Yevgenii Sheludko’s scientific contributions

It is known that the physicochemical characteristics of amorphous SiO2 are influenced by the raw material, process temperature, pH of the reaction medium, the ratio of reagents, the addition of coagulant, and modes of washing and drying. Previously, a waste-free technology for the production of biogenic silicon dioxide was described. However, there was a question of the ability to control the grain size of the final product. Therefore, the aim of our work was to study the effect of the ratio of mass concentrations of silicon-containing solution and coagulant (5:100; 5:500; 5:1000) on the physicochemical properties of the final product. The obtained samples of silicon dioxide were studied by various physicochemical methods. XRD pattern of the obtained silica showed that the 2-theta region between 5° to 80° at long collection times indicates no crystalline peaks. The FT-IR spectrum of the whole silica samples shows typical functional groups corresponding to pure silicon dioxide at 1074, 982, 800 and 457 cm−1. There are two distinct mass loss steps in termograms (TGA). It was established that obtained samples had a specific surface area of 86.8, 318.3 and 310.2 m2/g and pore size of 3.3, 13.8 and 9.2 nm depending on coagulant concentration (100, 500 and 1000), respectively. The atomic force microscope method established that the 3D image clearly shows the pointed vertices of SiO2 tetrahedral for the whole gels and some powders depending on the ratio of silicon-containing solution and coagulant (5:100; 5:500; 5:1000).

To mitigate the isopropylbenzene hydrocracking reaction on a classic industrial aluminum-nickel-molybdenum (ANM) catalyst , the latter was optimized by creating a composite membrane catalyst in combination with a proton current. In this work, the ANM-synthesized catalyst used as a component of the hydrocracking membrane catalyst simultaneously played the role of hydrogen splitting and recombination electrodes. The passivated and reduced ANM were analyzed for morphology and composition using different methods: low-temperature nitrogen sorption-desorption, XRD, XRF, FTIR-ATR, AFM, TGA and DSC. Using the XRD method, it was shown that the reduced in situ ANM catalyst contains metallic nickel particles on its surface, while on the passivated one it is in the maximally oxidized state of Ni 3+. The N 2 adsorption-desorption isotherms and pore size distribution curves of the ANM before and after reduction demonstrate a change in the specific surface area and pore size, which are caused solely by the transition of the catalyst from the oxide form to the fully or partially reduced form. In the example of a model reaction, the isopropylbenzene hydrocracking the high activity of the developed membrane catalysts was demonstrated in comparison with the granulated ones at temperatures of 240-290 °C and pressure of 4.0 MPa. The use of a composite membrane catalyst and the creation of a directed flow of protons through it that will, in our opinion, mitigate the conditions of the hydrocracking reactions. Experimental proof of this point of view was a tenfold increase in the activity.

The unique characters of nanocellulose (NC), such as superior mechanical properties, low density, high specific surface area, and low thermal expansion coefficient, make them an ideal building block for flexible functional compounds. That is why determining the structural and morphological characteristics of the obtained NC is a priority. From the microcrystalline cellulose obtained from air-dry soybean straw by the method of organ-solvent cooking described in [1] obtained NC by a known method [2]. Using the methods of XRD, XRF, FTIR-ATR, AFM, TGA and DSC, the structure and morphology of nanocellulose were studied. Due to the destruction of amorphous binders in the original MCC, regardless of the conditions of its production, we observe further ordering of the structure of the obtained NC. Which is expressed in narrower and more intense peaks in the range 2θ = 22-23 ° and IC values, as well as in reducing the degree of polymerization more than twice compared to the original MCC. As can be seen from the above FTIR-ATR spectra, the NC has all the characteristic peaks for the MCC. The increase in the crystallinity of the NC parts after MCC treatment is confirmed by thermogravimetric analysis and differential thermogravimetric analysis of samples. It is shown that to obtain nanocellulose it is necessary to take a high-purity MCC since the further destruction of amorphous components of cellulose occurs exclusively upon receipt of NC. It should be noted that, unlike previous MCCs, the NC forms an anisotropic relief, which consists of many parallel bands (ridges). The surface roughness is Ra = 12.6 nm, and the difference between depressions and heights is from -53.6 nm to + 63.6 nm. If you select and cut out the minimum possible fragment from the scan of the NC surface and present it in a 3D image, you can see the parallel planes of nanocellulose 3 nm thick.

From the microcrystalline cellulose obtained from air-dry soybean straw by the method of organ-solvent cooking obtained nanocellulose (NC). Using the methods of XRD, XRF, FTIR-ATR, AFM, TGA and DSC, the structure and morphology of nanocellulose were studied. Due to the destruction of amorphous binders in the original MCC, regardless of the conditions of its production, we observe further ordering of the structure of the obtain 22 23° and IC values, as well as in reducing the degree of polymerization more than twice compared to the original microcrystalline cellulose (MCC). As can be seen from the FTIR-ATR spectra, the NC has all the characteristic peaks for the MCC. The increase in the crystallinity of the NC parts after MCC treatment is confirmed by thermogravimetric analysis and differential thermogravimetric analysis of samples. According to AFM, the NC forms an anisotropic relief which consists of many parallel bands (ridges) and striped reliefs with almost parallel-oriented linear stripes.

Шляхом водної екстракції, описаної раніше, одержано зразок гарбузового пектину. Структуру та морфологію гарбузового пектину досліджено різними фізико-хімічними методами: низько температурною адсорбцією-десорбцією азоту, рентгенівською дифрактометрією (XRD), інфрачервоним спектральним аналізом із Фур’є перетворенням (FTIR-ATR) у режимі неповного відбивання, атомно-силовою мікроскопією (AFM), рентгено-флюорисцентною спектроскопією (XRF) термогравіметричним аналізом (TGA) разом зі скануючою калориметрією (DSC).

Mechanical activation is a simple, fast, cost-effective green technology that has been used for the upgrading and modification of microcrystalline cellulose (MCC). However, there is no information on the effect of short-term grinding on its physicochemical properties, as it is widely used for obtaining MCC powder or smaller particle with a size below 50 µm. Thus, the aim of our work was the investigation of physico-chemical properties of the flax unground and short-term ground MCC. In that study MCC was derived from air-dry flax in the medium ‘‘acetic acid–hydrogen peroxide–water’’ in the presence of 2 wt% sulfuric acid catalyst and then in the dry state it was ground in the laboratory mill for 1, 2 and 5 min. The morphology and composition of mechanically unground and ground MCC samples were analysed by different methods: XRD, XRF, FTIR-ATR, AFM, TGA and DSC. According to the XRD patterns of MCC samples, mechanical activation did not change the crystalline form of cellulose, but obviously, it destroyed the crystal structure of ground MCC, resulting in the increase of amorphization and the decrease of crystallinity index (from 86.2 to 78.2%). The FT-IR spectra also showed that the band corresponded to symmetric CH2 bendings at 1435–1429 cm−1, known as the crystallinity band, decreased with MCC samples grinding. AFM indicated that relief of the surface of original MCC changed by mechanical grinding (from the relief with large and small aggregates to the relief consisted of long-chain cellulose molecules parallel layers).

Plant-based biogenic silicon dioxide nanoparticles are used to produce catalysts, additives, templates for deposition of other semiconductors and metals, nanomaterials with novel properties, bio-nanocomposites for biomedical, energy and environmental fields. There are too many ways of bio-SiO2 production. Dependent on the way and obtaining condition some properties of the plant-based biogenic silicon dioxide nanoparticles can be changed. The most amount of silicon is accumulated in stalks and husk biomass of rice, buckwheat and oats. The aim of our work was the investigation of physic-chemical properties of the biogenic silicon dioxide obtained from the rice husk by both ecologically- and economically-friendly technology. The fluoric technology was used for silicon dioxide isolation. Our technology allows us to restore used catalysts. Thus this technology is ecologically and economically efficient. The synthesised SiO2 was studied by using the following methods: low-temperature nitrogen sorption–desorption, XRD, XRF, ICP-MS, AFM, FTIR-ATR, SEM-EDS, TGA. It was established that obtained samples had a specific surface area 107 m2/g. The XRD of the powdered SiO2 showed 100% amorphous characteristics of the material. FTIR, XRF SEM-EDS, ICP-MS and X-ray diffraction indicated that samples contain only SiO2. AFM results show obtained silica particles were having shape from spherical to lamellar. According to SEM investigated sample consists of spherical small aggregates.