IM-5:: A highly thermal and hydrothermal shape-selective cracking zeolite

Zeolite IM-5 shows a higher thermal and hydrothermal stability than that of ZSM-5, the rate of dealumination being slower, as shown by Si-29 and Al-27 magic-angle spinning nuclear magnetic resonance. This is responsible for the larger acidity of IM-5 after calcination and steaming. When cracking paraffin, cycloparaffin, and olefin model compounds, this zeolite gives a higher activity than ZSM-5 with similar shape selectivity. When used as a fluid catalytic cracking additive, the improved hydrothermal stability of IM-5 is responsible for its higher activity and for increasing the olefin-to-paraffin ratios in the products, having a special impact on the production of propylene. (C) 2002 Elsevier science (USA).