Tailoring mesoscopically structured H-ZSM5 zeolites for toluene methylation

[Display omitted] •Design of catalysts for toluene methylation based on mesoscopically structured H-ZSM5.•Path length reduction by post-synthetic treatments is beneficial for catalyst activity.•SiO2 overlayer increases p-xylene selectivity due to enhanced tortuosity.•Final catalyst material combines better utilization with higher p-xylene selectivity.•Exploring influence of transport and acidic properties on catalyst performance. Mesoscopically structured zeolites based on H-ZSM5 were designed and synthesized as highly active and shape selective catalysts for methylation of toluene by tuning diffusion and acid site concentration of the catalysts. This was achieved by combining desilication, subsequent dealumination and chemical deposition of a mesoporous SiO2 overlayer of several nanometer thickness. The decreasing effective diffusion length in zeolite crystals achieved by desilication and dealumination increased the turnover rate of toluene by favoring activation of methanol and facilitating desorption of the produced xylenes, albeit with some loss in p-xylene selectivity. The presence of the SiO2 overlayer increased the p-xylene selectivity by enhancing the tortuosity of the zeolite, randomly blocking pore openings at the surface, and increasing the effective diffusion path length. The final material combines the higher catalyst utilization with enhanced selectivity leading to rates comparable to the parent zeolite, but at significantly higher selectivity.