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No 2 (2023)
Articles
Сatalysts for Electrooxidation of Biomass Processing Products
Abstract
In recent years, active research has been carried out in the field of catalysts for the electrooxidation of water-soluble products of biomass processing on the anodes of electrolysers, coupled with the process of producing hydrogen at the cathodes of these devices. Biomass processing products that are promising for electrooxidation are glycerol, glucose, furfural and 5-hydroxymethylfurfural. The review examines studies of catalysts for the electrooxidation of glycerol, glucose, furfural, and 5-hydroxymethylfurfural based on metals of various groups. Electrooxidation of these organic compounds on catalysts based on noble metals (platinum group metals and gold) and their alloys begins in the potential range from 0.3 to 0.7 V [reversible hydrogen electrode (RHE)], reaching a maximum at ~1 V (RHE). The main disadvantage of catalysts based on noble metals is their high cost. Nickel and сobalt are considered promising among the non-noble metals studied as components of catalysts for these reactions. But in the presence of catalysts based on these metals, the electrooxidation reactions of the noted organic compounds begin at potentials above 1 V (RHE). Glyceraldehyde, dihydroxyacetone, glyceric, tartronic, glycolic, oxalic, glyoxalic and mesoxalic acids can be obtained from the electrooxidation of glycerol. Valuable products of the electrooxidation of glucose, furfural, and 5-hydroxymethylfurfural are gluconic, 2-furancarboxylic, and 2,5-furandicarboxylic acids, respectively.
123-146
Esters of Inulin and Tall Oil Fatty Acids
Abstract
The possibility of obtaining polysaccharide esters based on large-scale products of plant origin: inulin and tall oil fatty acids, was studied. Carbohydrate esters of the biopolymer inulin and higher unsaturated acids were synthesized by acylation with acid chlorides under various conditions: in a water–chloroform mixture in the presence of sodium hydroxide and sodium salts of tall oil fatty acids, as well as in a pyridine–1,4-dioxane mixture. The yield of polysaccharide esters was 67–82%, the maximum yield was detected during the acylation of inulin in the pyridine–1,4-dioxane system
147-150
Calculation and Simulation of Flowsheets for Processing Flue Gases from Thermal Power Plants to Methanol
Abstract
Several flowsheets for processing flue gases from thermal power plants to commercial-quality methanol, differing in the steps of producing the feedstock for the methanol synthesis, were considered. The dependence of the methanol yield, energy efficiency, and carbon footprint of the technology as a whole (from the step of СО2 capture from flue gases to the step of methanol extraction) on the composition of flue gases (СО2 concentration) and temperature of their flow was studied. The option of processing flue gases with high initial flow temperature using the flowsheet involving high-temperature steps of СО2 separation and electrolysis was considered. Taking into account the recovery of the heat from flows and steam generation, this flowsheet has high efficiency.
151-161
Catalytic Activity of Highly Dispersed Systems PdО/Mn0.20Ce0.80O2–δ and PdО/M0.05Mn0.15Ce0.80O2–δ, where M = Cu, Bi, in Complete Oxidation of Methane
Abstract
Highly dispersed solid solutions Mn0.20Ce0.80O2–δ and M0.05Mn0.15Ce0.80О2–δ, where M = Cu, Bi, were prepared by coprecipitation followed by heat treatment. The materials were characterized by X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, low-temperature nitrogen adsorption, transmission electron microscopy, and gas chromatography. The compounds prepared exhibit high activity in complete oxidation of methane. The solid solutions show promise as palladium supports. The 0.5% PdО/Mn0.20Ce0.80O2–δ and 0.5% PdО/Cu0.05Mn0.15Ce0.80O2–δ samples synthesized surpass in the catalytic activity the reference catalyst 0.5 PdО/γ-Al2O3. Thus, it is appropriate to use the complex oxide formulations as supports of the active component.
162-168
Effect of Nanodispersed Carbon Black on the Aggregative Stability of Butadiene–Styrene Latex in Liquid-Phase Filling in an Ultrasonic Field
Abstract
The influence of the morphology of dispersed particles, sorption ability, and oxygen-containing groups of carbon black on the destabilization of the SKS-30ARK emulsion rubber latex in liquid-phase filling with nanodispersed carbon black in an ultrasonic field was studied. The latex destabilization is caused by sorption of emulsifying agents onto carbon black from the protective surface of latex globules, which is indirectly confirmed by an increase in the surface tension coefficient of the latex system. The complete coagulation of the butadiene–styrene latex is reached without using coagulants in the course of liquid-phase filling with carbon black at the component ratio carbon black : rubber 100 : 100 (wt parts) and рН ≤ 4.3 when using K354 carbon black and at the same component ratio and рН ≤ 3.6 when using P324 carbon black. Liquid-phase filling of emulsion rubbers in the step of their recovery from the latex ensures uniform distribution of nanodispersed carbon black throughout the volume of the elastomer compound due to the dispersing effect of the emulsifying components of the latex. These components migrate from the surface of latex globules to the developed active surface of carbon black under the action of ultrasonic field.
169-176
Isoprene Polymerization in the Presence of Phosphate Catalytic Systems Based on a Mixture of Neodymium and Gadolinium Salts
Abstract
Coordination polymerization of isoprene in the presence of Ziegler–Natta catalytic systems based on a mixture of neodymium and gadolinium bis(2-ethylhexyl) phosphates at the neodymium/gadolinium molar ratios of 25/75, 50/50, and 75/25 was studied. These catalytic systems exhibit high catalytic activity in isoprene polymerization, equal to that of the catalytic system based on neodymium bis(2-ethylhexyl) phosphate. The influence of the Nd/Gd ratio on the molecular-mass characteristics and microstructure of the polymers obtained was examined. The kinetic parameters of the isoprene polymerization using catalytic systems based on a mixture of neodymium and gadolinium salts were determined. The possibility of using such systems in the synthesis of stereoregular cis-1,4-polyisoprene with the optimum level of molecular masses was demonstrated
177-183
Impact of the Chelate Complex of Nitrilotris(methylenephosphonic Acid) with Copper on the Corrosion-Electrochemical Behavior of Carbon Steel in an Aqueous Medium
Abstract
The effect of the Na4[CuN(CH2PO3)3]·13H2O complex compound with a chelate structure on the corrosion-electrochemical behavior of 20# steel in a borate buffer solution at pH 7.4 and natural aeration was studied using the potentiodynamic method and methods of X-ray photoelectron spectroscopy and surface scanning electron microscopy with microanalysis. It was established that in the concentration range of 0.2–1.0 mM the complex under study inhibits the anodic dissolution of the metal and drives it at higher concentrations. In terms of its effect on the corrosion-electrochemical behavior of steel, the Na4[CuN(CH2PO3)3]·13H2O complex differs significantly from the previously studied complexes Na4[ZnN(CH2PO3)3]·13H2O and Na4[Cd(H2O)N(CH2PO3)3]·7H2O. In the potential range –0.66…–0.05 V relative to the Ag,AgCl|KCl-electrode (SSCE) a layer of metallic copper is generated on the surface in the form of nano-sized crystals, shielding the surface of the steel. In the potential range of 0.05–0.13 V (SSCE), metallic copper is oxidized, and with a further increase in the potential, a layer of mixed iron and copper oxides is formed.
184-199
Modification of Quartz Ceramics by Applying a Sol-Gel Composition of MgO–Al2O3–ZrO2–SiO2 System
Abstract
Composite sol-gel materials of the MgO–Al2O3–ZrO2–SiO2 system were synthesized and the processes of their thermal evolution and crystallization were studied. Application of sol-gel compositions of the MgO–Al2O3–ZrO2–SiO2 system to the surface of quartz ceramics leads to a significant increase in the mechanical strength of the material. The processes of thermal evolution of the sol-gel composition were studied using IR spectroscopy, X-ray diffraction, electron microscopy, and energy dispersive analysis. It was shown that the formation of the oxide composite structure of materials begins at the stage of wet gels. Treatment of quartz ceramics with composite sols followed by drying and heat treatment up to 1200°C results in modification of the surface layers of the material, which makes it possible to increase the mechanical strength of the material by more than 20%. Sol-gel modifying compositions, upon drying and subsequent heat treatment, form polycrystalline structures bonded to quartz ceramic particles and consisting of various oxide crystals.
200-208
Adsorption of Rhodamine G from Aqueous Solutions onto Particles of Few-Layer Graphene Prepared by Self-Propagating High-Temperature Synthesis
Abstract
The ability of few-layer graphene prepared by self-propagating high-temperature synthesis to adsorb Rhodamine G was studied. The dependences of the sorption capacity of few-layer graphene particles on the Rhodamine G concentration in aqueous solution, solution temperature, and adsorption time were determined. The adsorption of Rhodamine G on the surface of few-layer graphene is satisfactorily described by the Langmuir and Freundlich models. The process occurs under mixed diffusion control and can be described by a pseudo-second-order rate equation.
209-216
Magnesium Hydrogen-generating Materials and a Hydrogen Generation Setup
Abstract
The reaction of composites consisting of MgH2 and a graphene-like or nickel–graphene material with water or citric acid solutions of various concentrations was studied. The composites were prepared by mechanochemical treatment in a hydrogen atmosphere. The reaction of an aqueous citric acid solution with the composites is fast: 98% hydrogen yield is reached at the MgH2 : citric acid molar ratio of 1 : 1. A setup for preparing compressed hydrogen from the composites was developed. It can be used in autonomous mobile installations for hydrogen generation under high pressure, followed by filling balloons.
217-224