Selective hydrogenation of cinnamaldehyde on nickel nanoparticles supported on titania: Role of catalyst preparation methods

Article abstract of DOI:10.1039/c4cy01379d

With nickel acetate as the precursor, 15% (w/w) Ni/TiO₂ (P-25) catalysts have been prepared by using four different methods, namely, direct impregnation (IM), deposition-precipitation (DP) with urea and chemical reduction using hydrazine hydrate (HH) and glucose (GL) as reducing agents. XRD, hydrogen chemisorption, TEM and TPR analyses reveal that smaller Ni crystallites, 8-12 nm in size, are obtained by adopting HH & GL methods compared to 15-20 nm crystallites obtained by using IM and DP methods. The nature of metal-support interactions (MSI) varies depending on the method of preparation. XPS studies reveal the presence of residual Ni²⁺ ions along with the Ni metal. All the catalysts exhibit good conversion of cinnamaldehyde (CAL) (in methanol, at 20 Kg cm^-2 H₂ pressure and 80-140 °C) and selectivity to cinnamyl alcohol (COL)/hydrocinnamaldehyde (HCAL) up to 1 h, beyond which further hydrogenation of COL to hydrocinnamyl alcohol (HCOL) occurs. The catalysts prepared by HH & GL display higher CAL conversion and selectivity to COL. Conversion of HCAL to HCOL proceeds at a slower rate compared to that of COL to HCOL. Introduction of HCAL along with CAL as a feed increases selectivity to HCOL, while introduction of COL in the same manner decreases selectivity to HCAL. Infrared spectra of CAL adsorbed on the catalysts reveal surface bonding through CC and CO groups. The steric hindrance due to adsorption of COL and the presence of small amounts of Ni²⁺ favour adsorption of CAL through the CO group leading to higher selectivity to COL.

Full text of DOI:10.1039/c4cy01379d

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Selective hydrogenation of cinnamaldehyde on nickel
nano particles supported on titania- Role of catalyst
preparation methods
Cite this: DOI: 10.1039/x0xx00000x
Murthiyamma Gengatharan Prakasha,b, Rajaram Mahalakshmyb, Konda
Received ,
Accepted
Ramaswamy Krishnamurthya and Balasubramanian Viswanathan,a,
*
DOI: 10.1039/x0xx00000x
With nickel acetate as the precursor, 15% (w/w) Ni/TiO2(P-25) catalysts have been prepared by four
different methods, namely, direct impregnation (IM), deposition precipitation (DP) with urea and by
chemical reduction, using hydrazine hydrate (HH) and glucose (GL) as reducing agents. XRD, hydrogen
chemisorption, TEM and TPR analyses reveal that smaller Ni crystallites, 8-12 nm in size, are obtained
by adopting HH & GL methods compared to 15-20 nm crystallites by IM and DP methods. Nature of
metal support interactions (MSI) vary depending on the method of preparation. XPS studies reveal the
presence of residual Ni2+ ions along with Ni metal. All the catalysts exhibit good conversion of
cinnamaldehyde (CAL) (in methanol, at 20 Kg/cm2 H2 pressure, 80-140°C) and selectivity to cinnamyl
alcohol (COL) / hydrocinnamaldehyde (HCAL) up to 1hr, beyond which, further hydrogenation of COL
to hydrocinnamyl alcohol (HCOL) occurs. Catalysts prepared by HH & GL display higher CAL
conversion and selectivity to COL. Conversion of HCAL to HCOL proceeds at a slower rate compared
to that of COL to HCOL. Introduction of HCAL along with CAL as feed increases selectivity to HCOL,
while introduction of COL in the same manner decreases selectivity to HCAL. Infra-red spectra of CAL
adsorbed on the catalysts reveal surface bonding through C=C and C=O groups. Steric hindrance due to
adsorption of COL and the presence of small amounts of Ni2+ favour adsorption of CAL through C=O
group leading to higher selectivity to COL.
www.rsc.org/
Key words: Nickel nano particles, Chemical reduction, Titania, Selective hydrogenation,
Cinnamaldehyde, C=O activation
manifest in different modes of adsorption of CAL and in the
selectivity displayed by different crystal planes exposed (facet
selectivity), are related to the nature of the active metal. While a
7-17
Introduction
number of reports
attribute activity and COL selectivity to the
Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl
alcohol (COL) is a challenging proposition, as it involves the
competitive hydrogenation of carbonyl double bond vis-à-vis
thermodynamically favourable hydrogenation of olefinic double
bond.1 Design of suitable catalysts and adopting appropriate reaction
conditions are the two key factors to be addressed. A number of
noble metal (Pt, Pd, Ir, Ru, Rh and Os), non-noble metal (Fe, Co, Ni,
Cu), as well as bimetallic (noble and non-noble) catalysts on
different supports (carbon, alumina, silica & titania etc.,) are known
to be effective for this conversion.2-4 In general, Os, Ir, Ru, Pt, Co &
Cu are reported to be selective for the formation of COL, while, Rh,
Pd & Ni towards hydrocinnamaldehyde (HCAL) and hydrocinnamyl
alcohol (HCOL). A number of parameters, like, the nature of the
active metal, its surface structure and exposed crystal planes, method
of catalyst preparation, characteristics of the support, solvent
(polarity and solubility of hydrogen), reaction conditions and
additives/promoters/second element used could influence the activity
and selectivity.5,6 Electronic as well as geometric factors, that
metal nano particle size and shape, a recent publication by Zhu and
18
Zaera
has concluded that the selectivity is independent of the
particle size within a narrow range of 1.25 to1.5 nm Pt nano particles
supported on silica. Hence the final word on this front is yet to
emerge.
From the process economics point of view, it is always
19
desirable to develop non-noble metal based catalysts. Lin et al.
have reported that the addition of Ir to Ni/TiO2 brings in several
changes, like, formation of bimetallic Ni-Ir species, the reducibility
of Ni2+ is improved, the electronic structure of Ni is modified and
hydrogen spill over is promoted. The improvement in activity of Ni-
Ir/TiO2 vis- a-vis Ni/TiO2 is attributed to these changes. Ni2P
supported on SiO2 20 Cu-Ni based hydrotalcites,21 layered Zn-Ni-Cu-
Al hydrotalcites,22 Co-Al and Ni-Al based hydrotalcites23 are some
of the non-noble metal based catalysts explored for this reaction.
Earlier work24 in this laboratory has shown that supported cobalt
catalysts, especially on titania, display high activity and good
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selectivity for COL. However, arriving at non-noble metal based temperature, centrifuged, washed with anhydrous ethanol and dried
catalysts with maximum activity and selectivity remains a challenge. at 60ºC for 24h.
Unlike the noble metals, Co, Ni & Cu based catalysts are
Method 4 Chemical reduction by D-Glucose (GL) 27
characterized by relatively strong metal support interactions (SMSI)
which influence the degree of reduction, metal dispersion and the
0.74 g of nickel acetate and 40 ml of D-glucose solution
evolution of the active phase. Metal support interactions are to be (0.15M) were mixed and stirred for 30 min at room temperature. 10
moderated to a desirable extent, by adopting suitable methods of ml of liquor ammonia was added drop-wise to the mixture.
preparation, so as to maximize the activity and selectivity. We have Refluxing the mixture for 5 h at 80ºC turned its colour to black
therefore, attempted to address these issues through a series of indicating reduction of Ni2+ ions to Ni metal, which was confirmed
investigations on nickel based catalysts, which are active for by UV spectroscopic analysis (Fig.1). 1 g of TiO2 (P25) was added
selective hydrogenation of α-β unsaturated aldehyde like CAL. Since to the solution containing Ni nano particles and stirred for 2h. The
the desired characteristics of supported Ni catalysts evolve during mixture was cooled to ambient temperature, centrifuged, washed
the preparation, as the first step, influence of different preparation with anhydrous ethanol and dried at 60ºC for 24h.
methods on the characteristics and performance supported Ni
Both HH and GL catalysts were pre-reduced in hydrogen gas
catalysts has been investigated. For this investigation, Ni (15% w/w) flow at 300°C for two hours. All characterization and hydrogenation
loaded on titania (P-25), a well-known reactive support, has been experiments were carried out with pre-reduced catalysts.
selected.
2.2 Characterization of catalysts
2. Experimental
Quantitative estimation of nickel contents in the finished
2. 1 Preparation of catalysts
catalysts were carried out by XRF, after due calibrations. Powder X-
ray diffraction patterns for the catalysts were recorded by Rigaku
P25 TiO2 (Evonik), Ni(CH3COO)2.4 H2O (CDH), NaOH
Miniflex II diffractometer, using Cu-Kα (=0.15418 nm) in 2Ө range
of 10º to 80º and a scan rate of 3º/min.
(SRL),Hydrazine Hydrate, Poly ethylene glycol, 400 Urea, D-
glucose (all from Merck), Methanol, Ethanol, Methanol (all from
Temperature Programmed reduction (H2-TPR) and hydrogen
Qualigens) and Cinnmaldehyde (ALDRICH), were used as such.
pulse chemisorption studies were carried out on Micromeritics
Autochem II 2920 chemisorption analyser. Catalysts by IM & DP
methods were calcined in air at 450°C and the catalysts by HH and
GL methods at 300°C, prior to TPR experiments. 50 mg of catalyst
was pre-treated at 300 ºC in high purity Ar gas (25cc/min) for 1 h
and then cooled to room temperature in Ar flow. The gas was
changed in 10 % H2 in Ar (25cc/min) at room temperature. After the
stabilization of the baseline TPR was started from RT to 700º C with
a heating rate 10º C/ min.
Four different methods were adopted for the incorporation of
nickel on to the support titania.
Method 1 Impregnation (IM)
0.74 g of nickel acetate was dissolved in 20 ml of water with
continuous stirring for 30 min. at room temperature, followed by
addition of 1 g of TiO2 (P25). The slurry was refluxed for 5 h at
80ºC, cooled to room temperature, centrifuged, washed with
anhydrous ethanol and dried at 60ºC for 24h. The catalyst was
calcined at 450ºC for 4 h in air and then pre-reduced at 400ºC for 4 h
in hydrogen gas flow.
Ni metal surface area measurements were performed by H2
pulse chemisorption. 50 mg of catalysts were pre-treated at 300 ºC in
high puity Ar gas (25cc/min) for 1 h and then cooled to room
temperature under Ar flow. The catalysts were reduced (at 400º C
for IM & DP catalysts and 300°C for HH &GL catalysts) for 2 h
under 10 % H2/Ar flow, cooled down to RT under Ar. H2 pulses
were injected with Ar as carrier gas, until the eluted peak area of
consecutive pulses was constant.
Method 2 Deposition Precipitation with urea (DP)25
0.74 g of nickel acetate and 1 g of TiO2 were mixed in 20 ml of
water and stirred for 30 min at room temperature. 0.5 g of urea was
added to the mixture and refluxed for 5 h at 80ºC. The slurry was
cooled at room temperature, centrifuged, washed with anhydrous
ethanol and dried at 60ºC in 24 h. The catalyst was calcined at 450ºC
for 4 h in air and then pre-reduced at 400ºC for 4 h in hydrogen gas
flow.
Transmission electron microscopic (TEM) investigations on the
pre-reduced catalysts were studied on a CM 20 Phillips transmission
electron microscope with an acceleration voltage of 120 KV.
CAL in vapour phase was adsorbed on self-supported disc of
the catalysts at 120°C in the IR gas cell attached to Perkin-Elmer
FT-IR unit. After equilibration, the sample was cooled to room
temperature, excess vapour evacuated and spectra of adsorbed CAL
were recorded.
Method 3 Chemical reduction by Hydrazine Hydrate (HH) 26
0.74 g of nickel acetate and 1.2 g of Poly ethylene glycol were
dissolved in 20 ml of anhydrous ethanol and stirred for 30 min at
room temperature. 1.5 ml of 0.1M NaOH in ethanol was added drop-
wise, followed by 8 ml of hydrazine hydrate. The mixture, after
refluxing for 5h at 80ºC, changed to black in colour, indicating the
reduction to Ni metal and confirmed by UV spectroscopic analysis
(Fig1). 1 g of TiO2 (P25) was added to the solution containing Ni
nano particles and stirred for 2h. The mixture was cooled to ambient
X-ray photoelectron spectra of the catalysts were recorded
using Omicron Nanotechnology instrument with Mg Kα radiation.
The base pressure of the analysis chamber during the scan was 2*10-
10 millibar. The pass energies for individual scan and survey scan are
20 and 100 eV, respectively. The spectra were recorded with step
width of 0.05 eV. The data were processed with the Casa XPS
2 | J. Name., 2012, 00, 1-3
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program (Casa Software Ltd, UK), and calibrated with reference to
the adventitious carbon peak (284.9 eV) in the sample.
2.3 Reaction studies
Hydrogenation reactions were performed in liquid phase, in a
100 ml Parr reactor (Model-4848). The autoclave was charged with
150 mg of pre-reduced catalyst, 1.2 g of cinnamaldehyde and 16 ml
of methanol. After purging first with nitrogen (three times) and then
with hydrogen (three times) the autoclave was pressurized with
hydrogen to the desired value of 20 Kg/cm2 at 298K. The reaction
was performed at 120º C for 1 h with stirring at 600 rpm. No
increase in conversion was observed at stirring rates higher than 600
rpm indicating that at this rate mass transfer limitations could be
ruled out. Actual pressure during reaction was 23 Kg/cm2. Further
experimental details on reaction studies are given in ESI-1. The
reaction products were separated by filtration and analysed on Perkin
Elmer Clarus-500 GC with ZB-1 capillary column and FID detector
Fig. 2 XRD patterns for the catalysts in reduced state: a-IM, b-DP, c-
HH and d-GL methods.
Table 1 lists the physico-chemical properties of the catalysts. Nickel
contents estimated by XRF method match closely with the expected
values. XRD patterns for all the four catalysts in reduced state are
shown in Fig.2. Along with the d-lines for P-25-titania, two major
lines corresponding to Ni metal with fcc structure,(JCPDC #870712)
at 2θ values at 44.4- 44.6° and 51.8° (corresponding to (111) and
(200) planes respectively) are observed. Absence of d-lines due to
NiO indicates nearly complete reduction to Ni metal in all the four
catalysts. However, presence of residual NiO, at levels below the
detection limits of XRD, could not be ruled out.
3. Results and discussion
XRD patterns for the catalysts prepared by IM and DP methods
indicate the presence of NiO and titania P-25 phases after drying and
calcination in air at 450°C. Low temperature chemical reduction of
Ni2+ ions to Ni metal in solution by HH and GL methods is
confirmed by the absence of absorption maximum at 396 nm due to
d-d transition for Ni2+ (Fig.1)
Ni crystallite sizes estimated by Debye-Scherer method are
given in Table.1, which also includes the values obtained by pulse
chemisorption of hydrogen and TEM techniques (Fig.3). Fairly good
agreement between the size values from three different methods,
XRD, chemisorption and TEM is observed. As expected, the
crystallite size values obtained by chemical reduction at lower
temperature (HH & GL methods), are smaller than those by
reduction with hydrogen at higher temperature (IM & DP methods).
Ni crystallite size values for the IM & DP catalysts are higher (15-20
nm) compared to 12.7 nm reported earlier for 11% w/w Ni on high
surface area titania.19 Chemical reduction methods, HH and GL,
yield Ni crystallites of smaller size, 8-12 nm, comparable with
earlier report, 19 in spite of higher Ni loading (15- 16 Vs 11 %w/w)
and lower surface area of TiO2 support (50 Vs 150 m2/g).
Fig. 1 Electronic spectra of impregnation solutions by HH & GL
methods- a-before and after reduction by b-HH and c-GL methods
Table 1 Properties of catalysts prepared by different methods
Support being the same, the influence of preparation methods on
the degree of Ni-support interactions is clearly evident in the TPR
patterns (Fig.4). TPR reduction maxima observed in each case are
listed in Table.1. For the catalysts prepared by IM & DP the
reduction behaviour is as per the literature report.19 In the case of the
catalyst by IM method, major TPR maximum located at 448°C is
due to the Ni species having strong interaction with the support. A
shoulder on the low temperature side, at 288°C, signifies free/weakly
bound NiO. Two high temperature reduction maxima at 388°C and
448°C are due to the species that have strong interaction with the
support. Other higher temperature reduction peaks could possibly be
due to the reduction of the support.
Ni
content
(wt %)a
Metal Cryst.
Disp.b Size c
Cryst.
Sizee
(nm)
Prepn.
Method
Cryst.
Sized
TPR Redn.
Maxima (ºC)
%
(nm)
299, 388,
IM
DP
16.1
16.5
5.3
19
16.6
18
15
16
448,611,637
4.6
20
370, 502,570
293, 320,
668
HH
GL
15.2
15.5
8.7
11
11
12
8
10.7
9.5
10
352,690
The catalyst prepared by DP method shows two reduction
maxima at 370 & 505°C and the third one at 570°C due to reduction
a-by XRF, b & c-by H2 chemisorption, d- by TEM, e- by XLBA
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Fig. 3 TE micrographs with histograms for the catalysts by: a-IM, b-DP, c-HH and d- GL methods
Fig. 4 TPR profiles for the catalysts by -a- IM, b-DP, c-HH and d- Fig. 5 XPS line profile for pre-reduced catalyst prepared by GL
GL methods. method
of the support. Compared to the sample by IM method, DP method at 690°C. To summarize, TPR data indicate that preparation methods
results in stronger metal-support interactions, as indicated by the profoundly influence the degree of metal-support interactions.
shift in reduction maxima to higher temperatures. On the contrary, XPS line profile for pre-reduced GL catalyst is presented in Fig.5.
the catalyst prepared by HH method shows a well-defined reduction
Major peaks at 870.2 eV and 853.2 eV are close to the respective
maxima at lower temperatures, at 295°C and a shoulder at 320°C, values of 870 eV and 853 eV reported in literature for Ni2p3/2 and Ni
both due to relatively weaker MSI. This is expected, since the 2p1/2 lines. On deconvolution, a minor peak at 853.8 eV due to
chemical reduction of Ni2+ takes place at lower temperature. A small residual NiO is observed. XPS data for other catalysts also indicate
high temperature peak at 668°C, possibly due to the reduction of the the presence of very small quantities of Ni2+. Since the NiO contents
support, is observed. The catalyst by GL method shows a single are very small they are not revealed in X-ray diffractograms.
reduction peak at 352°C and a weak high temperature reduction peak
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The data on the conversion and selectivity for hydrogenation of CAL Table 4 Conversion and selectivity data for hydrogenation with
on the four catalysts at 120°C for one hour reaction time are given in different feeds at 120°C
Table.2. Based on the TOF values, catalysts prepared by IM & DP
methods with larger Ni crystallite size (15-20 nm) are a shade more
active than catalysts prepared by HH & GL methods with relatively
smaller crystallite sizes, (8-12 nm) respectively.
Products composition %
Conv.
%
Feed
COL
HCAL
COL
11.4
0.0
HCOL
88.0
Others
0.6
88.6
19.0
HCAL
81.0
33.0
18.8
0.2
Table 2 Conversion and selectivity data for hydrogenation of
COL+HCAL-
50/50
66.0
0.1
cinnamaldehyde at 120°C
Catalyst GL wt.-150 mg, Feed-1.2 g, Methanol-16 ml, Pressure-20
Kg/cm2, Reaction time-1hr
Catalyst
Prepn.
Products selectivity %
Conv.
%
TOF s-1
x 104
HCAL COL HCOL Others
COL and HCAL, which on further hydrogenation yield HCOL.
Based on the data presented in Table 4, conversion of COL to HCOL
proceeds with a rate of 20.7 hr-1 (moles of COL converted per hour
per mole of Ni) while the corresponding rate for the conversion of
HCAL is 4.4 hr-1. It is clear that HCOL is formed from COL and not
from HCAL
method
IM
DP
HH
GL
84
70
99
91
38.9
64.6
25.3
31.0
43.6
29.9
53.2
61.0
17.4
5.3
0.1
0.2
0.2
1.1
7.7
6.7
6.0
6.0
21.3
6.9
Scheme 1 Reaction pathways for hydrogenation of cinnamaldehyde
on Ni/TiO2 catalysts
Wt. of catalyst -150 mg, CAL-1.2 g, Methanol-16 ml, Pressure-20
Kg/cm2, Reaction time -1 hr
Crystallite size effects on activity are not expected in this size range
(10-20 nm). However, contrary to the literature reports, all the four
catalysts display significant but moderate selectivity towards COL
and lower selectivity for HCOL during the initial 1 hr reaction time.
The catalysts prepared by low temperature chemical reduction
methods display relatively higher selectivity towards COL indicating
that factors other than size could play a role in directing selectivity at
the initial stages. On continuing the reaction beyond 1 hr, further
hydrogenation of COL to HCOL is observed, as indicated by the
typical data given in Table.3 for the catalyst prepared by GL method.
Table 3 Typical conversion and selectivity data for extended runs
Products selectivity %
Similar observations have been reported by Nitta et al.28 on Co/SiO2
catalysts and Mahmoud et al.29, Hammmudeh et al.30, and Cairns et
al.31 on Pd based catalysts. Weak adsorption of HCAL on the
surface, relative to that of CAL & COL, could lead to its slower rate
of hydrogenation. Besides, addition of small amount HCAL (0.1g)
along with feed CAL (1.1g) increases the selectivity to HCOL at
120°C, while the addition of COL (0.13g) to CAL (1.07g) in the
same manner, lowers the selectivity towards HCAL, from 31.0% to
19.6% on GL catalyst and 38.9% to 25.1% on IM catalyst. It is likely
that adsorbed COL promotes adsorption of CAL in on-top η1
mode5,32 via C=O due to steric hindrance. Breen et al.33 have
observed that on Ir supported on carbon, adsorbed COL causes steric
hindrance, thus inhibiting the adsorption of CAL via C=C bond.
On increasing the reaction temperature from 80 to 120°C, the
selectivity to COL increases on all four catalysts. But at 140°C,
HCOL is formed at the expense of COL (Table 5). Like Pd, Ni
Prepn.
Conv.
%
method
HCAL
31.0
20.1
-
COL
HCOL
6.9
Others
1.1
GL (1 hr)
GL (4 hrs)
GL (8hrs)
91
61.0
100.0
100.0
-
-
79.0
99.4
0.9
0.6
Catalyst GL wt.-150 mg, CAL-1.2 g, Methanol-16 ml, Pressure-20
Kg/cm2, Temp.120°C
In order to unravel the mechanistic pathways during
hydrogenation, experiments have been conducted with different
feedstock compositions and reaction temperatures and the results are
presented in Table 4 & 5. Results on experiments with HCAL, COL
and mixture of HCAL and COL as feed on catalyst GL are given in
Table.4. In the absence of CAL, COL gets hydrogenated completely
to HCOL. The rate of hydrogenation of HCAL is very slow and the
same trend is observed with 50/50 (V/V %) mixture of COL &
HCAL as well, resulting mainly in HCOL.
surface facilitates adsorption of CAL in η4 or η2 (di π) mode5,32
,
wherein the formation of both HCAL and COL are possible.
This is corroborated by the FT-IR spectra for CAL adsorbed on the
catalysts at 120°C presented in Figure.6. CAL in vapour phase
displays absorption bands at 1625 cm-1 due to conjugated C=C bond
stretching vibration and at 1720 cm-1 due to C=O bond asymmetric
Accordingly, a reaction pathway is depicted in Scheme.1.
Conversion of CAL proceeds simultaneously through two routes, to
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Table.5 Effect of reaction temperature on CAL conversion and
selectivity to different products
Catalysts
CAL
Conv.
%
Selectivity (%)
HCAL COL HCOL others
GL-80 ºC
GL-100º C
GL-120 ºC
GL-140 ºC
IM-80 ºC
IM-100 ºC
IM-120º C
IM-140 ºC
DP-80 ºC
DP-100 ºC
DP-120 ºC
DP-140 ºC
HH-80 ºC
HH-100º C
HH-120 ºC
HH-140 ºC
44.6
73.0
91.0
98.0
38.6
63.5
84.0
89.2
27.9
43.2
70.0
74.3
49.1
78.3
99.0
99.2
72.8
53.9
31.0
29.0
81.2
63.3
38.9
35.4
88.4
76.3
64.6
61.0
71.0
52.0
25.3
24.9
23.8
40.1
61.0
27.3
13.2
24.2
43.6
19.8
10.1
18.3
29.9
14.2
19.3
34.7
53.2
23.3
2.9
5.0
6.9
43.6
5.2
12.1
17.4
43.8
1.1
3.4
5.3
23.7
8.6
12.6
21.3
44.5
0.5
1.0
1.1
0.1
0.4
0.4
0.1
1.4
0.4
2.0
0.2
1.1
1.1
0.7
0.2
7.3
1
2
3
4
Fig. 6 FTIR spectra of adsorbed cinnamaldehyde on: a) GL b) HH
c) IM d) DP catalysts. e) CAL in vapour phase
Catalyst wt.-150 mg, CAL-1.2 g, Methanol-16 ml, Pressure-20
Kg/cm2
stretching vibration of unsaturated aldehyde34,35. Corresponding
spectra for all the four catalysts show shifts on the absorption
maxima due to bonding of CAL with the surface.
and the experimental conditions adopted vary widely, thus making
comparison, a difficult task. Lin et al (19), in their studies on
hydrogenation of CAL on Ni/TiO2 with iso-propyl alcohol as solvent
at 80°C, have reported conversion of 66.2% in one hour, with nearly
total selectivity to HCAL and COL is not observed. Besides, it is to
be noted that HCOL formation is less, even after 5 hr of reaction,
when conversion reaches 71%.
However, experimental data from the present work indicate that the
formation of kinetically controlled product, COL, is favoured in the
first one hour of reaction. With the increase in reaction time or
temperature, HCOL, which is thermodynamically the most stable
product, is formed.
Table 7 presents activity/selectivity data as observed by Lin et
al., along with the data for the catalyst GL from the present study,
but under the experimental conditions adopted by them (19). It is
observed that CAL conversion is less (42 & 51%) in the present
case, compared to 66.2% reported by Lin et al.
Supported Ni catalysts are reported to be selective for C=C
hydrogenation, with nearly zero selectivity for COL,29, 36-40 while in
the present work, significant COL selectivity is observed, with all
four catalysts when the reaction is carried out for 1 hr. Though
studies on supported Ni catalysts have been reported earlier (Table
6), the nature of support, Ni dispersion, metal-support interactions,
Table 6 Liquid phase hydrogenation of cinnamaldehyde over Ni based catalysts-Data from the literature
Temp. (°C)
Ni
Cryst. Solvent
Time
(h)
Conv.
(%)
COL
Catalyst/ (Wt. mg)
/Pressure
(Kg/cm2)
Ref
Size (nm)
(Vol-ml)
Selec (%)
15%Ni/TiO2(150)
11%Ni/ TiO2(50)
10-20
12.7
Methanol (16)
120/20
1
70-99
66.2
30-61
1.8
1.6
-
Present work
Iso-propyl
80/20
1
19
36
39
alcohol (80)
Propylene
5% Ni/ SBA-15(265)
10%Ni/CNF/AC (50)
3.6
150/ atmos
160/30
3
57.2
carbonate (25)
4.2-5.5
Toluene (20)
Ethanol (100)
1.5
80-90
Ni w/o support (1000) 50
100/15
120/30
3
2
97.0
78.1
-
37
20
10%
Ni12P5/SiO2
Cyclohexane
(115)
3
(500)
6 | J. Name., 2012, 00, 1-3
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Table 7 Conversion and selectivity data at 80°C for GL catalyst
and kinetic analysis of hydrogenation of CAL (with iso-propyl
alcohol as solvent) on Cu/SiO2, Cu-Al binary oxide, Cu-Al-Zn
ternary and Cu-Al-Zn-Ni/Co quaternary oxides with spinel structure.
With metallic Cu as the active phase, HCAL was formed as the
major product on Cu/SiO2 and Cu-Al binary oxides. However,
modification of the Cu-Al spinel matrix composition by the
introduction of Zn, Ni & Co and controlled pre-reduction (with
TOF
s-1
x 104
Products selectivity %
Conv.
%
Solvent
HCAL COL HCOL Others
Methanol
42.0
51.0
72.2
81.0
23.2
12.4
2.6
3.1
2
7.7
6.7
Iso-propyl
alcohol
Lin et al
(19)
hydrogen
at 473K) resulted
in
the generation of
3.5
Cu00.5[MO]0.5ZnAl2O4 phase, with M= Zn, Co or Ni, which
displayed increase in activity as well as selectivity towards COL
when compared to Cu/SiO2 and Cu-Al binary spinel. Under the pre-
reduction conditions employed, only Cu2+ could be reduced to
metallic state, leaving the divalent cations as such. Such a situation
resulted in the formation of Cu0-M2+ sites which facilitate adsorption
of CAL in a linear configuration, via C=O, thereby leading to higher
selectivity towards COL. However, kinetic runs over extended
periods lead to further hydrogenation of COL to HCOL. Similar
observations have been reported by Dragoi et al. on non-calcined
66.2
98.2
n d
1.8
-
-
Cat. (GL) Wt.- 50 mg, CAL-3 mmol., Temp-80°C, Solvent-10 ml,
Pressure-20 kg/cm
Nature of titania supports used (low surface area P-25 Vs high
surface area nano size titania) and metal-support interactions, could
in part, explain the difference in activity. Ni crystallite sizes are in
the same range and in this size range no significant variations in the
coordinative unsaturated sites or relative population exposed crystal
planes, (111),(110),100), are expected. Besides, the effect of solvent
is seen clearly, with higher TOF values and higher selectivity for
COL with GL catalyst, when methanol is used instead of isopropyl
alcohol. Higher solubility of hydrogen in methanol41 and its higher
dipole moment vis-à-vis isopropyl alcohol42 which could activate
C=O, could be one of the factors responsible for higher selectivity.
21
and mildly reduced (at 150°C) hydrotalcites based on Mg & Al
and Zn-Al 22with propylene carbonate as solvent. Partial substitution
of Mg2+ /Zn2+ in the hyrotalcites with Cu2+-Ni2+ resulted in the
increase in COL selectivity, due to the formation of Cu0-Ni2+ sites,
which are likely to act as Lewis acid sites, promoting preferential
43--47
adsorption of CAL through C=O
of COL .
and leading to the formation
Ungureanu et.al36 have investigated selective hydrogenation of
CAL with propylene carbonate as solvent on Ni, Cu and Ni-Cu
bimetallic nano particles confined in the channels of ordered meso
porous SBA-15 and observed that mono metallic Ni nano particles (5
wt Ni, 3.5 nm in size) are moderately active (57.2 % conversion)
with very high selectivity to HCAL (94.2%). Addition of Cu up to
atomic fraction 0.2, increases conversion from 57.2% to 99.3% with
a concurrent decrease in HCAL selectivity (94.2 to 90.8%) and small
increase in COL selectivity (1.6 to 5.4%).
However, Ni-Al and Co-Al based catalysts derived from
takovite type LDH precursors, on calcination and high temperature
reduction form Ni & Co metal nano particles of size 3.6-5.8 nm and
<3.0 nm respectively.23 While COL is formed selectively on Co-Al
based catalysts, (60% selectivity at 50% conversion) Ni-Al based
catalysts yield HCAL with 95% selectivity at complete conversion
with propylene carbonate as solvent. Presence of M0-Nn+ sites are
thus essential for polarization and activation of C=O bond.
However, Zhao et al.37 have reported that unsupported Ni nano
particles of size 50 nm are highly active (94.2 % conversion after 3
hrs, at 100°C, 15 MPa hydrogen pressure, with 20 ml of CAL and 1g
of catalyst dispersed in 100 ml of ethanol as solvent) with selectivity
to HCAL at ~55%, which increases drastically with the addition of
Ru. It is likely that with larger Ni crystallites, further hydrogenation
to HCOL is catalysed. Nickel phosphides, like Ni2P and Ni12P5,
when supported on silica20, display very high selectivity towards
HCAL. Chen et al.38 observed that Ni-Si intermetallics display
higher selectivity towards HCAL vis-a vis HCOL, due to the
electronegative character of Si and the consequent repulsive force
between Si & oxygen in C=O. Gryglewicz et al.39 have observed that
the hydrogenation of CAL on 10% w/w Ni supported on two
different types of CNF & activated carbon supports proceeds
selectively towards HCAL and hydrogenation of COL to HCOL is
faster than that of HCAL.
Scheme 2 Proposed mode of adsorption of cinnamaldehyde on
Ni/TiO2 - Adsorption and activation of cinnamaldehyde
In the present case, the observed selectivity to COL could be due to
the adsorption of CAL through C=O bond, which is facilitated by the
presence of small amounts of Ni2+ as observed in XPS studies, along
with Ni0, as depicted in Scheme 2. The quantity of Ni2+may be too
small to be revealed by XRD studies. The nature of metal- support
interactions, which vary depending on the method of preparation
(HH & GL) and the use of methanol as solvent could be the other
contributing factors for the higher selectivity to COL.
Structural and electronic environment of Ni in the catalyst
matrix could direct the orientation of the CAL molecule on the
surface (adsorption through C=C or C=O) and hence the
selectivity21-23,39. Apestiguia and co-workers40 have carried out
detailed investigations on the characterization, activity, selectivity
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VJieowuArrtnicalelONnlainme e
ARTICLE
DOI: 10.1039/C4CY01379D
11 W. Koo-amornpattana, J. M. Winterbottom, Catal. Today, 2001, 66,
277-287.
Conclusions
Nickel (15% w/w) supported on TiO2-P-25 catalysts have
12 M. Lashdaf, J. Lahtinen, M. Lindblad, T. Venäläinen, A. O. I. Krause,
Appl. Catal. A, 2004, 276, 129-137.
been prepared by conventional high temperature hydrogen
reduction (IM &DP) and low temperature chemical reduction
(HH & GL) methods. HH and GL methods yield relatively 13 A. J. Plomp, H. Vuori, A. O. I. Krause, K. P. de Jong, J. H. Bitter, Appl.
smaller Ni crystallites. Preparation methods adopted profoundly
influence the nature of metal-support interactions. All four
catalysts exhibit good conversion of CAL and significant
selectivity to COL in the initial stages of the reaction. With the
increase in reaction time, COL is hydrogenated further to
HCOL. Catalysts prepared by HH &GL methods display higher
CAL conversion and selectivity to COL. Presence of small
amounts of Ni2+ along with Ni0 and steric hindrance due to
adsorbed COL could favour the adsorption of CAL through
C=O, leading to the formation of COL, which gets
hydrogenated further to HCOL with the increase in reaction
time.
Catal. A, 2008, 1, 9-15.
14 J. C. Serrano-Ruiz, A. Lopez-Cudero, J. Solla-Gullón, A. Sepúlveda-
Escribano, A. Aldaz, F. Rodríguez-Reinoso, J. Catal, 2008, 253, 159-
166.
15 E. V. Ramos-Fernández, J. M. Ramos-Fernández, M. Martínez-
Escandell, A. Sepúlveda-Escribano, F. Rodríguez-Reinoso, Catal. Lett,
2009, 133, 267-272.
16 J. Shi, R. Nie, P. Chen, Z. Hou, Catal. Commun, 2013, 41, 101-105.
17 W. W. Yu, H. Liu, J. Mol. Catal. A Chem, 2006, 243, 120-141.
18 Y. Zhu, F. Zaera, Catalysis. Sci. Tech, 2014, 4, 955-962.
19 W. Lin, H. Chang, L. He, Y. Yu, F. Zhang, Journal of Catalysis, 2013,
303, 110-116.
Acknowledgements
The authors would like to express their gratefulness to the Dept.
of Science & Technology, Govt. of India for establishing research
facilities at NCCR. MGP is thankful to CSIR for the award of SRF
scholarship
20 H. Wang, Y. Shu, M. Zheng, T. Zhang, Catal. Lett, 2008, 124, 219-225.
21 B. Dragoi, A. Ungureanu, D. Meloni, M. Casula, A. Chirieac, A. Sasu,
V. Solinas, E. Dumitriu, Environmental Engineering and Management
Journal, 2010, 9, 1203-1210.
Notes and references
aNational Centre for Catalysis Research, Indian Institute of Technology,
22 B. Dragoi, A. Ungureanu, A. Chirieac, V. Hulea, E. Dumitriu, Acta.
Chem, 2010, 57, 677-685.
Madras, Chennai-600036, India.
bDepartment of Chemistry, Thiagarajar College, Madurai Kamaraj 23 C. Rudolf, B. Dragoi, A. Ungureanu, A. Chirieac, S. Royer, A. Nastro ,
University, Madurai-625009, India.
* Corresponding author.
E. Dumitriu, Catal. Sci. Tech, 2014, 4, 179-189.
24 K. J. A. Raj, M. G. Prakash, T. Elangovan, B. Viswanathan, Catal. Lett,
2011, 142, 87-94.
1
2
P. Gallezot, D. Richard, Catal. Rev.: Sci. Eng, 1998, 40, (1&2), 81-
25 R. Zanella, S. Giorgio, C. R. Henry, C. Louis, J. Phys. Chem. B, 2002,
106, 7634-7642.
126.
A. Giroir-Fendler, D. Richard, P. Gallezot, In. Stud. Surf. Sci. Catal. M.
Guisnet, J. Barrault, C. Bouchoule, D. Duprez, C. Montassier, G. Pérot, 26 Z. G.Wu, M. Munoz, O. Mantero, Adv. Powd. Tech,2010, 21, 165-168
Eds. Elsevier. Amsterdam, 1998, 41, 171-179.
D. Richard, J. Ockelford, A. Giroir-Fendler, P. Gallezot, Catal. Lett.
1989, 3, 53-58.
27 M. Vasseem, N. Tripathy, G. Khang, Y. Halm, RSC. Adv, 2013, 3, 9698-
9704.
3
4
5
28 Y. Nitta, K. Ueno, T. Imanaka, Appl. Catal, 1989, 56, 9-22.
N. Mahata, F. Goncalves, M. F. R. Pereira, J. L. Figueiredo, Appl. Catal. 29 S. Mahmoud, A. Hummoudeh S. Gharalibeh, J. Meisheimer, J.
2008, 339, 159-168.
Mol.Catal. A2002,178, 161-167
A.M. Simion, T. Arimura, C. Simion, C. R. Chim, 2013,16 , 476-481; B. 30 A. Hummoudeh, S. Mahmoud, Appl.Catal. A.General,2003, 243, 147-
M. Reddy, G. M. Kumar, I. Ganesh, A. Khan, J. Mol. Catal. A: Chem,
2006, 247, 80-87.
154
31 G. R. Cairns, R. J. Cross, D. Stirling, J.Catal.1997,166,89-97
6
M. S. Ide, B. Hao, M. Neurock, R. J. Davis , ACS. Catal . 2012, 2, 671- 32 F. Dalbecq, P. Sautet, J. Catalysis, 1995,152, 217-236
683.
33 J.P. Breen, R. Burcha, J. Gomez-Lopez, K. Griffin, M. Hayes, Appl.
Catal .A General, 2004, 268, 267-274.
7
8
W. W. Yu, H. Liu, J. Mol. Catal. A Chem, 2006, 243, 120-141.
P. G. N. Mertens, H. Poelman, X. Ye, I. F. J. Vankelecom, P. A. Jacobs, 34 Z. Tian, X. Xiang, L. Xie and F.Li Ind.Eng.Chem.Res.2013,52,288-296
D. E. De Vos, Catal. Today, 2007, 122, 352-360.
W.O.Oduro, N. Cailuo, K. M. K. Yu, H. Yang, S. C. Tsang, J. Phys.
Chem, 2011, 13, 2590-2602.
35 F. Zhao, S. Fujita, S. Akihara, M. Arai, J. Phys. Chem. A 2005, 109,
4419-4424
9
36 A. Ungureanu, B. Dragoi, A. Chirieac, C. Ciotonea, S. Royer, D. Duprez,
A. S. Mamede, E. Dumitriu, ACS. Appl. Mater. Interfaces, 2013, 5,
3010-3025.
10 A. Giroir-Fendler, D. Richard, P. Gallezot, Catal. Lett, 1990, 5, 175-
181.
8 | J. Name., 2012, 00, 1-3
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Journal Name
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View Article Online
ARTICLE
DOI: 10.1039/C4CY01379D
37 Z. F. Zhao, Z. J. Wu, L. X. Zhou, M. H. Zhang, W. Li, K. Y. Tao,
Catal.Commun, 2008, 9, 2191-2194.
38 X. Chen, M. Li, J. Guan, X. Wang , C. T. Williams, C. Liang, Ind. Eng.
Chem. Res, 2012, 51, 3604-3611.
39 S. Gryglewicz, A.S ´ liwak .J. C ´ wikła and G. Gryglewicz, Catal.Lett,
2014, 144, 62-69.
40 A. J. Marchi, D. A. Gordo, A. F. Trasarti, C. R. Apesteguia, Appl. Catal.
A General, 2003, 53 , 249-256.
41 T. Katayama, T. J. Nitta, Chem. Eng. Data, 1976, 21, 194-196.
42 H. Yamada, S. J. Goto, Chem. Eng. Jpn, 2003, 36, 586-589.
43 Z. Poltarzewski, S. Galvagno, R. Pietropaolo, P. Staiti J. Catal, 1986,
102, 190-198.
44 F. Coloma, A. Sepúlveda-Escribano, J. L. G. Fierro, F. Rodrıguez-
Reinoso, Appl. Catal. A General, 1996, 148 , 63-80.
45 S. Galvagno, A. Donato, G. Neri, R. Pietropaolo R, G. Capannelli, J.
Mol. Catal , 1993, 78, 227-236.
46 G. Neri ,L. Mercadante, C. Milone , R. Pietropaolo ,S. Galvagno, J. Mol.
Catal. A Chemical, 1996, 108, 41-50.
47 G. Neri, C. Milone, A. Donato, L. Mercadante, A. M. Visco, J.Chem.
Tech. Biotechnol, 1994, 60, 83-88.
This journal is © The Royal Society of Chemistry 2012
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