Why does the boiling range of methanol increase after long-term storage in tanks?
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Our factory uses methanol to produce esters. Due to a prolonged shutdown for maintenance (6 months), upon restarting operations, it was found that the boiling range of the methanol stored in the tanks had increased from ≤0.8 (at 0 degrees, 101325 Pa, within the range of 64–65.5) to 2.9. At the same time, the water content increased from ≤0.1 to 0.29. We would appreciate it if experts could analyze the reasons for these changes in the quality of the methanol stored in these tanks, determine what type of impurities are present, and advise whether it can still be used in the production of esters. (Due to manufacturing processes, the ethanol content in methanol is strictly controlled. If an increase in the boiling range is caused by excessive ethanol levels, is it possible to estimate the ethanol content based on the extent of that increase in boiling range?) ) I would be extremely grateful for your guidance!
This is likely an oxidation reaction, with methanol producing formaldehyde, formic acid, and other substances. The ethanol content will not increase; it may decrease due to oxidation. I think it’s okay to continue using it as a lipidation raw material.
It is possible that long-term storage has caused the top of the large tank to be exposed to air, allowing heat exchange; as a result, some of the moisture in the air was condensed and absorbed into the tank
I wonder what type of storage tanks you have? If the tank is well-sealed, has a vent valve on its top, and is protected by nitrogen, this situation should not occur ； If the methanol in the tank may come into contact with outside air, the moisture in that air is very likely to dissolve into the methanol, thereby causing the boiling point and water content to exceed acceptable levels
It is possible that prolonged storage has caused the top of the large tank to be exposed to air, allowing heat exchange to occur; as a result, some of the moisture in the air was condensed and absorbed into the tank, leading to oxidation processes in which methanol was converted into formaldehyde, formic acid, and other substances. This leads to an increase in water content.
It is likely that long-term storage has caused the top of the large tank to be exposed to air, leading to reactions that result in the condensation of some of the moisture in the air and its absorption into the tank. This leads to oxidation processes, during which methanol is converted into formaldehyde, formic acid, and other substances. This leads to an increase in water content. The reason is the lack of effective inert gas isolation measures. :)
Methanol evaporates rapidly; if it is left for an extended period, the moisture content will definitely exceed the limit. Pay attention to nitrogen protection to reduce losses.
What was said upstairs is right – water is everywhere, and so is oxygen. -There is still water to evaporate after 50 times
First of all, I would like to thank everyone above for their generous help. I conducted a chromatographic analysis today, and the butanol content was 1%. In that case, we need to consider the possibility of methanol being contaminated as a result of tank transfer during maintenance. I also would like to ask: how can we determine what kinds of impurities are present in methanol when its boiling range is above the specified limit, and what are their concentrations?
100 ML of methanol is taken in a test tube for distillation in order to determine the impurity content; a temperature range of 64.5–65.5°C serves as the threshold for pure methanol, allowing the impurity level in the methanol to be determined; the composition remains undetermined
But try using chromatography to determine the contents of ethanol, butanol, etc., and using Fehling’s reagent to determine the water content. One can only guess what’s inside and then verify it. An excessive boiling range is likely due to excess water; it may be caused by water absorption or oxidation. In short, the nitrogen protection is insufficient
An excessive boiling range of methanol could be due to either light components or heavy components. How can we determine more accurately which type of component is responsible? How can one determine whether it is a heavy component or a light component based solely on the boiling range value? Thank you for the advice
This issue has been resolved. Thank you to everyone upstairs!
Won’t something similar happen if proper nitrogen protection is in place? It’s mainly your negligence–you thought that nothing would change in the methanol inside the tank after parking it! Just be careful once you notice the problem
Our methanol storage tanks do not have a nitrogen protection system; they are equipped with internal floating roofs. I wonder if a similar situation could occur? If it is stored for a long time, the system should be shut down – where does the nitrogen come from?