Catalysis Communications
Short Communication
Selective benzylic oxidation of alkylaromatics over Cu/SBA-15 catalysts
under solvent-free conditions
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Chinna Krishna Prasad Neeli, Anand Narani, Ravi Kumar Marella, Kamaraju Seetha Rama Rao, David Raju Burri
Catalysis Laboratory, Indian institute of Chemical Technology, Hyderabad-500007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
With the purpose of benzylic oxidation of alkylaromatics into corresponding ketones selectively under
solvent-free conditions, cheap, simple and versatile Cu/SBA-15 catalyst system with the Cu loading of 5, 10, 15
and 20% has been prepared by impregnating SBA-15 support. Among Cu/SBA-15 catalysts, 10%Cu/SBA-15
exhibited superior activity and selectivity.
Received 12 March 2013
Received in revised form 27 April 2013
Accepted 29 April 2013
Available online 6 May 2013
© 2013 Elsevier B.V. All rights reserved.
Keywords:
Cu/SBA-15
Benzylic oxidation
Ethylbenzene
Acetophenone
1. Introduction
reports on copper containing heterogeneous catalytic systems, wherein,
moderate conversions and selectivities are obtained [21–25], which are
Ketones and aldehydes are important intermediates in the phar-
maceutical and fine-chemical industries, particularly in the produc-
tion of flavors, fragrances, and biologically active compounds [1].
Benzylic oxidation of alkylaromatics is one of the important methods
for the production of ketones and aldehydes, wherein, potassium per-
manganate and potassium dichromate are the generally used oxi-
dants in stoichiometric or excess quantities [2,3], which leads to
large amount of toxic waste. Development of oxidation methods
using a catalytic amount of metal reagent and an appropriate amount
of oxidant is the subject of interest. With this intention, in the last
decade, various catalytic methods are investigated using metal com-
plexes of Cr, Co, Mn, Rh, Ru, Zn, Fe etc. [4–16]. However, toxicity,
high cost, waste disposal and removal of residual metal from the
product are some of inherent problems still to be resolved. Some of
the above cited problems associated with the homogeneous metal
complex catalysts can be resolved in heterogeneous catalytic systems.
Of late, mesoporous silica materials like MCM-41, TUD-1 and
SBA-15 have attracted considerable attention as promising new hy-
drocarbon oxidation carriers [17]. Benzylic oxidation of ethylbenzene
to acetophenone over Ti/MCM-41, V/MCM-41 and Cr/MCM-41 catalysts
is reported with 12% conversion of ethylbenzene and 83% selectivity of
acetophenone [18]. Recently, SBA-15 supported cobalt catalysts are
reported with different oxidants [19]. In one of our recent report, highly
active SBA-15 supported silver catalysts are reported [20]. There are few
cost ineffective and involvement of carcinogenic solvents.
Herein, a highly efficient and cheap Cu/SBA-15 catalyst system
towards the benzylic oxidation of alkylaromatics into corresponding
ketones under solvent-free conditions is reported.
2. Experimental methods
2.1. Catalyst preparation
SBA-15 support was synthesized according to original report of Zhao
et al. [26] and our previous publications [27–30]. The calcined (at 823 K
for 8 h) SBA-15 support was dried at 423 K for 6 h and impregnated
with the requisite amounts of aqueous Cu(NO3)2.3H2O solution likely
to be around 5, 10, 15, 20 wt.% as Cu metal. Subsequently catalyst sam-
ples were dried at 393 K for 12 h and calcined at 723 K for 6 h, reduced
at 553 K for 3 h in H2 flow and denoted as xCu/SBA-15 where x indi-
cates the percentage (by weight) loading of Cu on SBA-15 support.
2.2. Catalyst characterization
XRD patterns were obtained from Ultima-IV (M/s. Rigaku Corporation,
Japan) diffractometer with a nickel filtered CuKα radiation. The N2
adsorption–desorption isotherms were measured by Quadrasorb-SI
V 5.06 (M/s. Quantachrome Instruments Corporation, USA). TPR ex-
periments were conducted using a home-made TPR system [30].
The XPS analysis was made on a photoelectron spectrometer (KRATOS
Axis 165, Shimadzu, Japan) with Mg Kα radiation (1253.6 eV).
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