DE2025052B - Method of purifying lactic acid - Google Patents

Description

of ammonium ions, which can be obtained completely by passing the lactic acid to which 300 g of water are added removed via a cation exchange resin.

The catalyst used during the hydrogenation was prepared by adding activated carbon successively with a 1N sodium bicarbonate solution and then with a palladium (II) chloride solution in hydrochloric acid was impregnated and then subjected to a reduction treatment with formaldehyde would.

The lactic acid used was obtained by hydrolysis of the product of the oxidation of propylene with Nitric acid and removal of the oxygen-containing nitrogen (II-IV) compounds formed in the course of the hydrolysis in proportion to their formation (addendum 92116 to French patent 1465 460). From the solution obtained the lactic acid is isolated by distillation.

Example 2

The procedure described in Example 1 is followed, except that the pressure is increased Bringing 50 bar and varying the temperature and the duration of treatment. One obtains those in the following Results given in the table:

0.057%

Example 3

ίο You work according to the method of example 1, but under a hydrogen pressure of 10 bar. After 30 minutes of reaction, the total level is on Nitrogen dropped to 0.036%, this nitrogen being in the form of ammonium ions.

Example 4

The procedure described in Example 1 is used at a hydrogen pressure of 50 bar and with a water content of the lactic acid of 10%, but the palladium is through 0.1 percent by weight (corresponding to 2 g of platinum-carbon catalyst with a metal content of 5%). After 30 minutes of reaction, a lactic acid is obtained which contains a total of 0.13% nitrogen,

as being this nitrogen in the form of quaternary Ammonium ions are present.

Claims (1)

^{to 510} ), under which one plant- _{Uche Qdej} . _{tjerjsche sorts of} charcoal, which, if necessary, processes for the purification of lactic acid, which may be activated, simple or complex by hydrolysis of the oxidation of pro-silicates, silicic acid, aluminum oxide and aluminates, pylene with nitric acid and / or nitrogen- 5 asbestos, pumice stone, Quartz, kaolin, coke, bauxite, intermediate products obtained from dioxyd can be called diatomaceous earth and sand. After partial or complete removal of the nitric acid, mixtures of silicic acid and aluminum oxide can also be used, thereby using ge or aluminosilicates. The metal content of the raw lactic acid carrier is not critical,
at a temperature of 20 to 250 ° C. and io The amount of metal used is generally a pressure of 1 to 200 bar in the presence of over 0.001 percent by weight, based on the lactic acid subjected to a hydrogenation catalyst on the basis of a treatment, and can be up to noble metal of the group VIII of the periodic amount to 5%. VerSystems can treat quantities over 5% with hydrogen. can be applied without leaving the rhyming of the 15, but this does not result in any achieved particular advantages. Sufficient in practice Metal amounts between 0.05 and 0.5%. The treatment temperature of lactic acid bc- The present invention relates to a method preferably between 50 and 180 ° C. In the for the purification of lactic acid, which practice by oxidation 20 are generally between 5 and of propylene with nitric acid and / or nitrogen - 100 bar. Dioxide to intermediate products and subsequent To carry out the VerHydrolysis according to the invention of these oxidation products is obtained. Drivingly, a stream of hydrogen can be passed into the lactic acid containing the catalyst according to French Patent 1,465,640, anhydrous or in aqueous and their additives 90 556 and 92116 as well as the aqueous solution. French patent 1 500 619 provides one can also let lactic acid trickle through a column with lactic acid by oxidation of propylene, the packing and the catalyst contains nitric acid and / or nitrogen dioxide, given and in the hydrogen in cocurrent or on a slope in the presence of Oxygen, with the formation of the opposite stream to the lactic acid stream, is introduced from intermediate products, which mainly consist of 30 The process according to the invention is particularly A-nitratopropionic acid, which is then advantageous, which almost all of the nitrogen-containing hydrolysis with water, possibly containing impurities Removal of the nitrogen in gaseous form (e.g. N ₂ , N ₂ O) destroyed in the presence of an acid such as nitric acid. It can happen that part of the nitrogen, nitric acid, is liberated and, at the end of the period, the extent of which, according to the treatment conditions, is an aqueous solution of lactic acid, variable, is converted into ammonium ions containing nitric acid . These two acids stay dissolved in the lactic acid. An additional treatment with cation exchange resins or the can be separated according to various methods. for example, by treating the reaction by electrodialysis made possible to remove this remaining mixture with tertiary or secondary amines 40 nitrogen. or more simply by azeotropic distillation of the process according to the invention enables in Nitric acid (French patent 1,500,619) easily adds lactic acid of high purity or obtained by extraction of the lactic acid with butanol, which is less than 15% nitrogen in the form (Belgian patent 707 424). of ammonium ions and in particular These pre-separation operations result in a 45 for use in the food industry and Lactic acid, which, even if it is free from nitric- pharmaceutical industry, »Acid is, still nitrogen-containing impurities The following examples illustrate the invention, contains indefinite nature. A procedure for purifying Example 1 was now followed
Lactic acid, which is obtained by hydrolysis of the intermediate products formed in the oxy-50 In a 500 cm x ¹ stainless steel autoclave, dation of propylene with nitric acid and / or the intermediate products shaken by means of a shaker, is brought in 300 g milk had been kept free of nitric acid, after partial or complete acid with a content of 0.34 percent by weight removal of the nitric acid, which is characterized by nitrogen, determined by the method of, that the crude lactic acid at 35 Dewarda, and 6 g of one Palladium-carbon catalyst at a temperature of 20 to 250 ° C and a sators with a content of 10 «Vo metal in. The pressure of 1 to 200 bar in the presence of a hydrogen autoclave is closed and hydrogenation catalyst based on a noble metal washes. Then, after having brought the contents of Group VIII of the Periodic Table to 120 ° C with water in the autoclave, treated on a fabric. 60 hydrogen pressure of 50 bar. After 5 minutes, the pressure drop to 40 bar, in particular, can be used as a catalyst. Hydrogen is introduced to bring metals, such as ruthenium and palladium, to a pressure of 50 bar. After 5 minutes, use rhodium and platinum. These metals adjust the pressure to 40 bar. These can be maintained alone in the form of a powder with variable conditions for 20 minutes. The contents of the particle size or in the form of spheres or 6s autoclave are cooled to 20 ° C. Then the grains will be used. They can also be degassed on apparatus. The catalyst is separated off by means of supports customarily used in catalysis. The lactic acid obtained contains (see S. Berkman and coworkers, Catalysis, p. 426 only 0.04 percent by weight nitrogen in the form