Search

We have reported a LaMnO-based, Pt free lean NO trap (LNT) catalyst shows promising NO reduction activities, but the mechanism of NO reduction or the role of the perovskite over this catalyst has not been addressed. This paper presented our investigation on the mechanistic aspects of NO adsorption and reduction over several LaMnO-based LNT catalysts. NO can be effectively oxidized to NO on LaMnO at 350 °C, while little NO (NO + NO) can be stored verified by the following temperature programmed desorption experiment; under the same conditions, a significant amount of NO (41 μmol NO/g washcoat) were stored over BaO/AlO/LaMnO indicating NO are adsorbed mainly on the BaO/AlO. The temperature programmed surface reaction with CO demonstrated that although it can store NO during the lean period, failed to reduce NO by CO over the BaO/AlO/LaMnO catalyst. After adding Pd into BaO/AlO/LaMnO, NO can not only be stored during the lean conditions but also reduced. It could be concluded that the Pd catalyst, not perovskite, is responsible for NO reduction during the rich conditions. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Single-crystalline La0.6Sr0.4MnO3+ δ microcubes of cubic perovskite phase were prepared hydrothermally. The adopted temperature and time of hydrothermal treatment and the amount of KOH used had great effects on the low-temperature reducibility of La0.6Sr0.4MnO3+ δ. The initial H2 consumption rate of La0.6Sr0.4MnO3+ δ played a vital role in determining its catalytic activity for toluene combustion. It is concluded that the perovskite-type oxide catalyst with a higher initial H2 consumption rate displayed a higher catalytic activity for the addressed reaction. [ABSTRACT FROM AUTHOR]

The role of Ag in simultaneously catalyzing NO reduction and C3H6 oxidation was shown to be strongly dependent on the redox properties of its local environment. Under an atmosphere of 1,000 ppm NO, 3,000 ppm C3H6, and 1% O2 and a GHSV of 30,000 h−1, a perovskite La0.88Ag0.12FeO3 prepared by reactive grinding is active giving a complete NO conversion and 92% C3H6 conversion at 500 °C. These values are much higher than the NO conversion of 55% and C3H6 conversion of 45% obtained over a 3 wt.% Ag/Al2O3 catalyst under the same conditions. Under an excess of oxygen (10% O2) a good SCR performance with a plateau of N2 yield above 97% over a wide temperature window of 350–500 °C along with C3H6 conversion of 90% at 500 °C was observed over Ag/Al2O3, while minor N2 yields (∼10% at 250–350 °C) and high C3H6 conversions (reaching ∼100% at 450 °C) were obtained over La0.88Ag0.12FeO3. Abundant molecular oxygen is desorbed from Ag substituted perovskite after 10% O2 adsorption as verified by O2- temperature programmed desorption (TPD). This reflects the strongly oxidative properties of La0.88Ag0.12FeO3, which lead to a satisfactory NO reduction at 1% O2 due to the ease of nitrate formation but to a significant C3H6 combustion above that value. The formation of nitrate species over the less oxidizing Ag/Al2O3 was accelerated under an excess of oxygen resulting in an excellent lean NO reduction behavior. The redox properties of silver catalysts could be adjusted via mixing perovskite with alumina for an optimal elimination of both NO and C3H6 over the whole range of oxygen concentration between 0 to 10%. [ABSTRACT FROM AUTHOR]

CoNdOx (Co/Nd = 1) is a highly promising catalyst for the carbon-free CO2 reforming of methane. Influence of the Co/Nd ratio on the catalyst performance in the CO2 reforming and also on the crystalline phases and reduction by temperature programmed reduction (TPR) of the CoNdOx catalyst has also been investigated. The CoNdOx (CoNd = 1.0) catalyst consisted of mainly NdCoO3 perovskite-type mixed metal oxide and it showed not only a high resistance to carbon formation at different process conditions (viz. temperature = 750-900 °C and gas hourly space velocity (GHSV) = 10000-50000 cm3 g-1 h-1) but also high activity and selectivity in the CO2 reforming process. The high resistance to carbon formation for this catalyst is attributed mostly to strong metal (Co°)-support (Nd2O3) interactions. [ABSTRACT FROM AUTHOR]