Diethanolamine melting points

Temperature-dependent data have been selected for 25°C as far as available in these sources, unless the solvent is not liquid at this temperature. Such solvents, from among the List, are /-butanol (No. 310), c-hexanol (No. 360), -dodecanol (No. 390), 1,4-butanediol (No. 540), phenol (No. 590), 2-methylphenol (No. 600), 4-methyl- phenol (No. 620), 2-methoxyphenol (No. 630), 3-chlorophenol (No. 650), phenyl-acetone (No. 1060), / -methylacetophenone (No. 1070), benzophenone (No. 1090), ethylene carbonate (No. 1350), diethanolamine (No. 1940), 2-cyanopyridine (No. 2040), N-methylacetamide (No. 2240), di- -butylsulfoxide (No. 2410), sulfolane (No. 2420) hexamethyl thiophosphoramide (No. 2520), hydrogen fluoride (No. 2540), ammonia (No. 2560), and sulfur dioxide (No. 2580). Several of these have melting points sufficiently close to 25°C, so that they are readily used in the slightly supercooled state, and values for this... 

When pure, diethanolamine is a crystalline, white solid which has a melting point of 28 C., or just above room temperature. The commerciol materiol has a mild, ommoniocal odor. 

A schematic flow diagram of the unit is shown in Figure 3-33. A solution of 48 wt% potassium hydroxide is added to the contaminated diethanolamine before it enters the top of a packed tower where it is contacted with superheated steam rising from the reboiler. Essentially all of the amine and water is vaporized, and the product is withdrawn at a point below the packed section into a condenser, which is held at a slightly lower pressure than that prevailing in the reboiler. A steam jet is used to maintain the required pressure. The salts drop into the reboiler and melt at 420 to 440°F, and any residual diethanolamine is flashed off. The temperature of the diethanolamine-water vapor withdrawn is 300 to 375°F. The temperatures in the column and reboiler are sufficient to vaporize practically all the amine without decomposition. Heat is supplied by circulating oil at 600°F through the reboiler tubes. Recovery of 90% of reusable diethanolamine is claimed. 

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