Manganese-cerium mixed oxides supported on rice husk based activated carbon with high sulfur tolerance for low-temperature selective catalytic reduction of nitrogen oxides with ammonia.

A rice husk-derived activated carbon supported manganese-cerium mixed oxide catalyst (Mn-Ce/RAC) was prepared by an impregnation method and tested for the selective catalytic reduction of nitrogen oxides with ammonia (NH-SCR). 5 wt% Mn-Ce/RAC catalyst showed the highest activity, yielding nearly 100% NO conversion and N selectivity at 240 °C at a space velocity of 30 000 h. Compared with commercial activated carbon supported manganese-cerium mixed oxide catalyst (Mn-Ce/SAC), a higher SCR performance with good SO tolerance could be observed in the tested temperature range over the Mn-Ce/RAC catalyst. The characterization results revealed that the Mn-Ce/RAC catalyst had a higher Mn/Mn ratio, amount of chemisorbed oxygen and more Brønsted acid sites than the Mn-Ce/SAC catalyst. The XRD analysis indicated that Mn-Ce oxides were highly dispersed on the RAC support. These properties of Mn-Ce/RAC assisted the SCR reaction. Moreover, DRIFTS results demonstrated that sulfate species formation on Mn-Ce/RAC was much less in the presence of SO than that of Mn-Ce/SAC, which might be ascribed to the reduced alkalinity of the catalyst by the presence of SiO in RAC.