Very few metal oxides are catalytically active for the direct carbonate synthesis from alcohol and CO2. The direct synthesis of organic carbonates from alcohols and carbon dioxide is a very attractive alternative because of the high atom efficiency, low toxicity and price of the reactants, and simplicity of the operations. Several types of catalysts have been reported for the direct synthesis of organic carbonates, especially dimethyl carbonates (DMCs): homogeneous metal complexes, complexes anchored to supports, and metal oxide catalysts. This chapter reviews the development of the metal oxide catalysts. Pure ceria and ceria-zirconia are frequently used in catalysis. In the case of direct synthesis of organic carbonates, ceria is an effective catalyst, although the acid and base properties can be important. Zirconia is also an active catalyst for the direct synthesis of organic carbonates. In contrast to ceria or ceria-zirconia, zirconia has multiple stable crystalline phases.
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