Unravelling the effect of Lewis acid properties of the support on the performance of palladium based catalyst in hydrogenation and hydrogenolysis reactions

Article abstract of DOI:10.1016/j.cattod.2013.11.068

A catalyst, Pd/B(OH)₃, based on the cheap and environmentally friendly support, was synthesized by using the impregnation method with the aim of investigating the Lewis acid effect on hydrogenation and hydrogenolysis reactions. The sample was reduced at 353 K under hydrogen flowing and characterized by various physico-chemical techniques, such as BET, TPR, XRD, TEM, FESEM and XPS. Its catalytic performance, in hydrogenation reactions of carbonyls and hydrogenolysis of aromatic alcohols, carried out at 0.1 MPa H₂ pressure and 323 K, was investigated. It was demonstrated that Pd/B(OH)₃ is active using cyclohexane as solvent and the reactivity depends on the steric hindrance of the substrate. Conversely, in ethanol, boric acid dissolves and does not influence catalytic reactions.

Full text of DOI:10.1016/j.cattod.2013.11.068

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Unravelling the effect of Lewis acid properties of the support on the
performance of palladium based catalyst in hydrogenation and
hydrogenolysis reactions
∗
Maria Grazia Musolino , Francesco Mauriello, Concetta Busacca, Rosario Pietropaolo
Dipartimento DICEAM, Università Mediterranea di Reggio Calabria, Loc. Feo di Vito, I-89122 Reggio Calabria, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A catalyst, Pd/B(OH) , based on the cheap and environmentally friendly support, was synthesized by
3
Received 3 October 2013
Received in revised form 8 November 2013
Accepted 10 November 2013
Available online xxx
using the impregnation method with the aim of investigating the Lewis acid effect on hydrogenation and
hydrogenolysis reactions. The sample was reduced at 353 K under hydrogen flowing and characterized
by various physico-chemical techniques, such as BET, TPR, XRD, TEM, FESEM and XPS. Its catalytic per-
formance, in hydrogenation reactions of carbonyls and hydrogenolysis of aromatic alcohols, carried out
at 0.1 MPa H2 pressure and 323 K, was investigated. It was demonstrated that Pd/B(OH)3 is active using
cyclohexane as solvent and the reactivity depends on the steric hindrance of the substrate. Conversely,
in ethanol, boric acid dissolves and does not influence catalytic reactions.
Keywords:
B(OH)3
Palladium catalyst
Carbonyl compounds
Hydrogenation
Aromatic alcohols
©
2014 Elsevier B.V. All rights reserved.
1
. Introduction
commercial availability, environmental compatibility, cheap cost
and facility to handle. It forms white needle-like crystals in which
B(OH)3 units, linked together by hydrogen bonds, form layers of
The increasing knowledge of chemical factors involved in a cat-
alytic reaction points to the most appropriate choice of a metal
support, in order to: (i) drive the selectivity towards a preferred
product; (ii) make possible a process, otherwise unlikely, such as
reduction of aliphatic carbonyls, in presence of palladium systems,
only possible by using Pd/CoO, Pd/NiO or Pd/Fe O co-precipitated
nearly hexagonal symmetry, stable until 448 K, when B(OH) trans-
3
forms to HBO . It is moderately soluble in water and hydroxylic
2
solvents and insoluble in apolar or hydrocarbon solvents and has
been also used as green, selective and recyclable catalyst [4–6]. It
behaves as very strong Lewis acid so that, in aqueous solution, the
low acidity observed stems from the acceptor properties of boron
[7].
Heterogeneous palladium based catalysts have been widely
investigated in hydrogenation [8,9] and hydrogenolysis [10–12]
reactions. However, studies focused on the role of Lewis acidity of
the support, with the exception of zeolites [13,14], on the catalytic
properties of palladium have been much less explored.
Therefore, in the present work, a Pd/B(OH)3 catalyst was pre-
pared by incipient wetness impregnation method and tested in
catalytic hydrogenation and hydrogenolysis reactions, involving
organic molecules bearing oxygen containing groups: carbonyls
or aromatic alcohols. In order to highlight the acidic properties of
B(OH)3 ethanol and cyclohexane were used as solvents and results
compared. In ethanol B(OH)3 dissolves and the acidic properties
of the support vanish since alcohol remains linked to the cen-
tral boron, affording an inactive tetrahedral structure so that the
catalytic activity depends only on the bare palladium. A detailed
investigation of the physico-chemical properties of the catalyst
by nitrogen adsorption (BET), temperature-programmed reduction
2
3
catalysts [1].
Lewis acids catalyze organic reactions such as the Friedel–Crafts
process or the Fries rearrangement, as well as petrochemical pro-
cesses aimed to produce bulk and base chemicals. Use of Lewis acids
supported on “inert” carriers of large surface area is an useful proce-
dure since the system is heterogeneous and facilitates the catalyst
recovery, reactivation and reuse [2]. The hard and soft acids and
bases (HSAB) general theory, formulated by R. Pearson, offers, in
the case, the basic principles to interpret the behaviour of Lewis
acids in catalytic reactions [3].
There is, however, another route for highlighting the contri-
bution of a strong solid Lewis acid in catalysis: to use it directly
as support, so taking advantage of both the activation activity of
the metal and the properties of the acidic support. On this regard,
boric acid, B(OH) , is a typical support to be used, because of its
3
∗ Corresponding author. Tel.: +39 0965 875312; fax: +39 0965 875248.
E-mail address: mariagrazia.musolino@unirc.it (M.G. Musolino).
0
920-5861/$ – see front matter © 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2013.11.068
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
palladium based catalyst in hydrogenation and hydrogenolysis reactions, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2013.11.068

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Table 1
(
(
TPR), X-ray diffraction (XRD), transmission electron microscopy
TEM), field emission scanning electron microscopy (FESEM) and
Main characteristics of B(OH)3 supported palladium catalyst.
X-ray photoelectron spectroscopy (XPS) is also included.
Catalyst
Pd loading (wt%)
BET surface
area (m /g)
Mean particle
size (nm)a
2
2
. Experimental
Nominal
5
XRF
3.8
Pd/B(OH)3
2.2
7.5
2.1. Catalyst preparation
a
Mean particles size from TEM.
5
% Pd/B(OH)3 was prepared by incipient wetness impregna-
tion of the commercial support B(OH) (Aldrich, purity 99.99%,
SBET = 1.9 m /g) with an acetone solution of palladium (II) acetyl-
3
2.3. Catalytic tests
2
acetonate, Pd(acac) , (Aldrich, purity 99%). After impregnation, the
sample was dried under vacuum at 353 K for 1 day and then reduced
for two hours, at the same temperature, under flowing hydrogen.
2
Liquid phase hydrogenation of both aliphatic and aromatic car-
bonyls and hydrogenolysis of aromatic alcohols were carried out
at 0.1 MPa partial hydrogen pressure in a 100 ml five-necked batch
reactor fitted with a reflux condenser. The reaction temperature
was maintained at a constant value (323 K) by circulation of sil-
icone oil in an external jacket connected with a thermostat. The
temperature of the reaction mixture was monitored by placing a
thermocouple inside the vessel. The catalyst (∼300 mg), previously
activated under H2 at 353 K for 2 h, was added to 25 ml of ethanol
(Fluka, 99.8% analytical grade) or cyclohexane (Sigma–Aldrich, 99%
analytical grade), and reduced in “situ” at 323 K for 1 h under H2
flow. Then, a solution of the organic compound (carbonyl or aro-
matic alcohol) in ethanol or cyclohexane (0.6 M, 15 ml), containing
tetradecane as internal standard, was added through one arm of the
flask. The reaction mixture was stirred with a magnetic stirrer head
coupled with a gas stirrer at a rate of 500 rpm. A TPR measurement,
carried out after reduction of the catalyst at 353 K, demonstrated
that palladium was completely reduced.
Preliminary runs, performed with different amounts of catalyst
and stirring rate, indicate that, under the experimental conditions
adopted, the reaction was carried out in absence of external and
internal mass-transfer limitations.
The progress of the reaction was followed by analyzing a suffi-
cient number of samples, withdrawn periodically from the reaction
mixture. Products analysis was performed with a gas chromato-
graph (HP model 5890), equipped with a wide-bore capillary
column (CP-WAX 52 CB, 50 m, i.d. = 0.53 mm) and a flame ionization
detector. Quantitative analysis was carried out by calculating the
areas of the chromatographic peaks with an electronic integrator
2.2. Catalyst characterization
BET surface area was determined by N2 adsorption desorp-
tion isotherms at the liquid nitrogen temperature by using a
Micromeritics Chemisorb 2750 instrument. The composition of the
flow gas was N :He = 30:70. Samples were outgassed under flowing
2
nitrogen for 1 h at 473 K, before measurements.
Temperature-programmed reduction (TPR) was employed to
evaluate the reduction profile of the catalyst. 50 mg of the dried
sample were placed in a quartz tube reactor and heated from 298
to 700 K with a constant heating rate of 10 K/min and exposed to
3
a flow of 5 vol.% H /Ar mixture (20 cm /min). H consumption was
2
2
monitored by using a thermal conductivity detector (TCD). A molec-
ular sieve cold trap (maintained at 193 K) and a tube filled with KOH,
placed before the TCD, were used to block water and CO , respec-
2
tively. The calibration of signals was made by injecting in the carrier
a known amount of H2.
Powder X-ray diffraction (XRD) patterns were acquired, at room
temperature, on a Philips X-Pert diffractometer, by using the Ni ␤-
filtered Cu-K␣ radiation (ꢀ = 0.15418 nm). Data were collected in
◦
◦
◦
the 2ꢁ range 10 –80 with a scanning rate of 0.5 /min. Diffraction
peaks were compared with those of standard compounds reported
in the JPCDS Data File.
Field Emission Scanning Electron Microscopy (FESEM) pictures
of the reduced sample were collected on a High Resolution FESEM
instrument (LEO 1525) equipped with a Gemini Field Emission
Column. The catalyst particles size and the relative morphology
were analyzed by transmission electron microscopy (TEM), using
a JEOL 2000 FX instrument operating at 200 kV and directly inter-
faced with a computer for real-time image processing. Particles size
distribution was obtained by counting several hundred particles
visible on the micrographs of the sample. The average value of the
(
HP model 3396).
2
.4. Analytical determination of boric acid in ethanol solution
In order to verify the complete dissolution of boric acid in
ethanol, 300 mg of catalyst were poured in 40 ml of C H5OH and
2
maintained at 323 K for 30 min. Then, after filtration of the solid,
2
.5 g of sorbitol, dissolved in water, were added and the proton
concentration ensuing from the reaction:
-
B
CHOH
CHOH
HC
HC
O
O
O
O
CH
CH
+
B(OH)3
+
2
+
H
+
3 H O
2
was determined by means of a conductometric titration, using a
standard solution 0.1 M of NaOH [15].
metal particles size was calculated by the following equation:
ꢀ
nidi
d¯ =
ꢀ
ni
3. Results and discussion
where n is the number of particles of diameter d .
i
i
3.1. Catalyst characterization
X-ray photoelectron spectroscopy (XPS) analysis was performed
using a Physical Electronics GMBH PHI 5800-01 spectrometer,
equipped with a monochromatic Al K␣ X-ray source. Binding ener-
gies (BE) values were referred to the carbon C 1s peak at 284.8 eV.
Physical and chemical properties of Pd/B(OH)3 were analyzed
by several techniques, including BET, TPR, XRD, XRF, TEM, FESEM
and XPS.
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
palladium based catalyst in hydrogenation and hydrogenolysis reactions, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2013.11.068

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3
300
360
420
480
540
600
660
Temperature (K)
Fig. 1. H2-TPR profile of B(OH)3 supported palladium catalyst.
Table 1 reports the real wt% of palladium, determined by X-ray
fluorescence analysis, the surface area and the mean particle size
value.
Fig. 3. TEM microphotographs of reduced B(OH)3 supported palladium catalyst.
The TPR profile of the fresh Pd/B(OH)3 catalyst is illustrated in
Fig. 1. A single peak, centred at ∼380 K (value close to the reduc-
energy value of 193 eV (B 1s) is found, as expected, for an oxidated
boron in a trigonal structure [18].
tion temperature of Pd(acac) , used as precursor in the catalyst
2
2+
◦
preparation), referring to the Pd → Pd reduction, is detected.
Characterization data point to the following features:
Fig. 2 shows the XRD patterns of the reduced Pd/B(OH) catalyst.
3
In addition to diffraction peaks related to the support structure, a
diffraction pattern at 2ꢁ = 40.1 , corresponding to the most intense
(
i) metal-support interactions in Pd/B(OH) are scarce and, in any
case, of poor importance;
3
◦
diffraction line of the (1 1 1) plane of metallic palladium is observed.
◦
◦
Furthermore, diffraction patterns at 2ꢁ = 46.8 and 68.2 are clearly
noticed and ascribed to diffraction lines relative to the (2 0 0) and
◦
(
2 2 0) plane of Pd , respectively.
TEM microphotographs of the catalyst reveal that palladium
particles are not homogeneously distributed and are poorly con-
trasted with respect to the matrix (Fig. 3). Therefore a reliable size
distribution cannot be obtained whereas an approximate average
metal particle size is calculated and reported in Table 1. FESEM
micrograph (Fig. 4) of reduced Pd/B(OH)3 shows a “star shape”
structure of the sample, depending on strong intermolecular hydro-
gen bonds that symmetrically link boric acid molecules.
Fig. 5 reports XPS plots, in the Pd 3d and B 1s binding energy (BE)
region, of the fresh and reduced Pd/B(OH)3 catalyst. The Pd 3d5/2
BE value, on the reduced Pd/B(OH)3 sample, is found at 335.0 eV,
as expected for metal Pd particles not interacting with the support
[
16,17] and is in accordance with TPR and XRD data. The binding
Pd
B(OH)
3
10
20
30
40
2
50
(degree)
60
70
80
Fig. 2. XRD patterns of reduced B(OH)3 supported palladium catalyst.
Fig. 4. FESEM images of reduced B(OH)3 supported palladium catalyst.
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
palladium based catalyst in hydrogenation and hydrogenolysis reactions, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2013.11.068

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3d
5/2
Pd 3d
B 1s
3d
3/2
Pd°
B(OH)
3
H , 353 K
2
2+
B(OH)
3
Pd
RT
345
342
339
336
333
196
194
192
190
Binding Energy (eV)
Fig. 5. XPS plots, in the Pd 3d and B 1s binding energy region, of 5% Pd/B(OH)3 specimens: (down) fresh sample; (up) sample after reduction at 353 K for 2 h under H2.
(
ii) agglomerates of palladium particles occur on the surface, as
expected from the very low surface area of B(OH)3;
100
1
-phenylethanol
1
-phenylethanone
(
iii) the symmetric distribution of boric acid molecules (star shape
structure), linked together through hydrogen bonds, makes the
support, through the trigonal central boron, suitable for Lewis
interactions with hard bearing groups reacting molecules. This
point is of remarkable interest, since, as XPS data confirm, in
solid B(OH)3 the trigonal structure is maintained so that the
Lewis acidity can be effectively expressed.
ethylbenzene
8
0
0
6
40
20
0
3.2. Catalytic activity
3.2.1. Reduction of carbonyl compounds
The reduction of carbonyl compounds (see Scheme 1) was car-
0
40
80
120
160
200
ried out in ethanol and cyclohexane at 323 K and 0.1 MPa H2
pressure. Preliminary results indicate that no reaction occurs by
using B(OH)3 alone.
Time (min)
Fig. 6. Composition-time plot of the hydrogenation reaction of 1-phenyethanone
A typical composition against time plot for the hydrogena-
tion reaction of 1-phenylethanone is shown in Fig. 6. Further
hydrogenolysis of the corresponding reduction products, aromatic
over 5% Pd/B(OH)3 at 323 K and 0.1 MPa H2 pressure, using ethanol as solvent.
sorbitol, dissolved in an equal volume of water. Furthermore, the
Lewis activity should be drastically reduced, in the case, since
C2H5OH should coordinate the central boron of B(OH)3 as an
analogous reaction in water suggests [7].
On the other hand, as expected, no hydrogenation reaction
occurs on using the filtered solution containing only boric acid and
carbonyl molecules.
alcohols, does also occur. Initial reaction rates, r , expressed as
i
moles of substrate/grams of palladium per second, are reported
in Table 2. It clearly appears that, in ethanol, benzaldehyde reacts
faster than 1-phenylethanone, whereas, in cyclohexane, the
activity of both carbonyls is levelled. Indeed, in alcohol B(OH)3
completely dissolves, as inferred from a conductometric acid–base
titration (see Section 2.4), carried out on a typical solution,
obtained after filtration of the solid, added with an excess of
Table 2
Activity of 5% Pd/B(OH)3 catalyst in carbonyl compounds hydrogenation at 323 K
and 0.1 MPa of H2 pressure, using ethanol and cyclohexane as solvent.
O
OH
5
Substrate
ri (mol/gPd s) × 10
R(H)
R(H)
Pd/B(OH)3
+
H2
Ethanol
Cyclohexane
Pentanal
Benzaldehyde
Pentan-2-one
u.d.
27.2
u.d.
10.9
u.d.
11.6
u.d.
10.8
(
R = alkyl group)
1-Phenylethanone
Scheme 1. Reaction pathway of carbonyl compounds hydrogenation on Pd/B(OH)3.
u.d. = undetectable value.
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
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5
OH
R
Table 3
Activity of 5% Pd/B(OH)3 catalyst in aromatic alcohols hydrogenolysis at 323 K and
0.1 MPa of H2 pressure, using ethanol and cyclohexane as solvent.
Pd/B(OH)3
R
+
H2
+
H O
2
5
Substrate
ri (mol/gPd s) × 10
Ethanol
Cyclohexane
(
R = H, CH , C H )
3 6 5
Benzyl alcohol
9.2
6.4
1.0
51.6
0.9
0.2
1-Phenylethanol
Scheme 2. Reaction pathway of aromatic alcohols hydrogenolysis on Pd/B(OH)3.
Diphenylmethanol
In principle carbonyls adsorption modes on
surface mainly occurs through the following configurations
a palladium
100
80
60
40
20
0
benzyl alcohol
toluene
benzaldehyde
[
19]:
and the ꢂ structure should be involved in catalytic reduction [1].
Therefore, in ethanol, the activity can be attributed to the
intrinsic steric hindrance of benzaldehyde lower than that of 1-
phenylethanone. Conversely, in cyclohexane, the Lewis interaction
of boric acid with the carbonylic oxygen is the main factor that
contributes to level the reactivity. Data included in Table 2, and
referring to cyclohexane, indicate that no reduction occurs with
aliphatic carbonyls, pentanal or pentan-2-one. It is well known
that transition metals, such as Pt, Ru and Rh hydrogenate both
0
10
20
30
40
Time (min)
Fig. 7. Composition-time plot of the hydrogenolysis reaction of benzyl alcohol over
% Pd/B(OH)3 at 323 K and 0.1 MPa H2 pressure, using cyclohexane as solvent.
5
discussed) and cyclohexane, where the Lewis acid effect is particu-
larly important, is considered. In this context data in ethanol are to
be regarded only as ancillary information to understand the boric
acid influence in hydrogenolysis reactions in cyclohexane. Data
of Table 3 indicate that r (cyclohexane) > r (ethanol) for benzyl
C
C and C O double bonds and Os and Ir are the most active
catalysts towards carbonyl hydrogenation [20–23]. Furthermore,
i
i
oxidated metal species (Sn2+, Fe , Fe , Ge ) on a surface of a
2+
3+
4+
alcohol and r (cyclohexane) < r (ethanol) for the more sterically
i
i
noble metal, acting as Lewis acids, may promote activation of the
hindered 1-phenylethanol and diphenylmethanol. In principle,
hydrogenolysis of aromatic alcohols can occur through one of two
possible paths [28]: (i) a SN2-type mechanism, in which the surface
palladium bonded hydrogen displaces the hydroxyl group bonded
to the carbon atom, or (ii) a more stepwise mechanism starting
with the dissociation of the C OH bond and temporary bonding of
the OH group and the hydrocarbon residue on the Pd surface, fol-
lowed by the transfer of a metal-bonded H atom to the unsaturated
hydrocarbon intermediate. Therefore, the higher activity of the
less hindered benzyl alcohol, in cyclohexane, has to be attributed
to a beneficial effect due to a possible coordination of the hydroxyl
moiety to boric acid that highlights the electrophilic ability of the
alcoholic carbon. The same interaction abundantly slows down
the reactivity of the more sterically hindered 1-phenylethanol and
diphenylmethanol acting as an additional steric hindrance factor.
Conversely, in ethanol, the boric acid contribution to the steric
effect, in aromatic alcohol hydrogenolysis, is absent. Therefore, a
better balance between steric and electronic factors occurs. Gen-
erally speaking, this is perfectly on line with the view that radical
substitutions, in catalytic reactions, depend both on electronic and
steric effects and activity values depend on the relative importance
of the one and/or the other factor.
C
O bond “via” the lone pair of oxygen [24–26]. The behaviour
of palladium systems is completely different since they generally
catalyze hydrogenation of aromatic carbonyls but lack to reduce
the analogous aliphatic [19,27]. Only recently bimetallic species
Pd–Co or Pd–Ni and Pd/Fe O systems were found able to promote
3
4
reduction of both aromatic and aliphatic aldehydes and ketones
and a theory, looking to the mechanism of activation of carbonyl
compounds on a palladium surface, was proposed in order to
explain the particular behaviour of palladium catalysts [1]. Data,
reported in Table 2, clearly suggest that aliphatic carbonyls are not
reduced, thus indicating that the strong hard acidity of B(OH)3 is
not sufficient to properly modify the electronic properties of the
carbonyl bond (ꢂ bonding and ꢂ* antibonding energy levels) so
that C O activation of aliphatic carbonyls on the palladium surface
is not allowed.
3.2.2. Reduction of aromatic alcohols
Scheme 2 reports the reaction pathway of aromatic alcohols
hydrogenolysis carried out, both in ethanol and cyclohexane, at
23 K and 0.1 MPa H2 pressure. Preliminary results indicate that
no hydrogenolysis occurs in presence of boric acid alone.
3
Table 3 and Fig. 7 report initial reaction rates, r , and a
i
typical composition against time plot, respectively. In both
solvents activity values follow the order benzyl alcohol > 1-
phenylethanol > diphenylmethanol, as it would be expected if the
steric hindrance of alcohols plays a role in determining the activity.
4. Conclusions
A 5 wt% palladium catalyst supported on the low cost, com-
mercial and environmentally compatible carrier, boric acid,
was prepared by impregnation method and characterized by
BET, TPR, XRD, FESEM, TEM and XPS. The catalytic performance
of Pd/B(OH)3 was investigated in the reduction of carbonyl
However, in order to highlight the effect of B(OH) , by itself, on the
3
reactivity of aromatic alcohols, a comparison between rate values
in ethanol (where no boric acid rate effect operates, as previously
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
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M.G. Musolino et al. / Catalysis Today xxx (2014) xxx–xxx
compounds and aromatic alcohols, carried out at 323 K and
.1 MPa H2 pressure, using ethanol and cyclohexane as solvents.
The reported results indicate that the substrate structure affects
the reactivity of the catalyst in cyclohexane, whereas is abun-
dantly reduced in ethanol where boric acid dissolves and should
coordinate an alcohol molecule. Furthermore, the strong hard
[9] F. Mauriello, M. Armandi, B. Bonelli, B. Onida, E. Garrone, J. Phys. Chem. C 114
42) (2010) 18233–18239.
10] C.-T. Wu, K.M.K. Yu, F. Liao, N. Young, P. Nellist, A. Dent, A. Kroner, S.C.E. Tsang,
Nat. Commun. 3 (2012) 1050.
(
0
[
[11] M.G. Musolino, L.A. Scarpino, F. Mauriello, R. Pietropaolo, Green Chem. 11
2009) 1511–1513.
12] M.G. Musolino, L.A. Scarpino, F. Mauriello, R. Pietropaolo, ChemSusChem 4
2011) 1143–1150.
(
[
(
Lewis acid B(OH)3 is not able to contribute to activate the C
O
[13] S.T. Homeyer, Z. Karpi n´ ski, W.M.H. Sachtler, J. Catal. 123 (1990) 60–73.
[14] R. Sasikala, A.R. Shirole, V. Sudarsan, V.S. Kamble, C. Sudakar, R. Naik, R. Rao,
S.R. Bharadwaj, Appl. Catal. A: Gen. 390 (2010) 245–252.
15] I.M. Kolthoff, E.B. Sandell, E.J. Meehan, S. Bruckenstein, Quantitative Chemical
Analysis, 4th ed., Macmillan Publishing Co., 1969.
group of aliphatic carbonyls on the palladium surface, whereas the
Pd/B(OH)3 system is very active in the hydrogenation of benzyl
alcohol in cyclohexane. The high reactivity has to be attributed to
a beneficial effect due to coordination of the hydroxyl moiety to
boric acid that highlights the electrophilic ability of the alcoholic
carbon.
[
[16] M.L. Cubeiro, J.L.G. Fierro, J. Catal. 179 (1998) 150–162.
[
17] N. Iwasa, S. Masuda, N. Ogawa, N. Takezawa, Appl. Catal. A: Gen. 125 (1995)
45–157.
1
[
18] P.Z. Si, E. Brück, Z.D. Zhang, O. Tegus, K.H.J. Buschow, W.S. Zhang, J.C.P. Klaasse,
F.R. De Boer, Phys. B 353 (2004) 1–8.
[
[
[
19] F. Delbecq, P. Sautet, J. Catal. 152 (1995) 217–236.
20] P. Gallezot, D. Richard, Catal. Rev. Sci. Eng. 40 (1998) 81–126.
21] U.K. Singh, M.A. Vannice, J. Catal. 199 (2001) 73–84.
References
[1] M.G. Musolino, C. Busacca, F. Mauriello, R. Pietropaolo, Appl. Catal. A: Gen. 379
[22] P. Reyes, H. Rojas, G. Pecchi, J.L.G. Fierro, J. Mol. Catal. A: Chem. 179 (2002)
(
2010) 77–86.
293–299.
[
[
[
[
2] A. Corma, H. Garcia, Chem. Rev. 103 (2003) 4307–4365.
3] R.G. Pearson, J. Am. Chem. Soc. 85 (1963) 3533–3539.
4] M.K. Chaudhuri, S. Hussain, J. Mol. Catal. A: Chem. 269 (2007) 214–217.
5] G.C.M. Kondaiah, L. Amarnath Reddy, K. Srihari Babu, V.M. Gurav, K.G. Huge, R.
Bandichhor, P. Pratap Reddy, A. Bhattacharyaa, R. Vijaya Ananda, Tetrahedron
Lett. 49 (2008) 106–109.
6] A. Rostami, J. Akradi, Tetrahedron Lett. 51 (2010) 3501–3503.
7] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann, Advanced Inorganic
Chemistry, 6th ed., Wiley, Chichester, 1999.
[23] P. Mäki-Arvela, J. Hájek, T. Salmi, D.Yu. Murzin, Appl. Catal. A: Gen. 292 (2005)
1–49.
[24] Z. Poltarzewski, S. Galvagno, R. Pietropaolo, P. Staiti, J. Catal. 102 (1986)
190–198.
[25] S. Galvagno, A. Donato, G. Neri, R. Pietropaolo, Catal. Lett. 8 (1991) 9–14.
[26] E. Tronconi, C. Crisafulli, S. Galvagno, A. Donato, G. Neri, R. Pietropaolo, Ind. Eng.
Chem. Res. 29 (1990) 1766–1770.
[27] S. Sato, R. Takahashi, T. Sodesawa, M. Koubata, Appl. Catal. A: Gen. 284 (2005)
247–251.
[
[
[
8] H.-U. Blaser, C. Malan, B. Pugin, F. Spindler, H. Steiner, M. Studer, Adv. Synth.
Catal. 345 (2003) 103–151.
[28] N. Thakar, N.F. Polder, K. Djanashvili, H. van Bekkum, F. Kapteijn, J.A. Moulijn,
J. Catal. 246 (2007) 344–350.
Please cite this article in press as: M.G. Musolino, et al., Unravelling the effect of Lewis acid properties of the support on the performance of
palladium based catalyst in hydrogenation and hydrogenolysis reactions, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2013.11.068