GB874507A - Method for isomerizing olefins - Google Patents

Abstract

Internal olefins are isomerised to a -olefins by first converting to the corresponding boron alkyl, heating the boron alkyl to above 100 DEG C. for a time sufficient to cause isomerisation and recovering the isomerised olefin from the boron alkyl. Mixtures of olefins which may also contain saturated or aromatic hydrocarbons may be treated; C4-C24 olefins may be treated including branched chain olefins such as tetrapropylene and alkenyl cycloalkanes or alkenyl aromatics. The boron alkyl may be prepared (1) by reaction with diborane, (2) by reaction in ether-type solvents with reagents producing diborane, e.g. NaBH4 + BF3.Et2O or (3) by a displacement reaction with a different boron trialkyl. Reaction (1) may be effected at - 50 to 150 DEG C. and 0-2,000 p.s.i.g., reaction (2) at -50 to 150 DEG C. and atmospheric pressure and reaction (3) at 50-250 DEG C. and 0-3,500 p.s.i.g. Non-olefinic materials do not react and may be separated. Isomerisation may be effected at 100-250 DEG C. and may be combined either with the formation of the boron alkyl or the recovery of the olefin. Recovery of the olefin may be by thermal decomposition to diborane or alkylborohydrides at 150-350 DEG C. and atmospheric or reduced pressure or by displacement with a different olefin to give a different boron trialkyl and the required olefin. The boron trialkyl may be recycled as such for further formation of boron alkyl by method (3) or reduced to diborane and recycled for use in method (1). Displacement may be effected at 50-250 DEG C. and 0-3500 p.s.i.g., if desired in the presence of nickel, cobalt, chromium dibenzene, ferrocene or cyclopentadienyl nickel and an amine or ether; preferably the desired olefin is removed as it is formed. Ethylene is the preferred displacing olefin.