An environmental and highly active Ce/Fe-Zr-SO42- catalyst for selective catalytic reduction of NO with NH3: The improving effects of CeO2 and SO4

A series of Ce/Fe-Zr-SO42- catalysts have been prepared and developed for selective catalytic reduction of NO with ammonia (NH3-SCR). The catalysts were characterized by XRD, H-2-TPR, N-2 adsorption-desorption, NH3-TPD and DRIFTS. The characterization results demonstrated that the coexistence of cerium and sulfuric acid on Fe-Zr catalyst could contribute to excellent SCR performance. Among all samples, Ce/Fe-Zr-0.3 S catalyst showed the optimal NOx conversion, reaching more than 80% at 250 degrees C at a GHSV of 60,000 h(-1). Moreover, the optimum concentration of SO42- ( to modify Ce/Fe-Zr catalyst was 0.3 mol/L. The low sulfuric acid concentration contributed to improving low-temperature activity, while high concentration leaded to outstanding high-temperature activity. According to H-2-TPR and NH3-TPD, the presence of SO42- ( increased the total amount of acid sites and more stable sulfate species were formed with higher concentration of sulfuric acid. In situ DRIFTS revealed the NH3 molecule was mainly activated at the Lewis acid site and reacted with the adsorbed NOx species (such as bidentate nitrates) to produce N-2 and H2O, which conformed to the L-H reaction mechanism.

Automated summary

A series of Ce/Fe-Zr-SO42- catalysts have been developed for selective catalytic reduction of NO with ammonia. Among them, Ce/Fe-Zr-0.3 S catalyst showed the optimal NOx conversion at 250 degrees C with a sulfuric acid concentration of 0.3 mol/L.