Study Of Catalysts For Reduction Of Sulfur Dioxide By Monoxide Carbon To Elemental Sulfur In The Presence Of Oxygen

Sulfur dioxide of flue gas of coal-fired power plants is one of the majorcomponents of atmospheric pollution. At present flue gas desulfurization(FGD) isemphasis on wet FGD. However this FGD have many disadvantages such as highinvestment, great operation cost and re-pollution. Direct reduction of SO2 by CO toelemental sulfur not only obtained sulfur but also got rid of re-pollution. Thereforeresearching and developing novel catalyst for reduction of SO2 with CO in thepresence of oxygen for FGD of coal-fired power plants is significant. This papermainly studied catalysts for reduction of SO2 by CO to elemental sulfur with oxygenand their catalytic performance. Based on different reaction mechanisms, catalytic reduction of SO2 with CO inthe presence of oxygen were studied over transition metal sulfides, sulfurizedperovskite (LaBO3 ), La2O2S, CeO2, TiO2-CoS2. There below is suggested: Transition metal sulfides, Sulfurized perovskite LaBO3 ,Lanthanum oxysulfide(La2O2S) were evaluated , for reduction of SO2 with CO to elemental sulfur in thepresence of oxygen. Results showed that oxidized catalysts to oxides so much assulfate lead to deactivation. Though fluorite CeO2 in the presence of oxygen, catalysthas been completely deactivated. Result of XPS, XRD showed that deactivation iscaused by oxygen adsorption on vacancies which don't make redox mechanismoccurred. TiO2-CoS2 has been deactivated in the presence of oxygen. Result of XRD,XPS indicated that catalyst is deactivated, the reason is oxygen adsorbed on oxygenvacancies so that modified redox mechanism don't occurred and CoS2 is oxidized toCo3O4 and CoSO4. After especial sulfurization LaBO3 we can find that only sulfurized LaCoO3 hasactivity of reduction of SO2 with CO in the presence of oxygen. While neithersulfurized LaFeO3 nor LaNiO3 has activity. XRD, XPS and in-situ FTIR diffusereflectance study on sulfurization process of LaCoO3 in the presence of oxygen foundthat sulfite(SO3 ) formed on the surface of catalyst in the process of pre-poisoning 2-SO2 converted to sulfide(S2-), and perovskite structure of LaCoO3 did not change aftersulfurization of LaCoO3. The experiments of SO2-TPD, O2-TPD and CO combustion in the presence ofSO2 showed that active site of CO combustion and active site of SO2 reduction wereon the surface of sulfurized LaCoO3 at certain temperature, CO on the perovskite bphase can combust with O2 quickly, at the same time SO2 on La2O2S phase can bereduced by CO, and both of the reactions can be stimulated each other. Sulfurized LaCoO3 was evaluated for reduction of SO2 by CO in the atmosphereof oxygen. The study of the effect of reactive condition on the reduction of SO2showed that the content of O2 in reactive composition do not have obviously effect onconversion of SO2 and yield of sulfur when CO/O2/SO2 ratio was equal tostoichiometric ratio of the reaction of combustion of CO and reduction of SO2.When Space velocity was 6000h-1 and temperature was 450℃, conversion of SO2reached to 85 percent which approached to the efficiency of wet FGD. The stability ofcatalyst were evaluated with 5 percent of O2 on space velocity 6000h-1 at 500℃.Conversion of SO2 keep at the range of 97-95% and yield of S 95-93%. All of theexperiment above showed that the sulfurized LaCoO3 catalyst has good catalyticactivity and high stability.