DE1287061B - Process for the production of lactic acid nitrate - Google Patents

Description

The present invention relates to a method of production of lactic acid nitrate ["a-nitratolactic acid", CH3 - CH (ONOr3 - COOH).

Lactic acid nitrate is an important intermediate product e.g. B. for the Production of lactic acid, acrylic acid or amino acid derivatives. Lactic acid nitrate However, it was previously difficult to access and was therefore used as the starting material for one technical production out of the question.

From previous studies on the accumulation of nitrous oxide on propylene to nitropropyl nitrate, nitropropanol and dinitropropane is known that this can also lead to the formation of lactic acid nitrate (cf. Journal of Chemical Society London "[1946], pp.1100-1101).

However, these known reactions do not lead to any technically useful one Process for the production of lactic acid nitrate.

It has now surprisingly been found that lactic acid nitrate is formed in almost quantitative yield from propylene and liquid nitrous oxide, if you have a mixture of 1 mole of propylene and at least 1 mole of oxygen, as such or as air, with at least 1 mole of dinitrogen tetroxide at a temperature of -10 to + 40 ° C and the reaction product, if appropriate freed in the usual way of any excess nitrous gases that are still present.

Only nitrogen and water are obtained as further reaction products. The reaction can be carried out continuously or batchwise.

Dinitrogen tetroxide or that which is always in equilibrium with it Nitrogen dioxide can easily be removed by catalytic ammonia combustion be won.

It can be assumed that in the reaction between propylene and dinitrogen tetroxide this is primarily attached to the double bond of propylene and through the dem Oxygen supplied to the mixture causes a further oxidation.

During the oxidation there is a reduction of N204 to N203, and the latter is oxidized again to N204 by oxygen. Therefore, for the The overall reaction does not require an excess of dinitrogen tetroxide.

Surprisingly, a perfect one takes place in the reaction solution Rearrangement of the addition product to form lactic acid nitrate.

Since in the practical implementation of the process a mixture of Propylene and air or oxygen are introduced into liquid N204 for a Rapid and complete absorption of the propylene in the liquid phase to be taken care of. For this purpose, all procedural measures are suitable that are used for Accelerating the absorption of a gas find use. It must be discontinuous Working method for the best possible gas distribution and sufficient residence time the gas bubbles in the liquid N204 are taken care of.

When working continuously, e.g. B. when converting the gas mixture with liquid N204 in countercurrent in a packed column it is necessary for the implementation favorable if the packing is uniformly wetted with liquid N20. Simultaneously should the gas phase flow through the column in a turbulent flow, whereby a good mixing of the two phases and thus a high reaction rate be achieved. This achieves a practically table perfect inclusion of the Propylene in the liquid phase and a high conversion to lactic acid nitrate. That Process can be carried out at normal or higher pressure. The rate of oxidation can by adding oxidation catalysts such as selenium dioxide or vanadium pentoxide, can be increased.

The reaction is exothermic. The temperature setting can therefore take place, for example, in such a way that the dinitrogen tetroxide which has not yet reacted is brought to a temperature in a cooling device is condensed near its boiling point (20 ° C) and returned to the reactor. Local overheating causes side reactions and thus a drop in the yield. Considerable amounts of oxalic acid are produced at temperatures above 400 C. It must therefore be ensured that there is good uniform cooling. At one temperature below 100 C the reaction is already slower. The optimal reaction temperature is 15 to 30 "C. The reaction proceeds in this range with a sufficiently large Speed and without significant side reactions.

According to a preferred embodiment of the method, equimolar Amounts of propylene, N204 and oxygen are used. Because the implementation to lactic acid nitrate is almost quantitative, only small amounts of NO2 or N204 need to be left out of the reaction mixture removed. However, it can also be used with any excess of N204 and Oxygen can be worked. To remove the nitrous gases from the reaction product are all common methods of removing low-boiling liquids from their Suitable for mixtures with high-boiling substances, e.g. B. Treatment in a thin film evaporator.

In the case of batch-wise operation, there is still air left after the conversion has ended or oxygen can be passed through the solution to blow out the nitrous gases.

In the continuous process, unconverted NO2 can reach the top of the column subtracted from.

The lactic acid nitrate obtained is practically free of by-products, apart from water, which inevitably arises from this reaction.

The following examples are intended to explain the process in more detail: Example 1 In a reactor equipped with a reflux condenser, 1 mol of liquid N204 presented, the liquid height being 60 mm. A mixture of 1 mole of propylene and 1 mole of oxygen passes through at a rate of 5 liters per hour a frit made of ceramic material is passed into the liquid and there completely absorbed. The temperature in the reaction space rises to 25 "C, with N204 evaporating, condensed in the cooler and returned to the reaction mixture. To Once the gas has been introduced, the liquid reaction product is stored in a thin-film evaporator freed from residual nitrogen oxides. The yield of lactic acid nitrate (b.p. 20 = 115 115 to 120 ° C) is 91010, based on the propylene used. This product can e.g. B. with methanol in pure methyl ester (bp.10 = 62 ° C) or converted to Lactic acid can be saponified.

Example 2 On a vertical one charged with packing rings Tube will be at the top Storage vessel for N204 and a cooling device attached and at the lower end a gas inlet pipe and a collecting vessel for a built in continuous removal of the reaction product. Also is the reaction tube provided with a cooling jacket on the outside. The reactor is opened through the gas inlet pipe charged with a mixture of propylene and oxygen (11.2 liters per hour each). This is sprinkled in countercurrent with liquid N204 (46 g per hour). The temperature in the lower part of the tube is kept at 200 C, with unreacted N204 is distilled off and condensed again at the upper end of the tube. The lactic acid nitrate, which is already free of nitrous gases is taken from the lower end of the column. The yield is 95% of theory.

Claims (6)

Claims: 1. Process for the production of lactic acid nitrate by reacting propylene with liquid dinitrogen tetroxide, d a du r c h g e k e n nz ei c h ne t that a mixture of 1 mole of propylene and at least 1 Mol of oxygen, which can be present as such or as air, with min- at least 1 Mol dinitrogen tetroxide converts at a temperature of -10 to +40 "C and that Reaction product, if appropriate, of any excess still present in the customary manner nitrous gases released. 2. The method according to claim 1, characterized in that 1 mol Reacts propylene with 1 mole of oxygen and 1 mole of nitrous oxide. 3. The method according to claim 1, characterized in that the Carries out reaction at 15-30 "C. 4. The method according to claim 1, characterized in that the Heat of reaction dissipates by evaporating nitrous oxide and this after Condensation is fed back to the reaction mixture. 5. The method according to claim 1, characterized in that the Reaction in the presence of oxidation catalysts such as selenium dioxide or vanadium pentoxide performs. 6. The method according to claims to 5, characterized in that one the liquid nitrous oxide continuously with oxygen and propylene im Countercurrent implemented.