CS232644B1 - The method of oxidizing a mixture of p-xylene and p-toluic acid methyl ester - Google Patents

Abstract

The essence of the method of oxidation of a mixture of p-xylene and p-toluyl acid methyl ester according to the invention is that the reaction takes place in the presence of heterogeneous metal catalysts containing cobalt, manganese or their mixture in a ratio of 0.1 to 99.9 parts by mass. of cobalt to 99.9 to 0.1 parts by mass. manganese or at least one of these metals· in a mixture with a maximum of 50% by mass. elements IV.A, IV.B, VI.A, VIII. groups of Mendeleev's periodic table, further lanthanides or actinides. The heterogeneous metal catalyst can be applied to a carrier with a surface area of 2 to 1500 m2. g_1, which must be stable against oxidation. Terephthalic acid and its dimethyl ester prepared by the method according to the invention serve as raw materials for the production of polyester fibers and foils.

Description

232644 3

BACKGROUND OF THE INVENTION The present invention relates to a method of oxidizing a mixture of β-xylene and p-toluyl methyl ester in a liquid phase.

The oxidation of the mixture of p-xylene and p-toluic acid methyl ester in the liquid phase is carried out at temperatures of 135 to 190 ° C in the presence of homogeneous metal catalysts, most often cobalt salts (Chem. Technik 1,1, 1966). cobalt amangan (NSR Pat. No. 2,163,031), nickel and manganese (U.S. Pat. No. 3,890,374), cobalt and thorium (Jap. Kokal 73, 32,835), cobalt, manganese, and medium (NSR Pat. 805), cobalt, manganese and nickel (NSR Pat. No. 2,733,917), in the form of acetates, naphthenates, acetylacetonates, alkanoates or their compounds, which are dissolved in the reaction medium. Toluyl, terephthalic acid and terephthalic acid mono-methyl ester The esterification step is further esterified with methanol and distilled to give terephthalic acid dimethyl ester as the final product and the methyl ester of p-toluic acid is returned to the oxidizer where together with sp The reaction may be carried out discontinuously or continuously with a variety of p-xylene to the p-toluic acid methyl ester depending on the desired composition of the resulting oxidation mixture. An 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 to the start of the reaction or to other oxidizers.

The principle of catalyzed oxidation of p-xylene and p-toluic acid methyl ester 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. of cobalt to 99.9 to 0.1 parts by weight. % of manganese or at least one of these in a mixture with a maximum of 50 wt. of elements IV.A, IV.B, VI.A, VIII. groups of the Mendele-periodic system, the other lanthanide or amino acids.

The heterogeneous metal catalyst may be supported on a support, but must be oxidation-resistant. The carrier used was silica gel, amorphous alumosilicates, zeolites and the like. The amount of metal on the support can vary within a wide range, usually from 1 to 25% by weight.

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

Various activators may also be added to the system to increase the activity of the catalyst, e.g. bromine compounds, but is disadvantageous due to the corrosivity of the added substances. Example 1

To a 250 ml stainless steel reactor, 120 g of p-toluyl methyl ester containing 2.1 wt. benzoic acid methyl ester, 0.8% w / w. % dimethyl tartrate and 0.3 wt. 4-carboxybenzaldehyde methyl ester, 60 g of p-xylene and a heterogeneous catalyst without carrier containing 0.19 g of cobalt. The oxidation is carried out at a temperature of 180 ° C and a pressure of 0.8 MPa with an air flow of 30 dm3. h_1 7 hours. The reaction water was drained from the system during the experiment, partially also carrying p-xylene (9.8 g total), which was collected together with the recycle water in the separator. The oxidation course was continually registered by oxygen and COa in the outgoing gas. Suspension of the oxidation and cooling of the reactor yielded 17 g of solid product with an acid number of 271 mg KOH. g_1. This contained 26.2 percent by weight. % p-toluic acid, 17.7 wt. % of terephthalic acid monomethyl ester, 14.6 wt. terephthalic acid and 2.3 wt. dimethyl terephthalate as the main oxidation products. The reaction resulted in a total of 5.15 g of carbon dioxide. Example 2

The procedure and conditions 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 a solid oxidation product having an acid number of 264 mg of KOH were formed. and 5.05 g of carbon dioxide. The product contained 25.5% w / w of toluene, 21.3% w / w. terephthalic acid mono-methyl ester, 12.5 wt. terephthalic acid and 1.7% dimethyl terephthalate. Example 3

The procedure and conditions were the same as in Example 2, but cobalt and manganese acetate mixtures were used as catalysts in a ratio of 1: 10 and in an amount corresponding to 0.21 g of cobalt and manganese. The reaction took place only 210 minutes and then spontaneously stopped. Oxidation product with an acid number of 80.6 mg KOII. g "1 contained 1.33% by weight of terephthalate acid. By comparison with Example 2, it can be seen that in the above mentioned conditions the homogeneous catalyst is less active than the heterogeneous catalyst.

The procedure and conditions of Example 1, the cobalt acetate was used in an amount corresponding to 0.19 g of cobalt. After 7 hours of reaction, 193 gooxidation product was obtained with an acid number of 158mg KOH. g-1 containing ≥ 4.5 wt. te-

With Refalic Acid. Compared to Example 1, this type of homogeneous catalyst is also substantially less potent than the heterogeneous catalyst. Example 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 oxidation product with an acid number was formed. 180 mg KOH. g_1 and containing 4.1 wt. terephthalic acid. As compared to Example 2, a mechanical mixture of heterogeneous catalysts is less active than when a mixed catalyst prepared simultaneously from both metals is used. Example 6

The reaction mixture as in Example 1 was oxidized at 170 ° C and 0.6 MPa with an air flow of 18 dm 3. li-1. A heterogeneous catalyst containing Mn and Ni in a 10: 1 weight ratio of 0.14grams per metal was used. After 7 hours of reaction, 187 g of product with an acid number of 172 mg of KOH were obtained. g_1 containing 2.9 wt. terephthalic acid. Example 7

The procedure and conditions of Example 1, ales, employed 2.06 g of a heterogeneous catalyst containing 6.2 wt. cobalt as the main component on a mordenite carrier having a surface area of 325 m 2. g-1. After 7 hours of oxidation, 195 g of solid product were obtained with an acid number of 252 mg KOH. g ~ h 10.6 g of p-xylene were collected in the separator. The main oxidation products were p-toluic 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). ). Example 8

Conditions as in Example 1, but 7.34 g of heterogeneous catalyst containing 3.0 wt. cobalt as the main constituent on a silica gel support having a surface area of 241 m 2.g_1. After 7 hours of reaction, 199 g of product were obtained with an acid number of 253 mg of KOH. g-1 containing 19.6% wt. terephthalic acid. 232644 6 A n d e 9

The conditions as in Example 1, but 0.3 g of heterogeneous manganese-molybdenum catalyst containing copper (I) were used in a molar ratio of 8: 1. After 7 hours, 177 g of the acid number 221.1 mg of KOH were obtained. . g_1 containing 9.5 wt. terephthalic acid. Example 10

The 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 of 201.2 mg KOH was formed. g_1 containing 8.7 wt. terephthalic acid. Example 11

The 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 formed with an acid number of 209.8 mgKOH. 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 the acid number191.8 mg of KOH were formed. Containing 1% by weight of terephthalic acid. Example 13

The conditions as in Example 1, but 0.25 g of Mn-Pb catalyst were used at a molar ratio of 15: 1. Oxidation after 7 hours resulted in 180 g of the acid number of 162.4 mg KOH. g_1 and a content of 5.1 wt. te-phthalic acid. Example 14

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

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

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