Patent ID: 11884617
Assignee: DAICEL CORPORATION
Field: Organic fine chemistry (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 5:
6. A method for producing acetic acid, the method comprising:
a carbonylation step of reacting methanol with carbon monoxide in a continuous system in the presence of a catalytic system, acetic acid, methyl acetate, and water, the catalytic system including a metal catalyst and methyl iodide,
an evaporation step of separating, in an evaporator, a reaction mixture from the carbonylation step into:
a vapor stream, and
a residue stream; and

a light ends-removing step of:
separating, by distillation in a first distillation column, the vapor stream into:
an overhead stream rich in at least one light end selected from methyl iodide and acetaldehyde, and
an acetic acid stream rich in acetic acid; and

subjecting the overhead stream sequentially to condensation and to a liquid-liquid separation in a decanter, to form:
an aqueous phase, and
an organic phase;

wherein, in the evaporation step, the residue stream is recycled to the two or more parallel reactors;
wherein the reactor or reactors are each operated where at least one of following conditions (a) to (c) is met:
(a) two or more reactors are used in parallel, and only one evaporator is used;
(b) the evaporator includes two or more evaporators disposed in parallel and coupled respectively to the two or more parallel reactors, and only one first distillation column is used; and
(c) the method comprising a dehydration step of subjecting the acetic acid stream from the light ends-removing step to a distillation treatment in a second distillation column so as to further purify acetic acid, wherein
the evaporator comprises two or more evaporators disposed in parallel and coupled respectively to the two or more parallel reactors;
the first distillation column comprises two or more distillation columns disposed in parallel and coupled respectively to the two or more parallel evaporators; and
only one second distillation column is used;

wherein a variation in acetic acid space time yield in the carbonylation step is held within ±40% when an acetic acid production volume is reduced down to a range of from 30% to 90%,
wherein the carbonylation step employs two or more reactors disposed in parallel,
wherein the acetic acid production volume is reduced by decreasing the number of reactors in operation, and
wherein the following conditions are met regardless of the number of reactors in operation:
variations in metal catalyst concentration and methyl iodide concentration in the reactor or reactors in operation fall within ±50%; and
a variation in reaction temperature in the reactor or reactors in operation falls within ±20° C.