| 摘要 |
The reaction mixture is evaporated and cooled to give pentaerythritol crystals which are then separated and dissolved in an aqueous mother liquor comprising pentaerythritol. The solution is purified and monopentaerythritol is crystallized and separated from the remaining mother liquor. A method for preparing high purity monopentaerythritol (I) comprises reacting formaldehyde (II) with acetaldehyde (III) in aqueous solution and in the presence of a strongly basic hydroxide, preferably an alkali(ne earth) metal hydroxide, at a molar ratio (II)/(III) of 5-10:1, preferably 6-9:1, and then neutralizing the reaction mixture. The reaction mixture is evaporated to a solids content of 50-70 wt.%, cooled and the pentaerythritol crystals are separated, preferably using a filter belt or centrifuge, and dissolved to a concentration of 35-55 wt.% in an aqueous mother liquor comprising pentaerythritol. The solution is purified and (I) is crystallized at 40-90 (45-80)[deg]C and separated from the remaining mother liquor, which is recycled. An independent claim is also included for (I) prepared by this method, which has a purity of more than 99 (99.3-99.9) wt.%. |
