Process for the purification of a dimethylphenol isomer
US5094722A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 16, 1990 |
| Grant date | Mar 10, 1992 |
| Priority date | — |
| Expiry date | Aug 16, 2010 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C37/84
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
A purified desired isomer which is either 3,4- or 3,5-dimethylphenol is separated with a high yield from a dimethylphenol-containing fraction which contains both 3,4- and 3,5-dimethylphenols. The fraction is distilled so as to give a distillate which is enriched with the desired dimethylphenol isomer to be separated and which contains at least 35% by weight of the desired isomer. The desired DMP isomer is crystallized from a melt of the enriched distillate in two stages with at least part of the filtrate separated from the precipitated crystals in the second crystallization stage being circulated to the first crystallization stage. The enriched distillate is introduced into the first crystallization stage when it contains the desired isomer in a concentration of from 35% to less than 70% by weight, or it is introduced into the second crystallization stage when it contains the desired isomer in a concentration of 70% by weight or higher.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.