Patent ID: 7518011

Claim:
A method for preparing an ester-substituted diaryl carbonate comprising the steps of: (a) forming a first reaction mixture comprising phosgene, an ester-substituted phenol, an organic solvent, and a catalyst selected from the group consisting of a tertiary amine catalyst and a phase transfer catalyst, said first reaction mixture having an organic phase and an aqueous phase, wherein the first reaction mixture is formed with less than 15% water of formulation, (b) forming a second reaction mixture by allowing the first reaction mixture to react wherein during the reaction, (i) the aqueous phase has a pH, and the pH is adjusted, if necessary, by the addition of an alkali metal hydroxide solution in amounts such that the pH is greater than or equal to 9.0 during at least some portion of the reaction, and (ii) the aqueous phase has brine strength, and the brine strength of the aqueous phase is adjusted, if necessary, by varying the concentration of the alkali metal hydroxide solution being added to maintain the pH such that the brine strength is between 15% and a saturated brine solution during at least some portion of the reaction, (c) adding to the second reaction mixture at least 0.50 mole % of a tertiary amine catalyst per mole of ester-substituted phenol introduced to the first reaction mixture, (d) allowing the second reaction mixture to react, wherein the second reaction mixture has an organic phase and an aqueous phase, wherein said aqueous phase has a pH and a brine strength, and wherein during the reaction of the second reaction mixture, (i) the pH of the aqueous phase is adjusted, if necessary, by the addition of an alkali metal hydroxide solution in amounts such that the pH is greater than or equal to 9.0 during at least some portion of the reaction to form the second reaction mixture, and (ii) the brine strength of the aqueous phase is adjusted, if necessary, by varying the concentration of the alkali metal hydroxide solution being added to maintain the pH such that the brine strength is between 15% and a saturated brine solution during at least some portion of the reaction of the second reaction mixture, thereby forming an ester-substituted diaryl carbonate, wherein the brine strengths of the first and second reaction mixtures are maintained at or above 15% and the pHs of the first and second reaction mixture are maintained at or above 9 for a sufficient portion of the process that the ester-substituted diaryl carbonate is formed with a conversion of at least 90% and a selectivity of at least 98%.