Development of membranes for industrial gas separation

The gas mixture was therefore not easy to separate, and thousands of separation stages were needed. 

The adaptation of the principles used in the development of the membranes for the desalination of water via reverse osmosis was all that was needed to develop membranes for gas separation. It was realized that gas separation through dense polymer films was not practicable (due to the low gas flux) unless ultrathin dense films could be obtained. A thin film ensures a high flux even if the intrinsic permeability of the polymer is low. In 1970, using Loeb Sourirajan CA membranes which were dried, Merten and Gantzel obtained a separation factor of approximately 40 for He/N2, with high fluxes equivalent to those of a silicone rubber film 10 pm thick, but which would have a corresponding separation factor of only 1.5. 

But undoubtedly the biggest breakthrough in the last 20 years or so was brought about by the Monsanto Company. Polysulfone, a polymer which at that time was considered to have a high intrinsic selectivity for gases but a low permeability, was utilized in the form of hollow fibres. The Monsanto 

The United States Patent 4230463 (1980) by Henis and Tripodi describes multicomponent membranes for gas separations. This patent makes 78 claims and contains 7 figures. Sixty-three examples are given in all to demonstrate the flexibility of the invention, its limitations and successful use. A summarized description of the invention is given below. 

In the patents and papers whieh deseribe the resistance model, it is shown that permeation through composite hollow fibre membranes is analogous to electrical resistance. The symbols used to denote flux or permeation rate are the ones used by Henis and Tripodi. The permeation rate or flux Qi is given by Eq.(11.3)  

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