Том 53, № 1 (2019)

A catalytic distillation process reacting in a column bottom was experimentally studied for the transesterification of methyl and ethyl esters of bromodifluoroacetic acid with trifluoroacetic acid. Sulfuric acid was used as a catalyst. Experiments were performed at different column bottom heat duties. As a result of the experiments, we had bromodifluoroacetic acid with a purity above 97.0 mol % at a product yield of 87.4%.

Some calculation aspects of natural gas properties based on limited numbers of initial experimental parameters, namely temperature, pressure, and speed of sound, were considered. The application possibilities for a wide range of compositions, temperatures, and gas mixtures pressure, simulating natural gases of various fields using the previously proposed Farzaneh-Gord method were discussed. It has been shown, that this method, in reality, yields fairly accurate results, calculating molecular weight of natural gas and its density. We note that good calculation results of mass flow rate make it possible to recommend this method for practical express calculations.

The results of the development of a generalized mathematical model for the fermentation method of lactic acid production have been presented. The mathematical model includes nonsteady-state equations for the production of biomass, the consumption of the substrate, and the production of lactic acid and metabolism byproducts and equations for the formation of an additional amount of the main substrate from the components of raw materials. We acquired the results of the modeling process using constants of the basic variant from studies. The dependences of the characteristics of the process on time for the basic variant and the dependence of the productivity of lactic acid (Q_P, g/(L h)) on time with estimation of time t reaching the maximum value of Q_P (max Q_P) have been presented. The mathematical model takes into account all possible variants of inhibition, namely, concerning the biomass, product, and substrate. The results of modeling with allowance for the intensity of inhibition from each of the factors have shown the following. An increase in biomass inhibition constant X_max decreases the duration of the process, an increase in product inhibition constant P_max slightly increases the duration of the process, and a decrease in substrate inhibition constant K_i (the intensity of inhibition increases) considerably increases the duration of the process. Time of process completion t_k for all conditions of modeling was determined by reaching one of the following conditions: X = X_max or P = P_max or S = 0. In modeling, it has also been found that the variation of constants in the equation for the formation of byproducts does not affect the variation in the characteristics of the process except for the numerical value of the concentration of byproducts.

The macrokinetics of the synthesis of butyl rubber in a cylindrical-type tubular turbulent reactor (cationic suspension copolymerization of isobutylene with isoprene, catalyst is aluminum chloride, solvent is methyl chloride, and the synthesis temperature is higher than 173 K) was described mathematically. A relation of the reaction mixture velocity and reactor diameter to the molecular weight characteristics of butyl rubber was found.

Synthesis gas for an electrochemical generator is produced in a thermochemical generator with autothermal air conversion of methane (natural gas). From the heat balances of the reactor, the batteries of solid oxide fuel-cell elements, and a boiler-utilizer designed for heating the primary and secondary cathodе air and methane, the following are calculated: temperature at the anode, the electromotive force of the cell element, the electrical coefficient of the efficiency factor for the gross-electrochemical generator, the fraction of hydrogen oxidized in the anode of solid oxide fuel-cell elements, and the cost per unit for production of electric and heat energy.

A method of reducing the nonuniformity of a galvanic coating on the basis of disableable anode sections in the inverse current reversal regime was proposed in a relatively simple technical implementation, thus providing the possibility to broaden the variety of articles treated for mass production. The galvanic process in the inverse current reversal regime with disableable anode sections was formalized by the formulation of an optimal control problem and the development of a mathematical model. Some results of computer-aided modeling were presented alongside with the results of verifying the developed mathematical model for adequacy with the use of experimental data to demonstrate the efficiency of the method proposed.

A nonideal solubility equation is developed based on crystallinity and is applied to model the solid-liquid equilibrium for crystalline low-density polyethylene (LDPE) in a set of pure and blended nonpolar organic solvents experimentally at 338–379 K and atmospheric pressure. The polymer concentration ranges from 0.5 to 35 g in 100 mL solvent. Modified correlation based on the heat of fusion and the melting temperature was attained by using SSPS software based on experimental data. The ideal solubility and nonideal solubility equations were applied with two different regular methods for activity coefficient calculation, which do not correlate with the experimental data in large. The data collected from developed nonideal equation and modified correlation were found in good agreement with experimental data.

Performance of sulfur hexafluoride, nitrogen, argon, and helium inert gases was investigated in a view to produce fuel grade ethanol by diffusion distillation. Stefan–Maxwell equations based mathematical model was used for this study. Modeling results were also compared with the own experimental data. Shifting of azeotrope to different extents was observed by using different inert gases as selective filter. As the selected inert gas becomes lighter, narrow concentration range for positive selectivity was found. Sulfur hexafluoride was found to be the most suitable inert gas for ethanol dehydration by diffusion distillation, and quantity \({{S}_{{{\text{az}}}}}({{N{}_{2}} \mathord{\left/ {\vphantom {{N{}_{2}} {{{N}_{1}}}}} \right. \kern-0em} {{{N}_{1}}}})\), which represents the overall performance of any inert gas, was also found to be highest for this gas out of all the inert gases studied. Sulfur hexafluoride gas also allows to work at high vaporization temperature, which facilitates the high transfer efficiency. If light gases are to be used they should be used for high feed concentrations and at low vaporization temperatures to achieve the high degree of separation.

A theoretical study on a TiO₂-based photo fuel cell (PFC) is presented. The different types of overpotentials which the PFC could face with were investigated in this research. In addition, the effect of temperature on the overpotentials was studied. Moreover, it was shown that electron transfer overpotential increased versus the Schottky barrier height (SBH) at higher current densities. Also, higher flux density of photons and higher quantum efficiencies resulted in more photocurrent density. This paper provides a good view for the prospective researches at the areas of PFC modeling.