ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The preparation of carbonate-containing rare-earth compounds and their thermal decomposition in 0%–17% CO2/N2 gas streams has been studied. Three types of rare-earth carbonate or hydroxycarbonate were produced by precipitation; with ammonium bicarbonate as the precipitant, La2 (CO3)3,CeOCO3 and Ln (OH) x (CO3) y (Sm, Tb, and Yb) were obtained, whereas with Na2CO3, only the normal carbonate, Ln2(CO3)3 (La, Sm, Tb, Er and Yb) was found. Temperature programmed decomposition studies revealed that the normal carbonate decomposed stepwise via a dioxocarbonate, Ln2O2CO3, to the oxide. In contrast, the hydroxycarbonates decomposed directly to the oxide. The presence of CO2 during heating had minimal effect on the decomposition of Ln2(CO3)3 to La2O2CO3 but raised significantly the decomposition temperature of Ln2O2CO3 to the oxide. As CO2 is a major product of the rare-earth oxide catalysed oxidative coupling of methane, these observations indicate that the state of catalyst carbonation will be dependent on the reaction temperature, overall catalyst selectivity and preparative method.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00553839
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