The Study On Properties Of Desulfurization And Denitrification By Mn/Al Catalysts

The main electric source in China is electricity generation by thermal power, which relies mainly on coal combustion. However, the environmental problems made by coal combustion have restricted our national economy and social sustainable development. The regenerative metal oxide processes is a promising technology for simultaneous removal of SO₂ and NOx from flue gas, which generates no wastes, reduces energy consumption, and the by-products decreasing the costs.MnOx/γ-Al₂O₃ catalyst-sorbents were prepared by sol-gel process. CeO₂ were added as promoter to improve its low temperature selective catalytic reduction (SCR) characteristics, The denitrification efficiency of the catalysts was measured in a fixed-bed reactor. To obtain more information about the adsorption behaviors of NH₃ and NO in this system, oxidation and desorption experiments had been carried out. And then, NH₃/O₂ and NO/O₂ adsorption processes on the MnOx-CeO₂/γ-Al₂O₃ catalyst and the transient response of NH₃ and NO were investigated by in situ diffuse reflectance infrared transform spectroscopy (DRIFTS) to study the SCR mechanism. Eventually, large quantities of CuFeMn/Al catalyst-sorbents were prepared by improved impregnation. Performance of the catalyst-sorbents for the simultaneous removal of SO₂ and NOx was explored in a co-generation plant.The main and important results of this paper are described as follows: the sol-gel-derived sorbents have typically good structural characteristics and higher denitrification activity. MnOx-CeO₂/γ-Al₂O₃ catalysts maintained at more than 85% NO conversion efficiency at low temperature range (80-150℃) because of its stronger oxidation of NH₃. It was found that the SCR reaction on the MnOx-CeO₂/γ-Al₂O₃ catalysts occured between adsorbed NH₃ on Lewis acid site and gasous NO, and the NH4+ adsorbed on Br?nsted acid site did not participate in the SCR reaction. It accords with the Eley-Rideal mechanism. The adsorbed NO was oxidized to nitrate and nitrite species, only nitrite and bridge nitrate took part in the SCR reaction. In the actual flue gas of thermal power plant condition, the CuFeMn/Al catalyst-sorbents prepared by improved impregnation showed excellent performance of simultaneous removal of SO₂ and NOx. It was due to the solid solutions formed between active ingredient and carrier, which made active ingredient dispersed better in these catalysts. And sulfuration also promoted the NO conversion efficiency. Furthermore, improved impregnation method is relatively simple and can be brought into industrial applications soon.