CS228927B2 - Method of preparing fumaric acid - Google Patents

Abstract

Fumaric acid is produced from the wash waters of exhaust gases resulting from hydrocarbon oxidation, which contain maleic acid. The process comprises a thermal pre- treatment of the impure maleic acid solution, with optional concurrent concentration, with transformation of part of the impurities to facilitate their elimination from the final product, subsequent hot filtration, isomerization of the maleic acid to fumaric acid, crystallization according to a pre-set time/temperature chart, removal of the mother liquors by filtration, subsequent dissolution in water or in a fumaric acid solution, decolorization, recrystallization and drying.

Description

The invention relates to a process for the industrial production of fumaric acid.

The most commonly used process for producing fumaric acid today is isomerization of maleic acid to fumaric acid using known catalysts such as thiourea, mercaptan and the like, crystallization of the acid obtained, separation of the precipitate, dissolution of the precipitate in hot water, decolourising the solution using coloring agents such as, in particular, activated carbon, hot filtration, crystallization under cooling, separation of the precipitated fumaric acid and subsequent drying.

Due to the high diversity of raw materials, working conditions and catalyst activities, impurities such as quinones, especially naphthoquinone, benzoic acid, toluic acid, toluic acid, citraconic acid, phthalide, phthalic acid, other aliphatic and aromatic acids and aldehydes, condensed products are present in the starting solution. and polymer products and inorganic acids and salts. In the known processes, not all of the above-mentioned impurities can be completely removed from the product and these impurities remain present in the end product and prevent its further use in chemistry in general and especially in the manufacture of pharmaceutical products and foodstuffs. In this context, it should be pointed out that if fumaric acid is pure, it can be used to replace traditional citric acid, tartaric acid and / or ascorbic acid, as permitted by the legislation of several countries which are very strict in matters of this type. Of course, it is clear that the presence of impurities, such as those mentioned above, in fumaric acid, which is obtained as the final product, drastically limits the possibilities and field of its industrial use.

SUMMARY OF THE INVENTION The present invention provides a process for the manufacture of fumaric acid by using isomerization of maleic acid, comprising washing the acid-containing wash water. the maleic anhydride obtained by washing the water of maleic anhydride-containing waste gases originating from the oxidation of hydrocarbons is subjected to a preliminary heat treatment by heating to a temperature in the range of 70 to 100 degrees Celsius, preferably 90 to 100 ° C. , the resulting filtrate is isomerized by heating from 30 to 50 ° C. 100 ° C over a period of 2 to 6 hours, preferably over 4 hours, wherein the heating course corresponds to an exponential temperature versus time, the isonization mixture is maintained for 2 to 6 hours, preferably 4 hours, at 100 degrees Celsius, then 1-5 hours, preferably over 3 hours, cooled to 50 ° C to give product crystals, which are separated, dissolved in water or fumaric acid solution, the solution is decolorized, the product is recrystallized, and the separated crystals are dried.

The maleic acid-containing wash waters generally derived from the hydrocarbon oxidation unit may be, for example, the wash waters obtained in the oxidation of o-xylene, naphthalene, mixtures thereof, alkylnaphthalenes, benzene, benzene analogues, butane, butene and the like, or their mixtures or mixed scrubbing effluents from any of the hydrocarbon oxidation units.

The process of the invention provides a product having higher purity and better physical and chemical properties compared to a product obtainable according to prior art methods. This effect is mainly due to the pretreatment in combination with the subsequent isomerization, in particular of the pure product.

The process of the invention is better understood from the following detailed description, which provides a non-limiting example of a suitable embodiment of the process of the invention to obtain fumaric acid.

In the accompanying drawing, FIG. 1 is a block diagram of an exemplary embodiment of a process for producing fumaric acid according to the invention. This method consists of the following operating steps (reference numerals refer to Fig. 1):

Pre-heat treatment

Filtration

Isomerization

Pressure filtration

Filter wash

Dissolution and discoloration

Pressure filtration

Crystallization

Centrifuging

Drying

Packing

Adding thiourea

Introduction of tap water

Intermediate storage of mother liquors from the second separation

Addition of decolorizing coal

Addition of diatomaceous earth

Removal of combustion residue

Extraction of mother liquors from the first separation to combustion

Waste water and gas removal

Removal of solid residue.

Figure 2 shows two graphs of temperature in ° C (Y-axis) versus time in hours (X-axis), both for the deposition and cooling phases and for the pretreatment phase according to the invention. Poison-

the affected sections of the graphs relate to the following operating stages:

A Elimination and cooling

В Performance л

C Warming up

D Pre-heat treatment

E Cooling

F Emptying

As in Figures 3 and 4, the symbol "V" in Fig. 2 represents the volume of the mixture.

Fig. 3 shows two graphs of temperature in ° C (Y-axis) versus time in hours (X-axis), both for the isomerization phase and for the filtering and filtering phase. Individual sections of graphs relate to the following operational stages:

And Performance

В Warming up

C Isomerization

IZOMERIZACE

D Cooling and crystallization

E Emptying

F Filling and filtration

G Strip strip drying

H Allowing mother liquors from the second separation

I Washing

J Discharge of mother liquors

К Air drying

L Emptying

FILTRATION

AND WASHING ON

FILTER

Figure 4 shows two graphs of temperature in ° C (Y-axis) versus time in hours (Xj-axis), both for the dissolution and discoloration phase, and for the crystallization and centrifugation phase of the process of the invention. the following operational stages:

A Filling with raw fumaric acid crystals and mother liquors SOLVING Heating and dissolving it and adding decolorizing charcoal and filter aids, decolorizing

D Filtration in pressure filter

E Filling

F Crystallization G Spin

CRYSTALIZATION AND FROM CENTRATION

Example 1

The off-gas from the oxidation of the mixture of o-xylene and naphthalene (30% o-xylene and 70% naphthalene) has the following average composition after separation of phthalic anhydride:

Sample composition of waste gas

Substance Content [g / m ⁵ ] Ftalanhydrid 0.5 Maleic anhydride 2,0 Sulfuric acid 0.27 1,4-naphthoquinone 0.1 Benzoic acid 0.05 Other by-products 0.01 Total 2.93 Example 2 Sample composition of solution maleic acid Substance Content [% by weight] Maleic acid 15 Dec Naftochinon 0.65 Phthalic acid 1.5 Other organic acids 0.42 Sulfuric acid 0.12

The process according to the invention consists essentially of the following phases:

Phase 1

Pre-heat treatment of the maleic acid solution (100 kg) obtained by any method and any impure, in this particular case treatment of a solution of the type mentioned in Example 2 containing the impurities shown in Example 2. The treatment consists in heating the solution to higher than 90 ° C. The time course of heating is shown in the graph shown in Fig. 2.

This operation can be carried out at the same time as concentrating the maleic acid solution from 15 to 25% by weight if such concentration of the solution is required. During pretreatment, some of the impurities are transformed, preventing them from being present in the final product. Decolorizing charcoal or other similarly acting substance can also be added to the mixture in this pre-treatment stage.

Phase 2

Hot filtration at a temperature above 90 ° C (at the pre-heat treatment stage 1) through a suitable pressure or vacuum, flat or rotary continuous or discontinuous filter with optional washing and air drying.

Phase 3

The maleic acid contained in the solution that has been filtered can now be isomerized using thiourea (0.34 kg) as a catalyst. The resulting fumaric acid crystallizes during cooling. This phase, which is included in the block diagram of Fig. 1, can be performed according to the graph shown in Fig. 3.

The whole process of isomerization and crystallization is carried out according to the temperature-time curve shown in FIG. The efficiency achieved is 92 percent, which corresponds to a yield of 13.8 kg of fumaric acid. The resulting product is suitable for further processing.

It should be noted that when working under different conditions, the resulting product is of inferior quality and its manufacturing cost is higher.

It should also be pointed out that the graph is to be understood as an optimal diagram for industrial production. By prolonging the isomerization time, an even higher efficiency than that described herein can be achieved, but the slowness of the reaction makes this solution unsuitable.

Phase 4

The fumaric acid crystals are separated from the mother liquors by filtration using a suitable flat or rotary, continuous or discontinuous filter. This filtration, which is accompanied by suitable washing with saturated fumaric acid solutions at 25 ° C and air drying or other drying methods, may be carried out. use equipment such as a rotary filter for pressure filtration or flat-pressure filters with automatic emptying, which are equipped with either a cup-type centrifuge or a continuous panel wash centrifuge.

Even at this stage, it is important to maintain the temperature-time dependence shown in the graph, especially the dependency illustrated on the right-hand side of Fig. 3, which relates to filtration and suspension washing using a pressure filter.

As can be seen from the block diagram shown in FIG. 1, the mother liquors resulting from this operation must be disposed of by incineration or biological treatment using activated sludge.

Phase 5

The crude fumaric acid in the form of crystals is dissolved in water or in a solution of fumaric acid, which is saturated at 25 ° C and which consists of mother liquors from the second crystallization (see flow diagram in Fig. 1). This operation is optimized by appropriate temperature control, which must be in the range of from 95 to 98 ° C / min and, if necessary, pressure control to increase the temperature and consequently increase the solubility of fumaric acid.

Phase 6

Decolorizing charcoal (0.2 kg) was added to the above solution, and the solution was maintained at 95-98 ° C while operating at ambient pressure. Various products which are commercially available can be used as decolorizing coal.

The mixture was stirred and filtered hot. The course of this phase is shown on the left side of Fig. 4.

F o z 7

The filtered solution is cooled and the fumaric acid crystallizes. The crystals are collected in a centrifuge. The centrifuge may be of the semi-automatic type with horizontal axis and automatic emptying. Using this type of centrifuge, the resulting product contains about 5-7% residual moisture.

Phase 8

Fluid bed hot-air dryers may be used for drying. Of course, any device can be used to remove moisture and trace amounts of impurities that can be removed by a stream of air or steam, such as benzoic acid. Starting from 15 kg of maleic acid, 13 kg of pure fumaric acid is obtained, corresponding to a yield of 86.5%.

Example 3

The fumaric acid obtained by the above industrial process has the following characteristics:

Fumaric acid content in the product 99.7% Color (3% solution in ethanol) 0 to 10 Throwing Moisture content 0.2 · ·%

Ash content 0.01%

Iron content 2 ppm

Example 4

For the sake of completeness, the following are indicative values of the efficiency of the individual phases of the procedure:

Isomerization efficiency% based on maleic acid contained in the starting solution

Purification efficiency% based on crude · fumaric acid

Overall efficiency

86.5% based on maleic acid

The various stages of the process according to the invention, illustrated by way of illustration in the above-described embodiments, are not intended to be limiting. Of course, the individual process parameters, such as time, amount of various substances, temperatures and catalysts, can be varied within the scope of the skilled artisan without constituting an escape from the claimed protection.

Claims (3)

A process for the manufacture of fumaric acid using maleic acid isomerization, characterized in that the washing waters containing maleic acid, obtained by washing the water of maleic anhydride-containing waste gases originating from the oxidation of hydrocarbons, are subjected to a preliminary heat treatment by heating to 70 to 100 ° C, preferably from 90 to 100 ° C, then the washings are filtered at a pre-heat treatment temperature, the filtrate obtained isomerized by heating from 30 to 100 ° C for 2 to 6 hours, preferably for 4 hours, heating corresponds to an exponential temperature versus time, the isomerization mixture is maintained for 2 to 6 hours, preferably 4 hours at 100 degrees Celsius, then cooled to 50 ° C over 1 hour, preferably 3 hours, to form product crystals which are separated, dissolved in water or an acid solution f The resulting solution was decolorized, the product was recrystallized, and the separated crystals were dried. 2. The process of claim 1, wherein the isomerization phase is combined with the pretreatment phase of the maleic acid solution. 3. Process according to claim 1, characterized in that the pre-heat treatment phase is combined with the concentration phase of the maleic acid solution, both phases being carried out simultaneously.