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Molecular formula : C8H6O4
MW : 166.13
CAS, DSC-21-0
nature : the white needle crystal or powder. Combustible. Low toxicity. Density 1.510, under normal pressure at about 402 ° C sublimation, if in a confined container heating, melting at 425 ° C. Soluble alkali solution, ethanol-soluble heat, do not dissolve in water, ether, chloroform and acetic acid.
Preparation : industry on the most widely used, the most economical production methods, xylene is right for the high-temperature liquid raw materials oxidation. On the other PTA production methods still low temperature oxidation of p-Xylene, o-switch method, oxidation of toluene disproportionation law. 1. Right xylene high temperature oxidation of xylene solvent to acetic acid, acetic acid to cobalt-manganese acetate as a catalyst to help to Tetrabromoethan catalyst, in ,2.5 221-225 ° C - 3.0 MPa of terephthalic acid oxidation. Terephthalic acid solubility in acid little oxidation products were in slurry form, centrifugal separation, after drying in crude terephthalic acid. One of the most harmful impurities of the carboxyl benzaldehyde, in 1000 - 5,000. Crude goods at 280-290 ° C, about reached 7MPa pressure dissolved in water, then put in the presence of catalysts for hydrogenation, to remove the carboxyl acid, crystal, filtering, washing, drying, in terephthalate fiber level. 2. Right xylene low temperature oxidation of the materials in acetic acid solvent xylene, cobalt acetate (or manganese acetate) and bromide as the catalyst to three METALDEHYDE to promote the oxidation agent, 100-130 ° C in temperature and pressure 3MPa, using low-temperature air oxidation step, the reaction product of acetic washing , and then drying the products of terephthalic acid.
purposes : most of the materials used in the production of polyethylene terephthalate (PET), is a polyester fiber, film, plastic products, insulation and paint plasticizers important raw materials, but also for medicine, dyes and other products production.
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