Preparation of Al–SBA-15 pellets with low amount of additives: Effect of binder content on texture and mechanical properties. Application to Friedel–Crafts alkylation

Colloidal silica sol was used as a binder for the preparation of Al–SBA-15 pellets. Only 18 wt.% of silica was sufficient to form pellets that possessed mechanical strength comparable with industrial catalysts. Moreover, these pellets exhibited only minor changes in texture parameters in comparison with parent powder (the decrease of mesopore surface area and mesopore volume was not higher than 25%). However, even such small amount of binder caused a substantial reduction of reaction rate in Friedel–Crafts alkylation of toluene with benzyl alcohol. The time to reach 50% conversion of benzyl alcohol was for the pellets containing 18 wt.% of silica about five times higher in comparison with binder-free pellets. This decrease in the reaction rate was due to a partial decay of acid sites by alkali ions present in the binder solution and increased diffusion hindrances inside catalyst pellets.