Selective Catalytic Reduction of NO over Ag/Al_2O_3 and Improved Silver Catalysts

摘要

The selective catalytic reduction of NO by hydrocarbons (HC-SCR) over Ag/Al_2O_3 has attracted considerable attention as a new de-NO technology for diesel engine exhaust. However, the C_3H_6-SCR of NO is usually suppressed in the presence of water vapor, which inevitably exists greatly in various exhausts, resulting in a difficulty for utilization of the catalysts. Another major disadvantage is that the NO conversion over Ag/Al_2O_3 is quite low at temperature range of 300-400°C using C_3H_6 as a reductant. On the other hand, using C_2H_5OH as a reductant, Ag/Al_2O_3 was extremely effective for the NO reduction even in the presence of water vapor. In this paper, the influence of water vapor on the SCR of NO over Ag/Al_2O_3 was investigated, and improved silver catalysts have been developed with relatively higher de-NO activity than Ag/Al_2O_3, especially at low temperature.