Preparation and thermal studies of chloride containing cerous carbonate compounds

Abstract

Two chloride containing cerous carbonate compounds, formulated as Ce 3Cl(CO 3) 4 and Ce 4Cl(OH) 3(CO 3) 4, have been synthesized by carbonation of cerous oxychloride in pyridine/H 2O mixtures at elevated temperatures. Pyridinium chloride has been identified as a reaction product. These compounds have been characterized by IR spectral and X-ray diffraction techniques. Thermal decomposition studies indicate that the final solid product at 873 K in the absence of steam is a mixture of ceric oxide and cerous oxychloride, the amount of each being dependent upon the Cl −/Ce ratio in the initial compound. The thermal reaction pathway of both compounds involves initial decomposition to cerous dioxymonocarbonate and cerous oxychloride with concomitant carbon dioxide evolution. The cerous dioxymonocarbonate subsequently oxidizes at higher temperature to ceric oxide via carbon monoxide evolution. The utility of these new cerium(III) chlorocarbonate phases in heat cycles for water splitting is discussed.