Highly dispersed CuyAlOx mixed oxides as superior low-temperature alkali metal and SO2 resistant NH3-SCR catalysts

Abstract

For NOx removal from the exhaust gases of municipal solid waste (MSW) incinerators by selective catalytic reduction (SCR) technology, a suitable SCR catalyst which is active at low temperatures and robust to the presence of alkali metals and SO2 is highly desired. In this contribution, we report the successful fabrication of a highly dispersed CuyAlOx (y=2–4) mixed oxides for NH3-SCR catalyst using high surface area, flower-like highly dispersed AMO-Cu-Al-CO3 LDHs precursors. The influence of the Cu/Al ratio (2, 3, 4, and 5), calcination temperature (400, 500, 600, and 700°C), and testing temperature (150, 200, 250, and 300°C) on the activity of the CuyAlOx mixed oxide catalysts were systematically investigated. Among all samples, Cu4AlOx showed the highest NOx conversion of 91.1% at 200°C. After being thermally treated at 700°C, the NOx conversion of Cu4AlOx was still as high as 84.7%, which is much higher than that of the control catalyst 10wt% CuO/γ-Al2O3 (57.5%). XRD and HR-TEM analyses suggested that the highly dispersed CuO nanoparticles are the active species for the SCR reaction. The catalytic De-NOx performance of Cu4AlOx in the presence of alkali metals (K and Na) and SO2 was also studied. In the presence of 50ppm SO2, the NOx conversion of Cu4AlOx (78.4%) was much higher than that of CuO/γ-Al2O3 (48%). The selectivity of NOx conversion to N2 and resistance to H2O (and co-existence of H2O and SO2) for Cu4AlOx catalyst were also evaluated. In all, we have demonstrated that the newly obtained Cu4AlOx catalyst not only possesses higher thermal stability and higher low temperature (150–250°C) catalytic activity, but also has much better alkali metal (K and Na), SO2, and H2O resistance than a conventional CuO/γ-Al2O3 catalyst.