Keywords: modeling

Synthesis of 4,4’-methylenedianiline (MDA) in the microchannel

https://doi.org/10.58224/2619-0575-2024-7-3-34-48
Abstract
The work is devoted to the method of obtaining 4,4’-methylenedianiline (MDA) in a microchannel. MDA is produced on an industrial scale, mainly as a precursor to polyurethanes. This compound is also used as a hardener for epoxy resins, wire coatings, as well as in reinforced composite materials. The synthesis of MDA is accompanied by high temperature fluctuations, and the limiting factor is the rate of mass transfer. Microfluidics can solve these problems. The microreactors operate in a flow-through design in a laminar flow mode. Due to the small diffusion path of the molecules, the distribution of concentrations and temperatures is fast. This in turn increases the yield of the product, improves reaction control. It is also important in multiphase processes, where the mass transfer process takes place at the phase interface. It is microfluidics that allows precise control of the area of interfacial interaction, which is critical for these processes. However, during the synthesis of MDA, viscosity increases due to the formation of oligomers, which can clog the microchannel. A numerical simulation process was carried out, which revealed the projectile flow in the microchannel, which was also confirmed during the synthesis. A multifactorial experiment has been compiled, which is necessary to determine the optimal synthesis conditions. Parameters such as reaction temperature, component ratio, and residence time varied. The design of the experi-ment was used for successful synthesis. Based on the above parameters, two-dimensional and three-dimensional contour diagrams are constructed, representing mathematical models of the process under study. Due to their combination, the optimal technological parameters of the process were established.
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STUDY OF THE EFFECT OF ANIONS ON THE DISSOLUTION RATE OF CO2O3 AND CR(OH)3

Abstract
Сhromium compounds are widely used in industry, therefore, studies related to the study of the process of dissolution of oxides in various environments, including aggressive ones, are relevant. Currently, a huge amount of experimental material has been accumulated on the dissolution of metal oxides and hydroxides. Despite this, the effect of anions on the dissolution rate of these compounds has not yet been sufficiently studied, models have not been developed and generalized dissolution mechanisms have not been found. This article presents experimental studies on the effect of nitrate and sulfate ions on the dissolution rate of chromium (III) oxide and hydroxide. It was found that chromium (III) oxide and hydroxide dissolve better in sulfuric acid in the presence of nitrate ions than sulfate ions. Moreover, chromium (III) hydroxide dissolves better in acids with the addition of anions than chromium (III) oxide. Based on the data obtained, using the equation of the chain mechanism (the Barton-Stransky model), we found the functional dependence of the specific rate of dissolution on the concentration of anions in an acidic medium. With the help of the mathematical computer program MathCad, models of the dissolution of chromium oxide phases were selected. A scheme of the mechanism of the heterogeneous process of dissolution of chromium oxide and hydroxide in acidic media was proposed.
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