| 摘要 |
Methacrylic acid is produced from acetone cyanohydrin by a process involving reaction with sulfuric acid in presence of an inert polar solvent to give easy stirring, conversion of the amide sulfate-containing product to yield alpha -hydroxyisobutyric acid (HIBA) and distillation of the HIBA in presence of an HIBA metal salt. - Production of methacrylic acid comprises - (1) reacting acetone cyanohydrin at below 80 deg. C with a maximum of 1.2 equivalents of sulfuric acid in presence of water (0.05-1.0 equivalents) and an inert polar solvent forming under the reaction conditions an easily stirrable solution of the corresponding amide sulfate in the solvent; - (2) after adding water converting the solution in presence (or after removal) of the inert solvent to a solution containing water, ammonium hydrogensulfate and alpha -hydroxyisobutyric acid (HIBA); - (3) separating off the HIBA by extraction using a suitable agent; - (4) removing the extractant and distilling the high concentration of hydroxyisobutyric acid liquid in presence of a metal salt of HIBA at 160-300 deg. C to give a distillate mixture containing methacrylic acid and water; and - (5) distillatively recovering the methacrylic acid in highly pure form or using the product mixture (methacrylic acid + water) from step (4) as an extractant for the HIBA isolation in step (3) and then separating the valuable products distillatively.
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