Klaus Elfert, Hans Jurgen Rosenkranz, Hans Rudolf: Separation of aromatic hydrocarbons from mixtures, using polyurethane membranes. Bayer Aktiengesellschaft, Burgess Dinklage & Sprung, September 19, 1978: US04115465 (66 worldwide citation)

A process for separating an aromatic hydrocarbon of the general formula ##STR1## wherein R represents an alkyl group having 1 to 3 carbon atoms and

Separation of aromatic hydrocarbons from mixtures using polyurethane membranes. Bayer, December 29, 1978: GB1520867-A (1 worldwide citation)

1520867 Separating aromatic hydrocarbons from mixtures BAYER AG 15 June 1977 [19 June 1976] 25017/77 Heading C5E Benzene or aromatic hydrocarbons containing up to 3 C 1 -C 3 alkyl substituents are separated from a mixture with aliphatic or cycloaliphatic hydrocarbons, alcohols, ethers, ketones or ca ...