Comparison of the surface and catalytic properties of rare earth-promoted CaO catalysts in the oxidative coupling of methane

• Published in: Journal of chemical technology and biotechnology (1986) Vol. 81; no. 2; pp. 208 - 215
• Main Authors: Rane, Vilas H, Chaudhari, Sopan T, Choudhary, Vasant R
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.02.2006; Wiley
• Subjects: Applied sciences; basicity/base strength distribution; Catalysis; catalytic activity/selectivity; Catalytic reactions; Chemical engineering; Chemistry; Exact sciences and technology; General and physical chemistry; oxidative coupling of methane; rare earth-promoted CaO catalysts; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Catalytic reaction; basicity/base strength distribution; rare earth-promoted CaO catalysts; catalytic activity/selectivity; Catalyst activity; Oxidative coupling; Catalyst; Strength; oxidative coupling of methane
• ISSN: 0268-2575; 1097-4660
• DOI: 10.1002/jctb.1387

Rare earth (viz. La, Ce, Sm, Nd and Yb) promoted CaO catalysts have been investigated, comparing their surface properties (viz. surface area and basicity/base strength distribution) and catalytic activity/selectivity in the oxidative coupling of methane at different reaction conditions (temperatures, 650–800 °C, CH4/O2 ratios, 2.0–8.0 and space velocity, 51 360 cm3 g−1 h−1). The surface properties and catalytic activity/selectivity are strongly influenced by the rare earth promoter and its concentration. Apart from the Sm‐promoted CaO catalyst, both the total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) are decreased due to the promotion of CaO by rare earth metals (viz. La, Ce, Nd and Yb). The catalytic activity/selectivity is strongly influenced by the temperature, particularly below ⩽700 °C, whereas at higher temperature no further effect is seen. The La2O3CaO, Nd2O3CaO and Yb2O3CaO catalysts showed high activity and selectivity, and also their results are comparable. Among the catalysts, Nd‐promoted CaO (with Nd/Ca = 0.05) showed the best performance (19.5% CH4 conversion with 70.8% C2+ selectivity) in the oxidative coupling of methane. A close relationship between the surface density of total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) and the C2+ selectivity and/or C2+ yield has been observed. Copyright © 2005 Society of Chemical Industry