Patent ID: 7884237

Claim:
A method of making acetic acid while controlling aldehyde and aldehyde-derived impurities comprising: (a) carbonylating methanol or reactive derivatives thereof in a reactor of a production system in the presence of a Group VIII metal catalyst and a methyl iodide promoter while maintaining a concentration of water in the reactor of from 1-10% by weight of the reaction medium and concurrently maintaining in the reactor a predetermined partial pressure of carbon monoxide; (b) venting non-condensibles from the production system as to provide vent gas containing light ends and aldehyde impurity; (c) feeding the vent gas from the production system to an absorber tower; (d) supplying a scrubber solvent to the absorber tower, the scrubber solvent comprising acetic acid, methanol, methyl acetate or mixtures thereof; (e) contacting the vent gas with the scrubber solvent thereby removing light ends and aldehyde impurity from the gas and absorbing into the scrubber solvent; (f) stripping absorbed light ends and aldehyde impurity from the absorber solvent to provide a vent-recovered light ends stream having more than 1 percent acetaldehyde by weight; (g) purifying the vent-recovered light ends stream to remove aldehyde impurity; and (h) recycling purified light ends from the vent-recovered light ends stream to the production system.