Platinum-tin nano-catalysts supported on alumina for direct dehydrogenation of n-butane

Article abstract of DOI:10.1166/jnn.2015.11241

Al₂O₃ supports were prepared by a precipitation method using various basic solutions (NaOH, KOH, NH₄OH, and Na₂CO₃) as precipitation agents, and Pt/Sn/Al₂O₃ nano-catalysts were then prepared by a sequential impregnation method. The prepared catalysts were applied to the direct dehydrogenation of n-butane to n-butenes and 1,3-butadiene. The effect of precipitation agents on the physicochemical properties and catalytic activities of Pt/Sn/Al₂O₃ nano-catalysts in the direct dehydrogenation of n-butane was investigated. Catalytic performance of Pt/Sn/Al₂O₃ nanocatalysts decreased in order of Pt/Sn/Al₂O₃ (NaOH) > Pt/Sn/Al₂O₃ (KOH) > Pt/Sn/Al₂O₃ (NH₄OH) > Pt/Sn/Al₂O₃ (Na₂CO₃). Among the catalysts tested, Pt/Sn/Al₂O₃ (NaOH) nano-catalyst showed the best catalytic performance in ter ms of yield for total dehydrogenation products (TDP, n-butenes and 1,3-butadiene). Hydrogen chemisorption experiments revealed that platinum surface area of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing platinum surface area of the catalyst.

Full text of DOI:10.1166/jnn.2015.11241

Article
Journal of
Nanoscience and Nanotechnology
Vol. 15, 8305–8310, 2015
Copyright © 2015 American Scientific Publishers
All rights reserved
Printed in the United States of America
www.aspbs.com/jnn
Platinum-Tin Nano-Catalysts Supported on Alumina for
Direct Dehydrogenation of n-Butane
1
1
1
2
2
Jong Kwon Lee , Hyun Seo , Ung Gi Hong , Gle Park , Yeonshick Yoo ,
2
2
1ꢀ∗
Jinsuk Lee , Hosik Chang , and In Kyu Song
1School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University,
Shinlim-dong, Kwanak-ku, Seoul 151-744, South Korea
2
Samsung Total Petrochemicals Corporation, Daesan 356-711, South Korea
Al O supports were prepared by a precipitation method using various basic solutions (NaOH,
2
3
KOH, NH OH, and Na CO ꢀ as precipitation agents, and Pt/Sn/Al O nano-catalysts were then
4
2
3
2
3
prepared by a sequential impregnation method. The prepared catalysts were applied to the direct
dehydrogenation of n-butane to n-butenes and 1,3-butadiene. The effect of precipitation agents
on the physicochemical properties and catalytic activities of Pt/Sn/Al O3 nano-catalysts in the
2
direct dehydrogenation of n-butane was investigated. Catalytic performance of Pt/Sn/Al O nano-
2
3
catalysts decreased in order of Pt/Sn/Al O (NaOH) > Pt/Sn/Al O (KOH) > Pt/Sn/Al O (NH OH) >
2
3
2
3
2
3
4
Pt/Sn/Al O (Na CO ꢀ. Among the catalysts tested, Pt/Sn/Al O (NaOH) nano-catalyst showed the
2
3
2
3
2
3
best catal yD t iec l ipv ee r rf oe rdm ba yn cPe ui nb l ti es rh mi nsgo Tf ye i ce hl dn foo l ro tgo yt a tl od :e Rh yi cd er o Ug en ni va et i or sn it py r, o Fd ou cn t ds r (eT nD LP ,i bnr- ab ru ytenes and
1
,3-butadiene). Hydro IgPe :n 4 c6 h. 1e m7 .i 2s o3 r8p . t1i o3 n8 eOx pn e: rMi m oe nn ,t s1 2r e Ov e ca tl e2 d0 1t h5 a 0t 5p :l a2 t8i n: 0u 4m surface area of the
catalyst was closely relate dC ot op yt hr ei g hc at :t aA l ymt i ce r pi ce ar f no r Sm ca i ne cn et .i f iYc i eP l du bf ol irs hT eD rPs increased with increasing
platinum surface area of the catalyst.
Keywords: Direct Dehydrogenation of n-Butane, n-Butene, 1,3-Butadiene, Precipitation Method,
Pt/Sn/Al O Nano-Catalyst.
2
3
1
. INTRODUCTION
is thermodynamically unfavorable, on the other hand,
side reactions such as coke formation and cracking are
inevitable. Nonetheless, high selectivity and high yield for
dehydrogenation products can be obtained in the direct
Butenes and butadiene are important raw materials for
synthetic rubbers, plastics, and other valuable chemical
products. Butenes and butadiene currently supplied in the
market are mainly produced as a by-product of naph-
tha cracking process. The explosive growth of shale gas
industry has reduced the production of butenes and buta-
diene available from naphtha cracking process because
of the switch to lighter feed stocks. On the other hand,
the demand for butenes and butadiene has continuously
increased due to the development of rubber industry for
motor vehicle tires. For these reasons, dehydrogenation
of n-butane has been extensively studied as an alternative
6
ꢀ7
dehydrogenation of n-butane.
Direct dehydrogenation of n-butane has been inves-
8
9ꢀ10
tigated over chromia-, vanadia-,
catalysts
or platinum-based
supported on alumina. Among these cat-
alysts, alumina-supported platinum catalysts have been
1
1–13
1
1–13
widely used in the direct dehydrogenation of n-butane.
It is known that alumina-supported platinum catalysts are
very active but the catalysts are less selective and easily
deactivated. The catalytic activity and stability of alumina-
supported platinum catalysts can be improved by adding a
1
–3
route for the production of butenes and butadiene.
1
2–14
There are two methods in the dehydrogenation of
n-butane.4 Oxidative dehydrogenation reaction is ther-
modynamically favorable, but this reaction has some prob-
lems such as total combustion of n-butane to carbon
dioxide.4 Although direct dehydrogenation of n-butane
second metal such as tin.
The role of second metal is
–7
to weaken the platinum-olefin interaction selectively with-
out affecting the platinum-paraffin interaction.
In this work, Al O supports were prepared by a pre-
2
3
ꢀ5
cipitation method using various basic solutions (NaOH,
KOH, NH OH, and Na CO ꢁ as precipitation agents,
4
2
3
∗
Author to whom correspondence should be addressed.
and Pt/Sn/Al O nano-catalysts were then prepared by a
2 3
J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 10
1533-4880/2015/15/8305/006
doi:10.1166/jnn.2015.11241
8305

Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane
Lee et al.
sequential impregnation method. The prepared catalysts
were applied to the direct dehydrogenation of n-butane
to n-butenes and 1,3-butadiene. The effect of precipita-
tion agent on the physicochemical properties and catalytic
activities of Pt/Sn/Al O nano-catalysts in the direct dehy-
N (20 ml/min). The signal of outlet gas was collected
2
using a thermal conductivity detector (TCD). Hydrogen
chemisorption experiments (BELCAT-B, BEL Japan) were
conducted to measure the platinum dispersion and plat-
inum surface area of the catalysts. 50 mg of each catalyst
was preliminarily reduced with a mixed stream of hydro-
2
3
drogenation of n-butane was investigated.
ꢀ
gen (2.5 ml/min) and argon (47.5 ml/min) at 570 C for
3
5
h, and then it was purged with argon (50 ml/min) at
70 C for 10 min and cooled to 50 C. The amount of
2
. EXPERIMENTAL DETAILS
ꢀ
ꢀ
2
.1. Preparation of Pt/Sn/Al O Nano-Catalysts
2
3
hydrogen uptake was measured by periodically injecting
diluted hydrogen gas (5% hydrogen and 95% argon) into
the reduced catalyst. X-ray photoelectron spectroscopy
(XPS) analyses (ThermoVG, SIGMA PROBE) were con-
ducted to measure the binding energies of Pt 4f7/2 and Sn
A series of Al O supports were prepared by a precipita-
tion method using various basic solutions (NaOH, KOH,
NH OH, and Na CO ꢁ as precipitation agents, accord-
ing to the similar methods reported in the literatures.
2
3
4
2
3
1
5–17
A known amount of aluminum precursor (Aluminum
nitrate nonahydrate, Sigma-Aldrich) was dissolved in dis-
tilled water. The basic solution and aluminum precur-
sor solution were then slowly added into distilled water
under vigorous stirring. The pH of the mixed solution was
adjusted to 9 by controlling the amount of basic solution
for precipitation. After the resultant was stirred vigorously
at room temperature for 3 h, it was aged overnight at
room temperature. The precipitate was separated, and sub-
3
d5/2 in the nano-catalysts using C 1s peak (284.5 eV) as
a reference.
2
.3. Direct Dehydrogenation of n-Butane
Direct dehydrogenation of n-butane to n-butenes and 1,3-
butadiene over Pt/Sn/Al O (X) nano-catalysts was carried
out in a continuous flow fixed-bed reactor at 550 C under
atmosphere pressure. Each catalyst (0.25 g) was prelimi-
narily reduced with a mixed stream of H (150 ml/h) and
2
3
ꢀ
ꢀ
2
sequently, it was washed and dried overnight at 80 C. The
ꢀ
N (150 ml/h) at 570 C for 3 h. For the reaction, n-butane
was continuously supplied into the reactor with nitrogen
ꢀ
2
dried product was finally calcined at 600 C for 4 h to
yield Al O support.
2
3
carrier. Feed composition was fixed at n-butane:nitrogen=
For the preparation of Pt/Sn/Al O nano-catalyst, Sn
2
3
1
6
:1. Gas hourly space velocity (GHSV) was fixed at
00 ml/h·g-cat on the basis of n-butane. Reaction products
Delivered by Publishing Technology to: Rice University, Fondren Library
precursor (Tin(II) chloride dihydrate, Sigma-Aldrich) was
IP: 46.17.238.138 On: Mon, 12 Oct 2015 05:28:04
impregnated on the Al O support using hydrochloric acid
2
3
Copyright: American S cw i ee rn eti pf i ec r iPo ud bi cl ai sl lhy e sr sa mpled and analyzed using a gas chro-
ꢀ
solution. It was dried at 80 C overnight and calcined at
00 C in air for 4 h. Pt precursor (Chloroplatinic acid
matograph (Varian CP-3380) equipped with a GS-alumina
column and a flame ionization detector (FID). Conversion
of n-butane and selectivity for total dehydrogenation prod-
ucts (TDP, n-butenes and 1,3-butadiene) were calculated
on the basis of carbon balance as follows. Yield for TDP
was calculated by multiplying conversion of n-butane and
selectivity for TDP.
ꢀ
6
hexahydrate, Sigma-Aldrich) was then impregnated on the
ꢀ
Sn/Al O sample, followed by drying at 80 C overnight
2
3
ꢀ
and calcination at 550 C in air for 4 h. The contents of
Pt and Sn in the Pt/Sn/Al O nano-catalysts were fixed
2
3
at 1 wt%, respectively. The prepared Pt/Sn/Al O nano-
2
3
catalysts were denoted as Pt/Sn/Al O (X) (X = NaOH,
2
3
KOH, NH OH, and Na CO ꢁ, where X represented the
moles of n-butane reacted
Conversion of n-butane=
4
2
3
basic solution used for the precipitation.
moles of n-butane supplied
moles of n-butenes formed
2
.2. Characterization
+
moles of 1,3-butadiene formed
Formation of Pt/Sn/Al O (X) nano-catalysts was con-
Selectivity for TDP=
2
3
moles of n-butene reacted
firmed by XRD measurements (Rigaku, D-MAX2500-
PC) using Cu–Kꢂ radiation (ꢃ = 1ꢄ541 Å) operated
at 50 kV and 100 mA. Platinum and tin contents in
the prepared nano-catalysts were determined by ICP-
AES (Shimadz, ICP-1000IV) analyses. Brunauer-Emmett-
Teller (BET) surface area, pore volume, and average pore
diameter of Pt/Sn/Al O (X) nano-catalysts were mea-
Yield for TDP =(Conversion of n-butane)
(Selectivity for TDP)
×
3
. RESULTS AND DISCUSSION
3.1. Formation of Pt/Sn/Al Nano-Catalysts
Successful formation of Pt/Sn/Al O (X) nano-catalysts
O
3
2
3
2
sured by N adsorption–desorption measurements using
2
2
3
a BELSORP-mini II (BEL Japan) instrument. For the
temperature-programmed reduction (TPR) measurements,
was confirmed by XRD and ICP-AES measurements.
Figure 1 shows the XRD patterns of Pt/Sn/Al O (X) nano-
2
3
0
.2 g of each catalyst was charged into the U-shaped
catalysts. Crystalline phase of Al O was identified using
2 3
quartz reactor. Furnace temperature was then increased
JCPDS. As shown in Figure 1, characteristic diffraction
ꢀ
from room temperature to 550 C at a heating rate of
peaks of ꢅ-Al O were observed in all the Pt/Sn/Al O
2
3
2
3
ꢀ
5
C/min under a mixed flow of H2 (2 ml/min) and
(X) nano-catalysts. XRD peaks corresponding to Pt and
8306
J. Nanosci. Nanotechnol. 15, 8305–8310, 2015

Lee et al.
Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane
γ -Al O3
55
2
Pt/Sn/Al O (NaOH)
2
3
Pt/Sn/Al O (KOH)
2
3
Pt/Sn/Al O3 (NaOH)
2
Pt/Sn/Al O (NH OH)
2
3
4
5
4
0
5
Pt/Sn/Al O (Na CO )
2
3
2
3
Pt/Sn/Al O3 (KOH)
2
Pt/Sn/Al O3 (NH OH)
2
4
40
35
Pt/Sn/Al O3 (Na CO )
2
2
3
1
0
0
2
0
30
40
50
60
70
80
6
0
90 120 150 180 210 240 270 300 330 360
2
Theta (Degree)
Time on stream (min)
Figure 1. XRD patterns of Pt/Sn/Al O (X) (X = NaOH, KOH,
2
3
Figure 2. Catalytic performance of Pt/Sn/Al O (X) (X = NaOH, KOH,
ꢀ
2
3
NH OH, and Na CO ) nano-catalysts reduced at 570 C for 3 h.
4
2
3
NH OH, and Na CO ) nano-catalysts with time on stream in the direct
4
2
3
ꢀ
dehydrogenation of n-butane at 550 C.
Sn were not detected, indicating that Pt and Sn species
were finely dispersed on the support. This result was well
catalytic performance of Pt/Sn/Al O (X) nano-catalysts
2
3
1
8ꢀ19
consistent with the previous works
in a sense that
was strongly influenced by the identity of precipitation
agent. Detailed catalytic performance of Pt/Sn/Al O (X)
ꢅ-Al O peaks were only detected in the XRD patterns
2
3
2
3
of Pt/Sn/Al O nano-catalysts with low Pt and Sn con-
nano-catalysts obtained after a 360 min-reaction is shown
in Figure 3. As shown in Figure 3, iso-butane, iso-
butene, and cracking products (methane, ethane, ethylene,
propane, and propylene) were produced as by-products
together with main products (n-butenes and 1,3-butadiene).
2
3
tents. Pt and Sn contents in the Pt/Sn/Al O (X) nano-
2
3
catalysts are summarized in Table I. The measured Pt and
Sn contents were in good agreement with the designed
values. These results indicate that Pt/Sn/Al O (X) nano-
2
3
catalysts were succes sDf ue l ll iyv ep rr ee pd a br ey d Pi nu bt hl iiss h wi no gr k T. eP ch hy ns i oc loo -gy t oY: i Re l idc ef o Ur nT i Dv eP r s( it toy t ,a lF do en hd yr de rno gL ei bn ar at i roy n products, n-butenes
IP: 46.17.238.138 On: Mon, 12 Oct 2015 05:28:04
chemical properties of the catalysts are also summarized in
and 1,3-butadiene) after a 360 min-reaction decreased in
Copyright: American Scientific Publishers
Table I. BET surface area, pore volume, and average pore
the order of Pt/Sn/Al O (NaOH) > Pt/Sn/Al O (KOH) >
2
3
2
3
diameter of Pt/Sn/Al O (X) nano-catalysts decreased in
Pt/Sn/Al O (NH OH) > Pt/Sn/Al O (Na CO ꢁ. Among
2 3 4 2 3 2 3
2
3
the order of Pt/Sn/Al O (NaOH) > Pt/Sn/Al O (KOH) >
the catalysts tested, Pt/Sn/Al O (NaOH) nano-catalyst
2
3
2
3
2 3
Pt/Sn/Al O (NH OH) > Pt/Sn/Al O (Na CO ꢁ. Among
showed the best catalytic performance in terms of yield
for TDP in the direct dehydrogenation of n-butane (Figs. 2
and 3).
2
3
4
2
3
2
3
the catalysts examined, Pt/Sn/Al O (NaOH) nano-catalyst
2
3
retained the highest surface area, the largest pore volume,
and the largest average pore diameter. From these results,
it is inferred that the identity of precipitation agent strongly
affects the physicochemical properties of Pt/Sn/Al O (X)
3
.3. TPR Result of Pt/Sn/Al O Nano-Catalysts
2 3
2
3
TPR measurements were carried out to investigate
the reduction behavior of metal species and to examine
the interaction between metal species and support in the
Pt/Sn/Al O (X) nano-catalysts. Figure 4 shows the TPR
nano-catalysts.
3
.2. Catalytic Performance of Pt/Sn/Al O
2
3
2
3
Nano-Catalysts
profiles of Pt/Sn/Al O (X) nano-catalysts. Pt/Sn/Al O
2
3
2
3
Figure 2 shows the catalytic performance of Pt/Sn/Al O3
(NaOH), Pt/Sn/Al O (KOH), and Pt/Sn/Al O (NH OH)
2 3 2 3 4
2
(
X) nano-catalysts with time on stream in the direct dehy-
catalysts exhibited a broad reduction bands at around
ꢀ
ꢀ
ꢀ
drogenation of n-butane at 550 C. All the Pt/Sn/Al O
(
ing the direct dehydrogenation reaction. However, the
260 C with a shoulder at around 400 C. The major reduc-
tion band appearing at low temperature was attributed to
the reduction of Pt oxide species interacted with alumina,
2
3
X) nano-catalysts exhibited a significant deactivation dur-
Table I. Metal content, BET surface area, pore volume, and average pore diameter of Pt/Sn/Al O (X) nano-catalysts.
2
3
a
a
2
b
3
c
d
Nano-catalyst
Pt content (wt%)
Sn content (wt%)
BET surface area (m /g)
Pore volume (cm /g)
Average pore diameter (nm)
Pt/Sn/Al O (NaOH)
1.0
1.0
1.0
1.0
1.1
1.1
1.1
1.2
190
189
155
42
0.35
0.34
0.30
0.10
8.2
7.2
5.5
3.8
2
3
Pt/Sn/Al O (KOH)
2
3
Pt/Sn/Al O NH OH)
2
3
4
Pt/Sn/Al O (Na CO ꢁ
2
3
2
3
Notes: aDetermined by ICP-AES analyses; bCalculated by the BET equation; cBJH desorption pore volume; dBJH desorption average pore diameter.
J. Nanosci. Nanotechnol. 15, 8305–8310, 2015
8307

Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane
Lee et al.
2
0
Table II. Hydrogen chemisorption results for Pt/Sn/Al
catalysts reduced at 570 C for 3 h.
2
O
3
(X) nano-
1
-Butene
ꢀ
trans-2-Butene
cis-2-Butene
1
,3-Butadiene
Pt
Pt surface
area (m /g)
Pt partice
16
iso-Butane
a
2
a
a
Nano-catalyst
dispersion (%)
size (nm)
iso-Butene
Cracking products
Pt/Sn/Al O (NaOH)
21ꢄ8
21ꢄ3
19ꢄ4
5ꢄ1
53.9
52.5
47.9
12.5
5ꢄ2
5ꢄ3
5ꢄ8
2
3
12
Pt/Sn/Al O (KOH)
2
3
Pt/Sn/Al O (NH OH)
2
3
4
Pt/Sn/Al O (Na CO ꢁ
22ꢄ4
2
3
2
3
8
Note: aCalculated by assuming stoichiometry factor (H /Pt) = 1.
2
4
0
Pt/Sn/Al O (X) catalysts decreased in the order of
2
3
Pt/Sn/Al O (NaOH) > Pt/Sn/Al O (KOH) > Pt/Sn/Al O
2
3
2
3
2
3
(NH OH) > Pt/Sn/Al O (Na CO ꢁ. Platinum particle size
4
2
3
2
3
Pt/Sn/Al O
Pt/Sn/Al O
(KOH)
Pt/Sn/Al O
Pt/Sn/Al O
2
3
2
3
2
3
2
3
of the catalysts increased in the order of Pt/Sn/Al O
2 3
(NaOH)
(NH OH)
(Na CO )
4
2
3
(
NaOH) < Pt/Sn/Al O (KOH) < Pt/Sn/Al O (NH OH) <
2 3 2 3 4
Pt/Sn/Al O (Na CO ꢁ. Among the catalysts examined,
Figure 3. Yield for product over Pt/Sn/Al O3 (X) (X = NaOH, KOH,
2
3
2
3
2
NH OH, and Na CO ) nano-catalysts after a 360 min-reaction in the
Pt/Sn/Al O (NaOH) nano-catalyst exhibited the highest
4
2
3
2 3
ꢀ
direct dehydrogenation of n-butane at 550 C.
platinum dispersion, the highest platinum surface area, and
the smallest platinum particle size. This might be due to
the highest surface area and the largest pore volume of
Pt/Sn/Al O (NaOH) nano-catalyst (Table I), which effec-
while the minor shoulder appearing at high temperature
4
+
2+
2+
was due to the partial reduction of Sn to Sn and Sn
2
3
0
20–22
to Sn .
On the other hand, Pt/Sn/Al O (Na CO ꢁ cat-
tively suppressed the aggregation of platinum species dur-
ing the impregnation step.
2
3
ꢀ
2
3
ꢀ
alyst showed two reduction bands at 275 C and 420 C.
Low-temperature reduction peak was attributed to the
reduction of Pt oxide species, while high-temperature
3.5. XPS Result of Pt/Sn/Al O Nano-Catalysts
2
3
2
+
reduction peak was ascribed to the reduction of Sn to
In order to investigate the chemical state of metals
in the reduced nano-catalysts, XPS analyses were con-
0
Delivered by Publishing20–22echnology to: Rice University, Fondren Library
T
Sn strongly interacted with alumina support.
IP: 46.17.238.138 On: Mon, 12 Oct 2015 05:28:04
ducted. All the reduced nano-catalysts exhibited binding
Copyright: American Scientific Publishers
.4. Pt Dispersion and Pt Surface Area of
energy of single Pt 4f
3
component at 71.3–72.3 eV
7
/2
Pt/Sn/Al O Nano-Catalysts
(not shown here), indicating the presence of zerovalent
2
3
2
3
Hydrogen chemisorption measurements were conducted
in order to determine the platinum dispersion and
platinum surface area in the Pt/Sn/Al O (X) nano-
platinum. This means that all platinum species were
completely reduced to zerovalent platinum during the
reduction process. Figure 5 shows the binding energies
of Sn 3d5/2 level of reduced Pt/Sn/Al O (X) nano-
2
3
catalysts. Hydrogen chemisorption results for reduced
Pt/Sn/Al O (X) nano-catalysts are listed in Table II.
2
3
2
4–26
catalysts. According to literatures,
three peaks are
2
3
The platinum dispersion and platinum surface area of
generally observed at around 485.0 eV, 486.0 eV, and
Sn(0) Sn(0)alloy
Pt/Sn/Al O (NaOH)
Sn(II, IV)
Pt/Sn/Al O3 (NaOH)
2
260 °C
257 °C
2
3
Pt/Sn/Al O (KOH)
Pt/Sn/Al O3 (KOH)
2
3
2
Pt/Sn/Al O3 (NH OH)
Pt/Sn/Al O (NH OH)
2 3 4
2
4
254 °C
Pt/Sn/Al O (Na CO )
2
3
2
3
420 °C
Pt/Sn/Al O3 (Na CO )
2
2
3
275 °C
483
484
485
486
487
488
489
490
1
00
200
300
400
500
Binding energies of Sn 3d5/2 (eV)
Temperature (°C)
Figure 5. Binding energies of Sn 3d5/2 level of Pt/Sn/Al O (X) (X =
2
3
ꢀ
Figure 4. TPR profiles of Pt/Sn/Al O (X) (X = NaOH, KOH, NH OH,
NaOH, KOH, NH OH, and Na CO ) nano-catalysts reduced at 570
C
2
3
4
4
2
3
and Na CO ) nano-catalysts.
for 3 h.
2
3
8308
J. Nanosci. Nanotechnol. 15, 8305–8310, 2015

Lee et al.
Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane
5
4
3
2
1
0
0
0
0
0
0
4
. CONCLUSIONS
Pt/Sn/Al O3 (NaOH)
2
Al O supports were prepared by a precipitation method
using various basic solutions (NaOH, KOH, NH OH,
and Na CO ꢁ, and Pt/Sn/Al O nano-catalysts were then
prepared by a sequential impregnation method for use
in the direct dehydrogenation of n-butane. The effect
of precipitation agent on the physicochemical proper-
ties and catalytic activities of Pt/Sn/Al O nano-catalysts
was investigated. All the Pt/Sn/Al O (X) nano-catalysts
2
3
Pt/Sn/Al O3 (KOH)
2
4
Pt/Sn/Al O3 (NH OH)
2
4
2
3
2
3
2
3
2
3
exhibited a significant deactivation during the reaction.
Yield for TDP decreased in the order of Pt/Sn/Al O
2
3
(
NaOH) > Pt/Sn/Al O (KOH) > Pt/Sn/Al O (NH OH) >
2 3 2 3 4
Pt/Sn/Al O3 (Na CO )
2
2
3
Pt/Sn/Al O (Na CO ꢁ. It was observed that yield for
2
3
2
3
1
0
20
30
40
50
60
TDP increased with increasing platinum surface area of
the catalyst. Among the catalysts tested, Pt/Sn/Al O
2
Platinum surface area (m /g)
2
3
(
NaOH) nano-catalyst with the highest platinum surface
Figure 6. A correlation between yield for TDP after a 360 min-
reaction and platinum surface area of Pt/Sn/Al O (X) (X = NaOH, KOH,
area showed the best catalytic performance in the reaction.
Thus, platinum surface area served as an important factor
determining the catalytic performance of Pt/Sn/Al O (X)
2
3
NH OH, and Na CO ) nano-catalysts.
4
2
3
2
3
in the direct dehydrogenation of n-butane.
4
87.7 eV, corresponding to zerovalent Sn (Sn(0)), alloyed
tin (Sn(0)alloyꢁ, and oxidized species of tin (Sn(II,IV)),
respectively. As shown in Figure 5, however, only two Sn
Acknowledgments: The authors wish to acknowl-
edge support from the Samsung Total Petrochemicals
Corporation.
3
d5/2 components (Sn(0)alloy and Sn(II,IV)) were observed
in the Pt/Sn/Al O (NaOH), Pt/Sn/Al O (KOH), and
2
3
2
3
Pt/Sn/Al O (NH OH) catalysts. Any peaks related to
2
3
4
References and Notes
zerovalent tin were not detected in these three catalysts.
Delivered by Publishing Technology to: Rice University, Fondren Library
1
. L. Rodriguez, D. Romero, D. Rodriguez, J. Sanchez, and
On the other hand, Pt/Sn/Al O (Na CO ꢁ showed three
2
3
IP: 46.17.238.138 On: Mon, 12 Oct 2015 05:28:04
2
3
F. Dominguez, Appl. Catal. A 373, 66 (2010).
peaks (Sn(0), Sn(0)alloy, and Sn(II,IV C) ) .o pT yh rei g ph rt e: sAe nm c ee r ioc fa n Scientific Publishers
2. S. A. Bocanegra, A. A. Castro, O. A. Scelza, and S. R. de Miguel,
zerovalent tin in the Pt/Sn/Al O (Na CO ꢁ catalyst and
2
3
2
3
Appl. Catal. A 333, 49 (2007).
the absence of zerovalent tin in the Pt/Sn/Al O (NaOH),
3. S. D. Jackson, S. Rugmini, P. C. Stair, and Z. Wu, Chem. Eng. J.
120, 127 (2006).
2
3
Pt/Sn/Al O (KOH), and Pt/Sn/Al O (NH OH) catalysts
2
3
2
3
4
4
5
. N. Kijima, M. Toba, and Y. Yoshimura, Catal. Lett. 127, 63 (2009).
. W. Liu, S. Y. Lai, H. Dai, S. Wang, H. Sun, and C. T. Au, Catal.
Today 131, 450 (2008).
were well supported by TPR results (Fig. 4). In general,
the state of Sn in the Pt–Sn catalyst strongly affects the
catalytic properties. When Sn exists as a metallic state
6
7
8
9
. M. J. Ledoux, F. Meunier, B. Heinrich, C. Pham-Huu, M. E. Harlin,
and A. O. I. Krause, Appl. Catal. A 181, 157 (1999).
. S. Veldurthi, C.-H. Shin, O.-S. Joo, and K.-D. Jung, Catal. Today
0
(
Sn ꢁ, it serves as a poison. When Sn exists as a nonmetal-
4
+
2+
lic state (Sn or Sn ꢁ, however, it acts as a promoter.
Therefore, it can be inferred that metallic tin unalloyed
with platinum in the Pt/Sn/Al O (Na CO ꢁ catalyst is
185, 88 (2012).
. M. M. Bhasin, J. H. McCain, B. V. Vora, T. Imai, and P. R. Pujado,
Appl. Catal. A 221, 397 (2001).
. S. D. Jackson and S. Rugmini, J. Catal. 251, 59 (2007).
2
3
2
3
responsible for its low catalytic activity (Figs. 2 and 3).
1
1
1
0. Y. Xu, J. Lu, M. Zhong, and J. Wang, J. Nat. Gas Chem. 18, 88
(2009).
3
.6. Correlation Between Catalytic Performance and
Pt Surface Area
1. S. A. Bocanegra, A. A. Castro, A. Guerrero-Ruiz, O. A. Scelza, and
S. R. de Miguel, Chem. Eng. J. 118, 161 (2006).
2. S. R. de Miguel, S. A. Bocanegra, I. M. J. Vilella, A. Guerrero-Ruiz,
and O. A. Scelza, Catal. Lett. 119, 5 (2007).
Figure 6 shows the correlation between platinum surface
area and catalytic performance in the direct dehydrogena-
tion of n-butane. It is interesting to note that yield for TDP
increased with increasing platinum surface area. Although
platinum surface area of the catalyst is not the sole factor
determining the catalytic performance in the direct dehy-
drogenation of n-butane, it can serve as an important corre-
lating parameter for the catalytic performance in the direct
dehydrogenation of n-butane. Among the catalysts tested,
Pt/Sn/Al O (NaOH) nano-catalyst with the highest plat-
13. S. A. Bocanegra, P. D. Zgolicz, O. A. Scelza, and S. R. de Miguel,
Catal. Commun. 10, 1463 (2009).
1
1
1
1
1
4. A. D. Ballarini, P. Zgolicz, I. M. J. Vilella, S. R. de Miguel, A. A.
Castro, and O. A. Scelza, Appl. Catal. A 381, 83 (2010).
5. J. K. Lee, H. Lee, U. G. Hong, J. Lee, Y.-J. Cho, Y. Yoo, H.-S. Jang,
and I. K. Song, J. Ind. Eng. Chem. 18, 1096 (2012).
6. Y. Bang, S. J. Han, J. Yoo, J. H. Choi, J. K. Lee, J. H. Song, J. Lee,
and I. K. Song, Appl. Catal. B 148, 269 (2014).
7. J. G. Seo, M. H. Youn, D. R. park, I. Nam, and I. K. Song, Int. J.
Hydrogen Energ. 34, 8053 (2009).
8. I. H. Cho, S. B. Park, S. J. Cho, and R. Ryoo, J. Catal. 173, 295
(1998).
2
3
inum surface area showed the best catalytic performance
in the direct dehydrogenation of n-butane.
J. Nanosci. Nanotechnol. 15, 8305–8310, 2015
8309

Platinum-Tin Nano-Catalysts Supported on Alumina for Direct Dehydrogenation of n-Butane
Lee et al.
1
2
2
2
9. M.-Y. Kim, J.-H. Park, C.-H. Shin, S.-W. Han, and G. Seo, Catal.
Lett. 133, 288 (2009).
0. O. A. Barias, A. Holmen, and E. A. Blekkan, J. Catal. 158, 1
23. B. K. Vu, M. B. Song, S.-A. Park, Y. Lee, I. Y. Ahn, Y.-W. Suh,
D. J. Suh, W.-I, Kim, H.-L. Koh, Y. G. Choi, and E. W. Shin, Korean
J. Chem. Eng. 28, 383 (2011).
24. N. Homs, J. Llorca, M. Riera, J. Jolis, J. Fierro, J. Sales, and P. R.
de la Piscina, J. Mol. Catal. A-Chem. 200, 251 (2003).
25. J. Llorca, P. R. de la Piscina, J. L. G. Fierro, J. Sales, and N. Homs,
J. Mol. Catal. A: Chem. 118, 101 (1997).
(
1996).
1. F. B. Passos, D. A. G. Aranda, and M. Schmal, J. Catal. 178, 478
1998).
(
2. S. R. de Miguel, G. T. Baronetti, A. A. Castro, and O. A. Scelza,
Appl. Catal. 45, 61 (1988).
26. K. Balakrishhan and J. Schwank, J. Catal. 127, 287 (1991).
Received: 24 June 2014. Accepted: 7 November 2014.
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Copyright: American Scientific Publishers
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J. Nanosci. Nanotechnol. 15, 8305–8310, 2015