Nano-flowered Ce@MOR hybrids with modulated acid properties for the vapor-phase dehydration of 1,3-butanediol into butadiene

Article abstract of DOI:10.1039/c7gc02223a

A series of Ce@MOR hybrids based on CeO_x nanoparticles (1-2.5 nm) encapsulated in mordenite exhibiting a genuine flower-like morphology were prepared by simple hydrothermal synthesis. The cerium content in the catalysts could be easily tuned by adjusting the Si:Al:Ce composition of the preformed gel, affecting the textural properties and the density of acid sites of the catalysts. The genesis of acid sites with medium strength was directly correlated to the catalytic activity for the vapor-phase dehydration of 1,3-butanediol into butadiene. A Ce@MOR hybrid with a Si/Ce atomic ratio of 50 displayed a superior activity and selectivity compared to the parent MOR at a comparable Si/Al atomic ratio (10), as well as to control Ce-MOR catalysts post-synthesized by incipient wetness impregnation from the parent mordenite. A higher density of Br?nsted acid sites with medium strength induced by encapsulated CeO_x nanoparticles was argued as the main reason for such an enhanced catalytic performance.

Full text of DOI:10.1039/c7gc02223a

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: L. Fang, F. Jing, J.
Lu, B. Hu and M. Pera-Titus, Green Chem., 2017, DOI: 10.1039/C7GC02223A.
Volume 18 Number
7
7
April 2016 Pages 1821–2242
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1463-9262
CRITICAL REVIEW
G. Chatel et al.
Heterogeneous catalytic oxidation for lignin valorization into valuable
chemicals: what results? What limitations? What trends?
rsc.li/green-chem

Page 1 of 11
Green Chemistry
Dynamic Article Links ►
Green Chem.
View Article Online
DOI: 10.1039/C7GC02223A
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/greenchem
ARTICLE
Nano-flowered Ce@MOR hybrids with modulated acid properties for the vapor-
†
phase dehydration of 1,3-butanediol into butadiene
a
b
a
c
a
Lin Fang, * Fangli Jing, Jingya Lu, Bingwen Hu, and Marc Pera-Titus *
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x)
A series of Ce@MOR hybrids based on CeO nanoparticles (1ꢀ2.5 nm) encapsulated in mordenite exhibiting a genuine flowerꢀlike
x
morphology were prepared by simple hydrothermal synthesis. The cerium content in the catalysts could be easily tuned by adjusting the
Si : Al : Ce composition of the preꢀformed gel, affecting the textural properties and the amount of acid sites of the catalysts. The genesis
of acid sites with medium strength was directly correlated to the catalytic activity for the vaporꢀphase dehydration of 1,3ꢀbutanediol into
butadiene. A Ce@MOR hybrid with a Si/Ce atomic ratio of 50 displayed a superior activity and selectivity comꢀpared to the parent MOR
at a comparable Si/Al atomic ratio (10), as well to control CeꢀMOR catalysts postꢀsynthesized by incipient wetꢀness impregnation from
1
0
the parent mordenite, due to a higher density of Br
φ
nsted acid sites with medium strength induced by encapsulated CeO nanoparticles.
x
Introduction
45
Acid zeolites have been widely explored for the dehydration
of 1ꢀ and 2ꢀbutanol into butenes, showing the formation of byꢀ
products resulting from oligomerization, cracking and aromaꢀ
1
,3ꢀbutadiene (BD) is a relevant industrial intermediate used
1
1
2
2
5
0
5
for the production of synthetic rubbers and resins. Current BD
production processes rely on naphtha cracking and on the
catalytic oxidative dehydrogenation of nꢀbutane and nꢀbutene,
1
4
tization side reactions. The acid properties of zeolites depend
primarily on the topology and Si/Al atomic ratio, but can also be
affected by the presence of heteroatoms. In particular, exꢀ
2
50
which are all nonꢀsustainable feedstocks. As an attempt to move
III
III
2+
framework rareꢀearth cations such as Ce , [Ce (OH)] ,
to more sustainable technologies, it would he highly desirable to
design alternative routes for BD production using renewable raw
materials. For instance, the Lebedev process has attracted much
III
+
IV
+
[Ce (OH) ] and [Ce O(OH)] can be generated in the pores/
2
cavities of zeolites. Ceꢀexchange can affect to an important extent
interest for BD production, since bioethanol issued from the
fermentation of sugars can be used as starting raw material. This 55 activity, selectivity and stability. A wellꢀknown example can be
the acid strength of zeolites, conditioning in turn the catalytic
3
15
reaction is usually catalyzed over catalysts combining basic and
found in the formulation of Ceꢀexchanged Yꢀtype zeolites for the
1c,4
1b.5
6
acid sites, including MgO/SiO ,
ZrO /SiO ,
ZnO/γꢀAl O ,
16
2
2
2
2
3
catalytic conversion of hydrocarbons. Indeed, the Ce cation
1
b
and ZnO/ZrO /SiO .
2
2
speciation and location in the supercages and cavities of the FAU
framework are strongly conditioned by the Ce loading, as well as
As an alternative to the Lebedev process, butanediols (BDO)
are competitive biobased substrates that can be derived from
glucose, sucrose, glycerol and mixtures of glucose and xylose by
17
6
6
7
7
0
5
0
5
by the calcination and hydrothermal protocols. The exchange
capacity of rareꢀearth cations is favored for zeolite topologies
with high Al content, producing sufficient charge density, comꢀ
bined with large pores and/or cavities.
7
3
3
4
0
5
0
fermentation. The dehydration of BDOs can lead to different
8
products depending on the starting diol and the catalyst used. For
instance, 1,2ꢀBDO dehydration over ZnSO in supercritical water
4
In addition to Ceꢀexchange, preferential dispersion of ceria
nanoparticles at the external surface of zeolites (e.g., mordenite or
MOR) using impregnation, ion exchange or mechanochemical
methods can be used for deactivating strong acid sites, tuning in
9
yields preferentially nꢀbutyraldehyde. In the case of 1,3ꢀBDO
and 1,4ꢀBDO, dehydration over CeO and weak acid oxides (e.g.,
2
ZrO ) results mainly in unsaturated alcohols at moderateꢀtoꢀhigh
2
1
0
temperatures and tetrahydrofuran (THF). Nonetheless, BD can
be obtained at yields up to 60% at 473ꢀ573 K upon 1,3ꢀBDO
18
turn the selectivity and mitigating coke formation. Finally, ceria
nanoparticles can also be encapsulated in zeolites, affording a deꢀ
crease of the acid strength and thus a higher resistance against
dehydration over HZSMꢀ5 and AlꢀSBA enriched with Brφnsted
11
acid sites with medium strength. Finally, 2,3ꢀBDO dehydration
19
coking in the fast pyrolysis of glucose (Ce@ZSMꢀ5).
over H(B)ZSMꢀ5 and ZrO modified with alkaline earth metal
2
Here, we report the preparation of a series of hybrids based
on encapsulated CeOx nanoparticles in MOR using a simple
hydrothermal synthetic approach followed by drying and calcinaꢀ
tion. For comparison, control CeꢀMOR catalysts were postꢀ
synthesized by incipient wetness impregnation (IWI) over the
parent MOR. The different hybrids were denoted as Ce@MOR_
Green Chem., [year], [vol], 00–00 | 1
oxides leads mainly to methyl ethyl ketone (MEK) and 3ꢀbutenꢀ
1
2
2
4
ꢀol, respectively. In contrast, promising BD selectivities up to
2% and >90% at full 2,3ꢀBDO conversion were reported over
1
3
Al O and Sc O below 623 K, respectively.
2
3
2
3
This journal is © The Royal Society of Chemistry [year]

CREATED USING THE RSC ARTICLE TEMPLATE (VER. 3.0) - SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS
Green Chemistry
Page 2 of 11
View Article Online
ARTICLE TYPE
www.rsc.org/xxxxxx | XXXXXXXX
DOI: 10.1039/C7GC02223A
X, while the Ceꢀimpregnated catalysts were denoted as Ceꢀ
The phases present in the different catalysts were analyzed by
MOR_X(IWI). In these labels, the term ‘X’ refers to the nominal 55 powder Xꢀray diffraction (PXRD). The PXRD patterns were
bulk Si/Ce atomic ratio. The different catalysts were further
tested in the vaporꢀphase dehydration reaction of 1,3ꢀBDO to BD.
recorded on a Rigaku D/max 2200 diffractometer using Cu Ka
radiation (1.5418 Å) and operated at 40 mA and 40 kV. The
diffraction patterns were collected in the 2ꢀtheta range 5ꢀ50° at a
scanning rate of 4°/min and a scan step of 0.01°. The patterns
were indexed using the Joint Committee on Powder Diffraction
5
Experimental
60
Chemicals
(JCPDS) database and interpreted using MDI JADE 7.0 software.
Sodium silicate (Sinopharm, reagent grade), aluminum nitrate
The textural properties of the catalysts were measured from N
adsorption/desorption isotherms at ꢀ196 C using a Micromeritics
Tristar 3020 Surface Area Analyzer. The specific surface areas
2
o
(Sinopharm, ≥98%), cerium nitrate (Aldrich, 99.99%), sodium
carbonate (sinopharm, ≥99.5%), sulfuric acid (Sinopharm, ≥95%)
10
and ammonium chloride (Aldrich, 99.5%) used for catalyst 65 were calculated using the BrunauerꢀEmmettꢀTeller (BET) method
2
synthesis. Ceria (Solvay HSA5, 250 m /g) was used as reference
for DRUV spectra. Finally, (±)ꢀ1,3ꢀbutanediol (Aldrich, >99%)
was used for the catalytic tests, whereas methyl ethyl ketone
in the relative pressure range 0.05 < P/P
< 0.25, while the pore
0
volumes were measured at P/P = 0.95. The BarrerꢀJoynerꢀ
0
Halenda (BJH) and tꢀplot methods were used for measuring the
(MEK) (Aldrich, USP Reference Standard), methyl vinyl ketone
average mesopore sizes and the external and micropore surface
15
(MVK) (Aldrich, 99%), 3ꢀbutenꢀ1ꢀol (3B1ol) (J&K, 98%), 3ꢀ 70 areas, respectively. Prior to the measurements, the catalysts were
o
butenꢀ2ꢀol (3B2ol) (J&K, 97%), 1ꢀbutanol (J&K, 99.5%) and 2ꢀ
butanol (J&K, 99%), were used as standards for GC analysis.
outgassed at 300 C for 6 h under vacuum (<50 Pa).
The morphology of the different catalysts was inspected first by
Scanning Electron Microscopy (SEM) using a Zeiss EVOꢀ18
microscope equipped with Oxford Energy Dispersive Xꢀray
Synthesis of Ce@MOR_X hybrids
The Ce@MOR_X hybrids were synthesized by oneꢀpot hydroꢀ 75 (EDX) analysis. A more refined inspection was conducted by
20
25
30
35
thermal synthesis at 453 K for 20 h using a preꢀformed gel with a
Si : Al : Ce atomic ratio of 1 : 0.08ꢀ0.11 : 0.005ꢀ0.05. The
Si/(Al+Ce) molar ratio was kept constant at a value of ca. 10 for
all the samples. In a typical preparation, an aqueous solution of
Transmission Electron Microscopy (HRꢀTEM) using a JEOL
2010 microscope equipped with a Hamamatsu CDD camera and
using 200ꢀmesh Cꢀcovered Cu grids (SPI Inc.).
Thermogravimetric analysis (TGA) was employed to study the
the Ce and Al precursors was prepared by dissolving 0.53 g of 80 thermal behavior of the spent catalysts. The experiments were
Ce(NO ) and 1.82 g of Al(NO ) in 5.5 mL of deionized water
performed on a TAꢀSDT600 instrument. In a typical test, ∼10 mg
3
3
3 3
containing 0.64 M H SO (pH = 0.19). A second aqueous soluꢀ
of a given catalyst was loaded into an open alumina crucible and
2
4
o
tion was prepared by dissolving 12.5 g of sodium silicate in 10
mL of deionized water, showing a final pH in the range 9ꢀ10. A
was heated from room temperature to 800 C at a rate of 10
o
C/min under a diluted O stream (5 v/v.% in He).
2
third aqueous solution was prepared by dissolving 5.3 g of 85 The Diffuse Reflectance UVꢀVis (DRUVꢀVis) spectra of both the
Na CO in 34 mL of deionized water. The three solutions were
dried and calcined catalysts were recorded in diffuse reflectance
mode on Lambda 650 PerkinꢀElmer spectrophotometer
equipped with 60 mm integrating sphere. BaSO was used as
standard. The spectra displayed a shift line or cutoff wavelength
2
3
stirred for 2 h at room temperature under mild stirring. Subꢀ
sequently, the first and second solutions were added dropwise to
the third solution and the asꢀformed gel was vigorously stirred for
a
4

2
h at room temperature. Then, the gel was sealed in a Teflon ꢀ 90 ~300 nm due to switching of the lamp. The SchusterꢀKubelkaꢀ
o
2
lined autoclave and subjected to hydrothermal synthesis at 180 C
for 20 h. The resulting white solid powder was filtered, washed
Munk (SKM) function, expressed by F(R)= (1ꢀR
∞ ∞
) /2 R = K/S,
was applied for data interpretation, where R is the reflectance of
∞
o
with deionized water, activated, and calcined at 450 C for 4 h
a thick solid layer, and K and S indicate the absorption and
diffusion coefficients, respectively.
o
under static air with a heating rate of 1 C/min.
95
The H ꢀTPR profiles were collected on a Micromeritics
2
Synthesis of Ce-MOR_X(IWI)
AutoChem II2920 system equipped with a quartz Uꢀtype tubular
reactor and a TCD detector. A cold trap was used before the
detector to avoid any interference of water in the TPR plot. In
40
The CeꢀMOR_X(IWI) catalysts were synthesized by the IWI
method. The parent MOR was first synthesized by oneꢀpot hydroꢀ
o
thermal synthesis at 180 C for 20 h using a preꢀformed gel with a
each test, 50 mg of the given catalyst was loaded into the reactor
o
molar composition 1 Si : 0.1 Al. The protocol was analogous to 100 and purged with 30 mL(STP)/min He at 300 C for 1 h to remove
that used in the preparation of the Ce@MOR_X hybrids, but
without dissolving the ceria precursor in the first solution. The asꢀ
synthesized MOR was then soaked over aqueous solution of
adsorbed moisture and vapors, and then cooled down to room
o
temperature. The temperature was then increased up to 750 C at
45
o
a heating rate of 10 C/min under a H flow diluted in Ar (10
2
v/v%). The system was calibrated using an Ag O standard (>99%
Ce(NO3)3 with a volume equaling the pore volume of MOR.
2
o
After Ceꢀimpregnation, the samples were calcined at 450 C for 4 105 purity) to measure the H
consumption in the TPR profiles. All
2
o
h under static air with a heating rate of 1 C/min.
the profiles were normalized to a constant mass of wafer.
NH ꢀTPD was used to measure the density and strength of acid
3
50
Catalyst characterization
sites in the catalysts. The measurements were performed on a
Micromeritics AutoChem II 2920 system equipped with a quartz
10 Uꢀtype tubular reactor and a thermal conductivity (TCD)
detector. A typical test was carried out as follows: 70 mg of
The Si/Al and Si/Ce atomic ratios of the Ce@MOR_X and Ceꢀ
MOR_X(IWI) catalysts were measured by Xꢀray Fluorescence
Spectroscopy (XRF) on a TORNADO instrument from Bruker.
1
2
|
Green Chem., [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 11
Green Chemistry
Dynamic Article Links
►
Green Chem.
View Article Online
DOI: 10.1039/C7GC02223A
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
catalyst were preꢀtreated at 250 °C for 2 h under a He flow [40 50 tetramethylsilane (TMS) and 1 M Al(NO ) aqueous solution,
3
mL(STP)/min] to remove adsorbed moisture and vapors, and then
cooled down to room temperature. Subsequently, NH3 was
chemisorbed at 100 °C using pulsed injections until saturation.
The temperature was then increased up to 1000 °C at a heating
rate of 10 °C/min and the TPD profiles were recorded from 100 to
respectively. The (Si/Al)
from the SiꢀNMR MAS spectra using the following expression
atomic ratios could be estimated
NMR
29
(2)
It
5
0
5
0
5
0
5
Si Al
=
(
)NMR
0
.25IQ3 +0.5IQ2 +0.75IQ1
1
000 °C. The quantification method used for measuring the
1
1
Catalytic tests
number of acid sites can be found elsewhere. All the profiles
were normalized to a constant mass of wafer.
5
6
6
7
7
8
5
0
5
0
5
0
The catalytic dehydration of 1,3ꢀBDO into BD was carried out in
a fixedꢀbed reactor (stainless steel, i.d.: 10 mm, length: 200 mm)
under atmospheric pressure. In a typical test, 200 mg of the given
catalyst were diluted with 400 mg of SiC (φ = 0.21 mm) and
loaded into the reactor center to ensure thermal stabilization at the
1
1
2
2
3
3
The in situ pyridine adsorption experiments were carried out on a
FTꢀIR spectrometer from ThermoNicolet (NEXUS 470) equipped
with a KBr beam splitter and a DTGS detector. In a typical test,
the given catalyst (~20 mg) was pressed into a wafer with 16 mm
diameter. The wafer was then loaded into the cell and outgassed
o
reaction temperature (350 C). The feed reactant (1,3ꢀBDO, 10
o
at 450 C for 2 h under vacuum. After activation, pyridine (133
wt.% in water) was pumped into a vaporization chamber kept at
o
ꢀ1
Pa) was introduced into the cell at room temperature and the
1
90 C with a flowrate of 2.8 mL/h (WHSV = 14 h ) ensuring the
o
wafer was heated to 150 C for 15 min to ensure optimal pyridine
absence of external diffusion limitations. The vaporized mixture
was then introduced into the reactor under a He flow (60 mL
(STP)/min).
The lighter products such as 1,3ꢀBDO and propylene (PE) were
analyzed online using a GC equipped with two semiꢀcapillary
columns (WAX plus: 0.53 mm i.d., 30 m length; and Porapak Q:
diffusion. The wafer was then evacuated at 200 °C and the IR
o
o
spectra were collected every 50 C until 450 C using 64 scans
ꢀ
1
with a resolution of 4 cm . For comparison, the IR spectra were
collected on the parent catalysts before pyridine adsorption. All
the spectra were normalized to a constant mass of wafer.
Xꢀray photoelectron spectroscopy (XPS) surface analyses were
carried out on a Thermo Scientific ESCALAB 250Xi spectroꢀ
meter equipped with a 180° double focusing hemispherical anaꢀ
lyzer and a dual detector system for spectroscopy and imaging.
The analyses were performed using AlꢀKα radiation (hν = 1486.6
eV) and operated at 15 mA and 15 kV with a pass energy of 20
eV (0.1 eV/step) for high resolution spectra and a pass energy of
160 eV (1 eV/step) for the survey spectrum in hybrid mode and
slot lens mode, respectively. The Cꢀ(C,H) component of the C1s
peak of adventitious carbon was set at 284.8 eV as a reference.
Despite the intrinsic complexity of estimating the reduction level
of ceria from the different components from the XPS Ce 3d coreꢀ
0
.53 mm i.d., 30 m length) and a flame ionization detector (FID).
Heavier products such as methyl ethyl ketone (MEK), methyl
vinyl ketone (MVK), 1ꢀbutanol, 2ꢀbutanol, 3ꢀbutenꢀ1ꢀol (3B1ol)
and 3ꢀbutenꢀ2ꢀol (3B2ol) were condensed in a cold trap and furꢀ
ther analyzed offline using a GCꢀFID equipped with a semiꢀ
capillary column (Alltech ECꢀ1000: 0.53 mm i.d., 30 m length).
The reaction data were collected after 6 h stabilization to ensure
that steady state was attained. On the guidance of previous
studies, the time on stream (TOS) was established at 8 h ensuring
1
1
a proper measurement of the intrinsic catalytic activity.
The 1,3ꢀBDO and the selectivity and yield to the different
products were defined as follows:
20
21
level spectrum, we used the following expression
nBDO
(3)
Conversion % =1−
(
1)
(
)
0
3+
v'+ u'
Σ v + u
(
n
BDO
Ce % =
(
)
)
ni
(4)
Selectivity % =
i
( )
0
n
BDO
− nBDO
where v and u are the spinꢀorbit components of the 3p and 3 p3/2
5/2
states of the Ce 3d core level.
ni
(5)
2
7
29
Yield % =
i
(
)
The AlꢀNMR and SiꢀNMR solidꢀstate experiments were conꢀ
ducted on a DSX Bruker spectrometer operated with a magnetic
field strength of 18.8 T and Larmor frequencies of 208.6 MHz
and 159.0 MHz, respectively, using a 3.2 mm MAS probe head.
0
n
BDO
4
0
(6)
MBD
BD productivity = ρBDO
F
YieldBD
MBDO
2
7
The AlꢀNMR MAS spectra were recorded at a spinning rate of
0 kHz using a single pulse excitation sequence with small pulse
angle (π=12) to ensure a quantitative excitation of central
0
85
where nBDO and nBDO refer to the inlet and outlet mole number of
2
1
,3ꢀBDO, respectively, i = methyl ethyl ketone (MEK), methyl
vinyl ketone (MVK), 1ꢀbutanol, 2ꢀbutanol, 3ꢀbutenꢀ1ꢀol (3B1ol),
ꢀbutenꢀ2ꢀol (3B2ol), propylene (PE) and BD, ρ is the 1,3ꢀ
BDO density (1.0053 g/cm ), F is the reactant flowrate (mL/h),
90 and MBD and MBDO refer to the BD and 1,3ꢀBDO molecular
weight, respectively.
4
5
2
2
29
transitions (see ref. ) and a recycle delay of 4 s. The SiꢀNMR
MAS spectra were recorded at a spinning rate of 159.5 kHz using
a single pulse excitation with an angle of π/2 and a time of 4 ꢀs.
3
BDO
3
27
29
The Al and Si chemical shifts were referenced relative to
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 3

Green Chemistry
Page 4 of 11
View Article Online
DOI: 10.1039/C7GC02223A
Figure 1. 1,3ꢀBDO conversion and yield to main products (BD, PE, 3B1ol) over Ce@MOR_X hybrid catalysts: Ce@MOR_200, Ce@MOR_100,
Ce@MOR_50 and Ce@MOR_20. For comparison, the catalytic performance of the parent and Ceꢀimpregnated MOR (i.e. CeꢀMOR_200(IWI), Ceꢀ
MOR_50(IWI)) is also presented. Other detected products (<1% selectivity) include MEK, MVK, 1ꢀbutanol, 2ꢀbutanol and 3B2ol. The numbers in
o
5
parentheses on top of the yield bars indicate the carbon balance. Reaction conditions: ambient pressure; temperature, 350 C; time on stream, 8 h; catalyst
2
loading, 200 mg; liquid flowrate, 2.8 mL/h; carrier gas (N ) flowrate, 60 mL(STP)/min.
Table 1. BD yield, BD productivity, BDꢀtoꢀPE selectivity ratio, sum of 35 increase of the 1,3ꢀBDO conversion to a value higher than 60%,
selectivities and carbon balance for 1,3ꢀBDO dehydration over Ce@MOR
but the BD selectivity kept almost unchanged. In contrast, the
*
_
X hybrid catalysts
Ce@MOR_X hybrids with lower Si/Ce atomic ratios (i.e. X = 50,
100) exhibited a positive effect on both the 1,3ꢀBDO conversion
and BD selectivity. As a matter of fact, the BD selectivity reaꢀ
BD
BD yield
ΣS
C
Catalyst
productivity
SBD/SPE
(%)
ꢀ1 ꢀ1
(%) balance
(g
BD.gcat .h )
MOR
16
13
24
25
39
46
5.4
1.32
1.09
1.98
2.08
3.29
3.84
0.46
1.16
0.93
1.84
1.58
1.83
1.90
0.49
o
102
54
62
64
78
83
66
0.95 40 ched a value up to 46% for Ce@MOR_50 at almost full 1,3ꢀBDO
CeꢀMOR_200(IWI)
CeꢀMOR_50(IWI)
Ce@MOR_200
Ce@MOR_100
Ce@MOR_50
Ce@MOR_20
0.77
0.80
0.75
0.83
conversion. Opposing this behavior, the Ce@MOR_20 hybrid
with the lowest Si/Ce atomic ratio displayed a drastic decline of
the 1,3ꢀBDO conversion and BD selectivity with values lower
0.85
ꢀ
than 30% and 6%, respectively.
4
5
5
6
5
0
5
0
Table 1 lists the BD yields and productivities, BD/PE selectiꢀ
vity ratios, sum of selectivities (ΣS) and carbon balance for the
Ce@MOR_X hybrids and Ceꢀimpregnated MOR catalysts. The
latter two parameters provide an indication of the level of oligoꢀ
merization and coke formation for the different catalysts. The
BD/PE selectivity ratios increased inversely with the Si/Ce atoꢀ
mic ratio for the Ce@MOR_X hybrids in the range X = 50ꢀ200,
reaching a maximum value of 1.90 for Ce@MOR_50. Moreover,
the sum of selectivities and carbon balance were enhanced upon
decreasing the Si/Ce ratio, suggesting a higher resistance against
BD oligomerization and coke formation. In the case of impregꢀ
nated MOR catalysts, excluding CeꢀMOR_50(IWI), comparatiꢀ
vely lower BD/PE selectivity ratios were obtained, as well as
lower sum of selectivities and carbon balances, reflecting a lower
resistance compared to Ce@MOR_X hybrids for CꢀC cleavage.
In light of the benefits of Ce@MOR_X hybrids for 1,3ꢀBDO
dehydration into BD, we carried out a detailed characterization
study to establish structureꢀactivity correlations and understand
the role of ceria on modulating the acid properties of MOR. This
body of results is presented in the forthcoming chapters.
*
10
Reaction conditions: ambient pressure, temperature, 350 C; time on stream, 8
h; catalyst loading, 200 mg; 1,3ꢀBDO flowrate, 2.8 mL/h; carrier gas (N
rate, 60 mL(STP)/min
2
) flowꢀ
Results and Discussion
Catalytic results
15
20
25
30
Figure 1 and Table S1 compile the conversion and yield to
the different products in the vaporꢀphase dehydration of 1,3ꢀBDO
over the different Ce@MOR_X hybrids, as well over the parent
MOR and the Ceꢀimpregnated MOR. In all cases, the main proꢀ
ducts detected were BD, PE and 3B1ol, suggesting a reaction
mechanism proceeding by a first dehydration step encompassing
the formation of 3B1ol and 3B2ol as intermediates followed by
two parallel reactions: (1) dehydration of 3B1ol into BD, and (2)
CꢀC cleavage of either 3B1ol or 3B2ol into PE. Heavy products
might be further generated via PE and BD oligomerization,
promoting coke formation. Minor byproducts were also detected
including MEK, methyl vinyl ketone (MVK), 3ꢀbutenꢀ2ꢀol
(
3B2ol), 1ꢀbutanol and 2ꢀbutanol. However, no ether products
were detected. The different Ce@MOR_X hybrids exhibited a
stable performance during 8 h on stream (Figure S1).
65
Morphology and crystallinity of Ce@MOR_X hybrids
XRD patterns
The incorporation of ceria into the parent MOR by incipient
wetness impregnation at a Si/Ce atomic ratio of 200 encompassed
almost no change in neither the 1,3ꢀBDO conversion nor the BD
selectivity, the latter keeping at a value lower than 14%. Ceꢀ
impregnation at lower Si/Ce ratios (i.e. 100 and 50) exerted an
The structure of the Ce@MOR_X hybrids was first inspected by
XRD (Figure 2). Ce@MOR_200 and Ce@ MOR_50 (patterns c,
d) displayed the same reflections as for the parent MOR (pattern
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 4

Page 5 of 11
Green Chemistry
Dynamic Article Links
►
Green Chem.
View Article Online
DOI: 10.1039/C7GC02223A
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
a), suggesting a lack of structural modification of the MOR
framework upon Ceꢀincorporation. Likewise, a similar XRD
pattern was observed for CeꢀMOR_200(IWI) (profile b). In all
cases, no visible modification of the catalysts was observed
during the reaction by comparison of the XRD patterns for the
fresh and spent catalysts (not shown). Opposing to reported
studies on Ceꢀmodified zeolites, no positive displacement of 2ꢀ
theta angles was observed for the different reflections, indicating
a lack of substitution of bulky Ce atoms into the aluminosilicate
framework. No reflections belonging to ceria (i.e. 28.5°, 33°,
5
0
5
2
3
1
4
7.5°) could be distinguished for the different hybrids, suggesting
a high Ce dispersion promoted by either a partial exꢀframework
+
III
III
H
[
exchange by Ce or hydroxylated Ce cations (e.g.,
III
2+
Ce (OH)] ) in the MOR channels, or by the genesis of very
1
small CeO nanoparticles. Finally, the crystallinity of Ce@MOR_
x
X hybrids was drastically reduced with the Si/Ce atomic ratio,
with Ce@ MOR_20 displaying almost no crystallinity.
Figure 3. DRUV absorption spectra of: (a) MOR, (b) CeꢀMOR_200
(
IWI), (c) Ce@MOR_200, (d) Ce@MOR_50, (e) Ce@MOR _20 and (f)
DRUV spectra
40 CeO . Deconvoluted spectra can be found in the SI (Figure S2, Table S2).
2
The chemical states of the Ce@MOR_X hybrids were further
inspected by DRUVꢀVis and compared to the parent MOR and
CeꢀMOR_200(IWI) (Figure 3). The parent MOR (profile a) exhiꢀ
bited a tiny yet detectable band at about 282 nm that can be attriꢀ
buted to an impurity in the Si precursor (e.g., Fe) and that was
also observed after Ce incorporation. Additional bands centered
at about 230ꢀ240 nm, 320 nm and 345 nm appeared for Ce@
MOR_200 and Ce@MOR_50 (profiles c, d), as well as for Ceꢀ
MOR_ 200(IWI) (profile e) (see deconvoluted plots in Figure S2,
The position of the adsorption edge was found in the range
80ꢀ420 nm for Ce@MOR_X hybrids, whereas this range was
2
2
3
0
5
0
3
redꢀshifted for CeꢀMOR_200(IWI) (400ꢀ450 nm). Noteworthy,
the latter range is very similar to that found on nanoceria with a
crystallite size of 6.5 nm (profile f). Since the adsorption edge is
known to be sensitive on the crystallite size of ceria nanoparꢀ
45
25
ticles, our results suggest the presence of ceria nanoparticles on
the Ce@MOR_X hybrids with a size lower than 6.5 nm. Furtherꢀ
2ꢀ
IV
2ꢀ
more, the presence of O → Ce charge transfer occurring on
Table S2). The first and second bands can be assigned to O →
IV
III
2ꢀ
IV
50 lowꢀcoordinated Ce cations cannot be ruled out.
Ce and O → Ce charge transfer transitions, whereas the third
band can be ascribed to interꢀband transitions belonging to
SEM and TEM-EDX images
24
ceria. These results confirm the incorporation of ceria on the
different catalysts both in the reduced and oxidized states
irrespective of the preparation protocol.
The SEM micrographs of Ce@MOR_200 and Ce@MOR_50
revealed a genuine crystal morphology and crystal growth pattern
compared to the parent MOR (Figure 4, Figure S3). Regardless of
5
6
6
7
5
0
5
0
the Ce loading, both hybrids showed the presence of needles
grown perpendicularly on the MOR crystals, leading to a nanoꢀ
flowered external surface. The growth density of needles was
drastically boosted for Ce@MOR_50, suggesting a major role of
hydrated Ce cations in the preꢀformed gel on the nucleation and
growth of needles at the external surface of MOR crystals.
Opposing this morphology, the SEM micrographs of CeꢀMOR_
III
2
00(IWI) and CeꢀMORꢀ50ꢀIWI (not shown) did not reveal the
formation of needles over the crystals.
TEM imaging was further conducted to gain more insight into
ceria dispersion on the Ce@MOR_X hybrids (Figure 5, Figure 6).
Interestingly, very small ceria nanoparticles (size <3 nm) were
visible on the MOR crystals for Ce@MOR_200 and Ce@MOR_
5
(
0. Furthermore, for the latter hybrid, small ceria nanoparticles
size <6 nm) also appear to be supported over the needles. EDX
analysis revealed a very homogeneous distribution of silica (blue)
3
5
Figure 2. XRD patterns of: (a) MOR, (b) CeꢀMOR_200(IWI); (c) Ce@
MOR_200, (d) Ce@MOR_50 and (e) Ce@MOR_20.
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 5

CREATED USING THE RSC ARTICLE TEMPLATE (VER. 3.0) - SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS
Green Chemistry
Page 6 of 11
View Article Online
ARTICLE TYPE
www.rsc.org/xxxxxx | XXXXXXXX
DOI: 10.1039/C7GC02223A
and ceria (yellow) on Ce@MOR_50 (Figure 6), whereas Al
shifted adsorption edges in the DRUV spectra can be explained
by the high dispersion and small particle size of ceria nanoꢀ
particles. On the other hand, the loss of crystallinity of the
(green) was not present in the needles, suggesting that these are
mainly composed of amorphous silica. These observations are
consistent with the XRD patterns and DRUV spectra presented 10 samples upon Ce loading can be well accounted by the formation
5
above for the Ce@MOR_X hybrids. On the one hand, the lack of
reflections belonging to ceria in the XRD patterns and blueꢀ
of amorphous silica needles.
(a)
(b)
(c)
1
ꢀm
1 ꢀm
2 ꢀm
Figure 4. SEM micrographs of: (a) MOR, (b) Ce@MOR_200 and (c) Ce@MOR_50.
(a)
(b)
CeOx
CeOx
d= 2.77 Å
(c)
(d)
15
Figure 5. TEM micrographs of: (a) Ce@MOR_200 and (bꢀd) Ce@MOR_50. Image (d) zoomed in for the part cycled in the image for Ce@MOR_50 (c).
2
00 nm
200 nm
200 nm
Figure 6. TEMꢀEDX images of Ce@MOR_50 showing the location of Si (blue), Al (green) and Ce (yellow). Additional images can be found in the SI
Figure S3).
(
6
|
Green Chem., [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 7 of 11
Green Chemistry
View Article Online
DOI: 10.1039/C7GC02223A
5
Figure 7. Ce 3d XPS spectra for: (a) CeꢀMOR_200, (b) Ce@MOR_50,
c) Ce@MOR_20, (d) Ce@MOR_200(IWI) and (e) CeꢀMOR_50(IWI).
Deconvoluted spectra can be found in the SI (Figure S4, Table S3).
Figure 8. O 1s XPS spectra for: (a) MOR, (b) CeꢀMOR_200(IWI), (c)
Ce@MOR_200 and (d) Ce@MOR_50. Additional spectra and results
from deconvolution can be found in the SI (Figure S5, Table S4).
(
Table 2. Composition and Ce speciation in Ce@MOR_X hybrids and Ceꢀimpregnated MOR
d
Al (atoms/uc)
Al
Al
Ce
Si/Ala
Si/Ce
ratio
Acid sitesb
B/L
(ꢀ)
III e
f
Catalyst
a
a
a
c
%Ce
%Ceex
(
mmol/g) (mmol/g)
ratio
(mmol/g)
Al
F
AlNF
MOR
2.19
1.85
1.73
1.89
1.59
1.44
ꢀ
8 (7.3)
ꢀ
1.97
1.35
0.84
1.48
1.60
1.39
4.7
4.5
4.7
8.1
8.1
8.3
5.68
3.89
4.18
4.94
4.58
4.15
b
4.68
3.21
3.45
4.40
4.08
3.70
1.00
0.68
0.73
0.54
0.50
0.45
0% (0%)
>95% (28%)
90% (21%)
12% (40%)
4.5% (40%) <2%
2.4% (43%) 3%
0%
0%
51%
2%
CeꢀMOR_200(IWI)
CeꢀMOR_50(IWI)
Ce@MOR_200
Ce@MOR_100
Ce@MOR_50
a
0.085
0.36
0.08
0.20
0.34
12 (8.5) 262 (12)
11 (7.4) 53 (2.9)
9 (13) 213 (132)
10 (ꢀ)
10 (17) 42 (23)
80 (ꢀ)
1
0
3
Bulk values measured by ICPꢀOES (values in parentheses refer to surface values measured by XPS); Measured from NH ꢀTPD profiles in the temperature range
o
26
c
27
d
e
4
00ꢀ900 C (ref. ); Measured from AlꢀNMR MAS spectra; Molecular formula for MOR: [H
x
Al
x
Si48ꢀx
O96]; Measured from H
+
2
ꢀTPR profiles in the temperature
o
f
3+
range 250ꢀ550 C (values in parentheses measured from XPS spectra using Ce 3d core level, Eq. 1); % of H exchanged by nonꢀhydrated Ce in the MOR channels
III
XPS spectra
To gain more insight into the surface distribution of Si, Al
indicates the presence of a high proportion of Ce species on the
III
4
4
5
5
6
6
0
5
0
5
0
5
catalyst surface (by 35ꢀ40%, Table 2). For comparison, Ce was
also detected at the surface of Ceꢀimpregnated catalysts, but at a
lower level (21ꢀ28%). The Ce 3d XPS spectrum for Ce@MOR_
1
2
2
3
3
5
0
5
0
5
and Ce at the surface of the Ce@MOR_X hybrids, the different
catalysts were examined by XPS. Table 2 lists the bulk and surꢀ
face Si/Al atomic ratios of the different catalysts measured by
ICP and XPS, respectively. The surface Si/Al atomic ratios
declined slightly compared to the bulk values for the parent MOR
and the Ceꢀimpregnated catalysts, suggesting a partial surface Alꢀ
enrichment on the MOR crystals. Conversely, the Ce@MOR_X
hybrids exhibited the opposite trend, namely the surface Si/Al
ratios were higher than the corresponding bulk ratios. In agreeꢀ
ment with the SEM and TEMꢀEDX micrographs (Figures 4ꢀ6),
this latter observation can be explained by the partial coverage of
MOR crystals by amorphous silica needles.
Figure 7 plots the Ce 3d and O 1s core level XPS spectra for
Ce@MOR_200, Ce@MOR_50 and Ce@MOR_20, as well as for
MOR, CeꢀMOR_200(IWI) and CeꢀMOR_50(IWI). The deconvoꢀ
luted Ce 3d XPS spectra could be assigned to eight spinꢀorbit
coupling levels corresponding to the 3d5/2 (v) and 3d3/2 (u) states
2
00 exhibited very low intensities, suggesting that only a reduced
proportion of ceria particles was located on the catalyst surface.
Indeed, the surface Si/Ce atomic ratios for Ce@MOR_X hybrids
measured by XPS displayed slightly lower values compared to
the corresponding bulk ratios (Table 2). This observation can be
explained by a partial ceria encapsulation in the MOR crystals. In
contrast, the Ceꢀimpregnated catalysts exhibited much higher
surface Si/Ce atomic ratios compared to the bulk ratios, pointing
out both/either a preferential location of ceria nanoparticles at the
III
MOR surface, and/or partial Ce exchange into the MOR
channels during the synthesis. Additional insight into the location
of Ce in the hybrids and Ceꢀexchanged catalysts is provided
below.
The XPS spectra of the O 1s core level for MOR, CeꢀMOR_
00(IWI), CeꢀMOR_50(IWI), Ce@MOR_200, Ce@MOR_50
and Ce@MOR_20 (Figure 8, Figure S5, Table S4) showed the
presence of a major band centered in the range 530.0ꢀ530.9 eV
matching the BE of lattice O in silica and ceriaꢀsilica composites.
A second band was also apparent in the range 528.0ꢀ529.5 eV
that could be attributed to lattice O in pure ceria. An additional
band was observed for CeꢀMOR_50(IWI) at 527.7 eV, which was
be ascribed to weakly bounded oxygen (e.g., hydroxyl groups,
vacancies) in ceria nanoparticles.
2
(
Figure S4, Table S3). The v components showed binding enerꢀ
gies (BE) centered at 880.7ꢀ881.8 eV (v), 882.9ꢀ884.5 eV (v’),
85.4ꢀ887.3 eV (v”) and 896.7ꢀ897.9 eV (v’”), while the u
components showed BEs centered at 899.2ꢀ900.3 eV (u), 900.6ꢀ
8
20,27
9
02.8 eV (u’), 904.7ꢀ905.7 eV (u”) and 915.0ꢀ916.3 eV (u’”).
The presence of v’ and u’ components combined with large bands
for v’” and u’” components for the Ce@MOR_X hybrids
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 7

CREATED USING THE RSC ARTICLE TEMPLATE (VER. 3.0) - SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS
Green Chemistry
Page 8 of 11
View Article Online
ARTICLE TYPE
www.rsc.org/xxxxxx | XXXXXXXX
DOI: 10.1039/C7GC02223A
Table 3. Textural properties of Ce@MOR_X hybrids measured
from N adsorption/desorption at ꢀ196 C
2
and effect was not observed for the Ceꢀimpregnated catalysts
with no needle formation. Noteworthy, Ce@ MOR_20 displayed
50 a dramatic reduction of the specific surface down to 13 m /g,
o
a
2
S
m /g)
BET
S
EXT
V
g
Catalyst
MOR
2
2
3
(
(m /g)
27 (49)
20 (ꢀ)
(cm /g)
0.20 (0.17)
0.19 (ꢀ)
confirming the lack of crystallinity of this sample.
550 (472)
CeꢀMOR_200(IWI) 526 (ꢀ)
The main porous features of the catalysts were preserved after
reaction without any qualitative change on the shape of the
isotherms (not shown). Notwithstanding this fact, the textural
properties of the spent catalysts were altered due to the formation
of carbon deposits (see TGA profiles in Figure S8). The specific
surface area decreased by 50% for the Ce@MOR_X hybrids,
whereas this reduction was lower (ca. 30%) for the Ceꢀ
impregnated catalysts. Noticeably, all the catalysts exhibited a
decline of the micropore surface area, which was more moderate
for the hybrids.
CeꢀMOR_50(IWI)
Ce@MOR_200
Ce@MOR_100
Ce@MOR_50
Ce@MOR_20
a
464 (312)
454 (ꢀ)
420 (252)
467 (231)
13 (ꢀ)
32 (33)
45 (ꢀ)
45 (51)
61 (52)
8 (ꢀ)
0.17 (0.13)
0.17 (ꢀ)
0.16 (0.10)
0.23 (0.16)
0.02 (ꢀ)
5
5
In parentheses, values measured on the spent catalysts
60
Catalyst reducibility (H -TPR)
2
5
0
5
0
5
0
The reducibility of the different catalysts was assessed by H2ꢀ
TPR (Figure S6). The H ꢀTPR profile of the parent MOR exhiꢀ
Acid properties
2
o
bited only positive bands centered at 180 C and to minor extent
The nature of the acid centers in the parent MOR, Ceꢀimꢀ
pregnated catalysts and Ce@MOR_X hybrids was first assessed
o
o
at 500 C and 750 C that could be attributed to bound water.
Water desorption bands were also visible for Ce@MOR_200 and
Ce@MOR_100, but became more moderate for Ce@MOR_50
and Ce@MOR_20, especially at higher temperatures. Finally,
27
27
6
7
7
8
8
9
9
5
0
5
0
5
0
5
by AlꢀNMRꢀMAS (Figure 9a). In all cases, the AlꢀNMR MAS
spectra consisted of two main peaks centered at 54.3 ppm and ꢀ
1
1
2
2
3
1
.3 ppm that could be attributed to fourfold coordinated frameꢀ
CeꢀMOR_50(IWI) exhibited only a tiny water desorption band by
work Al atoms in the MOR framework and sixfold coordinated
exꢀframework Al. The ratio between framework and exꢀframeꢀ
work Al characterizing the relative contribution of Brφnsted acid
o
1
80 C.
The H ꢀTPR profiles of the different catalysts displayed an
2
o
adsorption band in the temperature range 250ꢀ550 C that can be
sites and Lewis acid sites (i.e. B/L) kept almost unchanged for the
Ceꢀimpregnated catalysts compared to the parent MOR at a value
of 4.7 (Table 2). In contrast, the B/L ratio exhibited a pronounced
increase for the Ce loading for the Ce@MOR_X hybrids at a
value of 8.2ꢀ8.3. The structural organization and B/L ratios of the
different catalysts kept almost unchanged after the reaction.
Pyridine adsorptionꢀIR was further conducted on some selecꢀ
ted Ce@MOR_X hybrids (Figure S9a). In these tests, the chaꢀ
IV
III
ascribed to the reduction of Ce to Ce at the surface of ceria
nanoparticles. Interestingly, no additional adsorption band (belonꢀ
ging to the reduction of bulk ceria) was observed in the temperaꢀ
ture range 600ꢀ900 C, confirming the very small size of ceria
nanoparticles (<2.5 nm) in the hybrids.
o
2
8
Irrespective of the Ce loading, the Ce@MOR_X hybrids exꢀ
III
hibited a percentage of Ce in the range 2.4ꢀ12% (Table 2). Interꢀ
estingly, these values are much higher than the corresponding
percentages measured from the Ce 3d XPS spectra (range 40ꢀ
ꢀ
1
racteristic band at around 1545 cm is attributed to the formation
of pyridinium ions by interaction of pyridine with Brønsted acid
sites (e.g., bridged SiꢀO(H)ꢀAl sites), while the band at around
III
45%, vide supra), pointing out that most of the Ce species were
present near to the surface of MOR crystals in the hybrids. Oppoꢀ
ꢀ
1
1
455 cm originates from the interaction between pyridine and
III
sing this observation, the percentage of Ce measured form H2ꢀ
29
27
Lewis acid sites. In agreement with the results from AlꢀNMRꢀ
MAS, the relative intensity of Lewis acid sites decreased with the
Ce loading. Interestingly, for Ce@MOR_100 and Ce@MOR_50,
a new band appeared by 1442 cm , which could be ascribed to
Brønsted acid sites with weakꢀtoꢀmoderate strength. All the cataꢀ
TPR (90ꢀ95%) was found to be much higher than the values meaꢀ
sured from the Ce 3d XPS spectra (21ꢀ28%, vide supra) for Ceꢀ
III
impregnated catalysts. Accordingly, Ce species appear to be
ꢀ
1
located far from the surface in the Ceꢀimpregnated catalysts.
ꢀ
1
lysts exhibited a broad band centered at 3616 cm after pyridine
adsorption that were attributed to SiꢀO(H)ꢀAl weak acid sites
Textural properties
3
0
Table 3 compiles the textural properties of the fresh and spent
(Figure S9b). This band became narrower for Ce@MOR_50,
suggesting a high degree of hydrophobicity for this catalyst.
MOR, Ce@MOR_X and CeꢀMOR_200(IWI) as measured from
o
ꢀ
1
35
40
45
N adsorption/desorption at ꢀ196 C, whereas Figure S7 plots the
2
Interestingly, no bands were observed at 3735 cm , pointing out
the absence of weakly acid SiꢀOH groups both located both in
corresponding isotherms. The different catalysts displayed
characteristic Type I isotherms that are reminiscent of microꢀ
porous materials. In the case of Ce@MOR_50, a population of
mesopores was also present with a BJH size in the range 3.4ꢀ4.8
nm, as inferred from the hysteresis loop between the adsorption
and desorption curves.
30
internal defects and at the external surface of the catalysts.
29
The SiꢀMASꢀNMR spectra measured on Ce@MOR_200,
Ce@MOR_50 and CeꢀMOR_50(IWI) exhibited a visible peak
broadening compared to the spectrum of the parent MOR due to
the presence of paramagnetic Ce species (Figure 9b). After deꢀ
III
The BET specific surface of the Ce@MOR_X hybrids disꢀ
played a moderate decrease upon Ce incorporation (from 550
convolution, three species could be identified for the different
1
00 catalysts with a chemical shift centered at ꢀ112 ppm, ꢀ106 ppm
and ꢀ100 ppm that can be attributed to Q4 [Si(0Al)], Q3 [Si(1Al)]
and Q2 [Si(2Al)] (Figure S10, Table S5). Interestingly, the Q3
contribution decreased from 39% for MOR to 28% for Ce@
MOR_50 while promoting Q2 and Q4 bands. Such an effect,
2
2
m /g for the parent MOR to 467 m /g for Ce@MOR_50). In
contrast, Ce incorporation impacted to an important extent the
external surface area and the pore volume of the samples due to
the formation of needles over the MOR crystals. However, such
8
|
Green Chem., [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 9 of 11
Green Chemistry
Dynamic Article Links
►
Green Chem.
View Article Online
DOI: 10.1039/C7GC02223A
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
even if more moderate, was also observed for CeꢀMOR_50(IWI). 25 nNH associations promoted by Hꢀbonding between 100ꢀ400 °C
3
These results point out a decline of SiꢀO(H)ꢀAl acid centers upon
ceria incorporation, which can be explained by three possible
(bands I and II), (2) medium acid sites between 400ꢀ550 °C
(bands III/IV), and (3) strong acid sites between 550ꢀ900 °C
(bands IV/V). In this analysis, we assumed that all the hydroxyl
+
3+
effects: (1) partial exꢀframework H exchange by Ce or hydroꢀ
III
III
2+
5
xylated Ce cations (e.g., [Ce (OH)] ) in the MOR channels,
groups that could be titrated by NH corresponded to medium and
3
o
(2) capping of external Siꢀ(OH)ꢀAl acid centers by ceria nanoꢀ 30 strong acid sites in the temperature range 400ꢀ900 C, which is an
26
particles, and (3) genesis of amorphous silica needles at the
external surface of MOR crystals (i.e. Q4 species). We will
discuss in the following lines the main implications of the three
effects on the acid loading and strength on the different catalysts.
accepted temperature range for MOR.
1
0
3
Figure 10. NH ꢀTPD profiles for: (a) HꢀMOR, (b) Ce@MOR_100, (c)
35
Ce@MOR_50 and (d) CeꢀMOR_50(IWI), as well as density of medium
and strong acid sites and corresponding ratio (e). Total amount of acid
sites measured by integration between 400ꢀ900 C (see also Table 2).
29
27
Figure 9. SiꢀMASꢀNMR and AlꢀMASꢀNMR spectra of: (a) HꢀMOR,
b) Ce@MOR_200, (c) Ce@MOR_50 and (d) CeꢀMOR_50(IWI). Deconꢀ
voluted spectra can be found in the SI (Figure S9, Table S5).
o
(
Additional profiles for fresh and spent catalysts can be found in the SI
1
5
(Figure S11, S12).
The total amount and distribution of acid sites on the Ce@
MOR_X hybrids and Ceꢀimpregnated catalysts was measured by
NH ꢀTPD. It is commonly accepted that NH is a suitable probe
4
0
The NH loading measured for the different catalysts decreaꢀ
3
sed after Ceꢀincorporation (Table 2), matching the results obserꢀ
3
3
29
ved by SiꢀMASꢀNMR. Furthermore, unlike the parent MOR,
molecule for titrating acid hydroxyl groups accessible through
pores, channels or windows in zeolites with a size <4 Å due to its
the Ce@MOR_X hybrids and Ceꢀimpregnated catalysts displayed
a markedly smaller surface area of the first band in the NH ꢀTPD
3
profiles (Figure 10aꢀd) corresponding to very weak acid sites.
This observation reinforces the idea of a higher degree of hydroꢀ
phobicity of the catalysts upon Ce incorporation. Another conseꢀ
quence of Ceꢀloading can be found on the acid site distribution in
2
0
3
31
small molecular dimensions (3.70 x 3.99 x 3.11 Å ). The acid
site strength of the different catalysts was broadly classified in
45
three groups after deconvolution of the NH ꢀTPD profiles (Figure
3
3
2
+
1
0aꢀd, Figure S11, Table S6): (1) weak acid sites and NH .
4
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 9

CREATED USING THE RSC ARTICLE TEMPLATE (VER. 3.0) - SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS
Green Chemistry
Page 10 of 11
View Article Online
ARTICLE TYPE
www.rsc.org/xxxxxx | XXXXXXXX
DOI: 10.1039/C7GC02223A
the medium and strong acid regions (Figure 10e, Table 5). As a 55 and Dr. Benjamin Katryniok from UCCS Lille for fruitful
matter of fact, the ratio of medium over strong acid sites
increased from 0.73 for the parent MOR to >4.0 for Ce@MOR_
discussions.
1
00 and Ce@MOR_50. Interestingly, the Ceꢀimpregnated cataꢀ
Notes and references
5
0
5
0
5
0
lysts (i.e. CeꢀMOR_200(IWI) and CeꢀMOR_50(IWI)) displayed
lower ratios (<2.5), suggesting a lower capacity for acid modulaꢀ
tion upon Ceꢀincorporation. Also noteworthy, the high acid
modulation capacity of Ce@MOR_X hybrids became more
pronounced for the spent catalysts, for which the ratio of medium
over strong acid sites reached a value of ca. 5.0. This ratio was
also higher for the spent MOR (2.4), whereas it remained almost
unchanged for CeꢀMOR_50(IWI) (2.2). The reader will find
a
EcoꢀEfficient Products and Processes Laboratory (E2P2L), UMI
464 CNRSꢀSolvay, 3966 Jin Du Road, Xin Zhuang Ind. Zone,
3
6
0
201108 Shanghai, China. Email: marc.peraꢀtitusꢀext@solvay.com
b
School of Chemical Engineering, Sichuan University, No 24,
South section 1, Yihuan Road, 610065 Chengdu, China.
c
1
1
2
2
3
School of Physics and Materials Science & Shanghai Key
Laboratory of Magnetic Resonance, East China Normal
detailed deconvoluted spectra for the spent catalysts in Figure 65 University, 3663 N. Zhongshan Road, Shanghai 200062, China
S12 and Table S6.
†
Electronic Supplementary Information (ESI) available: XXX.
By combining the results of elemental analysis (ICP), XPS,
See DOI: 10.1039/b000000x/
2
7
H ꢀTPR, TEMꢀEDX, AlꢀNMR MAS and NH ꢀTPD, and taking
2
3
into account the molecular formula of MOR (i.e. [H (H O) ]
x
2
3
1. a) Wm. Claude White, Chem-Biol. Inter. 2007, 166, 10ꢀ14; b) M. D.
Jones, C. G. Keir, C. D. Iulio, R. A. M. Robertson, C. V. Williams,
D. C. Apperley, Catal. Sci. Technol. 2011, 1, 267ꢀ272; b) E. V.
Makshina, W. Janssens, B. F. Sels, P. A. Jacobs, Catal. Today 2012,
[
Al Si O ]), we could ascertain and quantify the location of
x 48ꢀx 92
ceria on the different catalysts (Table 2). On the one hand, Ceꢀ
MOR_200(IWI) and CeꢀMOR_50(IWI) showed CeOx nanoꢀ
particles mainly located at the external surface of MOR crystals.
70
1
98, 338ꢀ344.
+
III
2. a) C. Angelici, B. M. Weckhuysen, P. C. A. Bruijnincx,
ChemSusChem 2013, 6, 1595ꢀ1614; b) H. M. Torres Galvis, K. P. de
Jong, ACS Catal. 2013, 3, 2130ꢀ2149.
In particular, in the latter case, a partial H exchange by Ce
cations was also regarded as possible at a level of 51% of the exꢀ
framework positions by assuming partial exchange by nonꢀ
75
3
.
Z. Wang, in Comprehensive Organic Name Reactions and Reagents,
John Wiley & Sons, Inc., 2010, pp. 1728ꢀ1730.
3
+
hydrated Ce . On the other hand, in the case of Ce@MOR_X
IV
hybrids, Ce is expected to be located in CeO nanoparticles
2
4
.
a) M. Lewandowski, G. S. Babu, M. Vezzoli, M. D. Jones, R. E.
Owen, D. Mattia, P. Plucinski, E. Mikolajska, A. Ochenduszko, D. C.
Apperley, Catal. Commun. 2014, 49, 25ꢀ28; b) C. Angelici, M. E. Z.
Velthoen, B. M. Weckhuysen, P. C. A. Bruijnincx, ChemSusChem.
2014, 7, 2505ꢀ2515; c) C. Angelici, M. E. Z. Velthoen, B. M.
Weckhuysen, P. C. A. Bruijnincx, Catal. Sci. Technol. 2015, 5, 2869ꢀ
supported over the external surface of MOR crystals and over the
silica nanosheets, as well as encapsulated in the MOR crystals in
a homogeneous fashion. In the latter case, we can argue about the
80
85
IV
generation of Ce ꢀO(H)ꢀAl acid sites with medium strength at
the interface between the encapsulated ceria nanoparticles and the
2
879; d) W. Janssens, E. V. Makshina, P. Vanelderen, F. De Clippel,
+
III
MOR framework. Finally, a very low H exchange by Ce
K. Houthoofd, S. Kerkhofs, J. A. Martens, P. A. Jacobs, B. F. Sels,
ChemSusChem. 2015, 8, 994ꢀ1008; e) A. Chieregato, J. V. Ochoa, C.
Bandinelli, G. Fornasari, F. Cavani, M. Mella, ChemSusChem. 2015,
species (<3%) in the hybrids is also regarded as possible.
8
, 377ꢀ388; f) O. V. Larina, P. I. Kyriienko, S. O. Soloviev, Catal.
Conclusions
Lett. 2015, 145, 1162ꢀ1168.
35
40
45
Ce@MOR hybrids based on CeO nanoparticles (1ꢀ2.5 nm) 90 5. V. L. Sushkevich, I. I. Ivanova, V. V. Ordomsky, E. Taarning,
x
ChemSusChem 2014, 7, 2527ꢀ2536.
encapsulated in mordenite and exhibiting a flowerꢀlike morphoꢀ
6
.
a) S. K. Bhattacharyya, S.K. Sanyal, J. Catal. 1967, 7, 152ꢀ158; b) G.
O. Ezinkwo, V. F. Tretjakov, R. M. Talyshinky, A. M. Ilolov, T. A.
Mutombo, Catal. Commun. 2014, 43, 207ꢀ212.
logy were prepared by one pot hydrothermal synthesis. The texꢀ
tural properties and the amount of acid sites of the hybrids could
be simply tuned by adjusting the cerium content of the synthesis
gel. The genesis of acid sites with medium strength was directly
correlated to the catalytic activity for the vaporꢀphase dehydration
of 1,3ꢀbutanediol into butadiene. A Ce@MOR hybrid with a
nominal Si/Ce atomic ratio of 50 displayed a superior activity and
selectivity compared to the parent mordenite at a comparable
Si/Al atomic ratio (10), as well to a control Ceꢀimpregnated MOR
catalyst due to a higher density of acid sites with medium
9
5
7. a) T. A. Werpy, J. E. Holladay, J. F. White, 2004, pp. 1ꢀ67; b) N.
Itoh, M. Nakamura, K. Inoue, Y. Makino, Appl. Microbiol.
Biotechnol. 2007, 75, 1249ꢀ1256; c) X.ꢀJ. Ji, H. Huang, P.ꢀK.
Ouyang, Biotechnol. Adv. 2011, 29, 351ꢀ364; d) H. Yim, R.
Haselbeck, W. Niu, C. PujolꢀBaxley, A. Burgard, J. Boldt, J.
Khandurina, J. D. Trawick, R. E. Osterhout, R. Stephen, J. Estadilla,
S. Teisan, H. Brett Schreyer, S. Andrae, T. H. Yang, S. Y. Lee, M. J.
Burk, S. van Dien, Nat. Chem. Biol. 2011, 7, 445ꢀ452; e) N. Kataoka,
A. S. Vangnai, T. Tajima, Y. Nakashimada, J. Kato, J. Biosci.
Bioeng. 2013, 115, 475ꢀ480; f) J. Baek, T. Y. Kim, W. Kim, W. Kim,
H. J. Lee, J. Yi, Green Chem. 2014, 16, 3501ꢀ3507.
1
1
00
05
strength induced by encapsulated CeO nanoparticles.
x
8
9
.
.
H. Duan, Y. Yamada, S. Sato, Chem. Lett. 2016, 45, 1036ꢀ1047.
L. Ott, S. Kohl, M. Bicker, H. Vogel, Chem. Eng. Technol. 2005, 28,
Acknowledgements
The authors would like to express their gratitude to Solvay and
CNRS for funding. The Science and Technology Commission of
Shanghai Municipality is also acknowlegded for a postdoctoral
innovation grant (14301ꢀ412212ꢀ16017). The authors thank Dr.
Marc Airiau from Solvay for performing the pyridine adsorptionꢀ
IR tests, as well as to Prof. Frank Dumeignil, Prof. Sebastien Paul
1
561ꢀ1568.
50
1
0. 1,3ꢀBDO: a) S. Sato, R. Takahashi, T. Sodesawa, N. Honda, H.
Shimizu, Catal. Commun. 2003, 4, 77ꢀ81; b) H. Gotoh, Y. Yamada,
S. Sato, Appl. Catal. A: Gen. 2010, 377, 92ꢀ98; c) S. Sato, F. Sato, H.
Gotoh, Y. Yamada, ACS Catal. 2013, 3, 721ꢀ734; 1,4ꢀBDO: a) R.
Takahashi, T. Sodesawa, N. Yamamoto, Catal. Commun. 2004, 5,
110
3
97ꢀ400; b) N. Yamamoto, S. Sato, R. Takahashi, K. Inui, Catal.
1
0
|
Green Chem., [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 11 of 11
Green Chemistry
Dynamic Article Links
►
Green Chem.
View Article Online
DOI: 10.1039/C7GC02223A
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Commun. 2005, 6, 480ꢀ484; c) H. Duan, T. Hirota, S. Ohtsuka, T.
Yamada, S. Sato, Appl. Catal. A: Gen. 2017, 535, 9ꢀ16.
Hicks, ACS Catal. 2012, 2, 642ꢀ646; c) G. T. Neumann, J. C. Hicks,
Top Catal. 2012, 55, 196ꢀ208.
1
1
1. a) F. Jing, B. Katryniok, M. Araque, R. Wojcieszak, M. Capron, S.
Paul, M. Daturi, JꢀM. Clacens, F. De Campo, A. Liebens, F.
Dumeignil, M. PeraꢀTitus, Catal. Sci. Technol. 2016, 6, 5830ꢀ5840;
b) F. Jing, B. Katryniok, S. Paul, L. Fang, A. Liebens, B. Hu, F.
Dumeignil, M. PeraꢀTitus, ChemCatChem. 2017, 9, 258ꢀ262.
20. A. Bensalem, F. BozonꢀVerduraz, M. Delamar, G. Bugli, Appl.
Catal. A: General, 1995, 121, 81ꢀ93.
5
0
5
0
6
5
21. A. Laachir, V. Perrichon, A. Badri, J. Lamotte, E. Catherine, J. C.
Lavalley, J. El Fallah, L. Hilaire, F. le Normand, E. Quemere, G N.
Sauvion, O. Touret, J. Chem. Soc., Faraday Trans. 1991, 87, 1601ꢀ
1609.
2. a) W. Zhang, D. Yu, X. Ji, H. Huang, Green Chem. 2012, 14, 3441ꢀ
3
450; b) A. Multer, N. McGraw, K. Hohn, P. Vadlani, Ind. Eng.
2
2. A. Samoson, E. Lippmaa, Phys. Rev. B 1983, 28, 6567ꢀ6570.
1
1
2
Chem. Res. 2013, 52, 56ꢀ60; c) H. Duan, Y. Yamada, S. Sato, Appl.
Catal. A: Gen. 2014, 487, 226ꢀ233; H. Duan, Y. Yamada, S. Kubo, S.
Sato, Appl. Catal. A: Gen. 2017, 530, 66ꢀ74.
7
7
8
0
5
0
23. a) Y. Wu, J. Wang, P. Liu, W. Zhang, J. Gu, X. Wang, J. Am. Chem.
Soc., 2010, 132, 17989ꢀ17991; b) W. J. Roth, B. Gil, W. Makowski,
A. Slawek, A. Korzeniowska, J. Grzybek, M. Siwek, P. Michorczyk,
Catal. Sci. Technol. 2016, 6, 2742ꢀ2753.
1
1
3. a) H. Duan, D. Sun, Y. Yamada, S. Sato, Catal. Commun. 2014, 48,
1
ꢀ4; b) H. Duan, Y. Yamada, S. Sato, Appl. Catal. A: Gen. 2015, 491,
2
2
2
4. a) K. N. Rao, P. Bharali, G. Thrimurthulu, B. M. Reddy, Catal.
Commun. 2010, 11, 863ꢀ866; b) Sk. Mahammadunnisa, P. M. K.
Reddy, N. Lingaiah, C. Subrahmanyam, Catal. Sci. Technol. 2013, 3,
163ꢀ169.
4. a) H. Vinek, J. A. Lercher, H. Noller, J. Mol. Catal. 1985, 30, 353ꢀ
3
59; b) M. A. Makarova, C. Williams, J. M. Thomas, K. I. Zamaraev,
7
30ꢀ736.
Catal. Lett. 1990, 4, 261ꢀ264; c) M. A. Makarova, C. Williams, K. I.
Zamaraev, J. M. Thomas, J. Chem. Soc. Faraday Trans. 1994, 90,
2147ꢀ2153; d) M. A. Makarova, E. A. Paukshtis, J. M. Thomas, C.
Williams, K. I. Zamaraev, J. Catal. 1994, 149, 36ꢀ51.
5. A. Bensalem, J. C. Muller, F. BozonꢀVerduraz, J. Chem. Soc.,
Faraday Trans. 1992, 88, 153ꢀ154; A. Bensalem, F. Bozonꢀ
Verduraz, M. Delamar, G. Bugli, Appl. Catal. A: Gen. 1995, 121, 81ꢀ
9
3.
1
5. a) P. B. Venuto, L. A. Hamilton, P. S. Landis, J. Catal. 1966, 5, 484ꢀ
6. F. Lónyi, J. Valyon, Micropor. Mesopor. Mater. 2001, 47, 293ꢀ301.
4
93; b) J.W. Ward, J. Catal. 1969, 13, 321ꢀ327; c) E. F. T. Lee, L. V.
C. Rees, Zeolites 1987, 7, 446ꢀ450; d) A. Guzman, I. Zuazo, A.
Feller, R. Olindo, C. Sievers, J. A. Lercher, Micropor. Mesopor.
Mater. 2005, 83, 309ꢀ318; e) H.S. Cerqueira, G. Caeiro, L. Costa, F.
Ramôa Ribeiro, J. Mol. Catal. A: Chem. 2008, 292, 1ꢀ13; f) X. Du,
X. Gao, H. Zhang, X. Li, P. Liu, Catal. Commun. 2013, 35, 17ꢀ22; g)
Y. Qin, Z. Mo, W. Yu, S. Dong, L. Duan, X. Gao, L. Song, Appl.
Surf. Sci. 2014, 292, 5ꢀ15; h) C. W. Kim, HꢀC. Kang, N. H. Heo, K.
Seff, J. Phys. Chem. C 2015, 119, 24501ꢀ24511.
27. a) F. Le Normand, L. Hilaire, K. Kili, G. Krill, G. Maire, J. Phys.
Chem. 1988, 92, 2561ꢀ2568; b) A. Kotani, T. Jo, J. C. Parlebas, Adv.
Phys. 1988, 37, 37ꢀ85.
2
3
5
0
85
2
2
8. A. Trovarelli, Catalysis Reviews 1996, 38, 439ꢀ520
9. a) D. P. Serrano, R. A. García, G. Vicente, M. Linares, D.
Procházková, J. Čejka, J. Catal. 2011, 279, 366ꢀ380; b) W. Zhu, H.
Yang, J. Chen, C. Chen, L. Guo, H. Gan, X. Zhao, Z. Hou, Green
Chem. 2014, 16, 1534ꢀ1542.
90
1
1
6. a) C. J. Plank, E. J. Rosinski, W. P. Hawthorne, Ind. Eng. Chem.
Prod. Res. Dev. 1964, 3, 165ꢀ169; b) W. Kladnig, React. Kinet.
Catal. Lett. 1979, 12, 273ꢀ280; c) E. F. SousaꢀAguiar, F. E.
Trigueiro, F. M. Z. Zotin, Catal. Today, 2013, 218-219, 115ꢀ122.
3
0. Z. Kónya, Y. Sugi, I. Kiricsi, J. Mol. Structure 2001, 563-564, 413ꢀ
4
16.
31. C. V. Hidalgo, H. Itoh, T. Hattori, N. Niwa, Y. Murakami, J. Catal.
984, 85, 362ꢀ369.
3
5
1
7. a) D. H. Olson, G. T. Kokotailo, J. F. Chamell, J. Colloid Interface
Sci. 1968, 28, 305ꢀ309; b) F. D. Hunter, J. Scherzer, J. Catal. 1971, 95 32. B. Hunger, M. Heuchel, L. A. Clark, R. Q. Snurr, J. Phys. Chem. B
2
1
0, 246ꢀ259; c) J. Martí, J. Soria, F. H. Cano, J. Colloid Interface Sci.
978, 67, 266ꢀ271; d) T. Frising, P. Leflaive, Micropor. Mesopor.
2002, 106, 3882ꢀ3889.
4
0
Mater. 2008, 114, 27ꢀ63; e) J. Li, P. Zeng, L. Zhao, S. Ren, Q. Guo,
H. Zhao, B. Wang, H. Liu, X. Pang, X. Gao, B. Shen, J. Catal. 2015,
3
29, 441ꢀ448.
1
8. a) Y. Sugi, T. Matsuzaki, T. Hanaoka, Y. Kubota, JꢀH. Kim, Catal.
Lett. 1994, 27, 315ꢀ324; b) JꢀH. Kim, Y. Sugi, T. Matsuzaki, T.
Hanaoka, Y. Kubota, X. Tu, M. Matsumoto, S. Nakata, A. Kato, G.
Seo, C. Pak, Appl. Catal. A: Gen 1995, 131, 15ꢀ32; c) T. Inui, T.
Yamada, A. Matsuoka, SꢀB. Pu, Ind. Eng. Chem. Res. 1997, 36,
4
5
5
5
0
5
4
827ꢀ4831; d) IꢀM. Tseng, JꢀF. Wu, YꢀW. Chen, React. Kinet. Catal.
Lett. 1998, 63, 359ꢀ364; e) S. Tawada, Y. Sugi, Y. Kubota, Y. Imada,
T. Hanaoka, T. Matsuzaki, K. Nakajima, K. Kunimori, JꢀH. Kim,
Catal. Today 2000, 60, 243ꢀ253; g) K. Krishna, G. B. F. Seijger, C.
M. van den Bleek, M. Makkee, H. P. A. Calis, Top. Catal. 2004, 30-
3
2
Hayashi, JꢀH. Kim, G. Seo, Appl. Catal. A: Gen. 2006, 299, 157ꢀ166;
j) N. Rahimi, R. Karimzadeh, Appl. Catal. A: Gen. 2011, 398, 1ꢀ17;
k) HꢀG. Jang, K. Ha, JꢀH. Kim, Y. Sugi, G. Seo, Appl. Catal. A: Gen.
1, 115ꢀ121; h) S. Zheng, A. Jentys, J. A. Lercher, J. Catal. 2006,
41, 304ꢀ311; i) Y. Sugi, Y. Kubota, K. Komura, N. Sugiyama, M.
2
014, 476, 175ꢀ185.
1
9. a) M. M. Mohamed, T. M. Salama, A. I. Othman, G. A. ElꢀShobaky,
6
0
Appl. Catal. A: Gen. 2005, 279, 23ꢀ33; b) G. T. Neumann, J. C.
This journal is © The Royal Society of Chemistry [year]
Green Chem., [year], [vol], 00–00 | 11