Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study

Article abstract of DOI:10.1016/j.jallcom.2021.159047

In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N₂ adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m²g^?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.

Full text of DOI:10.1016/j.jallcom.2021.159047

Journal of Alloys and Compounds 868 (2021) 159047
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jalcom
Phosphorus and nitrogen-doped palladium nanomaterials support on
coral-like carbon materials as the catalyst for semi-hydrogenation of
phenylacetylene and mechanism study
1
1
Lei Ma , Pengbo Jiang , Kaizhi Wang, Kai Lan, Xiaokang Huang, Ming Yang, Li Gong, Qi Jia,
⁎
Xiao Mu, Yucong Xiong, Rong Li
State Key Laboratory of Applied Organic Chemistry (SKLAOC), The Key Laboratory of Catalytic Engineering of Gansu Province, College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou, Gansu 730000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are
prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-
doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by se-
lective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nano-
particles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The
Received 3 September 2020
Received in revised form 28 January 2021
Accepted 1 February 2021
Available online 12 February 2021
results of N
2
adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is
Keywords:
2
−1
1307 m g . In addition, the experimental exploration shows the intervention of P in carbon-nitrogen
Phenylacetylene
Phenylethylene
Selective reduction
Kinetic study
materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that
P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the
activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of
the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in
the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies
demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also
provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has
high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst
can be reused several times without significant reduction in reaction activity.
Heterogeneous catalysis
©
2021 Elsevier B.V. All rights reserved.
1
. Introduction
selectivity alkene catalysts to replace the industrial catalyst is at-
tracting the research interest. There a number of metals such as Pd,
Au, Pt, Rh, Ni and Ru [5], which can catalyze selective hydrogenation
of phenylacetylene [6–9]. Nonetheless, the catalytic effects of these
catalysts still need to be improved in terms of selectivity to alkene.
Hence, it is still of great significance to develop a catalyst for im-
proving the selectivity of alkene.
Many studies have reported the use of palladium modified by
doping other metals or changing the support to improve the se-
lectivity of the catalyst [10,11]. At present, the most researched is the
modification of palladium with transition metals. Ni modified Pd
nanoparticles catalyst (Pd/Ni-N/C) perform high selectivity of alkene
with 96.8% [12]. And Cu modified Pd nanoparticles catalyst of PdCu/
Reaction of selective reduced acetylene compounds plays an
important role in industrial and chemical research. Production of
sedatives, anesthetics, vitamins and fragrances require the selective
reduction of acetylene compounds [1,2]. In particular, the selective
hydrogenation of phenylacetylene to styrene has been widely used
in the polymerization industry, and the catalyst for the industrial
reaction is Pd/CaCO
3
treated with Pd [3,4]. However, the dis-
advantage of this type of catalyst is that the selectivity to alkene is
low and the introduced Pb element is very harmful to the environ-
ment and human health. Researching other Pb-free and high
2 3
Al O produce 86.3% selectivity [13]. Ag also can modify Pd to pre-
⁎
pare the catalyst Ag75Pd25, which selectivity is 87.5%. In general,
there are many reports investigated transition metals modification
the Pd and performed highly selective hydrogenation of the
Corresponding author.
E-mail address: liyirong@lzu.edu.cn (R. Li).
These authors contributed equally to this work and should be considered co-first
1
authors.
https://doi.org/10.1016/j.jallcom.2021.159047
0925-8388/© 2021 Elsevier B.V. All rights reserved.

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
phenylacetylene to styrene [14–18]. Although these catalysts could
perform well with regard to conversion and selectivity, the partici-
pation of noble metals and high reaction pressure also restrict the
application in industry. At the same time, a good carrier is also one of
the factors that affect the reaction conversion [5,19–21]. Carriers can
not only increase the dispersion of palladium nanoparticles but also
change the electronic state of palladium to increase selectivity of
2
reaction [18,22,23]. Pd/CeO catalyst produces 97.4% selectivity with
conversion of 70.3% [24]. Pd/MCF-ss catalyst produces 88% yield of
the styrene with conversion of 100% [25]. Nitrogen doped carbon
material is believed a great carrier [26,27], which has high surface
area, better stability and electrical conductivity [28–30]. The lone
pairs of electrons of nitrogen or phosphorus atom can modify
the palladium nanoparticles and fix the Pd nanoparticles to increase
the recyclability of the catalyst [25,31]. Up to now, Pd catalyst doped
with P has been extensively studied in oxidation reaction [32–34].
However, to our knowledge, there has been no report on the doping
of P and N elements on Pd-supported carbon materials in the se-
lective hydrogenation of phenylacetylene to styrene.
Fig. 1. Preparation of the carbon materials and catalysts.
In this work, two types of high surface area polyporous and coral-
like carbon materials were synthesized from sodium glutamate [11].
Moreover, the P and N doped Pd nanoparticles supported on poly-
porous and coral-like carbon materials are also prepared and applied
to selectively hydrogenate phenylacetylene under mild reaction
conditions. Experimental exploration shows the prepared catalyst
has high surface area (1307 m g ) and the Pd nanoparticles are
uniformly dispersed on the surface of the carrier from TEM images.
Furthermore, the catalyst can reach high selectivity (98.1%) and high
obtained. Finally, the mixture was calcined at 400 °C for 4 h under H
2
atmosphere. After cooled to room temperature, the CN-Pd catalyst
was collected and thoroughly ground. In addition, the preparation of
the CN-P-Pd was the same as the CN-Pd except adding 2 g phosphate
2
−1
2
source when calcined under H atmosphere.(Fig. 1).
2.4. Catalysts test
2
conversion rate (99.9%) under the conditions of 25 °C and H (1 atm).
In addition, recyclability was also implemented, and it was found
that the conversion rate and selectivity did not significantly decrease
after 5 cycles. Finally, the mechanism and kinetics of the reaction
were also studied.
The selective hydrogenations of the substrate reactions were
conducted in round-bottom flask under H (1 atm). The progress of
2
the catalysts test was as follows: substrate (1.5 mmol), catalysts
(5 mg) and solvent (15 mL) were mixed in the round-bottom flask
and the reaction was continued for 0.5 h under vigorous stirring at
temperature of 25 °C and hydrogen pressure of 1 atm. Subsequently,
the product was collected, filtered, extracted and further analyzed by
GC-MS (Agilent 6, 890 N/5, 937 N).
2. Experimental section
2.1. Materials
The activity of the catalysts were calculated as follows: conver-
All the reagents and solvents used in the synthesis of catalyst
sion (%) = 100 × ([C
TOF = (C -C ) × V/(MPd), The substrate concentration at the beginning
and end of the reaction was represented by [C ] and [C ], respec-
tively. Similarly, [C՛] and [C՛՛] were the concentrations of the product
and target product at the end of the reaction, respectively. And MPd
was mole number of Pd in catalyst.
0 1 0
]-[C ]/[C ]), selection (%) = 100 × ([C՛]-[C՛՛])/[C՛],
were purchased from commercial sources without further purifica-
tion unless otherwise stated. Palladium acetate and phenylacetylene
were purchased from Sigma Aldrich.
0
1
0
1
2
.2. Preparation of the precursor (CN)
Firstly, to a one-necked 50 mL round-bottomed flask equipped
3. Results and discussion
with a mechanical stirrer were added sodium glutamate (2 g), so-
dium salt (4 g) and deionized water (15 mL). The reaction was heated
at 80 °C for 2 h with vigorous stirring until the water was completely
evaporated. Subsequently, the mixture was cooled to room tem-
perature and collected, followed by washing with ethanol (3 ×
3.1. Characterization of catalysts
The crystal structure and phase composition of the catalysts were
systematically investigated by using X-ray powder diffraction (XRD)
patterns and Raman. The XRD pattern is shown in Fig. 2a, which
shows that the catalyst has two strong orthogonal peaks. The two
strong peaks at 40° and 46° are corresponding to the (111) and (200)
crystal planes, respectively. Which showing the typical crystal-
lization mode of Pd particles (JCPDS-65–2867). Besides, the XRD
pattern also showed that the Pd supported on the CN material is in
the form of the elementary substance. Raman scattering spectro-
scopy is shown the detail defect information of the catalyst and CN
(Fig. 2b). The two peaks at about 1350 cm−1 and 1580 cm corre-
spond to the characteristic D band and G band of graphitized carbon,
respectively, indicating the formation of structural defects in the
graphitic plane and the E2 g vibrational mode of the sp2 bond gra-
2
0 mL) and drying in a drying oven at 80 °C overnight. Lastly, the
powder was fully ground and calcined at 800 °C for 2 h under
atmosphere. The black powder was obtained and washed by
N
2
deionized water for three times, followed by drying in a vacuum
drying oven at 60 °C for 24 h. Finally, the synthesized powder was
named by CN. Furthermore, different ratios of CN were produced
separately. And named CN
.3. Preparation of the CN-Pd and CN-P-Pd
Firstly, a mixture of CN (50 mg) and palladium acetate solution in
x
(x = m (sodium chloride)/m (sodium glutamate)).
−1
2
-
acetonitrile (2 mg/mL, 0.5 mL (0.25 or 1 mL)) was added to round-
bottom flask and then 5 mL of absolute ethyl alcohol was also added.
Next, the absolute ethyl alcohol was evaporated to dry at 80 °C under
magnetic stirring, and then a mixed powder of Pd and CN was
phitic carbons [35,36]. The intensity of the D band and G band (I
shows the degree of lattice defects and graphitization of the carbon
materials. In addition, it is worth noting that the I /I ratios of the
D G
/I )
D
G
2

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 2. (a) XRD pattern of the catalyst, (b) Raman of the CN and CN-P-Pd.
CN and CN-P-Pd are both 0.92, indicating that the carbon materials
have a strong degree of graphitization and doped P and loaded Pd do
not affect its graphitization.
Fig. 3d is the pattern of the CN-P-Pd-1.4, which clearly indicates that
the structure of the carbon material is altered by doping of P and Pd,
and part of the coral-like porous structure characteristics has
changed significantly due to the collapse of the structure. Generally,
it also indicates that the structure of carbon materials does not
change significantly with the intervention of P and Pd. The AFM
image in Fig. S2 demonstrates the diameter of Pd nanoparticles on
the CN-P-Pd-1.4 is about 15 nm and highly dispersed on the CN
materials.
The transmission electron microscopy (TEM) images showed in
Fig. 4. The TEM image of the CN-P-Pd-1.4 is illustrated in Fig. 4a and
b. In detail, according to the particle size statistics, the particle size
of the Pd nanoparticles range from 2 to 8 nm. It is worth noting that
The scanning electron microscopy (SEM) images shown in Fig. 3.
The morphology of CN and CN-P-Pd-1.4 is shown in Fig. 3a and b,
which demonstrate the polyporous and coral-like structural char-
acteristics. By carefully observing its structure, we can find that the
porous structure has slightly changed after phosphating, which may
be attributed to the temperature change and the loading of palla-
dium particles for the second calcination. Similarly, Fig. 3c and d
show the projection electron microscope images of CN and CN-P-Pd-
1.4, respectively. It can be seen from Fig. 3c that CN exhibits a porous
structure, which is consistent with the result of Fig. 3a. However,
Fig. 3. (a) and (b) SEM image of the CN, (c) and (d) SEM image of the CN-P-Pd-1.4.
3

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 4. (a) HRTEM of the CN-P-Pd-1.4, (b) TEM images of the CN-P-Pd-1.4, (c) HAADF-STEM image of the CN-P-Pd-1.4, (d−g) mapping of the C, N, P and Pd.
particles with the particle size of 3.5 nm are about 40% of all the
particles. Moreover, the average size of the Pd nanoparticles is about
volume are shown in Table 1. The surface area of the CN-P-Pd, which
2
−1
is 1307 m g lower than the surface area of CN, reveals that doped
Pd and P can decrease the surface area. Meanwhile, the surface area
of the CN-P-Pd-1.4 is also pleasant. The volume of the CN and CN-P-
4
.4 nm (the inset in Fig. 4b). HRTEM and Fourier transformation
(
FFT) images are shown in Fig. 4a which is the enlarged view of the
3
−1
3 −1
Fig. 3d, the lattice fringes of the Pd can further explain that the
particles are Pd nanoparticles. In Fig. 4a, the spacing of lattice fringes
are 0.23 nm and 0.195 nm, which correspond the lattice plane of the
Pd (111) and Pd (200), respectively. Additionally, the angle of the two
lattice fringes is 54.7°, which is the characteristic angle of the Pd
nanoparticles, corresponding to JCPDS 65–2867 and the result of the
XRD (Fig. 2a) [37]. High angle annular dark field scanning trans-
mission electron microscopy (HAADF-STEM) image and the Mapping
results of different element in Fig. 4(c−g). The Mapping of the C
and N element indicating that they are uniform distribution. Ad-
ditionally, the P and Pd are successful doped on the carbon materials.
Moreover, the mapping images also show that content of the Pd and
P are lower than the content of the C and N.
The surface area and pore size are all have a large impact on the
activity of the catalyst. The surface area and pore size of the pre-
pared catalyst are analyzed by Nitrogen adsorption–desorption.
Fig. 5 demonstrates that both CN and CN-P-Pd-1.4 have mesoporous
properties. Minutely, Fig. 5a exhibits that the initial quantity ad-
sorbed are not from zero, which due to the unique micropore
character of the carbon materials and catalyst. In addition, the order
of the initial quantity adsorbed of the materials sort from large to
small are CN and CN-P-Pd-1.4, which indicates that the CN has a
large micropore volume and the doped Pd can reduce the micropore
volume. The microporous characters of CN were investigated by
nitrogen adsorption-desorption as shown in Fig. 5c and d, which
reveals that the CN have micropore characteristic. Pore width images
shown in Fig. 5b, revealing that the pore width rages from 2 nm to
Pd are 0.91 cm g and 0.72 cm g , respectively. Which not only
indicates that the introduction of Pd and P effectively reduces the
volume of CN, but also explains that Pd nanoparticles are uniformly
dispersed in the tunnel. The pore size analysis of CN and CN-P-Pd-1.4
indicate the loaded Pd and P doping have little effect on the pore
size. In general, the prepared carbon materials and catalyst have
characteristics of large surface area, large pore volume and small
pore size. Meanwhile, the enhance in the reactivity of the optimum
catalyst is closely related to the porous structure and these char-
acteristics.
X-ray photoelectron spectroscopy (XPS) is employed to de-
termine the chemical composition and valence states on the surface
of the catalyst. Generally, Fig. 6a shows the full scan spectra of the
CN-Pd-1.4 and CN-P-Pd-1.4. The two strong peaks of 285 eV and
532 eV correspond to C 1s and O 1s respectively. In addition, two
weak peaks are N 1s and Pd 3d, demonstrating the surface of catalyst
is composed of C, N, O, P, and Pd elements. High resolution spectra of
C 1s is shown in Fig. 6b, which can be deconvoluted two peaks of C−C
and C−N correspond to 284.6 eV and 285.7 eV, respectively [38,39].
High resolution spectra of N 1s (Fig. 6c) is deconvoluted into two
peaks of graphite nitrogen and pyridine nitrogen at 401.1 eV and
399.1 eV, respectively [40,41]. Fig. 6d shows the high resolution
spectra of P, peak at 133.5 eV is assigned to oxidized phosphorus
[42]. Similarly, Fig. 6e illustrates the high resolution spectra of Pd,
two peaks observed at binding energies 335.6 eV and 341.2 eV cor-
0
0
responding to the Pd 3d5/2 and Pd 3d3/2, revealing that the valence
state of Pd in catalyst is zero [43,44]. The high resolution spectra of
Pd in CN-P-Pd-1.4 and CN-Pd-1.4 are shown in Fig. 6f and it can be
5
nm. The surface area and average of the pore width and pore
4

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 5. (a, b) N
2
adsorption–desorption isotherms and the corresponding pore size distribution of the catalyst, (c, d) mesoporous and micropore analysis of CN.
Table 1
adsorption-desorption analysis of the CN and CN-P-Pd-1.4.
reflecting that prolong reaction time did not achieve expected goal.
N
2
Besides, the selectivity of the catalyst can be significantly improved
when phosphorus is incorporated as illustrated entry 14, and it can
be seen that when doped the P element, the electron density of Pd
decrease in the 3d from Fig. 6f. Hence, we conclude that this catalyst
perform highly selectivity is due to the fact that intervention of P can
change the electron cloud density of Pd. Generally, we can draw a
conclusion that catalyst of CN-P-Pd-1.4 perform the highest se-
lectivity and conversion, which is demonstrated by the higher TOF
Sample
Surface area
Average pore
width (nm)
Pore volume
(cm /g)
2
3
(
m /g)
CN
1632
1307
2.25
2.22
0.91
0.72
CN-P-Pd-1.4
0
found that the Pd peak of CN-P-Pd-1.4 is shift by 0.8 eV compared to
0
−1
the Pd peak of CN-Pd-1.4. Similarly, an offset occurred at 338 eV.
value (4542 h ).
The shift of the binding energy reveals that the electron density of Pd
decrease in the 3d, and the center of the D-band in Pd have a slight
down-shift, which is attributed to the P-Pd bond formed by P and
Pd [45].
The effect of solvent on selective reduction of phenylacetylene
are shown in Table 3. From entry 1, it is known that high conversion
and selectivity can be achieved when methanol is used as a solvent.
However, the ethyl acetate as the solvent could not promote the
reaction, we can infer that H
2
is insoluble in ethyl acetate, which
3.2. Performance of catalysts
makes it difficult for H to contact with phenylacetylene and thus
2
cannot promote the reduction of phenylacetylene. Compared the
results of entry 1–5 and entry 6–11, we can conclude that catalyst
exhibits a higher catalytic activity when alcohol compounds as the
solvent than other compounds as the solvent. It can be easily found
that the alcohol compounds are more suitable as the solvent for
selective hydrogenation of phenylacetylene. Hence, we choose the
methanol as the optimal solvent for semi-hydrogenation of pheny-
lacetylene to styrene.
The catalytic performances of all catalysts are shown in Table 2.
Generally, entry 1–4 indicate that the CN material is not reactive
toward the phenylacetylene hydrogenation reaction. Effect of Pd
loading on catalytic activity is shown in entry 5–14, demonstrating
that the Pd catalyst with mass fraction is 1.4 wt% has the best cat-
alytic activity. Obviously, lower or higher mass fraction of Pd all not
perform the well activity. In addition, the optimal ratio of catalysts
such as entry 5 and entry 9 can have a significant effect on catalytic
activity. This may be attributed to the better dispersion of Pd par-
ticles on the CN material. The reaction time of the entry 12 is 1 h,
Furthermore, the progress of the reaction is also affected by the
concentration of phenylacetylene. Fig. 7 shows the relationship be-
tween reaction rate and concentration of phenylacetylene. As can be
5

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 6. (a) Full scan XPS spectra of the catalyst, high resolution spectra of (b) C, (c) N, (d) P, (e) Pd, (f) Pd.
Table 2
Table 3
Effect of solvent on selective reduction of phenylacetylene .
a
a
Catalytic performances of all the catalysts .
Entry
Solvent
Conversion (%)
Selectivity (%)
TOF h−1
1
2
3
4
5
6
7
8
Methanol
Ethanol
99.9
95.2
92.3
50.1
78.4
0
71.3
40.8
52.1
61.3
50.6
98.1
93.7
95.2
28
61.5
0
78.2
21.6
40.5
98.5
59.2
4542
4323
4192
2290
3560
0
3238
1853
2366
2784
2298
+
H
2
+
Isopropanol
Tertiary butanol
n-butyl alcohol
Ethyl acetate
Cyclohexane
Acetonitrile
Methylbenzene
1,4 dioxane
o-xylene
1
2
3
TOF (h−1
)
Entry
Catalyst
CN
Conversion (%)
Selectivity for 2 (%)
1
2
3
4
5
6
7
8
9
0
0
0
0
0
0
0
0
0
0
0
9
10
11
CN
1
CN1.5
CN2.5
0
a
CN-Pd-1.4
CN -Pd-1.4
CN1.5-Pd-1.4
CN2.5-Pd-1.4
CN-Pd-0.8
CN1.5-Pd-0.8
CN2.5-Pd-0.8
CN-Pd-0.8
99.9
84.4
95.6
90.1
41.1
35.2
37.4
75.2
99.9
99.9
91.3
65
71
84.2
99.5
91.1
94.3
96.1
78.2
98.1
4544
2263
2979
3654
3267
2551
2875
2989
1060
4542
Reaction condition: Phenylacetylene (1.5 mmol), catalyst (5 mg), solvent (15 mL),
(1 atm) reaction time (0.5 h), reaction temperature (25 °C).
H
2
1
1
0
1
1
b
c
1
2
1
3
CN-Pd-3.0
CN-P-Pd-1.4
14
Reaction condition:
a
2
Phenylacetylene (1.5 mmol), catalyst (5 mg), solvent (15 mL), H (1 atm), reaction
time (0.5 h), temperature (25 °C).
b
Reaction time (1 h).
ICP shows the mass fraction of the P is 0.8 wt%.
c
seen in Fig. 7, we can conclude that when 5 mL of methanol is added,
the reaction rate is significantly lower than other volumes of solvent.
Therefore, it can be inferred that the dissolution rate of hydrogen is
lower than its hydrogenation rate when the solvent is less, thus
resulting in a decrease in the rate of reaction. Inversely, the reaction
rate also demonstrated downward trend when the amount of the
solvent was too large, which is attributed to the fact that the phe-
nylacetylene cannot not adsorbed well to the catalyst, thus making
the reaction did not proceed smoothly. Based on the above experi-
mental exploration and analysis, 15 mL methanol as the optimum
solvent volume.
Fig. 7. Relationship between reaction rate and concentration of phenylacetylene.
Reaction condition: phenylacetylene (1.5 mmol), catalyst (5 mg), solvent (methanol),
H (1 atm), temperature (25 °C).
2
6

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Table 4
CN-P-Pd-1.4 selective hydrogenation of other acetylene compounds. .
a
Entry
Substrate
Product
Conversion (%) Selectivity (%)
OH
OH
1
2
99.9
99.9
98.6
89.1
3
4
99.9
99.9
95.2
99.3
b
5
99.9
99.1
6
7
8
99.9
99.9
99.5
90.3
98.3
99.1
OH
OH
b
9
99.9
98.6
(a) Reaction condition: acetylene compounds (1.5 mmol), catalyst (5 mg), methanol (15 mL), H2 (1 atm), reaction
time (30 min), reaction temperature (25 °C). (b) Reaction time (50 min) other reaction condition are the same as
the (a).
Through exploring experimental conditions, the best reaction
condition of semi-hydrogenation of phenylacetylene to styrene is
CN-P-Pd-1.4, methanol (15 mL), H (1 atm) at 25 °C for 0.5 h.
2
In order to more comprehensively and extensively evaluate the
excellent universality of the CN-P-Pd-1.4, experiments with different
alkyne substrates are carried out and the results are illustrated in
Table 4. Obviously, the CN-P-Pd-1.4 also has excellent catalytic ac-
tivity for other acetylene compounds. Aromatic alkyne such as
solution for filtering out the catalyst after one recycle and continue
react under the hydrogen atmosphere and 25 °C for other 30 min.
The conversion and selectivity are also the same as the conversion
and selectivity of one cycle, indicating that only a small amount of
4
-methylphenylacetylene and 4-aminophenylacetylene as the sub-
strate, the catalyst performs well conversion and selectivity than
other acetylene compounds. In addition, entry 1, 4 and 7 prove that
when the substrate contains an electron withdrawing group, the
catalyst performs higher selectivity than other substrate containing
electron withdrawing groups selectivity. Moreover, we also prolong
the reaction time of entry 4 and 7 for other 20 min, and find that the
selectivity of the two compounds slightly decreased. In general, the
prepared catalyst of CN-P-Pd-1.4 have well performance for selective
hydrogenation other acetylene compounds.
In addition to favorable catalytic activity, an outstanding het-
erogeneous catalyst should also have reliable recyclability and stable
reusability.[46] Thus the recyclability and reusability of the CN-P-Pd-
1.4 were investigated for selectivity hydrogenation of the phenyla-
cetylene to styrene and illustrated in Fig. 8. The conversion and
selectivity are also reliable after three times recycle of the catalyst.
While the conversion rate drops to 90% after four or five recycle
times, the selectivity remains reliable. We also collected the reaction
Fig. 8. The recyclability and reusability of the CN-P-Pd-1.4. Reaction condition: phe-
nylacetylene (1.5 mmol), catalyst (5 mg), methanol (15 mL), H2 (1 atm), reaction time
(30 min), reaction temperature (25 °C).
7

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 9. Kinetic study of the selective hydrogenation of phenylacetylene (a and b) and styrene (c and d) with the CN-P-Pd-1.4 as the catalyst. Reaction condition: phenylacetylene
3 mmol), catalyst (5 mg), methanol (15 mL), H (1 atm).
(
2
palladium is detached from the catalyst. In general, the prepared
catalyst (CN-P-Pd-1.4) performs well recyclability and reusability.
To further understand the reaction mechanism, the kinetic study
was investigated the reaction of selectivity hydrogenation phenyla-
cetylene to styrene. The reaction conditions are phenylacetylene
respectively. The relation between concentration of the phenylace-
tylene and reaction time was shown in Fig. 9a and the reaction rate
can be obtained by analyzed. In addition, the relation between re-
action rate and concentration of the phenylacetylene is shown in
Fig. 9b. From Fig. 9b, we can know that lnk25 ℃ and lnk35 ℃ are 0.72
and 0.78, respectively. The activation energy Ea of the reaction was
found to be 4.5 kJ/mol by the calculation of the Allenbius formula for
the selective hydrogenation of phenylacetylene with a CN-P-Pd-1.4
catalyst. Fig. 9c and d illustrate the kinetic study of the hydrogena-
tion of the styrene with Ea is 17.5 kJ/mol. Kinetic study of selective
hydrogenation of phenylacetylene and styrene demonstrates that
the CN-P-Pd-1.4 performs distinguished selectivity for selective
reduction of phenylacetylene.
(
3 mmol), methanol (15 mL), H
reaction rate and reactants is expressed by formula (1). Additionally,
the pressure of H can be considered with a constant due to the H
2
(1 atm). The relationship between
2
2
pressure is always maintained at 1 atm as the reaction progresses.
The formula (2) can be changed from the formula (1), and the re-
action is pseudo b order reaction for substrate. Hence, the reaction
rate is derived from the concentration of phenylacetylene varies
with reaction time and the order of reaction can be obtained from
formula (2). The activation energy can be calculated by Arrhenius
formula (formula (3)).
To investigate the mechanism of the semi-hydrogenation of
phenylacetylene to styrene, FT-IR and XPS conducted in-depth
exploration of the reaction process. The FT-IR of the adsorption of
phenylacetylene by CN-P-Pd-1.4 and CN-P-Pd-1.4 is illustrated in
r = k Pa [c]b
(H2)
(1)
(2)
(3)
Fig. 10a. It can be distinctly observed that two new peaks appear at
r = k[c]b
−1
6
94 and 756.3 cm after the adsorption of phenylacetylene, which
indicates that the phenylacetylene has been adsorbed on the surface
of the catalyst before the reaction occurs. To explore the adsorption
site for adsorption of phenylacetylene, XPS characterization of cat-
alysts adsorbing phenylacetylene was performed (Fig. 10b). In detail,
Fig. 10b is the fine spectrum C 1s of CN-P-Pd-1.4 and CN-P-Pd-1.4
after adsorbing phenylacetylene. It can be found that one new peak
occurred at 288.8 eV, which reveals that the phenylacetylene is
ln K = ln A Ea/RT
Where [c] is the concentration of phenylacetylene, P is the pressure
of the H , k and k represents the rate constant, and the a and b are
the reaction order of the H and [c], respectively. The activation
energy is represented by Ea. The ideal gas constant (8.314 J mol
2
2
−1
−
1
K
) and the reaction temperature are represented R and T,
8

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Fig. 10. (a) FT-IR and (b) XPS of CN-P-Pd-1.4 and CN-P-Pd-1.4 adsorption of phenylacetylene.
Fig. 11. Proposed reaction mechanism.
successfully adsorbed on the C atom. As a result, we infer the
emergence of the new peak is attributed to the interaction between
the C atom in phenylacetylene and the π electron of the ben-
zene ring.
Based on the above experimental results, a possible reaction
pathway of the chemo-selective hydrogenation process catalyzed by
CN-P-Pd-1.4 catalyst is proposed in Fig. 11. The semi-reduction of
phenylacetylene to styrene would proceed in several consecutive
steps. Firstly, the phenylacetylene was adsorbed on the surface of
carbon materials and the C atoms in the phenylacetylene interact
nanoparticles is 1.4 wt%, and we also find that doping with P element
can significantly improve the selectivity of the catalyst. In addition,
we acknowledge that the solvent affects the reaction rate and has a
great influence on the selectivity of the catalyst. The optimum cat-
alyst of the CN-P-Pd-1.4 have remarkable conversion and selectivity
to hydrogenation of phenylacetylene to styrene and have highly
reaction activity to other acetylene compounds. After kinetic study,
the activation energy of the selectivity hydrogenation of phenyla-
cetylene to styrene is 5.4 kJ/mol. Furthermore, mechanism study
shows the carbon atoms is the adsorption site. Moreover, the catalyst
still maintains excellent catalytic activity after recycling many times.
Generally, the prepared CN-P-Pd-1.4 catalyst is outstanding hetero-
geneous catalysts for semi-hydrogenation of phenylacetylene to
styrene.
2
with the π electrons of the benzene ring. Meanwhile, the H was
adsorbed on the surface of Pd nanoparticles and decomposed into
hydrogen atoms on electronically Pd surface.[47] Secondly, –C≡CH is
2
combined with hydrogen and converted into–CH=CH , and then the
product of styrene is desorbed from the surface of the C atom, which
can effectively prevent further hydrogenation reactions and improve
the selectivity of the catalyst. Moreover, CN-P-Pd-1.4 also has a
larger specific surface area, which can provide more adsorption sites
and promote the distribution of palladium nanoparticles with a
smaller particle size. Besides, the intervention of phosphorus can
change the electron density of Pd, thereby increasing the selectivity
of the catalyst to styrene. These properties together promote the
significant improvement of the catalytic activity and selectivity of
CN-P-Pd-1.4. These properties all co-contributed to the significant
improvement of catalytic activity and selectivity of the CN-P-Pd-1.4.
CRediT authorship contribution statement
Lei Ma, Pengbo Jiang and Kaizhi Wang are responsible for the
selection of manuscripts. Lei Ma, Li Gong and Xiao Mu are re-
sponsible for the design and implementation of the experiment. Lei
Ma, Kai Lan, Xiaokang Huang, Ming Yang, Qi Jia, Xiao Mu, Yucong
Xiong are responsible for the analysis and processing of experi-
mental data. Lei Ma wrote the manuscript and Rong Li has revised
the manuscript.
4. Conclusions
Declaration of Competing Interest
The results of the study present an efficient Pd supported on a
large surface area carbon materials catalyst for selective hydro-
genation of phenylacetylene to styrene. Through experimental
exploration and screening, the optimal loading of palladium
The authors declare that they have no known competing fi-
nancial interests or personal relationships that could have appeared
to influence the work reported in this paper.
9

L. Ma, P. Jiang, K. Wang et al.
Journal of Alloys and Compounds 868 (2021) 159047
Appendix A. Supporting information
[24] A.R.S. Couplingreactions, H.A. Elazab, S. Moussa, B. Frank Gupton, M. Samy El-
Shall, Highly efficient and magnetically recyclable graphene-supportedPd/
3 4
Fe O nanoparticle catalysts for Suzuki and Heck cross-couplingreactions, Appl.
Catal. A Gen. 491 (2015) 58–69.
[25] C. Na-Chiangmai, N. Tiengchad, P. Kittisakmontree, O. Mekasuwandumrong,
J. Powell, J. Panpranot, Characteristics and catalytic properties of mesocellular
foam silica supported Pd nanoparticles in the liquid-phase selective hydro-
genation of phenylacetylene, Catal. Lett. 141 (2011) 1149–1155.
Supplementary data associated with this article can be found in
the online version at 10.1016/j.jallcom.2021.159047.
References
[
26] C. Celik, N. Ildiz, I. Ocsoy, Building block and rapid synthesis of catecholamines-
inorganic nanoflowers with their peroxidase-mimicking and antimicrobial ac-
tivities, Sci. Rep. 10 (2020) 2903.
[
1] P. Kittisakmontree, B. Pongthawornsakun, H. Yoshida, S.-i Fujita, M. Arai,
J. Panpranot, The liquid-phase hydrogenation of 1-heptyne over Pd–Au/TiO 2
catalysts prepared by the combination of incipient wetness impregnation and
deposition–precipitation, J. Catal. 297 (2013) 155–164.
[27] F.D. Koca, D. Demirezen Yilmaz, N. Ertas Onmaz, I. Ocsoy, Peroxidase-like activity
and antimicrobial properties of curcumin-inorganic hybrid nanostructure, Saudi
J. Biol. Sci. 27 (2020) 2574–2579.
[28] Y. Long, Y. Liu, Z. Zhao, S. Luo, W. Wu, L. Wu, H. Wen, R.Q. Wang, J. Ma, Distinctive
morphology effects of porous-spherical/yolk-shell/hollow Pd-nitrogen-doped-
carbon spheres catalyst for catalytic reduction of 4-nitrophenol, J. Colloid
Interface Sci. 496 (2017) 465–473.
[29] S. Rostamnia, S. Kholdi, Polymeric hybrid mesoporous silica hollow nanospheres
as a support for palladium and application of the PdNPs@PANI/HNS nano-
composite for aerobic benzyl alcohol oxidation, Adv. Powder Technol. 29 (2018)
1167–1174.
[30] F. Goettmann, A. Fischer, M. Antonietti, A. Thomas, Chemical synthesis of me-
soporous carbon nitrides using hard templates and their use as a metal-free
catalyst for Friedel-Crafts reaction of benzene, Angew. Chem. 45 (2006)
4467–4471.
[31] S. Rostamnia, S. Kholdi, Synthesis of hybrid interfacial silica-based nanospheres
composite as a support for ultra-small palladium nanoparticle and application of
PdNPs/HSN in Mizoroki-Heck reaction, J. Phys. Chem. Solids 111 (2017) 47–53.
[32] R. Rego, A.M. Ferraria, A.M. Botelho do Rego, M.C. Oliveira, Development of PdP
nano electrocatalysts for oxygen reduction reaction, Electrochim. Acta 87 (2013)
73–81.
[33] L. Zhang, D. Lu, Y. Chen, Y. Tang, T. Lu, Facile synthesis of Pd–Co–P ternary alloy
network nanostructures and their enhanced electrocatalytic activity towards
hydrazine oxidation, J. Mater. Chem. A 2 (2014) 1252–1256.
[34] H. Xu, B. Yan, K. Zhang, C. Wang, J. Zhong, S. Li, P. Yang, Y. Du, Facile synthesis of
Pd-Ru-P ternary nanoparticle networks with enhanced electrocatalytic perfor-
mance for methanol oxidation, Int. J. Hydrog. Energy 42 (2017) 11229–11238.
[35] X. Wang, X. Huang, W. Gao, Y. Tang, P. Jiang, K. Lan, R. Yang, B. Wang, R. Li,
Metal–organic framework derived CoTe2 encapsulated in nitrogen-doped carbon
nanotube frameworks: a high-efficiency bifunctional electrocatalyst for overall
water splitting, J. Mater. Chem. A 6 (2018) 3684–3691.
[
[
2] M. Al-Herz, M.J.H. Simmons, J. Wood, Selective hydrogenation of 1-heptyne in a
mini trickle bed reactor, Ind. Eng. Chem. Res. 51 (2012) 8815–8825.
3] Árpád Molnár, Antal Sárkány, M.ónika Varga, Hydrogenation of carbon–carbon
multiple bonds:chemo-, regio- and stereo-selectivity, J. Mol. Catal. A: Chem.
173 (2001) 185–221.
[
4] J.G. Ulan, E. Kuo, W.F. Maier, R.S. Rai, G. Thomas, Effect of lead acetate in the
preparation of the Lindlar catalyst, J. Org. Chem. 52 (1987) 3126–3132.
5] M.Y. Lu Peng, C. Wu, D. Han, I. €Oc-soy, T. Chen, Z. Chen, W. Tan*, Reversible
phase transfer of nanoparticles based on photoswitchable host guest chemistry,
ACS Nano 8 (2014) 2555–2561.
[
[
[
[
[
6] L. Shao, X. Huang, D. Teschner, W. Zhang, Gold supported on graphene oxide: an
active and selective catalyst for phenylacetylene hydrogenations at low tem-
peratures, ACS Catal. 4 (2014) 2369–2373.
7] F.R. Lucci, M.T. Darby, M.F.G. Mattera, C.J. Ivimey, A.J. Therrien, A. Michaelides,
M. Stamatakis, E.C.H. Sykes, Controlling hydrogen activation, spillover, and
desorption with Pd–Au single-atom alloys, J. Phys. Chem. Lett. 7 (2016) 480–485.
8] M. Niu, Y. Wang, W. Li, J. Jiang, Z. Jin, Highly efficient and recyclable ruthenium
nanoparticle catalyst for semihydrogenation of alkynes, Catal. Commun.
3
8 (2013) 77–81.
9] T. Mitsudome, M. Yamamoto, Z. Maeno, T. Mizugaki, K. Jitsukawa, K. Kaneda,
One-step synthesis of core-gold/shell-ceria nanomaterial and its catalysis for
highly selective semihydrogenation of alkynes, J. Am. Chem. Soc. 137 (2015)
13452–13455.
[
[
[
[
[
[
10] F.D. Koca, D. Demirezen Yilmaz, N. Ertas Onmaz, E. Yilmaz, I. Ocsoy, Green
synthesis of allicin based hybrid nanoflowers with evaluation of their catalytic
and antimicrobial activities, Biotechnol. Lett. 42 (2020) 1683–1690.
11] E. Gokturk, I. Ocsoy, E. Turac, E. Sahmetlioglu, Horseradish peroxidase‐based
hybrid nanoflowers with enhanced catalytical activities for polymerization re-
actions of phenol derivatives, Polym. Adv. Technol. (2020) pat.4956.
12] W. Wu, W. Zhang, Y. Long, J. Qin, H. Wen, J. Ma, Ni modified Pd nanoparticles
immobilized on hollow nitrogen doped carbon spheres for the simehy-
drogenation of phenylacetylene, J. Colloid Interface Sci. 531 (2018) 642–653.
13] Z. Wang, L. Yang, R. Zhang, L. Li, Z. Cheng, Z. Zhou, Selective hydrogenation of
phenylacetylene over bimetallic Pd–Cu/Al 2 O 3 and Pd–Zn/Al 2 O 3 catalysts,
Catal. Today 264 (2016) 37–43.
14] F. Studt, F. Abild-Pedersen, T. Bligaard, R.Z. Sorensen, C.H. Christensen,
J.K. Norskov, On the role of surface modifications of palladium catalysts in the
selective hydrogenation of acetylene, Angew. Chem. 47 (2008) 9299–9302.
15] T. Mitsudome, T. Urayama, K. Yamazaki, Y. Maehara, J. Yamasaki, K. Gohara,
Z. Maeno, T. Mizugaki, K. Jitsukawa, K. Kaneda, Design of core-Pd/shell-Ag na-
nocomposite catalyst for selective semihydrogenation of alkynes, ACS Catal.
[36] J. He, W. Lv, Y. Chen, K. Wen, C. Xu, W. Zhang, Y. Li, W. Qin, W. He, Tellurium-
impregnated porous cobalt-doped carbon polyhedra as superior cathodes for
lithium–tellurium batteries, ACS Nano 11 (2017) 8144–8152.
[37] W. Guo, S. Niu, W. Shi, B. Zhang, W. Yu, Y. Xie, X. Ji, Y. Wu, D. Su, L. Shao, Pd–P
nanoalloys supported on a porous carbon frame as an efficient catalyst for
benzyl alcohol oxidation, Catal. Sci. Technol. 8 (2018) 2333–2339.
[38] Y. Tang, Z. Zhao, X. Hao, Y. Wang, Y. Liu, Y. Hou, Q. Yang, X. Wang, J. Qiu,
Engineering hollow polyhedrons structured from carbon-coated CoSe2 nano-
spheres bridged by CNTs with boosted sodium storage performance, J. Mater.
Chem. A 5 (2017) 13591–13600.
[39] P. Jiang, X. Li, W. Gao, X. Wang, Y. Tang, K. Lan, B. Wang, R. Li, Highly selective
hydrogenation of α, β-unsaturated carbonyl compounds over supported Co na-
noparticles, Catal. Commun. 111 (2018) 6–9.
[40] K. Wang, W. Gao, P. Jiang, K. Lan, M. Yang, X. Huang, L. Ma, F. Niu, R. Li, Bi-
functional catalyst of porous N-doped carbon with bimetallic FeCu for solvent-
free resultant imines and hydrogenation of nitroarenes, Mol. Catal. 465 (2019)
43–53.
[41] M. Zhao, L. Meng, L. Ma, G. Wu, F. Xie, L. Ma, W. Wang, B. Jiang, Y. Huang,
Stepwise growth of melamine-based dendrimers onto carbon fibers and the
effects on interfacial properties of epoxy composites, Compos. Sci. Technol.
138 (2017) 144–150.
[42] S.-P. Lee, Y.-W. Chen, Selective hydrogenation of furfural on Ni−P, Ni−B, and
Ni−P−B ultrafine materials, Ind. Eng. Chem. Res. 38 (1999) 2548–2556.
[43] X. Li, W. Zhang, Y. Liu, R. Li, Palladium nanoparticles immobilized on magnetic
porous carbon derived from ZIF-67 as efficient catalysts for the semihy-
drogenation of phenylacetylene under extremely mild conditions,
ChemCatChem 8 (2016) 1111–1118.
6
(2016) 666–670.
[
16] H. Zea, K. Lester, A.K. Datye, E. Rightor, R. Gulotty, W. Waterman, M. Smith, The
influence of Pd–Ag catalyst restructuring on the activation energy for ethylene
hydrogenation in ethylene–acetylene mixtures, Appl. Catal. A: Gen. 282 (2005)
2
37–245.
17] H.-H. Wei, C.H. Yen, H.-W. Lin, C.-S. Tan, Synthesis of bimetallic Pd‐Ag colloids in
CO -expanded hexane and their application in partial hydrogenation of pheny-
[
[
[
2
lacetylene, J. Supercrit. Fluids 81 (2013) 1–6.
18] S. Sitthisa, T. Pham, T. Prasomsri, T. Sooknoi, R.G. Mallinson, D.E. Resasco,
Conversion of furfural and 2-methylpentanal on Pd/SiO
lysts, J. Catal. 280 (2011) 17–27.
2
and Pd–Cu/SiO2 cata-
19] N. Ildiz, A. Baldemir, C. Altinkaynak, N. Ozdemir, V. Yilmaz, I. Ocsoy, Self as-
sembled snowball-like hybrid nanostructures comprising Viburnum opulus L.
extract and metal ions for antimicrobial and catalytic applications, Enzym. Micro
Technol. 102 (2017) 60–66.
20] A. Baldemir, N.B. Köse, N. Ildız, S. İlgün, S. Yusufbeyoğlu, V. Yilmaz, I. Ocsoy,
Synthesis and characterization of green tea (Camellia sinensis (L.) Kuntze) ex-
tract and its major components-based nanoflowers: a new strategy to enhance
antimicrobial activity, RSC Adv. 7 (2017) 44303–44308.
[
[44] J. Li, Q.-L. Zhu, Q. Xu, Pd nanoparticles supported on hierarchically porous
carbons derived from assembled nanoparticles of a zeolitic imidazolate frame-
work (ZIF-8) for methanol electrooxidation, Chem. Commun. 51 (2015)
10827–10830.
[
[
[
21] I.S. Unal, A. Demirbas, I. Onal, N. Ildiz, I. Ocsoy, One step preparation of stable
gold nanoparticle using red cabbage extracts under UV light and its catalytic
activity, J. Photochem. Photobiol. B Biol. 204 (2020) 111800.
22] M. Ren, C. Li, J. Chen, M. Wei, S. Shi, Preparation of a ternary Pd–Rh–P amorphous
alloy and its catalytic performance in selective hydrogenation of alkynes, Catal.
Sci. Technol. 4 (2014) 1920–1924.
23] N. Pino, S. Sitthisa, Q. Tan, T. Souza, D. López, D.E. Resasco, Structure, activity, and
selectivity of bimetallic Pd-Fe/SiO 2 and Pd-Fe/ γ -Al 2 O 3 catalysts for the
conversion of furfural, J. Catal. 350 (2017) 30–40.
[45] K. Wu, X. Mao, Y. Liang, Y. Chen, Y. Tang, Y. Zhou, J. Lin, C. Ma, T. Lu, Multiwalled
carbon nanotubes supported palladium–phosphorus nanoparticles for ethanol
electrooxidation in alkaline solution, J. Power Sources 219 (2012) 258–262.
[46] Z.-Z. Yang, L.-N. He, C.-X. Miao, S. Chanfreau, Lewis basic ionic liquids-catalyzed
conversion of carbon dioxide to cyclic carbonates, Adv. Synth. Catal. 352 (2010)
2233–2240.
[47] X. Chen, L. Zhang, B. Zhang, X. Guo, X. Mu, Highly selective hydrogenation
of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C N4
3
nanosheets catalysts in water, Sci. Rep. 6 (2016) 28558.
10