CHEMICALS FROM n-BUTENES 238

The three isomers constituting n-butenes are l-butene, cis-2-butene, and trans-2-butene. This gas mixture is usually obtained from the olefinic C₄ fraction of catalytic cracking and steam cracking processes after separation of isobutene. The mixture of isomers may be used directly for reactions that are common for the three isomers and produce the same intermediates and hence the same products. Alternatively, the mixture may be separated into two streams, one constituted of l-butene and the other of cisand trans-2-butene mixture. Each stream produces specific chemicals. Approximately 70% of l-butene is used as a comonomer with ethylene to produce linear low-density polyethylene (LLDPE). Another use of l-butene is for the synthesis of butylene oxide. The rest is used with the 2-butenes to produce other chemicals. n-Butene could also be isomerized to isobutene. This section reviews important reactions leading to various chemicals from n-butenes.