Effect of HCl and o-DCBz on NH3-SCR of NO over MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts

• Published in: Applied catalysis. A, General General, 2020-09, Vol.605, p.1, Article 117801
• Main Authors: Wang, Qiulin, Lin, Feng, Zhou, Jianjian, Zhang, Jianchao, Jin, Jing
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonium chloride; Catalysts; Catalytic oxidation; Ce addition; Cerium oxides; Chemical reduction; Chlorine; Chlorine compounds; Chlorine poisoning; Deactivation; Effect of o-DCBz; Hydrogen chloride; Incinerators; Low temperature; Medical wastes; MnOx-based catalyst; Municipal waste management; NH3-SCR; Organic compounds; Oxidation; Regeneration; Selective catalytic reduction; Solid waste management; Titanium dioxide
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2020.117801

[Display omitted] •HCl severely poisons the MnOx/TiO2 catalyst towards NH3-SCR of NO.•Surface acid sites and reactive oxygen species are ruined in catalyst chlorination.•Ce addition improves Cl-resistance of catalyst by preferentially reacting with HCl.•Cl atom prefers to anchor on the uncoordinated sites of Ce atom.•Competitive effect between o-DCB, NO and NH3 aggravates the catalyst deactivation. A novel selective catalytic reduction (SCR) catalyst with strong chlorine resistance ability is urgently needed to extend the catalyst life, when SCR technique is applied in plants with high chlorine content (e.g. municipal solid waste and medical waste incinerators). This study investigates the influences of typical chlorine-containing inorganic/organic compounds (i.e. hydrogen chloride (HCl) and o-dichlorobenzene (o-DCBz)) on NH3-SCR of NO over MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts at low temperatures (100−250 °C). The results indicate the presence of HCl severely inhibits the NH3-SCR reaction. On one hand, the reaction between NH3 and HCl causes the deposition of NH4Cl on catalyst surface and reduces the amount of NH3; on the other hand, HCl consumes the surface acid sites which is essential to the adsorption and activation of NH3; moreover, chlorine (Cl) atom prefers to anchor on the uncoordinated metal sites that restrains the regeneration of surface reactive oxygen species and interrupts the redox cycle of catalysts. Ce addition enhances the chlorine resistance property of MnOx-CeO2/TiO2 catalyst by interacting with HCl preferentially. The negative effect of o-DCB on NH3-SCR reaction is more serious than that of HCl below 200 °C. That’s because the competitive effect between o-DCB catalytic oxidation and deNOx via NH3-SCR reaction as well as the accumulation of o-DCB incomplete oxidation byproducts on catalyst surface further aggravates the catalyst deactivation induced by Cl atom.