Patent ID: 7652167

Claim:
A process for the continuous esterification of a hydroxylated organic acid to produce an organic acid ester in vertical columns by reactive distillation comprising: (a) feeding a mixture of a hydroxylated organic acid comprising about 10 to 50% water by weight and comprising the organic acid having between 2 to 8 carbon atoms into an upper port of a first continuous multistage reactive distillation column and an alcohol having 1 to 8 carbon atoms into a lower port of the first reactive distillation column; (b) contacting in the first continuous multistage reactive distillation column, the organic acid and the alcohol in countercurrent flow in a reaction zone between the ports at a temperature which reacts the organic acid and the alcohol over an acidic ion exchange resin as a catalyst mounted in structured packing elements and supported as a single unit of the elements in the first reactive distillation column within the reaction zone to form the organic acid ester; (c) removing vaporized unreacted alcohol and water from the top of the first reactive distillation column; (d) collecting a product stream comprising the organic acid ester, unreacted organic acid, and byproducts selected from the group consisting of organic acid dimers, trimers and oligomers, and organic acid ester dimers, trimers, and oligomers, and combinations thereof from the bottom of the column, wherein the product stream is partially reboiled by a heat exchanger at the bottom of the reactive distillation column so as to heat the organic acid and the alcohol in the reaction zone; (e) separating the organic acid ester from the unreacted organic acid and the byproducts in a separation column, wherein the organic acid ester is removed through the top of the separation column and the unreacted organic acid and the byproducts are removed through the bottom of the separation column; and (f) reacting the byproducts from the separation column in a second reactive distillation column to at least partially form the organic acid, wherein the organic acid formed in the second reactive distillation column is recycled back to the first reactive distillation column so that the organic acid formed can react with the alcohol to form the organic acid ester when recycled into the first reactive distillation column.