Synthesis and catalytic application of SAPO-5 by dry-gel conversion for the epoxidation of styrene with air

• High silica SAPO-5 is synthesized by dry-gel conversion method.
• Co-SAPO-5 is prepared and applied in the epoxidation of alkenes with air.
• Co-SAPO-5-0.6 by dry-gel conversion method is the most active.
• 94.5 mol% conversion of styrene with 87.2% epoxide selectivity is obtained.
• The catalysts are highly reusable heterogeneous ones.

High silica content SAPO-5(d) with an AFI topology has been synthesized by dry-gel conversion (DGC) method. Various techniques have been used to characterize the structures of molecular sieves. XRD patterns show high crystallinity and purity of the DGC samples. XRF analyses prove high silica content of SAPO-5(d). The SAPO-5(d) has small particle size of 0.5–1 μm with large BET surface area. Co-SAPO-5-0.6(d) exhibits a high activity for the epoxidation of alkenes with air to achieve 94.5 mol% conversion of styrene and 87.2% selectivity of epoxide. Recycling studies and control experiments show the recyclable stability of Co-SAPO-5-0.6(d) as a heterogeneous catalyst. As a comparison, SAPO-5(h) samples by hydrothermal synthesis (HTS) method have also been prepared and applied in the epoxidation reaction. However, the catalytic activity of Co-SAPO-5-x(d) (82.2–94.5 mol%) is higher than that of Co-SAPO-5-x(h) (72.9–85.5 mol%), which can be correlated with high silica content, high cobalt content, small particle size and large surface area.

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