| 摘要 |
<p>In a process for the purification of a polyhydric alcohol containing at least three methylol groups per molecule by fractional distillation under reduced pressure, the crude alcohol is purified, e.g. by treatment with an ion-exchange material, before it is submitted to distillation. The process is particularly suitable for the purification of 1,1,1-trimethylol-propane obtained by reacting formaldehyde with butyraldehyde in the presence of alkali. The reaction product is evaporated to a high degree, and alkali formate crystals are then separated from the alcohol by centrifuging. After treatment with ion-exchange material, the alcohol is sumitted to batch distillation at a temperature of not more than 180-190 DEG C. using a column maintained at a pressure of 5 mm. Hg or less. Two prefractions are distilled over, and then the main alcohol fraction is collected while the refractive index of the distillate is between 1.467 and 1.469. The prefractions and afterfraction may be returned to the still with a following charge. The residue in the still is preferably removed after each third batch. The process may also be used for the purification of 1,1,1-trimethlol-ethane, 2,2,6,6-tetramethylolcyclohexanol and 4 - hydroxy - 3,3,5,5 - tetramethylol - tetrahydropyran.ALSO:In a process for the purification of a polyhydric alcohol containing at least three methylol groups per molecule by fractional distillation under reduced pressure, the crude alcohol is pre-purified, e.g. by treatment with an ion-exchange material, before it is submitted to distillation. The process is particularly suitable for the purification of 1, 1, 1-trimethylolpropane obtained by reacting formaldehyde with butyraldehyde in the presence of alkali. The reaction product is evaporated to a high degree, and alkali formate crystals are then separated from the alcohol by centrifuging. After treatment with ion-exchange material, the alcohol is submitted to batch distillation at a temperature of not more than 180 DEG -190 DEG C. using a column maintained at a pressure of 5 mm. Hg. or less. Two prefractions are distilled over, and then the main alcohol fraction is collected while the refractive index of the distillate is between 1.467 and 1.469. The prefractions and after-fraction may be returned to the still with a following charge. The residue in the still is preferably removed after each third batch. The process may also be used for the purification of 1, 1, 1-trimethylolethane, 2, 2, 6, 6-tetramethylolcyclohexanol, and 4-hydroxy-3, 3, 5, 5-tetramethylol-tetrahydropyran.</p> |
