I’d like to ask everyone! Problems encountered in the distillation separation of acetic anhydride
Thread Content
This post was last edited by lxzzl on 2009-5-27 at 15:02. The laboratory is conducting experiments on the distillation and separation of acetic acid and acetic anhydride; acetic acid comes out of the top of the tower, while acetic anhydride comes out of the bottom. Recently, a strange phenomenon has occurred: the acetic acid content in the liquid coming from the top of the tower is lower than that of the samples taken from the upper sections of the tower. The acetic acid content at the top is around 95%, whereas it remains at 98% in the upper sections. This is quite confusing. Which expert can help me deal with this problem on my chin? Thank you
This post was last edited by lxzzl on 2009-5-27 at 15:03. An analysis shows that there may be light components present, which is why the situation you described occurs.
In 2# rhdhuo, the raw materials consist only of acetic acid and acetic anhydride; acetic acid is the light component. The liquid coming out of the top of the tower is analyzed after a certain amount has accumulated, using gas chromatography. In the middle and upper sections of the tower, samples are taken directly for analysis. Is it possible that in the initial stages, only acetic acid reached those sections, but over time acetic anhydride also made its way up to the top of the tower, resulting in a decrease in the acetic acid content there? But we conducted 6 rounds in a row, and the result was consistently low tower top content.
Is the full reflux time at the tower top too short, preventing the product from entering the receiving vessel right from the start? The total reflux time is over 30 minutes; is the reflux ratio too low? Acetic acid is extracted and analyzed under appropriate reflux.
For 4# rhdhuo, the reflux ratio we chose is 10:1. We conducted many rounds of experiments; if the first sample was not very stable, the subsequent samples should be more stable. Could it be that there are too many theoretical plates, resulting in high levels already reached in the middle and upper sections of the column? Is that possible?
It seems that the anhydride that should have been carried to the middle section is missing. During testing, this missing anhydride reacts with water to form acetic acid, thereby increasing the concentration of acetic acid. It’s also possible that a small amount of water is dissolved in the acetic acid at the top, and this is the cause!
There cannot be any water in this mixture system.