Oxidation of 2,3,6-trimethylphenol on titanium dioxide xerogel by hydrogen peroxide in the absence of an organic solvent

Article abstract of DOI:10.1134/S1070427211090163

Fundamental aspects of the synthesis of 2,3,5-trimethylbenzoquinone by oxidation of 2,3,6-trimethylphenol adsorbed on the surface of a titanium dioxide xerogel and on TiO₂ modified with powdered cellulose with hydrogen peroxide without any organic solvent involved in the process were studied.

Full text of DOI:10.1134/S1070427211090163

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 9, pp. 1555−1559. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.B. Shishmakov, Yu.V. Mikushina, O.V. Koryakova, M.S. Valova, S.Yu. Men’shikov, L.A. Petrov, 2011, published in Zhurnal
Prikladnoi Khimii, 2011, Vol. 84, No. 9, pp. 1505−1509.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Oxidation of 2,3,6-Trimethylphenol on Titanium Dioxide
Xerogel by Hydrogen Peroxide in the Absence
of an Organic Solvent
A. B. Shishmakov, Yu. V. Mikushina, O. V. Koryakova, M. S. Valova,
S. Yu. Men’shikov, and L. A. Petrov
Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia
Received October 11, 2010
Abstract—Fundamental aspects of the synthesis of 2,3,5-trimethylbenzoquinone by oxidation of
2
,3,6-trimethylphenol adsorbed on the surface of a titanium dioxide xerogel and on TiO modified with powdered
2
cellulose with hydrogen peroxide without any organic solvent involved in the process were studied.
DOI: 10.1134/S1070427211090163
The heterogeneous catalytic oxidation of 2,3,6-tri-
methylphenol (TMP) by hydrogen peroxide is of great
practical interest as one of the most ecologically safe
ways to obtain 2,3,5-trimehylbenzoquinone (TMBQ),
which is the main half-product for synthesis of vita-
min E. As catalysts serve aerogels TiO and TiO –SiO
The goal of our study was to assess the possibility
of synthesizing TMBQ by oxidation of TMP adsorbed
on the surface of a TiO xerogel and on TiO –PCe with
2
2
hydrogen peroxide in the absence of an organic solvent.
EXPERIMENTAL
2
2
2
[
1], sol-gels of the TiO –SiO system [2], titanosili-
2 2
cates SBA-15 [3], and commercial silica grafted with
Ti(IV) [4]. The reaction of TMP oxidation into TMBQ
is conventionally performed with an aqueous solution
of hydrogen peroxide in an organic solvent, whose role
is played by alcohols, aldehydes, and carboxylic acids.
The titanium dioxide xerogel was produced by
hydrolysis of a methanolic solution of TBT with
water (TBT : methanol = 1 : 1 v/v). The solution was
hydrolyzed with a triple volume of water at 20°C
under vigorous agitation. The resulting precipitate was
washed on a vacuum-filter until no butanol was found
in washing water. The washed precipitate was dried at
The oxidation of TMP is a heterogeneous process
mostly occurring at the catalyst surface [5], which
suggests that this process can be performed without an
organic solvent. This satisfies the increasingly stringent
requirements to the ecological safety and efficiency
of chemical processes and markedly simplifies the
technology for synthesis of the target product.
1
00°C to constant weight. The specific surface area S
sp
2
–1
of the xerogel was 60 m g .
Powdered cellulose was produced by hydrolysis
of sulfate cellulose from Baikal pulp-and-paper
combine [TU OP (Technical Specification for Nature
Preservation) 13-027 94 88-08–91] in 2.5 N hydrochloric
acid at 100°C. The hydrolysis was performed for 2 h.
The resulting product was washed with distilled water
on a vacuum-filter to neutral pH and dried at 100°C.
We chose a titanium dioxide xerogel and TiO2
modified with powdered cellulose (PCe) as catalysts
for peroxide oxidation. The choice of the TiO –PCe
2
composite was due to previously obtained experimental
data on formation and stabilization of highly dispersed
To obtain a composite material of composition
TiO particles by hydrolysis of tetrabutoxititanium
TiO : PCe = 0.4 : 0.6 (w/w), we dissolved 60 ml of
2
2
(TBT) in the matrix of powdered cellulose [6, 7].
TBT in 60 ml of methanol and added 20 g of PCe to
1
555

1556
SHISHMAKOV et al.
A, %
accuracy of 5%.
IR spectra were recorded with a Perkin–Elmer
Spectrum One IR Fourier spectrometer in the frequency
–
1
range 4000–370 cm for solid powders with a diffuse-
reflection attachment. The band assignment was made
using the data of [8].
The spectral intensitieswere processedandcalculated
using special programs from the software package of the
spectrometer.
The reaction of TMP oxidation was performed
in a thermostated 150-ml reactor (thermostating
temperature 24 ± 0.1°C) equipped with a thermometer
and mechanical stirrer. A 0.25-g portion of TMP
(1.84 mmol) was heated in the reactor to the melting
point (62°C), a weighed portion of the titanium dioxide
xerogel (0.3–0.5 g, 3.8–62.5 mol) or the TiO –PCe
2
composite (0.6–3.5 g, 3.0–17.5 mmol TiO ) was added,
2
and the mixture was agitated. Visually, the sorption
ν, cm–1
interaction of TMP and TiO was accompanied by
2
a change in the xerogel coloration from white to bright
orange.Themixturewasagitatedtoahomogeneousmass
and then 24 ml of a 3.9 M aqueous solution of hydrogen
peroxide was introduced into the reactor at 24°C. The
choice of the H O concentration was governed by the
Fig. 1. IR spectra of TMP sorbed on the TiO xerogel. (A)
2
Absorption and (ν) wave number. (1) TMP; TiO : TMP mass
2
ratio: (2) 1 : 2, (3) 1 : 1, and (4) 1 : 0.5.
A, %
2
2
need to provide a sufficient rate of the oxidation process
of TMP at its minimum desorption from the xerogel
surface under conditions of self-heating of the reaction
mass. The reaction was performed under agitation
with a stirrer rotation speed of 2 rps for 2 h, with the
temperature of the reaction mass measured.
TMP and TMBQ were quantitatively determined
by GLC on a Kristall-2000 M chromatograph with an
MDN-5s capillary column (L = 30 m, d = 0.25 mm) in
the programmed-temperature mode. The flow rate of
the carrier-gas through the capillary column was 1 ml
ν, cm–1
–
1
min . Decane was used as the internal standard.
Fig. 2. IR spectrum of the TiO xerogel. (A) Absorption and
2
To reveal interactions occurring in adsorption of the
(ν) wave number.
substrate onto the TiO surface, we carried out an IR
2
spectroscopic study of the TiO –TMP system.
2
the resulting solution. The mixture was hydrolyzed with
00 ml of water at 20°C under agitation. The precipitate
formed was washed on a vacuum-filter until no butanol
4
An analysis of the IR diffuse-reflection spectra
of TMP (Fig. 1) demonstrated that the absorption at
1578, 1493, and 1468 cm–1 is due to bond vibrations
in the aromatic ring. Stretching vibrations of the C–O
bond and deformation vibrations of the hydroxy group,
δ(OH), appear as absorption bands peaked at 1310 and
was fond in washing water. The washed precipitate
was dried at 100°C to constant weight. The S of the
sp
2
–1
composite was 270.5 m g .
The specific surface area of the samples was
determined by the method of thermal desorption of
nitrogen on a SoftSorbi-II ver. 1.0 instrument with an
–
1
1
241 cm , respectively.
The IR spectrum of the titanium dioxide xerogel
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

OXIDATION OF 2,3,6-TRIMETHYLPHENOL ON TITANIUM DIOXIDE XEROGEL
Fig. 2) contains a high-intensity band in the range
T, °C
1557
(
–1
4
00–900 cm , which can be regarded as a superposition
of vibrations of Ti–O bonds and symbate vibrations
of water. The absorption band peaked at 1633 cm–1
corresponds to deformation vibrations of water. The
broad high-intensity band peaked at 3334 cm–1 is
associated with stretching vibrations of hydroxy groups
and water.
The sorption interaction of TMP with the surface of
the titanium dioxide xerogel results in that the absorption
bands associated with vibrations of not only the hydroxy
group of the sorbate, but also the aromatic ring (Fig. 1).
For example, already at a TiO : TMP ratio of 1 : 2,
2
–
1
there appear a new absorption band peaked at 1400 cm
and an absorption band peaked at 1226 cm on the low-
frequency wing of the band at 1241 cm . The intensity of
both new bands increases with the TiO : TMP ratio, and
there is no absorption band peaked at 1241 cm in the
–
1
–
1
τ, min
2
Fig. 3. Reaction mass temperature T vs. the reaction duration
τ. H O /TiO molar ratio: (1, 6) 1.5, (2, 7) 2.1, (3, 8) 3.1, (4, 9)
–
1
2
2
2
6
.2, and (5) 12.5–25.0. (1–5) In the presence of the substrate,
spectra beginning at TiO : TMP = 1 : 1. In the spectrum
2
(6–9) in the absence of a substrate.
of the sample with TiO : TMP = 1 : 1, the intensity
2
ratio of the absorption bands 1493/1468 changes, with
2
.1–4.1 (H O /TiO = 12.5–25.0) (Fig. 3, straight
2 2 2
–
1
the band at 1493 cm disappearing at TiO : TMP = 1 :
2
line 5), the initial temperature remains unchanged.
Apparently, the active centers of the catalyst are largely
blocked by the adsorbed substrate. The reaction is slow
and the exothermic effect is neutralized by the cooling
0
.5. Beginning at TiO : TMP = 1 : 0.5, the intensity of
2
–
1
the absorption band 1310 cm decreases.
As a result of the interaction between the sorbent
and TMP, the absorption band associated with
of the reactor. An increase in the TiO /TMP ratio leads
2
deformation vibrations of water, δ(H O), is shifted to
not only to a better accessibility of the xerogel surface
to the oxidizing agent, but also to a stronger dispersion
of the substrate in the titanium dioxide matrix, and
just this circumstance intensifies the reaction (Fig. 3,
curves 1–4).
2
–
1
–1
lower frequencies, from 1633 cm (Fig. 2) to 1623 cm
TiO : TMP = 1 : 1) (Fig. 1).
(
2
Thus, our analysis of the IR spectra suggests that an
OH group and the π-electron system of the aromatic ring
of the sorbate are involved in the sorption interaction.
In the case of the xerogel, the sorption activity is
exhibited by its hydroxy-hydrate cover. Similar
results have been obtained previously in a sorption of
The TMBQ formed in the course of the reaction is
partly desorbed from TiO and comes to the surface of
2
the reaction mass, which prevents the reaction product
from further oxidation. The melting point of TMBQ is
32°C; the elevated temperature in the reactor promotes
its desorption from the catalyst surface. This opens up
new active centers for sorption of subsequent portions
of hydrogen peroxide.
2
,3,5-trimethylhydroquinone on a titanium dioxide
xerogel and TiO –PCe composite [6, 9].
2
To determine the dynamics of TMP oxidation
by hydrogen peroxide on a TiO xerogel matrix, we
2
analyzed how the reaction mass temperature depends on
Similar conclusions are applicable in analysis of the
data in Fig. 4, when the TiO –PCe composite is used as
the amount of TiO (Fig. 3).
2
2
the matrix.
The observed exothermic effect (Fig. 3, curves 1–4)
is a sum of two components: (i) exothermic effect
appearing in interaction of hydrogen peroxide with
the xerogel surface (Fig. 3, curves 6–9) and (ii)
increase in temperature due to the reaction of substrate
Using the results presented in Figs. 3 and 4, we
plotted the dependence of the maximum temperature
Tmax to which the reaction mass warms up on the content
of titanium dioxide (Fig. 5).
oxidation. At molar ratios in the range TiO /TMP =
In the given case, Tmax is regarded as an indication
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

1558
SHISHMAKOV et al.
TMP oxidation by hydrogen peroxide on TiO (TiO –PCe)
T, °C
2
2
Selectivity
with respect to
TMBQ
TMP
conversion
Molar ratio
TiO /TMP
H O /TiO
%
2
2
2
2
TiO sample
2
3
2
1
4.0
4.5
6.3
1.5
2.1
99.1
70.7
69.0
69.0
66.9
56.5
58.7
98.3
98.4
98.3
54.3
19.1
3.1
8
4
2
.2
.1
.1
6.2
12.5
25.0
TiO –PCe sample
2
τ, min
9
8
.5
.2
5.4
6.2
98.9
98.9
98.8
98.9
95.8
44.9
43.9
42.3
43.1
40.1
Fig. 4. Reaction mass temperature T vs. the reaction duration τ
on TiO –PCe. H O /TiO molar ratio: (1) 5.4, (2) 6.2, (3) 9.4,
4) 18.7, and (5) 31.2 (in the presence of the substrate); (6) 4.7,
7) 5.9, (8) 9.4, and (9) 18.7 (in the absence of a substrate).
2
2
2
2
(
(
5.4
9.4
2
1
.7
.6
18.7
31.2
a modified sample.
It should be noted that the bulk density of TiO –PCe
2
3
–1
3
–1
is 2.6 cm g , and that of the xerogel, 2.13 cm g .
Consequently, the substrate on the composite is
distributed in a larger volume of the substance, which
makes the catalyst more accessible to an interaction
with H O .
2
2
The table lists results of a chromatographic
analysis of the oxidate after 2 h of the reaction of
TMP oxidation, when, according to the temperature
dependences, the process is nearly complete in
the whole range of TiO /TM and H O /TiO ratios.
2
2
2
2
The TiO /TMP ratio of 16.3–34.0 in the reaction
space provides a ~98% conversion of the substrate at
a selectivity of 69% with respect to the main product.
2
Fig. 5. Maximum temperature Tmax of the reaction mass vs.
the TiO content c. (1, 2) TiO –PCe and (3, 4) TiO . (1, 3)
2
2
2
Reaction in the presence of TMP and (2, 4) without a substrate.
Our experiment demonstrated that TMP deposited
onto the PCE surface is not oxidized by hydrogen
peroxide and the inorganic component is the active
origin in TiO –PCe. In the composite at TiO /TMP
of the intensity of the processes occurring in the reactor.
The exothermic effect starts to be noticeable in the
TMP–TiO –H O system on the composite at a titanium
2
2
2
2
2
dioxide content 3 times lower than that on the TiO2
xerogel. Apparently, this distinction can be attributed
to the higher dispersity of titanium dioxide particles in
ratios of 2.7–9.5, the substrate conversion approached
99%; however, the selectivity with respect to TMBQ
was 40% lower than that in the case of the unmodified
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

OXIDATION OF 2,3,6-TRIMETHYLPHENOL ON TITANIUM DIOXIDE XEROGEL
1559
K, wt %
after the reaction onset (Fig. 6, curve 1), whereas in
the presence of TiO –PCe (curve 2), this time is about
2
6
0 min, which corresponds to the time in which the
maximum in the temperature dependences is reached
Figs. 3 and 4).
(
CONCLUSIONS
It was demonstrated that the reaction of trimethyl-
phenol oxidation by hydrogen peroxide on a TiO xero-
2
gel can be performed without using an organic solvent.
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1
2
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τ, min
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catalyst. Apparently, side processes are more active
in the presence of TiO –PCe. It should be noted that,
2
7
33.
according to IR spectroscopic data, the cellulose matrix
of the composite does not undergo oxidative destruction
under our experimental conditions.
5
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A comparison of chromatographic data with the
temperature dependences we obtained demonstrated
that there is no correlation between Tmax and the yield
of TMBQ at a titanium dioxide content at which the
6
7
. Shishmakov, A.B., Mikushina, Yu.V., Valova, M.S., et al.,
Zh. Prikl. Khim., 2007, vol. 80, no. 12, pp. 2029–2032.
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nanotekhnologiyam, Moskva, 3–5 dekabrya 2008 g. (Int.
Symp. on Nanotechnologies, Moscow, December 3–5,
substrate conversion is the highest (TiO 1.2–5 g, TiO –
2
2
PCe 0.4–1.4 g of TiO2).
2
008), pp. 343–344.
Figure 6 shows curves describing the substrate
consumption in the course of oxidation. The time
dependence of the TMP conversion indicates that
the main amount of TMP (>95%) is consumed in the
presence of a titanium dioxide xerogel during 35 min
8. Bellamy, L.J., The Infra-red Spectra of Complex Molecules,
London: Methuen, 1958.
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011