• C 2 H 2 O 4 and H 6 O 39 SiW 12 exhibited a similar regeneration efficiency with H 2 SO 4 for K-CuNbTi. • K species could be removed from catalyst surface while Cu species was preserved. • Both of surface active oxygen and Cu+ species increased after regeneration. • Surface acidity was obviously enhanced, especially for the Brønsted acid sites. The K 2 O poisoned CuNbTi as a model catalyst (K-CuNbTi) was regenerated by various type and strength acids, among which H 2 SO 4 , C 2 H 2 O 4 and H 6 O 39 SiW 12 exhibited higher regeneration efficiencies. In contrast to H 2 O treatment, most potassium depositing on the surface of K-CuNbTi could be removed successfully for the acids regenerated catalysts. All the regenerated catalysts showed above 90% NO x conversion and 98% N 2 selectivity in the temperature range of 300–350 °C under a high GHSV of 177,000 h−1. And the regenerated catalysts were characterized by different analytic techniques. Both of the surface chemical active oxygen species and the Cu+ species were obviously improved while KNbO 3 was transformed into Nb = O and Nb–OH after regeneration process. Furthermore, the quantity and strength of surface acidity were enhanced and more acid sites were generated, especially Brønsted acid sites. The main acid sites of K-CuNbTi was Lewis acid sites while Brønsted acid sites became the dominating acid sites for the regenerated K-CuNbTi catalysts. Also, acid regeneration process promoted –NH 2 active species formation on the catalyst. All above induced a better catalytic activity of regenerated catalyst, indicating that oxalic acid and silicotungstic acid could be the potential substitutes for sulfuric acid to regenerate alkali poisoning SCR catalysts. [ABSTRACT FROM AUTHOR]