Role of Brønsted acidity in NH3 selective catalytic reduction reaction on Cu/SAPO-34 catalysts

• Cu/SAPO-34 catalysts with varying amounts of Brønsted acid sites were synthesized.
• The number of Brønsted acid sites was estimated via acid site generation mechanism.
• DRIFTS measurements were used for quantification of Brønsted acid sites.

In the present work, a series of Cu/SAPO-34 catalysts with varying number of Brønsted acid sites has been prepared by ion exchanging with potassium to investigate the role of Brønsted acidity in the NH3-SCR reaction. The impact of potassium on the structural and acidic properties of Cu/SAPO-34 catalysts has been studied. No significant changes in both the SAPO-34 structure and the copper species were observed in the presence of potassium. With increasing potassium loading, the NH3-SCR activity of the Cu-K/SAPO-34 catalysts decreased in accordance with the decreasing Brønsted acidity. The quantification method of Brønsted acid sites in the Cu-(K)/SAPO-34 was developed by using IR spectroscopy, which was confirmed by acid site generation mechanism and NH3-TPD results. A linear relationship was found between the amounts of Brønsted OH groups determined by DRIFTS and the NH3 desorbed at high temperatures from NH3-TPD.

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