Abstract: A distillation column reactor which provides a relatively long residence time with a minimum drop in pressure which comprises a distillation column containing standard trays with downcomers, a liquid reservoir between the trays, and vapor ports provided through said reservoir, whereby liquid from said downcomers enters said reservoir thereby providing increased liquid residence time in said column.

Abstract: A process for making terephthalic acid of high purity by feeding an aqueous equilibrium hydrolysis solution of terephthalonitrile to a reactive distillation column operated at a temperature of from about 200.degree. C to about 260.degree. C at autogenous pressure where the equilibrium solution is subjected simultaneously to further hydrolysis and distillation of ammonia while maintaining the concentration of aromatic materials in the aqueous liquid in said column sufficiently high to effect precipitation of dissolved terephthalic acid, removing the water vapor and ammonia from the top of the column, subjecting bottoms product in said column to further hydrolysis and distillation in a reboiler, returning vapor from the reboiler to the distillation column, removing an aqueous slurry of terephthalic acid from the reboiler and separating terephthalic acid product.

Abstract: A process for making an aromatic carboxylic acid of high purity by feeding an essentially equilibrium hydrolysis mixture of an aromatic nitrile to a reactive distillation column operated at a temperature of from about 200.degree. C. to about 325.degree. C. at autogenous pressure where the equilibrium mixture is subjected simultaneously to further hydrolysis and distillation of ammonia, removing water vapor and ammonia from the top of the column, subjecting remaining equilibrium hydrolysis mixture to further hydrolysis and distillation in a reboiler, returning vapor from the reboiler to the distillation column, removing an aqueous solution of product acid from the reboiler, cooling said separated solution, separating acid product, and in order to improve product purity, returning the aqueous filtrate from said separated acid product to a lower portion of said column.