Preparation of cylindrical extrudates of mesoporous silica-alumina without use of binder and their activity in cracking of cumene

Abstract

A series of mesoporous silica–aluminas (MSA) containing 24–59 wt% Al₂O₃ was synthesized from sodium metasilicate and aluminum nitrate and extruded in 1/16″ cylinders without use of a binder. This was followed by slow hydrogel drying, extraction by water and calcination at 500 °C. This procedure gave stable hard extrudates and the absence of binder allowed to keep the surface area, mesoporosity and cracking activity of MSA at the original high values. The resistance to crushing was much better as compared to commercial molecular sieve 13X. The extrudates have average pore size around 3.5 nm. Their properties were affected by the contents of Al₂O₃ and residual sodium. The MSA containing 50 wt% Al₂O₃ possessed the maximum values of surface area, pore volume and activity in cumene cracking. The calcined extrudates showed good water sorption capacity and were stable in aqueous environment. This predestinates the MSA extrudates as the shaped mesoporous acidic carriers for preparation of different supported catalysts.