Calculation of Copolymer Component Composition near Interface
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RESEARCH, DESIGN, NUMERICAL ANALYSES, AND OPERATING EXPERIENCE PROCESSES AND EQUIPMENT OF CHEMICAL AND OIL-AND-GAS TECHNOLOGIES CALCULATION OF COPOLYMER COMPONENT COMPOSITION NEAR INTERFACE A. G. Mukhametzyanova and K. A. Alekseev
UDC 66.021.3.06
A mathematical description of interconnected processes of mass transfer and chemical conversion in a copolymerization reactor is given. Two cases are investigated: simultaneous transfer of two monomers from a gas to a liquid with chemical reaction in the liquid (for example, copolymerization of ethylene and propylene in ethylene-propylene synthetic rubber production) and copolymerization in a liquid near a solid surface (for example, copolymerization of isobutylene and isoprene in butyl rubber production). The dependence of the component composition of the copolymer on the diffusion resistance to the transfer of monomers near the interface is established. Keywords: synthetic rubber, mass transfer, polymerization, mathematical modeling.
Processes of copolymerization of two or more monomers are implemented in both single-phase and multiphase systems. An example of copolymerization in a two-phase (gas-liquid) system is the industrial practice of ethylene-propylene rubber production in a solvent through which a mixture of gaseous monomers is passed [1]. Since the process occurs in a two-phase system, the monomers must be transferred from the gas phase to the liquid for chemical reaction. Our calculations showed that in real production conditions equilibrium between the gas and the liquid is not established at 8–14 wt.% polymer concentration in the solvent because of considerable resistance to mass transfer in the liquid phase (due to high viscosity of the polymer solution and high rates of catalytic polymerization reactions). If the process occurs outside the kinetic region (i.e., the chemical reaction rate is much lower than the diffusion rate), the macrokinetics of polymerization is a result of combined effect of chemical and mass transfer kinetics. Like any copolymer obtained this way, ethylene-propylene synthetic rubber is a compositionally heterogeneous product (compositional heterogeneity is the difference in differential composition of different macromolecules of the given copolymer). The differential composition of a macromolecule, in turn, is defined as the ratio of the amounts of the linked units of the first and second monomers. The results of investigations of the influence of the factors of chemical kinetics on the compositional heterogeneity of the copolymers are furnished in [2]. It is also known that in heterogeneous systems diffusional Kazan National Research Technological University (Kazanskii Natsional’nyi Issledovatel’skii Tekhnologicheskii Universitet), Russia; e-mail: [email protected]. Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, Vol. 56, No. 7, pp. 3–5, July, 2020. 0009-2355/20/0708–0511
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Springer Science+Business Media, LLC
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resistances affect the compositional heterogeneity of
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