| 摘要 |
PURPOSE:The contaminants in the crude methacrylic acid resulting from the catalytic gas-phase oxidation of isobutylene is treated with an aqueous bisulfite solution and a hydrazine to enable the purification of methacrylic acid into high purity. CONSTITUTION:The catalytic gas-phase oxidation of isoburylene, t-butanol, methacrolein or isobutyl aldehyde is carried out and the reactin mixture gas containing methacrylic acid from the oxidation reactor is condensed by cooling to give an aques methacrylic acid solution. At first, lower-boiling fractins are removed. Then, the extract containing methacrylic acid and the solvent which is recycled after the following treatment is combined with an aqueous bisulfite solution such as an alkali metal salt, then a hydrazine is added to the product at an arbitrary stage selected from solvent separation, low-boiling fraction separation, higher boiling fraction separation, and redistillation to effect the purification of methacrylic acid. A trace amount of contaminant causing coloration can be effectively removed.
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