Direct Hydrogenolysis of Glycerol to Biopropanols over Metal Phosphate Supported Platinum…
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The required amounts of aluminium and phosphorous
precursors(P/Al ratio of 0.9) were dissolved in water under
constant stirring and then acidified with nitric acid. The
pH of the solution was adjusted to 8 by addition of aque-
ous ammonia. After 1 h of continuous stirring, the hydrogel
thus obtained was filtered, washed with distilled water to
remove excess solvent and dried overnight at 110°C fol-
lowed by calcinations in air for 30 min at 500°C.
and the catalysts are hereafter notated as 2Pt/AlP, 2Pt/TiP,
2Pt/ZrP and 2Pt/NbP in the following discussion. In addi-
tion, a series of platinum catalysts supported on TiP with
different platinum loadings (0.5–3 wt%) were prepared by
following the same procedure.
2.2 Catalyst Characterization
Preparation of Titanium Phosphate In a typical hydro-
thermal process [21], Titanium phosphate (TiP) was syn-
and n-butanol to which 30 mL of 0.1 M phosphoric acid
solution was added drop wise and kept under stirring for
2 h at room temperature. The mixture obtained was aged
for 24 hat 80°C in a Teflon-lined autoclave. The product
was then filtered, washed with water, dried at 60°C for 12 h
and finally calcined at 500°C for 2 h.
X-ray diffraction (XRD) analysis of the fresh and used
catalysts were performed in the 2θ range of 2° to 65°, on
Rigaku miniflex X-ray diffractometer at a scan rate of 2°/
min with the beam voltage and a beam current of 30 kV
and 15 mA respectively.
The textural properties such as surface area, pore vol-
ume and pore diameter of the catalysts were analyzed using
N2-adsorption at −196°C by the multipoint BET method
on Autosorb 1(Quantachrome instruments, USA).
Preparation of Zirconium Phosphate Zirconium phos-
phate (ZrP) was prepared by adding 0.01 mol of Zirconium
n-propoxide (70 wt% solution in 1-propanol, Aldrich) to a
solution of 85% phosphoric acid (60 mL of 0.1 mol L−1)
under stirring at room temperature. The mixture obtained
after 2 h of stirring was transferred into a Teflon lined auto-
tered, dried and calcined at 400°C for 5 h [22].
TPD experiments were carried out on AutoChem
2910(Micromeritics, USA) instrument. In a typical experi-
ment, 100 mg of oven dried sample was pretreated by
passage of high purity (99.995%) helium (50 mL/min) at
200°C for 1 h. After pretreatment, the sample was satu-
rated with highly pure anhydrous ammonia (50 mL/min)
with a mixture of 10% NH3–He at 80°C for 1 h and sub-
sequently flushed with He flow (50 mL/min) at 80°C for
30 min to remove physisorbed ammonia. TPD analysis was
carried out from ambient temperature to 600°C at a heating
rate of 10°C/min. The amount of NH3 desorbed was calcu-
lated using GRAMS/32 software.
was synthesized by the procedure reported elsewhere [23].
In a typical procedure, 2.73 g of NbCl5 was dissolved in
50 mL of H2O and 2.30 g of H3PO4 (Aldrich, 85% aque-
ous solution) was added followed by an additional 50 mL
of H2O. The reaction mixture was allowed to stir for 30 min
by maintaining the pH of the solution to 2.60 with aque-
ous ammonia. The resulting slurry was filtered and washed
by deionised water. The obtained gel then was mixed with
10 mL of H2O and 1.45 g of hexadecylamine and stirred
for 30 min. About 0.92 g H3PO4 (85%) was added to the
above solution and the pH was adjusted to 3.88 by add-
ing ammonia solution. The formed slurry was heated in
a Teflon-lined autoclave and aged statically at 110°C for
48 h. The final product was filtered, washed with deionised
water, dried 100°C overnight, and subsequently calcined at
550°C in air for 6 h.
The investigation of nature of acid sites was analyzed
by pyridine adsorption on the catalysts followed by FTIR
experiments. The FTIR spectra of the samples were taken
on the IR (Model: GC-FT-IR Nicolet 670) spectrometer by
KBr disc method under ambient condition.
CO-chemisorption measurements were carried out on
AutoChem 2910 (Micromeritics, USA) instrument. Prior
to adsorption measurements, ca. 100 mg of the sample was
reduced in a flow of hydrogen (50 mL/min) at 400°C for
3 h and flushed out subsequently in a pure helium gas flow
for an hour at 400°C. The sample was subsequently cooled
to ambient temperature in the same He stream. CO uptake
was determined by injecting pulses of 9.96% CO balanced
helium from a calibrated on-line sampling valve into the
helium stream passing over the reduced samples at 400°C.
Platinum surface area, percentage dispersion and Pt aver-
age particle size were calculated assuming the stoichiomet-
ric factor (CO/Pt) as 1. Adsorption was deemed to be com-
plete after three successive runs showed similar peak areas.
2.1.2 Preparation of Supported Platinum Catalysts
The metal phosphate supported platinum catalysts were
prepared by wet impregnation method. An aqueous solution
of H2PtCl6·6H2O was impregnated with required amounts
of different metal phosphates individually under vigor-
ous stirring. After the excess amount of water is lost, the
impregnated sample was allowed to dry overnight at 110°C
and the resulting material was calcined at 450°C for 3 h.
The platinum loading in all the catalysts is fixed to 2 wt%
2.3 Catalyst Testing
The vapour phase hydrogenolysis of glycerol was carried
outin a vertical fixed bed quartz reactor (40 cm length,
1 3