Method for producing acetic acid

A method for producing acetic acid, the method comprising:

• a carbonylation reaction step of reacting methanol with carbon monoxide in the presence of:
• a catalytic system containing a metal catalyst and methyl iodide;
• acetic acid;
• methyl acetate;
• and water in a reactor to form acetic acid;
• a separation step of separating, using at least one selected from evaporators and distillation columns, a reaction mixture from the carbonylation reaction step into:
• a stream including the metal catalyst;
• an acetic acid stream rich in acetic acid;
• and
• a stream richer in a low boiling component than the acetic acid stream, the method optionally further comprising (i) condensing the stream rich in a low boiling component to obtain a condensed liquid and (ii) an acetaldehyde separation and removal system that is configured to separate, using a distillation column or columns, acetaldehyde from at least a portion of the condensed liquid,
• the method further comprising
• an absorption step of:
• supplying, to an absorption column, one or more offgas(es) selected from the group consisting of:
• an exhaust gas from the reactor;
• an exhaust gas from the evaporator or evaporators;
• an exhaust gas from the distillation column or columns in the separation step;
• and
• an exhaust gas from the distillation column or columns in the acetaldehyde separation and removal system;
• bringing the offgas into contact with an absorbent containing one or more liquids selected from the group consisting of a hydrocarbon, an ester of a carboxylic acid having 3 or more carbon atoms, an ester of a carboxylic acid and an alcohol having 2 or more carbon atoms, and an ether to allow the absorbent to absorb an iodine compound in the offgas, and separating into:
• a gas component having a lower iodine compound concentration than the offgas;
• and
• a solution containing the absorbent and the iodine compound,
• wherein the absorbent comprises a hydrocarbon.

A method for producing acetic acid, comprising:

• a carbonylation reaction step of reacting methanol and carbon monoxide in a reactor in the presence of a catalytic system, acetic acid, methyl acetate, and water to form acetic acid, the catalytic system including a metal catalyst and methyl iodide;
• an evaporation step of separating, using an evaporator, a reaction mixture from the carbonylation reaction step into:
• a vapor stream;
• and
• a residual liquid stream;
• a low-boiling component-removing step of subjecting the vapor stream to distillation and separating the vapor stream into:
• an overhead stream rich in a low boiling component;
• and
• a first acetic acid stream rich in acetic acid;
• and
• a dehydration step of subjecting the first acetic acid stream to distillation and separating the first acetic acid stream into:
• an overhead stream rich in water;
• and
• a second acetic acid stream richer in acetic acid than the first acetic acid stream,
• the method optionally further comprising:
• a high-boiling component-removing step of distilling the second acetic acid stream and separating the second acetic acid stream into:
• a bottoms stream rich in high boiling components;
• and
• a third acetic acid stream richer in acetic acid than the acetic acid stream before being subjected to the distillation;
• and/or
• (i) condensing the stream rich in a low boiling component to obtain a condensed liquid and (ii) an acetaldehyde separation and removal system that is configured to separate, using a distillation column or columns, acetaldehyde from at least a portion of the condensed liquid,
• the method further comprising:
• an absorption step of supplying, to an absorption column, one or more offgas(es) selected from the group consisting of:
• an exhaust gas from the reactor;
• an exhaust gas from the evaporator;
• an exhaust gas from the distillation column in the low-boiling component-removing step;
• an exhaust gas from the distillation column in the dehydration step;
• an exhaust gas from the distillation column in the high-boiling component-removing step;
• and
• an exhaust gas from the distillation column in the acetaldehyde separation and removal system;
• bringing the offgas into contact with an absorbent containing one or more liquids selected from the group consisting of a hydrocarbon, an ester of a carboxylic acid having 3 or more carbon atoms, an ester of a carboxylic acid and an alcohol having 2 or more carbon atoms, and an ether to allow the absorbent to absorb an iodine compound in the offgas;
• and
• separating into:
• a gas component having a lower iodine compound concentration than the offgas;
• and
• a solution containing the absorbent and the iodine compound,
• wherein the absorbent comprises a hydrocarbon.