Oxidation of soot promoted by Fe-based spinel catalysts

Diesel engine has attracted much attention because of its good power performance, fuel economy, reliability and durability, but the exhaust gas containing soot has a great impact on the environment and human health. Catalyzed diesel particulate filter (CDPF) that reduces the activation energy of soot oxidation and combustion by catalysts are used to eliminate soot. In this paper, MFe2O4 spinel (M=Cu, Ni and Co) was synthesized by sol-gel method to catalyze the combustion of soot. The Characterization results of MFe2O4 showed that CuFe2O4 possessed the smallest average grain size (65.6nm) and the best redox performance. The activity test of the catalyst shows that the activity order of the catalyst is CuFe2O4 (330 °C > CoFe2O4 (411 °C > NiFe2O4 (464 °C). DFT results showed that carbon is more easily adsorbed on the oxygen-terminal surface of CuFe2O4 and reacts with oxygen vacancies, resulting in the promotion of soot oxidation by the diffusion of oxygen from the inside to the surface. It also proves that CuFe2O4 has the best catalytic effect on soot.

Experimental Evaluation on the Catalytic Activity of a Novel CeZrK/rGO Nanocomposite for Soot Oxidation in Catalyzed Diesel Particulate Filter

A nanostructured solid solution catalyst CeZrK/rGO for soot oxidation in catalyzed diesel particulate filter was synthesized using the dipping method. The reduced graphene oxide (rGO) was used as the catalyst carrier, and CeO2, ZrO2, and K2O were mixed with the molar ratio of 5:1:1, 5:2:2 and 5:3:3, which were referred to as Ce5Zr1K1/rGO, Ce5Zr2K2/rGO, and Ce5Zr3K3/rGO, respectively. The structure, morphology and catalytic activity of the CeZrK/rGO nanocomposites were thoroughly investigated and the results show that the CeZrK/rGO nanocomposites have nanoscale pore structure (36.1–36.9 nm), high-dispersion quality, large specific surface area (117.2–152.4 m2/g), small crystallite size (6.7–8.3 nm), abundant oxygen vacancies and superior redox capacity. The 50% soot conversion temperatures of Ce5Zr1K1/rGO, Ce5Zr2K2/rGO, and Ce5Zr3K3/rGO under tight contact condition were decreased to 352 °C, 339 °C and 358 °C respectively. The high catalytic activity of CeZrK/rGO nanocomposites can be ascribed to the following factors: the doping of Zr and K ions causes the nanocrystalline phase formation in CeZrK solid solutions, reduces the crystallite size, generates abundant oxygen vacancies and improves redox capacity; the rGO as a carrier provides a large specific surface area, thereby improving the contact between soot and catalyst.