Kinetics of Xylene Isomerization on Modified ZSM-5 Zeolites

Xylene isomerization over HZSM - 5 . MgO - HZSM -5 and CaO -HZSM -5 zeolites have been studied using the pulse microreactor chromatograph technique and dynamic modeling method. The rate constants, activation energies and activation entropies for each step of the reaction network have been obtained. These results indicate that the strong acidity can favor the conversions of m-and o-Xylene.while the isomerization of p- Xylene not only takes place on the strong acidic sites, but also on the weaker acidic sites. The parameters also indicate that under the loading amount of MgO or CaO in the mole ratio to framework aluminum equal 1 :1, the influence of steric encumbrance caused by the intruduction of MgO or Cao is less as compared with the changes of the surface acidity.