DE930327C - Process for the production of carboxylic acid anhydrides - Google Patents

Description

Process for the production of carboxylic acid anhydrides It is known, that one methanol with carbon oxide to organic compounds, especially acetic acid and methyl acetate. This carbonylation proceeds particularly well, if the catalysts used are carbonyl-forming metals or their compounds, in particular using halogen in free or bound den of the form. Man has already proposed that instead of methanol in such carbonylations To use dimethyl ether or, in the presence of water, ester of 3 / tetha- nols, which should deliver the methanol to be carbonylated during the implementation. Also in these Acetic acid is obtained in the form of its methyl ester.

It has now been found that the known carbonylation of Ethers and esters of methanol take a different course and in the main Anhydrides are obtained when the pressure is above 200 atm, advantageously above 400 at, works with exclusion of water at temperatures below 2500 and Complex group-free nickel or cobalt halides used as catalysts. Instead of these halides, in particular the bromides or iodides, or mixtures the halides of both metals, one can use the rivets themselves or other compounds this Use metals in combination with halogen in free or bound form.

The reaction takes place according to the following equations: In case of Ether: I. CH5-OR + 2CO -> CH3-CO-O-CO-R, in the case of the esters: H CH3-CO-OR + CO -> CH3-CO-O-CO-R.

Since the reaction via the formation of esters as a partial reaction in the sense the equation CH3-O-R + COCH3-COO-R runs, if the implementation is incomplete the ether can be isolated to anhydrides and the corresponding ester. Depending on the The ethers or esters used can be symmetrical or mixed anhydrides obtain. Because of the absence of water in the implementation, it is not necessarily required to use stainless steel as building material; it is also generally sufficient ordinary high pressure steel.

The carbon dioxide used can contain hydrogen, something special when using cobalt halides is sometimes advantageous, but is a such addition is not absolutely necessary.

The hydrogen content should not exceed 8o / o.

The carbon dioxide can also contain inert gases, but it should If possible, it should be free of hydrogen sulfide. The reaction gas is also advantageous freed from water vapor by drying.

The pressure should be more than 200 at, advantageously over 400 at. In general, pressures between 400 and 800 at are used. The reaction temperature is generally between 100 and 2500, preferably 150 and 2000.

The process is advantageously carried out so that the catalyst one of the reactants is always in solution. As the catalysts generally do not dissolve in the starting materials used, it is advantageous to To use solvents, such as. B. carboxylic acid anhydrides, carboxylic acids or N-alkyl or N-aryl pyrrolidones. It is particularly advantageous to use the reaction products themselves to be used as a solvent.

The reaction can be carried out batchwise or continuously carry out. It is not necessary to be exposed to the carbon-hydrogen mixture to continue on the starting material until the reaction is complete; the unused portion is recovered and put back into implementation. Work-up is expediently carried out by distillation, if appropriate with increased or reduced pressure. The catalyst used is found in unchanged Most of the form in the still residue. He can usually without further cleaning can be reused. The catalyst concentration is expediently between 0.2 and 2 0 / o nickel or cobalt, based on the ether or ester used.

The parts given in the following examples are parts by weight.

Example I A mixture is left in a high pressure autoclave 150 parts of N-methylpyrrolidone, 150 parts of methyl acetate, 10 parts of nickel iodide and Act 5 parts of ethyl iodide at 190 ° carbon oxide under 700 at pressure for 11 hours. In the work-up, in addition to unchanged N-methylpyrrolidone, and not converted methyl acetate I67 parts of acetic anhydride. With practically quantitative The yield is the conversion to anhydride 81% of the theoretically possible amount.

Example 2 A mixture is left in a high pressure autoclave 150 parts of N-methylpyrrolidone, 150 parts of dimethyl ether and 10 parts of nickel iodide Soak in carbon monoxide for 15 hours at 190 ° and 700 at. Receives in the work-up one next to unchanged N-methylpyrrolidone and unreacted dimethyl ether 6.5 Parts of methyl acetate and 40 parts of acetic anhydride. With practically quantitative The theoretical yield is the conversion to anhydride I20 / o and to ester 2.80 / o possible amount.

Example 3 A mixture is left in a high pressure autoclave 150 parts of methyl acetate, 150 parts of N-methylpyrrolidone and 10 parts of cobalt iodide a gas mixture of 93% carbon oxide and 7 ovo hydrogen at 700 atm and 190 ° Leave on for 17 hours. When working up by distillation, one obtains besides unchanged N-methylpyrrolidone and unreacted methyl acetate I25 parts acetic anhydride, corresponding to a 600 / above conversion of the methyl ester. The yield is practical quantitatively. The distillation residue consists of the cobalt iodide used.

Example 4 A mixture is left in a high pressure autoclave 150 parts of methyl acetate, 150 parts of N-methylpyrrolidone, 10 parts of cobalt bromide and 5 parts of ethyl iodide, a gas mixture of 970% carbon and 30% hydrogen act at 190 ° and 700 for 15 hours. When working up, one obtains in addition to unchanged N-methylpyrrolidone and unconverted methyl acetate 103 parts Acetic anhydride, corresponding to a 500 / above conversion of the methyl ester. The still residue consists of a mixture of cobalt bromide and cobalt iodide.

Example 5 A mixture is left in a high pressure autoclave 150 parts of N-methylpyrrolidone, 150 parts of dimethyl ether, 10 parts of cobalt bromide and 5 parts of ethyl iodide at 210 ° and 700 atm, a gas mixture of 960 / o carbon oxide and 40 / (act on hydrogen for 12 hours. Working up gives in addition to unchanged N-methylpyrrolidone and unreacted dimethyl ether, 8.6 parts Methyl acetate and 46 parts acetic anhydride. With a practically quantitative yield the conversion to anhydride In is 30 / (1 and to ester 40/0 of the theoretically possible Lot.

Example 6 The mixture is left in a high pressure autoclave from 150 parts of acetic anhydride, 150 parts of methyl acetate and 10 Parts of cobalt iodide at 1950 carbon oxide under 700 atm pressure act for 20 hours. In the distillation, 76 parts of newly formed acetic anhydride are obtained, accordingly a 370% conversion of the methyl acetate.

Example 7 A mixture is left in a high pressure autoclave 150 parts of N-methylpyrrolidone, 150 parts of methyl acetate, 4 parts of cobalt bromide and 6 parts of nickel iodide, a gas mixture of 97% carbon oxide and 3% hydrogen act at 180 ° and 700 at pressure for 25 hours. One receives in the distillation I30 parts of acetic anhydride, corresponding to a 620% conversion of the methyl ester.

Example 8 A mixture is left in a high pressure autoclave 150 parts of ethyl propionate, 150 parts of N-methylpyrrolidone, and 12 parts of nickel iodide and 6 parts of ethyl iodide at 190 ° carbon oxide under 700 atm pressure for 10 hours. Working up the reaction product gives unreacted ethyl propionate as well as unconverted ethyl propionate and the unchanged N-methylpyrrolidone used as solvent 65 parts Propionic anhydride, corresponding to a 350% conversion of the ethyl propionate.

Claims (2)

PATENT CLAIMS: 1. Process for the production of carboxylic acid anhydrides, characterized in that carbon dioxide, optionally mixed with hydrogen, on ethers or esters of methanol at pressures above 200 atm, advantageously above 400 at, and at elevated temperatures below 2500, advantageously below 2000, in the presence of complex group-free nickel or cobalt halides or mixtures thereof and lets act in the absence of water. 2. The method according to claim I, characterized in that one nickel or cobalt or their halogen-free compounds in combination with free or Bound halogen uses instead of nickel or cobalt halides.