Patent ID: 7989659
Filing Date: 2011-08-02
Classification: B01D,C07C

Abstract:
1. A carbonylation process for producing acetic acid comprising: (a) carbonylating methanol or its reactive derivatives in the presence of water, a catalyst selected from rhodium catalysts, iridium catalysts and mixtures thereof, and a methyl iodide promoter to form an acetic acid reaction mixture in a reactor; (b) separating the stream of the acetic acid reaction mixture into is liquid recycle stream and a crude product stream including acetic acid, methyl iodide, methyl acetate and water; (c) feeding the crude product stream to a light ends column having a distillation zone including an upper portion, a lower portion and a central portion provided with a product sidedraw, wherein the crude product stream is fed to the light ends column as a hot vapor at the lower portion thereof; (d) purifying the crude product stream in the distillation zone of the light ends column to remove methyl iodide and methyl acetate and generate a purified product stream, the purified product stream having a lower concentration of methyl iodide and methyl acetate than the crude product stream, and wherein the step of purifying the crude product stream includes (i) condensing overhead vapor from the upper portion of the distillation one of the light ends column, (ii) returning at least a portion of the condensed overhead vapor as liquid reflux to the distillation zone of the light ends column, and (iii) condensing vapor from the central portion of the distillation zone of the light ends column at a level above the level of the product sidedraw in a second condenser, and feeding the condensed liquid back into the light ends column at a point above the liquid sidedraw such that the hydraulic load on the light ends column is reduced in the column above the liquid sidedraw as compared to a substantially identical light ends column without a second condenser operated under substantially identical conditions; and (e) drawing a purified product stream from the sidedraw of the light ends column, wherein the purified product stream is drawn from the light ends column at a mass flow rate, R, and vapor from the central portion of the light ends column is condensed in the second condenser at a rate of 0.05R to 0.5R, and wherein the purity of the purified product stream produced using the light ends column having the second condenser at the reduced hydraulic load on the hot ends column is substantially identical to the purity of a purified product stream produced using a substantially identical light ends column without said second condenser when operated under substantially identical conditions.