Supakit Tiewcharoen

Chompunuch Warakulwit

Veronique Lapeyre

Patrick Garrigue

Lucas Fourier

Catherine Elissalde

Sonia Buffiere

Philippe Legros

Marion Gayot

Jumras Limtrakul

A Kuhn

Anisotropic metal deposition on TiO2 particles by electric-field-induced charge separation

come

TiO2

) results in hybrid materials combining the interesting properties of both materials in a single Janus particle. Out of the large number of techniques that have been proposed to generate Janus particles, one of them is bipolar electrochemistry. This concept can be employed in a straightforward way for the site selective modification of conducting particles. However, it is much less obvious to apply to semiconductors. In this work we report the successful bulk synthesis of asymmetric isotropic M-TiO2 particles based on the synergy of bipolar electrochemistry and photochemistry, thus overcoming important intrinsic limitations when they are used separately. We were able to break the symmetry of micro-and nanoparticles suspended in an electrolyte by modifying selectively and in a wireless way one side with either gold or platinum. Hybrid materials synthesized in this way are a first step towards high performance catalyst particles for example for photosplitting of water.

An efficient use of sun light as the primary and inexhaustible energy source is an essential precondition for the replacement of fossil fuels. Photocatalysis [START_REF] Natarajan | [END_REF]2 is one of the many ways to benefit from solar energy, e.g. to produce chemicals. Several types of semiconductors, including TiO2, ZnO, CdS, Fe2O3, MoO3, etc. are frequently applied as photocatalysts since they have band gaps suitable for harvesting sun light. [3][4][5][6][7] Titaniumdioxide (TiO2) is the most famous of these candidates and its properties include furthermore non-toxicity, high stability and efficiency.

Photocatalysts absorb solar energy quanta with energies larger than the band gap and generate electron-hole pairs (e --h + ); electrons in the valence band are excited to the conduction band, leaving holes behind. The electrons and holes then migrate to the surface to react with chemical species in order to form products. The major drawback of semiconductor materials is usually charge carrier recombination. Furthermore, the band gap of some semiconductors such as TiO2 has limitations with respect to the utilization of visible light, thus reducing the overall quantum efficiency. 3,[7][8][9] Metal-TiO2 semiconductor (M-TiO2) hybrids combine the properties of two materials in one, a good strategy to solve such problems. The deposition of plasmonic metals with high work functions, such as Au, Pt, Pd, etc., on a semiconductor enhances the efficiency of charge separation because these metals act as an electron sink to overcome the Schottky barrier at the metal-semiconductor interface and also enhance light absorption in the visible region. [10][11][12] For example, the modification of TiO2 with gold improves the charge separation in TiO2 by promoting under irradiation the transfer of the generated electrons from the semiconductor to the gold nanoparticles because the Fermi level of gold shifts close to the Fermi level of the semiconductor. 13 Many reports studying the deposition of different metals on TiO2 with various methods have shown that the catalytic activity of hybrid materials is much higher compared to an unmodified semiconductor. [14][15][16][17] In addition, the morphology of the deposited materials is gaining importance in engineering as it affects the surface plasmon resonance (SPR) properties, the optical absorption and the generation of electron-hole pairs for photocatalysis. 18 In this context so-called Janus particles 19,20 are outstanding candidates as multi-functional catalysts, since their surfaces have two or more distinct physico-chemical properties. M-TiO2 Janus objects in particular are very promising and interesting materials because the junction which combines the metal and the dielectric oxide can generate strong local electric near-fields. 18 For this reason, many literature examples demonstrated a high catalytic activity of M-TiO2 Janus particles with respect to various reactions. 18,21,22 Seh et al found that the photocatalytic hydrogen generation on Janus Au-TiO2 materials is much more efficient due to the stronger localization of the plasmonic near-field close to the Au-TiO2 interface at one side of the particles. 18,23 M-TiO2 Janus particles can be synthesized by several methods. 18,21,24,25 Bipolar electrodeposition, based on the polarization of conducting objects in electric fields is often used to break the symmetry, and in this way generates asymmetric objects. [26][START_REF] Ulrich | Angew[END_REF][28][29][30][31] This lowcost and easy to set up approach allows the bulk synthesis of Janus particles [32][33][34][35] However, this strategy cannot be applied directly to the deposition of metal on semiconductor materials due to their low conductivity. Therefore, an additional light source is required to activate the formation of charge carriers inside the semiconductor. Based on this concept, Ongaro et al 22 reported for the first time a site selective deposition of gold on TiO2 nanofibers as anisotropic substrates, using UV light and a strong external electric field. The authors assumed that the redox reactions occurred by activation with incident light, while the electric field enhances charge separation, leading to electric field assisted photochemistry.

In this work, we report on two major advances with respect to the controlled bipolar modification of semiconductor particles: -the successful modification of isotropic TiO2 semiconductor objects by light-induced bipolar electrochemistry. Compared to anisotropic objects, such as tubes, rods or fibers, which orient parallel to the electric field upon polarization 36 , this is much more challenging because they can rotate during the deposition process, thus preventing the generation of well-defined Janus particles.

-the modification of nanosized objects, which is usually not possible with bipolar electrochemistry. This is due to the fact that in classic bipolar electrochemistry the electric field which needs to be applied is indirectly proportional to the characteristic size of the object, meaning that nanoparticles usually require fields in the range of MV/m. Investigating the mechanism of metal deposition on TiO2, we were able to demonstrate that it is possible to achieve metal deposition with electric fields three orders of magnitude lower than the ones required by the concept of classic bipolar electrochemistry. Consequently, even particles in the 10nm range can be for the first time selectively modified due to the synergetic combination of electric field and light. The so-obtained Janus objects might be used for a wide variety of applications such as hydrogen and oxygen evolution [37][38][39] as well as the catalytic degradation of organic compounds 13,24 .

Experimental Section

Chemicals

Gold(III) chloride trihydrate (>99.9%, HAuCl4.3H2O), hexachloroplatinic acid hydrate (>99.9%, H2PtCl6.xH2O), absolute ethanol, ammonium chloride (99.99% NH4Cl), agarose (low gelling temperature), TiO2 powder (rutile-type structure-99.5% purityaverage particle size of 100 nm) and nanoparticles based on a titanium(IV)oxide mixture of rutile and anatase (< 150 nm, dispersion 33-37%wt in water) were purchased from Sigma Aldrich. Titanium(IV) oxide, anatase (TiO2, 99.6%, 3-6 mm sintered pieces), was purchased from Alfa Aesar. The metal deposition solution was prepared in a 95:5%V mixture of milliQ water (resistivity =18 MΩ cm) and absolute ethanol (abs EtOH) .

Materials and Cells

A DC high power supply, Heinzinger, PNC 10000-200POS, was used for this work. The light source was a LC8, HAMAMATSU, 200W mercury-xenon lamp (irradiation between 300 and 450 nm, UV). Reactions were performed by using two kinds of cells. Cell1: Home-made glass cell composed of threecompartments, open on the upper side to allow UV irradiation. The central chamber, in which the substrates and the reagents are located, is separated from the two electrode compartments by a glass septum (thickness 2 mm, porosity G2). The feeder electrodes in the cathodic and anodic compartment are a gold plate and a platinum wire, respectively. Cell2: Home-made plastic-glass cell without membranes, the distance between the two feeder electrodes is 3cm. The reaction compartment volume is about 1mL. The feeder electrodes are graphite plates.

Instruments

Scanning Electron Microscopy (SEM) images were obtained with a Hitachi Tabletop Microscope TM-1000. High Resolution Scanning Electron Microscopy (HRSEM) investigations were conducted using a JEOL 6700F. The TiO2 nanoparticles were examined with a JEOL high-resolution transmission electron microscope (HRTEM). The samples were prepared by casting a drop of the particle suspension (∼1 mg/mL) in water onto a 200-mesh carboncoated copper grid. For determination of the chemical nature of the deposited elements, Energy Dispersive X-ray Spectroscopy (EDX) has been used (JEOL detector Si-Li).

Bipolar deposition of metal nanoparticles (M = Au and Pt) on macroscopic TiO2 objects (macro-TiO2)

Rather big TiO2 objects (macro-TiO2) (Anatase, ~3-6 mm sintered pieces) particles were placed in a 2 mM HAuCl4.3H2O or 5 mM H2PtCl6.xH2O solution in the reaction compartment, while the electrode compartments were filled with 1 mM NH4Cl in abs EtOH.

Subsequently, three kinds of experiments were performed in cell1: 1) Application of an external electric field (3-33 kV/m) without UV irradiation; 2) Exposure to UV irradiation with varying intensity (5 -100 %) without an external electric field; 3) Combining UV irradiation and external electric field. These experiments were carried out for periods varying from 10 to 60s. After the reaction, the samples were washed with distilled water and ethanol, and dried at room temperature.

Synthesis of TiO2 microsphere (micro-TiO2)

TiO2 micro-spheres were prepared by a spray-drying technique (B-290 Buchi apparatus) from a suspension of TiO2 powder (Rutile) in demineralised water. The solid loading of the suspension was fixed to 25wt% to ensure a correct formation of droplets and a homogeneous shaping of the final particles. The mixing of liquid feed with hot air within a nozzle initiates the drying stage through rapid evaporation of the solvent and formation of dense and regular spheres. The particles pass through a cyclone to be separated from the humid air and dry spherical granules are collected. The conditions such as inlet temperature, aspiration rate, feed rate and gas flow were set at 220°C, 100%, 20% and 45ml/min respectively. The size of the as-obtained microspheres ranging from 10 up to 65 µm was determined by SEM analysis.

Deposition of metal nanoparticles (M = Au and Pt) on TiO2 microspheres (M/micro-TiO2) and nanoparticles (M/nano-TiO2)

micro-TiO2 or nano-TiO2 powder was dispersed in a mixture of agarose gel (1.4%w/v in milliQ water) containing 2 mM HAuCl4.3H2O or 5 mM H2PtCl6.xH2O in the reaction compartment (0.05% w/v), while the electrode compartments were filled with a mixture of agarose gel and 1 mM NH4Cl in abs EtOH. Subsequently, the three types of experiments were performed in cell2 analogue to the experiments with macro-TiO2.

Results and Discussion

Deposition of metal nanoparticles (M = Au and Pt) on macro-TiO2 objects

When a semiconductor object absorbs light with an energy greater than its band gap energy (Eg), electrons in the valence band (VB) are promoted to the conduction band (CB), leaving holes behind. Then e -and h + are migrating to the surface of the object and can locally trigger redox reactions if the object is in a solution containing active redox species. However if at the same time a strong electric field is applied to this solution it leads to a positive (𝛿 + ) and negative (𝛿 -) polarization at the extremities of the semiconductor object (Figure 1). The external strong electric field and the induced polarization effect result in band bending and lead to an internal electric field which facilitates the separation of the charge carriers (e --h + pairs) and their transport to opposite sides of the particle, where then reduction and oxidation reactions occur (Figure 1). This mechanism implies a remarkable difference when compared to normal bipolar electrodeposition on classic conductors. In the latter case the reduction occurs on the negatively polarized side of an object (the part facing the feeder anode), whereas for light induced bipolar deposition the reduction should occur on the positively polarized extremity of the semiconductor (the part facing the feeder cathode). In order to better understand and illustrate this mechanism of asymmetric reduction on semiconductor particles, we carried out a first experiment in which metal ions are reduced on macro-TiO2 particles made out of anatase with dimensions in the millimetre range (about 3-6mm). For the first study, gold has been chosen as a deposit (Au/macro-TiO2). The initial color of TiO2 is completely white, but selectively turns into deep gray on the right or positive polarized side (𝛿 + ) (Fig. 2b) after applying an external electric field (E) of about 6kV/m and in the simultaneous presence of 100% UV light intensity for 60s reaction time in HAuCl4.3H2O media. This seems to indicate that gold particles are deposited on macro-TiO2. In order to confirm the asymmetric deposition, SEM images were recorded at both sides of the object (Fig. 2a andc). The amount of gold particles at the 𝛿 + side is much higher than on the 𝛿 -part which is indeed opposite of what would be obtained for conventional bipolar electrochemical deposition on conducting objects. 19,40 Furthermore, when depositing platinum instead of gold in a second series of experiments an identical result is obtained. Platinum is exclusively observed on the 𝛿 + side (Fig. 3a-c) at an field of 15kV/m 50% UV intensity and 90s reaction time. In order to verify that the deposition is due to a synergistic effect of light and electric field, control experiments were performed by applying only an external electric field or exposing the particle only to UV light. Without light, the color of TiO2 in Fig. 3e does not change and the corresponding SEM images in Fig. 3d andf show no metal deposit. On the contrary, platinum particles are observed on the whole TiO2 object when only UV light is applied (Fig. 3g-i). (d-f) No metal deposition is observed when only an electric field is applied; (g-i) Non-specific metal deposition is obtained when only UV light is used but no electric field.

Deposition of metal nanoparticles (M = Au and Pt) on micro-TiO2

These first encouraging results obtained on macro-particles have led us to validate the process while addressing two main challenging issues: the downscaling of the particle size and the use of isotropic particles. Therefore, TiO2 microspheres (micro-TiO2) were then modified based on the same strategy. The asymmetric gold deposition on micro-TiO2 was achieved by exposure to an external electric field of 33 kV/m and 20% UV light intensity for 30s (Fig. 4a-b). Even when the electric field is reduced to 17 and 3 kV/m, the deposition still results in asymmetric particles (Fig. 4c-d ande-f respectively). In order to confirm the chemical nature of the deposits elemental analysis of gold (Au) and titanium (Ti) was performed by energy dispersive X-ray spectroscopy (EDX) (Fig. 5).

It is interesting to note that asymmetric gold deposition in a conventional bipolar electrochemical process with conductive objects of comparable diameter (>10m) requires theoretically electric fields >24 kV/m for triggering the chemical reactions ( 1) and ( 2). 33 In the present series of experiments we could achieve electrodeposition even with an electric field as low as 3kV/m, that means almost one order of magnitude lower than the theoretical value needed for classic bipolar electrodeposition. Reduction side:

AuCl4 -+ 3e -⇌ Au + 4Cl - E o = +0.99V (1) Oxidation side: 2H2O ⇌ O2(g) + 4H + + 4e - E o = +1.23V
(2) This is due to the fact that in the present case, and in contrast to normal bipolar electrochemistry, it is not the electric field which generates the chemical driving force, but the light induced separation of charges provides the chemical energy. The electric field has only a secondary function, namely establishing an internal electric field inside the particle and thus dragging the charges towards the opposite extremities of the microparticles. Therefore, even an electric field strength which is far below the one theoretically required for inducing a bipolar electrochemical reaction will have a significant impact on the symmetry of the synthesized particles (see Figure 5). The results in Figure 6 obtained by replacing the gold salt by a platinum salt confirm the pronounced asymmetric deposition of the metal even for 3kV/m, which should not lead to bipolar electrodeposition with normal electric conductors. This is very encouraging and allows speculating whether similar experiments can be carried out with nanoobjects instead of microobjects. Normal bipolar electrochemistry encounters severe limitations when experiments need to be carried out with very small objects because the driving voltage that has to be applied between the feeder electrodes scales inversely with the object size 40 . According to what has been observed with the above microparticles (Figures 456) this seems not to be the case for semiconductors because the electric field is not the driving force, but is just spatially directing the redox chemistry. Therefore, experiments with TiO2 nanoparticles were carried out in the following.

Deposition of metal nanoparticles (M = Pt) on nano-TiO2

From the above discussion, it becomes clear that the synergy between electric field and light should allow modifying also TiO2 nanoparticles (nano-TiO2). It is worth noting that using normal bipolar electrochemical deposition, an electric field with an amplitude of more than 5 MV/m is theoretically needed for a 100nm size nanoparticle. The corresponding involved chemical reactions are described as follows:

Reduction side: [PtCl6] 2-+ 4e -⇌ Pt + 6Cl - E o = +0.71V (3) Oxidation side: 2H2O ⇌ O2(g) + 4H + + 4e - E o = +1.23V (4)
The difference of the standard potentials of the two involved redox couples in equation ( 3) and ( 4) is 0.52V and at least this polarization potential difference has to exist between the extremities of the object (100 nm). Taking into account that the distance between the two feeder electrodes is 3.3 cm in the present set-up, this implies a potential difference of over 170 kV that has to be applied, which is impossible from a practical point of view.

However, when using the concept of light induced bipolar electrochemistry things change completely, because the electric field does not need to provide the direct driving force for the two redox reactions. This allows breaking the symmetry of modification even with relatively low electric fields. Figure 7 nicely illustrates this aspect. When a suspension of nano-TiO2 is exposed just to UV light in the presence of platinum salt, the generated electron-hole pairs trigger the redox reactions (3) and ( 4) in a completely unspecific way everywhere on the semiconductor surface. As a result, Pt clusters with a typical size of 2-4 nm are covering the entire surface of the nano-TiO2 objects. However when applying simultaneously an electric field of 3kV/m, the situation drastically changes. The metal is no longer distributed homogeneously over the semiconductor particles, but rather undergoes single point electrodeposition, thus giving access for the first time to this kind of Janus nanoobjects (Fig. 8a). Statistically only one or very few platinum nanoclusters (black spots) are attached to one side of the nano-TiO2, indicating that it is possible to break the deposition symmetry with electric fields that are more than three orders of magnitude lower compared to those required by classic bipolar electrochemistry. Figure 8b shows a HRTEM image of a typical junction between the metal and the semiconductor. Both of them exhibit crystalline order and seem to be well attached to each other.

Conclusion

The concept of bipolar electrodeposition has been considerably extended by overcoming two major challenges: -so far it was not possible to modify isotropic semi-conductor objects by bipolar electrodeposition of metals due to their rotation in the electric field during the modification step -classic bipolar electrodeposition intrinsically requires very high electric fields for the modification of nanoobjects and therefore was so far mostly used for micron-sized particles We could demonstrate that by taking advantage of the synergy between light and an electric field it is possible to induce bipolar behavior also on isotropic semiconductor particles suspended in a gel, and, most importantly, trigger metal deposition on particles with a characteristic size in the 10-30nm range. This only requires modest electric fields, which are over three orders of magnitude lower pared to what would be theoretically needed in a classic bipolar electrodeposition experiment without light. Furthermore it has been possible to provide evidence that the deposition mechanism on semi-conducting particles is opposite to what has been observed for normal conductors, meaning that metal ion reduction occurs at the positively polarized pole of the object due to the electric field generated inside the semiconductor. The process is simple and low-cost and therefore can also be scaled up for industrial production. The so-obtained hybrid nanomaterials open the door for the synthesis of high-performance bifunctional catalysts for various applications, including water splitting and depollution of organic waste.

Figure 1 .

 1 Figure 1. Schematic mechanism of metal deposition on TiO2 particles.In order to better understand and illustrate this mechanism of asymmetric reduction on semiconductor particles, we carried out a first experiment in which metal ions are reduced on macro-TiO2 particles made out of anatase with dimensions in the millimetre range (about 3-6mm). For the first study, gold has been chosen as a deposit (Au/macro-TiO2). The initial color of TiO2 is completely white, but selectively turns into deep gray on the right or positive polarized side (𝛿 + ) (Fig.2b) after applying an external electric field (E) of about 6kV/m and in the simultaneous presence of 100% UV light intensity for 60s reaction time in HAuCl4.3H2O media. This seems to indicate that gold particles are deposited on macro-TiO2.

Figure 2 .

 2 Figure 2. (a) SEM image revealing that only very few gold particles are deposited on the negatively polarized side, (b) Optical microscopy of the whole macro-TiO2 object, and (c) SEM of the positively polarized side showing a high density of gold particles (white spots).

Figure 3 .

 3 Figure 3. Deposition of platinum on macro-TiO2 (a-c) For simultaneous application of an electric field (E) and UV light, SEM images show no platinum on the 𝛿 -side and platinum particles (white spots) on the 𝛿 + side; (d-f) No metal deposition is

Figure 4 .

 4 Figure 4. Asymmetric gold deposited on micro-TiO2 obtained for simultaneous exposure for 30s to 20% UV light intensity and an electric field of (a-b) 33kV/m (c-d) 17kV/m and (e-f) 3kV/m.

Figure 5 .

 5 Figure 5. (a) and (c) SEM images of gold deposited on micro-TiO2 by a simultaneous exposure for 30s to 20% UV light intensity and an electric field of 3kV/m. (b) and (d) EDX analysis of (a) and (c) respectively, red colour for Ti and green for Au.

Figure 6 .

 6 Figure 6. (a-c) and (e) SEM images of platinum deposited asymmetrically on micro-TiO2 by a simultaneous exposure for 90s to 50% UV light intensity and an electric field of 3kV/m in a solution containing 5 mM H2PtCl6.xH2O; (d) and (f) EDX analysis of (c) and (e) respectively, red colour for Ti and green for Pt.

Figure 7 .

 7 Figure 7. TEM image of nano-TiO2 particles covered with platinum nanoclusters generated in an unspecific way by exposure for 90s to 50% UV light intensity.

Figure 8 .

 8 Figure 8. (a) TEM image of platinum nanoclusters generated in a selective way on nano-TiO2 by exposure for 90s simultaneously to 50% UV light intensity and an electric field of 3kV/m. (b) HRTEM image for a typical deposit obtained under these conditions, zooming on the junction between the metal nanocluster and a nano-TiO2 particle (scale bars are 20 and 2 nm respectively).


Olga V Larina

Nataliya D Shcherban

Pavlo I Kyriienko
email: pavlo_kyriienko@ukr.net

Ivan M Remezovskyi

Pavlo S Yaremov

Ivan Khalakhan

Gregor Mali

Sergiy O Soloviev

Svitlana M Orlyk

Stanislaw Dzwigaj
email: stanislaw.dzwigaj@sorbonne-universite.fr.

L V Pisarzhevsky

Design of Effective Catalysts Based on ZnLaZrSi Oxide Systems for Obtaining 1,3-Butadiene from Aqueous Ethanol

Keywords: ethanol-water mixture, 1, 3-butadiene, ZnLaZrSi oxide system, silica support

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Large investments in the development of ethanol production technology from renewable raw materials contribute to a significant reduction in the costs for manufacture, and accordingly make it quite feasible to partially replace industrially important processes based on petroleum with eco-friendlier processes based on bioethanol in the near future. [START_REF] Abdulrazzaq | Catalytic Conversion of Ethanol to Commodity and Specialty Chemicals[END_REF][START_REF] Grim | Growing the Bioeconomy through Catalysis: A Review of Recent Advancements in the Production of Fuels and Chemicals from Syngas-Derived Oxygenates[END_REF][START_REF] Angelici | Chemocatalytic Conversion of Ethanol into Butadiene and Other Bulk Chemicals[END_REF] A number of publications [START_REF] Patel | Sustainability Assessment of Novel Chemical Processes at Early Stage: Application to Biobased Processes[END_REF][START_REF] Posada | Potential of Bioethanol as a Chemical Building Block for Biorefineries: Preliminary Sustainability Assessment of 12 Bioethanol-Based Products[END_REF][START_REF] Cespi | Butadiene from Biomass, a Life Cycle Perspective to Address Sustainability in the Chemical Industry[END_REF] are also provided justification (primarily from an environmental point of view) the starting the production of such an industrially important substrate as 1,3-butadiene (1,3-BD) from ethanol (EtOH). In particular, the project for bio-butadiene production has been initiated in 2013. [START_REF] Axens | IFPEN and Michelin Join Forces to Create a Synthetic Rubber Production Channel Using Biomass[END_REF] Development of active and highly selective catalysts of the ethanol-to-butadiene (ETB) technology is one of the main tasks for the process implementation in industry. 8 A modern approach to the process implementation of both 1,3-BD and ethylene production from ethanol involves the use of cheaper ethanol-water mixtures as raw materials that can be obtained by flash separation of fermentation ethanol, instead of expensive rectified or 100 vol% ethanol. For instance, the 50 vol% ethanol can be obtained by pervaporation of fermentation broth through a membrane. Micheline company has patented the technology of the 1,3-BD production from 80 vol% ethanol. [START_REF] Dastillung | Method for the Production of Butadiene from Ethanol in One Low-Water-and Low-Energy-Consumption Reaction Step[END_REF] Moreover, the presence of over 5-10 % water in the feed has been shown to significantly affect activity and selectivity of the ETB process catalysts. [START_REF] Velasquez Ochoa | An Analysis of the Chemical, Physical and Reactivity Features of MgO-SiO2 Catalysts for Butadiene Synthesis with the Lebedev Process[END_REF][START_REF] Larina | The Effect of ZnO on Acid-Base Properties and Catalytic Performance of ZnO/ZrO2-SiO2 Catalysts in 1,3-Butadiene Production from Ethanol-Water Mixture[END_REF][START_REF] Cabello González | Ethanol Conversion into 1,3-Butadiene over a Mixed Hf-Zn Catalyst: Effect of Reaction Conditions and Water Content in Ethanol[END_REF][START_REF] Talalay | The Russian Synthetic Rubber from Alcohol. A Survey of the Chemistry and Technology of the Lebedev Process for Producing Sodium-Butadiene Polymers[END_REF][START_REF] Zhang | The Deactivation of ZnO Doped ZrO2-SiO2 Catalyst in the Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene[END_REF] Thus, development of the catalysts able to convert ethanol-aqueous mixtures containing 50-80 vol% ethanol into 1,3-BD is a very important task which is insufficiently studied now.

Based on the studies of various catalytic systems presented in the literature, activity and selectivity of catalyst in the ETB process can be concluded to equally depend on both catalyst composition and its preparation method. Most of the known catalysts contain silicon dioxide. It has been suggested that active sites of the key step of ETB process, aldol condensation, are acid-base pairs formed in contact of catalytically active metal cation and silicon oxide, usually depicted as M-O-Si. 8,[START_REF] Makshina | Review of Old Chemistry and New Catalytic Advances in the On-Purpose Synthesis of Butadiene[END_REF] Effect of the used silica materials (along with catalyst composition) on activity of the ETB process catalysts is also shown in some papers. Using ZrO 2 -ZnO/SiO 2 and ZrO 2 -ZnO-La 2 O 3 /SiO 2 systems, Jones et al. [START_REF] Lewandowski | Process for the Production of 1,3-Butadiene[END_REF][START_REF] Jones | Investigations into the Conversion of Ethanol into 1,3-Butadiene[END_REF] have shown that a pore size of SiO 2 used for the catalysts preparation affects their activity in the conversion of ethanol and ethanol-acetaldehyde (EtOH-AA) mixture into 1,3-BD. Sushkevich et al. [START_REF] Sushkevich | Ethanol Conversion into Butadiene over Zr-Containing Molecular Sieves Doped with Silver[END_REF] and Dagle et al. [START_REF] Dagle | Effect of the SiO2 Support on the Catalytic Performance of Ag/ZrO2/SiO2 Catalysts for the Single-Bed Production of Butadiene from Ethanol[END_REF] have observed a relationship between butadiene selectivity and concentration of Lewis acid sites for Ag/ZrO 2 -silica systems that depends on the nature of the used silica component. Pomalaza et al. [START_REF] Pomalaza | ZnTa-TUD-1 as an Easily Prepared, Highly Efficient Catalyst for the Selective Conversion of Ethanol to 1,3-Butadiene[END_REF][START_REF] Pomalaza | Properties and Activity of Zn-Ta-TUD-1 in the Lebedev Process[END_REF] have recently shown that ZnTa oxide catalyst based on mesoporous silica TUD-1 is more active in ETB process than similar system based on SiO 2 or dealuminated BEA zeolite. Chae et al. [START_REF] Chae | Butadiene Production from Bioethanol and Acetaldehyde over Tantalum Oxide-Supported Ordered Mesoporous Silica Catalysts[END_REF] have studied the effect of ordered mesoporous silica (OMS) on activity of Ta 2 О 5 /OMS in 1,3-BD production from EtOH-AA mixture. The pore size and particle size of OMS samples are shown to be more important than mesopore structure such as pore size and pore shape to optimize catalytic performance of Ta 2 О 5 -containing catalysts. Gao et al. [START_REF] Gao | 1,3-Butadiene Production from Bioethanol and Acetaldehyde over Zirconium Oxide Supported on Series Silica Catalysts[END_REF] have come to a similar conclusion during studying ZrO 2 -SiO 2 systems prepared using various silica materials in EtOH-AA mixture conversion into 1,3-BD. Cheong et al. [START_REF] Cheong | Highly Active and Selective Zr/MCF Catalyst for Production of 1,3-Butadiene from Ethanol in a Dual Fixed Bed Reactor System[END_REF] have shown that high-performance ZrO 2 -containing catalysts of 1,3-BD production from EtOH-AA mixture can be obtained using mesocellular siliceous foam (MCF) as a silica component. The use of zeolite as a matrix for the formation of M-O-Si active sites also allows preparing highly selective catalysts for the conversion of both EtOH and EtOH-AA mixture. [START_REF] Kyriienko | Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)[END_REF][START_REF] Kyriienko | Effect of the Niobium State on the Properties of NbSiBEA as Bifunctional Catalysts for Gas-and Liquid-Phase Tandem Processes[END_REF][START_REF] Kyriienko | High Selectivity of TaSiBEA Zeolite Catalysts in 1,3-Butadiene Production from Ethanol and Acetaldehyde Mixture[END_REF][START_REF] Sushkevich | With Open Arms: Open Sites of ZrBEA Zeolite Facilitate Selective Synthesis of Butadiene from Ethanol[END_REF][START_REF] Klein | Formation of 1,3-Butadiene from Ethanol in a Two-Step Process Using Modified Zeolite-β Catalysts[END_REF][START_REF] Klein | Influence of Structural Parameters on the Conversion of Ethanol into 1,3-Butadiene Using Mesoporous Zeolites[END_REF][START_REF] Kurmach | Hierarchical Zr-MTW Zeolites Doped with Copper as Catalysts of Ethanol Conversion into 1,3-Butadiene[END_REF] In view of the foregoing considerations, the type (nature) of a silica component is assumed to have a decisive influence on activity of silica-based catalysts in 1,3-BD production from EtOH-H 2 O mixture as raw materials. As previously shown, catalytic systems containing zinc, lanthanum, zirconium and siliceous oxides exhibit quite high activity in the conversion of both ethanol and ethanol-water mixtures into 1,3-BD. [START_REF] Larina | 1,3-Butadiene Production from Ethanol-Water Mixtures over Zn-La-Zr-Si Oxide Catalyst[END_REF][START_REF] Larina | Effect of Lanthanum in Zn-La(-Zr)-Si Oxide Compositions on Their Activity in the Conversion of Ethanol into 1,3-Butadiene[END_REF][START_REF] Kyriienko | Effect of the Composition of Ethanol -Water Mixtures on the Properties of Oxide (Zn-Zr-Si) and Zeolitic (Ta/SiBEA) Catalysts in the Production of 1,3-Butadiene[END_REF] Thus, we have used ZnLaZrSi oxide systems to study the effect of the silica component type on their catalytic properties in 1,3-BD production from EtOH-H 2 O mixture. Since there is no univocal opinion in the literature concerning the best silica support, a series of the samples based on commercially available silica (KSKG, A-175, A-380), ordered mesoporous silica (SBA-15, MCM-41, MCM-48), mesocellular siliceous foam (MCF) and dealuminated BEA zeolites was investigated.

MATERIALS AND METHODS

Catalyst preparation

KSKG industrial silica gel, aerosils A-175 and A-380, ordered mesoporous silica SBA-15, MCM-41 and MCM-48, mesocellular siliceous foam (MCF) and dealuminated BEA zeolites were used for the preparation of ZnLaZrSi oxide samples. KSKG industrial silica gel (silica gel granular with large pores, specific surface area is 283 m 2 g -1 ) was pre-treated with dilute nitric acid, washed with double distilled water and calcined at 773 K. Dealumination of a parent tetraethylammonium BEA zeolite (Si/Al = 17) was carried out by its treatment in a 13 mol•L -1 HNO 3 solution at 353 K for 4 h. The resulting dealuminated BEA zeolite with Si/Al ratio of 1000 was marked as SiBEA.

Introduction of zirconium (6 wt % relative to ZrO 2 ) into the silica samples (namely pre-treated KSKG, Aerosils A-175 and A-380, ordered mesoporous silica SBA-15, MCM-41, MCM-48, mesocellular siliceous foam and SiBEA) was carried out by wet kneading (fraction < 0.1 mm) with analytical grade ZrO(NO 3 ) 2 •2 H 2 O, followed by drying (393 K, 2 h) and calcination (773 K, 3 h). Introduction of zirconium into SiBEA was also carried out by stirring for 3 h at 353 K in 200 mL of isopropanol solution containing 1 • 10 -3 mol•L -1 of Zr(NO 3 ) 4 •4 H 2 O (Sigma Aldrich, 99.9 %). The obtained suspensions (pH = 6.8) were stirred in an evaporator under vacuum of a water pump in air at 353 K for 1 h until isopropanol was evaporated. The resulting solids, washed three times in distilled water and dried in air at 353 K for 24 h, were finally calcined at 773 K in flowing air for 3 h. The samples contained 1 and 3 wt % of Zr were labelled as

Catalyst characterization

X-ray diffraction (XRD) patterns of the powder samples were recorded using a D8 Advance (Bruker AXS GmbH, Germany) diffractometer with monochromatized Cu Kα radiation (nickel filter, λ = 0.15418 nm).

Nuclear magnetic resonance (NMR) spectra were recorded using a Varian VNMRS 600 MHz spectrometer (14.1 Tesla 51mm bore Oxford superconducting magnet) operating at a 29 Si Larmor frequency of 119.229 MHz and using a 3.2 mm magic angle spinning (MAS) probe head. [START_REF] Kyriienko | Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)[END_REF] Si MAS NMR spectra were recorded with cross-polarization ( 1 H- [START_REF] Kyriienko | Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)[END_REF] Si CP/MAS NMR) and without it ( 29 Si MAS NMR). Chemical shifts of silicon were measured relative to tetramethylsilane (TMS). [START_REF] Kyriienko | Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)[END_REF] Si MAS NMR spectra were obtained with rotors spinning with a frequency of 20 kHz, using a single pulse acquisition and a recycle delay of 4 s. All measurements were carried out at room temperature.

The morphology of the samples was observed by means of scanning electron microscopy (SEM) using a Tescan MIRA 3 microscope (electron beam energy of 20 keV).

The nitrogen adsorption-desorption isotherms were measured at 77 K with the porous analyzer Sorptomatic-1990. Before measurements, the samples were evacuated at 473 K for 2 h. The specific surface area of the samples was determined by the Brunauer-Emmett-Teller (BET) method. External surface area and micropore volume of the investigated samples were estimated from t-plot method. The mesopore size of the samples were obtained by the Barrett-Joyner-Halenda (BJH) method.

Analysis of acid properties of the catalyst samples was performed by adsorption of pyridine followed by Fourier Transform Infrared (FTIR) spectroscopy using a Spectrum One FTIR spectrometer (Perkin Elmer, USA). Typically, 24 scans with a resolution of 1 cm -1 were codded to give one spectrum. The catalyst sample was pressed at ~ 2 ton · cm -2 into thin wafers of ca.

12 mg · cm -2 and placed inside the IR cell. Before adsorption of pyridine, the cell was connected to a vacuum-adsorption apparatus allowing a residual pressure below 10 -3 Pa. The samples were outgassed (10 -3 Pa) at 693 K for 1 h. Then, pyridine was adsorbed at 423 K for 15 min. The spectra were recorded under ambient conditions after pyridine desorption at 423, 523 and 623 K for 30 min. All measured spectra were recalculated to a "normalized" wafer weight and surface.

Catalytic activity measurements

Catalytic activity tests were carried out in a fixed-bed flow quartz reactor with an inner diameter of 4 mm at 648-673 K and atmospheric pressure. Samples with grains of 0.25-0.5 mm were loaded into the reactor. Aqueous ethanol feed (96-50 vol% EtOH -4-50 vol% H 2 O) was introduced to an evaporator via a syringe infusion pump, and argon with flow of 7 mL · min -1 was carried the feed into the reactor. Reaction was carried out at weight hourly space velocity (WHSV) by EtOH of 0. where M EtOH is molar mass of ethanol (g•mol -1 ); S BET is specific surface area of the samples determined by the Brunauer-Emmett-Teller method (m 2 •g -1 ); S ext. is external surface area of the samples (m 2 •g -1 ). (5-80) 75 d) 425 0.43 a calculations using t-plot method, b micropore parameters according to Dubinin-Radushkevich equation TVFM, c total pore volume at р/р 0 = 1.0, d total mesopore and external surface area, * not determined.

RESULTS AND DISCUSSION

The particle size and morphology of ZnLaZrSi oxide samples were determined by the SEM analysis and are shown in Figure S2. The samples based on KSKG, A-175 and A-380 contain randomly amorphous particles and small sphere-like primary particles with particle diameters of around 10-20 nm. SEM image of ZnLaZr-SBA-15 shows a typical hexagonal rod-like SBA-15 morphology with a primary particle size of around 1 µm. ZnLaZr-MCM-41 appears as spherical particles with a regular surface. ZnLaZr-MCM-48 possesses the particles of an irregular shape.

In turn, ZnLaZr-MCF consists of mainly spherical particles with a partial preservation of the cellular morphology. The images of the samples based on dealuminated BEA zeolite (ZnLa-Zr 1 SiBEA and ZnLa-Zr 3 SiBEA) indicate a macrostructure similar for BEA zeolites; 39 size of the spherical aggregates is about 100-200 nm. Thereby, BEA zeolite does not deteriorate after treatment with nitric acid and introduction of the heteroelement (Zr) into SiBEA.

Analysis of the nitrogen ad(de)sorption measurements (Table 1, Figure S3) shows that the prepared catalysts are characterized by the developed surface area (up to 615 m 2 /g) and high total adsorption up to ~ 1.15 cm 3 /g (at p/p 0 = 1.0). The porosity of KSKG and aerosil supported catalysts is formed as interparticle space between the aggregated silica particles. A-380 support consisting of smaller particles in comparison with A-175 provides the formation of smaller particles of the active phase. The resulting smaller particles lead to mesoporous structure with a visible bend on the isotherm in contrast to A-175 support providing larger particles of the active phase which is expressed by an adsorption increase in the region of higher relative pressures.

Deposition of the active phase on silica MMS results in a decrease of the structural characteristics (specific surface area and total pore volume) of the prepared supported catalysts in comparison with the initial silica supports. The obtained materials are characterized by a comparatively homogeneous mesoporous structure indicating preferred uniform deposition of the active phase. For the samples based on SiBEA zeolite an increase in the characteristic adsorption energy in micropores Е 0 is observed (3.9, 4.1, 4.3 kJ/mol, Table 1; Dubinin-Radushkevich equation, TVFM) with an increase in the content of active catalytic phase, which is also confirmed by a corresponding decrease in micropore volume (Table 1). It indicates the formation of a finely dispersed phase of the catalyst components inside the micropores, and not only on the surface and their corresponding blocking. As postulated in the Introduction section, selection of the catalyst for ETB process should be based on their acid-base properties. Figure 3 shows the results of investigation of acid sites on the catalyst surface by FTIR spectroscopy of adsorbed pyridine.

Acid characteristics of the catalysts

The IR adsorption bands are observed at 1614, 1602, 1578, 1492, 1454 and 1448 cm -1 for all samples. The additional bands at 1597 and 1446 cm -1 are found for ordered mesoporous silica and mesocellular siliceous foam. For dealuminated BEA zeolites one more band at 1444 cm -1 is detected. The bands at 1597, 1578 and 1444 cm -1 represent physically adsorbed and hydrogenbonded pyridine, as proved by their almost complete disappearance after desorption of pyridine at 523 K. The band at 1578 cm -1 remaining at 523 K arises from coordinately bonded pyridine.

The band at 1492 cm -1 corresponds to both Brønsted and Lewis acid sites. [START_REF] Yurdakoç | Acidity of Silica-Alumina Catalysts by Amine Titration Using Hammett Indicators and FT-IR Study of Pyridine Adsorption[END_REF][START_REF] Connell | The Generation of Brønsted and Lewis Acid Sites on the Surface of Silica by Addition of Dopant Cations[END_REF] However, no evidence is found for the band at 1570-1540 cm -1 on the samples indicating that there are no Brønsted sites on the surface strong enough to react with pyridine. Intensive bands at 1614, 1454 and 1448 cm -1 and the shoulder at 1602 cm -1 correspond to pyridine interacting with Lewis acid sites.

Several types of Lewis acid sites (LAS) can be formed on the surface of ZnLaZrSi oxide systems: lanthanum-, zirconium-, and zinc-containing ones. We have previously shown that only weak acid sites with a pyridine desorption temperature of up to 423 K are formed on the surface of LaSi oxide catalysts (the bands at 1602 and 1446 cm -1 ). [START_REF] Larina | Effect of Lanthanum in Zn-La(-Zr)-Si Oxide Compositions on Their Activity in the Conversion of Ethanol into 1,3-Butadiene[END_REF] In support of this, the poorly marked shoulder at 1602 cm -1 disappears at a pyridine desorption temperature of 523 K.

Therefore, for ZnLaZrSi oxide samples, the FTIR spectra of adsorbed pyridine after its desorption at 523 and 623 K contain IR adsorption bands of coordinatively bonded pyridine only with zinc-and zirconium-containing LAS. The bands at 1614 and 1454 cm -1 corresponds to Zncontaining acid sites, as proved by the absence of these bands in the FTIR spectra of adsorbed pyridine for the samples without zinc (Figure S4). The band at 1610 and 1448 cm -1 represents Zr-containing acid sites. [START_REF] Larina | Effect of the Addition of Zirconium Dioxide on the Catalytic Properties of ZnO/MgO-SiO<inf>2</Inf> Compositions in the Production of 1,3-Butadiene from Ethanol[END_REF][START_REF] Larina | Ethanol Conversion to 1,3-Butadiene on ZnO/MgO-SiO2 Catalysts: Effect of ZnO Content and MgO:SiO2 Ratio[END_REF] Catalytic properties of the ZnLaZrSi-oxide systems 1). With an increase in WHSV, the target process indices (ethanol conversion and 1,3-BD selectivity) are decreased with a simultaneous increase in the selectivity of acetaldehyde (AA) and ethanol dehydration products (ethylene and diethyl ether, DEE). For ZnLaZr-A-175, a decrease in the target process indices is more significant than for the catalysts with a higher S BET (ZnLaZr-KSKG, ZnLaZr-A-380). That may be a consequence of the fact that the concentration of Lewis acid sites on the ZnLaZr-A-175 surface is lower than for the samples based on KSKG and A-380 supports (Figure 3). At WHSV = 0.8-1.2 h -1 , in the presence of ZnLaZr-KSKG and ZnLaZr-A-380 ethanol conversion is higher than for ZnLaZr-A-175. At WHSV = 1.2 h -1 , the catalyst productivity of 1,3-BD formation changes in the following sequence: ZnLaZr-A-175 < ZnLaZr-A-380 < ZnLaZr-KSKG, which is consistent with a change in the values of S BET .

At similar ethanol conversion values (34-39%), the most active catalyst is ZnLaZr-KSKG with 1,3-BD selectivity of 65% and the productivity of 0.155 g 1,3-BD •g cat -1 •h -1 . The ZnLaZr-KSKG sample is also more selective for 1,3-BD formation at ethanol conversion values of 38.9-40.1%

(at WHSV = 0.8 h -1 ). In the ref. [START_REF] Dagle | Effect of the SiO2 Support on the Catalytic Performance of Ag/ZrO2/SiO2 Catalysts for the Single-Bed Production of Butadiene from Ethanol[END_REF] , higher 1,3-BD selectivity and yield are also achieved in the presence of the 1 %Ag/4 %ZrO 2 /SiO 2 catalyst based on KSKG support (in comparison with the samples based on A-380 or other types of silica). Wherein, ZnLaZr-KSKG catalyst has a maximum mesopore size of 10 nm. In the ref. [START_REF] Jones | Investigations into the Conversion of Ethanol into 1,3-Butadiene[END_REF] , the 150 A˚ ZnZrSi oxide system gave a high selectivity to 1,3-BD compared to the 40 and 60 A˚ ones at a similar ethanol conversion too.

Among the MMS-based catalysts (Table 3), at WHSV = 0.4 h -1 the highest 1,3-BD selectivity of 63.1 % and the yield of 31.0 % are achieved over ZnLaZr-SBA-15, although ethanol conversion does not exceed 49.2 %. In the presence of ZnLaZr-MCM-48 (a sample with porous structure characteristics comparable to the ZnLaZr-SBA-15 catalyst, Table 1), a comparable 1,3-BD yield of 30.8 % is achieved. Although the ethanol conversion accounts for 69.0 %, the selectivity of 1,3-BD formation is 44.7 %, which is much lower than for ZnLaZr-SBA-15. In the presence of ZnLaZr-MCM-41 and ZnLaZr-MCF (the samples with the highest S BET and pore diameters/volumes, respectively, Table 1) the selectivity of 1,3-BD formation and the yield are lower than for ZnLaZr-SBA-15, also with an increase in WHSV. It should be noted that higher selectivity values towards by-products of ethanol dehydration are achieved in the presence of the catalysts based on MCM-41, MCM-48 and MCF which surface is characterized by a higher amount of weak acid sites (Figure 3, the intensity of adsorption band at 1446 cm -1 at 423 K).

Thus, the target process indices are less affected by the structural-dimensional characteristics of ZnLaZrSi oxide systems based on MMS than acid properties of the catalysts.

At similar ethanol conversion (47.6-52.0%), the highest selectivity of 1,3-BD formation among the MMS-based catalysts is achieved in the presence of ZnLaZr-SBA-15. Wherein, 1,3-BD productivity of ZnLaZr-MCM-48 is the highest under such comparison conditions, but the main conversion products are ethylene and DEE. At similar ethanol conversion (32.8-36.7 %), the highest 1,3-BD selectivity among the microporous crystalline systems is achieved over ZnLa-Zr 1 SiBEA. The selectivity of ethylene+DEE formation is comparable for both Zr-containing dealuminated BEA zeolites, but the residual quantity of AA is higher for ZnLa-Zr 3 SiBEA. In contrast, in the presence of ZnLa-Zr 1 SiBEA, higher selectivity towards others products is observed, probably, because of nonselective transformation of AA. In the presence of ZnLaZr-SiBEA, ethanol is preferably converted to ethylene and DEE.

It is worth emphasizing that ethanol conversion decreases with an increase in zirconium content in ZnLa-ZrSiBEA samples (Table 4). Such tendency may be due to an excess of zirconium cations in comparison with vacant T-atom sites formed in the BEA zeolite framework upon dealumination step with nitric acid treatment and, as a result, subnanoclusters of zirconium oxide could be formed. This assumption is consistent with the results of FTIR spectroscopic measurements of adsorbed pyridine (Figure 3): at 523 K the intensity of the bands corresponding to Lewis acid sites is higher for ZnLa-Zr 1 SiBEA than for ZnLa-Zr 3 SiBEA. The formation of subnanoclusters with an increase of the heteroelement content in dealuminated BEA zeolite involves a decrease in ethanol-acetaldehyde mixture conversion (without a decrease in 1,3-BD selectivity) as was previously observed for Nb-containing catalysts. [START_REF] Kyriienko | Effect of the Niobium State on the Properties of NbSiBEA as Bifunctional Catalysts for Gas-and Liquid-Phase Tandem Processes[END_REF] With an increase in WHSV, a decrease in ethanol conversion is observed for both ZnLa-ZrSiBEA samples, but in the presence of ZnLa-Zr 1 SiBEA 1,3-BD selectivity increases markedly (Figure 4). This may occur because, at a high linear flow rate, the reacting molecules primarily The development of catalysts containing Lewis acid sites, represented by isolated Zr 4+ species, is the pathway to obtain high performance zeolite catalysts. In the presence of ZnLa-Zr 1 SiBEA, [START_REF] Sushkevich | Ag-Promoted ZrBEA Zeolites Obtained by Post-Synthetic Modification for Conversion of Ethanol to Butadiene[END_REF] At the same time, the ZnLa-Zr 3 SiBEA catalyst productivity of 1,3-BD formation does not reach the value for ZnLa-Zr 1 SiBEA even with a triple increase in WHSV.

In general, among the studied ZnLaZrSi-oxide systems, during the conversion of 80 vol% EtOH aqueous mixture (WHSV=1.2 h -1 , T=648 K) the highest catalyst productivity of 1,3-BD formation (0.155 g 1,3-BD •g cat -1 •h -1 ) is achieved for ZnLaZr-KSKG sample and a slightly lower productivity (0.146 g 1,3-BD •g cat -1 •h -1 ) for ZnLaZr-SBA-15 sample. The productivity values for ZnLa-Zr 1 SiBEA account for 0.239 g 1,3-BD •g cat -1 •h -1 at WHSV = 1.44 h -1 and 0.324

g 1,3-BD •g cat -1 •h - 1 at WHSV = 2.88 h -1 .
Analyzing the data presented in Tables 234, it is concluded that no significant change in the target product selectivity, i.e. in a relative change in 1,3-BD selectivity within 10 % for one catalyst, with the ethanol conversion variations in the range of 20-60 %.

This is consistent with the data obtained by Baba et al. [START_REF] Hayashi | Experimental and Computational Studies of the Roles of MgO and Zn in Talc for the Selective Formation of 1,3-Butadiene in the Conversion of Ethanol[END_REF][START_REF] Akiyama | Selective Conversion of Ethanol to 1,3-Butadiene Using Germanium Talc as Catalyst[END_REF] for Zn-talk and ZnGe-talk catalysts in the mentioned ethanol conversion range.

For ZnLaZr-KSKG and ZnLaZr-SBA-15 catalysts, EtOH conversion has been studied as a function of time-on-stream (Figure 5). In the presence of the catalysts, the values of EtOH conversion and 1,3-BD yield do not reduce significantly with time-on-stream up to 700 min. The constancy of 1,3-BD selectivity is also observed. A slight decrease in the selectivity to ethanol dehydration products with an increase in AA selectivity is observed after 9 h of operation.

The data in Figure 6 allow comparing the formation rates of 1,3-BD, acetaldehyde and ethylene+DEE, calculated per unit mass (r m ), per unit surface area (r s ) and per unit external surface area (r extern. ) of the catalyst. In the case of 1,3-BD formation, r m values are higher for ZnLaZr-KSKG and ZnLaZr-SBA-15 catalysts. The highest r s value of BD formation (as well as AA formation) is observed for ZnLaZr-A-175, which may be attributed to the lowest S BET for this sample. Comparing the values of r extern. , the degree of external surface use is supposed to be lower for ZnLaZr-A-175 as opposed to the samples based on KSKG and SBA-15. Furthermore, the r extern. value for ZnLaZr-A-175 is comparable to that for ZnLaZr-MCF probably because of the similar values of S ext . Overall, the 1,3-BD formation rates are changed in the following sequences (the samples are marked as the silica support used): The high r m , r s , and r extern. values of ethylene+DEE formation are achieved in the presence of ZnLaZr-MCF, while the r s and r extern. values are generally low for ZnLa-Zr 3 SiBEA. The lowest values of 1,3-BD formation over zeolite supported catalysts are obviously associated with the support microporosity which can be involved into the catalytic process only partially due to a limited micropore size and corresponding pore blocking. Therefore, acid characteristics of the resulting catalyst for ETB process are suggested to be more significant than high S BET and S ext.

values of the silica support used for preparation of ZnLaZrSi oxide systems.

Water vapor effect on catalytic performance of the ZnLaZrSi oxide systems for ETBprocess

The water content in aqueous EtOH feed is a very important parameter affecting the target indices of ETB process. [START_REF] Larina | 1,3-Butadiene Production from Ethanol-Water Mixtures over Zn-La-Zr-Si Oxide Catalyst[END_REF][START_REF] Velasquez Ochoa | An Analysis of the Chemical, Physical and Reactivity Features of MgO-SiO2 Catalysts for Butadiene Synthesis with the Lebedev Process[END_REF][START_REF] Cabello González | Ethanol Conversion into 1,3-Butadiene over a Mixed Hf-Zn Catalyst: Effect of Reaction Conditions and Water Content in Ethanol[END_REF][START_REF] Kyriienko | Effect of the Composition of Ethanol -Water Mixtures on the Properties of Oxide (Zn-Zr-Si) and Zeolitic (Ta/SiBEA) Catalysts in the Production of 1,3-Butadiene[END_REF] An absolute change in the values of ethanol conversion and the yields of 1,3-butadiene, acetaldehyde and ethylene+diethyl ether can be estimated using Figure 7. The complete data of catalytic performance of ZnLaZrSi-oxide systems in EtOH-water mixture conversion are summarised in Table S1. S1).

The obtained data are consistent with the results and conclusions of the ref. [START_REF] Larina | 1,3-Butadiene Production from Ethanol-Water Mixtures over Zn-La-Zr-Si Oxide Catalyst[END_REF] : the reason for the deactivation of ETB process catalyst is water adsorption on the LAS responsible for aldol condensation of acetaldehyde. Let's consider the effect of water vapor on activity of the catalysts to dehydrogenation (selectivity to AA and 1,3-BD as the main product of AA aldol condensation) and dehydration (selectivity to ethylene and DEE). The selectivity of 1,3-BD formation declines however AA selectivity increases (see Table S1), and a fraction of noncondensed AA rises in the product stream. Therefore, the effect of water vapor on ethanol dehydrogenation is considered less significant than on aldol condensation. The selectivity of ethylene+DEE formation rises noticeably, herewith, ethylene+DEE yield is reduced along with 1,3-BD one but to varying degrees (Figure 7).

In the refs. [START_REF] Velasquez Ochoa | An Analysis of the Chemical, Physical and Reactivity Features of MgO-SiO2 Catalysts for Butadiene Synthesis with the Lebedev Process[END_REF][START_REF] Cabello González | Ethanol Conversion into 1,3-Butadiene over a Mixed Hf-Zn Catalyst: Effect of Reaction Conditions and Water Content in Ethanol[END_REF] the reason for the deactivating effect of water vapor are proposed to be Н 2 О adsorption on LAS with their transformation to Brønsted acid sites (BAS) responsible for EtOH dehydration. However, this explanation seems to be incomplete. The water vapor released in the conversion of rectified EtOH into 1,3-BD and ethylene would be sufficient to hydrate the catalyst surface with the formation of low amount of BAS. Moreover, as mentioned in the ref. [START_REF] Santos | The Role of Brønsted and Water-Tolerant Lewis Acid Sites in the Cascade Aqueous-Phase Reaction of Triose to Lactic Acid[END_REF] , only partial blocking of LAS occurs on the hydrated surface of ZrO 2 . Lebedev et al. [START_REF] Talalay | The Russian Synthetic Rubber from Alcohol. A Survey of the Chemistry and Technology of the Lebedev Process for Producing Sodium-Butadiene Polymers[END_REF] have noted the negative effect of the presence of water in EtOH feed on 1,3-BD yield in ETB process, whereas an increase in AA yield and a decrease in ethylene yield are observed. According to the ETB process mechanism proposed by Lebedev, C-C coupling occurs between ethylene and acetaldehyde via the Prins reaction. Therefore, the main reason for the decrease in 1,3-BD yield has been determined as a decrease in the rate of ethylene formation. Based on the thermodynamic calculations, [START_REF] Angelici | Chemocatalytic Conversion of Ethanol into Butadiene and Other Bulk Chemicals[END_REF] in ETB process the formation of C 4 products via the Prins reaction has shown to be unlikely. An increase in AA yield and a decrease in ethylene yield can be explained by a deactivation of EtOH dehydration sites. A decrease in the selectivity towards dehydration products with an addition of water to the feed mixture of EtOH/AA is also observed in ref. [START_REF] Zhang | The Deactivation of ZnO Doped ZrO2-SiO2 Catalyst in the Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene[END_REF][START_REF] Zhu | Conversion of Ethanol and Acetaldehyde to Butadiene over MgO-SiO2 Catalysts: Effect of Reaction Parameters and Interaction between MgO and SiO2 on Catalytic Performance[END_REF] Therefore, LASs responsible for aldol condensation of acetaldehyde just remain blocked by water without forming new EtOH dehydration sites.

The ZnLa-Zr 3 SiBEA sample is an exception in this respect. In the presence of this catalyst 1,3-BD selectivity is even higher during the conversion of 50 vol% EtOH aqueous mixture as opposed to 96 vol% EtOH one, while AA selectivity remains almost unchanged (Table S1).

Besides, in the presence of ZnLa-Zr 1 SiBEA an absolute decrease of 1,3-BD selectivity is less than for the studied non-zeolite catalysts. A similar tendency with a change in ethanol conversion, 1,3-BD and AA selectivity is also observed during the conversion of 50 vol% and 96 vol% EtOH aqueous mixtures in the presence of Zn 1 Ta 1 SiBEA catalyst (in contrast to Cu 1 Ta 1 SiBEA and Ag 1 Ta 1 SiBEA). [START_REF] Kyriienko | Effect of the Composition of Ethanol -Water Mixtures on the Properties of Oxide (Zn-Zr-Si) and Zeolitic (Ta/SiBEA) Catalysts in the Production of 1,3-Butadiene[END_REF] Perhaps, in the case of Zn-M-containing zeolite catalysts, the bifunctional sites like Zn-La, Zn-Zr, Zn-Ta species are formed in the SiBEA structure, as it has been previously noted for Zn-Y/Beta catalysts. [START_REF] Yan | Mechanistic Insights into One-Step Catalytic Conversion of Ethanol to Butadiene over Bifunctional Zn-Y/Beta Zeolite[END_REF] The intermediates react with each other on these sites to generate 1,3-BD rather than desorb as unwanted byproducts. Therefore, H 2 O as a Lewis base is adsorbed on the catalyst surface blocking of a part of LASs responsible for aldol condensation of acetaldehyde without the formation of new EtOH dehydration sites.

It should be noted that higher 1,3-BD selectivity is achieved during the conversion of ethanolaqueous mixtures in the presence of ZnLaZr-KSKG as opposed to ZnZr-KSKG (see Table S2, [START_REF] Larina | The Effect of ZnO on Acid-Base Properties and Catalytic Performance of ZnO/ZrO2-SiO2 Catalysts in 1,3-Butadiene Production from Ethanol-Water Mixture[END_REF] ). This may be attributed to the fact that Brønsted basic sites being active in aldol condensation [START_REF] Singh | Green Synthesis of 1,4-Benzodiazepines over La2O3 and La(OH)3 Catalysts: Possibility of Langmuir-Hinshelwood Adsorption[END_REF][START_REF] Lippert | Secondary Reactions of the Base-Catalyzed Aldol Condensation of Acetone[END_REF][START_REF] Frey | Supported La2O3 and MgO Nanoparticles as Solid Base Catalysts for Aldol Reactions While Suppressing Dehydration at Room Temperature[END_REF] (including ETB process) [START_REF] Kyriienko | Effect of the Composition of Silver Doped M-Si Oxide Systems (M: Mg, Zr, La) on Their Catalytic Properties in the Conversion of Ethanol to 1,3-Butadiene[END_REF] are formed during deposition of lanthanum oxide or hydroxide on SiO 2 . [START_REF] Mekhemer | Surface Structure and Acid-Base Properties of Lanthanum Oxide Dispersed on Silica and Alumina Catalysts[END_REF] The similar lanthanum effect on EtOH conversion rates and 1,3-BD selectivity can be observed by comparing the data of the ref. [START_REF] Jones | Investigations into the Conversion of Ethanol into 1,3-Butadiene[END_REF] (the conversion of 96 vol% EtOH aqueous mixture in the presence of the 1.5%Zr-0.5%Zn/SiO 2 catalyst) and the ref. [START_REF] Lewandowski | Process for the Production of 1,3-Butadiene[END_REF] (the conversion of 92 vol% EtOH aqueous mixture in the presence of the ZrZn-La/SiO 2 catalyst). The addition of 2 wt % lanthanum to the ZrZn/SiO 2 system promotes an increase in 1,3-BD selectivity, and an increase in the lanthanum content up to 3 wt % increases 1,3-BD yield.

However, the productivity of 1,3-BD formation is higher for the unpromoted ZrZn/SiO 2 catalyst, as in our case.

In the lattice of dealuminated BEA zeolite, there are many unsaturated vacancies. Therefore, in the presence of ZnLa-ZrSiBEA catalysts unvaried high 1,3-BD selectivity with the change of 96 vol% EtOH aqueous mixture feed to 50-80 vol% EtOH one (see Table S1) can be explained by a larger number of Si-O-La-OH sites formed in the dealuminated BEA zeolite.

There is another problem of slow deactivation of ZnLaZrSi oxide systems in ETB process at long time-on-stream, 20 e.g. due to the formation of heavy by-products via condensation reactions. . [START_REF] Bonardet | Use of NMR Techniques for Studying Deactivation of Zeolites by Coking[END_REF] The signals of alkenes, alkynes, aromatic compounds, esters, acids, aldehydes and ketones are absent, likely because these products are not formed during ETB process or are easily desorbed from the catalyst surface. Thus, the presence of water vapor in the feed prevents carburizing of the catalyst during its operation in the ETB process, [START_REF] Zhang | The Deactivation of ZnO Doped ZrO2-SiO2 Catalyst in the Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene[END_REF] in particular by reducing the formation of C 6+ compounds. [START_REF] Cabello González | Ethanol Conversion into 1,3-Butadiene over a Mixed Hf-Zn Catalyst: Effect of Reaction Conditions and Water Content in Ethanol[END_REF] In the reaction conditions water vapor, being more efficient oxidizing agent than O 2 , 56 can oxidize C 6+ compounds at the time of their formation, when their reactivity is still high. Also, the blocking of strong acid sites being active in the formation of C 6+ compounds, [START_REF] Zhang | The Deactivation of ZnO Doped ZrO2-SiO2 Catalyst in the Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene[END_REF][START_REF] Zhang | Study of Ethanol/Acetaldehyde to 1,3-Butadiene Over MgO-SiO2 Catalyst: Comparative Investigation of Deactivation Behaviour Due to Carbon Deposition[END_REF] as a result of water vapor adsorption, helps to reduce the formation rate of these compounds. However, this topic will be the subject of a separate study.

CONCLUSIONS

The The main reason for the decrease in 1,3-BD yield in the presence of water vapor in the reaction mixture is shown to be the deactivation of acetaldehyde condensation sites on the catalyst surface, while the rate of acetaldehyde formation decreases slightly. In the presence of lanthanum-containing ZnLaZrSi oxide system the selectivity of 1,3-BD formation is enhanced.

According to 1 H- [START_REF] Lewandowski | Process for the Production of 1,3-Butadiene[END_REF] C CP/MAS NMR spectroscopic results, the use of aqueous ethanol as the feed for ETB process is found to prevent carburization of the catalysts.

To prepare the ZnLa-(6%)Zr-KSKG catalyst, KSKG industrial silica gel (silica gel granular with large pores) has been used; it is the cheapest silica material among the used ones. Therefore, a highly efficient catalyst for ETB process can be prepared in a simple method (by wet kneading) using the mentioned inexpensive material, that will enhance the prospects for successful implementation of 1,3-butadiene production from ethanol in the future. However, the constancy of 1,3-BD selectivity is observed in the presence of the systems based on ZrSiBEA with isolated tetrahedral Zr(IV) species even using 50 vol% EtOH aqueous mixture as a feed. Moreover, the productivity of ZnLa-Zr 1 SiBEA catalyst accounts for 0.324 g 1,3-BD •g cat -1 •h -1 (T = 648 К, WHSV

Zr 1

 1 SiBEA and Zr 3 SiBEA. Then, all Zr-Si oxide samples were sequentially impregnated to incipient wetness with aqueous solutions of chemically-pure-grade La(NO 3 ) 3 •6H 2 O and Zn(O 2 CCH 3 ) 2 with intermediate drying at 393 K (2 h) and calcination at 773 K (3 h). The 2 wt % ZnO-3 wt % La-containing samples were prepared and marked as ZnLaZr-KSKG (A-175, A-380, SBA-15, MCM-41, MCM-48, MCF) and ZnLa-Zr 1 SiBEA and ZnLa-Zr 3 SiBEA.

  Structural and textural characteristics of the catalystsXRD patterns (Figure1) of the prepared catalysts indicate amorphous structure of the supported silica materials typical of the initial silica mesoporous molecular sieves (MMS). The low-angle reflexes characteristic for the MMS supports are absent in the XRD patterns due to the filling of the support pores with the active phase resulting in an increase the number of atoms per a unit cell. The only low-intense reflection present in these XRD patterns can be attributed to monoclinic ZrO 2 phase. XRD patterns of the zeolite supported samples demonstrate highly crystalline structure characteristic of BEA zeolite with main well-defined reflections at 2θ = 7.7°; 22.5°.

Figure 1 .

 1 Figure 1. XRD patterns of the prepared catalysts: 1 -ZnLaZr-KSKG; 2 -ZnLaZr-A-175; 3 -

Figure 3 .

 3 Figure 3. FTIR spectra of adsorbed pyridine the samples after their treatment at appropriate

  interact with open Zr 4+ Lewis acid sites, represented by isolated Zr(IV) in tetrahedral positions of the zeolite crystalline structure and connected to three -O-Si linkages and one OH-group. According to Sushkevich et al. 32 , open Zr 4+ Lewis acid sites are more active towards 1,3-BD formation.

Figure 4 .

 4 Figure 4. Effect of WHSV on ethanol conversion and selectivity to 1,3-butadiene, acetaldehyde,

  r m : KSKG > SBA-15> MCF ≥ A-175 > Zr 3 SiBEA, r s : A-175 > KSKG > SBA-15 > MCF > Zr 3 SiBEA, r extern. : KSKG > SBA-15 > MCF ≥ A-175 > Zr 3 SiBEA.

Figure 5 .

 5 Figure 5. Ethanol conversion, 1,3-butadiene yield, and selectivity to products over ZnLaZr-

Figure 6 .

 6 Figure 6. The formation rates of 1,3-butadiene, acetaldehyde and ethylene+diethyl ether,

Figure 7 .

 7 Figure 7. Effect of water vapor on absolute change of ethanol conversion and the yields of 1,3-

1 H- 13 C

 13 CP/MAS NMR investigations of organic deposits on a spent catalyst allow finding out the nature of occluded organic compounds and evaluating mechanistic aspects of deactivation.[START_REF] Zhang | The Deactivation of ZnO Doped ZrO2-SiO2 Catalyst in the Conversion of Ethanol/Acetaldehyde to 1,3-Butadiene[END_REF][START_REF] Yan | On the Deactivation Mechanism of Zeolite Catalyst in Ethanol to Butadiene Conversion[END_REF]

Figure 8 .

 8 Figure 8. 1 H -13 C CP/MAS NMR spectra of the samples after catalysis: 1 -ZnLaZr-KSKG;

  ZnLaZrSi oxide systems prepared with a silica component of the different type (nature) have been studied in the 1,3-BD production from aqueous ethanol. The commercially available silica (KSKG, A-175, A-380), ordered mesoporous silica (SBA-15, MCM-41, MCM-48), mesocellular siliceous foam (MCF) and dealuminated BEA zeolites have been used. The characteristics of the silica support porous structure, such as total porosity, pore size distribution, specific and external surface areas, are found not to be critical parameters for achieving a high 1,3-BD yield during the EtOH-H 2 O mixture conversion in the presence of ZnLaZrSi oxide catalysts. The quantity and strength of Lewis acid sites, which in turn differ depending on the choice of the silica material, have a significant impact on 1,3-BD selectivity and yield. Ethylene and diethyl ether selectivity is increased with the concentration of weak Lewis acid sites, thereby a decrease in 1,3-butadiene selectivity is observed.The highest values of the selectivity of 1,3-BD formation and yield as well as stability toward deactivation in the presence of water vapor are achieved over ZnLa-(6 %)Zr-KSKG, ZnLa-(6 %)Zr-SBA-15 and ZnLa-Zr 1 SiBEA prepared by incorporation of zirconium cations in the framework of BEA zeolite as isolated tetrahedral Zr(IV) species. In the presence of ZnLaZrSi oxide catalysts based on MCM-41, MCM-48 and MCF with a developed porous structure, a high selectivity to ethanol dehydration products is observed, which is caused by a high amount of weak Lewis acid sites on the surface.

Table 1 .

 1 Structural

	Sample	V mi	a) ,	D mi , E 0 ,	V me ,	S me	a) , D me.max ,	S ext.	a) , S BET ,	V ∑	c) ,	|Δµ o |,

characteristics (nitrogen ad(de)sorption, 77 К) of the prepared catalysts.

Table 2 .

 2 The indices of ETB process in the presence of ZnLaZrSi oxide systems prepared with amorphous silicon oxides a T = 648 K, TOS = 1-5 h, 80 vol% EtOH in water as an EtOH source. Table 2 presents catalytic performance of ZnLaZrSi oxide systems prepared with amorphous silicon oxides (KSKG, A-175, A-380) for EtOH conversion. At WHSV = 0.4 h -1 , the highest values of ethanol conversion (63.6 %) and 1,3-BD yield (41.7 %) are achieved in the presence of ZnLaZr-A-175 (the sample with the lowest S BET and the highest S ext. among the studied systems, see Table

	Catalysts	WHSV,	EtOH	Selectivity, %			1,3-BD	1,3-BD
		h -1	Conv., %	1,3-BD AA	+DEE Ethylene	Others	Yield, %	Product., g 1,3-BD •g cat -1 •h -1
	ZnLaZr-KSKG	0.4	58.4	68.0	7.3	18.1	6.7	39.7	0.093
		0.8	40.1	61.4	11.3 22.3	5.0	24.6	0.116
		1.2	33.8	65.0	10.8 19.8	4.4	22.0	0.155
	ZnLaZr-A-175	0.4	63.6	65.5	9.9	18.6	6.0	41.7	0.098
		0.8	37.0	58.1	15.7 22.3	3.9	21.5	0.100

a

Table 3

 3 The indices of ETB process in the presence of ZnLaZr-MMS mesoporous amorphous systems a Lewis acid sites in the framework of zeolite as isolated tetrahedral Zr(IV) species. These sites are more active in aldol condensation of acetaldehyde than zirconium present as zirconium oxide.[START_REF] Sushkevich | With Open Arms: Open Sites of ZrBEA Zeolite Facilitate Selective Synthesis of Butadiene from Ethanol[END_REF][START_REF] Sushkevich | Ag-Promoted ZrBEA Zeolites Obtained by Post-Synthetic Modification for Conversion of Ethanol to Butadiene[END_REF]

	Catalysts	WHSV,	EtOH	Selectivity, %			1,3-BD	1,3-BD
		h -1	Conv., %	1,3-BD AA	+DEE Ethylene	Others	Yield, %	Product., g 1,3-BD •g cat -1 •h -1
	ZnLaZr-SBA-15	0.4	49.2	63.1	10.6 19.4	6.8	31.0	0.073
		0.8	39.8	58.9	13.4 23.1	4.6	23.4	0.11
		1.2	33.1	62.6	11.0 22.7	3.7	20.7	0.146
	ZnLaZr-MCM-41	0.4	60.8	57.1	5.0	32.3	5.6	34.7	0.082
		0.8	51.3	55.4	6.3	34.1	4.2	28.4	0.133
	ZnLaZr-MCM-48	0.4	69.0	44.7	4.8	45.0	5.5	30.8	0.072
		1.2	52.0	41.3	5.2	48.7	3.8	21.5	0.151
	ZnLaZr-MCF	0.4	54.5	48.2	10.4 36.9	4.3	26.3	0.062
		0.8	47.6	45.4	9.5	41.1	4.0	21.6	0.101
		1.2	35.0	44.6	10.7 42.0	2.7	15.6	0.110
	ZnLaZr-SiBEA, the highest ethanol conversion of 67.4 % is achieved, while 1,3-BD selectivity
	is only 34.6 % because of the preferred occurrence of by-product dehydration. The selectivity of
	ethylene and diethyl ether formation accounts for 51.3 %. For the catalyst samples prepared by
	post-synthetic method of zirconium incorporation (ZnLa-Zr 1 SiBEA, ZnLa-Zr 3 SiBEA), the
	conversion of ethanol is lower (less than 58.0 %), but the selectivity of 1,3-BD formation is
	higher (more than 46.4 %). Such increase in 1,3-BD selectivity, despite a lower (several-fold)

a T = 648 K, TOS = 1-5 h, 80 vol% EtOH in water as an EtOH source.

The data of catalytic performance of ZnLaZrSi oxide systems prepared with dealuminated BEA zeolite for EtOH conversion are presented in Table

4

. At WHSV = 0.4 h -1 in the presence of zirconium content in the ZnLa-Zr 1 SiBEA catalyst sample, can be explained by the presence of

Table 4

 4 The indices of ETB process in the presence of ZnLa-ZrSiBEA microporous crystalline

	systems a
	Catalysts	WHSV,	EtOH	Selectivity, %			1,3-BD	1,3-BD Product.,
		h -1	Conv., %	1,3-BD AA	Ethylene	Others	Yield, %	-1 •h -1 g 1,3-BD •g cat
						+DEE
	ZnLaZr-SiBEA	0.4	67.4	34.6	7.5	51.3	6.1	23.3	0.055
		1.6	32.8	30.5	8.8	53.3	7.4	12.4	0.070
	ZnLa-Zr 1 SiBEA	0.4	58.0	46.4	12.3	31.6	9.7	24.1	0.057
		2.88	31.1	61.7	3.4	12.0	22.9	19.2	0.324
	ZnLa-Zr 3 SiBEA	0.4	36.7	50.8	19.9	11.8	17.5	18.6	0.044
		0.8	19.9	51.1	12.5	10.3	17.1	10.2	0.048
		1.2	14.5	52.0	21.7	9.9	16.1	7.5	0.053

a T = 648 K, TOS = 1-5 h, 80 vol% EtOH in water as an EtOH source.

chemical industry" (0119U101562), grant of National Academy of Sciences of Ukraine for implementation of research projects of young scientists groups. P.I. Kyriienko acknowledges the CERIC-ERIC Consortium for access to experimental facilities at FESEM at the Charles University in Prague (Proposal number: 20172060) and NMR Spectrometer "Magic" at Slovenian NMR Centre (Proposal number: 20192025).

= 2.88 h -1 , 80 vol% EtOH in water as an EtOH source). Therefore, for industrial realization of ETB process the development of the effective catalysts based on dealuminated BEA zeolites is also promising.

ASSOCIATED CONTENT

Supporting Information. The following file is available free of charge.

29

Si and 1 H - [START_REF] Kyriienko | Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)[END_REF] Si CP MAS NMR spectra of ZnLa-Zr 3 SiBEA sample, SEM images of the ZnLaZrSi samples at three magnifications, the indices of EtOH-water mixture conversion in the presence of ZnLaZrSi oxide systems, the indices of ETB process in the presence of 2 %ZnO/6 %ZrO 2 -KSKG (DOCX).

AUTHOR INFORMATION Corresponding Authors

* E-mails: pavlo_kyriienko@ukr.net (P.K.) and stanislaw.dzwigaj@sorbonne-universite.fr.

upmc.fr (S.D.).

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

ACKNOWLEDGMENT