Supported noble metal catalyst with a core-shell structure for enhancing hydrogenation performance

Article abstract of DOI:10.1016/j.mcat.2021.111543

Supported noble metal nanoparticles are a kind of high efficiency of catalysts in aromatics hydrogenation, and the properties and structures of supports are of great importance to improve hydrogenation behaviors. In this work, an efficient Pd/S-1@ZSM-5 core-shell catalyst with an enhanced naphthalene hydrogenation ability was prepared by building acidic nano-ZSM-5 shells surrounding silicalite-1 supported Pd NPs. The acidic nano-ZSM-5 shell can strengthen the spillover hydrogenation due to the increase of the strong acid sites around Pd NPs, and the strong acid sites around metal NPs can be regulated by controlling the coverage of nano-ZSM-5 shell. Additionally, the formed mesoporous structure of nano-ZSM-5 shell is beneficial for the diffusion of bulky reactants. These are the two important factors for enhancing hydrogenation ability of Pd/S-1@ZSM-5 catalyst. Furthermore, Pd/S-1@ZSM-5 catalyst also shows good sulfur-tolerance in the presence of thionaphthene. This work presents an elegant example for enhancing hydrogenation abilities of noble metal catalysts by constructing a core-shell structure.

Full text of DOI:10.1016/j.mcat.2021.111543

Molecular Catalysis 506 (2021) 111543
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.journals.elsevier.com/molecular-catalysis
Supported noble metal catalyst with a core-shell structure for enhancing
hydrogenation performance
Ningyue Lu, Jiaxin Zhao, Qi Dong, Yanpeng Zhao, Binbin Fan*
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, 030024, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Supported noble metal nanoparticles are a kind of high efficiency of catalysts in aromatics hydrogenation, and
the properties and structures of supports are of great importance to improve hydrogenation behaviors. In this
work, an efficient Pd/S-1@ZSM-5 core-shell catalyst with an enhanced naphthalene hydrogenation ability was
prepared by building acidic nano-ZSM-5 shells surrounding silicalite-1 supported Pd NPs. The acidic nano-ZSM-5
shell can strengthen the spillover hydrogenation due to the increase of the strong acid sites around Pd NPs, and
the strong acid sites around metal NPs can be regulated by controlling the coverage of nano-ZSM-5 shell.
Additionally, the formed mesoporous structure of nano-ZSM-5 shell is beneficial for the diffusion of bulky re-
actants. These are the two important factors for enhancing hydrogenation ability of Pd/S-1@ZSM-5 catalyst.
Furthermore, Pd/S-1@ZSM-5 catalyst also shows good sulfur-tolerance in the presence of thionaphthene. This
work presents an elegant example for enhancing hydrogenation abilities of noble metal catalysts by constructing
a core-shell structure.
Core-shell structure
Acid sites
Spillover hydrogen
Naphthalene
1. Introduction
supports for metal NPs, and zeolite supported noble metal catalysts, due
to their high hydrogenation activities, are promising candidates for deep
Aromatics hydrogenation is an industrially important reaction, and
the hydrogenated products derived from aromatics have various appli-
cations [1–5]. Tetralin, as one of the extended products of naphthalene,
is a very useful high boiling point solvent, and has been wildly used in
paint, pharmaceuticals, hydrogen donors and other fields [6,7]. In
addition, with increasingly severe environment and fuel legislation and
growing demand for the transportation fuels with a high quality, cata-
lytic hydrogenation of aromatics in diesel fuel is of great practical sig-
nificance for upgrading fuel quality [1,8]. Aromatics hydrogenation is
an exothermic reaction and thus thermodynamically favored at low
temperatures. Thus, compared to the conventional Co-Mo and Ni-Mo
sulfides with weak hydrogenation abilities at low temperature, noble
metal catalysts are more favorable [9,10].
aromatics hydrogenation at lower temperatures [16–18].
In hydrogenation reactions over supported noble metal catalysts, the
acidity of the supports greatly influences the hydrogenation perfor-
mances of the supported catalysts. Generally, acid supported noble
metal catalysts show activity enhancements compared with non-acid
supported metal catalysts, especially in hydrogenation. This is due to
that hydrogenation activities obtained over the acid supported noble
metal catalysts are mainly contributed by two parts: one is the metal-
catalyzed hydrogenation, and the other is spillover hydrogenation
[19–22]. In the process of spillover hydrogenation, the adsorbed aro-
matic compound can be hydrogenated through spillover hydrogen,
which is formed on the metal sites and migrates onto acid sites in the
interfacial region between metal and acid sites [23,24]. In our previous
work on naphthalene hydrogenation over Pt/HZSM-5 and the related
literatures [19,25], the contribution from spillover hydrogenation
greatly affects the hydrogenation ability of the supported noble metal
catalysts, and the acid amounts with proximity to the metal play a
decisive role for spillover hydrogenation. However, in the zeolite sup-
ported metal catalysts prepared by the conventional supporting
methods, such as wetting impregnation and ion-exchange, the supported
Supported noble metal nanoparticles (NPs), as a significant class of
catalysts, have been extensively applied in various industrial reactions.
The catalytic performances of the supported catalysts are dependent on
the physicochemical properties of the supported metal NPs, its surface
property and pore structure as well as the interaction between metal NPs
and the supports [11–15]. Zeolites with well-defined channels and
facilely adjustable acid-base properties, are widely employed as
* Corresponding author.
E-mail address: fanbinbin@tyut.edu.cn (B. Fan).
https://doi.org/10.1016/j.mcat.2021.111543
Received 23 December 2020; Received in revised form 4 March 2021; Accepted 20 March 2021
Available online 5 April 2021
2468-8231/© 2021 Elsevier B.V. All rights reserved.

N. Lu et al.
Molecular Catalysis 506 (2021) 111543
metal nanoparticles (NPs) are mainly located on the external surface of
the zeolite supports upon calcination and reduction, while the acid sites
are mainly located in the zeolite channels. As a consequence, the acid
amounts with a proximity to the supported metal NPs are very limited,
greatly restricting the enhancement of the hydrogenation ability of the
zeolite-supported metal catalysts [26]. Hence, the rational design and
preparation of aromatics hydrogenation catalysts with an appropriate
metal/acid matching relationship is still a challenge. In addition, for
zeolite-supported catalysts, it is difficult to individually evaluate the
effects of the acidity of the zeolite supports on hydrogenation reactions
because the acidity not only can influence the dispersions and electronic
states of the supported metal species, but also the acid sites on the
supports can induce spillover hydrogenation. Thus, in order to under-
stand the influences of the acidity of the supports on hydrogenation
reactions, it is also desirable to design appropriate catalysts.
composition of 1 SiO2: 0.3 TPABr: 0.2 NaOH: 100 H2O. In a typical
experiment, 2.24 g tetrapropylammonium bromide (TPABr) and 0.22 g
NaOH were dissolved in 50 mL deionized H2O, and then 6.3 mL TEOS
was dropwise added to the solution. After the mixture was homogenized
by vigorous magnetic stirring at ambient temperature for 4 h, it was
transferred into a 100 mL Teflon-lined steel autoclave and crystallized at
160 ◦C for 2 days. The obtained solid was washed with deionized H2O,
dried at 100 ◦C overnight, and calcined at 550 ◦C for 6 h in air atmo-
sphere. The resultant final product was denoted as S-1.
2.1.2. Pd/S-1
Pd/S-1 was synthesized according to the following procedures. 1 g S-
1 and 1 mL 3-aminopropyltrimethoxysilane (APTMS) were added into
the flask with 30 mL dichloromethane, and then the mixture was stirred
for 24 h at room temperature. After the white solid was filtered, washed
with dichloromethane and dried under vacuum, APTMS-functionalized
S-1 was obtained. The obtained APTMS-functionalized S-1 was added
into the 5 mL Na2PdCl4 aqueous solution (0.05 mol/L) and the mixture
was stirred at room temperature for 24 h. Afterwards, 10 g tetrapropy-
lammonium hydroxide water solution (TPAOH, 15 wt%) was dropwise
into the above resulting mixture and transferred into a 50 mL Teflon-
Encapsulation of metal NPs inside zeolite has been developed as a
powerful strategy for preparing intriguing catalysts with the distinct
selectivity, activity as well as stability (against sintering) [27–36].
Meanwhile, enhancing proximity of the acid sites to the supported metal
NPs is one of the significant features of zeolite-encapsulated metal NPs
[37–39]. Depending on Si/Al ratios, pore sizes of the zeolite hosts and
stability/size of the metal precursors, many approaches, including
host-guest assembling of metal precursors inside the zeolites,
re-transformation, in-situ encapsulation involving ligand-stabilized
methods or precursor-stabilization methods and shell-caged methods,
have been developed for encapsulating metal NPs inside zeolites
[40–44]. However, zeolite hosts, especially the small-aperture zeolites,
generally exert heave diffusion limitations on the reactions involving
bulky substrates and products due to the steric restriction from zeolite
channels.
◦
lined autoclave. After hydrothermal treatment at 160 C for 24 h, the
solid products were collected by centrifugation, washed with deionized
water to dislodge excess amount of TPA+ and OHꢀ and dried at 100 ◦C.
Finally, the powder was added in the 50 mL sodium borohydride solu-
tion (0.15 mol/L), and the mixture was stirred for 6 h to ensure the
reduction of Pd2+
.
2.1.3. Pd/S-1@ZSM-5
Pd/S-1@ZSM-5 with a core-shell structure was prepared by epitaxial
growth. Typically, 1 g TPABr, 0.034 g NaAlO2 and 0.085 g NaOH were
dissolved in the 20 mL deionized H2O in turn, and 2.1 g TEOS was
dropwise added to the above solution to form synthesis gel of ZSM-5
with the molar composition of 1 SiO2: 0.014 Al2O3: 0.37 TPABr: 0.25
NaOH: 110 H2O. Then 1 g Pd/S-1 was added into synthesis gel of ZSM-5
and treated by ultrasonic for 30 min. The formed mixture was trans-
ferred to a Teflon-lined steel autoclave and crystallized at 180 ◦C for a
period of time. The obtained solid product was calcined at 550 ◦C for 6 h
in an air atmosphere and denoted as Pd/S-1@ZSM-5-x (x = crystalli-
zation time (h)). Pd/S-1@HZSM-5-x was prepared by ion-exchange of
the corresponding Pd/S-1@ZSM-5-x with NH4NO3 solution (1 mol/L)
Similar to zeolite-encapsulated catalysts, core-shell catalysts, in
which the metal NPs are totally encapsulated in zeolite shells formed by
zeolite nanocrystals, are also an attractive class of materials and have
received much attention in the last few years due to combining the
properties of the metal with those of the zeolite membrane [26,45–48].
Zeolite shell not only can increase the sintering-resistant of the encap-
sulated metal NPs and endow core-shell catalysts with the shape selec-
tive properties, but also can maximize the contact between metal and
zeolite supports. In addition, the mesoporous structure of the zeolite
shell can also improve the diffusion limitation. Therefore, core-shell
catalysts provide an insight and possibility for design and preparation
of the catalyst with enhanced hydrogenation ability in the reactions
involving bulky substrates. However, the work on this field is rarely
reported.
◦
◦
three times at 80 C for 2 h, and then calcined at 550 C for 4 h. In
addition, based on the synthesis of Pd/S-1@ZSM-5ꢀ 48 sample, Pd/S-
1@ZSM-5ꢀ 48-1 and Pd/S-1@ZSM-5ꢀ 48-2 with different Si/Al atomic
ratios were synthesized by adjusting the amounts of NaAlO2 in synthesis
gel of ZSM-5 shell.
Herein, we design an efficient hydrogenation core-shell catalyst by
constructing the acidic nano-ZSM-5 shell around silicalite-1 supported
Pd NPs core (Pd/S-1@ZSM-5). The core-shell catalysts have the
following features: acidic nano-ZSM-5 shell increases the acid sites with
a high proximity to the encapsulated metal NPs, and strengthens the
spillover hydrogenation; nano-ZSM-5 shell can form mesoporous struc-
ture, which is beneficial for the accessibility of the encapsulated metal
NPs to bulky reactants; the acidic nano-ZSM-5 shell can protect the
noble metal from poisoning by organic sulfide to some extent in naph-
thalene hydrogenation (model compound of light cycle oil). In addition,
the designed catalyst is also of interest for individually exploring the
influences of the acidity of the zeolite supports on the hydrogenation
performance of the zeolite-supported metal catalysts by only changing
the acid amounts with a proximity to metal via regulating the coverage
of the zeolite shells.
2.1.4. Preparation of the reference samples
Pd/S-1@NaZSM-5ꢀ 48 was prepared by ion-exchange of Pd/S-
1@ZSM-5ꢀ 48 with NaCl solution (1 mol/L) three times at 80 ◦C for 2 h
and calcination at 550 ◦C for 4 h. S-1@HZSM-5ꢀ 48 was synthesized
according to the preparation procedure of S-1@HZSM-5ꢀ 48 without the
addition of Pd source, and Pd/[S-1@HZSM-5ꢀ 48] was prepared by
conventional incipient wetness impregnation with S-1@HZSM-5ꢀ 48 as
the support. Pd contents in Pd/[S-1@HZSM-5ꢀ 48] are 0.63 wt% (ICP
analysis). Pd/S-1+HZSM-5 was obtained by physically mixing Pd/S-1
with HZSM-5 in a certain mass proportion, in which the Pd and
HZSM-5 contents are similar to Pd/S-1@HZSM-5ꢀ 48. Pd/HZSM-5 with
a similar acid property and Pd content to Pd/S-1@HZSM-5ꢀ 48 was
prepared by incipient wetness impregnation.
2. Experimental
2.2. Characterization
2.1. Sample synthesis
X-ray powder diffraction (XRD) patterns were recorded on a Shimazu
XRD-6000 diffractometer with Cu Ka radiation. Nitrogen adsorption/
desorption isotherms were measured on a Quantachrome NOVA 1200e
2.1.1. Silicalite-1 (S-1)
Silicalite-1 was synthesized from a synthesis gel with the molar
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N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Scheme 1. The reaction route for the naphthalene hydrogenation.
Scheme 2. The preparation procedure for Pd/S-1@ZSM-5.
apparatus at -196 ◦C. The samples were evacuated at 300 ◦C for 3 h prior
to measurement. Scanning electron microscope (SEM) images were
conducted on a Hitachi S-4800 scanning electron microscope operating
at 20 kV. Transmission electron microscopy (TEM) measurement was
conducted on a JEOL JEM-2100 F electron microscope operating at 200
kV. The ammonia temperature programmed desorption (NH3-TPD) was
measured on a XIAN QUAN TP-5076 dynamic adsorption apparatus.
Metal contents were measured by inductively coupled plasma-atomic
emission spectrometer (ICP-AES, Autoscan16 TJA). X-ray photoelec-
tron spectra (XPS) were attained on a Kratos AXIS ULTRA DLD XPS
spectrometer with a monochromated Al Kα target. The binding energies
were calibrated by the C 1s peak at 284.8 eV as the reference. H2
chemisorption was carried out on the Micromeritics AutoChem II 2920.
Sample (100 mg) was reduced with 10 % H2/Ar at 350 ◦C for 2 h and
◦
purged in Ar for 1 h. Then the temperature was cooled to 30 C, H2
pulses were performed by a calibrated on-line sampling value. The
calculation was based on a H/Pd stoichiometry of 1.
2.3. Catalytic measurement
Fig. 1. XRD patterns of the different samples.
Naphthalene hydrogenation (Scheme 1) over the different samples
was performed on a micro and high-pressure fixed bed reactor (12 mm ×
2 mm × 500 mm). 200 mg sample was diluted with quartz sand and
loaded in the constant temperature zone of the reactor. Prior to the re-
rate of 7.2 mL h-1 by micrometer pump and the H2 flow was 90 mL
minꢀ 1. The liquid products were collected and analyzed off-line by an
Agilent 7820A gas chromatograph equipped with a HP-5 capillary col-
action, the samples were in-situ reduced under 1 atm H2 (90 mL minꢀ 1
)
at 350 ◦C for 2 h. After reduction, the reactor was cooled to the reaction
temperature (280 ◦C) and the pressure was raised to 4 MPa. The feed (5
wt% naphthalene in the n-octane solvent) was injected to reactor at a
umn (30 m * 0.32 mm * 0.25 μm) and a flame ionization detector.
3

N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Fig. 2. SEM images of S-1 (a), Pd/S-1 (b), Pd/S-1@ZSM-5-2 (c), Pd/S-1@ZSM-5-7 (d), Pd/S-1@ZSM-5-48 (e), Pd/S-1@ZSM-5-48-broken (f).
3. Results and discussion
Table 1
Pd dispersion and acidity properties of the various samples.
3.1. Catalyst characterization
Area under NH3-TPD peaks (a.u./
Pd
mg)c
ZSM-5 shell
Samples
Dispersion
Scheme 2 shows the preparing procedure toward Pd/S-1@ZSM-5
core-shell samples. For facile characterization of the core-shell struc-
ture and improvement of the dispersion of supported Pd NPs, S-1
coverage (%)b
(%)a
Weak
Medium
Strong
Pd/S-1
Pd/S-
12.4
11.7
–
1.2
–
0.4
(204.1)
2.5
(431.6)
4.4
composed of regular quadrel-like crystals with 2ꢀ 3
μm in length, 2ꢀ 3
40.9
0.6
μ
m in width and 1ꢀ 1.5 μm in thickness and functionalized with APTS
1@ZSM-
(205.7)
(273.0)
(362.7)
was used as the core. In order to coat ZSM-5 shell around Pd/S-1 core via
epitaxial growth, Pd/S-1 was treated with TPAOH to form the rough
surface and more structure defects. Four typical samples with the
different coverage of the zeolite shells, termed as Pd/S-1@ZSM-5-x (x
denoting the crystallization time in constructing shell), were prepared.
The XRD patterns of the different samples are shown in Fig. 1. S-1 ex-
hibits well-resolved diffraction peaks of MFI zeolite. The diffraction
peak intensity of Pd/S-1 is weaker than that of S-1, suggesting the zeolite
frameworks were partially etched upon hydrothermal treatment with
TPAOH. No XRD peaks attributed to Pd phase are observed, indicating
the Pd NPs are relatively small and highly dispersed. All the Pd/S-
1@ZSM-5-x samples show MFI typical diffraction reflections with the
similar reflection intensities to S-1.
5ꢀ 2
Pd/S-
12.7
11.9
49.2
53.8
2.0
1.3
5.7
1@ZSM-
(198.6)
(264.4)
(384.1)
5ꢀ 7
Pd/S-
2.2
1.3
6.3
1@ZSM-
(201.7)
(277.9)
(386.3)
5ꢀ 48
a
b
c
Determined by H2 chemisorption.
Based on Pt loading.
Determined by NH3-TPD (desorption temperature in parenthesis).
by SEM images shown in Fig. 2. As shown in Fig. 2, all the Pd/S-1@ZSM-
5-x samples obtained at the different crystallization time show the
presence of ZSM-5 shells over Pd/S-1 core. For Pd/S-1@ZSM-5ꢀ 2, only
Successful coating of ZSM-5 shell over Pd/S-1 core can be confirmed
4

N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Fig. 3. TEM images of Pd/S-1@ZSM-5-2 (a), Pd/S-1@ZSM-5-7 (b) and Pd/S-1@ZSM-5-48 (c,d).
sparse ZSM-5 nanocrystals are gathered and attached to the surface of
Pd/S-1. Upon increasing crystallization time, more ZSM-5 nanocrystals
are accumulated on the surface of Pd/S-1 core. A relative integrated
shell loosely assembled by ZSM-5 nanocrystals is gradually formed over
Pd/S-1 core as the crystallization time is beyond 7 h. With the further
extension of crystallization time to 48 h, a completely integrated ZSM-5
shell, composed of ZSM-5 nanocrystals with a size of 50ꢀ 100 nm, is
formed, and its thickness reaches ca. 100 nm (Fig. 2 (f)). The above
results indicate the ZSM-5 shell is successfully formed over Pd/S-1 core
by the continuous epitaxial growth and the coverage of ZSM-5 nano-
crystals on Pd/S-1, that is the integration of the formed shell, can be
facilely tailored via controlling crystallization time (Table 1).
region surrounding the one with darker contrast (Fig. 3d).
The chemical states of Pd NPs on Pd/S-1 and Pd/S-1@HZSM-5ꢀ 48
were evaluated by XPS analysis, and the results are shown in Fig. 5. For
Pd/S-1, two peaks at 335.7 and 341.0 eV assigned to the 3d5/2 and 3d3/2
levels of metallic Pd can be observed [26]. Pd/S-1@HZSM-5ꢀ 48 gave
the similar 3d binding energy (BE) values of Pd to Pd/S-1, indicating
that the ZSM-5 shell over Pd/S-1 has a little effect on the chemical state
of the supported Pd NPs. This is different from the results observed by
Chai et al. over zeolite-encapsulated Pd NPs [38]. They found that Pd 3d
BE values obviously shifted toward higher values by 0.5ꢀ 0.6 eV upon
encapsulation due to the electron transfer from Pd to zeolite framework.
From Fig. 5, it also can be found that the intensities of Pd 3d XPS signals
in Pd/S-1@HZSM-5 are much lower than that in Pd/S-1. Except the
lower Pd loadings, the Pd NPs in Pd/S-1@HZSM-5ꢀ 48 are covered by
ZSM-5 shell is also another rational reason. This is in accordance with
those obtained over zeolite-encapsulated Pd samples reported in the
references [38] and provide an indirectly evidences for the successfully
constructing core-shell structure.
The TEM images of Pd/S-1@ZSM-5-x samples are present in Fig. 3.
As shown in Fig. 3, Pd NPs in Pd/S-1@ZSM-5ꢀ 2 are evenly dispersed in
the crystal, and the size of Pd NPs are approximately 10 nm, which is
similar to that of Pd NPs in Pd/S-1 (Figure S1). However, with the
crystallization of ZSM-5 shell, Pd NPs are difficult to be captured for Pd/
S-1@ZSM-5-x samples due to the ZSM-5 shell cover. In order to confirm
the distribution of Pd NPs, the EDX elemental mapping of Pd/S-1@ZSM-
5ꢀ 48 are measured and shown in Fig. 4, it can be seen that Pd NPs are
well dispersed in the Pd/S-1@ZSM-5ꢀ 48 crystal (Fig. 4). From the H2
chemisorption results, it can be seen that these Pd/S-1@ZSM-5-x core-
shell samples have a similar Pd dispersion to Pd/S-1 (Table 1). In
addition, the mesoporous pores were formed in Pd/S-1 upon TPAOH
etching, which is favored for coating ZSM-5 shells over Pd/S-1 core, and
the mesoporous pores in Pd/S-1 disappear in the process of ZSM-5 shell
construction. In the TEM image of Pd/S-1@ZSM-5ꢀ 48, the ZSM-5 shell
with a thickness of 100 nm can be further strongly evidenced by bright
The N2 adsorption-desorption isotherms of Pd/S-1 and Pd/S-
1@HZSM-5-x samples are shown in Fig. 6. The curve of S-1 displays a
type I sorption isotherm, indicating the microporous structure of S-1
(Figure S2). Hysteresis loops appeared at p/p0 = 0.15~0.4 in the curves
of all samples (Fig. 6a and Figure S2) are caused by fluid-to-crystal-like
phase transition of N2 molecules in the micropores [49]. Thus, the
mesopores centered at around 2.8 nm in pore diameter curves of all the
samples are illusory actually (Fig. 6b). Pd/S-1 displays a lower surface
area and microporous volume than S-1, indicating treatment with
TPAOH has an effect on the framework of S-1. Treatment S-1 with
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N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Fig. 4. EDX elemental mapping of Pd/S-1@ZSM-5-48.
Pd/S-1@HZSM-5-x samples display significant ammonia desorption
peaks contributed by the acidic ZSM-5 shell over Pd/S-1, in which the
peaks at around 200 ◦C and 380 ◦C are corresponding to the weak and
strong acid sites, respectively. From the integrated areas of the desorp-
tion peaks, it can be seen that the strong acid amounts on Pd/S-
1@HZSM-5-x samples increase with the secondary crystallization time
and basically is proportional to coverage of the shell over Pd/S-1
(Table 1). These results indicate that the strong acid amount around
Pd NPs is related with the shell coverage and can be tuned by the con-
trolling the secondary crystallization time.
3.2. Catalytic performance
Naphthalene hydrogenation was employed as the model reaction to
evaluate the hydrogenation performances of the prepared core-shell
catalysts, and the reaction scheme is presented in Scheme 1. Under
the employed reaction conditions, S-1 and HZSM-5 were inactive in the
absence of Pd (Table 3). The catalytic performances of the core-shell
catalysts with the different shell coverage for the naphthalene hydro-
genation are shown in Fig. 8. Pd/S-1 shows just 5.1 % of naphthalene
conversion at 6 h and remains basically below 5% with the reaction
time. It is intriguing that Pd/S-1@HZSM-5-x samples exhibit much
stronger hydrogenation abilities than Pd/S-1, and their activities in-
crease with the shell integrity. The naphthalene conversion reaches 98.3
% at 6 h over Pd/S-1@HZSM-5ꢀ 48 with a completely integrated shell
and no significant decrease is observed with the reaction time. Pd/S-
1@HZSM-5ꢀ 48 has slightly lower Pd content than Pd/S-1 due to the
presence of ZSM-5 shell. Furthermore, the chemical states of the Pd NPs
on the two samples are similar. Therefore, the enhancement in hydro-
genation ability over Pd/S-1@HZSM-5ꢀ 48 is closely related to the
acidity of the ZSM-5 shell. This can be confirmed by the gradually
enhanced activities with the coverage of nano-ZSM-5 over Pd/S-1. For
Pd/S-1@HZSM-5-x samples, the increase in ZSM-5 shell coverage boosts
the acid amounts around Pt NPs, which are beneficial for spillover
Fig. 5. Pd 3d XPS spectra for Pd/S-1 and Pd/S-1@ZSM-5-48.
TPAOH generates mesoporous in Pd/S-1 crystals, which is evidenced by
the presence of hysteresis loop at P/P0 >0.45 in the N2
adsorption-desorption isotherm of Pd/S-1. During constructing ZSM-5
shell over Pd/S-1, the mesoporous volumes of the Pd/S-1@ZSM-5-x
samples drop as the increase of secondary crystallization time
(Table 2), and basically keep constant after the crystallization time was
beyond 7 h. In addition, as shown in Fig. 6a, the hysteresis loops at P/P0
>0.45 became smaller with the secondary crystallization time, sug-
gesting that Pd/S-1 is re-crystallized in the process of constructing
ZSM-5 shell.
The influences of the shell on the acidity of Pd/S-1 were evaluated by
NH3-TPD. As shown in the Fig. 7, Pd/S-1 just has weak acid sites,
originating from silanol groups on the surface of S-1. In contrast, all the
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N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Fig. 6. N2 adsorption-desorption isotherms (a) and pore size distribution (b) of different samples.
Table 2
Textural properties of the different samples.
Samples
Si/Al Atomic ratiosa
Pd loadinga (wt%)
SBETb (m2/g)
Smicrob (m2/g)
Smesob (m2/g)
Vtotalb (cm3/g)
Vmesob (cm3/g)
S-1
–
–
426.4
417.2
426.8
434.3
442.3
429.0
387.9
307.1
323.1
364.7
372.5
368.5
38.5
110.1
103.7
69.6
69.8
60.5
0.21
0.28
0.26
0.25
0.23
0.22
0.04
0.14
0.13
0.09
0.07
0.06
Pd/S-1
–
1.0
Pd/S-1@ZSM-5ꢀ 2
Pd/S-1@ZSM-5ꢀ 7
Pd/S-1@ZSM-5ꢀ 48
Pd/S-1@ZSM-5ꢀ 96
133.5
99.8
94.8
92.1
0.71
0.67
0.65
0.64
a
Determined by ICP.
b
Determined by N2 adsorption.
Table 3
Catalytic behaviors of the different reference catalysts in naphthalene
hydrogenation.
Selectivity (%)
Entry
Catalysts
Conversion (%)
Tetralin
Decalin
1
S-1
–
–
–
2
HZSM-5
–
–
–
3
Pd/S-1
4.3
100
94.8
97.6
97.8
88.6
96.2
95.7
99.8
98.2
0
4
Pd/S-1@HZSM-5ꢀ 48
Pd/S-1@NaZSM-5ꢀ 48
Pd/S-1@HZSM-5ꢀ 48-1
Pd/S-1@HZSM-5ꢀ 48-2
Pd/[S-1@HZSM-5ꢀ 48]
Pd/HZSM-5
96.1
27.7
57.6
95.8
71.5
77.4
8.8
5.2
2.4
2.2
11.4
3.8
4.3
0.2
1.8
5
6
7
8
9
10
Pd/S-1+HZSM-5
11
Pd/S-1@HZSM-5ꢀ 96
61.2
(Reaction conditions: WHSV:1.3 hꢀ 1, H2/feed:750, 4 MPa H2, 280 ◦C, time on
stream:10 h).
◦
200 to 350 C (Figure S3), while the one from the strong acid sites is
Fig. 7. NH3-TPD profiles of the different samples.
absent. Combined with the reaction and characterization results, it can
be deduced that the strong acid sites on ZSM-5 shell play a vital role in
enhanced hydrogenation ability of Pd/S-1. To further illustrate this
point, two Pd/S-1@HZSM-5ꢀ 48 samples were synthesized in the syn-
thesis system with SiO2/Al2O3 ratios of 126 and 45, respectively
(Figure S4). Even if it is difficult to accurately measure the Si/Al ratios in
the shell, for the different core shell catalysts, the Si/Al ratios deter-
mined by ICP also can reflect the acidity of the constructing shell. Pd/S-
1@HZSM-5ꢀ 48-1 with a Si/Al ratio of 147 shows a lower hydrogenation
activity than Pd/S-1@HZSM-5ꢀ 48. In contrast, Pd/S-1@HZSM-5ꢀ 48
with a Si/Al ratio of 72 shows the similar naphthalene conversion and
slightly higher selectivity to decalin than Pd/S-1@HZSM-5ꢀ 48 with a
hydrogenation. Hence, the acid induced spillover hydrogenation is the
main factor for the enhancement in hydrogenation ability over Pd/S-
1@HZSM-5ꢀ 48.
In order to confirm this, Pd/S-1@NaZSM-5ꢀ 48 was prepared by ion-
exchange with NaCl solution, and its catalytic performance was also
evaluated in naphthalene hydrogenation. As expected, Pd/S-1@NaZSM-
5ꢀ 48 has much lower hydrogenation ability than Pd/S-1@HZSM-5ꢀ 48,
and the naphthalene conversion is just 27.7 % (Table 3). NH3-TPD
measurement shows that Pd/S-1@NaZSM-5ꢀ 48 displays the ammonia
desorption peaks from the weak and medium acid sites at range from
7

N. Lu et al.
Molecular Catalysis 506 (2021) 111543
Table 4
Sulfur tolerance tests of the core-shell catalysts.
Selectivity (%)
Thionaphthene-
containing
Conversion
Catalysts
(%)
Tetralin
Decalin
Pd/S-1@HZSM-
5ꢀ 48
0
96.1
73.9
71.5
39.5
94.8
95.4
96.2
98.1
5.2
4.6
3.8
1.9
500
0
Pd/[S-1@HZSM-
5ꢀ 48]
500
(Reaction conditions: WHSV:1.3 hꢀ 1, H2/feed:750, 4 MPa H2, 280 ◦C, time on
stream:10 h).
prolonging the crystallization time (Figure S6). As shown in Table 3, it
can be seen that Pd/S-1@HZSM-5ꢀ 96 shows the lower hydrogenation
ability than Pd/S-1@HZSM-5ꢀ 48 even it has more strong acid sites
(Figure S3). Thus, the ZSM-5 nanocrystal shells in Pd/S-1@HZSM-5ꢀ 48
show superior structural features than other supported Pd catalysts for
naphthalene hydrogenation.
Fig. 8. Catalytic performances of naphthalene hydrogenation over different
core-shell catalysts. (Reaction conditions: WHSV = 1.3 hꢀ 1, H2/feed = 750, 4
MPa H2, 280 ◦C).
3.3. Sulfur-tolerant tests
Si/Al ratio of 94.8. This can be ascribed to less/more strong acid amount
The sulfur-tolerant performances of Pd/[S-1@HZSM-5ꢀ 48] and Pd/
S-1@HZSM-5ꢀ 48 were evaluated in the presence of thionaphthene. As
shown in Table 4, the naphthalene conversions over both two catalysts
decrease to some extent. However, Pd/S-1@HZSM-5ꢀ 48 in sulfur-
tolerant test still keep 76.8 % of its original activity at time on stream
of 10 h, while Pd/[S-1@HZSM-5ꢀ 48] drops to its 55.2 % of the original
activity at identical time on stream. These results indicate that Pd/S-
1@HZSM-5ꢀ 48 has better sulfur tolerance ability than Pd/[S-1@HZSM-
5ꢀ 48]. This can be explained by the reason that the acidic nano-ZSM-5
shells can protect the Pd NPs from poisoning by organic sulfide to some
extent.
on
Pd/S-1@HZSM-5ꢀ 48-1/-2
than
on
Pd/S-1@HZSM-5ꢀ 48
(Figure S5). The above results further demonstrate that the strong acid
sites of Pd/S-1@ZSM-5 core-shell catalyst play an important role for
enhancing hydrogenation ability.
To reveal the structural features of the prepared core-shell catalyst in
naphthalene hydrogenation, the following control experimental were
done. First, Pd/[S-1@HZSM-5ꢀ 48] were prepared by wet impregnation
method using S-1@HZSM-5ꢀ 48 as the support and Na2PdCl4 as Pd
precursor. Even if Pd/[S-1@HZSM-5ꢀ 48] has the similar Pd loading,
and strong acid amounts to Pd/S-1@HZSM-5ꢀ 48, it shows the lower
hydrogenation ability than Pd/S-1@HZSM-5ꢀ 48 (Table 3). The
different catalytic performances obtained over the two catalysts can be
ascribed to the different positions of Pd NPs on the two catalysts. In
naphthalene hydrogenation, reaction substrate naphthalene (0.703 ×
0.907 nm) is hard to diffuse into the ZSM-5 channel (0.51 × 0.55 and
0.52 × 0.58 nm), thus, naphthalene hydrogenation over the samples
prepared mainly occurs on the Pd NPs/acid sites located on the external
surface of supports. In the case of Pd/S-1@HZSM-5ꢀ 48, all Pd NPs was
covered all round by the nano-ZSM-5 shell, while not all Pd NPs can be
covered by nano-ZSM-5 shell for Pd/[S-1@HZSM-5ꢀ 48]. This may
cause the acid amount with a proximity to Pd NPs on Pd/S-1@HZSM-
5ꢀ 48 is more than on Pd/[S-1@HZSM-5ꢀ 48]. Second, Pd/HZSM-5 was
prepared by impregnating Na2PdCl4 on HZSM-5, and the prepared Pd/
HZSM-5 has a similar Pd loading and acid amount to Pd/S-1@HZSM-
5ꢀ 48 (Figure S3). As shown in Table 3, the hydrogenation activity of
Pd/HZSM-5 was lower than Pd/S-1@HZSM-5ꢀ 48. Pd NPs in Pd/HZSM-
5 were mainly located on the external surface of HZSM-5, while the acid
sites are mainly on the surface of the channel wall, thus, the accessible
acid sites with proximity to supported Pd NPs were limited, resulting in
lower hydrogenation ability of Pd/HZSM-5. Third, Pd/S-1+HZSM-5 was
prepared by mixing Pd/S-1 with HZSM-5. The chosen HZSM-5 has a
similar Si/Al ratio, morphology (hexagonal) and particle size to the
HZSM-5 coated on Pd/S-1 (Figure S6), thus the acid amount accessible
to naphthalene is also approximate for Pd/S-1@HZSM-5ꢀ 48 and Pd/S-
1+HZSM-5 two samples. However, Pd/S-1+HZSM-5 gives much lower
naphthalene conversion (below 10 %) than Pd/S-1@HZSM-5ꢀ 48. This
is mainly due to the poor proximity between Pd NPs and the accessible
acid sites, which is unfavorable for acid induced spillover hydrogena-
tion. These results further demonstrate that the enhanced hydrogenation
ability over Pd/S-1@HZSM-5ꢀ 48 is closely related to the accessible acid
amounts with proximity to Pd NPs. Apart from this, the nano-ZSM-5
shell in Pd/S-1@HZSM-5ꢀ 48 also plays a vital role in observed cata-
lytic performance of Pd/S-1@HZSM-5ꢀ 48 in naphthalene hydrogena-
tion. Pd/S-1@HZSM-5ꢀ 96 with a dense ZSM-5 shell was prepared by
4. Conclusion
In summary, an efficient Pd/S-1@ZSM-5 core-shell catalyst with
enhanced hydrogenation ability was designed and prepared via epitaxial
growth. The nano-ZSM-5 shell coverage increases with the extension of
crystallization time. Meanwhile, the strong acid amounts of Pd/S-
1@ZSM-5 core-shell catalyst also increase. Pd/S-1@HZSM-5 core-shell
catalysts exhibit stronger hydrogenation capacity for naphthalene hy-
drogenation, which greatly attributed to increase of strong acid amounts
around Pd NPs and rational structural design of nano-ZSM-5 shell. The
strong acid sites of Pd/S-1@ZSM-5 core-shell catalyst play a decisive
role for enhancing hydrogenation ability. Moreover, Pd/S-1@ZSM-5
core-shell catalyst also shows good sulfur-tolerance for naphthalene
hydrogenation in the present of thionaphthene. The core-shell provides
a new alterative way for constructing high-efficient noble metal hy-
drogenation catalysts.
CRediT authorship contribution statement
Ningyue Lu: Conceptualization, Validation, Writing - original draft.
Jiaxin Zhao: Investigation. Qi Dong: Methodology. Yanpeng Zhao:
Validation. Binbin Fan: Supervision, Funding acquisition, Writing -
review & editing.
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgments
This work was supported by the National Natural Science Foundation
of China (No. 21576177) and Shanxi Provincial Key Research and
Development Projects (No. 201903D121036).
8

N. Lu et al.
Molecular Catalysis 506 (2021) 111543
[26] Z.-Q. Li, X. Fu, C. Gao, J. Huang, B. Li, Y. Yang, J. Gao, Y. Shen, Z. Peng, J.-H. Yang,
Z. Liu, Enhancing the matching of acid/metal balance by engineering an extra
Si–Al framework outside the Pd/HBeta catalyst towards benzene hydroalkylation,
Catal. Sci. Technol. 10 (2020) 1467–1476.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2021.111543.
[27] J. Zhang, L. Wang, B. Zhang, H. Zhao, U. Kolb, Y. Zhu, L. Liu, Y. Han, G. Wang,
C. Wang, D.S. Su, B.C. Gates, F.-S. Xiao, Sinter-resistant metal nanoparticle
catalysts achieved by immobilization within zeolite crystals via seed-directed
growth, Nat. Catal. 1 (2018) 540–546.
References
[28] J. Zhang, L. Wang, Y. Shao, Y. Wang, B.C. Gates, F.-S. Xiao, A Pd@zeolite catalyst
for nitroarene hydrogenation with high product selectivity by sterically controlled
adsorption in the zeolite micropores, Angew. Chem. Int. Ed. 129 (2017)
9747–9751.
[1] A. Stanislaus, B.H. Cooper, Aromatic hydrogenation catalysis: a review, Catal. Rev.
36 (1994) 75–123.
[2] M. Zahmakıran, Y. Tonbul, S. Ozkar, Ruthenium (0) nanoclusters stabilized by a
nanozeolite framework: isolable, reusable, and green catalyst for the
hydrogenation of neat aromatics under mild conditions with the unprecedented
catalytic activity and lifetime, J. Am. Chem. Soc. 132 (2010) 6541–6549.
[3] S. Miao, Z. Liu, B. Han, J. Huang, Z. Sun, J. Zhang, T. Jiang, Ru nanoparticles
immobilized on montmorillonite by ionic liquids: a highly efficient heterogeneous
catalyst for the hydrogenation of benzene, Angew. Chem. 118 (2006) 272–275.
[4] B. Pawelec, R. Mariscal, R.M. Navarro, S.V. Bokhorst, S. Rojas, J.L.G. Fierro,
Hydrogenation of aromatics over supported Pt-Pd catalysts, Appl. Catal. A Gen.
225 (2002) 223–237.
[29] N. Wang, Q. Sun, J. Yu, Ultrasmall metal nanoparticles confined within crystalline
nanoporous materials: a fascinating class of nanocatalysts, Adv. Mater 31 (2019),
1803966.
[30] J. Wang, L. Liu, X. Dong, L. Alfilfil, C.-E. Hsiung, Z. Liu, Y. Han, Converting
hierarchical to bulk structure: a strategy for encapsulating metal oxides and noble
metals in zeolites, Chem. Mater. 30 (2018) 6361–6369.
[31] T.L. Cui, W.Y. Ke, W.B. Zhang, H.H. Wang, X.H. Li, J.S. Chen, Encapsulating
palladium nanoparticles inside mesoporous MFI zeolite nanocrystals for shape-
selective catalysis, Angew. Chem. Int. Ed. 55 (2016) 9178–9182.
[32] H.J. Cho, D. Kim, J. Li, D. Su, B. Xu, Zeolite-Encapsulated Pt nanoparticles for
tandem catalysis, J. Am. Chem. Soc. 140 (2018) 13514–13520.
[5] L. Zhu, S. Shan, V. Petkov, W. Hu, A. Kroner, J. Zheng, C. Yu, N. Zhang, Y. Li,
R. Luque, C.-J. Zhong, H. Ye, Z. Yang, B.H. Chen, Ruthenium–nickel–nickel
hydroxide nanoparticles for room temperature catalytic hydrogenation, J. Mater.
Chem. A Mater. Energy Sustain. 5 (2017) 7869–7875.
[33] N. Wang, Q. Sun, R. Bai, X. Li, G. Guo, J. Yu, In situ confinement of ultrasmall Pd
clusters within nanosized Silicalite-1 zeolite for highly efficient catalysis of
hydrogen generation, J. Am. Chem. Soc. 138 (2016) 7484–7487.
[34] Z. Jin, L. Wang, E. Zuidema, K. Mondal, M. Zhang, J. Zhang, C. Wang, X. Meng,
H. Yang, C. Mesters, F.S. Xiao, Hydrophobic zeolite modification for in situ
peroxide formation in methane oxidation to methanol, Science 367 (2020)
193–197.
[6] M. Pang, C. Liu, W. Xia, M. Muhler, C. Liang, Activated carbon supported
molybdenum carbides as cheap and highly efficient catalyst in the selective
hydrogenation of naphthalene to tetralin, Green Chem. 14 (2012) 1272.
[7] Y. Cheng, H. Fan, S. Wu, Q. Wang, J. Guo, L. Gao, B. Zong, B. Han, Enhancing the
selectivity of the hydrogenation of naphthalene to tetralin by high temperature
water, Green Chem. 11 (2009) 1061–1065.
[35] Q. Sun, B.W.J. Chen, N. Wang, Q. He, A. Chang, C.M. Yang, H. Asakura, T. Tanaka,
M.J. Hulsey, C.H. Wang, J. Yu, N. Yan, Zeolite-encaged Pd-Mn nanocatalysts for
CO2 hydrogenation and formic acid dehydrogenation, Angew. Chem. Int. Ed. 59
(2020) 20183–20191.
[8] B.H. Cooper, B.B.L. Donnis, Aromatic saturation of distillates: an overview, Appl.
Catal. A Gen. 137 (1996) 203–223.
[9] C. Song, A.D. Schmitz, Zeolite-supported Pd and Pt catalysts for low-temperature
hydrogenation of naphthalene in the absence and presence of benzothiophene,
Energy Fuel 11 (1997) 656–661.
[36] S. Song, V. Fung Kin Yuen, L. Di, Q. Sun, K. Zhou, N. Yan, Integrating Biomass into
the Organonitrogen Chemical Supply Chain: Production of Pyrrole and d-Proline
from Furfural, Angew. Chem. Int. Ed. 59 (2020) 19846–19850.
[10] T. Tang, C. Yin, L. Wang, Y. Ji, F. Xiao, Good sulfur tolerance of a mesoporous Beta
zeolite-supported palladium catalyst in the deep hydrogenation of aromatics,
J. Catal. 257 (2008) 125–133.
[37] C. Wang, E. Guan, L. Wang, X. Chu, Z. Wu, J. Zhang, Z. Yang, Y. Jiang, L. Zhang,
X. Meng, B.C. Gates, F.S. Xiao, Product selectivity controlled by nanoporous
environments in zeolite crystals enveloping rhodium nanoparticle catalysts for CO2
hydrogenation, J. Am. Chem. Soc. 141 (2019) 8482–8488.
[11] M. Du, Z. Qin, H. Ge, X. Li, Z. Lü, J. Wang, Enhancement of Pd–Pt/Al2O3 catalyst
performance in naphthalene hydrogenation by mixing different molecular sieves in
the support, Fuel Process. Technol. 91 (2010) 1655–1661.
[38] Y. Chai, S. Liu, Z.-J. Zhao, J. Gong, W. Dai, G. Wu, N. Guan, L. Li, Selectivity
modulation of encapsulated Palladium nanoparticles by zeolite microenvironment
for biomass catalytic upgrading, ACS Catal. (2018) 8578–8589.
[12] K. Cheng, J. Kang, S. Huang, Z. You, Q. Zhang, J. Ding, W. Hua, Y. Lou, W. Deng,
Y. Wang, Mesoporous Beta zeolite-Supported ruthenium nanoparticles for selective
conversion of synthesis gas to C5–C11 isoparaffins, ACS Catal. 2 (2012) 441–449.
[13] K. Na, N. Musselwhite, X. Cai, S. Alayoglu, G.A. Somorjai, Promotional effects of
mesoporous zeolites with Pt nanoparticle catalysts during reforming of
methylcyclopentane, J. Phys. Chem. A 118 (2014) 8446–8452.
[14] S.A. D’Ippolito, A.D. Ballarini, C.L. Pieck, Influence of support acidity and Ir
content on the selective ring opening of Decalin over Ir/SiO2–Al2O3, Energy Fuel
31 (2017) 5461–5471.
[39] H. Cho, D. Kim, S. Li, D. Su, D. Ma, B. Xu, Molecular level proximity of metal and
acid sites in zeolite encapsulated Pt nanoparticles for selective multistep tandem
catalysis, ACS Catal. 10 (2019) 3340–3348.
[40] M. Moliner, J.E. Gabay, C.E. Kliewer, R.T. Carr, J. Guzman, G.L. Casty, P. Serna,
A. Corma, Reversible transformation of Pt nanoparticles into single atoms inside
high-silica chabazite zeolite, J. Am. Chem. Soc. 138 (2016) 15743–15750.
[41] Z. Wu, S. Goel, M. Choi, E. Iglesia, Hydrothermal synthesis of LTA-encapsulated
metal clusters and consequences for catalyst stability, reactivity, and selectivity,
J. Catal. 311 (2014) 458–468.
´
[15] M.A. Arribas, P. Concepcion, A. Martın
́
ez, The role of metal sites during the
coupled hydrogenation and ring opening of tetralin on bifunctional Pt(Ir)/USY
catalysts, Appl. Catal. A Gen. 267 (2004) 111–119.
[42] S. Goel, Z. Wu, S.I. Zones, E. Iglesia, Synthesis and catalytic properties of metal
clusters encapsulated within small-pore (SOD, GIS, ANA) zeolites, J. Am. Chem.
Soc. 134 (2012) 17688–17695.
[16] T. He, Y. Wang, P. Miao, J. Li, J. Wu, Y. Fang, Hydrogenation of naphthalene over
noble metal supported on mesoporous zeolite in the absence and presence of sulfur,
Fuel 106 (2013) 365–371.
[43] S. Goel, S.I. Zones, E. Iglesia, Encapsulation of metal clusters within MFI via
interzeolite transformations and direct hydrothermal syntheses and catalytic
consequences of their confinement, J. Am. Chem. Soc. 136 (2014) 15280–15290.
[44] X. Yang, Q. Liu, Y. Zhang, X. Su, Y. Huang, T. Zhang, In situ synthesis of metal
clusters encapsulated within small-pore zeolites via a dry gel conversion method,
Nanoscale 10 (2018) 11320–11327.
[17] X. Meng, Y. Wu, Y. Li, Tailoring the pore size of zeolite Y as the support of diesel
aromatic saturation catalyst, J. Porous Mater 13 (2006) 365–371.
[18] T. Tang, C. Yin, L. Wang, Y. Ji, F. Xiao, Superior performance in deep saturation of
bulky aromatic pyrene over acidic mesoporous Beta zeolite-supported palladium
catalyst, J. Catal. 249 (2007) 111–115.
[19] H. Chen, H. Yang, O. Omotoso, L. Ding, Y. Briker, Y. Zheng, Z. Ring, Contribution
of hydrogen spillover to the hydrogenation of naphthalene over diluted Pt/RHO
catalysts, Appl. Catal. A Gen. 358 (2009) 103–109.
[45] Y. Chen, X. Wang, L. Zhang, A strategy for fast and facile embedding platinum
nanoparticles in silicalite‑1 crystallites with a stable and catalytic active structure,
Chem. Eng. J. 394 (2020), 124990.
[20] S.D. Lin, M.A. Vannice, Hydrogenation of aromatic hydrocarbons over supported Pt
catalysts. I. Benzene hydrogenation, J. Catal. 143 (1993) 539–553.
[21] S.D. Lin, M.A. Vannice, Hydrogenation of aromatic hydrocarbons over supported Pt
catalysts. II. Toluene hydrogenation, J. Catal. 143 (1993) 554–562.
[22] S.D. Lin, M.A. Vannice, Hydrogenation of aromatic hydrocarbons over supported Pt
catalysts. III. Reaction models for metal surfaces and acidic sites on oxide supports,
J. Catal. 143 (1993) 563–572.
[46] M. Javed, S. Cheng, G. Zhang, P. Dai, Y. Cao, C. Lu, R. Yang, C. Xing, S. Shan,
Complete encapsulation of zeolite supported Co based core with silicalite-1 shell to
achieve high gasoline selectivity in Fischer-Tropsch synthesis, Fuel 215 (2018)
226–231.
ˇ
[47] J. Prech, D.R. Strossi Pedrolo, N.R. Marcilio, B. Gu, A.S. Peregudova, M. Mazur, V.
V. Ordomsky, V. Valtchev, A.Y. Khodakov, Core–Shell metal zeolite composite
catalysts for in situ processing of Fischer–Tropsch hydrocarbons to gasoline type
fuels, ACS Catal. 10 (2020) 2544–2555.
[23] S. Lee, K. Lee, J. Im, H. Kim, M. Choi, Revisiting hydrogen spillover in Pt/LTA:
effects of physical diluents having different acid site distributions, J. Catal. 325
(2015) 26–34.
[48] C. Liu, L. Lin, Y. Cao, H. Liu, Y. Guo, X. Zhang, Amino-functionalized seeds-induced
synthesis of encapsulated Pd@Silicalite-1 core-shell catalysts for size-selective
hydrogenation, Catal. Commun. 109 (2018) 16–19.
[24] J. Im, H. Shin, H. Jang, H. Kim, M. Choi, Maximizing the catalytic function of
hydrogen spillover in platinum-encapsulated aluminosilicates with controlled
nanostructures, Nat. Commun. 5 (2014) 3370.
[49] H. Tao, H. Yang, Y. Zhang, J. Ren, X. Liu, Y. Wang, G. Lu, Space-confined synthesis
of nanorod oriented-assembled hierarchical MFI zeolite microspheres, J. Mater.
Chem. A Mater. Energy Sustain. 1 (2013) 13821.
[25] J. Liu, H. Zhang, N. Lu, X. Yan, B. Fan, R. Li, Influence of acidity of mesoporous
ZSM-5-supported Pt on naphthalene hydrogenation, Ind. Eng. Chem. Res. 59
(2020) 1056–1064.
9