Patent ID: 9561994
Date: 2017-02-07
CPC Classifications: C07C

Claim:
1. A process comprising: carbonylating at least one member selected from the group consisting of methanol, dimethyl ether, and methyl acetate in the presence of 0.1 to less than 14 wt. % water, a rhodium catalyst, methyl iodide and lithium iodide, to form a reaction medium comprising acetic acid in a reactor; separating the reaction medium into a liquid recycle stream and a vapor product stream; separating the vapor product stream in up to 2 distillation columns in a primary purification train to produce a crude acid product comprising acetic acid comprising up to 10 ppm lithium cations; contacting the crude acetic acid product with a first purification resin comprising a cationic exchanger in the acid form within a first treatment device to produce an intermediate acid product having a lithium ion concentration of less than 50 ppb; and contacting the intermediate acetic acid product with a second purification resin comprising a metal-exchanged ion exchange resin having acid cation exchange sites within a second treatment device to produce a purified acetic acid stream; the first treatment device, the second treatment device, or both individually comprising at least one sampling port disposed through a side of the treatment device comprising a first open flow path between a sample inlet located within the treatment device and a first flow control element located external to the treatment device, which is operable between an open and a closed position to obtain a sample of the resin proximate to the sample inlet, and a second flow path comprising a porous element disposed between the sample inlet and a second flow control element located external to the treatment device, which is operable between an open and a closed position to obtain a sample of only the liquid proximate to the sample inlet; opening the first flow control element to obtain a sample of the purification resin at a point in the treatment device proximate to the sample inlet of the corresponding sample port; determining a concentration of an impurity in the sample of the purification resin; comparing the impurity concentration of the sample to a previously determined impurity concentration value; and determining if the impurity concentration of the sample indicates exhaustion of the purification resin at the point in the treatment device proximate to the sample inlet.