Process for the recovery of acetic acid from compositions comprising acetic acid and water

Claim 2

The use as claimed in claim 1 in which the composition comprising acetic acid and water is subjected to elevated temperature and pressure and then introduced, together with or separately from the iodide compound, into a flash zone from which the vapour phase and liquid phase are withdrawn separately.

Claim 3

The use as claimed in claim 1 in which the composition comprising acetic acid and water is introduced into a fractional distillation zone comprising one or more separation stages, together with, or separately from, the iodide compound; lower boiling components of the composition are recovered as a head product stream from the distillation zone; higher boiling components of the composition are recovered as a base product stream and at least a portion of the acetic acid together with part of the water from the composition is recovered at a point above the base of the distillation zone.

Claim 4

The use as claimed in any one of the preceding claims in which the composition comprising acetic acid and water comprises the liquid reaction composition from a carbonylation process for the production of acetic acid.

Claim 5

The use as claimed in any one of the preceding claims in which the iodide compound comprises hydrogen iodide, calcium iodide, lithium iodide, aluminium iodide, potassium iodide and/or sodium iodide.

Claim 6

The use as claimed in any one of the preceding claims in which the iodide compound is formed in situ in the composition or liquid phase.

Claim 7

The use as claimed in any one of claims 1 to 5 in which the iodide compound is added to the composition prior to partitioning into vapour and liquid phases.

Claim 8

The use as claimed in any one of the preceding claims in which the composition is partitioned into vapour and liquid phases at a temperature in the range 50°C to 300°C.

Claim 9

The use as claimed in any one of the preceding claims in which the composition is partitioned into vapour and liquid phases at a pressure in the range 0.1 bara to 50 bara.

Claim 10

A process for recovering acetic acid from a liquid composition comprising acetic acid and water by the steps of (a) subjecting the composition to conditions of temperature and pressure to produce a vapour phase comprising at least a portion of the acetic acid in the composition and a liquid phase comprising the remaining portion of the acetic acid in the composition and (b) separating the vapour and liquid phases characterised in that the liquid phase further comprises, one or more iodide compounds of the elements of Group IA or Group IIA of the Periodic Table of the Elements or of hydrogen or aluminium to suppress the volatility of the water relative to the acetic acid.

Claim 11

A process as claimed in claim 10 in which the composition comprising acetic acid and water is subjected to elevated temperature and pressure and then introduced, together with or separately from the iodide compound, into a flash zone from which the vapour phase and liquid phase are withdrawn separately.

Claim 12

A process as claimed in claim 10 in which the composition comprising acetic acid and water is introduced into a fractional distillation zone comprising one or more separation stages, together with, or separately from, the iodide compound; lower boiling components of the composition are recovered as a head product stream from the distillation zone; higher boiling components of the composition are recovered as a base product stream and at least a portion of the acetic acid together with part of the water from the composition is recovered at a point above the base of the distillation zone.

Claim 13

A process as claimed in any one of claims 10 to 12 in which the composition comprising acetic acid and water comprises the liquid reaction composition from a carbonylation process for the production of acetic acid.

Claim 14

A process as claimed in any one of claims 10 to 13 in which the iodide compound comprises hydrogen iodide, calcium iodide, lithium iodide, aluminium iodide, potassium iodide and/or sodium iodide.

Claim 15

A process as claimed in any one of claims 10 to 14 in which the iodide compound is formed in situ in the composition or liquid phase.

Claim 16

A process as claimed in any one of claims 10 to 14 in which the iodide compound is added to the composition prior to partitioning into vapour and liquid phases.

Claim 17

A process as claimed in any one of claims 10 to 16 in which the composition is partitioned into vapour and liquid phases at a temperature in the range 50°C to 300°C.

Claim 18

A process as claimed in any one of claims 10 to 17 in which the composition is partitioned into vapour and liquid phases at a pressure in the range 0.1 bara to 50 bara.

Claim 19

A process for the production of acetic acid which comprises: a) reacting methanol, methyl iodide, methyl acetate and/or dimethyl ether with carbon monoxide in the liquid phase in a reaction zone in the presence of a carbonylation catalyst and at least a finite amount of water at a temperature of 50 to 400°C and a carbon monoxide pressure of 1 to 15000 psig to produce acetic acid, b) withdrawing liquid reaction composition from the reaction zone, c) introducing the liquid reaction composition into a flash zone at a pressure below that of the reaction zone with or without additional heating to produce a vapour phase comprising a portion of the acetic acid carbonylation product and water and a liquid phase, d) introducing to the flash zone together with or separately from the liquid reaction composition, one or more iodide compounds of the elements of Group IA or Group IIA of the Periodic Table of the Elements or of hydrogen or aluminium to suppress the volatility of the water relative to the acetic acid, and e) separately removing from the flash tank the vapour phase and the liquid phase.