Patent ID: 6235924
Filing Date: 2001-05-22
Classification: C07C

Abstract:
A method for preparing benzoic acid esters, said method comprising conducting a first reaction, at least one intermediate reaction, and a final reaction, whereinthe method for conducting said first reaction comprises:forming a first reaction mixture comprising(1) a mixture of carboxylic acids consisting essentially of benzoic acid and at least trace amounts of at least one compound selected from the group consisting of the three isomeric phthalic acids and phthalic anhydride; and(2) at least one alcohol selected from the group consisting of monohydric alcohols containing from 6 to 12 carbon atoms and dihydric alcohols containing from 2 to 8 carbon atoms, wherein the total number of moles of alcohol-bonded hydroxyl groups is equivalent to at least 1.02 times the number of moles of all carboxyl groups and carboxylic acid anhydrides present in said first reaction mixture;heating said first reaction mixture at the boiling point sufficiently to remove substantially all of the water generated as a by-product of the resultant reaction while maintaining a stoichiometric excess of said alcohol in said reaction mixture, and continuing said heating until substantially all of the carboxylic acids in said reaction mixture have reacted;distilling from said first reaction mixture under subatmospheric pressure substantially all unreacted alcohol and reaction products exhibiting a lower boiling point than said esters;distilling from said first reaction mixture under subatmospheric pressure substantially all benzoic acid esters and substantially none of any phthalic acid esters to form a first reaction residue;the method for conducting said intermediate reaction comprises:forming an intermediate reaction mixture comprising(1) a mixture of carboxylic acids consisting essentially of benzoic acid and at least trace amounts of at least one compound selected from the group consisting of the three isomeric phthalic acids and phthalic anhydride;(2) at least one alcohol selected from the group consisting of monohydric alcohols containing from 6 to 12 carbon atoms and dihydric alcohols containing from 2 to 8 carbon atoms, wherein the total number of moles of alcohol-bonded hydroxyl groups is equivalent to at least 1.02 times the number of moles of all carboxyl groups and carboxylic acid anhydrides present in said intermediate reaction mixture;(3) at least a portion of a residue selected from the group consisting of said first reaction residue and the residue from a preceding intermediate reaction;heating said intermediate reaction mixture sufficiently to remove substantially all of the water generated as a by-product of the resultant reaction while maintaining a stoichiometric excess of said alcohol in said intermediate reaction mixture, and continuing said heating until substantially all of the carboxylic acids in said intermediate reaction mixture have reacted;distilling from said intermediate reaction mixture under subatmospheric pressure substantially all unreacted alcohol and reaction products exhibiting a lower boiling point than said esters;distilling from said intermediate reaction mixture under subatmospheric pressure substantially all benzoic acid esters and substantially none of any phthalic acid esters to form an intermediate reaction residue; andthe method for conducting said final reaction comprisesforming a final reaction mixture comprising(1) a mixture of carboxylic acids consisting essentially of benzoic acid and at least trace amounts of at least one compound selected from the group consisting of the three isomeric phthalic acids and phthalic anhydride;(2) at least one alcohol selected from the group consisting of monohydric alcohols containing from 6 to 12 carbon atoms and dihydric alcohols containing from 2 to 8 carbon atoms, wherein the total number of moles of alcohol-bonded hydroxyl groups is equivalent to at least 1.02 times the number of moles of all carboxyl groups and carboxylic acid anhydrides present in said third reaction mixture; and(3) at least a portion of said intermediate reaction residue;heating said final reaction mixture sufficiently to remove substantially all of the water generated as a by-product of the resultant reaction while maintaining a stoichiometric excess of said alcohol in said final reaction mixture, and continuing said heating until substantially all of the carboxylic acids in said final reaction mixture have reacted;distilling from said final reaction mixture under subatmospheric pressure substantially all unreacted alcohol and reaction products exhibiting a lower boiling point than said esters; anddistilling from said final reaction mixture under subatmospheric pressure substantially all benzoic acid esters and substantially none of any phthalic acid esters.