Influence of the nature, size and shape of the solvent molecules on their diffusion in the polymer

Abstract

Using polymeric membranes for separating mixtures of liquid hydrocarbons, such as crude oil, gas condensate, shale oil, pyrolysis liquid is very important and promising direction for the oil refining industry and obviously can be an alternative to convection technologies. The paper investigates the possibilities of using non-porous polymeric membrane based on silicone synthetic rubber with stiff matrix. The stiffness of the matrix was achieved by increasing the degree of crosslinking. The high degree of crosslinking decreases sharply macromolecular segmental mobility, which in turn allows to reduce the permeability of the membrane elements for complex heavy molecules. Thus, by adjusting the pervaporation parameters, only those substances can be extracted from a gas condensate in the temperature range of 35 - 65°C, which are components of the gasoline fraction with a boiling point of 35°C and the end boiling point of 215oC. Moreover, using the differences between the values of diffusion activation energies and diffusion coefficients of various substances in the gasoline fraction, as well as the dependence of these values on the temperature and time allows to achieve the decomposition of fraction into components. Using an experimental membrane setup at atmospheric pressure and relatively low temperatures (35 - 65°C), all the gasoline fraction components were extracted, which were in turn were decomposed into four groups of substances depending on the size, shape and nature of the molecules.