210
VERESHCHAGINA et al.
Table 3. Influence of the molar ratio of the reactants on the conversion of tertꢀbutyl hydroperoxide and the selectivity for
dicyclopentene epoxide
Degree of conversion, %
Selectivity
DCP : TBHP molar ratio
for epoxide, mol %
DCP
TBHP
1 : 1
2 : 1
3 : 1
4 : 1
51.6
40.1
33.0
24.9
53.2
80.6
95.6
99.9
94.6
97.9
99.7
99.6
–3
Temperature, 363 K; solvent, toluene; catalyst: molybdenyl propanediolate,
C
= 1 × 10 mol/L; reaction time is 80 min.
cat
crystalline compounds under standard conditions. In
Selecting the temperature conditions of dicycloꢀ
order to reduce the dicyclopentene recycle or elimiꢀ pentene oxidation, we paid attention to the fact that
nate it altogether, it is reasonable to consider whether the controllable process of Н2О2 thermal decomposiꢀ
the molar excess of dicyclopentene over tertꢀbutyl tion in the presence of sodium tungstate or sodium
hydroperoxide can be lowered to a minimal value phosphotungstate as a catalyst occurs in the range of
(Table 3).
343–373 K [10].
The oxidation with hydrogen peroxide takes place
at a certain pH value of the medium when the nonproꢀ
ductive decomposition of the peroxide is minimal. In
this case, the formation of epoxide does not require
the use of a significant molar excess of the oxidizing
agent. It was found that an increase in the hydrogen
peroxide excess from 2 : 1 to 3 : 1 does not lead to
noticeable increase in the conversion of the hydrocarꢀ
bon or in the selectivity for its epoxide.
When hydrogen peroxide is used as an oxidant in
the heterogeneous system, the ratio of the hydrocarꢀ
bon to the aqueous phase is of great importance. To
achieve high degree of conversion of the substrate
hydrocarbon, the volume of the aqueous phase should
be taken in a twoꢀ to threefold excess over that of the
hydrocarbon phase, and it is this approach that has
been used in the present work.
The simultaneous loading of the components does
not ensure the proper efficiency of the dicyclopentene
oxidation process to give the corresponding epoxide;
therefore, the option of dosed hydrogen peroxide supꢀ
ply into the oxidation reactor was considered. The
implementation of the dosed supply leads to an
improvement in the characteristics of the oxidation
process. The epoxide yield per converted dicyclopenꢀ
tene increases to 97.1% (Table 4). The dosed supply of
hydrogen peroxide suggests that a certain steadyꢀstate
concentration of the peroxide is maintained in the
reaction mixture, which is noticeably below its initial
concentration created upon the simultaneous loading
of the components.
However, the decrease in the oxidant concentraꢀ
tion in the reaction mixture does not affect the rate of
its consumption during dicyclopentene oxidation,
since the reaction of the catalytic decomposition of
hydrogen peroxide is zero order in peroxide [10].
The dicyclopentene oxidation process is especially
The data presented in Table 3 show that such a
decrease in the DCP : TBHP molar ratio from 3 : 1 to
2 : 1 and further to the equimolar value leads to a
growth in the dicyclopentene conversion from 33 to
52%, but no more than that. In addition, the degree of
conversion of TBHP strongly decreases (from 99.9 to
53%) with a decrease in the molar ratio of the reacꢀ
tants. Thus, the use of the reactant mixture with a
dicyclopentene : TBHP molar ratio less than 2 : 1 is
unreasonable.
In connection with this, we turned to alternative
processes for preparing dicyclopentene epoxide.
Aqueous solutions of hydrogen peroxide can be used
to obtain epoxides from unsaturated hydrocarbons.
According to the published data [7–10], the applicaꢀ
tion of hydrogen peroxide as an oxidant is promising
for functionalization of a wide variety of organic comꢀ
pounds with different compositions and structures.
The process with an aqueous hydrogen peroxide
solution as an oxidant proceeds in the heterogeneous
liquid/liquid system, since the unsaturated hydrocarꢀ
bon subjected to oxidation is used as a solution in tolꢀ
uene. To provide the pseudohomogeneity of the sysꢀ
tem, intense stirring and the presence of a phaseꢀ
transfer catalyst are required [11].
The use of hydrogen peroxide as an oxidizing agent
assumes its decomposition with release of active oxyꢀ
gen. It was previously shown [10] that the waterꢀsoluꢀ
ble sodium salts of molybdic, tungstic, phosphotungꢀ
stic, and vanadic acids can be used as a hydrogen perꢀ
oxide decomposition catalyst. However, of these
catalysts providing the effective decomposition of
hydrogen peroxide, only sodium tungstate and phosꢀ
photungstate (Na2WO4, Na2Н5[P(W3O10)4]) catalyze
the substrate oxidation per se. During hydrogen perꢀ
oxide degradation, the anions of these salts form quite
stable peroxyanions which can play the role of carriers
of active oxygen to molecules of the compound to be effective at 368 K to provide a substrate conversion of
oxidized [10, 12].
72.4% with the selectivity for epoxide of 97–98%. The
PETROLEUM CHEMISTRY Vol. 54
No. 3 2014