Propene monomers, physical properties

When polymerization occurs in a mixture of monomers there will be competition between the different kinds of monomers to add to the growing chain and produce a copolymer. Such a polymer will be expected to have physical properties quite different from those of a mixture of the separate homopolymers. Many copolymers, such as GRS, ethene-propene, Viton rubbers, and Vinyon plastics are of considerable commercial importance. 

At petrochemical plants there are numerous gas streams that contain valuable components which need to be recovered and reused. These are typically non-reacted monomers, by-products from reactors, inerts, solvents and carrier gas. There is a nice potential for using CMS membranes for many of these applications, and thereby also save money if complicated systems with columns, refrigeration and compressors can be avoided. A study on separation of alkanes-alkenes was performed by Hagg et alP Their systems were the separation of propane-propene and propan-ethene. As the alkanes-alkenes are chemically and physically quite similar compounds with almost identical critical properties, they must be separated on the basis of their molecular size. The Lennard-Jones diameter is 4.7 A and 5.1 A for propene and propane, respectively hence, a carefully tailored CMS membrane would be able to separate these two components according to the molecular sieving mechanism. A selectivity of 23 for this gas pair was documented at 30 °C, and even much higher selectivity at 50 °C this is believed to be a result of a transition of separation mechanisms for propane at lower temperature propane will... 

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