Sulfur-Resistant Cu0.7Ni0.3Fe2O4 Catalyst for Removing NO from Diesel Exhausts

Abstract

The catalyst in the NH3-SCR process for removing NO from diesel exhaust is prone to poisoning by relatively high sulfur contents in diesel in China. The catalyst should have not only favorable catalytic activity for NO removal, but also high sulfur resistance. The spinel-type Cu1−xNixFe2O4 (x = 0–0.5) catalysts with different Ni contents were prepared by sol–gel method using citric acid as complexing agent. The catalytic activities for NO removal in sulfur-free and sulfur-containing (SO2, 0.035%, volume fraction) air were investigated in a fixed bed reactor. Meanwhile, the sulfur resistance was tested in sulfur-containing air. Moreover, the catalysts before and after the reaction were characterized by XRD, SEM, N2-adsorption, EDS, NH3-TPD, FT-IR and XPS technologies, and the mechanism of sulfur poisoning of the catalyst was also discussed. The results showed that when the Ni content was 0.3, the formed Cu0.7Ni0.3Fe2O4 spinel catalyst had the optimal catalytic performance, of which the NO conversion could be 95.87% in sulfur-free air with 5% oxygen content, and it maintained above 90.12% in the sulfur-containing air within 240 min. Characterization results illustrated that sulfur poisoning of catalyst might be caused by many pathways. The introduction of Ni into catalyst could inhibit destruction of the catalyst structure and make the catalyst become more stable in sulfur-containing air and show high sulfur resistance.