JP2696736B2 - How to recover Glauber's salt from vanillin wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering sodium sulfate from vanillin waste liquid. In vanillin waste liquid,
Since the active ingredient contains vanillin and other impurities as an organic component and also contains an inorganic component of sodium sulfate, if the waste liquid treatment is performed as it is, the active ingredient will be lost, so the vanillin component used for industrial raw materials from the vanillin waste liquid will be lost. Perform separation. In addition, the remaining waste liquid from which the sodium sulfate is separated becomes a liquid that is easily subjected to a suitable pollution prevention treatment.

[0002]

2. Description of the Related Art Vanillin has various production methods depending on the raw materials for its production. Lignin vanillin using lignin in wood is oxidized at high temperature and high pressure in the presence of a catalyst by adding an alkali hydroxide after concentrating a waste liquid. This process has met most of the world's demand in terms of volume, but the low yield of vanillin and the large amount of wastewater discharged make it increasingly difficult to implement this process due to environmental pollution. It is thought to go. As a typical chemical synthesis method, there is a method called guaiacol vanillin as vanillin synthesized using catechol as a raw material. This is a method using guaiacol, one of the catechol derivatives, as a raw material. This method is a method in which glyoxylic acid is added to guaiacol in an alkaline state, and then vanillin is obtained by oxidative decarboxylation in the presence of a copper catalyst.

[0003] As described above, in the production by a typical method for synthesizing vanillin, alkalinity is required at the time of the synthesis reaction. Therefore, alkali hydroxide, which is usually used as an alkali, is neutralized by neutralization with sulfuric acid. Inevitably, wastewater contains sodium sulfate. Therefore, in the ordinary pollution prevention treatment method, the sodium sulfate interferes with various processes during the treatment, and it is therefore desirable to remove the sodium sulfate from the organic waste liquid. Known methods for adding a non-aqueous solution of methanol to a vanillin reaction solution include U.S. Pat. S. Pat3,049,56
No. 6 discloses a method for purifying a lignin oxidized solution by removing vanillin using methanol and an aqueous solution, and precipitating and separating an alkali salt.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to industrially render a vanillin waste liquor harmless in terms of pollution prevention by performing a pretreatment and performing a pollution elimination treatment to remove the mirabilite component contained in the vanillin waste liquor. The present invention relates to a method for separating sodium sulfate. As described above, in the method for producing vanillin, since lignin or catechol is used as a starting material, a waste liquid containing an organic component is produced as a by-product from the vanillin production process. Therefore, it is necessary to detoxify the vanillin waste liquid in order to prevent pollution. However, in order to synthesize the vanillin intermediate, the wastewater must contain a strong alkali by using caustic soda, and then generate and contain a high concentration of sodium sulfate in order to neutralize with sulfuric acid. Normal.

In general, as a treatment method which can employ an organic waste liquid as a waste liquid treatment for preventing pollution, detoxification is performed by an activated sludge method or a combustion method. In the case of the activated sludge method, aerobic microorganisms are aerated in an air atmosphere together with organic wastewater to decompose and remove organic substances in the wastewater. In the activated sludge treatment method, how to form and multiply floc-like activated sludge which is easy to settle and separate is the most important factor for forming the treatment conditions. However, the presence of high-concentration sodium sulfate in the wastewater to be treated interferes with the activity of microorganisms and impairs the formation of floc-shaped sludge suitable for solid-liquid separation, resulting in suspended sludge or minute sludge. As a result, the specific gravity difference between the sludge and the purified water is reduced, so that the solid-liquid separation of the sludge and the purified water is not sufficiently performed at the time of sedimentation and separation.

As another method used to prevent pollution of high-concentration organic waste liquid, a combustion method is generally used, but high-concentration sodium sulfate containing inorganic components is contained in the waste liquid to be treated. If present, it burns at a high temperature, so that the sodium sulfate becomes a molten state and adheres to the furnace wall, hinders heat transfer and blocks the outlet of the ash. Further, Glauber's salt is decomposed at high temperature to generate sulfur dioxide which is a harmful gas, which causes secondary pollution of air pollution.

Therefore, when the wastewater treatment for preventing pollution of the organic wastewater containing the sodium sulfate is performed, the sodium sulfate component interferes with the wastewater treatment during the wastewater treatment. Separation and removal of interfering components for waste liquid treatment facilitates pollution prevention treatment.
The separated sodium sulfate is further used as an industrial raw material to utilize the active ingredient. Furthermore, the organic waste liquid from which the sodium sulfate is removed is subjected to a separation treatment such as distillation and extraction to remove the vanillin component, and the residual vanillin waste liquid can be easily subjected to waste liquid treatment. It is an important issue to separate sodium sulfate from waste liquid.

[0008]

DISCLOSURE OF THE INVENTION For the chemical synthesis of vanillin, the present inventors synthesized an intermediate of guaiacol using catechol as a starting material, and then reacted with glyoxylic acid to react 4-hydroxy-3. In order to overcome the above-mentioned problems in a conventionally known method for producing vanillin which obtains vanillin by oxidative decarboxylation via methoxymandelic acid, intensive studies have been made on a method for separating an inorganic component of sodium sulfate in vanillin waste liquid. Was. The present invention is characterized by adding 0.1 to 2 volume ratio of acetone to wastewater and mixing to separate the sodium sulfate contained in vanillin wastewater, and separating and separating sodium sulfate from vanillin wastewater. Regarding the collection method.

As a general method for synthesizing vanillin, there is a method in which catechol is methylated to obtain guaiacol, and 4-hydroxy-3-methoxymandelic acid produced by reacting this with glyoxylic acid under alkaline conditions is oxidatively decarboxylated. Are known. The vanillin reaction product contains sodium sulfate, which is produced by neutralizing the alkali sodium hydroxide used with sulfuric acid, and o-vanillin, isophthalvanillin and methyl vanillin which are by-produced as impurities in the organic phase. (A compound in which the benzene nucleus of p-vanillin or o-vanillin is methylated, for example, 4-hydroxy-3
-Methoxy-5-methylbenzaldehyde, 4-hydroxy-3-methoxy-6-methylbenzaldehyde, 2
-Hydroxy-3-methoxy-6-methylbenzaldehyde and the like. ).

Therefore, the residue obtained by distilling and extracting vanillin from the reaction product necessarily contains the above-mentioned by-product. When chemically synthesizing vanillin, wastewater containing a large amount of complicated organic by-products in addition to sodium sulfate and the above-mentioned impurities is generated. Therefore, in order to prevent pollution, wastewater treatment is an indispensable means.

Conventionally, a method of removing a salt by adding a non-aqueous solution to an aqueous solution containing a salt is known. However, in the present invention, a good sodium sulfate crystal is obtained by adding the solution to a vanillin waste liquid containing sodium sulfate. As a result of studying the resulting non-aqueous organic solvent, the present inventors have found that, in particular, the addition of acetone can remove and separate the unusual sodium sulfate crystals.

In the method of adding a non-aqueous solution of methanol to vanillin waste liquid to remove the sodium sulfate, and obtaining the sodium sulfate crystals, the crystal form of the sodium sulfate obtained is small. Therefore, in the filtration step for separating the crystals from the solution, the crystals are removed. If the filter cloth is too small, the mesh of the filter cloth must be reduced.In that case, the filter cloth may be clogged.If the filter cloth is not sufficiently small, fine crystals of sodium sulfate may be removed from the filter cloth. Thus, the filtration is not easy and the removal rate of Glauber's salt separation is not sufficient.

The present invention relates to a method for obtaining a sodium sulfate crystal by adding a non-aqueous solution of an organic solvent of acetone to a vanillin waste liquid to remove sodium sulfate. It has been found that when acetone is used as the non-aqueous solution additive in the aqueous solution containing sodium sulfate as in the present invention, the crystal to be eliminated can be obtained as a highly crystallizable sodium sulfate crystal which has grown to a large crystal form. When non-aqueous acetone is added to the wastewater containing sodium sulfate, the hydration phase equilibrium changes, the solubility of sodium sulfate is reduced, and sodium sulfate crystals precipitate. This involves supersaturation, as well as cooling and concentrating the solution, but because the solubility of Glauber's salt is greatly reduced, it is almost as effective as concentrating. In the recovery method in which the used acetone organic solvent is recovered and reused, when heating in the step of concentration and distillation, the latent heat of evaporation of acetone is only a fraction of the latent heat of evaporation of water. This has a great operational effect, such as a small amount of heat required when recovering acetone.

In the present invention, the waste liquid in the vanillin production process is
It is desirable to add acetone to the vanillin waste liquid at a ratio of 0.1 to 2 by volume for 0.5 to 3 hours with stirring. The amount and time of addition of acetone need to be changed depending on the contents of water and sodium sulfate in the waste liquid composition. As a method of addition, a batch type and a semi-batch type are preferable, but in the case of a continuous type, it is also possible to continuously extract with adding a seed crystal instead of nucleation instead of nucleation. The crystallization pressure is not particularly limited, but since the compound to be treated has a low boiling point, in order to prevent evaporation of the raw material from the crystallization system,
It is preferable to carry out under normal pressure to slightly pressurized (1-2 kg / cm ² G). When the reaction is carried out at normal pressure, it is preferable to install a condenser in the crystallizer, condense the evaporation with cold water, and sufficiently reflux acetone.

As a preferable operating condition for obtaining particularly large crystals, stirring can be performed at 100 to 400 rpm, preferably 200 to 350 rpm, and most preferably 250 to 350 rpm. When the stirring speed is low, the growth rate from the crystal nuclei becomes slow, and the generation of crystal nuclei increases, resulting in fine crystals, which is not preferable. If the stirring speed is high, the grown crystals are crushed, which is not preferable. The crystallization temperature can be preferably 20 to 40 ° C., and particularly preferably 25 to 40 ° C.
Most preferably, it is performed in the range of 35 ° C. When the crystallization temperature is lowered, the solubility of sodium sulfate in water decreases, so the residual ratio of sodium sulfate in the liquid decreases and the separation efficiency of sodium sulfate increases, but it is necessary to cool with cold water to lower the deposition temperature. In addition, a large amount of cooling energy is required, which undesirably increases the processing cost economically in operation.

[0014] As in the present invention, the waste liquid pretreated by separating and removing the sodium sulfate can be suitably treated with activated sludge, and scaling is performed when the sodium sulfate is contained when water is removed and concentrated for combustion treatment. The heat transfer deteriorates, but if Glauber's salt is removed in advance, concentration becomes possible in order to increase the calorie burned, and pollution in which the concentrated waste liquid is incinerated by the combustion method without causing the above-mentioned trouble during combustion. Prevention processing becomes possible.

[0015]

Next, the method of the present invention will be described in more detail by way of examples, which do not limit the method of the present invention in any way. Example 1 Vanillin wastewater discharged from a vanillin manufacturing process (Glauber's salt concentration: 9.95 wt%, organic matter: 2 wt%, PH;
7) was put into a three-necked separable flask having a capacity of 1000 ml and 400 g of acetone was added thereto using a dropping funnel.
g was dropped continuously over 1 hour. The waste liquid in the flask is
The temperature is controlled to maintain the temperature at 30 ° C with warm water,
Glauber's salt was removed at 300 rpm using a V-shaped stirring blade. 5CN to separate the removed Glauber's salt crystals from the waste liquid
Glauber's salt crystals were separated by filtration using o1 filter paper. The filtered and separated Glauber's salt crystals were dried in a hot air drier at 30 ° C. for 7 hours to obtain 88.8 g of Glauber's salt crystals (decahydrate) (39.1 g in terms of pure sodium sulfate). Is 98.2%
Met. The obtained sodium sulfate crystals were further added to 10, 18, 2
Table 1 shows the particle size distribution of each mesh and the filterability of the crystals separated by a sieve of 4, 60 mesh.

Comparative Example 1 For comparison, the same operation as in Example 1 was carried out using 400 g of methanol as an additive, and the results are shown in Table 1.

Examples 2 to 4 The amount of acetone added in Example 1 was changed, and
g, Example 3 was set to 200 g, and Example 4 was set to 100 g.

Comparative Examples 2 to 4 The amount of methanol added in Comparative Example 1 was changed,
The procedure was the same as in Example 1 except that 0 g, 200 g in Comparative Example 3, and 100 g in Comparative Example 4, and the results are shown in Table 1.

[Table 1]

Claims (1)

(57) [Claims] 1. A method for separating sodium sulfate from vanillin waste liquid, characterized in that 0.1 to 2 volume ratio of acetone is added to and mixed with the waste liquid to precipitate and separate sodium sulfate. Collection method.