The poisoning effect of PbO and PbCl on CeO-TiO catalyst for selective catalytic reduction of NO with NH.

The poisoning effect of PbO and PbCl on CeO-TiO catalyst for selective catalytic reduction of NO with NH was investigated and compared. Both Pb species could deactivate the CeO-TiO catalyst and PbO had a stronger poisoning effect than PbCl. From the characterization results of BET, XRD, XPS, NH-TPD and H-TPR, it was concluded that the more serious deactivation by PbO could be ascribed to smaller BET surface area, fewer surface Ce and chemisorbed oxygen, stronger interaction between PbO and CeO-TiO catalyst, lower redox properties and surface acidity. The in situ DRIFT study results revealed that the NH-SCR reaction over CeO-TiO catalyst was governed by both E-R and L-H mechanisms, which wasn't changed over the Pb-poisoned samples. The greater loss of Brønsted acid sites attributed to fewer surface Ce and more serious inhibition of NO oxidation to NO due to fewer surface chemisorbed oxygen were two key factors responsible for more serious deactivation by PbO. Furthermore, the presence of Pb species inhibited the NH adsorption on the Lewis acid sites, aggravating the deactivation of CeO-TiO catalyst.