G Model
CATTOD-9282; No. of Pages8
ARTICLE IN PRESS
R. Yadav et al. / Catalysis Today xxx (2014) xxx–xxx
3
Table 1
Textural properties of different mesoporous and microporous silicoaluminophosphate materials.
Sample name
Al:P:Si
Surface area (m2/g)
BJH pore
Average desorption pore
diameter (nm)
volume (cm3/g)
BET
DFT
BJH
H-K
DFT
MESO-SAPO-37-0.43S
MESO-SAPO-37-0.80S
MESO-SAPO-34
MESO-SAPO-5
SAPO-37
1:1.00:0.215
1:1.00:0.400
1:1.06:0.540
1:1.00:0.100
1:1.00:0.215
1:1.06:0.540
1: 1.00::0.100
458
426
448
487
146
246
155
555
445
587
655
–
0.33
0.31
0.47
0.39
0.15
0.22
0.13
3.1
3.7
2.9
3.1
–
1.5
1.6
1.5
1.6
–
0.88
1.2
0.88
0.88
–
SAPO-34
SAPO-5
–
–
–
–
–
–
–
–
Praying Mantis diffuse-reflectance accessory designed to minimize
parasite specular reflectance. About 100 mg (10% of sample was
mixed with KBr) of sample was placed in the sample cup and was
pre-activated at 350 ◦C for 6 h. For pyridine adsorption, helium
gas was passed through a pyridine saturator. A partial pressure of
27 mmHg of pyridine was maintained in the saturator. After pyri-
dine adsorption, the sample was heated to 150 ◦C with ultra-high
pure helium flush for 1 h to ensure that the physically adsorbed
pyridine was recovered completely. Sample spectrum was col-
lected with KBr background once the sample temperature reached
25 ◦C. Subsequently, the sample was degassed at a desired tempera-
ture and spectra were collected at different temperatures. Thermal
gravimetric analysis (TGA) and differential thermo gravimetric
analysis (DTA) of spent catalyst was carried out on PerkinElmer.
About 5–10 mg of sample was heated in air with rate 10 ◦C/min
from 21 ◦C to 1200 ◦C. Diffuse reflectance infrared (DRIFT-IR) spec-
tra of spent catalyst have been recorded on Brüker optic model
tensor 27 FT-IR spectrometer. It is equipped with gold coated cube
corner mirror optics and Harrick Mantis diffused reflectance acces-
sory. The spectra were recorded in absorbance mode with 64 scans
per sample.
analogs are relatively broad compared to those of the microporous
analogs, indicating that the secondary building units are discrete
and present on the walls of mesoporous channels. It is evident
preformed microporous materials possessing structural subunits
of the corresponding SAPO-n on the walls of mesoporous channels.
The powder X-ray diffraction (XRD) patterns for MESO-SAPO-37
with different silica contents are shown in Fig. 2. All the samples
show well-resolved reflection at a 2Â angle of ∼2◦, correspond-
ing to the (1 0 0) plane of the hexagonal mesoporous phase. The
observed 2Â values of MESO-SAPO-37 for the (1 0 0) plane are
2.25◦, 2.24◦, 2.19◦, and 2.09◦ for MESO-SAPO-37-0.43S, MESO-
SAPO-37-0.50S, MESO-SAPO-37-0.60S, and MESO-SAPO-37-0.80S,
respectively. The corresponding unit cell value “a” obtained based
on (1 0 0) plane possesses a value of 3.9 nm, 3.9 nm, 4.0 nm and
4.2 nm, the increase in unit cell value (shift in the 2Â values towards
lower angle) with increase in silica content can be attributed
to the incorporation of more amount of large tetravalent sili-
cate ions (Si4+, 0.04 nm) in the framework position of smaller
pentavalent phosphorous sites (P5+, 0.03 nm) [41]. Moreover, the
low-angle powder XRD of mesoporous SAPOs assembled from
other microporous precursors (MESO-SAPO-5 and MESO-SAPO-
34) showed relatively broad reflection with 2Â values of 1.7◦ and
of hierarchical MCM-41-type (MCM = mobile crystalline material)
hexagonal mesoporous structure. The powder XRD patterns of the
representative calcined samples obtained from MESO-SAPO-37,
MESO-SAPO-5, and MESO-SAPO-34 (Fig. 3) exhibited broad peaks
at 2.5◦, 1.8◦, and 2.5◦, respectively, indicating that the hierarchi-
cal mesoporosity remained intact. Moreover, the d-spacing of the
2.3. Catalytic studies on hydroisomerization of 1-octene
1-Octene (Sigma–Aldrich, 98%) hydroisomerization was studied
using a fixed-bed reactor (Chemito, India) under hydrogen flow.
The flow of hydrogen was controlled using an Aalborg mass flow
controller. Prior to each catalytic activity measurement, the cata-
lysts were activated in air at 400 ◦C for 6 h. A wide range of reaction
conditions was studied, including temperature from 300 to 450 ◦C
and different WHSV = 5, 8, and 12 h−1. The products were analyzed
using gas chromatography connected to a HP-5 capillary column
(Agilent 7890A series).
(f)
(e)
3.1. Materials characterization
(d)
(c)
Fig. 1 shows the Fourier transform infrared (FT-IR) spectra of the
mesoporous SAPO materials obtained from various microporous
precursors and the corresponding microporous analogs. Both the
microporous and mesoporous analogs showed asymmetric stretch-
ing ∼1080 cm−1 corresponding to the framework vibrational bands
respectively are typical of crystalline structural framework unit.
tional bands in the region 530–565 cm−1 [32,36,37], 530–630 cm−1
[38], and 526–640 cm−1 [34,39,40], respectively, representing the
structural secondary building units of SAPO-37, SAPO-5, and SAPO-
34, respectively (Fig. 1). The vibrational bands in the mesoporous
(b)
(a)
400
800
1200
1600
-1
2000
Wavenumber (cm )
Fig. 1. FTIR of (a) MESO-SAPO-37 (b) SAPO-37, (c) MESO-SAPO-5, (d) SAPO-5, (e)
MESO-SAPO-34 and (f) SAPO-34.
Please cite this article in press as: R. Yadav, et al., Mesoporous silico-aluminophosphates derived from microporous precursors as