Search

It is shown that palladium-cobalt oxide-cerium catalyst deposited on cordierite catalyzes the reduction of nitrogen(II) oxide with carbon monoxide, and cobalt-iron catalysts in simultaneous reduction of NO + NO with C-C alkanes retained high activity in the presence of water vapor and sulfur dioxide. The Pd-CoO/cordierite catalyst exceeds the Pt-CoO/codierite catalyst in the conversion of NO and CO in the reaction mixture CO + NO + O + HO + SO. Modification of the Pd-CoO/cordierite with cerium oxide considerably increases its sulfur resistance. [ABSTRACT FROM AUTHOR]

In order to improve the catalytic performance of supported-Ir catalysts for the selective reduction of NO with CO, the effect of H2 was investigated. While adding H2 showed no or negative effect on NO conversion on Ir/SiO2, Ba/Ir/SiO2 and Ir/WO3/SiO2 catalysts, the activity of Ba-doped Ir/WO3/SiO2 catalyst for NO reduction was significantly increased by H2 addition. The role of H2 was found to stabilize the catalytically active Ir-WO x sites during the reaction. [ABSTRACT FROM AUTHOR]

Nitromethane (NM) is a very efficient reductant for converting NO2 to N2 over Ag/Y: Between 140 °C and 400 °C, the N2 yield is close to 100%. This high N2 yield results from the ability of Ag/Y to effectively catalyze the reaction between NM and NO2. This high catalytic activity of Ag/Y is minimally affected by surface bound CN−, NC−, or acetate, all of which are stable at temperatures below ∼300 °C. At T ≥ 400 °C, there is a reaction path that yields N2 from NM even in the absence of NO2. However even at 400 °C, under typical deNO x conditions, most N2 molecules are formed as a result of the reaction of NM and NO2. [ABSTRACT FROM AUTHOR]

The catalytic activity for the selective reduction of NO with CO over Ir/SiO2 was greatly increased by the addition of a W species. The active site for reduction of NO over Ir/WO3–SiO2 was an Ir–WO x species (2.92 ≤ x ≤ 3). The role of the Ir–WO x active site was to promote the NO dissociation step. [ABSTRACT FROM AUTHOR]

The H2/NO/O2 reaction under lean-burn conditions has been studied by means of in situ DRIFTS, reactor measurements and temperature-programmed desorption with the aim of understanding the very different behavior of Pd/TiO2 and Pd/Al2O3 catalysts. The former deliver very high NOx conversions (70-80%) with good N2 selectivity whereas the latter show very low activity. In addition, PdTiO2 exhibits two distinct NOx reduction pathways, thus greatly extending the useful temperature range. It is shown that the PdTiO2 low-temperature channel involves adsorption and subsequent dissociation of NO on reduced (Pd0) metal sites. The low activity of PdAl2O3 is a consequence of palladium remaining in an oxidized state under reaction conditions. The high-temperature NO reduction channel found with PdTiO2 is associated with the generation and subsequent reaction of NHx species. [ABSTRACT FROM AUTHOR]

Sn0.5Ti0.5O2 shows excellent catalytic performance both for the CO-SO2 reaction and the CO-SO2-NO reaction. At 350 ° C, 525 ppm SO2/520 ppm NO/2085 ppm CO, SV = 3000 h-1, the conversion of SO2 is nearly complete in the CO-SO2 reaction and above 89% in the CO-SO2-NO reaction; NO conversion is above 98% in the latter reaction. The selectivities of S and N2 are both close to 100%. SO2 shows a significant promoting effect on the activity of the Sn0.5Ti0.5O2 catalyst for NO reduction by CO. Combining transient response experiments, catalytic tests and TPD results, we propose a SO2-assisted NO-CO reaction concept. The existence of a surface sulfur species, which was formed during the CO-SO2 or CO-SO2-NO reaction, is proved by XPS analysis. It is the active site for NO reduction in the CO-SO2-NO reaction, and through which SO2 accomplishes its promoter role. On the basis of the results obtained, the SO2-assisted redox mechanism of simultaneous reduction of SO2 and NO by CO is proposed. [ABSTRACT FROM AUTHOR]