| 摘要 |
1376452 Two-stage crystallization DYNAMIT NOBEL AG 12 Nov 1971 [14 Nov.1970] 52786/71 Heading B1G [Also in Division C2] Dimethyl terephthalate is purified by a continuous two-stage process by passing a solution of dimethyl terephthalate in methanol through a seed-forming apparatus in which the solution is cooled to a temperature of from 100 to 88‹C to supersaturate the solution and for a time sufficient to form seed crystals of grain size from 10 to 130Á, and then passing the seedcontaining solution through a crystal growth apparatus where the seed crystals form crystals of larger grain size. The seed-form and crystal-growth apparatus are preferably both thin layer condensers and the cooling surface in the crystallizer is cleaned by scrapers attached to a rotating shaft. As shown a solution in methanol of the terephthalate is passed through input 9 into container 1, from where it passes into a tubular crystallizer 3 regulated by a coolant which enters the crystallizer at 10 and leaves at 11. The seed-containing solution on leaving 3, immediately enters at 5 crystalgrowth scraping condenser 6, provided with a jacket for coolant entering at 12 and leaving at 13. The crystal slurry leaves the scraper at 7 and passes to centrifuge 8 from which the crystals are recovered at 14 and the solvent at 15. |
