Guaiacol is a lignin model compound often used to study of the lignin and bio-oil hydrodeoxygenation (HDO) pathways, as well as to determine the efficiency of the catalysts used. In the present work, the guaiacol HDO process was studied in the presence of nickel, ruthenium and bimetallic Ni/Ru catalysts prepared on the basis of the pre-oxidized carbon support "Sibunit". The hydrodeoxygenation process was carried out at temperatures of 200-250 degrees C, an initial H-2 pressure of 1.5 MPa in a medium of water, ethanol and dodecane. The bimetallic catalyst containing 10 wt.% Ni and 3 wt.% Ru (3Ru10Ni/C) turned out to be the most active and selective in the conversion of guaiacol into aromatic compounds and cyclic derivatives of alkanes in an aqueous medium. A catalytic study of the guaiacol HDO process in the presence of this bimetallic catalyst was carried out. The influence of the catalyst nature and characteristics on the HDO process routes is discussed.

Lignin is the largest renewable source of aromatic chemicals and has great potential for the production of high valueadded chemicals. In this work, we describe the process of hydrogenation of aspen wood ethanol-lignin in supercritical ethanol in the presence of Ni/C catalyst and in the absence of added catalysts. It is shown that at a temperature of 250 degrees C, the catalyst reduces the yield of solid residue from 7.3 to 1.9 wt%. The total yield of phenolic compounds during non-catalytic hydrogenation does not exceed 5.8 wt%. The bifunctional nickel-containing catalyst increases almost twofold (up to 10.1 wt%) the yield of liquid phenolic products, among which 4-propylsyringol predominates. Increasing the process temperature of catalytic hydrogenation to 300 degrees C leads to an increase in the yields of monomeric phenolic compounds to 13.4 wt%. In the presence of a catalyst, the molecular weight distribution of liquid products of ethanol lignin hydrogenation shifts to the low molecular weight region, due to an increase in the content of monomeric phenolic compounds in the liquid products.

Heterogeneous nanocomposite ZrO2@SBA-15 catalysts containing 10 wt

The catalysts containing Pd, Ru, Ni deposited on a carbon support oxidized to create acid sites allow to intensify lignin depolymerization and increase monomer yields. To design bifunctional catalysts, it is necessary to understand the mechanisms of reactions occurring on individual (metal or acid) catalytic sites. The hydrogenation process of 2-phenylethyl phenyl ether (PEPE) was studied, simulating the structure of lignin fragments connected by an ether beta- O-4 bond in the presence of Pd, Ru, Ni catalysts on a graphite- like support Sibunit. It was shown that the main route of PEPE conversion was hydrogenolysis of PEPE molecules with the formation of ethylbenzene and phenol with their subsequent hydrogenation, respectively, to ethylcyclohexane and cyclohexanol. The presence of acidic species on the support increases the activity of catalysts both in relation to the reaction of hydrogenolysis of the ether bond and in relation to the reaction of hydrogenation of the aromatic ring. The 3 %Ru/C-Ox catalyst on oxidized Sibunit exhibits the highest activity in hydrogenation of aromatic rings of PEPE, without breaking the ether bond. The yield of hydrogenated dimers in the presence of Pd/C-ox is noticeably lower with a simultaneously higher activity in breaking the ether bond.

In the paper, nanocomposites based on diisopropylammonium iodide (DIPAI.) and Al2O3 nanoparticles (sized 100 nm) have been synthesized with varying a volume fraction of the latter (0.05, 0.10, 0.20). Temperature dependences of the permittivity and a signal of differential thermal analysis of the samples (in the range of 300 - 400 K) were studied in heating and cooling modes. Their infrared spectra were recorded at room temperature as well. An analysis of the measured temperature dependences indicated a change in the sequence of phase transitions in nanocomposites compared with the pure DIPAI. The totality of the results obtained allowed us to conclude that a change in hydrogen bonds with the participation of amino groups manifested itself in the nanocomposite structure took place. This can lead to the appearance of a ferroelectric state in the DIPAI.

In order to make material with improved properties, nanocomposites based on nanoporous Al2O3films (having different pore sizes) filled with ferroelectric, namely, caesium nitrate CsNO3, have been fabricated, and their electrophysical charactistics have been investigated. The film surfaces were tested by electron microscopy. Temperature dependences of the effective permittivity & epsilon;' and of the third harmonic coefficient were measured for the nanocomposites. The phase-transition points were determined by the maximum value of the d & epsilon;'/dT derivative. The reduction in pore was found to lead to a decrease in the Curie temperature (by more than 30 K) and a phase transition blur. This phenomenon is associated with the influence of intrinsic size effects.

The present work reports the experimental results of studying linear and nonlinear dielectric properties of a ferroelectric nanocomposite from RbNO3 embedded in pores of an Al2O3 matrix. The dielectric relaxation times were determined above and below the phase transition temperature of pure RbNO3 (436 K). It was shown that for RbNO3 incorporated into nanosized pores of the Al2O3 matrix, a decrease in the phase transition temperature and a change in relaxation times were observed.

Background: The research of nanocomposites based on ferroelectrics has been recently stimulated by the discovery of a number of their unique properties. These properties are of particular interest from both fundamental and applied points of view Objective: This paper presents the results of comparative studies of the linear and nonlinear dielectric properties of potassium nitrate embedded from the solution and from the melt into aluminum oxide films with a pore diameter of 100 nm. Methods: An E7-25 impedance meter with a frequency range of 25 Hz – 1 MHz was used to investigate the linear dielectric properties. The setup for researching nonlinear dielectric properties has a sinusoidal oscillator with an operating frequency of 2 kHz. Results: The temperature dependences of the permittivity ε' and the third harmonic coefficient γ3ω were measured in the heating and cooling mode. It was found that for a nanocomposite obtained from the solution, the ferroelectric phase of KNO3 was formed only upon cooling in the temperature range 397 – 360 K. At the same time, when KNO3 was embedded into the Al2O3 film from the melt, the polar phase occurred both upon heating and cooling in the temperature range of 300 – 432 K and 300 – 421 K, respectively. Conclusion: Thus, the conducted studies of the dielectric properties showed a significant difference in the phase transition temperatures for the KNO3/Al2O3 nanocomposites obtained from the solution and from the melt compared to the bulk sample. The phase transition shifts during heating had a different sign for the nanocomposites obtained from the solution and from the melt. The temperature range of the existence of the ferroelectric phase significantly depends on the method of embedding KNO3 into aluminum oxide films. For the nanocomposite obtained from a solution, the polar phase is formed only upon cooling, whereas when potassium nitrate is embedded from the melt, the polar phase is formed both upon heating and cooling.

The study suggests a simple approach to improve phase transition properties and ferroelectricity of a typical ferroelectric metal-organic framework of [NH4][Zn(HCOO)(3)] (AmZn) using silicon dioxides nanoparticles (nSiO(2)). It is shown that the first-order transition type of AmZn is not changed under the influence of nSiO(2). Moreover, the phase transition temperature of AmZn significantly increased with increasing the nSiO(2) content from 0 to 40 wt%. Besides, the addition of small nSiO(2) content (< 11%) led to rising spontaneous saturation and remnant polarizations. The study also indicated difficulties in obtaining the saturation P-E loops at high nSiO(2) content.

Some samples of the (KNO3)(1)-(x)/(CsNO3)(x) composite with different x values have been prepared, and their temperature dependences of the differential thermal analysis signal, of the dielectric constant, and the amplitude of the third harmonic (to find an existence domain of the polar phase) were studied. The sample surfaces were investigated by scanning electron microscopy. An increase in the proportion of CsNO3 was revealed to lead to a decrease in the coefficient of nonlinearity of the composite and to narrowing of the existence domain's temperature range of the KNO3 ferroelectric phase III. Also it was found that the composite properties nonlinearity at x beyond 0.5 was determined by the CsNO3 properties.

The results of studies of phase transitions in mixtures of C6H16NBr (DIPAB) powders with PbTiO3 and Pb(Zr0.52Ti0.48)O3 (PZT) by the method of differential thermal analysis (DTA) are presented. The measurements were carried out in the heating and cooling mode in the range from 300 to 440 K. It was found that electrical interactions between ferroelectric particles led to the appearance of additional phase transitions for DIPAB in powder mixtures. Interaction effects in mixtures of DIPAB and PbTiO3 as well as DIPAB and PZT powders depend on the magnitude of the dipole moments of the particles.

In the paper, the temperature dependences of the differential thermal analysis signal, permittivity, and amplitude of the third harmonic of the (KNO3)(1-x)/Sn-x composites have been studied. It was shown that the temperature of the alpha -> beta phase transition decreased by 2 - 3 K in the potassium nitrates being parts of the composites, and the temperature of the gamma -> alpha phase transition decreased up to 360 K. This result can be explained within the framework of the Landau - Ginzburg theory, taking into account the shielding of potassium nitrate particles by tin metal particles.

The paper presents findings of an investigation of the linear and nonlinear dielectric properties of (R)-3-quinuclidinol embedded in porous aluminum oxide (pores of size 300 nm), in comparison with the properties of bulk (R)-3-quinuclidinol. A decrease in the Curie temperature in the nanocomposite, both upon heating and cooling, in comparison with a bulk sample is revealed. A decrease in the phase transition temperature allows for interpretation on the basis of the known theoretical models for ferroelectric small particles.

For the first time, the fractionation of birch wood into microcrystalline cellulose, xylose and methoxyphenols is suggested based on the integration of alkali-acid pretreatments and hydrogenation in ethanol over a bifunctional Ru/C catalyst. It is established that removal of hemicelluloses during pretreatments of birch wood influences the yields of the liquid, gaseous and solid products of the non-catalytic and catalytic hydrogenation of pretreated samples in ethanol at 225 °C. The bifunctional Ru/carbon catalyst affects in different ways the conversion and yields of products of hydrogenation of the initial and acid- and alkali-pretreated birch wood. The most noticeable influence is characteristic of the hydrogenation of the acid-pretreated wood, where in contrast to the non-catalytic hydrogenation, the wood conversion and the yields of liquid products increase but the yields of the solid and gaseous products decrease. GC-MS, gel permeation chromatography and elemental analysis were used for characterization of the liquid product composition. The molecular mass distribution of the liquid products of hydrogenation of the initial and pretreated wood shifts towards the low-molecular range in the presence of the catalyst. From the GC-MS data, the contents of monomer compounds, predominantly 4-propylsyringol and 4-propanolsyringol, increase in the presence of the ruthenium catalyst. The solid products of catalytic hydrogenation of the pretreated wood contain up to 95 wt% of cellulose with the structure, similar to that of microcrystalline cellulose.

Abstract The temperature dependences of the dielectric constant ε' and the third harmonic coefficient γ3ω for composite ceramics (СuO)1- x /(BaTiO3) x in the temperature range 100–300 K were studied. It is shown that the ε´(T) dependence for СuO has insignificant anomalies at transition temperature ТN 2 = 230 K. The maximum values of the third harmonics fit in the middle of the temperature interval [ТN 1 ; TN 2]. With an increase in the content of barium titanate, an increase in the dielectric constant and a shift of the polar region toward low temperatures are observed.

Lignin is a large-scale waste product of hydrolysis and the pulp-and-paper industries. The problem of lignin utilization is addressed by developing techniques for the comprehensive processing of wood biomass that are based on preliminary catalytic fractionation into its key components, which are subsequently used for obtaining target products. Hemicelluloses of larch wood are known to undergo effective depolymerization (~95 wt %) in ethanol at 250°C. Using hydrogen in combination with a catalyst enables us to increase the lignin conversion to 61 wt %, with 47 wt % of the cellulose left in the solid residue. The highest lignin conversion (67 wt %) is achieved using formic acid, but there is undesirable cellulose depolymerization (conversion, 66 wt %) under these conditions. The main monomer products of the catalytic conversion of lignin are 4-propenylguaiacol and 4-propylguaiacol. The content of 4-propenylguaiacol among the liquid products obtained using ethanol and formic acid as reducing agents can be as high as 36 and 33 rel %, respectively. The content of 4-propylguaiacol among the liquid products obtained using hydrogen grows to 33 rel % when a catalyst is used. This work describes the first study of the catalytic fractionation of larch wood in supercritical ethanol in the presence of the bifunctional 3%Ru/C catalyst containing acidic groups. The aim is to identify the effect of the catalyst and the nature of the hydrogen donor (ethanol, H2, or formic acid) on the yield and composition of the product.

Ferroelectric nanocomposites have great potential applications and are in the focus of modern studies. Their polar properties are due to spontaneous polarization in nanoparticles confined to insulator matrices. The crucial problem is the persistence of ferroelectricity under nanoconfinement as the ferroelectric phase transition can shift because of size effects and other grounds. We report the 31P nuclear magnetic resonance studies of nanoparticles of well known ferroelectric potassium dihydrogen phosphate (KDP) embedded into silica opal matrices. Two NMR techniques, static and magic angle spinning (MAS), were applied to confined KDP particles with different levels of deuteration, 80% and > 95%. Measurements were carried out using a Bruker Avance400 pulse spectrometer. Our findings proved unambiguously the pronounced reduction of the ferroelectric transition temperatures in the deuterated KDP/opal nanocoposites compared to the bulk counterparts in striking contrast to previous results.

Catalytic hydrogenolysis in the medium of supercritical organic solvents is a promising way of wood lignins depolymerization into liquid products. In this study, for the first time, the catalytic properties of bifunctional catalysts Ru/C, Pt/ZrO2, NiCuMo/SiO2, containing nanosized metal particles on acidic groups are compared in the processes of aspen wood and ethanol lignin hydrogenolysis in supercritical ethanol. The most active catalysts are Ru/C and Pt/ZrO2 which provide the high conversion of wood (to 78.0 wt%), significant yield of liquid products (to 50.6 wt%) and low yield of solid rest (to 22.0 wt%) at temperature 250 degrees C and H-2 pressure 9.0 MPa. These catalysts increase the yield of monomeric compounds in liquid products from 10.5 % to 50.4 % on mass of lignin. GC-MS analysis shows that alkyl derivatives of methoxyphenols (mainly propyl syringol and propyl guaiacol) are dominated in liquid products. Solid products of aspen wood catalytic hydrogenolysis contain mainly cellulose (to 82.2 wt%). Therefore, the catalytic hydrogenolysis in supercritical ethanol in the presence of by functional catalysts Ru/C and Pt/ZrO2 allows to fractionate the aspen wood biomass on cellulose and liquid products enriched with propyl syringol and propyl guaiacol. In catalytic hydrogenolysis of ethanol lignin the yield of alkyl derivatives of methoxyphenols is lower compared to wood. This is probably due to the reduced content of reactive beta-O-4 bonds in the structure of ethanol lignin compared to native lignin of aspen wood. As follows from the results obtained, native lignin of wood is easier depolymerized to monomeric compounds in the process of catalytic hydrogenolysis than ethanol lignin, isolated from wood. According to GPC data, the catalysts shift to the region of lower molecular mass the molecular mass distribution of liquid products of aspen wood and ethanol lignin hydrogenolysis.

The study aims at investigating dielectric properties and DTA signal of composite ceramics (BiFeO3)(1-) (x) /(BaTiO3) (x) (x = 0, 0.25, 0.50, 0.75) from 300 to 720 K. The obtained results indicated that the Neel temperature determined at the peaks of dielectric constant near the antiferromagnetic phase transition in (BiFeO3)(1-) (x) /(BaTiO3) shifted toward lower temperatures with increasing barium titanate content. This anomaly was also confirmed by the movement of DTA signal peaks.

Temperature evolution of the crystal structure and the third harmonic coefficient of potassium nitrate KNO3 nanoparticles embedded in the pores of porous alumina oxide Al2O3 films with nanometer size channels has been studied. A significant expansion of the temperature range of the ferroelectric phase was found under conditions of the restricted geometry compared to the bulk material. Coexistence of the ferroelectric and paraelectric phases was revealed.