Novel catalyst with layered structure: Metal substituted magadiite

Article abstract of DOI:10.1016/j.molcata.2016.02.014

In this work, aluminum- and vanadium-modified magadiites with Si/Al?=?15 and Si/V?=?33 molar ratios were obtained by Seed Induced Crystallization (SIC) method and the solid was investigated in relation to its acidity. The catalysts were characterized using X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectrometry (ICP–OES), solid state magic angle spinning nuclear magnetic resonance (MAS-NMR), temperature-programmed desorption of ammonia (NH₃-TPD) and Fourier transformed infrared spectroscopy in situ (FTIR). Crystalline [Al]-and [V]-magadiites were successfully obtained in which metal ions were inserted in the structure of the solid in tetrahedral coordination. The acidities of [M]-magadiites were used in catalytic ethanol conversion monitored by in situ FTIR: ethylene (949?cm^?1) and acetaldehyde (1760–1730?cm^?1) were the products obtained.

Full text of DOI:10.1016/j.molcata.2016.02.014

Accepted Manuscript
Title: Novel catalyst with layered structure: Metal substituted
magadiite
Author: Gizeuda L. Paz Erica C.O. Munsignatti Heloise O.
Pastore
PII:
S1381-1169(16)30048-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.02.014
MOLCAA 9780
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
23-9-2015
12-2-2016
13-2-2016
Please cite this article as: Gizeuda L.Paz, Erica C.O.Munsignatti, Heloise O.Pastore,
Novel catalyst with layered structure: Metal substituted magadiite, Journal of Molecular
Catalysis A: Chemical http://dx.doi.org/10.1016/j.molcata.2016.02.014
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1
Novel catalyst with layered structure: Metal substituted magadiite
Gizeuda L. Paz, Erica C. O. Munsignatti and Heloise O. Pastore
Institute of Chemistry, University of Campinas, Monteiro Lobato St., 270, 13084-971,
Campinas, SP, Brazil (gpmmm@iqm.unicamp.br)*

Corresponding author. E-mail: gpmmm@iqm.unicamp.br. Phone number: 55 19 35213095

2
Graphical abstract
Highlights





Crystalline [Al]- and [V]-magadiites were prepared by the SIC method.
The materials were characterized in relation to local structure of Al and V.
The catalysts were used in the conversion of ethanol and monitored by FTIR.
Ethylene and acetaldehyde are the products observed in ethanol conversion.
Diethylether was not found among the products.
ABSTRACT
In this work, aluminum- and vanadium- modified magadiites with Si/Al=15 and Si/V=33
molar ratios were obtained by Seed Induced Crystallization (SIC) method and the solid was
investigated in relation to its acidity. The catalysts were characterized using X-ray diffraction
(
XRD), inductively coupled plasma - atomic emission spectrometry (ICP-OES), solid state
magic angle spinning nuclear magnetic resonance (MAS-NMR), temperature-programmed
desorption of ammonia (NH -TPD) and Fourier transformed infrared spectroscopy in situ
FTIR). Crystalline [Al]- and [V]-magadiites were successfully obtained in which metal ions
3
(
were inserted in the structure of the solid in tetrahedral coordination. The acidities of [M]-
magadiites were used in catalytic ethanol conversion monitored by in situ FTIR: ethylene
-1
-1
(
949 cm ) and acetaldehyde (1760-1730 cm ) were the products obtained.
Keywords: Ethanol conversion. [Al]-magadiite. [V]-magadiite. Ethylene. Acetaldehyde.

3
1
. Introduction
The lamellar silicate magadiite is a member of the family of silicic acids, which also
includes makatite, kanemite, octosilicate and kenyaite [1]. In spite of the fact that it was
reported in the literature as early as 1967 [2], magadiite’s crystalline structure has not been
determined yet [3]. The general formula of magadiite is Na
2
Si14
O
29(5-10)H O and is formed
2
by silicon atoms connected to four oxygen atoms; the tetrahedra share corners forming the
lamella that characterize the solid [1,3–5]. The excess negative charge present on the surface
is counterbalanced by hydrated sodium ions located in the interlayer spaces. Due to this
arrangement, the lamella of this silicate displays three different silicon environments; Q ((O-
2
3
-
4
/
HO)
2
Si(OSi)
The silanol groups in magadiite surface are considered very weak Brønsted acid sites
6], however, the acidity of these materials may be improved by the isomorphous substitution
2
), Q ((O /HO)Si(OSi)
3
) and Q (Si(OSi)
4
) sites.
[
of silicon atoms by trivalent atoms such as aluminum, creating a negative charge for each
atom replaced [7–9]. Naturally, these negative charges are counterbalanced by compensation
+
+
+
cations, generally Na . When these ions are exchanged by H , directly or by NH
4
ion-
exchange followed by thermal treatment, Brønsted acid sites appear in the solid. In addition to
its high ion exchange capacity, this silicate may also be used as precursor for obtaining other
porous solids [10,11].
Superti et al. [8] studied the surface properties of [Al]-magadiite by direct and
aluminum induced crystallization (AIC) methods. The authors observed that the direct
synthesis, that is, addition of Al to the synthesis gel, resulted in amorphous or highly
contaminated magadiite, whereas the Al-induced crystallization provided crystalline materials
in shorter reaction time. Moura et al. [7] improved the Al-crystallization method by showing
that is possible to insert aluminum into the framework of magadiite through the addition of
seeds directly into the gel; this method was named Seed Induced Crystallization (SIC). SIC
consists in the addition of the aluminum source in the synthesis gel of the reaction along with
a small amount of crystals of siliceous magadiite. Crystallization is induced by the seeds and
reduces the number of steps in the procedure, optimizing and simplifying the synthetic route.
The addition of seed drives the synthesis to the desired phase and reduces the formation of
impurities [12].
Ethanol dehydration has been performed over many catalysts such as zeolites,
aluminas and heteropolyacids [13–17]. Ethanol dehydration can take place by two
competitive paths accompanied by a side reaction (reactions 1-3).

4
Reaction (1) is the intramolecular dehydration of ethanol to ethylene, which is the
dominant product obtained at high temperatures while reaction (2) is the intermolecular
dehydration of ethanol to diethylether (DEE), which is the main product observed at low
temperatures. Acetaldehyde can be obtained as the product of a side reaction (3), at high
temperatures.
Ethanol can be dehydrated through an unimolecular pathway to generate ethylene or
through a bimolecular route to produce DEE [14,18]. The mechanism for formation of DEE
involves the adsorption of a molecule ethanol on a Brønsted acid site followed by the
adsorption of a second molecule on the same acid site, thus forming an ethanol dimer.
Dehydration of this dimer adsorbed form DEE and H O and regenerates the site acid. Another
2
mechanism involving DEE conversion includes adsorption of a molecule ethanol, followed by
dehydration, forming ethoxy group which reacts with a second molecule of ethanol adsorbed,
generating DEE. On the other hand, the desorption of ethoxy group generate ethylene. This
product can also be an intermediate in dehydrating ethanol to ethylene.
The selective oxidation of ethanol over vanadium silicate molecular sieves with MEL
topology was investigated by Sivasanker et al. [19]. Acetaldehyde, DEE and ethylene were
the main products obtained. It is important to mention that the nature of the active sites
present control the selectivity of any specific product: V=O sites associated with extralattice
and lattice vanadium is responsible for the formation of acetaldehyde and both V=O and V-O-
Si associated with vanadium in the lattice are responsible for DEE formation.
The dehydration of ethanol over H-FER, H-MFI, H-MOR, H-BEA and H-Y zeolites,
silica-alumina and alumina was recently investigated by Phung et al. [15], who concluded that
these zeolites (in these particular Si/Al molar ratios) are most active in the ethanol conversion
to ethylene and DEE when compared to alumina and silica-alumina. The authors assigned
their findings to the presence of Brønsted acid sites in zeolitic cavities and, mainly, the role of
pore size and morphology - shape selectivity and confinement - as well as Al content. Silica
alumina and alumina do not present cavities, therefore the effects observed in zeolites are not
operative.

5
Besides catalysts such as alumina and zeolites, the calcined hydrotalcite was also used
in this reaction and DEE cracking. The study showed that the both reactions are catalyzed
efficiently over all catalysts, except on calcined hydrotalcite. The last catalyst is weakly active
in these reactions due its weak acidic, highlighting the role of acid sites for both reactions
[14].
Ethanol dehydrogenation to acetaldehyde on metals supported on silica has been
widely used [20], but highly dehydrated silica or silicalite-1 have also shown to be active
21,22] in that reaction. Silica surface is only slightly acidic due to the presence of silanols.
The best results were obtained for silica treated at 897 °C from reactions at temperatures
above 277 °C. To study the acid-base properties of highly dehydrated silica, NH and CO
TPD were performed on the solids. For samples treated at high and low temperatures the
desorption of NH and CO occurred at room temperature, indicating there is no acidic or
[
3
2
-
3
2
basic sites on the silica surface and that, in this case, ethanol dehydrogenation is not catalyzed
by acidic or basic sites. As the heating of silica at high temperatures causes condensation of
silanol groups to form siloxane bridges (reaction 4), the authors suggested that the active sites
for the dehydrogenation of ethanol are the bridged oxygen atoms.
Regarding the use of layered silicates in catalysis, montmorillonite was used in
reactions such as benzophenone cyanotrimethysilylation with cyanotrimethylsilane over Sn-
montmorillonite [23] and nitration of aromatic compounds on montmorillonite treated with
phosphoric acid [24]. No other clays or layered silicates materials were found as acid
catalysts.
Taking all these facts into account, the aim of this work is to investigate the catalytic
performance of [V]- and [Al]-magadiite on ethanol conversion reactions. To the best of our
knowledge, conversion of ethanol over layered silicates has not been reported in the literature.
The reactions were monitored using in situ FTIR of surface and gas phase at various reaction
temperatures.

6
2
. Experimental
2
.1. Catalysts preparation
The lamellar [M]-magadiites were synthesized according to the SIC method described
previously [7] with modifications. In order to obtain a material free of aluminum
contamination, the sodium metasilicate was synthesized at laboratory by dispersing of the
0
.1457 mol of SiO
molar ratio was equal to 2:1. The mixture obtained was stirred and heated at 100 ºC for 24 h.
To the gel was added HNO until pH 10.4 – 10.6. The gel was aged during 4 h at 74-76 ºC.
Then Al[OCH(CH or VOSO .4.2H O was added to the gel to yield Si/Al = 15 and Si/V =
3 molar ratios and a small amount of siliceous magadiite, previously synthesized as
2
in 250 ml of a NaOH solution (0.2914 mol), to obtain a gel with the Na:Si
3
3
)
2
]
3
4
2
3
described in literature [25], was added to the gel. The reactions were performed under argon
atmosphere until transfer to autoclave.
In order to obtain samples in the ammonium form, NH +
-magadiite, NH +
-[Al]- and
4
4
+
-1
NH
4
-[V]-magadiite, each sample was dispersed in 0.1 mol L NH
4
Cl solution (1 g of
sample/0.1 L of solution) [8]. This system was kept under magnetic stirring for 24 h. After
that, the solid was filtered and washed with deionized water until the supernatant tested
-
negative for Cl ions. This procedure was performed in triplicate for each sample.
+
The treatment for NH
4
decomposition was carried out under the following conditions:
-1
the materials were heated at 5 °C min under argon atmosphere from room temperature to
50 °C, temperature at which each sample was kept for 3 h under O flow. The final samples
4
2
+
+
+
were named H -magadiite, H -[Al]-magadiite and H -[V]-magadiite.
2
.2. Characterization
X-ray diffractograms were obtained using a Shimadzu equipment, XRD 7000, with
CuKα radiation source obtained with 40 kV in filament and current of 30 mA. Data were
-1
collected in the range of 1.5-55° 2θ with a scan speed of 2° min at room temperature. The
interplanar distances were calculated using Bragg’s Law (nλ = 2dsin θ).
The ICP-OES analyzes were performed using a Thermo Scientific iCAP 6000.
Previously, the samples were thermally decomposed by heat treatment at 900 ° C for 10 h in a
furnace under dry oxygen atmosphere. Next, 100 mg of these materials were digested in an
acidic mixture of HF (48%) and HNO (65%) under microwave irradiation.
3

7
The Brunauer-Emmett-Teller (BET) specific surface area was obtained by nitrogen
adsorption using a Quantachrome Analysis at cryogenic temperature. The samples were
heated at 100 °C under vacuum for 15 h prior to the measurement.
The absorption spectra in the UV-Vis region were obtained on a Cary Model 5000
spectrophotometer using a quartz cell. The spectra were recorded between 190 - 2500 nm
without dilution of the sample. The background adopted was different for each catalyst: Na-
magadiite was used for samples as synthesized and NH +
-magadiite was used for the
4
+
exchanged sample and H -magadiite for calcined sample.
2
7
The Al solid state nuclear magnetic resonance (NMR) spectra were obtained on a
+
Bruker Avance 400 equipment with a frequency of 10 kHz in a zirconia rotor, applying a
single pulse of 1.5 s (/12) duration and 2 s delay time. Al(NO
3
3
) acid solution was used as
reference and the High Power Decoupling (HPDEC) technique was applied. The Altd/Aloct
ratios were obtained using the MasterC program.
The TPD-NH
3
measurements were carried out on a Quantachrome TPD/TPR
+
ChemBet-3000 equipment. Approximately 100 mg of H -[Al]-magadiite were placed in a
-1
quartz reactor and treated for 2 h at 300 °C under flow of He (30 mL min ). Then, the sample
was cooled to 100 °C and saturated with NH /He (4 vol %) for 2 h; weakly bound ammonia
was removed by He flow (30 mL min ) for 1 h. Finally, the sample was heated to 400 °C at a
3
-1
-1
heating rate of 10 °C min under flow of He and the release of ammonia was monitored using
thermal conductivity detector.
2
.3. In situ FTIR experiments
These experiments were performed in order to study the catalytic conversion of
ethanol over the samples synthesized in this work. In situ FTIR spectra were obtained at a
-1
resolution of 2 cm and a total of 128 scans using a Nicolet 6700 FTIR spectrometer. For
-
2
+-
+-[V]-magadiite)
were prepared and placed into an IR cell equipped with KBr windows and connected with a
carrying out this experiment, self-supporting pellets (thickness of 8.6 mg cm for NH
4
-2
+
-2
magadiite, 7.5 mg cm for NH
4
-[Al]-magadiite and 7.0 mg cm for NH
4
-5
+-[Al]- and NH +
-[V]-magadiites were
conventional high vaccum line (10 mbar). The NH
4
4
treated at 350 °C in vacuum in order to remove water and ammonia, thus obtaining the acidic
material and, successively, by heating at the same temperature in oxygen (300 mbar) to
remove carbonaceous impurities. After that, ethanol was added (PEtOH = 3.1 mbar) and spectra
were collected from room temperature up to 350 °C in static conditions. The gas phase in the

8
cell was used as background and the spectra of the dry pellet was subtracted from all the
spectra obtained from the pellet. The absorbance values were divided by the thickness of the
pellet.
3
. Results and discussion
3
.1. Characterization
3
.1.1 Long Range Structure
The XRD patterns of the samples are displayed in Fig. 1. Curves (a), (b) and (c) show
the characteristic peaks of magadiite [25] at 5.6° (1.55 nm), 11.3° (0.77 nm) 17.11° 2θ (0.52
nm) corresponding to (001), (002) and (003) diffraction planes, respectively. In addition,
peaks between 23 and 30° 2θ indicate the crystalline nature of the layer. These results confirm
that the addition of aluminum or vanadium does not cause the appearance of contaminating
phases or amorphization of the structure, as shown before [7,8,25].
Magadiite interlayer space changes according to the counter-ion and the amount of
water present; sodium ion is easily exchanged and this process makes it possible to modify
the acidity of this silicate [3,4]. For this purpose the samples were exchanged with NH +
and
4
the XRD patterns displayed in Fig. 1(curves (a), (b) and (c) compared with (d), (e) and (f))
show that there was a displacement of the (001) diffraction towards slightly larger values of
2
θ, indicating the reduction of the interlayer space from ca. 1.55 nm to aproximately 1.36 nm.
These differences may be explained based on the size of hydrated radius of these ions, 0.358
+
+
[26], respectively. Thus, the size of hydrated NH +
and 0.331 nm for Na and NH
4
4
is about
+
8
% smaller than the hydrated Na , explaining the reduction of the basal spacing. It is also
possible to observe that the region between 20° and 30° 2θ lost the usual resolution observed
when the counterion is sodium.

9
3
.1.2 Short-range Structure
The amount of aluminum and vanadium present in the solids is shown in the Table 1.
[Al]-magadiite sample presents a larger amount of Al in comparison with the
concentration in the synthesis gel. This is due to the higher solubility of silicon species, at the
reaction pH (10.4 - 10.6), when compared to aluminum species. Surface area of these
2
materials calcined at 450 °C range from 76 to 269 m /g showing that indeed the active sites
are accessible to the ethanol molecules.
The 27Al MASNMR spectra of as-synthesized and NH +
Al]-magadiite are displayed in Fig. 2. All spectra show signals around 57 ppm which are
assigned to the presence of aluminum in tetrahedral coordination in the structure [9,29].
Another peak is observed at 8 ppm in Na- and NH +
-[Al]-magadiite corresponding to
octahedral aluminum [7,8] (Figs. 2(a) and 2(b)). These materials were exchanged with NH Cl
-exchanged magadiite and
4
[
4
4
to remove any possible cationic aluminum species trapped in the interlayer space. The ratios
between the areas of the peaks corresponding to the aluminum atoms into octahedral and
tetrahedral coordination before and after NH +
exchange enabled us to shed light on Al
4
coordination. On Na-[Al]-magadiite Altd/Aloct was 0.65 and decreased to 0.58 after ion
exchange. These results indicate that there is no cationic Al-species in this material [8].
The presence of octahedral Al is possibly due to partially extraframework Al ions in
the form ≡Al-OH. When hydrated, these sites become octahedral Al sites, as shown before by
Superti et al. [8]. The same analysis was performed with Na-magadiite (Fig. 2, curve (a)) and
Na-[V]-magadiite (Fig. 2, curve (b)) and no Al peak was observed.
The presence of aluminum in tetrahedral coordination is the first evidence that this
material can exhibit Brønsted acidity and activity in acid catalysed reactions.
As for vanadium (Table 1), it has been shown before [27,28] that the concentration of
framework V can be very low, therefore the small amount of this heteroatom in [V]-magadiite
is no surprise. The UV-Vis spectroscopy, Fig. 3, show the sites where the metal can be found
in this structure.
There is abundant literature [28–30 and references therein] concerning the situation of
V ions in silicate structures, a general agreement points to the existence of two sites for V in
such structures: a more distorted one with four bonds to the structure (Fig. 4(a)) and a less

1
0
distorted site where one of the bonds bear an OH group (Fig. 4(b)). The absorption frequency
5
+
of the energy charge transfer bands (O → V) for tetrahedral V sites is related to the degree
5
+
of distortion of the V site, thus sites observed at ca. 210 and 238 nm are the most distorted
sites while the less distorted appear at 260-280 nm. The band at 335 nm is also assigned to
5
+
tetrahedral framework V but it seems to be related to the counterion in the structure [27,28].
Transitions around 400 nm, corresponding to octahedral vanadium species are observed only
for the acidic sample. Having these information in mind, it is possible to observe that samples
+
+
NH
4
-[V]-magadiite. (Fig. 3, curve (a)) and H -[V]-magadiite (Fig. 3, curve (b)) 3 present
both more and less distorted V sites.
3
.1.3 Acidity and Catalytic Conversion of Ethanol
The acidities of these materials were evaluated using the temperature-programmed
desorption (TPD) of ammonia. Ammonia was adsorbed on the acid sites of the materials and
removed by thermal desorption. The desorption temperature depends on the strength of the
acid sites: weak sites desorb NH in the range from 150 to 250 °C, moderate acid sites desorbs
3
from 250 to 350 °C and strong acid sites liberate ammonia from 350 °C to 500 °C [33,34].
+
Fig. 5 exhibits the NH
3
-TPD profile of [Al]-magadiite. It can be seen that H -[Al]-
magadiite exhibits a broad peak at around 200 °C tailing in the direction of higher
temperatures (Fig. 5(a)), an indication of the presence of weak to moderate acid sites in these
samples. This result is a further indication that the inclusion of aluminum in the structure of
2
7
magadiite generates acid sites, as discussed by Al MASNMR. The same experiment was
+
performed with H -magadiite and no signal was observed (Fig. 5(b)).
3
.1.3.1.. Catalytic conversion of ethanol: FTIR study
The FTIR spectra of dehydrated, calcined, NH +
+-[Al]-magadiite are presented in Fig. 6. The absence of the NH +
-magadiite, NH +
-[V]-magadiite and
characteristic band
4
4
NH
4
4
-1
(
3150 cm ) [35] indicates that this cation was completely removed. The samples exhibit two
-1
-1
main bands in the range 3800 - 3400 cm [8,36–38]: a low intensity band at 3745 cm ,
attributed to the presence of weakly acidic isolated silanol groups; this band is also observed
-1
in zeolitic structures [36,38,39] and a broad band centered at 3658 cm which is composite of
two contributions: the bridging Si-O(H)-Al groups and OH silanol groups weakly
perturbed due the interaction with other neighboring groups (Fig. 6, curve (b)) [8,40]. A

1
1
-1
+
+
shoulder is also observed at ca. 3470 cm on H -magadiite and H -[V]-magadiite and may be
assigned to a portion of SiOH groups involved in the chain H-bonded in different
-1
configuration from that which originated the band at ca. 3650 cm and V-OH groups,
+
respectively. The band assigned to isolated silanols is more intense in H -[Al]-magadiite (Fig.
+
6
, curve (b)) and on H -[V]-magadiite (Fig. 6, curve (c)) samples as heteroelement insertion
into the framework creates silanol defects [8].
The catalytic activity of magadiite samples discussed above was investigated by
ethanol conversion. Fig. 7 shows the spectra of 3.1 mbar ethanol adsorbed on magadiite
samples. Several modifications appear because of ethanol adsorption on the silicate and [Al]-
-
1
or [V]- silicates. The first one is the displacement of the 3745 cm band on all samples (Fig.
-1
-1
-1
7
) to 3659 cm , a 86 cm difference, typical of Si-OH weak acidity. The 3659 cm band is
+
+
+
wider in H -[Al]- and H -[V]-magadiite than in H -magadiite (compare curve (a) with (b) and
+
+
(
c) on Fig. 7). This is probably due to diverse nature of Si-OH groups in H -[Al]- or H -[V]-
+
magadiite in comparison to H -magadiite. Makarova et al. [41] showed in a very elegant work
that both, increase in intensity and in width of bands corresponding to OH stretching
vibrations upon base adsorption on zeolites and aluminophosphates, are in direct correlation
with the bands displacement, in wavenumbers. The band displacement is approximately the
same for the three samples in this work, however, the variation in width and intensity is
different. This observation supports the idea of a band composite of different contributions
+
+
especially in the case of H -[Al]-magadiite, but also for H -[V]-magadiite. It is important to
comment that the negative band due to subtraction of the dry pellet was not observed in H+-
+
[
Al]-magadiite. That means that for H -[Al]-magadiite, not all Si-OH groups were accessible
to ethanol molecules and thus the base line levels off on subtraction of the dry pellet. These
non-accessible Si-OH groups may exist due to two main reasons: difficulty of ethanol
diffusion to the places where the sites are located or the ethanol interaction in not capable of
displacing previously established interactions between Si-OH groups.
The introduction of ethanol on to the pellet causes also the displacement of the 3658
-1
-1
-1
cm band to 3330 cm , a difference of 328 cm much larger than the displacement observed
when ethanol is adsorbed on Si-OH groups. Again, although the maxima of this band is very
close for all samples the band shown in the spectrum of the Al-sample is wider than the bands
observed in the other two samples, probably as an effect of the ethanol interaction with
several slightly different ≡Si-O(H)-Al(or V)≡ environments as also shown by a large peak on

1
2
TPD-NH
3
. Again, the conclusions of Makarova´s study [41], previously cited, apply to these
+
bands. The heterogeneity of ≡Si-O(H)-Al≡ sites in H -[Al]-magadiite was reported before in
the literature [8]
-1
The bands between 2975 and 2876 cm are due to CH stretching vibration of the
adsorbed ethanol molecules [36].
After ethanol adsorption, the samples were heated at 100, 150, 200, 250, 300 and 350
°
C and remained at each of these temperatures for 1 h. It is worth mentioning that all spectra
were collected at room temperature. Fig. 8 shows the spectra of the solid surface (Fig. 8A)
+
and gas phase (Figs. 8B, 8C and 8D) of the reaction performed on H -[Al]-magadiite.
Fig. 8A displays the species on the pellet after ethanol adsorption and heating at
increasing temperatures. Right at 100 °C it is possible to observe that a fraction of Si-OH
adsorbed ethanol molecules have desorbed: a negative band appears at 3745 cm-1
-1
accompanied by a wide band at 3340 cm probably due to the restoration of the extensive H-
bonded Si-OH groups in the solid. From 150 °C to 250 °C small variations were observed in
the FTIR spectra.
-1
At 300 °C, there is a sudden increase in the bands at ca. 3340 cm (OH of acidic OH groups,
-
1
ethanol and H
2
O) and in the region of 2900 cm due to CH stretching vibrations. At 350 °C
the negative band of free Si-OH begins to disappear, indicating that the products of ethanol
-1
conversion adsorb on Si-OH groups. The band appearing at 3676 cm is slowly displaced to
-1
3
643 cm suggesting that the species adsorbing on to Si-OH groups are stronger bases than
ethanol.
Figs. 8B, 8C and 8D help to clear the nature of the species formed from ethanol. As
for the pellet observed in Fig. 8A, hardly any difference can be observed in the gas phase of
the cell from room temperature up to 250 °C: the bands observed are typical of ethanol [42]
-1
(
3675 OH, 2800-3000 CH, 1453 CH, 1394 OH, 1241 CH, 1085-1048 and 880 cm (C-O/

C-
)
C .
When the temperature arrives at 300 °C, and after at 350 °C, new bands appear at 3106
-1
and 2988 cm (observed also for ethanol but in lower intensity) (Fig. 8B curves (f) and (g))
-1
and at 949 cm (Fig. 8D): the first two assigned to ethylene C-H stretching and the last CH
2
wagging vibrations of ethylene [14,16]. The presence of water becomes evident at ca. 3360-
-1
-1
3
390 cm (Fig. 8B) and at 1640 cm (Fig. 8C) due to its production in reaction (1). It is

1
3
-1
necessary to point out that liquid water and ethanol (at 1085, 1048 and 880 cm , Fig. 8D)
42,43] were observed after the reaction at 300 °C and 350 °C. This is due to the formation of
[
an aqueous ethanolic film on the windows of the FTIR cell.
Besides these new bands in the gas phase, signals due to the presence of acetaldehyde
-
1
were observed at 2735-2700 cm (Fig. 8B, curves (f) and (g)-CH stretching vibration) and at
-1
1
760-1730 cm (C=O, Fig. 8C, curves f and g) [44,45]. The presence of this compound is not
unexpected since it was also observed in the dehydrogenation of ethanol using dehydrated
silica or silicalite-1 [21,22]. In these materials siloxane bridges were considered the active
sites for ethanol dehydrogenation. The results of the ammonia desorption in NH +
-magadiite
4
discussed in the present work are in accordance with those observed for the highly dehydrated
silica active in acetaldehyde production thus allowing to conclude that no effective acids sites
are needed for the formation of acetaldehyde in the catalytic reaction, indicating that the
oxygen bridge catalyzes it (reaction 5).
+
Fig. 9 shows the results of H -[V]-magadiite in the conversion of ethanol. The general
+
appearance of these spectra points to the same behavior discussed for H -[Al]-magadiite with
slight but important differences.
Analyzing the spectra on Fig. 9A, there is not the presence of water at higher
+
temperatures, as observed in Sample H -[Al]-magadiite (compare curves (f) and (g) in fig. 8A
-
1
with 9A and the band in 1640 cm in curves (f) and (g) in Fig. 8C with 9C). Ethanol is
+
+
consumed in a more extensive way in H -[V]-magadiite in comparison with H -[Al]-
magadiite, as shown by the comparison of curves (d)-(g) of Figs. 8A e 9A in the region
-1
around 3000 cm in the pellet and in the gas phase on curves (f) and (g) of Figs. 8B e 9B.
-1
Also impressive is the difference in relative intensity of the bands at ca. 1400 cm in frames
-1
C of Figs. 8 and 9 and the bands at 1085, 1048 and 880 cm (C-O/C-C) in frames D of Figs. 8
and 9. These bands become more intense because these vibrations are sensitive to hydrogen
bonding.
Considering the bands corresponding to carbonyl groups in the range of 1760-1730
-1
cm , it is possible to conclude that acetaldehyde is produced in a more extensive fashion in
+
+
H -[V]-magadiite than in H -[Al]-magadiite according to reaction 3 and 5. Ethylene is also

1
4
+
+
produced in H -[V]-magadiite but in smaller amounts than in H -[Al]-magadiite, the lower
concentration of water, in the gas phase and in the pellet, indicates that reaction 1 is not the
main responsible for ethanol consumption.
+
Ethanol conversion to ethylene was also observed in H -magadiite but in minute
amounts (see Supplementary Materials, Fig. S1). The possibility that ethanol dehydration to
ethylene could occur in the absence of a catalyst was ruled out by performing the catalytic test
in the IR cell in the absence of the silicate pellet; no product was observed.
Summarizing, acid-metal-substituted magadiites are catalysts for ethanol conversion.
+
Despite the variation in the properties of active sites in H -[Al]-magadite [8], both acid and
o
redox sites and the siloxane bridges produce acetaldehyde and ethylene at 350 C, in different
concentration.
4
. Conclusions
It was shown that acid [Al]-and [V]-magadiite samples were prepared by the seed-
induced crystallization method. The materials display weak to moderate acid sites capable of
promoting ethanol conversion at temperatures of 300 and 350 °C. It was shown here that
ethanol can be converted to ethylene and acetaldehyde by acid [Al]- and [V]-magadiites. The
larger activity of such solids in conversion to one or the other product is connected to the
+
framework heteroelement: ethylene is largely produced by ethanol dehydration on H -[Al]-
magadiite while acetaldehyde can come either from ethanol oxidation catalyzed by siloxane
+
+
bridges with production of H
2
or by V-oxidizing sites in H -[Al]-magadiite and H -[V]-
magadiite, respectively.
As far as we could search, no works were published before where clay lamellar
aluminosilicates were the acid catalysts. The majority of studies were performed on
montmorillonite, a natural clay used for nitration and cyanotrimethylsylilation reactions.
Having in mind that magadiite, contrarily to zeolites and molecular sieves, can have its
+
interlayer spaces expanded and pillared, the success of ethanol conversion on H -[Al]- and
+
H -[V]-magadiite shows that a set of weak-to-moderate acid-catalysed reactions can be
performed on large sized molecules on an expandable layered material. The use of magadiite
and other lamella solids as catalysts bridges the gap between pure zeolitic systems, with
reactions occurring in cages and channels, and silica or alumina with mainly catalytic active
open surfaces.

1
5
Acknowledgements
The authors are grateful to Fundação de Amparo à Pesquisa no Estado de São Paulo
FAPESP) for the financial support to this work (Process 2014/06942-0). GLP and HOP
(
acknowledge CNPq for the fellowships. The collaboration of Prof. Marco Aurélio Zezzi
Arruda, Dr. Gustavo Pessoa and Francisca Solânea de O. Ramos for ICP-OES analyses is
gratefully acknowledged.

1
6
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1
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1
9
2
0000 cps/g
(f)
(e)
(d)
(
c)
b)
(
(a)
5
10 15 20 25 30 35 40 45 50 55
degree
2
Fig. 1. X-ray diffratograms of (a) Na-magadiite, (b) Na-[V]-magadiite, (c) Na-[Al]-magadiite,
d) NH -[Al]-magadiite.
+-magadiite, (e) NH +-[V]-magadiite and (f) NH +
(
4
4
4

2
0
(a)
(b)
(
c)
(d)
1
50
100
50
0
-50
-100
-150

/ppm
2
7
+-[Al]-magadiite.
Fig. 2. Al NMR of (a) Na-[Al]-magadiite and (b) NH
4

2
1
1
1
1
0
0
0
0
0
,4
,2
,0
,8
,6
,4
,2
,0
2
07
2
38
70
2
2
80
3
35
400
400
(c)
(b)
(a)
2
00
300
500
600
700
800
Wavenumber (nm)
Fig. 3. UV-Vis spectra of (a) Na-[V]-magadiite, (b) NH +
magadiite.
-[V]-magadiite and (c) H -[V]-
+
4
Si
O
V
O
O
O
OH
V
O
O
O
Si
Si
Si
Si
(a)
(b)
Fig. 4. Proposed sites of V inclusion into magadiite structure: (a) more distorted and (b) less
distorted site.

2
2
(b)
(a)
1
00
150
200
250
300
350
400
Temperature (°C)
+
+
Fig. 5. NH
3
-TPD curves of (a) H -magadiite and (b) H -[Al]-magadiite.
-
2
-1
0
.025 a.u. cm . mg
(
c)
(b)
(a)
4
000
3800
3600
3400
-13200
3000
2800
Wavenumber (cm )
+
+
+
Fig. 6. FTIR spectra of (a) H -magadiite, (b) H -[Al]-magadiite and (c) H -[V]-magadiite
after treatment at 350 °C.

2
3
-
2
-1
0
.025 a.u. cm . mg
(
c)
(b)
(a)
4
000
3500
13000
2500
-
Wavenumber (cm )
+
Fig. 7. FTIR spectra of surface species arising from ethanol adsorbed on (a) H -magadiite, (b)
+
+
H -[Al]-magadiite and (c) H -[V]-magadiite at room temperature.

2
4
-
2
-1
0
.05 a.u. cm . mg
A
B
-
2
-1
0
.05a.u. cm . mg
(
(
g)
(
g)
f)
(
f)
e)
(
(
(
d)
c)
(e)
(d)
(c)
(
b)
a)
(
b)
a)
(
(
4
000
3500
3000
Wavenumber (cm )
2500
2000
4000 3800 3600 3400 3200 3-1000 2800 2600
Wavenumber (cm )
-
1
C
D
-
2
-1
-2
-1
0
.025 a.u. cm . mg
0.025 a.u. cm . mg
(
g)
(
f)
(
g)
(
e)
(
d)
(
f)
(
e)
(
c)
(
(
d)
(
b)
c)
b)
a)
(
(
(
a)
1
900
1800
1700
1600
1500
1400
1300
1300
1200
1100
1000
900
-1
800
700
-1
Wavenumber (cm )
Wavenumber (cm )
Fig. 8. FTIR spectra of pellet (A) and (B, C, and D) gas phase after ethanol was
+
adsorbed on H -[Al]-magadiite at (a) room temperature, (b) 100 °C, (c) 150 °C, (d) 200
°
C, (e) 250 °C, (f) 300 °C, and (g) 350 °C.

2
5
-
2
-1
-
2
-1
A
B
0
.05 a.u. cm . mg
0
.05 a.u. cm . mg
(
g)
(
g)
(f)
(
f)
(
e)
d)
c)
(
e)
(
d)
(
(
(
c)
(
(
b)
a)
(
b)
a)
(
4
000
3500
3000
2500
2000
4000 3800 3600 3400 3200 3-1000 2800 2600
Wavenumber (cm )
-
1
Wavenumber (cm )
-
2
-1
C
D
-
2
-1
0.025a.u. cm . mg
0
.025 a.u. cm . mg
(
(
g)
f)
(
(
g)
f)
(
e)
(
e)
(
d)
(
d)
(
c)
(
c)
(
(
b)
a)
(
(
b)
a)
1
900
1800
1700
1600
1500
1400
1300
1300
1200
1100
1000
900
800
700
-1
-1
Wavenumber (cm )
Wavenumber (cm )
Fig. 9. FTIR spectra of pellet (A) and (B, C, and D) gas phase after ethanol was
+
adsorbed on H -[V]-magadiite at (a) room temperature, (b) 100 °C, (c) 150 °C, (d) 200
°
C, (e) 250 °C, (f) 300 °C, and (g) 350 °C.

2
6
Table 1. Elemental analysis by ICP-OES
Samples
(Si/Al)gel
(Si/V)gel
(Si/Al)solid
(Si/V)solid
S
BET
2
(
m /g)*
Magadiite
-
-
∞
-
-
76
129
[
Al]-magadiite 15
V]-magadiite
-
9.25  0.06
[
-
33
∞
80.91
 269
3
.35
*
Samples in the protonic form