Mixture eutectic

The reaction is exothermic, and multitubular reactors are employed with indirect cooling of the reactor via a heat transfer medium. A number of heat transfer media have been proposed to carry out the reactor cooling, such as hot oil circuits, water, sulfur, mercury, etc. However, the favored heat transfer medium is usually a molten heat transfer salt which is a eutectic mixture of sodium-potassium nitrate-nitrite. 

Steam is by far the most widely used medium, useful up to about 475 K. Up to about 700 K organic liquids such as the dowtherms and mineral oil may be used. Mercury and molten salts, such as the eutectic mixture of sodium nitrite, sodium nitrate and potassium nitrate may be used up to 875 K, while above this temperature air and flue gases must be used. 

Substance is a eutectic mixture of two or more compounds. The chance of a given mixture containing two compounds... 

In just the proportion to give a sharp-melting eutectic mixture is so remote that this possibility may be neglected. [Occasionally arbitrary mixtures of two substances which (usually) are chemically related may melt fairly sharply at temperatures intermediate between the melting-points of the two components, but this phenomenon is rarely encountered.]... 

A large number of thermodynamic studies of binary systems were undertaken to find and determine eventual intermolecular associations for thiazole Meyer et al. (303, 304) discovered eutectic mixtures for the following systems -thiazole/cyclohexane at -38.4°C, Wt = 0.815 -thiazole/carbon tetrachloride at -60.8°C, Mt = 0.46 -thiazole/benzene at -48.5°C, nr = 0.70. 

Physical properties of glycerol are shown in Table 1. Glycerol is completely soluble in water and alcohol, slightly soluble in diethyl ether, ethyl acetate, and dioxane, and insoluble in hydrocarbons (1). Glycerol is seldom seen in the crystallised state because of its tendency to supercool and its pronounced freesing point depression when mixed with water. A mixture of 66.7% glycerol, 33.3% water forms a eutectic mixture with a freesing point of —46.5°C. 

Hitec Heat-Transfer Salt. Hitec heat-transfer salt, manufactured by Coastal Chemical Co., is an eutectic mixture of water-soluble inorganic salts potassium nitrate (53%), sodium nitrite (40%), and sodium nitrate (7%). It is suitable for Hquid-phase heat transfer at temperatures of 150—540°C. 

Some reactors are designed specifically to withstand an explosion (14). The multitube fixed-bed reactors typically have ca 2.5-cm inside-diameter tubes, and heat from the highly exothermic oxidation reaction is removed by a circulating molten salt. This salt is a eutectic mixture of sodium and potassium nitrate and nitrite. Care must be taken in reactor design and operation because fires can result if the salt comes in contact with organic materials at the reactor operating temperature (15). Reactors containing over 20,000 tubes with a 45,000-ton annual production capacity have been constmcted. 

Only a few commercial uses for TDA per se have been found. In epoxy curing appHcations, 2,4- I DA has been used as a component of a eutectic mixture with short chain aUphatic glycidal ether resins (46) as well as by itself (46,47) TDA (46) and single isomers (47) are also used as amine curatives. TDA can be used as a chain extender in polyurethanes (48,49). TDA is cited as a monomer in making aromatic polymers with unique properties, eg, amorphous polyamides (50), powdered polyamides (51), and low melting, whoUy aromatic polyamides (52). 

This relative work is an important consideration when comparing separation techniques. Some leave much of the work undone, as, for example, in crystallisation (qv) involving an unseparated eutectic mixture. 

Heat Treatment and Heat-Transfer Salts. Mixtures of sodium nitrite, sodium nitrate, and potassium nitrate are used to prepare molten salt baths and heat-transfer media. One of the most widely used eutectic mixtures uses 40% NaN02, 7% NaNO, and 53% KNO [7757-79-1] to give a... 

BaCl2 is used in heat treating baths because of the eutectic mixtures it readily forms with other chlorides. The melting points of some eutectic mixtures are BaCl2 KCl, 672—680°C BaCl2 N Cl, 39 mol % BaCl2) 654°C 631°C. BaCl2 is so used to set up porcelain enamels for sheet... 

Condensing Organic Va.por, The eutectic mixture of diphenyl and diphenyl oxide is an excellent vapor medium for precise temperature control at temperatures higher than those practical using steam. This mixture can achieve 315°C while holding pressure at 304 kPa (3 atm) absolute. In contrast, steam would require 10.6 MPa (105 atm) pressure. 

Conarrhimine, C2iH3i(NH)(NH2), has not been obtained pure owing to its tendency to form eutectic mixtures, m.p. 160° and 175°, with holarrhimine, but its presence has been established by the isolation from such mixtures of nitrosohydroxyopoconarrhimine, C2iH3i(N. NO)(OH), m.p. 160-3° (Siddiqui ). 

Sodium metal is produced commercially on the kilotonne scale by the electrolysis of a fused eutectic mixture of 40% NaCl, 60% CaCh at 580°C in a Downs cell (introduced by du Pont, Niagara Falls, 1921). Metallic Na and Ca are liberated at the cylindrical steel cathode and rise through a cooled collecting pipe which allows the calcium to solidify and fall back into the melt. Chlorine liberated at the central graphite anode is collected in a nickel dome and subsequently purified. Potassium cannot be produced in this way because it is too soluble in the molten chloride to float on top of the cell for collection and because it vaporizes readily... 

The rate of reaction is variable requiring from 1-4 days. Fresh catalyst is added whenever the rate of hydrogen uptake markedly decreases. Added catalyst must first be wet with solvent. The hydrogen must be well evacuated, for opening the mixture to the atmosphere without such evacuation will produce a mixture that may explode on contact with fresh catalyst, t A eutectic mixture of diphenyl and diphenyl ether, available from Dow Chemical Co. 

---