SU739062A1 - Method of preparing terephthalic acid - Google Patents

Description

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Known spssO5 received:. Tereft -, .... left sour. :::;:.; leks - -: p-kc ;: weak acid-trainer; kg-shi; gas from the industrial gas catalysis of detritus of cobalt and marganium and;: ps;: ktsov and medium of f., with hs acid, with gcd. melted: Oscaro7l check: oh reaction; acetic acid- .. Get terzphtalez -; o acid with a content of n - ;; apo; ss:; 5 anzaltseg-5da O, 03 sec-%, for ksvosti zkpazhen l optical plst -: o: gd 0.02-0.05 lt

Terephthalic acid with the indicated color is not transparent; it is suitable for direct polymerization,

Known for such a method is the half-shelves of a tereft. The left one, which is suitable for 25 kaposredstviy. :: no-; polymerization by the use of acid-phase oxidation of p-cc-u5ol g; when using a catalyst / co.sec of 0.05-0-05 c of a metallic hydrogen cobalt calculated on the basis of dissolving jg

-On manganese by weight ––– bromine nA r--, impurity content: g-ls.yute is

 Part of impurities in TPA 1C. ska: - due to polishing method of treating tereft: - from impurities in the osstano: 1O: -: in the presence of a pallalizer of the main gtri: j: 5 GH3 aldehyde 3 or:; The oxidation of the products of the acid (aldehydes, mineral acids) oksley; n.; epf with the permangate of katslsii. connected with 4. f; .31; methods of cleansing the process of dissolving acetic acid or orchids 5}.

similar to the technical; ocT; -rae-MbTivi results of the collection of K 5 terephthalic acid by oxidizing acetic acid to a presence of bromine at 180220s and a pressure of 3.5-17.6 these in the presence of a catalyst containing cobalt salts (manganese and additions of compounds of metals selected from the group (nickel, copper, zinc, tin or iron), the total concentration of cobalt and manganese is 0.05-0.10 wt.%, the concentration of nickel in the reaction mixture exceeds 0.01%, the ratio Co : Mp 0.8; Mp: Ni. 0.15 1.0; The chromaticity of the obtained terefapic acid is 0,39-0,06 b

The disadvantage of the method is not high enough for use directly in the polymerization, the quality of the target acid, which leads to the need for an additional stage of purification of TPA,

The purpose of the invention is to simplify the process and improve the quality of the target product.

This goal is achieved by the fact that to obtain terephthalic acid by liquid-phase oxidation of p-xylene in acetic acid, oxygen-containing 11 (with gas in the presence of a bromine ion initiator at a temperature in the first stage of 210-230 ° C and a pressure of 24-27 ati in the presence of a catalyst containing cobalt, margane and nickel, with a total concentration of cobalt and manganese of 0.045-0.15 wt.% to the initial reaction mixture, with a weight concentration of nickel of 0.00050, 005% and with a ratio of Mn: Ni - 3.0-100. p-xylene reaction mixture to the second stage, where, at 160-2 and .5-10 athy, in a liquid medium, it is treated with a vapor-gas mixture containing nsipH water, acetic acid and oxygen in the following amounts,%: acetic acid 40-70, water 10-20, nitrogen 15-50, oxygenation 0.11, 5.

Next, the reaction mixture is cooled stepwise and the terephthalic acid is isolated by known methods. The resulting terephthalic acid has a color of 0.007-0.01 (given in the form of optical density) and as impurities of p-carboxybenzyldehyde 0.012-0, 026% and less than 0.005% of p-that.

The proposed method for the oxidation of p xylene to pure terephthalic acid differs from the known ones by the exceptionally high selectivity and, consequently, the purity of the obtained terephthalic acid.

In order to obtain fiber, terephthalic acid must be purified to at least 9a, 9% by content of the basic substance.

Purification to such high purity is very difficult and requires a high cost of 30-35% of the product cost.

The resulting terephthalic acid has a color D of 0.007-0.01 (given as optical density) and E as impurities of p-carboxybenzaldehyde O, 01 2-0., 026% and less than 0.005% of p-toluic acid. Such amount of impurities of monocarboxylic acids in terephthalic acid is permissible and it can be used without additional purification for processing into fiber {in existing specifications impurities can be 0.005% for benzoic acid, 0.004% for p-carbroxybenzaldehyde and p-toluic acid acids (p-TK) 0.025% (total amount 0.034%).

This method allows to obtain TPA of very high purity 99.97 - 99, in one stage, thereby eliminating the complex and expensive purification.

The supply of gas-vapor mixture to the second stage in the specified amounts and compositions provides the necessary temperature conditions for mass exchange and reaction transformations. Treatment with water vapor and nickel contained in the reaction mass reduces the rate of undesirable side processes of destructive oxidation of the solvent and reaction products.

The oxygen contained in the vapor contributes to a more complete oxidation of the intermediate to the reaction by-products (p-CBA, p-TC, colored product), which are in solution, and the transition to the solution from the crystalline phase due to mass transfer during heating and cooling of the reaction mass ( partial evaporation of the warmer solvent during throttling and the return of the cooled solvent from the condenser) and improves the quality of TPA.

Example 1 Into a titanium reactor equipped with a 2.8 m mixing device, the initial mixture is continuously fed in an amount of 2il, including 315 kg of p-xylene, 1728.4 kg of acetic acid, 52 f 5 kg of water, 3.68 kg of cobap acetate, ta (tetrahydrate), 2.22 kg manganese acetate (tetrahydrate), 0.084 kg nickel acetate (tetrahydrate), and 3.24 kg sodium bromide. There are 1120 air supplied, providing an oxygen excess of 1.8%, the reaction temperature is maintained within 210-230 C and a pressure of 24-27 atm. After complete conversion of p-xylene, the reaction mass from the first reactor is continuously fed to the second, where, at 160–210 ° C and 5–10 atm pressure, 160 steam-gas mixture containing 1.5% oxygen, 20.0% nitrogen, 14, is heated 5% water, 64% acetic acid. Next, the reaction mass is cooled in steps: 180-170 ° C, 160-140 ° C, 5-110-100 ° C, centrifuged, the precipitate is successively treated with acetic acid, water and sent for drying. The resulting terephthalic acid contains an impurity p-carboxybenealdehyde of 0.016%, p-toluic acid 0.005%, benzoic acid, traces: chromaticity (represented as optical density).

The following examples are carried out analogously to example 1 and the results are presented in the table.

Claims (6)

Carrying out the process in this way allows one to shorten the purification stage of terephthalic acid and to obtain an acidic one suitable for making fiber. The invention The method of producing terephthalic acid by liquid-phase oxidation of p-xylene in an acetic acid medium with an oxygen-containing gas in the presence of a catalyst containing cobal manganese and nickel, as well as an initiator of bromine ion at elevated temperature and pressure, characterized in that, in order to simplify the process and improve quality the target product, the oxidation is carried out in 2 stages at the first stage - at 210-230 ° C and a dissolution of 24-27 mp in the presence of a catalyst, with a total concentration of cobalt and manganese of 0.045-0.15% on the initial the reaction mixture, with a weight concentration of nickel of 0.0005-0.005% and with a ratio of Mn: Ni - 3.0100 until complete conversion of p-xylene, followed by treatment of the reaction mass, at the second stage - at 160210 s and pressure of 5-10 MPa steam-gas mixture containing: 40-70 acetic acid, 10-20 water, 15-50 nitrogen, 0.1-1.5 oxygen, followed by step cooling and separation of the target product. Sources of information taken into account in the examination 1. USSR Patent 257374, cl. From 07 to 63/26, 1967. 2. The patent of the USSR 499799, cl. C 07 C 63/26, 1971. 3. The patent of France 1480013, cl. from 07 C, 1971. 4. USSR author's certificate number 313829, cl. 63/26, 1969. 5. US patent 3.708.532, cl. 260-525, 1973. 6. The patent of Great Britain I 851562, cl. C 2 (3), 1960.