Hydrocracking of vacuum gas oil in the presence of catalysts NiMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–amorphous aluminosilicates and NiW/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–amorphous aluminosilicates

Supported nickel–molybdenum and nickel–tungsten hydrocracking catalysts prepared using a support that consists of 70% Al₂O₃ and 30% amorphous aluminosilicate were characterized by nitrogen and mercury porosimetry, IR spectroscopy of adsorbed CO, and high-resolution electron microscopy. The catalytic tests in hydrocracking of vacuum gas oil containing 3.39% sulfur showed that the nature of the hydrogenating component (NiMo or NiW) only slightly influences the vacuum gas oil conversion and the diesel fraction yield, but noticeable influences the properties of the diesel fraction obtained. The catalyst NiMo/Al₂O₃–amorphous aluminosilicates, compared to NiW/Al₂O₃–amorphous aluminosilicates, ensures lower sulfur content in the diesel fraction obtained, whereas the catalyst NiW/Al₂O₃–amorphous aluminosilicates allows obtaining a diesel fraction with lower content of polyaromatic compounds.     

Modifying additives affect the properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system

The effects caused by modifying additives, namely nonionic surfactants (Tween 80 and Neonol AF 9-6) and oxides (B₂O₃ and HfO₂), on the rheology, film formation, and phase formation in the yttrium aluminum silicate system prepared by sol–gel technology were studied. The effect of 1 wt % HfO₂ additions on the activation energy of crystallization was studied.     

Catalytic properties of Fe/SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> systems,obtained via sol–gel method

The high efficacy of iron-containing catalysts based on SiO₂–Al₂O₃ systems obtained via sol–gel method in the oxidative destruction of carmoisine azo dye in aqueous solutions is demonstrated. It is found that the stability of the catalysts with respect to the leaching of iron ions into a solution during catalysis grows along with the aluminum content in the composition of aluminosilicate supports. It is concluded that the synthesized catalysts are promising materials for purifying wastewaters contaminated with organic dyes.     

Pd/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the selective liquid-phase hydrogenation of acetylene to ethylene

The structure of Ga₂O₃–Al₂O₃ supports and Pd/Ga₂O₃–Al₂O₃ catalysts and the performance of these catalysts in liquid-phase acetylene hydrogenation have been investigated. The deposition of Ga(NO₃)₃ onto Al₂O₃ by impregnation followed by calcination of the impregnated support at 600°C yields γ-Ga₂O₃–Al₂O₃ solid solutions containing up to 50 wt % Ga₂O₃. X-ray diffraction characterization of model palladium catalysts and their temperature-programmed reduction with hydrogen have demonstrated that, while palladium in Pd/Ga₂O₃ is in the form of a Pd₂Ga alloy, in the Pd/γ-Ga₂O₃–Al₂O₃ catalyst there is no direct interaction between PdО and Ga₂O₃ particles and palladium is in the monometallic state. The introduction of 10–20 wt % gallium oxide into Al₂O₃ lowers the activity of the supported palladium catalyst relative to that of the initial Pd/Al₂O₃ but increases the ethylene yield by enhancing the ethylene formation selectivity.     

Atmospheric control of gel-oxide transformation in sol–gel derived Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> fibers

Via sol–gel processing metal–organic fibers were produced and dried up to 140 °C. For these gel fibers the influence of a treatment in different atmospheres was investigated for the temperature range of 200–850 °C. The atmospheres were nitrogen, water vapor, evaporated nitric and hydrochloric acid and evaporated hydrogen peroxide. In the presence of moisture and especially with acidic moisture fibers were transformed almost completely to their oxide composition (82 mol% Al₂O₃·18 mol% Y₂O₃). In these inorganic amorphous structures considerable differences were observed on several structural levels. On the atomic scale, the coordination of Al ions was investigated by ²⁷Al MAS NMR and skeletal density by He-pycnometry. Porosity in the nm scale was characterized by N₂-sorption. As a macroscopic effect of different treatment atmospheres, the longitudinal shrinkage was observed. For fibers treated at 500 °C the relative shrinkage varied by 100% (comparing water vapor and nitrogen atmosphere). No simple correlation between the release of organic constituents, the formation of porosity and the shrinkage could be found. These aspects were controlled by the rigidity of the inorganic network against atomic reconstitution. The kind of atmosphere was found to be an effective parameter to control various aspects of the xerogel structure.     

Glass Formation in the Ternary System La<Subscript>2</Subscript>O<Subscript>3</Subscript>–As<Subscript>2</Subscript>S<Subscript>3</Subscript>–Er<Subscript>2</Subscript>O<Subscript>3</Subscript>

The boundaries of the glass formation region in the ternary system La₂O₃–As₂S₃–Er₂O₃ were found. Transparent glass of composition (La₂O₃)_0.03(As₂S₃)0.90(Er₂O₃)0.07 was studied by X-ray photoelectron and Raman spectroscopy. The intensities of the bands characterizing As–S, La–O, and Er–O bonds increased, and these bands were shifted toward higher energies. This was due to an increase in the covalence of these bonds and probably due to the formation of new bonds in the glasses. Samples in the glass formation region are resistant at 300 K to air, water, and organic solvents.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Synthesis and properties of γ-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

The textural and structural properties of mixed oxides Ga₂O₃–Al₂O₃, obtained via impregnating γ-Al₂O₃ with a solution of Ga(NO₃)₃ and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga₂O₃–Al₂O₃ up to a Ga₂O₃ content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga₂O₃ content exceeds 50 wt %, the β-Ga₂O₃ phase is observed along with γ-Ga₂O₃–Al₂O₃ solid solution. ⁷¹Ga and ²⁷Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga₂O₃–Al₂O₃.     

New bimetallic Mo<Subscript>2</Subscript>C–WC/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> membrane catalysts in the dry reforming of methane

Bimetallic membrane catalysts based on the Mo₂C–WC binary carbides were obtained. Their structural characteristics and catalytic properties in a reaction of dry reforming of methane were compared with those of monocarbide catalysts. The advantage of the use of the mixed carbide catalysts was established.     

Selective deoxygenation of vegetable oils in the presence of Pt–Sn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

We studied deoxygenation of individual fatty esters and fatty acid triglycerides from vegetable oils and lipid extracts from microalgae in the presence of catalysts prepared by deposition of Pt–Sn-containing compounds onto the γ-aluminum oxide surface. Using individual esters as an example, selective reduction of oxygen into water was demonstrated for the first time to proceed on a catalytic system at the 5 : 1 molar ratio of Sn and Pt active components to afford hydrocarbon components of substrates in virtually quantitative yield. Transformation of vegetable oil in the presence of this catalyst affords the C₃–C₁₈ hydrocarbon fraction in yield up to 99% at the content of C₃ and C₁₈ hydrocarbons up to 90%. The fraction of C₁ and C₂ hydrocarbons and carbon oxides is not higher than 0.5%. The possibility of carbon weight loss minimization during transformation of lipids was shown for the first time.     

Hydrodeoxygenation of Vegetable Oil on NiMoS/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

Tungstate-containing aluminum oxide is suitable as a catalyst support for hydrodeoxygenation of sunflower oil, ensuring 81–83 wt % yield of liquid products at 380°С, 4.0 MPa, and feed space velocity of 1 h^–1. The catalyst acidity increases with increasing tungsten oxide content, leading to an increase in the content of decarboxylation/decarbonylation products and isoparaffins in the product mixture.     

Structure and thermal properties of the fritted glazes in SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–CaO–MgO–Na<Subscript>2</Subscript>O–K<Subscript>2</Subscript>O–ZnO system

In this work, the structure and thermal properties of aluminosilicate fritted glazes in SiO₂–Al₂O₃–CaO–MgO–Na₂O–K₂O–ZnO system with (4.0 mol%) and without addition of ZnO were examined by GIXRD, FTIR, MAS-NMR and thermal methods (DTA, DIL). It has been found that the all experimental glazes are amorphous material (transparent glazes). On the base of spectroscopic investigations, it was found that zinc ions exist in the network glazes in the octahedral coordination—Zn²⁺ ions play a network modifier role in structure of glazes. An analysis of the data obtained from thermal tests showed that addition of ZnO into chemical composition results in decrease in glass transition temperature value (T _g) for all glazes (DTA, DIL). The coefficient of thermal expansion (α) is decreased as the whole measurement range for one series of fritted glazes.     

Structural characterisation and thermo-physical properties of glasses in the Li<Subscript>2</Subscript>O–SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–K<Subscript>2</Subscript>O system

This article aims to shed some light on the structure and thermo-physical properties of lithium disilicate glasses in the system Li₂O–SiO₂–Al₂O₃–K₂O. A glass with nominal composition 23Li₂O–77SiO₂ (mol%) (labelled as L₂₃S₇₇) and glasses containing Al₂O₃ and K₂O with SiO₂/Li₂O molar ratios (3.13–4.88) were produced by conventional melt-quenching technique in bulk and frit forms. The glass-ceramics (GCs) were obtained from nucleation and crystallisation of monolithic bulk glasses as well as via sintering and crystallisation of glass powder compacts. The structure of glasses as investigated by magic angle spinning-nuclear magnetic resonance (MAS-NMR) depict the role of Al₂O₃ as glass network former with four-fold coordination, i.e., Al(IV) species while silicon exists predominantly as a mixture of Q ³ and Q ⁴ (Si) structural units. The qualitative as well as quantitative crystalline phase evolution in glasses was followed by differential thermal analysis (DTA), X-ray diffraction (XRD) adjoined with Rietveld-reference intensity ratio (R.I.R.) method, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The possible correlation amongst structural features of glasses, phase composition and thermo-physical properties of GCs has been discussed.     

Characterization of gold supported on Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–CuO–Mn<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts obtained by thermal decomposition of aerosols

The purpose of this work was to employ the differential thermal analysis (DTA) technique to compare variations in the collapse energy of the zeolite Y crystalline structure in a fresh catalyst and in the same catalyst impregnated with nickel and vanadium. A small exothermic signal in the DTA curve at 950–1150 °C indicated the collapse of the crystalline structure. The areas of the exothermic signals in the DTA curves of the two samples indicated a reduction in the curve of the metal impregnated catalyst. These results were compared with X-ray data, leading to the conclusion that metal impregnation affects the zeolite Y crystalline structure and that the DTA technique is a potentially useful tool for measuring the integrity of zeolite Y in catalysts.     

Mass attenuation coefficients of B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–CaF<Subscript>2</Subscript> glass system at 0.662 and 1.25 MeV gamma energies

The total mass attenuation coefficients, partial interaction and the effective atomic numbers (Z_eff) of glass system (80−x)B₂O₃–10Al₂O₃–10SiO₂–xCaF₂ (where x = 5, 10, 20, 25, 30, 35 and 40 mol %) have been calculated at photon energies 0.662 and 1.25 MeV using the WinXCom software on the basis of mixture rule. Results indicated that the total mass attenuation coefficients showed a decrease with increasing the CaF₂ concentration, due to a decrease in Compton scattering probability, which gave a dominant contribution to the total mass attenuation coefficients for the studied glass samples at both energies. However, the photoelectric absorption and coherent scattering showed an increase with increasing the CaF₂, concentrations at same energies. For a comparison, the total mass attenuation coefficients of the glass system had lower values at the energy 1.25 MeV than that at 0.662 MeV. Z_eff was found to increase linearly with the increase of CaF₂ concentrations. It was concluded that low CaF₂ concentrations in glass system, under study, have Z_eff close to that of human tissue and have higher total absorption coefficients at energy of 0.662 MeV than that at 1.25 MeV. These results are very useful in designing gamma radiation detectors using thermoluminescence technique. Therefore, it is recommended to use low CaF₂ concentration of our glass system as good gamma detectors at energy of 1.25 MeV.     

Physicochemical properties of (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>NH<Subscript>2</Subscript>Cl–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Composite solid electrolytes were synthesized from the organic salt dimethylammonium chloride (1–x)C₂H₈NCl–xAl₂O₃. Their physicochemical properties were studied. In the starting C₂H₈NCl salt, there is a phase transition at 39°C accompanied by an increase in conductivity by two orders of magnitude. The conductivity of the high-temperature phase is 9.3 × 10^–6 S/cm at 160°C. A differential scanning calorimetry study showed that the salt in the composites spreads over the oxide surface and at x > 0.6 the salt melting enthalpy decreases to zero. The conductivity of the resulting composites was studied by impedance spectroscopy. It was shown that heterogeneous doping leads to a sharp increase in ion conductivity to 7.0 × 10^–3 S/cm at 160°C and a decrease in the activation energy to 0.55 eV.     

Sol–gel synthesis and characterization of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiO<Subscript>2</Subscript> nanocrystalline powder

Al₂O₃–TiO₂ nanocrystalline powders were synthesized by sol–gel process. Aluminum sec-butoxide and titanium isopropoxide chemicals were used as precursors and ethyl acetoacetate was used as chelating agent. Thermal and crystallization behaviors of the precursor powders were investigated by thermal gravimetric-differential thermal analysis, Fourier-transform infrared spectrum and X-ray diffraction. The average crystalline size of heat treated Al₂O₃–TiO₂ powders at 1,100 °C is ~100 nm.