GB518558A - Improvements in the depolymerisation of mono-olefine polymers - Google Patents

Abstract

518,558. Depolymerizing olefine polymers. I. G. FARBENINDUSTRIE AKT.-GES. Sept. 5, 1938, No. 25930. Convention date, Sept. 7, 1937. [Class 2 (iii)] The catalytic depolymerization of polymers of low boiling mono-olefines is effected in the presence of appreciable amounts, usually more than 20 per cent. by volume of the vaporized polymers, of steam. The life of the catalyst is thereby prolonged. Temperatures are usually 200-400‹ C., preferably 230-330‹ C. and pressure atmospheric but it may be reduced or increased. Surface-acting catalysts such as bleaching earths which may be pre-treated with acids, e.g., hydrofluoric or hydrochloric acid, are specified. Polymers - boiling above 170‹ C. of olefines boiling below 100‹ C., e.g., trimer, tetramer and higher polymers of isobutene or isohexene, and higher polymers of propene, pentenes, hexenes, and heptenes are suitable initial materials. In an example, tri-isobutene is vaporized and mixed with steam to form a mixture containing 42 per cent. of steam ; this is led at 230‹ C. over " tonsil" to produce isobutene and diisobutene. The Specification as open to inspection under Sect. 91 also states that the amount of steam is usually not more than 80 per cent. and is. preferably from 40 to 60 per cent. In addition, it includes two further examples which describe the passage of a mixture of (1) di-isoheptene vapour and steam over "Frankonit H" to give isoheptene, and (2) tetra-isobutene and steam over "Frankonit H" to yield a mixture of isobutene, di-isobutene and. tri-isobutene. This subject-matter does not appear in the Specification as accepted.