Catalytic synthesis of triazine compounds using a flexible technology

Based on laboratory pilot studies, we have developed a flow sheet for the catalytic synthesis of triazine compounds from carbamide using a flexible technology and a catalyst for this process. The main process parameters are as follows: a carbamide melt is fed into the reactor under a pressure of 0.8 MPa at 140–160°C; the volume rate of feeding the circulating gas into the reactor is 500–750 h⁻¹, its temperature is 350–500°C, and the melt-to-gas mass ratio is 1: (7–9). The temperature of synthesis in the reactor is 350–450°C; the pressure in the reactor is 0.1–0.2 MPa. The sublimation temperature is 180–200°C. The conversion of carbamide is ∼98%. The content of the target component in the product is ∼98.8%. Depending on the composition of the circulating gas, it is possible to obtain products of melamine, cyanuric acid, or melamine cyanurate. A catalyst in the form of promoted active aluminum oxide with an inner surface of 300 to 400 m²/g and a technique for its preparation have been developed.     

A mechanism of anomalous dust settling in a catalyst bed

Anomalous dust settling by a working catalyst bed is considered. The proposed mechanism of dust settling is based on electrical phenomena near the catalyst surface.     

Simulation of the ammonia oxidation process over an oxide monolith catalyst

A mathematical model of ammonia oxidation over an oxide monolith honeycomb catalyst has been developed. Experimental data from a pilot unit operating under process conditions equal to those in a type UKL-7 commercial nitric acid plant were used to refine the parameters of the mathematical model. The results from calculating the NO yield are in satisfactory agreement with the pilot unit data. There is now computer program that allows us to calculate the conditions of an industrial reactor functioning.     

Effect of the Charge of Solid Particles on the Activation Energy of Acid Decomposition of Phosphorus-Containing Raw Material

Experimental data on the effect of ionogenic surfactants on the charge of fluorapatites and hydroxyapatites in aqueous solutions are analyzed. The effect of cetylpyridinium chloride (a cationic surfactant) and sodium dodecyl sulfate (an anionic surfactant) on the activation energy of decomposition of phosphate raw material by nitric, sulfuric, and phosphoric acids is experimentally studied. It is shown that, regardless of the nature of the solid and liquid reactants, the activation energy is minimal in the isoelectric state of the surface of the solid-phase particles.__________Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 4, 2005, pp. 440–443.Original Russian Text Copyright © 2005 by Dobrydnev, Bogach, Kol’tsova, Beskov.     

Analysis of the Mass Transfer in Acid Decomposition of Phosphorus-Containing Raw Material

Experimental data on the effect of surfactants on the rate of acid decomposition of apatites are discussed using the mathematical tools of systems analysis of chemical engineering processes (synergetic method). An analytical expression relating the mass-transfer rate to the interfacial electrical properties is derived. It is shown that the limiting step in decomposition of fluorapatite and hydroxylapatite by nitric, sulfuric, and orthophosphoric acids is the mass transfer from the surface layer into the bulk of the solution.     

Mathematical simulation of a belt crystallizer for molding of coagulants

The existing methods for mathematical simulation of the bulk crystallization of supersaturated solutions (pastes) are analyzed. A method for calculating the characteristics of paste drying on a belt conveyor is developed. This method is necessary to analyze proposals of process equipment manufacturers and also serves as the basis for calculating the optimal operating conditions and intensifying the preparation of a granulated coagulant.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 140–145.Original Russian Text Copyright © 2005 by Kutepov, Beskov, V. Getmantsev, S. Getmantsev.Deceased.     

Kinetic method of calculation of chemical equilibrium

A method of calculating the equilibrium composition of multicomponent multiphase mixtures is considered. The method is based on a natural process, specifically, the chemical conversion of the initial mixture until the establishment of the equilibrium. The computational algorithm is discussed.     

Influence of Surfactants on the Rate of Decomposition of Apatites by Mineral Acids

The dependence of the true rate of decomposition of fluorapatite and hydroxylapatite in nitric, sulfuric, and orthophosphoric acids on the concentration of a surfactant (cetylpyridinium chloride and sodium dodecyl sulfate) was experimentally studied. The electrokinetic potential in the slip plane of the double electric layer at the interface between apatite and an aqueous solution of a surfactant was measured by the electroosmotic method. The concentrations of cetylpyridinium chloride (5.5 × 10^–6 mol/l) for fluorapatite and sodium dodecyl sulfate (1 × 10^–4 mol/l) for hydroxylapatite were found, which correspond to the isoelectric state of the surface of the solid phase. It was established that the true rate of decomposition of apatites is maximal when the electrokinetic potential is zero.     

Ionometric Study of the Acid Decomposition of Phosphate Minerals

A setup allowing computer processing of experimental data is suggested for studying the acid decomposition of phosphate minerals. A potentiometric technique using ion-selective electrodes is proposed for determining the starting substances and reaction products in solution.