Weihong Wu

Effects of PbCl2 on selective catalytic reduction of NO with NH3 over vanadia-based catalysts

The effects of PbCl2 on the selective catalytic reduction of NO with NH3 over vanadia-based catalysts were studied with BET, XRD, SEM, XPS, NH3-TPD, NH3 chemisorption, FT-IR and catalytic activity measurements. The results showed that PbCl2 deactivated the catalysts to a very high extent. The doping of PbCl2 could decrease the surface acidity, especially that of Brønsted acid sites. XPS characterization reveals that the presence of PbCl2 resulted in the transformation of V(5+) into V(4+), which decreased the reducibility of vanadia species. Based on the analysis of physical and chemical properties of the catalysts, the PbCl2-poisoning mechanism model of the vanadia-based SCR catalysts was proposed.

Adsorption of NO on ordered mesoporous carbon and its improvement by cerium

Ordered mesoporous carbon (OMC) was synthesized through a solvent evaporation-induced self-assembly method and used for NO adsorption. The structural properties, surface chemistry, and adsorption mechanism were investigated using nitrogen sorption, X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption of CO and CO2. Results showed that the ordered mesoporous structure was synthesized and remained stable after exposure to NO and O2. The NO adsorption capacity of OMC was 16.35 mg gcat−1, which was 7.5 times that of activated carbon. This finding may be due to the large surface area of OMC and the full use of its mesopores. Characterization results showed that monodentate nitrito (–O–NO) was the adsorbed species, and it originated from the adsorption of NO on the oxidized C(O) sites formed by the oxidation of active free Cf sites. In addition, cerium was introduced into OMC to further improve its NO adsorption capacity to 18.61 mg gcat−1. The redox cycle between Ce4+ and Ce3+, which can provide excess adsorbed oxygen atoms to react with Cf sites and generate C(O) sites, may be responsible for the improved adsorption capacity.