Pillared H-MCM-36 mesoporous and H-MCM-22 microporous materials for conversion of levoglucosan: Influence of varying acidity

Article abstract of DOI:10.1016/j.apcata.2011.01.008

Catalytic transformation of levoglucosan (1-6-anhdyro-β-d- glucopyranose) was carried out in a fixed bed reactor at 573 K over H-MCM-22 and pillared H-MCM-36 with different acidities. The yield of the products, phases and product distribution was influenced mainly by the acidity of the zeolite catalysts. Oxygenated species were the main liquid product, consisting foremost of aldehydes and furfural. The formation of the liquid products was higher over MCM-36 pillared materials than over MCM-22 for all the oxygenated species except acetone. The deactivation due to coking was less severe over the pillared materials compared to the microporous precursor. However, it was possible to successfully regenerate the spent zeolites without changing the structure.

Full text of DOI:10.1016/j.apcata.2011.01.008

Applied Catalysis A: General 397 (2011) 13–21
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Pillared H-MCM-36 mesoporous and H-MCM-22 microporous materials for
conversion of levoglucosan: Influence of varying acidity
M. Käldströma, N. Kumara, T. Heikkiläb, D.Yu. Murzina,∗
a Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, FIN-20500 Åbo/Turku, Finland
b Laboratory of Industrial Physics, Department of Physics, University of Turku, FI-20014 Turku, Finland
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalytic transformation of levoglucosan (1-6-anhdyro-␤-d-glucopyranose) was carried out in a fixed
bed reactor at 573 K over H-MCM-22 and pillared H-MCM-36 with different acidities. The yield of the
products, phases and product distribution was influenced mainly by the acidity of the zeolite catalysts.
Oxygenated species were the main liquid product, consisting foremost of aldehydes and furfural. The
formation of the liquid products was higher over MCM-36 pillared materials than over MCM-22 for all
the oxygenated species except acetone. The deactivation due to coking was less severe over the pillared
materials compared to the microporous precursor. However, it was possible to successfully regenerate
the spent zeolites without changing the structure.
Received 30 September 2010
Received in revised form 5 January 2011
Accepted 6 January 2011
Available online 12 January 2011
Keywords:
Pillared
Zeolite
MCM-36
Levoglucosan
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
surface wherever there are stacking faults [4]. The adsorption of
2,2-dimethyl butane suggested that pillaring leading to MCM-36
The transformation of layered zeolite precursors into pillared
derivatives was originally driven by the potential of producing a
large pore, possibly mesoporous material with high catalytic activ-
ity present in the layers.
increases accessibility of one kind of pores while others (most
likely the 10-member channels) are unaffected [5].
Layered zeolite materials are gaining a lot of interest at the
moment and Roth et al. has recently reported a new zeolite entitled
EMM-10 based on MWW topology, which is rather similar to MCM-
22 microporous material [6]. Corma et al. reported, for the synthesis
of MCM-22 zeolite, a requirement in a relatively narrow range of
SiO2/Al2O3 ratio compared to other high silica materials [7]. The
explanation for this behavior was linked to difficulties in nucle-
ation in the gels. Reported means of partly avoiding this problem
were progressive lowering the pH when increasing the ratio and by
lowering the synthesis temperature from 423 K to 408 K. Dumitriu
et al. showed, however, that a relatively broad range of acidity can
be obtained for the MCM-22 type materials by isomorphous substi-
tution of Al, Ga and Fe for silicon in the lattice of the zeolite [8]. The
materials were furthermore successfully tested in the gas-phase
condensation of isobutylene with formaldehyde, confirming the
different properties of the materials.
The synthesis of MCM-36 proceeds through the synthesis of
MCM-22 and the subsequent swelling and pillaring of the pre-
cursor. The swelling has been successful by addition of 29%
cetyltrimethylammonium hydroxide through anion exchange of
the concentrated chloride solution [1]. The swelling taking place
at high pH is specific by deprotonation of surface silanols with
associated disruption of the hydrogen bonds that keep the layers
connected to each other. Maheshwari reported that the swelling
usually takes place at elevated temperatures (353 K) but that it
The molecular sieve MCM-22, belonging to the MWW materi-
als, is a quite unique zeolite in the sense that it can be used as a
precursor for synthesizing pillared MCM-36 but also used directly
as such in catalytic transformations [1]. MCM-22 contains two
different independent pore systems; one of these pore systems
is defined by two-dimensional sinusoidal channels, the other
˚
consists of large super cages whose inner free diameter, 7.1 A is
defined by 12 T-O species (12-rings) and whose inner height is
˚
18.2 A [2]. Corma et al. confirmed that the structure of MCM-22
comprises of 10 membered ring (MR) channels together with cav-
ities of larger dimensions (12 MR), both of which can be reached
from the external surface [3]. The dimensions of the two types of
˚
void systems were furthermore determined to be 5.9 and 7.0 A,
respectively and these cavities are believed to be responsible for
the unique catalytic activity of MCM-22, referred to as “surface
pocket catalysis” [1,3]. Ravishankar et al. reported that the reason
for the precursor to behave like a wide pore (12-MR) catalyst, is
thought to be cracks in the crystallites which access the 12-MR
cages directly and that the large cages may open out at the external
∗
Corresponding author.
E-mail address: dmurzin@abo.fi (D.Yu. Murzin).
0926-860X/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcata.2011.01.008

14
M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
also can be successful at low temperatures (room temperature)
[9]. The difference between the swelling at elevated temperatures
compared to room temperature is that in the former case layer
atomization along with partial dissolution of the framework silica
is achieved, whereas higher crystallinity and well-preserved layer
structure is achieved by carrying out the swelling at room tem-
perature [10]. This is shown through X-ray diffraction (XRD) with
less broadening of peaks of the material swollen at low tempera-
ture compared to the results when the material is swollen at high
temperature. Reversibility of the room temperature swelling pro-
cess was also demonstrated by the same group, which represents
a major difference from high-temperature methods that yield irre-
versibly swollen materials [9]. The reversing process of the swelled
material is done by acidification, and the limit of the reversibility
behavior has been determined to about 328 K, above this temper-
ature the reversibility was lost due to the partial dissolution of
framework silica and destruction of the layered structure.
Pillaring with alumina or magnesia-alumina species has also
been investigated yielding mesoporous materials with lower sur-
face area than those pillared with silica [11]. The pillaring procedure
in general does not yield mesopores of perfect regular size as for
example in the MCM-41 type materials. Instead, the interlayer dis-
tances depend upon the process of swelling and formation of the
intercalating pillars, i.e. the synthesis conditions. The successful
preparation of pillared or delaminated zeolite is confirmed using
X-ray diffraction and TEM, which also allow detection of M41S
impurities if present in significant amount. MCM-36 complements
furthermore the more common and easier to produce M41S mate-
rials as a mesoporous catalyst because of high zeolitic activity [12].
Roth et al. presented recently an expanded view unifying the tra-
ditional 3-D zeolite frameworks with the layered zeolite structures
[13]. They reported that the conventional 3-D frameworks can even
be regarded as particular cases of the layers assemblies.
MCM-22 and MCM-36 catalysts have been used in a number of
different applications. Iron modified MCM-22 has been shown to be
effective in oxidation of benzene with N2O [14], whereas MCM-36
has for example proven to be a stable, active and selective catalyst in
isobutene/2-butene alkylation [15], as well as alkylation of benzene
with propylene [16]. Among other reactions m-xylene transfor-
mation over the pillared zeolite has been reported [17]. Lipase
immobilization on MCM-36 support for acylation of 1-butanol and
1-octanol by vinyl acetate and vinyl stearate as a test reaction
has been investigated [18]. MCM-36 additives with mixed alkaline
earth aluminum oxide pillars have furthermore been demonstrated
to be highly active as additives for the reduction of NO with CO
under reaction conditions similar to the oxygen depleted zone of
the FCC regenerator [19]. Ni modified MCM-22 and MCM-36 have
been used in oligomerization of ethylene [20], and the Ni modified
MCM-36 has been shown to perform very well in the oligomers for-
mation. Ti modified MCM-36 has exhibited superior performance
compared to Ti-MCM-22 in catalytic activity and selectivity in 1-
hexene and propylene epoxidation using H2O2 (30%, aqueous) as
an oxidant [21].
The conversion of carbohydrates on zeolites has gained a lot
of interest recently and has been reported by a number of dif-
ferent research groups [22–25]. In this paper, the influence of
mesoporous H-MCM-36 and H-MCM-22 microporous zeolite cata-
lysts on transformation of levoglucosan was investigated, changing
also the residence time and by varying the substrate to cata-
lyst ratio between 0.8 and 2.5. The aim with the work was to
study the reaction pathways present and products formed in cat-
alytic upgrading of levoglucosan as a means of learning more
about cellulose pyrolysis. The monosaccharide levoglucosan (1-6-
anhydro-␤-d-glycopyranose) is an interesting compound since it
is the intermediate through which cellulose decomposes pyrolyti-
cally forming lower molecular compounds.
The zeolite and the mesoporous materials synthesized and used
in the study were characterized by different physico-chemical tech-
niques such as nitrogen sorption, XRD, SEM and FTIR.
2. Experimental
2.1. Catalyst synthesis and characterization
The Na-MCM-22 microporous molecular sieve with three differ-
ent acidities was synthesized according to the procedure described
elsewhere [26–29] with some modifications. The synthesis of the
zeolite was carried out using the following procedure: water and
sodium aluminate (Riedel-de Haën, purity ≥95%) was added to
sodium hydroxide (Merck, purity ≥99%) and the mixture was
stirred for 10 min. After the stirring hexamethyleneimine (Aldrich,
purity 99%) and fumed silica (Aldrich purity 99.8%) were added and
the blend was stirred for another 20 min. After forming a homoge-
nous phase the mixture was transferred to teflon cups and inserted
into autoclaves. The synthesis was carried out at 423 K for 7 days.
After completion of synthesis the material was filtered, washed
with distilled water to neutral pH, dried at 373 K and calcined at
823 K for 8 h.
MCM-36 zeolite was prepared by swelling the MCM-22 zeolite
precursor with organic molecules followed by pillaring with poly-
meric silica [18]. The synthesis of Na-MCM-36 consisted of three
different processes: swelling, pillaring and hydrolysis.
2.1.1. Swelling process
Wet cake of MCM-22 was mixed with cetylmethylammo-
nium chloride solution (25%, Aldrich) and tetrapropyl ammonium
hydroxide solution (20%, Aldrich) and the pH was adjusted to 13.5
with NaOH solution. The mixture was then heated and stirred at
373 K for 68 h, and later stirred at room temperature for 4 h. This
was followed by washing with distilled water and drying at room
temperature.
2.1.2. Pillaring process
Swollen MCM-22 was mixed with TEOS and stirred at 351 K for
25 h. The material was then filtered and dried at room temperature.
2.1.3. Hydrolysis process
Distilled water was added to MCM-36 and the pH was adjusted
to 8. The hydrolysis was carried out at 313 K for 6 h. The material
was later filtered and dried at room temperature and calcined at
823 K in air.
Na-MCM-22 microporous and Na-MCM-36 mesoporous mate-
rials were transformed to NH4-MCM-22 and NH4-MCM-36 by
ion-exchange using ammonium nitrate solution. H-MCM-22 and
H-MCM-36 catalysts were obtained by calcination of NH4-MCM-
22 and NH4-MCM-36 at 773 K. In the nomenclature given to the
H-MCM-22 microporous matererials the numbers 28, 50 and 100
indicate the molar ratio of Si/Al in the framework structure, thus
a large number indicates low aluminum content and fewer acid
sites. The complete nomenclature of the pillared molecular sieves
is hence H-MCM-36-P22–28, H-MCM-36-P22–50 and H-MCM-36-
P22–100.
The determination of structure and phase purity of the MCM-
22 and MCM-36 molecular sieves was carried out by an X-ray
powder diffractometer (Phillips pW 1820) and scanning electron
microscopy (SEM). The specific surface area of fresh, used and
regenerated H-MCM-22 and H-MCM-36 catalysts was measured
by the nitrogen adsorption method (Sorptometer 1900, CarloErba
Instruments). The fresh and regenerated catalysts were out gassed
at 473 K, whereas the spent catalyst were outgassed at 393 K prior
to the measurement and BET equation was used to calculate the
specific surface area.

M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
15
The H-MCM-22 and H-MCM-36 catalysts were regenerated in
an oven by calcination at 723 K for 120 min.
2.3.2. GC-MS-solid phase micro extraction
The volatile compounds were analyzed with GC/MS and
headspace solid phase micro extraction (SPME). 2 ml of the solu-
tion containing the reaction products were transferred into a small
4 ml flask equipped with a rubber cap. The sample flask was heated
to 320 K. The needle with the fibre was penetrated through the cap
into the bottle and the fibre was exposed to the headspace of the
sample for 30 min. The fibre used for extraction was coated with
carboxen/polymethylsiloxane (CAR/PDMS). The components were
enriched on the surface when equilibria were reached between the
headspace and the fibre, thereafter the syringe was injected into the
GC–MS for analysis. The inlet chamber was set on 543 K, where the
absorbed and adsorbed analytes were thermally desorbed in the
hot injector of the gas chromatograph. The GC–MS was equipped
with a capillary column (DB-Petro 50 m × 0.2 mm × 0.5 ␮m). The
following temperature program was used: dwelling for 10 min at
313 K, heating 0.9 K/min to 348 K followed by heating 1.1 K/min
to 393 K, heating 10 K/min to 473 K and dwelling at 473 K for
20 min.
The acidity of the synthesized zeolites was measured by infrared
spectroscopy (ATI Mattson infinity spectrometer) using pyridine
(≥99.5%) as a probe molecule for qualitative and quantitative
determination of both Brønsted and Lewis acid sites. The FTIR
spectrometer was equipped with an in situ cell containing ZnSe
windows. The samples were pressed into thin self-supported discs
(weight 15–20 mg and radius 0.65 cm). Pyridine was first adsorbed
for 30 min at 373 K and then desorbed by evacuation at different
temperatures (523, 623 and 723 K) to obtain a distribution of acid
site strengths. All spectra were recorded at 373 K with a spectral
resolution equal to 2 cm−1. Spectral bands at 1545 and 1450 cm−1
were used to identify Brønsted acid sites (BAS) and Lewis acid sites
(LAS). The amounts of BAS and LAS were calculated from the inten-
sities of corresponding spectral bands, using the molar extinction
coefficients reported by Emeis [30].
The Si/Al ratio of the micro-and mesoporous materials was
determined by laser ablation-ICP-MS. The laser ablation instrument
was of the type UP-213, from New Wave Research, Merchantek
System. The ICP-MS instrument was a PerkinElmer Sciex, ICP Mass
Spectrometer of the type Elan 6100 DRC+.
2.3.3. GC–MS–MTBE extraction
Since the mixture of formed products was quite complex, the
product analysis was challenging and the water phase could not
directly be injected into the GC–MS, extraction with MTBE was
utilized as an additional means to detect any product formed in
large amount and not yet determined. The components in the liq-
uid phase were therefore extracted with the organic solvent and
analyzed with GC–MS. 0.5 ml of both the sample and MTBE were
mixed in a tube to extract the polar compounds into the MTBE-
phase. The organic solvent was removed after extraction from
the tube and inserted into GC-vials and analyzed with GC–MS.
The same column was used as in the solid phase micro extrac-
tion and the temperature program used was as follows: dwelling
for 1 min at 313 K, heating 6 K/min to 553 K and dwelling for
5 min.
2.2. Experimental set-up for catalyst testing
Transformation of levoglucosan (1-6-␤-d-glucopyranose) in gas
phase at atmospheric pressure was chosen as the model test reac-
tion. The catalyst testing equipment consisted of a quartz mini
reactor, an oven, an evaporator and a condenser.
Levoglucosan (Aldrich, purity 99%) was dissolved in deionised
water to make a 1% solution, which was fed through an evaporator
operating at 573 K into the quartz fixed bed reactor with an inner
diameter of 9 mm. This quartz mini reactor was packed with the
zeolite catalyst (150–250 ␮m) and inserted into the oven. In order
to get a narrow particle size range for the zeolite catalyst, pellets of
the zeolite powder were pressed and thereafter crushed and sieved.
The temperature of the catalyst bed was measured using a thermo-
couple and the temperature of the reactor was monitored with a
temperature controller. Nitrogen gas with a flow of 58.1 ml/min
was used as a carrier gas. The products were cooled down with
a condenser containing glycol solution at 268 K and collected in a
flask.
The feed of levoglucosan was adjusted to 4 ml/h. The catalyst
testing and the evaporation of levoglucosan were carried out at
temperature 673 K and the catalyst amount was 0.08, 0.125 and
0.25 g. The catalyst bed height was measured before the exper-
iments giving a possibility to calculate the weight hourly space
velocity (WHSV) and residence time. In every experiment the lev-
oglucosan solution was fed into the reactor for 5 h which gave a total
volume of 20 ml liquid and 200 mg of pure levoglucosan. After each
experiment the total amount of liquid was weighted. The follow-
ing day the evaporator was thoroughly washed by passing water
through it to rinse out levoglucosan that was left and could affect
the mass balance. The water used for washing was always weighted
and analyzed for determining the amount of levoglucosan.
2.3.4. High performance liquid chromatography (HPLC)
The products from the test reaction with levoglucosan were also
analyzed with HPLC equipped with an acid Aminex HPX-87C col-
umn connected to a refractive index (RI) detector. Diluted calcium
sulphate solution (CaSO4, 1.2 mM was used as a mobile phase. The
flow was 0.4 ml/min and the temperature was set to 353 K. The
samples were injected into the HPLC directly after the experiments
without any pretreatment other than filtering. Varying concen-
trations of different standards were made and analyzed with the
HPLC. The standards were purchased from Aldrich or Fluka and
had a purity of ≥99%. The HPLC was calibrated with the differ-
ent standards and upon the results calibration curves were drawn
which made it possible to calculate the molar yields of the achieved
products. HPLC was also used to calculate the conversion rate of
levoglucosan.
2.3.5. Coke analysis
2.5 ml of hydrofluoric acid (HFA) (Merck 40%) was added to
0.15 g of zeolite for dissolving for 1 h. The mixture was agitated
between short time intervals. 10 ml of dichloromethane was added
to the dissolved mixture. The soluble particles were extracted
for 24 h and the non-soluble components were recovered. HFA
and dichloromethane formed two phases which were separated
with an extraction funnel. The dichloromethane phase was fil-
trated and analyzed with GC–MS. The filter paper was dried and
weighted prior to, and after filtering to determine the total amount
of non-dissolvable coke. The following temperature program was
used: dwelling for 10 min at 373 K, heating 277 K/min to 493 K
followed by heating 275 K/min to 573 and dwelling at 573 K for
20 min.
2.3. Product analysis
Liquid samples were analyzed with HPLC and the volatiles with
a gas chromatograph connected to a mass-spectrometer (GC–MS).
2.3.1. Total organic carbon
The total organic carbon (TOC) was determined of the liquid
phase after each experiment. The analyses were performed using a
Total organic carbon analyzer, TOC-V CSN, delivered by Shimadzu
Corporation.

16
M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
Na-MCM-36-P22-100
Na-MCM-36-P22-50
Na-MCM-36-P22-28
Na-MCM-22-50
0
20
40
60
80
2θ
Fig. 1. X-ray powder diffraction pattern of Na-MCM-22–50 microporous material
along with Na-MCM-36-P22–28, Na-MCM-36-P22–50 and Na-MCM-36-P22–100
mesoporous material.
Fig. 2. Scanning electron micrograph of Na-MCM-36-P22–50 mesoporous material.
Table 2
Si/Al ratio as determined by LA-ICP-MS.
2.3.6. TGA
Catalyst
Si/Al ratio
The amount of coke formed on the precursor H-MCM-22–50
and the pillared H-MCM-36-P22–50 were determined by thermo-
gravimetrical analysis (TGA) using a Cahn D-200 digital recording
balance under the flow of synthetic air. The following temperature
program for the oven was used: heating 2 K/min from 298 K to 873 K
and dwelling at 873 K for 180 min.
H-MCM-22–50
35
47
65
92
H-MCM-36-P22–28
H-MCM-36-P22–50
H-MCM-36-P22–100
[15,31]. The Lewis acid sites have been reported to both increase
and decrease during the formation of the pillared mesoporous
material [17,31].
3. Results and discussion
3.1. Catalyst characterization results
The difference in the amount of Brønsted acid sites between H-
MCM-36-P22–50 and its precursor H-MCM-22–50 is a factor of 3.6
in favour of the latter, which means that only 27% of the Brønsted
sites are left after pillaring. The difference between the amount of
Lewis sites is much smaller. The ratio in Lewis acidity between the
same catalysts is 1.2 in favour of the precursor. The acidity, both
Brønsted and Lewis, decreases as expected in the following order
H-MCM-36-P22–28 > H-MCM-36-P22–50 > H-MCM-36-P22–100.
The actual Si/Al ratio of the different catalysts as determined
by laser ablation-ICP-MS is reported in Table 2. The ratio for the
microporous material was rather low since the theoretical value
was expected to be 50. The H-MCM-22–50 microporous material
was, however, considerably more acidic then synthesized H-MCM-
22–30 catalysts [32]. This could indicate that the reason for the low
value for the H-MCM-22–50 microporous material could originate
from some imprecision in the calibration of the analysis equipment.
The surface area for the fresh microporous MCM-22 and meso-
porous MCM-36 was measured with nitrogen adsorption and
calculated with BET equations (Table 3). With silica as the pillar-
ing material, the surface area of MCM-36 has been reported to be
between 1.5 and 3 times larger than that of MCM-22 [15,18]. The
surface area of successfully synthesized MCM-22 has been reported
to vary between 343 [16] and 560 m2/g [9], whereas the surface area
of MCM-36 catalysts has been declared to vary greatly, between 535
XRD patterns of Na-MCM-22 microporous and Na-MCM-36
mesoporous materials were similar to those reported in the lit-
erature, indicating phase purity of the synthesized materials. The
XRD patterns of all the materials are given in Fig. 1 and scanning
electron micrograph of Na-MCM-36-P22–50 is given in Fig. 2. The
XRD of the MCM-36-P22–100 mesoporous material is somewhat
less crystalline then the XRDs of the other pillared catalysts. Fur-
thermore a very faint irregularity was detected at 4.7◦ which could
indicate a trace impurity in the sample. The sample bulk was, how-
ever, identified as MCM-36.
The Brønsted and Lewis acidities of the studied H-MCM-22 and
H-MCM-36 catalysts, as determined by pyridine adsorption (FTIR),
are presented in Table 1. There is a substantial difference in the acid-
ity between the catalysts. The difference is especially substantial
when comparing the Brønsted acid sites of the two materials.
Compared to other mesoporous materials such as MCM-41 and
MCM-48, MCM-36 exhibits considerably higher acidity. There is
always a decrease in the Brønsted acidity during the synthesis of
MCM-36 from MCM-22 due to the delamination and pillarization.
This is a fact since the number of acid sites at the actual external
surface is diminished by between 17–82%, as confirmed by acid-
ity measurements with ammonia and pyridine as probe molecules
Table 1
Lewis and Brønsted acid sites of H-MCM-22 and H-MCM-36 catalysts.
Brønsted acid sites (␮mol/g)
Lewis acid sites (␮mol/g)
Catalyst
523 K
623 K
723 K
523 K
623 K
723 K
H-MCM-22–50
208
87
57
191
70
48
141
44
23
47
61
40
31
19
32
23
15
5
6
5
3
H-MCM-36-P22–28
H-MCM-36-P22–50
H-MCM-36-P22–100
36
32
12

M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
17
Table 3
Surface area of fresh and used H-MCM-22 and H-MCM-36 catalysts.
Catalyst
Surface area (m2/g), BET
Pore specific
volume (cm3/g)
Amount (g)
Fresh
387
Used
Regenerated
350
H-MCM-22–50
0.08
0.125
0.25
7
47
97
0.20
0.70
0.57
0.76
H-MCM-36-P22–28
H-MCM-36-P22–50
H-MCM-36-P22–100
0.08
0.125
0.25
513
560
618
85
174
204
520
560
611
0.08
0.125
0.25
102
180
273
0.08
0.125
0.25
331
274
378
[17] and 934 m2/g [9]. This indicates that for the synthesis of MCM-
36 to be successful the surface area should exceed 500 m2/g. The
specific pore volume was also determined and the volume of the
pores was about three times larger for the mesoporous material
compared to the microporous precursor, which also indicates the
successful pillaring (Table 3).
TOC yield, (%)
80
H-MCM-36-P22-50
60
40
20
H-MCM-36-P22-28
H-MCM-22-50
H-MCM-36-P22-100
3.1.1. Characterization of the used catalysts
The surface area of spent and regenerated catalysts was also
measured with nitrogen adsorption and calculated with BET equa-
tion (Table 3). The decrease in surface area was inversely related
to the amount of catalyst as expected. The decrease in surface
area was more severe in the case of MCM-22 than in the case
of the different MCM-36 samples. It seemed furthermore that H-
MCM-36-P22–100 was least affected by the deactivation due to
coke formation of the different MCM-36 catalysts. It was possi-
ble to successfully regain the surface area of all the catalysts by
regeneration in air at 723 K for 2 h (Table 3). Furthermore recent
studies of mesoporous materials in the same reactor system have
shown full recovery of the acidic sites as well as of the cat-
alytic activity by regeneration in air at 723 K [33]. Differences in
deactivation and coke formation between MCM-22 and MCM-36
have also been reported by other research groups. Corma et al.
reported that the amount of coke was higher on MCM-36 than
over MCM-22 in the conversion of olefins to paraffins [31]. This
was thought to be due to the much lower catalytic activity of
MCM-36, which was assumed to be responsible for the important
contribution of the nonselective thermal cracking to the global con-
version and selectivities observed. Deactivation has, however, also
been shown to be much slower over MCM-36 than over MCM-
22 [1], in the transformation of m-xylene, which indicates that
coking and deactivation of MCM-36 takes place not only in the
supercages but also in part of the supermicropores created by pil-
laring [17].
0
0.07
0.12
0.17
0.22
Catalyst mass (g)
Fig. 3. Total amount of organic carbon detected in the condensed phase from cat-
alytic transformations over microporous H-MCM-22–50 and H-MCM-36-P22–28,
H-MCM-36-P22–50 and H-MCM-36-P22–100 mesoporous materials.
H-MCM-36-P22–100 mesoporous materials were rather similar.
The amount of total carbon which was condensed decreased with
increasing residence time indicating larger generation of gases due
to consecutive reactions.
Molar yield
0.4
H-MCM-36-P22-50
0.3
H-MCM-36-P22-100
3.2. Product characterization results
H-MCM-36-P22-28
0.2
3.2.1. Product distribution between the gas and liquid phases
The product distribution between phases after condensation of
gases was evaluated through measuring total amount of carbon.
The results shown in Fig. 3 report the yield of total organic car-
bon in the liquid phase compared to the total amount of carbon
inserted into the system with the introduction of levoglucosan.
The least total organic carbon was found in the liquid phase from
the transformation of levoglucosan over MCM-22 catalyst fol-
lowed by H-MCM-36-P22–28, whereas the amounts detected in the
liquid phase from transformations over H-MCM-36-P22–50 and
H-MCM-22-50
0.1
0
0.07
0.12
0.17
0.22
Catalystmass(g)
Fig. 4. Generation of glycolaldehyde over H-MCM-22–50, H-MCM-36-P22–28, H-
MCM-36-P22–50 and H-MCM-36-P22–100 catalysts.

18
M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
Fig. 5. Reaction scheme for the formation of glycolaldehyde from levoglucosan based on experimental results and literature [1,28].
3.2.2. Products/selectivity
went through a maximum after 120 min, and thereafter started to
decline because of catalyst deactivation due to coke formation, the
generation over the microporous precursor increased during the
whole experiment.
The conversion of levoglucosan was 100% with all the catalysts.
The product distribution varied, however, between different cata-
lysts and residence time.
Since acidity is crucial for the formation of the low molecular
products such as glycolaldehyde, one explanation for the product
increase over H-MCM-22–50 is that the material is initially too
active leading to consecutive products forming gases such as carbon
monoxide and carbon dioxide. The production of glycolaldehyde
3.2.2.1. Formation of glycolaldehyde. Formation of the major prod-
uct, glycolaldehyde, was the highest over H-MCM-36-P22–50
catalyst followed by H-MCM-P22–100 and H-MCM-P22–28 (Fig. 4).
The formation is reported as molar yield, which refers to the total
amount of moles of formed glycolaldehyde compared to the total
amount of input levoglucosan. All the three forms of MCM-36
showed higher amounts of glycolaldehyde than MCM-22 allowing
to conclude that the pillaring process was favorable in the forma-
tion of glycolaldehyde from levoglucosan. Srokol et al. reported that
especially base catalyzed reactions of d-glucose results in the for-
mation of glycolaldehyde, claming that important hydrothermal
reactions of glucose and other C6 sugars starts with a retroaldol
condensation to form glycolaldehyde [34]. They reported further-
more that the second product in the reaction should be a C4 sugar
such as d-erythrose which was proposed to further also react into
glycolaldehyde (Fig. 5). However, as in the experiments performed
by Srokol et al., no d-erythrose was detected in the transforma-
tion of levoglucosan, indicating that the consequent reaction into
glycolaldehyde is very fast.
The formation of glycolaldehyde over the pillared catalyst was
higher throughout the whole experiment compared to the microp-
orous precursor (Fig. 6). The values are reported as yield, comparing
the concentration of formed glycolaldehyde with the concentra-
tion of levoglucosan input solution. Starting from a similar value as
the production over H-MCM-22–50 the formation over the meso-
porous catalyst increased fast and was detected at elevated levels
during the whole experiments compared to the former catalyst.
While the generation of glycolaldehyde over H-MCM-36-P22–50
Table 4
Molar yields of minor products detected in the transformation of levoglucosan over
MCM-22 and MCM-36 catalysts.
Products, H-MCM-22–50
Residence time (s)
0.13
0.23
0.46
Acetic acid
Glyoxal
0.01
0.01
0.11
0.16
0.17
–
0.01
–
0.1
0.13
0.06
–
0.02
0.07
–
–
–
0.08
0.06
–
0.01
0.01
Formaldehyde
Acetaldehyde
Acetone
Furfuryl alcohol
5-Hydroxymethyl furfural
Furfural
0.04
0.7
Products, H-MCM-36-P22–28
Residence time (s)
0.20
0.30
0.56
Acetic acid
Glyoxal
–
–
–
0.01
0.01
0.12
0.23
0.06
0.01
–
0.01
0.14
0.33
0.05
0.01
0.02
0.09
Formaldehyde
Acetaldehyde
Acetone
Furfuryl alcohol
5-Hydroxymethylfurfural
Furfural
0.16
0.32
0.1
0.01
0.01
0.09
0.04
Products, H-MCM-36-P22–50
Residence time (s)
Yield
0.20
0.30
0.56
0.2
Acetic acid
Glyoxal
–
–
0.02
0.01
0.1
0.17
0.05
–
0.01
0.01
0.1
0.17
0.04
–
H-MCM-36-P22-50
Formaldehyde
Acetaldehyde
Acetone
Furfuryl alcohol
5-Hydroxymethylfurfural
Furfural
0.16
0.25
0.09
–
0.06
0.1
0.16
0.12
0.06
0.06
0.06
0.05
H-MCM-22-50
0.08
Products, H-MCM-36-P22–100
Residence time (s)
0.20
0.30
0.56
0.04
0
Acetic acid
Glyoxal
–
–
–
–
0.02
0.09
0.14
0.06
–
0.01
0.14
0.12
0.06
–
Formaldehyde
Acetaldehyde
Acetone
Furfuryl alcohol
5-Hydroxymethylfurfural
Furfural
0.14
0.13
0.06
0.01
0.01
0.07
0
100
200
300
TOS (min)
0.04
0.07
0.05
0.08
Fig. 6. TOS generation of glycolaldehyde over H-MCM-22–50 and H-MCM-36-
P22–50 catalysts at residence times of 0.23 and 0.3 s respectively.

M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
19
H-MCM-36-P22-100
H-MCM-36-P22-50
H-MCM-36-P22-28
H-MCM-22-50
0
20
40
60
80
100
RT (min)
Fig. 7. GC–MS spectra combined with SPME for product mixture obtained over 0.25 g of H-MCM-22 and three H-MCM-36 catalysts with different acidities.
Table 5
is thereby benefitted by the decrease in acidity originating from
Increase of reactor weight due to tar and coke formation over H-MCM-22–50 and
H-MCM-36 catalysts.
catalyst deactivation due to coke formation. The other detected
products, shown in Table 4, and determined by comparing the
retention times with standard solutions, consisted of different alde-
hydes, furfurals, acetone and acetic acid.
Catalyst
Mass (mg)
Reactor weight
increase (mg)
Yield (wt%)
H-MCM-22–50
80
125
250
15
21
23
8
11
12
3.2.2.2. Formation of furfurals. Signals with similar retention times
as those of furfural, furfuryl alcohol and 5-hydroxy methyl fur-
fural (5HMF) were detected with HPLC when analyzing the liquid
samples (Table 4). Furfural was the most abundant of the detected
furfural compounds. At a low residence time it was found to be
formed at the same extent over all catalysts. However, at the longest
residence time (0.25 g of catalyst) some differences between the
different molecular sieves were detectable, i.e. furfural generation
increased in the following order H-MCM-22–50 < H-MCM-36-
P22–28 < H-MCM-36-P22–50 < H-MCM-36-P22–100. 5HMF and
furfuryl alcohol were formed to lower extent. Most 5HMF
was detected with H-MCM-36-P22–50 followed by H-MCM-
36P22–100.
H-MCM-36-P22–28
H-MCM-36-P22–50
H-MCM-36-P22–100
80
125
250
16
22
29
8
11
14
80
125
250
18
19
20
9
10
10
80
125
250
19
9
16
10
4
8
Other detected products were acetone, ethyl acetate, 3-
buten-2-one, toluene, 1,2-butanediol, 4-cyclopentene-1,3-dione,
1-indanone, benzo[1,2-b;4,3-b]difuran and different naphthalenes.
3-buten-2-one and 1,2-butanediol were only seen over H-MCM-
22–50, whereas toluene was only observed over the mesoporous
materials.
3.2.2.3. Formation of acetaldehyde and formaldehyde. Formation of
formaldehyde was higher over all MCM-36 mesoporous materi-
als compared to MCM-22 (Table 4). The amount of it decreased
with increasing residence time over MCM-22, whereas it was not
possible to establish any trend for the mesoporous materials. Gen-
eration of acetaldehyde was also higher for MCM-36 than in case
of MCM-22. The amount formed decreased with increasing resi-
dence time for all the tested catalysts except H-MCM-36-P22-100,
for which the yield remained at a constant level even though the
residence time changed. As for the pillared materials the following
order was observed in the formation of acetaldehyde: H-MCM-36-
P22-28 > H-MCM-36-P22-50 > H-MCM-36-P22-100, which was in
line with acidity decrease.
3.2.3.1. Extraction with MTBE. The products detected by extraction
were furfural, ethanol, 2-cyclopentene-1-one, 5-methyl-(2H)-
furanone, 4-cyclopentene-1,3-dione, furfuryl alcohol and 5-methyl
furfural. Furfural was by far formed to the largest extent, based on
compared peak areas, which indicates that the other products were
formed in only minor quantities.
3.2.3.2. Formation of tar. It should be mentioned that there was
also some formation of tar on the inside of the reactor walls. The
total weight of formed tar and coke on the catalyst was determined
by weighing the dry reactor prior to, and after the experiments
(Table 5). The formed coke and tar varied between 9 and 29 mg,
resulting in a total coke and tar yield that substituted between 5 and
15% of the input levoglucosan. The tar and coke formation increased
with increasing catalyst amount over H-MCM-22–50, H-MCM-36-
3.2.3. SPME combined with GC–MS
The main volatile products detectable with HPLC were also
observed with GC–MS (Fig. 7). The largest peak corresponding
to furfural, increased in the order H-MCM-22–50 < H-MCM-36-
P22–28 < H-MCM-36-P22–50 < H-MCM-36-P22–100, in line with
HPLC analysis.

20
M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
Table 6
Mass balance calculated for microporous H-MCM-22–50 and mesoporous H-MCM-36-P22–50.
Residence time (s)
Levoglucosan left in
prereactor (mg)
Reactor weight increase
TOC (mg)
Total mass (mg)
Mass balance (%)
Total (mg)
Coke (mg)
H-MCM-22–50
0.13
0.23
0.46
9
8
8
15
21
23
11
18
(27)
124
96
74
148
125
105
74
63
53
H-MCM-36-P22–50
0.2
0.3
0.56
7
8
10
18
19
20
10
15
(23)
152
132
120
177
159
150
89
80
75
Table 7
Formation of insoluble coke over the MCM-22 and MCM-36 catalysts.
P22–28 and H-MCM-36-P22–50 while no clear trend was visible
with H-MCM-36-P22–100.
Zeolites
Insoluble coke of total
catalyst mass (wt%)
3.3. Coke characterization results
H-MCM-22
28
14
6
H-MCM-36-P22–28
H-MCM-36-P22–50
H-MCM-36-P22–100
The total amount of coke formed and analyzed with TGA was
larger over microporous H-MCM-22–50 than over pillared H-MCM-
36-P22–50 catalyst (Fig. 8). The products detected from the coke
analysis after dissolving the zeolites were mainly long hydrocarbon
chains like hexadecane, heptadecane, 1-heptadecene, octadecane,
1-octadecene and 1-nonadecane. Aho et al. have previously also
reported about linear alkanes and alkenes extracted from coke on
mesoporous materials used in catalytic transformations of cellulose
[35]. The percentage of insoluble coke for the different catalysts
is shown in Table 7. The amount of insoluble coke formed on H-
MCM-22 was two-threefold compared to the amount formed on
the pillared zeolites.
11
lyzing the water used for rinsing it with HPLC. The reason for the
increase in the weight of the reactor was due to coke formation on
the catalyst as well as tar formation on the reactor wall beneath
the catalyst bed. The values for the formation of coke on the two
largest amounts of catalyst (0.25 g, residence time 0.46 and 0.56)
are probably too large and are therefore shown in parenthesis, since
the numbers are even larger than the total reactor weight increase.
The values for the amount of coke were calculated by taking the
percentage of the catalysts being coked given by TGA (Fig. 8) for
the different amount of catalysts, multiplied with the fresh total
catalyst mass. One explanation for the high values could be that
the catalyst was not evenly deactivated, being more coked on the
top of the bed, and that this part was used in the analysis with
TGA. When comparing the values for the insoluble coke (Table 7)
with the values based on the TGA analysis one can furthermore see
that the values for insoluble coke seem too large which indicates
that some zeolite particles most probably were left non-dissolvable,
despite treatment with HF, and thereby influencing the weight. The
error should, however, be similar for all the catalysts since they
were treated in a similar manner during analysis, which means
that one can conclude that the amount of non-dissolvable coke
was substantially larger over microporous MCM-22 than MCM-
36 mesoporous material. The mass balance was closest to being
complete with 0.08 g of pillared MCM-36-P22–50 (residence time
0.2 s) indicating that only a small part was lost as non-condensable
gases. With increasing residence time the value for the mass bal-
ance decreased, indicating higher formation of gases. Microporous
MCM-22–50 being more acidic than mesoporous MCM-36-P22–50
formed more gases, which can be seen as lower values compared
to the corresponding amounts of the pillared catalyst used.
3.4. Mass balance
The mass balance was calculated based on the increase in weight
of the reactor, the amount of left-over levoglucosan in the prereac-
tor and the measured TOC on the liquid phase (Table 6). The sum of
the masses of the different products was compared with the total
amount of input levoglucosan (200 mg). The values for TOC were
determined by dividing the measured values of the total amount
of organic carbon detected in the liquid with the total amount of
carbon in the input levoglucosan. This ratio was then multiplied
with the input levoglucosan (200 mg). The total amount of coke
was calculated based on TGA measurements, whereas the amount
of left-over levoglucosan in the prereactor was determined by ana-
Weight ratio
1
0.98
0.96
0.94
0.92
4. Conclusions
H-MCM-36-P22-50
0.9
The catalytic activity of H-MCM-22 and H-MCM-36 catalysts
was investigated in the conversion of levoglucosan at 573 K. Ther-
mal transformations were negligible. The yields of the main and
minor products, different oxygenated species (glycolaldehyde,
formaldehyde, acetaldehyde, furfural, 5-methyl furfural, acetic
acid), varied depending on residence time. Aldehydes were the
predominant products followed by different furfural species. The
pore sizes of the used materials are all larger than the cross sec-
0.88
0.86
H-MCM-22-50
0.84
300
400
500
600
700
800
Temperature (K)
˚
˚
tion of levoglucosan 4.2 A × 5.3 A [36] as well as the cross sections
Fig. 8. TGA of 0.25 g of spent H-MCM-22–50 and H-MCM-36-P22–50 catalyst.

M. Käldström et al. / Applied Catalysis A: General 397 (2011) 13–21
21
of the formed products. This means that the shape selectivity most
probably did not have a large effect on the product distribution.
A mass balance excluding the non-condensable gases and
comparing transformations over microporous H-MCM-22–50 and
mesoporous H-MCM-36-P22–50 was calculated. The balance was
the most complete with transformations over H-MCM-36-P22–50
mesoporous material and low residence time. At longer residence
times the mass balance was less complete indicating that there is
an increase in the formation of gases (CO2, CO). There was also a sig-
nificant difference in the formed products between H-MCM-22 and
H-MCM-36 catalysts. The former one yielded lower amounts for all
the main liquid products except acetone. H-MCM-22–50 is much
more acidic than H-MCM-36 catalyst, and thus more active, thereby
splitting most of the bonds in levoglucosan into CO2 and CO. The
degree of deactivation of the tested catalyst was quite severe, being
more significant over MCM-22 than over the pillared catalysts. It
was, however, possible to regenerate the catalysts and regain the
surface area.
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