Two-step processing of C 8 aromatic mixture over modified ZSM-5 catalysts

Abstract

The isomerization of C 8 aromatic feed over NiZSM-5 catalysts was investigated in an integral pressure reactor. A series of catalysts containing 30 wt.-% of NiZSM-5 were prepared from ZSM-5 samples having a similar composition and acidity but different para selectivity as shown by the conversion of toluene. Catalytic tests with real C 8 aromatic feed indicated that at near equilibrium isomerization, xylene loss can be more reduced on the non para selective catalysts with a very low reaction temperature than by increasing the para selectivity of the zeolite. On the other hand, increasing the para selectivity of the zeolite increases the selectivity of the ethylbenzene conversion. It was shown that the high selectivity in isomerization of non para selective catalysts and in ethylbenzene conversion of para selective zeolite can be effectively utilized by processing the feed in two steps. Non para selective catalysts were used for xylene isomerization and para selective catalysts for the optimization of the ethylbenzene conversion.