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Silicon carbide (SiC) supported vanadium catalysts were obtained using the wet chemical impregnation method, and their removal of NOx with the presence of SO 2 at low temperature was evaluated. The effect of carbon was observed by comparing different carbon-based catalysts. V 2 O 5 /SiC (1 wt.%) catalyst had a NOx removal efficiency of 86% in the presence of SO 2 at 250 °C with a GHSV of 180,000 h −1 . In this study, the temperature-programmed desorption of NH 3 (NH 3 -TPD) and temperature-programmed decomposition (TPDC) of NH 4 HSO 4 deposited on the catalysts and reaction were performed to determine the influence of carbon on the performance of a carbon-based catalyst in the presence of SO 2 . The NO on the carbon support can effectively react with the NH 4 HSO 4 formed on the catalyst surface at low temperatures. Additionally, the adsorption of NH 3 was higher on carbon-based catalysts that were pre-adsorbed with SO 2 + O 2 . Thus, SO 2 promotes the activity of a carbon-based catalyst at low temperatures, and carbon has very important effect on the promotion of that activity. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) supported copper oxide catalysts were prepared, and the morphology and structure of the catalyst were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and temperature-programmed desorption experiments. The CuO/CNT catalysts demonstrated high catalytic activities during the selective catalytic reduction (SCR) of NO with NH over a temperature range of 150-250 °C. The amount of NH adsorbed on the catalyst surface was greater than that of NO or NO + O adsorbed on the catalyst surface. These results suggest that the SCR reaction might proceed on the surface of the CuO/CNT catalysts and occur between the adsorbed ammonia and gas phase NO or weakly adsorbed NO. The CuO/CNT catalysts exhibited good stability at low temperatures, which makes them suitable for potential applications in industry. Graphical Abstract: [InlineMediaObject not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Pt- and Pd-promoted CexZr1-xO2 mixed oxides were characterized and investigated for passive NOx adsorber applications. X-ray diffraction analysis revealed a phase transition from tetragonal to cubic with increasing cerium content in CexZr1-xO2, while H2 and CO chemisorption data in all cases indicated average Pt and Pd particle sizes of close to 2 nm. H2-temperature programmed reduction (TPD) measurements revealed a shift of the Pt reduction peak to higher temperature with increasing Ce content, consistent with a corresponding increase in the degree of Pt oxidation. According to microreactor data, doping Ce into the ZrO2 lattice resulted in a significant improvement in low temperature (80-160 °C) NOx storage efficiency. Diffuse reflectance infrared Fourier transform spectroscopy measurements on Pt/CexZr1-xO2 showed that as Ce content increased, relatively more nitrite species were generated during NOx storage. However, oxidation of nitrite to nitrate during subsequent NOx-TPD increasing the concentration of more thermally stable nitrate also correlated with increased Ce content. The use of Pd as a promoter resulted in decreased NOx storage efficiency compared to Pt, although low-temperature NOx desorption behavior was improved. This is attributed to decreased formation of nitrate during NOx storage compared to that of Pt, as well as the lower activity of Pd for oxidation of nitrite to nitrate during subsequent NOx-TPD. To achieve more balanced NOx storage and desorption behavior, Ce0.2Zr0.8O2 was promoted with both Pt and Pd, resulting in superior overall NOx performance relative to its Pt and Pd analogues. After hydrothermal aging at 750 °C for 16 h, the copromoted sample still maintained excellent NOx adsorption-desorption performance. [ABSTRACT FROM AUTHOR]