ISOMERIZATION OF 2-METHYLPENTANE AND RING-OPENING OF METHYLCYCLOPENTANE OVER PT-CO NAY CATALYSTS/

The catalytic transformations of 2-methylpentane (2MP), and methylcycl opentane (MCP), over Co/NaY, Pt-Co/NaY, Pt-Co/Al2O3 and NaY samples ha ve been investigated. Co/NaY was found to be an excellent isomerizatio n catalyst, in contrast to Co/Al2O3 on which the main route was observ ed to be cracking. This is attributed to the difference in cobalt redu cibility over the two supports. The use of C-13-labelled 2-methyl pent anes made the elucidation of the mechanism of isomerization on these s amples possible. A cyclic mechanism (CM) operates only on metal partic les, while for both metal particles and support, a bond shift mechanis m (BS) is the main route for isomerisation. On Pt-Co/NaY samples, the contribution of the cyclic mechanism to isomerisation relative to isom erisation by bond shift route is significantly enhanced on the catalys ts with cobalt loading higher than 22 at.%. The results are discussed in terms of small metal particles inserted into NaY supercage and the enhanced reduction of cobalt ions.