1. A potentiometric titration method for testing the acid value of industrial Purified Terephthalic Acid (PTA) is characterized by selecting a PTA acid value testing method on a potentiometric titrator.

2. The potentiometric titration test method according to claim 1, wherein the titration is carried out with 0.5mol/L sodium hydroxide standard solution until the potentiometric breakthrough point is the end point.

Background

In the current petrochemical industry and national standards, the PTA acid value test adopts a manual titration method, PTA is used as a main raw material in the polyester production process, the quality has a very important influence on the production, the existing test method always adopts a terminal point when dropping and shaking to light purple are carried out and the color is kept unchanged for 30 seconds, and the error is relatively large.

Disclosure of Invention

The invention aims to provide a potentiometric titration test method for acid value of industrial Purified Terephthalic Acid (PTA), which has relatively small error, no misjudgment of a terminal point and high accuracy.

The technology of the invention comprises the following steps: potentiometric titration test method for acid value of industrial Purified Terephthalic Acid (PTA)

The required reagents: sodium hydroxide Standard titration solution C_NaOH=0.5mol/L, dimethyl sulfoxide, AR grade; absolute ethanol, AR grade; 1g/L phenolphthalein indicator: 0.1g phenolphthalein was dissolved in ethanol and diluted to 100 mL.

The required instrumentation: G20S potentiometric titrator + water phase pH glass electrode, 5 special 100mL sample cups, 20mL liquid 2 in the bottle mouth.

The method comprises the following operation steps: the weighed PTA powder is dissolved in dimethyl sulfoxide and titrated by 0.5mol/L sodium hydroxide standard titration solution. The method is characterized by comprising the steps of accurately weighing 0.8 +/-0.01 g (accurately to 0.0001 g) of sample powder, putting the sample powder into a 100mL sample cup, adding 20mL of dimethyl sulfoxide into the sample cup, shaking the sample cup until PTA is basically dissolved, adding 20mL of carbon dioxide-free water, adding 0.1mL of phenolphthalein indicating solution, fixing the sample on an instrument sample rack, selecting a PTA measuring method on the instrument, automatically titrating to a potential jump point by using a 0.5mol/L sodium hydroxide standard solution instrument, automatically identifying a terminal point, measuring a blank sample by using an instrument under the same condition, automatically calculating the result value by using a custom formula, washing an electrode by using absolute ethyl alcohol after the test is finished, wiping the electrode by using filter paper, and storing the electrode in an electrode sheath containing dimethyl sulfoxide for later use.

Compared with the prior art, the method has the following improved effects: relative error: less than or equal to 0.5mg/g, high accuracy and safe and convenient operation.