Conversion of methanol to olefins: Stabilization of nanosized SAPO-34 by hydrothermal treatment

• Nano-SAPO-34 has been stabilized by hydrothermal treatment toward contact with moisture.
• The stabilization effect is due to the migration of silicon to larger silicon islands.
• Thermal treatment in the absence of water does not stabilize nano-SAPO-34.
• Steaming of non-stabilized nano-SAPO-34 at low temp. (400 °C) causes amorphization.
• Hydrothermal tests for SAPO-34 should include steaming at low temperatures.

Nano-SAPO-34 zeolite catalyst (20 nm crystal size) has been stabilized by hydrothermal treatment. After steamed at high temperatures (T ⩾ 550 °C), its textural properties and high lifetime during the reaction of methanol to olefins (MTO) are preserved, despite the decrease in acidity, even after months of contact with moisture. The stabilization effect is attributed to the migration of silicon to larger silicon islands in which the contribution of silicon on the edge is lower after steaming. Stabilization is not successful by a thermal treatment in air in the absence of water. Steaming at temperature >400 °C is required for achieving hydrothermal stabilization. A stability test for SAPO-34 in MTO reaction is proposed.

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