Catalytic soot combustion of α-Fe/Ce–K–O nanocomposites via citrate-gel route

摘要

The binary phase, porous, nanocomposite xα-Fe/(1 − x)Ce_0.9–K_0.1–O (x = 0.05–0.2) catalysts and the catalyst-coated honeycomb ceramic device have been prepared by the citrate-gel thermal decomposition-reduction process and the sol–gel assisted dip-coating method, respectively. The nanocomposite of fluorite-type structure CeO₂ nanoparticles about 18–51 nm and α-Fe nanoparticles about 32 nm is obtained at 600 °C for 2 h in a deoxidization atmosphere and the α-Fe in nanocomposite has the suppression effect on grain growth of CeO₂. With Fe content increasing from 0.05 to 0.1, the specific surface area for the nanocomposites increases dramatically from about 4.4 to 43.0 m2/g, reaching a maximum value 57.7 m2/g at x = 0.15, and the pores vary from macropores to micro- or mesopores. Due to the presence of nano α-Fe, all the catalysts exhibit a very high soot catalytic activity, with the lowest T₂₀ (255 °C) and T₅₀ (291 °C) for the nanocomposite with x = 0.15, and it is confirmed by the bench test under practical diesel exhaust gases.