SrAgTiO (, 0.1) perovskite-structured catalysts for the flameless combustion of methane

Abstract

Several samples of Sr1-xAgxTiO3 (x = 0, 0.1) perovskite-structured catalysts have been prepared and tested for the title reaction under lean-burn conditions. For the same overall nominal composition, catalyst activity and durability depend strongly on the method of preparation and, for the samples prepared by the same method, mainly on temperature and on residence time at such a temperature during preparation. In Sr0.9Ag0.1TiO3 catalysts Ag is present either as intra-crystalline Ag 2+ , likely substituting for Sr 2+ in the perovskite lattice, or as inter-crystalline metallic Ag. The catalytic activity of Sr0.9Ag0.1TiO3 is connected with the presence of O2 -/Ti 4+ , Ox -/Ag and Ox -/Ag 2+ or of O3 -/Ti 4+ , O -/Sr 2+ and of O -/Ti 4+ species, depending on preparation method and conditions. Furthermore, intercrystalline metallic Ag plays an important role in improving catalyst resistance to sintering, the most durable samples being those calcined for a sufficient residence time at the highest temperature during preparation, i.e. under conditions better favouring the segregation of this metal from the perovskite lattice.

La–Ag–Co perovskites for the catalytic flameless combustion of methane

“…Ag +2 ions could interact with some Ox -species, leading to Ox -/Ag +2 couples and so influencing oxygen mobility and catalytic activity. However, it was found that a much lower Ag +2 substitution degree occurred for samples prepared by flame-based techniques (flame pyrolysis and flame hydrolysis [18]) with respect to the sol gel samples. This is very likely a consequence of the milder sol-gel preparation conditions, allowing the perovskite lattice to allocate a higher amount of extraneous ions.…”

“…In a previous investigation it was found [18] that in Sr1-xAgxTiO3 perovskites silver may exist as intra-crystalline framework Ag…”

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

“…Since the SG method using citric acid is a well-established synthetic method [33][34][35], we only changed the Ta/Ni ratio and did not vary any other parameters.…”

Novel mixed conducting SrSc0.05Co0.95O3‐δ ceramic membrane for oxygen separation

“…The ceramic membranes made from such materials allow oxygen to permeate through with infinite oxygen selectivity under the driven of oxygen partial pressure difference across the membrane 4–8. Such membranes have several potential applications including: pure oxygen production, partial oxidation of methane to syngas, oxidative coupling of hydrocarbon to value‐added products, and oxygen‐enriched combustion, and so on 4–15. As compared with the traditional oxygen separation process, such as the distillation of cryogenic air, the advantages of ceramic membrane process are obvious: simple in operation, substantially reduction in capital cost both for plant construction and the daily operation, and capable of coupling reaction.…”