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Comparison of the surface and catalytic properties of rare earth‐promoted CaO catalysts in the oxidative coupling of methane
Author(s) -
Rane Vilas H,
Chaudhari Sopan T,
Choudhary Vasant R
Publication year - 2006
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.1387
Subject(s) - catalysis , selectivity , oxidative coupling of methane , chemistry , methane , inorganic chemistry , rare earth , yield (engineering) , base (topology) , mineralogy , materials science , metallurgy , organic chemistry , mathematical analysis , mathematics
Abstract 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, CH 4 /O 2 ratios, 2.0–8.0 and space velocity, 51 360 cm 3 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 CO 2 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 La 2 O 3 CaO, Nd 2 O 3 CaO and Yb 2 O 3 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% CH 4 conversion with 70.8% C 2+ selectivity) in the oxidative coupling of methane. A close relationship between the surface density of total and strong basic sites (measured in terms of CO 2 chemisorbed at 50° and 500 °C respectively) and the C 2+ selectivity and/or C 2+ yield has been observed. Copyright © 2005 Society of Chemical Industry