Maxim V. Tsvetkov

The conversion of ethanol to syngas by partial oxidation in a Swiss-roll reactor was studied experimentally. For varied flowrate and stoichiometric ratio of the ultra-rich ethanol-air mixtures the temperature pattern in the reactor and gaseous products were measured. Owing to efficient heat recuperation from the products to the reaction mixtures, the conversion is stable for the studied oxygen excess ratios ranging from 0.4 down to 0.18. However, the conversion remains incomplete with a substantial yield of methane and ethylene. The reaction mixture ignites in the inflow channel, thus reducing the effective heat exchange surface and limiting the combustion temperature. The temperature in the central chamber does not exceed 600°C. The use of a non-premixed Swiss-roll reactor is proposed to overcome this limitation.

An experimental investigation into the conversion of ethanol to syngas by partial oxidation in a non-premixed counterflow moving bed filtration combustion reactor was carried out. Regimes of conversion depending on the mass flow rates of fuel and air (separate feeding), as well as a granular solid heat carrier, were studied. Depending on the mass flow rate of the heat carrier, two combustion modes were realized—reaction trailing and intermediate—with different temperature patterns in the gas preheating, combustion, and cooling zones along the reactor. The product gas composition is far from the predictions of the equilibrium model; it contains substation fractions of methane and ethylene. Combustion temperature and conversion are limited by the relatively high level of heat loss from the laboratory-scale reactor. The effect of the heat loss can be reduced by enhancing the absolute flow rate of the reactants.

A novel meso-scale 3-channel 5-turn Swiss-roll type combustor was designed and tested. The non-catalytic combustion of lean ethanol–air mixtures was experimentally investigated in relation to the oxygen excess ratio (α), which varied from 1.5 to 7. Depending on the control parameters used, two distinct regimes of combustion were experimentally observed: one with a combustion zone within the central chamber and another with a combustion zone in the inflow channel. The combustion temperature was virtually independent of stoichiometry. For richer mixtures and lower flow rates, the combustion zone is established in the inflow channel, thus limiting the combustion temperature. A qualitative model was proposed for the process and solved analytically; it described how the combustion regime self-adjusted, with the reaction zone moving into the inflow channel from the central chamber. This study confirmed the possibility of the sustainable combustion of ultra-lean fuel mixtures in a Swiss-roll combustor.

In the present paper, the case of the brown algae Saccharina japonica from Aniva Bay (Sea of Okhotsk, Sakhalin Island) was investigated by a thermogravimetric analysis up to 700°C at different atmospheres. The elemental composition, lower heating value, ash content, and biochar yield of the algae were examined. The analysis showed that carbohydrates like alginate, mannitol, fucoidan, and laminarin were decomposed between 250-350°C, while proteins and lipids were burned out between 500-550°C.

In the present paper, biochar from the Laminaria japonica from brackish lagoons (Sea of Okhotsk, Sakhalin Island) was obtained by a stepwise pyrolysis at 500 °C. The properties of concerned biochar (elemental composition, specific surface area, particle size distribution) were studied. It was shown that the Laminaria japonica biochar has 0.2–18 μm particle sizes with a complex branched surface of high microporosity and a specific surface area of 38.6 m²g^-1. Aforementioned biochar has the high content of carbon (~60 at%) and high content of oxygen (~34 at.%).

The current study focuses on the production of biochars derived from aquatic plants, specifically red seaweed Ahnfeltia and seagrass Zostera and Ruppia, found in brackish lagoons in the Sea of Okhotsk, Sakhalin Island. These biochars were obtained through a stepwise pyrolysis process conducted at temperatures of 500 and 700 °C. The characteristics of the biochars, including their elemental composition, specific surface area, and particle size distribution, were found to be influenced by both the type of biomass used and the pyrolysis temperature. The primary objective of this research was to investigate the potential of these biochars to be used as negative electrodes for lithium ion batteries. Among the various samples we tested, the biochar derived from the macroalgae Ahnfeltia tobuchiensis, produced at 700 °C, exhibited the highest carbon content (70 at%) and nitrogen content (>5 at%). The reversible capacity of this particular biochar was measured to be 391 mAh g⁻¹ during the initial cycles and remained relatively stable at around 300 mAh g⁻¹ after 25 cycles. These findings suggest that biochars derived from aquatic plants have the potential to be utilized as effective electrode materials in lithium ion batteries. The specific properties of the biochar, such as its elemental composition and surface area, play a significant role in determining its electrochemical performance. Further research and optimization of the pyrolysis conditions may lead to the development of biochar-based electrodes with improved capacity and cycling stability, thereby contributing to the advancement of sustainable and environmentally friendly energy storage systems.

The work is devoted to the study of the influence of synthesis conditions on the properties of water-insoluble rubidium salts of phosphotungstic acid (PTA). Such heteropoly compounds have a wide range of applications, including in the field of electrocatalysts and solid electrolytes for various electrochemical devices. The acid salts of PTA with high activity of acid sites on the particle surface are of particular interest. It is known that the properties of water-insoluble PTA salts strongly depend on synthesis conditions, such as the ratio of reagents, temperature, concentrations, and other parameters. The work examines the influence of the ratio and concentration of reagents on the sizes of crystallites and agglomerates, specific surface area (SSA), porosity, water content, and ionic conductivity of the synthesized PTA salts. The SSA value of the obtained samples varied in the range of 84–123 m² g⁻¹, and the ionic conductivity was 13–90 mS cm⁻¹ at room temperature and 75% RH. An increase in the acid concentration and the degree of proton substitution led to an increase in SSA, accompanied by an increase in particle sizes without changing the size of crystallites. The results of the work may be useful for the development of new materials based on the obtained salts in many fields, including hydrogen energy.