Study On Removal Of Gaseous Hg⁰ By Sulfuric Acid Modified Montmorillonite Supported V₂O₅

China is a major energy consumer,and coal accounts for more than 50%of the primary energy structure.China’s coal utilization is mainly based on direct combustion（power generation and heating）,which provides energy while generating a large amount of pollutants（such as smoke,SO₂,NO_x,heavy metal mercury,etc.）.The Hg emitted from smoke can enter the human body through the food chain and cause serious and long-lasting harm to the human body,which has attracted widespread attention.Therefore,advanced coal-fired NO_xand Hg emission control technologies have become one of the major key issues that urgently need to be addressed in the coal utilization process.In this paper,vanadium based acidified montmorillonite catalyst was prepared by impregnation method to remove Hg⁰from coal-fired flue gas.Firstly,H₂SO₄acidified montmorillonite（MMT）was used to modify montmorillonite.10S-MMT,20S-MMT and 30S-MMT were obtained by modifying montmorillonite with different mass fractions（10%,20%and 30%）of H₂SO₄.Then,V₂O₅with different mass fractions was loaded on the modified montmorillonite support by impregnation method,and the influence of preparation methods on the removal of Hg⁰from the catalyst was explored.The results showed that the 10S-V₃/MMT-500 catalyst with 3%V₂O₅calcined at 500℃and10%H₂SO₄modified montmorillonite had the best Hg⁰removal performance,and the Hg⁰removal efficiency remained above 98%for 2 h.This is because the catalyst prepared by this method has the largest pore size and the calcination temperature does not cause significant damage to the structure of the catalyst,which is conducive to the loading of active components and the adsorption and oxidation of Hg⁰.The effect of reaction conditions on the removal of Hg⁰by 10S-V₃/MMT-500 catalyst was studied,and the effects of O₂,SO₂,NO,and H₂O（g）in flue gas on the removal of Hg⁰by10S-V₃/MMT-500 catalyst were studied.The results indicate that the 10S-V₃/MMT-500catalyst exhibits the best mercury removal performance at GHSV≤6000 h^-1and 150℃,as Hg⁰can fully come into contact with the active component and be oxidized under these conditions;O₂and NO in the flue gas have a promoting effect on the removal of Hg⁰by the catalyst,H₂O（g）has an inhibitory effect on the catalyst,and low concentration SO₂has an inhibitory effect on the catalyst.When the concentration is increased to 1500 ppm,it actually improves the mercury removal performance of the 10S-V₃/MMT-500 catalyst.This is because when SO₂is low,it will compete with Hg⁰for adsorption.When the concentration increases,SO₂will be oxidized on the catalyst surface to produce a large amount of SO₃,thereby promoting the oxidation of Hg⁰.The mercury removal mechanism of 10S-V₃/MMT-500catalyst was investigated through TPD and XPS,and the characterization results confirmed that Hg exists on the catalyst surface in the forms of Hg⁰,Hg O,and Hg SO₄.The stability and regeneration performance of 10S-V₃/MMT-500 catalyst were studied.The results showed that the performance of the 10S-V₃/MMT-500 catalyst for removing Hg⁰began to decrease after 11 hours of use.The regeneration of the catalyst after Hg⁰removal in an air atmosphere has the strongest performance when the regeneration temperature is 400℃.The mercury removal performance of the 10S-V₃/MMT-500 catalyst decreases with the increase of regeneration times.This is because during the regeneration process,the structure of the 10S-V₃/MMT-500 catalyst underwent changes,resulting in the loss of active components and the accumulation of mercury containing substances,thereby reducing the performance of the regenerated catalyst in removing Hg⁰.In summary,the 10S-V₃/MMT-500 catalyst has high mercury removal performance,stability,and regeneration performance,making it a promising catalyst for the removal of Hg⁰from coal-fired flue gas.