Xylenes Reactions and Diffusions in ZSM-5 Zeolite based Catalyst

Xylenes transformations have been investigated over ZSM-5 zeolite in a riser simulator that mimics closely the operation of commercial fluidized-bed reactors. P-xylene was found to be more reactive than the other isomers followed by o-xylene and m-xylene was found to be least reactive. The order of reactivity is consistent with the order of diffusivity. At low temperature (400°C), isomerization and disproportionation yields for all xylenes were found equal at constant conversion. However, as reaction temperature increases to 500°C, m-xylene reaction will be more selective to disproportionation than other xylene isomers. The effectiveness factor for all xylene isomers reactions was found based on two different diffusivities used from the literature. Generally m-xylene effectiveness factor was estimated to be less than 0.1 indicating to a high diffusion obstacle inside ZSM-5 zeolite. While o-xylene was found to have effectiveness factor in a range of 0.35-0.45, p-xylene effectiveness factor was found to be close to unity indicating no diffusion limitation.