Deactivation of Cu/SAPO-34 during low-temperature NH3-SCR

• The synthesised Cu/SAPO-34 is deactivated after contact with water vapour at 70 °C.
• Deactivation in this study is not reversible with a treatment at 600 °C.
• Crystalline structure and Brønsted sites are not damaged by humidity at 70 °C.
• Active copper sites may be deactivated by low-temperature exposure to water.

The sensitivity of NH3-SCR activity to water vapour at 70 °C is tested for Cu/SAPO-34 (morph.) catalysts. The synthesised Cu/SAPO-34 (morph.) is remarkably susceptible to low-temperature activity loss. After only 3 h at 70 °C, the NOx conversion decreases from an initial 87% to 66% at 200 °C, after another 9 h to 6%. This deactivation is accompanied by a partial loss of microporous volume, but the SAPO-34 framework remains crystalline. We postulate that a transformation of the active copper sites into an inactive form could be the cause for the deactivation. Regeneration of the catalyst was attempted, but had no impact on activity.

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