CO₂ catalytic purification issued from oxy-fuel combustion

Global warming, mainly due to high CO₂ emissions, reference greenhouse gas, motivates researchers to find solutions to combat this phenomenon. The techniques of capturing and storing or reuse of CO₂ are relevant solutions, but which require a CO₂ as pure as possible. Among these techniques, oxy-fuel combustion seems promising enough to produce CO₂ in high concentration. However, depending on the nature of the fuel and the oxygen purity, some pollutants may appear such as CO and NO_x. To carry out this purification, catalysis is an effective means for simultaneously converting NO and CO respectively into N₂ and CO₂. The objective of this study is to develop active catalysts for NO_x reduction in N₂ by CO, in oxidizing conditions and presence of water. Two types of catalysts were chosen: supported noble metals (Pd, Pt, Rh) and transition metal oxides (Co, Cu, Al). The results obtained show that the Pt-based catalysts were more efficient and that their catalytic activity increases for the samples supported on a neutral support (SiO₂) or reducible (TiO₂) whether in the presence or absence of water. The mixed oxides of transition metals, obtained by hydrotalcite, show that the nature of the bivalent cation plays an important role. Co-Cu mixed oxides showed better activity than materials composed of only one of these two elements. However, the addition of water to the reaction flow led to a decrease in activity of the Cu-containing catalysts. (author)