Ethanol specifications in the national standards for pure methanol
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What is the basis for the national standard specifying that the ethanol content in pure methanol should be less than 200 ppm? Why 200ppm?
Personal opinion: Methanol has a boiling point of 64.7°C, while ethanol’s is 78.4°C. The two are mutually soluble and have boiling points that are close to each other; moreover, the temperature at the top of the distillation tower is usually around 73–75°C. Therefore, ethanol is inevitably present in refined methanol. If excessive purity is sought for refined methanol, it not only increases the complexity of the processing but also imposes high demands on the tower equipment, which is not cost-effective. A small amount of ethanol in refined methanol does not affect its functional properties. Based on these considerations, the optimal level of ethanol content in refined methanol is determined to be 200 ppm as a benchmark.
Agree with what was said above; in the past, for monoalcohol manufacturers, the standard products obtained through two-column distillation were those that met national standards.
GB338-2011 does not specify any requirements for ethanol in methanol; it is determined through negotiation between the parties.
Currently, the process for producing acetic acid from methanol has requirements regarding the ethanol content in order to reduce the formation of propionic acid. However, the hydrogen content in the feed gas carbon monoxide has a greater impact on the amount of propionic acid produced.
The main thing is to choose the right catalyst
I came up with this strategy: add a small secondary column to the atmospheric distillation column for the refined product, and collect the ethanol that accumulates in the other columns in the atmospheric distillation column.
It seems that national standards don’t impose any requirements; the two parties can negotiate it