also evidenced by the smaller crys-
tallite size of ZrO2 (11.2 vs. 7.4 nm) as shown in Table 1.
To confirm the influence of SC condition on the pore
structure of SBA-15, a control, SBA-15(SC), was con-
ducted by treating SBA-15 in SC ethanol at 270ꢀC for
3 hr. A mild decrease in BET surface area and pore vol-
ume was obtained. The corresponding XRD pattern, N2
physisorption isotherm and pore size distribution are
shown Figures S2 and S3, which displays only small
changes in the pore structure after treating SBA-15 in SC
ethanol.
In the small angle diffraction region, three distinct
diffraction peaks corresponding to (100), (110), (200)
planes of 2D-hexagonal p6mm symmetry are visible for
pure SBA-15.[15] After the deposition of either tungsten
oxide or WZ onto SBA-15, remarkable decreases in (100)
peak are observed, and the (110) and (200) diffraction
peaks almost disappear. Such results are due to the
decrease in the diffraction contrast or the ordered hexag-
onal channels of SBA-15 being disturbed after filling the
volume of mesoporous channels with oxides. Moreover,
the (100) signal of Pt/WZ(IM)/SBA-15 shifts slightly
toward high angle and is more pronounced in lowering
the intensity than that of Pt/WZ(SC)/SBA-15.
Table 1 summarizes the surface area and pore volume
of the aforementioned samples. Pure SBA-15 shows a sur-
face area of 698 m2/g and pore volume of 0.79 cm3/g. A
much lower Brunauer–Emmett–Teller (BET) surface area
and pore volume of Pt/WZ(IM)/SBA-15 (33 m2/g and
0.04 cm3/g) than SBA-15 demonstrate that the pore chan-
nels have been blocked by or filled with WZ during con-
ventional impregnation. On the other hand, loading WZ
2.2 | Catalytic evaluation
Isomerization of n-pentane is performed at 250ꢀC for
20 hr, and the products were analyzed every 30 min.
Figure 2 shows the time-on-stream catalytic perfor-
mances of various samples in n-pentane isomerization.
Higher conversions of n-pentane were observed in the
TABLE 1 Physical properties and catalytic activities in n-pentane isomerization of porous silica, oxides, and Pt-promoted catalysts
Sample
W/Za
-
Z/SBAa
-
dZrO2 (nm)b
SBET (m2/g)
698
Vp (cm3/g)
0.79
Conv. (%)c
Select. (%)c
Yield (%)c
SBA-15
SBA-15(SC) d
-
-
-
n.d.
n.d.
54
44
1
n.d.
n.d.
98
n.d.
n.d.
53
44
1
-
-
613
0.78
Pt/HY
-
-
565
0.39
WZ(SC)
0.2
-
-
46
0.19
100
100
97
W(SC)/SBA-15
Pt/WZ(IM)/SBA-15
Pt/WZ(SC)/SBA-15
-
-
189
0.38
0.5
0.3
0.5
0.1
0.3
0.5
0.3
0.4
0.5
0.6
0.7
0.5
1.0
0.3
0.3
0.5
0.5
0.5
1.0
1.0
1.0
1.0
1.0
1.5
11.2
n.d.e
n.d.
n.d.
n.d.
5.9
33
0.04
25
6
24
4
480
0.70
73
397
0.60
15
2
100
62
15
1
431
0.61
358
0.57
36
48
37
44
66
48
49
36
99
36
48
37
44
65
48
49
36
331
0.61
100
99
7.9
237
0.46
7.4
216
0.42
99.
99
7.4
219
0.50
7.5
167
0.39
99
8.1
164
0.38
99
9.8
154
0.40
99
aW/Z and Z/SBA stand for the weight ratios of WO3 to ZrO2, and ZrO2 to SBA-15.
bThe crystalline size of ZrO2 was calculated by Scherrer's equation on the XRD peak 2θ at 30.5ꢀ.
cThe conversions and selectivities were obtained at 10 hr on feed. Reaction condition: 250ꢀC, H2: N2: n-pentane = 2: 10: 0.37 (ml/min).
WHSV = 1,484.4 ml/gcat-h.
dSBA-15 was treated in supercritical ethanol at 270ꢀC for 3 hr.
en.d., not-determined.

412
LEE ET AL.
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
Pt/WZ(SC)
Pt/WZ(IM)/SBA-15
Pt/WZ(SC)/SBA-15
Pt/W(SC)/SBA-15
Pt/HY
WO /ZrO
ZrO /SBA-15
3
2
2
0.5
0.5
0.3
0.1
0.5
0.3
1
0.5
0.5
0.5
0.3
0.3
0
2
4
6
8
10
12
14
16
18
20
0
10
20
30
40
50
60
70
80
Conversion (%)
FIGURE 2 Time on stream profiles of catalytic activities in n-
pentane isomerization over various catalysts: Pt/WZ(SC) (■),
Pt/WZ(IM)/SBA-15s (●), Pt/WZ(SC)/SBA-15 (▲), Pt/W(SC)/SBA-
15 (▼), and Pt-HY (◆). Pt/WO3/ZrO2 loadings = 1/20/40 wt%.
Reaction condition: 250ꢀC, H2: N2: n-pentane = 2:10: 0.37
(ml/min). WHSV = 1,484.4 ml/gcat-h
FIGURE 3 Catalytic activities of the Pt/WZ(SC)/SBA-15
catalysts with different weight ratios of WO3/ZrO2 and ZrO2/SBA-
15 in n-pentane isomerization. Reaction condition: reaction
temperature = 250ꢀC, H2: N2: n-pentane = 2:10: 0.37 (ml/min).
WHSV = 1,484.4 ml/gcat-h
initial stage (less than 1 hr) and the conversion decreases
with time-on-stream gradually for all the tested samples.
In contrast, iso-pentane selectivities were lower in the ini-
tial stage and then increased to and retained above 95%
after 1 hr on stream. The conversions of n-pentane as well
as the selectivities and yields of iso-pentane at 10 hr of
reaction are summarized in Table 1. W/Z and Z/SBA rep-
resent the weight ratios of WO3/ZrO2 and ZrO2/SBA-15,
respectively. It is noticeable that the yields of iso-pentane
are close to the n-pentane conversions since most of the
iso-pentane selectivities are close to 100%. Over the
unsupported Pt/WZ(SC) catalyst, 40% conversion of n-
pentane and nearly 100% selectivity of iso-pentane were
obtained. However, only half of the conversion (25%) and
slightly lower selectivity (97%) was reached over Pt/WZ
(IM)/SBA-15 (W/Z = 0.5, Z/SBA = 1). These results indi-
cate that loading WZ on SBA-15 by conventional impreg-
nation failed to promote the catalytic activity. In contrast,
the counterpart prepared by SC impregnation, Pt/WZ(SC)/
SBA-15 (W/Z = 0.5, Z/SBA = 1) gave 66% conversion of
n-pentane and 99% selectivity of iso-pentane. The catalytic
activity is markedly improved in comparison with that of
unsupported Pt/WZ(SC).
isomerization. Less than 1% conversion of n-pentane was
achieved albeit 100% selectivity of iso-pentane was
obtained, inferring that zirconia is an essential ingredient
in the mixed oxide catalyst. On the other hand, Pt-pro-
moted H+-form Y-typed zeolite prepared by conventional
impregnation (Pt/HY) was found to give rather high n-
pentane conversion (54%) and iso-pentane selectivity
(98%). However, the activity of Pt/HY is still lower than
that of Pt/WZ(SC)/SBA-15.
2.3 | Optimization of WO3/ZrO2 loading
Since SC impregnation is efficient in preparing SBA-15
supported WZ catalysts with high activities in n-pentane
isomerization, an extensive study on the effects of WO3
and ZrO2 loadings on Pt/WZ(SC)/SBA-15 catalysts is car-
ried out and the results are listed in Table 1. Both WO3/
ZrO2 (W/Z) and ZrO2/SBA-15 (Z/SBA) weight ratios
show impacts on catalytic activities. Relatively low n-
pentane conversions were obtained over the catalysts
with the W/Z < 0.3 and Z/SBA < 0.5. The n-pentane
conversion increases with the increases in WO3 and ZrO2
loadings, and an optimal n-pentane conversion of 66%
with iso-pentane selectivity of 99% was obtained over the
catalyst with W/Z = 0.5 and Z/SBA = 1. However, fur-
ther increases in WO3 and ZrO2 loadings would lower n-
pentane conversion, probably due to the accompanying
blockage of pores and decrease in surface area.
Pentane isomerization is a thermodynamic equilib-
rium reaction. At reaction temperature of 250ꢀC, the
equilibrium iso-pentane composition in pentane isomers
is about 70%.[16] Accordingly, 70% conversion of n-
pentane and 100% selectivity of iso-pentane would be the
optimal values to achieve. The catalytic result obtained
over Pt/WZ(SC)/SBA-15 (W/Z = 0.5, Z/SBA = 1) is close
to this optimal values.
The conversion-selectivity plots shown in Figure 3
demonstrate that high iso-pentane selectivities (nearly
100%) are achieved when the samples have relatively
high loadings of both WO3 and ZrO2. That is both W/Z
SBA-15 supported tungsten oxide, Pt/W(SC)/SBA-15,
was also tested to study the role of zirconia in n-pentane

LEE ET AL.
413
and Z/SBA ratios need to be larger than 0.3. On the other
hand, high ZrO2 loadings enhance the n-pentane conver-
sion, and the maximum conversion is obtained at Z/
SBA = 1. When fixing the Z/SBA ratio at 1, there is an
optimal loading of WO3. The conversion increases from
36 to 67% as the W/Z ratio is increased from 0.3 to 0.5,
but it decreases to 49% as W/Z is further increased to 0.7.
Figure 4 shows the XRD patterns of the series of cata-
lysts with the Z/SBA ratios fixed at 1 and the W/Z ratios
varied from 0.3 to 0.7. Triplet diffraction peaks between
2θ = 22ꢀ and 25ꢀ of monoclinic WO3 are observed when
the W/Z ratio is higher than 0.5. In the small angle
region of Figure 4, the intensity of the (100), (110), and
(200) diffraction peaks of SBA-15 decreases with the WO3
loading. Moreover, BET surface areas and pore volumes
of these samples decrease with WO3 loading (Table 1).
These results imply that the WO3 crystallites should fill
in the pores of SBA-15 and the size of the WO3 crystal-
lites increases with WO3 loading.
Figure 5. In comparison of their catalytic activities in n-
pentane isomerization, the one with Z/SBA = 1 has the
highest n-pentane conversion of 66% while the one with
Z/SBA = 1.5 has the lowest conversion of 36%. The poor
catalytic activity of the latter sample may be attributed to
the formation of large WO3 and ZrO2 crystallites, which
not only reduce the active surface area of WO3 but also
block the channeling pores of SBA-15.
Figure 6 depicts the n-pentane conversion over
Pt/WZ(SC)/SBA-15 with different surface concentrations
of WO3 and ZrO2. The surface concentrations were
WO /ZrO ZrO /SBA-15
3
2
2
(a)
(b)
(c)
0.5
0.5
0.5
0.5
1.0
1.5
(a)
Figure 5 shows the XRD patterns of the series of the
catalysts with the W/Z ratio fixed at 0.5 and the Z/SBA
ratio varied from 0.5 to 1.5. With the increase in ZrO2
loading, the diffraction peak of tetrahedral ZrO2 at
2θ = 30.5ꢀ becomes sharper and more intense, inferring
the increase in size and crystallinity of ZrO2. Again, the
deposition of WZ inside the pore channels of SBA-15 is
evidenced by the diminishing of diffraction peaks of SBA-
15 in small angle region as the Z/SBA ratio increases.
Apart from the ZrO2 crystallites, diffraction peaks of
monoclinic WO3 become predominant on the catalyst
with the highest Z/SBA ratio of 1.5. Table 1 also shows
that this sample has the lowest BET surface (154 m2/g)
and pore volume (0.4 cm3/g) among the three shown in
(b)
(c)
1
2
3
4
20
40
60
2 θ
FIGURE 5 XRD patterns of Pt/WZ(SC)/SBA-15 catalysts with
ZrO2/SBA-15 weight ratios varied in (a) 0.5, (b) 1.0, (c) 1.5. The
WO3/ZrO2 weight ratio is 0.5 for all the samples
90
80
70
WO /ZrO ZrO /SBA-15
3
2
2
8.9 - 11.1 Zr-atom/nm2
(a) 0.3
(b) 0.4
(c) 0.5
(d) 0.6
(e) 0.7
1.0
1.0
1.0
1.0
1.0
60
3.6 - 4.3 Zr-atom/nm2
50
40
(e)
(d)
14.6 Zr-atom/nm2
30
20
(c)
(b)
(a)
monoclinic WO on XRD
10
0
3
2.2 - 2.5 Zr-atom/nm2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
WO3 concentration (W-atom/nm2)
1
2
3
4
10
20
30
40
50
60
70
2 θ
FIGURE 6 Conversions of n-pentane over Pt/WZ(SC)/SBA-15
catalysts with different surface WO3 and ZrO2 concentrations.
Reaction condition: 250ꢀC, H2: N2: n-pentane = 2:10: 0.37
(ml/min). WHSV = 1,484.4 ml/gcat-h
FIGURE 4 XRD patterns of Pt/WZ(SC)/SBA-15 catalysts with
WO3/ZrO2 weight ratios varied in (1) 0.7, (2) 0.6, (3) 0.5, (4) 0.4,
(5) 0.3. The ZrO2/SBA-15 weight ratio is 1.0 for all the samples

414
LEE ET AL.
determined by the loading of the component (WO3 or
ZrO2) and the surface area of the catalyst.[17] The surface
ZrO2 concentrations were found to vary in a broad range
from 2.2 to 14.6 Zr-atoms/nm2, and tetrahedral ZrO2
phase (2θ = 30.5ꢀ) were observed in the XRD patterns.
The n-pentane conversion increases with WO3 concentra-
tion and achieves an optimal value when WO3 concentra-
tion is around 2.5 W-atoms/nm2. The n-pentane
conversion drops as WO3 concentration is higher than
3.5 atoms/nm2, and the XRD patterns show monoclinic
WO3 phase (2θ = 23.1ꢀ, 23.6ꢀ, and 24.4ꢀ) in these sam-
ples. Naito et al.[18] reported that monolayer of WO3 on
ZrO2 corresponds to the surface concentration of 3.5–4.0
atoms/nm2, and surface WO3 concentration predomi-
nantly influences the conversion of n-pentane. Over-
dosing WO3 of more than a monolayer leads to the
formation of bulk WO3 and lowers the catalytic activity
of the catalysts. However, among the Pt/WZ(SC)/SBA-15
samples, the highest conversion in n-pentane isomeriza-
tion to iso-pentane lies in the one with WO3/ZrO2 = 0.5
and ZrO2/SBA-15 = 1, corresponding to the surface con-
centration of 2.4 W-atoms/nm2 and 8.9 Zr-atoms/nm2.
The discrepancy may be caused by different catalytic sys-
tems. Herein, we tend to focus on the change in surface
concentration, as plotted in Figure 6. The optimized load-
ing of WO3/ZrO2/SBA-15 is used for the further discus-
sions on the H2 effect.
pressures of hydrogen in the stream of n-pentane and
nitrogen. Nitrogen is used as the inert component to keep
the total flow rate of hydrogen and nitrogen at 12
ml/min. In the absence of hydrogen in the gas stream,
the catalytic activity of the catalyst decreases dramati-
cally with time-on-stream. The n-pentane conversion
continuously decreases from 75 to 19% after 10 hr of
reaction and the iso-pentane selectivity decreases from
96 to 65% after 18 hr of reaction. Introduction of hydro-
gen significantly retards the decay of catalytic activity.
With 2 ml/min hydrogen, the conversion decreases
from 74% at beginning to 66% and selectivity retains
~99.4% after 10 hr on-stream. When H2 flow-rate is
raised to 4 ml/min, the conversion after 10 hr on-
stream is retained at 70% while the selectivity only
decreases slightly to 97%. Further increasing the H2
flow-rates up to 10 ml/min have little impact on
improving the conversion, while the iso-pentane selec-
tivity decreases. Analyzing the products by means of
mass spectroscopy, C1-C6 alkanes and branched com-
pounds were found as the byproducts of n-pentane
isomerization. Figure 8 shows that more methane, eth-
ane, propane, and butane are formed as byproducts
when the hydrogen flow rate increases from 2 to
10 ml/min. According to the literature reports,[19,20]
increasing hydrogen concentration would enhance
hydrogenolysis of alkanes. Therefore, the selectivity of
iso-pentane decreases with the increase in hydrogen
partial pressure.
2.4 | Effect of hydrogen on catalytic
activity and regeneration
2.5
Figure 7 shows the time-on-stream catalytic profiles of
the Pt/WZ(SC)/SBA-15 catalyst with different partial
different H2 flow rate
10mL/min
2.0
1.5
1.0
0.5
0.0
6mL/min
4mL/min
2mL/min
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
H2 flow rate (mL/min)
0
2
4
6
10
00
22
44
66
88 10
12
14
16
18
20
22
Time on stream (h)
FIGURE 8 By-product distributions (except for iso-pentane)
in n-pentane isomerization over Pt/WZ(SC)/SBA-15 catalyst in
different hydrogen pressures. Reaction condition: 250ꢀC, 5 hr, H2:
N2:n-pentane = x: (12 − x): 0.37 (ml/min), where x = 2, 4, 6, or 10.
WHSV = 1,484.4 ml/gcat-h
FIGURE 7 Effect of hydrogen pressure on the catalytic
activities of Pt/WZ(SC)/SBA-15 catalyst in n-pentane isomerization.
Reaction condition: 250ꢀC, H2: N2:n-pentane = x: (12 − x): 0.37
(ml/min), where x = 0, 2, 4, 6, or 10. WHSV = 1,484.4 ml/gcat-h

LEE ET AL.
415
Khurshid et al.[21] reported a slightly negative rate of
the n-pentane conversion and iso-pentane selectivity
heptane isomerization over Pt/WO3-ZrO2 in a high H2
pressure range (<0.3 MPa) and a positive rate in a low H2
pressure range (<0.3 MPa). In the present study, 2 ml/min
of H2 in a total flow of 12.37 ml/min corresponds to
~0.016 MPa of H2 pressure, and 10 ml/min of H2 corre-
sponds to ~0.08 MPa of H2 pressure. In other words, our
experimental conditions were in low H2 pressure range
(<0.3 MPa) of Khurshid et al. A similar positive effect on
n-pentane isomerization was found in our study. On the
other hand, the report that cracking products were mark-
edly suppressed under a high H2 pressure is different
from what was observed in the present study. According
to Figure 8, more cracking products were detected at
higher H2 flow (10 ml/min) than in lower H2 flow
(2 ml/min) condition. Since the selectivity of the target
product iso-pentane was much more pronounced than
the cracking byproducts, further investigations of the
influence of H2 partial pressure on the cracking reaction
was not carried out.
Coke deposition during the isomerization reaction
is the inherent problem for the catalyst deactivation.
Many studies have reported the coke formation during
n-alkane isomerization over solid acid catalysts.[22–25]
Figure S4 shows the thermal gravimetric analyses and
the differential profiles of the fresh and used Pt/WZ
(SC)/SBA-15 catalysts. There is a distinguishable
weight loss between 350 and 450ꢀC, attributing to the
burned coke. In order to investigate the deactivation
and regeneration behavior of the catalyst, the used
Pt/WZ(SC)/SBA-15 catalyst was heated in air at 450ꢀC
for 6 hr to regenerate. The results of the recycling
experiments for three times are shown in Figure 9, and
are well resumed after regeneration.
2.5 | Surface acid sites of the Pt/WZ/
SBABA-15 catalysts
TPD of adsorbed ammonia is used to characterize the
amount of acid sites over the catalysts.[6,26] Figure S5 com-
pares the profiles of desorbed NH3 over SBA-15 supported
or unsupported WZ by recording the NH2+ (m/z = 16) sig-
nals during desorption. All the catalysts show similar
TPD-Mass profiles of a wild desorption between 150 and
500ꢀC, mainly corresponding to the weak acid sites. As
observed in Figure S5, the SBA-15 supported WZ catalysts
display larger peak areas than that of the unsupported
one. Furthermore, the supported WZ catalyst prepared by
conventional impregnation has lower amount of acid sites
than that prepared by SC impregnation. The NH2+ signals
are normalized by the weight of the catalysts and
expressed in the unit of 10−3 mol NH3/g-cat, and the
values are displayed in Table S1.
The quantified acid sites of the samples after different
treated conditions are summarized in Table 2. The acid
number of fresh WZ(SC)/SBA-15 without Pt promoter is
the highest, 1.41 mol NH3/g-cat. Loading Pt on SBA-15
supported WZ catalysts leads to a decrease in NH3
desorption signals. In comparison to the unsupported
Pt/WZ, that supported on SBA-15 markedly enhances the
acidity of the catalyst. The fresh Pt/WZ(SC)/SBA-15 has
~three times increase in the numbers of the acid sites
(1.17 vs. 0.37 mol NH3/g-cat). These results demonstrate
that dispersion of WZ on SBA-15 can effectively increase
the surface acidity, while deposition of Pt may cover-up a
portion of acid sites.
100
95
90
85
80
75
70
65
60
55
50
100
95
90
85
80
75
70
65
60
55
50
After exposing the catalyst to the reaction mixture of
n-pentane and hydrogen at 250ꢀC for 1 hr, the acidity of
WZ(SC)/SBA-15 decreases from 1.41 to 1.14 mol NH3/g-
cat. However, the acidity decreases only slightly from 1.17
to 1.12 mol NH3/g-cat over Pt/WZ(SC)/SBA-15 after the
same treatment. The gas pretreatment is to mimic the
reaction condition of n-pentane isomerization in the pres-
ence of hydrogen. That is to say that after exposing the cat-
alysts in the reaction atmosphere for 1 hr, the acid amount
decreases 19.1% over WZ(SC)/SBA-15 without Pt pro-
moter, whereas only 4.7% decrease over Pt/WZ(SC)/SBA-
15. These results strongly evidence that Pt promoter can
retain the acid sites, presumably by less formation of coke.
Pyridine adsorption/desorption observed by diffuse
reflectance infrared Fourier transform (DRIFT) spectros-
copy was performed to distinguish the acid sites on the
catalysts to be Brønsted or Lewis in nature. Figure 10 shows
the DRIFT spectra of WZ(SC)/SBA-15 and Pt/WZ(SC)/SBA-
fresh catalyst
st
1
used catalyst
nd
2
used catalyst
0
2
4
6
8
10
12
14
16
18
20
Time on stream (h)
FIGURE 9 Reusability of Pt/WZ(SC)/SBA-15 catalyst in n-
pentane isomerization. Reaction condition: 250ꢀC, H2: N2: n-
pentane = 4:8: 0.37 (ml/min). WHSV = 1,484.4 ml/gcat-h. The used
catalyst was regenerated by heating under flowing air at 450ꢀC
for 6 hr

416
LEE ET AL.
TABLE 2 Acidities of Pt/WZ(SC), WZ(SC)/SBA-15, and Pt/WZ(SC)/SBA-15 determined by NH3-TPD
Sample
Condition
Pt/WZ(SC)
Fresh
WZ(SC)/SBA-15
Fresh
Pt/WZ(SC)/SBA-15
a
H2 + C5
1.14
Fresh
1.17
-
H2 + C5
Acidity (×10−3 mol of NH3/g)b
0.37
-
1.41
-
1.12
Loss of acidity after gas treatment (%)
19.1
4.3
aPrior to the NH3-TPD experiments, the samples were heated in 10% H2/Ar saturated with n-pentane at 250ꢀC for 1 hr.
bNH2 signals were determined by integration of the peak area between 150 and 500ꢀC during desorption and normalized by per gram of the catalysts used.
+
pretreatment at 250ꢀC, IR peaks of both Brønsted and
L
L
B
0.2
B
Lewis acid sites were retained but the peak intensities
were reduced. Moreover, the IR peaks of adsorbed pyri-
dine on the Brønsted and Lewis acid sites shift slightly
from 1,541 to 1,537 cm−1 and from 1,446 to 1,444 cm−1,
respectively. Similar phenomena were seen on both WZ
(SC)/SBA-15 and Pt/WZ(SC)/SBA-15, although the peaks
corresponding to Brønsted acid sites almost vanish for
Pt/WZ(SC)/SBA-15. These results confirm that adding
hydrogen into the reactant stream can effectively retard
coke formation. Table 3 lists the consumption percentages
of both acid sites after pretreatment with n-pentane and
hydrogen. The losses in Brønsted and Lewis acid sites are
31.9 and 39.2%, respectively, over WZ(SC)/SBA-15,
whereas 81.9 and 16.5% over Pt/WZ(SC)/SBA-15. It is,
therefore, to say that Pt incorporation enhances the con-
sumption of Brønsted acid sites but inhibits that of Lewis
acid sites during n-pentane isomerization. These results
infer that Pt may assist the generation of acid sites from
hydrogen, which explains the promotion in conversion as
compared to the case without hydrogen.
WZ(SC)/SBA-15
(after H2 + n-C5)
B + L
WZ(SC)/SBA-15
(fresh)
Pt/WZ(SC)/SBA-15
(after H2 + n-C5)
Pt/WZ(SC)/SBA-15
(after n-C5)
Pt/WZ(SC)/SBA-15
(fresh)
1800 1750 1700 1650 1600 1550 1500 1450 1400 1350 1300
-1
Wavenumber (cm )
FIGURE 10 In-situ DRIFT spectra of pyridine adsorbed on
the fresh and pretreated catalysts. The pretreatment was done by
exposing the catalysts to n-pentane/nitrogen with or without
hydrogen, followed by heated at 250ꢀC for 1 hr. The spectra were
recorded after introduction of the pyridine vapor and evacuated at
room temperature under 10−5 Torr
15 before and after pretreated either in n-pentane or in the
mixture of n-pentane and hydrogen at 250ꢀC for 1 hr, prior
to the adsorption of pyridine. The spectra were recorded
after exposing the pretreated catalysts to pyridine vapor for
30 min. at room temperature and then evacuated to
10−5 Torr. The peaks corresponding to pyridine adsorbed on
Brønsted acid site (~1,541 and 1,638 cm−1) or Lewis acid site
(1,446 and 1,599 cm−1) were observed on the catalysts, while
the peak at 1,490 cm−1 was attributed to pyridine associated
with both Brønsted and Lewis acid sites.[27–29] In compari-
son of the fresh catalysts WZ(SC)/SBA-15 and Pt/WZ(SC)/
SBA-15, all these peaks are less intense on Pt loaded sample,
in agreement with the NH3-TPD results shown in Table 2.
This observation also implies that Pt may cover both Brøn-
sted and Lewis acid sites on WZ(SC)/SBA-15.
2.6 | Reaction mechanism of n-pentane
isomerization over Pt/WZ/SBABA-15
Solid acids loaded with Pt are considered bifunctional
catalysts in alkane isomerization.[19] Pt owns the activity
in hydrogenation/dehydrogenation. In this study, Pt is
considered to be the site for hydrogen adsorption and
dehydrogenation of n-pentane to form 2-pentene,[30] as
shown in Equations (1) and (2) of Scheme 1. Hydrogen
molecules are considered to undergo heterolytic fission
on Pt surface, and the generated proton and hydride spill-
over to tungstate,[19,30] as shown in Equation (3).
Protonation of 2-pentene should take place at the
Brønsted acid sites on tungstate. Equation (4) illustrates
that carbocation is formed and stabilized by the adjacent
oxygen of the Brønsted acid sites. The carbocation gener-
ated in Equation (4) is a secondary carbocation, which
tends to rearrange into a more stable tertiary carbocation
through methyl migration (Equation 5). The tertiary car-
bocation combines with the hydride formed from
The gas pretreatment is to mimic the reaction condi-
tion of n-pentane isomerization. Nearly all the IR peaks of
adsorbed pyridine on Brønsted and Lewis acid sites disap-
pear, if only pretreating Pt/WZ(SC)/SBA-15 in n-pentane.
If the mixture of n-pentane and hydrogen was used for

LEE ET AL.
417
TABLE 3 Consumption of
Brønsted and Lewis acid sites over WZ
(SC)/SBA-15 and Pt/WZ(SC)/SBA-15
after pretreating in H2 and n-pentane at
250ꢀC for 1 hr
WZ(SC)/ SBA-15
Pt/WZ(SC)/ SBA-15
Sample
Acide site
Brønsted
Lewis
Brønsted
Lewis
16.5
Loss in acid sites (%)a
31.9
39.2
81.9
aBrønsted and Lewis acid sites were calculated based on the peak height at 1,541 and 1,446 cm−1
respectively, using the intensity at 1,315 cm−1 as the baseline.
,
hydrogen, probably due to that the de-protonated acid
sites cannot be efficiently regenerated. However, the con-
version is leveling-off when too much hydrogen is added
into the reactant stream, attributed to that the dehydroge-
nation of pentane (Equation 2) is inhibited. Instead,
hydrogenolysis of pentane becomes a competing process.
3 | EXPERIMENTAL
3.1 | Catalysts preparation
SBA-15 was synthesized following the method reported by
Zhao et al.[32] Four grams of the Pluronic triblock copoly-
mer (P123, Mn = 5,800) was dissolved in 160 ml of 2 M HCl
solution. After adding 8.4 g of tetraethyl orthosilicate, the
solution was stirred at 35ꢀC for 24 hr, followed by the
hydrothermal treatment at 90ꢀC for another 24 hr. The as-
synthesized SBA-15 powders were collected by filtration
and dried at 100ꢀC overnight. Finally, the samples were cal-
cined at 560ꢀC for 6 hr (ramping rate of 1ꢀC/min) to
remove the organic templates.
SCHEME 1 Proposed mechanism of the n-pentane
isomerization over Pt/WZ/SBA-15
heterolytic fission of H2 to produce iso-pentane, as shown
in Equation (6). The overall reaction mechanism of the
n-pentane isomerization over the Pt/WZ/SBABA-15 cata-
lyst is shown in Scheme 1.
Tungstated zirconia deposited on SBA-15 was
achieved by conventional and SC impregnation. The con-
ventional impregnation method was based on the proce-
dures described by Li et al.[6] SBA-15 powders were
dispersed in a methanol solution of zirconium(IV) ace-
tylacetonate under vigorous stirring. An aqueous solution
of ammonium metatungstate hydrate was added and
stirred for 1 hr. After removing the solvent in a rotary
evaporator, the solid was dried at 100ꢀC overnight and
calcined at 800ꢀC for 3 hr with a ramping rate of 1ꢀC/
min (Figure S1). The resulted sample is labeled “Im” in
the bracket. For SC impregnation, a 50 ml beaker con-
taining the aforementioned slurry of SBA-15,
zirconium(IV) acetylacetonate/water and ammonium
metatungstate hydrate/methanol was transferred to a
600 ml autoclave containing 150 ml of 99.5% ethanol.
The autoclave was then heated at 270ꢀC for 3 hr. Under
such a condition, ethanol should achieve SC condition in
the high pressure Parr reactor. After cooling down to
room temperature, the solid products were collected by
filtration and dried at 100ꢀC overnight. After calcination
at 800ꢀC for 3 hr, the impregnated samples were obtained
and denoted as “SC” for discrimination. A further
Triwahyono et al.[31] investigated the effects of hydro-
gen on acid sites of WO3-ZrO2 and Pt/WO3-ZrO2. In the
presence of hydrogen, the number of Brønsted acid sites
was reported to increase and that of Lewis acid sites
decrease as the temperature was raised from 25 to 120ꢀC.
In the present study, in-situ IR experiments (Figure 10)
show that Brønsted acid sites on the Pt/WZ(SC)/SBA-15
catalyst are nearly consumed, while the ones on the WZ
(SC)/SBA-15 catalyst without Pt promoter still have a
portion remained after the pretreatment in hydrogen and
n-pentane. It is also noted that the consumption of Brøn-
sted acid sites is more apparent than that of Lewis acid
sites over Pt-promoted WZ(SC)/SBA-15 (Table 3). Such
spectral observations suggest that Brønsted acid sites are
the catalytic active centers for n-pentane isomerization
and the de-protonated acid sites can be regenerated by
the protons produced on the surfaces of Pt from hetero-
lytic fission of H2. It explains that addition of hydrogen
(2 ~ 10 ml/min) not only increases the conversion of n-
pentane, but also enhances the stability of the catalytic
performance (Figure 7). In contrast, a fast decline of con-
version and selectivity was seen in the absence of

418
LEE ET AL.
optimization of WO3 and ZrO2 loadings was included in
this study. Pt-deposition on WZ/SBA-15 was obtained by
conventional impregnation. The samples were suspended
in an aqueous solution of platinum(IV) chloride, dried at
100ꢀC overnight, and calcined at 500ꢀC for 3 hr (ramping
rate 2ꢀC/min).
To elucidate the sole effect of WO3, SBA-15 supported
tungsten oxide was prepared by SC impregnation, and
termed as W(SC)/SBA-15. The composition of the sample
was 20 wt% WO3 and 80 wt% SBA-15. As a control, WZ
without SBA-15 support was also prepared by SC impreg-
nation, and named as WZ(SC), of which the composition
was 20 wt% WO3 and 80 wt% ZrO2.
0.5 g of the catalyst was packed into the reactor and
pretreated in dry air at 450ꢀC for 3 hr, followed by cooling
down to 250ꢀC in a nitrogen flow. The reactants stream
containing n-pentane, hydrogen and nitrogen (0.37: 2:
10 ml/min) flew through the catalyst bed in a weight
hourly space velocity (WHSV) of 1,484.4 ml/gcat-h. The
products were separated and analyzed by a gas chromatog-
raphy (Shimadzu 14A), equipped with a capillary column
(RTX-1, 60 m), and a flame ionization detector. Heating
the sample in an air stream at 450ꢀC for 6 hr was con-
ducted to regenerate the used catalyst.
The n-pentane conversion as well as product selectiv-
ities and yields were calculated based on the following
equations.
Conversion ð%Þ = ðinlet moles−outlet moles of n−pentaneÞ
=ðinlet moles of n−pentaneÞ × 100
3.2 | Catalyst characterization
Powder X-ray diffraction (PXRD) patterns were recorded with
a Panalytical X'Pert diffractometer using Cu Kα radiation in
an operating mode of 45 kV and 40 mA. Nitrogen phy-
sisorption was carried out in a Micromeritics TriStar 3000 sys-
tem. Prior to the physisorption, 0.1 g of the sample was
degassed at 200ꢀC under 10−3 Torr for at least 8 hr. Acidity of
the catalysts was determined by TPD of NH3 using an
AutoChem 2910 system with a Thermo ONIX ProLab quadru-
pole detector. 0.25 g of the sample was heated in a 50 ml/min
of He flow at 500ꢀC for 1 hr to remove the adsorbed moisture.
Three percentage of ammonia in He (50 ml/min) was intro-
duced to the sample at 100ꢀC for 1 hr, followed by purging
the sample with pure He (30 ml/min) for another hour. While
the sample was heated to 800ꢀC with a ramping rate of 10ꢀC/
min, the NH2+ (m/z = 16) signal from the effluent was
recorded with a quadrupole mass spectrometer.
Adsorption of pyridine was used to distinguish Brøn-
sted and Lewis acid sites by in situ DRIFTS. The
adsorption–desorption of pyridine over the samples was
conducted in an in-situ sample cell (Harrick) using a
BOMEM MB155 FT-IR spectrometer. The resolution of
the recorded spectra is 4 cm−1. 0.1 g of the sample was
pressed into a disk and placed inside the cell. After
heated at 200ꢀC under 10−5 Torr for 3 hr and cooled
down to room temperature, the sample was exposed to
pyridine vapor for 30 min and evacuated to 10−5 Torr for
another 30 min to remove pyridine vapor in the gas
phase. The IR spectra were recorded under 10−5 Torr
while elevating the temperature to 500ꢀC.
ð1Þ
Selectivity ð%Þ = ðmoles of specific productÞ
=ðinlet moles−outlet moles of n−pentaneÞ
× 100
ð2Þ
Yield ð%Þ = Selectivity of specific product
ð3Þ
× n−pentane conversion × 100
4 | CONCLUSIONS
Well dispersed WZ supported on SBA-15 was prepared by
impregnation in SC ethanol. In comparison with the cat-
alyst prepared by conventional impregnation, better dis-
persion of WZ on SBA-15 support was achieved by the
SC treatment. The optimal catalytic activity was achieved
on Pt/WZ(SC)/SBA-15 catalyst with the loading ratio of
WO3/ZrO2/SBA-15 in 20/40/40 wt%, which corresponds
to the surface concentration of 2.4 W-atoms/nm2 and 8.9
Zr-atoms/nm2. The nearly monolayer dispersion of WO3
leads to catalysts of high surface areas and pore volumes
because the blockage or filling the pore channels of SBA-
15 by bulk WO3 particles is avoided.
Infrared spectroscopic investigations showed that
Brønsted acid sites on WZ/SBA-15 catalyst were the
active centers for n-pentane isomerization. With 1 wt% Pt
as the promoter, the SBA-15 supported WZ prepared by
SC impregnation gave 66% n-pentane conversion and
99% selectivity of iso-pentane. The role of Pt is considered
to enhance the dehydrogenation of n-pentane. However,
the pentane conversion decreased rapidly after ~5 hr on-
stream. Introduction of hydrogen (2 ~ 10 ml/min, or
0.016 ~ 0.08 MPa) into the gas stream of reactants was
3.3 | Catalytic test of n-pentane
isomerization
Isomerization of n-pentane was performed in a fixed-bed
reactor at atmospheric pressure. Prior to the reaction,

LEE ET AL.
419
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acidic sites were retained in the presence of hydrogen.
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the surface of Pt through heterolytic fission to form pro-
ton and hydride. The proton regenerated the acid site,
which was consumed in isomerization and consequently
retarded the deactivation of the solid acid catalysts. Over-
dosing hydrogen (10 ml/min, 0.08 MPa) leaded to a
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with generation of more cracking products from
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ACKNOWLEDGMENTS
The authors gratefully thank Ministry of Science and
Technology, Taiwan for the financial supports.
[32] D. Y. Zhao, Q. S. Huo, J. L. Feng, B. F. Chmelka, G. D. Stucky,
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Dr. Wenchao Lee obtained B.S. in
Chemistry from National Central
University and Ph.D. in Chemistry
from National Taiwan University in
2008. After being an Engineer at
ALEEES Co, Ltd in 2011–2014, he
has been an Assistant Manager at
Taiwan Surfactant since 2014.
Dr. Chieh-Chao Yang obtained B.S.
and M.S. in Chemical Engineering
from National Taiwan University,
Ph.D. from University of Twente, the
Netherlands in 2011. After doing
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sity and Northwestern University,
USA, he has been working at DuPont, Taiwan as
Riston® RD Chemist and lab supervisor, Asia-Pacific
Analytical Competency Leader, Adhesive RD Leader,
Pyralux® RD and Asia-Pacific Application Develop-
ment Leader. Currently, he is Global Pyralux® Tech-
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Dr. Soofin Cheng obtained B.S. in
Chemistry from National Tsinghua
University, Taiwan and Ph.D. from
Texas A&M University, USA in 1982.
She has been the associate professor
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and full professor at Department of
Chemistry, National Taiwan Univer-
sity in 1985–2019. Her research interests have been in
synthesis and preparation of new materials, especially
nano-porous and nano-composite materials as cata-
lysts for utilization in synthesis of fine chemicals and

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LEE ET AL.
sustainable energies, as well as photo-catalysts for
decomposition of pollutants. Since 2019, she is Profes-
sor Emeritus.
How to cite this article: Lee W, Yang C-C,
Cheng S. Isomerization of n-pentane over platinum
promoted tungstated zirconia supported on
mesoporous SBA-15 prepared by supercritical
impregnation. J Chin Chem Soc. 2021;68:409–420.
https://doi.org/10.1002/jccs.202000473
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