Infrared Study of the Formation and Stability of La2O2CO3 During the Oxidative Coupling of Methane on La2O3

doi:10.1006/jcat.1993.1185

Journal of Catalysis

Volume 142, Issue 1, July 1993, Pages 18-26

https://doi.org/10.1006/jcat.1993.1185 Get rights and content

Abstract

The formation and stability of La₂O₂CO₂ under CO₂/He and the CH₄/O₂/He reaction mixture were investigated by infrared spectroscopy in the 650-750°C range. La₂O₂CO₃ is not stable under flowing He at 650°C. Bulk La₂O₂CO₃ is formed during the oxidative coupling of CH₄ at 650°C, although thermodynamic considerations predict that it cannot be generated from the gaseous CO₂ produced by the catalytic reaction. On this basis, it is suggested that the dioxymonocarbonate is formed via the surface deep oxidation of CH₄ and/or the reaction products. FTIR spectroscopy indicates that 15% of the starting catalyst La₂O₃ is transformed into La₂O₂CO₃ by the catalytic reaction at 650°C.

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Citation Excerpt :
Specifically, the absorption bands between ~1500 and 1400 cm−1 arose from the v3 asymmetric stretching vibration of carbonate (Levan et al., 1993; Wang et al., 2013; Stoyanova et al., 2019). The v1 (symmetric), v2 (out-of-plane bending) and v4 (in-plane bending) vibrations of carbonate group were also observed via the bands located at ~1040, 850 and 730 cm−1, respectively (Levan et al., 1993; Wang et al., 2013). The bending vibration of La-OH groups were related to the absorption bands at ~1140 and 1115 cm−1 (Li et al., 2020).
A novel activation route for the preparation of carbon-based adsorbents functionalized with lanthanum and their application for arsenic adsorption was proposed. This procedure is based on carbon dioxide activation at room temperature, which could allow to reduce the energy consumption and adsorbent cost. A comparison of this novel activation approach with respect to the conventional thermal activation at 800 °C under N₂ atmosphere was performed on biochar from avocado seeds and functionalized with lanthanum. Results showed that the arsenic adsorption properties of the lanthanum-functionalized adsorbent activated with CO₂ at room temperature were higher up to 179% than those activated with N₂ at 800 °C. The carbonation of lanthanum oxygenated functionalities on the adsorbent surface favored the ligand exchange and surface complexation interactions during the arsenic adsorption. Arsenic adsorption using this engineered lanthanum-based adsorbent was endothermic and transited from a multi-molecular process at 25 °C to a multi-anchorage process at 30 °C. The estimated arsenic adsorption capacities at saturation for these novel adsorbents were 15 – 20 mg/g at 25 – 40 °C, respectively.

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Regular ArticleInfrared Study of the Formation and Stability of La2O2CO3 During the Oxidative Coupling of Methane on La2O3

Abstract

Regular Article
Infrared Study of the Formation and Stability of La₂O₂CO₃ During the Oxidative Coupling of Methane on La2O3