Sol-gel synthesis of silicalite/γ-alumina granules

Spherical silicalite/γ-Al₂O₃ composite granules of about 2 mm in diameter were prepared by a sol-gel process from a mixture of the stable boehmite and silicalite sols. The stable silicalite sol was prepared by a hydrothermal method. Silicalite/γ-Al₂O₃ composite granules with a zeolite content of up to 70 wt % were formed by the sol-gel 'oil-drop' process in which a paraffin oil and ammonia solution were used as the media to facilitate shape forming and consolidation of the gel structure. The sol-gel-derived silicalite/γ-Al₂O₃ granules have a pore structure reassembling that of a mixture of silicalite and γ-Al₂O₃ powders. The crush strength of the sol-gel-derived silicalite granules is about six times that of a similar commercial silicalite granule. In addition, the sol-gel-derived silicalite/γ-Al₂O₃ granules exhibit better sorption properties for SO₂ at a lower SO₂ partial pressure than pure silicalite powder.