CS232644B1 - Oxidating method of mixture of p-xylene and methyl ester of p-to-luic acid - Google Patents

Abstract

The principle of the process of oxidizing the p-xylene mixture and methyl p-toluic acid according to the invention The invention is based on the fact that the reaction is carried out in the presence of heterogeneous metal cobalt-containing catalysts manganese or a mixture thereof in a ratio of 0.1 to 99.9 parts of mass. cobalt to 99.9 to 0.1 parts wt. manganese or at least one of these % metal in a mixture with a maximum of 50 wt. elements IV.A, IV.B, VI.A, VIII. the Mendelejev Group of the Periodic System, hereinafter Lanthanides or actinides. A heterogeneous metal catalyst may be provided apply to a support having a specific surface area of 2 to 1500 m2. g_1, which must be stable to oxidation. Terephthalic acid and its dimethyl ester prit the process according to the invention serve as raw materials for polyester fiber production and foil.

Description

The invention relates to a process for the liquid phase oxidation of a mixture of p-xylene and methyl p-toluyl ester.

The liquid phase oxidation of the mixture of p-xylene and methyl p-toluyl ester is carried out at temperatures of 135 to 190 ^° C in the presence of homogeneous metal catalysts, which are most commonly cobalt salts (Chem. Ing. Technik 1,1, 1966), cobalt and manganese. (U.S. Pat. No. 2,163,031), nickel and manganese (U.S. Pat. No. 3,890,374), cobalt and thorium (Jap. Kokai 73, 32,835), cobalt, manganese, and media (U.S. Pat. No. 2,420,805), cobalt, of manganese and nickel (NSC Pat. 2,733,917), in the form of acetates, naphthenates, acetylacetonates, alkanoates or other compounds dissolved in the reaction medium. P-toluylic acid, terephthalic acid and terephthalic acid monomethyl ester are mainly formed as oxidation products. The oxidation mixture is esterified with methanol in further steps and distilled to give the terephthalic acid dimethyl ester as the final product, and the intermediate methyl p-toluyl ester is returned to the oxidizer, where it is subjected to further oxidation together with the p-xylene. The reaction can be carried out batchwise or continuously with different ratios of p-xylene to p-toluylic acid methyl ester, depending on the desired composition of the resulting oxidation mixture. The industrial process for the production of dimethyl terephthalate is based on this principle.

Catalysts have a considerable influence on the course of the reaction. The catalysts are added either at the start of the reaction or up to other oxidizers.

The principle of the catalyzed oxidation of p-xylene and methyl p-toluyl ester according to the invention is that the reaction is carried out in the presence of heterogeneous metal catalysts containing cobalt, manganese or a mixture thereof in a ratio of 0.1 to 99.9 parts by weight. % cobalt to 99.9 to 0.1 parts by weight of cobalt; % of manganese or at least one of these metals in admixture with a maximum of 50 wt. elements IV.A, IV.B, VI.A, VIII. the Mendeleyev Periodic System, other lanthanides or actinides.

The heterogeneous metal catalyst may be supported, but must be stable to oxidation. As carriers, silica gel, amorphous aluminosilicates, zeolites and the like can be used. The amount of metal on the support can vary within wide limits, usually from 1 to 25% by weight.

Catalytic activity and selectivity are dependent on many factors but strongly dependent on the combination of metals, carrier and catalyst preparation method. Catalysts are not aggressive, toxic and do not require special handling ·

Various activators may be added to the system to increase catalyst activity, e.g. bromine compounds, but this is disadvantageous due to the corrosivity of the added substances.

Example 1

To a 250 ml stainless steel reactor was weighed 120 g of methyl p-toluyl ester containing 2.1 wt. % methyl benzoate, 0.8% w / w. % dimethyl terephthalate and 0.3 wt. 4-carboxybenzaldehyde methyl ester, 60 g of p-xylene, and a heterogeneous unsupported catalyst containing 0.19 g of cobalt. The oxidation takes place at a temperature of 180 ° C and a pressure of 0.8 MPa with air at a flow rate of 30 dm ³ . h ^_1 7 hours. The reaction water was evacuated from the system during the experiment, partly carrying also p-xylene (total 9.8 g), which was collected along with the reaction water in a separator. The course of the oxidation was continuously registered according to the oxygen and COa content of the off-gas. After the oxidation was stopped and the reactor was cooled, 17 g of solid product with an acid number of 271 mg KOH were obtained. g ^_1 . This contained 26.2 weight percent. % p-toluic acid, 17.7 wt. % terephthalic acid monomethyl ester, 14.6 wt. % terephthalic acid and 2.3 wt. dimethyl terephthalate as the main oxidation products. The reaction yielded a total of 5.15 g of carbon dioxide.

Example 2

The procedure and conditions were the same as in Example 1, but the heterogeneous catalyst contained cobalt and manganese in a weight ratio of 1:10, a total of 0.21 g. After 7 hours of oxidation, 186 g of solid oxidation product with an acid number of 264 mg KOH were formed. . g ^-1 and 5.05 g carbon dioxide. The product contained mainly 25.5 wt. % p-toluylic acid, 21.3% w / w; % terephthalic acid monomethyl ester, 12.5 wt. % terephthalic acid and 1.7 wt. DMT.

Example 3

The procedure and conditions were the same as in Example 2, but the catalyst used was a 1: 10 mixture of cobalt acetate and manganese in an amount corresponding to 0.21 g of cobalt and manganese. The reaction was allowed to proceed for only 210 minutes and then stopped spontaneously. Oxidation product with an acid number of 80.6 mg KOII. g ¹ contained 1.33 wt. terephthalate acid. From the comparison with Example 2 it can be seen that under the mentioned conditions the homogeneous catalyst is less active than the heterogeneous catalyst.

Example 4

Procedure and conditions as in Example 1 but using cobalt acetate in an amount corresponding to 0.19 g of cobalt as catalyst. After 7 hours of reaction, 193 g of oxidation product with an acid number of 158 mg KOH were obtained. g ^-1 containing ≥ 4.5 wt. te5 of reftalic acid. Compared to the example, this type of homogeneous catalyst is also substantially less effective than a heterogeneous catalyst.

Example 1 and d 5

Conditions as in Example 2, but using a mechanical mixture of heterogeneous cobalt and manganese catalysts in the same amount and relative to each other as in Example 2. After 7 hours of oxidation, 190 grams of the oxidation product with an acid number of 180 mg KOH were formed. g ¹ and the content of 4,1% by weight. terephthalic acid. Carbon dioxide gave 4.66 g. Compared to the example, it can be seen that the mechanical mixture of heterogeneous catalysts is less active than when using a mixed catalyst prepared simultaneously from both metals.

Example 6

The reaction mixture as in Example 1 was oxidized at 170 ^° C and 0.6 MPa with air at a flow rate of 18 dm ³ . li ^-1 . A heterogeneous catalyst containing Mn and Ni in a weight ratio of 10: 1 in an amount of 0.14 grams per metal was used. After 7 hours the reaction was formed. 187 g of product with an acid number of 172 mg KOH. g ¹ containing 2.9 wt. terephthalic acid.

Example 7

Procedure and conditions as in Example 1, but 2.06 g of heterogeneous catalyst containing 6.2 wt. cobalt as the main constituent on a mordenite carrier with a specific surface area of 325 m ² . g ^-1 . After 7 hours oxidation yielded 195 g of solid product with an acid number of 252 mg KOH. g ¹ . 10.6 g of p-xylene were collected in a separator. As mainly oxidation products were p-toluylic acid (28.0% w / w), terephthalic acid (13.9% w / w), its monomethyl ester (17.6% w / w) and dimethyl terephthalate (1.8% w / w). j.

Example 8

Conditions as in Example 1, but 7.34 g of heterogeneous catalyst containing 3.0 wt. cobalt as the major, component it supported silica with a specific surface of 241 m ² .g ^_1. After 7 hours the reaction yielded 199 g of product with an acid number of 253 mg KOH. g ^-1 containing 19.6% w / w. terephralic acid.

β

Example 1 and d 9

Conditions as in Example 1 but 0.3 g of a heterogeneous manganese-molybdenum catalyst containing copper metals in a molar ratio of 8: 1 were used. After 7 hours 177 g of product with an acid number of 221.1 mg KOH were obtained. ^_1 g containing 9.5% by weight. terephthalic acid.

Example 10

Conditions as in Example 9, but the catalyst consisted of manganese and zirconium in a molar ratio of 10: 1. After 7 hours, 181 g of product with an acid number were obtained.

201.2 mg KOH. g ¹ containing 8.7 wt. terephthalic acid.

Example 11

Conditions as in Example 9, but the catalyst consisted of cobalt and chromium in a 5: 1 molar ratio. After 7 hours, 188 g of product having an acid number of 209.8 mg KOH were formed. g ¹ containing 7.8 wt. terephthalic acid.

Example 12

Conditions as in Example 9, but the catalyst consisted of manganese and uranium in a molar ratio of 15: 1. After 7 hours of oxidation, 186 g of product having an acid number were obtained

191.8 mg KOH. % containing 7.7 wt. terephthalic acid.

Example 13

Conditions as in Example 1, but 0.25 g of Mn-Pb catalyst in a molar ratio of 15: 1 were used. Oxidation after 7 hours gave 180 g of product with an acid number

162.4 mg KOH. g ¹ and a content of 5.1 wt. terephthalic acid.

Example 14

Conditions as in Example 13, but the catalyst was Mn-Ce with a metal molar ratio of 10: 1. After 7 hours, 178 g of product with an acid number of 169.3 mg KOH were obtained. • g “ ¹ ·

Terephthalic acid and its dimethyl ester serve as raw materials for the production of polyester fibers and foils.

Claims (2)

předm 1. A process for oxidizing a mixture of p-xylene and methyl p-toluyl ester in a liquid phase with an oxygen-containing gas at a temperature of 110 to 220 ° C and a pressure of 0.1 to 0.2 MPa in the presence of cobalt, manganese, nickel or mixtures thereof, characterized in that the reaction is carried out in the presence of heterogeneous metal catalysts containing cobalt, manganese or a mixture thereof in a ratio of 0.1 to 99.9 parts by weight. % cobalt to 99.9 to 0.1 parts by weight of cobalt; or at least one of these metals in admixture with a maximum of 50 wt. elements IV.A, IV.B, VI.A, VIII. groups of Mendeleyev periodic system, furthermore lanthanides or actinides. 2. Process according to claim 1, characterized in that a heterogeneous metal catalyst is applied in an amount of 1 to 25% by weight. on an oxidation-stable support with a specific surface area in the range of 2 to 1500 m ² . • g “ ¹ · Severography, n. p.> plant 7, Most 0 * 9 «0,80 Eurs