Performance Study Of CO-catalyzed SO₂ Reduction Over Ir/CeO₂ Catalysts

China is one of the world’s major coal consumers,in the process of coal use produces a large number of SO₂,seriously endangering the natural ecological environment and the health of the residents of China.At present,the vast majority of SO₂ purification technology is to convert SO₂ into sulfate treatment,China’s SO₂generation in the steel industry alone in 2020 is about 7.70 million tons,of which more than 80%in the form of sulfate removal,resulting in the waste of sulfur resources and secondary pollution.However,China’s sulfur resources are highly dependent on foreign countries,with a total domestic sulfur consumption of 17.021million tons in 2021,of which 8.535 million tons are imported,with an import dependence of 50.1%.CO is often produced in metal smelting production,and as a reducing agent,CO can reduce SO₂ to produce sulfur.While solving CO and SO₂pollution,sulfur,a valuable resource,can be obtained,so CO reduction of SO₂ to sulfur is a highly promising way to desulfurize.The reaction of CO catalytic reduction of SO₂ is difficult to achieve under conventional conditions and usually requires the assistance of catalysts,which are currently immature in design.In this thesis,a series of Ir/CeO₂ catalysts were prepared by impregnation method with CO-catalyzed SO₂ reduction resourcefulness as the research objective,and the effects of the morphology and preparation conditions of the CeO₂ carrier on the catalytic performance of the catalysts were investigated,and the key factors affecting the catalytic performance of the catalysts were deeply explored.Firstly,a series of Ir/CeO₂ catalysts were synthesized by impregnation using a hydrothermal method to prepare CeO₂ supports with controllable morphology and synthesize rod（R）,cubic（C）and polyhedral（P）morphologies.The effect of the change of CeO₂ support morphology on the valence state of the active components and the interaction between Ir-O-Ce was investigated.The results of the activity tests showed that the Ir/CeO₂ catalyst with a rod-shaped CeO₂ support had the best activity at a reaction rate of 10,000 h^-1 volumetric air velocity,reaching 60.2%SO₂ conversion and nearly 55.8%sulfur yield at 350℃,while the Ir/CeO₂ catalyst with cubic-shaped CeO2 carrier had the worst activity,reaching 34.9%SO₂ conversion and nearly 33.1%sulfur yield under the same conditions.The sulfur yield was close to 33.1%.The test results showed that the concentration of oxygen vacancies in the catalyst had an influence on the catalytic reaction,and the Ir/CeO₂-R catalyst had the highest percentage of Ce³⁺（22.41%）and Ir⁰（52.92%）content on the surface,Ir interacted with CeO₂-R to the strongest extent,and Ir/CeO₂-R catalysts had the highest content of oxygen vacancies and thus showed the best catalytic activity.Secondly,a series of Ir/CeO₂ catalysts were synthesized by impregnation method by controlling the catalyst synthesis method and varying the stirring time of the liquid phase mixing of CeO₂ precursors to prepare CeO₂ carriers with different stirring times（CeO₂-0.25,CeO₂-3,CeO₂-6）.The focus is on the effect of structural differences on the catalytic reaction of Ir/CeO₂ catalysts caused by CeO₂ carriers prepared by different stirring times.The results show that changing the stirring time of the liquid phase mixing of the CeO₂ precursors has an effect on the grain size of the Ir/CeO₂catalysts.The longer the stirring time,the smaller the grain size of Ir/CeO₂ catalysts.The test results showed that the Ir/CeO₂ catalysts with smaller grain size had more active oxygen vacancies on the surface.The Ir/CeO₂ catalyst with CeO₂-6 stirring time of 6 h,for example,exhibited the optimal catalytic performance due to its smallest grain size（12.4 nm）and highest Ir⁰（59.18%）content percentage on the catalyst surface,thus reaching 98.6%SO₂ conversion and 96.7%sulfur yield at375℃,while the Ir/CeO₂ catalyst with larger grain size（12.4 nm）exhibited the optimal catalytic performance.CeO₂-0.25 catalyst（13.7 nm）with a lower Ir⁰ content share（53.82%）on the surface and poorer activity,showed a SO₂ conversion of 73.9%and sulfur yield of 72.2%at 375℃.In this paper,we investigated the effect of different morphological CeO₂ carriers and the interaction between different grain size CeO₂ carriers and metal Ir on the CO-catalyzed SO₂ reduction reaction.We demonstrated the impact of the interfacial effect between Ir-O-Ce on this catalytic reaction,which is of great value and guidance for the design and application of such catalysts.