In this work four different supports of varying degree of Bronsted and Lewis acid sites and textural properties were used to evaluate the influence of degree of ammonia interaction and Mn species formation in the catalysts and its effect on NOx conversion. A series of Mn deposited on TiO2, ferrierite (FER), Engelhard titanium silicate (ETS-10) and Montmorillonite (Mont-K10) were prepared by impregnation method. The catalysts were characterized by different techniques. FTIR analysis showed only Mn/FER catalyst to possess significant amount of Bronsted and Lewis acid sites. No correlation was found between surface area, type and amount of acid sites and NOx conversion of the catalysts. XRD analysis of catalysts showed predominantly MnO2 species, especially in Mn/FER catalyst, and Mn2O3 species was not detected. However, the Raman studies indicated the presence of MnO2 and Mn2O3 bands. TPR revealed lower onset reduction temperatures of MnOx species in Mn/FER compared with other catalysts. Among different catalysts tested, Mn/FER showed highest NOx conversion between 160 and 400 degrees C. Based on the obtained results, it was concluded that even though acid sites are needed to activate NH3, its amount and strength were found to have less influence than the redox properties, arising from MnO2 active species. (C) 2011 Elsevier B. V. All rights reserved.