U.S. standards for methanol

I. High-quality three-column distillation process: If the goal is simply to reduce the ethanol content in purified methanol, even to a purity level of 99.95%, foreign countries have long since improved the distillation processes for crude methanol; for example, the three-column process for producing high-purity methanol described in U.S. patents. The characteristic of this process is that the three columns operate at essentially constant pressure, with the product being obtained from the third distillation column. The key is to separate water from Tower 2, ensuring that the water content in the distillate at the top of Tower 2 (which serves as the feed for Tower 3) is low, in order to reduce the water content in the bottom liquid of Tower 3; this content is generally around 10%, with a requirement that it be less than 50%. Due to the very low water content in the liquid from column 3, with methanol being the predominant component, ethanol and the remaining high-boiling-point impurities can be concentrated; only a small amount of liquid taken from the bottom of the column is sufficient to remove ethanol. In this way, the ethanol content in the refined methanol can be