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-CeO2/TiO2 (CuCeTi) catalyst. Hg-0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 degrees 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/TiO2 (CuTi), CeO2/TiO2 (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 NO2. In the absence of NO, NH3 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 NH3 and Hg-0. In the presence of NO, although NH3 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 NH3.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 coalfired power plants. (C) 2016 Elsevier B.V. All rights reserved.