The effect of water on methane oxidation over Pd/Al₂O₃ under lean, stoichiometric and rich conditions

Abstract

Methane conversion during cooling ramp: water inhibits methane conversion more severely in high oxygen concentration.

Role of Water on the Structure of Palladium for Complete Oxidation of Methane

“…The temperature delay is 100°C, which correlates well with the methane combustion reactivity tests on palladium catalysts 24,60 . Typically, when water is added to the reaction mixture, a positive shift (35-120°C temperature range) of T 50 (temperature at which 50% methane conversion is achieved) is measured 25,68 . The turnover rate for methane oxidation was found to decrease by 95% when PdO decomposed to Pd metal at 888 K, showing that PdO is more active than Pd metal for methane combustion at this temperature 69 .…”

Palladium dispersion effects on wet methane oxidation kinetics

“…[15][16][17] The methane oxidation over palladium-alumina formulations is known to be inhibited by water present in the combustion exhaust and/or generated by the complete methane oxidation reaction itself. [18][19][20][21] Previous studies report that the inhibition is caused by formation of hydroxyl groups and/or adsorbed water blocking the catalytically active PdO sites. [22][23][24][25][26][27][28][29][30][31] Also the formation of an inactive PdIJOH) 2 phase and site blocking by carbonates have been brought forward as additional deactivation mechanisms.…”

“…[18][19][20][21] Previous studies report that the inhibition is caused by formation of hydroxyl groups and/or adsorbed water blocking the catalytically active PdO sites. [22][23][24][25][26][27][28][29][30][31] Also the formation of an inactive PdIJOH) 2 phase and site blocking by carbonates have been brought forward as additional deactivation mechanisms. [32][33][34] In the case of water inhibition, infrared spectroscopic measurements evidence that hydroxyl groups build up on the alumina surface both by spill-over of reaction products and direct water dissociation.…”

Pd4S/SiO2: A Sulfur-Tolerant Palladium Catalyst for Catalytic Complete Oxidation of Methane

“…It has therefore found great applications in modern industry, such as catalytic exhaust converters aimed to reduce methane emission and catalytic gas turbine combustors designed to combust fuel under mild conditions [9,10]. Supported PdO catalysts have shown excellent catalytic property in methane oxidation, and currently are under extensive study [11][12][13][14][15][16][17][18]. However, once sulfur species (e.g., H 2 S or SO 2 ) are present in the reaction atmosphere, the poisoning of PdO catalyst which would lead to inactive PdO-SO x is irreversible and the activity of the catalyst cannot be recovered at relatively low temperature [19][20][21][22][23][24][25].…”