Addition of alcohols to acrylic compounds catalyzed by Mg-Al LDH

Article abstract of DOI:10.1007/s10562-013-1108-1

This study reports the preparation of hydrotalcite with Mg/Al molar ratio 3 by co-precipitation under low suprasaturation conditions of Mg and Al nitrated solutions with Na2CO3 and NaOH at pH 10. The solid was thermally decomposed at 460°C in air atmosphere in order to obtain mixed oxides which, by means of memory effect, can reconstruct the hydrotalcite structure by hydration with bidistilled water. The hydrotalcite and reconstructed samples by memory effect were characterized by elemental analysis, powder XRD, DRIFT and TG-DTG. Determination of the catalysts surface base sites was made using a method based on the irreversible adsorption of organic acids with different pKa values and N2 adsorption-desorption isotherms. The catalytic activity of these solids was evaluated in 1,4-addition of saturated linear alcohols to different acrylic compounds. All these reactions arose with high selectivity in the desired product. No by-products were detected by means of GC-MS chromatography and 1H NMR.

Full text of DOI:10.1007/s10562-013-1108-1

Catal Lett (2014) 144:117–122
DOI 10.1007/s10562-013-1108-1
Addition of Alcohols to Acrylic Compounds Catalyzed
by Mg–Al LDH
F. Teodorescu
R. Z a˘ voianu
•
M. Deaconu
O. D. Pavel
•
E. Bartha
•
•
Received: 3 July 2013 / Accepted: 19 September 2013 / Published online: 12 October 2013
Ó Springer Science+Business Media New York 2013
Abstract This study reports the preparation of hydrotal-
cite with Mg/Al molar ratio 3 by co-precipitation under low
suprasaturation conditions of Mg and Al nitrated solutions
with Na CO and NaOH at pH 10. The solid was thermally
1 Introduction
The application of heterogeneous catalysis in organic
reactions, despite of homogenous catalysis, has become a
rapidly growing research field due to the known advanta-
ges: operational simplicity, mild reaction conditions and
easy separation of the catalyst from reaction mixture at the
end of the process through a simple separation process.
These advantages eliminate or minimise the need for
additional work-up procedures which can often be expen-
sive and can lead to generation of large volumes of wastes,
which are often toxic.
2
3
decomposed at 460 °C in air atmosphere in order to obtain
mixed oxides which, by means of memory effect, can
reconstruct the hydrotalcite structure by hydration with bi-
distilled water. The hydrotalcite and reconstructed samples
by memory effect were characterized by elemental ana-
lysis, powder XRD, DRIFT and TG-DTG. Determination
of the catalysts surface base sites was made using a method
based on the irreversible adsorption of organic acids with
different pK values and N adsorption–desorption iso-
In this context, the use of layered double hydroxides
(LDHs) [1–12] received a high interest. The thermal
decomposition of these solids, under relatively mild con-
ditions, leads to mixed oxides which are unstable spinels
due to octahedral position of cations. After hydration, due
to the memory effect, the reconstruction of the initial
structure takes place whit the increase of the basic
character.
a
2
therms. The catalytic activity of these solids was evaluated
in 1,4-addition of saturated linear alcohols to different
acrylic compounds. All these reactions arose with high
selectivity in the desired product. No by-products were
1
detected by means of GC–MS chromatography and H
NMR.
Keywords Heterogeneous catalysis Á Thermal
desorption Á Alcohols Á DRIFTS Á XRD
LDHs and congener mixed oxides were reported to
substitute with good results basic and acid corrosive
homogeneous catalysts in different chemical reactions such
as: isomerization of alkenes and alkynes [13], aldol con-
densation [14], Knoevenagel condensation [15], nitroaldol
reactions [16], Michael addition [17], nonconjugate addi-
tion of alcohols [18], nucleophilic addition of phenylacet-
ylene [19], nucleophilic ring opening of epoxides [20],
oxidation reactions [21], cyanoethylation [18, 22–24] and
so on.
F. Teodorescu Á R. Z a˘ voianu Á O. D. Pavel
Department of Organic Chemistry, Biochemistry and Catalysis,
Faculty of Chemistry, University of Bucharest, 4-12 Regina
Elisabeta Blv., S3, 030018 Bucharest, Romania
Particularly, cyanoethylation represents an attractive
route for the direct formation of a carbon–oxygen bond in
the valuable building blocks for natural products and
important intermediates in organic synthesis [5, 25].
However, up to date, there are no literature examples on
F. Teodorescu (&) Á M. Deaconu Á E. Bartha
‘‘C.D. Nenitzescu’’ Center of Organic Chemistry, 202 B Spl.
Independen ¸t ei, S6, 060023 Bucharest, Romania
e-mail: fteodorescu@cco.ro
123

1
18
F. Teodorescu et al.
using hydrotalcites or congeners for 1,4-addition of alco-
hols to substrates with a lower reactivity such as acrylates
and unsaturated nitriles substituted by alkyl or phenyl
groups in the b carbon position.
up to 500 °C on a Setaram-92 equipment with a heating
rate of 10 °C/min under air atmosphere. The surface base
sites of the catalysts were determined using a method based
on the irreversible adsorption of organic acids with dif-
Based on this state of the art, the aim of this study was to
-
investigate the behavior of LDHs with different OH /
ferent pK values corresponding to the total number of base
a
sites, e.g. acrylic acid, pK = 4.2 and strong base sites, e.g.
a
2
-
CO3 ratios in the 1,4-addition of alcohols to substrates
with a lower reactivity as those mentioned above. The
phenol pK = 9.9 [21, 28]. The number of weak base sites
a
was measured as the difference between the amount of
adsorbed acrylic acid and the adsorbed phenol. Surface
areas and pore size distributions were determined from N2
adsorption–desorption isotherms, using the BET equation.
-
OH /CO
2-
ratios were controlled by thermal decompo-
3
sition of hydrotalcite and reconstruction by means of
memory effect. A correlation of the catalytic performances
with the physico-structural characteristics induced by these
treatments has also been considered.
2.3 Catalytic Tests
The activity tests were performed in a thermostatic glass
reactor provided with water cooled condenser. The alcohol
2
Experimental
(0.03 mol) and the acrylic compound (0.01 mol, Merck
2
.1 Catalysts Preparation
p.a. reagents) were added in the reactor and heated under
stirring up to the reflux temperature. After reaching this
temperature, the catalyst (3 %wt of the reaction mixture)
was added in the reactor. The duration of each catalytic test
was of 4 h. The reaction product was identified by mass
spectrometer coupled-chromatography, using a GC/MS/
MS VARIAN SATURN 2100 T equipped with a CP-SIL 8
CB Low Bleed/MS column of 30 m length and 0.25 mm
A hydrotalcite with Mg/Al molar ratio of 3 was obtained at
pH 10 by co-precipitation under low supersaturation [26,
2
7] of two solutions A and B. Solution A was obtained by
dissolving 0.2 mol Mg(NO ) Á6H O and 0.066 mol
3
2
2
Al(NO ) Á9H O in bi-distilled water, at 1.5 M. Solution B
3
3
2
was prepared by dissolving 0.178 mol Na CO and
3
2
1
0
.444 mol NaOH in bi-distilled water; the concentration of
diameter, and by H NMR. The NMR spectra were recor-
solution was 1 M Na CO . Both solutions were mixed at
2
ded with Varian Gemini 300 BB instrument, operating at
1
300 MHz for H in CDCl solution at room temperature.
3
room temperature and under vigorous stirring (600 rot/
3
-
1
min) at the feeding flow of 60 mL h . The gel obtained
was aged 18 h at 75 °C and then cooled to room temper-
ature, filtered and washed with bi-distilled water until pH 7.
The drying of the hydrotalcite gel was performed at 90 °C
for 24 h in an air flow. The resulting sample was named
HT. Then, the HT sample was thermally decomposed at
3 Results and Discussion
3.1 Structural Catalysts Characterization
4
60 °C for 18 h in air flow in order to prepare the corre-
The results of the chemical analysis of the samples
(Table 1) showed that there are no significant differences
sponding mixed oxides. These mixed oxides were
immersed in bi-distilled water for 24 h at 25 °C and then
dried at 90 °C for 24 h in air flow for the reconstruction of
hydrotalcite structure, HyHT samples.
Table 1 Chemical composition and structural data of HT and HyHT
Samples Chemical composition Structural data
(
wt%)
2
.2 Catalysts Characterization
a
Mg Al
a
b
c
O
˚
a (A) c (A)
˚
C
H
2
IFS
D
(%)
d
e
˚
A)
(
The analysis of the metal content in the samples was per-
formed by atomic absorption spectroscopy (AAS) using a
Varian AAS spectrometer. Elemental analysis was per-
formed on a Perkin Elmer CHN 240B. Powder X-ray dif-
HT
HyHT
a
24.1 8.9 2.1 10.7 3.069 23.643 3.08
23.8 8.8 0.5 12.0 3.061 23.347 2.98
2.48
0.97
Mg and Al concentrations were determined by AAS
fraction patterns were recorded with a Shimadzu XRD
˚
b
C and N were determined by elemental analysis, N content was 0
for both samples
7
000 diffractometer using Cu Ka radiation (k = 1.5418 A,
0 kV, 40 mA) at a scanning speed of 0.10°/min in the 5°–
8° 2h range. DRIFTS spectra obtained from the accu-
4
c
As calculated considering the loss of weight determined by TG–
DTA analysis in the range 105–200 °C [1]
6
-
1
d
mulation of 400 scans in the domain 400–4,000 cm
IFS represents the interlayer free distance
-
1
(
4 cm resolution) and were recorded with NICOLET
700 spectrometer. The TG-DTG analyses were performed
e
D (%) refers to the degree of disorder along c-axis calculated as the
ratio between the FWHM and the area of the (0 0 3) line
4
1
23

Addition of Alcohols to Acrylic Compounds
119
between the Mg and Al content in HT and HyHT samples.
Meanwhile, the results of the elemental analyses showed
the absence of nitrogen. Using the data provided in
Table 1, the chemical formulas of HT and HyHT solids
HyHT
were calculated (e.g. Mg3.01Al(OH)7.96(CO )
9 1.97
3 0.53
H O, and Mg3.0Al(OH)8.95(CO )
2
9 2.04H O, respec-
2
3 0.025
tively). The absence of nitrogen in the results of the ele-
mental analysis as well as the good concordance between
the theoretical (Mg Al(OH) (CO ) 9 2H O) and the
3
8
3 0.5
2
determined formula of HT sample are good evidences for
the total precipitation. The smaller amount of carbon in
HyHT, compared to HT, is a consequence of the removal
of the carbonic anions during the thermal decomposition
process undergone by HT before reconstruction.
HT
Figure 1 presents the typical XRD patterns of a pure
LDH (HT sample) and of the corresponding mixed oxide
resulted after thermal decomposition. The purity of HT
accounts the symmetric and sharp reflections of (003),
4
000
3500
3000
2500
2000
1500
1000
500
-1
Wavelength (cm )
Fig. 2 DRIFT spectra of HT and HyHT samples
(
006), (110) and (113) planes and broad asymmetric dif-
fraction reflections of (012), (015) and (018) planes
JCPDS 70-2151). The cell parameters, Table 1, have been
determined through a = 2Ád and c = 3/2Á(d ? 2d006),
to a change in the composition of anionic interlayer; (iii)
the decrease of the degree of disorder along the ‘‘c’’ axis
following a more orderly arrangement of anionic species;
(iv) the recovery of the hydrotalcite structure (memory
effect) that was consistent with the increase of the intensity
of the reconstructed diffraction lines (Ihy003/I003, respec-
tively Ihy110/I110); this process was characterized by an
increase in the degree of crystallinity due to a more orderly
assembly of layers. It appears that the hydration results into
a more ordered structure, most likely due to the increase of
(
1
10
003
respectively. After thermal decomposition only mixed
3
?
oxides corresponding to Mg(Al )O solid solutions of
MgO-periclase type (JCPDS-45-0946) were determined. In
addition, it was found that the planes (012), (015), and
(
018) which are asymmetrical in the ‘‘as-synthesized’’ form
become more symmetrical in the hydrated form. According
to data already reported [23], the memory effect in the
transformation of the samples from hydrotalcite to mixed
oxide and back to LDH occurred via the following devel-
opments: (i) the decrease of the IFS parameter due to an
-
the ratio of the OH groups to the number of carbonate
anions.
DRIFT spectra showed a series of absorption bands
-1
-
increased number of OH groups at the expense of car-
(Fig. 2). Those at 3,700–3,400 cm
correspond to the
bonate groups; (ii) the increase of the I003/I110 ratio that led
t(O–H) group vibration in the hydrotalcite, that at cca.
3
-
,050 cm to hydrogen bonding between water and car-
1
bonate in the interlayer of the hydrotalcite, that at
-
1
,640 cm to H O bending vibration of interlayer water in
1
2
-
1
2-
the hydrotalcite, those at 1,400 and 698 cm to CO3
group vibration bands in the hydrotalcite, and those in the
-
1
range 627–400 cm to Mg–O and Al–O bonds. The
1
spectra also show bands in the region 1,200–627 cm
-
HyHT
characteristic to carbonates that indicates that these species
were not completely removed from the structure even after
the decomposition at 460 °C. After hydration of mixed
oxides the absorption bands returned to the previous
intensities certifying thus that the LDH structure was
rebuilt.
mixed
oxides
The comparison of the TG-DTG curves (Fig. 3) of HT
HT
(
a) and HyHT (b), indicated that the maximum of the
10
20
30
40
50
60
70
derivative weight loss, in the temperature range 40–240 °C
occurred at the same temperature [206 °C for HT (a) and
04 °C for HyHT (b)]. As it may be seen from table 1, the
loss of weight corresponding to interlayer water (in the
2
theta
2
Fig. 1 XRD patterns of hydrotalcite, corresponding mixed oxides
and reconstructed sample by means of memory effect
123

1
20
F. Teodorescu et al.
Table 3 Activity of HT and HyHT in 1,4-addition of saturated linear
alcohols to acrylic compounds
O
R1
EWG
+
ROH
R
EWG
R1
1
2
3
a
Entry
EWG
R
1
R
Conversion (%)
HT
HyHT
1
2
3
4
5
6
7
8
a
CN
CN
CN
CN
CN
CN
CO
CO
H
H
H
Me
Et
78.3
61.2
38.7
20.0
8.5
100
97.9
97.6
89.0
26.5
24.2
85.3
81.4
n-Pr
Me
Et
Me
Me
Me
H
n-Pr
Et
7.4
2
Me
Et
53.7
46.8
2
H
Et
Reaction conditions 1 acrylic compound (0.01 mol), 2 alcohol
0.03 mol), catalyst concentration 3 %wt of the reaction mixture,
(
reaction time 4 h, temperature—under reflux conditions
groups in the temperature range beyond 350 °C: HT
-
(16.8 %) and HyHT (19.6 %). The higher amount of OH
Fig. 3 TG-DTG of samples: a HT, and b HyHT
released in this step for HyHT (19 %) compared to HT
(
15 %) certified that by hydration of mixed oxides the ratio
-
Table 2 Specific surface areas and determinations of base sites using
the irreversible adsorption of organic acids with different pK
2-
between OH /CO
3
is changing. Increased number of
a
-
2-
OH compared with CO3 induces a higher basic char-
acter for HyHT, Table 2. The increase in the basicity was
also found to be correlated with the catalytic activity.
The surface area showed a dramatic decrease from HT
towards HyHT (Table 2). This phenomenon was also
noticed by Palomeque et al. [29], Palomares et al. [30] and
Takehira et al. [31] which report specific surface areas of
Catalysts Specific
surface
area
Total number
of base sites
(mmol acrylic
acid/g catalyst)
Distribution of base sites
Strong Weak and
base sites medium
(BET)
m /g
2
(mmol
phenol/g
catalyst)
strength base
sites (mmol/g
catalyst)
a
HT
HyHT
a
122
6.91
7.29
0.26
0.36
6.65
6.93
2
only a few m /g for the reconstructed structures. The
8.9
decrease of the surface area may be explained by the fact
that the reconstruction leads to relatively close-packed
structures (see the lower values of a parameter in Table 1)
characterized by different textural properties compared to
the parent HT. The change of the morphologies during the
reconstruction is a consequence of a retro-topotactic
transformation as it was proposed by Marchi and Apeste-
guia [32]. Using TEM analysis, Angelescu et al. [33]
showed that after the hydration of the mixed oxide phase,
vermiculate shaped irregularities on the edges and defects
on the plates appeared. Therefore the surface morphology
appears considerably different from the initial hydrotal-
cites. Since the irregularities and defects block the entrance
of nitrogen molecules into the lamellar structure, lower
values of the surface areas were determined [23]. The
increased basicity noticed for HyHT sample may be related
to the higher number of punctual defects on the external
surface of the solid.
Weak and medium strength base sites = total number of base
sites - strong base sites)
range 105–200 °C) was higher by 1.3 % for HyHT. Dif-
ferences were however determined at higher temperatures.
Meanwhile, the weight loss in the temperature range
240–343 °C corresponding to elimination of the interlayer
OH anions linked to the network cations were smaller for
HyHT (5.3 %) than for HT (6.2 %).
The strength of the bonds between the anionic groups
and the cations was also different as resulted from the
temperature at which the maximum derivative weight loss
occurred. The bond strength was weaker for HyHT
(338 °C) as compared to HT (346 °C). Differences were
also determined for the loss of the OH groups belonging
-
2
-
to the brucite-type structure and the rest of the CO3
1
23

Addition of Alcohols to Acrylic Compounds
121
100
O
R1
+
CN
ROH
R
CN
R1
8
6
4
2
0
0
0
0
0
Scheme 1 Addition of alcohols to acrylic compounds
3
.2 Catalytic Performances
Saturated aliphatic alcohols could react with acrylonitrile
with moderate to good isolated yields. Under similar
reaction conditions, the 1,4-addition of alcohols on HT
catalysts decreased with the increase of the chain length of
the alkoxide radical, due to their higher hydrophobicity. In
the presence of HyHT, the addition of alcohols afforded the
reaction products in excellent yields, reaching 100 % in the
case of methanol. This behavior could be easily correlated
0
1
2
3
4
5
6
Time (h)
Fig. 4 Conversion of the acrylic compounds in their reaction with
ethanol as a function of the reaction time. Reaction conditions acrylic
compound (0.01 mol), ethanol (0.03 mol), catalyst concentration
–
to the increased population of HO groups on the catalyst
3
%wt of the reaction mixture, temperature—under reflux conditions;
HyHT (Table 3, entries 1, 2, 3).
open symbols HT catalyst, dark symbols HyHT catalyst, acrylic
compounds: opened square/closed square acrylonitrile, opened circle/
closed circle crotonitrile, opened triangle/closed triangle methyl
acrylate
The influence of the chain length of the alcohols was
also verified in the reaction of unsaturated nitriles substi-
tuted by a methyl or phenyl group in the b carbon position.
As nitriles were considered crotonitrile (R = Me) and
1
cinnamonitrile (R = Ph), Scheme 1.
1
R-OH
I
R1
The acrylic nitriles showed strong reluctance to enter
addition due to the congested b reaction center. For this
reason the crotonitrile reacts with low conversions
O
C
N
B:-
R
C
N
R1
R-O-
(
Table 3, entries 4, 5, 6) while the substrate with phenyl
III
B:H
substituent in b position does not afford the formation of
the desired products (not shown). As the chain length of the
alcohols is longer and the b substituent is more voluminous
a lower reactivity was observed. Increased reaction time of
crotonitrile with alcohols in the presence of HyHT (24 h)
led to conversions exceeding 90 %. The addition product
resulted as mixture of diastereoisomers.
II
δ+
δ−
N:
R1
C
O
R
C N
R1
Scheme 2 Reaction route of 1,4-addition of alcohols to acrylic
compounds
The replacement of –CN group with less electron-defi-
cient conjugate acceptors, such as –COOR, leads to the
obtaining with good yields of the corresponding b-alkoxy
compounds (Table 3, entries 7, 8). However, the yields
were lower than those obtained for acrylonitrile. By elec-
tron releasing effect the alkyl group increases the electron
density on the b carbon and makes the attack of the alk-
oxide anion difficult.
indicates the similarity of the active sites involved in the
reaction mechanism.
Our results are consistent with the reaction mechanism
depicted in Scheme 2, which been previously proposed by
Hattori and Valente [34, 35]. In the first step, abstraction
of a proton from the hydroxyl group of the alcohol by the
base sites of the catalyst produced an alkoxide anion
which is stabilized on a conjugated acid site. The adsor-
bed alkoxide then attacks in a second step the terminal
carbon atom of carbon–carbon double bond of the acrylic
compounds to give an adsorbed anion. The attack is more
Figure 4 presents the variation of the conversion as a
function of time for the reactions of different types of
acrylic compounds with ethanol (Table 3, entries 2, 5, 7).
As it may be seen, for all three cases involved, the con-
version of the acrylic compound increases rapidly in the
first 3 h until it reaches a plateau level. Even in the early
stages of the reaction, the levels of the conversions on HT
catalyst are in each case lower than those obtained with
HyHT catalyst. However, the fact that there are no sig-
nificant modifications of the slopes between the two types
of catalysts when the same acrylic compound is used
difficult when R = Me or Ph due to the sterically
1
encumbered reaction center. The adsorbed anion is finally
protonated in a third step to yield the corresponding b-
alkoxy compounds and to conclude the catalytic cycle
with regeneration of the base site. This mechanism
obviously points out the main role played by the acid–
base pairs on the reactivity.
123

1
22
F. Teodorescu et al.
Development 2007–2013. The research was also supported by a Grant
of the Romanian National Authority for Scientific Research, CNCS -
UEFISCDI, project number PN-II-RU-TE-2011-3-0026.
Table 4 Temporal variation of the conversion of acrylonitrile during
three reaction cycles
Time Acrylonitrile conversion on
HT catalyst (%)
Acrylonitrile conversion on
HyHT catalyst (%)
References
(
h)
Cycle 1 Cycle 2 Cycle 3 Cycle 1 Cycle 2 Cycle 3
1
2
. Cavani F, Trifiro F, Vaccari A (1991) Catal Today 11:173
. Tichit D, Bennani MN, Figueras F, Tessier R, Kervennal J (1998)
Appl Clay Sci 13:401
0
1
1
2
3
4
5
.5
.5
14.1
25.0
32.5
48.0
57.4
61.2
63.1
13.9
24.5
32.2
46.9
56.6
60.6
61.5
13.4
23.0
30.5
45.3
53.4
58.8
59.3
37.1
54.6
76.9
89.8
95.4
97.9
98.2
36.5
53.0
75.5
88.9
94.0
96.6
96.2
35.4
51.6
73.8
86.6
90.6
93.9
94.1
3. Gil A, Gandia LM, Vicente MA (2000) Catal Rev -Sci Eng
2:145
4
5
4
. Sels BF, De Vos DE, Jacobs PA (2001) Catal Rev Sci Eng 43:443
. Kabashima H, Hattori H (1998) Catal Today 44:277
6. Ono Y (2003) J Catal 216:406
. Dumitriu E, Hulea V, Chelaru C, Catrinescu C, Tichit D, Durand
R (1999) Appl Catal A 178:145
7
8
9
. Fernandes CI, Nunes CD, Vaz PD (2012) Curr Org Chem 9:670
. Centi G, Perathoner S (2008) Microporous Mesoporous Mater
3
.3 Catalyst Reusability
1
07:3
1
0. Chmielarz L, Rutkowska M, Ku s´ trowski P, Drozdek M, Pi-
wowarska Z, Dudek B, Dziembaj R, Michalik M (2011) J Therm
Anal Calorim 105:161
1. Macala GS, Robertson AW, Johnson CL, Day ZB, Lewis RS,
White MG, Iretskii AV, Ford PC (2008) Catal Lett 122:205
2. Queiroz RM, Pires LHO, Souza RCP, Zamian JR, Souza AG,
Rocha Filho GN, Costa CEF (2009) J Therm Anal Calorim 97:163
3. Handa H, Baba T, Yamada H, Takahashi T, Ono Y (1997) Catal
Lett 44:119
4. Roelofs JCAA, van Dillen AJ, de Jong KP (2001) Catal Lett 74:91
5. Angelescu E, Pavel OD, Birjega R, Zavoianu R, Costentin G, Che
M (2006) Appl Catal A 308:13
6. Bulbule VJ, Deshpande VH, Velu S, Sudalai A, Sivasankar S,
Sathe VT (1999) Tetrahedron 55:9325
In order to check the stability of the catalysts, they were
used in three consecutive reaction cycles. After the third
reaction cycle the conversion decreased only with 5 %
compared to the initial value. The temporal variation of the
conversion during three reaction cycles for the reaction
presented in Entry 2, Table 3 is displayed in Table 4. Since
the data in Table 4 show that there are no sensible changes
of the conversion in the early stages of the process it may
be concluded that the kinetics is not affected by the recy-
cling. Both samples, HT and HyHT, were stable during
reaction with no modification in XRD patterns or DRIFT
spectra of the used catalysts.
1
1
1
1
1
1
1
7. Ando T (1994) Acid–base catalysis II: Proceedings of the inter-
national symposium on acid-base catalysis II. Sapporo-Japan,
Kodansha, Tokyo and Elsevier, Amsterdam
1
1
8. Birjega R, Pavel OD, Costentin G, Che M, Angelescu E (2005)
Appl Catal A 288:185
9. Baba T, Kizuka H, Handa H, Ono Y (2000) Appl Catal A
4
Conclusions
1
94:203
20. Yamaguchi K, Ebitani K, Yoshida T, Yoshida H, Kaneda K
1999) J Am Chem Soc 121:4526
Besides their already known activity for cyanoethylation
reaction, HT and its corresponding reconstructed form
HyHT, present also a good activity for the 1,4-addition of
other alcohols to substrates with lower reactivity than acry-
lonitrile such as acrylates and unsaturated nitriles substituted
by alkyl or phenyl groups in the b carbon position.
(
2
2
2
2
1. Ionescu R, Pavel OD, Birjega R, Zavoianu R, Angelescu E (2010)
Catal Lett 134:309
2. Angelescu E, Pavel OD, Che M, Birjega R, Constentin G (2004)
Catal Commun 5:647
3. Pavel OD, Birjega R, Che M, Costentin G, Angelescu E, Serban S
(
2008) Catal Commun 9:1974
The catalysts show excellent yields with no oligomeri-
zation of the substrates and no by-products. HyHT obtained
by reconstruction of the LDH structure by memory effect
4. Pavel OD, Zavoianu R, Birjega R, Angelescu E (2011) Catal
Commun 12:845
25. Astle MJ, Etherington RW (1952) Ind Eng Chem 44:2871
-
2
6. Jyothi TM, Raja T, Sreekumar K, Talawar MB, Rao BS (2000) J
Mol Catal Chem 157:193
under mild conditions have a higher density of HO groups
than the parent structures which leads to its higher activity.
The nucleophilic addition of saturated linear alcohols is very
intense when the substrate is acrylonitrile or its corresponding
esters (e.g. methylacrylate and ethylacrylate, respectively).
Meanwhile, the reaction seems to be significantly influenced by
the nature of the substituent in b carbon position.
2
2
7. Corma A, Fornes V, Rey F (1994) J Catal 148:205
8. Parida K, Das J (2000) J Mol Catal Chem 151:185
29. Palomeque J, Lopez J, Figueras F (2002) J Catal 211:150
3
3
0. Palomares AE, Prato JE, Rey F, Corma A (2004) J Catal 221:62
1. Takehira K, Kawabata T, Shishido S, Murakami K, Ohi T, Shoro
D, Honda M, Takaki K (2005) J Catal 231:92
2. Marchi AJ, Apesteguia CR (1998) Appl Clay Sci 13:35
3. Angelescu E, Pavel OD, Birjega R, Florea M, Zavoianu R (2008)
Appl Catal A 341:50
3
3
Acknowledgments FT acknowledge support from the strategic
grant POSDRU/89/1.5/S/58852, Project ‘‘Postdoctoral program for
training scientific researchers’’ co-financed by the European Social
Found within the Sectorial Operational Program Human Resources
34. Hattori H (2001) Appl Catal A 222:247
35. Valente JS, Pfeiffer H, Lima E, Prince J, Flores J (2011) J Catal
279:196
1
23