Help needed: the pH value of crude methanol is very low, around 4. I’m using a Topsoe MK-121 catalyst; I hope experts can give me some advice
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Since the unit was put into operation, the pH value of crude methanol has remained around 4. I would appreciate it if experts could explain the reasons for this, suggest solutions, and discuss the impact on the system. Thank you.
There is a high amount of acid substances produced; it is likely due to system purging or gases. Is it wax formation?
The CO2 dissolved in crude methanol gives it an acidic character, and a pH of 4 is considered a relatively normal value. NaOH is added to the distillation system to adjust the pH value and prevent equipment corrosion.
It is mainly caused by the large amount of organic acids produced; distillation and the addition of alkali are used for adjustment
There was a period when wax formation was quite severe; after adjusting the hydrogen-to-carbon ratio and system pressure, the situation has improved a lot, but the pH value is still a bit low.
What is the amount of alkali added? Do not use no alkali, and certainly do not use too much alkali