Highly dispersed Pt catalyst supported on nanoporous carbon derived from waste PET bottles for reductive alkylation

Article abstract of DOI:10.1039/c9ra04976b

Nanoporous carbon (NPC) derived from waste polyethyleneterephthalate (PET) bottles was prepared by a MgOlated method and employed as a support for a highly dispersed platinum catalyst. The NPCs and Pt/NPCs catalysts were characterized by BET, SEM, TEM, XRD and ICP-OES. The catalytic performance of the NPC supported Pt catalysts for reductive alkylation of p-aminodiphenylamine (p-ADPA) with methyl isoamyl ketone (MIAK) was investigated. The textural properties of the NPC prepared could be tailored by changing the size of the MgOlate and the MgO/waste PET powder mass ratio. When the pore size was below 14 nm, the catalytic performance of the Pt/NPCs for the reductive alkylation could be improved with increasing the pore size of the NPCs. Profiting from the higher mechanical strength and the ideal pore structure, Pt/O?NPC50(1/1)-PTA had excellent reusability, which could maintain 98% conversion of p-ADPA after reused 10 times.

Full text of DOI:10.1039/c9ra04976b

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Highly dispersed Pt catalyst supported on
nanoporous carbon derived from waste PET bottles
Cite this: RSC Adv., 2019, 9, 31092
for reductive alkylation†
* *
Chen Zhe, Yu Shitao, Ding Junwei, Shan Yuling, Liu Fusheng
Yu Wenlong,
and Li Ming
Nanoporous carbon (NPC) derived from waste polyethyleneterephthalate (PET) bottles was prepared by
a MgO-templated method and employed as a support for a highly dispersed platinum catalyst. The NPCs
and Pt/NPCs catalysts were characterized by BET, SEM, TEM, XRD and ICP-OES. The catalytic
performance of the NPC supported Pt catalysts for reductive alkylation of p-aminodiphenylamine (p-
ADPA) with methyl isoamyl ketone (MIAK) was investigated. The textural properties of the NPC prepared
could be tailored by changing the size of the MgO-template and the MgO/waste PET powder mass ratio.
When the pore size was below 14 nm, the catalytic performance of the Pt/NPCs for the reductive
alkylation could be improved with increasing the pore size of the NPCs. Profiting from the higher
mechanical strength and the ideal pore structure, Pt/O@NPC50(1/1)–PTA had excellent reusability, which
could maintain 98% conversion of p-ADPA after reused 10 times.
Received 1st July 2019
Accepted 29th August 2019
DOI: 10.1039/c9ra04976b
rsc.li/rsc-advances
activation method, the narrow pore structures of the
conventional activated carbon are not conducive to the
1. Introduction
diffusion of the reactants with relatively larger molecule
size.
Reductive alkylation of amines with ketones is an effective path
for the synthesis of higher alkylated amine derivatives. An
important class of these alkylated amines is N,N0-disubstituted
p-phenylenediamine (DPPD), which plays an signicant role in
rubber additives.1–8 The reductive alkylation for DPPDs is
carried out by condensation reaction between p-phenylenedi-
amine compounds and ketones to form imines,9 also known as
Schiff bases, which are converted to N-alkylated products via
catalytic hydrogenation.10–12 CuO–ZnO–Al2O3 composite cata-
lysts were widely used in industrial production of DPPDs
because of their low cost. However, the low catalytic activity and
selectivity of the copper-based catalyst can't meet the quality
requirements of the DPPD products. Therefore, supported
precious metal catalysts were employed for the preparation of
DPPDs with high quality and efficiency.13–15
It is well known that the support of heterogeneous cata-
lyst has a great inuence on the adsorption and diffusion of
reactants, as well as the accessibility of reactants with the
active sites, especially for the reactants with relatively larger
molecule size.16–22 However, most commonly used support
for reductive alkylation catalysts was conventional activated
carbon.14,15,23 Unfortunately, limited by raw material and
In recent carbon science, nanoporous carbon preparation
processes have been proposed, using template method to
control pore structure, instead of any activation process.24
Nanoporous carbons have attracted more and more attention in
the elds of adsorption,25,26 energy storage27 and catalysis20
owing to their adjustable pore structures. A hard-template
method is generally used for the preparation of nanoporous
carbons, with easily adjustability of their nanostructure by
varying the template nano size and proportion. Typically, MgO-
templated nanoporous carbon has achieved the commercial
application on account of its advantages, such as the reusability
of MgO and convenience for dissolving MgO using a diluted
acidic solution under more mild conditions.28–32 Furthermore,
the MgO-templated nanoporous with interconnected short-
range pore structure can effectively reduce the molecular
diffusion resistance.33–35
Polyethyleneterephthalate (PET) is one of the most
common synthetic polymers widely used in industry and our
daily life. However, its excessive use has also caused a grave
environmental problem of countless PET wastes.36,37 For
several years, incineration and landll have been the
common ways for the treatment of PET residues. However,
above-mentioned processes may also cause new environ-
mental problems such as uncontrollable release of heat and
volatile compounds. Interestingly, the properties of the PET
wastes, for instance, thermoplasticity and relatively high
College of Chemical Engineering, Qingdao University of Science and Technology, 53
Zhengzhou Road, Qingdao 266042, Shandong, China. E-mail: yushitaoqust@126.
com; djwnsfc@126.com
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra04976b
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percentage of carbon, make PET an excellent candidate used samples were labeled “O&NPC”s, and their PZCs were measured
as a promising precursor in the preparation of hard-tem- approximately equal to 3 following the same method as that
plated nanoporous carbons.38–41
used for the pristine carbons.
In this study, nanoporous carbons (NPCs) with various pore
Pt/NPCs with a calculated Pt content of 3.0 wt% were
structures were prepared using MgO particles as nano- prepared via the dry impregnation technique combined with
templates and PET powders derived from waste PET bottles as the strong electrostatic adsorption. H2PtCl6 and [Pt(NH3)4]Cl2
carbon precursor. Innovatively using PET-based NPCs as purchased from Sino-Platinum Metals Corp. Ltd. (Kunming,
supports, highly dispersed Pt/NPC catalysts with very small China) were used as anionic (CPA) and cationic (PTA) platinum
platinum particles were prepared. The structure–property rela- precursors, respectively. In a typical synthesis, a volume of Pt
tionships of NPCs supported Pt catalysts were investigated, and precursor aqueous solution measured beforehand with desired
the catalytic performance of Pt/NPCs for the reductive alkylation mass of CPA or PTA was added using a microinjector on the
of p-ADPA with MIAK to N-(1,4-dimethylamyl)-N0-phenyl-p-phe- NPCs until it was just wet.
nylenediamine (antioxidant 7PPD) were evaluated.
To achieve 3 wt% of Pt with the NPC–CPA pair, 0.158 g of
H2PtCl6$6H2O were dissolved in 2.2 mL deionized water, and
the initial pH was adjusted to 2 with dilute HNO3; this H2PtCl6
solution was slowly dropped on 2 g of non-oxidized NPC using
a 50 mL microinjector. In the case of the O&NPC–PTA pair, and
for a similar 3 wt% Pt/O&NPC, the Pt precursor solution was
prepared by dissolving 0.103 g [Pt(NH3)4]Cl2 in 2.2 mL deion-
ized water; the pH was adjusted to 12 with ammonia. Subse-
quently, 2 g of O&NPC was mixed with the PTA chloride solution
by adding the latter 50 mL at a time to the O&NPC until it was
just wet. For the sake of comparison, 3 wt% Pt/NPC with the
non-oxidized NPC–PTA pair was prepared following the same
method as that used for the O&NPC–PTA pair described above.
All the samples were then dried in a ow of high purity N2 at
room temperature for 24 h, and reduced at 200 ꢀC in high purity
H2 ow for 2 h. The owing rate of N2 and H2 were 20 mL minꢁ1
and 50 mL minꢁ1, respectively. The reagents used in the prep-
aration process, such as H2SO4, HNO3 and PVA were purchased
from Aladdin Biochemical Technology Co., Ltd. (Shanghai,
China) and the gases were provided by Deyi Gas Co., Ltd.
(Yantai, China).
2. Experimental
2.1. Preparation of the NPCs
Waste PET bottles collected from refuse dump were thoroughly
washed with water and cut into small pieces. Then the PET
pieces were crushed into 100 to 200 mesh powder in a pulver-
izer. Three nano-MgO samples with 15 nm, 50 nm and 100 nm
particle sizes were purchased from Veking New Materials Co.,
Ltd. (Hangzhou, China). The MgO/PET ratio was dened as the
mass ratio of MgO to the waste PET powders.
An extremely convenient procedure for preparation of the
NPC with a MgO/PET ratio of 1/1 is described as follows. Waste
PET powder (10 g) and nano-MgO (10 g) were mixed mechan-
ically in an agate mortar (powder mixing). The mixtures were
ꢀ
pyrolyzed in an electric tubular atmosphere furnace at 850 C
ꢀ
foꢀr 2 h, in a ow of high purity N2. Heating rate to 850 C was
3 C minꢁ1 and owing rate of N2 was 20 mL minꢁ1. MgO was
dissolved out using 10 wt% H2SO4 aqueous solution (40 mL
H2SO4 aqueous solution/g MgO) from carbon–MgO mixtures at
The catalysts obtained were labeled using the carbon
support name and the Pt precursor name. For instance, Pt/
O@NPC50(1/1)–PTA was prepared with the oxidized NPC–
PTA pair, while NPC50(1/1) represents the carbon support
prepared with 1/1 mass ratio of 50 nm MgO to the waste PET
powder.
ꢀ
50 C for 5 h. The mixtures were repeatedly dissolved 3 times
until the ltrate did not contain Mg2+. Subsequently, the
residual solid was washed thoroughly with deionized water
until the ltrate was neutral. The NPCs, dried at 120 ꢀC for 12 h,
were denoted as NPC15, NPC50 and NPC100, where 15, 50 and
100 refer to the nano-size of the MgO used, 1/3, 1/1, and 3/1 refer
to the MgO/PET mass ratio. As a comparison, polyvinyl alcohol
(PVA) was also used as carbon precursor. The NPC with a MgO/
PVA mass ratio of 1/1 was prepared via the same powder mixing-
carbonization method. The PVA-based nanoporous carbon ob-
tained was named as PVA-NPC as a distinction. More than 4 g of
each nanoporous carbon was prepared for the subsequent
preparation of the supported Pt catalyst.
2.3. Characterization
The micro- and nanostructures of the NPCs were imaged using
a cold eld emission scanning electron microscope (JSM-7500F,
JEOL Ltd.) with an accelerating voltage of 5.0 kV. The specic
surface area, pore volume and pore size distribution of the NPCs
and Pt/NPC catalysts were determined using a nitrogen
adsorption–desorption analyzer (ASAP 2020, Micromeritics
Instrument Corp.). The specic surface area and the pore
2.2. Catalyst preparation
Prior to catalyst preparation, the points of zero charge (PZC) of distribution were analyzed using the Brunauer–Emmet–Teller
pristine carbon samples were measured approximately equal to (BET) and Barrett–Joyner–Halenda (BJH) equations, respec-
9 following the method described in the ref. 42. Subsequently, tively. Dispersion of Pt nanoparticles supported on varied NPCs
the NPC samples were oxidized via immersion in HNO3 (5 N) were analyzed using a transmission electron microscopy (JEM-
during 24 h at room temperature in order to obtain a low PZC 2100F, JEOL Ltd.). The accelerating voltage of the TEM was
carbon support for Pt/NPC preparation with platinum cations. 200 kV. X-ray diffraction patterns of the NPCs derived from
The samples were then washed and heated in high purity N2 at different carbon precursors were obtained using a D/max 2500
200 ꢀC for 2 h to remove the most unstable components. These diffractometer (Rigaku Corp.) with CuKa radiation carrying out
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Table 1 Textural parameters of the NPCs
MgO/PET (PVA)
mass ratio
Samples
MgO size/nm
SBET/m2 gꢁ1
SMicroa/m2 gꢁ1
VTotal/cm3 gꢁ1
VMicroa/cm3 gꢁ1
Ddeb/nm
NPC15(1/1)
NPC50(1/3)
NPC50(1/1)
NPC50(3/1)
NPC100(1/1)
PVA-NPC50(1/1)
15
50
50
50
100
50
1/1
1/3
1/1
3/1
1/1
1/1
733
407
452
481
205
413
104
93
97
112
76
101
0.61
0.99
1.02
1.07
0.79
0.97
0.03
0.09
0.14
0.17
0.10
0.11
3.8
14.0
13.6
13.8
22.8
15.4
a
Calculated by t-plot method. b The peak pore size in the pore distribution calculated by BJH desorption method.
at 40 kV and 150 mA. The metal contents of different catalysts was then pressurized with H2 to 3.0 MPa and heated up to 383 K
were analyzed using an ICP-AES analyzer (Agilent 725, Agilent with high stirring speed (750 rpm). The catalyst used was
Technologies, Inc.). The particle sizes of the catalysts were separated from the hydrogenation suspension by ltering aer
determined using a Mastersizer 3000 laser particle size analyzer reaction. The nal products were analyzed using an 7890B gas
(Malvern Panalytical Corp.). The N content of the used catalysts chromatography (Agilent Technologies, Inc.) equipped with an
was quantied using an elemental analyzer (Vario EL Cube, HP-5 capillary column (30 m ꢂ 0.32 mm ꢂ 0.25 mm) and an FID
Elementar).
detector.
The conversion and conversion rate of p-ADPA, the selectivity
of the product (7PPD) can be calculated using the following
equations respectively:
2.4. Reductive alkylation reaction
The catalytic reaction was performed in a 500 mL stainless steel
autoclave reactor provided by Huixin Chemical Machinery
Corp. Ltd. (Weihai, China), in which 50 g of p-ADPA, 120 g of
MIAK and 0.5 g of catalyst were added. The autoclave reactor
Cp0-ADPA ꢁ Cp-ADPA
X ¼
ꢂ 100%
Cp0-ADPA
Fig. 1 Pore width distribution of the NPCs.
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Fig. 2 SEM images of NPC samples ((a) NPC15(1/1); (b) NPC50(1/1); (c) NPC100(1/1); (d and e) the interior of the NPC50(1/1) with high
magnification; (f) PVA-NPC50(1/1)).
3. Results and discussion
3.1. Physical properties of NPCs and catalysts
Xp-ADPA
W ¼
t
To investigate the porous structure of nanoporous carbon
materials, all the samples were analyzed by nitrogen adsorp-
C7PPD
Cp0-ADPA ꢁ Cp-ADPA
tion–desorption method. The pore characteristics of NPCs were
S ¼
ꢂ 100%
listed in Table 1 and the nitrogen adsorption isotherms of the
samples were described in Fig. S1.† At the same MgO/PET ratio,
the pore volume and BET specic surface area of the NPCs
decreased with increased particle sizes of the MgO used as
where X is the p-ADPA conversion, W is the p-ADPA conversion
rate, S is the 7PPD selectivity, t is the reaction time, C0 and C
denote the initial and nal mole fraction, respectively.
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templates. However, using the same nano-MgO (50 nm), the precursors, instead of the structural properties of the carbon
properties mentioned above of the NPC50s increased with an materials. The strong interaction between the carbon support
increased MgO/PET mass ratio. Fig. 1 shows the pore size and platinum precursor could effectively improve the disper-
distributions of the NPC samples calculated by the BJH method. sion of Pt nanoparticles. By contrast, the carbon supported
The peak pore size in the pore distribution for the NPC15 was platinum catalysts synthesized with the NPC–PTA pair
about 4 nm. With the nano size of the MgO used increased, the (Fig. 4g, h and j) present large platinum particles from 5 to
pore size of NPC50 and NPC100 became larger than that of 20 nm with obvious nanoparticles aggregation.
NPC15, presenting a shoulder peak centered at mesopore size,
which was 14 nm for the former and 23 nm for the latter.
Interestingly, for all the NPCs prepared at different MgO/PET
3.2. Catalytic performances
The reaction pathways for the synthesis of antioxidant 7PPD is
shown in Scheme 1. The catalytic performances of various
catalysts were presented in Table 2 and reaction time vs.
conversion of p-ADPA over the Pt/NPCs was shown in Fig. S2.† It
is indicated that with the increase of the catalyst pore size, the
conversion of p-ADPA was obviously improved. The selectivity of
7PPD over various catalysts had the similar changing trend. All
the results above-mentioned show that the catalysts with larger
pore structure show better catalytic performance. However,
there was just a small difference in catalytic performance
between NPC50 (PVA-NPC50) and NPC100 supported platinum
catalysts, which indicated that the effect of the pore size of the
support on the catalytic performance decreases when the pore
size is larger than that of 13 nm. Interestingly, with the same
physical structure of the supports, the catalyst prepared with
the O&NPC–PTA pair had faster reaction rate but lower selec-
tivity to 7PPD. The main reason for this result may be that the
oxidized NPCs had more acidic sites, which catalyzed the
formation of the imine. The oxygen-containing functional
groups probably acting as acidic sites on various NPCs sup-
ported Pt catalysts is shown in Table S1.† According to the
literatures, the main by-products were possibly derived from the
hydrogenolysis of the intermediate product.
mass ratios with 50 nm nano-MgO as templates, the peak
pore sizes in the pore distributions were approximately 14 nm,
which indicates that the pore size of the NPC is signicantly
affected by the size of the template. These results have similar
regularity to our previous work, which can also demonstrate
that the pore structure of the NPCs can be modied via
changing the nano size of MgO templates and the MgO/PET
ratio. Furthermore, for the sake of comparison, the PVA-
NPC50(1/1) prepared with 1/1 mass ratio of 50 nm MgO to the
PVA powders as carbon precursors shows the specic surface
area of 413 m2 gꢁ1 with pore volume of 0.97 cm3 gꢁ1. The
surface structure difference between NPC50(1/1) and PVA-
NPC50(1/1) may result from the pyrolysis characteristics of the
two carbon precursors.
The surface morphology and microstructure of various NPC
samples was investigated by means of SEM. As shown in Fig. 2a–
e, the NPCs prepared exhibit 3D foam-like structure with quite
a number of macropores and mesopores when the waste PET
was used as carbon precursor. At the same MgO/PET mass ratio,
larger pores could form on the NPCs prepared when bigger
sized nano-MgO templates (Fig. 2a–c) were used. The high
magnication SEM images (Fig. 2d and e) clearly show that the
carbon wall presents sheet nanostructure, and huge amounts of
micropore and mesoporous scale ssures in the carbon layers.
The 3D foam-like structure with nanoporous ssures and ake-
like carbon walls looking thick and strong, had interconnected
channels, which is favorable for the highly efficient diffusion of
the reactant molecules. By contrast, the PVA-NPC50(1/1)
prepared using PVA powders as carbon precursors also shows
hierarchically porous nanostructure with thinner carbon walls
compared with the PET-based NPCs from Fig. 2f.
The reusability of the catalyst for reductive alkylation reac-
tions of p-ADPA with MIAK was tested using the same condi-
tions as before. Fig. 5 shows that the p-ADPA conversion
remained above 98% aer the Pt/O@NPC50(1/1)–PTA and Pt/
The XRD characterization results of NPC50(1/1) and PVA-
NPC50(1/1) are presented in Fig. 3. It was observed that both
the PET-based and PVA-based NPCs had no sharp characteristic
diffraction peaks (broad peaks at 2q ¼ 25ꢀ attributed to the
amorphous carbon), which indicates that the NPCs derived
from the two different carbon precursors at 850 ꢀC both had
negligible graphitization.
The TEM images of the Pt catalysts supported on various
NPCs (given in Fig. 4) show that, in all Pt/NPC catalysts
synthesized by the SEA method, whether using the NPC–CPA
pair or the O&NPC–PTA pair, the platinum nanoparticles (1 to 2
nm) are highly dispersed and present an extremely low degree of
agglomeration (Fig. 4a–f and i). These results indicate that the
dispersion state of platinum nanoparticles is signicantly
affected by the matching relationship between the surface
chemical properties of carbon supports and the platinum 1).
Fig. 3 XRD characterization results of NPC50(1/1) and PVA-NPC50(1/
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Fig. 4 TEM images of the fresh Pt catalysts supported on NPCs ((a) Pt/NPC15(1/1)–CPA, (b) Pt/O@NPC15(1/1)–PTA, (c) Pt/NPC50(1/1)–CPA, (d)
Pt/O@NPC15(1/1)–PTA, (e) Pt/NPC100(1/1)–CPA, (f) Pt/O@NPC100(1/1)–PTA, (g) Pt/NPC15(1/1)–PTA, (h) Pt/NPC50(1/1)–PTA, (i) Pt/O@PVA-
NPC50(1/1)–PTA and (j) the detail of the Pt/NPC50(1/1)–PTA with high magnification).
O@NPC100(1/1)–PTA reused 10 times, respectively. However, narrow pore structure of the NPC surely inhibits the perfor-
the p-ADPA conversion was reduced to 91% over Pt/ mance of the Pt/NPC. It is noteworthy that, compared with the
O@NPC15(1/1)–PTA reused 10 times, which indicates that the Pt/O@NPC50(1/1)–PTA, an obvious decrease of the p-ADPA
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Scheme 1 Reaction pathways of the reductive alkylation of p-ADPA with MIAK.
conversion was obtained with the increase of the Pt/O@PVA- NPC50(1/1). However, the carbon structure of the Pt/O@PVA-
NPC50(1/1)–PTA reused times.
NPC50(1/1)–PTA reused 10 times seemed to have broken
somewhat, with some small carbon pieces.
As show in Table 3, the BET specic surface area and pore
volume of the Pt/O@NPC50(1/1)–PTA decreased slightly aer 10
times of reuse. In our previous work,43 one of the main reasons
for the deactivation of traditional activated carbon supported Pt
catalyst in reductive alkylation is the blockage of pores and
covering of active centers by organic matter. These organics
adsorbing on the catalyst mainly contain the product and its
3.3. Deactivation of the Pt/NPCs
Fig. 6 shows the TEM characterization results of the Pt/
O@NPC50(1/1)–PTA and Pt/O@PVA-NPC50(1/1)–PTA reused 10
times, respectively. It is obvious that both the two used catalysts
still had the highly dispersed Pt nanoparticles, just like fresh
catalysts. In order to explore the surface morphology of the used
catalysts, SEM characterization was carried out, as shown in
Fig. 7. The used Pt/O@NPC50(1/1)–PTA still exhibited the 3D
foam-like pore structure with thick carbon walls connected with
each other, which was no signicant difference from the fresh
Table 2 Reductive alkylation over Pt catalysts supported on various
NPCsa
Selectivity/%
p-ADPA
Catalyst
conversion/% 7PPD Imine Others
Pt/NPC15(1/1)–CPA
Pt/O@NPC15(1/1)–PTA
Pt/NPC50(1/1)–CPA
Pt/O@NPC50(1/1)–PTA
Pt/NPC100(1/1)–CPA
Pt/O@NPC100(1/1)–PTA
85.2
87.8
96.5
96.8
99.0
99.2
89.3
90.9
96.5
97.3
98.4
99.0
96.8
10.2
8.5
3.3
2.4
1.6
0.9
3.0
0.5
0.6
0.2
0.3
—
0.1
0.2
Pt/O@PVA-NPC50(1/1)–PTA 97.2
a
Reaction conditions: p-ADPA ¼ 50 g, MIAK ¼ 120 g, catalyst ¼ 0.5 g, T
¼ 80 ꢀC, P ¼ 2.5 MPa (pure H2), reaction time ¼ 3 h, stirring speed ¼
750 rpm.
Fig. 5 Reusability of various Pt/NPCs for the synthesis of antioxidant
7PPD. Reaction conditions: p-ADPA ¼ 50 g, MIAK ¼ 120 g, catalyst ¼
0.5 g, T ¼ 100 ꢀC, P ¼ 3.0 MPa (pure H2), stirring speed ¼ 750 rpm.
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Fig. 6 TEM characterizations of used Pt/O@NPC50(1/1)–PTA (A) and Pt/O@PVA-NPC50(1/1)–PTA (B).
Fig. 7 SEM images of used Pt/O@NPC50(1/1)–PTA (A) and Pt/O@PVA-NPC50(1/1)–PTA (B).
derivatives generating by side reactions. The deactivated cata- same conditions as the catalyst stability experiments, except for
lyst usually shows a signicant decrease both in the micropo- the absence of the p-ADPA. It is evident from Table 3 that the
rous specic surface area and mesoporous specic surface area. used Pt/O@PVA-NPC50(1/1)–PTA-V aer the verication exper-
However, the Pt/O@PVA-NPC50(1/1)–PTA reused 10 times iment had the same changes as the stability experiment, which
showed some abnormal information, such as a signicant could indicate that the blockage of the pores by various reaction
decrease of the BET specic surface area with a slight increase species should not be the real reason for the signicant
of the micropore specic surface area. In order to explain this decrease of the mesoporous specic surface area. Considering
anomaly, the verication experiments were carried out with the the SEM characterization of the used catalysts, it can be
Table 3 Textural parameters of the fresh and used Pt/NPCs
Catalyst samples
SBET/m2 gꢁ1
SMicroa/m2 gꢁ1
VTotal/cm3 gꢁ1
Fresh Pt/O@NPC50(1/1)–PTA
Fresh Pt/O@PVA-NPC50(1/1)–PTA
Used Pt/O@NPC50(1/1)–PTA
Used Pt/O@PVA-NPC50(1/1)–PTA
Pt/O@NPC50(1/1)–PTA-Va
421
394
398
258
409
270
86
95
77
102
84
0.98
0.94
0.93
0.63
0.97
0.68
Pt/O@PVA-NPC50(1/1)–PTA-Va
105
a
Verication experiments conditions: MIAK ¼ 120 g, catalyst ¼ 0.5 g, T ¼ 100 ꢀC, P ¼ 3.0 MPa (pure H2), stirring speed ¼ 750 rpm.
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Table 4 Pt content and average particle size of fresh and used Pt/NPCs
Average particle
Catalyst samples
Pt content/%
N content/%
size/mm
Fresh Pt/O@NPC50(1/1)–PTA
Fresh Pt/O@PVA-NPC50(1/1)–PTA
Used Pt/O@NPC50(1/1)–PTA
Used Pt/O@PVA-NPC50(1/1)–PTA
Pt/O@NPC50(1/1)–PTA-Va
2.91
2.93
2.82
2.22
2.86
2.13
—
—
0.51
0.48
—
40
44
37
28
38
30
Pt/O@PVA-NPC50(1/1)–PTA-Va
—
a
Verication experiments conditions: MIAK ¼ 120 g, catalyst ¼ 0.5 g, T ¼ 100 ꢀC, P ¼ 3.0 MPa (pure H2), stirring speed ¼ 750 rpm.
concluded that the breakage and collapse of the carbon walls in the Taishan Scholars Construction Projects of Shandong
the PVA-based NPC led to a sharp decrease of the mesopores.
(ts201511033). The authors are grateful for the nancial
As listed in Table 4, the N content of both used catalysts support.
(used Pt/O@NPC50(1/1)–PTA and used Pt/O@PVA-NPC50(1/1)–
PTA) was about 0.5%, which probably caused by a small amount
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