Titanium dioxide xerogel modified with powder cellulose in oxidation of trimethylhydroquinone

Article abstract of DOI:10.1134/S1070427207120212

A procedure was developed for modification of titanium dioxide xerogel by addition of powder cellulose in the stage preceding hydrolysis of tetramethoxytitanium. The resulting catalytic systems based on the new material were studied in a model liquid-phase catalytic process of oxidative dehydrogenation of trimethylhydroquinone with atmospheric oxygen.

Full text of DOI:10.1134/S1070427207120212

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 12, pp. 2107 2110.
Original Russian Text A.B. Shishmakov, Yu.V. Mikushina, M.S. Valova, O.V. Koryakova, L.A. Petrov, 2007, published in Zhurnal Prikladnoi Khimii,
007, Vol. 80, No. 12, pp. 2029 2032.
Pleiades Publishing, Ltd., 2007.
2
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Titanium Dioxide Xerogel Modified with Powder Cellulose
in Oxidation of Trimethylhydroquinone
A. B. Shishmakov, Yu. V. Mikushina, M. S. Valova,
O. V. Koryakova, and L. A. Petrov
Institute of Organic Synthesis, Ural Division, Russian Academy of Sciences, Yekaterinburg, Russia
Received May 2, 2007
Abstract A procedure was developed for modification of titanium dioxide xerogel by addition of powder
cellulose in the stage preceding hydrolysis of tetramethoxytitanium. The resulting catalytic systems based
on the new material were studied in a model liquid-phase catalytic process of oxidative dehydrogenation
of trimethylhydroquinone with atmospheric oxygen.
DOI: 10.1134/S1070427207120212
Titanium dioxide is widely used as a sorbent and
solved in 20 ml of methanol. Hydrolysis was per-
formed with 500 ml of water at 20 C. The precipitate
was washed on a filter until the absence of butanol
in the wash water and dried at 100 C.
a catalyst support. The efficiency of its application is
mainly governed by the structural and texture charac-
teristics, development of the surface, and accessibility
of its active centers throughout the entire volume.
To prepare modified xerogels (MXs) with the TiO2 :
PC ratios of 0.45 : 0.55, 0.26 : 0.74, and 0.06 : 0.94,
9-, 3-, and 1.5-ml portions of TBT, respectively, were
dissolved in 20 ml of methanol. To each of these
solutions, 1 g of PC was added. Hydrolysis was per-
formed at 20 C in 500 ml of water with stirring.
The solutions were kept for 10 min and by this time
the major fraction of the precipitate settled. The aque-
ous phase was decanted from the modified TiO2.
The precipitate was treated as described above.
Synthesis of xerogels of element oxides by any
method is accompanied by their shrinkage and, as
a result, by a decrease in the specific surface area
on drying. There are several ways to eliminate this
phenomenon: variation of the composition of disper-
sion medium, drying for longer time, and the use of
special additives [1 9].
The aim of this study was modify titanium dioxide
with powder cellulose (PC) and to study the resulting
materials in a model catalytic process of oxidative
dehydrogenation of trimethylhydroquinone (TMHQ)
with atmospheric oxygen.
The TiO2 and TiO : PC gels of compositions
2
0.31 : 0.69, 0.62 : 0.38, and 0.81 : 019 were prepared
from a solution of 9 ml of TBT in 20 ml of methanol.
Modification was performed by addition of 2, 1, and
0.5 g of PC, respectively, to the solution. Hydro-
lysis was performed in 500 ml of water. The precip-
itate was separated on a filter without preliminary
decantation and washed. After completion of wash-
ing, the paste was placed in a flask filled with 50 ml
of water.
EXPERIMENTAL
Powder cellulose was prepared by hydrolysis of
kraft cellulose produced at the Baikal Paper and Pulp
Plant (Technical Specification OP 13-027 94 88-08
9
1) in 2.5 N hydrochloric acid at 100 C. Hydrolysis
was performed for 2 h. The resulting product was
washed with distilled water on a filter until neutral
pH of the aqueous extract. The product was dried at
The IR spectra of the samples in the form of solid
powders were recorded on a Perkin-Elmer Spectrum
One IR Fourier spectrophotometer in the range 4000
1
00 C.
70 cm 1 using diffuse reflection attachment (DRA).
3
Three samples of titanium dioxide xerogels K1,
K2, and K3 were prepared as follows: 1.5, 3, and 9 ml
of tetrabutoxytitanium (TBT), respectively, was dis-
The sorption of 1,4-hydroquinone (HQ) was performed
by addition of a solution of HQ in methanol into MX
[weight ratio HQ : MX = 1 : (0.25 8)], followed by
2107

2
108
SHISHMAKOV et al.
3
1
drying of the sample at room temperature for 3 days.
The bands were assigned on the basis of reference data
in the C H OH group, and the band at 1035 cm , to
the stretching modes of the primary alcoholic group
in various conformations. In the spectrum of PC in
[
10]. The intensities of the spectra were processed
using the spectrometer software.
1
the range 860 400 cm , there is a broad diffuse ab-
sorption on whose background a series of ill-defined
bands characterizing various vibrations of the pyra-
nose ring and bending modes of hydroxy groups are
observed. The interaction of PC with hydrated tita-
nium dioxide in the modified samples results in vari-
The kinetic experiments were carried out in a tem-
perature-controlled reactor equipped with a reflux
condenser, with stirring of the aqueous-methanol so-
lution (volume ratio water : methanol = 1 : 1) by air
1
bubbling. The air flow rate was 3.1 l h .
ation of the intensities of the absorption bands corre-
1
TMHQ was oxidized at 50 0.2 C. The concentra-
sponding to hydroxy groups (the band
at 2900 cm
as
tion of the substrate was 66, and that of CuCl2 2H O,
was used as an internal reference). The most signif-
icant increase in the intensity (by a factor of 1.2 2) is
observed for the bands at 1159, 1054, and 1035 cm .
Variations in the spectrum of PC increase with
the fraction of the inorganic component in the sample.
Thus, variation of the spectral characteristics of PC
suggests that its hydroxy groups are involved in inter-
2
6
mM.
1
The kinetic measurements were performed by stop-
ping the reaction and determining the content of
the starting substance. The resulting functions of con-
centrations were subjected to polynomial approxima-
tion. The initial reaction rates were found by numeri-
cal differentiation and interpolation. The error in their
determination was no more than 10%. The TMHQ
content was determined by gas-liquid chromatography
on a Chrom-4 chromatograph [11].
particle interaction with TiO via hydrogen bonds.
2
Previously, [15] we have studied the model cata-
lytic liquid-phase oxidation of TMHQ with atmo-
spheric oxygen in the medium of TiO gel:
2
The resulting cellulose-inorganic materials were
studied by IR spectroscopy. The IR spectrum of ti-
tanium dioxide xerogel contains a strong absorp-
tion band peaked at 340 and 560 cm , which can
be regarded as a superposition of vibrations of
OH
O
CH3
CH3
2+
CH3
CH3
Cu , O , TiO
2
2
1
CH3
CH3
OH
O
the Ti O bonds and water librations. In the range
1
1
000 1200 cm , there are three extremely weak
It has been established by ESR spectroscopy [16]
peaks, which can be assigned to bending modes of
the Ti OH groups (1192, 1168, and 1090 cm ).
that, depending on the Cu(II)/TiO ratio, several types
2
1
of Cu(II) compounds are formed in the titanium diox-
ide phase: mono complexes, associates of mono com-
plexes, copper(II) hydroxide, and polynuclear bridged
compounds. The last kind of compounds was the most
reactive.
For modified samples of TiO , there are no changes
2
in the range of vibrations of the Ti O bonds. Weak
peaks corresponding to the Ti OH groups are not ob-
served on the background of the bands of PC. The IR
spectrum of cellulose is mainly determined by ab-
sorption of three hydroxy groups incorporated in
a glucopyranose unit. In the spectrum of PC there
Addition of powder cellulose does not affect the
course and parameters of the catalytic process. Ap-
parently, Cu(II) does not react with PC under the re-
action conditions.
1
are the following absorption bands: 3348 cm , stretch-
ing modes of hydroxy groups; in the range 3000
1
2
800 cm , stretching modes of methylene and
The dependences of the initial rate of TMHQ oxi-
dation on the Cu(II) content of the MX phase for
the samples of various compositions are shown in
Fig. 1. The dependences are nonlinear because of
the formation of various Cu(II) compounds and also
because of limitations imposed by the sorption capaci-
ty of xerogel for Cu2 ions. The maximum observed
in the dependences is caused by the formation of
the most catalytically active Cu(II) species on the sur-
face of titanium dioxide. The number of these com-
pounds increases with the fraction of PC in the sam-
1
methine groups of cellulose; 1640 cm , HOH, bend-
ing modes of water of crystallization. The band at
1
451 cm 1 corresponds to (OH); 1427, to (CH ) +
2
(
CH); 1369, to (CH); 1335, to (OH) (in-plane);
1
1
315, to (CH ) (wagging vibrations); 1281, 1248,
235, and 1203, to (OH) + (CH) [12]. According
2
+
1
to published data [13], the band at 1159 cm corre-
sponds to asymmetric stretching modes of the C O C
bridge; however, in some publications [14] this band
is assigned to the C O stretching or O H bending
modes of the C OH group. The band at 1054 cm 1
is assigned to the stretching modes of the C O bond
ple. The sample of the composition of TiO : PC =
2
0.06 : 0.94 did not affect the reaction due to the small
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 12 2007

TITANIUM DIOXIDE XEROGEL MODIFIED WITH POWDER CELLULOSE
2109
amount of TiO in the weighed portion, whose in-
2
crease hampers stirring of the reaction mixture.
One of the ways to produce gels of element oxides
with various specific surface areas is to vary the con-
centrations of substances being hydrolyzed [17]. How-
ever, these distinctions are lost in the course of drying
to the xerogel state (Fig. 1, curve 1). Modification
of PC allows us to prevent to a certain extent these
undesirable changes.
To elucidate the interactions occurring in the sys-
tem MX substrate, we studied the sorption of hydro-
quinone on MX by IR spectroscopy. The choice of
HQ is caused by its resistance to air, minimal over-
lapping of the spectra of HQ and MX, fairly simple
spectrum of HQ, and higher intensity of its bands,
allowing detection of HQ in the analytical range of
optical densities even at its low content in the system.
Fig. 1. Initial rate of TMHQ oxidation (IOR) vs. the
Cu(II)/MX ratio c in the reaction area. Concentration of
Cu(II) 6 mM; the same for Fig. 3. (1) K1-K3, (2) PC :
TiO = 0.35 : 0.45, and (3) PC : TiO = 0.74 : 26; the same
2
2
for Fig. 3.
The absorption bands of the aromatic ring,
1515
1
and 1470 cm , are manifested fairly clearly in the IR
spectra, and analysis using these bands presents no
problems.
The absorption bands of hydroquinone were as-
signed on the basis of published data [10]. The ab-
sorption bands corresponding to the skeleton vibra-
tions of aromatic rings are manifesed at 517, 1009,
1
1
470, and 1515 cm . The stretching absorption bands
1
of OH groups appear at 3255 cm ; the absorption
bands of C OH group appear at 1240 (C O stretching
modes) and 1210 cm (bending modes).
1
In the spectrum of HQ sorbed on TiO : PC =
.45 : 0.55 at the ratio HQ : MX = 1 : 0.5, we ob-
2
0
served redistribution of the intensities of the absorp-
tion bands corresponding to the skeleton vibrations of
1
the aromatic ring of HQ, 1515 and 1470 cm . At
1
the ratio HQ : MX = 1 : 1, a shoulder at 1500 cm ap-
Fig. 2. Initial rate of TMHQ HCO oxidation (IOR) vs.
the Cu(II)/TiO ratio c in the reaction area. Gel: (1) TiO ,
1
pears in the band at 1514 cm ; at the ratio HQ : MX =
1
1
2
2
1
: 4 the band at 1515 cm is shifted to 1500 cm
(
2) TiO : PC = 0.81 : 0.19, (3) TiO : PC = 0.62 : 0.38,
1
2 2
and the intensity of the band at 1470 cm decreases.
The apparent variation of the intensities of the bands
corresponding to vibrations of the C C bonds of HQ
suggests that the MX surface interacts with the -elec-
tron system of the ring. Analysis of the other bands
of HQ is difficult because of super-position of
the spectra of HQ and PC.
and (4) TiO : PC = 0.31 : 69.
2
The kinetic data recalculated to TiO are presented
2
in Fig. 2. For the samples of MX, the maximum of
copper activity is shifted to higher Cu(II)/TiO ratios
2
as the PC fraction increases, i.e., the most catalytically
active polynuclear Cu(II) compounds in the material
The spectral changes observed are in good agree-
ment with data on sorption of HQ on previously ob-
phase are formed at a lower amount of TiO . This fact
2
is caused by an increase in the specific surface area
of titanium dioxide in MX with increasing PC/TBT
ratio in the stage of hydrolysis.
tained TiO gels [15]. Based on this fact and also
2
on the insensitivity of the homogeneous catalytic
reaction to addition of PC, we can conclude that
the sorption-active component in MX is its inorganic
component.
To elucidate which stage of xerogel formation is in-
fluenced by the modifying additive, it was of interest
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 12 2007

2
110
SHISHMAKOV et al.
2
3
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4
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Fig. 3. Initial rate of TMHQ HCO oxidation (IOR) vs.
the Cu(II)/TiO ratio c in the reaction area.
2
to perform the model reaction with the modified TiO2
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8
9
. Fenelonov, V.B., Tarasova, D.V., and Gavrilov, V.Yu.,
Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk,
1
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i poroshkov (Fluidity of Suspensions and Powders),
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2
+
is shifted to higher Cu /TiO ratios. Thus, the influ-
2
ence of PC goes beyond the stage of drying, but is
manifested even in the stage of gel formation and re-
sults in the formation of more sorption-active TiO2
particles of a smaller size.
1
1
0. Bellamy, L.J., The Infra-Red Spectra of Complex
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1
1
1
1
2. Mam, I. and Marrian, H., Trans. Faraday Soc., 1956,
vol. 52, p. 492.
(1) Samples of titanium dioxide xerogels modified
3. Liang, C.Y. and Marchesssault, R.H., J. Polym. Sci.,
with powder cellulose with various ratios of TiO to
2
1
959, vol. 37, pp. 385 395.
the modifying additive were prepared.
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pp. 623 628.
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methylhydroquinone in the Presence of Hydrogels of
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sertation, Yekaterinburg, 2006.
(2) The activity of Cu(II) in the matrix of modified
samples in catalysis of oxidative dehydrogenation of
trimethylhydroquinone is higher than that in the pro-
cess occurring in the presence of unmodified titanium
dioxide xerogel.
1
1
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1
. Physical and Chemical Aspects of Adsorbents and
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