Influence of metal ions on the hydrogenation of chlorobenzene over polymer-stabilized platinum nanoparticles

Article abstract of DOI:10.1080/15533174.2012.753628

The effect of metal ions on the hydrogenation of chlorobenzene over poly(vinylpyrrolidone)-stabilized platinum (PVP-Pt) colloidal catalysts was studied in methanol at 298 K and atmospheric pressure. It showed that some metal cations significantly affected the catalytic performances of the colloidal nanocatalysts. Almost all the metal cations studied decreased both the activity and the selectivity to cyclohexane, which might be due to the electron-deficient state of the surface Pt atoms resulting from the adsorbed metal ions. It is therefore essential to remove some metal ions, especially Sn²⁺, Cu²⁺, Zn²⁺, and Mn²⁺ from wastewaters for efficient catalytic hydrodechlorination. Copyright Taylor and Francis Group, LLC.

Full text of DOI:10.1080/15533174.2012.753628

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Influence of Metal Ions on the Hydrogenation of
Chlorobenzene Over Polymer-Stabilized Platinum
Nanoparticles
a
a
b
a
a
c
Manhong Liu , Hailian Xiao , Hongbin Shan , Xinghua Li , Yanyan Liu & Aimin Wang
a
College of Materials Science and Engineering , Qingdao University of Science and
Technology , Qingdao , P. R. China
b
Qilu Antibiotics Pharmaceutical Co. , Jinan , P. R. China
c
Center of Chemical Examination of Qingdao Customs , Qingdao , P. R. China
Accepted author version posted online: 11 Feb 2013.Published online: 13 Mar 2013.
To cite this article: Manhong Liu , Hailian Xiao , Hongbin Shan , Xinghua Li , Yanyan Liu & Aimin Wang (2013) Influence of
Metal Ions on the Hydrogenation of Chlorobenzene Over Polymer-Stabilized Platinum Nanoparticles, Synthesis and Reactivity
in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:6, 699-704, DOI: 10.1080/15533174.2012.753628
To link to this article: http://dx.doi.org/10.1080/15533174.2012.753628
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:699–704, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.753628
Influence of Metal Ions on the Hydrogenation
of Chlorobenzene Over Polymer-Stabilized
Platinum Nanoparticles
1
1
2
1
1
Manhong Liu, Hailian Xiao, Hongbin Shan, Xinghua Li, Yanyan Liu,
3
and Aimin Wang
1
College of Materials Science and Engineering, Qingdao University of Science and Technology,
Qingdao, P. R. China
2
Qilu Antibiotics Pharmaceutical Co., Jinan, P. R. China
Center of Chemical Examination of Qingdao Customs, Qingdao, P. R. China
3
demands and less toxic emissions. Besides, catalytic HDC
The effect of metal ions on the hydrogenation of chlorobenzene not only converts toxic substances into safer or less toxic
over poly(vinylpyrrolidone)-stabilized platinum (PVP-Pt) colloidal compounds, but also often makes useful products from the
catalysts was studied in methanol at 298 K and atmospheric pres-
sure. It showed that some metal cations significantly affected the
catalytic performances of the colloidal nanocatalysts. Almost all
the metal cations studied decreased both the activity and the selec-
[5–7]
chlorinated wastes.
The catalysts used for HDC are mainly
supported mono- or bimetallic catalysts; some of them, such
as Pd and Pd/Fe, have been extensively studied for the hy-
tivity to cyclohexane, which might be due to the electron-deficient drodechlorination of halogenated hydrocarbon in both organic
state of the surface Pt atoms resulting from the adsorbed metal and aqueous media with molecular hydrogen.[
8–11]
However,
ions. It is therefore essential to remove some metal ions, especially
most of the reactions over Pd-based catalysts usually produce
aryl compounds, such as benzene, aniline, naphthalene, which
are still not good to the environments.
2+
2+
2+
2+
Sn , Cu , Zn , and Mn from wastewaters for efficient catalytic
hydrodechlorination.
Nanoscopic metal particles with diameter of 1–10 nm are ex-
pected to be significant in both the fundamental research and the
applied engineering due to their quantum confinement effect and
other unique electrical, optical and catalytic properties. Their
application to catalysis is one of the most active research di-
rections. Polymer-stabilized metal colloidal particles are of im-
portance to understand the relationship between homogeneous
and heterogeneous catalysis, and they have shown good stability
against acids, temperature, pressure, and additives. Researchers
have reported a series of singular properties of colloidal metal
nanoparticles as catalysts for many organic reactions, such as
Keywords chlorobenzene, hydrogenation, metal ion modification,
platinum colloidal catalyst
INTRODUCTION
Wastewaters from chemical industry, agricultural chemistry
and medical chemistry often contain hazardous chlorinated or-
ganic compounds. With the ever-increasing concern of environ-
ment protection and sustainable development, the removal of
chlorinated organic compounds from wastewaters has gained
great attention.[1–4]
[
12–14]
the hydrogenation of monoenes or dienes,
the hydration of
Among the various techniques used in the remediation of
acrylonitrile,[ the hydroformylation of propylene, the car-
13]
[15]
these toxic pollutants in wastewaters, catalytic hydrodechlo-
[
13]
rination (HDC)[1] is widely employed due to its advantages
bonylation of methanol, and the selective hydrogenation of
unsaturated aldehydes[
13,16]
and chloronitrobenzene.
[17,18]
Some
over other traditional treatments: it is nondestructive, simple,
safe, and efficient; it runs at low temperatures with low energy
[
19]
nanoparticles have shown high enantiomeric selectivity.
On the other hand, it is known that additives, for example
metal cations, can remarkably affect the performance of cata-
lysts. Based on this concept, improvement of catalytic perfor-
mance by metal ions has been reported in a number of cases
in heterogeneous catalysis. This has been firstly described by
Received 13 November 2012; accepted 24 November 2012.
Financial support for this work was from the National Natural Sci-
ence Foundation of China (NSFC, 21077062), the Taishan Scholar, and
the Shandong Province Natural Science Foundation (ZR2012FZ007).
Address correspondence to Manhong Liu, College of Materials Sci-
[20]
[21]
Adams et al.,
Maxted,
and recently reviewed in detail
by Ponec[ and Gallezot and Richard.
22]
[23]
However, there are
ence and Engineering, Qingdao University of Science and Technology, few reports about the influence of additives to the homoge-
Qingdao 266042, P. R. China. E-mail: liumanhong68@126.com.
neous dispersion of neat metal colloidal catalysts owing to their
699

700
M. LIU ET AL.
intrinsic thermodynamic instability. Yu et al.[24,25] reported the
significant promotion effect of metal cations on hydrogenation
reactions over the unsupported and supported metal colloid cat-
alysts. Yu et al.[ recently reviewed the singular modification
effects of metal cations on the selective catalytic hydrogenation
reactions over noble metal colloidal nanocatalysts. The under-
standing of the metal cation effect on the catalytic HDC will be
beneficial to the mechanism study and the practical remediation
applications, because metal cations often coexist with chlori-
nated organic compounds in wastewaters, which may affect the
efficacy of the catalytic processes.
3
0 mL was used as the reaction solvent. The reaction temper-
ature was kept constant by a thermostatic water bath. After
H2 was charged several times to replace the air, the mixture
was stirred vigorously with a magnetic stirrer and the reaction
started. Chemical analysis of the products was analyzed by a gas
chromatography equipped with a FID detector and an AC-10
column. Reactants and products were identified by comparing
with authentic samples.
26]
RESULTS AND DISCUSSION
Figure 1 shows the TEM photograph of PVP-Pt colloidal
nanoparticles. The nanoparticles are non-aggregated and their
diameters are in the range of 2.3–5.6 nm with an average
value of 3.63 nm. The hydrogenation of chlorobenzene fol-
lows the reaction pathways described in a previous work.[
PVP-Pt colloidal nanoparticles were highly effective in favor
of the selective hydrogenation of chlorobenzene under ambient
conditions. The initial products consisted of benzene and cyclo-
hexane, and benzene could be completely converted to cyclo-
hexane with an extended reaction time of 15 h. In this study,
the modification of various metal cations to the hydrogenation
of chlorobenzene over the PVP-Pt catalysts (containing 2.5 ×
We recently reported a dehalogenation and hydrodearom-
atization method using molecular hydrogen catalyzed by
poly(N-vinyl-2-pyrrolidone)-stabilized platinum colloidal cat-
alysts (PVP-Pt).[
27–29]
Nearly 100% selectivity to cyclohex-
27]
ane could be obtained over PVP-Pt colloidal nanocatalysts at
100% conversion in the hydrogenation of chlorobenzene at
98 K and atmospheric pressure. In this work, the influence
∼
2
of metal cations on the dehalogenation and hydrodearomati-
zation of chlorobenzene (CB) over PVP-Pt colloidal catalysts
was studied. We found that metal cations significantly affected
the catalytic performances of the colloidal nanocatalysts. Most
of the metal cations studied in this system decreased both the
activity and the selectivity to cyclohexane.
−5
10
mol Pt) was investigated with a reaction time of 10 h.
The products consisted of benzene and cyclohexane during the
reactions.
−
EXPERIMENTAL
It is known that Cl usually inhibits the hydrodechlorina-
tion. This deactivation is generally due to the strong adsorption
of the halide species and a consequent blocking of the active
Materials and Instrument
Poly(N-vinyl-2-pyrrolidone) (PVP; average molecular
weight 10,000) was purchased from Shanghai Chemicals Co
[31]
−
sites. To elucidate whether Cl would influence the proper-
ties of our nanocatalysts, a controlled experiment was conducted
(
China). Hexachloroplatinic acid (H2PtC16·6H2O) of analytical
grade was supplied by Beijing Chemicals Co (China). Hydrogen
H2) with a purity of 99.999% was produced by an extra-pure
−5
by adding 2.5 × 10 mol NaCl into PVP-Pt catalyst system
+
(
entry 3; Na content was equivalent to that of NaNO3 added to
(
the catalyst system). With the introduction of NaCl, the activity
hydrogen generator (HA-300). Chlorobenzene was distilled be-
fore use. Other reagents were of analytical grade supplied by
Qingdao Chemicals Co (China).
Preparation of Polymer-Stabilized Platinum Colloids
[
27,30]
PVP-Pt was prepared by a reported method
in a form
of dark-brown homogeneous dispersion. Briefly, hexachloropla-
−
4
−3
tinic acid (1.00 × 10 mol) and PVP (0.222 g, 2.00 × 10 mol
as monomeric unit) were dissolved in a methanol-water (v/v =
1
/1) mixed solvent. The solution was refluxed for 3 h with vig-
orous stirring to make Pt colloidal nanoparticles, and then the
methanol-water solvent was evaporated by a rotary evaporator at
room temperature. The dry residue was redispersed in methanol
(designated as PVP-Pt) for catalytic applications.
Hydrogenation Reactions
Hydrogenation of chlorobenzene was carried out at 298 K un-
[
27]
der 0.1 MPa of hydrogen. 1.00 mmol chlorobenzene, 10.0 mL
−5
PVP-Pt methanol dispersion (containing 2.50 × 10 mol Pt)
with metal salts (usually as nitrates), 1.00 mmol octane (as an
internal standard for GC) were mixed, and totaling methanol
FIG. 1. TEM photograph of PVP-Pt colloidal nanoparticles.

INFLUENCE OF METAL IONS ON PLATINUM NANOCATALYSTS
701
and selectivity of PVP-Pt remained similar to that of the one modification of various metal cations to hydrogenation of cit-
−
with NaNO3 (entry 2). Obviously Cl species does not deacti- ronellal (3,7-dimethyl-6-octenal) over polymer-stabilized Pt and
+
+
+
vate the colloidal PVP-Pt catalyst in the hydrodechlorination of Ru colloidal catalysts. It was observed that Li , Na , and K
chlorobenzene, which is different from those reported[
may be due to a different catalyst used.
31,32]
; this did not affect the catalytic properties of PVP-Pt. Mg and Ca
2+
2+
increased a little on the selectivity and the activity of the cata-
lysts. Yang et al.[ reported that Na , K , and Al had little
influence on either the activity or the selectivity of the Pt col-
loidal catalysts in the hydrogenation of o-chloronitrobenzene
33]
+
+
3+
Modification of Main Group Metal Ions to the PVP-Pt
Catalysts
+
+
The influence of some main group metal ions of Na , K , (o-CNB) to o-chloroaniline (o-CAN). It is shown in Table 1 that
2+
2+
3+
Ca , Mg , and Al on the hydrogenation of chlorobenzene SnCl2 poisoned the catalyst (entry 8). As mentioned previously,
catalyzed by PVP-Pt was investigated and the results are listed this catalytic behavior affected by SnCl2 could be due to the
in Table 1. From Table 1, it can be seen that Na (entry 2) and introduction of Sn but not Cl . Yang et al. also found that
K (entry 6) increased a little on the activity of the catalysts Sn poisoned the catalyst in the hydrogenation of o-CNB over
with the selectivity to cyclohexane decreased; Ca (entry 7) the Pt cluster catalyst.
+
2+
−
[33]
+
2+
2+
Hirai et al.[ suggested that some carbonyl groups of PVP
14]
almost did not affect the activity but decreased the selectivity
to cyclohexane. The activity of the PVP-Pt colloidal catalysts coordinated to palladium atoms on the surface of the palladium
−
4
−4
increased from 8.6 × 10 (mol CB)/(mol Pt)·s to 9.6 × 10
mol CB)/(mol Pt)·s, but the selectivity to cyclohexane decreased dispersions, but also to impede the efficient adsorption of reac-
from 65.6% to 49.1% by using Mg ion as a modifier in the tants and desorption of products on the catalyst. The hydration
particles. Thus, PVP works not only to stabilize the colloidal
(
2+
3+
reaction system (entry 4). Among these cations, the most favor- enthalpy of the studied main group ions is in an order of Al
able influence on the activity and selectivity was obtained when (–4665 kJ/mol) > Mg (–1921 kJ/mol) > Ca (–1577 kJ/mol)
Al was used as a modifier. The conversion of chlorobenzene > Na (–406 kJ/mol) > K (–322 kJ/mol). From Table 1, it can
was enhanced remarkably from 77.5% to 92.6%, and the selec- be seen that the activity influenced by these ions is in a simi-
tivity for cyclohexane was increased from 65.6% to 79.8%. lar tendency: Al > Mg > Ca ≈ Na ≈ K . It indicates
In most catalytic hydrogenation reaction systems, the main that these ions can diminish the interaction of PVP with metal
group metal ions have little effect on the selectivity and activity colloids and thus reduce the inhibiting effect of PVP in that or-
2+
2+
3+
+
+
3+
2+
2+
+
+
[
16]
[26]
of metal catalysts. For example, Yu et al.
investigated the der. Although many mechanisms have been discussed, there
TABLE 1
Influence of metal ions on the hydrogenation of chlorobenzene over PVP-Pt colloidal catalysts
Selectivity (%)
4
Average rate × 10
No.
Catalyst
PVP-Pt
PVP-Pt-NaNO3
PVP-Pt-NaCl
PVP-Pt-Mg(NO3)2
PVP-Pt-Al(NO3)3
PVP-Pt-KNO3
PVP-Pt-Ca(NO3)2
PVP-Pt-SnCl2
(mol CB)/(mol Pt)·s
Conversion (%)
Cyclohexane
Benzene
1
2
3
4
5
6
7
8
9
8.6
9.0
9.2
9.6
10.3
9.1
8.7
0
7.8
0
3.3
4.3
8.0
0
77.5
81.1
83.0
86.8
92.6
82.1
78.6
0
70.0
0
29.2
38.4
72.0
0
65.6
59.1
57.0
49.1
79.8
47.1
50.0
0
38.1
0
58.2
33.4
56.4
0
34.4
40.9
43.0
51.0
20.2
52.9
50.0
0
62.0
0
41.8
66.6
43.6
0
PVP-Pt-Cr(NO3)3
PVP-Pt-MnCl2
10
11
12
13
14
15
16
17
PVP-Pt-Fe(NO3)3
PVP-Pt-Co(NO3)2
PVP-Pt-Ni(NO3)2
PVP-Pt-Cu(NO3)2
PVP-Pt-Zn(NO3)2
PVP-Pt-La(NO3)3
PVP-Pt-Pr(NO3)3
0
7.7
9.1
0
69.6
81.7
0
46.6
60.4
0
53.4
39.6
Reaction conditions: PH2 = 0.1 MPa, T = 298 K, V = 30 mL, chlorobenzene (CB) = 1 mmol, Pt = 2.5 × 10− mol, metal ion = 2.5 × 10−5
5
mol, reaction time = 10 h.

702
M. LIU ET AL.
is still no conclusive interpretation on these experiment facts.
Metal cations in different reaction system adsorbed on colloidal
particles have different modification effects to the particle’s sur-
face electronic structures; as a result alter their catalytic perfor-
mances differently.
Modification of Transition Metal Ions to the PVP-Pt
Colloidal Catalysts
Table 1 lists the hydrogenation results with the presence of
some conventional transition metal ions. It can be seen from
3
+
Table 1 that the activity dropped with the introduction of Fe
3
+ 2+
(
entry 11). Actually, Fe was reduced to Fe in the reac-
[
16]
2+
whereas the selectivity changed slightly. Ni (entry
tion,
1
3) did not affect the catalytic properties of the PVP-Pt col-
2+
loidal catalyst. The addition of Co (entry 12) poisoned the
PVP-Pt colloidal catalyst, decreased both the selectivity and
the activity of the catalyst. Such a situation was very differ-
FIG. 2. Modification of transition metal ions on the hydrogenation of
ent from the selective hydrogenation of citronellal to citronellol chlorobenzene over PVP-Pt colloidal catalysts: ( ꢀ) conversion of chloroben-
[
16]
2+
(
3,7- dimethyl-6-octene-1-ol), in which Co enhanced the zene, (◦) selectivity to cyclohexane.
selectivity of PVP-Pt colloidal catalyst from 44.5% to 98.5%.
3+
2+
2+
The metal cations (Fe , Co , Ni ) also increased both the configurations, which are quite stable or inert to redox process.
selectivity and the activity of PVP-Pt colloidal catalyst in the When PVP-Pt nanoparticles were covered by these ions, the cat-
selective hydrogenation of cinnamaldehyde to cinnamyl alco- alyst was poisoned. We reported previously[ that there was an
36]
hol.[ It was said that Fe , Co , and Ni could modify most weak interaction of PVP and metal cations and the stability con-
34]
3+
2+
2+
3+
2+
2+
of the colloidal catalysts to some extent. In the hydrogenation stants of PVP-Fe > PVP-Co > PVP-Ni , similar to main
of o-CNB over PVP-Pt colloidal catalysts, Fe , Co , and group ions, the weak interaction diminished the interaction of
Ni exerted favorable influences on both the activity and the PVP with metal colloids and decreased the inhibiting effect of
[
33]
3+
2+
2+
selectivity of the reaction. In the hydrogenation of o-CNB over PVP. Lower stability constant brought about stronger inhibiting
[
35]
PVP-stabilized ruthenium colloidal catalysts, the maximum effect of PVP.
3+
activity was obtained by using Fe ion as a modifier.
As shown in Table 1, Cr3 (entry 9) decreased the selectivity Modification of Lanthanide Ions to the PVP-Pt Catalysts
to cyclohexane with a slight effect on the activity of PVP-Pt.
The effects of lanthanide ions on the hydrogenation of
The result is similar to the hydrogenation of o-CNB catalyzed chlorobenzene over PVP-Pt colloidal catalysts are shown in
+
by PVP-Pt.[ With Mn (entry 10), Cu (entry 14) and Zn
33]
2+
2+
2+
3+
Table 1 (entries 16 and 17). Adding La decreased the selectiv-
(
entry 15) introduced, the PVP-Pt colloidal catalyst lose all the ity to cyclohexane compared with the neat Pt colloidal catalyst,
2+
3+
activity in the reaction system. It is well known that Zn and whereas the activity was slightly changed. Pr influenced little
Cu ion usually acted as poisons to a hydrogenation metal on both of the selectivity and the activity; it just acted as a spec-
catalyst. Actually, the addition of Zn and Cu ion almost tator ion. This is different from the findings of Han et al., who
inhibits the reaction in the hydrogenation of o-CNB to o-CAN studied the modification of metal ions to supported platinum cat-
and the selective hydrogenation of citronellal to citronellol over alysts in the selective hydrogenation of p-chloronitrobenzene.
2+
2+
2+
[37]
[16,33]
2+
3+
PVP-Pt colloidal catalysts.
However, Mn has different By introducing Pr into the reaction system, the selectivity
effect in other systems. It has little effect on either the selectivity to p-chloroaniline was enhanced despite the decrease of activ-
or the activity of Pt colloidal catalysts in the literature,[ but ity. This may due to a different reactant (chlorobenzene in this
enhanced both the conversion and the selectivity to citronellol work).
33]
[
16]
over PVP-Pt colloidal catalysts.
The results indicated that
most of the transition metal ions have inferior influences on Effects of the Amount of Al3 to the PVP-Pt Catalyst
+
the hydrogenation of chlorobenzene over the PVP-Pt colloidal
catalysts.
Among those studied cations, the most favorable influence
on the activity and selectivity was obtained by using Al . This
3+
The influence of some transition metal ions on the hydro- may be due to its high hydration enthalpy (–4665 kJ/mol), which
genation of chlorobenzene over PVP-Pt colloidal catalysts is makes it interact with PVP strongly to decrease the inhibiting
3
+
2+
summarized in Figure 2. With the introduction of Fe , Co , effect from the coordination of PVP to Pt particles. The influ-
2+
3+
and Ni , the selectivity and the activity of PVP-Pt increased; ence of molar ratio of Al /Pt on hydrogenation of chloroben-
but PVP-Pt was completely inactivated by Mn , Cu , and zene to cyclohexane was further investigated and the results are
Zn . It was known that Mn , Cu , and Zn have 3d or 3d
2+
2+
5
2+
2+
2+
2+
10
shown in Figure 3. When employing neat PVP-Pt colloid as the

INFLUENCE OF METAL IONS ON PLATINUM NANOCATALYSTS
703
thus, the insoluble Al3 covered the PVP-Pt nanoparticles and
+
then decreased the activity and selectivity.
CONCLUSIONS
The main group metal ions of IA and IIA, such as Mg2 and
+
+
K , can enhance the activity of PVP-Pt colloidal catalysts on the
hydrogenation of chlorobenzene and influence a little on the se-
lectivity to cyclohexane. However, most of the transition metal
2+
ions acted as poisons to the PVP-Pt catalyst, especially Cu ,
2+
2+
Zn , and Mn that lead to a complete loss of the catalytic activ-
ity. Lanthanide ions mainly decrease the selectivity of the cata-
lysts. In general, the catalytic properties of platinum clusters for
the hydrogenation of chlorobenzene to cyclohexane are remark-
ably affected by the metal cations. It is therefore suggested to re-
2+
2+
2+
2+
move some metal ions, especially Sn , Cu , Zn , and Mn ,
from wastewater for efficient catalytic hydrodechlorination.
FIG. 3. Molar ratio effect of Al3 /Pt in the selective hydrogenation of
+
3+
chlorobenzene to cyclohexane over PVP-Pt- Al : (ꢀ) conversion of chloroben-
zene, (◦) selectivity to cyclohexane.
REFERENCES
catalyst, 65.6% selectivity to cyclohexane with 77.5% conver-
sion of chlorobenzene was obtained. The incorporation of 0.2:1
1
. Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2002, 102, 4009–4092.
. Ghaffar, A.; Tabata, M.; Mazher, F.; Mashiatullah, A. Environ. Chem. Lett.
2012, 10, 171–176.
2
3+
3+
(molar ratio of Al to Pt) Al made the selectivity to cyclohex-
3
. Teevs, L.; Vorlop, K. D.; Pr u¨ ße, U. Catal. Commun. 2011, 14, 96–100.
ane reach 86.0% and the conversion 73.1%. When adding 0.5:1
3+
4. Jing, J.; Liu, M.; Colvin, V. L.; Li, W.; Yu, W. W. J. Mol. Catal. A: Chem.
011, 351, 17–28.
Al , the selectivity to cyclohexane and the conversion almost
reached their maximums as 92.4% and 77.9%, respectively. The
conversion (activity) did not change much when the molar ratio
2
5. Keane, M. Chemcatchem 2011, 3, 800–821.
6. Kim, P.; Kim, Y.; Kang, T.; Song, I.; Yi, J. Catal. Surv. Asia 2007, 11,
3+
of Al /Pt increased from 0.5:1 to 1:1, but dropped with more
49–58.
3
+
3+
7. Keane, M. J. Chem. Technol. Biotechnol, 2005, 80, 1211–1222.
Al , and the selectivity declined when Al /Pt ratio was higher
than 1:1. Detailed mechanism is unknown at this time, but under
investigation in the lab.
8
9
. Nangoi, I.; Kiyohara, P.; Rossi, L. Appl. Catal. B 2010, 100, 42–46.
. Kopinke, F., Angeles-Wedler, D.; Fritsch, D.; Mackenzie, K. Appl. Catal.
B 2010, 96, 323–328.
The variation of molar percentage of metal cation (Al3 as
+
1
0. Ukisu, Y. Appl. Catal. A 2008, 349, 229–232.
the example) in this system does not affect the activity and se- 11. Mekhaev, A.; Chupakhin, O.; Uimin, M.; Ermakov, A.; Pervova, M.; Gor-
bunova, T.; Mysik, A.; Saloutin, V.; Yatluk, Y. Russ. Chem. Bull. 2009, 58,
lectivity in the way of other PVP-stabilized metallic colloidal
1
321–1324.
2. Widegren, J. A.; Finke, R. G. J. Mol. Catal. A, Chem. 2003, 191, 187–
07.
3. Roucoux, A.; Schulz, J.; Patin, H. Chem. Rev. 2002, 102, 3757–3778.
catalysts, where the curves of activity and selectivity changed lit-
tle after reaching their maximum. In the selective hydrogenation
of o-CNB to o-CAN over PVP-Pt, the activity and the selectivity
1
1
2
2+
grew gradually with the increase of the addition of Ni . When 14. Hirai, H.; Chawanya, H.; Toshima, N. Reactive Polym. 1985, 3, 127–141.
2+
15. Han, M.; Liu, H. Macromol. Symp. 1996, 105, 179–183.
the molar ratio of Ni /Pt reached 6:1, the activity and the se-
lectivity reached their maximums, and changed little with more
1
6. Yu, W.; Liu, H.; Liu, M.; Liu, Z. React. Funct. Polym. 2000, 44,
1–29.
2
2+
[16]
2+
Ni [33]. For C O double bond, Yu et al. used Co as a
modifier in the hydrogenation of citronellal to citronellol over
1
7. Liu, M.; Mo, X.; Liu, Y.; Xiao, H.; Zhang, Y.; Jing, J.; Colvin, V. L.; Yu,
W. W. Appl. Catal. A: Gen. 2012, 439–440, 192–196.
PVP-Pt and PVP-Ru colloidal catalysts, respectively. A little 18. Liu, M.; Zhang, J.; Liu, J.; Yu, W. W. J. Catal. 2011, 278, 1–7.
2
+
3+
2+
19. Zuo, X.; Liu, H.; Guo, D.; Yang, X. Tetrahedron 1999, 55, 7787–7804.
amount of Co or Fe (e.g., Co :Pt = 0.05:1) made the ac-
2
2
2
2
0. Bray, R. H.; Adams, R. J. Am. Chem. Soc. 1927, 49, 2101–2106.
1. Maxted, E. B. Adv. Catal. 1951, 3, 129–178.
2. Ponec, V. Appl. Catal. A., Gen. 1997, 149, 27–48.
tivity and the selectivity increase promptly to very high values.
2+
When adding 0.2:1 Co , the selectivity to citronellol and the
conversion of citronellal reached their maximums as 100% and
3. Gallezot, P.; Richard, D. Catal. Rev.-Sci. Eng. 1998, 40, 81–126.
9.6%, respectively. More Co2+ did not decrease them although 24. Yu, W.; Liu, H.; An, X.; Ma, X.; Liu, Z.; Qiang, L. J. Mol. Catal. A: Chem.
9
1
999, 147, 73–81.
5. Yu, W.; Liu, H.; Liu, M.; Tao, Q. J. Mol. Catal., A: Chem. 1999, 138,
73–286.
the promotion effect in the PVP-Ru colloidal catalysts was not
as prominent as that of the PVP-Pt system.
2
2
In this paper, when adding too much Al3 to the hydrogena-
+
2
2
6. Yu, W. W.; Liu, H. J. Mol. Catal., A: Chem. 2006, 243, 120–141.
7. Liu, M. H.; Han, M. F.; Yu, W. W. Environ. Sci. Technol. 2009, 43,
2519–2524.
tion of chlorobenzene over the PVP-Pt catalysts, the solution of
Al was saturated and some Al was insoluble in the methanol,
3+
3+

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M. LIU ET AL.
2
2
3
3
8. Liu, M.; Wang, C.; Yu, W. W. J. Nanosci. Nanotechnol. 2010, 10, 32. Cesteros, Y.; Salagre, P.; Medina, F.; Sueiras, J. E.; Tichit, D.; Coq, B. Appl.
715–7720. Catal. B 2001, 32, 25–35.
9. Liu, M.; Zhang, J.; Han, M.; Liu, J. Synth. React. Inorg. Met.-Org. Nano- 33. Yang, X.; Liu, H. Appl. Catal. A 1997, 164, 197–203.
Met. Chem. 2010, 40, 785–789. 34. Yu, W.; Liu, H.; Tao, Q. Chem. Commun. 1996, 32, 1773–1774.
0. Yu, W.; Liu, M.; Liu, H.; Zheng, J. J. Colloid Interface Sci. 1999, 210, 35. Liu, M.; Yu, W.; Liu, H. J. Mol. Catal., A: Chem. 1999, 138, 295–303.
18–221. 36. Liu, M.; Yan, X.; Liu, H.; Yu, W. React. Funct. Polym. 2000, 44, 55–64.
1. Amorim, C.; Yuan, G.; Patterson, P. M.; Keane, M. A. J. Catal. 2005, 234, 37. Han, X.; Zhou, R.; Lai, G.; Zheng, X. Catal. Today 2004, 93–95,
68–281. 433–437.
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