Reaction Between Carbon Dioxide and Diols

Cyclic carbonates can be produced from diols and C02 in the presence of suitable catalysts (Equation 7.24). 

Catalyst Conversion of alcohol [%) Yield (%) of carbonate Selectivity of carbonate (%) 

The thermodynamics of this reaction were not very favorable, and the major drawback related to the coproduction of water that may have involved the modification or deactivation of the catalyst, with negative effects on the conversion rate. 

Ceria-based catalysts [219] and Ce02 Zr02 solid solution catalysts [220] have each been reported to be very efficient catalysts for the synthesis of EC and PC by reaction of C02 with ethene glycol and propene glycol, respectively. The catalytic activity has been shown to depend heavily on the composition and calcination temperature of the catalysts. 

Different metallic acetates [221] have also been used in acetonitrile, which acts not only as a solvent but also as a dehydrating agent to eliminate the effect of any water produced during the reaction. In this way, the thermodynamic equilibrium could be shifted and the yield of CCs improved. By using 1,2-propene glycol as the reactant (100 mmol) and anhydrous zinc acetate (2.5 mmol) as catalyst in acetonitrile (10ml) with a C02 reaction pressure of 10 MPa, at a reaction temperature of 343 K and a reaction time of 12h, the yield of 1,2-propene carbonate was shown to be 24.2% and the conversion of 1,2-propene glycol 38.9%. 

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