Catalytic conversion of 4-tert-butylphenol in hydrogen peroxide solutions in the presence of titanium oxide compounds and titanosilicates

Article abstract of DOI:10.1134/S0965544117050115

The catalytic conversion of 4-tert-butylphenol (TBP) in hydrogen peroxide solutions in the presence of titanium oxide samples with different phase compositions and crystalline and amorphous titanosilicate samples has been studied. It has been shown that microporous crystalline titanosilicate TS-1 exhibits low activity in the TBP conversion owing to steric restrictions to the diffusion of the substrate molecules to catalytically active sites. The samples of titanium oxide compounds and mesoporous titanosilicates exhibit similar activity, while the selectivity of the latter for 4-tert-butylcatechol (TBC) is higher. The effect of the mesoporous titanosilicate concentration in the reaction mixture and the test temperature and duration on the TBP conversion and the TBC selectivity has been determined.

Full text of DOI:10.1134/S0965544117050115

ISSN 0965-5441, Petroleum Chemistry, 2017, Vol. 57, No. 5, pp. 395–402. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © R.R. Talipova, R.U. Kharrasov, V.A. Veklov, A.D. Badikova, B.I. Kutepov, 2017, published in Neftekhimiya, 2017, Vol. 57, No. 3, pp. 284–291.
Catalytic Conversion of 4-tert-Butylphenol in Hydrogen Peroxide
Solutions in the Presence of Titanium Oxide Compounds
and Titanosilicates
a
a
a
b
a,
R. R. Talipova , R. U. Kharrasov , V. A. Veklov , A. D. Badikova , and B. I. Kutepov *
a
Institute of Petroleum Chemistry and Catalysis, Russian Academy of Sciences, Ufa, Bashkortostan, Russia
b
Bashkir State University, Ufa, Bashkortostan, Russia
*
e-mail: kutepoff@inbox.ru
Received October 4, 2016
Abstract⎯ The catalytic conversion of 4-tert-butylphenol (TBP) in hydrogen peroxide solutions in the pres-
ence of titanium oxide samples with different phase compositions and crystalline and amorphous titanosili-
cate samples has been studied. It has been shown that microporous crystalline titanosilicate TS-1 exhibits low
activity in the TBP conversion owing to steric restrictions to the diffusion of the substrate molecules to cata-
lytically active sites. The samples of titanium oxide compounds and mesoporous titanosilicates exhibit similar
activity, while the selectivity of the latter for 4-tert-butylcatechol (TBC) is higher. The effect of the meso-
porous titanosilicate concentration in the reaction mixture and the test temperature and duration on the TBP
conversion and the TBC selectivity has been determined.
Keywords: tert-butylphenol, titanium oxide compounds, titanosilicates, hydrogen peroxide
DOI: 10.1134/S0965544117050115
4
-tert-Butylcatechol (TBC) is commonly used as only one commercially used— is titanosilicate TS-1
an inhibitor of polymerization of diene hydrocar- [5, 6], which is a crystalline microporous material with
bons; a stabilizer for polymer materials, unsaturated a ZSM-5 zeolite structure, in which a portion of the
aldehydes, and synthetic ethyl cellulose resins; and silicon atoms in the lattice is isomorphically replaced
an oxidation retarder of animal fats, oils, and waxes by titanium atoms. However, it can be assumed that,
[
1–4].
The currently available TBC synthesis techniques
owing to steric restrictions, this catalyst will be inef-
fective for bulky TBP molecules.
This study is focused on the TBP oxidation with
hydrogen peroxide solutions in the presence of crystal-
line and amorphous titanosilicates and titanium
oxides with different phase compositions and pore
structure characteristics.
are based on the alkylation of catechol with olefins or
alcohols in the presence of inorganic acids (mostly
sulfuric acid). The commercial TBC synthesis process
consists of two stages: the alkaline melting of o-chlo-
rophenol or o-phenylsulfonic acid to produce pyrocat-
echol and the alkylation of the resulting pyrocatechol
with isobutyl alcohol over a KU-2 cation-exchange
resin. The process has the following disadvantages: the
formation of di- and trialkyl derivatives of pyrocate-
chol; the formation of undesired effluent water, and a
complex production technology [3, 4].
EXPERIMENTAL
We studied TBP conversion in the presence of tita-
nium oxide samples with different phase compositions
and samples of amorphous mesoporous and crystal-
line microporous titanosilicates. Samples of TiO ⋅
2
The selective oxidation of 4-tert-butylphenol
1
00
250
350
450
nH O, designated as TiO , TiO , TiO2 , TiO2
,
(
TBP) with H O solutions in the presence of titanos-
2
2
2
2
2
5
50
ilicate catalysts can become an alternative procedure
for the production of TBPC. However, there are no
literature data concerning this issue.
and TiO2 , were prepared by the hydrolysis of TiCl4
followed by calcining at 100–550°C. The samples of
amorphous mesoporous titanosilicate catalysts (TSm
To date, the best heterogeneous catalyst for the liq- set) and a SiO sample were synthesized by the sol–gel
2
uid-phase oxidation of various organic substrates with method using ethylsilicate-40 (commercially available
an aqueous solution of hydrogen peroxide—and the mixture of oligomeric oligoethoxysiloxanes; Specifi-
395

3
96
TALIPOVA et al.
The decomposition of the hydrogen peroxide solu-
cations TU 2435-427-05763441-2004) and TiCl alco-
4
hol solutions [7, 8]. The TS-1 crystalline titanosilicate tion was run using the above laboratory setup. In most
sample containing 1.9 wt % titanium was synthesized as of the tests, the decomposition of hydrogen peroxide
described in [5].
contained in the water–acetonitrile solution (initial
H O concentration of 0.24 mol/L) was studied. In
2
2
The composition of the synthesized samples was
determined on a Shimadzu EDX-800HS energy dis-
persive X-ray fluorescence spectrometer (rhodium
anode, 15–50 kV, 20–1000 μA, under vacuum, a col-
addition, acetonitrile in some tests was replaced by an
identical amount of water, while the H O concentra-
2
2
tion remained unchanged. The tests were conducted
limator of 3–5 mm). The phase composition of the in the presence of the catalyst in an amount of 10% of
samples was determined using a DRON-4-07 X-ray the weight of the reaction mixture at 35°C for 20 min.
diffractometer (MoK , 35 kV, 30 mA, a scanning step The residual H O content in the sample was deter-
α
2
2
of 0.02°, an exposure time of 5 s). The incorporation mined by iodometric titration.
of titanium atoms into the silicate framework was esti-
mated using an Advance Bruker Vertex 70V FTIR
–1
spectrometer (KBr, 4000–400 cm ). Pore structure
characteristics were determined by low-temperature
nitrogen adsorption–desorption (77 K) using a
Micromeritics ASAP-2020 sorption meter.
RESULTS AND DISCUSSION
1
00
According to XRD, the TiO sample is hydrated
2
250
titania. The TiO2
sample is X-ray amorphous,
The tests were conducted using a laboratory setup
comprising an isothermal batch reactor equipped with
a stirrer (200 rpm), a reflux condenser, and a ther-
mometer. Five milliliters of acetonitrile, 0.09 g of
350
450
550
whereas the TiO2 , TiO2 , and TiO2 samples are
anatase.
The XRD pattern of the TS-1 counterpart exhibits
TBP, and a calculated amount of the catalyst (0.10– reflections characteristic of microporous crystalline
0
.66 g) were charged into the reactor and subjected to
titanosilicate [11].
thermal conditioning to a given temperature with stir-
All the titanosilicates samples (TSm set) prepared
by the sol–gel synthesis are amorphous.
ring; after that, a required amount of a 35% H O
2
2
aqueous solution (0.12–0.36 mL) was added into the
reactor; this instant was taken as the reaction start
time. The feed TBP concentration was 0.12 mol/L; the
ratio of the initial TBP and H O molar concentrations
The IR spectra of TS-1 and the TSm samples
–1
exhibit an absorption band at ~960 cm , which indi-
2
2
cates the formation of a Ti–O–Si bond [12].
0
0
C
(
С
was 1/2 or 1/6. The tests were con-
TBP
H O
2
2
)
The pore structure characteristics of the samples
tested as catalysts in TBP oxidation with aqueous
H O solutions are shown in Table 1. All the synthe-
ducted at 35, 50, and 75°C in the presence of the cat-
alyst in an amount of 2.5–15.0% of the weight of the
reaction mixture. The test duration was 20–60 min.
2
2
The catalyst fraction of 80–100 μm was used. Prelim- sized TSm titanosilicates have a mesoporous structure
inary tests showed that under these conditions, the with an extremely narrow pore size distribution.
reaction occurs in the kinetic region. The resulting
The data in Table 1 show that an increase in the Ti
reaction mixture was separated from the catalyst by fil-
content in the amorphous mesoporous titanosilicates
tering; the residual H O content in the sample was
2
2
leads to a slight decrease in the specific surface area
and total pore volume. The authors of [13] attribute
this change in the pore structure characteristics to the
fact that, with an increase in the Ti content in a titano-
silicate, a portion of Ti can exist in the form of a sepa-
determined by iodometric titration [9]. To remove
high-molecular-weight products of the oxidative con-
densation of TBP, the reaction mixture was passed
through a column packed with a silica gel (100–
2
00 μm fraction) and then analyzed by HPLC on an
HP 1050 chromatograph (reversed-phase column, rate oxide phase, which leads to changes in the pore
K20050133;
phase,
Zorbax
C18;
eluent, structure.
7
0CH CN/30H O + 0.01CH COOH; eluent flow
3
2
3
According to the current concepts [14, 15], the oxi-
dation of organic compounds with aqueous solutions
of H O in the presence of titanosilicate catalysts
rate, 0.7 mL/min; pressure, 60 bar; UV detector; λ =
2
75 nm). The reaction mixture composition was cal-
culated with allowance for calibration coefficients.
Biphenyl was used as an internal standard. The ele-
2
2
occurs on their surface through the reaction of the oxi-
mental composition of the high-molecular-weight dizing agent molecules with the titanium atoms to
products of the oxidative condensation of TBP was form three stable types of titanium hydroperoxo com-
determined as described in [10].
plexes:
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CATALYTIC CONVERSION OF 4-tert-BUTYLPHENOL
397
H
H
H
H O
O
H O
Ti
O
O
O
O
O
OH2
O
+H2O2
H
OH2
O
Ti
Ti
Ti
O
O
O
O
O
O
H
Si
H
Si
Si
H
Si
O O O
Si
H
Si
Si
Si
O O O
O
O
O
O
O
O
O
O
O
O O O
O
O
O
O
O O
O
O
O O
O
O
O O
1
2
2
Ti(µ -OOH) (I)
Ti(µ -OOH) (II)
Ti(µ -O ) (III)
2
1
The subsequent reaction of the Ti(μ -OOH) and ence of the samples calcined at 350–550°C. Hence,
2
the amorphous–anatase phase transition in TiO leads
2
Ti(μ -OOH) titanium hydroperoxo complexes with
the substrate molecules leads to the selective oxidation to an increase in the concentration of sites exhibiting
of the organic compounds. In addition, oxidation- catalytic activity in hydrogen peroxide decomposition.
active complexes I and II are also involved in the oxi-
It should be noted that the amorphous and crystal-
2
dative decomposition of H O , whereas the Ti(μ -O ) line titanosilicate samples containing the same
2
2
2
oxo complex is inactive in the oxidation of either H O
or organic substrates [16].
amount of titanium (1.9 wt % Ti) provided different
X H2O2 and AH2O2 values (Table 2). In the presence of
crystalline titanosilicate TS-1, these parameters are
2
2
Therefore, the activity of the samples listed in
Table 1 in the H O decomposition was studied first. It
2
lower (7% and 0.6 μmol H O /m ) than the values
2
2
2
2
obtained in the presence of amorphous TSm-2 (19%
was found that H O does not undergo decomposition
2
2
2
and 1.1 μmol H O /m ). An increase in the Ti content
2
2
in the presence of the SiO sample. This result con-
2
in the amorphous TSm samples from 1.0 to 3.7 wt %
firms the fact that titanium-containing sites are
responsible for the activation and decomposition of
H O . Table 2 shows the results of studying the H O
leads to an increase in the X H2O2 and A
14 to 27% and from 0.8 to 1.7 μmol/m , respectively.
values from
H2O2
2
2
2
2
2
decomposition in the presence of the synthesized tita-
According to published data [17], the Ti(IV) atoms,
nium-containing samples. It is evident that, in the which partially replace silicon atoms in the silicon–
presence of TiO samples calcined at different tem- oxygen matrix of crystalline titanosilicate TS-1 and
2
are in the tetrahedral environment of –SiO groups, are
less active in Н О decomposition than the Ti species
peratures, the highest H O conversion (X
= 72%)
2
2
2
H O
2
2
2
2
50
is exhibited by the TiO2 sample, which is character-
present in titanium oxide (Ti–OН, Ti–O(Н)–Ti).
2
ized by the highest specific surface area (230 m /g). At
Our results confirm this conclusion.
the same time, the amount of H O converted per
2
2
At the condensation stage of the synthesis of amor-
square meter of surface (AH2O2 ) is higher in the pres- phous titanosilicates, the interaction of the hydroxyl
Table 1. Pore structure characteristics of the synthesized samples
Specific surface area
Mesopore volume,
Micropore volume,
Sample
SiO2
С(Ti), wt %
2
3
3
(
BET), m /g
cm /g
cm /g
0
557
35
0.99
0
0.03
0
1
00
59.9
59.9
59.9
59.9
59.9
TiO
2
2
2
50
50
50
50
230
90
59
0.27
0.27
0.27
0.26
0.07
0.02
0.02
0.02
TiO
TiO
TiO
TiO
3
2
4
2
5
2
50
TS-1
1.9
1.0
1.9
3.7
360
560
505
495
–
0.21
0.04
0.05
0.05
ТSm-1
ТSm-2
ТSm-3
0.99
0.92
0.89
PETROLEUM CHEMISTRY Vol. 57 No. 5 2017

3
98
Table 2. Catalytic properties of titanium-containing materials in H O decomposition (10 wt % catalyst,C = 0.24 mol/L,
H2O2
TALIPOVA et al.
2
2
CCH3CN = 19 mol/L, 35°C, 20 min)
AH2O2, μmol/m2
Sample
С(Ti), wt %
X H2O2, %
1
00
59.9
59.9
59.9
59.9
59.9
67
72
54
41
43
57.4
9.3
TiO
2
2
2
50
50
50
50
TiO
TiO
TiO
TiO
3
2
18.0
20.8
25.8
4
2
5
2
TS-1
1.9
1.0
1.9
3.7
7
14
19
27
0.6
0.8
1.1
1.7
ТSm-1
ТSm-2
ТSm-3
groups of the metal complexes with the hydroxyl samples and, accordingly, the catalytic properties of
groups of the silicon complexes can lead to the incor- the samples.
poration of Ti atoms into the silica matrix resulting in
Figure 1 shows the effect of replacement of aceto-
the partial substitution of silicon atoms in the silicon–
nitrile by the same amount of water on the H O con-
2
2
oxygen tetrahedra and the formation of a Ti–O–Si
5
50
bond. At the same time, titanium complexes can pre- version in the presence of the TiO , TSm-2, and
2
cipitate in the form of a highly dispersed crystalline TS-1 samples. It is evident that the H O conversion
2
2
hydroxide phase; after heat treatment, in the form of in an acetonitrile–water solution is lower than that in
an oxide phase with surface sites exhibiting activity in an aqueous solution. It can be assumed that CH CN
3
hydrogen peroxide decomposition. Apparently, an molecules have a higher polarity (η = 3.5 D) than that
increase in the Ti concentration in the TSm samples of water molecules (η = 1.8 D) and undergo a more
leads to an increase in the TiO phase content and, as severe competition with H O molecules (η = 2.1 D)
2
2
2
a consequence, an increase in their activity in hydro- for the titanium-containing adsorption sites on the
gen peroxide decomposition. Thus, by varying the catalyst surface.
synthesis conditions and Ti content, it is possible to
As noted above, the oxidative conversion of TBP in
control the state of titanium atoms in titanosilicate
acetonitrile–water solutions of H O in the presence
2
2
of titanium catalysts has not been described in the lit-
erature; therefore, in the preliminary tests, we have
shown that TBP and H O do not undergo conversion
X H O , %
2
2
2
2
50
40
30
20
2
in the absence of a catalyst. It should be noted that, in
the absence of hydrogen peroxide, TBP does not
undergo conversion over any of the tested catalyst
samples. The composition of the gas phase (air or
nitrogen) has no effect on the TBP conversion and the
reaction product composition. Thus, to provide the
oxidative conversion of TBP under the studied condi-
tions, it is necessary to provide the simultaneous pres-
ence of a catalyst and H O in the reactor.
1
2
1
2
2
2
Table 3 shows the results of studying the oxidative
conversion of TBP in the presence of titanium oxide
compounds with the different phase composition. It is
evident that, in the presence of H O , all the tested
1
0
1
0
2
2
TiO2
TSm-2
TS-1
oxides mediate the TBP conversion. In the presence of
1
00
the hydrated titanium oxide sample (TiO ), an
2
Fig. 1. Effect of solvent on the H O conversion: (1) ace-
2
2
increase in the test duration from 20 to 60 min leads to
tonitrile + water and (2) water (10 wt % catalyst, C 0
=
an increase in the TBP conversion from 39 to 57 mol %.
H2O2
0.24 mol/L, 5 mL of the solvent, 35°C, 20 min).
With a change in the CTBP СH2O2 ratio from 1/2 to 1/6
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CATALYTIC CONVERSION OF 4-tert-BUTYLPHENOL
399
Table 3. Catalytic conversion of TBP in the presence of TiO samples with different phase compositions (10 wt % catalyst,
2
0
C
= 0.12 mol/L, СCH3CN = 19 mol/L, 75°C)
TBP
Sample
τ, min
CTBP
С
XTBP, mol %
X H2O2, mol %
STBC, mol %
STBPE, mol %
2
H O
2
20
20
60
20
without H O2
0
39
57
58
–
0
2
2
2
0
70
65
80
2
1/2
1/2
1/6
92
93
85
1
00
TiO
2
2
50
60
60
60
60
1/2
1/2
1/2
1/2
67
30
28
30
98
97
97
94
5
19
20
19
37
3.5
0.5
0
TiO2
3
2
50
50
50
TiO
4
TiO2
5
2
TiO
in favor of H O , the TBP conversion also increases—
Calculations show that the degrees of conversion of
H O listed in Table 3 are significantly higher than the
2 2
values required for providing the oxidation conversion
of TBP. Hence, the decomposition of the oxidizing
agent molecules into water and oxygen molecules
simultaneously occurs.
2
2
from 39 to 58 mol %—at the same test duration. In
these tests, the H O conversion is 85–93%.
2
2
It should be noted that the main product of TBP
1
00
conversion in the presence of the hydrated (TiO
)
2
2
50
The results suggest that the successive switching
from hydrated to amorphous titanium oxide and then
to anatase leads to the transformation of the catalyti-
cally active surface sites of these materials, which
results in a change in their catalytic activity in TBP
and amorphous (TiO2 ) forms of titanium oxide is
di-4-tert-butylphenyl ether (TBPE). The highest
TBPE selectivity is 80 mol %, whereas the TBPC
selectivity does not exceed 2 mol %. In addition, high-
molecular-weight products of the oxidative condensa-
tion of TBP are formed (chromane, chromene, and
conversion in acetonitrile–water solutions of H O .
2
2
flavone derivatives (resins)). Their elemental compo- However, in general, most of the resulting sites are cat-
sition corresponds to the formula CH
O
; the alytically active in the oxidative condensation of TBP
.0–2.4 0.6–0.8
2
and the hydrogen peroxide decomposition. In this
case, the selectivity for TBPE and resins can achieve
selectivity for these products varies in the range of 18–
1 mol %.
8
8
0 and 81 mol %, respectively, while the maximum
In the presence of the amorphous titanium oxide
TBC selectivity does not exceed 20 mol %.
2
2
50
sample (TiO ), the TBP conversion is higher than
The results of studying the catalytic properties of
the synthesized titanosilicate samples in the oxidative
conversion of TBP in acetonitrile–water solutions of
1
00
that in the presence of the TiO sample under com-
2
parable conditions; this finding is apparently
H O are shown in Fig. 2. It is evident that, in the pres-
attributed to the larger specific surface area of the for-
2
2
mer (Table 1). At the same time, the TBPE ence of the TS-1 sample, the TBP conversion does not
selectivity (S
) is significantly lower: it does not exceed 3 mol %. The low activity of the crystalline
TBPE
microporous titanosilicate in TBP conversion is
attributed to steric restrictions to the diffusion of the
TBP molecules to catalytically active sites. The sites
remain accessible to significantly smaller H O mole-
exceed 37 mol %; the main TBP conversion product is
resins.
Under the same test conditions, in the presence of
the anatase samples, the TBP conversion decreases to
2
2
cules, as evidenced by the extremely high conversion
of the oxidizing agent owing to the decomposition of it
in the pores of the TS-1 sample.
2
8–30%. In this case, S
is even lower than the
TBPE
value provided by amorphous TiO ; in the presence of
2
5
50
the TiO sample, no ether was detected in the reac-
In the presence of sample TSm-2, the TBP conver-
2
tion products. In the presence of the TiO samples sion under the conditions shown in Fig. 2 is 55 mol %.
2
after heat treatment in a temperature range of 350– It should be noted that TBPE is not produced in the
5
50°C, the selectivity for TBC, hydroquinone, presence of the TSm samples. The TBC selectivity is
and quinone does not exceed 20, 1, and 3 mol %, 44 mol %. The TBP conversion products also com-
respectively. The main TBP conversion product is also prise resins. However, the resin selectivity is lower
resins.
than that in the presence of the anatase samples at the
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4
00
TALIPOVA et al.
XTBP, mol %
00
(а)
(b)
STBC, mol %
00
1
2
2
2
1
80
60
40
20
0
2
8
0
0
0
0
0
1
1
1
6
4
2
1
TS-1
TSm-1 TSm-2 TSm-3
TSm-1
TSm-2
TSm-3
Fig. 2. (a) Conversion of (1) TBP and (2) H O and (b) TBC selectivity in the presence of titanosilicate samples: 10 wt % catalyst,
2
2
75°C, 1 h.
same degrees of conversion. The contribution of the of titanium oxide compounds with different phase
decomposition of the oxidizing agent molecules into compositions (Table 2).
water and oxygen molecules is also lower.
The results of studying the effect of temperature,
the catalyst content in the reaction mixture, and the
TBP/H O molar ratio on the conversion of TBP and
With an increase in the titanium content from 1.0
to 3.7 wt % (upon switching from the TSm-1 sample
to the TSm-3 sample), the TBP conversion slightly
increases—from 51 to 57 mol %, while the TBC selec-
tivity decreases from 45 to 38 mol %.
2
2
H O and the selectivity for TBC and resins in the
2
2
presence of the TSm-2 sample at varying test duration
are shown in Table 4.
It is evident that, in the presence of 2.5% of titano-
Thus, the TBC selectivity of the synthesized meso- silicate, at 35°C, the conversion of TBP and H O is
porous titanosilicates is higher than that of the samples the lowest (11 and 23 mol %, respectively, within
2
2
Table 4. Effect of reaction temperature and TSm-2 catalyst content on the TBP and H O conversion and the TBC selec-
2
2
tivity (C0 = 0.12 mol/L, CCH3CN = 19 mol/L)
TBP
C , %
T, °C
TBP/H O , mol
τ, min
X
, mol %
2 2
H O
XTBP, mol %
STBC, mol %
cat
2
2
20
60
20
60
20
60
20
60
20
60
20
60
20
60
20
60
10
23
16
35
43
76
22
41
39
79
51
89
58
92
52
79
8
11
9
10
35
16
36
27
42
31
47
38
52
38
43
53
53
39
43
3
5
1/2
2
.5
50
1/2
1/2
1/2
1/2
1/2
16
16
38
15
25
28
38
35
54
36
42
37
46
75
35
10
50
75
1
/2
/4
15
50
1
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CATALYTIC CONVERSION OF 4-tert-BUTYLPHENOL
401
6
0 min). An increase in temperature to 75°C leads to
X, mol %
S, mol %
a more than 3 times increase in the conversion of
TBP and H O (up to 38 and 76 mol %, respectively).
2
2
60
An increase in temperature from 35 to 75°С also leads
to an increase in the TBC selectivity—from 35 to
1
50
2
4
2 mol % within 60 min of reaction—with a respective
4
0
0
increase in the TBP conversion from 11 to 38 mol %.
In the presence of 2.5% of the catalyst, the highest
TBC selectivity is 42 mol % at a TBP conversion of
1
1
3
2
3
8 mol % at 75°C.
20
2
In the presence of 10% catalyst, an increase in tem-
1
0
perature from 35 to 75°C leads to an increase in the
conversion of TBP and H O from 25 to 54 mol % and
0
2
2
Acetonitrile
Acetone
Ethanol
from 41 to 89 mol %, respectively, within 60 min.
Under similar reaction conditions (temperature, dura-
tion), an increase in the catalyst concentration from
Fig. 3. Effect of the solvent type on (1) the TBP conversion
and (2) the TBPC selectivity in the presence of TSm-2
(10 wt % catalyst, C0
2
.5 to 10% results in a significant increase in the yield
of the desired product: the TBC selectivity is higher at
a higher TBP conversion (maximum S value is
= 0.12 mol/L, СH2O2 =
TBP
TBC
0.24 mol/L, 75°C, 60 min).
5
2 mol % at X of 38 mol %).
TBP
An increase in the catalyst concentration from 10 to
OH
OH
1
5% makes it possible to maintain fairly high TBC
selectivity values (53 mol %) at a higher TBP conver-
sion (42 mol %). An increase in the oxidant content
OH
+H O
2
2
(
increase in the TBP/H O molar ratio from 1/2 to
2 2
+
nH O
Resins
2
2
1
/4) leads to a slight increase in the TBP conversion
OH
OH
O
O
(
from 42 to 46 mol %); however, the TBC selectivity
+H2O2
significantly decreases (from 53 to 43 mol %) in that
case.
+
It is known [14] that the use of a polar solvent is
favorable for decreasing the degree of homolytic
decomposition of H O , which leads to the formation
TBP oxidation with aqueous solutions of hydrogen perox-
ide in the presence of titanosilicates.
2
2
of radical oxo intermediates and is responsible for
nonselective oxidation. In addition, by analogy with
phenol oxidation with aqueous H O solutions in the
2
2
The study of the effect of the chemical and phase
composition of titanium-containing porous materials
on their catalytic activity in H O decomposition and
presence of TS-1, it can be assumed that the selective
oxidation of TBP to TBC involving titanium hydrop-
eroxo complexes also occurs by the mechanism of
electrophilic substitution, for which the use of the fol-
2
2
TBP oxidation in acetonitrile–water solutions has
lowing solvents was proposed: water, methanol, etha- shown that mesoporous titanosilicates containing
nol, acetic acid, acetone, acetonitrile, DMSO, DMF, 1.0–3.7 wt % Ti are not inferior in activity and supe-
nitromethane, and sulfolane [18]. Figure 3 shows the
results of studying the TBP oxidation with aqueous
solutions of H O in the presence of TSm-2 in differ-
rior in TBC selectivity to titanium oxide compounds.
It has been found that under the test conditions, the
maximum TBC selectivity does not exceed 53 mol %;
it is achieved in the presence of 15 wt % mesoporous
titanosilicate (1.9 wt % Ti) at 50°C over 1 h with a TBP
conversion of 42 mol %.
2
2
ent solvents (acetonitrile, acetone, and ethanol). In
acetone and ethanol media, the TBP conversions are
similar, but the TBC selectivity in acetone is higher
than that in ethanol. The highest TBP conversion
(
(
54 mol %) and the highest TBC selectivity
43 mol %) are observed in the case of reaction in an
acetonitrile medium.
ACKNOWLEDGMENTS
In accordance with the experimental data, the fol-
lowing consecutive – parallel scheme of chemical
transformations that occur during the heterogeneous
catalytic oxidation of TBP with aqueous solutions of
This work was supported by the Russian Science
Foundation, DSF grant no. 16-43-02010 “Develop-
ment of New Heterogeneous Catalytic Methods for
H O in the presence of titanosilicate catalysts was the Synthesis of Industrially Important N-Heterocy-
2
2
proposed.
clic Compounds.”
PETROLEUM CHEMISTRY Vol. 57 No. 5 2017

4
02
TALIPOVA et al.
10. A. T. Pilipenko and I. V. Pyatnitskii, Analytical Chemis-
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Translated by M. Timoshinina
PETROLEUM CHEMISTRY
Vol. 57
No. 5
2017