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The reaction mechanism of typical 3-way catalysts (TWC) has been already deeply studied. However, fewer efforts have been made to understand TWC compressed natural gas applications. Thus, the role of water in reducing atmospheres is still not well understood. In the present paper we show the positive impact of water on pollutants abatement at high temperature on commercial converters. [ABSTRACT FROM AUTHOR]

Abstract: The total oxidation of methane was carried out within a dielectric barrier discharge (DBD) reactor. The effect of energy deposition was studied, with energy deposition ranging from 36 to 100JL−1. In the current study, we also investigated the combined process of a dielectric barrier discharge and γ-alumina catalyst in the total oxidation of methane. In order to separate the catalytic effects from the plasma activation, the work included both purely catalytic and plasma activation processes. It was found that the catalytic activity depended on the energy deposition and the temperature. The plasma process leads to methane conversion in the temperature range of 300–500°C, whereas, methane conversion was only active above 425°C when only a catalyst was present. Moreover, the addition of NO x and CO2 in the feed was also studied. This addition does not affect the methane conversion in the absence or in the presence of catalyst. Finally, the presence of γ-alumina leads to CO+CO2 as products of the total oxidation of methane, whereas for the plasma-induced process, CO is the major product of the reaction. [Copyright &y& Elsevier]

Abstract: The methane oxidation reaction was studied as a function of temperature for a gas mixture representative of a combined heat power (CHP) within a dielectric barrier discharge (DBD) reactor. The effect of energy deposition was studied, with energy deposition ranging from 36 to 58JL−1, to maintain a low NO x formation at high temperature. In the current study, we also investigated the combined process of a dielectric barrier discharge and γ-alumina noble metal catalysts such as platinum and palladium. In order to separate the catalytic effects from the plasma activation, the work included both purely catalytic and plasma activation processes using a complete CHP mixture with 4% of water in the feed. It was found that the presence of water leads to increase the methane conversion in purely plasma activation processes. Moreover, a higher efficiency for methane oxidation in CHP conditions was observed with the plasma–Pd(X)/Al2O3 systems. [Copyright &y& Elsevier]

Abstract: The aim of the present work is to study the selective reduction of NO x from natural gas sources using unburned methane or hydrogen as reducing agents. The results suggest that the NO x are reduced by H2 at low temperature, when methane is not activated and at higher temperature the methane is then the main reducing agent. Similar results are obtained for alumina supported palladium and alumina supported cobald-palladium catalysts at low temperature in presence of hydrogen suggesting that the active phase for the reaction NO/H2 is the palladium. However, at high temperature the higher activity is obtained on bimetallic catalyst. The presence of cobalt enhances the catalytic activity. This result suggests that cobalt and palladium both in cationic form are the active sites when the reducing agent is the methane. [Copyright &y& Elsevier]

Abstract: The aim of the present work is to study the selective reduction of NO x from natural gas sources. The unburned methane can be used as reductant. Another reductant such as hydrogen can be created in situ, using a microreformer. The results suggest that the NO x are reduced by H2 at low temperature, when methane is not activated and at higher temperature the methane is then the main reductant. However, the catalytic behaviour depends on the metal precursor and the catalyst treatment. The most prominent result is obtained on the palladium catalyst prepared from Pd(NH3)4(NO3)2 precursor. Comparing the reduction and the calcination step in the course of catalyst preparation, one can conclude that calcination lead to the higher activity in deNO x , since reduced catalysts are oxidized during the deNO x process. [Copyright &y& Elsevier]

Abstract: Pd/Al2O3 was tested for the selective reduction of NO and simultaneous oxidation of methane by NO and O2 from reverse spillover on alumina supported palladium. The results of CH4/Ar and CH4/NO/Ar experiments clearly demonstrated the two sources of surface oxygen species able to oxidize the methane. When oxygen from the reverse spillover is totally consumed, the reaction NO/CH4 is stoichiometric, all oxygen come from the NO dissociation. The role of methane is similar to CO in TWC since methane removes the oxygen, from NO dissociation on the cationic sites of Pd atoms, and permits the reaction to proceed further. [Copyright &y& Elsevier]

Abstract: In order to improve a “Three Function Catalysts Model”, the present paper deals with alumina based catalysts containing cobalt and palladium for the NO reduction by methane. The deNO x temperature window was estimated by adsorption and subsequent desorption of NO in lean conditions. Two NO x desorption peaks were detected for both catalysts. For Pd(0.63)Co(0.58)/Al2O3, the two desorption peaks appeared at 205 and 423°C, whereas for Pd(0.14)Co(0.57)/Al2O3, the maxima desorption temperature peaks were at 205 and 487°C. In addition, NO oxidation was also studied to evaluate the catalyst first function. It was found that, the oxidation begins on Co–Pd/Al2O3 around 250°C. On Pd(0.63)Co(0.58)/Al2O3, 8% of deNO x were found in the range of the second NO x desorption peak temperature (410°C). During TPSR, C x H y O z species such as formaldehyde were detected. These oxygenate species are the reactive intermediate for deNO x by methane. [Copyright &y& Elsevier]