title: SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst.
abstract: CuO-CeO2/TiO2 (CuCeTi) catalyst synthesized by a sol-gel method was employed to investigate mercury conversion under a selective catalytic reduction (SCR) atmosphere (NO, NH3 plus O2). Neither NO nor NH3 individually exhibited an inhibitive effect on elemental mercury (Hg(0)) conversion in the presence of O2. However, Hg(0) conversion over the CuCeTi catalyst was greatly inhibited under SCR atmosphere. Systematic experiments were designed to investigate the inconsistency and explore the in-depth mechanisms. The results show that the copresence of NO and NH3 induced reduction of oxidized mercury (Hg(2+), HgO in this study), which offset the effect of catalytic Hg(0) oxidation, and hence resulted in deactivation of Hg(0) conversion. High NO and NH3 concentrations with a NO/NH3 ratio of 1.0 facilitated Hg(2+) reduction and therefore lowered Hg(0) conversion. Hg(2+) reduction over the CuCeTi catalyst was proposed to follow two possible mechanisms: (1) direct reaction, in which NO and NH3 react directly with HgO to form N2 and Hg(0); (2) indirect reaction, in which the SCR reaction consumed active surface oxygen on the CuCeTi catalyst, and reduced species on the CuCeTi catalyst surface such as Cu2O and Ce2O3 robbed oxygen from adjacent HgO. Different from the conventionally considered mechanisms, that is, competitive adsorption responsible for deactivation of Hg(0) conversion, this study reveals that oxidized mercury can transform into Hg(0) under SCR atmosphere. Such knowledge is of fundamental importance in developing efficient and economical mercury control technologies for coal-fired power plants.
authors.affiliation: †School of Energy Science and Engineering, Central South University, Changsha, China, 410083.|∥Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Hailong
authors.initials: H
authors.lastname: Li
authors.affiliation: †School of Energy Science and Engineering, Central South University, Changsha, China, 410083.
authors.forename: Shaokang
authors.initials: S
authors.lastname: Wu
authors.affiliation: ‡Department of Environmental Engineering Sciences, Engineering School of Sustainable Infrastructure and Environment, University of Florida, Gainesville, Florida 32611, United States.
authors.forename: Chang-Yu
authors.initials: CY
authors.lastname: Wu
authors.affiliation: §Department of Occupational and Environmental Health, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73126, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: †School of Energy Science and Engineering, Central South University, Changsha, China, 410083.
authors.forename: Liqing
authors.initials: L
authors.lastname: Li
authors.affiliation: ∥Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Kaimin
authors.initials: K
authors.lastname: Shih
mesh_terms: D000327:Adsorption; D000641:Ammonia / Q000737:chemistry; D001272:Atmosphere; D002384:Catalysis; D002563:Cerium / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D008628:Mercury / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D014025:Titanium / Q000737:chemistry*
chemical_list: D005740:Gases; C009495:titanium dioxide; D002563:Cerium; D009569:Nitric Oxide; C030583:ceric oxide; D000641:Ammonia; D003300:Copper; D014025:Titanium; D008628:Mercury; D010100:Oxygen; C000520:cuprous oxide