A systematic study of the behavior of different SCR-DeNO(x) catalysts - commercial ones and newly developed ones - was performed with the aim of developing new SCR-DeNO(x) catalysts with a high mercury oxidation rate. Besides the increase of mercury oxidation rate, also the SO2-SO3-conversion could be influenced if the catalyst's composition is modified. The focus of this study is to gain a greater insight into the SO2-SO3-conversion at copper impregnated catalysts and to evaluate the DeNO(x)-performance change due to catalyst impregnation by this metal oxide. Data is presented, which shows the catalyst's SO2-SO3-conversion measured by the controlled condensation method at variable operating conditions. Temperature was varied between 250 and 420 degrees C and the linear velocity between 0.3 and 1.5 m/s. In addition, the concentration dependency and the influence of water content were studied. Depending on the operating conditions and the bulk composition, copper impregnated catalysts show higher SO2-SO3-conversion rates compared to the commercial reference one. An exponential dependency of the SO2-SO3-conversion rate on the temperature and a non-linear dependency on the residence time was shown. Within this study, the potential for reducing the SO2-SO3-conversion was identified. (C) 2010 Elsevier Ltd. All rights reserved.