Study Of Catalysts And Catalytic Reaction For Reduction Of Sulfur Dioxide And Nitrogen Monoxide By Methane In Flue Gas

Sulfur dioxide(SO2) and Nitrogen Monoxide(NO) are serious pollutant in the earth's atmosphere. They are also two of the main source of acid rain. Directly reducing Nitrogen Monoxide in exhaust gases to nitrogen is an attractive way to solve the environmental problem. Moreover, if we can select reduct Sulfur dioxide in the flue gas to elemental sulfur simultaneously, we will benefit a lot from the saleable product----elemental sulfur. There is abundant Natural Gas in the west of China and the price is cheap. In this paper, the properties of perovskite-type composite oxide catalysts and transition metal oxide catalysts for reduction of sulfur dioxide and nitrogen monoxide were systematically studied. Based on these results, the catalytic active phase and the reaction mechanisms were discussed.LaBO3 perovskite-type composite oxide catalysts with different B-ions(B=Cr,Mn,Fe,Co,Ni) were prepared by Sol-Gel methods and evaluated for the reduction of sulfur dioxide and nitrogen monoxide by methane. Results showed that, the activity of the catalysts for the reduction of sulfur dioxide by methane exhibits the following orders: LaFeO3>LaCrO3>LaCoO3>LaMnO3≈LaNiO3. the activity of the catalysts for the reduction of nitrogen monoxide by methane has the following orders: LaCrO3> LaMnO3≈LaCoO3>LaFeO3> LaNiO3. The characterization of these catalysts were described by XRD,TEM and TPR technology. It was shown that the particle sizes of the catalysts were nano scale, ABO3 perovskite-type structure was the main reason for its high activity. The characterization of d-electron of B-ions mainly determined the properties of catalysts. The more active of d-electron of B-ions, the more active of properties of catalysts. However, the stability of structure is reduced incidentally. We should make balance between activity and stability of catalyst. Various transition metal oxides supported onγ-Al2O3 were prepared with the method of incipient impregnation. The properties of the catalysts were investigated in two sample reactions----the reduction of sulfur dioxide and nitrogen monoxide by methane. the activity of the catalysts for the reduction of sulfur dioxide by methane exhibits the following orders: Fe3O4/γ-Al2O3>MnO/γ-Al2O3>Cr2O3/γ-Al2O3>iO/γ-Al2O3>oO/γ-Al2O3. XRD results show that MnO/γ-Al2O3,CoO/γ-Al2O3 and NiO/γ-Al2O3 produced metal sulfides after desulfurization. the activity of the catalysts for the reduction of nitrogen monoxide by methane exhibits the following orders: Cr2O3/γ-Al2O3> CoO/γ-Al2O3>Fe3O4/γ-Al2O3> NiO/γ-Al2O3>MnO/γ-Al2O3.As we all know, there are some oxygen in the flue gas. Considering the activity and stability of the two kinds of catalysts above during the two sample reactions, we selected two sample catalysts----LaCrO3 and Cr2O3/γ-Al2O3 and evaluated their activity and stability though the reduction of sulfur dioxide and nitrogen monoxide simultaneity and the reaction of desulfurization in oxygen environment. The result indicated that the introduction of O2 enhanced the activity of desulfurization and denitrification, but it is harmful for catalytic reduction of sulfur dioxide.