DE1074028B - Process for the preparation of carboxylic acids or their mixtures with their esters - Google Patents

Description

Process for the production of carboxylic acids or their mixtures with their esters It is known that carboxylic acids are obtained when unsaturated ones are obtained Hydrocarbons with carbon monoxide and water in the presence of metal carbonyls or carbonyl-forming metals, in particular metals of the iron group, implemented. Further is known for the production of carboxylic acids with halogenated hydrocarbons Carbon oxide and steam over active charcoal, pumice stone or silica gel at elevated temperature to direct. In addition, U.S. Patents 2,565,461 to 464 disclose processes known for the carbonylation of aromatic halogenated hydrocarbons, in which one on halogenated hydrocarbons nickel carbonyl or other metal carbonyls Metals of the iron group without the addition of diluents or in the presence of Water, alcohols, phenols, aliphatic carboxylic acids or carboxylic acid esters and optionally inert diluents, such as benzene and cyclohexane, act leaves.

These known processes in which the metal carbonyl is used as a carbon oxide carrier in an amount of at least 0.25 mol per g atom of halogen in the chlorinated hydrocarbon is used, have the disadvantage that by the liberated hydrogen halide severe corrosion damage to the apparatus occurs, so that this process have not yet been able to enforce in practice.

From US Pat. No. 2,734,912 it is also known in which Reaction of a halogen aromatic hydrocarbon with carbon oxide and a Alkoxydonator as a catalyst to use one that consists essentially of metallic nickel and copper or chromium. This procedure has, as well is set out in the patent, especially when using halogenated hydrocarbons with more than one halogen atom has the disadvantage that side reactions, z. B. reduction, take place so that a mixture is obtained as the reaction product will, in addition to products in which only a partial conversion of the halogen atoms took place, also has halogen-free products that have fewer carbonyl or ester groups contain as the halogenated aromatic hydrocarbons, the same disadvantages also shows the method of manufacture known from U.S. Pat. No. 2,773,090 of dimethyl terephthalate by carbonylation of p-dichlorobenzene with carbon monoxide in the presence of methanol or dimethyl ether using nickel carbonyl as a catalyst. An increase in the compounds containing ester groups in the resulting According to the known process, carbonylation mixture should be achieved by that the liquid carbonylation mixture subsequently again with methanol at higher Temperatures such as 200 to 325aC is esterified. In addition to the already mentioned disadvantages of the carbonylation stage of this process, another disadvantage of this process is that under the carbonylation hydrogen chloride is released and the carbonylation can therefore only be carried out in corrosion-resistant pressure vessels.

It has now been found that aromatic carboxylic acids or their Mixtures with their esters are obtained in a simple manner without the disadvantages mentioned, if you have aromatic chlorine or bromine hydrocarbons, which are optionally by Cyano, carboxyl, ester or ether groups can be substituted with methyl formate and an anhydrous alkali salt of an organic acid or with an alkali carbonate Reacts at elevated temperature and pressure.

Suitable aromatic chlorine or bromine hydrocarbons are, for. B. chlorobenzene, bromobenzene, chlorotoluene, dichlorobenzene and dibromobenzene and chlorinated ones or brominated derivatives of biphenyl, naphthalene and anthracene.

Of the anhydrous compounds used in the implementation Of the alkali salts of organic acids are in particular the sodium and potassium salts of organic acids such as formic acid, acetic acid, oleic acid or stearic acid, called.

Particularly suitable carbonates are, for. B. sodium carbonate and potassium carbonate.

The reaction is preferably carried out at temperatures between about 200 and 4000 C, in particular at 250 to 3500 C, and under increased pressure, in particular from 5 to 300 at. For example, this is done in such a way that one the aromatic Chlorinated hydrocarbon or chlorinated hydrocarbon mixtures with methyl formate and an anhydrous salt of an organic carboxylic acid, z. B. heated with sodium formate in a closed vessel, in general the pressure necessary for the reaction adjusts itself. Will the required Pressure not reached, or if you want to work at higher pressure, you can get through Pressing gases, e.g. B. carbon dioxide, set the desired pressure. The work under higher carbon dioxide pressure has the advantage that decomposition of the formates is completely or largely avoided.

The methyl formate and the anhydrous alkali salt of the organic Carboxylic acids or carbonate is generally used in the form of halogen per g atom in the chlorine or an equivalent amount of bromohydrocarbon used. One works appropriately with a slight excess of these compounds.

Solvents, especially hydrocarbons, e.g. benzene, gasoline, and alcohols, such as methyl alcohol or ethyl alcohol, can be present in the reaction be. The concomitant use of methanol is particularly advantageous when the reaction is carried out the chlorine or bromine hydrocarbons with methyl formate and alkali metal formate, because then the methyl formate required for the reaction is formed back. the Implementation, for example, of dichlorobenzene, methyl formate and sodium formate in The presence of methanol can be represented schematically by the following equations: C6H4CI2 + 2CHaOOCHoC6H4 (COOCH3) 2 + 2HCl 2HCl + 2NaOOCH2NaCl 2NaCl + 2HCOOH 2HCOOH + 2CH8OH2CH3OOCH + 2H2O The amount of alcohol used, if any, is essential for the implementation not critical. However, it is advantageous to use the alcohol in excess, expediently in at least the equivalent amount of that contained in the chlorinated or bromine hydrocarbon Halogen. Reaction accelerating substances are not required for the implementation, because the reaction takes place quickly enough even without catalysts.

However, it is advantageous to use catalysts to achieve a rapid To use sales. Suitable catalysts are in particular metal carbonyl compounds, such as the carbonyls of nickel, cobalt, iron, molybdenum and chromium, as well as metal carbonyl hydrogen z. B. cobalt carbonyl hydrogen, or complex compounds such as Fe (CO) 4Br2, [R3P] 2Ni (CO) 2 or [R3P] Ni (CO), in which R is a hydrocarbon radical, in particular a Alkyl group, means. It is not necessary to use the metal carbonyl compounds add as finished connections.

Rather, they can also use their building blocks during implementation are formed. So it is enough z. B. when working under carbon dioxide pressure, the carbonyl-forming To add metals to the reaction mixture, with the carbon oxide used as well may contain other gases, especially hydrogen.

The process can be either continuous or discontinuous carried out, it is not necessary, in corrosion-resistant equipment to work.

The parts given in the examples are parts by weight.

Example 1 147 parts of p-dichlorobenzene, 120 parts of methyl formate, 106 Parts of Na2 C 03 and 3 parts of Ni (C 0) 4 under a carbon pressure of 200 at Heated for 6 hours at 3200 C in a copper roll autoclave.

After cooling, the pressure vessel is released and extracted Reaction product with benzene.

The benzene extract is freed from benzene by distillation and the remaining residue is treated with petroleum ether. From the in petroleum ether Soluble fractions are 22.5 parts of p-dichlorobenzene and 8.0 by distillation Parts of dimethyl terephthalate obtained. The parts not dissolved in petroleum ether consist of 30.0 parts of dimethyl terephthalate with a temperature of 1400 C.

The undissolved residue remaining after the benzene extraction is treated with water and the aqueous solution of undissolved parts that consist of 46 parts of terephthalic acid, filtered off. The aqueous solution is acidified with hydrochloric acid and separates the precipitate. After the Dry a further 56 parts of terephthalic acid.

Including the dimethyl terephthalate (38 parts) contained amount of terephthalic acid, so 134.5 parts of terephthalic acid are obtained. Based on the converted dichlorobenzene, the yield is accordingly 95%, of which the proportion present in the form of the dimethyl ester is 24%.

Example 2 147 parts of p-dichlorobenzene, 136 parts, are placed in a pressure vessel Parts of sodium formate, 200 parts of methanol and 1000 parts of methyl formate were introduced and the vessel is heated to 3600 ° C. The pressure rises during the heating 480 at. After the vessel has been held at 3600 ° C. for a further 2 hours, it is left cool and relax the pressure vessel.

The reaction product is filtered and the residue with water extracted. 140 parts of dimethyl terephthalate remain (mp 1420 ° C.). By Evaporation of the filtrate gives a further 13.5 parts of dimethyl terephthalate. The aqueous extraction solution is acidified, whereby 14 parts of terephthalic acid are precipitated will. The total yield of dimethyl terephthalate and terephthalic acid is 87.5 per cent of theory.

Example 3 157 parts of bromobenzene, 73 parts of potassium formate, 300 parts Ethanol, 1000 parts of ethyl formate and 3 parts of nickel carbonyl are in a pressure vessel heated and held at 3600 ° C. for 2 hours under the pressure that established. To After cooling, the reaction product is filtered, the ethyl formate and ethanol are evaporated and the residue is distilled.

At 20 mm of mercury and 104 to 1190 C, 52.5 parts are obtained Ethyl benzoate. The higher-boiling tail consists of 5.6 parts of benzoic acid.

The yield of ethyl benzoate is 34% and that of benzoic acid 4.5%, based on the bromobenzene used.

Example 4 123 parts of 4-chloroanisole, 58.7 parts of sodium formate, 200 Parts of methanol, 300 parts of methyl formate and 3 parts of nickel powder are placed in a pressure vessel filled in and heated after pressing in 70 atmospheres of carbon oxide. Under the emerging The vessel is kept under pressure at 3600 ° C. for a further 2 hours, allowed to cool and then poured the reaction product through a filter. The filtrate is removed by evaporation of methanol and methyl formate freed and the remaining residue under reduced pressure distilled. Man receives a p-methoxybenzoic acid methyl ester at a pressure of 0.6 Torr containing flow up to 880 C.

It consists of 29.2 parts. From 88 to 1180 C and 0.6 to 1.7 Torr distilled 85 parts of methyl p-methoxybenzoate with a melting point of 470.degree. In arrears 2.5 parts of p-methoxybenzoic acid remain. The yield of pure methyl p-methoxybenzoate is 59.5% of theory, p-methoxybenzoic acid 2% of theory.

Example 5 156.5 parts of p-chlorobenzoic acid in the form of the sodium salt are together with 200 parts of methanol, 1000 parts of methyl formate and 5 parts Triphenylphosphine nickel carbonyl heated to 3600 C in a pressure-tight vessel and held at this temperature for 2 hours. After the vessel has cooled down, filtered the reaction product and the filter residue extracted with water. It remains 143 parts of dimethyl terephthalate of 1420 C. from the residue The extraction solution becomes 8.2 parts of terephthalic acid by acidification with a mineral acid obtain. When evaporating the resulting by filtration of the reaction mixture A further 16.5 parts of dimethyl terephthalate are obtained from the filtrate solution. the Yield of terephthalic dimethyl ester is 82.2% of theory of terephthalic acid 5 O / o of theory, so that the overall yield is 87.2 O / o of theory.

PATENT CLAIM: 1. Process for the production of aromatic carboxylic acids or their mixtures with their esters by reacting aromatic halogenated hydrocarbons with derivatives of formic acid, characterized in that aromatic, if appropriate by nitrile, carbonyl, ester or ether groups substituted chlorine or. Bromocarbons with methyl formate and an anhydrous alkali salt of an organic acid or an alkali carbonate at elevated temperature and under elevated pressure.

Claims (1)

2. The method according to claim 1, characterized in that the Reaction in the presence of alcohols, in particular methanol, is carried out. 3. The method according to claim 1 and 2, characterized in that one carries out the reaction in the presence of metal carbonyl compounds. References considered: U.S. Patents No. 2,734 912, 2 773 090.