Post-synthetic preparation of Sn-, Ti- and Zr-beta: A facile route to water tolerant, highly active Lewis acidic zeolites

Article abstract of DOI:10.1039/c3dt52972j

A two-step procedure for the post-synthetic preparation of Lewis acidic Sn-, Zr- and Ti-zeolite β is reported. Dealumination of a commercially available Al-β zeolite leads to the formation of highly siliceous material containing silanol nests, which can be filled in a second step via the solid-state ion-exchange or impregnation of an appropriate metal precursor. Spectroscopic studies indicate that each metal is subsequently coordinated within the zeolite framework, and that little or no bulk oxides are formed-despite the high metal loadings. The synthesised catalysts demonstrate excellent activity for the isomerisation of glyceraldehyde to dihydroxyacetone, a key model reaction for the upgrading of bio-renewable feedstocks, and the epoxidation of bulky olefins.

Full text of DOI:10.1039/c3dt52972j

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PAPER
Post-synthetic preparation of Sn-, Ti- and Zr-beta:
a facile route to water tolerant, highly active Lewis
acidic zeolites†
Cite this: Dalton Trans., 2014, 43,
4514
Patrick Wolf, Ceri Hammond, Sabrina Conrad and Ive Hermans*
A two-step procedure for the post-synthetic preparation of Lewis acidic Sn-, Zr- and Ti-zeolite β is
reported. Dealumination of a commercially available Al-β zeolite leads to the formation of highly siliceous
material containing silanol nests, which can be filled in a second step via the solid-state ion-exchange or
impregnation of an appropriate metal precursor. Spectroscopic studies indicate that each metal is sub-
sequently coordinated within the zeolite framework, and that little or no bulk oxides are formed – despite
the high metal loadings. The synthesised catalysts demonstrate excellent activity for the isomerisation of
glyceraldehyde to dihydroxyacetone, a key model reaction for the upgrading of bio-renewable feed-
stocks, and the epoxidation of bulky olefins.
Received 22nd October 2013,
Accepted 3rd January 2014
DOI: 10.1039/c3dt52972j
www.rsc.org/dalton
5
,6
various fuels and chemicals. In addition to the promising
Introduction
catalytic results obtained with Sn-β, exciting results have also
IV
In recent times, water tolerant, heterogeneous Lewis acids been obtained by other Lewis acidic zeolites. For example, Zr -
have found widespread applicability for a number of liquid containing β-zeolite has recently been shown to be a promising
1
phase oxidation and isomerization reactions. Most notable catalyst for the production of γ-valerolactone from bio-renew-
7
amongst this class of materials are Lewis acid-containing zeo- able furfural, and the cascade transformation of citral to
8
IV
lites. Unlike traditional stoichiometric and/or homogeneous ±-menthol. Zr -containing silicates have recently also shown
II
III
9
IV
Lewis acids, e.g. Zn and Al , these heterogeneous materials promising activity as CO
2
adsorbents. Furthermore, Ti is
avoid the (co)-production of copious amounts of inorganic also the critical component of many highly active and selective
1
0
and/or toxic waste, and avoid a number of downstream hand- oxidation catalysts, such as TS-1, Ti-β and Ti-MWW zeolites.
ling problems viz. separation. Moreover, the encapsulation of Despite increasing academic and industrial interest in this
the Lewis acid inside a water-resistant, hydrophobic framework class of catalyst, some significant practical hurdles remain that
as found for highly siliceous zeolites) prevents the hydrolysis currently curtail industrial implementation. Amongst these,
(
and subsequent deactivation of the Lewis acid, and thereby the lengthy and complicated hydrothermal synthesis pro-
allows these promising materials to be utilised for aqueous cedure, the low amount of active metal typically incorporated
2
phase oxidation and isomerisation reactions.
per kilogram of the final catalyst, and the large crystallite sizes
IV
Of particular interest is Sn -containing zeolite β (Sn-β). remain the most prohibitive. Therefore alternative methods
This catalyst has demonstrated an exceptional ability to acti- which do not suffer from these drawbacks are of great
vate carbonyl-containing molecules, and has thus found wide- interest.
spread applicability as a promising catalyst for the Baeyer– Recently, some of us reported a convenient post-synthetic
Villiger oxidation of ketones to lactones using H O , and the route for the incorporation of Sn into the framework of
upgrading of bio-renewable platform molecules, such as zeolite β. In brief, the desired Lewis acid was incorporated
1
1
3
IV
2
2
1
2
4
glucose. Indeed, Sn-β-catalysed isomerization of glucose to into the vacant tetrahedral (T)-sites of a pre-dealuminated
fructose is the first step in perhaps the most promising route framework by solid-state ion-exchange. Not only does this
towards the upgrading of glucose (and eventually cellulose) to approach avoid the long synthesis times associated with con-
ventional hydrothermal synthesis routes, but also it allows for
the synthesis of a material with significantly smaller crystallite
sizes, higher metal content, and more favourable catalytic pro-
perties. Indeed, the catalytic productivity of post-synthetically
prepared Sn-β was found to be five to ten times larger than
ETH Zurich, Department of Chemistry and Applied Biosciences, Wolfgang-Pauli-
Strasse 10, 8093 Zurich, Switzerland. E-mail: hermans@chem.ethz.ch;
Fax: +41 44 6331514; Tel: +41 44 6334258
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
c3dt52972j
previously reported for the Baeyer–Villiger oxidation of
4514 | Dalton Trans., 2014, 43, 4514–4519
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2 2
cyclohexanone with H O , and the conversion of dihydroxyace-
tone into ethyl lactate. In this publication, we extend our post-
synthetic route for the preparation of Sn-β to other Lewis acids,
IV
IV
such as Zr and Ti , with the aim of developing more con-
venient synthetic routes for other promising Lewis acidic
zeolites.
Results and discussion
Dealumination of H-zeolite β
To create the necessary vacant framework sites for the incor-
poration of the desired Lewis acidic species, a parent alumino-
2 2 3
silicate zeolite β (SiO /Al O molar ratio = 25 (3.1 wt% Al),
H-form) was first dealuminated by an established literature pro-
1
3
cedure, by treatment with concentrated HNO (13 M, 100 °C,
3
2
3
0 h). Unlike steaming, dealumination by HNO ensures that
Fig. 1 XRD patterns for (a) untreated H-zeolite β (SiO
b) HNO -treated zeolite β (SiO /Al ≥ 1000).
2 2 3
/Al O = 25) and
III
little or no extra-framework Al , a strong Lewis acid, remains
in the material, thereby ensuring a clean, naked framework
into which other Lewis acid centres can be incorporated.
(
3
2
2 3
O
III
ICP-OES analysis demonstrated that Al was easily removed
from the material (Table 1), with no negative changes to the
structural integrity of the zeolite cf. pore volume, surface area
and XRD patterns (Fig. 1).
Transmission FT-IR spectroscopy of the parent H-zeolite β
demonstrates that the untreated material contains both
Brønsted acid sites (charge compensatory protons occupying
−
1
the cation-exchange sites, Si–O(H)–Al, 3610 cm ) and isolated
−
1
silanol groups (–SiOH, 3740 cm ) at the external surface(s) of
the zeolite (Fig. 2). Following HNO treatment, the Si–O(H)–Al
3
stretch is completely removed from the FT-IR spectrum,
III
further indicating the complete removal of framework Al and
the corresponding loss of cation-exchange sites. Along with an
increased signal associated with isolated silanol species Fig. 2 FT-IR spectra for (bottom) untreated H-zeolite β (SiO
2
/Al
2
O
3
=
(
3740 cm− ), the dealuminated material also contains a broad
1
2
3 2 2 3
5) and (b) HNO -treated zeolite β (SiO /Al O ≥ 1000). These data were
−1
partly published previously in Angew. Chem., Int. Ed., 2012, 51, 11736.
absorbance at ±3550 cm . This broad feature is indicative of a
network of hydrogen bonding within the structure of the
zeolite, and has been attributed to the presence of silanol
1
3
Lewis acids or other transition metals into the framework of
zeolite β. Having achieved this aim, we subsequently turned
nests, (SiOH)4.
IV
IV
IV
our focus to the incorporation of Sn , Zr and Ti . In order to
prepare these samples, two preparation procedures were
employed. For Sn- and Zr-β, we employed a solid-state ion-
exchange procedure, which involves the mechanical grinding
of dealuminated zeolite β with an appropriate solid metal pre-
cursor (Sn(II) acetate and Zr(IV) ethoxide, respectively). For Ti-β,
the absence of a suitable solid precursor forced us to employ
an impregnation methodology, involving the wet impregnation
of dealuminated zeolite β with an ethanolic solution of Ti(IV)
ethoxide. The preparation of each as synthesised sample was
Synthesis of Sn-, Zr- and Ti-zeolite β
Our previous work in this area has demonstrated that the for-
mation of silanol nests is a pre-requisite for incorporating
Table 1 Physicochemical properties of Lewis acidic zeolites
b
S
BET
Metal loading
a
(m g−1) (wt%)
2
Entry Catalyst Treatment
1
2
3
4
5
H-β
—
600
620
600
3.1
<0.1
10.1
7.7
+
deAl-β
Sn-β
Zr-β
H
completed by a high-temperature calcination procedure
+
H /SSIE (Sn(II) acetate)
+
(550 °C, 3 h, flowing air) in order to remove the residual
acetate/ethoxide species, and to ensure complete encapsula-
tion of the Lewis acid into the vacant framework sites. We note
that each sample was prepared to contain the same molar
ratio (i.e. 0.84 mmol metal per g catalyst), but that for
H /SSIE (Zr(IV) ethoxide) 580
+
Ti-β
H /IMP (Ti(IV) ethoxide) 610
4.0
a
+
H
3
= acidic pre-treatment (HNO , 13 M, 100 °C, 20 h); SSIE = solid-
b
state ion-exchange reaction; IMP = impregnation. Brunauer–Emmett–
Teller surface area calculated by N physisorption.
2
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simplicity each sample will be denoted by its total
IV
metal content, i.e. wt%. Therefore, Sn zeolite β, containing
1
0.1 wt% Sn, will be denoted as 10Sn-β.
Characterisation of Sn-, Zr- and Ti-zeolite β
III
Unlike trivalent metals, e.g. Al , the coordination of tetra-
IV
valent metals into the zeolite framework, e.g. Sn , does not
give rise to a negatively charged framework or cation-exchange
sites. Thus, other than the complete consumption of the
−
1 14
silanol nests feature (±3550 cm ), FT-IR spectroscopy pro-
vides very little information on these Lewis acidic zeolites.
However, analysis of the Diffuse Reflectance spectra in the
UV-Vis region (DRUV-Vis) provides a great deal of information
on the nature of the as synthesised species. The spectrum
Fig. 4 In situ CD
3 3
CN adsorption/desorption profile for 10Sn-β. CD CN
obtained for 10Sn-β features a sharp maximum at ca. 216 nm,
was desorbed under static vacuum for various time periods (increasing
IV
which is indicative of isolated, tetrahedral Sn species in the from top to bottom), and all spectra are background-referenced against
zeolite framework. As can be observed (Fig. 3), the spectrum the dehydrated zeolite sample.
for 10Sn-β is significantly blue-shifted with respect to the bulk
metal oxide, SnO . In contrast, the spectra obtained for 8Zr-β
2
and 4Ti-β are somewhat broader and less defined than 10Sn-β.
Originally, we presumed that the broad patterns indicated the
formation of multiple metal species, e.g. isolated metal sites,
dimers/oligomers and/or bulk metal oxides. Nevertheless, no
indication of absorbance at ±350 nm was observed for 4Ti-β,
3
catalysts with CD CN absorption (i.e. probe molecule studies).
It has previously been demonstrated that when coordinated
within the zeolite framework, Lewis acidic centres dosed with
16
CD
2310 cm . This feature has been attributed to the coordi-
nation of CD CN onto the isolated, framework-incorporated
3
CN give rise to an absorption in the FT-IR spectrum at
−1
±
2
suggesting little or no presence of TiO (nano)particles, and
the observed UV-Vis spectrum is very similar to those reported
3
3
Lewis acidic centre (CD CN–Lewis acid), and is not observed
by Mania et al., Hereijgers et al., and Blasco et al., where iso-
−1
for bulk metal oxides. The presence of this band at 2310 cm
thus provides information on the degree of Lewis acidity in a
sample.
IV
lated Ti sites were found following detailed spectroscopic
1
5
analysis. Similarly, despite the DRUV-Vis pattern of 8Zr-β
being somewhat broader than that of 10Sn-β, no absorbances
were found above ±250 nm. From this, we conclude that
each catalyst contains (predominantly) isolated, tetrahedrally
coordinated Lewis acids within the framework of the zeolite,
and few (or no) bulk oxides. However, in the absence of e.g.
XAS or STEM analysis, the complete absence of bulk oxides is
not yet conclusive.
Fig. 4 presents the full adsorption/desorption spectrum for
1
0Sn-β. Following adsorption of CD CN, two major adsorption
3
−1
features are observed at ±2270 and ±2310 cm . The first
feature is indicative of CD
3
CN weakly physisorbed onto the
−1
sample. The second feature at 2310 cm
corresponds to
3
CN coordinated onto the Sn Lewis acid centre, and con-
IV
CD
clusively demonstrates that Sn is isolated and present in the
zeolite framework. It is noticeable that shoulder at
2275 cm−1 is present on the physisorbed CD
CN feature. This
has previously been attributed to CD CN coordinated to a
Brønsted acid site. Its presence in the adsorption spectrum for
0Sn-β is likely due to the residual silanol species that are
IV
For further information on the Lewis acid speciation within
each sample, we subsequently turned to in situ analysis of the
a
±
3
3
1
present in the material; even at a loading of 10 wt%, only
around 90% of the silanol nests have been fully occupied by
Sn, and thus a small fraction of vacant silanol nests – impart-
ing weak Brønsted acidity – remain. This fraction could also be
somewhat larger if not all the metal is present in the frame-
work. Following desorption under static vacuum for various
time periods, it is clear that the weakly-bound physisorbed
CD CN is first removed, followed by the CD CN species bound
3
3
to the Brønsted acid sites. It is apparent that the strength of
the CD CN–Lewis acid species is quite high, as full removal of
3
these species was not observed even following 16 minutes of
evacuation.
A similar analysis of 8Zr-β and 4Ti-β demonstrated that
these samples also contain isolated Lewis acid sites (Fig. 5),
Fig. 3 DRUV-Vis spectra for (a) 10Sn-β (b) 8Zr-β and (c) 4Ti-β. Dashed
lines overlaid with each spectrum are the DRUV-Vis spectrum obtained
for the corresponding bulk metal oxide (SnO
and rutile)).
2 2 2
, ZrO and TiO (anatase
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3
Fig. 5 CD CN adsorption/desorption profile for (a) 10Sn-β, (b) 8Zr-β,
and (c) 4Ti-β following desorption for 4 minutes.
Fig. 6 Catalytic activity of (*) 10Sn-β, (o) 8Zr-β, (△) 4Ti-β, and (x) no
catalyst for the isomerisation of glyceraldehyde to dihydroxyacetone.
Catalytic activity of supernatant solution after removal of 10Sn-β at
though the strength of these Lewis acidic centres appears to be
somewhat lower than those found in 10Sn-β. For example,
whilst evacuation of 10Sn-β for 4 minutes removed only weakly
1
0 minutes is also indicated (●). Reaction conditions: 5 mL solution,
0
.4 M glyceraldehyde in H O, 90 °C, substrate/metal ratio = 100.
2
physisorbed CD CN, a similar treatment of 8Zr-β and 4Ti-β
had a larger influence on the spectra (Fig. 5), with around one-
3
be formed. Thus, as a simpler and more facile model reaction,
we utilised the analogous 1,2-hydride shift reaction involving
isomerisation of glyceraldehyde to dihydroxyacetone as a
means of exploring the relative reactivities of the synthesised
catalysts. Nevertheless, in order to be fully representative
of the isomerisation of glucose to fructose, the isomerisation
of glyceraldehyde to dihydroxyacetone was performed in the
aqueous phase.
half of the CD CN–Lewis acid absorption feature being lost.
3
Whilst both 8Zr-β and 4Ti-β are apparently much less Lewis
acidic than 10Sn-β, it is clear that the order of acidity follows
the trend Sn ≫ Zr ≅ Ti.
Isomerisation of glyceraldehyde to dihydroxyacetone
Having established that each material contains isolated Lewis
acid sites within the zeolite framework, we aimed to explore
their relative catalytic activities for a series of reactions. As
mentioned above, Lewis acid catalysed isomerisation has
emerged as one of the most promising routes towards utilising
cellulose-based feedstocks for the synthesis of chemicals and
A recent theoretical analysis has proposed that for this
specific aqueous phase reaction, the order of reactivity for
1
8
these catalysts should be: Sn ≫ Zr > Ti. As can be seen
Fig. 6), all synthesised solids demonstrate catalytic activity for
(
this reaction, confirming their successful synthesis by post-
synthetic methods. Furthermore, and in excellent agreement
with the theoretical calculations, our preliminary experiments
demonstrate that 10Sn-β displays exceptional activity for the
1
6
fuels. Although there remains much debate as to the struc-
ture of the active Lewis acid site (whether the Lewis acid is
fully coordinated to the zeolite framework (closed) or partially
hydrolysed (open)), this isomerisation is known to proceed via
a 1,2-hydride shift, and is catalysed by the bidentate coordi-
nation of the reacting molecule (glucose) to the Lewis
init
−1
isomerisation of glyceraldehyde (R = 15.8 mmol min ), and
that 8Zr-β and 4Ti-β are around one order of magnitude less
active (2.8 and 1.2 mmol min− , respectively). In all cases,
dihydroxyacetone was the major product obtained at >95%
selectivity, though trace quantities of pyruvic aldehyde were
observed above 95% conversion.
1
1
7
acidic centre (Scheme 1). The isomerisation of glyceralde-
hyde to dihydroxyacetone is therefore an ideal model reaction
to investigate the catalytic activity of Lewis acidic zeolites for
such isomerisation reactions.
It is clear that the order of reactivity is in agreement with
both the apparent Lewis acid strength as obtained from in situ
CD CN adsorption studies and the order of reactivity proposed
3
by theoretical studies. To further examine this link between
experiment and theory, we explored the catalytic activity of
However, despite its potential as a route towards utilising
bio-renewable feedstocks, this isomerisation is a relatively slow
reaction, and many consecutive and/or side products can also
10Sn-β over a temperature range of 50–100 °C (ESI Fig. S1†),
and found that the obtained Arrhenius temperature depen-
dence (16.6 kcal mol− ) for 10Sn-β agrees to an excellent
degree with the theoretical predictions of Assary and Curtiss
1
15.4 kcal mol− ; Fig. 7).
1
18
(
Epoxidation of cyclooctene with H O
2
2
Despite the activity of all the catalysts for the isomerisation of
Scheme 1 Schematic representation of the isomerisation of glycer-
aldehyde to dihydroxyacetone, catalysed by Lewis acidic zeolites.
glyceraldehyde to dihydroxyacetone, the low activity of 4Ti-β
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Conclusions
A two-step procedure for the post-synthetic preparation of
Lewis acidic Sn-, Zr- and Ti-zeolite β has been reported. Follow-
ing dealumination of a parent aluminosilicate H-β zeolite,
Lewis acidic centres can be incorporated into the vacant frame-
work sites by solid-state ion-exchange (for Sn and Zr) or
impregnation (Ti). The synthesised catalysts demonstrate excel-
lent catalytic activity for the isomerisation of glyceraldehyde to
dihydroxyacetone and/or the epoxidation of bulky olefins with
H O . We believe that the ability to post-synthetically prepare
2
2
such Lewis acidic zeolites from readily-available aluminosili-
cate analogues will lead to significant increases in the utilis-
ation of these promising catalysts on an academic and
industrial scale.
Fig. 7 Arrhenius plot for 10Sn-β for the isomerisation of glyceraldehyde
to dihydroxyacetone between 50 and 100 °C. An Arrhenius expression
−1
−1
of k(T) = 16.8 s exp(−16.6 ± 0.7 kcal mol )/RT) was obtained.
Experimental details
Commercial zeolite H-β (ZeoChem) was dealuminated by treat-
−
1
a
3 3
ment in HNO solution (13 M HNO , 100 °C, 20 h, 20 mL g
Table 2 Catalytic activity of 4Ti-β for cyclooctene epoxidation
zeolite). Solid-state ion-exchange was performed by grinding
the appropriate amount of tin(II)acetate or zirconium(IV)ethox-
ide with the necessary amount of pre-dealuminated zeolite.
Impregnation was performed by stirring dealuminated zeolite
β in an ethanolic solution of titanium(IV)ethoxide. Following
this procedure, the samples were heated in a combustion
furnace to 550 °C for 3 h (20 °C min− ramp rate) under a dry
c
Preparation
route
TOF
−1
a
b
Entry
Catalyst
Ti-β
TON
[h
]
Ref.
This work air flow.
1
1
2
3
Dealumination/
impregnation
Hydrothermal
synthesis
Hydrothermal
synthesis
48
8
FT-IR spectroscopy was performed on self-supporting
Ti-β
20
10
18
18
wafers using a Bruker Alpha Spectrometer inside a glovebox in
transmission mode. Intensities were normalized to the Si–O–Si
overtones of the zeolite framework. DRUV-Vis analysis was per-
formed with an Ocean Optics UV-Visible Spectrophotometer in
Ti-MWW
147
73.5
a
2 2
Reaction conditions: 80 °C, 0.5 M in 2-butanol, olefin/H O =
, 1 mol% catalyst. Defined as mole epoxide produced per mole Ti. diffuse reflectance mode. Si, Al, and other metal contents were
Mole epoxide produced per mole Ti per hour, over the entire time
b
2
c
determined by ICP-OES. Porosimetry measurements were per-
course of the reaction.
formed on a Micromeritics Asap 2020 apparatus. The samples
were degassed prior to use (275 °C, 3 h). Adsorption isotherms
were obtained at 77 K and analyzed using BET and t-plot
methods.
makes an overall assessment of its synthesis difficult, particu-
The isomerization of glyceraldehyde to dihydroxyacetone
larly since its activity for isomerisation reactions is predicted was carried out in a 50 mL round-bottomed flask equipped
to be very low. Thus, to further verify the activity and nature with a reflux condenser. The vessel was charged with the reac-
of 4Ti-β, we also explored the epoxidation of bulky olefins tant solution (5 mL, 0.4 M glyceraldehyde in H O) and heated
2
by H
reaction in the bulk and fine chemical industries, and when was initiated by adding the desired amount of catalyst (corres-
performed with H , is a particularly green method for intro- ponding to a substrate/metal ratio of 100) and stirred vigor-
2 2
O with this catalyst. The epoxidation of olefins is a key to the desired reaction temperature (50–100 °C). The reaction
2 2
O
ducing functionality into key platform molecules. As can be ously for the required reaction period. Samples were taken
seen (Table 2, ESI Fig. S2†), 4Ti-β demonstrates excellent periodically and quantified by HPLC.
catalytic activity for the epoxidation of cyclooctene, and is com-
The oxidation of cyclooctene was carried out in a 50 mL
parable in activity to other reported Ti-β catalysts prepared by round-bottomed flask equipped with a reflux condenser. The
more established preparation procedures, though it is still vessel was charged with the reactant solution (10 mL, 0.5 M
somewhat lower in activity than the current state of the art cyclooctene in 2-butanol) and heated to the desired reaction
1
9
Ti-containing epoxidation zeolite (Ti-MWW).
here that both Zr and Sn-containing β zeolites are known to be to the vessel, and the reaction was subsequently initiated by
inactive for such epoxidation reactions.
adding the desired amount of H O (0.5 M, H O /olefin = 1)
We note temperature (80 °C). The desired amount of catalyst was added
2
2
2 2
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and stirred vigorously for the required reaction period.
Samples were taken periodically and quantified by GC-FID
against a biphenyl internal standard (30 m FFAP column).
C. Sievers, T. Kamegawa, H. Yamashita and C. W. Jones,
Chem.–Eur. J., 2012, 18, 16649.
10 F. Cavani and J. H. Teles, ChemSusChem, 2009, 2, 508;
P. Wu, T. Tatsumi, T. Komatsu and T. Yashima, J. Catal.,
2001, 202, 245; M. A. Camblor, M. Costantini, A. Corma,
L. Gilbert, P. Esteve, A. Martinez and S. Valencia, Chem.
Commun., 1996, 1339.
Notes and references
1
A. Corma and H. Garcia, Chem. Rev., 2003, 103, 4307; 11 Q. Guo, F. Fan, E. A. Pidko, W. N. P. van der Graaff, Z. Feng,
Y. Román-Leshkov and M. E. Davis, ACS Catal., 2011, 1,
566; A. Corma, Catal. Rev. Sci. Eng., 2004, 46, 369.
M. E. Domine and S. Valencia, J. Catal., 2003, 215, 294;
A. Corma, F. X. Llabrés, I. Xamena, C. Prestipino, M. Renz
and S. Valencia, J. Phys. Chem. C, 2009, 113, 11306–
C. Li and E. J. M. Hensen, ChemSusChem, 2013, 6, 1352;
C. Chang, Z. Wang, P. Dornath, H. J. Cho and W. Fan, RSC
Adv., 2012, 2, 10475–10477; J. Dijkmans, D. Gabriëls,
M. Dusselier, F. de Clippel, P. Vanelderen, K. Houthoofd,
A. Malfliet, Y. Pontikes and B. F. Sels, Green Chem., 2013,
15, 2777–2785; P. Li, G. Liu, H. Wu, Y. Liu, J.-g. Jiang and
P. Wu, J. Phys. Chem. C, 2011, 115, 3663.
1
2
1
1315.
3
4
A. Corma, L. T. Nemeth, M. Renz and S. Valencia, Nature,
2
001, 412, 423; M. Boronat, A. Comra, M. Renz, G. Sastre 12 C. Hammond, S. Conrad and I. Hermans, Angew. Chem.,
and P. M. Viruela, Chem.–Eur. J., 2005, 11, 6905; M. Renz,
Int. Ed., 2012, 51, 11736.
T. Blasco, A. Corma, V. Fornés, R. Jensen and L. Nemeth, 13 S. Dzwigaj, M. J. Peltre, P. Massiani, A. Davidson, M. Che,
Chem.–Eur. J., 2002, 8, 4708.
T. Sen and S. Sivasanker, Chem. Commun., 1998, 87.
M. Moliner, Y. Román-Leshkov and M. E. Davis, Proc. Natl. 14 P. Wu, T. Komatsu and T. Yashima, J. Phys. Chem., 1995,
Acad. Sci. U. S. A., 2010, 107, 6164; M. S. Holm,
99, 10923.
S. Saravanamurugan and E. Taarning, Science, 2010, 328, 15 P. Mania, R. Verel, F. Jenny, C. Hammond and I. Hermans,
6
02; M. S. Holm, Y. J. Pagán-Torres, S. Saravanamurugan,
A. Riisager, J. A. Dumesic and E. Taarning, Green Chem.,
012, 14, 702; A. Corma, M. E. Domine, L. Nemeth and
Chem.–Eur. J., 2013, 19, 9849; B. P. C. Hereijgers,
R. F. Parton and B. M. Weckhuysen, ACS Catal., 2011, 1,
1183; T. Blasco, M. A. Camblor, A. Corma, P. Esteve,
J. M. Guil, A. Martinez, J. A. Perdigon-Melon and
S. Valencia, J. Phys. Chem. B, 1998, 102, 75.
2
S. Valencia, J. Am. Chem. Soc., 2002, 124, 3194.
J. M. R. Gallo, D. M. Alonso, M. A. Mellmer and J. Dumesic,
5
Green Chem., 2013, 15, 85; E. Nikolla, Y. Román-Leshkov, 16 C. M. Osmundsen, M. S. Holm, S. Dahl and E. Taarning,
M. Moliner and M. E. Davis, ACS Catal., 2011, 1, 408;
E. Taarning, C. M. Osmundsen, X. Yang, B. Voss,
S. I. Andersen and C. H. Christensen, Energy Environ. Sci.,
Proc. R. Soc. London, Ser. A, 2012, 468, 2000; S. Roy,
K. Bakhmutsky, E. Mahmoud, R. F. Lobo and R. J. Gorte,
ACS Catal., 2013, 3, 573; M. Boronat, P. Concepción,
A. Corma, M. T. Navarro, M. Renz and S. Valencia, Phys.
Chem. Chem. Phys., 2009, 11, 2876; M. Boronat,
P. Concepción, A. Corma, M. Renz and S. Valencia,
J. Catal., 2005, 234, 111.
2
011, 4, 793.
P. Bai, J. I. Siepmann and M. W. Deem, AIChE J., 2013, 59,
523.
6
7
8
9
3
L. Bui, H. Luo, W. R. Gunther and Y. Román-Leshkov,
Angew. Chem., Int. Ed., 2013, 52, 1.
Y. Nie, S. Jaenicke and G.-K. Chuah, Chem.–Eur. J., 2009,
17 Y. Román-Leshkov, M. Moliner, J. A. Labinger and
M. E. Davis, Angew. Chem., Int. Ed., 2010, 49, 8954.
18 R. S. Assary and L. A. Curtiss, J. Phys. Chem. A, 2011, 115,
2011.
1
5, 1991.
Y. Kuwahara, D.-Y. Kang, J. R. Copeland, N. A. Brunelli,
S. A. Didas, P. Bollini, C. Sievers, T. Kamegawa, 19 P. Wu, D. Nuntasri, J. Ruan, Y. Liu, M. He, W. Fan,
H. Yamashita and C. W. Jones, J. Am. Chem. Soc., 2012, 134,
0757; Y. Kuwahara, D.-Y. Kang, J. R. Copeland, P. Bollini,
O. Terasaki and T. Tatsumi, J. Phys. Chem. B, 2004, 108,
19126.
1
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Dalton Trans., 2014, 43, 4514–4519 | 4519