Simultaneous Removal Of HCHO And Elemental Mercury From Flue Gas Over Co-Ce Oxides Supported On Activated Coke Impregnated By Sulfuric Acid

In our country,compared to other fossil energy,coal resource is more abundant and plays a very important role in the whole energy structure,its production and utilization is related to the social and economic development.Coal combustion is a major anthropogenic emission source of pollution,which produces NO_X,SO_X,elemental mercury（Hg⁰）and VOC_S.As far as we know,NO_X and SO_X emission control and treatment technologies have been relatively mature and efficient.Hg⁰ and VOC_S have received increased attention due to their ecological environment and human health threat.Hg⁰ is a global pollutant with toxicity,bio-accumulation and volatility,VOCs can cause serious air pollution problems such as photochemical pollution,ozone layer destruction and smog.In this paper,formaldehyde is selected as the research object of volatile organic compounds,and catalytic oxidation is used to remove elemental mercury and formaldehyde from flue gas simultaneously.A series of CoM/ACs（M for Ce,Fe,Mn,Cu,Ni）catalysts were prepared by impregnation method in the paper,the performance of CoM/ACs catalysts for simultaneous removal of Hg⁰ and HCHO was studied in the range of 110 to 310℃from simulated flue gas,the best CoCe/ACs catalyst was selected for follow-up study.Meanwhile,the effects of Co/Ce molar ratio and different flue gas components（O₂、NO、SO₂、H₂O）on the activity of CoCe/ACs catalysts were investigated.The interaction between Hg⁰ and HCHO removal and stability test of the catalyst were also studied.In addition,crucial characterizations including BET,XRD,SEM,XPS,H₂-TPR and FT-IR of catalysts were conducted to examine the physicochemical properties of catalysts and further reveal the mechanisms of simultaneous removal of Hg⁰ and HCHO over Co₈Ce₃/ACs catalyst.The experimental results showed that CoCe/ACs catalysts had relatively higher mercury and formaldehyde removal efficiency at 190℃,compared with CoM/ACs.The Co₈Ce₃/ACs catalyst showed the highest removal efficiency of mercury and formaldehyde by 69.43%and 71.07%respectively.The effects of flue gas components on Hg⁰ and HCHO removal were investigated,O₂ played an important role on the removal of Hg⁰ and HCHO,the presence of H₂O and SO2 exhibited a slight inhibitive effect on Hg⁰ and HCHO removal in the presence of 6%O2,but NO had a slight promotion effect on the removal of mercury and adverse effect on the removal of formaldehyde.The characterization results showed that the excellent performance of Co₈Ce₃/ACs catalyst might be related to the stronger redox ability,better texture properties with highly dispersed Co and Ce species and the high active hydroxyl group.Besides,the synergy between Co and Ce species improved the mobility of activated oxygen species,which facilitated the removal of Hg⁰ and HCHO greatly.In the process of mercury removal,oxidization occupied a major part of the removal efficiency over Co₈Ce₃/ACs catalyst.The Co₈Ce₃/ACs catalyst had good stability in the removal process of Hg⁰ and HCHO during 60 h.Combined with the advantages of Co₈Ce₃/ACs samples,further optimization may have better application prospects in real industrial application.