Processes for purifying acetic and hydrating anhydride
AssigneeCelanese International Corporation
InventorsRonald D. Shaver, Yaw-Hwa Liu, Mark O. Scates
Life of this patent
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Abstract
Processes for purifying acetic acid by distilling a process in a column in which acetic anhydride is formed in the lower portion of the column. The product stream withdrawn from the column comprises acetic acid, water at a concentration of no more than 0.2 wt. %, and acetic anhydride at a concentration of no more than 600 wppm. The process further comprises hydrating the acetic anhydride in the product stream to form a purified acetic acid product comprising acetic anhydride at a concentration of no more than 50 wppm.
Claims20
A process for purifying acetic acid, comprising:
- a. distilling a process stream in a column, the process stream comprising acetic acid at a concentration of greater than 90 wt. %, water at a concentration from 1 to 3 wt. %, one or more C1-C14 alkyl iodides in a total concentration of no more than 6 wt. %, and methyl acetate at a concentration of no more than 6 wt. %;
- b. forming acetic anhydride in a lower portion of the column;
- c. withdrawing a product stream from the lower portion of the column, the product stream comprising acetic acid, water at a concentration of no more than 0.2 wt. %, and acetic anhydride at a concentration of no more than 600 wppm;
- and
- d. hydrating the acetic anhydride in the product stream to form a purified acetic acid product comprising acetic anhydride at a concentration of no more than 50 wppm.
A process for producing acetic acid comprising:
- a. carbonylating, in a reactor, at least one member selected from the group consisting of methanol, dimethyl ether, and methyl acetate in a reaction medium comprising water at a concentration from 0.1 to 14 wt. %, a rhodium catalyst, methyl iodide, and an iodide salt;
- b. separating the reaction medium to form a liquid recycle stream and a vapor product stream;
- c. distilling at least a portion of the vapor product stream in a first column to obtain a side stream comprising acetic acid at a concentration greater than 90 wt. %, water at a concentration from 1 to 3 wt. %, one or more C1-C14 alkyl iodides in a total concentration of no more than 6 wt. % and methyl acetate at a concentration of no more than 6 wt. %;
- d. distilling the side stream in a second column to obtain a product stream comprising acetic acid, water at a concentration of no more than 0.2 wt. % and acetic anhydride at a concentration of no more than 600 wppm;
- and
- e. contacting the product stream with a cation exchange resin to form a purified acetic acid product comprising no more than 50 wppm acetic anhydride.
Dependencies are inferred from the claim text.