The authors reveal aspects of the formation of platinum nanoparticles and chemical coating of carbon support surfaces when preparing model (0.5

The peculiarities of formation of platinum nanoparticles and chemical coating of carbon support surface during preparation of model (0.5%Pt/Sibunit) as well as industrial (0.5%Pt/Graphite) catalysts for hydroxylamine sulfate synthesis by NO hydrogenation in H2SO4 solution have been disclosed. It is shown that functionalization of the support surface with nitrogen-containing groups in the course of platinum deposition promotes not only metal dispersion but also a significant increase in its selectivity towards hydroxylamine sulfate. Based on experimental data, it is suggested that the maximal selectivity is inherent in the active centers representing single atoms or small clustersof platinum bound to nitrogen-containing ligands at the carbon surface.

A comparison is made of the thermoanalytical characteristics and the composition and structure of solid products of the thermal decomposition of ortho -phthalates [Cu(H 2 O) 2 (C 8 H 4 O 4 )], [CuNi(H 2 O) 4 (C 8 H 4 O 4 ) 2 ], and [Ni(H 2 O) 2 (C 8 H 4 O 4 )](H 2 O) 2 . It is found that the thermal decomposition of these compounds upon heating to 500°C in a He atmosphere can be conditionally divided into two stages: dehydration and decarboxylation. Polymer conglomerates containing uncoated Cu nanoparticles as large as 75 nm are embedded into the polymer matrix of the composite obtained via the thermal decomposition of [Cu(H 2 O) 2 (C 8 H 4 O 4 )]. Three types of nanoparticles with sizes of 40–85, 15–25, and 10–15 nm are embedded in the polymer matrices of composites. The particles are Cu x /Ni 1− x solid solutions of different compositions, obtained via the thermolysis of [CuNi(H 2 O) 4 (C 8 H 4 O 4 ) 2 ]. It is found that the onset temperature of [CuNi(H 2 O) 4 (C 8 H 4 O 4 ) 2 ] decarboxylation at the third part of the second stage with the formation of a three-phase region correlates with the temperature of decomposition of Cu x /Ni 1 – x solid solutions in the binary metal system, due apparently to the quantum size effect.

Исследованы процессы фазообразования при допировании скандием системы Y—Ba—Co—O в области составов 1:1:4:7. Механизм взаимодействия исходных реагентов меняется в зависимости от концентрации скандия — при малом его количестве образование допированного (Y1–yScy)BaCo4O7+x (R114) оксида осуществляется аналогично недопированной системе через фазу YBaCo2O5+x (R112), при значительном увеличении содержания скандия (≥0.2) промежуточной и конкурирующей становится фаза BaCo1–yScyO3–x, представляющая собой ряд твердых растворов, устойчивых в широком интервале температур и содержаний скандия. Показано, что скандий в структуре R114 предпочтительно размещается в иттриевой позиции (Y1–yScyBaCo4O7+x) и максимальная степень замещения составляет ymax ≈ 0.3—0.35. Замещение иттрия на скандий, имеющий меньший ионный радиус, приводит к почти изотропному уменьшению размеров элементарной ячейки с максимальным изменением ее объема на 2.0 % (от 353.0 Å3 до 345.9 Å3).

Powder X-ray diffraction and the thermoanalytical characteristics of solid solutions with compositions [(CoxNi1 – x)(H2O)4(C4H3O4)2], [(CoxZn1 – x)(H2O)4(C4H3O4)2], [(NixZn1 – x)(H2O)4(C4H3O4)2] (0 < x < 1) are compared. The decomposition of solid solutions and their constituents when heated to 500°C in a flow of He is conventionally divided into three stages. Products of the thermolysis of solid solutions are found to be Co/Ni, Co/ZnO, and Ni/Zn bimetallic nanoparticles, respectively, embedded into the polymeric matrix of composites. It is shown that the thermal decomposition of solid solutions in the Curie curve upon a second order phase transition with the formation of the two-phase region found in Co/Ni bimetallic nanoparticles is a quantum size effect. The decomposition of [(Co0.1Zn0.9)(H2O)4(С4H3O4)2] solid solution removes the Co atoms (d = 2.5 Å) embedded in channels of the ZnO structure. These atoms also serve as catalysts for the growth of a nanobrush of carbon nanotubes (CNTs) on the composite’s surface at ≤500°C, another consequence of the quantum size effect. It is concluded that using a similar catalyst of CNT growth can appreciably lower the energy of the process.

The processes of phase formation in the Y-Ba-Co-O system doped with scandium are studied in the region of compositions 1:1:4:7. The mechanism of interaction of initial reagents changes with scandium concentration: at low scandium contents, the (Y1−yScy)BaCo4O7+x (R114) doped oxide is formed, similarly to the undoped system, through the YBaCo2O5+x (R112) phase; at significantly higher scandium contents (≥0.2), the role of the intermediate and the competing phase is played by BaCo1−yScyO3−x representing a number of solid solutions which are stable in wide ranges of temperatures and scandium contents. It is shown that scandium in the R114 structure preferably occupies the yttrium position (Y1−yScyBaCo4O7+x), and the maximum degree of substitution is ymax ≈ 0.3–0.35. When yttrium is substituted with a smaller (in terms of ionic radii) scandium atom, the size of the unit cell diminishes nearly isotropically, the maximum change of its volume being 2.0% (from 353.0 Å3 to 345.9 Å3).

A relationship is established between the structural and thermoanalytical characteristics of the decomposition of hydrogen maleates and phthalates of Fe(II), Co(II), Ni(II), Cu(II). The temperatures of the onset of the first and second stages of decomposition grow in the series of both hydrogen maleates Cu ≤ Fe < Co < Ni and phthalates Fe ≤ Co < Ni < Cu, while the lengths of M– $${{{\text{O}}}_{{{{{\text{H}}}_{2}}{\text{O}}}}}$$ and M–Oanion bonds shrink in these structures. At the third stage, the temperature of the onset of the decarboxylation of hydrogen maleates and phthalates falls in the order Fe > Co > Ni > Cu. The size of metal nanoparticles additionally contained in a polymer or graphene shell grows from 3.5 to 5 nm (Co) and from 4.5 to 7 nm (Ni) upon moving from composites obtained through the decomposition of hydrogen maleates to hydrogen phthalates. Polymeric conglomerates containing shell-less copper nanoparticles, the average size of which ranges from 7.5 to 50 nm, are incorporated into a polymer matrix of composites obtained via the thermolysis of Cu(II) hydrogen maleate and phthalate.

Mn-substituted cordierites, 2(Mg1-xMnx)O center dot 2Al(2)O(3)center dot 5SiO(2) (x = 0-1), were prepared from natural components (talc, clay, alumina) and MnO2. Sintering behavior, phase transformation, and microstructural features of the samples were investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), dilatometric measurements and scanning electron microscopy (SEM) with energy dispersive analysis (EDS). The results of DTA and XRD analysis indicate that MnO2 is successively reduced to Mn2O3 and MnO in the sintering process. Mn2+ ions incorporate into the crystal structure of alpha-cordierite substituting Mg2+ ions in octahedral sites and thus increasing the cordierite unit cell volume. Mn promotes the sintering process: the crystallization temperature, melting point, density and open porosity of Mn-substituted cordierites lowered, whereas the shrinkage and medium pore diameter enlarged with an increase in MnO2 content in the mixture of raw materials. Surface enrichment with Mn with the formation of manganese oxide crystallites was found for the samples with high substitution degree.

This work is a continuation of the studies devoted to the synthesis of nanostructured carbon (NSC) as a result of the pyrolysis of a mixture of H 2 + C 3 –C 4 alkanes on supported Ni catalysts. Mesoporous alumina (γ-Al 2 O 3 ) and titania (TiO 2 ), on which Ni(II) compounds are deposited by impregnation or homogeneous precipitation, are studied as carriers. Using the methods of thermogravimetric analysis and scanning electron microscopy, it is shown that the activity of Ni catalysts (carbon yield) and the morphology of synthesized NSC are largely determined by the chemical nature of the support. It is found that the synthesis of NSC in the form of carbon nanofibers with a pronounced filamentary structure proceeds only on a Ni catalyst supported on titanium dioxide. The mesoporous carbon–mineral supports obtained after catalytic pyrolysis were studied in the adsorptive immobilization of the enzyme such as Thermomyces lanuginosus lipase. The adsorption properties of the supports, as well as the enzymatic activity and stability of the prepared biocatalysts in the esterification of saturated fatty acids (capric, C10: 0) with aliphatic alcohols (isopentanol, C 5 ) in the non-aqueous media of organic solvents (hexane and diethyl ether) at ambient temperature, are studied. Biocatalysts prepared by lipase adsorption on NSC/TiO 2 show the maximum esterification activity of 100 EA/g, which is 20–45 times higher than the activity of lipase adsorbed on NSC/Al 2 O 3 .

The effect of techniques for introducing Pd into gamma-Al2O3 from palladium chloride solutions on physicochemical and catalytic properties of PdO(Pd)/Al2O3 catalysts was examined. A series of catalysts were investigated by SEM, XPA, BET, XPS, and H-2-TPR. As shown, the use of various methods for introducing Pd into alumina granules enables control of active component distribution along the Al2O3 granule section. The localization of Pd in a catalyst grain determines the nature of the reduction in H 2-TPR and activity in the reaction of deep oxidation of methane, which is connected with a varying degree of the interaction of the active component with the support. The active component is demonstrated to be formed on the granule surface mainly as PdO when using the adsorption-deposition method followed by calcination at a temperature of 1000 degrees C ensuring high reactivity in the methane oxidation reaction.

Conditions of synthesis are optimized and XRD and thermoanalytical studies are performed for normal maleate [Zn(H 2 O) 2 (C 4 H 2 O 4 )] and acid maleate [Zn(H 2 O) 4 (C 4 H 3 O 4 ) 2 ], along with acid Co(II)–Zn(II), Ni(II)–Zn(II) maleates. It is shown that when solid solutions thermally decompose in acidic maleate systems, the kinetically less stable component causes the temperature of decomposition of the more stable component to fall. It is established that the solid residue of Zn(II) maleate after heating to 500°C in a He atmosphere is a composite containing Zn oxide whose reduction to metal begins at 675°C. The decomposition of [(Co 0.1 Zn 0.9 )(H 2 O) 4 (С 4 H 3 O 4 ) 2 ] leads to the oozing of metallic cobalt atoms embedded in the channels of the ZnO structure that act as a catalyst for the spontaneous growth of uniform carbon nanotubes on the surface of the composite. After thermal decomposition of the samples in a system of acid Ni(II) maleate–acid Zn(II) maleate, only the bimetallic phase is observed in the composites, and there is no zinc oxide.

The physicochemical state of supported platinum and the surface of the support is studied for a number of industrial 0.5 wt % Pt/graphite (freshly prepared, after the synthesis of hydroxylamine sulfate via NO hydrogenation in sulfuric acid, and regenerated) by scanning electron microscopy (SEM), transmission electron microscopy(TEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and CO chemisorption. It is shown that platinum particles agglomerate in a catalyst during operation, and its regeneration results in finer dispersity of the supported metal. Despite the common opinion that a platinum surface is modified by sulfur during the synthesis or regeneration of such catalysts, no evidence of this is found via XPS. Data showing that the surface nitrogen-containing graphite groups formed during the preparation of a catalyst are responsible for the modification of the absorption properties of platinum particles with respect to CO are obtained for the first time. The latter seems to be one of the factors that influence the catalytic properties of platinum in NO hydrogenation.

Composite multi-component biocatalysts were prepared by entrapping lysates of a recombinant rE. coli/lip strain producing Thermomyces lanuginosus lipase into composite nanocarbon-containing matrices based on a SiO2 xerogel. The dependence of the lipase activity and operational stability on the type of the carbon component (nanotubes or nanospheres of different diameters) was studied in the bioconversion of triglycerides (hydrolysis and interesterification), as well as in the esterification of saturated fatty acids—namely, butyric (C4:0), capric (C10:0), and stearic (C18:0) acids—with isoamyl alcohol. It was shown that the biocatalytic properties were determined by both the texture parameters of the nanostructured carbon included and the type of enzymatic reaction performed. Biocatalysts without a nanocarbon component had the highest operational stability in the batch process of interesterification of sunflower oil with ethyl acetate; the half-life time was found to be 720 h at 40°C. Biocatalysts containing carbon nanotubes of ~21 nm in diameter were five to six times more active in the batch esterification process than biocatalysts without a nanocarbon component. Biocatalysts containing carbon nanotubes catalyzed the synthesis of esters in a binary organic solvent (hexane and diethyl ether) without a loss of activity for more than 500 h at 40°C.