S. Ganesh Babu et al.
the catalysts could be separated from the products and
recycled.
were done on 200 kV Hitachi transmission electron
microscope. Product analyses were done using Shimadzu-
2010 gas chromatograph. Thermal stability of the catalyst
was examined using EXSTAR6200 TG/DTA analyzer.
Present-day interest in the chemistry of RuO2 nanoparti-
cles (RuO2NPs) is primarily due to the existing or possible
applications of the material in advanced technologies. It is an
attractive metallic oxide for electrochemical, catalytic and
electronic applications [38]. Chemistry of RuO2NPs is more
multifaceted than that of many other metal oxide nanopar-
ticles. The reason is very simple; ruthenium easily changes
its oxidation number depending on the experimental condi-
tions [39]. RuO2/V2O5–Al2O3 has been found to be an
effective catalyst for the oxidation of cyclohexane [40]. But
this system necessitated either H2O2 or t-BuOOH to intro-
duce oxygen functionality in alkanes. RuO2NPs were suc-
cessfully decorated over CNT and used as an effective
catalyst for the aerobic oxidation of primary alcohols [41].
Yu et al. [42] studied the deactivation of RuO2ÁxH2O/CNT
nanocatalyst during the aerobic oxidation of benzyl alcohols
and also suggested a route to regenerate the active catalyst.
Faujasite zeolite can also be used as a rigid support for
RuO2NPs to carry out aerobic oxidation of alcohols [43]. All
these aerobic oxidation methodologies were effective but
required continuous blow of molecular oxygen. Aerial oxi-
dation of alcohols is the greener alternate path way to pro-
duce carbonyl compounds from alcohols. Very recently,
RuO2NPs–graphene was utilized as a recoverable nanocat-
alyst for the aerial oxidation of alcohols [44]. This system is
also restricted from economic point of view, because of the
usage of costly graphene nanosheets. Hence, we herein
report a cheap, efficient, reusable and heterogeneous RuO2/
V2O5 catalyst for the aerial oxidation of aromatic, aliphatic
and alicyclic alcohols.
2.2 Preparation of RuO2/V2O5 Catalyst
Dry synthesis method was adopted to prepare RuO2/V2O5.
Ru(acac)3 (60 mg) was grinded with commercial V2O5
(3 g) powder using a mortar and pestle for half an hour.
Then it was calcinated at 600 °C for 6 h to get RuO2/V2O5.
Calcined sample was cooled to room temperature under N2
atmosphere.
2.3 Aerial Oxidation of Alcohol
In a typical procedure, RuO2/V2O5 (5 mg, 0.36 mol%) and
1-phenylethanol (138 lL, 1 mol) were added to 4 mL of
toluene and stirred for 4 h at 110 °C. Afterwards the cat-
alyst was separated by centrifugation. The centrifugate was
analysed by GC. The crude product was purified by column
chromatography with n-hexane:ethanol (4:1) mixture as an
eluant to give acetophenone. The used catalyst was washed
with diethyl ether and then reused.
2.4 Product Analysis
Gas chromatograph is equipped with 5 % diphenyl and
95 % dimethyl siloxane, Restek-5 capillary column (60 m
length, 0.32 mm dia) and a flame ionization detector (FID).
The initial column temperature was increased from 60 to
150 °C at the rate of 10 °C/min and then to 220 °C at the
rate of 40 °C/min. N2 was used as a carrier gas. The
temperatures of the injection port and FID were kept
constant at 150 and 250 °C, respectively during product
analysis. Authentic samples of both reactant and product
were used to verify the retention times and to confirm the
product formation.
2 Experimental
2.1 Materials and Methods
Ru(acac)3 was prepared by following a literature procedure
[45]. All the reagents used were of chemically pure and
analar grade. Commercial grade solvents were distilled
according to standard procedures and dried over molecular
sieves before use.
3 Results and Discussion
3.1 Dry Synthesis of RuO2/V2O5 Nanocatalyst
To understand the crystalline nature of the proposed
nanocatalyst, XRD pattern was recorded using Xpert
PROPANalytical X-ray powder diffractometer with Cu
Ru(acac)3 was mixed thoroughly with V2O5 and the mix-
ture was calcinated at 600 °C to achieve RuO2/V2O5 nan-
ocatalyst. Then it was characterized by XRD, FT-IR, TG/
DTA, SEM–EDS and TEM analyses.
˚
anode (Cu Ka radiation k = 1.54186 A) in the range of
20° B 2h B 80° at 30 kV. FT-IR spectra were recorded on
a Spectrum RXI Perkin Elmer spectrophotometer with KBr
pellets. Hitachi S-3700 N SEM–EDS instrument with an
accelerating voltage of 20 kV was used to investigate the
surface morphology of RuO2/V2O5 and also to determine
the weight percentage of Ru in the catalyst. TEM studies
3.2 Characterization of RuO2/V2O5
Ru(acac)3, V2O5 and RuO2/V2O5 were characterized by
XRD and the results are given in Fig. 1. The peaks
123