Pore size effect on the methanol anomalous diffusion in the mesoporous catalyst pellets for methanol-to-olefin reaction

The methanol transport in the H-ZSM-5/Al2O3 catalyst pellets with various porosities was studied. The methanol mass transfer in the catalysts was found to be anomalous and is characterized by the fractional exponent value 1.18 ± 0.01. The measurements of the fractional exponent for the pellets of different porous structures demonstrate that the fractional exponent is independent on the porous structure. These findings support an idea that the methanol anomalous diffusion in the porous catalyst grain may be mainly caused by the adsorption process in the pores of the media comparing to the geometrical constraints of the pores.