Development, Synthesis, and Study of Nanomaterials of Titania Doped by Zirconium for Selective Hydrogenation of 2-Methyl-3-Butyn-2-ol in a Microcapillary Reactor

Article abstract of DOI:10.1134/S0023158419040116

Abstract: An ordered mesoporous titanium–zirconium Ti_xZr_1–xO₂ matrix for introducing catalytic nanoparticles was synthesized by self-assembly using titanium isopropoxide and zirconium oxychloride as precursors and amphiphilic triblock copolymer F127 as a template. The process of self-assembly occurs without the addition of an acid to preserve the morphology and structure of the catalytic nanoparticles. When controlling the initial molar ratios of the copolymer to metal precursors, titanium–zirconium nanocomposites with controlled texture and composition were obtained in a wide range of titania content, from 15 to 80 mol % TiO₂. The structural and phase properties of the composites were studied by X-ray diffraction, low-temperature nitrogen adsorption, and transmission electron microscopy. Composites have an ordered mesoporous structure, a high specific surface area, a large pore volume, and a uniform pore size distribution. Catalytic coatings of 1 wt % Pd–Zn/Ti_xZr_1–xO₂ (x = 1.0, 0.8, 0.5) on the inner surface of a capillary reactor were prepared by the dip-coating method using a colloidal solution of Pd–Zn nanoparticles. The developed catalytic coatings based on titanium–zirconium composites exhibit high activity and selectivity (> 96%) in the hydrogenation of 2-methyl-3-butyn-2-ol.

Full text of DOI:10.1134/S0023158419040116

ISSN 0023-1584, Kinetics and Catalysis, 2019, Vol. 60, No. 4, pp. 474–483. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Kinetika i Kataliz, 2019, Vol. 60, No. 4, pp. 509–519.
Development, Synthesis, and Study of Nanomaterials of Titania
Doped by Zirconium for Selective Hydrogenation of 2-Methyl-3-
Butyn-2-ol in a Microcapillary Reactor
L. B. Okhlopkovaa, *, M. A. Kerzhentseva, and Z. R. Ismagilova, b
aBoreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Kemerovo, 630090 Russia
bInstitute of Coal Chemistry and Material Science, Siberian Branch, Russian Academy of Sciences, Kemerovo, 650000 Russia
*e-mail: mila65@catalysis.ru
Received November 19, 2018; revised February 5, 2019; accepted March 14, 2019
Abstract—An ordered mesoporous titanium–zirconium TixZr1–xO2 matrix for introducing catalytic
nanoparticles was synthesized by self-assembly using titanium isopropoxide and zirconium oxychloride as
precursors and amphiphilic triblock copolymer F127 as a template. The process of self-assembly occurs with-
out the addition of an acid to preserve the morphology and structure of the catalytic nanoparticles. When
controlling the initial molar ratios of the copolymer to metal precursors, titanium–zirconium nanocompos-
ites with controlled texture and composition were obtained in a wide range of titania content, from 15 to
80 mol % TiO2. The structural and phase properties of the composites were studied by X-ray diffraction, low-
temperature nitrogen adsorption, and transmission electron microscopy. Composites have an ordered meso-
porous structure, a high specific surface area, a large pore volume, and a uniform pore size distribution. Cat-
alytic coatings of 1 wt % Pd–Zn/TixZr1–xO2 (x = 1.0, 0.8, 0.5) on the inner surface of a capillary reactor were
prepared by the dip-coating method using a colloidal solution of Pd–Zn nanoparticles. The developed cata-
lytic coatings based on titanium–zirconium composites exhibit high activity and selectivity (> 96%) in the
hydrogenation of 2-methyl-3-butyn-2-ol.
Keywords: mesoporous structure, titanium–zirconium composites, Pd–Zn nanoparticles, selective hydroge-
nation, 2-methyl-3-butyn-2-ol
DOI: 10.1134/S0023158419040116
INTRODUCTION
nonmetals, and metal oxides for various catalytic reac-
tions, namely dehydrogenation, oxidation, hydroge-
nation, hydroprocessing, deNOx and photocatalytic
oxidation of volatile organic compounds [9]. Such
improved mixed oxides of titanium and zirconium
combine the advantages of TiO2 (active catalyst and
support) and the acid–base properties of ZrO2 and
expand their use by creating new catalytic sites due to
strong metal–support interaction. The most com-
monly used methods for obtaining mixed oxides
TiO2–ZrO2 are coprecipitation and the sol–gel
World technical progress has led to serious global
environmental problems. To solve them, work is cur-
rently underway to develop environmentally friendly
and efficient processes. In this context, processes in
microstructured reactors are a key technology. A
microreactor with a catalyst located on its walls pro-
vides several orders of magnitude greater a surface-to-
volume ratio than periodic reactors and maintains bet-
ter heat and mass transfer [1, 2]. In microreactors,
reactions are controlled by kinetics and this leads to an
increase in the selectivity of product formation, while method. One of the significant advantages of the sol–
the laminar flow allows precise control of the contact gel method is the fact that multicomponent single-
time [3, 4]. Moreover, the continuous operation of phase metal oxides can be formed at relatively low
microreactors allows simple and fast process optimi- temperatures compared with the solid-phase reaction
zation and, hence, lower costs [5]. To create highly [10]. TiO2–ZrO2 composites have a high specific sur-
efficient capillary reactors, reproducible methods for
the deposition of a porous catalytic coating are devel-
oped [6, 7]. Multicrystalline oxide coatings have high
mechanical strength and thermal stability compared to
titania-based coatings [8]. Mixed oxides TiO2–ZrO2
face area, pronounced acid–base surface properties,
high thermal stability, and mechanical strength [11–
13]. In recent years, a number of structured materials
have been obtained by combining the sol–gel method
with surfactants. Amphiphilic surfactant molecules
are widely used as catalysts and supports with metals, self-organize into various structures. The evaporation-
474

DEVELOPMENT, SYNTHESIS, AND STUDY OF NANOMATERIALS
475
induced self-assembly process (EISA) includes the weight of 0.85 g was dissolved in 2 mL of a mixture of
natural and spontaneous ability of surfactants to orga- ethanol and methanol (volume ratio, 1 : 1) at room
nize themselves in various forms through hydrogen temperature. Ti[CH3(CH2)3O]4 and ZrOCl2 · 8H2O
bonds and π–π interactions, as well as electrostatic
and van der Waals forces. Cooperative nucleation and
aggregation leads to the formation of an organic–inor-
ganic hybrid structure. The removal of surfactant mol-
ecules leads to the formation of a mesoporous mate-
rial. The EISA process was developed to produce thin
films of structured silica and was first proposed by
Brinker [14, 15] and Stucky [16]. Over the past decade,
the main efforts have been focused on the synthesis of
ordered mesoporous TiO2–ZrO2 composites for use in
photocatalysis [17–21]. Currently, it remains import-
ant to obtain catalytic mesoporous coatings based on
mixed TiO2–ZrO2 oxides with an integrated active
ingredient for the selective hydrogenation of acetylene
alcohol. Such a mesoporous structure with a large spe-
cific surface area and connected pores improves the
catalyst properties, since it provides access to the
active component of reactants and reaction products.
The introduction of zirconia into the titania matrix
contributes to the preservation of the ordered meso-
porous structure of titania [22]. In this case, the parti-
cles of the active component are in the mesoporous
space of the nanostructured support, which limits
their growth in the course of the catalytic reaction and,
consequently, increases the stability of the catalyst. In
order to prevent the dissolution of metal nanoparti-
cles, the synthesis of such coatings should be carried
out at low acidity of the sol.
were added to the solution (overall Ti + Zr amount,
6 mmol) with intense stirring. After stirring for 2 h at
room temperature, the homogeneous sol was trans-
ferred to an oven to evaporate the solvent. After two
days of aging at 303 K and a relative humidity (RH)
50%, the gel was dried at 373 K for 1 day. Then, the tem-
perature was slowly raised from room temperature to
673 K (heating rate, 1 K/min) and calcined at 673 K for
2 h in air. High-temperature treatment (873, 1073 K) was
carried out in air for 1 h at a heating rate of 5 K/min.
Synthesis of Pd–Zn/TixZr1–xO2 Coatings
Mesoporous films doped with nanoparticles were
obtained by one-step synthesis using a precursor solu-
tion according to the procedure described in [23]. The
colloid solution of Pd–Zn nanoparticles (molar ratio,
Pd : Zn = 1 : 1) stabilized by polyvinylpyrrolidone
(Mav = 50000, Acros) was prepared by the reduction of
Pd(CH3COO)2 (46.5% Pd, Aurat) and ZnCl2 (98%)
salts in an ethylene glycol solution [24]. The catalysts
Pd–Zn/TiO2, Pd–Zn/Ti0.8Zr0.2O2, and Pd–
Zn/Ti0.5Zr0.5O2 were synthesized in the form of pow-
der and films on the inner surface of a capillary. The
weights of catalytic films Pd–Zn/TiO2, Pd–
Zn/Ti0.8Zr0.2O2, and Pd–Zn/Ti0.5Zr0.5O2 were 1.95,
3.85, and 6.50 mg, respectively.
This work is devoted to the synthesis and study of
the physicochemical properties of mesoporous tita-
nia–zirconia composites, as well as catalytic coatings
based on them. Titania–zirconia composites with differ-
ent Ti : Zr ratios were obtained by the EISA method
without addition of acid using the amphiphilic Pluronic
F127 triblock copolymer as a structure-forming additive.
The catalytic properties of TixZr1–xO2-based coatings
(x = 1.0, 0.8, 0.5) with Pd–Zn-embedded nanoparti-
cles were studied in the selective hydrogenation of
2-methyl-3-butyn-2-ol (MBY).
Study of Physicochemical Properties of TixZr1–xO2
Composites and Pd–Zn/TixZr1–xO2 Catalysts
The phase composition of the samples was studied
by X-ray diffraction (XRD). Powder ХRD patterns
were recorded using a HZG-4C diffractometer
(Freiberger Prazisionmechanik, Germany) with CoKα
radiation in the range 4° < 2θ < 50° with a counter rate
of 1°/min. Transmission electron microscopic (TEM)
images were obtained using a JEM-2010 instrument
(JEOL, Japan) operating at 200 kV with a resolution of
0.14 nm. Nitrogen adsorption and desorption iso-
therms at 78 K were measured using an ASAP 2400
analyzer (Micromeritics, USA). The specific surface
area was calculated by the Brunauer–Emmett–Teller
(BET) theory. The pore volume and pore size distri-
bution were obtained using the Barrett–Joyner–Hal-
enda model (BJH) from the desorption branch of iso-
therms. The content of Pd, Zn, Ti, and Zr in powder
catalysts was found by X-ray fluorescence (XRF)
spectroscopy using a VRA-30 analyzer (Ther-
moFisher Scientific, Switzerland) with a Cr anode of
an X-ray tube. The catalyst content in the microcapil-
lary reactor was determined by inductively coupled
plasma atomic emission spectroscopy (ICP-AES)
EXPERIMENTAL
Synthesis of TixZr1–xO2 Composites
For the synthesis, we used Pluronic F127 (Mav =
12600, EO106PO70EO106) (Sigma-Aldrich Chemical
Inc.), zirconium oxychloride (ZrOCl2 · 8H2O) (Vek-
ton), titanium tetraisopropoxide (Ti[CH3(CH2)3O]4)
(Acros), methanol (99.8%), and ethanol (99.9%)
(Baker). The mesoporous TiO2–ZrO2 composites
were synthesized by the sol–gel method in the pres-
ence of a template. The molar ratio of reagents was
Pluronic F127 : [(CH3)2O]4Ti : ZrOCl2 · 8H2O : alco-
hol = 0.0112 : 0–1 : 1–0 : 34. Pluronic F127 with a using an OPTIMA 4300 DV instrument (Perkin
KINETICS AND CATALYSIS Vol. 60 No. 4 2019

476
OKHLOPKOVA et al.
inlet and outlet tubes were 250 μm before the capillary.
(а)
The flow rate was varied from 5 to 100 μL/min, the gas
flow was 6 mL/min. Three to five samples were taken
after the system reached a steady state for 20 min,
diluted with methanol (5 : 1) and analyzed using a
Kristall 2000M gas chromatograph (Khromatek, Rus-
sia) equipped with a capillary column with a stationary
SKTFT-50Х phase; diameter, 0.22 mm; length, 30 m
(Boreskov Institute of Catalysis, Siberian Branch,
Russian Academy of Sciences); a flame ionization
detector. The carbon balance for these systems was
100 2%, i.e., the major products were 2-methyl-3-
butyn-2-ol (MBY), 2-methyl-3-buten-2-ol (MBE),
and 2-methyl-2-butanol (MBA). The conversion x,
selectivity to MBE SMBE, product yield Y, reactor pro-
ductivity Q, catalyst productivity A were calculated as
follows:
Intensity
3
2
1
0
1
2
3
4
5
6
2θ, deg
(b)
Intensity
C
− CМBY
CМBY,0
CМBЕ
(
)
МBY,0
x =
SМBЕ
×100,
×100,
=
3
(CМBY,0 − CМBY
)
CМBЕ
CМBY,0
− CМBY vYM
ρ
− CМBY vYM
ρmPd
Y =
×100,
2
1
C
(
)
МBY,0
l
Q =
A =
×100,
×100,
C
(
)
МBY,0
l
0
1
2
3
4
5
6
where CMBY,0 is the initial concentration of MBY;
CMBY and CMBE are the current concentrations of MBY
and MBE, respectively; vliquid is flow rate of liquid; m is
the molecular weight of MBY; ρ is the density of a liq-
uid; and mPd is the weight Pd.
2θ, deg
Fig. 1. XRD patterns in the region of low angles for TiO –
ZrO composites with different Ti : Zr ratios calcined at (a)
673 and (b) 873 K: (1) Ti Zr O ; (2) Ti Zr O ;
2
2
0.15 0.85
2
0.30 0.70 2
(3) Ti Zr O .
MATLAB was used to calculate the kinetic param-
eters. The system of differential equations was solved
using the function ode45, minimizing the sum of
square deviations between the experimental and cal-
culated concentrations at the reactor outlet was per-
formed using the fminsearch function.
0.70 0.30
2
Elmer, USA). Thermogravimetric analysis (TG) and
differential thermal analysis (DTA) were performed
using a Q-1500 derivatograph (MOM Budapest, Hun-
gary). The measurements were carried out at a heating
rate of 10 K/min from 293 to 873 K in an air atmo-
sphere.
RESULTS AND DISCUSSION
TixZr1–xO2 Composites
Catalytic Tests
By varying the molar ratio TixZr1–xO2 (x = 0, 0.15,
0.30, 0.50, 0.70, 0.8, 1), a number of samples were
prepared. According to XRD data for TixZr1–xO2 sam-
ples (x = 0, 0.15, 0.30, 0.70) in the region of low angles,
a peak is observed at 1.63°, which indicates an ordered
structure of pores with a small length (Fig. 1). In the
region of high angles, there are anatase peaks (JCPDS
21−1272) of pure TiO2 and Ti0.80Zr0.20O2 (Fig. 2). In
[26], it was suggested that ZrO2 can diffuse into the
TiO2 matrix and there is no ZrO2 in that case. An
The catalyst in a microcapillary reactor was prelim-
inarily reduced in situ in a flow of hydrogen
(2 mL/min) at a temperature of 573 K for 2 h. A
description of the equipment for carrying out the reac-
tion in a microcapillary reactor and the experimental
technique are given in [25]. The capillary was placed in
a thermostatic oven at 313 K. Hydrogen and a solution
of MBY or 2-methyl-3-buten-2-ol (MBE) in methanol
were fed to a T-shaped mixer, the inner diameters of the
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DEVELOPMENT, SYNTHESIS, AND STUDY OF NANOMATERIALS
477
(а)
Intensity
Intensity
* – m-ZrO2
o – t-ZrO2
3
2
7
6
5
o
4
3
1
o
o
*
2
1
*
o o
*
o
*
o
*
*
0
1
2
3
4
5
6
2θ, deg
20
40
60
80
2θ, deg
Fig. 3. XRD patterns in the region of low angles for the
Ti Zr O composite calcined at (1) 673, (2) 873, and
0.30 0.70
2
(b)
(3) 1073 K.
Intensity
+ – Ti2ZrO5
× – TiO2 – anatase
+
+
×
×
+
×
×
×
×
×
+
+
+
+
+
+
+
+
+
+
5 nm
7
6
5
4
3
100 nm
2
1
Fig. 4. Electron microscopic image of Ti Zr O cal-
0.30 0.70
2
cined at 673 K. The inset shows the high-resolution image.
– m-ZrO2
– t-ZrO2
that prevent the growth of oxide crystals [27]. The ort-
horhombic ZrO2 phase (JCPDS 34–1084) and the
monoclinic ZrO2 phase in trace amounts (JCPDS 37–
1484) are formed after calcining the Ti0.15Zr0.85O2 sam-
ple at 873 K. The crystallization of binary oxides
occurs at higher temperatures. On XRD patterns in the
region of large angles, the samples Ti0.70Zr0.30O2 and
Ti0.50Zr0.50O2 after treatment at 873 K contain reflec-
tions related to the anatase phase (JCPDS 21–1272)
and Ti2Zr2O6 (JCPDS 46–1265). Upon the calcina-
tion of the Ti0.30Zr0.70O2 sample at 1073 K, the pore
walls crystallize to ZrTiO4 (JCPDS 34–0415), which is
consistent with the literature data [28].
20
30
40
50
60
70
80
2θ, deg
Fig. 2. XRD patterns of TiO –ZrO composites with differ-
2
2
ent Ti : Zr ratios calcined at (a) 673 and (b) 873 K: (1) ZrO ;
2
(2) Ti Zr O ; (3) Ti Zr O ; (4) Ti Zr O ;
0.15 0.85
2
0.30 0.70
2
0.50 0.50 2
(5) Ti Zr O ; (6) Ti Zr O ; (7) TiO .
0.70 0.30
2
0.80 0.20
2
2
increase in the content of Zr inhibits crystallization
because samples Ti0.15Zr0.85O2, Ti0.30Zr0.70O2,
Ti0.50Zr0.50O2, and Ti0.70Zr0.30O2 are in the amorphous
state. This phenomenon is probably due to the pres-
After treatment at 873 K, the mesoporous structure
of the Ti0.70Zr0.30O2 sample is destroyed, while the
ence of Ti–O–Zr bonds in the interblock boundaries mesoporous structures of the samples with a higher Zr
KINETICS AND CATALYSIS Vol. 60 No. 4 2019

478
OKHLOPKOVA et al.
Table 1. Physicochemical properties of TiO2–ZrO2 composites obtained by varying the Ti : Zr ratio and calcination tem-
perature
Specific surface
area, m2/g
Calcination
temperature, K
Pore volume, cm3/g
Sample
Pore size, nm
TiO2
673
673
673
673
673
873
1073
673
673
81.6
185.5
156.9
116.2
150.4
103.2
79.5
7.3
3.6
3.7
3.8
3.8
3.7
5.1
3.6
4.9
0.098
0.084
0.132
0.136
0.208
0.162
0.152
0.187
0.094
Ti0.80Zr0.20O2
Ti0.70Zr0.30O2
Ti0.50Zr0.5O2
Ti0.30Zr0.70O2
Ti0.30Zr0.70O2
Ti0.30Zr0.70O2
Ti0.15Zr0.85O2
ZrO2
126.0
65.2
content are retained (Ti0.30Zr0.70O2 and Ti0.15Zr0.85O2)
(Fig. 1b). As the temperature increases to 873 K, the
peaks in the spectra in the region of large angles
become narrower and more intense (Fig. 2b). The
crystallite size of the Ti0.8Zr0.2O2 sample slightly
increases from 9 to 15 nm. For Ti0.15Zr0.85O2,
Ti0.50Zr0.50O2, and Ti0.70Zr0.30O2, the crystallite diame-
ter increases from 1.4 to 17 nm, from 1.2 to 15 nm, and
from 1.2 nm to 17 nm, respectively. In the case of
Ti0.30Zr0.70O2, this change is manifested to a lesser
extent: the particle size calculated by the Scherrer
equation increases from 1.3 to 1.5 nm. Upon calcina-
tion at 1073 K, the pore walls of Ti0.30Zr0.70O2 crystallize
to ZrTiO4, the crystallite diameter increases to 25 nm. It
is obvious that the growth of crystallites leads to the
destruction of the mesoporous structure (Fig. 3).
(а)
Volume, сm3/g
150
100
50
3
2
5
6
4
7
1
0
0.2
0.4
0.6
0.8
1.0
P/P0
(b)
dV/dD, сm3 g–1 nm–1
0.03
The electron microscopic images of the
Ti0.30Zr0.70O2 sample in the form of a film calcined at
673 K show areas with an ordered pore structure
(Fig. 4). The open and regular pore structure provides
reagent access to the active component. The cell
parameter is 9 nm. The cell walls are in an amorphous
state and their thickness is about 5 nm.
3
0.02
0.01
4
5
The low-temperature nitrogen adsorption iso-
therms of the mixed TiO2–ZrO2 composite with dif-
ferent Ti : Zr ratios are of type IV according to the
Brunauer classification with a sharp rise at Р/Р0 =
0.4–0.8, indicating a narrow pore size distribution
(Fig. 5a). Hysteresis loops of type H1 are observed,
which implies a uniform cylindrical geometry of the
pores. Mixed composites have a high specific surface
area of 116–185 m2/g (Table 1). Pore sizes calculated
from nitrogen desorption using the BJH model are in
the range 3.6–3.8 nm (Table 1) and do not depend on
the Ti : Zr ratio. However, as Ti : Zr increases, the pore
size distribution becomes wider (Fig. 5b), which indi-
cates a decrease in their degree of order. The calcu-
6
1
7
2
0
10
D, nm
Fig. 5. Isotherms of low-temperature adsorption of nitro-
gen (а) and pore size distribution calculated from the
desorption branch of the isotherm (b): (1) ZrO ;
2
(2) Ti Zr O ; (3) Ti Zr O ; (4) Ti Zr O ;
0.15 0.85
2
0.30 0.70
2
0.70 0.30
2
(5) Ti Zr O ; (6) Ti Zr O ; (7) TiO .
0.70 0.30
2
0.80 0.20
2
2
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DEVELOPMENT, SYNTHESIS, AND STUDY OF NANOMATERIALS
Pd–Zn/TixZr1–xO2 Coatings
479
TG, %
90
DTA μV/mg
Microscopic images of the Pd–Zn/Ti0.8Zr0.2O2
sample in the form of a powder reduced at 573, are
shown in Fig. 7. The sample has a homogeneous
amorphous worm-like structure with a pore size of 5–
6 nm, which agrees with the data of low-temperature
nitrogen adsorption (Fig. 8). The HRTEM images
(Fig. 8a) show Pd–Zn nanoparticles, which repeat the
pore structure of the support (Fig. 4), with an average
diameter of 3.7 nm. The resulting value corresponds to
the pore diameter of the original matrix. With the
introduction of the active component into the
Ti0.8Zr0.2O2 matrix, a porous system with a larger pore
size is formed (5.2 nm instead of 3.6 nm for the car-
rier). Therefore, we can assume that nanoparticles of
the active component are located inside the pores of
the support. For samples based on pure titania, the
particle size of TiO2 after reduction at 573 K is 6.5 nm
according to TEM data [20]. When zirconia is added
to the support matrix, the specific surface area and
pore volume increase from 85 to 143 m2/g and from
0.10 to 0.18 cm3/g, respectively. The walls of the sup-
port pores hold embedded nanoparticles and hinder
their migration over the support surface. The partial
degradation of the mesoporous structure of the
undoped matrix leads to sintering and agglomeration
of nanoparticles. Thus, in samples based on mixed
oxide, the nanoparticles of the active component are
sintered to a lesser extent.
3
exo
60
30
2
1
0
0
200
400
600
800
1000
1200
Temperature, К
Fig. 6. Thermal analysis data for the Ti Zr O com-
0.30 0.70
2
posite.
lated pore wall thickness is ~5.3 nm, which is consis-
tent with the TEM data.
Thermal analysis curves (TG–DTA) of the
Ti0.30Zr0.70O2 sample during decomposition in air are
shown in Fig. 6. The maximum on the TG curve is
observed at 567 K, the weight loss is about 50 wt % In
the temperature range from 473 to 673 K, the decom-
position of Pluronic F127 amphiphilic triblock copo-
lymer proceeds and water is removed, both adsorbed
and from the Ti–Zr hydroxide. The exothermic effect
at 573 K on the DTA curve refers to the decomposition
of F127 and the dehydration of Ti–Zr hydroxide. The
exothermic effect at 573 K on the DTA curve refers to
the decomposition of F127 and the dehydration of Ti–
Zr hydroxide. The exothermic effect at 993 K corre-
sponds to the crystallization of the ZrTiO4 phase,
which leads to the destruction of the mesoporous
Ti0.30Zr0.70O2 sample.
A comparative study of the catalytic properties of
Pd–Zn/TixZr1–xO2 (x = 1.0, 0.8, and 0.5) in the MBY
hydrogenation reaction was carried out. In earlier pub-
lications [23, 25], we showed that the activity and
selectivity of the MBY hydrogenation reaction on Pd–
Zn/TiO2 coatings increase with increasing reaction
time as a result of the removal of carbonaceous depos-
its. Similar patterns were observed for titanium–zirco-
nium coatings (Fig. 9). As the reaction time increases
(а)
(b)
(c)
Frequency Ni, %
80
60
40
20
0
Average size
of particles 3.7 nm
25 nm
2
3
4
5
6
7
10 nm
100 nm
Average size, nm
Fig. 7. TEM images (a, b) and histograms of particle distribution over sizes (c) of the Pd–Zn/Ti Zr
O
powder catalyst
0.8 0.2
2
reduced at 573 K.
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480
OKHLOPKOVA et al.
(а)
(а)
Adsorption, сm3 g–1
100
Q, g/day
12
10
8
t = 32
80
60
40
20
1
2
6
3
4
2
0
10
20
30
40
0
0.2
0.4
0.6
0.8
1.0
P/P0
Time on stream, h
(b)
(b)
SМBЕ, %
dV/dD, сm3 g–1 nm–1
0.008
t = 32
98
2
1
96
94
92
90
0.006
0.004
0.002
3
0
10
20
30
40
0
5
10
15
20
25
Size, nm
30
Time on stream, h
Fig. 9. Effect of time on stream on the productivity of the
reactor (a) and selectivity (b) in MBY hydrogenation on
(1) Pd–Zn/Ti Zr O , (2) Pd–Zn/Ti Zr O , and
0.5 0.5
2
0.8 0.2
2
(3) Pd–Zn/TiO films. Reaction conditions: С
=
2
MBY, 0
Fig. 8. Isotherms of nitrogen adsorption (a) and pore size
distribution (b) of Pd–Zn/Ti Zr powder catalyst
1.0–2.0 mol/L; gas flow rate, 6.0 mL/min;
= 1 atm,
P
H2
O
0.8 0.2
2
Т = 313 K.
reduced at 573 K.
viscous sol and thickening of the catalytic layer. Thus,
the high performance of the reactor is due to the
greater loading of the catalyst.
from 1 to 32 h, the reactor productivity rises from 0.8
to 8.6 g/day for Pd–Zn/Ti0.8Zr0.2O2 catalysts and from
1.6 to 4.5 g/day for Pd–Zn/TiO2. The selectivity to
MBE also increases from 95.4 to 97.2% for Pd–
Zn/Ti0.8Zr0.2O2 and from 89.0 to 94.6% for Pd–
Zn/TiO2.
For comparison, Fig. 10 shows the kinetic depen-
dences of the concentrations of the starting reagent
and MBY hydrogenation reaction products on the
contact time on Pd–Zn/TiO2 and Pd–Zn/Ti0.8Zr0.2O2
coatings after 32 and 20 h on stream, respectively.
Under these conditions, the selectivity to MBE was
maximal (Fig. 9). The contact times were calculated
from the values of the liquid flow velocity using the
Lockhart–Martinelli–Chisholm equation under the
assumption that a circular two-phase flow was realized
under the experimental conditions [29]. When adding
Zr to the support matrix the rate of MBE hydrogena-
The reactor productivity after 32 h of continuous
flow of the MBY solution in methanol and hydrogen
increases in the series Pd–Zn/TiO2
< Pd–
Zn/Ti0.8Zr0.2O2 < Pd–Zn/Ti0.5Zr0.5O2, and the selec-
tivity and productivity of the catalysts are almost inde-
pendent on their composition (Table 2). The weight of
the catalytic coating on the inner surface of the capil-
lary increases in the same order with increasing Zr : Ti
molar ratio, which is due to the formation of a more tion reaction increases (Figs. 10c, 10d). Table 3 shows
KINETICS AND CATALYSIS
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2019

DEVELOPMENT, SYNTHESIS, AND STUDY OF NANOMATERIALS
481
Table 2. Effect of the catalyst composition and the time on sible for the high selectivity of the Pd–Zn/Ti0.8Zr0.8O2
stream on the reactor productivity and selectivity of 2-methyl-
3-butyn-2-ol hydrogenation
coating at a conversion of 97%.
At = 32
gMBE s–1
,
Qt = 32
MBE/day
,
CONCLUSIONS
Sx = 97, %
Sample
g
−1
In this work, it was shown that ordered mesoporous
titanium–zirconium composites using titanium iso-
propoxide and zirconium oxychloride as precursors of
titania and zirconia and F127 triblock copolymer as a
template can be obtained by self-assembly. In most
cases, the EISA process in the synthesis of meso-
porous oxide materials requires the addition of acid to
slow down the hydrolysis–condensation of metal pre-
cursors. In our case, no acid is added to control the
rate of hydrolysis, which is important in the produc-
tion of catalytic coatings for microreactors. A series of
titanium–zirconium nanocomposites with controlled
properties was prepared by varying the TiO2 content in
the mixture of oxides from 15 to 80 mol %. The com-
posites have an ordered mesoporous structure, a high
specific surface area (up to 185 m2/g), a large pore vol-
ume (0.08–0.21 cm3/g) and their uniform size distri-
bution (3.6–3.8 nm). Catalytic coatings 1 wt % Pd–
Zn/TixZr1 – xO2 (x = 1.0, 0.8, 0.5) were synthesized on
the inner surface of a capillary reactor with a diameter
of 0.53 mm and a length of 10 m. Coatings have been
tested in the selective hydrogenation of 2-methyl-3-
butyn-2-ol at 333 K and 1 atm H2. The productivity of
the reactor after 32 h of continuous flow of the MBY
solution in methanol and hydrogen increases in the
series Pd–Zn/TiO2 < Pd–Zn/Ti0.8Zr0.2O2 < Pd–
Zn/Ti0.5Zr0.5O2 due to increasing the catalyst loading,
and the high selectivity (> 96%) and the performance
of the catalysts are almost independent of the coating
composition.
g
Pd
4.51
8.62
11.02
Pd–Zn/TiO2
1.5
96.9
97.2
96.5
Pd–Zn/Ti0.8Zr0.2O2
Pd–Zn/Ti0.5Zr0.5O2
1.9
1.6
1
Reaction conditions: [MBY] = 0.8 M, v
= 6.00 mL/min,
= 6.00 mL/min,
liquid
= 1 atm, T = 313 K.
Reaction conditions: [MBY] = 1.0 M, v
P
H2
2
liquid
1 atm H , T = 313 K.
2
the kinetic parameters of the reaction calculated from
the kinetic dependencies shown in Figs. 10a, 10b, 11.
To find the adsorption constant KMBE, the effect of the
MBE concentration in the range 0.1–3.1 mol/L on the
initial reaction rate was studied. The kinetic parame-
ters were calculated using the Langmuir–Hinshel-
wood model according to the methodology described
previously in [18]. The observed increase in the MBE
hydrogenation rate for mixed oxide catalysts can be
explained by a decrease in the KMBA/KMBY adsorption
constant ratio and an increase in the MBE hydrogena-
'
tion rate constants
The alkyne adsorption constant
k2.
decreased with the addition of zirconium, but its value
was 60 times higher than the alkene adsorption con-
stant. The rate constant of direct hydrogenation of
'
MBY to MBA
nium catalyst. Low values of KMBE/KMBY were respon-
was lower for the titanium–zirco-
k3
Table 3. Kinetic parameters of the MBY hydrogenation on Pd–Zn/TixZr1–xO2 coatings
1
2
Parameter
Pd–Zn/TiO2
Pd–Zn/Ti0.8Zr0.2O2
−1
714
132
750
230
'
mol
mol
mol
k1,
gPd
−1
'
k2,
gPd
−1
20
61
10
38
'
k3,
gPd
KMBY, L/mol
3
0.84
8
0.62
0.5
KMBE
KMBA
KMBE/KMBY
KMBA/KMBE
KMBA/KMBY
0.013
10
0.016
0.8
1.3 × 10–2
14
0.13
20
Maximum deviation, %
1
Reaction conditions: v
Reaction conditions: v
Fixed value.
= 6.0 mL/min,
= 6.0 mL/min,
= 1 atm, Т = 313 K, Pd–Zn/TiO after 32 h of time on stream.
P
H2
liquid
liquid
2
2
= 1 atm, Т = 313 K, Pd–Zn/Ti Zr O after 20 h of time on stream.
P
H2
0.8 0.2 2
3
4
Calculated from the dependence of Pd–Zn/Ti Zr
O activity on the MBE concentration.
2
x
1 – x
KINETICS AND CATALYSIS Vol. 60 No. 4 2019

482
OKHLOPKOVA et al.
dC/dt, mol L–1
(а)
(b)
–1
Pd
g
s–1
C, mol/L
100
0.8
2
1
1
0.6
0.4
0.2
2
50
3
3
0
10
20
30
40
0
10
20
30
t × 103, s gPd
t × 103, s gPd
(c)
(d)
–1
dC/dt, mol L–1
g
s–1
Pd
C, mol/L
100
1.0
2
0.8
0.6
0.4
0.2
1
3
3
1
2
50
0
10
20
30
40
50
0
10
20
30
40
t × 103, s gPd
t × 103, s gPd
Fig. 10. Dependences of (1, j) MBY, (2, d) MBE, and (3, m) MBA concentrations on the contact time on Pd–Zn/TiO films
2
after 32 h time on stream (a) and on Pd–Zn/Ti Zr O after 20 h time on stream (c); dependences of the reaction rate on the
0.8 0.2
2
contact time on Pd–Zn/TiO film after 32 h time on stream (b) and Pd–Zn/Ti Zr O film after 20 h time on stream (d).
2
0.8 0.2 2
Reaction conditions: v
= 6.0 mL/min,
= 1 atm, Т = 313 K.
P
H2
liquid
–1 –1
Activity, mol L
g
s–1
Pd
15
2
10
5
1
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
CMBE, mol/L
Fig. 11. Effect of the initial concentration of 2-methyl-3-buten-2-ol on the reaction rate on (1) Pd Zn /TiO and (2)
50
50
2
Pd Zn /Ti Zr O films. Reaction conditions: С
= 0.1–3.1 mol/L; v
= 6.0 mL/min,
= 1 atm; 313 K.
P
H2
50
50
0.8 0.2
2
MBE,0
liquid
KINETICS AND CATALYSIS
Vol. 60
No. 4
2019

DEVELOPMENT, SYNTHESIS, AND STUDY OF NANOMATERIALS
483
ACKNOWLEDGMENTS
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