Supported Ru_xIr_1‐xO₂ Mixed Oxides Catalysts for Propane Combustion: Resistance Against Water Poisoning

Abstract

Mixed oxide catalysts Ru x Ir 1-x O 2 with varying composition x (x = 0, 0.25, 0.5, 0.75, 1.0) supported on CeO 2 , γ-Al 2 O 3 or ZrO 2 are successfully prepared and tested in the catalytic propane combustion in terms of activity and stability. Pure IrO 2 reveals a significantly lower activity than Ru x Ir 1-x O 2 with x � 0.25. For low conversion, pure RuO 2 on CeO 2 turns out to be the most active catalyst, while at higher conversion, Ru 0.75 Ir 0.25 O 2 on ZrO 2 is found to be more active than RuO 2 , pointing towards synergism of Ru and Ir sites. Long-term stability and also the resistance against water poisoning are highest for ZrO 2 -supported catalysts. The higher the Ir concentration in the active component Ru x Ir 1-x O 2 the more susceptible is the catalyst to water poisoning. Water poisoning is shown to be reversible, consistent with a blocking of catalytically active sites by water adsorption.

Operando CO Infrared Spectroscopy and On-Line Mass Spectrometry for Studying the Active Phase of IrO2 in the Catalytic CO Oxidation Reaction

“…Reducible oxides [15] are particularly prone to reaction-induced changes in that they can transform between the metallic and the oxide phase depending on the specific reaction conditions. Here, we consider IrO 2 supported on rutile TiO 2 , which has revealed high activity in the combustion of methane [16,17], propane [18], and CO [19,20]. How-ever, even more important than in thermal catalysis may be the use of these materials in electrocatalysis, including the chlorine and oxygen evolution reaction [21][22][23][24][25].…”

Oxidative Redispersion-Derived Single-Site Ru/CeO2 Catalysts with Mobile Ru Complexes Trapped by Surface Hydroxyls Instead of Oxygen Vacancies

“…7−12 For example, at the same feed gas and gas hourly space velocity, the propane turnover frequencies over Ru/CeO 2 were reported to be 3.8 and 1.8 times higher than those over Ru/γ-Al 2 O 3 and Ru/ZrO 2 at 210 °C, respectively. 11 Within such a framework, the size of supported RuO 2 is of great importance because the atomic species and small clusters give rise to longer RuO 2 perimeters and added RuO 2 −CeO 2 interfacial sites, which may therefore benefit more from the support reducibility in contrast to larger supported RuO 2 particles. 13,14 A conventional strategy to obtain Ru/CeO 2 catalysts with maximized Ru dispersion is reducing the Ru loading amount to, e.g., ≤0.25 wt %.…”

“…Given that the RuO 2 –support interface is directly involved in the activation of hydrocarbon molecules, − literature teaches that Ru catalysts with reducible supports are better hydrocarbon oxidizers, and Ru/CeO 2 is usually considered more reactive for hydrocarbon combustion compared to other Ru catalysts. − For example, at the same feed gas and gas hourly space velocity, the propane turnover frequencies over Ru/CeO 2 were reported to be 3.8 and 1.8 times higher than those over Ru/γ-Al 2 O 3 and Ru/ZrO 2 at 210 °C, respectively . Within such a framework, the size of supported RuO 2 is of great importance because the atomic species and small clusters give rise to longer RuO 2 perimeters and added RuO 2 –CeO 2 interfacial sites, which may therefore benefit more from the support reducibility in contrast to larger supported RuO 2 particles. , A conventional strategy to obtain Ru/CeO 2 catalysts with maximized Ru dispersion is reducing the Ru loading amount to, e.g., ≤0.25 wt %. , Such loadings are, however, significantly lower than those in commercial oxidation catalysts (e.g., 1 wt % Pt/γ-Al 2 O 3 ) and may lead to limited overall catalytic performance per unit reactor volume or area in large-scale processes.…”

Surface Lattice-Embedded Pt Single-Atom Catalyst on Ceria-Zirconia with Superior Catalytic Performance for Propane Oxidation

“…, supported on refractory metal oxides (Al 2 O 3 , CeO 2 , ZrO 2 , etc. ) are still the most promising candidates for HC oxidation from vehicle exhaust to meet the requirement for excellent low-temperature activity and high (hydro)­thermal stability simultaneously. − To ensure the high catalytic performance of PGM catalysts for HC oxidation, the precise control of PGM dispersion, the development of new supports combined with surface defect engineering, and the fine-tuning of metal–support interaction strength were reported as the most commonly used strategies. ,,− For example, Zhan’s group systematically studied the impact of spatial distribution of Ru nanoparticles and morphology/exposed facets of CeO 2 support on the C 3 H 8 oxidation performance of Ru/CeO 2 catalysts. , They highlighted that the strong metal–support interaction between Ru and CeO 2 could stabilize Ru and also provide active oxygen species for the oxidation of C 3 H 8 adsorbed on Ru nanoparticles . Fang et al .…”