кінетика

A conversion scheme for pentyl acetate, ethanolamine, and the products resulting from their interaction through aminolysis, transesterification, and O-N-acyl migration reactions catalyzed by homogeneous and heterogeneous Brønsted-Lowry bases and acids is proposed. It has been determined that acid and base catalysts significantly enhance the aminolysis reaction of esters with amino alcohols when compared to the non-catalytic process. The impact of the catalyst on each reaction has been assessed.

Phenolformaldehyde resins were obtained by polycondensation of concentrated phenols with formaldehyde in the presence of hydrochloric acid. Concentration of phenols is carried out by treating the phenolic fraction of coal tar with an aqueous solution of sodium hydroxide followed by neutralization of water-soluble phenolates with hydrochloric acid. The kinetic dependences of resin yield and softening temperature on the duration of the process at 333, 353, and 373 K were obtained.

The kinetics of the process of drying hot (80°C) and cold (20°C) candied pears were studied. The drying coefficient is found and an analytical dependence is derived for the drying time calculation. Experimental data of the change in the temperature of the thermal agent along with the height of the candied fruit layer was obtained.

In this paper, the dissolution kinetics of cement copper powder in sulfuric acid solutions containing cupric ions was examined. It was observed that the dissolution rate of copper increased with increasing the acid concentration, temperature, and stirring speed. It was determined that the dissolution rate of copper enhanced with increasing the cupric ion concentration up to 0.025 M. It was found that the temperature and concentration of cupric ion had more considerable effects on the dissolution of copper powder.

The kinetics of adsorption of ammonium ions under dynamic conditions has been studied. A mathematical model of the process was built. The mass transfer coefficient was calculated depending on the intensity of the change of location. It was established that ion exchange occurs in external and internal diffusion regions. The rate constants of ion exchange for the region of external and internal diffusion were calculated.

The dissolution process of potassium chloride particles in the apparatus with two-blade mechanical stirrer was investigated and the mass transfer coefficient was determined. The experimental results were generalized by criterion dependence. The independence of the mass transfer coefficient from the solid particles diameter was confirmed. A countercurrent process of potassium salt dissolution in two apparatuses with a mechanical stirring was considered. A mathematical model for countercurrent dissolution was developed and the efficiency of this process was determined.

The process of paraffin formation has been considered, including the peculiarities of the paraffin structure as a result of phase transitions with a decreasing temperature. Mathematical models for thermodynamic and kinetic calculations of the "solid-liquid" system phase equilibrium have been developed. To shift the "fuel oil-paraffin" balance towards the liquid, it is necessary to reduce the activity ratio of solid and liquid phases by introducing into the system a substance with a lower solubility parameter.