SKELETAL ISOMERIZATION OF OLEFINS WITH THE ZEOLITE FERRIERITE AS CATALYST

Ferrierite (FER) is an excellent catalyst for the skeletal isomerisation of n-butenes and n-pentenes, combining attractive process conditions with a high iso-olefin selectivity and a high stability. This isomerisation process is now being commercialised. The excellent performance of FER is explained in this paper on the basis of the proposed reaction mechanism, combined with the product shape selectivity and the mild cracking activity of FER. The reaction mechanism for butene isomerisation might follow a route of dimerisation of butenes, skeletal isomerisation and subsequent mild and selective cracking to n- and iso-butenes. The shape selectivity of FER allows branched butene dimers in the channels, but inhibits their migration through the channels, which combined with the selective cracking, results in a low C5+ and a high isobutene selectivity.