Low-temperature CO selective catalytic reduction denitrification and sulfuric acid regeneration mechanism of Cu-Ce/AC catalyst poisoned with zinc salt

Abstract

To explore Cu–Ce/activated carbon (AC) catalyst poisoned of with zinc salt and its mechanism of low-temperature CO selective catalytic reduction (CO-SCR) denitrification following sulfuric acid regeneration, this paper uses ZnCl2 and ZnSO4 to poison Cu–Ce/AC catalyst and H2SO4 pickling to regenerate the poisoned catalyst. Not only the catalyst denitrification activity was investigated but also the surface morphology, pore structure, variation of active component phases and elemental valence, surface functional groups, reduction characteristics and adsorption mechanism of catalyst before and after regeneration were systematically characterized. The low-temperature CO-SCR denitrification mechanism of the poisoned Cu–Ce/AC catalyst was revealed. After being poisoned with zinc salt, the oxide on the catalyst surface aggregated, causing the blockage of the pore, thereby inhibiting the adsorption capacity of the reaction gas and the synergistic reaction between Cu-Ce. Moreover, zinc salt not only occupies the active site, but also destroys the -C=O and –OH oxygen-containing functional groups. This not only reduces the chemically adsorbed oxygen (Oβ) and oxygen vacancy but also leads to the reduction of Cu+–CO species, the reduction of catalyst redox capacity, and the reduction of NO conversion rate. The regeneration mechanism of the sulfuric acid method was as follows. First, the solid particles deposited on the catalyst surface are removed, thereby restoring its specific surface area and pore structure, and increasing the adsorption area of reaction gas. Additionally, the content of Cu and Ce active components was increased, which promoted the synergistic reaction, and the content of Cu+–CO species, oxygen vacancy, and Oβ was increased, resulting in enhanced redox capacity. Finally, sulfuric acid impregnation generated S2O82− groups, which sulfated the surface of the catalyst, and its S=O reacted with Zn to form S–O–S, which prevented zinc salt from destroying the oxygen-containing functional groups and improved the reducing capacity and CO adsorption capacity of the catalyst, thereby restoring the denitrification activity of the catalyst.