N. Pasupulety et al. / Applied Catalysis A: General 512 (2016) 52–62
53
to the author the improved ACN selectivity was due to the higher
adsorption ability for NH3 on W–V–Sb/Al surface compared to
V–Sb/Al [10]. Centi et al. [11] have studied the propane ammox-
idation on VO P O7, V–Ti mixed oxide, V–Sb and Fe–Sb catalysts.
Step-3: 9.23 g of ammonium tungstate was dissolved partially
in 20 cm3 of deionized water and to this 5 cm3 of di ammonium
hydrogen phosphate (2.15 g) solution was added.
The slurry obtained from step-1 was slowly added to step-3
solution under continuous stirring. Later, the step-2 suspension
was added to this solution quickly under continuous stirring.
The excess water was evaporated under continuous stirring on a
2
2
They found high activity and ACN selectivity on vanadium phos-
phate and vanadium antimonite catalysts. Mikolajska et al. [12]
have studied the vanadium phosphorus mixed oxides supported
on Al O for propane ammoxidation. The authors attributed the
◦
preheated oil bath at 120 C. The resultant solid was dried in a
2
3
+5
◦
high activity of VPO to V site stability and tuned acid-base prop-
erties on Al O support. Bilde et al. [13] described the catalytic
preheated oven at 120 C overnight in static air.
2
3
behavior of thermally induced Sb O spread on V/Al catalyst in the
2.3. Preparation B
2
3
propane ammoxidation and the greater acrylonitrile selectivity was
endorsed to V–Al–SbO4 rutile phase. Therefore, all the above stud-
ied catalysts in the propane ammoxidation showed the significant
role of Al as an element in the active phase and/or as a support.
Accordingly, catalysts of different performance can be obtained
depending on the type of alumina precursor used. Thus, it is essen-
tial to study the characteristics and performance of V–Sb–W/Al O
V–Sb–P–W (1:3.5:0.5:1 atomic ratio) containing 50% Al O pro-
duced from aluminum chloride precursor.
Aluminum chloride was used instead of aluminum hydroxide
(dry gel) in step-2 and reaming procedure was identical to prepa-
ration A.
2
3
3
Step-2: 47.8 g of AlCl ·6H O was dissolved in 2.5 m of deion-
2
3
3
2
3
catalyst obtained through different alumina precursors for propane
ammoxidation.
ized water. In another beaker 77.0 cm of 12N ammonia solution
was diluted with deionized water to 500 cm3 and quickly added
to the AlCl3 solution under continuous stirring. As formed white
gelatinous precipitate (pH 8.0) was aged for overnight. The resul-
tant precipitate was separated by means of filtration and washed
Vanadium and molybdenum sites can be isolated to a certain
extent by incorporation of phosphorous (P) and P also improves
the acidity moderately which intern minimizes the complete oxi-
dation of propane using VPO and V–Mo–P–O [10–12,14] catalysts.
Keeping this in mind, in the present work, the influence of phospho-
rous addition and Al O prepared from different alumina precursor
−
thoroughly with deionized water to remove the Cl ions. Further,
47.0 cm3 of 10% acetic acid solution was added to the gel and the
remaining steps were identical to preparation A.
2
3
on V–Sb–W phase was examined with the catalyst composition
of V1.0–Sb3.5–P0.5–W1.0/50% Al O . The preparation method and
2.4. Preparation C
2
3
the V–P–Sb–W atomic composition was adopted from the US
patent obtained by Brazdil and Guttmann [7]. The physico-chemical
characteristics of these catalysts was analyzed by BET-pore size
V–Sb–P–W (1:3.5:0.5:1 atomic ratio) containing 50% Al O3
produced from aluminum nitrate (aluminum hydroxide dry
2
method, XRD, NH -TPD-mass, XPS and HAADF-EDS techniques
gel + HNO ) precursor.
3
3
and correlated to propane ammoxidation activity and acrylonitrile
selectivity.
Synthesized, aluminum nitrate was used instead of aluminum
hydroxide (dry gel) in step-2 and reaming procedure was identical
to preparation A.
One hundred and forty cubic centimeter of 60% HNO was added
3
2
. Experimental
to 48 g aluminum hydroxide (dried gel) and the resulting solution
◦
temperature was maintained at 80 C under continues stirring until
2.1. Reagents
the color of the solution turns to clear yellow which, is indicative
of aluminum nitrate formation. Here, the resultant solution was
Ammonium metavanadate (NH VO , assay ≥ 98%), antimony
4
3
weakly acidic (pH 5.0) due to the presence of excess HNO . The
3
oxide (Sb O , assay ≥ 99%), Aluminum hydroxide dried gel
2
3
remaining steps were identical to preparation A.
(
Al(OH) ), ammonium tungstate ((NH ) WO , assay ≥ 99.99%),
3
4
2
4
Further, the powder samples were pelletized and sieved to
di ammonium hydrogen phosphate ((NH ) HPO , assay ≥ 99%),
4
2
4
◦
◦
0
3
.5–2.0 mm size and calcined at 350 C, 5 h followed by 610 C for
h under static air conditions.
Aluminum chloride (AlCl ·6H O, assay ≥ 99%), ammonia solution
3
2
(
NH OH, 30 wt.%) and Nitric acid (HNO 60%) were purchased from
4 3
For example, V–Sb–P–W (1:3.5:0.5:1 atomic ratio) containing
ACROS chemical suppliers and used without further purification.
The preparation method and the V–P–Sb–W atomic composition
was adopted from the US patent obtained by Brazdil and Guttmann
5
0% Al O3 catalyst produced from aluminum hydroxide (dry gel)
2
precursor denoted as AlH, likewise, for aluminum chloride precur-
sor as AlC and aluminum nitrate precursor as AlN.
[
7].
2.5. Catalyst characterization
2.2. Catalyst preparation A
The BET surface area and pore size distribution of calcined
V–Sb–P–W (1:3.5:0.5:1 atomic ratio) containing 50% Al O pro-
duced from aluminum hydroxide dry gel precursor (this considered
as a base catalyst).
samples used in the present study were determined by using Quan-
tachrome Nova Station adsorption equipment at liquid nitrogen
temperature after out gassing the samples at 200 C under the flow
2
3
◦
Step-1: 3.81 g of ammonium metavanadate was dissolved in
0.0 cm of hot (80 C) deionized water and followed by the addi-
of N2 for 2 h.
3
◦
9
The X-ray patterns of the samples used in the present study
were obtained on a EQUINOX 1000 inel XRD instrument using Co
K␣ = 1.7902 Å with X-ray source generator settings at 40 kV and
tion of 16.6 g of Sb O to this solution. The resulting slurry was
2
3
refluxed for 17 h under continuous stirring. The color of the mixture
turned to gray-green.
◦
30 mA and real time acquisition for 2ꢀ = 110 . The FTIR analysis of
Step-2: 47.88 g of aluminum hydroxide (dried gel) was added
to 140.0 cm of 10% acetic acid and stirred for 3 h to form a homo-
geneous suspension. The suspension was kept under continuous
stirring for 3 h. No gelling was observed. The pH of the slurry
recorded as 6.0.
calcined AlN, AlH and AlC samples were performed on a Bruker
Vertex 70/70 v FTIR spectrometer using a KBr pellet method.
High angle angular dark field (HAADF)-scanning transmission
microscopy (STEM) and energy dispersive X-ray (EDS) analysis with
focused/parallel beam results of calcined samples were collected on
3