Selective reduction of nitrogen oxides by hydrocarbons on hydrotalcite Co and Ni catalysts

Abstract

Hydrotalcitelike Co-Al and Ni-Al catalysts of different compositions (with the atomic ratio M 2+/Al3+ = 0.5–3.0) were studied in the reaction of selective reduction of NO by propane, propylene, and n-decane in the presence of O2. The higher activity of the catalysts with M 2+/Al3+ = 0.5 is connected with high dispersity of Ni or Co cations stabilized by a significant amount of Al3+ ions. Propylene was shown to be the most efficient reducing agent for nitrogen oxide. The highest degree of conversion to the extent of 90–99% was attained at 400 and 420–440°C for Ni-Al and Co-Al samples, respectively. When propane and decane were used as reducing agents, the conversion of both catalysts was characterized by the volcano-shaped dependence on temperature due to the fact that the catalyst took part in the concurrent reaction of hydrocarbon (reducing agent) oxidation. Hydrotalcitelike materials are promising representatives of inexpensive bi- and multicomponent systems. The design strategy for new active catalysts for processes of purification of gas exhausts from NO x , that are stable in the presence of water and sulfur oxides, may be based on usage of hydrotalcites with modified ions introduced into them.