Effect of cobalt oxide on performance of Pd catalysts for lean-burn natural gas vehicles in the presence and absence of water vapor

On the development of active and stable Pd–Co/γ-Al2O3 catalyst for complete oxidation of methane

“…Thus, it appears that manganese oxides act as inhibitors of PdO decomposition, as a consequence of the higher oxygen mobility in the manganese oxide spinel phase. Pd-based catalysts, modified by cobalt, were tested in a simulated exhaust gas similar to that of lean-burn natural gas vehicles [9]. The effect of Co on the performance of Pd catalysts, resistant to water vapour poisoning, was estimated in the simulated exhaust gas in the presence and in the absence of water vapour.…”

Catalytic performance of LaCo0.5M0.5O3 (M=Mn, Cr, Fe, Ni, Cu) perovskite-type oxides and LaCo0.5Mn0.5O3 supported on cordierite for CO oxidation

“…It also suggested that the presence of H 2 O has a negative effect on the catalytic activity just at lower temperature. It is mainly attributed to the higher coverage of the active sites by H 2 O at lower temperature, in other words, it is due to the competition of H 2 O with CO for adsorption on the active sites [24,25]. …”

Selection of modifying additives for improving the steam tolerance of methane afterburning palladium catalysts

“…The presence of steam in a gas flow can considerably change the ranking of catalysts. For example, Co additives reduce the activity of a Pd cat alyst during the oxidation of CH 4 in dry feed, whereas no lowering of activity is observed in wet feed [21]. A more pronounced effect is observed for PdNiO/Al 2 O 3 catalysts, the ignition temperature on which is higher (372°C) than that on the Pd/Al 2 O 3 catalyst (345°C) in dry feed , but falls (to 372 and 400°C, respec tively) upon the addition of 1% of steam, and the differ ence between the ignition temperatures grows with an increase in the wetness of the feed [22].…”

“…In [18,20], however, it was stated that the mod ification of Al 2 O 3 with Mn oxides (up to 18 wt %) increases the activity of Pd catalysts and improves their resistance to deactivation, and some decrease in the activity of Pd catalysts upon the introduction Co or Ni is noted in [19]. It seems likely that the influence of the second component on the activity of a Pd catalyst depends on of the temperature range of the reaction [17] and on the method which is used for the prepara tion of a catalyst and determines its phase composition and dispersion, sa well as the degree of the interaction between its components [21]. In most works [17][18][19][20], the activity of catalysts was studied without adding steam to initial methane-air mixtures, thus creating a fundamental distinction in the operational conditions of such catalysts.…”

“…At higher temperatures (>500°C), the C-H bond rupture in the methane molecule becomes the limiting reac tion stage, and the reaction order with respect to water is reduced to zero [16]. One of the methods for increasing the activity of supported Pd catalysts and/or their resistance to deac tivation under the action of steam is replacing them with PdO-MeO x /Al 2 O 3 bimetallic systems (where Me is Cu, Mn, Cr, Ni, Co, Ce, or Fe) [17][18][19][20][21]. The con tradictory information in the literature hampers the choice of a suitable oxide promoter.…”