Effects of flue-gas parameters on low temperature NO reduction over a Cu-promoted CeO2–TiO2 catalyst

Abstract

A sol–gel synthesized Cu-promoted CeO2–TiO2 (CuCeTi) catalyst was used in the low temperature selective catalytic reduction (SCR) of nitrogen monoxide (NO) with ammonia (NH3). The combination of copper oxide (CuO) and cerium oxide (CeO2) improved SCR performance at low temperatures by increasing the dispersion of active species and the volume of surface oxygen (O2) with low-temperature activity. NO conversion on the CuCeTi catalyst exceeded 90% at temperatures higher than 200°C. Although the gas hourly space velocity (GHSV) was much higher than that in a real SCR reactor, reaching 27,000h−1, its inhibitory effect on NO conversion became insignificant as the temperature increased. Within its flue gas concentration range, O2 had a negligible effect on NO conversion. The inhibitory effect of water vapor (H2O) was reversible, and almost indiscernible at 300°C. Sulfur-dioxide (SO2) concentration affected NO conversion. At concentrations lower than 100ppm, SO2 promoted NO conversion and at SO2 concentrations higher than 100ppm, NO conversion decreased. The ammonium sulfates deposited on the surface of the catalyst as a product of the reaction with SO2 were primarily responsible for the irreversible deactivation of the catalyst at low temperatures. Thus, high temperatures were found to alleviate the inhibitory effect of SO2. NO conversion exceeded 80% at 300°C, even when the concentration of SO2 was as high as 800ppm. Mercury vapor and adsorbed mercury oxide (HgO) had negligible effects on NO reduction over the CuCeTi catalyst. This study provides new information on the promotional and inhibitory effects of individual flue-gas parameters and components on NO conversion over a novel CuCeTi catalyst. This information has fundamental implications for industrial applications of the CuCeTi catalyst in coal-fired power plants.