| abstract |
Olefins are cracked in the presence of bromine to give mixtures of either a diolefin and a paraffin or two new olefins; the cracking occurs at a position beta to the double bond. A diluent may be present, e.g. steam, carbon dioxide, nitrogen, hydrogen paraffins or C2-C4 olefins in amounts of 0,5-15 mols per mol of olefin. Bromine or a bromine producing compound, e.g. ethyl bromide, 2-bromopropene, n-butyl bromide, n-propyl bromide, a -bromotoluene, bromobenzene, bromochloromethane, 1,2-dibromoethane, hydrogen bromide or ammonium bromide, is added in an amount to provide 0,5-50% mol based on the olefin and may be introduced dissolved in the olefin or water when steam is used as the diluent. Temperature may be 300-1000 DEG C., pressure 10 mm. Hg to 500 p.s.i.g., and cracking times of 0,001-3 seconds corresponding to GHSV of 3,600,000-1,200. The production of isoprene from 2- and 3-methylpentene-2 is exemplified and lists of materials are given for the production respectively of 2-, 3- and 4-methylpentadiene-1,3, 2,3-dimethylbutadiene-1,3, 2-ethylbutadiene-1,3, butadiene, isoprene, piperylenes, propylene, isobutylene, butene-1 and -2, 2-and 3-methylbutene-1 and 2-methylbutene-2, pentene-1 or 2, and 2,3-dimethylbutene-1 or -2. |