DE523693C - Process for the preparation of methylamine - Google Patents

Description

Process for the preparation of methylamine It is known that by Effect of formaldehyde on ammonia or ammonium salts methylation of ammonia nitrogen can cause; however, one always obtains a mixture that is largely different methylated amines, which are difficult to separate from one another.

It has now been found that the formation of mixtures of different Avoid methylated amines from the start and go straight to pure methylamine can get if you formaldehyde under pressure and at elevated temperature Imides of dicarboxylic acids or sulfonic acids or their methylol compounds act leaves and saponified the methylimides obtained. As for the present proceedings suitable ammonia compounds come into consideration, for. B. the phthalimide, the imide o-sulfobenzoic acid, cyanuric acid, etc.

The methylation of the compounds mentioned with the aid of formaldehyde as a methylating agent proceeds according to the following equation: It is best to work at temperatures between 15o ° and 25o °. The easy-to-separate, pure methylimide compound is saponified by one of the customary processes, where it decomposes i% methylamine or methylamine salt and the corresponding acid according to the following equation: The free acid obtained can optionally be converted back into the imide in a known manner.

Instead of the imide compounds as starting material, one can also starting from the methylolimide compound, which is easily obtained in pure form, what should be considered the resulting lower amount of formaldehyde can be an advantage. The formaldehyde, in its place just as well its polymerization products, Polyoxymethylene and trioxymethylene can occur, it is expedient to use a more concentrated, aqueous solution Solution on. The use of an addition of methanol or ethanol or another water-soluble organic solvent that acts against the reaction components themselves is indifferent to the reaction mixture is very advantageous, as this is a disruption the desired course of the reaction largely avoided, the yield increased and the methylimide compound is easily obtained pure.

The method described can be used discontinuously of autoclaves that are periodically filled and emptied after the reaction has ended, are executed. But you can also work continuously, where you z. B. that The reaction mixture, which is expediently preheated, is brought to the reaction temperature by a The held pipe or snake system presses or pumps. Example i 50 parts by weight Phthalimide are in an autoclave with 50 parts by volume (z. B. liters) 30% Formaldehyde and 50 parts by volume of methanol heated to 220 ° for 2 hours, -, vobei the pressure to 7o to 9o atm. increases, but almost after the autoclave has cooled down disappears completely. The phthalomethylimide which has crystallized out is filtered off. the Yield is 65 to 70 ° (0 of theory. It is after washing twice with aqueous 50% methanol and can readily undergo cleavage be subjected. This is done by pressure saponification with about 10% sulfuric acid in a manner known per se. The resulting phthalic acid is derived from the sulfuric acid Methylamine solution separated by filtration and the methylamine from the latter distilled off after the addition of excess alkali or alkaline earth lye. The yield based on phthalmethylimide, 98% of theory is about 98 to 9% Methylamine. When working up the entire reaction product without prior separation of the Phthalmetbylimids one obtains a yield of 98 '/, the theory of bases with 93 to 98% methylamine. Example e 37 parts of o-sulfobenzoic acid imide are in one Autoclave together with 10 parts of trioxyniethylene, 5 parts of water and 40 parts Methanol heated to 220 ° for 2 hours. After the autoclave has cooled down, it adds 120 parts of 4N aqueous sodium hydroxide solution are added to the liquid reaction product and the mixture is heated the autoclave to 15o to 16o ° for 2 hours. It is allowed to cool to 100 °, relaxed the contents of the autoldaven, insofar as it is gaseous. by a descending cooler into a receiver which is charged with methanol and distilled at atmospheric pressure the remaining methylamine and the methanol in the same template. That in the The product collected is neutralized with concentrated hydrochloric acid and the Methanol was separated from the remaining methylamine hydrochloride by distillation. The yield of the chloride is 80 ° / "of theory with a content of 85 ° 10 of pure methylamine hydrochloride. Example 3 88.5 parts of N-methylolphthalimide (obtained by reaction of molecular amounts of phthalimide and formaldehyde in aqueous solution at 100 °, filtration of the solution, cooling and allowing to crystallize and drying the N-methylol compound obtained in quantitative yield) are in an autoclave en together with 25 parts of 30% aqueous formaldehyde solution and 64 parts of methanol Heated to 22o ° for 2 hours, during which the pressure rises to 80 atm. You let it cool down and the phthalmethylimide which has crystallized out is filtered off. It's after two times Wash out with aqueous alcohol at pure melting point. The yield is 60 parts : = 74.51 of theory.

The saponification of the phthalmethylimide takes place with slightly more than the calculated amount of aqueous 13.85% sodium hydroxide solution in an autoclave at 150 °. The resulting free base is distilled off with the methanol after the saponification has ended. Yield of methylamine 99.5% o of theory, based on phthalmethylimide, the 74.0 % of theory, based on the N-methylolphthalimide used. If the entire reaction product is saponified without prior separation of the phthalic methylimide, a yield of 98% theoretical of bases with a content of 93 to 94 ° 10 of methylamine is obtained. EXAMPLE 4 50 parts of phthalimide are heated in an autoclave together with 50 parts of 30 ° / aqueous formaldehyde for 2 hours at 220 °, the pressure being 70 to 100 atmospheres. increases. It is allowed to cool and the phthalmethylimide which has crystallized out is filtered off. The yield is 27.5 parts - 6o.7 % of theory. The saponification takes place in the autoclave at 150 ° with a little more than the calculated amount of 13.85% sodium hydroxide solution. The resulting free base is distilled off after the saponification and collected in water. The methylamine yield is 99.0% of theory, based on phthalimide, or 60.7% of theory, based on ththalimide.

Example 2o parts of succinimide are in an autoclave together with 9.5 parts of trioxymethylene, 1.5 parts of water and 60 parts of methanol d. For hours heated to 20o °. After the autoclave has cooled down, it is added to the liquid reaction product 80 parts of 6N aqueous sodium hydroxide solution and heated the autoclave for a further a hours on 15o to 16o0. It is allowed to cool to zoo °, and the autoclave is released through a descending condenser in a template, which is charged with methanol, and distilled at atmospheric pressure the remaining methylamine and the methanol in the same receiver above. The product collected in the receiver is neutralized with concentrated hydrochloric acid and then the methanol by distillation from the remaining methylamine hydrochloride separated. The yield of chloride is 74% of theory with a content of 79% pure methylamine hydrochloride.

Claims (1)

PATENT CLAIM: Process for the preparation of methylamine, thereby characterized in that formaldehyde is added under pressure and at elevated temperature Dicarboxylic acid imides or sulfonic acid imides or their N-methylol compound can act and saponified the methy limide obtained.