The influence of K+ cation on the MnOx-CeO2/TiO2 catalysts for selective catalytic reduction of NOx with NH3 at low temperature

• Catalysts of Mn-Ce-M/TiO2 (M = Fe, Ni) prepared by co-precipitation method for low temperature selective catalytic reduction (SCR).
• Using carbamide solution, ammonia and hydrogen peroxide as precipitation agents, showed good activity in low temperature and resistance performance of K+ cation (K/Mn = 0.5).
• Poisoning mechanism occurs via chemical bonding of the K+ cation to the MOH sites, the so-called Brønsted acid sites.

Alkali metals were considered to be poisonous to not only V-based catalysts but also Mn-based catalysts. Catalysts of Mn-Ce-M/TiO2 (M = Fe, Ni) prepared by co-precipitation method for low temperature selective catalytic reduction (SCR) of NO with NH3 under the influence of alkali metals were investigated in this study. As the experiment result, the low temperature SCR activity showed greatly enhanced which near at 150 °C the substitution of the Fe content to Mn-Ce/TiO2 catalyst could obviously increased to 87% without alkali metals and the best NO conversion of Mn-Ce-Ni/TiO2 catalyst under alkali metals in the temperature range of 150–300 °C was 88% (K/Mn = 0.5). The addition of alkali metal not only generates physical adsorption but also reduces the surface chemisorbed oxygen and causes a decline in Brønsted acid sites. These catalysts showed higher SCR activity and better resistance to alkali poisoning, because the characteristics of the large surface area and pore volume, the increased chemisorbed oxygen, the enhanced oxidative ability of manganese species and the presence of many weak acid sites.

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