Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

Synergy for low temperature Hg 0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO 2 /TiO 2 (CuCeTi) catalyst. Hg 0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200   °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect , comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO 2 (CuTi), CeO 2 /TiO 2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O 2 to surface oxygen, which are favorable for Hg 0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg 0 oxidation in the absence of gas-phase O 2 . Cerium oxides in the combination promoted Hg 0 oxidation through enhancing the transformations of NO to NO 2 . In the absence of NO, NH 3 exhibited no inhibitive effect on Hg 0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH 3 and Hg 0 . In the presence of NO, although NH 3 lowered Hg 0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg 0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH 3 . This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg 0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg 0 oxidation co-benefit from SCR units in coal-fired power plants.