


Том 90, № 2 (2017)
- Жылы: 2017
- Мақалалар: 24
- URL: https://journals.rcsi.science/1070-4272/issue/view/13363
Processes Using Various Catalyst Systems
Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3
Аннотация
Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3.



Catalytic dehydration of ethanol into ethylene in a tubular reactor of the pilot installation on alumina catalysts with varied grain size
Аннотация
Synthesis of ethylene on trefoil and cylindrical experimental acid-modified aluminum oxide samples was studied under an ethanol (94%) gas load of 920–2200 h–1 and heat-carrier temperature of 400–440°C. In the conditions of a 98% ethanol conversion, the higher activity of the trefoil made it possible to reduce the height of the bed and its hydraulic resistance and, accordingly, raise the specific catalyst throughput for ethylene. Compared with industrial aluminum oxide, the throughput of 1 g of the catalyst for ethylene on experimental samples is higher by 2.5–6.5 kg yr–1, and the specific expenditure of ethanol is lower by 0.22–0.23 kg kg–1. The endothermic process in a tubular reactor is characterized by a high parametric sensitivity of the average integral temperature along the catalyst bed, with the average temperature being higher on the less active catalyst. Thus, the higher average temperature can compensate for the lower activity of the catalyst without additional increase in the contact duration and(or) heat-carrier temperature.



Photocatalytic activity of titanium dioxide nanoparticles produced by methods of high-energy physical dispersion
Аннотация
Photocatalytic activity of titanium dioxide nanoparticle samples under study is almost uncorrelated with their phase composition and, in particular, with the content of the anatase phase. The photocatalytic activity depends on the annealing temperature of the nanoparticles. The photocatalytic activity is positively affected by an ultrasonic radiation of the nanoparticles. The highest photocatalytic activity, comparable with that of the AEROXIDE P25 reference nanopowders, is observed for nanoparticles produced by a method of electrical explosion of wires.



Photocatalytic activity and physicochemical characteristics of modified potassium polytitanates in the reaction of decomposition of aqueous-alcoholic solutions
Аннотация
Study of the photocatalytic activity of nanomaterials based on potassium polytitanate modified with transition metal ions (Ni2+, Cr3+, Cu2+) demonstrated that the cation composition, morphology of photocatalyst particles, and their size strongly affect the photocatalytic activity. The rate of the photoinduced hydrogen evolution from the aqueous-alcoholic solution grows in the series of potassium polytitanates modified with Cu2+, Ni2+, Cr3+ ions, and that from pure water, for potassium polytitanates modified with Ni2+,Cr3+, Cu2+ ions. The capacity for intercalation of water into the interlayer space does not strongly affect the rate of the photoinduced hydrogen evolution. It was shown that potassium polytitanate modified with Cr3+ ions has the maximum quantum efficiency (30%).



Physicochemical Studies of Systems and Processes
Hydrothermal synthesis of potassium titanate nanotubes doped with magnesium, nickel, and aluminum
Аннотация
Study of the phase formation in the systems TiO2‒MO(M2O3)‒KOH‒H2O (M = Mg, Ni, Al) from crystalline and coprecipitated X-ray-amorphous mixtures demonstrated that doped potassium titanate nanotubes can be obtained in a hydrothermal treatment of coprecipitated hydroxides in the temperature range 170‒220°C. The average outer diameter of the thus synthesized nanotubes strongly depends on the element being introduced and is 5 to 10 nm. The nanotubes have a large specific surface area (200‒300 m2 g‒1) and are stable up to a temperature of 500°C, above which they decompose to give potassium hexatitanate. The nanotubes can be used as sorbents, photocatalysts, and components of composite materials for frictional and construction purposes.



Electrometric monitoring of water adsorption by porous glass modified with copper(II) oxide
Аннотация
Modification of porous glass with copper(II) oxide with planar structure does not change the run of the water-adsorption isotherm, whereas in the case when nanoparticles are formed from the supported oxide, a cluster-type adsorption mechanism is operative when a relative pressure p/p0 > 0.5 is reached. These specific features are reflected in the different dependences of the electrical resistance of the samples on humidity. It was shown that a porous glass with distributed copper(II)oxide planar layer can be used as a sensitive element of a resistive humidity sensor.



Mass transfer in bodies of classical shapes in a semicontinuous complete mixing apparatus
Аннотация
Analytical solutions of problems of the diffusion revovery of a substance from solid bodies of classical shapes in a semicontinuous complete mixing apparatus (batch for the solid phase and continuous for the liquid phase) were found using the method of integral Laplace transforms. The mathematical models developed were applied to studying leaching of zinc chloride from vulcanized fiber.



Study by inverse gas chromatography of the solubility of rifabutin in water in the presence of cyclodextrin
Аннотация
Inverse gas chromatography was used to study the stability of rifabutin and cyclodextrin complexes in water. The thermodynamic mixing functions were determined in the system rifabutin‒cyclodextrin‒water. Addition of hydroxypropyl-β-cyclodextrin to rifabutin creates in water a thermodynamically stable complex, with the solubility of rifabutin in water thereby raised and this antibiotic made more bioavailable in curing of tuberculosis.



Study of the process for obtaining special-purity potassium dihydrophosphate
Аннотация
Method of radioactive tracers was used to study the coprecipitation of 3d-element impurities from KH2PO4 solutions on hydrated potassium-aluminum phosphate. The influence exerted by the mass of the collector, its contact duration with solution, pH value and concentration of KH2PO4 on the process efficiency was examined. The purification coefficients were calculated. The high efficiency of the process of KH2PO4 purification was demonstrated.



Microparticles based on chitosan–hyaluronic acid interpolyelectrolyte complex, which provide stability of aqueous dispersions
Аннотация
Turbidimetric titration and laser scattering methods were used to assess the phase behavior of mixtures of chitosan and hyaluronic acid in aqueous solutions in relation to interaction conditions. Conditions were found in which stable water dispersions with particle size of up to 573 nm can be obtained. It was found that the molar ratios and the overall concentration mode of the starting-polyelectrolyte solutions affect the particle size.



Influence of the surface functionalization conditions on the properties of carbon fibers and supported palladium
Аннотация
The influence exerted by the conditions of oxidation and calcination in an inert medium on the properties of Karbopon and Busofit activated carbon fibers were studied using a set of physicochemical methods. The maximal concentration of thermally stable phenol groups in Busofit is reached by its oxidation with a 20% aqueous HNO3 solution, followed by calcination in an inert medium at 500°С for 1.5 h. Experiments with catalysts supported on Busofit samples functionalized with 20% HNO3 have shown that palladium supported on Busofit that was calcined at 500°C after oxidative treatment is characterized by monodisperse nanocluster distribution. The prepared catalysts containing 1 wt % Pd exhibit higher activity in oxidation of carbon monoxide than their presently known analogs do.



Macromolecular Compounds and Polymeric Materials
Chemical modification of rolivsans with epoxy resins
Аннотация
New glassy network copolymers exhibiting enhanced heat resistance were prepared by thermochemical transformations of rolivsans modified with small amounts (5 ± 3%) of epoxy resins. The influence of the composition of these copolymers on their thermomechanical properties was evaluated by performing dynamic mechanical and thermal analysis and by studying the temperature dependences of the ultimate strength at three-point bending.



Polycondensation procedure for compounding the components in production of phenol–formaldehyde polymer matrix composites
Аннотация
The choice of parameters of the polycondensation procedure for combining the components in forming polymer matrix composites based on fibrous and dispersed fillers and phenol–formaldehyde resin is substantiated. The materials formed using the polycondensation procedure for compounding the components considerably surpass in the physicochemical and mechanical properties the composites prepared using the traditional technology.



Physicochemical properties of hydrogels based on cellulose methyl ether
Аннотация
Rheological and spectral characteristics of hydrogels in the form of methyl cellulose based formulations containing methyluracil and nanodispersed silver stabilized with polyvinylpyrrolidone were studied. The concentration and temperature intervals of stability of the systems were determined.



Physicomechanical, thermal, and flame-retardant properties of elastomer compounds based on ethylene–propylene–diene rubber and filled with hollow aluminosilicate microspheres
Аннотация
The effect of hollow aluminosilicate microspheres on the Payne effect and on physicomechanical, thermal, fire-retardant, and heat-protecting properties of elastomer compounds based on ethylene–propylene–diene rubber was studied. Based on the results obtained, the mechanism of the interaction of the elastomer matrix with the microspheres was suggested. Enhancement of the filler–matrix and filler–filler interaction favors additional three-dimensional cross-linking, which influences the set of the physicomechanical and thermal properties, and manifestation of the reinforcing effect in a coke layer under the conditions of erosion removal and detachment of the material with a high-velocity gas flow.



Copolymers based on (p-vinylphenyl)cyclopropylmethyl chlorocinnamate and methyl methacrylate
Аннотация
Abstract—Copolymers of (p-vinylphenyl)cyclopropylmethyl chlorocinnamate with methyl methacrylate were prepared by radical copolymerization. The copolymerization constants were determined, and the Alfrey–Price Q–e parameters were calculated. The possibility of photochemical cross-linking of the copolymer via double bond conjugated with the carbonyl group in the chlorocinnamate moiety and via the cyclopropane ring was demonstrated. The copolymer obtained exhibits sufficiently high photosensitivity (54.5 cm2 J–1) and high refractive index (nD20 1.5890), which opens prospects for using it as a photosensitive base of negative photoresists and in optics.



Controlling the properties of epoxy composites filled with brick dust
Аннотация
Treatment of the filler surface with a silane dressing agent, ensuring the chemical interaction on the filler–binder interface, and ultrasonic treatment of the compound enhance the physicomechanical properties of the epoxy composite: The failure stress and bending elastic modulus increase by a factor of 2–3. Considerable (2.5- fold) increase in the impact resilience even at 50% filling should be particularly noted. Introduction of modified brick dust enhances the heat resistance and thermal conductivity of the epoxy composite.



Various Technological Processes
Effects of TiO2 on the hydrophilicity of сotton/polyester (50/50) blend fabric under UV irradiation
Аннотация
Alkaline TiO2 nanoparticles treated cotton/polyester (50/50) blend fabric were prepared, and then exposed to UV irradiation. It was found that the addition of a small amount of TiO2 nanoparticles to the coating solution improves the hydrophilicity and mechanical strength of the fabrics. The treated fabrics exhibited high water absorption as well as better hydrophilicity compared to the untreated sample. Compared to the surface of untreated blend fabric, scanning electron microscopy showed that the surface of the modified blend fabric becomes rough and covered by a layer of other materials. Furthermore, X-ray diffraction demonstrated the formation of crystalline material. In addition, thermograms showed that the modification process improved the thermostability of blend fabric.



Optimization of modification condition of nano-kaoline as an adsorbent for textile dye removal
Аннотация
In this study, adsorption capacity of textile red dye on alkylated kaolin was investigated through batch mode. Accordingly, raw kaolin was alkylated via NaOH treatment. The work was carried out in two steps. At first step, the effect of various alkylation conditions of kaolin on its dye adsorption performance was studied using the model equation designed by 2-level factorial design. Three factors were changed in two level including NaOH solution temperature (45–75°C), mixing time (3–24 h), and NaOH solution concentration (0.1–2 M). The resultant model showed 91% of the variability in data used to fit dye adsorption capacity values. However, the analysis of variance revealed that the fitted model is high significant. Based on the predicting model, the optimal alkylation conditions with desirability factor of 0.911 were obtained at temperature of 75°C, NaOH concentration of 0.1 M and after 24 h mixing. At step two, chemical content, bonds and functional groups of the treated kaolin, which was prepared based on the optimum condition and compared with the raw kaolin via X-ray fluorescence (XRF) analysis and Fourier transform infrared analysis (FTIR). The results show slight reduction in SiO2 content. Finally, the adsorption capacity of dye on both treated and raw kaolin was investigated.



Synthesis and characterization of CdS nanoparticles prepared by precipitation in the presence of span 20 as surfactant
Аннотация
Cadmium sulfide nanoparticles with average size of ≈16 nm have been synthesized using chemical precipitation reaction of CdCl2 and Na2S in the presence of nonionic surfactant stabilized reverse emulsions. Sorbian monolaurate (Span 20) is used for the stabilization of emulsions. The influence of Span 20 on controlling the size and properties of CdS nanoparticles were studied. The obtained CdS nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy-dispersive x-ray (EDX), and X-ray diffraction (XRD). The optical properties of CdS nanoparticles are investigated systematically by UV-visible absorption spectroscopy. The blue shift in the absorption region and increase in the bandgap to the larger value (2.77 eV) are attributed to the nanosize of the obtained particles.



Preparation, magnetic properties and microwave absorption of Zr–Zn–Co substituted strontium hexaferrite and its nanocomposite with polyaniline
Аннотация
M-type strontium hexaferrite substituted by Zr4+, Zn2+, and Co2+ was firstly synthesized by a sol-gel auto combustion method. Then the polyaniline/hexaferrite nanocomposite with 20 wt % hexaferrite was prepared by in situ polymerization method. The structure, morphology, and composition of substituted hexaferrite, polyaniline and their composition were investigated by using XRD, FTIR, TGA-DSC, UV-Vis spectroscopy, and FESEM techniques. The results showed that M-type hexaferrite nanoparticles were formed and nanoparticles were effectively coated by polyaniline chains. The magnetic properties of samples were measured by the vibrating sample magnetometer (VSM). The saturation magnetization (Ms), magnetic remanence (Mr), and coercivity (Hc) of composite are lower than those of pure hexaferrite. The microwave absorption properties of samples were measured by vector network analyzer (VNA). The results indicated that the minimum reflection loss (RL) of composite is–20 dB at 10.1 GHz and its bandwidth with more than 90% absorption is up to 3.5 GHz which has covered the overall X-band.



Effect of promoter on selective hydrogenation of furfural over Cu-Cr/TiO2 catalyst
Аннотация
The selective hydrogenation of furfural has been investigated over the titania-supported monometallic (Cu) and bimetallic (Cu–Cr) catalysts. The catalytic performances were assessed over 4 h of run length under atmospheric pressure at the hydrogen-to-hydrocarbon ratio of 10.6 and 453 K. The results represented that the level of furfural conversion over the non-promoted catalyst was very low (below 10%) while the promoted one showed considerable furfural conversion during this period (higher than 70%). However, both catalysts exhibited high durability and selectivity towards furfuryl alcohol.



Synthesis and characterization of water-sensitive core-shell type microspheres for water shut-off in the oil field
Аннотация
Polyacrylamide (PAM)-silica microspheres with core-shell structure are synthesized by inverse microemulsion polymerization in this study for the application of water shut-off due to high strength of nanosilica, crosslinked shell of PAM and strong interaction between PAM and silica. The core-shell microspheres flow into the high permeable layers along with injected water, meanwhile, swell after absorbing water and migrate into the deeper layer under the pressure by deformation, which efficiently increase the pressure of low and medium permeable layers, and decrease the loss of water into high permeable layers. Most resources of crude oil locate in low and medium permeable layers, and this work plays a very important role in the enhancement of recovery ratio of crude oil by new material. Transmission electron microscope (TEM), digital microscopes, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) are used to study the shape, size and high temperature resistant of the microsphere. Moreover, capillary flow experiments, nuclear-pore film filtration, and sand packed tube displacement experiment are applied to analysis the mechanisms of deep profile control.



Brief Communications
Polymer composites based on polythiourethane and fluorinated organomontmorillonite
Аннотация
The effect exerted on the mechanical properties and thermal oxidative stability of polythiourethane elastomers by new organomineral complexes based on 1,13-trihydroperfluoro-1-propanol and montmorillonite, introduced into the polymer in the step of its synthesis, was studied. The structural-morphological features of the fluorinated polymer composites obtained were examined by X-ray diffraction analysis and electron microscopy. An exfoliated composite is formed in the process.


