CS276959B6 - Process for preparing lactic acid - Google Patents

Abstract

It represents waste-free technology using by esterification carried out by blow molding thin layer technical intermediate methanol vapors prepares from the fermentation mash emerging fermentation from heavy juice, glucose solutions or molasses. Fermentation mash during fermentation neutralizes with ammonia water; \ tor potassium hydroxide, then concentrate, with sulfuric acid to ammonium sulphate, or potassium and lactic acid. acid the milk is equilibrated with methanol in proportion 1: 1. Then heat, decant, centrifuge and subsequently subjected to esterification. The resulting esterification product is further rectification into methanol and methyl lactate, which is hydrolyzed with water. The resulting lactic acid is concentrated to the desired level concentration.

Description

Lactic acid production process

Testimonials technique

The invention relates to a process for the production of lactic acid with high product purity by waste-free technology and with high yield.

Prior art

Lactic acid is produced by fermentation technology from various carbohydrate substances such as glucose and sucrose. Therefore, for example, starch, molasses, raw sugar, heavy juice, sweetened molasses and the like can be used as starting materials. However, due to the quality of the fermented or fermented mash that is subsequently prepared from them, the actual use of these substances is limited.

It is more advantageous to start from a relatively pure raw material, but even in this case the decomposition of the fermented mash does not result in a product of sufficiently high purity, and even when pure substrates are used, a significant amount of ballast remains from lactic acid from added nutrients, unfermented sugar.

To isolate lactic acid from fermented mash, where it is in the form of a calcium salt, a method for the crystallization of calcium lactate has hitherto been used. The fermented mash is heated to a temperature of about 80 ° C while adding lime milk for clarification. The clarified and concentrated mash is subjected to crystallization and affinity of calcium lactate, which is relatively well soluble in cold water in a ratio of 1:20, causing low crystallization and affinity yields. The total fermentation and isolation yield in this process does not exceed 30%, which prompted the search for other isolation methods.

The individual partial extracts in the production of edible lactic acid from molasses by crystallisation of calcium lactate can be divided as follows:

fermentation extract ........................ 78 to 90% (observed) yield on clarification, filtration and concentration .......... ......................... 90% (estimate) crystallization yield .................. 61% (observed) affinity yield ....................... 79% (detected) decomposition yield ............ ....... 95% (estimate) yield during concentration and filtration .... 95% (estimate) filling and handling during shipment! .... 98% (estimate) total total yield ............. 30%

Yield on crystallization and affinity together below 50%.

The fact that the lowest yield is obtained with crystallization and affinity below 50% has prompted the search for more viable routes of isolation and purification of lactic acid from fermented mash, such as extractions, steam distillation, esterifications and the like, which would replace lossy crystallization. Extraction using ethyl ether and ethyl acetate has proved to be disadvantageous in that the extraction is not selective and other substances pass through the extraction in addition to lactic acid. Extraction with ethyl ether also has a disadvantage from a safety point of view.

A single steam distillation of technical lactic acid has also proved unsuitable for its isolation. This method is also not effective in distilling crude lactic acid made from glucose. It gives relatively low quality acid and a lot of lactic acid decomposes during distillation. In a single steam distillation even under vacuum, lactic acid can form lactyllactic acids, which do not distill with steam and remain at the bottom of the distillation boiler. This is the main cause of low yields in a single distillation.

Similarly, neither a single esterification of technical lactic acid with methanol (Z. Ostrovský, A. Šepitka) nor continuous continuous esterification of lactic acid with methanol in a packed column (V. Hummel) gave satisfactory results, as ballast substances clog the esterification kettle and the packed esterification column.

The shortcomings of the described methods are largely eliminated by the esterification of lactic acid with methanol from the film (Czechoslovak Patent No. 104,398).

In this technology, the principle must be observed that the flow rate of lactic acid through the sieves must be within the limits of the esterification rate, and the technology has several advantages:

1. Any ballast substances do not clog the mesh, but gradually flow to the bottom of the esterification column.

2. The esterification can be carried out continuously.

3. The inclination of the nets as well as their number can be used to control the flow rate and flow time of the lactic acid solution through the sieves and thus the perfect methanol vapor transfer, which guarantees a high yield on one sieve above 80%.

4. When an excessive amount of methanol vapor is used, the esterification reaction, which is a second-order reaction, becomes a first-order reaction, the rate of the reaction being dependent only on the concentration of lactic acid. Since the concentration of lactic acid during its passage through the reaction zone varies from the initial to the zero concentration, a certain constant constant esterification rate prevails in the reaction zone, to which the flow rate can be adjusted.

5. The large reaction area provided by the nets allows the reaction products formed to evaporate rapidly, which disturbs the reaction equilibrium and thus aids in the further formation of the desired product.

6. In the case of isolation by esterification of technical lactic acid with methanol from the film, it is possible to obtain a yield of well above 80%, which previous isolation methods have not allowed.

The essence of the invention

The process for producing lactic acid and its salts from fermentation broth prepared from heavy juice, molasses, glucose or raw sugar by a waste-free technology using esterification from a film with methanol vapor consists in first neutralizing the fermentation mash during fermentation with ammonia water or potassium hydroxide, it is then concentrated, decomposed with sulfuric acid into ammonium or potassium sulphate and lactic acid, which is equalized with methanol in a ratio of 1: 1. It is then heated, decanted, centrifuged and subsequently subjected to esterification from the film. The resulting esterification product is further separated by rectification into methanol and methyl lactate, which is hydrolyzed with water. The resulting lactic acid is concentrated to the required concentration.

The process according to the invention gives lactic acid of purity 100, suitable for pharmaceutical, chemical, plastic, food, technical and other purposes.

The production technology is practically waste-free, methanol and water are recirculated and all products and intermediates are in a liquid state and are usable; ammonium sulphate as a fertilizer.

Example of an embodiment of the invention

Example

Fermented mash was prepared from heavy juice. Fermentation was performed at 50 ° C using Lactobacillus delbrúckii. The resulting lactic acid was neutralized with ammonia water to pH 6.0 to 6.5. After fermentation and concentration of the fermented mash, it was decomposed with sulfuric acid into lactic acid and ammonium sulfate. The thus obtained technical lactic acid with a concentration of 50 to 60% was equalized with methanol in a ratio of 1: 1. After removing the precipitated ammonium sulfate, the equalization mixture was continuously esterified with methanol from the film formed on the conical meshes in the column by blowing with methanol vapor. The methanol was separated from the esterification mixture in a rectification column and led again to equalization and esterification from the film. Methanol consumption only manifested itself in the form of losses, for example below 0.1%. After hydrolysis of the lactic acid methyl ester, the lactic acid was concentrated and the condensates from the concentration were used to dilute the heavy juice to the brewers. This method is shown in Scheme 1.

Since all products and intermediates were in the liquid state, much of the thermal energy can be recovered. Operating temperatures are around 100 ° C, so the dissipation of thermal energy is minimal.

Hydrolysis of the esterification mixture yields lactic acid suitable for pharmaceutical, chemical, plastic, food, tannery and other purposes.

The film equipment can also work in other cases, especially where there is a chemical or physical interaction, such as esterification, steam distillation, deodorization, hydrogenation, absorption, neutralization and the like, which can be used to solve environmental problems.

Claims (1)

PATENT CLAIM Process for the production of lactic acid from fermentation broth prepared from heavy juice or glucose solutions or molasses by a waste-free technology using esterification carried out by purging a thin layer of technical intermediate with methanol vapor and subsequent hydrolysis, characterized in that the fermentation is first neutralized with water during fermentation. potassium hydroxide, then concentrated, decomposed with sulfuric acid into ammonium or potassium sulphate and lactic acid, which is equalized with methanol in a ratio of 1: 1, heated, decanted, centrifuged and subsequently subjected to esterification, the resulting esterification product is further divided into methanol by rectification. and methyl lactate, which is hydrolyzed with water, and the resulting lactic acid is concentrated to the required concentration. End of document