Palladium nanoparticles supported on mpg-C3N4 as active catalyst for semihydrogenation of phenylacetylene under mild conditions

Article abstract of DOI:10.1039/c3gc40779a

Palladium nanoparticles supported on a mesoporous graphitic carbon nitride, Pd@mpg-C₃N₄, has been developed as an effective, heterogeneous catalyst for the liquid-phase semihydrogenation of phenylacetylene under mild conditions (303 K, atmospheric H₂). A total conversion was achieved with high selectivity of styrene (higher than 94%) within 85 minutes. Moreover, the spent catalyst can be easily recovered by filtration and then reused nine times without apparent lose of selectivity. The generality of Pd@mpg-C₃N₄ catalyst for partial hydrogenation of alkynes was also checked for terminal and internal alkynes with similar performance. The Pd@mpg-C₃N₄ catalyst was proven to be of industrial interest.

Full text of DOI:10.1039/c3gc40779a

View Article Online
View Journal
Green Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: D. Deng, Y. Yang, G. Yutong, Y. Li, X. Xu
and Y. Wang, Green Chem., 2013, DOI: 10.1039/C3GC40779A.
This is an Accepted Manuscript, which has been through the RSC Publishing peer
review process and has been accepted for publication.
Accepted Manuscripts are published online shortly after acceptance, which is prior
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
Volume 12 | Number 9 | September 2010 | Pages 1481–1676
to technical editing, formatting and proof reading. This free service from RSC
Publishing allows authors to make their results available to the community, in
citable form, before publication of the edited article. This Accepted Manuscript will
be replaced by the edited and formatted Advance Article as soon as this is available.
To cite this manuscript please use its permanent Digital Object Identifier (DOI®),
which is identical for all formats of publication.
More information about Accepted Manuscripts can be found in the
Information for Authors.
Please note that technical editing may introduce minor changes to the text and/or
graphics contained in the manuscript submitted by the author(s) which may alter
content, and that the standard Terms & Conditions and the ethical guidelines
that apply to the journal are still applicable. In no event shall the RSC be held
responsible for any errors or omissions in these Accepted Manuscript manuscripts or
any consequences arising from the use of any information contained in them.
ISSN 1463-9262
COMMUNICATION
CRITICAL REVIEW
Luque, Varma and Baruwati
Dumesic et al.
Magnetically seperable organocatalyst Catalytic conversion of biomass
for homocoupling of arylboronic acids to biofuels
1463-9262(2010)12:9;1-U
www.rsc.org/greenchem
Registered Charity Number 207890

Page 1 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C3GC40779A
Table of Contents entry
Pd@mpg-C3N4
1bar H2, 303K
Styrene
Phenylacetylene
Palladium nanoparticles supported on a mesoporous graphitic carbon nitride is an efficient catalyst
for semihydrogenation of phenylacetylene under mild conditions.

View Article Online
DynamiDcOAI: 1r0t.i1c0l3e9/LC3iGnCk4s07►79A
Green Chemistry
Page 2 of 7
Green Chemistry
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/green chemistry
PAPER
Palladium nanoparticles supported on mpg-C3N4 as active catalyst for
semihydrogenation of phenylacetylene under mild conditions
Dongshun Deng,*a Yang Yangb, Yutong Gongb, Yi Lib, Xuan Xub and Yong Wang*b
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
Palladium nanoparticles supported on a mesoporous graphitic carbon nitride, Pd@mpg-C3N4, has been
developed as an effective, heterogeneous catalyst for the liquid phase semihydrogenation of
phenylacetylene under mild conditions (303 K, atmospheric H2). A total conversion was achieved with
the high selectivity of styrene (higher than 94%) within 85 minutes. Moreover, the spent catalyst can be
10 easily recovered by filtration and then reused nine times without apparent lose of selectivity. The
generality of Pd@mpg-C3N4 catalyst for partial hydrogenation of the alkynes was also checked on
terminal and internal alkynes with similar performance. The Pd@mpg-C3N4 catalyst was proven to be of
industrial interesting.
Their results suggested that Pd/NTs was a stable catalyst in
performance with high selectivity of 95% after 5 cycles. Cazorla-
Amorós et al. also prepared metallic nanoparticles with different
50 compositions, mainly including Ni-Pd, Fe-Pd, Mg-Pd, Pd and Pt.
Under 1 bar of H2 and 323 K, these catalysts provided high
selectivity and activity.7 Oligomeric aramides were also used as
support for palladium, the catalytic performance was relative low,
especially in the region of 100% conversion of phenylacetylene. 8
55 The somewhat similar behavior was observed with the
Pd/carbon.9 Kaneda et al. applied Pd/SiO2-DMSO catalyst system
for this reaction, and selectivity of 100% at conversion of 98%
was obtained under 1 bar of H2 and 303 K.10
In the construction of heterogeneous catalysts for
60 semihydrogenation of phenylacetylene, it is evident that
palladium was basically chosen as catalytic center because of its
specific dissociation power for hydrogen gas.11 The choice of
support is vital because the interaction between metal and active
phase plays crucial role in the comprehensive performance of the
65 catalysts. It is well known that the alkyne is relatively easy to be
hydrogenated to form olefin, but the deep hydrogenation is
inescapable.12 Therefore how to improve the selectivity,
especially persist high selectivity of olefin near the complete
conversion of alkyne, is still a challenging. One method usually
70 used is the addition of various modifiers such as metal13 or
organic base14. Another effective way is the selection of suitable
support with special properties to modify the metal nanoparticles,
including dispersion capability, stability and electron effect.
Mesoporous graphic carbon nitrides are new emerging dotted
75 carbon materials and possess suitable surface areas, small
particles size, tunable pore diameter, extreme chemical and
thermal stability, interesting electrical and semiconducting
properties.15 They have the potentiality to modify the central
palladium metal and can be used as support material for
80 heterogenous catalyst. In our previous work16, taking the
Introduction
15 Semihydrogenation of phenylacetylene possesses considerable
importance because phenylacetylene is regarded as a harmful
component in feedstock for the industrial manufacture of
polystyrene. It is mandatory to control the concentration of
phenylacetylene below 10 ppm because the residual
20 phenylacetylene will deactivate the polymerization catalyst and
decrease the degree of polymerization.1 Therefore it is desirable
to develop new catalysts which can still maintain the high
selectivity of styrene at phenylacetylene conversion near 100%.
For practical point of view, the hydrogenation process
25 extensively utilizes the heterogeneous catalysts which are
economically attractive for industrial applications due to their
advantages of simple separation processes as well as good
recycling properties. With the considerable attention on the
liquid-phase hydrogenation of phenylacetylene, many
30 heterogeneous catalysts have been reported. For example,
Mastalir et al reported the use of Pd nanoparticles on hydrotalcite
with selectivity around 90% at total conversion under mild
reaction condition. 2 Their results are similar with those obtained
by Guczi et al using pumice-supported Cu-Pd catalyst.3
35 Tiengchad et al4 investigated phenylacetylene hydrogenation
using Pd/SBA-15, and a 85% of selectivity of styrene was
obtained at the complete conversion of phenylacetylene, which
was attributed to the geometrical confinement effect of the
support. The similar effect was also illustrated in the Pd
40 nanoparticles encapsulated in the MCM-41 supports via
simultaneous synthesis method with a 96% selectivity of styrene.
5
The presence of strong metal-support interaction in Pd /SiO2
could enhance the styrene selectivity to 86-90% near the 100%
conversion of phenylacetylene.6 Cazorla-Amorós et al. compared
45 catalysts with different carbon supporting materials, including
multiwall carbon nanotubes, black carbon and activated carbon.1b
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

View Article Online
DOI: 10.1039/C3GC40779A
Page 3 of 7
Green Chemistry
advantage of lewis base of nitrogen functionalities on the surface
Solvents are often used in heterogenous catalytic hydrogenation
reactions. Solvents may be one of the best means available for
markedly altering the rate as well as selectivity, a fact not
sufficiently appreciated. So, the initial attempt was performed to
of mpg-C3N4, Pd@mpg-C3N4 was successfully prepared and used
for selective hydrogenation of phenol and nitrile with perfect
performance. Despite many efforts devoted to the study of
5
heterogeneous hydrogenation of phenylacetylene, no example 55 investigate the influence of different solvents on the reaction. The
using doped carbon as supports can be found in the literature. In
this paper, we hope to extend the Pd@mpg-C3N4 to the present
semihydrogenation reaction. The electron-donation effect of
mpg-C3N4 can increase the density of the anchored palladium. In
corresponding conversion and selectivity are summarized in
Table 2, along with the properties of the used solvents. Although
the mechanistic basis of the solvent influences on the
heterogeneous hydrogenation is not clear, some conclusions have
10 turn, increasing electron density of palladium leads to favoring 60 been rationalized by correlating the reaction rate and selectivity
desorption of the monoenes to give a high yield of partially
with H2 solubility or polarity. However, in present system, no
systematic correlation can be discerned between the catalytic
performance of Pd@mpg-C3N4 and H2 solubility or solvent
17
hydrogenated styrene.
An increase in alkene selectivity by
addition of electron donor compounds such as ammonia or
piperidine to supported palladium catalysts has been reported by
15 Del Angel and Boitiaux.18
polarity. This phenomenon is also observed in the chemselective
20
65 hydrogenation of quinoline using Pd@ompg-C3N4
and the
earlier study on the same system. 2 Among the organic solvents
tested, tetrahydrofuran gave high activity but relative lower
selectivity toward styrene. Ethanol was found to be the most
effective, which gave both high conversion and selectivity
70 relatively. Other solvents demonstrated low activity. In fact,
because of the hydrophilcity of the nitrogen doped carbon support,
the catalyst pd@mpg-C3N4 couldn’t be dispersed well even with
vigorous stirring in the non-polar and less polar solvents, which
might produce unfavorable influence on mass transfer process. It
Result and discussion
Catalyst characterization
The obtained mpg-C3N4 material and supported Pd@mpg-C3N4
20 catalysts were systematically characterized using serials
parameters, including BET surface area and pore volume, TEM,
WAXS, FT-IR, and XPS, with the results illustrated in our
previous work.16 The supported Pd particles were well-dispersed 75 is well known that ethanol is a cheap and versatile medium and
and existed mainly as Pd0 on the surface of the catalyst (∼70%).
25 The π-bonded planar C-N-C-layers along with incompletely
condensed amino groups in mpg-C3N4 are suitable for stabilizing
highly dispersed Pd0 particles and prevent their re-oxidation.
its relative low boil point can simplify the separation process for
the products. According, we selected ethanol as the reaction
medium in the subsequent research. Furthermore, the amount of
ethanol was also optimized, with the results listed in Table 3. It is
Such characters were helpful for the selective semihydrogenation 80 evident that the amounts of ethanol made significant effect on the
of phenylacetylene. It needed to specify here is that the surface
30 areas and average pore diameters of Pd@mpg-C3N4 samples
decreased a little compared with those of the mpg-C3N4, which
illustrated the metal potions attached to the surface of the pores in
reaction rate but less influence on the selectivity. The
concentration of phenylacetylene in entry 1 was almost 5 times
higher than that in entry 5, but the reaction rate was much lower,
which is very interesting. This result illustrated that the reaction
the support. This process made the pore diameters decrease, but 85 rate had nothing to do with the concentration of phenylacetylene
the structures of the pore unchanged. The ICP-AES was used to
35 determine the practical palladium contents in the prepared
Pd@mpg-C3N4 catalysts, the experimental results are basically
consistent with the desired compositions (as shown in table 1).
in the system, which suggested this reaction probably was a zero
order reaction.21 On the basis of the saturation concentration of
H2, the low concentration of phenylacetylene and high reaction
rate suggested that the absorption and activation of H2 may be the
The results demonstrated that the ultrasonic-assisted 90 rate controlling step in the reaction kinetics.
impregnation method was a simple and feasible way to control
40 the palladium contents on the support of mpg-C3N4.
Table2 Semihydrogenation of phenylacetylene with Pd@mpg-C3N4 in
various solvents a
Table 1 Practical palladium content in the Pd@mpg-C3N4 catalysts.
sem ihy drgenation
Entry
Catalysts
ICP-AES results
0.67%
1
2
3
4
1%Pd@mpg-C3N4
4%Pd@mpg-C3N4
6%Pd@mpg-C3N4
12%Pd@mpg-C3N4
Entry
Solvents
Conv. b (%) Sel. b (%)
δ c
p d
3.56%
5.64%
11.30%
1
2
3
4
5
6
7
8
n-hexane
cyclohexane
toluene
tetrahydrofuran
ethyl acetate
chloroform
dioxane
24
39
58
93
44
10
45
62
81
96
96
89
96
97
95
96
4.70
3.97
3.40
3.50
3.77
--
0.06
0.10
2.40
4.20
4.30
4.40
4.80
4.30
Semihydrogenation of phenylacetylene
The ideal destination of the semihydrogenation of
phenylacetylene is the single reduction of carbon-carbon triple
45 bond to form styrene. However, the deep reduction involving the
formation of ethyl benzene is inevitable and will decrease the
selectivity of styrene. Therefore, it is desirable to minimize the
side reaction by utilizing the new catalyst with excellent
performances.
1.90
2.90
ethanol
95 a Reaction conditions: 5.85 mmol phenylacetylene, 10 mg Pd@mpg-C3N4
(5.64wt% Pd), 303 K, 50 cm3 solvent, atmospheric H2 balloon, 60 minutes.
bAnalysed by GC and GC-MS . cSolubility of H2 (106 mol.cm-3, taken
from Ref.(2, 21). d Solvent polarity.
50 The effect of solvent
2 | Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

View Article Online
DOI: 10.1039/C3GC40779A
Green Chemistry
Page 4 of 7
Table 3 Hydrogenation of phenylacetylene with different amounts of
45 catalyst, while keeping the high selectivity of 97%.
ethanol a
It is evident that the nature of the support materials plays a vital
role in the performance of the palladium for present reaction. The
mpg-C3N4 possesses the advantages of specific surface areas and
electron density, which benefit the interaction of palladium with
50 support, the morphorlogy and distribution of the palladium ion,
and desorption of styrene. The comprehensive effects may be
decisive for the satisfactory selectivity.
It was reported that the addition of second metal would enhance
the selectivity,13 so we prepared and applied Au-Pd@mpg-C3N4
55 with the molar ration of Au with Pd at 2.5 in the reaction, but the
catalytic activity was much lower than that of Pd@mpg-C3N4.
Comparing the results obtained by using various catalysts, it was
indicated that the Pd@mpg-C3N4 provided both high conversion
and selectivity relatively, and because of its convenient
60 preparation method and good characteristics of the mesoporous
graphitic carbon nitride (mpg-C3N4), it was easier to get catalyst
with distributed active portion on the surface, which made a
steady catalytic activity. Furthermore, when the catalyst was lost
activity completely, it is easy to recycle the expensive palladium
65 by a simple burning process.
Entry
Amount (cm3)
Conv. b (%)
Sel. b (%)
1
2
3
4
5
10
20
30
40
50
20
49
57
59
62
97
96
96
96
96
a Reaction conditions: 5.85 mmol phenylacetylene, 10 mg Pd@mpg-C3N4
(5.64wt% Pd), 303 K, atmospheric H2 balloon, 60 minute. bAnalysed by GC.
5
The comparison of various catalysts
In order to investigate the detailed catalytic performance of the
Pd@mpg-C3N4, we compared the catalytic hydrogenation results
obtained under the same reaction conditions by using Pd@mpg-
C3N4 and several other heterogeneous catalysts, including Lindlar
10 catalyst, commercially available Pd@carbon, as well as several
inorganic oxide supported catalysts of Pd@TiO2, Pd@MgO,
Pd@γ-Al2O3, and Pd@CeO2, with the results listed in Table 4.
Table 4 Hydrogenation of phenylacetylene catalyzed by various
catalystsa
Entry
1c
Catalyst
Pd@carbon
Pd@mpg-C3N4
2.5Au-Pd@mpg-C3N4
Pd@γ-Al2O3
Pd@TiO2
Time/min Conv. b (%) Sel. b (%)
15
85
60
85
>99
29
88
94
96
Kinetic analysis and reusability studies of Pd@mpg-C3N4
catalyst on semihydrogenation of phenylacetylene
2d
3d
4d
45
20
105
150
270
60
>99
100
>99
95
5
17
90
86-90
91
91
>99
97
For heterogeneous catalytic hydrogenation reaction, it is
necessary to eliminate the influences of mass transfer limitations
70 on the hydrogenation activity and selectivity of the catalyst. On
the basis of previous experiments performed with different
stirring rates and hydrogen flows, we carried out the experiments
using phenylacetylene (5.85 mmol), ethanol (50 cm3), 303 K, H2
(atmospheric flow, 30 cm3.min-1) and magnetic stirring (1500
75 rpm) under different weights of catalysts (2-12mg). The evolution
of material was monitored with reaction time. As illustrated in the
literature9, 23, the reaction can be regarded to follow zero order
kinetics with respect to concentration of phenylacetylene. So, the
apparent rate (k) can be obtained from the slope by linear fitting
80 of concentration of phenylacetylene vs. time. The apparent
reaction rates are measured for applying the Koros-Nowak
criterion24, and the results are illustrated in Figure 1. As can be
seen, the apparent reaction rate is proportional to the amount of
catalyst. It is proven that the performance of catalyst under the
85 experimental conditions is within the kinetic regime and the
reaction is free of artifacts.
5e
6d
Pd@MgO
Pd@CeO2
Lindlar catalyst
Pd@mpg-C3N4
7d
8f
9g
15 a Reaction conditions: 10 mg catalyst, 5.85 mmol phenylacetylene, 50 cm3
ethanol, 303 K, atmospheric H2 bubbling. bAnalysed by GC. c Data taken
from ref 9, 1 wt% Pd, 0.2 MPa H2 and 323 K. d 5.64 wt% Pd. e Data taken
from ref 6b,1 wt% Pd, 5 bar H2 and 303K. f 1 wt% Pd , provided by NHU
company. g 0.67 wt% Pd.
20 In general, all the catalysts demonstrated high selectivity of
styrene but evidently different activity in the semihydrogenation
of phenylacetylene. Carbon material was extensively used as
support in this reaction22, when commercial Pd@carbon was used
as catalyst, the results demonstrated that high selectivity of 88%
25 was maintained up to conversion of 85% (Table 4, entry 1), while
the selectivity decreased markedly with the further consumption
of substrate. If replaced the support with multiwall carbon
nanotubes, the selectivity was still better than 95% after five
recycles because of the geometrical confinement effect.7
In the following reutilization studies of Pd@mpg-C3N4 for
semihydrogenation of phenylacetylene, the reaction scale was
enlarged. 29.25 mmols of Phenylacetylene and 50 mg of catalyst
90 were stirred in 150 cm3 of ethanol at 303 K under atmospheric H2
flow of 30 cm3min-1. When the conversion of phenylacetylene
arrived at about 90%, the reaction was terminated. The catalyst
was separated from the reaction mixture by simple centrifugation,
and then was thoroughly washed with ethanol and dried at 343 K.
95 This catalyst was used for another eight reaction cycles. The
reaction course was monitored with time for every cycle to
evaluate the performance of the catalyst. For best illustration, the
conversions of phenylacetylene vs time for several cycles were
plotted in Figure 2. Using the method mentioned above, the
100 apparent reaction rate for each cycle can be determined and listed
in Table 5, along with the ultima conversion and selectivity.
Actually, the reaction rate decrease gradually with the recycling
30 The inorganic oxide supported palladium catalysts were relatively
effective for this reaction, while affording lower selectivity of
styrene than Pd@mpg-C3N4 (Table 4, entry 2, 4-6). The reasons
may arise from the uneven distribution of active position of
palladium on the inorganic oxide surface. On the same time,
35 because of the strong correlation between palladium and the
metal oxides, it isn’t easy to recover the expensive Pd from the
used catalysts with low activity, which would increase the total
cost without doubt.
It is well acknowledged that Lindlar catalyst is widespread-used
40 in semihydrogenation of acetylene. Under the same reaction
condition, the catalytic performance of Lindlar catalyst was
compared with Pd@mpg-C3N4 (Table 4, entry 8, 9), the former
gave nearly 100% selectivity but low conversion. The catalytic
activity of Pd@mpg-C3N4 is 15 times faster than that of Lindlar
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

View Article Online
DOI: 10.1039/C3GC40779A
Page 5 of 7
Green Chemistry
runs. For the heterogeneous catalysis, metal species leaching
5
activity of the Pd@mpg-C3N4 was primarily due to progressive
palladium leaching during the separation and purification
operation.
during the recycle reaction is one problem. Palladium content of
the used catalyst after nine recycles was 2.18 wt% by ICP-AES
analysis, which demonstrated that the gradually decreased
100
80
2.5
2.0
1.5
1.0
0.5
0.0
60
First Cycle
Third Cycle
40
Fifth Cycle
Sixth Cycle
Ninth Cycle
20
20 40 60 80 100 120 140
Time, min
2
4
6
Weight of catalyst, mg
8
10
12
Fig. 1 The reaction rate vs weight of catalyst
Fig. 2 The conversion of phenylacetylene vs time
10
Table 5 Reusability studies of Pd@mpg-C3N4 catalysta
Reaction cycle
Reaction time (min)
Conversion of phenylacetylene (%)
Selectivity of styrene (%)
kapp (mol.dm-3min-1)
1st
70
95
95
1.37
2nd
70
91
94
1.29
3rd
90
95
94
1.07
4th
100
93
95
0.93
5th
120
96
94
0.83
6th
120
89
95
0.75
7th
140
95
94
0.68
8th
160
98
93
0.63
9th
140
85
96
0.61
a Reaction conditions: phenyacetylene 29.25 mmol, Pd@mpg-C3N4(5.64 wt% Pd, recovered) 50 mg, ethanol 150 cm3, 303 K, H2 (atmospheric, 30
cm3.min-1).
selectivity to styrene (△) or ethyl benzene (□).
Possible reaction pathway and mechanism for the
15 semihydrogenation of the phenylacetylene
As depicted in Schem 1, the hydrogenation of phenylacetylene to
styrene or ethyl benzene is considered to occur by two-pathway
35 mechanism. The first pathway involves the completely
hydrogenation of triple bond to saturated single bond, while
another pathway is the successive hydrogenation reactions
involving styrene as the intermediate. Therefore, in order to
improve the selectivity of styrene, the further hydrogenation of
40 styrene and direct hydrogenation of phenylacetylene must be
minimized. Applying density function theory in simulations of
selective hydrogenation using Lindlar catalyst, M. García-Mota et
al.26 proposed that the heterogenous catalyst with the high
selectivity should possess three positive contributions including
45 high thermodynamic factor, no generation of β-PdH phase, and
no promotion for formation of oligomerization. As for Pd@mpg-
C3N416, its surface is electron negative. The HRTEM images
revealed well-dispersed Pd particles with a mean size of 3.3 nm,
which is helpful to decrease the formation of the palladium β-
50 hydride phase.27 The lewis base moisture in the mpg-C3N4 is able
to increase the electron density of palladium, in turn, leads to
decreasing the strength of adsorption of intermediate styrene.
Desorption of styrene is favored and the overall selectivity is
enhanced. This is consistent with the reported result.17 As
55 reported in a recent paper28, the nitrogen base can promote the
formation of Pdδ+-Hδ- in the polarization of Pd-H bond, which
prefer to attack the triple bond.
As the Pd@mpg-C3N4 demonstrated excellent performance in the
present reaction, more studies were applied for further understand
of the catalytic process. The plot of phenylacetylene conversion
and product selectivity versus reaction time was shown in Figure
20 3. The reaction was fast and styrene was obtained as the
predominant product (96% in selectivity) until the conversion
reached 90%, and then styrene slowly transferred to ethyl
benzene but the selectivity was still above 94% at the total
conversion of phenylacetylene after reaction for 85 minutes. The
25 mechanism and kinetic model for the phenylacetylene
hydrogenation have been investigated in the literatures.23b, 23c, 25
100
80
60
40
20
0
20
40
60
80
Time, min
Fig.3 Variation of conversion and selectivity with reaction time on the
semihydrogenation of phenylacetylene. Reaction conditions: 10 mg 5.64
30 wt% Pd@mpg-C3N4, 5.85 mmol phenylacetylene, 50 cm3 ethanol, 303 K,
atmospheric H2 bubbling. (▼) Conversion of phenylacetylene and
4 | Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

View Article Online
DOI: 10.1039/C3GC40779A
Green Chemistry
Page 6 of 7
Schem
2
illustrates the hydrogenation process of the
phenylacetylene. In the initial step, phenylacetylene was absorbed
23b
H
5
on two catalyst sites as earlier research suggested
and and H2
2
H
2
k
1
k
is dissociated by the electronically supported Pd (Schem 2a). The
triple bond is converted to double bond by the attack of the
activated hydrogen atom (Schem 2b). Another activated hydrogen
inserts and the formed styrene is rejected from the support, being
2
2 H
2
k
3
Scheme 1 The pathway for the semihydrogenation of phenylacetylene.
10 replaced by a new phenylacetylene molecular (Schem 2c).
c
a
b
H
H
H
H
H
H
H
H
H
H
Pd
e
Pd
Pd
e
e
H
Carbon Nitride
Scheme 2 Proposed reaction mechanism for semihydrogenation of phenylacetylene catalyzed over Pd@mpg-C3N4
demonstrated excellent activity and selectivity for the
Catalytic performance
of Pd@mpg-C3N4 for the
semihygrogenation of various terminal alkynes as well as internal
alkynes (Table 6, entry 4-6), which is of great importance. But it
25 should be noted that the hydrogenation of aliphatic alkyene
existed double bond isomer products (Table 6, entry 5, 6). Unlike
some catalysts are just able to catalyze one kind of alkynes, the
results show that the Pd@mpg-C3N4 is extensively capable of
semihydrogenation for different kinds of alkynes with high
30 selectivity.
semihydrogenation of various alkynes
15 To explore the scope of the Pd@mpg-C3N4 catalytic system for
the partial reduction of alkynes to alkyene, a serial of alkynes
with structurally divergent functional groups or triple bond
position were examined, with the results listed in Table 6. The
catalytic system was effective for aromatic alkyene regardless of
20 the benzene ring substituted by electron-donating or electron-
withdrawing group (Table 6, entry 1-3). The catalyst
Table 6 Semihydrogenation of various alkynes catalyzed by Pd@mpg-C3N4 catalysta
Entry
1
Substrate
Product
Time (min)
150
Conv. b (%)
38
Sel.b (%)
94
H 3 C O
H 3 C O
2
90
>99
94
H 3
C
H 3
C
3
4
30
60
99
93
72
F
F
>99
5c
6c
1-Octyne
4-Octyne
1-Octene and isomer alkenes
4-Octene and isomer alkenes
80
20
>99
>99
93
99
a Reaction conditions: 10 mg 5.64 wt% Pd@mpg-C3N4, 5.85 mmol substrate, 50 cm3 ethanol, 303K, atmospheric H2 balloon. bDetermined by GC using an
c
internal standard. Determined by GC-MS, including double bond isomer products.
were obtained according to literature.19
Experimental
Typical procedure for semihydrogenation of phenylacetylene
35 Materials and analytical methods
Liquid-phase selective hydrogenation of phenylacetylene was
50 carried out in a 100 cm3 round-bottled flask. In a typical
Unless specific stated, all the chemicals were analytical grade and
procedure, 10 mg Pd@mpg-C3N4, 5.85 mmol phenylacetylene
and 50 cm3 ethanol were placed in the vessel. After the
replacement of air with H2 for 3 times, the mixture was then
magnetically stirred at 1500 rpm under atmospheric hydrogen
55 ball and 303 K. The reaction process was monitored by gas
chromatographic analysis.
commercially purchased from Sigma–Aldrich, Acros, Merck, or
Aladdin chemical reagents Co. Ltd. (Shanghai, China). The
chemicals were used without further purification as received. The
40 conversion and selectivity of the reaction were determined by
chromatographic analysis using SHIMADZU GC-2011 with FID
detector.
Preparation of catalysts
Conclusions
The support material of mpg-C3N4 and heterogenous catalysts
45 Pd@mpg-C3N4 were prepared according to our reported
method.16 The inorganic oxides supported palladium catalysts
In summary, as a heterogeneous catalyst, the Pd@mpg-C3N4
demonstrated
considerable
catalytic
activity
in
the
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5

View Article Online
DOI: 10.1039/C3GC40779A
Page 7 of 7
Green Chemistry
16 (a)Y. Wang, J. Yao, H. R. Li, D. S. Su and M. Antonietti, J. Am. Chem.
Soc., 2011, 133, 2362;
65 (b)Y. Li, X. Xu, P.F. Zhang, Y. T. Gong, H. R. Li and Y. Wang, RSC
Advance, Dio: 10.1039/c3ra41397g;
(c)Y. Li, Y. T. Gong, X. Xu, P. f. Zhang, H. R. Li and Y. Wang, Catal.
Commun., 2012, 28, 9.
17 Z. M. Michalska, B. Ostaszewski, J. Zientarska and J. W. Sobczak, J.
semihydrogenation of phenylacetylene at mild conditions (303 K,
atmospheric H2). Especially, the Pd@mpg-C3N4 demonstrated
quite stable performance in the recycling tests, which is proven as
a
novel, effective, and environment-friendly catalyst. Our
5
experimental results also show that the Pd@mpg-C3N4 is widely
applicable for different kinds of alkynes with quite high
conversion and selectivity.
70
Mol. Catal. A: Chem., 1998, 129, 207.
18 (a) G. Del Angel, J.L. Benitez, J. Mol. Catal., 1994, 94, 409;
(b) J. P. Boitiaux, J. Cosyns, S. Vasudevan, Appl. Catal., 1985, 15, 317.
19 X. Xu, Y. Li, Y. T. Gong, P. F. Zhang, H. R. Li and Y. Wang, J. Am.
Chem. Soc., 2012, 134, 16987.
75 20 Y. T. Gong, P. F. Zhang, X. Xu, Y. Li, H. R. Li and Y. Wang, J.
Catal., 2013, 297, 272.
21 U. K. Singh and M. A. Vannice, Applied Catalysis A: General, 2001,
213, 1.
22 R. A. Sheldon and H. V. Bekkum, Fine Chemicals Through
Acknowledgements
Financial support from the Joint Petroleum and Petrochemical
10 Funds of the National Natural Science Foundation of China and
China National Petroleum Corporation (U1162124), the Zhejiang
Provincial Natural Science Foundation for Distinguished Young
Scholars of China (LR13B030001), the Specialized Research
Fund for the Doctoral Program of Higher Education (J20130060),
15 the Fundamental Research Funds for the Central Universities, the
Program for Zhejiang Leading Team of S&T Innovation, and the
Partner Group Program of the Zhejiang University and the Max-
Planck Society are greatly appreciated.
80
Heterogeneous Catalysis, Wiley-VCH, 2001.
23 (a) B. M. Choudary, K. M. Lakshmi, R. N. Mahender, R. K.
Koteswara, Y. Haritha, V. Bhaskar, F. Figueras and A. Tuel, Appl.
Catal. A General, 1999, 181, 139;
(b) D. Duca, L. F. Liotta and G. Deganello, J. Catal., 1995, 154, 69;
85 (c) N. Martín-Astorga, G. Pecchi, T. J. Pinnavaia, G. Alvez-Manoli and P.
Reyes, J. Mol. Catal. A: Chem., 2006, 247, 145;
(d) B. A. Wilhite, M. J. McCready and A. Varma, Ind. Eng. Chem. Res.,
2002, 41, 3345.
24 R. J. Madon and M. Boudart, Ind. Eng. Chem. Fundam. 1982, 21, 438.
90 25 Á. Molnár, A. Sárkány and M. Varga, J. Mol. Catal. A: Chem., 2001,
173, 185.
26 M. García-Mota, J. Gómez-Díaz, G. Novell-Leruth, C. Vargas-Fuentes,
L. Bellarosa, B. Bridier, J. Pérez-Ramírez and N. López, Theor.
Chem. Acc., 2011, 128, 663.
20 a Zhejiang Province Key Laboratory of Biofuel, College of Chemical
Engineering and Material Science, Zhejiang University of Technology,
Hangzhou 310014, China; E-mail: dengdsh@zjut.edu.cn
b Key Lab of Applied Chemistry of Zhejiang Province, Department of
Chemistry, Zhejiang University, Hangzhou 310028, China; Tel: 86 571
25 87951895; E-mail: chemwy@zju.edu.cn
95 27 G. Carturan, G. Facchin, G. Cocco, S. Enzo and G. Navazio, J. Catal.,
1982, 76, 405.
28 J. Yu and J.B. Spencer, Chem. Commun., 1998, 1103.
References
1 (a) B. R. Maurer and M. Galobardes, US Patent 4,822,936, 1989;
(b) S. Domínguez-Domínguez, Á. Berenguer-Murcia, B. K. Pradhan, A.
30
Linares-Solano and D. Cazorla-Amoros, J. Phys. Chem. C, 2008, 112,
3827.
(c) K. H. Lee, B. Lee, K. R. Lee, M. H. Yi and N. H. Hur, Chem.
Commun., 2012, 48, 4414.
2 Á. Mastalir and Z. Király, J. Catal., 2003, 220, 372.
35 3 L. Guczi, Z. Schay, Gy. Stefler, L. F. Liotta, G. Deganello and A. M.
Venezia, J. Catal., 1999, 182, 456.
4
N. Tiengchad, O. Mekasuwandumrong, C. N. Chiangmai, P.
Weerachawanasak and J. Panpranot, Catalysis Communications,
2011, 12, 910.
40 5 S. Domínguez-Domínguez, Á. Berenguer-Murcia, Á. Linares-Solano
and D. Cazorla-Amorós, J. Catal., 2008, 257, 87.
6 (a) P. Weerachawanasak, P. Praserthdam, M. Arai and J. Panpranot, J.
Mol. Catalysis A: Chem., 2008, 279, 133;
(b) P. Weerachawanasak, O. Mekasuwandumrong, M. Arai, S. I. Fujita,
45
P. Praserthdam and J. Panpranot, J. Catal., 2009, 262, 199.
7 S. Domínguez-Domínguez, Á. Berenguer-Murcia, D. Cazorla-Amoros
and A. Linares-Solano, J. Catal., 2006, 243, 74.
8 F. Arena, G. Cum, R. Gallo and A. Parmaliana, J. Mol.Catal. A: Chem.,
1996, 110, 235.
50 9 S. D. Jackson and L. A. Shaw, Applied Catalysis A: General, 1996, 134,
91.
10 Y. Takahashi, N. Hashimoto, T. Hara, S.Shimazu, T. Mitsudome, T.
Mizugaki, K. Jitsukawa and K. Kaneda, Chem. Lett. 2011, 40, 405.
11 M. Y. Ni and Z. Zeng, J. Mol. Struct.: THEOCHEM, 2009, 910, 14.
55 12 P. N. Rylander, Hydrogenation Methods, Academic Press, London,
New York, 1985.
13 H. Lindlar and R. Dubuis, Org. Synth., 1966, 46, 89.
14 A. S. Kende, P. Fludzinski, J. H. Hill, W. Swenson and J. Clardy, J.
Am. Chem. Soc., 1984, 106, 3553.
60 15 (a) A. Thomas, A. Fischer, F. Goettmann, M. Antonietti, J. O. Muller,
R. Schlogl and J. M. Carlsson, J. Mater. Chem., 2008, 18, 4893;
(b) J. S. Lee, X. Wang, H. Luo and S. Dai, Adv. Mater., 2010, 22, 1004.
6 | Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]