Process for recovering halogen promoters and removing permanganate reducing compounds

摘要

This invention relates to processes for producing acetic acid and, in particular, to improved processes for recovering C2+ alkyl halides and removing permanganate reducing compounds formed during the carbonylation of methanol in the presence of a Group VIII metal carbonylation catalyst to produce acetic acid.

主权项

1. A process for removing permanganate reducing compounds (PRC's) from a crude acetic acid composition, the process comprising the steps of:
separating the crude acetic acid composition in a light ends column into an overhead vapor stream comprising halogen promoter, water, acetic acid, methyl acetate and at least one PRC, and an acetic acid product stream; condensing and biphasically separating the overhead vapor stream into a heavy phase and a light phase; separating the light phase in a distillation column into an overhead PRC stream and a bottoms stream, wherein the overhead PRC stream is enriched with PRC with respect to the bottoms stream; condensing the overhead PRC stream and extracting with a first extractant in a first extractor the condensed overhead PRC stream to obtain a first aqueous stream comprising water, halogen promoter and at least one PRC, and a first raffinate comprising methyl acetate; and extracting with a second extractant in a second extractor the first aqueous stream to obtain a second raffinate comprising water and at least one PRC, and an extract stream comprising halogen promoter, and the second extractant; wherein the second extractant comprises a C6 to C16 alkane.