Influence Type and Temperature of Activation on the Catalytic Activity of Derived Form of Au101 Nanocatalysts

Article abstract of DOI:10.1134/S0023158420020056

Abstract: Recently, gold nanoparticles attracted an increased attention due to unusual and somewhat unexpected catalytic properties especially pronounced in the oxidation of some organic compounds. Gold nanoparticles, which was immobilized on powder Norit^? activated carbon as a support (1.0 wt percent Au₁₀₁/AC) exhibited high activity and selectivity for benzyl alcohol oxidation particularly with the gold catalysts subjected to a specific type of activation and temperature. The interaction between Au₁₀₁ particles and its support was studied by measuring the catalytic activity and selectivity as a function of activation procedure. The first method included washing with a solvent (i.e., toluene) at elevated temperature, and/or followed by heat treatments at mild temperatures (i.e., 100 and 200°C for 3 h). The highest catalytic activity of benzyl alcohol oxidation was however obtained when gold catalysts were pre-washed with hot toluene at 100°C for 2 h followed by thermal treatment under vacuum. In these cases, the gold core diameters was ～3.5 nm. In a number of experiments, the reaction time was 3 h, whereas in other runs it was extended to 24 h. The conversion level of benzyl alcohol oxidation was affected by the type of activation and its temperature related to the gold particles size.

Full text of DOI:10.1134/S0023158420020056

ISSN 0023-1584, Kinetics and Catalysis, 2020, Vol. 61, No. 2, pp. 291–298. © Pleiades Publishing, Ltd., 2020.
Influence Type and Temperature of Activation on the Catalytic
Activity of Derived Form of Au101 Nanocatalysts
S. Ghadamgahi*
Department of Chemistry, East Tehran Branch, Islamic Azad University, Tehran, Iran
*e-mail: maghadamgahi@gmail.com
Received July 14, 2019; revised October 29, 2019; accepted November 5, 2019
Abstract—Recently, gold nanoparticles attracted an increased attention due to unusual and somewhat unex-
pected catalytic properties especially pronounced in the oxidation of some organic compounds. Gold
nanoparticles, which was immobilized on powder Norit® activated carbon as a support (1.0 wt % Au101/AC)
exhibited high activity and selectivity for benzyl alcohol oxidation particularly with the gold catalysts sub-
jected to a specific type of activation and temperature. The interaction between Au101 particles and its support
was studied by measuring the catalytic activity and selectivity as a function of activation procedure. The first
method included washing with a solvent (i.e., toluene) at elevated temperature, and/or followed by heat treat-
ments at mild temperatures (i.e., 100 and 200°C for 3 h). The highest catalytic activity of benzyl alcohol oxi-
dation was however obtained when gold catalysts were pre-washed with hot toluene at 100°C for 2 h followed
by thermal treatment under vacuum. In these cases, the gold core diameters was ∼3.5 nm. In a number of
experiments, the reaction time was 3 h, whereas in other runs it was extended to 24 h. The conversion level of benzyl
alcohol oxidation was affected by the type of activation and its temperature related to the gold particles size.
Keywords: activated carbon, activation Au101 particles, size effect, ligands removal, oxidation, benzyl alcohol
DOI: 10.1134/S0023158420020056
INTRODUCTION
ligands. Earlier, a number of solvents were applied in
ligand-removing by washing procedure and ensuing
effects on the catalytic activity of gold particles were
described earlier [1, 7, 8]. Lopez-Sanchez et al. used
washing procedure at 90°C for 1 h to remove PVA
ligands from supported gold catalysts and studied the
efficiency of different types of solvents, such as water,
tetrahydrofuran and ethanol. Pre-washed gold catalysts
with water solvent demonstrated full conversion for CO
oxidation [1]. In the same way, Anderson et al. utilized
hot toluene washing procedure at 100°C for 2 h to remove
PPh3 ligands from gold core particles/clusters to improve
interactions with TiO2 support [9].
Ligands are frequently used to protect some noble
metal particles like gold particles during synthesis, but
their presence can be detrimental to the catalytic
activity of nanocatalysts [1] because they shield the
gold cores from reactants [2, 3]. Many factors can
affect the catalytic activity of gold nanocatalysts, and
several studies demonstrated the importance of better
understanding of the catalyst activation conditions
effected through the ligands removal [4]. Although,
thermal treatments can be used to remove organic res-
idues from the core gold particles, they can also cause
an increase in the particle size [5, 6]. The key problems
that may emerge from the removal of the stabilizing
ligands include the loss of stability and agglomeration
of gold particles on the support during activation pro-
cess. Hutchings et al. enhanced the catalytic activity of
gold catalysts for benzyl alcohol oxidation by the use of
the catalysts and this effect was ascribed to the removal
of polyvinyl alcohol ligands from gold particles. How-
ever, TEM images showed that after the catalyst acti-
vation the gold particles aggregated and the gold core
diameter increased from 3 to 4.8 nm [1].
Heat treatments of gold catalysts can result in a
stronger interaction between Au particles and a sup-
port, and in this way change the activity of nanocata-
lysts [10]. For example, Turner and co-workers
showed that removal of stabilizing ligands by a thermal
treatment significantly increases the catalytic activity
of gold particles with gold core diameters about 1.5 nm
or even smaller [11]. The authors heated the gold cat-
alysts at 200°C under vacuum for 2 h to remove PPh3
from Au101 particles immobilized on silicon dioxide
and boron nitride. Later, heat treatment under vac-
uum at 200°C for 2 h of Au101 particles immobilized on
TiO2 was investigated by Anderson et al. who utilized a
synchrotron-based XPS technique [9]. The results
Solvents can be used to remove ligands establishing
equilibrium between free and coordinatively bound
Abbreviations: TEM, transmission electron microscopy;
HPLC, high-performance liquid chromatography.
291

292
GHADAMGAHI
confirmed that PPh3 detached from the gold particle gold catalysts for benzyl alcohol oxidation as well on
the effects of activation conditions on the size of gold
particles.
core became bonded (possibly in oxidized form) to the
support surface. This ligand removal strengthened the
interaction between gold particles and the TiO2 sup-
port [12]. It has been reported that the chemical nature
of the atmosphere used during activation can exert an
influence on the final structure and catalytic activity
of the supported gold particles [13–15]. Activations in
oxidative atmospheres, such as air, can remarkably
improve the catalytic activity of gold catalysts [10, 16].
Yuan et al. heated supported [Au(PPh3)(NO3)] and
[Au9(PPh3)8]3 in air flow to remove the PPh3 ligand.
The resultant materials were used as catalysts for low-
temperature CO oxidation. The Fourier-transform
extended X-ray absorption fine structure oscillations
technique was applied to verify the catalyst structure
[16]. Based on X-ray diffraction and TEM images, the
authors suggested that by removing ligands an intimate
contact between the gold nanocatalysts and reactants
was achieved. However, the air treatment following
the ligands removal invariably led to a substantial
growth of particle diameter from ∼1 to 25 nm [17].
By varying the activation temperature, it is possible
to have multiple conditions for the ligand removal
from the nanocatalyst surfaces [18–20]. These varia-
tions can have a pronounced effect on the properties of
the final material [6]. High-temperature activation has
been widely used to remove organic ligands, but its
main drawback is the facile sintering of metal particles
[21]. Yin et al. showed that the size of as-synthesized
gold particles supported on silica increased from 2.1 to
3.3, 4.5 and 4.8 nm following the activation in H2
reducing atmosphere at 300, 500 and 600°C, respec-
tively. The gold catalyst activated at 300°C, showed
full conversion in CO oxidation [21]. Hence, a signif-
icant decrease in the gold catalyst activity can be
related to the gold particles sintering at high activation
temperature [22]. Chang et al. reported a detailed
investigation into the effect of activation at tempera-
tures ranging from 100 to 475°C on 2.0 wt % gold cat-
alysts supported on Mg2AlO, made by a co-precipita-
tion method [23]. The result showed that samples
heated at 100°C were the most active catalyst for CO
oxidation [23]. Therefore, activation at mild tempera-
ture is preferred for the fabrication of structure-sensi-
tive gold catalysts because higher temperatures gener-
ally lead to the enhanced agglomeration phenomena
[13, 24–27].
EXPERIMENTAL
Materials and Apparatus
Dichloromethane, sodium borohydride, sodium
citrate, and chloroform were purchased from “Fisher
Scientific.” Toluene, tetraoctylammonium bromide,
triphenylphosphine, acetonitrile and sodium hydrox-
ide were purchased from “Merck.” Benzyl alcohol,
anisole, benzaldehyde, methyl benzoate and benzoic
acid were purchased from “Sigma-Aldrich.” Metha-
nol was purchased from “Fisher Chemical” and then
dried using activated alumina column. Research grade
O2, H2 and N2 gases were obtained from “BOC.”
1H NMR measurements were made using Agilent
MR 400 or Varian Anova 500 spectrometer to study
PPh3 groups in the gold nanoparticles [30]. In addi-
tion, a bright-field high-resolution transmission elec-
tron microscopy (TEM) was utilized to measure parti-
cle-size distribution. The average gold core diameter
was estimated by using TEM images of the gold cata-
lysts before and after the activation process that can
indirectly indicate the removal of capping agents
(PPh3) [31]. The TEM instrument was a Philips
CM20, operating at 200 kV and equipped with the
energy-dispersive spectrometer (EDS) for electron
probe microanalysis. Product mixtures were analyzed
by a Dionex high-performance liquid chromatography
(HPLC) system fitted with a Luna 5μ C18 reverse-
phase column and a UV detector.
Synthesis
Au101 particles were synthesized according to the
procedure earlier published by Wear et al. [30]. After
that, the gold catalysts were fabricated from pre-syn-
thesized Au101 particles, according to the method pre-
viously published by Lopez-Sanchez et al. [1]. That
involves mixing the specific amounts of Au101 particles
with powder Norit® activated carbon (BET: 813 m2/g)
at 200 mL of dichloromethane as a solvent.
Activations
Next, “as synthesized” 1.0 wt % Au101/AC catalysts
were activated using three methods [32, 33].
It is generally assumed that ligand removal is fairly
crucial for the efficient control of particles size of gold
supported on carbon [28]. Activity of gold particles
immobilized on activated carbon is also likely to
depend on the type of the treatment and activation
temperature [29]. The aim of this work was to address
the possibility to activate small Au nanocatalysts
through the removal of PPh3 ligands over a wide range
of various types of mild activations process. The main
According to the method (a) catalysts were washed
with 200 mL toluene at 100°C for 2 h and placed into
a 500 mL round-bottom flask fitted with a reflux con-
denser with stirring at 750 rpm. The mixture was then
allowed to cool to room temperature and then centri-
fuged, washed and dried under vacuum for one day.
Following the method (b) the solid powder gold
focus was put on the catalytic activity and selectivity of catalyst to be activated was placed in a Schlenk tube
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INFLUENCE TYPE AND TEMPERATURE OF ACTIVATION
293
2.8 0.2 nm
0
2
4
6
8
10 nm
Particle diameter, nm
Fig. 1. TEM image and micrograph of pre-washed Au /AC with toluene at 100°C for 2 h.
101
pre-heated by an aluminum heating block (200 2°C) could be related to the ability of hot toluene to remove
or oil bath (100 2°C) and then heated under vac- the organic ligands from the gold core particles. Addi-
uum, in O2, H2 and O2 followed by H2 at 100 and tionally, the TEM image of the washing procedure
(Fig. 1) shows that the average gold particles diameter
(i.e., “as-synthesized”) increased very slightly from
2.6 0.1 nm, as described by Ghadamgahi et al., to 2.8
0.2 nm after washing procedure [34]. Therefore,
aggregation of washed Au catalysts, if any, was negligi-
ble. Slight aggregation upon washing procedure was
previously reported for PPh3-protected gold parti-
cles/clusters immobilized on TiO2 [9] but the catalytic
activity of the activated gold catalysts was attributed to
gold crystallites with size about 3 nm [35, 36].
200°C for 3 h. After the thermal treatment, the catalyst
was cooled to room temperature and kept in a freezer
below –4°C.
In the (c) method, a sequence of stage (a) was fol-
lowed by the stage (b). The washing procedure was
adopted from Anderson et al., who demonstrated
removal of PPh3 stabilizing ligands by washing gold
catalysts in toluene at 100°C for 2 h, in the (a) proce-
dure [9]. A washing procedure and following heating
treatments in (c) procedures were undertaken accord-
ing to a protocol similar to that described by Lopez-
Sanchez et al., who demonstrated removal of PVA
from gold particles immobilized on TiO2 [1].
Thermal treatments of the gold catalysts were stud-
ied using various environments (i.e., vacuum, O2, H2
and O2–H2) at 100 and 200°C for 3 h to remove PPh3
ligands from Au101 particles. The gold core diameters
determined before and after the heat treatments were
different due to the ligand removal. Donoeva et al.
demonstrated that activated gold catalysts cannot
agglomerate when the ligands were still bound to the
gold cores [31]. The average diameter of gold core
increased after the PPh3-stabilized gold particles were
subjected to activation. A reason may lie in the
removal of PPh3 from Au nanoparticles. In addition,
the results of the catalysts heated in different atmo-
spheres for 24 h reaction time showed varying conver-
sions (Table 1). However, conversions close to 100%
made it hard to choose conditions for the best treat-
ment. Some thermal treatments of the gold catalysts
were clearly detrimental, resulting in catalysts incapa-
ble of achieving full conversions after 24 h of reaction
time. These included heat treatment in O2‒H2 at
200°C (58% conversion), in H2 at 100°C (14% conver-
sion) and in H2 at 200°C (20% conversion). Most of
the activated Au101 catalysts selectively produced
methyl benzoate as the main product; those that
favored production of benzoic acid were heated in H2
and in H2–O2. Benzaldehyde appeared as the minor
product for the gold catalysts heated in H2 at 100 and
200°C.
Catalytic Tests
The impact of activations on the catalytic activity
of the gold catalysts was studied for benzyl alcohol oxi-
dation under the mild reaction conditions according to
the earlier published protocol by Ghadamgahi et al.
[34]. The reaction conditions are as follows: benzyl
alcohol (2.5 mmol) as a reactant, K2CO3 (2.5 mmol)
as a base, methanol (25 mL) as a solvent, a reaction
temperature of 80°C, O2 pressure of ∼5 bar, 750 rpm
stirring, 50 mg of 1.0 wt % Au101/AC catalysts, reaction
times of 24 and 3 h and a stainless-steel pressurized
mini reactor. The products were analyzed by a HPLC
system.
RESULTS AND DISCUSSION
The effect of various types of activation processes
was studied with the main emphasis on the catalytic
activity and selectivity of 1.0 wt % Au101/AC catalysts
for benzyl alcohol oxidation. The pre-washing process
improved the catalytic activity of “as-synthesized”
Au101/AC catalysts from ~70 to ~100%, while the
selectivity to methyl benzoate vs. benzoic acid
increased from ~55 : 45 to ~67 : 33. The enhancement
It is difficult to explain the effect of average gold
of conversion and selectivity after washing process particle diameters on benzyl alcohol conversion.
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GHADAMGAHI
Table 1. The effect of different heat treatments atmospheres (vacuum, O2, H2 and O2–H2) and heating temperatures (100 and
200°C for 2 h) on the catalytic activity (C) and selectivity (S) of Au101/AC for benzyl alcohol oxidation during 24 h reaction time
S, %
Heat treatments
V*
T, °C
C, %
benzaldehyde
benzoic acid
methyl benzoate
200
100
200
100
200
100
200
100
99
98
95
98
14
20
58
96
0
0
26
24
40
32
55
54
66
33
74
76
60
68
34
35
33
67
O2
H2
0
0
11
11
1
O2–H2
0
* V—Heat treatment under vacuum.
Available literature indicates that the gold particles
Figure 3 shows some TEM images of catalysts
larger than 3 nm can be active gold entities for benzyl washed and then heat treated at 100°C for 2 h of
alcohol oxidation [35, 37]. It is clear that the average Au101/AC in O2, H2, O2–H2 and under vacuum with
gold particle size is not the only element to be consid-
ered and other elements, such as size distribution and
gold dispersion are also important. Figure 2 shows that
the average gold particle diameter increased from ∼2.6 nm
for the non-activated sample [34] to approximately
5.4, 5.6, 6.6 and 4.3 nm for the samples subjected to
heat treatments in O2, H2, O2–H2 and under vacuum,
respectively. These changes indicate that particle aggre-
gation was associated with partial removal of PPh3
ligands [9]. In addition, this could be due to the nature of
carbon as a support, which may drastically influence the
gold particles size after heat treatments [38].
the gold core approximately 4.4, 4.9, 5 and 3.5 nm,
respectively. Similarly, Ghadamgahi et al. subjected
Au catalysts with ~3 nm gold core diameter to pre-
washing procedure followed by heat treatment in static
air of at 100°C for 3 h [34]. TEM images proved that
the average gold particles bigger than 3 nm can be
active gold catalysts for benzyl alcohol oxidation [34,
35, 37]. It appears that pre-washing before heat treat-
ments may stabilize Au particles on the carbon support
and decrease the degree of agglomeration [39].
According to procedures suggested for kinetic
investigations of catalytic reactions it is convenient to
measure the initial rate of a reaction from a fixed, ini-
tial reactant concentration to minimize complications
due to reversible reactions and the inhibition by prod-
ucts [40, 41]. In order to be able to distinguish the rel-
ative merits of different reactions, it is important that
the reactions are reasonably well advanced without
being “saturated” (i.e., without having proceeded to
full conversion). Correspondingly, in this work all
other reaction parameters were kept the same as before
(i.e., 24 h reaction time), and then the reaction time
was reduced to 3 h to ensure conversions significantly
lower than 100%. It was hoped that this approach
serves to reveal the best catalysts.
The results of gold catalysts washed with hot tolu-
ene and then heated in different atmospheres at 100
and 200°C during 24 h reaction time showed a range of
conversions (Table 2). Although in the presence of
many catalysts full conversions were reached, some
activation procedures for gold catalysts were clearly
unsuccessful resulting in catalysts incapable of achiev-
ing full conversions after 24 h reaction time. These
included washing followed by heat treatments at
200°C in O2 (20% conversion), in H2 (53% conver-
sion) and in O2–H2 (49% conversion). Most of the
activated gold catalysts selectively produced methyl
benzoate as the main product. Those that favored ben-
zoic acid were washed with hot toluene and followed
by thermal treatments in O2–H2 at both temperatures.
Benzaldehyde appeared as the minor product for the
gold catalysts when the catalysts were washed and then
heated in O2, H2 and in O2–H2 at 100, 200 and at
200°C, respectively (2 h). The highest selectivity
towards benzaldehyde (21%) at benzyl alcohol conver-
sion of 94% was achieved with the gold catalysts pre-
Table 3 shows the initial rates of benzyl alcohol oxi-
dation, conversion and selectivity towards detectable
products found for reactions conducted for 3 h in the
presence of the gold catalysts from the same batches as
were used for reactions carried out for 24 h (as dis-
cussed above). No conversion was observed for sam-
ples activated by heat treatment alone at 100°C in O2,
H2 and under vacuum, while conversion was very low
washed with hot toluene followed by heat treatment in (5% conversion) for a sample treated only in O2‒H2.
O2 at 100°C for 2 h.
Low or moderate conversions were achieved within
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INFLUENCE TYPE AND TEMPERATURE OF ACTIVATION
4.3 0.2 nm
295
0
0
0
2
4
6
8
10 12 14
5 nm
(а)
Particle diameter, nm
5.4 0.2 nm
2
4
6
8
10 12 14
5 nm
(b)
Particle diameter, nm
5.6 0.3 nm
2
4
6
8 10 12 14 16 18
5 nm
(c)
Particle diameter, nm
6.6 0.3 nm
0
2
4
6
8 10 12 14 16 18
5 nm
(d)
Particle diameter, nm
Fig. 2. TEM images (a)–(d) and micrographs of heat treatments of Au /AC (a), in O (b), H (c), and O ‒H (d) at 100°C for 3 h.
101
2
2
2
2
3 h, when using the gold catalysts heated in O2, H2, ∼2 : 1 : 3, 3 : 1 : 4, 5 : 1 : 7 and 2 : 1 : 3, respectively. The
samples with small (~2.8 nm) and large (~5 nm) aver-
age gold particle sizes revealed low activities at a reac-
tion time of 3 h. Exceptions were the catalysts washed
with hot toluene and then heated under vacuum at
200°C (2 h), which provided 44% conversion. In gen-
eral, the selectivity for benzaldehyde was much higher
when a reaction time of 3 h instead of 24 h was used.
O2‒H2 and under vacuum without pre-washing pro-
cess. Of the samples heated at 200°C, conversion lev-
els of 3, 5, 12 and 5% were achieved with catalysts
heated at 200°C for 2 h in O2, H2, O2–H2 and under
vacuum, respectively. All types of activations produced
catalysts selective to methyl benzoate rather than to
benzoic acid. In some cases, in which conversions
were low, benzaldehyde was one of the major prod-
In addition, Table 3 exhibited the results obtained
ucts. When the gold catalyst was heated at 200°C for by combining activations for Au101/AC catalysts. It is
2 h in O2, H2, O2‒H2 and under vacuum proportions
noteworthy that activation of the gold catalysts at a
of aldehyde and benzoic acid to methyl benzoate were higher temperature (200°C) brought about systemati-
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GHADAMGAHI
Table 2. The effect of different types of activation procedure (washing followed by heat treatment under vacuum, in O2, H2
and in O2–H2) and heating temperatures (100 and 200°C) on the catalytic activity (C) and selectivity (S) of Au101/AC for
benzyl alcohol oxidation (24 h reaction time)
S, %
Activations
W* + V
T, °C
C, %
benzaldehyde
benzoic acid
methyl benzoate
200
100
200
100
200
100
200
100
100
99
20
94
53
95
74
0
0
29
24
60
44
60
28
90
86
71
76
23
35
29
61
6
W + O2
W + H2
17
21
11
11
4
W + O2–H2
94
4
10
* W—Washing.
cally lower conversions except for the W + O2 activa- causing excessive particle sintering, which would be
otherwise detrimental to the efficiency of benzyl alco-
hol oxidation [33].
The gold catalysts subjected to the most successful
activation showed selectivity for methyl benzoate, with
methyl benzoate to benzoic acid ratios of ~3 : 1. Of the
methods investigated in this paper, the catalysts pre-
washed with hot toluene and exposed to mild heat
tion (15% conversion) and W + O2‒H2 activation
(21% conversion). The highest (91%) conversion was
achieved using the Au catalyst that was heated under
vacuum at 100°C after pre-washing with hot toluene.
This gold catalyst had one of the smallest average par-
ticle sizes (Fig. 3a) in series studied (ca. 3.5 0.1 nm
prior to reaction). Therefore, the use of similar treat-
ment serves to activate the gold nanoparticles without
3.5 0.1 nm
0
2
4
6
10 nm
(а)
Particle diameter, nm
0
6
2
6
4
6
6
10 nm
(b)
Particle diameter, nm
Fig. 3. TEM images (a)‒(d) and micrographs of pre-washed and followed by heat treatments of Au /AC under vacuum (a), in
101
O (b), H (c) and in O ‒H (d) at 100°C.
2
2
2
2
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INFLUENCE TYPE AND TEMPERATURE OF ACTIVATION
297
Table 3. Benzyl alcohol oxidation catalyzed by Au101/AC (with different types of activation methods at 100 and 200°C)
during 3 h reaction time
S, %
Activations
T, °C
C, %
benzaldehyde
benzoic acid
methyl benzoate
W
V
100
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
3
0
47
0
15
0
38
0
5
37
0
15
0
48
0
O2
H2
0
3
35
0
12
0
53
0
0
5
36
31
32
0
8
56
50
48
74
87
0
O2–H2
W + V
3
19
20
26
13
0
12
91
44
0
0
W + O2
W + H2
W + O2–H2
0
15
5
4
12
15
11
0
84
69
47
0
16
42
0
1
0
21
4
21
75
treatments are promising materials to fabricate the forming gold catalysts, the highest catalytic activity
most active gold catalysts for benzyl alcohol oxidation. and selectivity were achieved when the gold catalysts
were pre-washed with hot toluene and activated under
vacuum at 100°C for 3 h (91% selectivity) with methyl
CONCLUSIONS
benzoate as the main product. By contrast, treatments
that did not involve prewashing were found to be rela-
tively ineffective. The results of this study indicate that
conversion in the presence of Au101 immobilized on
activated carbon can be remarkably influenced by the
treatments conditions. For an inert support like car-
bon, the other important contributions came from the
type, temperature of activations and their combination
with pre-washing process with hot toluene.
The structural properties of the catalytic activities
of supported gold particles for benzyl alcohol oxida-
tion depend on the choice of the different types of
treatment and temperature of activations. Activations
including a hot toluene washing procedure and heat-
ing under vacuum conditions as a rule resulted in full
conversions within a reaction time 24 h. However,
some activation processes proved to be far from suc-
cessful resulting in catalysts incapable of achieve full
conversions after 24 h of reaction time.
ACKNOWLEDGMENTS
Carbon-supported gold nanoparticles including
untreated, washed with the hot toluene or activated
only through thermal treatment, were inactive after
3 h of reaction time. However, the materials pre-
washed with hot toluene with subsequent activation
Authors like to acknowledge the University of Canter-
bury for the facilities.
under mild conditions produced
a significant
REFERENCES
enhancement in the catalytic activity for benzyl alco-
hol oxidation. In this reaction, the conversion level
was affected by the gold nanoparticle size. The gold
particles after activation treatments were larger than
the gold cores in the pristine particles, meaning that
sintering occurred during treatment. For the best-per-
1. Lopez-Sanchez, J.A., Dimitratos, N., Hammond, C.,
Brett, G.L., Kesavan, L., White, S., Miedziak, P., Tiru-
valam, R., Jenkins, R.L., Carley, A.F., Knight, D.,
Kiely, C.J., and Hutchings, G.J., Nat. Chem., 2011,
vol. 3, p. 551.
KINETICS AND CATALYSIS Vol. 61 No. 2 2020

298
GHADAMGAHI
2. Schmid, G., Pugin, R., Meyer-Zaika, W., and Simon, U., 22. Dondur, V., Lampa, S., and Vucelic, D., J. Chem. Soc.
Eur. J. Inorg. Chem., 1999, vol. 1999, p. 2051.
3. Schmid, G., Chem. Soc. Rev., 2008, vol. 37, p. 1909.
Faraday Trans. 1, 1983, vol. 79, p. 1633.
23. Chang, C.T., Liaw, B.J., Chen, Y.P., and Chen, Y.Z., J.
Mol. Catal. A: Chem., 2009, vol. 300, p. 80.
4. Zou, X., Qi, S., Suo, Z., An, L., and Duan, X., Chin. J.
24. Abd El-Moemen, A., Karpenko, A., Denkwitz, Y., and
Catal., 2004, vol. 25, p. 153.
Behm, R.J., J. Power Sources, 2009, vol. 190, p. 64.
5. Beck, A., Horváth, A., Schay, Z., Stefler, G., Kop-
pány, Z. Sajó, I., Geszti, O., and Guczi, L., Top. Catal.,
2007, vol. 44, p. 115.
6. Maciejewski, M., Fabrizioli, P., Grunwaldt, J.-D.,
Sven, B.O., and Baiker, A., Phys. Chem. Chem. Phys.,
2001, vol. 3, p. 3846.
25. Minicò, S., Scirè, S., Crisafulli, C., and Galvagno, S.,
Appl. Catal., B, 2001, vol. 34, p. 277.
26. Kung, H.H., Kung, M.C., and Costello, C.K., J.
Catal., 2003, vol. 216, p. 425.
27. Lee, S.J., Gavriilidis, A., Pankhurst, Q.A., Kyek, A.,
Wagner, F.E., Wong, P.C.L., and King, L.Y., J. Catal.,
2001, vol. 200, p. 298.
7. Yin, H., Wang, C., Zhu, H., Overbury, S.H., Sun, S.,
and Dai, S., Chem. Commun., 2008, p. 4357.
28. Chiang, C.W., Wang, A., and Mou, C.-Y., Catal. To-
8. Abad, A., Corma, A., and García, H., Chem. Eur. J.,
day, 2006, vol. 117, p. 220.
2008, vol. 14, p, 212.
29. Bulushev, D.A., Yuranov, I., Suvorova, E.I., Buffat, P.A.,
9. Anderson, D.P., Alvino, J.F., Gentleman, A., Qa-
htani, H.A., Thomsen, L., Polson, M.I.J., Metha, G.F.,
Golovko, V.B., and Andersson, G.G., Phys. Chem.
Chem. Phys, 2013, vol. 15, p. 3917.
and Kiwi-Minsker, L., J. Catal., 2004, vol. 224, p. 8.
30. Weare, W.W., Reed, S.M., Warner, M.G., and Hutchi-
son, J.E., J. Am. Chem. Soc., 2000, vol. 122, p. 12890.
31. Donoeva, B.G., Ovoshchnikov, D.S., and Golovko, V.B.,
10. Zhang, R.R., Ren, L.H., Lu, A.H., and Li, W.C.,
ACS Catal., 2013, vol. 3, p. 2986.
Catal. Commun., 2011, vol. 13, p. 18.
32. Wang, L.C., He, L., Liu, Y.M., Cao, Y., He, H.Y., and
Fan, K.N., Zhuang, J.H., J. Catal., 2009, vol. 264,
p. 145.
33. Pritchard, J., Piccinini, M., Tiruvalam, R., He, Q.,
Dimitratos, N., Lopez-Sanchez, J.A., Morgan, D.J.,
Carley, A.F., Edwards, J.K., Kiely, C.J., and Hutch-
ings, G.J., Catal. Sci. Technol., 2013, vol. 3, p. 308.
11. Turner, M., Golovko, V.B., Vaughan, O.P.H., Ab-
dulkin, P., Berenguer-Murcia, A., Tikhov, M.S., John-
son, B.F.G., and Lambert, R.M., Nature, 2008,
vol. 454, p. 981.
12. Bond, G.C., Thompson, D.T., Catal. Rev. Sci. Eng.,
2001, vol. 641, p. 319.
13. Park, E.-D. and Lee, J.S., J. Catal., 1999, vol. 186, p. 1.
34. Ghadamgahi, S., Williamson, B.E., and Golovko, V.B.,
14. Tsubota, S., Cunningham, D.A.H., Bando, Y., and
Catal. Lett., 2016, vol. 146, p. 1027.
Haruta, M., Stud. Surf. Sci. Catal., 1995, vol. 91, p. 227.
35. Oliveira, R.L., Kiyohara, P.K., and Rossi, L.M., Green
15. Ho, K.Y., and Yeung, K.L., J. Catal., 2006, vol. 242,
Chem., 2009, vol. 11, p. 1366.
p. 131.
36. Nielsen, I.S., Taarning, E., Egeblad, K., Madsen, R.,
and Christensen, C.H., Catal. Lett., 2007, vol. 116,
p. 35.
16. Yuan, Y., Kozlova, A.P., Asakura, K., Wan, H., Tsai, K.,
and Iwasawa, Y., J. Catal., 1997, vol. 170, p. 191.
17. Kilmartin, J., Molecular Gold Clusters as Precursors to
Heterogeneous Catalysts Chemistry, London: University
College London, 2010, p. 243.
37. Su, F.-Z., Ni, J., Sun, H., Cao, Y., He, H.-Y., and
Fan, K.-N., Chem. Eur. J., 2008, vol. 14, p. 7131.
38. Porta, F., Prati, L., Rossi, M., Coluccia, S., and Mar-
18. Gardner, S.D., Hoflund, G.B., Schryer, D.R., and
tra, G., Catal. Today, 2000, vol. 61, p. 165.
Upchurch, B.T., J. Phys. Chem., 1991, vol. 95, p. 835.
39. Qi, C., Okumura, M., Akita, T., and Haruta, M., Appl.
19. Maciejewski, M., Fabrizioli, P., Grunwaldt, J.D.,
Becker, O.S., and Baiker, A., Phys. Chem. Chem. Phys.,
2001, vol. 3, p. 3846.
Catal., A, 2004, vol. 263, p. 19.
40. Sergio, N., Roberto, M., Mercedes, A., and Hermene-
gildo, G., ChemSusChem, 2011, vol. 4, p. 650.
20. Ghadamgahi, S., Lat. Am. Appl. Res., 2018, vol. 48, p. 15.
41. Wang, Z.J., Brown, C.J., Bergman, R.G., Raymond, K.N.,
and Toste, F.D., J. Am. Chem. Soc., 2011, vol. 133,
p. 7358.
21. Yin, H., Ma, Z., Overbury, S.H., and Dai, S., J. Phys.
Chem. C, 2008, vol. 112, p. 8349.
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2020