The reason why methanol distillation wastewater is acidic
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These past two days, there have been some issues with our distillation system. The pH value at the bottom of the pre-tower is normally between 7 and 9, and the product obtained is of high quality. However, analyses show that the distillation wastewater is acidic; previously, such analyses indicated that the wastewater was alkaline with a pH level above 10. It’s not clear why it has become acidic now
Why isn’t anyone replying? Have everyone not encountered this situation? Yesterday, I conducted analyses at several different points in time; the pH value in the pre-treatment tower was around 7-8, while the distillation wastewater was acidic (with a pH of about 5.2). I then increased the amount of alkali added. Initially, the pH in the pre-treatment tower dropped and even became acidic, but it gradually increased afterward. Currently, the pH in the pre-treatment tower is 7-8, while the pH of the distillation wastewater has become alkaline, at around 9-10. But why does this phenomenon occur? Can anyone help explain it? !
Consider 2 or 3 towers as one system: the input is alkaline, the output product is acidic; the wastewater cannot be acidic, otherwise balance cannot be maintained. Check if there is any leakage of medium somewhere in the system. Continuously increasing the amount of alkaline solution may cause the pH to drop, due to lipid hydrolysis; however, it is impossible for the pH to become acidic. Please check your pH test strip. It’s best to use instruments if possible.
Pay attention to controlling the amount of fusel oils extracted from the three towers; if the situation you mentioned occurs, try to extract as much fusel oil as possible, as it is the fusel oils that cause acidity!
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What is the difference in the status of your synthesis system when posting messages compared to when it was functioning normally in the past? In terms of components, system pressure, hotspot temperature, temperature after water cooling, system circulation rate, etc.? I hope you can reply with the process and results of the solution
It’s normal; acid itself is considered a reconstituent component, and either too much or too little alkaline solution can lead to this phenomenon
How can one make a solution acidic if there is too much alkali in it? . . :sleepy:
Fats and alcohols undergo dehydration to form ethers under basic conditions, with hydrogen ions being produced. And generally, testing for pH involves measuring hydrogen ions, which is why it becomes acidic
Alkaline hydrolysis of lipids causes the pH to drop, but it cannot become acidic, as strong bases are stronger than weak acids.
My statement is incorrect; as the hydrogen ions increase, the pH value decreases