Xylenol

Химические свойства

White, crystalline solid. Only slightly soluble in water; soluble in most organic solvents and caustic soda solution. Combustible.

Использование

Disinfectants, solvents, pharmaceuticals, insecticides and fungicides, plasticizers, rubber chemicals, additives to lubricants and gasolines, manufacture of polyphenylene oxide (2,6-isomer only), wetting agents, dyestuffs.

Методы производства

Xylenes are obtained mainly (80%) from petroleum reformate streams in the form of "mixed xylenes." A typical composition of this stream is about 18 percent p-xylene, 40 percent m-xylene, 22 percent o-xylene, and 20 percent ethylbenzene. The major chemical uses of xylene, however, require the pure isomers. The purification process involves a number of steps. First the a-xylene is separated from the other aromatics by distillation, with the meta and para isomers going overhead along with the ethylbenzene. p-Xylene can be recovered by either adsorption or crystallization processes. In the adsorption process, the stream is charged to a fixed bed of molecular sieves, and the selectively adsorbed p-xylene is recovered by washing the bed with solvent. Because the demand for p-xylene is far greater than that for m-xylene, the raffinate usually is isomerized to form more ofthe para isomer. Toluene may also be disproportionated to form equivalent amounts of benzene and xylenes without any ethylbenzene. Recently, this TOP process became more favorable. Today, it contributes to 18.5 percent of xylene production.
In 1999, the total demand for the xylenes (12.3 billion lb) was roughly comparable to that for toluene. The volume of 0-, m- and p-xylene were approximately 1.1 , 0.27, and 9.9 billion lb, respectively. The principal uses of the three xylene isomers are the production of terephthalic acid (or di-methyl terephthalate), phthalic anhydride, and isophthalic acid, respectively.

Химическая реактивность

Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.

Профиль безопасности

A poison. When heated to decomposition it emits acrid smoke and irritating fumes. See also other xylenol entries.