DEHYDROGENATION OF ALPHA-LIMONENE OVER CE PROMOTED, ZEOLITE-SUPPORTEDPD CATALYSTS

The dehydrogenation of the natural terpene alpha-limonene to the indus trially important p-cymene was studied over zeolite supported Pd catal ysts. Transalkylation of the product p-cymene can be avoided by employ ing a medium-pore ZSM-5 catalyst via the well known product selectivit y. The addition of a Ce promoter leads to an enhanced p-cymene selecti vity and a slower catalyst deactivation. Surprisingly deactivation can be drastically reduced by the addition of hydrogen to the carrier gas .