Effects of pore structure of MgO-templated mesoporous carbon on its supported Pt catalysts for reductive alkylation of p-aminodiphenylamine with methyl isobutyl ketone

Article abstract of DOI:10.1039/C8NJ05948A

Mesoporous carbon (MC) was prepared by the nano-MgO template method and used as a support for the preparation of a Pt-based reductive alkylation catalyst. N₂ physical adsorption-desorption, scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterize the carbon supports and supported Pt catalysts. The effects of the pore structure of the Pt/MC catalyst on its performance for reductive alkylation of p-aminodiphenylamine with methyl isobutyl ketone were investigated. The results show that the surface area and pore structure of the MgO-templated mesoporous carbons can be modulated directionally by varying the size of nano-MgO particles and the MgO/PF mass ratio. The catalytic activity and stability of the catalysts for N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine synthesis increases with an increase in the pore size of the mesoporous carbons. Complete conversion of p-ADPA and 100% selectivity to 6PPD were obtained over Pt/MC50(1/1) within 4 hours, which could maintain a high catalytic activity after being reused 10 times. The characterization results indicate that there was an obvious decrease in the BET specific surface area, pore volume and Pt specific surface area of all used catalysts compared with the fresh catalysts, and the trend was more obvious with the decrease of catalyst pore size, which should be the primary reason for the degradation of catalytic performance.

Full text of DOI:10.1039/C8NJ05948A

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PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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New Journal of Chemistry
Effects of pore structure of MgO-templated mesoporous carbon on its supported Pt
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catalysts for reductive alkylation of p-aminodiphenylamine with methylDiOsIo: 1b0.1u03t9y/Cl8NkJe05t9o48nAe
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YU Wenlong, YU Shitao#, DING Junwei*, CHENG Qiuzhen, LIU Fusheng
College of Chemical Engineering, Qingdao University of Science and Technology, 53 Zhengzhou Road,
Qingdao 266042, Shandong, China
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Abstract: Mesoporous carbon (MC) was prepared by nano-MgO template method and used as support for
the preparation of a Pt-based reductive alkylation catalyst. N2 physical adsorption-desorption, scanning
electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterize the
carbon supports and supported Pt catalysts. The effects of pore structure of the Pt/MC catalyst on its
performance for reductive alkylation of p-aminodiphenylamine with methyl isobutyl ketone were
investigated. The results show that the surface area and pore structure of the MgO-templated mesoporous
carbons can be modulated directionally by varying the size of nano-MgO particles and the MgO/PF mass
ratio. The catalytic activity and stability of the catalysts for N-(1,3-dimethylbutyl)-N’-phenyl-p-
phenylenediamine synthesis increases with increased pore size of the mesoporous carbons. Complete
conversion of p-ADPA and 100% selectivity to 6PPD were obtained over Pt/MC50(1/1) within 4 hours,
which could maintain high catalytic activity after reused 10 times. The characterization results indicate that
there was obviously decreasing of the BET specific surface area, pore volume and Pt specific surface area of
all used catalysts comparing with the fresh catalysts, and the trend was more obvious with the decrease of
catalyst pores, which should be the primary reason for the degradation of catalytic performance.
Key words: Mesoporous carbon, Nano-MgO template, Pt-based catalyst, Pore structure, Reductive
alkylation
1. Introduction
Reductive alkylation of amine compounds is commercially practiced in a variety of industrial processes
for the manufacture of higher alkylated (secondary and tertiary) amine derivatives, which find applications
as intermediates in fine chemicals and specialty products1-4. An important example of this class of reaction is
the
reductive
alkylation
of
p-aminodiphenylamine
(p-ADPA)
to
N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD), which is widely used for rubber
antioxidant5-8. This reaction goes through a condensation dehydration reaction between p-ADPA and methyl
isobutyl ketone (MIBK) to form the imine (Schiff base), followed by hydrogenation to 6PPD in the presence

New Journal of Chemistry
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of metal catalysts9-11
.
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Ordinary copper catalysts were employed in industrial processes to manufacture the 6PPDVdiewuAertictloe Otnhlineeir
DOI: 10.1039/C8NJ05948A
cheap costs, however, these catalysts have the obvious defects, such as low-activity and selectivity resulting
in harsh reaction conditions and ketone converting into alcohol, copper-leaching aggravating rubber aging.
Supported noble metal catalysts12, 13 were then developed to overcome the disadvantages of traditional
copper-based catalysts, synthesizing 6PPD with high quality and efficiency. Most of the previous works on
reductive alkylation were focused on the development of hydrogenated active site with the aim of improving
the catalytic activity and selectivity14-17. However, the research on the influence of support structural
characteristics is rarely reported to the best of our knowledge.
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Support is one of the most important parts of heterogeneous catalyst18-20, which plays a vital role in
loading active components and improving their dispersion and also provides a space for the reactants to
react. Catalyst support affects the diffusion and adsorption of the reactants directly determining the
accessibility of the reactants with the active sites21-25 and thereby, it has a significant effect on the reductive
alkylation catalytic activity. The conventional used reductive alkylation catalyst support is activated carbon
but it has relatively small pore size and narrow pore channels, which is not conductive to the active
component dispersion and macromolecular reaction.
Mesoporous carbons have attracted a lot of attention in the fields of sorption and separation of
macromolecules, catalysis, and synthesis of nanomaterials because of their high surface area and tunable
pore diameters at the nanoscale26-29. A hard‐template method30-33 is generally used in the preparation of
mesoporous carbon materials. The pore structure of the carbon materials can be easily adjusted by varying
the template types and sizes. As a typical kind of hard‐template mesoporous carbons, MgO-templated
mesoporous carbon34-37 has become commercially available due to the MgO-template recoverability and
easy removability by washing with a diluted acidic solution.
In this work, mesoporous carbons (MC) with different pore diameters and surface areas were prepared
by using nano-MgO as a hard template and phenolic resin (PF) as a carbon precursor. The effects of pore
structure on the performance of supported Pt‐based catalyst, Pt/MC, for reductive alkylation to 6PPD were
investigated.
2. Experimental
2.1. Preparation of mesoporous carbon
Phenolic resin was purchased from Jinan Shengquan Group Share Holding Co., Ltd. (Jinan, China), and
nano-MgO was provided by Nanjing Hongde nanomaterials Co., Ltd. (Nanjing, China). Three nano-MgO
samples with particle size of 15 nm, 30 nm and 50 nm were used. The MgO/PF ratio was defined as the

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New Journal of Chemistry
mass ratio of nano-MgO to phenolic resin.
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A typical process for preparation of the MgO-templated mesoporous carbon material with a MgO/PF
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DOI: 10.1039/C8NJ05948A
ratio of 1/1 is described as follows. Phenolic resin (10 g) was dissolved in 50 ml of ethanol (AR, Sinopharm
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Chemical Reagent Co., Ltd., Shanghai, China). Nano-MgO (10 g) was dispersed in 100 ml of ethanol via
ultrasonic treatment. The ethanol-phenolic resin solution was then added dropwise to the ethanol-MgO
dispersion liquid. The mixture was stirred for 12 h at room temperature and then dried in a vacuum oven at
50 ℃ for 12 h. The obtained solid was carbonized in a pipe furnace (Hefei Kejing materials technology Co.,
Ltd., Hefei, China ) at 900 ℃ for 2 h, in a flow of high purity N2 gas (99.999%, Qingdao Heli Gases Co.,
Ltd., Qingdao, China ) at a rate of 20 ml/min. The heating rate up to 900 ℃ was 3 ℃ /min. From
carbon-coated MgO particles thus obtained, template MgO was dissolved out using 10 w% H2SO4 (AR,
Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) aqueous solution (40 ml H2SO4 aqueous solution /
g MgO ) at 50 ℃ for 5 h. The dissolution process of MgO was repeated 3 times until the magnesium ion in
the filtrate could not be detected by ICP-OES. The solid was then filtered and washed with deionized water
until the pH reached to 7. The mesoporous carbons, which were obtained by drying at 110 ℃ for 24 h,
were designated as MC15, MC30, MC50 and MC50, where MC refers to mesoporous carbon, 15, 30 and 50
refer to the size (nm) of the MgO used, 1/3, 1/1, and 3/1 refer to the MgO/PF mass ratio.
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2.2. Preparation of catalyst
Mesoporous carbon supported Pt catalysts with a nominal Pt loading of 3.0 w% were prepared by the
conventional impregnation method. Prior to impregnation, the synthesized MgO-templated mesoporous
carbon was pretreated with 10 % HNO3(AR, Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) at 50
℃ for 5h, followed by washing with distilled water until the pH reached to 7 and then dried under vacuum
at 110 ℃ for 12 h. The point of zero charge (PZC) of all HNO3 treated supports determined by mass
38
titration was controlled at about 5 . 15 ml of H2PtCl6 (Sino-Platinum Metals Corp. Ltd.) aqueous solution
(0.01 g/ml) was then added dropwise into 50 ml of aqueous suspension containing 5 g of pretreated
mesoporous carbon, and then the pH of the suspension was adjusted to 10 by adding NaOH (AR, Sinopharm
Chemical Reagent Co., Ltd., Shanghai, China) aqueous solution. The precipitated Pt(OH)4 was reduced by
NaBH4(AR, Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) at room temperature, which was then
washed with deionized water until the pH of the filtrate was 7 and no chloride ions could be observed in the
filtrate by the AgNO3 titration method. This sample was then dried under the vacuum at 110 ℃ for 12 h.
The catalyst was designated as Pt/MC, where MC can be represented by MC15, MC30 or MC50.
As a comparison, Pt/AC catalyst with a nominal Pt loading of 3.0 w% were prepared using the same
method as mentioned above. A commercial activated carbon (Calgon Carbon Corp. Ltd.) was used as the

New Journal of Chemistry
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catalyst support.
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2.3. Catalyst characterization
View Article Online
DOI: 10.1039/C8NJ05948A
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Scanning electron microscopy (SEM) was performed on a JSM-7500Fmicroscope (JEOL Ltd.) with an
accelerating voltage of 8.0 kV. The samples were then gold coated by cathodic sputtering. Transmission
electron microscopy (TEM) images of the catalysts were obtained using a JEM-2100F microscope(JEOL
Ltd.) operating at an accelerating voltage of 200 kV. The samples for TEM were prepared by dropping the
ethanol suspensions of the catalysts on copper grids. The powder X-ray diffraction (XRD) patterns of the
samples were recorded on D/max2500 diffractometer (Rigaku Corp.) with Cu Kα radiation at 40 kV and
150 mA. The metal content of the catalysts were quantitatively determined by inductively coupled plasma
atomic emission spectroscopy (ICP-OES) using a Varian715-ES (Varian Inc.). The surface area and pore
structure of the catalysts were determined by N2 physical adsorption-desorption using a ASAP 2020 surface
area analyzer (Micromeritics Instrument Corp.).The surface area of the samples was calculated by the BET
equation. The specific surface area of Pt supported on the carbon was determined by CO chemical
adsorption using an AutoChemII 2920 analyzer (Micromeritics Instrument Corp.).
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2.4. Catalyst performance
The reductive alkylation to 6PPD was carried out in an autoclave (Weihai Huixin Chemical Mechanic
Corp. Ltd.) which was made of 316L stainless steel with a working volume of 500 ml. The reaction
conditions were as follows: p-ADPA = 50 g, MIBK = 109 g, catalyst = 0.5 g, T = 373 K, P = 2.5 MPa (pure
H2, 99.9%, Qingdao Heli Gases Co., Ltd., Qingdao, China), stirring speed = 700 r/min. The catalyst was
recycled by filtration after reaction. The reaction products were analyzed by gas chromatography
(Agilent7820A) equipped with an FID detector and a capillary column HP-5(30 m×0.32 mm×0.25 μm).
The conversion of p-ADPA and selectivity of 6PPD can be calculated by the following equations
respectively：
퐶0p ADPA ― 퐶p ― ADPA
-
푋 =
푆 =
× 100%
× 100%
퐶p0
ADPA
-
퐶6PPD
퐶0p ADPA ― 퐶p ― ADPA
-
where X is the p-ADPA conversion, S is the 6PPD selectivity, C0 and C denote the initial and final mole
fraction, respectively.
3. Results and discussion
3.1. Structural properties of mesoporous carbon and catalyst

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New Journal of Chemistry
The effects of nano-MgO particle size and MgO/PF ratio on the pore structure and surface area of the
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prepared mesoporous carbons were studied. Table 1 gives the physical properties of prepared VmieweAsroticpleoOrnloinue s
DOI: 10.1039/C8NJ05948A
4
carbons and commercial activated carbon. Sample C-none, which was directly carbonized with PF without a
nano-MgO template, mainly consisted of micropores, with a minimal specific surface area of 22 m2/g. At the
same MgO/PF ratio, the total specific surface area and pore volume of the mesoporous carbons decreased
with an increased particle size of the nano-MgO templates. However, using the same nano-MgO template,
the total specific surface area and pore volume of prepared mesoporous carbons increased with an increased
MgO/PF ratio. From the pore size distribution (Fig.1) and the data in Table 1, a sharp pore size distribution
at about 6 nm for the MC15 was displayed. As the nano size of MgO templates increased, the pore size of
MC30 and MC50 became larger than that of MC15, having pore size distribution with maxima at 10 and 17
nm, respectively. Furthermore, for all the mesoporous carbons prepared at different MgO/PF ratios with 30
nm nano-MgO as templates, the pore diameters were approximately 10nm, which indicates that the amount
of nano-MgO does not affect the pore size of the mesoporous carbon significantly. All these results
demonstrate that the surface area and pore structure of the MgO-templated mesoporous carbon samples can
be modulated by varying the size of nano-MgO particles and the MgO/PF ratio.
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Table 1 Textural properties of different carbon samples.
a
a
b
MgO size /
SBET
m2g-1
22
/
SMicro
m2g-1
20
/
VTotal
cm3g-1
0.01
/
VMicro
cm3g-1
0.01
/
Dde /
MgO/PF
Samples
C-none
mass ratio
nm
--
nm
--
--
MC15(1/1) 15
MC30(1/3) 30
MC30(1/1) 30
MC30(3/1) 30
MC50(1/1) 50
1/1
1/3
1/1
3/1
1/1
--
661
532
610
832
348
1570
58
0.65
0.61
0.63
1.06
0.59
0.92
0.03
0.07
0.06
0.08
0.08
0.23
5.9
9.8
10
152
136
145
135
551
9.7
17
AC
--
2.3
a Calculated by t-plot method.
b The peak pore size in the pore distribution calculated by BJH desorption method.

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2.0
1.5
1.0
0.5
2.5
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DOI: 10.1039/C8NJ05948A
MC15(1/1)
MC30(1/1)
2.0
1.5
1.0
0.5
0.0
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0.0
2.0
0
5
10
15
20
25
30
0
5
10
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20
25
30
Pore size / nm
Pore size / nm
3.0
2.5
2.0
1.5
1.0
0.5
0.0
AC
MC50(1/1)
1.5
1.0
0.5
0.0
0
5
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25
30
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40
45
50
0
5
10
15
20
Pore size / nm
Pore size / nm
Fig. 1 Pore size distribution of various mesoporous carbons and activated carbon.
In order to explore the surface structure and morphology of various carbon samples, SEM
characterization was carried out. Fig.2 shows the SEM images of different carbon material samples. It was
observed that the carbon marked as C-none (Fig. 2a) which was directly carbonized with PF without a
nano-MgO template had a flat surface and a non-porous structure. The porous carbons prepared exhibit
alveolate structures as shown in Fig. 2b to 2e when nano-MgO templates were used. The amount of pores
increased noticeably with the addition of MgO as shown in Fig. 2b to 2f. At the same MgO/PF ratio, larger
pores could form on the carbon material using bigger sized MgO-template (Fig. 2b, Fig. 2d and Fig. 2f),
replicating the size of MgO nanocrystals correspondingly. Under high magnification conditions(Fig. 2h and
Fig. 2i), it can be seen that these larger pore structures are connected with each other though smaller pores
on all of the MgO-templated mesoporous carbons constructing interconnected carbon walls, which can
provide ideal channels for the diffusion of reactant molecules. In contrast, the commercial activated carbon
shows less mesoporous-macroporous morphology from Fig. 2g.

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DOI: 10.1039/C8NJ05948A
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Fig. 2 SEM images of carbon samples (a:C-none; b: MC15(1/1); c: MC30(1/3); d: MC30(1/1); e:
MC30(3/1); f: MC50(1/1); g: commercial activated carbon; h and i: the interior of MC30(3/1) and
MC50(1/1) with high magnification).
Fig.3 presents the XRD patterns of MC30 (1/1) and activated carbon. It was observed that both carbon
material samples had only broad diffraction peaks at 2θ = 25°attributed to the amorphous carbon and no
other characteristic diffraction peaks were found, which indicates that the MgO-templated mesoporous
carbon prepared at 900 ℃ had negligible graphitization.

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DOI: 10.1039/C8NJ05948A
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MC30(1/1)
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AC
0
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40
50
60
70
80
2θ(degree)
Fig. 3 XRD patterns of MC30(1/1) and the commercial activated carbon(AC).
Fig. 4 TEM images of fresh Pt/MC15 (1/1) (a), MC30 (1/1) (b), Pt/MC50 (1/1) (c) and Pt/AC (d).
The TEM images of the Pt catalysts with different carbon supports are given in Fig.4. It was noted that
the highly dispersed Pt nanoparticles,1-3 nm in size, were uniformly distributed within the supports and no
obvious nanoparticles aggregation was observed in all the catalyst samples. The XRD result is in accordance
with the conclusion of TEM analysis. It was obvious from the XRD patterns (Fig. 5) that all the catalysts

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New Journal of Chemistry
had only broad diffraction peaks at 2 θ = 25 °attributed to the amorphous carbon and no characteristic
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diffraction peaks of Pt were found, which was possibly due to Pt nanoparticles being highly diVsiepweArrsticeledOnilnineto
DOI: 10.1039/C8NJ05948A
amorphous state both within mesoporous carbons and commercial activated carbon.
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Pt/MC15(1/1)
Pt/MC30(1/1)
Pt/MC50(1/1)
Pt/AC
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70
80
2θ(degree)
Fig. 5 XRD patterns of fresh Pt/MC15(1/1) , MC30(1/1) , Pt/MC50(1/1) and Pt/AC.
3.2. Performance of Pt/MC catalyst for reductive alkylation
CH3
- H2O
NH
NH2
O
C
+
(1)
CH2CHCH3
CH3
( p-ADPA )
( MIBK )
CH3
CH3
CH
NH
+ H2
(2)
C
NH
N
NH
CH2CHCH3
CH3
CH2CHCH3
CH3
( 6PPD )
( Imine )
Scheme 1. Reaction pathways for the synthesis of N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine
(6PPD) .
The reaction for the synthesis of N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD) is
shown in Scheme. 1. The activities of all catalysts are shown in Table 2. 99.5% conversion of p-ADPA was
obtained over Pt/MC15(1/1) with a selectivity (99.2%) to 6PPD, while p-ADPA were completely converted
both over Pt/MC30 and Pt/MC50 with higher selectivity close to 100%. It is obvious that the reaction time
decreased with increased pore size of catalyst supports from 6 h to 4 h. However, it should be noted that the
surface areas of MC30s differing from each other because of the differences in the MgO/PF ratios, had little
effect on catalytic performance. More specifically, the correlation between the reaction rate and pore size of

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catalyst supports is given in Fig. 6. It is obvious that the p-ADPA conversion rate increased linearly with the
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pore size of mesoporous carbon increases. For comparison，a lower conversion of p-ADPA (9V8ie.w5A%rtic)leaOnnlidne a
DOI: 10.1039/C8NJ05948A
lower selectivity (98.2%) to 6PPD with the reaction time extended to 8 h were obtained over commercial
6
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activated
carbon
supported
Pt
catalyst.
The
main
by-products
were
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N-(1,3-dimethylbutyl)-N’-cyclohexane-p-phenylenediamine and aniline, which were derived from the
hydrogenation of 6PPD and the hydrogenolysis of imine, respectively.
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Table 2 Catalytic performance of Pt catalysts supported on various mesoporous carbon and activated carbon
in the synthesis of 6PPDa.
Selectivity / %
6PPD
99.2
Reaction time
p-ADPA conversion
Catalyst
/ h
6
/ %
Imine
0.5
0.1
0
Others
0.3
0.1
0.1
0
Pt/MC15(1/1)
Pt/MC30(3/1)
Pt/MC30(1/1)
Pt/MC30(1/3)
Pt/MC50(1/1)
Pt/AC
99.5
100
100
100
100
98.5
4.5
4.5
4.5
4
99.8
99.9
99.8
0.2
0
100
0
7.5
98.2
0.8
1.0
a Reaction condition: p-ADPA = 50 g, MIBK = 109 g, catalyst = 0.5 g, T = 373 K, P = 2.5 MPa (pure H2),
stirring speed = 700 r/min.
30
25
20
15
10
0
5
10
15
20
Pore size (nm)
Fig. 6 Relationship between catalytic activity and pore size of catalyst supports. P-ADPA conversion rate
푋p
-
was calculated by the following equation：
p-ADPA conversion, t is the reaction time.
ADPA, where W is the p-ADPA conversion rate, X is the
푊 =
푡

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New Journal of Chemistry
The stability of catalysts in reductive alkylation reactions of p-ADPA with MIBK was investigated via
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the reuse of catalysts under the same reaction conditions as mentioned above. As shown inVieFwiAgrt.icle7O,nlitnhe e
DOI: 10.1039/C8NJ05948A
p-ADPA conversion remained above 96% after the Pt/MC50 (1/1) reused 10 times. However, varying
degrees of decrease of p-ADPA was obtained over the rest of catalysts with the increase of catalysts reused
times. In particular, the p-ADPA conversion reduced to 73.5 % after the Pt/AC reused 10 times. All of the
above results show that the pore structure of the carbon support significantly affects the performance of the
supported Pt catalyst.
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90
Pt@AC
Pt@MC15(1/1)
Pt@MC30(3/1)
80
Pt@MC30(1/1)
Pt@MC30(1/3)
Pt@MC50(1/1)
70
60
50
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10
Used Times
Fig. 7 Recyclability of Pt catalysts supported on various mesoporous carbon and activated carbon in the
synthesis of 6PPD. Reaction condition: p-ADPA = 50 g, MIBK = 109 g, catalyst = 0.5 g, T = 373 K, P = 2.5
MPa (pure H2), stirring speed = 700 r/min.
3.3. Catalyst deactivation

New Journal of Chemistry
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DOI: 10.1039/C8NJ05948A
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Fig. 8 TEM images of used Pt/MC15(1/1) (a), MC30(1/1) (b), Pt/MC50(1/1) (c) and Pt/AC (d).
Fig. 8. shows the TEM images of catalysts reused 10 times, respectively. It is seen that the highly
dispersed Pt nanoparticles were still distributed on the carbon supports and no nanoparticles sintering was
observed, just like fresh catalysts.
Table 3 Pt content of fresh and used catalysts.
Catalyst samples
Fresh Pt/MC15(1/1)
Fresh Pt/MC30(1/1)
Fresh Pt/MC50(1/1)
Fresh Pt/AC
Pt content / %
2.92
2.93
2.92
2.94
Used Pt/MC15(1/1)
Used Pt/MC30(1/1)
Used Pt/MC50(1/1)
Used Pt/AC
2.88
2.88
2.89
2.90
Pt content of fresh and used catalysts are listed in Table 3. It can be seen that very slight Pt loss was
observed for all the used catalysts, which won't significantly reduce the catalytic performance.
Table 4 Textural properties of the fresh and used catalysts.
Catalyst samples
SBET / m2g-1
Vtotal / cm3g-1
SPt / m2g-1

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New Journal of Chemistry
Fresh Pt/MC15(1/1)
Fresh Pt/MC30(1/1)
Fresh Pt/MC50(1/1)
Fresh Pt/AC
643
585
331
1502
514
495
314
766
0.64
79.33
81.03
80.55
84.67
61.88
67.05
74.82
38.01
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0.62
0.57
0.90
0.51
0.52
0.53
0.46
View Article Online
DOI: 10.1039/C8NJ05948A
Used Pt/MC15(1/1)
Used Pt/MC30(1/1)
Used Pt/MC50(1/1)
Used Pt/AC
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Furthermore, N2 physical adsorption and CO chemical adsorption characterization of fresh and used
catalysts were carried out. The BET specific surface area and pore volume of used catalysts all decreased
obviously comparing with fresh catalysts, and the trend was more obvious with the decrease of catalyst
pores. Correspondingly, Pt specific surface area of used catalysts had a similar trend. According to the
results of catalyst characterization, it can be concluded that during the reductive alkylation of p-ADPA with
MIBK, narrow pore structure would hinder mass transfer and diffusion of reactants and products,
accentuating the deposition and blockage of organic matter in the pores, covering active centers, which
should be the primary reason of lower catalytic performance.
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4. Conclusions
The preparation of the nano-MgO templated mesoporous carbon with different pore structures as well
as the effects of pore structure on the performance of supported Pt catalysts for reductive alkylation of
p-aminodiphenylamine with methyl isobutyl ketone were investigated. The pore structure and surface area
of the mesoporous carbon can be controlled by modulating the size of nano-MgO and the mass ratio of
MgO/PF. However, the surface areas of mesoporous carbons differing from each other because of the
differences in the MgO/PF mass ratio had little effect on catalytic performance. The catalytic activity and
stability of catalysts for N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine synthesis increases with
increased pore size of the mesoporous carbons. Complete conversion of p-ADPA and 100% selectivity to
6PPD were obtained over Pt/MC50(1/1) within 4 hours, which could maintain high catalytic activity after
reused 10 times. The BET specific surface area and Pt specific surface area of used catalysts all decreased
obviously comparing with fresh catalysts, and the trend was more obvious with the decrease of catalyst
pores. Narrow pore structure would hinder mass transfer and diffusion of reactants and products,
accentuating the deposition and blockage of organic matter in the pores, covering active centers, which
should be the primary reason for the degradation of catalytic performance.

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DOI: 10.1039/C8NJ05948A
Acknowledgements
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This work was financially supported by the Major Program of Shandong Province Natural Science
Foundation (ZR2017ZC0630), and the Taishan Scholars Construction Projects of Shandong (ts201511033).
The authors are grateful for the financial support.
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Graphical Abstract