DE674149C - Process for the production of formamide - Google Patents

Description

Process for the preparation of formamide It is known that by catalytic association of carbon monoxide and ammonia at elevated pressure and elevated pressure Temperature formamide can win. The catalyst used was inter alia. dissolved in alcohol Sodium alcoholate applied.

It has now been found that the catalyst with advantage Can use products obtained after exposure to alcohol on barium oxide has been shown that the catalytic effect of alkali metal alcoholate also by The effect of barium oxide on reaction products obtained from alcohol occurs. as Alcohol is expediently used methyl alcohol, but other alcohols are also which react with barium oxide, such as ethyl alcohol or butyl alcohol can be used. Nevertheless the best results are obtained with methyl alcohol, as this is the case with barium oxide reacts easily and extensively and thus provides a solution in which the Catalyst is present in the highest concentration, which is naturally the most effective is. In addition, with regard to the work-up of the reaction mixture, the methyl alcohol cheapest because of its low boiling point.

The reaction is expediently carried out in a heated to about 70 to xoo ° Pressure vessel under a pressure of 3o bi, 9o atm. The speed of reaction decreases as the temperature rises, but it is advisable not to set the temperature too high drive, as z. B. at z2o ° already a noticeable cleavage of the formamide formed occurs in hydrocyanic acid and water, which react with the catalyst and convert it into Transfer catalytically inactive products (barium cyanide, barium formate, etc.). The introduction of the reaction components ammonia and carbon dioxide can either be carried out simultaneously or one after the other. Care must also be taken to ensure that each other reacting gases in intimate contact with the alcoholic solution of the catalyst step. For this purpose, the reaction vessel can be provided with a stirrer or the gas mixture or the alcoholic solution of the catalyst in the circuit pump the reaction vessel. Finally you can also use a gas mixture and a catalyst solution pass through the reaction vessel in countercurrent, whereby by attaching more suitable Distribution devices (packing) for intimate contact between gas mixtures and catalyst solution.

After the reaction has ended, the excess ammonia is removed first by relaxing drained, then the alcohol is distilled off and finally the formamide formed is driven off under reduced pressure.

Of course, the process can also be carried out continuously, by constantly injecting an ammonia-carbon oxide mixture into the pressure vessel, the the formed formamide-containing reaction liquid is continuously drawn off and constantly introduces a corresponding new amount of catalyst solution.

To maintain the longest possible service life of the catalytic converter is to use reaction gases that are as dry as possible and alcohol that is as dry as possible necessary because any water present is barium oxide or its products Action on alcohol would soon turn into barium hydroxide, which in further detail Processes with the carbon monoxide with the formation of catalytically inactive barium formate reacted. It is also important to ensure that the reaction gases, primarily the Carbon dioxide, are free of carbon dioxide, since the latter also leads to the formation of ineffective Barium carbonate.

Compared to the use of alkali alcoholate, the new catalyst has the advantage that the starting material, barium oxide, is considerably cheaper than alkali metal and is much safer to handle. In addition, the mixture of barium formate and (little) barium carbonate present after the catalyst has been exhausted can be regenerated to barium oxide by simple annealing with coal. plan can also first glow, which all things are transformed into barium carbonate, then treat the barium carbonate in a red heat with steam, whereby it passes into barium hydroxide, and annealing this for over- conversion into barium oxide in a hydrogen stream or vigorous air stream. Finally, the barium carbonate can also be converted into nitrate by treatment with nitric acid, which easily converts to barium oxide when the heat is low. The latter method avoids contamination of the barium oxide with carbon residues. Exemplary embodiment: suction technical barium oxide is mixed with 25o ccm of anhydrous methyl alcohol in a stirred autoclave (capacity 2.51) and dissolved by heating the sealed pressure vessel down to the impurities contained in the technical barium oxide. As soon as the temperature of the contents of the autoclave is 75 to 85 ' , liquid ammonia in a lock is pressed into the autoclave by means of carbon dioxide, which is taken from a storage bottle, and the autoclave is brought to a pressure of 30 atm by means of additional carbon dioxide. brought. The uptake of carbon dioxide starts immediately, which can be recognized by both the rise in temperature and the fall in pressure.

After every 10 atm. If the pressure drops, the CO pressure will return to 3o atm. brought, until the CO uptake comes to a standstill. The temperature will be throughout Experiment held at about 85 to 95 °.

A new amount of ammonia is now introduced in the same way and converted to formamide by CO. A total of i2 servings will take about 4 hours j e38 g N H3-456 g NH3 introduced into the autoclave.

After releasing the pressure, the autoclave and its contents are opened (137o g) of existing sludge consisting of barium carbonate and barium formate, freed. By fractional distillation at 5o to 85 °, 26o ccm flow, Mainly methanol with little free ammonia (10 g) and little formaemide (15 g) received; at 113 to 118, the formamide formed distilled under reduced Print (2o now) water clear over.

A small residue remains in the flask; the formamide yield is 95g, thus 94 ° jp of the theory, based on the converted ammonia.

Claims (2)

PATENT CLAIMS: i. Process for the production of formamide by reaction of ammonia with carbon dioxide at elevated temperature and pressure in the presence of catalysts in alcoholic solution, characterized in that the catalysts the products of the action of barium oxide on alcohols, such as methyl, ethyl, butyl alcohol, used and for intimate contact of the starting materials with the catalyst solution cares .. 2. The method according to claim i, characterized in that in the absence moisture and carbon dioxide are used.