Improvement of low-temperature NH3-SCR catalytic activity over Mn-Ce oxide catalysts supported on sewage sludge char activated with KOH and H3PO4

Pyrolysis is a very potential sludge treatment technology that is low-cost and environmentally friendly; particularly, the pyrolysis sewage sludge char (SC) can be used as a catalyst support. To improve the NO conversion efficiency of sludge char based catalysts, they were activated by potassium hydroxide and phosphoric acid, respectively. The catalysts of activated sludge char with or without Mn-Ce impregnation in the application of NO removal by low-temperature SCR were investigated. The higher NO conversion efficiency of sludge char based Mn-Ce catalysts at low temperature were obtained. Compared with the 59% NO conversion efficiency of Mn-Ce/SC catalyst, the conversion efficiency of catalyst supported on KOH activated char (SCK) achieved 89% at 220 degrees C and of catalyst supported on H3PO4 activated char (SCP) reached 87% at 240 degrees C. The catalysts were analytically characterized using N-2 adsorption-desorption, XRD, FTIR, NH3-TPD and XPS measurements. The higher specific area, excellent dispersion of Mn-CeOx and more Bronsted acid sites are responsible for the higher NO conversion efficiency of Mn-Ce/SCK, while the higher NO conversion efficiency of Mn-Ce/SCP is enhanced by more Bronsted acid sites, oxygen-containing and some unique phosphorus-containing oxygen functional groups. It indicates that sludge char activated by KOH and H3PO4 is a potential low-temperature catalyst support.