Full text of DOI:10.1166/jnn.2015.10424

Article
Journal of
Nanoscience and Nanotechnology
Vol. 15, 5334–5337, 2015
Copyright © 2015 American Scientific Publishers
All rights reserved
Printed in the United States of America
www.aspbs.com/jnn
Ring Opening of Naphthenic Molecules Over Metal
Containing Mesoporous Y Zeolite Catalyst
1ꢀ2
1ꢀ2
1ꢀ∗
1
1
You-Jin Lee , Eun Sang Kim , Tae-Wan Kim , Chul-Ung Kim , Kwang-Eun Jeong ,
2
1
Chang-Ha Lee , and Soon-Yong Jeong
1Research Center for Green Catalysis, Korea Research Institute of Chemical Technology, 141,Gajeong-Ro, Yuseong-Gu,
Daejeon 305-600, South Korea
2
Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 120-749, South Korea
Mesoporous Y zeolite (Meso-Y) with a uniform mesopore was synthesized via pseudomorphic syn-
thesis. The Meso-Y supported Ni-W catalyst (NiW/Meso-Y) was introduced as a catalyst for the
selective ring opening of naphthenic rings. The catalytic test for the ring opening of naphthalene
as a model compound of multi-ring aromatics was performed using a batch-type reaction system
with both sulfided 20 wt% NiW/Meso-Y and NiW/Y catalysts under different reaction conditions.
The catalytic results reveal that the Meso-Y supported NiW catalyst experiences a naphthalene
conversion similar to the NiW/Y catalyst, but the NiW/Meso-Y catalyst has higher product yields
for BTEX (benzene, toluene, ethyl benzene, and xylene) and the middle distillate than those of the
NiW/Y catalyst at a low reaction temperature. These results suggest that the mesoporosity of the
NiW/Meso-Y catalyst is more advantageous for the ring opening reaction of multi-ring aromatics
due to the easier access for the bulky molecules compared to the NiW/Y catalyst.
Keywords: Ring Opening, Multi-Ring Aromatics, BTEX, Mesoporous Zeolite, Heavy Oil
Upgrading.
2
1
. INTRODUCTION
fuel. While the selective ring opening (SRO) of naph-
thenic molecules is a promising pathway for heavy residue
upgrading and it has been studied by many researchers,
SRO still presents challenges due to a complex chemistry,
product selectivities, operation conditions, composition of
The heavy residue upgrading process has attracted
significant interest due to the stringent environmental reg-
ulations of transportation fuel quality, such as low multi-
ring aromatics and sulfur contents in middle distillates.
Obtaining higher cetane numbers is also an essential
property to improve fuel quality. Aromatic saturation
and hydrocracking have been proved as commercial
3
the final products, and the catalytic system. In the cat-
alytic system, a bi-functional catalytic system (metallic
and acidic functions) is required in the SRO of naphthenic
4
1
molecules. A suitable acidic function is needed for the
upgrading technologies. However, aromatic saturation or
ring contraction step and a metallic function for the ring-
opening step. Even though noble metals (Pt, Pd, or Ir)
supported on an acidic zeolite catalyst are typically used
for the SRO reaction, multi-ring aromatics are not easily
converted into desired products over microporous zeolites
due to the diffusion resistance of bulky molecules.
hydrocracking alone is limited due to their low cetane
number increase and excessive cracking degree, respec-
tively. A potential route is needed to produce middle
distillates with low aromatics and aromatic saturation and
selective ring opening. Aromatic saturation of a low-sulfur
middle distillate stream is followed by the selective ring
opening of partially hydrogenated naphthenic rings with-
out loss of reactant molecular weight because the selec-
tive ring opening increases the cetane value in diesel
To overcome that kind of diffusion resistance and deac-
tivation of the catalyst in the microporous zeolites, there
have been extensive efforts to synthesize mesoporous
5
zeolites or zeolite nanocrystals. Among the synthetic
methods, pseudomorphic synthesis has recently been con-
sidered as a useful and convenient method for the synthesis
∗
Author to whom correspondence should be addressed.
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J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 7
1533-4880/2015/15/5334/004
doi:10.1166/jnn.2015.10424

Lee et al.
Ring Opening of Naphthenic Molecules Over Metal Containing Mesoporous Y Zeolite Catalyst
6
of mesoporous zeolite. Mesoporous zeolite with well-
controlled intracrystalline mesoporosity was prepared via
pseudomorphic synthesis, which is recrystallization of zeo-
lite in the presence of a surfactant.
In this study, we synthesized mesoporous Y (Meso-Y)
zeolite materials by pseudomorphic synthesis with differ-
ent surfactant ratios and prepared a 20 wt% NiW supported
Meso-Y catalyst with a uniform mesopore. The ring open-
ing of naphthalene as a model compound of multi-ring
aromatics was investigated using a sulfide NiW/Meso-Y
catalyst with different reaction conditions.
2
. EXPERIMENTAL DETAILS
2
.1. Catalyst Preparation
Meso-Y zeolite materials were synthesized by a mod-
ified pseudomorphic synthesis in our lab with differ-
6
ent surfactant ratios. In typical synthesis, zeolite HY
(
1.67 g, CBV720) and hexadecyltrimethylammonium bro-
mide (0.83 g, CTAB) were added to 50 ml of a 0.09 M
trimethylammonium hydroxide (TMAOH) and stirred for
Figure 1. (a) Low and (b) wide angle XRD patterns, (c) N isotherms,
and (d) pore size distributions of Meso-Y with different surfactant molar
ratios (TMAOH:CTAB).
2
3
0 min at room temperature. The mixture was moved
to a Teflon-lined autoclave and hydrothermally treated at
ꢀ
1
50 C. After 20 h, the resultant product was filtered
ꢀ
and washed with water. The product was dried at 75 C
and calcined at 550 C. To obtain optimum Meso-Y with
3
. RESULTS AND DISCUSSION
ꢀ
Figure 1 shows the XRD patterns and N physisorption
2
both well-developed mesoporosity and retain the microp-
orous zeolitic structure, the molar ratios of TMAOH:CTAB
were varied from 0.5 to 3. The 20 wt% NiW supported
Meso-Y catalyst was prepared by impregnation of nickel
results of the Meso-Y materials prepared by pseudomor-
phic synthesis with different surfactant ratios. The low
angle XRD patterns and pore size distributions revealed
that the mesoporosity of the zeolite increased with an
increase of the TMAOH:CTAB molar ratio up to 2. The
highest surfactant molar ratio (TMAOH:CTAB = 3) had
(
II) nitrate hexahydrate (Ni(NO ꢀ ·6H O) and ammonium
3
2
2
metatungstate hydrate ((NH ꢀ H W O · H O) in water.
4
6
2
12 40
2
Prior to the reaction tests, the catalyst was sulfidated in a
ꢀ
tubular furnace by 10 mol% H S in hydrogen at 350 C
2
for 3 h.
2
.2. Catalyst Characterization
Powder X-ray diffraction (XRD) patterns were recorded
using a Rigaku Multiplex (40 kV, 1.6 kW, Cu-Kꢁ
radiation). N isotherms were measured by ASAP2020
2
(
Micromeritics). The ammonia temperature programming
desorption (NH -TPD) was carried out using BELCAT-B.
3
2
.3. Catalytic Performance Tests
The reaction was carried out with a batch-type reactor sys-
tem (100 ml, Parr Instrument Co.) For the ring opening of
naphthalene, the reactor was charged with 30 g of 10 wt%
naphthalene in tridecane (TCI) and 0.3 g of a sulfided cat-
alyst. The reactor was purged with nitrogen. After pressur-
ization to the desired pressure (3–5 MPa) by hydrogen the
ꢀ
reaction was performed at 350, 375, and 400 C for 5 h
with stirring (500 rpm). The reaction products were ana-
lyzed by gas chromatography-mass spectrometry (GC-MS)
Figure 2. (a) XRD patterns and (b) N isotherms and pore size distri-
2
(
HP7890A/5975C, Agilent) with a packed column (DB-5).
butions of zeolite supports and NiW supported catalysts.
J. Nanosci. Nanotechnol. 15, 5334–5337, 2015
5335

Ring Opening of Naphthenic Molecules Over Metal Containing Mesoporous Y Zeolite Catalyst
Lee et al.
Table I. Physicochemical properties of zeolite supports and NiW supported zeolite catalysts.
2
3
Surface area (BET) (m /g)
Pore volume (cm /g)
Pore
Sample
Total
Micropore
> 2 nm
Total
Micropore
Mesopore
diameter (nm)
Y zeolite
Meso-Y
NiW/Y zeolite
NiW/Meso-Y
739
785
524
472
527
224
393
123
212
561
131
349
0ꢀ49
0ꢀ59
0ꢀ31
0ꢀ33
0ꢀ24
0ꢀ10
0ꢀ18
0ꢀ06
0ꢀ25
0ꢀ49
0ꢀ13
0ꢀ28
–
3ꢀ21
–
3ꢀ20
a mesoporosity similar to TMAOH:CTAB = 2, but the
microporous structure of the HY zeolite almost disap-
peared as shown in the wide angle XRD patterns. From
these analyses, we concluded that the optimum surfac-
tant molar ratio is two to obtain Meso-Y with both
well-developed mesoporosity and a retained microporous
zeolitic structure. To investigate the effect of the Meso-Y
zeolite support on the ring opening reaction of naphtha-
lene, we introduced 20 wt% NiW into the Meso-Y synthe-
sized with TMAOH:CTAB = 2. Figure 2 shows the XRD
affected both the weak and the strong acid sites. The weak
acidities of the catalysts increased, while the strong acidi-
ties significantly decreased by metal loading (Table II).
That indicates a big loss in the number of strong acid sites,
which might result from direct metal anchoring on proton
7
sites.
The NiW/Meso-Y was applied in the SRO of naph-
ꢀ
thalene at 400 C under various reaction pressures. The
naphthalene conversion and yields of middle distillates and
BTEX of both the catalysts increased as the reaction pres-
sure increased (Table III). Interestingly, the yields of the
middle distillates and BTEX for the NiW/Meso-Y cata-
lyst were similar to these for the NiW/Y zeolite while the
total acidity of the NiW/Meso-Y catalyst was about half of
that of the NiW/Y zeolite (Table II). That might be due to
facile access for the bulky reactant coming from the meso-
porosity of the NiW/Meso-Y compared with the NiW/Y
zeolite. The yield of saturated products in the NiW/Meso-
Y had a higher value than that of the NiW/Y zeolite, which
might have been caused by the NiW/Meso-Y having a
weaker acidity than the NiW/Y. These results indicate that
the SRO of naphthalene strongly depends on the reaction
pressure and the higher pressure has a higher conversion
and yield of middle distillates and BTEX.
and N physisorption results for the 20 wt% NiW/Y zeolite
2
and NiW/Meso-Y catalysts. After NiW loading, the low
angle XRD patterns were slightly shifted to the left side
with similar peak shapes. However, the relative XRD peak
intensities of the NiW supported catalysts decreased com-
pared with the zeolite support. In addition, the mesopore
volumes and BET specific surface area of the catalysts also
decreased after impregnation of NiW metal (Table I). This
indicates that the mesopores of the catalysts were filled
with NiW metal.
Figure 3 shows the NH -TPD profiles to investigate the
3
surface acidic site and the strength of the acidity. NH3-
TPD profiles of two supports show two distinct NH des-
3
ꢀ
ꢀ
orption peaks at around 170 C (weak acid site) and 380 C
strong acid site) The intensities of the two NH -TPD
(
The NiW/Meso-Y was used to investigate the effects of
reaction temperature and determine the optimum temper-
ature for SRO for naphthalene. The reaction temperatures
3
peaks of the Meso-Y support decreased compared with
those of the Y zeolite. This means that the surface acidities
in the Y zeolite decreased during the pseudomorphic syn-
thesis. After impregnation with metals, the metal loading
ꢀ
were varied from 350 to 400 C at 50 bar. The naphthalene
conversion and yields of middle distillates for NiW/Meso-
Y decreased as the reaction temperature increased, but the
yields of BTEX and aromatic saturated products increased
(
Table IV). The NiW/Y zeolite also had a trend similar
to the NiW/Meso-Y. However, the NiW/Meso-Y exhibited
higher yields of BTEX, tetralin and decalin, and middle
distillates than the NiW/Y zeolite at the lowest tempera-
Y zeolite
ꢀ
ture (350 C), which might imply that the mesoporosity of
Meso Y zeolite
Table II. NH -TPD results of zeolite supports and NiW supported zeo-
lite catalysts.
3
NiW/Y zeolite
NiW/Meso Y zeolite
Amount of desorbed ammonia (mmol/g) Total amount
of NH3
ꢀ
ꢀ
Sample
170 C (l-peak)
380 C (h-peak)
(mmol/g)
1
00
200
300
400
500
Y zeolite
Meso-Y
NiW/Y zeolite
NiW/Meso-Y
0ꢀ226
0ꢀ147
0ꢀ275
0ꢀ380
0ꢀ741
0ꢀ534
0ꢀ453
—
0ꢀ967
0ꢀ681
0ꢀ728
0ꢀ380
Temperature (ºC)
Figure 3. NH -TPD profiles of zeolite supports and NiW supported
catalysts.
3
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J. Nanosci. Nanotechnol. 15, 5334–5337, 2015

Lee et al.
Ring Opening of Naphthenic Molecules Over Metal Containing Mesoporous Y Zeolite Catalyst
Table III. Catalytic performance of catalysts in ring opening of naph-
thalene with different pressure at 400 C for 5 h.
Meso-Y support via pseudomorphic synthesis compared
with Y zeolite.
ꢀ
Product yield (wt%)
Pressure
(bar)
Conv.
(%)
Middle
distillates
Saturated
product
4. CONCLUSION
Catalyst
BTEX
The optimum Meso-Y was synthesized by the
TMAOH:CTAB molar ratio = 2, which yielded both a
microporous zeolitic structure and well-developed meso-
pores. The catalytic tests for SRO of naphthalene over
both the NiW/Meso-Y and NiW/Y under different reaction
conditions revealed that the NiW/Meso-Y and NiW/Y
zeolite had a similar naphthalene conversion. However,
the NiW/Meso-Y catalyst had higher product yields for
BTEX, aromatic saturated products, and middle distillates
than NiW/Y at a low reaction temperature. This suggests
that the mesoporosity of NiW/Meso-Y is more advanta-
geous for the SRO of multi-ring aromatics due to easy
access for the bulky molecules compared with NiW/Y.
NiW/Y zeolite
30
75ꢀ2
85ꢀ4
88ꢀ4
74ꢀ5
80ꢀ4
89ꢀ8
36ꢀ1
40ꢀ6
41ꢀ6
35ꢀ5
38ꢀ5
41ꢀ3
3ꢀ2
3ꢀ0
3ꢀ8
11ꢀ1
7ꢀ0
7ꢀ3
10ꢀ2
18ꢀ0
20ꢀ6
7ꢀ7
16ꢀ5
20ꢀ3
4
5
0
0
NiW/Meso-Y
30
4
5
0
0
Notes: Conv., naphthalene conversion; Saturated product, total yield of tetralin and
decalin; BTEX, total yield of benzene, toluene, ethyl benzene, and xylene.
Table IV. Catalytic performance of catalysts in ring opening of naph-
thalene with different temperature at 50 bar for 5 h.
Product yield (wt%)
Acknowledgment: This work was supported by the
Korean Institute of Energy Technology Evaluation and
Planning (20122010200050).
Temperature Conv.
Middle
distillates
Saturated
product
ꢀ
Catalyst
( C)
(%)
BTEX
NiW/Y zeolite
350
93ꢀ7
93ꢀ2
88ꢀ4
94ꢀ4
92ꢀ4
89ꢀ8
44ꢀ0
43ꢀ5
41ꢀ6
45ꢀ8
43ꢀ5
41ꢀ3
25ꢀ9
14ꢀ1
3ꢀ8
30ꢀ0
14ꢀ7
7ꢀ3
7ꢀ3
14ꢀ1
20ꢀ6
11ꢀ4
17ꢀ7
20ꢀ3
3
4
75
00
References and Notes
NiW/Meso-Y
350
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3
4
75
00
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1, 770 (2010).
9
4. G. B. McVicker, M. Daage, and M. S. Touvelle, J. Catal. 210, 137
(2002).
the NiW/Meso-Y catalyst should provide good accessibil-
ity of the bulky molecule to catalytic active sites without
significant diffusion resistance even at the lowest reaction
temperature. In addition, the higher yield of BTEX by the
SRO of naphthalene might be due to the mild acidity of the
5
6
. K. Moller and T. Bein, Chem. Soc. Rev. 42, 3689 (2013).
. J. Garcia-Martinez, M. Johnson, J. Valla, and K. Li, Catal. Sci. Tech-
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Received: 19 October 2013. Accepted: 11 July 2014.
J. Nanosci. Nanotechnol. 15, 5334–5337, 2015
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