Carbon Monoxide Catalytic Reduction Of Sulfur Dioxide Experimental Research

The sulfur dioxide is one of the most serious air pollutions that mainly comes from the burning of fossil fuels. It can change into acid rains to destroy the existence environment of mankind and other creatures. The methods of the reduction of SO₂ can be classified into three kinds: the desulfurization before, during, after the burning of the fuels. In so many methods, the reduction of SO₂ by catalysts has the obvious advantages: it can change SO₂ into element sulfur, in order to decrease the air pollution by SO₂ and lighten the situation of lacking sulfur in China.In this paper, the reduction of SO₂ on catalysts by CO is studied. First, the catalysts are made;then, the mixed gas of CO, SO₂ and N₂ is made to imitate the actual flue gas of coal-fired powerplant;Finally, the activity of the catalysts will be tested to get the information of their performance, and some useful conclusions are also reached.In this paper, the transition metal(Fe, Co, Ni)and Mo are supported on γ -Al₂O₃ to form the supported catalysts with multi-typed active components. The process is: first, to make the solution of Fe(NO₃)₃, Co(NO₃)₂ and Ni (NO₃)₂ separately with certain concentration;then, mixed by the solution of (NH₄)₆Mo₇O₂₄;thirdly, put a certain amount of γ-Al₂O₃ into the mixed solution, and after drying, baking, deoxidizing the final catalysts are formed, such as the catalyst of Co-Mo/γ -Al₂O₃. Every kind of Fe-Mo/γ -l₂O₃, Co-Mo/γ -l₂O₃,Ni-Mo/γ-l₂O₃ has three types, which are different from each other by the ratio of the active components, for example, in the number one catalyst of Ni-Mo/γ-l₂O₃, there are 10% of NiO and 10% of MoO₃;in the number two, there are 15% of NiO and 5% of MoO₃;in the number three, there are 5% of NiO and 15% of MoO₃.After the catalysts have been made, their activity will be tested by the mixed gas of CO, SO₂ and N₂ under different reaction conditions. Those tests are performedin a certain reactor, and the main parameter is the S02 conversion, which can be calculated by the concentration of the S02 going in and out of the reactor. In addition, the concentration of S02 can be tested by the method of I2.The results of the experiments show that catalysts with only one kind of metal supported on y^A1203 are less active than the multi-typed catalysts, for example, the activity of CoO/ y —A12O3 or Mo03/ Y —A12O3 is obviously lower than the catalyst of Co-Mo/Y ^A12O3. Among the three kinds of catalysts, the activity of Co-Mo/ Y —A12O3 is higher than the other two, while Fe-Mo/y ^A12O3 has a higher activity than Ni-Mo/ y —A12O3. The three kinds of catalysts all performs better as the temperature goes up, and at 400°C, they all reach the maximum activity, then their activity goes down as the temperature increases. Among the three types of the same kind of catalysts, take Co-Mo/ y ^<sup>A12O3 for example, the number two catalyst has a higher activity than the other two. At 300°C, with smaller flow rate of flue gas , the S02 conversion is higher;while the bigger flow rate with a lower S02 conversion;but at 400*C when the activity of the catalysts is higher, the bigger flow rate of flue gas is related to higher S02 conversion;then as the temperature increases, smaller flow rate is again related to higher S02 conversion. In addition, when the other conditions are the same, more catalysts have more surface areas, which supply more areas for S02 to react with CO, so the S02 conversion will be increased. The S02 conversion is higher when the ratio of CO and S02 in the flue gas is bigger than 2, but lower when the ratio is exactly 2.