Ag-promoted ZrBEA zeolites obtained by post-synthetic modification for conversion of ethanol to butadiene

Article abstract of DOI:10.1002/cssc.201600572

1,3-Butadiene was synthesized from ethanol using zirconium-containing zeolite beta (ZrBEA) catalysts doped with 1 wt% silver. The Zr was planted using post-synthesis modification by dealumination of the parent zeolite followed by treatment with ZrOCl₂ in a DMSO solution. FTIR and NMR spectroscopy were used to investigate the planting process by preparing materials with different Si/Al ratios and crystal sizes. The results showed preferential grafting of Zr to the terminal silanols present on the external surface of the zeolite crystals instead of incorporation of Zr into silanol nests. The grafting yielded highly accessible Zr(OSi)₃OH open sites with high Lewis acidity, as confirmed by FTIR spectroscopy of adsorbed CO. These sites are shown to be extremely active for the conversion of ethanol to butadiene. Ag/ZrBEA catalysts prepared using the post-synthesis method showed significant advantages compared with Ag/ZrBEA catalysts synthesized using a conventional hydrothermal procedure. The best catalyst performance in terms of butadiene formation rate (3 mmolg^-1s^-1) was observed over Ag/Zr(3.5)BEA(75) (containing 3.5 wt% Zr), which had the smallest crystal size and the highest content of Zr open sites of the prepared catalysts.

Full text of DOI:10.1002/cssc.201600572

DOI: 10.1002/cssc.201600572
Full Papers
Very Important Paper
Ag-Promoted ZrBEA Zeolites Obtained by Post-Synthetic
Modification for Conversion of Ethanol to Butadiene
Vitaly L. Sushkevich[a] and Irina I. Ivanova*[a, b]
1,3-Butadiene was synthesized from ethanol using zirconium-
containing zeolite beta (ZrBEA) catalysts doped with 1 wt%
silver. The Zr was planted using post-synthesis modification by
dealumination of the parent zeolite followed by treatment
with ZrOCl2 in a DMSO solution. FTIR and NMR spectroscopy
were used to investigate the planting process by preparing
materials with different Si/Al ratios and crystal sizes. The results
showed preferential grafting of Zr to the terminal silanols pres-
ent on the external surface of the zeolite crystals instead of in-
corporation of Zr into silanol nests. The grafting yielded highly
accessible Zr(OSi)3OH open sites with high Lewis acidity, as
confirmed by FTIR spectroscopy of adsorbed CO. These sites
are shown to be extremely active for the conversion of ethanol
to butadiene. Ag/ZrBEA catalysts prepared using the post-syn-
thesis method showed significant advantages compared with
Ag/ZrBEA catalysts synthesized using a conventional hydro-
thermal procedure. The best catalyst performance in terms of
butadiene formation rate (3 mmolgꢀ1 sꢀ1) was observed over
Ag/Zr(3.5)BEA(75) (containing 3.5 wt% Zr), which had the
smallest crystal size and the highest content of Zr open sites
of the prepared catalysts.
Introduction
The recent discovery of metallosilicates such as Sn-, Zr-, and Ti-
substituted zeolites has opened new possibilities for the devel-
opment of environmentally friendly solid Lewis acid catalysts
for sustainable chemistry.[1–7] These materials have been ap-
plied as catalysts in various reactions for the conversion of bio-
mass-derived compounds, including Baeyer–Villiger oxidation
and Meerwein–Ponndorf–Verley–Oppenauer (MPVO) reduction
reactions,[8–11] aldol condensation,[12,13] carbohydrate isomeriza-
tion and epimerization,[14–20] Cannizzaro-type reactions,[21–23]
and butadiene synthesis from ethanol.[24,25] The latter process
has attracted a lot of attention in the past decade owing to its
industrial applications.
of butadiene from biomass feedstocks is highly desirable.[26–29]
A wide variety of catalytic systems have been synthesized and
tested for the conversion of ethanol into butadiene, including
bulk and mixed oxides, clay materials, and zeolites.[28,29] Recent
studies performed by our group have indicated that the silver-
promoted Zr-containg zeolite beta (ZrBEA) is among the most
efficient catalysts for the conversion of ethanol to buta-
diene.[24,25]
However, to achieve widespread industrial application of
ZrBEA, a thorough improvement of its synthesis is needed.
Current synthesis procedures use corrosive and toxic hydrogen
fluoride (HF) in the synthesis gel and the hydrothermal synthe-
sis takes up to 30 days to ensure crystallization of zeolite BEA
with high Zr content in the framework.[11,24,30] Moreover, the
large ZrBEA crystals formed under these conditions may face
mass transfer limitations during the catalytic processes.
Post-synthesis is a useful alternative route for implanting
transition metal ions into a zeolite framework. There have
been many examples of the preparation of metallosilicates
through the reaction of highly siliceous zeolites with metal
chloride vapors. This so-called “atom-planting method” has
proven to be an efficient way of incorporating Al, Ga, Sb, As, In
and Ti into the zeolite framework types MFI, MOR, and
BEA.[31–35] It has also been applied successfully for the post-syn-
thesis of SnBEA catalysts by solid–gas reaction of dealuminated
BEA with tin chloride,[36,37] tin acetate,[22] and various organo-
metallic compounds.[38] Another approach, which uses the dep-
osition of SnCl4 in dried isopropanol under reflux conditions,
has been proposed by Sels et al.[19,39–41] This method avoids the
application of vapor phase deposition and the formation of
a large amount of extra framework tin oxide.
Nowadays, butadiene is an important industrial monomer
used for the production of rubbers, plastics and different
chemicals. Typically, it is obtained as a co-product from naph-
tha crackers used for ethylene and propylene production.
However, the increased production of shale gas has led to
a lightening of the feedstocks for steam crackers and has re-
sulted in a shortage of longer-chain hydrocarbons in pyrolysis
products, including butadiene. Therefore the development of
an alternative, cheap, and sustainable process for the synthesis
[a] Dr. V. L. Sushkevich, Prof. I. I. Ivanova
Department of Chemistry
Lomonosov Moscow State University
Leninskye Gory 1, bld. 3, 119991 Moscow (Russia)
Fax: (+7)495-939-3570
E-mail: iiivanova@phys.chem.msu.ru
[b] Prof. I. I. Ivanova
A.V. Topchiev Institute of Petrochemical Synthesis
Russian Academy of Science
Leninskiy prospect, 29, 119991 Moscow (Russia)
Supporting Information for this article can be found under http://
dx.doi.org/10.1002/cssc.201600572.
ChemSusChem 2016, 9, 1 – 11
1
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
In contrast to SnBEA, post-synthesis of ZrBEA is not well
documented in the literature. Recently, Tang et al. reported
a post-synthetic strategy leading to mesoporous ZrBEA by
dealumination, desilication and incorporation of Zr. However,
expensive zirconium cyclopentadienyl compounds were used
for Zr deposition.[42] Wolf et al. used zirconium ethoxide (less
expensive but sensitive to water ) for a solid state exchange re-
action to incorporate Zr atoms into the framework.[43] There-
fore, the development of a simple procedure for post-synthesis
of ZrBEA using cheaper and stable precursors is an important
goal.
Here, we report a simple and cheap synthetic route for the
synthesis of ZrBEA by the treatment of dealuminated BEA zeo-
lites with ZrOCl2 in dimethyl sulfoxide (DMSO) under reflux
conditions. This procedure yields ZrBEA catalysts with high
content of open Zr Lewis sites, as confirmed by FTIR spectros-
copy of adsorbed CO. When doped with Ag, the catalysts
showed extremely high catalytic performance for the synthesis
of butadiene from ethanol. Comparison with Ag/ZrBEA cata-
lysts synthesized by the conventional hydrothermal procedure
indicates that the proposed post-synthetic method has signifi-
cant advantages.
Figure 1. SEM images of a) BEA(19), b) BEA(25), c) BEA(38) and d) BEA(75)
(scale bars correspond to 100 (a,c) and 200 nm (b,d)).
order. These results were confirmed by SEM analysis of the
parent zeolites (Figure 1). Indeed, the average crystal size in-
creased from 50 nm for BEA(75) up to 300 nm for BEA(19).
Dealumination of AlBEA zeolites was performed using a pro-
cedure that does not lead to any significant destruction of the
zeolite.[44] The standard procedure proposed in Ref. [44] takes
20 h and uses 13m HNO3 at 373 K for the complete removal of
aluminum. In the present work, we used slightly milder condi-
tions including slightly diluted nitric acid and a lower tempera-
ture. The dealumination procedure was repeated four times
and the resultant samples were essentially free of Al. The deal-
umination of the zeolites did not lead to any significant
changes in their structure and texture. A slight decrease in the
micropore volume and an increase in the mesopore volume
was observed (Table 1) owing to the removal of Al atoms from
the zeolite framework but the pore structure remained largely
intact. SEM images (Figure S3b) showed that the dealumina-
tion resulted in slight destruction of the zeolite crystal agglom-
erates.
Results and Discussion
Structure, texture and morphology of the catalyst
The chemical and textural characteristics of the parent and
modified zeolites are presented in Table 1. The parent zeolites
include a series of highly crystalline BEA samples with Si/Al=
19, 25, 38, and 75 [BEA(x), where x is the Si/Al ratio]. Nitrogen
adsorption–desorption data showed an equal micropore
volume (0.16 cm3 gꢀ1) for all the parent samples, whereas the
total pore volume differed substantially between 0.31–
0.75 cm3 gꢀ1 (Table 1). The nitrogen adsorption–desorption iso-
therms (Figure S1, Supporting Information) showed an increase
of N2 uptake at high relative pressures owing to the increase
of the intercrystalline porosity in the samples in the order
BEA(19)<BEA(25)<BEA(38)<BEA(75). This observation indicat-
ed that the crystal size of the catalysts decreases in the same
The incorporation of zirconium into the framework of dealu-
minated zeolites was performed in DMSO using ZrOCl2 as a pre-
cursor. DMSO was chosen as a solvent owing to the
high solubility of zirconyl chloride. Furthermore,
DMSO prevents the polymerization of ZrO2+ cations
Table 1. Catalyst characteristics.
in solution and relieves the interaction of Zr with the
Sample
Si/Al ratio Si/Zr ratio BET
[m2 gꢀ1
Total pore volume Micropore volume
silanol groups of the zeolite. The SEM images (Fig-
ure S3c) indicate that Zr grafting does not lead to
any changes in the catalyst morphology. It should be
noted that ZrBEA samples obtained by post-synthet-
ic treatment show a larger mesopore volume than
the hydrothermally synthesized benchmark sample
ZrBEA-HT (Table 1) owing to the smaller zeolytic crys-
tals of the former. As confirmed by SEM, the hydro-
thermally synthesized ZrBEA-HT sample had large
crystals with a size above 5 mm and a broad size dis-
tribution (Figure S2).
]
[cm3 gꢀ1
]
[cm3 gꢀ1
]
BEA(19)
BEA(25)
BEA(38)
BEA(75)
DeAlBEA(19)
DeAlBEA(25)
DeAlBEA(38)
DeAlBEA(75)
Zr(1.3)BEA(19)
Zr(2.1)BEA(25)
Zr(3.3)BEA(38)
Zr(3.5)BEA(75)
19
25
38
75
–
–
–
–
495
0.31
0.45
0.66
0.75
0.33
0.48
0.68
0.76
0.33
0.48
0.68
0.76
0.31
0.16
0.16
0.16
0.16
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.20
530
510
525
505
520
520
515
505
520
515
520
470
traces
–
traces
traces
traces
traces
traces
traces
traces
–
–
–
157
97
63
59
130
The structure of the catalysts before and after
treatments was analyzed by XRD (Figure 2). The
Zr(1.5)BEA-HT n/a
&
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
2
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
Figure 2. XRD patterns of the catalysts.
powder XRD patterns of BEA, DeAlBEA and ZrBEA samples
show typical features of crystalline zeolite BEA. No peaks of
crystalline ZrO2 or any other crystalline impurity phases were
detected. All ZrBEA samples synthesized by dealumination of
AlBEA zeolites exhibited broader XRD patterns with respect to
the conventional ZrBEA-HT, which is in line with SEM measure-
ments and indicated the significantly larger crystals in the case
of hydrothermally synthesized ZrBEA.
to 19 in the parent zeolite led to an increase of the Si/Zr ratio
from 59 to 157 in ZrBEA materials. This unexpected behavior
prompted us to investigate other possible mechanisms for Zr
planting using NMR and IR spectroscopy.
29Si magic angle spinning (MAS) NMR spectra presented in
Figure 3 show the evolution of the silicon environment during
dealumination and Zr planting. The 29Si MAS NMR spectra of
the parent zeolites show NMR peaks in the regions from ꢀ113
to ꢀ110 ppm and from ꢀ104 to ꢀ102 ppm. The former signals
correspond to Si atoms in Si(OSi)4 species in nonequivalent T
crystallographic sites of BEA (9 sites), which are not well re-
solved. The latter signals are owing to overlapping lines of
(SiO)3Si(OAl) and (SiO)3Si(OH) species. The presence of the
latter is confirmed by the appearance of the signal at approxi-
mately 101.5 ppm in the 1H–29Si cross-polarization (CP)MAS
NMR spectra (Figure S4).
Chemical state and location of Zr atoms
It is generally accepted that the mechanism of post-synthetic
planting of heteroatoms in the framework of zeolites involves
the formation of so-called silanol nests through the dealumina-
tion of AlBEA followed by the interaction of these silanol nests
with the metal source leading to tetrahedral metal sites incor-
porated into the zeolite framework (Scheme 1).[34–43] Based on
these literature hypotheses, we were expecting that an in-
crease of the Al content in the parent BEA zeolite would lead
to a higher amount of silanol nests and therefore a higher
degree of Zr incorporation. However, the opposite tendency
was observed (Table 1). The decrease of the Si/Al ratio from 75
The Si(OSi)4 signals in the region of ꢀ110 to ꢀ113 ppm do
not change after dealumination, confirming that the zeolite
structure remains intact. However, the (SiO)3Si(OAl) signal at
approximately ꢀ103.5 ppm disappears, which is a clear indica-
tion of the aluminum leaching from the parent material. At the
same time, the signal at ꢀ101.5 ppm increases owing to the
formation of (SiO)3Si(OH) defects.[39–41] This observation is con-
firmed by 1H–29Si CPMAS NMR spectra (Figures S4 and S5),
which point to the formation of new SiꢀOH groups.
After grafting of Zr, the relative intensity of the signal at ap-
proximately ꢀ101.5 ppm decreases in both the one-pulse
(Figure 3) and CPMAS NMR (Figure S4) spectra, indicating par-
tial consumption of the silanol groups during the post-synthe-
sis treatment. Therefore, NMR data indicated that there was an
interaction between the Zr atoms and the silanol groups, but
this method did not allow us to determine the type of silanol
Scheme 1. Generally accepted scheme for post-synthesis modification of
zeolites by dealumination followed by incorporation of heteroatoms.
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
3
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 3. 29Si MAS NMR spectra of the catalysts.
involved in the grafting. This information can be best obtained
by FTIR spectroscopy.
increased in the order BEA(19)<BEA(25)<BEA(38)ꢁBEA(75),
indicating an increase of the content of terminal silanols. This
observation could be associated with the decrease of the size
of zeolite crystals, as confirmed by SEM (Figure 1) and nitrogen
adsorption measurements (Figure S1).
Figure 4 shows the FTIR spectra in the region of the hydrox-
yl groups vibrations of the parent zeolites, dealuminated sam-
ples and ZrBEA catalysts. The bands at approximately
3608 cmꢀ1 and 3783 cmꢀ1 were assigned to Brønsted acid sites
and non-framework AlꢀOH, respectively. A broad signal at ap-
proximately 3660 cmꢀ1 was attributed to the perturbed AlꢀOH.
The sharp intense band at 3745 cmꢀ1 was attributed to OꢀH vi-
brations in terminal isolated silanol groups.[45,46] It should be
noted that the relative intensity of this band for the samples
After dealumination, the signals at 3783, 3660 and
3608 cmꢀ1 disappeared and a broad band spanning from 3750
to 3400 cmꢀ1 appeared (Figure 4). This band originates from
hydrogen bonded silanols, that is, silanol nests.[34–43] A slight in-
crease of the intensity of the band at 3745 cmꢀ1 indicated that
there was partial destruction of the zeolite crystal aggregates
Figure 4. FTIR spectra showing the OH vibration region.
&
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
4
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
followed by the formation of isolated SiꢀOH groups on the
surface (Figure S5).
In summary, the NMR and FTIR data suggest that the intro-
duction of Zr into the DeAlBEA samples is associated with pref-
erable consumption of the terminal isolated silanols during the
treatment in ZrOCl2 solution, whereas the silanol nests are not
affected significantly. The amount of planted Zr atoms corre-
lates with the amount of isolated SiꢀOH groups located on the
external surface of the crystal. The latter observation suggests
that treatment of dealuminated zeolite BEA with ZrOCl2 in
DMSO leads to grafting of the Zr atoms predominantly on the
external surface of the crystal or in the mouths of the pore
close to the external surface (Scheme 2), which is favored on
smaller zeolite crystals.
The introduction of Zr resulted in a decrease of the 3745
and 3600 cmꢀ1 bands (Figures 4 and S5) owing to the interac-
tion of the corresponding silanols with ZrOCl2 and the forma-
tion of Zr sites. A careful analysis of the intensities of these
bands (Figure S5) showed that the treatment of dealuminated
zeolite in the ZrOCl2 solution leads to the preferential con-
sumption of isolated terminal silanol groups and only a slight
decrease in the amount of silanol nests. These results indicate
the preference of the Zr atoms to graft on the surface of the
zeolite rather than incorporate into the silanol nests.
To further clarify the mechanism of Zr planting, the inter-
mediate products obtained at different stages of the post-syn-
thesis procedure were analyzed (Figure 5). Two alternatives
Scheme 2. Schematic representation of Zr grafting by treatment of dealumi-
nated zeolites with ZrOCl2 in DMSO.
Several reasons can be proposed to account for such behav-
ior of zirconium during grafting: i) diffusion limitations of the
solvated ZrO2+ species in the porous system of the zeolite;
ii) steric hindrance, which restricts the formation of four SiꢀOꢀ
Zr linkages in silanol nests owing to the larger atomic size of
Zr with respect to Al, and iii) energetically unfavorable forma-
tion of Zr(OSi)4 species in the silanol nests formed after dealu-
mination.
Figure 5. a) 29Si MAS NMR and b) 1H–29Si CPMAS NMR spectra of DeAlBEA
and Zr(1.3)BEA(19) catalysts.
were considered: i) grafting of Zr during the treatment of DeAl-
BEA with ZrOCl2 in DMSO solution and ii) adsorption of Zr spe-
cies on DeAlBEA [the different samples are DeAlBEA(x) where
x is Si/Al ratio in the parent zeolite] during the treatment in
DMSO solution followed by grafting to silanol groups during
the calcination process.
Acidic properties
The catalytic properties of ZrBEA materials are closely related
to their Lewis acidity. FTIR spectroscopy of adsorbed pyridine
is usually used for the characterization of Lewis acid sites.[30,42]
However, pyridine is a not very sensitive probe molecule for
different types of Lewis acid sites and OH groups and does not
allow for the determination of their nature and strength. In our
previous study[47] we showed that the use of CO for the exami-
nation of the acidic properties of ZrBEA catalysts is more bene-
ficial owing to the high sensitivity of carbon monoxide as
a probe molecule.
29Si MAS NMR (Figure 5a) and 1H–29Si CPMAS NMR (Fig-
ure 5b) spectra of DeAlBEA(19), DeAlBEA(19) treated in pure
DMSO, DeAlBEA(19) treated with ZrOCl2 in DMSO and calcined
Zr(1.3)BEA(19) (the number after Zr corresponds to the Zr con-
tent) samples were obtained. The comparison of the spectra
indicates that treatment in pure DMSO does not have a signifi-
cant effect on the peak at approximately ꢀ101.5 ppm corre-
sponding to the Q3 resonance of (SiO)3Si(OH) groups. On the
contrary, the intensity of this peak decreased drastically after
the addition of ZrOCl2 to DMSO, whereas further calcination
does not affect the spectrum. These observations indicate that
the interaction of the silanol groups with the Zr source occurs
during the treatment of the zeolite with ZrOCl2 in the DMSO
solution and that the subsequent calcination does not affect
the Zr sites.
Therefore, the nature of the ZrBEA acid sites was investigat-
ed by FTIR spectroscopy of CO adsorbed at low tempera-
ture.[47,48] The adsorption of CO on the acidic catalysts leads to
the formation of hydrogen bonds with the OH groups and to
coordination of CO to the Lewis acid sites. Because of these in-
teractions the n(C=O) vibration band of adsorbed carbon mon-
oxide shifts to higher wavenumbers with respect to the band
of physisorbed CO (2138 cmꢀ1). This shift is characteristic of
the nature (Lewis or OH) and strength of the site. Furthermore,
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
5
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 6. FTIR spectra of CO adsorbed over the catalysts.
CO can easily access all the sites because of its small size. This
has an additional advantage for the investigation of the acidity
of microporous solids.[48]
orders of magnitude as compared to the parent BEA zeolites,
whereas the Lewis sites disappear completely. However, it has
to be noted that leaching with nitric acid four times did not
lead to complete dealumination of the zeolites. All DeAlBEA
samples preserved some amount of Brønsted acid sites
(Table 2).
In a typical experiment, carbon monoxide was gradually in-
troduced in the IR cell and the adsorption spectra were collect-
ed. The experiment was stopped after the appearance of the
band of physisorbed CO (2138 cmꢀ1) in the spectra. The results
obtained after saturation are shown in Figure 6. The adsorption
of CO over BEA samples led to the appearance of bands at
2228, 2190, 2174 and 2156 cmꢀ1 (Figure 6). The bands at 2228
and 2190 cmꢀ1 was attributed to the vibrations of CO ad-
sorbed over Al Lewis sites in tetrahedral (Al4c3+) and octahedral
(Al6c3+) positions, respectively.[49] An intense band at 2174 cmꢀ1
is typical of the adsorption of CO over Brønsted acid sites
SiꢀO(H)ꢀAl,[45,48] and finally, the band at 2156 cmꢀ1 was as-
signed to the vibrations of CO interacting with silanol groups
on the surface of the zeolites.[48] BEA samples with a low Si/Al
ratio showed a high amount of Al Lewis acid sites (Figure 6),
indicating a high concentration of crystal defects owing to the
high aluminum content.
The adsorption of CO over ZrBEA catalysts led to the appear-
ance of a new band centered at 2188 cmꢀ1, which was attribut-
ed to CO interacting with Zr Lewis sites. According to our pre-
vious study,[47] this band corresponds to the open Lewis sites
associated with Zr atoms linked to three oxygen atoms in the
zeolite framework and one OH group. The intensity of the
band corresponding to CO adsorbed on Zr open Lewis sites in
the catalysts increases in the following order: Zr(1.3)BEA(19)<
Zr(2.1)BEA(25)<Zr(3.3)BEA(38)ꢁZr(3.5)BEA(75) (Table 2). This
order of acidity correlates with the amount of Zr grafted on
the external surface of the zeolite crystals (Table 1). The ZrBEA-
HT sample showed the lowest amount of open sites (Table 2)
and a considerable contribution from closed sites, as evi-
The amount of CO adsorbed was quantified using
a curve-fitting procedure for the FTIR spectra that is
Table 2. Relative intensities of the IR bands observed after CO adsorption.
based on the application of Gauss–Lorentz compo-
nents with a fixed full width at half maximum cen-
tered at the maxima of the bands. The results are
shown in Table 2. The intensity of the band at
2174 cmꢀ1 correlates with the number of Al atoms in
the BEA samples and shows that there was an in-
crease in the amount of Brønsted sites with the in-
crease of aluminum content. The BEA(38) and
BEA(75) samples do not show any Lewis acid sites,
which indicates that all the aluminum atoms were in-
corporated into the framework and confirms the
high quality of the parent materials.
Sample
Area of band centered at
2174 cmꢀ1
2228 cmꢀ1
2188 cmꢀ1
(Al3+ Lewis acid sites)
(Brønsted acid sites)
(Zr4+ Lewis sites)
BEA(19)
BEA(25)
BEA(38)
BEA(75)
DeAlBEA(19)
DeAlBEA(25)
DeAlBEA(38)
DeAlBEA(75)
Zr(1.3)BEA(19)
Zr(2.1)BEA(25)
Zr(3.3)BEA(38)
Zr(3.5)BEA(75)
Zr(1.5)BEA-HT
0.49
0.46
0.02
3.15
2.77
1.65
1.12
0.07
0.06
0.07
0.10
0.06
0.07
0.07
0.11
0.00
–
–
–
–
–
–
–
–
0.99
1.50
2.36
2.49
0.36
0.02
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.00
Dealumination of the BEA samples caused a dra-
matic decrease in the amount of acid sites. The
amount of Brønsted acid sites decreased by two
&
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
denced by the appearance of an intense band at 2176 cmꢀ1
(Figure S6).[25,47]
Evaluation of catalyst performance for the conversion of
ethanol to butadiene
Notably, the post-synthetic treatment with ZrOCl2 in DMSO
did not lead to the formation of closed Lewis sites, which are
expected if Zr is incorporated into silanol nests (Scheme 1).
The formation of only open sites confirmed our proposed
mechanism of Zr deposition through grafting onto the isolated
silanol groups (Scheme 2) rather than the incorporation into si-
lanol nests.
The main reaction products observed using the catalysts in
this study were typically the same as in the previous study
over metal-promoted oxide catalysts (Scheme 3).[49]
The main reaction pathway that leads to butadiene involves
five reaction steps: i) ethanol dehydrogenation into acetalde-
hyde, ii) aldol condensation of acetaldehyde followed by iii) fast
dehydration, iv) MPVO reduction of crotonaldehyde with etha-
nol and v) dehydration of crotyl alcohol into butadiene. Be-
sides dehydrogenation, ethanol undergoes dehydration to give
diethyl ether and ethylene. Furthermore, acetaldehyde is very
reactive and initiates two side reactions: i) Tischenko reaction
leading to ethyl acetate, which is further converted into ace-
tone and propylene, and ii) cross-condensation with crotonal-
dehyde and other aldehydes leading to heavier products such
as hexatrienes. Another side reaction pathway involves hydro-
genation of crotyl alcohol to give 1-butanol and its further de-
hydration and isomerization into a mixture of butenes.
Although a lot of effort has recently focused on the investi-
gation of the nature of the acid sites in post-synthetically treat-
ed BEA materials,[19,23,34,36,38–42] the structure of the acid sites in
these materials is still under debate. It is generally accepted
that post-synthesis modification of dealuminated BEA zeolites
can give both open and closed Lewis acid sites,[40–42] the struc-
tures of which have been proposed previously for hydrother-
mally synthesized SnBEA. However, in a recent paper by Dijk-
mans et al.[39] it was clearly demonstrated that the nature of
the Sn sites introduced by a post-synthetic procedure can
differ substantially from those obtained by hydrothermal syn-
thesis. In particular, extended X-ray absorption fine structure
(EXAFS) and X-ray absorption near edge structure (XANES)
data pointed to 3-fold anchoring of SnIV and charge balancing
by distant SiꢀO linkages. Our observations, which indicate the
formation of highly accessible open Zr sites located near the
external surface of the crystal (Scheme 2) are in line with these
findings.
The catalytic properties of the parent, dealuminated and Zr-
containing catalysts are compared in Figure 7 for BEA(75) zeo-
lites. The parent and dealuminated zeolites show high initial
rates of ethanol conversion, however the only reaction prod-
ucts obtained are ethylene and diethyl ether. When DeAl-
BEA(75) is doped with Ag, significant dehydrogenation of etha-
nol into acetaldehyde is observed along with ethanol dehydra-
tion. However further transformation into butadiene does not
occur because no Zr Lewis sites are present in the Ag/DeAl-
BEA(75) catalyst. Grafting of Zr onto the dealuminated zeolite
changes the reaction pathway towards butadiene synthesis
owing to the successful incorporation of catalytically active Zr
sites in the dealuminated zeolite.
It has been repeatedly demonstrated that the open Lewis
sites are the main active sites of the reactions studied over
metal-substituted BEA catalysts (e.g., SnBEA, ZrBEA and
TiBEA).[25,34,36,38,42] In our previous study we showed that Zr
open sites are more active than closed sites in the synthesis of
butadiene from ethanol.[25] Therefore, the formation of only
Zr(OH)(OSi)3 sites during the post-synthetic preparation of
ZrBEA from dealuminated materials opens new possibilities for
the design of catalysts with high intrinsic activity. In the pres-
ent study, the activity of such catalysts was evaluated for the
synthesis of butadiene from ethanol.
To compare the activity of different Zr-containing catalysts,
the initial rates of butadiene formation were estimated, as de-
scribed in the Experimental Section; the results are presented
in Table 3. The initial rates of butadiene formation were found
to increase in the following order Ag/Zr(1.3)BEA(19)<Ag/
Zr(2.1)BEA(25)<Ag/Zr(3.3)BEA(38)ꢁAg/Zr(3.5)BEA(75).
The
comparison of the results with Ag/Zr(1.5)BEA-HT indicates a 2-
to 3-fold higher activity of the materials obtained by post-syn-
thesis treatment (Table 3).
Our previous studies on the synthesis of butadiene from
ethanol[24,25] indicated that Zr open Lewis sites played a key
Scheme 3. Main reaction pathways.
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 7. Initial formation rates of butadiene, acetaldehyde and dehydration products over BEA(75), DeAlBEA(75), Ag/DeAlBEA(75) and Ag/Zr(3.5)BEA(75) cata-
lysts.
Table 3. Initial butadiene formation rates, ethanol conversions and products distribution over Ag-doped ZrBEA catalysts (T=593 K, time on stream=3 h).
Sample
Initial formation
rate [mmolgꢀ1 sꢀ1
Ethanol con-
version [%]
Selectivities [mol%]
]
butadiene ethylene propylene butenes ethyl ether ethyl acetate 1-butanol C6 +
Ag/Zr(1.3)BEA(19)
Ag/Zr(2.1)BEA(25)
Ag/Zr(3.3)BEA(38)
Ag/Zr(3.5)BEA(75)
Ag/Zr(1.5)BEA-HT
1.81
2.25
2.90
2.99
1.32
14.3
15.9
15.0
14.9
15.5
62.2
61.1
60.3
58.7
67.1
8.1
8.3
8.9
9.8
1.9
2.0
2.0
1.8
1.9
2.3
5.0
4.9
5.2
5.0
6.6
10.2
10.0
10.5
11.9
5.9
2.4
2.5
2.0
2.2
4.0
0.8
0.4
0.7
0.6
1.4
9.3
10.8
10.6
9.9
10.8
role in this process. Our current study confirms the above con-
clusion: the order of catalyst activity correlates linearly with
the relative amount of open Lewis acid sites determined by
FTIR (Figure 8). The order of the activity also correlates with
the total Zr content in the samples (Figure S7), which can be
expected because of the correlation between the amount of
Zr open sites and Zr content (Table 2). The only sample that
does not correlate is the Zr(1.5)BEA-HT catalyst, which has a sig-
nificant amount of closed sites that have been shown to be
less active for this reaction.[25] This sample has the lowest buta-
diene formation rate per Zr atom, hence confirming the higher
activity of the open sites (Figure S7). All these observations
support our previous conclusion on the high importance of
open Lewis sites for the activity of the catalyst.[25]
The analysis of the product distribution and selectivity of
the catalysts was performed at similar conversion levels of eth-
anol (Table 3). Similar ethanol conversions of 14–16% were
achieved by variation of the WHSV in the range of 1.2–
3 ggꢀ1 hꢀ1. The results show that ZrBEA catalysts obtained by
post-synthesis had a selectivity towards butadiene in the range
of 59–62%, which is close to the selectivity of ZrBEA-HT (67%).
This observation suggests that the Zr4+ sites located in the
molecular sieve frameworks exhibit the same selectivity in the
overall reaction regardless of the method of incorporation:
post-synthetic treatment or hydrothermal synthesis. However,
some differences are observed for ethanol dehydration prod-
ucts such as diethyl ether and ethylene, the content of which
was higher when using Ag/Zr(y)BEA(x) catalysts obtained by
post-synthesis methods (Table 3). This result is most probably
owing to traces of Brønsted acid sites in these samples, as evi-
denced by the FTIR spectra of adsorbed CO (Figure 6, Table 2).
A small amount of Brønsted acid sites promotes the ethanol
dehydration reactions, which leads to higher selectivity to-
wards ethylene and diethyl ether. The increase of ethanol con-
version increases the amount of these products, which is in
line with our previous study.[49]
The comparison of different Ag-doped ZrBEA samples ob-
tained by post-synthesis shows that the highest butadiene for-
mation rate of 3 mmolgꢀ1 sꢀ1 is achieved over Ag/
Zr(3.5)BEA(75). This value is two times higher than that ob-
tained over Ag/ZrBEA-HT. The productivity of Ag/Zr(3.5)BEA(75)
under the steady state conditions is estimated to be
0.58 ggꢀ1 hꢀ1. To the best of our knowledge, this is the highest
value obtained so far for a one step butadiene process and
Figure 8. Initial butadiene formation rate versus relative amount of open
Lewis sites measures by FTIR of adsorbed CO.
&
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
8
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
Before the introduction of zirconium, the dealuminated zeolites
were activated for 8 h at 423 K to remove adsorbed water. The
approaches those achieved in
(350 mgLꢀ1 hꢀ1).[29]
a
two-step process
samples (3 g) were then added to
a solution of 24.0 g of
ZrOCl2·8H2O in 170 g of DMSO. The solution was heated at 403 K
for 12 h and then added to 1 L of deionized water. The final sus-
pension was filtered, rinsed with water and dried at 353 K. The cal-
cination procedure was as follows: ramp at 3 Kminꢀ1 to 473 K,
dwell for 6 h, ramp at 3 Kminꢀ1 to 823 K and dwell for 6 h. The
samples were designated as Zr(y)BEA(x), were x is Si/Al ratio in the
parent zeolite and y corresponds to the Zr content (in wt%) in the
sample.
The hydrothermal synthesis of ZrBEA zeolite with a Si/Zr ratio of
100 was performed according to a previously reported proce-
dure.[50] The as-synthesized material was calcined at 823 K for 5 h
under a flow of dry air. The sample was denoted as ZrBEA-HT.
All catalysts were doped with 1 wt% of silver by incipient wetness
impregnation with a AgNO3 solution followed by calcination and
reduction under a flow of hydrogen. Elemental analysis confirmed
the silver content to be within 0.9–1.1 wt%. After the introduction
of silver, “Ag/” was added as a prefix to the name of the catalyst.
Conclusions
A new approach for the preparation of highly efficient Ag/
ZrBEA catalyst for butadiene synthesis from ethanol has been
proposed. The method involves post-synthetic treatment of
dealuminated BEA zeolite with ZrOCl2 in DMSO solution under
reflux conditions. The FTIR and 29Si MAS NMR analysis indicates
that the terminal isolated silanol groups are involved in the Zr
grafting process. Silanol nests generated during the dealumi-
nation of BEA have a very low, if any, contribution to Zr graft-
ing. The materials obtained contain only open Zr Lewis sites
(Zr(OSi)3OH) as confirmed by FTIR spectroscopy of adsorbed
carbon monoxide. Closed Zr Lewis sites are not detected,
probably owing to the low involvement of silanol nests in the
grafting process.
The content of the open Lewis sites correlates with the
amount of Zr atoms grafted. It does not depend on the con-
centration of Al in the parent zeolite or the amount of nests
formed during the dealumination. On the contrary, it is gov-
erned by the size of the zeolite crystal; the smaller the crystal
size, the higher the amount of terminal silanols, the higher the
content of Zr Lewis sites.
Catalyst characterization
The elemental analysis was performed using energy dispersive X-
ray fluorescence spectroscopy (EDXRF). Prior to the analysis the
samples were mixed with B(OH)3 and pressed in self-supporting
wafers. The wafers were analyzed using a Thermo Scientific ARL
Perform’x WDXRF spectrometer. N2 sorption–desorption isotherms
were measured at 77 K using a Micromeritics ASAP-2000 automatic
surface area and pore size analyzer. Scanning electron microscopy
(SEM) images of samples were obtained on a LEO EVO 50XVP
(Zeiss) microscope. Powder X-ray diffraction (XRD) patterns of the
samples were recorded on a Bruker PHASER D2 diffractometer
using CuKa radiation at a wavelength of 1.5456 ꢁ. 29Si solid-state
MAS (magnetic angle spinning) NMR spectroscopy was performed
using a Bruker Avance-400 spectrometer, operating at a resonance
frequency of 79.46 MHz with a spinning rate of 10 kHz, pulse
length of 3 ms, and recycle time of 20 s. The 29Si chemical shifts are
reported relative to tetramethylsilane.
The acidic properties were studied by FTIR spectroscopy of the ad-
sorbed CO. IR spectra were recorded on a Nicolet Protꢂgꢂ 460 FTIR
spectrometer at a 4 cmꢀ1 optical resolution. Prior to the measure-
ments, the catalysts were pressed in self-supporting discs and acti-
vated in the IR cell attached to a vacuum line at 723 K for 4 h. A
low temperature vacuum cell cooled with liquid nitrogen was used
for CO adsorption measurements. The pressure was measured by
a Barocell gauge. Difference spectra were obtained by the subtrac-
tion of the spectra of the activated samples from the spectra of
samples with the adsorbate. The subtraction was performed using
the OMNIC 7.3 software package.
It is proposed that the post-synthetic treatment of dealumi-
nated BEA zeolite with ZrOCl2 in DMSO leads to Zr grafting
preferentially to the terminal silanols on the external surface of
the zeolite crystals, which yields highly accessible Zr(OSi)3OH
open sites with high Lewis acidity. These sites are shown to be
extremely active in the synthesis of butadiene from ethanol.
The initial rates of ethanol conversion into butadiene over Ag-
promoted ZrBEA catalysts shows a linear correlation with the
amount of these sites. The Ag/ZrBEA catalysts synthesized
using the post-synthesis modification show significant advan-
tages over Ag/ZrBEA catalysts synthesized by a conventional
hydrothermal procedure.
The best catalyst performance in terms of butadiene forma-
tion rate (3 mmolgꢀ1 sꢀ1) was observed over Ag(3.5)/ZrBEA(75),
which has the smallest crystal size and the highest content of
Zr open sites. This catalyst shows the highest productivity of
butadiene synthesis (0.58 ggꢀ1 hꢀ1) under steady state condi-
tions at a selectivity close to 60%.
Experimental Section
Evaluation of catalyst performance
Preparation of the catalysts
Catalytic experiments were performed in a flow-type fixed-bed re-
actor under atmospheric pressure. In a typical experiment, 2 g of
catalyst (size fraction 0.5–1 mm) was packed into the quartz tubu-
lar reactor and purged with nitrogen at 873 K for 0.5 h followed by
subsequent reduction in a flow of hydrogen at 593 K. Ethanol
(95 wt%) was used as a feed. The reaction mixture was fed using
a syringe pump (Razel). Helium was used as a carrier gas (molar
ratio EtOH/He=1). The weight hourly space velocity (WHSV) was
varied from 1.2 to 3.0 hꢀ1, the reaction temperature was 593 K.
Gaseous products were analyzed on a Crystal 2000M gas chroma-
BEA zeolites with a Si/Al ratio of 19, 25, 38 and 75 (supplied by
Zeolyst and denoted as BEA(x), where x is the Si/Al ratio) were
dealuminated by stirring 10 g of the parent material in 300 mL of
10m aqueous HNO3 solution at 363 K for 8 h. The resultant suspen-
sions were diluted with 1 L H2O and filtered. The samples were
washed thoroughly with water and dried at 333 K overnight. The
dealumination procedure was repeated four times. The samples
were designated as DeAlBEA(x), where x is Si/Al ratio in the parent
zeolite.
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
9
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
[18] R. Gounder, M. E. Davis, J. Catal. 2013, 308, 176–188.
[19] J. Dijkmans, D. Gabriels, M. Dusselier, F. de Clippel, P. Vanelderen, K.
Houthoofd, A. Maliet, Y. Pontikes, B. F. Sels, Green Chem. 2013, 15,
2777–2785.
[20] W. R. Gunther, Y. Wang, Y. Ji, V. K. Michaelis, S. T. Hunt, R. G. Griffin, Y.
Romꢃn-Leshkov, Nat. Commun. 2012, 3, 1109.
tograph using a 50 m SE-30 column. Liquid products were separat-
ed and analyzed using 50 m SE-30 and 2 m Porapak Q columns.
Methane was used as an external standard for gaseous products.
The conversion of ethanol, selectivity and yields of the products
were calculated as follows:
[21] E. Taarning, S. Saravanamurugan, M. S. Holm, J. Xiong, R. M. West, C. H.
Christensen, ChemSusChem 2009, 2, 625–627.
[22] C. Hammond, S. Conrad, I. Hermans, Angew. Chem. Int. Ed. 2012, 51,
11736–11739; Angew. Chem. 2012, 124, 11906–11909.
[23] M. Dusselier, P. Van Wouwe, A. Dewaele, E. Makshina, B. F. Sels, Energy
Environ. Sci. 2013, 6, 1415–1442.
[24] V. Sushkevich, I. Ivanova, E. Taarning, Green Chem. 2015, 17, 2552–2559.
[25] V. Sushkevich, D. Palagin, I. Ivanova, ACS Catal. 2015, 5, 4833–4836.
[26] A. D. Patel, K. Meesters, H. den Uil, E. de Jong, K. Bloka, M. K. Patel,
Energy Environ. Sci. 2012, 5, 8430–8444.
[27] J. A. Posada, A. D. Patel, A. Roes, K. Blok, A. C. Faaij, M. K. Patel, Biore-
sour. Technol. 2013, 135, 490–499.
[28] C. Angelici, B. M. Weckhuysen, P. Bruijnincx, ChemSusChem 2013, 6,
1595–1614.
[29] E. V. Makshina, M. Dusselier, W. Janssens, J. Degrꢄve, P. Jacobs, B. Sels,
Chem. Soc. Rev. 2014, 43, 7917–7953.
[30] J. Wang, K. Okumura, S. Jaenicke, G.-K. Chuah, Appl. Catal. A 2015, 493,
112–120.
m
Ethanol conversion ¼ reactedðEtOHÞ ꢂ 100%
ð1Þ
mfedðEtOHÞ
mj
kjF ꢂ 100%
mreactedðEtOHÞ=46
Mrj
ð2Þ
ð3Þ
Selectivity ¼
Yield ¼ Ethanol conversion ꢂ Selectivity=100,
where mj is the mass of product j in the reaction mixture, Mrj is
the molecular weight of product j, and kFj is the number of ethanol
molecules required for the production of product j.
The initial rate of butadiene formation was calculated from the ini-
tial slope of the kinetic curves in the range of ethanol conversion
from 4–15%. The variation of ethanol conversion was achieved by
changing the WHSV from 1.2–15 hꢀ1. The data were collected
under steady state conditions after 3 h on stream.
[31] C. Chang, C. Chu, J. Miale, R. F. Bridger, R. B. Calvert, J. Am. Chem. Soc.
1984, 106, 8143–8146.
[32] K. Yamagishi, S. Namba, T. Yashima, J. Phys. Chem. 1991, 95, 872–877.
[33] W. Ren, Z. Hu, T. Ge, X. Zhou, L. Chen, Y. Zhu, J. Shi, Chin. J. Catal. 2015,
36, 906–912.
[34] B. Tang, W. Dai, X. Sun, N. Guan, L. Li, M. Hunger, Green Chem. 2014, 16,
2281–2291.
Acknowledgements
The authors thank the Russian Science Foundation for the finan-
cial support (Grant No 14-23-00094) and Mr. Andrey Ivanov for
NMR measurements.
[35] P. Wu, T. Komatsu, T. Yashima, S. Nakata, H. Shouji, Microporous Mater.
1997, 12, 25–37.
[36] P. Li, G. Liu, H. Wu, Y. Liu, J.-g. Jiang, P. Wu, J. Phys. Chem. C 2011, 115,
3663–3670.
[37] W. N. P. van der Graaff, G. Li, B. Mezari, E. A. Pidko, E. J. M. Hensen,
ChemCatChem 2015, 7, 1152–1160.
Keywords: butadiene · domino reaction · heterogeneous
catalysis · zeolites · zirconium
[38] B. Tang, W. Dai, G. Wu, N. Guan, L. Li, M. Hunger, ACS Catal. 2014, 4,
2801–2810.
[39] J. Dijkmans, M. Dusselier, W. Janssens, M. Trekels, A. Vantomme, E. Brey-
naert, C. E. A. Kirschhock, B. F. Sels, ACS Catal. 2016, 6, 31–46.
[40] J. Dijkmans, J. Demol, K. Houthoofd, S. Huang, Y. Pontikes, B. Sels, J.
Catal. 2015, 330, 545–557.
[41] J. Dijkmans, D. Gabriꢅls, M. Dusselier, K. Houthoofd, P. C. M. M. Magusin,
S. Huang, Y. Pontikes, M. Trekels, A. Vantomme, L. Giebeler, S. Oswald,
B. F. Sels, ACS Catal. 2015, 5, 928–940.
[42] B. Tang, W. Dai, X. Sun, G. Wu, N. Guan, M. Hunger, L. Li, Green Chem.
2015, 17, 1744–1755.
[43] P. Wolf, C. Hammond, S. Conrad, I. Hermans, Dalton Trans. 2014, 43,
4514–4519.
[44] E. B. Lami, F. Fajula, D. Anglerot, T. Des Courieres, Microporous Mater.
1993, 1, 237–245.
[45] V. Ordomsky, V. Murzin, Yu. Monakhova, Y. Zubavichus, E. Knyazeva, N.
Nesterenko, I. Ivanova, Microporous Mesoporous Mater. 2007, 105, 101–
110.
[46] K. Hadjiivanov, Adv. Catal. 2014, 57, 99–318.
[47] V. Sushkevich, A. Vimont, A. Travert, I. Ivanova, J. Phys. Chem. C 2015,
119, 17633–17639.
[1] Y. Romꢃn-Leshkov, M. E. Davis, ACS Catal. 2011, 1, 1566–1580.
[2] M. Moliner, Dalton Trans. 2014, 43, 4197–4208.
[3] A. Corma, L. T. Nemeth, M. Renz, S. Valencia, Nature 2001, 412, 423–
425.
[4] M. S. Holm, S. Saravanamurugan, E. Taarning, Science 2010, 328, 602.
[5] J. J. Pacheco, M. E. Davis, Proc. Natl. Acad. Sci. USA 2014, 111, 8363.
[6] T. De Baerdemaeker, B. Steenackers, D. De Vos, Chem. Commun. 2013,
49, 7474.
[7] S. Van de Vyver, Y. Romꢃn-Leshkov, Angew. Chem. Int. Ed. 2015, 54,
12554–12561; Angew. Chem. 2015, 127, 12736–12744.
[8] A. Corma, M. E. Domine, S. Valencia, J. Catal. 2003, 215, 294–304.
[9] H. Y. Luo, D. F. Consoli, W. R. Gunther, Y. Romꢃn-Leshkov, J. Catal. 2014,
320, 198–207.
[10] M. Boronat, A. Corma, M. Renz, J. Phys. Chem. B 2006, 110, 21168–
21174.
[11] V. Sushkevich, I. Ivanova, S. Tolborg, E. Taarning, J. Catal. 2014, 316,
121–129.
[12] S. Van de Vyver, C. Odermatt, K. Romero, T. Prasomsri, Y. Romꢃn-Leshkov,
ACS Catal. 2015, 5, 972–977.
[13] D. Lewis, S. Van de Vyver, Y. Romꢃn-Leshkov, Angew. Chem. Int. Ed. 2015,
54, 9835–9838; Angew. Chem. 2015, 127, 9973–9976.
[14] M. Moliner, Y. Romꢃn-Leshkov, M. E. Davis, Proc. Natl. Acad. Sci. USA
2010, 107, 6164–6168.
[48] K. Hadjiivanov, G. Vayssilov, Adv. Catal. 2002, 47, 307–511.
[49] V. Sushkevich, I. Ivanova, V. Ordomsky, E. Taarning, ChemSusChem 2014,
7, 2527–2536.
[15] Y. Romꢃn-Leshkov, M. Moliner, J. A. Labinger, M. E. Davis, Angew. Chem.
Int. Ed. 2010, 49, 8954–8957; Angew. Chem. 2010, 122, 9138–9141.
[16] M. S. Holm, Y. J. Pagan-Torres, S. Saravanamurugan, A. Riisager, J. A. Du-
mesic, E. Taarning, Green Chem. 2012, 14, 702–706.
[17] R. Bermejo-Deval, R. Gounder, M. E. Davis, ACS Catal. 2012, 2, 2705–
2713.
[50] S. H. Liu, S. Jaenicke, G. K. Chuah, J. Catal. 2002, 206, 321–330.
Received: April 29, 2016
Published online on && &&, 0000
&
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
10
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

FULL PAPERS
V. L. Sushkevich, I. I. Ivanova*
&& – &&
Ag-Promoted ZrBEA Zeolites Obtained
by Post-Synthetic Modification for
Conversion of Ethanol to Butadiene
The Ag goes to Zeolites! Ag/ZrBEA (zir-
conium-containing zeolite beta) cata-
lysts prepared using a post-synthesis
method show significant advantages
compared with Ag/ZrBEA catalysts syn-
thesized using a conventional hydro-
thermal procedure. Parent AlBEA materi-
als with different Si/Al ratios and crystal
sizes are used to determine the best
catalyst for the conversion of ethanol to
butadiene.
ChemSusChem 2016, 9, 1 – 11
www.chemsuschem.org
11
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ