Selective ring opening of 1-methylnaphthalene over niw-supported catalyst using dealuminated beta zeolite

Article abstract of DOI:10.1166/jnn.2016.11997

Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity. Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeolites for acidic function, NiW for metallic function. 1-Methylnaphthalen

Full text of DOI:10.1166/jnn.2016.11997

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Nanoscience and Nanotechnology
Vol. 16, 1715–1719, 2016
Copyright © 2016 American Scientific Publishers
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Selective Ring Opening of 1-Methylnaphthalene Over
NiW-Supported Catalyst Using Dealuminated Beta Zeolite
Eun-Sang Kim1ꢀ2, You-Jin Lee1ꢀ2, Jeong-Rang Kim1ꢀ∗, Joo-Wan Kim1, Tae-Wan Kim1,
Ho-Jeong Chae1, Chul-Ung Kim1, Chang-Ha Lee2, and Soon-Yong Jeong1
1Research Center for Green Catalysis, Korea Research Institute of Chemical Technology, Daejeon 305-600, South Korea
2Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 102-749, South Korea
Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity.
Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeo-
lites for acidic function, NiW for metallic function. 1-Methylnaphthalene was selected as a model
compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction has been
investigated using the prepared bi-functional catalysts with different acidity in fixed bed reaction
system. The dealuminated Beta zeolites, which crystal structure and nanoporosity were maintained,
showed the higher SiO2/Al2O3 ratio and smaller acidity than their original zeolite. NiW-supported
catalyst using the dealuminated Beta zeolite with SiO2/Al2O3 mole ratio of 55 showed the highest
performance for the selective ring opening. The acidity of catalyst seemed to play an important
role as active sites for the selective ring opening of 1-methylnaphthalene but there should be some
Delivered by Publishing Technology to: Imperial College London
optimum catalyst acidity for the reaction. The acidity of Beta zeolite could be controlled by the acid
IP: 110.36.53.76 On: Fri, 01 Apr 2016 10:43:44
Copyright: American Scientific Publishers
treatment and the catalyst with the optimum acidity for the selective ring opening could be prepared.
Keywords: Selective Ring Opening, 1-Methylnaphthalene, BTEX, Beta Zeolite, Dealumination,
Acidity.
1. INTRODUCTION
Bi-functional catalytic system (metallic and acidic func-
tions) is required in the SRO of naphthenic molecules.2ꢀ4
A metallic function is required for hydrogenation step
(aromatic saturation) and an acidic function for the ring
opening step.5ꢀ6 The balance between the metallic func-
tion and the acidic function is necessary. Several studies
have been carried out for the production of mono aromatic
compounds, such as BTEX, by the SRO of naphthenic
molecules. Kim et al. carried out the SRO of naphthalene
for BTEX using Ni2P/zeolites (SiO2, ZSM-5, Beta, USY)
as catalyst and reported that Ni2P/Beta catalyst showed the
high performance.7
In this study, nanoporous Beta zeolite was dealuminated
by acid treatment for reducing the acidity. Bi-functional
catalysts were prepared using Beta zeolites and the dealu-
minated Beta zeolites for acidic function, NiW for metal-
lic function. 1-Methylnaphthalene (1mNap) was selected
as a model compound for multi-ring aromatics in heavy
oil, and its SRO has been investigated using the prepared
bi-functional catalysts with different acidity in fixed bed
reactor system.
Heavy oil, by-produced from petrochemical industries and
oil refinery, has been used as cheap fuel. The heavy oil
contains many heavy molecules, multi-ring aromatics, and
asphaltenes with high sulfur content. Rigorous environ-
mental regulations have restricted the use of the heavy oil
as the fuel. Due to the regulations and persistent high oil
prices, upgrading process of heavy oil to high-value mid-
dle distillates with low aromatics have attracted interest to
many researchers.1
Multi-ring aromatics, especially naphthenic molecules
such as naphthalene and methyl-naphthalenes, are the
major components of heavy oil. Partial aromatic satu-
ration of the naphthenic molecule can form tetralinic
molecule, and alkyl-benzenes including benzene, toluene,
ethyl-benzene, and xylene (BTEX) can be produced by
following cracking of the naphthenic ring of the tetralinic
molecule.2 In other words, selective ring opening (SRO)
should be a potential route for the production of valuable
compounds from heavy oil.3
∗Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2016, Vol. 16, No. 2
1533-4880/2016/16/1715/005
doi:10.1166/jnn.2016.11997
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Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite
Kim et al.
2. EXPERIMENTAL DETAILS
2.1. Catalyst Preparation
was collected every 2 or 3 hours. Gas yield was calculated
from the weight of the liquid product. The liquid product
was analyzed by gas chromatography coupled with mass
spectrometry (GC-MS, Agilent 7890A/5975C) for quali-
tative analysis and a frame ionization detector (GC-FID,
Younglin 6100) for quantitative analysis. Both of them
were equipped with DB-5MS UI capillary column.
The dealuminated Beta zeolites were synthesized by acid
treatment with oxalic acid.8 Beta zeolite (SiO2/AlO3 = 38,
CP814C) purchased from Zeolyst Co. was calcined in air
atmosphere at 550 ꢀC for 6 h in order to remove impurities
and obtain the hydrogen-form zeolite from the ammonium-
form. The zeolite (2 g) was added to the aqueous oxalic
acid solution ꢀ(100 cm3) with pH 2 and the sus-pension was
stirred at 60 C for 4 h or 8 h, filtered, and washed with
hot water to remove aluminum complexes formed. The
3. RESULTS AND DISCUSSION
The XRD patterns of the dealuminated Beta zeolites and
the prepared NiW/Beta catalyst were shown in Figure 1.
The XRD patterns of the dealuminated zeolites, Beta(55)
and Beta(80), showed the same patterns as its original zeo-
lite, Beta(38). It meant that the crystal structure of the
zeolite was not collapsed but maintained after dealumina-
tion. The XRD patterns of NiW/Beta(38) catalyst showed
the same patterns as Beta(38) zeolite and none of metal
diffraction peaks was observed in the XRD patterns of
the catalyst. It might be mainly owing to the nanosized
metal particles below the detection limit of this technique
and indicate that the metals should be well dispersed as
nanoparticles in the zeolite. In case of the catalysts using
ꢀ
dealuminated zeolites were dried in an oven at 120 C for
12 h. The SiO2/AlO3 mole ratio of the dealuminated zeo-
lites was determined by ICP-AES. The ratio of the zeolite
dealuminated for 4 h was 55, and 80 for 8 h.
The bi-functional catalysts including NiW were pre-
pared by wet impregnation method using two commercial
Beta zeolites of Zeolyst Co. (CP814E, CP814C) and the
two dealuminated Beta zeolites, which SiO2/Al2O3 mole
ratios were 25, 38, 55, and 80. Nickel(II) nitrate hex-
ahydrate (Ni(NO3ꢁ2 ·6H2O) and ammonium metatungstate
hydrate ((NH4ꢁ6H2W12O40 ·H2O) were used as the precur-
sor for each metal. Before reaction test,ꢀthe catalyst was
sulfidated in H2S(10%)/H2 flow at 350 C for 3 h using
a tubular furnace. The impregnation amount of Ni was
1.1 mmol/g-zeolite and the amount of W was the same.
The prepared catalysts were denoted as “NiW/Beta(a),”
Delivered by Publishing Technology to: Imperial College London
where ‘a’ is a SiO /Al O mole ratio of Beta zeolite.
IP: 110.36.53.76 On: Fri, 01 Apr 2016 10:43:44
2
2
3
Copyright: American Scientific Publishers
2.2. Catalyst Characterization
Powder X-ray diffraction (XRD) patterns were recorded
using a Rigaku Multiplex (40 kV, 1.6 kW, Cu-Kꢂ radia-
tion). Surface area and pore volume were measured by N2
adsorption using a Micromeritics ASAP2020 instrument.
Transmission electron micrographs (TEM) were taken on
a Philips Tecnai G220 device operated at 200 kV. Scan-
ning transmission electron microscopy (STEM)/energy-
dispersive X-ray spectroscopy (EDS) elemental mapping
images were taken with a Tecnai G2 F30 instrument
with an accelerating voltage of 300 kV. Temperature-
programmed desorption of ammonia (NH3-TPD) was car-
ried out for the total acidity of prepared samples using a
BELCAT-B instrument.
2.3. Catalytic Performance Tests
The performances of prepared catalysts for the SRO of
ꢀ
1mNap were measured at 400 C and 50 barg using a
fixed-bed reaction system. The sulfidated catalyst (1 g)
was loaded in the reactor, followed byꢀleak test. The cata-
lyst was pretreated in H2 flow at 400 C and atmospheric
pressure for 8 h and the pressure increased to 50 barg.
The liquid feed of 1mNap was delivered at flow rate of
0.037 cm3/min using a liquid pump along with H2 flow
of 175 SCCM (H2/1mNap mol ratio = 30). The reaction
Figure 1. XRD patterns of dealuminated Beta zeolites and NiW/Beta
catalyst.
ꢀ
product was cooled down to 5 C and the liquid product
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Kim et al.
Table I. Physical properties of Beta zeolites and NiW/Beta catalysts.
Surface area (m2/g) Pore volume (cm3/g)
Total Micropore Mesopore Total Micropore Mesopore
Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite
Sample
Beta(25)
Beta(38)
Beta(55)
Beta(80)
NiW/Beta(25) 399
NiW/Beta(38) 426
NiW/Beta(55) 384
NiW/Beta(80) 357
558
588
590
588
368
465
456
425
301
342
307
281
190
123
134
163
98
84
77
76
0ꢃ71
0ꢃ32
0ꢃ32
0ꢃ34
0ꢃ37
0ꢃ22
0ꢃ2
0.17
0.22
0.21
0.20
0.14
0.16
0.14
0.13
0.54
0.10
0.11
0.13
0.23
0.06
0.04
0.06
0ꢃ19
Beta zeolites with different SiO2/Al2O3 mole ratios, the
identical XRD patterns to Figure 1 were observed and the
results is not shown in this paper.
Surface area and pore volume of the Beta zeolites and
the NiW/Beta catalysts were shown in Table I. The total
surface area was calculated by the BET equation. The area
and volume of the nanosized pores (micropore and meso-
pore) were calculated by the t-plot method. The dealumi-
nated zeolites, Beta(55) and Beta(80), showed the slightly
high mesopore area and low micropore area. Anyway, their
nanoporosities were similar to its original zeolite, Beta(38)
and the pore structure of the zeolite was also maintained
after dealumination. NiW impregnation into Beta zeolites
decreased their micropore and mesopore, indicating that
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Copyright: American SFciigeunretif3i.c Publishers
NH3-TPD profiles of Beta zeolites and NiW/Beta catalysts.
the metal species are well distributed as nanoparticles in
both the micropore and mesopore of the zeolite.
The TEM image and the STEM/EDS elemental map-
ping images of NiW/Beta(38) catalyst were shown in
Figure 2. The characteristic porous structure of the zeolite
was observed with no noticeable particles of Ni and W in
the TEM image. The interstitial space between the zeolite
crystal particles in the agglomeration might act as meso-
pore. Each metal seemed to be well dispersed in the meso-
pore as well as the characteristic micropore of the zeolite
from the elemental mapping images. In case of the cata-
lysts using Beta zeolites with different SiO2/Al2O3 mole
ratios, the similar images to Figure 2 were observed and
the results is not shown in this paper.
The NH3-TPD profiles and total acidity of the Beta
zeolites and the NiW/Beta catalysts were displayed in
Table II. Total acidity of Beta zeolites and NiW/Beta catalysts.
Total
Total
Sample
acidity (mmol/g)
Sample
acidity (mmol/g)
Beta(25)
Beta(38)
Beta(55)
Beta(80)
1.113
0.911
0.836
0.583
NiW/Beta(25)
NiW/Beta(38)
NiW/Beta(55)
NiW/Beta(80)
1.081
0.842
0.776
0.673
Figure 2. (a) TEM image and (b) STEM/EDS elemental mapping
images of NiW/Beta(38) catalyst.
J. Nanosci. Nanotechnol. 16, 1715–1719, 2016
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Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite
Kim et al.
Table III. SRO performances of NiW/Beta catalysts: 1mNap conversion and product yield distribution.
Yield, wt%
Catalyst
1mNap conv., wt%
Gas
Light HC
Ring opening (BTEX)
Hydrogenation
Nap
2mNap
Alkyl-nap
Heavy HC
NiW/Beta(25)
NiW/Beta(38)
NiW/Beta(55)
NiW/Beta(80)
98.7
98.2
99.8
75.5
45.8
34.3
39.2
24.9
7
42.7 (33.2)
49.6 (39.5)
54.3 (44.9)
23.3 (16.2)
<1
1.6
<1
<1
1.3
<1
<1
1.3
3.6
<1
7.4
1.6
5.2
<1
3.1
<1
1.6
<1
<1
7.5
5.8
4.4
16.7
Figure 3 and Table II. The total acidity was determined by
NH3-TPD profile. According to the NH3-TPD profiles of
Beta zeolites, typical two NH3 desorption peaks for zeolite
were observed around 180 ꢀC (weak acid site) and 370 ꢀC
(strong acid site). The dealuminated zeolites, Beta(55) and
Beta(80), showed the smaller acidity than its original zeo-
lite, Beta(38), as expected. The larger SiO2/Al2O3 mole
ratio of Beta zeolite, the smaller total acidity was observed
in the NH3-TPD results as the well-known. It observed that
NiW impregnation into Beta zeolites decreased their acid-
ity, except for Beta(80) zeolite with small acidity. It would
be because the metals could block acid sites of zeolite but
themselves provide acid sites.9 Accordingly, the impreg-
nation of the metals could increase the acidity, especially
for the zeolites with small acidity. Anyway, the acidity of
the NiW/Beta catalysts was also inversely proportional to
SiO2/Al2O3 ratio of Beta zeolite.
than two-ring aromatics. In case of the catalysts using
the commercial Beta zeolites, both NiW/Beta(25) and
NiW/Beta(38) catalysts maintained the high 1mNap con-
version over 98%. NiW/Beta(38) with smaller acidity
showed the higher yields of ring opening species and
BTEX.
In order to prepare the catalyst with higher performance
for the SRO reaction, Beta(38) zeolite was dealuminated
by weak acid treatment and its acidity was diminished
as NH3-TPD results. The catalyst using the dealuminated
Beta zeolite, Beta(55), showed the improved performance
for the SRO reaction. However, in case of the catalyst
using Beta(80), the 1mNap conversion and yields of ring
opening species and BTEX decreased greatly and the yield
of hydrogenation species increased, which should be pro-
duced by relatively strong metallic function of the catalyst.
Therefore, it was confirmed that NiW/Beta(80) catalyst
could not provide the sufficient acidic function for the SRO
reaction.
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The SRO performances of NiW/Beta catalysts at reac-
IP: 110.36.53.76 On: Fri, 01 Apr 2016 10:43:44
tion time of 10 h were shown in Table III and compared
Copyright: American Scientific Publishers
with total acidity of the catalyst, based on SiO2/Al2O3
mole ratio of Beta zeolite, as shown in Figure 4. All
catalysts maintained the similar performance for about
12 h of reaction time. Most of gas product consisted
of alkanes (carbon number 1∼4) and light hydrocar-
bons was cycloalkanes lighter than BTEX. Ring open-
ing species, the most important for the SRO reaction,
consisted of alkyl-benzenes including BTEX. Hydrogena-
tion species included tetralin, decalin, and alkyl-tetralins,
and heavy hydrocarbons were multi-ring aromatics heavier
The trend between the catalytic performance and its
acidity was more obvious in Figure 4. The acidity of
NiW/Beta catalysts decreased with SiO2/Al2O3 ratio of
Beta zeolite. NiW/Beta(55) catalyst with the moderate
acidity showed the highest performance for the SRO reac-
tion, and consequently was believed as the most favorable
catalyst for the reaction. The acidity of catalyst seemed
to play an important role as active sites for the SRO of
1mNap but there should be some optimum catalyst acidity
for the reaction. The acidity of Beta zeolite could be con-
trolled by the weak acid treatment and the catalyst with the
optimum acidity for the SRO reaction could be prepared.
4. CONCLUSION
Nanoporous Beta zeolite was dealuminated by weak acid
treatment for reducing the acidity. Bi-functional catalysts
were prepared using commercial Beta zeolites and the
dealuminated zeolites for acidic function, NiW for metal-
lic function. 1mNap was selected as a model compound
for multi-ring aromatics in heavy oil, and its SRO reac-
tion has been investigated using the prepared bi-functional
catalysts with different acidity in fixed bed reaction sys-
tem. The dealuminated Beta zeolites, which crystal struc-
ture and nanoporosity were maintained, showed the higher
SiO2/Al2O3 ratio and smaller acidity than their original
zeolite. NiW-supported catalyst using the dealuminated
Figure 4. Total acidity and the reaction performances of NiW/Beta
catalysts.
1718
J. Nanosci. Nanotechnol. 16, 1715–1719, 2016

Kim et al.
Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite
Beta zeolite with SiO2/Al2O3 mole ratio of 55 showed the
highest performance for the SRO reaction. The acidity of
catalyst seemed to play an important role as active sites
for the SRO of 1mNap but there should be some optimum
catalyst acidity for the reaction. The acidity of Beta zeolite
could be controlled by the acid treatment and the catalyst
with the optimum acidity for the SRO reaction could be
prepared.
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Acknowledgment: This work was supported by the
Korean Institute of Energy Technology Evaluation and
Planning (20122010200050).
Received: 14 April 2015. Accepted: 21 April 2015.
Delivered by Publishing Technology to: Imperial College London
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Copyright: American Scientific Publishers
J. Nanosci. Nanotechnol. 16, 1715–1719, 2016
1719