Isomerization of meta-xylene over offretite catalysts

The conversion of meta-xylene has been investigated over offretites with different levels of ion exchange. The ratio isomerization/disproportionation increases with the degree of exchange, most probably due to an increased accessibility of the reactant to the internal surface and to a higher number and strength of acid sites. The addition of a hydrogenation function, in H2 atmosphere, slightly increases the activity and decreases the deactivation as a function of time. The conversion of 1−3-dimethylcyclohexene-1 yields experimental evidence that a bifunctional path exists for the reaction in these conditions. The supposed intermediate olefin isomerizes and disproportionates faster than meta-xylene, but the ortho/para selectivity remains unchanged.