Denitration Performance of SnO_x-CeO_x/Pitch-Based Spherical Activated Carbon Catalysts for Selective Catalytic Reduction of NO

Pitch-based spherical activated carbon (PSAC) is widely used in biomedicine, environmental protection and other practical fields because of its advantages of high specific surface area, high mechanical strength, high packing intensity and low fluid resistance. In this study, series of SnO_x-CeO_x/PSAC catalysts were prepared by the impregnation method using PSAC prepared from high softening point petroleum pitch as the support. Their catalytic performances were evaluated in the low-temperature selective catalytic reduction (SCR) of NO with NH₃. The catalysts obtained were characterized by nitrogen adsorption/desorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that SnO_x-CeO_x/PSAC catalyst exhibits higher SCR activity than CeO_x/PSAC catalyst, and the NO conversion rate first increases and then decreases with the increase of metal loading. The Sn(5%)Ce(13%)/PSAC catalyst exhibits the highest NO removal activity, and the highest NO conversion rate reaches 98% in the temperature range of 100~300 ℃. This is mainly due to the improved dispersion of cerium oxide on the surface of PSAC in the presence of SnO_x, and the formation of a solid solution between SnO_x and CeO_x with a fluorite-type structure probably caused by the incorporation of Sn⁴⁺ into the crystal lattice of CeO₂. Furthermore, a certain amount of Ce³⁺ and a high percentage of chemisorbed oxygen exist on the catalyst surface because of the synergistic effect between tin and cerium oxides. These factors result in the excellent NH₃-SCR performance of the Sn(5%)Ce(13%)/PSAC catalyst. Compared with CeO_x/PSAC catalyst, SnO_x-CeO_x/PSAC catalyst exhibits a higher resistance to SO₂ poisoning. The NO conversion rate of the Sn(5%)Ce(13%)/PSAC catalyst retains at 80% at 260 ℃ after the introduction of SO₂ in the feed gas for 420 min.