DD271513B5 - METHOD FOR SEPARATING N-METHYL UREA-N, N-DIMETHYL MUSHROOM MIXTURES - Google Patents

Description

The MMH obtained by the process according to the invention is separated off from the mother liquor and dried. The mother liquor, which also contains ammonia in addition to DMH, is recycled to the manufacturing process of the mixture. The ammonia released in the reaction of the urea with monomethylamine is precipitated with water and the product obtained is used for recrystallization after appropriate concentration adjustment. In comparison to all known processes, no waste products occur here; ultimately, the process according to the invention is an approximately waste-free technique

 The latter finding is to be substantiated on the basis of the exemplary embodiments.

Ausf Ol irungsbelspiele example 1

1 kg of the MMH-DMH-Gemischos (75% MMH / 25% DMH) are freshly added from the solidifying roll at a temperature of 60 ° C in 100 ml of 1 to 2% ammonia water with stirring and after filtration, the solution at normal temperature Crystallization provided. It is from the solution 650g MMH, which corresponds to a yield of 85%, obtained with a purity of more than 97%.

Example 2

1.5 kg of the MMH-DMH mixture (MMH 75%, DMH 25%) are added at a temperature of 6O ⁰ C in 100 ml of ammonia water. The resulting mixture is briefly heated to 80 ° C to complete the solution and stirred with 20ml

Diluted ammonia water. After the hot filtration, crystallization occurs at room temperature. It will be 920g MMH (82% Yield) having a melting point of 96.5 ° C, which corresponds to a purity of more than 95%. In addition to adhering water, the product still contained 0.8% DMH. Example 3

1.5 kg of the MMH-DMH melt (MMH 75%, DMH 25%) with a temperature of 110 ° C are stirred with 100 ml

Ammonia water mixed, after reaching a temperature of 8O ⁰ C again added 20 ml of ammonia water, filtered

and turned off to crystallize. After crystallization 940 g of MMH (84% yield) are obtained with a melting point of 98 ° C, which corresponds to a degree of purity of greater than 97%.

The product still contained 0.5% N, N'-DMH. Example 4 (Comparative Example) Starting amounts as in Example 2, but instead of ammonia water is normal distilled water to Recrystallization used. However, it must be spent for 1.5 kg of mixture 250ml of water. The product obtained

(850g = 76%) has a melting point of 91 ⁰ C and still contains 6.5% DMH. To the degree of purity of the invention

To reach the process, either the amount of water must be raised to 400 ml, then you get at a yield

of 95% a DMH content of 1 to 2% and a solidification point of 95.5 ⁰ C, or a second recrystallization are performed.

Claims (1)

A process for the separation of N-methylurea-N, N'-dimethylurea mixtures, which are formed in the reaction of about equimolar amounts of urea and methylamine at elevated temperature, by recrystallization, characterized in that the product mixture under utilization of the mixture heat at atmospheric pressure in the temperature range 20 to 11O ⁰ C is treated with aqueous, 1 to 2% ammonia solution, N-methyl urea by crystallization brought to crystallization and the Ν, Ν'-dimethylurea-containing mother liquor is recycled to the manufacturing process of the mixture. The invention relates to a process for the separation of binary mixtures of N-methylurea and N, N '· Dimethylurea. N-methyl! Urea, which is obtained in this case, is used in particular for the production of theobromine, a Purine derivative, and has many uses in synthetic chemistry, as a catalyst or stabilizer in the Polymer chemistry and is a sought after substance in the crop protection sector. The production of N-methylurea (MMH) from monomethylamine and urea has been known for over 50 years (US Pat 2253528 and U.S. Patent 2,257,717). In this case, MMH is approximately equimolar by heating urea with monomethylamine Produced quantities. To separate unreacted urea and Ν, Ν'-dimethylurea (DMH) are separators downstream. DMH is removed from the reaction product by washing with benzene, toluene or cyclohexane at 15 ^° C. MMH is separated from urea by washing with larger amounts of toluene, benzene or cyclohexane at 75 ⁰ C. Latter Separation can also be carried out with water at ⁰ ° C. or with aliphatic ketones. According to DE-PS 896640 a recrystallization from water is possible, but it must be done with a lot of water, thereby very poor yields can be achieved. Furthermore, water-dioxane mixtures (DE-PS 1029362) or gasoline-ligroin or decalin (DE-PS 1165579) are recommended. Although all proposed solutions provide relatively clean MMH, additional material cycles are required it causes drying problems, the exhaust air must be treated, and it is not certain to what extent the organic Solvent can be separated completely. The recrystallization from water (DE-PS 896640) provides only a relatively clean MMH, if with large amounts of water is working. However, losses of 25% can be expected and an additional water circuit has to be installed. According to DE-PS 2937331 MMH is from urea and monomethylamine at 110 to 170 ° C in chlorinated aromatics, alkylated Aromatics, nitrobenzene etc. prepared as a solvent. The implementation is quite selective, but there is little The prospect of removing adhering high-boiling solvent traces. In addition, the solvents mentioned belong in the Food and Pharmaceuticals to the undesirable substances, so that even from the production of an application ban for MMH can result. In DD-PS 220955 is for the separation of a ternary mixture urea-methylurea-N.N'-dimethylurea the Use of chlorinated hydrocarbons, especially chloroform recommended. The disadvantages are once through the Substance group itself conditioned, on the other separation problems occur. There must be additional environmental protection measures realized and set up a further material cycle. According to SU-PS 149428, it is possible to purify MMH by filtering through a layer of solidified MMH shred becomes. The impurities should then be in the filtrate. For a large-scale process, the last proposal is not feasible, the technical complexity is too high. In addition, it seems very questionable whether in this way, too Urea remains behind. The aim of the present invention is to obtain N-methyl urea from a binary mixture of MMH-DMH and thus to clean that no environmental problems occur and as free as possible production is guaranteed. It was therefore the object of a process for the separation of monomethylurea-dimethylurea mixtures which allows the recovery of monomethylurea in high purity, without additional separation and processing steps. This object is achieved with the separation of N-methylurea-N, N'-dimethylurea mixtures in the reaction approximately equimolar amounts of urea and methylamine formed at elevated temperature, dissolved by recrystallization, wherein according to the invention, the product mixture is treated using mixture heat at atmospheric pressure in the temperature range 20 to 110 ⁰ C with aqueous, 1 to 2% ammonia solution, N-methyl urea Cooling crystallized and the Ν, Ν'-dimethylurea-containing mother liquor is recycled to the manufacturing process of the mixture. The recrystallization of the binary mixture of water gave an enrichment of the MMH with normal amounts of water in the recrystallized product from 75% to 88%. If the amounts of water are doubled, then a 92% MMH can be obtained, but the losses are more than 25% and the amounts of water to be treated are unmanageable even in a small-scale plant. Surprisingly, these disadvantages can be avoided if used instead of water diluted ammonia water becomes. From ammoniacal water, the mixture is much better recrystallized with higher yields, the Amounts of the recrystallization agent can be lowered, after a single recrystallization a Methylurea with a purity of more than 95% is formed. That by changing the alkalinity of water and thus the pH value, an improvement in the recrystallization effect can be achieved, was not known. Is then at the same time still the product heat of the MMH-DMH mixture of about 60 ° C after leaving the cooling roller or Hardening used, or used directly from the reaction column coming liquid product, the about has a temperature of 100 ° C, so you can reduce the amount of solvent even further and comes to ratios of 1:10 to 1:15, i. with a liter of ammonia water a maximum of 15 kg of the mixture MMH-DMH can be recrystallized. This utilization of the product heat avoids further energy input for the recrystallization.