Zhokh O. Impact of the diffusional factor in the process of the methanol conversion on H-ZSM-5/Al2O3 catalysts

A new kinetic scheme of the process of the olefins and dimethyl ether synthesis from methanol is proposed which accounts for methanol conversion to olefins and dimethyl ether by different routes over strong and weak acid sites respectively. A new instrument for mass transfer processes investigations in solid porous media in flow regime is developed, which allows mass transfer kinetic study in a catalyst pellet under different experimental conditions. Methanol diffusion in catalyst pellet is anomalous and is described by the time-fractional diffusion equation. Fractional order for the methanol transport is independent on porous structure and depends on the catalyst substance. Fractional diffusion coefficient of methanol increases with the increase of the alumina content in a catalyst pellet. Obtained results reveal that the diffusion regime is an individual property for each combination of the diffusate and solid media and is governed by the reversible adsorption of the methanol molecules on a catalyst surface. The impact of the diffusional factor in the process of the methanol conversion demonstrates a symbatic dependence of the methanol conversion rate on the fractional diffusion coefficient of the methanol.