ISSN 0965-5441, Petroleum Chemistry, 2017, Vol. 57, No. 1, pp. 79–84. © Pleiades Publishing, Ltd., 2017.
Published in Russian in Neftekhimiya, 2017, Vol. 57, No. 1, pp. 82–87.
Effect of CO2 on the Oxidation of Cyclohexene by H2O2
Using Co1.5PW12O40 Catalyst1
R. Radman, A. Aouissi*, A. Al Kahtani, and W. Mekhamer
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
*e-mail: aouissed@yahoo.fr
Received February 26, 2016
Abstract⎯Oxidation of cyclohexene by cheap and environmentally friendly oxidants, namely H2O2 and CO2
has been catalyzed by Co1.5PW12O40. It has been found that the main products of the oxidation are 2-cyclo-
hexen-l-one (enone), 2-cyclohexen-l-ol (enol) and 1, 2-cyclohexanediol (diol) with the enone as the major
product. Oxidation by CO2 along with H2O2 remarkably increased the conversion compared to that by CO2
−
and H O separately. This might be due to the fact that CO increases the percarbonate species (
)
HCO4
respon2sible of the oxidation by oxygen transfer, which indicated that the CO2/H2O2 mixture is a useful
reagent system. The decrease of both the selectivity of the enone and epoxide in favor of that of diol at higher
conversions indicated that the diol was formed from the epoxide by consecutive reaction and/or directly from
cyclohexene.
2
2
Keywords: cyclohexene oxidation, carbon dioxide, hydrogen peroxide, Polyoxometalates
DOI: 10.1134/S0965544117010108
major and minor products, respectively [14]. More-
over, the industrial production of cyclohexanone and
cyclohexanol (K/A) mixture used in the manufacture
of nylon is achieved by oxidation of cyclohexane using
cobalt naphthenate salt catalyst [15]. Another type of
catalysts that have also shown high catalytic activities
in oxidation reactions are heteropolyoxometalates.
They are finding potential applications in the synthe-
sis of various chemicals, particularly in acid and mild
oxidation reactions [16, 17] thanks to an appropriate
selection of their counter cations or addenda [18, 19].
Thus it would be interesting to investigate a catalyst
possessing advantages of HP As as well as Co. Herein
we report the oxidation of cyclohexene by CO2/H2O2
in acetonitrile solvent. The reaction was catalyzed by
Co1.5PW12O40 · 13H2O, abbreviated as Co1.5PW12O40.
The effect of temperature, time, weight of catalyst and
H2O2 concentration on the conversion and the selec-
tivity was investigated.
Oxidation of olefins into added value oxygenated
compounds such as alcohols, epoxides, ketones, alde-
hydes and carboxylic acids is an important process for
chemical industries. Among olefins oxidation, that of
cyclohexene is still the subject of extensive investiga-
tions because the resulting products (e.g., 2-cyclo-
hexen-l-one, 2-cyclohexen-l-ol, epoxide, etc.) are
used as potential intermediates in the synthesis of high
value chemicals [1–4] and as main monomers in the
synthesis of various polymers materials [5]. The
2-cyclohexen-l-one (α,β-unsaturated ketone) which
can be obtained by allylic oxidation of cyclohexene has
received much attention because α,β-unsaturated
ketones are considered as important intermediates in
organic synthesis owing to the presence of a highly
reactive carbonyl group, widely utilized in cycloaddi-
tion reactions [6, 7]. That is why efficient catalysts for
its production is still the subject of extensive investiga-
tions [8–12]. Cobalt based catalysts are among the
catalysts that have shown high catalytic activities in
oxidation reactions. Y. Li et al. [13] reported that that
the addition of Со(ОАс)2 as a cocatalyst enhanced sig-
nificantly the oxidation of cyclohexene. Satokawa et
al. reported that Co(II) complexe of 2-pyrazine car-
boxylic acid encapsulated in the Y-zeolite showed
higher conversion of cyclohexene, and oxidation
occurs mainly at the allylic site, giving rise to 2-cyclo-
hexen-l-one (51%) and 1,2-epoxycyclohexane as the
EXPERIMENTAL
Catalysts Preparation
The H3PW12O40 acid was prepared according to the
method of Deltcheff et al. [20]. Co1.5PW12O40 was pre-
pared from H3PW12O40 by adding slowly the required
amount of Ba(OH)2 · 8H2O (to neutralize the three
protons) to the aqueous solution of the heteropolya-
cid, then the required amount of CoSO4 · 7H2O was
added. After eliminating the formed BaSO4 partici-
1
The article is published in the original.
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