Patent ID: 7772441

Claim:
A method for producing 3,4′dihydroxybenzophenone comprising in order: (a) combining m-hydroxybenzoic acid, phenol, a protonic acid and a Lewis acid to form a mixture, (b) heating an agitated mixture of step (a) to a temperature in a range of 27-33° C. and a pressure of at least 5 psig to form a reaction product of 3,4′dihydroxybenzophenone present as solids in a solution, (c) removing at least a portion of the protonic acid and Lewis acid from the formed reaction product of 3,4′dihydroxybenzophenone, (d) contacting the reaction product of step (c) with (i) water at a temperature not greater than 10° C. and (ii) ammonium hydroxide to obtain a pH in a range of 4.5 to 6; (e) filtering a mixture of step (d) to separate 3,4′dihydroxybenzophenone solids.