Conversion of decalin and 1-methylnaphthalene over AlSBA-15 supported Pt catalysts

Article abstract of DOI:10.1016/j.cattod.2012.06.011

Platinum catalysts (1.5 wt.%) containing AlSBA-15 obtained with various aluminium precursors were tested for activity in 1-methylnaphthalene hydrogenation. Experiments were carried out in a continuous-flow system at atmospheric pressure (240-350 °C, W/F = 0.8 g s/cm³). It was found that 1-methylnaphthalene conversion over Pt-loaded catalysts was not influenced by the aluminium precursor used in the preparation of the Pt/AlSBA-15 catalysts. However, the Pt catalyst prepared with AlSBA-15 obtained from aluminium sulphate provided a higher cis-methyldecalins/trans-methyldecalins ratio in the reaction products as compared to the catalysts obtained with aluminium nitrate or aluminium isopropoxide. Consideration was also given to the influence of platinum amount (0.5, 2.5 and 4.5 wt.%) on the catalytic performance of bifunctional Pt/AlSBA-15 catalysts (AlSBA-15 obtained with aluminium sulphate) in decalin hydroconversion. It was shown that impregnation of AlSBA-15 with H₂PtCl₆ increased Bronsted acidity. Investigations into decalin conversion were conducted in a continuous-flow system with a fixed-bed reactor (5 MPa, 300-380 °C, H₂:CH = 500 N m³/m³; WHSV = 2 h^-1). Incorporation of 0.5 wt.% Pt into AlSBA-15 yielded a catalyst with the highest dispersion of the platinum phase and the highest yield of ring opening products, amounting to 26.4 wt.% at 380 °C.

Full text of DOI:10.1016/j.cattod.2012.06.011

Catalysis Today 196 (2012) 110–118
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Catalysis Today
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Conversion of decalin and 1-methylnaphthalene over AlSBA-15 supported
Pt catalysts
K. Jaroszewska∗, A. Masalska, K. Ba˛czkowska, J.R. Grzechowiak
Wrocław University of Technology, Faculty of Chemistry, Gdan´ska 7/9, 50-340 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Platinum catalysts (1.5 wt.%) containing AlSBA-15 obtained with various aluminium precursors
were tested for activity in 1-methylnaphthalene hydrogenation. Experiments were carried out in a
continuous-flow system at atmospheric pressure (240–350 ◦C, W/F = 0.8 g s/cm3). It was found that 1-
methylnaphthalene conversion over Pt-loaded catalysts was not influenced by the aluminium precursor
used in the preparation of the Pt/AlSBA-15 catalysts. However, the Pt catalyst prepared with AlSBA-15
obtained from aluminium sulphate provided a higher cis-methyldecalins/trans-methyldecalins ratio in
the reaction products as compared to the catalysts obtained with aluminium nitrate or aluminium iso-
propoxide. Consideration was also given to the influence of platinum amount (0.5, 2.5 and 4.5 wt.%) on
the catalytic performance of bifunctional Pt/AlSBA-15 catalysts (AlSBA-15 obtained with aluminium sul-
phate) in decalin hydroconversion. It was shown that impregnation of AlSBA-15 with H2PtCl6 increased
Brønsted acidity. Investigations into decalin conversion were conducted in a continuous-flow system with
a fixed-bed reactor (5 MPa, 300–380 ◦C, H2:CH = 500 N m3/m3; WHSV = 2 h−1). Incorporation of 0.5 wt.%
Pt into AlSBA-15 yielded a catalyst with the highest dispersion of the platinum phase and the highest
yield of ring opening products, amounting to 26.4 wt.% at 380 ◦C.
Received 29 October 2011
Received in revised form 1 June 2012
Accepted 14 June 2012
Available online 12 July 2012
Keywords:
Decalin
Ring opening
1-Methylnaphthalene
Hydrogenation
Platinum catalyst
AlSBA-15
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
selectivity increases with the drop in reaction temperature and rise
in hydrogen pressure. The rate of tetralin to decalin hydrogenation
In view of obtaining greener and advanced diesel fuels, it is
highly desirable to enhance the efficiency of aromatics hydrogena-
tion, especially when an increased amount of oil fractions obtained
by FCC is used for transportation fuel production. Hydrogenation
of polynuclear aromatics (PAHs) (e.g., naphthalene, anthracene,
phenanthrene and their derivatives) and also, ring opening of
cycloparaffin hydrocarbons formed offer the possibility of signifi-
cantly reducing the content of aromatics and improving the cetane
number beyond what can be obtained with aromatic saturation
alone. The ideal process would be selective ring opening that
reduces the number of ring structures while the carbon number
of a product molecule is retained.
Taking into account the hydrocarbon content of the diesel
oil fraction, it is conventional to use naphthalene or 1-
methylnaphthalene as a model compound for assessing the activity
of hydrogenating catalysts [1–3]. When investigating the reac-
tion of selective ring opening, use is made, inter alia, of decalin
(a product of complete naphthalene hydrogenation), which acts
as the model compound [4,5]. Lin et al. have demonstrated
[6] that during hydrogenation of aromatics to decalin catalyst
is slower than that of naphthalene to tetralin hydrogenation. In con-
sequence, even under thermodynamically favourable conditions
of decalin formation, tetralin is the main product of naphthalene
hydrogenation, whereas decalin forms when naphthalene con-
version approaches 100% [2]. Hydrogenation of tetralin fails to
occur in the presence of naphthalene because of the competitive
adsorption of the latter [7]. It has also been reported that cis-
decalin and trans-decalin have different reactivities in the ring
opening reaction, and that trans-decalin is more stable in thermo-
dynamic terms [8]. The mechanisms governing the hydrogenation
of 1-methylnaphthalene over Pt/USY and the hydrogenation of
naphthalene over Pt(Pd)/mordenite and Pt(Pd)/H-Y have been
described by Arribas et al. [3] and Schmitz et al. [9].
Decalin conversion was investigated over monofunctional acidic
zeolites, H-Beta, H-Y, and H-Mordenite [10–15] and bifunctional
catalysts [5,14,16–19]. The mechanism of conversion over mono-
functional acidic zeolites has been discussed by Du et al. [14]. Corma
et al. [15] have examined the effect of zeolite pore topology of the
catalyst on product distribution in decalin cracking. Their research
involving zeolites with varying pore size distribution, e.g. ZSM-5,
ITQ-2 (medium sized), USY, Beta (large sized) and UTD-1 (ultra-
large sized), has led to the finding that larger pores (USY, Beta)
allow faster diffusion of product molecules, thereby reducing the
probability that secondary cracking and dealkylation may occur.
∗
Corresponding author. Tel.: +48 713206532; fax: +48 713221580.
E-mail address: karolina.jaroszewska@pwr.wroc.pl (K. Jaroszewska).
0920-5861/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2012.06.011

K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
111
In ring opening reactions over bifunctional catalysts, the activity
and selectivity of the catalyst is influenced by the following fac-
tors: the type of the metal used, the size of metal particles, the
acidity and pore size of the support, the distance between metal
and acid sites, and the reaction conditions (temperature, hydrogen
pressure) [14]. Decalin conversion over H-Beta, H-Y, H-Mordenite
and La-X zeolites with noble metal contents (mainly Pt and Ir) as
well as Ni and Mo has been the focus of several studies [5,16–18].
Kubicˇka et al. examined the ring opening of decalin over proton-
form and platinum-modified zeolites (H-Beta, H-Y, H-mordenite).
In their experiments the incorporation of a noble metal (2 wt.% Pt)
into the H-Beta zeolite framework produced yields of ring opening
products approaching 30 mol%, which were approximately 3 times
as high as over proton-form zeolites [11,19].
In the past few years, much consideration has been given to the
application of mesoporous materials, such as MCM-41 [20–22] and
SBA-15 [23–25], as supports for hydrotreating catalysts. Results
of decalin conversion over mesoporous MCM-41 loaded with Ru
(2.5 and 5 wt.%) or Pt(Ir) (0.22–1.88 wt.%) have been reported by
Murzin et al. [26] and by Mouli et al. [27], respectively. The low
acidity of mesoporous siliceous materials is an obvious limitation
to their use as supports for isomerization, hydrocracking, hydrode-
cyclization and hydrogenation catalysts. A common method of
upgrading their acidity involves substitution of Al atoms for Si
atoms. For the preparation of such supports use is made of a method
where Al atoms are incorporated either during synthesis of the
porous material [28,29] or during impregnation of the siliceous
material with the aluminium precursor [30,31]. The effect of the
aluminium precursor on the AlSBA-15 properties was examined by
Li et al. [32]. The degree of Si substitution (coprecipitation method)
increases in the following order: aluminium sulphate < aluminium
nitrate < aluminium isopropoxide [33].
was conducted in the presence of catalysts with a 0.5 wt.%, 2.5 wt.%
and 4.5 wt.% Pt content, supported on the AlSBA-15(S) material; the
catalysts were denoted by 0.5Pt/AlSBA-15(S), 2.5Pt/AlSBA-15(S)
and 4.5Pt/AlSBA-15(S), respectively.
2.2. Catalysts characterization
Texture: Nitrogen adsorption and desorption isotherms were
measured at 77 K with the Autosorb-1C Quantachrom sorption
analyser. Specific surface area was calculated using the BET model.
The BJH method was applied for determining the pore diameter.
XRD and MAS NMR: The powder X-ray diffraction patterns of
the AlSBA-15 materials were collected on a Siemens D5005 diffrac-
tometer using CuK␣ (ꢀ = 0.154 nm) radiation. 29Si MAS NMR and
27Al MAS NMR spectra were recorded with an AC200 Bruker spec-
trometer.
Acidity: Acidity was determined by adsorption of pyridine (Py-
IR) at 170 ◦C. Prior to acidity measurement, the samples were
activated at 450 ◦C for 30 min (10−5 mbar). IR spectra were recorded
with a Tensor 27 Bruker spectrometer. The A350/A170 ratio where
A170 is the intensity of the Py ion band upon evacuation at 170 ◦C
and A350 is the intensity of the same band upon desorption at
350 ◦C was taken as a measure of the acid strength. Acidity was
also evaluated by chemisorption of ammonia (NH3-TPD) at 180 ◦C
in through-flow system equipped with katharometer. The sample
was pretreated in the stream of argon at 550 ◦C for 2 h and then
cooled to180 ◦C. After desorption of physically adsorbed ammonia,
the sample was heated up to 550 ◦C at a rate of 10◦/min.
Chemical analysis and dispersion: Pt content was determined
by XRF (Canberra Packard, 1510). Pt dispersion was measured by
oxygen titration. The catalysts were made subject to reduction in
hydrogen at 500 ◦C for 5 h, followed by introduction of 0.05 ml
pulses of oxygen at RT. Dispersion of Pt over the AlSBA-15 surface
was calculated according to Bergeret et al. [35].
TOF-SIMS: The time-of-flight secondary ion mass spectrome-
try (TOF-SIMS) investigations were performed using an ION-TOF
instrument (TOF-SIMS IV) equipped with a 25 kV pulsed 69Ga+ pri-
mary ion gun in the static mode.
This work is focused on the contribution of aluminium sources
to the catalytic properties of Pt/AlSBA-15 (1.5 wt.% of Pt) in
1-methylnaphthalene (1-MeN) conversion as well as to the cis-
methyldecalins/trans-methyldecalins ratio. Consideration is also
given to the problem of how the Pt content (0.5–4.5 wt.% of Pt)
of the Pt/AlSBA-15 catalyst influences conversion and selectivity to
ring opening products in the transformation of decalin.
2. Experimental
2.3. Catalytic experiments
2.1. Catalysts preparation
The influence of the aluminium precursor in AlSBA-15 synthesis
on the catalytic performance of bifunctional Pt/AlSBA-15 (1.5 wt.%
of Pt) catalysts for the hydrogenation of 1-methylnaphthalene (1-
MeN) was examined using a continuous fixed-bed atmospheric
pressure reactor (240–350 ◦C, W/F = 0.8 g s/cm3).
The effect of platinum content of Pt/AlSBA-15(S) catalysts on
the ring opening of decalin was investigated in a continuous-flow
system with a fixed-bed reactor under the following condi-
tions: p = 5 MPa, H2:CH = 500 N m3/m3 and WHSV = 2 h−1. Decalin
(10 vol.% in n-heptane) was supplied by means of an HPLC Gilson
307 pump (model 5SC). Activity tests were performed using 0.25 g
of powder catalyst (grain size of 0.4–0.63 mm) diluted with SiC up
to 2 cm3. Before activity tests the samples were reduced with H2
at 300 ◦C for 1 h and 450 ◦C for 30 min (30 cm3 min−1, 5 MPa). The
activities of the catalysts were measured at reaction temperature
of 300, 340 and 380 ◦C.
Liquid samples (accumulated for 1 h) were weighed and ana-
lysed by GC–FID equipped with an RTX-1 capillary column (100%
dimethylpolysiloxane, 60 m, 0.53 mm, 1.0 ␮m). Since decalin con-
version yields numerous products, they were identified by means
of the GC–MS method. The GC–MS analysis was carried out in an
HP6890 instrument. The same column and separation conditions
as for the GC–FID analysis were used.
Mesoporous molecular sieves AlSBA-15 were synthesized
by the method described for SiSBA-15 in [34]. Samples with
Si/Al = 20 ratio were obtained via the direct hydrothermal method
using aluminium sulphate (Al2(SO4)3·18H2O; Aldrich), aluminium
nitrate (Al(NO3)3·6H2O; Aldrich) and aluminium isopropoxide
([(CH3)2CHO]3Al, Acros) as metal sources. These samples are
denoted by AlSBA-15(S), AlSBA-15(N), and AlSBA-15(IP), respec-
tively.
Pt/AlSBA-15 catalysts were prepared by impregnating the mix-
ture of AlSBA-15 and 20 wt.% of boehmite (Pural KR-1, Sasol GmBH;
SBET = 304 m2/g, 0.54 mmol NH3/g) with a solution of hexachloro-
platinic acid (POCh). After Pt impregnation the samples were dried
at 20 ◦C (24 h), 50 ◦C (30 min), 70 ◦C (30 min) and 100 ◦C (12 h),
and then calcined at 150 ◦C (1 h), 250 ◦C (1 h), and 350 ◦C (3 h).
The extrudates from the powder catalysts were obtained using 3%
nitric(V) acid. All extrudates were made subject to drying (110 ◦C,
12 h) and calcination (450 ◦C, 3 h). According to the Al precursor
applied, the catalysts (1.5 wt.% Pt) were denoted by Pt/AlSBA-
15(S), Pt/AlSBA-15(N) and Pt/AlSBA-15(IP). The experiment which
aimed at determining the effect of the amount of platinum on the
activity and selectivity of the catalysts in decalin hydroconversion

112
K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
same as that of the siliceous SBA-15 sample (not shown), indicating
a
that the hexagonally ordered two-dimensional structure is retained
even after incorporation of huge Al quantities into the wall struc-
ture of AlSBA-15 (Si/Al = 20). The same effect has been reported by
Shanbhag [37] and Vinu [38].
The nitrogen adsorption–desorption isotherms are shown in
Fig. 2. As can be seen from these plots, the AlSBA-15 samples
exhibit isotherms of type IV (IUPAC) typical of mesoporous mate-
rials. They also display an H1-type broad hysteresis loop, which
is typical of large-pore mesoporous solids. All isotherms show a
sharp condensation step at relative pressures within the range of
0.6–0.8. When use is made of Al(NO3)3·6H2O (AlSBA-15(N) sample),
the capillary condensation step is shifted to higher relative pres-
sures. The p/p0 position of the inflection point for AlSBA-15(N) is
correlated with the presence of macropores. When aluminium pre-
b
−
cursors are added, respective counterions such as NO3−, C3H7O3
,
0
10
20
30
40
and SO42− neutralize the micellar charge. Stronger charge neutral-
ization would help the formation of more rigid micelles and hence
better hexagonal structure [33]. Lower charge neutralization takes
place when Al(NO3)3·6H2O is used as the alumina precursor.
The mesoporous materials obtained display a similar porous
structure (Table 1). BET specific surface areas vary from 798 to
875 m2/g. Pore volume and mean pore diameter are within the
range of 1.1–1.4 cm3/g and 9.5–10.5 nm, respectively. The length
of the hexagonal unit cell a0 is calculated in terms of the formula
a0 = 2·d1 0 0/31/2. It is interesting to note that the unit cell param-
eter of AlSBA-15(S) decreases after aluminium incorporation as
compared with the unit cell of SiSBA-15 (not shown). For samples
obtained from aluminium nitrate and aluminium isopropoxide, a
rise is observed in the a0 parameter. The increase in the unit cell
parameter suggests the presence of metal in the SBA-15 walls [36].
This indicates that the incorporation of Al atoms into the SBA-15 sil-
ica framework is more successful for AlSBA-15(N) and AlSBA-15(IP)
than for AlSBA-15(S). These observations are in agreement with the
results of the 27Al MAS NMR measurements (Fig. 3), which revealed
the highest contribution of non-framework aluminium atoms in
AlSBA-15 prepared with aluminium sulphate (AlSBA-15(S)). Wide
angle XRD patterns make it clear that the AlSBA-15(N) and AlSBA-
15(IP) samples do not contain any other phase (Fig. 1).
The condensation ratio of the mesoporous matrix was deter-
mined by the 29Si MAS NMR method [39]. The 29Si MAS NMR
spectra (Fig. 3) of AlSBA-15 samples show three peaks around
the shifts of −91, −100 and −110 ppm. They are assigned to sil-
icon groups in the following structures: geminal silanol species
(OSi)2 Si(OH)2 (Q2), isolated silanol species (OSi)3 SiOH (Q3) and
the most polymerized Si (OSi)4 (Q4) units, respectively [37,40].
In the case of metal containing materials, the presence of
(OSi)2 Si (O X)2 and (OSi)3 Si (O X) units can be expected,
where X may stand not only for a hydrogen but also a metal atom
(Al in this study) [41,42]. Signals ␦29Si from aluminium contain-
ing groups are overlapped with peaks from geminal Q2 and single
Q3 silanol groups, respectively. Some authors [37,43,44] observed
a shoulder at about −107 ppm ascribed to Si(3Si,1Al) species. The
analysed spectra (Fig. 3) exhibit no additional signal that might
indicate the presence of Si(3Si,1Al) units. The absence of this peak
may be attributed to the low degree of Al substitution for Si atoms
2θ ( )
c
0
10
20
30
40
2θ (o)
0
1
2
3
4
5
6
2θ (o)
Fig. 1. XRD patterns of calcined materials (a) AlSBA-15(S), (b) AlSBA-15(N) and (c)
AlSBA-15(IP).
According to the literature data [12,27] all the reaction products
were grouped as follows:
(1) Cracking products (CP, compounds containing less than 10
carbons): mainly derivatives of cyclopropene, cyclopentane,
cyclopentene, cyclohexane and cyclohexene.
(2) Ring contraction products (RC, compounds containing 10 car-
bons): C6 rings fused to C5 or/and C3 rings, and two C5 rings.
(3) Ring opening products (RO, compounds containing 10 carbons):
mainly derivatives of cyclohexane, cyclohexene, cyclopentane
or benzene, and OCD – open chain decenes.
(4) Dehydrogenation products (DP): tetralin, naphthalene and
indane derivatives.
3. Results and discussion
3.1. Aluminium precursor used for the preparation of AlSBA-15
based supports for Pt catalysts and its influence on 1-MeN
hydroconversion
3.1.1. Influence of aluminium precursor on physicochemical
properties of AlSBA-15
The powder XRD patterns of AlSBA-15 samples obtained with
various aluminium sources (Fig. 1) demonstrate a high degree of
structural ordering. The low angle XRD patterns display three well
resolved peaks in the 2ꢁ range of 0.8–1.8◦: an intense peak (1 0 0),
as well as low-intensity (1 1 0) and (2 0 0) reflections, which are
associated with p6 mm hexagonal symmetry. This characteristic
XRD patterns of the AlSBA-15 hexagonal phase also matches well
with relevant XRD patterns reported in the literature [36]. The
shape of the XRD spectrum of the AlSBA-15 samples is almost the
Table 1
Textural properties of AlSBA-15 determined by powder XRD and N2 sorption.
Sample
SBET (m2/g) Vp (cm3/g) APD (nm) dp (nm) a0 (nm) wt (nm)
AlSBA-15(S) 875
AlSBA-15(N) 800
AlSBA-15(IP) 798
1.3
1.4
1.1
5.8
7.2
5.6
9.5
10.5
10.4
10.6
11.5
11.8
1.1
1.0
1.4
Note: Vp, pore volume; APD, average pore diameter; dp, pore diameter; a0, unit cell
parameter; wt, wall thickness.

K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
113
V = 200 cm3STP/g
a
b
a
b
c
c
0
0.2
0.4
0.6
0.8
1
3
4
5
6
7
8
9
10 11 12
Relaꢀve pressure (p/p0)
Pore diameter (nm)
Fig. 2. N2 adsorption–desorption isotherms (left) and pore size distribution calculated using the BJH method (right) of mesoporous materials (a) AlSBA-15(S), (b) AlSBA-15(N)
and (c) AlSBA-15(IP).
(but such statement would be inconsistent with the results of XRD,
N2 sorption and 27Al MAS NMR examinations) or to the fact that
these chemical shifts of low intensity would hardly be observable
due to the overlap with the strong signal of the SiOH groups occur-
ring at −100 ppm. Table 2 shows the relative amounts of the silicon
groups, determined by the deconvolution of 29Si MAS NMR spectra.
There are no significant differences in the 29Si MAS NMR spectra of
the investigated AlSBA-15 materials. The comparatively low por-
tion of Q4 units (which form during calcination via condensation
of nonconnected internal silanol groups, i.e. Q2 and Q3) is nearly
constant for all substituted samples. The frameworks of all the
AlSBA-15 samples exhibit a high contribution of isolated silanol
groups. The low framework connectivity could have been caused by
the high degree of isomorphous substitution. According to Kosslick
et al. [45], the steric hindrances caused by the different radii of
the substituted atom and by the minimum intertetrahedral bond
(Td-Al(IV)) [39,46]. The Td-Al(IV) species can be regarded as
Brønsted acid sites [21]. The signal at 0 ppm was ascribed to dis-
torted or octahedrally coordinated (Oh-Al(VI)) aluminium atoms at
extra-framework positions or in a separate phase [47,48]. Kosslick
et al. [49] report that non-framework aluminium species (Oh-
Al(VI)) are formed by dealumination of mesoporous aluminosilicate
during calcination at 550 ◦C. However, the formation of octahe-
drally coordinated aluminium atoms at some stage in synthesis
cannot be excluded.
The results show that for all samples Al was incorporated
into the molecular sieve framework predominantly by isomor-
phic substitution of Si (Td-Al(IV)). The signals from Td-Al(IV) for
samples obtained with aluminium nitrate and aluminium iso-
propoxide display high intensities. But the chemical shifts of 0 ppm
3+
with respect to Al(H2O)6 suggest that some of the aluminium
species were incorporated with an octahedral coordination. The
27Al MAS NMR spectrum displays a signal at about 0 ppm generated
by octahedrally coordinated aluminium atoms, which is signifi-
cantly higher for the AlSBA-15(S) material than for AlSBA-15(N)
and AlSBA-15(IS). However, most of the aluminium atoms remain
in a tetrahedral oxygen coordination at framework positions. The
foregoing results suggest that the contribution of Td-Al(IV) and Oh-
Al(VI) in the mesoporous materials can be controlled using different
aluminium precursors.
angles of the Si
O Si and the Si O Me bridges should make con-
densation within the framework more difficult, when the degree of
substitution is increased.
Fig. 3 shows solid state 27Al MAS NMR spectra of AlSBA-15. Each
spectrum exhibits a strong and sharp signal at about 50 ppm, as
well as a weak and broad one at about 0 ppm, regardless of the
Al precursor. The signal at 50 ppm was assigned to tetrahedrally
coordinated aluminium atoms located in framework positions
Table 2
Connectivities of the framework of AlSBA-15 determined by the deconvolution of 29Si MAS NMR spectra.
Sample
Q2
Q3
Q4
Q4/Q2 + Q3
ı (ppm)
% of area
ı (ppm)
% of area
ı (ppm)
% of area
AlSBA-15(S)
AlSBA-15(N)
AlSBA-15(IP)
−91.5
−91.5
−91.5
15.5
23.3
17.2
−99.9
−100.2
−99.9
59.4
50.4
59.5
−111.0
−109.6
−110.5
25.1
26.3
23.4
0.33
0.35
0.31

114
K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
Fig. 3. 29Si MAS NMR (left) and 27Al MAS NMR spectra (right) of the mesoporous materials (a) AlSBA-15(S), (b) AlSBA-15(N) and (c) AlSBA-15(IP).
3.1.2. Influence of aluminium precursor on 1-MeN
hydroconversion over Pt/AlSBA-15
The enhancement of the hydrogenation activity of the Pt/AlSBA-
15 catalysts in the range temperature of 280–350 ◦C can be
attributed to the Brønsted acid sites which contribute in hydro-
genation at relatively high temperatures. Aboul-Gheit et al.
investigated H-ZSM-5 and Pt/H-ZSM-5 in hydrogenation of cyclo-
hexene [50]. They have found that Pt sites are primarily responsible
for cyclohexene hydrogenation reactions at low reaction tempera-
tures (50–150 ◦C), whereas the Brønsted acid sites in the H-ZSM-5
zeolite are responsible for hydrogenation at relatively higher tem-
peratures than hydrogenation on the metallic sites. Lin and Vannice
[51–53] proved that the increase in benzene hydrogenation activity
of Pd and Pt supported on acidic supports compared to catalysts on
non-acidic supports is caused by the presence of extra hydrogena-
tion sites in the metal–acid interfacial region, which participate
in the hydrogenation of aromatic. These sites are the generally
Brønsted acid sites located close to the metal sites where the
spillover hydrogen could react with the adsorbed aromatic com-
pound.
The results of 1-MeN hydrogenation over AlSBA-15 supported
platinum catalysts (1.5 wt.% of Pt), at atmospheric pressure and
temperatures ranging from 240 to 350 ◦C, are shown in Table 3.
Measured data make it clear that the aluminium precursor does
not significantly affect the conversion of 1-MeN. For all the cata-
lysts examined, the reaction temperature of 240 ◦C provides 1-MeN
conversion of about 80%. Conversion passes through the minimum
with all the Pt catalysts tested (at 280 ◦C). The increase in reac-
tion temperature from 280 ◦C to 320 and 350 ◦C slightly increases
1-MeN conversion.
Table 3
Influence of the aluminium precursor in Pt/AlSBA-15 catalysts on 1-MeN conversion.
TR (◦C)
Pt/AlSBA-15(S)
Pt/AlSBA-15(N)
Pt/AlSBA-15(IP)
In our work, it was shown that incorporation of platinum
(1.5 wt.%) into AlSBA-15(S) material may bring an approximately
six-fold increase in Lewis acid site concentration and five-fold
increase in Brønsted acid site concentration as compared with
AlSBA-15(S) (Table 4). The interaction of pyridine with Pt crys-
tallites accounts for the increase of Lewis acidity, given that the
metal crystallites are known to be acceptors of electron pairs, i.e.
to act as Lewis acids [54]. The explanation for the increase in the
Brønsted acidity is more complicated. The chemical composition
of the surface of the Pt catalysts under this study determined by
TOF-SIMS method has revealed that the surface of all catalysts is
covered by chlorine species resulted from incomplete decompo-
sition of H2PtCl6 or HCl (HCl was incorporated during AlSBA-15
synthesis). The ratio of Cl−/total ion is comparable for all Pt cat-
alysts tested and it amounts to 0.04. The negative secondary ions
mass spectrum of Pt/AlSBA-15(S) as an example is presented in
Conversion (%)
240
280
320
350
78.2
63.4
68.1
69.6
79.9
65.6
69.4
69.4
79.0
62.5
67.6
67.8
MeTs yield (wt.%)
240
280
320
350
62.4
71.5
64.5
68.6
68.4
61.1
59.7
66.2
65.7
60.6
66.3
67.9
MeDs yield (wt.%)
240
280
320
350
15.8
8.4
1.1
0.8
1.0
17.9
2.8
1.4
2.8
1.8
1.7
2.1
cis-MeDs/trans-MeDs
240 0.4
0.2
0.3

K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
115
Table 4
Acidity results (Py-IR) of AlSBA-15(S) and AlSBA-15(S) supported Pt catalyst.
Catalyst
APyH+ (␮mol/g)
APyL (␮mol/g)
170 ◦
C
250 ◦
C
350 ◦
C
A350/A170
170 ◦
C
250 ◦
C
350 ◦
C
A350/A170
AlSBA-15(S)
Pt/AlSBA-15(S)
20
98
20
72
13
26
0.67
0.27
25
154
25
151
22
129
0.88
0.84
Fig. 4. According to the literature data the incorporation of Cl− ions
into various supports, either as part of the Pt precursor (incomplete
decomposition of H2PtCl6) or after noble metal impregnation (chlo-
rination) may cause Brønsted acid sites to appear [55–58]. Corma
et al. [55] observed that halogenation (in his work fluorination) of
␥-Al2O3 created Brønsted acid sites able to interact with pyridine
molecules. Recently Aboul-Gheit et al. [56] who investigated the
effect of hydrochlorination on the properties of Re/H-ZSM-5 cata-
lysts, observed that after hydrochlorination with 3% HCl, followed
by drying, calcination and reduction, about 50% of Cl−ions remained
in the catalyst. Karhu et al. [57] reported that in the Pt/Al2O3 and
Pt/SiO2Al2O3 (3 wt.% Al2O3) catalysts chlorine residues (incomplete
decomposition of H2PtCl6) remained in the vicinity of platinum
particles after reduction at 400 ◦C. They also demonstrated that Pt
catalyst supported on pure silica showed no chlorine residue upon
reduction. According to these authors, chlorine remaining on the
catalyst surface contributed significantly to the performance of the
catalysts in gas-phase ortho-xylene hydrogenation. The presence
of chlorine in SiMCM-41 and NbMCM-41 supported Pt catalysts as
a result of impregnation with of H2PtCl6 has been confirmed by
Sobczak [58].
saturated hydrogenation products, i.e. MeDs, irrespective of the Al
precursor. Considering the increasing yield of MeDs, the catalysts
can be ordered as follows: Pt/AlSBA-15(N) (8.4 wt.%) < Pt/AlSBA-
15(S) (15.8 wt.%) < Pt/AlSBA-15(IP) (17.9 wt.%). The results indicate
that the aluminium source influences not only the yield of
MeDs, but also the ratio of cis-MeDs/trans-MeDs. It was found
that Pt/AlSBA-15(S) provides a higher cis-MeDs/trans-MeDs ratio
in the reaction products as compared with Pt/AlSBA-15(N)
and Pt/AlSBA-15(IP). According to literature data [27], cis-
decalin is more reactive in the hydrodecyclization reaction than
trans-decalin.
3.2. Influence of platinum amount in Pt/AlSBA-15 catalysts on
decalin ring opening
In this study, consideration was also given to the prob-
lem of how metal (0.5, 2.5 and 4.5 wt.% of Pt) content
in the Pt catalysts influences conversion and selectiv-
ity to ring opening products during transformation of
decalin. AlSBA-15 synthesized with Al2(SO4)3·18H2O was selected
as a support for catalysts because of the relatively high yield
of MeDs (at 240 ◦C) and the highest cis-MeDs/trans-MeDs ratio
obtained in 1-MeN conversion over 1.5/Pt/AlSBA-15(S).
Activity results of our catalyst show that the main prod-
ucts of 1-MeN hydroconversion are methyltetralins (MeTs) and
methyldecalins (MeDs) (Table 3). Within the range of 240–350 ◦C,
the rise in temperature primarily leads to the formation of
incomplete hydrogenation products, i.e. MeTs. The tempera-
ture of 240 ◦C brought about the highest yield of completely
Table 5 shows the metal content of the catalysts (Pt atoms, nPt
;
accessible Pt atoms, nPt A) and summarizes the results of H2 O2
titration (metallic surface, SPt; metallic dispersion, D; average diam-
eter of Pt crystallites, d) as well as catalyst acidity (number of total
Fig. 4. Negative TOF-SIMS spectrum of Pt/AlSBA-15(S) catalyst.

116
K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
Table 5
Characterization of metal function and acidity of platinum catalysts.
−1
Catalyst
SBET (m2/g) Pt (wt.%) nPt (10−19 g−1
)
D (%)
D (nm) SPt (m2 gcat
)
nPt A (10−19 g−1
)
nNH
(10−19 g−1
)
nB (10−19 g−1
)
nL (10−19 g−1
)
-TPD
3
0.5Pt/AlSBA15(S)
2.5Pt/AlSBA-15(S) 511
4.5Pt/AlSBA-15(S) 491
556
0.50
2.50
4.50
0.11
7.72
13.9
100.0 1.1
36.2 3.1
24.2 4.6
249.1
90.2
60.4
0.14
2.79
3.37
16.9
21.7
25.3
3.6
10.7
6.3
5.2
21.6
11.0
Note: nPt, platinum atoms; D, Pt dispersion; d, average diameter of Pt crystallites; SPt, surface of the metal; nPt A, accessible platinum atoms, nNH -TPD, number of total acid
3
sites determined from NH3-TPD method; nB and nL number of Brønsted and Lewis acid sites determined from Py-IR method.
acid sites determined from NH3-TPD method, nNH -TPD; number of
demonstrates that the total acid sites number of 4.5Pt/AlSBA-15(S)
is by 8.4 and 3.6 × 1019g−1 higher than the total acid sites num-
bers of 0.5Pt/AlSBA-15(S) and 2.5Pt/AlSBA-15(S), respectively. This
discrepancy between NH3-TPD and Py-IR measurements can be
ascribed to the impact of platinum particle size on the diffusion
of probe molecules (pyridine or ammonia) into the pores of the
catalysts. The relatively large particle size of Pt species in high Pt
loaded catalysts i.e. 4.5Pt/AlSBA-15 sample might limit pyridine
adsorption on the acid sites.
3
Brønsted and Lewis acid sites determined by the Py-IR method, nB
and nL). As can be seen from these data, 0.5Pt/AlSBA-15(S) is char-
acterized by extremely high dispersion. Considering the decreasing
metallic surface of Pt, the catalysts can be ordered as follows:
0.5Pt/AlSBA-15(S) > 2.5Pt/AlSBA-15(S) > 4.5Pt/AlSBA-15(S).
The IR spectra of pyridine adsorbed are presented in Fig. 5 for
all the samples examined. Lewis acid sites (PyL) have formed on
the surface of all samples as can be seen from the absorption bands
around 1620 and 1454 cm−1 [59]. The bands at the frequency of
1638 and 1545 cm−1 represent Brønsted acid sites (PyH+) [60]. The
absorption band at 1490 cm−1 corresponds to the vibrations of pyri-
dine chemisorbed either on Lewis or Brønsted acid sites (PyL + PyH+)
[61]. The three absorption bands at approximately 1445, 1578
and 1603 cm−1 are ascribed to hydrogen-bonded pyridine [62],
physisorbed pyridine and pyridine coordinated through its aro-
matic ␲-electrons to 1607 cm−1 [63], respectively. Results indicate
that for all investigated catalysts the amount of pyridine molecules
associated with protons (PyH+) is lower than that associated with
coordinatively unsaturated sites (PyL). Py-IR measurements have
furthermore revealed that there is no correlation indicating that
the platinum enrichment of AlSBA-15(S) supported catalysts leads
to an increase in their acidity. As can be seen from Table 5, the
total amount of acid sites in the 2.5Pt/AlSBA-15(S) catalyst is
higher as compared to the 0.5Pt/AlSBA-15(S) and 4.5Pt/AlSBA-15(S)
catalysts. Acidity determined by the NH3-TPD method (Table 5)
27Al MAS NMR analysis of the platinum catalysts was carried
out to determine the ordering of the Al atoms in the framework
of AlSBA-15(S) after impregnation with hexachloroplatinic acid,
and the results are shown in Fig. 6. A Pt-free sample i.e. AlSBA-
15(S) (Fig. 3a, right) was compared with both 0.5Pt/AlSBA-15(S) and
4.5Pt/AlSBA-15(S). It is clearly observed that the peak assigned to
tetrahedrally coordinated aluminium atoms located in framework
positions (Td-Al(IV)) is significantly lower for the 0.5Pt/AlSBA-
15(S) material than for AlSBA-15(S) and completely disappeared in
4.5Pt/AlSBA-15(S) sample. Additionally, in the case of 4.5Pt/AlSBA-
15(S) a signal at −5.7 ppm is observed, which corresponds to the
extra-framework aluminium [45]. It indicates that incorporation
of Pt over the AlSBA-15(S) surface using hexachloroplatinic acid
leads to partly or completely dealumination. The determination of
the aluminium content in the catalysts shows that the Si/Al ratio
slightly increases (in comparison with AlSBA-15(S)) and it is about
21. It indicates that aluminium remains in the material as an extra-
framework species.
Catalytic activities and product distribution over Pt catalysts for
decalin hydroconversion are summarized in Table 6. The results
show that conversion increases with a rise in temperature, which
PyH+
1545
PyL+PyH+
1490
PyH+
1638
PyL
PyL
1620
1454
1578
1445
1603
a
b
2.8
49.2
b
a
-5.7
c
5.5
b
d
150
100
50
0
-50
-100
1700
1650
1600
1550
1500
1450
1400
Chemical shi from Al(H2O)63+ (ppm)
Wavenumber (cm-1)
Fig. 5. FT(IR spectra of pyridine adsorbed at 170 ◦
0.5Pt/AlSBA-15(S), (c) 2.5Pt/AlSBA-15(S) and 4.5Pt/AlSBA-15(S).
C
on (a) AlSBA-15(S), (b)
Fig. 6. 27Al MAS NMR spectra of the platinum catalysts (a) 0.5Pt/AlSBA-15(S) and
(b) 4.5Pt/AlSBA-15(S).

K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
117
Table 6
The products yield on Pt/AlSBA-15 catalysts (decalin hydroconversion).
Catalyst
0.5Pt/AlSBA-15(S)
2.5Pt/AlSBA-15(S)
4.5Pt/AlSBA-15(S)
Reaction temperature, ◦
C
300
340
380
300
340
380
300
340
380
ꢀ
CP
1.5
3.4
7.7
14.6
19.7
3.7
2.1
4.2
9.6
1.5
1.6
2.4
9.1
7.1
ꢀ
RC
13.1
10.2
18.3
12.8
ꢀ
RO
3.1
n.d.
3.1
n.d.
n.d.
n.d.
n.d.
n.d.
0.5
12.1
2.2
6.1
2.1
1.7
n.d.
0.1
2.7
2.7
38.3
26.4
7.2
10.3
3.8
3.2
1.6
0.4
8.5
3.9
73.1
1.2
n.d.
0.6
n.d.
n.d.
n.d.
n.d.
n.d.
0.2
6.2
0.8
3.5
0.5
1.0
0.4
0.1
1.4
1.0
23.0
18.6
4.0
7.0
2.9
2.5
2.0
0.2
11.7
3.6
1.5
0.7
0.7
n.d.
n.d.
n.d.
n.d.
n.d.
0.3
5.6
0.7
2.9
0.3
0.9
0.6
n.d.
3.8
0.8
21.7
14.2
2.8
5.2
1.7
2.2
2.1
0.2
17.4
2.4
Cyclohexane derivativesa
Cyclohexene derivativesb
Cyclohexane derivativesc
Cyclopentane derivatives
Benzene derivatives
OCDs
ꢀ
DP
C balance, wt.%
Conversion, wt.%
8.5
7.2
61.8
4.9
53.9
a
Absence of the double bond.
Double bond in the ring structure.
Double bond in the alkyl substituent.
b
c
holds true for all the Pt catalysts tested. The increase in Pt content
from 0.5 to 4.5 wt.% fails to improve decalin conversion. At any of
the test temperatures, the highest conversion was reached over
the 0.5 wt.% Pt catalyst. Incorporation of 2.5 and 4.5 wt.% of Pt into
AlSBA-15(S) produces catalysts with a lower activity than that of
0.5Pt/AlSBA-15(S).
activity of high Pt-loaded catalysts. Recently, Rabl et al. [17] have
demonstrated that Pt metal sites posses activity for ring contrac-
tion (isomerization) of decalin. Hence, we can postulate that over
0.5Pt/AlSBA-15(S) with extremely high Pt dispersion the amount
of the metal sites involved in ring contraction of decalin is higher
than over 2.5 wt.% and 4.5 wt.% Pt-loaded catalysts.
According to the classical mechanism [10,17], the hydrocon-
version of decalin over bifunctional catalyst occurs through two
parallel reactions: ring contraction of decalin on Brønsted acid
sites yielding skeletal isomers with five-membered naphthenic
rings (RC, i.e. ring contraction products, mainly spiro[4.5]decane,
bicyclononanes and bicyclooctanes) (step 1 in Fig. 7) followed by
hydrogenolysis of those isomers on metal sites to C10 one-ring
naphthenes (RO, i.e. ring opening products, mainly cyclohexane
derivatives) (step 2) as well as direct hydrogenolysis on metal sites
yielding RO which is less favoured in the case of six-membered
naphthenic rings (step 3). Conversion of decalin includes also a
second ring opening step leading from C10 one-ring naphthenes
to open chain decane isomers (OCD) (step 4), cracking of RO (CP,
i.e. cracking products containing less than 10 carbons) (step 5)
and dehydrogenation of decalin (DP, i.e. dehydrogenation prod-
ucts, mainly tetralin, naphthalene, and 1-methylindane) (step 6).
Fig. 7. does not include reactions which lead to heavy products and
carbonaceous deposits.
Concerning the effect of Pt content on the activity of AlSBA-15(S)
supported catalysts it was found that even though 2.5 wt.% and
4.5 wt.% Pt catalysts displayed a higher acidity, the their activities
were lower than over 0.5Pt/AlSBA-15(S), which at 380 ◦C provided
the highest yield of both ring contraction (19.7 wt.%) and ring open-
ing (26.4 wt.%) products. As Brønsted acid sites are crucial in ring
contraction followed by ring opening on metal sites, we expected
the lower activity of 0.5Pt/AlSBA-14(S) catalyst as compared to the
It is worth noticing that over 0.5Pt/AlSBA-15(S) the yield of
dehydrogenation products such as tetralin and naphthalene is the
lowest.
4. Conclusions
The objective of this work was to study 1-methylnaphtalene and
decalin conversion over bifunctional Pt/AlSBA-15 catalysts.
1. The type of the aluminium precursor used for the preparation of
the AlSBA-15 support does not significantly affect the activity of
Pt catalysts for 1-methylnaphthalene conversion.
2. The enhancement of the hydrogenation activity of the Pt/AlSBA-
15 catalysts in the range of 280–350 ◦C can be attributed to
Brønsted acid sites (additionally generated by the presence of
chlorine ions) which contribute in hydrogenation at relatively
high temperatures.
3. The Pt catalyst supported on AlSBA-15 precipitated with
aluminium sulphate provides a higher cis-methyldecalins/trans-
methyldecalin ratio than Pt catalysts supported on AlSBA-15
precipitated with aluminium nitrate or aluminium isopropoxide.
4. The decrease in Pt content from 4.5 wt.% to 0.5 increases decalin
conversion over Pt/AlSBA-15 catalysts. The yield of ring opening
productsis greatlyenhancedoverthecatalystwithlow(0.5 wt.%)
amount of Pt and amounted to 12.1 and 26.4 wt.% at 340 ◦C
and 380 ◦C, respectively. Extremely high Pt dispersion in cata-
lyst containing 0.5 wt.% of Pt enables to increase isomerization
function of catalyst (an increase in ring contraction products)
and hence its activity in the ring opening reaction.
Acknowledgements
This work was supported by the Polish Ministry of Science and
Higher Education (Grant 1T09B 073 30).
The authors wish to thank Karolina Sadowska, MSc., Institute
of Catalysis and Physical Chemistry of Surfaces, Polish Academy of
Sciences, Kraków for acidity determinations by Py-IR.
Fig. 7. Scheme of principle reactions during decalin hydroconversion.

118
K. Jaroszewska et al. / Catalysis Today 196 (2012) 110–118
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