| 摘要 |
A method for reducing nitrous oxide emissions in an exhaust gas, comprises contacting an exhaust gas containing ammonia and an inlet nitrogen monoxide concentration with selective catalytic reduction (SCR) catalyst composition containing small pore zeolite having silica- to-alumina ratio (SAR) of 3-15 and 1-5 wt.% of exchanged transition metal to produce a purified gas containing an outlet nitrogen monoxide concentration and an outlet nitrous oxide concentration. The inlet and outlet nitrogen monoxide concentrations have a relative ratio of greater than 4. The inlet nitrogen oxide and outlet nitrous oxide concentrations have relative ratio of greater than 50. Also claimed is a system for treating an exhaust gas comprising, in series and in fluid communication, a diesel oxidation catalyst, a source of nitrogen-based reductant, and SCR catalyst, where the SCR catalyst comprises a small pore zeolite having an SAR of 3-15 and having 1-5 wt.% of an exchanged transition metal, and the SCR catalyst is coated on a honeycomb wall-flow filter or flow-through monolith or is an extruded honeycomb body. The method improves environmental air quality, particularly exhaust gas emissions generated by power plants, gas turbines, lean burn internal combustion engines, by reducing nitrogen oxides and nitrous oxide concentrations over a broad temperature range. |
