Catalytic applications of OSDA-free Beta zeolite

Article abstract of DOI:10.1016/j.jcat.2013.05.025

Beta zeolite obtained from seeded synthesis without the use of organic structure directing agents (OSDAs) has been used as a catalyst in different types of reactions. The large number of strong acid sites resulted in a high activity for the alkylation of benzene with ethene and a high cracking activity in the hydroconversion of n-decane. However, the high framework polarity resulted in fast deactivation in the acylation of aromatic ethers. Dealumination treatments resulted in improved stability in alkylation reactions with the more reactive olefins like propene. In acylation reactions, the activity was significantly increased, and in hydroconversion, a better balance between the hydrogenation/dehydrogenation and the acid sites was obtained.

Full text of DOI:10.1016/j.jcat.2013.05.025

Journal of Catalysis 308 (2013) 73–81
Contents lists available at SciVerse ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
Catalytic applications of OSDA-free Beta zeolite
Trees De Baerdemaeker a, Bilge Yilmaz b, Ulrich Müller c, Mathias Feyen c, Feng-Shou Xiao d,
Weiping Zhang e, Takashi Tatsumi f, Hermann Gies g, Xinhe Bao h, Dirk De Vos a,
⇑
a Centre for Surface Chemistry and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Heverlee, Belgium
b BASF Corporation, Chemicals Research and Engineering, Iselin, NJ 08830, USA
c BASF SE, Chemicals Research and Engineering, 67056 Ludwigshafen, Germany
d Zhejiang University, 310028 Hangzhou, China
e State Key Laboratory of Fine Chemicals, Dalian University of Technology, 116024 Dalian, China
f Chemical Resources Laboratory, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
g Institute of Geology, Mineralogy and Geophysics, Ruhr-University Bochum, 44780 Bochum, Germany
h State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, 116023 Dalian, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Beta zeolite obtained from seeded synthesis without the use of organic structure directing agents
(OSDAs) has been used as a catalyst in different types of reactions. The large number of strong acid sites
resulted in a high activity for the alkylation of benzene with ethene and a high cracking activity in the
hydroconversion of n-decane. However, the high framework polarity resulted in fast deactivation in
the acylation of aromatic ethers. Dealumination treatments resulted in improved stability in alkylation
reactions with the more reactive olefins like propene. In acylation reactions, the activity was significantly
increased, and in hydroconversion, a better balance between the hydrogenation/dehydrogenation and the
acid sites was obtained.
Received 4 March 2013
Revised 17 May 2013
Accepted 21 May 2013
Available online 21 June 2013
Keywords:
Beta zeolite
OSDA-free synthesis
Dealumination
Alkylation
Ó 2013 Elsevier Inc. All rights reserved.
Acylation
Hydroconversion
1. Introduction
Tetraethylammonium hydroxide (TEAOH) is frequently used as
an organic structure directing agent (OSDA) in the synthesis of Beta
Zeolites have a wide area of application as catalysts, adsorbents,
and ion exchangers [1,2]. Of the more than 200 known zeolite
topologies with a framework code assigned by the Structure Com-
mission of the International Zeolite Association [3], Beta zeolite is
one of the handful of zeolite structures that constitute the majority
of the commercial zeolite catalyst production. It can be used for a
variety of applications, ranging from large-scale processes, such as
alkylations and transalkylations, to smaller scale fine chemical pro-
duction [4–10]. The first synthesis of Beta zeolite was reported by
Wadlinger et al. already in 1967 [11], but its structure, consisting
of the random intergrowth of two polymorphs, was only elucidated
in 1988 [12,13]. Like zeolite Y (FAU), which is one of the other
important structures in commercial zeolite synthesis, Beta zeolite
has a three-dimensional 12-membered ring pore structure, but
its pore dimensions are slightly smaller and it lacks the supercages
so typical for the FAU topology. These structural differences lead to
different catalytic properties [14,15].
zeolites, but a new method that does not require the use of OSDAs
was discovered in 2008 [16]. Seeding crystals are used to direct the
synthesis toward the formation of Beta zeolite. The resulting prod-
uct has properties that are different from those of Beta from TEAOH
synthesis, including a high aluminum content and relatively large
crystal size [17]. In this contribution, the progress in the OSDA-free
synthesis of Beta zeolite since its discovery is first briefly discussed.
We then report on some of the catalytic properties of Beta zeolite
from OSDA-free synthesis related to its specific characteristics and
on the possibility to post-synthetically modify the material. OSDA-
free Beta before and after different modification treatments is com-
pared to two commercially available Beta zeolites with different Si/
Al ratios. Their performance is investigated in the alkylation of
benzene with olefins of different chain lengths, in the acylation
of aromatic ethers, and in the hydroconversion of n-decane using
bifunctional catalysts.
2. OSDA-free synthesis of Beta zeolite
The first synthesis of Beta zeolite used tetraethylammonium
hydroxide as OSDA. Typical synthetic Beta zeolites have Si/Al ratios
in the range of 12–30 though purely siliceous Beta zeolites, and
⇑
Corresponding author. Address: Kasteelpark Arenberg 23, Post Box 2461, 3001
Heverlee, Belgium. Fax: +32 16321998.
E-mail address: Dirk.devos@biw.kuleuven.be (D. De Vos).
0021-9517/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.jcat.2013.05.025

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T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
aluminum-rich materials (Si/Al 5.2) have also been obtained using
the same OSDA [11,18–20]. Various other synthesis strategies have
been explored, resulting in a wide variety of zeolitic materials pos-
sessing the intergrown ꢀBEA topology. For instance, Beta zeolites
containing other heteroatoms than Al – e.g. B, Ga, Ti, Sn, Zn, or Zr
– have been synthesized [21–27], and other OSDAs such as
dibenzyldimethylammonium hydroxide, dicyclohexyldimethylam-
monium hydroxide or diaza-1,4-bicyclo[2.2.2] octane and methyl-
amine have successfully been applied [28–30]. Crystal sizes can
vary from the micrometer scale, typically for zeolites synthesized
in presence of fluoride anions, to nanosized crystals [18,31]. The
addition of seeds to the synthesis mixture has also been explored
[25,32,33]. For a long time, however, the addition of an OSDA to
the synthesis gel was required. The disadvantages of synthesis pro-
cedures using OSDAs are well known; they increase the cost of the
zeolite production because of the increase in raw material cost, and
they necessitate high-temperature calcination to remove the OSDA
from the structure. In addition, the calcination step causes the
emission of harmful gases. Of the five zeolite topologies that dom-
inate the commercial zeolite catalyst production – FAU, MFI, ꢀBEA,
MOR, and FER[4] – Beta was for a long time the only one that could
not be obtained synthetically in the absence of an OSDA [1,34,35]. It
should be noted, however, that the addition of OSDA can signifi-
cantly speed up the crystallization process or may still be required
to obtain alternative framework compositions for the above-men-
tioned topologies [28,36]. An indication that OSDAs are not strictly
indispensable for Beta zeolite synthesis appeared with the discov-
ery of Tschernichite, the natural mineral analogue of Beta zeolite
[37]. Tschernichite, which is a calcium aluminosilicate, shows the
same intergrowth of polymorphs as synthetic Beta zeolite, but it
has a high aluminum content (Si/Al 3.3) [38].
In 2008, Xiao and co-workers reported on the first synthesis of
Beta zeolite in absence of OSDA [16]. A seeded synthesis approach
was applied starting from an alkaline synthesis gel, and the synthe-
sis was completed after a hydrothermal treatment of less than a
day. The addition of Beta seeds to the gel was essential as other-
wise, no Beta zeolite was obtained. Additional investigation of this
type of Beta zeolite synthesis was performed by the group of
Mintova [39] and they identified the obtained product as alumi-
num rich (Si/Al 3.9–6.2). Variation in the type of inorganic cation
showed that the use of Na+ was more beneficial than use of Li+,
K+, or Ca2+, even if Ca2+ is abundantly present in the natural Tscher-
nichite. Nevertheless, only with Na+, Beta zeolite could be obtained
synthetically. The aluminum content in the synthesis gel was
found to be a limiting factor for the crystallization and a reduced
amount of seeds resulted in larger crystallite sizes. In a later report,
Okubo’s group successfully reused the Beta zeolites (Si/Al 5.4–6.6)
from OSDA-free seeded synthesis as seed crystals, and named the
obtained product ‘‘green Beta’’ as in this case, even the OSDA re-
quired for the seed crystals could be omitted [40]. In their synthe-
sis conditions, mordenite was the thermodynamically more stable
phase, but the addition of Beta seeds kinetically favored the forma-
tion of Beta zeolites. The induction of Beta crystal growth on the
seed surface was identified as an essential factor for obtaining
OSDA-free Beta zeolite.
[17]. They found that the Beta seeds first partially dissolve in the
alkaline synthesis medium, after which gradual crystal growth oc-
curs according to a core–shell mechanism. A possible explanation
for this switch from dissolution to growth could be the change in
composition of the liquid phase surrounding the amorphous gel
during hydrothermal treatment. This has also been suggested for
template-free LTA synthesis [42].
The seeded synthesis approach in absence of OSDA can be ex-
tended to other framework types such as LEV, HEU, MTW, RTH,
and SZR [17,43–46]. Depending on the synthesis gel composition,
the use of Beta seeds does not necessarily result in Beta zeolite
as crystallization product. Using a different composition of the alu-
minosilicate synthesis gel than for the synthesis of OSDA-free Beta,
Kamimura et al. [47] obtained MTW by addition of Beta seeds. Sim-
ilarly, high-silica ferrierite could be obtained from the addition of
RUB-37 seeds (CDO) to a synthesis gel that otherwise only yields
small amounts of mordenite [48]. These interesting discoveries
stimulated Okubo and co-workers to formulate a working hypoth-
esis, based on common composite building units, for broadening
the spectrum of zeolites that can be synthesized using OSDA-free
seeded synthesis [49].
Regarding the valorization of these materials from OSDA-free
seeded synthesis in catalysis, only few results have been published.
Yokoi et al. [45] have tested RTH-type zeolites from OSDA-free syn-
thesis in the methanol-to-olefins reaction (MTO) and obtained high
selectivities to propene at high methanol conversions. OSDA-free
ZSM-34, obtained from zeolite L seeds, was also used in MTO,
and higher selectivities to ethene and propene were obtained com-
pared to ZSM-5 [50]. The high aluminum content of MTW and Beta
from OSDA-free seeded synthesis implies a high cation-exchange
capacity. This has been used to load these materials with silver
and test their performance as antibacterial materials [51]. High cu-
mene cracking activities have been obtained for aluminum-rich
OSDA-free Beta, and preliminary experiments showed that the
material is active in benzene ethylation and anisole acylation
[17,52]. In the next sections, new results on the catalytic perfor-
mance of OSDA-free Beta are presented.
3. Experimental
3.1. Catalysts
OSDA-free Beta zeolite (OF-Beta) was synthesized using an
aluminosilicate gel with a molar ratio of 40 SiO2:1 Al2O3:14.4
Na2O:1412ꢁH2O and calcined Beta zeolite seeds (Si/Al 11.6, 4.6% rel-
ative to the Si-source). In a typical synthesis procedure, the Al
source (sodium aluminate, Al2O3 > 41.0%) was dissolved in distilled
water. Sodium hydroxide (NaOH > 96%) and fumed silica were
added after which the seeds were introduced. After stirring for
3 min, the synthesis gel was transferred into a Teflon-lined auto-
clave and kept at 120 °C for 120 h. The obtained powder was fil-
tered, washed with distilled water, and dried overnight at 80 °C.
To obtain the H+-form, ion exchange was performed in a 0.5 M NH4-
NO3 solution at 80 °C for 24 h, followed by washing with distilled
water and overnight drying at 70 °C. The NHþ4 -exchanged zeolites
were calcined in air at 450 °C for 5 h (heating rate 1 °C/min).
Steam dealumination of OF-Beta was performed by repeated
ion exchange with NH4NO3 followed by steam treatment. The sam-
ple was ion exchanged with a 4 M NH4NO3 solution at reflux then
hydrated and heated in a covered vessel to 600 °C (heating rate
1 °C/min) for 2 h. Ion exchange and steam treatment were repeated
three times. The obtained sample was labeled OF-Beta-ST.
Further investigation into the crystallization mechanism was
performed by the same group and resulted in a proposed synthesis
mechanism in which the crystallization proceeds on the outer sur-
face of the seeds; hence, the nucleation of Beta does not occur di-
rectly from the amorphous gel phase [41]. In order for Beta to
grow, the seed crystals cannot be completely surrounded by the
amorphous aluminosilicate phase. Dissolution of the initial gel
during hydrothermal treatment brings the seed crystals to the
interface of the aluminosilicate phase and the liquid phase where
they can serve as a growth surface for new Beta crystals. This
mechanism is in agreement with the one proposed by Xie et al.
Part of OF-Beta-ST was further dealuminated by acid leaching
with an aqueous HNO3 solution for 3 h at 80 °C, using 2 g OF-Beta-
ST per 100 ml HNO3 solution. After the acid treatment, samples were

T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
75
washed with distilled water and dried at 80 °C. The HNO3 concentra-
tions used were 0.1 M, 0.5 M, and 6.0 M resulting in the respective
samples OF-Beta-ST-0.1, OF-Beta-ST-0.5, and OF-Beta-ST-6.0.
Commercial Beta zeolites Beta-1 (CP811 BL-25, PQ Corp., ob-
tained in the H+-form) and Beta-2 (CP814C, Zeolyst, obtained in
the NHþ4 -form) were used as reference materials from templated
synthesis.
20), pressurized with 30 bar N2, and heated to 120 °C with stirring
speed 1250 rpm.
3.3.2. Acylation
Acylation of anisole (Acros, 98%) with acetic anhydride (VWR,
98%) was performed at 90 °C in glass crimp cap reactor vials loaded
under N2 atmosphere with 100 mg dried catalyst (H+-form), 5.3 g
anisole, and 1 g acetic anhydride (molar ratio anisole:acetic anhy-
dride 5). The reactor vials were placed in a heated copper block and
stirred at 500 rpm.
3.2. Catalyst characterization
Powder X-ray diffraction patterns (PXRD) were collected on a
STOE Stadi MP diffractometer in Debye–Scherrer geometry with
CuKa1 radiation, a linear position sensitive detector (PSD) (6° 2h
window), and the sample in a capillary sample holder. To deter-
mine the crystal size and morphology, scanning electron micros-
copy (SEM) images were taken using a Philips XL30 FEG. Textural
properties were analyzed based on N2 adsorption isotherms, deter-
mined by physisorption at 77 K on a Coulter Omnisorp 100 CX.
Prior to measurement, the samples were outgassed under vacuum
at 200 °C overnight. Bulk elemental analysis was performed on a
Varian Vista-PRO inductively coupled plasma optical emission
spectrometer (ICP-OES).
Acylation of 2-methoxynaphthalene (Acros, 98%) with acetic
anhydride was performed at 110 °C in glass crimp cap reactor vials
loaded under N2 atmosphere with 240 mg dried catalyst (H+-form),
6 mmol 2-methoxynaphthalene, 3 mmol acetic anhydride, and
4.5 mL chlorobenzene. The reactor vials were placed in a heated
copper block and stirred at 500 rpm.
During the acylation and alkylation reactions, samples were ta-
ken periodically and analyzed on a Shimadzu GC equipped with a
60 m CP-Sil-5CB column and FID detector. Peak identification was
performed using authentic samples and GC/MS.
3.3.3. Hydroconversion
FTIR spectrometry was used to investigate the hydroxyl stretch-
ing region and to determine the Lewis and Brønsted acidity using
pyridine as probe molecule. IR spectra of self-supporting wafers
of the zeolite samples (thickness 10–15 cm2/g) were measured
on a Nicolet 6700 FTIR spectrometer with DTGS detector (128
scans, 2 cmꢂ1 resolution). Reference spectra were recorded at
150 °C after heating under vacuum to 450 °C for 1 h. Acidity was
probed using pyridine adsorption. Pyridine (25 mbar) was allowed
to adsorb at 50 °C, and after saturation, the samples were evacu-
ated for 30 min to remove the physisorbed pyridine before reheat-
ing (4 °C/min) to 150 °C and recording IR spectra of the samples
containing chemisorbed pyridine. The number of acid sites was
evaluated from the integral intensities of the absorption bands cor-
For the hydroconversion of n-decane, the zeolite samples were
transformed into bifunctional catalysts. First, the samples were
transformed into the NHþ4 -form by three ion-exchange steps with
0.5 M NH4NO3 at 80 °C for 24 h followed by washing with distilled
water. After drying at 70 °C, Pt (0.5 wt.%) was loaded onto the cat-
alyst via competitive ion exchange as Pt(NH3)42+ using an aqueous
solution of Pt(NH3)4Cl2. The samples were compressed and the wa-
fers were broken up and sieved to obtain a fraction of 125–250 lm
particles. 50 mg of catalyst pellets was loaded into a quartz reactor
tube (internal diameter 2 mm).
Before reaction, the Pt containing samples were first treated
with an O2-flow of 1.9 ml/min at 400 °C for the oxidation followed
by a H2-flow of 3.8 ml/min at 400 °C for the reduction of platinum.
An intermediate cooling step was carried out under He atmo-
sphere. The n-decane hydroconversion experiments were per-
formed at temperatures ranging from 170 °C to 280 °C, under
4.5 bar H2 pressure, at a H2:decane molar ratio of 375 using a fixed
space time of 2522 kg s/mol and stepwise temperature increase.
Samples from the reactor outlet were injected into a capillary GC
equipped with a 25 m CP-Sil-5 column. Conversion values were
calculated from the integrated area of the n-decane peak before
and during reaction. Yields of isomerization and cracking products
were determined from the respective chromatograms.
responding to pyridine adsorbed on Lewis (1450 cmꢂ1
) and
Brønsted acid sites (1545 cmꢂ1) using the molar extinction coeffi-
cients of Emeis [53].
The number of acid sites on the samples was also quantified
using temperature-programmed desorption of ammonia (NH3
TPD) measured on a Micromeritics AutoChem II 2920 automated
chemisorption analysis unit with a thermal conductivity detector
(TCD) under helium flow. An online mass spectroscopy (MS) sys-
tem for continuous analysis of the desorbed species was used to
confirm that the TCD signal corresponded to ammonia desorption.
In all samples, two desorption peaks were observed, and the
amount of NH3 desorbing at each peak was obtained via
deconvolution.
4. Results
4.1. Characterization
3.3. Catalytic reactions
Elemental analysis and textural characterization data of se-
lected samples are shown in Table 1. OF-Beta has a low Si/Al ratio
typical for Beta zeolites from OSDA-free synthesis [17,39,40]. Using
steam dealumination (OF-Beta-ST), the aluminum content of OF-
Beta can be significantly reduced while simultaneously increasing
the mesopore volume. Further dealumination via acid leaching
leads to gradually increasing Si/Al ratios. The PXRD patterns
(Fig. 1) of the OSDA-free Beta zeolites show sharp peaks in the
low-angle region compared to the commercial Beta zeolites Beta-
1 and Beta-2. The sharp peak at 22.1° 2h is consistent with other
reports on aluminum-rich Beta zeolite and its natural mineral ana-
logue Tschernichite. Its position at lower angles compared to the
22.5–22.6° 2h of the commercial Beta zeolites has been related to
the high framework aluminum content [17,38,39]. Upon dealumi-
nation, the Bragg reflections show more resemblance to those of
the more Si-rich commercial Beta zeolites.
3.3.1. Alkylation
Alkylation of benzene (Sigma-Aldrich, 99.7%) with ethene (Air
Liquide, 99.95%) or propene (Air Liquide, 99.5%) was performed
in a Parr reactor (capacity 100 mL) at 150 °C. Prior to reaction,
the zeolite catalysts (calcined, H+-form) were activated at 200 °C
in an oven for 14 h. The reactor was loaded under N2 atmosphere
with 40 mL benzene and 62.5 mg dried catalyst. The reactor was
flushed and subsequently saturated with 5 bar ethene for 30 min
(molar ratio benzene:ethene 8) or with 1 bar propene for 60 min
(molar ratio benzene:propene 6), pressurized with 50 bar N2, and
heated to 150 °C. The reaction mixture was stirred at 1250 rpm.
Alkylation of 1-dodecene (Acros, 93–95%) was performed in a
60 mL reactor that was loaded under N2 atmosphere with
100 mg dried catalyst, 8.4 mL benzene, 21.1 mL n-decane (Acros,
99%), and 2.4 mL 1-dodecene (molar ratio benzene:1-dodecene

76
T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
Table 1
compared to the commercial Beta zeolites Beta-1 and Beta-2. Con-
Elemental composition and textural properties.
sistent with the diminished bridging hydroxyl vibration, the
amount of pyridine adsorbed also decreases after steam
dealumination.
Acidity of the samples was also characterized using tempera-
ture-programmed desorption of ammonia (Table 2). OF-Beta does
not only contain a large amount of acid sites, but also judging from
the temperature at which the NH3 desorbs, the acid sites seem to
be remarkably strong. Upon steam dealumination, the amount of
acid sites of OF-Beta is reduced to less than one-third.
b
c
Sample
Si/Ala
Naa (wt.%)
Vmicro (mL/g)
Vmeso (mL/g)
Beta-1
Beta-2
OF-Beta
OF-Beta-ST
OF-Beta-ST-0.1
OF-Beta-ST-0.5
OF-Beta-ST-6.0
12d
19d
4.5
12.4
25.2
36
<0.02d
<0.05d
5.4e
–
–
0.24
0.19
–
–
–
<0.01
0.05
0.01
<0.01
<0.01
<0.01
–
–
–
–
–
55
a
b
c
From bulk elemental analysis (ICP-OES).
Micropore volume, t-plot method.
Mesopore volume.
Data from manufacturer.
Before ion exchange.
4.2. Alkylation
d
e
The catalytic activity of OF-Beta and the derived materials was
investigated in the alkylation of benzene with olefins of different
chain lengths. In a first alkylation experiment, ethene was used
as alkylating agent, using an excess of the aromatic reactant as is
usual in industrial alkylation. Fig. 5 shows the activity and selectiv-
ity toward the monoalkylated product for the different tested
materials. Remarkably, OF-Beta shows the highest activity in this
reaction. Most of the activity is preserved after the steam dealumi-
nation treatment, but the subsequent acid leaching treatment with
HNO3 leads to a continuous drop in activity with increasing HNO3
concentration. For instance, OF-Beta-ST-6.0 is almost completely
inactive in this reaction. OF-Beta also shows a remarkably higher
selectivity toward the monoalkylated ethylbenzene than commer-
cial Beta zeolites Beta-1 and Beta-2. Besides a high activity and
selectivity, the OF-Beta sample is also least sensitive to coke forma-
tion; coke, as evaluated in TGA measurements, amounted to only
5 wt.% for a used OF-Beta sample, against 8–9 wt.% for the used
commercial samples Beta-1 and Beta-2. Coke formation in these
reactions is typically due to multiple alkylation, suggesting that
the desorption of the primary ethylbenzene product is easier in
the OF-Beta sample than in other, more Si-rich catalysts. The steam
dealumination treatment on the other hand does not only lead to a
reduced activity but also to a lower selectivity at higher conver-
sions. Given their low activity, the selectivity for OF-Beta-ST-0.1/
0.5/6.0 is not shown as it cannot be compared at similar
conversions.
The promising activity and selectivity of OF-Beta in the alkyl-
ation with ethene encouraged us to investigate its performance
in alkylations of benzene with more reactive, longer chain olefins
such as propene and 1-dodecene. Conversions in these reactions
are shown in Fig. 6. In contrast to the ethylation reaction, much
lower conversions are obtained with OF-Beta as catalyst than with
the commercial Beta zeolites in the alkylations with both propene
and 1-dodecene. The limited further increase in conversion after
the first 5 h of reaction indicates that deactivation could play a sig-
nificant role. The steam dealumination treatment, which intro-
duces an increase in mesopore volume in OF-Beta, has a positive
influence on the activity and stability of OF-Beta in the alkylation
with propene. In the alkylation with 1-dodecene, however, all Beta
zeolites obtained through OSDA-free synthesis suffered from fast
deactivation, and much lower conversions were obtained than
with commercial zeolites Beta-1 and Beta-2.
SEM images (Fig. 2) of OF-Beta show intergrown crystals with a
truncated octahedral morphology and well-defined surfaces. The
crystallites of OF-Beta measure up to 500–800 nm, which is clearly
much larger than those of the commercial Beta zeolites used as ref-
erence materials in this study. The latter consist of aggregates of
small particles in which no well-defined morphology can be recog-
nized. Steam dealumination of OF-Beta degrades part of the crys-
tals, but the truncated octahedral morphology can still be
distinguished.
The infrared hydroxyl stretching region of the different zeolite
samples is shown in Fig. 3. It is clear that OF-Beta contains a large
amount of bridging hydroxyl groups (3607 cmꢂ1), which can be re-
lated to its high aluminum content. It also contains a moderate
absorption band at 3660 cmꢂ1, which could correspond to hydrox-
ylated monomeric or polymeric extra-framework aluminum spe-
cies [54,55]. The absorption bands corresponding to non-acidic
hydroxyl groups at the outer surface (3742 cmꢂ1) and at defect
sides inside the crystals (3735 cmꢂ1) [54,55] are much less pro-
nounced for OF-Beta than for the commercial Beta zeolites Beta-
1 and Beta-2. This is consistent with the larger crystal size of OF-
Beta and also implies that OF-Beta contains less internal defects
and is more crystalline – a feature of Beta zeolites from seeded,
OSDA-free synthesis that has been suggested in previous reports
based on the sharpness of some reflections in PXRD, the high
micropore volume and micropore surface area compared to Beta
zeolites from templated synthesis [17,39,40]. After steam dealumi-
nation, the intensity of the bridging hydroxyl groups diminishes,
whereas the absorption bands corresponding to defect sites and
external hydroxyl groups become more prominent. Using adsorp-
tion of pyridine as a probe molecule, the relative contributions of
Brønsted and Lewis acid sites were determined (Table 2). Fig. 4
shows the difference spectra after adsorption of pyridine; it is evi-
dent that OF-Beta contains a larger amount of Brønsted acid sites
4.3. Acylation
The acylation activity of OF-Beta can be strongly enhanced by
post-synthesis dealumination treatment. Fig. 7 shows the conver-
sion of acetic anhydride in the acylation of anisole and of 2-
methoxynaphthalene. The poor conversion with OF-Beta in both
acylation reactions again seems to suggest strong deactivation.
Steam dealumination increases the activity of OF-Beta up to an
activity level that is comparable to that of the commercial Beta
zeolites Beta-1 and Beta-2. In the anisole acylation, acid leaching
Fig. 1. XRD patterns for BEA-1 (a), BEA-2 (b), OF-BEA (c), OF-BEA-ST (d), OF-BEA-ST-
0.1 (e), OF-BEA-ST-0.5 (f), and OF-BEA-ST-6.0 (g).

T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
77
Fig. 2. SEM images of Beta-1 (a), Beta-2 (b), OF-Beta (c), and OF-Beta-ST (d).
Fig. 4. Difference IR spectra of adsorbed pyridine on Beta-1 (a), Beta-2 (b), OF-Beta
(c), and OF-Beta-ST (d), normalized to 10 mg/cm2. The absorption bands at
1450 cmꢂ1 and 1545 cmꢂ1 correspond to pyridine adsorbed on Lewis and Brønsted
acid sites.
Fig. 3. Infrared hydroxyl stretching region of BEA-1 (a), BEA-2 (b), OF-BEA (c), and
OF-BEA-ST (d), normalized to 10 mg/cm2.
Table 2
Acidic properties determined with NH3 TPD and FTIR using pyridine as probe
molecule.
lene acylation. Acid treatment results in even lower conversions
than for the original OF-Beta. The main reaction products observed
in the acylation of 2-methoxynaphthalene are 1-acetyl-2-
methoxynaphthalene (1,2-AMN) and 2-acetyl-6-methoxynaphtha-
lene (Fig. 8) with a combined selectivity to the other side products
(other acetylmethoxynaphthalene isomers and diacetylated prod-
ucts) of less than 10% for all catalysts. Except for OF-Beta, all cata-
lysts show an increase in selectivity for 2,6-AMN and a decrease for
1,2-AMN with increasing conversion. The selectivity of OF-Beta-ST
for both 1,2-AMN and 2,6-AMN lies in between that of commercial
Beta-1 and Beta-2.
b
b
c
c
Sample
B/La T1 (°C) Peak1 (mmol/g) T2 (°C) Peak2 (mmol/g)
Beta-1
Beta-2
OF-Beta
1.6
2.3
3.2
197
203
208
194
0.69
0.46
1.99
0.47
291
348
364
333
0.41
0.45
1.19
0.37
OF-Beta-ST 2.4
a
Determined from the IR absorption bands of chemisorbed pyridine at 150 °C.
Temperature and amount of NH3 desorbed at the first, low-temperature
b
desorption peak.
c
Temperature and amount of NH3 desorbed at the second, high-temperature
desorption peak.
with 0.5 M HNO3 leads to an even slightly more active catalyst, but
treatment with 6 M HNO3 is no longer beneficial for the activity.
The selectivity toward p-methoxyacetophenone was higher than
98% for all catalysts.
The positive effect of acid leaching on the activity of OF-Beta-ST
in the anisole acylation does not extend to the 2-methoxynaphtha-
4.4. Hydroconversion
The Beta zeolite samples were transformed into bifunctional
catalysts by loading with 0.5 wt.% Pt and tested in the hydrocon-
version of n-decane using a constant space time (Fig. 9). OF-Beta

78
T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
Fig. 5. Benzene conversion (left) in the liquid-phase alkylation of benzene with ethene (benzene:ethene 8, reaction temperature 150 °C) and selectivity referred to ethene to
the monoalkylated ethylbenzene (right) for BEA-1 ( ), BEA-2 ( ), OF-BEA ( ), OF-BEA-ST ( ), OF-BEA-ST-0.1 ( ), OF-BEA-ST-0.5 ( ), and OF-BEA-ST-6.0 ( ).
Fig. 6. Benzene conversion in the liquid-phase alkylation of benzene with propene (left, benzene:propene 6, reaction temperature 150 °C) and dodecene conversion in the
alkylation of benzene with 1-dodecene (right, benzene:1-dodecene 8.6, reaction temperature 120 °C) for BEA-1 ( ), BEA-2 ( ), OF-BEA ( ), and OF-BEA-ST ( ).
Fig. 7. Acetic anhydride conversion in the acylation of anisole (left, molar ratio anisole/acetic anhydride 5) and 2-methoxynaphthalene (right, molar ratio 2-
methoxynaphthalene/acetic anhydride 2) for Beta-1 ( ), Beta-2 ( ), OF-Beta ( ), OF-Beta-ST ( ), OF-Beta-ST-0.1 ( ), OF-Beta-ST-0.5 ( ), and OF-Beta-ST-6.0 ( ).
shows full conversion of n-decane at temperatures as low as
190 °C. In addition, its isomerization yields at lower conversion
are rather low, which can be ascribed to an imbalance between
the Pt dehydrogenation/hydrogenation sites and the high amount
of acid isomerization sites related to the framework aluminum.
In comparison, commercial Beta-1 with the same Pt loading but
lower aluminum content reaches an isomerization yield of 13.0%
at 73.4% conversion, whereas OF-Beta yields only 1.5% of isomeri-
zation products at 79.5% conversion. The primary cracking prod-
ucts comprise the expected range of linear or branched
hydrocarbons, with carbon numbers between C2 and C8. As the
hydroconversions were performed under hydrogen using bifunc-
tional catalysts, olefins are quickly rehydrogenated to alkanes,
which effectively suppresses any formation of deactivating coke.
The steam dealuminated OF-Beta-ST is only slightly less active
than its parent material. Further dealumination by acid leaching
leads to a stronger decrease in activity, as can be seen from the
higher temperatures required to obtain the same level of conver-
sion. However, the gradual dealumination combined with constant
Pt loading results in higher isomerization yields (Fig. 10).
5. Discussion
The investigated probe reactions require different key charac-
teristics of zeolite catalysts for optimal performance. For instance,

T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
79
Fig. 8. Selectivity to 1-acetyl-2-methoxynaphthalene (left) and 2-acetyl-6-methoxynaphthalene (right) as function of acetic anhydride conversion in the acylation of 2-
methoxynaphthalene for Beta-1 ( ), Beta-2 ( ), OF-Beta ( ), OF-Beta-ST ( ), OF-Beta-ST-0.1 ( ), OF-Beta-ST-0.5 ( ), and OF-Beta-ST-6.0 ( ).
Fig. 9. Catalytic results from the n-decane hydroconversion:n-decane conversion ( ), yield of isomerization products ( ) and yield of cracking products ( ) for Beta-1 (a),
OF-Beta (b), OF-Beta-ST (c), OF-Beta-ST-0.1 (d), and OF-Beta-ST-0.5 and OF-Beta-ST-6.0 (e).
the zeolite catalyst is an important factor to avoid deactivation
caused by the competitive adsorption of the polar products
[57,58], and in the hydroconversion of alkanes, the balance be-
tween the acid sites and the hydrogenation/dehydrogenation sites
is vital to obtain high isomerization yields [59].
The influence of the aluminum content of Beta zeolite on the li-
quid-phase alkylation of benzene with short-chain olefins like eth-
ene or propene was investigated by Bellussi et al. [8]. They found
that higher Al-contents resulted in an increase not only of the
activity, but also of the selectivity for alkylation vs. side reactions
like olefin oligomerization. However, the range of Al-contents in
which they investigated this reaction (Si/Al 14–112) was limited
by the amount of aluminum that could be incorporated via tem-
plated synthesis. The OSDA-free synthesis of Beta zeolites has wid-
ened this range to even higher aluminum contents. For the
alkylation of benzene with ethene, this improvement in activity
Fig. 10. Yield of isomerized products as function of n-decane conversion for Beta-1
and selectivity seems to continue when Beta zeolites from OSDA-
(
), OF-Beta ( ), OF-Beta-ST ( ), OF-Beta-ST-0.1 ( ), OF-Beta-ST-0.5 ( ), and OF-
free synthesis are used. This is quite remarkable because the
activation of ethene requires strong acidity. For high aluminum
contents, a lower acid site strength would be expected [2,60].
The high activity, as proven by the results of Fig. 5, is, in addition
to the NH3-TPD and FTIR results, another indication that OF-Beta
indeed not only contains a large number of active sites, but also
Beta-ST-6.0 ( ).
in alkylation reactions with the rather unreactive ethene, the pres-
ence of strong acid sites is necessary to activate ethene [56]. In
acetylation reactions of aromatic ethers, framework polarity of

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T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
that these sites still possess very strong Brønsted acidity. More-
over, when the ethylbenzene selectivity is plotted vs. the benzene
conversion (Fig. 5), the OF-Beta produces systematically more of
the monoalkylation product than the templated zeolites. One pos-
sible explanation for the high selectivity toward ethylbenzene
could be the high framework polarity of OF-Beta, in comparison
with the templated Beta zeolites. For OF-Beta, this framework
polarity would increase the adsorption preference for benzene over
ethylbenzene, which would relatively favor alkylation of benzene
over a second alkylation of ethylbenzene to diethylbenzene. Never-
theless, besides the effect of the elemental composition, additional
effects of crystal size and texture cannot be excluded.
the influence of dealumination of Beta zeolites on the acylation of
anisole, using octanoic acid as acylating agent. They proposed that
the increase in activity resulted from increased accessibility, and
this may also contribute to the activity increase of OF-Beta-ST
compared to the parent OF-Beta.
The acylation of 2-methoxynaphthalene occurs preferentially
on two positions. Kinetically, the formation of 1,2-AMN is pre-
ferred over the thermodynamically more stable 2,6-AMN. Both
products can be formed via direct acylation, but consecutive reac-
tion can transform 1,2-AMN into the smaller 2,6-AMN or back to 2-
methoxynaphthalene through deacylation [10,69]. Inside the pores
of Beta, steric hindrance leads to a preferential formation of 2,6-
AMN, but on the outer surface, 1,2-AMN is mainly formed. Though
increased crystal size has been reported to be beneficial for 2,6-
AMN selectivity [10], this is not observed for OF-Beta. Its low activ-
ity can again be attributed to the high framework polarity leading
to fast deactivation. Comparison is difficult considering its low
activity, but the high selectivity to 1,2-AMN indicates that the ac-
cess to the inner surface is rapidly blocked and the subsequent
conversion proceeds mainly on the outer surface. The steam dealu-
mination again leads to an activity improvement with selectivities
in between those of the two commercial Beta catalysts. Subsequent
acid leaching leads to serious reductions in activity.
Hydroconversion of alkanes over bifunctional catalysts uses the
metallic sites for dehydrogenation and hydrogenation; the acid
sites catalyze isomerization and cracking steps. To obtain high
isomerization yields, the distance between the acid sites and the
metal sites should be small enough to hydrogenate the isoalkenes
before further reaction on acid site leads to cracking. On an ideal
hydroisomerization catalyst, the olefinic intermediates are trans-
formed only once on an acid site before being hydrogenated.
Alvarez et al. [59] investigated the balance of the hydrogenating
and acid functions in the n-decane hydroconversion to find the
ideal PtHY hydroisomerization catalyst. Beta-1, OF-Beta, and OF-
Beta-ST already reach a very high conversion of n-decane in the
investigated temperature window (Fig. 9a–c), and high cracking
yields are to be expected. These catalysts were also the most active
in the demanding ethylation reaction. Clearly, they contain such a
high concentration of active sites that it is impossible to balance
them with the fixed amount of Pt used, especially if large crystal-
lites are used. The acid treatment after steam dealumination leads
to a decrease in the number of acid sites, resulting in an improved
balance of hydrogenation and acid sites and much higher isomeri-
zation yields.
Bellussi et al. [8] also reported an increase in performance with
increasing aluminum content of Beta zeolite in the alkylation with
propene. However, in the alkylation with propene, this trend does
not continue when using OF-Beta with its very high Al-contents.
Even though propene and ethene both can be considered as ‘‘light
olefins,’’ their reactivities are markedly different and propene olig-
omerization is a much more important side reaction [61,62]. The
propene oligomers themselves can also lead to larger and heavier
by-products that can remain adsorbed on the zeolite surface or
that block the access to the pores. Given the relatively large crystal
size of OF-Beta, the material is more susceptible to deactivation
through pore blocking [63]. The alkylation of benzene with long-
chain olefins such as 1-dodecene is known to be even more sensi-
tive to deactivation through pore blocking because of the various
bulky by-products that can be formed through double-bond migra-
tion, dimerization, and alkylation with isomerized olefins [15].
Post-synthesis modifications to increase accessibility of sites and
stability are often performed; especially introducing mesoporosity
in mordenite has proven successful [64–66]. The steam dealumina-
tion that increases the mesopore volume of OF-Beta has a stabiliz-
ing effect in the alkylation with propene, and the dealuminated
sample performs much better than the as-synthesized Al-rich sam-
ple (Fig. 6). However, this modification does not suffice to prevent
deactivation when using longer olefins like 1-dodecene (Fig. 6).
Other modifications, such as an even more thorough dealumina-
tion or a modification of the synthesis procedure to obtain smaller
crystals, could be helpful in increasing accessibility of the sites and
preventing deactivation. It should be noted, however, that smaller
crystal sizes do not necessarily lead to better deactivation resis-
tance. In the alkylation of toluene with long-chain olefins, Da
et al. [15] noticed that even small Beta crystallites can suffer from
fast deactivation compared to a Y-type zeolite of similar acidity.
This was attributed to the slow desorption of the reaction products
from the narrow pores.
In the acylation of anisole, framework hydrophobicity plays an
important role because the products are more polar and heavier
than the reactants and tend to remain preferentially adsorbed on
the zeolite framework. Specifically, on hydrophilic frameworks,
this type of product inhibition is an important cause of deactiva-
tion [57,58,67]. Derouane et al. [58] investigated the influence of
the zeolite catalyst Si/Al ratio on the activity and deactivation of
Beta zeolite catalysts in acylations. At high aluminum contents
(Si/Al 12.5), deactivation by product inhibition was the cause of
low yields. Dealumination improved the activity, but at higher Si/
Al ratios (Si/Al 93.3), again, lower yields were obtained. This was
attributed to the small number of acid sites. In our experiments,
similar observations can be made. The framework polarity of OF-
Beta causes rapid deactivation through product inhibition. Steam
dealumination leads to a (bulk) Si/Al ratio comparable to that of
the commercial Beta zeolites used, and the activity increases
accordingly. Further dealumination through acid leaching eventu-
ally results in a decrease in activity when too high concentrations
of HNO3 are used (OF-Beta-6.0). This is probably caused by the
lower concentration of acid sites. Beers et al. [68] also investigated
6. Conclusion
In the various reactions that were probed, Beta zeolites from
OSDA-free synthesis have different properties than the usual com-
mercial Beta zeolites. Part of the differences can be explained by
the higher aluminum content and different crystal size. The high
aluminum content leads to a large number of acid sites of consid-
erable strength resulting in an active ethylation catalyst even at
150 °C.
The large crystal size of OSDA-free Beta zeolites makes them
sensitive to deactivation through pore blocking. In alkylation reac-
tions with propene and 1-dodecene, this resulted in low activities.
An appropriate dealumination treatment can improve the accessi-
bility and delay the deactivation. The high aluminum content also
leads to a high framework polarity which is a cause for fast deac-
tivation in acylation reactions. This can be prevented by dealumi-
nation where an activity optimum is obtained between
framework polarity and acid site concentration.
The high amount of strong acid sites also leads to a high yield of
cracked products in the n-decane hydroconversion at very low

T. De Baerdemaeker et al. / Journal of Catalysis 308 (2013) 73–81
81
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