JPH0611725B2 - Method for producing succinic acid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for hydrogenating maleic anhydride or maleic acid using a noble metal catalyst to produce succinic acid.

[Prior Art] As a method for producing succinic acid, a method for hydrogenating maleic anhydride or maleic acid in an aqueous medium using a noble metal catalyst is described in, for example, JP-B-44-29246. In this method, for example, after hydrogenating maleic acid, the catalyst is collected by filtration while hot, the filtrate is cooled to crystallize succinic acid, the succinic acid crystals are filtered off, and the mother liquor is hydrogenated again. It is recycled and used as an aqueous medium for the hydrogenation reaction in the hydrogenation reaction of maleic acid together with the recovered catalyst.

[Problems to be Solved by the Invention] As a catalyst used in this hydrogenation reaction, a noble metal such as platinum or rhodium is used, which is extremely expensive. Therefore, it is preferable that the catalyst retains its activity as long as possible. However, when the circulation and reuse of the catalyst is repeated in the above method, the activity of the catalyst gradually decreases (deactivation), the time required for hydrogenation increases, and finally it becomes impossible to reuse it as a catalyst in practical use. It will be replaced with a new catalyst.

An object of the present invention is to prevent deactivation of the noble metal catalyst used in the above hydrogenation reaction and to enable long-term circulation and reuse of the catalyst.

The present inventors have made extensive studies on the deactivation of the catalyst in the hydrogenation reaction, and the cause is poisoning by the impurities contained in the raw material maleic anhydride or maleic acid. It was found that the deactivation of the medium can be prevented.

It is not always clear what kind of compound is the impurity causing the deactivation of the catalyst, but for example, a polycondensate of maleic acid, or a compound added as a color preventive agent for maleic anhydride, such as copper. Compounds and the like are possible.

[Means for Solving Problems] The present invention achieves the object by using activated carbon for treating impurities contained in these raw materials.

That is, the present invention is a method for producing succinic acid by hydrogenating maleic anhydride or maleic acid in an aqueous medium using a noble metal catalyst, in which maleic anhydride or maleic acid is previously treated with activated carbon and then subjected to hydrogenation reaction. And a method for producing succinic acid.

Maleic anhydride or maleic acid used as a raw material in the present invention is generally a C4 fraction such as butene and butadiene, butane, or one produced by a catalytic gas phase oxidation reaction such as benzene, or a catalytic gas of orthoxylene. In the production of phthalic anhydride by a phase oxidation reaction, maleic anhydride and maleic acid by-products may be mentioned. In particular, maleic anhydride, which is usually commercially available, contains various chemicals in addition to impurities during production, in order to prevent deterioration and discoloration of maleic anhydride during storage, which poisons the catalyst. It is considered that the process according to the present invention is necessary and effective because it is considered to be a problem.

In the present invention, when an aqueous maleic acid solution is used, a commercially available maleic anhydride dissolved in water is used.After hydrogenating maleic acid, succinic acid produced by cooling the reaction solution is crystallized. It is possible to use a solution in which a predetermined amount of maleic anhydride is dissolved in the mother liquor from which succinic acid has been separated by filtration. That is, the aqueous medium of the hydrogenation reaction can be recycled and reused.

The activated carbon used in the present invention is not particularly limited in its type and shape as long as it is effective when practiced in the present invention. That is, although powdery, granular, or fibrous activated carbon is used, usually, one for liquid phase treatment is used.

The various activated carbons on the market have different activation methods depending on the manufacturer, and in some cases, during the production and activation of the activated carbon, the activated carbon may contain stains which adversely affect the hydrogenation catalyst used in the present invention. There is a possibility that
Therefore, when carrying out the present invention, it is preferable to remove the dirt on the activated carbon in advance.

As a method for removing dirt on activated carbon, there is a cleaning treatment, but in that case, it is necessary that the treatment agent remaining in the activated carbon is desorbed during maleic acid treatment and does not poison the precious metal catalyst in the hydrogenation reaction system. Is. An example of such a cleaning agent having an effective cleaning power is an aqueous solution of an acid or an organic solvent.

Examples of the acid include mineral acids such as sulfuric acid and nitric acid, and organic acids such as acetic acid and maleic acid. When using sulfuric acid,
Dilute sulfuric acid having a concentration of about 0.1 to 5%, particularly about 1 to 3% is preferable.
In the case of organic acid, it is used below its saturation concentration. The treatment temperature is preferably room temperature to about 80 ° C, and the reason for this is unknown, but a cleaning effect cannot be expected at a high temperature of 90 ° C or higher. It is sufficient to use the cleaning liquid in an amount of about 5 to 50 times the weight of activated carbon.

As a cleaning liquid, it is a preferred embodiment to use maleic anhydride or maleic acid used as a raw material of the present invention, as will be described later, when the raw material is subjected to activated carbon treatment in a packed column or a fluidized bed, initial contamination The maleic anhydride or maleic acid obtained only during the spillage is not used for the hydrotreatment, and after the spillage of dirt is no longer observed, the activated carbon is washed in the form of being used for the hydrogenation of the present invention. You can

Various organic solvents can be used as the cleaning liquid,
Methanol or the like, which is miscible with water and inexpensive, is preferable.

Of course, it is more convenient to use commercially available activated carbon that has already been acid treated.

In the present invention, as a method of treating maleic anhydride or an aqueous maleic acid solution with activated carbon, a known method generally used when activated carbon is applied, for example, using granular activated carbon, a single-stage or multi-stage packed column, A system of continuously treating in a fluidized bed or the like is adopted, but a packed tower is usually selected. Of course, it is also possible to use powdered activated carbon or granular activated carbon to perform processing in a batch system (batch system).

The treatment conditions of the packed column in the present invention include, when treating maleic anhydride with activated carbon, the treatment temperature is required to be liquid because maleic anhydride is a melting point (5
2.8 ℃), generally 120 ℃ or less, usually 60 ~ 100 ℃ temperature is adopted. SV (space velocity) is generally 0.1-10h
r ^-1 , usually 0.2 to 6 hr ^-1 . When treating a maleic acid aqueous solution, it can be basically carried out under similar treatment conditions, but due to the difference in liquidity, the concentration of maleic acid is below the saturation concentration, usually 20 to 50%, and the treatment temperature is at room temperature. As described above, a temperature of not higher than the boiling point, usually 50 to 100 ° C. is adopted. The SV may be almost the same as above. However, since the maleic acid aqueous solution is directly subjected to the hydrogenation reaction after the activated carbon treatment, it is convenient to adjust its concentration to the concentration of the hydrogenation reaction.
The pressure during the activated carbon treatment is not particularly limited,
You may pressurize at normal pressure.

Conditions for carrying out the activated carbon treatment in a batch system, the treatment temperature and the concentration of the maleic acid aqueous solution may be the same as in the case of the packed tower treatment, the treatment time is generally about 10 minutes or more under stirring, usually 30 minutes. ~ 2 hours is sufficient. In this case, the amount of the activated carbon used may be relatively small because the amount of impurities in the raw material is small, and may be about 0.005 to 1% by weight based on the raw material.

The amount of maleic anhydride or maleic acid treated cannot be clarified because it significantly depends on the adsorption capacity of activated carbon and the type or amount of impurities in the raw material, but it is generally not possible to treat maleic acid 10,000 to 60,000 times the weight of activated carbon. You can The breakthrough of impurities due to the decrease in the adsorptivity of activated carbon is the reaction rate (hydrogen absorption rate) in the hydrogenation reaction of the raw material after treatment.
Can be easily determined by the decrease of

When maleic anhydride or a maleic acid raw material treated according to the present invention is used, the method of hydrogenating a succinic acid with a noble metal catalyst is carried out by a known method. For example, a concentration of about 30
-50% maleic acid and / or maleic anhydride aqueous solution at a temperature of about 80-100 ° C under hydrogen pressure, usually 2-30 Kg /
The catalyst is hydrogenated in cm ² G in an abundance ratio of a noble metal catalyst, and after the reaction, the catalyst is filtered while hot, the filtrate is cooled, and the precipitated succinic acid crystals are separated by filtration and dried, while the catalyst and The filtrate is recycled to the reaction under hydrogen. Since the by-product accumulates in the filtrate, it is usually partially discharged, but in the present invention, since the impurities in the raw material have already been treated, the by-product itself in the circulating mother liquor is less accumulated. By treating the product with activated carbon and recycling it, it is possible to suppress the accumulation of impurities in the recirculation liquid.

Examples of the noble metal catalyst used in the present invention include catalysts such as palladium, ruthenium, rhodium, and platinum. Generally, these noble metals are supported on activated carbon, silica, alumina, silica-alumina, or the like, or The oxide is used, for example, a loading rate of 2%, 5% or 10
% Palladium-carbon (Pd-C), 5% ruthenium-carbon (R
uC), 5% rhodium-carbon (Rh-C) or platinum oxide. Usually, Pd-C is used, which is cost-effective, highly selective, and highly resistant to poisoning.

The amount of the catalyst used is generally 0.01 to maleic acid.
2%, usually 0.1-1%.

[Operation and Effect of the Invention] In the production of succinic acid, the present invention removes impurities that poison the noble metal catalyst used in the hydrogenation reaction by previously treating maleic anhydride or maleic acid as a raw material with activated carbon. Therefore, the deactivation of the catalyst is prevented, and the catalyst activity can be maintained for a long period of time. Moreover, by further treating the circulating mother liquor in the hydrogenation reaction with activity, the catalyst life can be further extended,
It is possible to significantly reduce the catalyst cost in the production of succinic acid.

[Examples] Hereinafter, the method of the present invention will be described in detail with reference to Examples.
The poisoning deactivation of the noble metal catalyst in the reaction under hydrogenation requires a long time for confirmation because the catalyst is repeatedly used. Therefore, the forced poisoning treatment test method described below was adopted as a method capable of relatively comparing the decrease in catalyst activity due to repeated use.

Note that "%" and "part" used in this specification
Means "% by weight" and "parts by weight" unless otherwise specified.
Indicates.

Forced poisoning treatment test method (1) Poisoning treatment Maleic anhydride or maleic acid to be tested 200
Part (2000 times the catalyst) is placed in a container, and 300 parts of pure water is added and dissolved. Poisoning treatment is performed by adding 0.1 part of 5% Pd-C as a catalyst and stirring at 95 ° C. for 3 hours in a nitrogen atmosphere. After hot filtration and washing 5 times with 20 parts of warm water, the catalyst obtained is dried at 65 ° C.

(2) Hydrogenation reaction experiment Commercially available maleic anhydride 10 g was taken in an autoclave equipped with a stirrer and a constant-pressure hydrogen introduction pipe, and 100 g of pure water was put,
Dissolve under stirring at 60 ° C for 10 minutes. Next, 0.045 g of the catalyst poisoned by (1) was added, and the mixture was stirred at 80% 8 Kg / cm ² G.
Measure the absorption rate of hydrogen with.

As a control, the hydrogen absorption rate was measured in the same manner using a new catalyst, and used as a criterion for determining the activity decrease due to the poisoning treatment.

Example 1 and Comparative Example 1 (1) Washing of activated carbon 1 part of granular activated carbon (palm-crushed coal) was washed with a 47% maleic acid aqueous solution containing 10 parts of maleic anhydride at 40 ° C. under stirring. Then, the filter cake was thoroughly washed with 20 parts of pure water and then dried.

(2) Treatment of Raw Material Maleic Acid with Activated Carbon To 100 parts of commercially available maleic anhydride, 0.01% by weight of activated carbon obtained by the above washing method was added, treated with stirring at 80 ° C. for 1 hour, and filtered while hot. The activated carbon was repeatedly reused in the same manner, and the raw material was treated 5 times in total.

Using maleic anhydride obtained by each treatment and untreated maleic anhydride as a comparative example, the above-mentioned forced poisoning treatment test method was applied to determine the hydrogen absorption rate of the hydrogenation reaction of the poisoned catalyst. The reaction rates were measured by the arrival times of 50%, 90% and 100%. The results are shown in Table 1.

According to this result, about 40,000 parts of maleic anhydride can be treated with respect to 1 part by weight of activated carbon. That is, the amount of maleic anhydride that can be treated with 0.01 part of activated carbon at one time is 100
And the activated carbon can be circulated four more times,
The treatable amount of maleic anhydride is (100 / 0.01) × 4 = 40,000.

Example 2 A control cock at the bottom and a maleic anhydride solution at the top at 80 ° C
Equipped with a separatory funnel kept warm at 80 ° C
A glass packed tower of m and height of 720 mm was packed with 53 ml of granular activated carbon treated in the same manner as in (1) of Example 1.

Put commercially available maleic anhydride in the separatory funnel above, SV0.5h
A maleic anhydride solution at 80 ° C. was passed through the packed bed at r ⁻¹ . A total of about 4,000 g of maleic anhydride was treated and measured by the forced poisoning treatment test method. As a result, the reaction time of maleic anhydride treated with granular activated carbon was 16% when the 50% reaction rate was reached.
Min, 90% for 35 minutes, and 100% for 44 minutes, which was substantially the same as the control new catalyst, and the activity reduction due to catalyst poisoning was not observed.

With respect to the succinic acid obtained by the hydrogenation reaction, the catalyst was hot filtered according to a conventional method, succinic acid was crystallized from the filtrate, filtered and dried to obtain high-purity succinic acid.

Example 3 Instead of 100 parts of maleic anhydride in (2) of Example 1, 250 parts of a 40% maleic acid solution prepared by dissolving commercially available maleic acid in pure water was used in the same manner to obtain a product. When the forced poisoning treatment test method was carried out on the obtained maleic acid aqueous solution in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Example 4 100 parts of a commercially available maleic anhydride treated with granular activated carbon in the same manner as in Example 2 was placed in an autoclave equipped with a stirrer and a hydrogen pressure introducing tube under constant pressure, and 200 parts of pure water was added, and the mixture was stirred. Dissolved. Next, 0.2 part of 5% Pd-G was added, and the hydrogenation reaction was carried out at 80 ° C. and 8 kg / cm ² G with stirring. When the hydrogen absorption was stopped, the reaction was stopped, the catalyst was filtered while hot, the filtrate was cooled, and the precipitated succinic acid was filtered and dried to obtain high-purity succinic acid.

The mother liquor and the catalyst were repeatedly used again in the hydrogenation reaction under the above conditions. Thus, the catalyst was subjected to the reaction 50 times repeatedly, but the activity of the catalyst was hardly reduced, and there was no practical problem. On the other hand, in the case of using the untreated commercially available maleic anhydride as a raw material and circulating the catalyst in the same manner as above,
From about the 25th time, the hydrogen absorption rate decreased remarkably, and it took a long time to achieve the reaction rate of maleic acid of 100%, which made it practically impossible to use.

Claims (5)

[Claims] 1. A method for producing succinic acid by hydrogenating maleic anhydride or maleic acid in an aqueous medium using a noble metal catalyst, wherein maleic anhydride or maleic acid is previously treated with activated carbon and then subjected to hydrogenation reaction. A method for producing succinic acid, which comprises: 2. The method for producing succinic acid according to claim 1, wherein the activated carbon has been previously washed with an acid or an organic solvent. 3. The method for producing succinic acid according to claim 2, wherein the acid is maleic acid. 4. The succinic acid according to any one of claims 1 to 3, wherein after the completion of the hydrogenation reaction, the mother liquor from which the crystallized succinic acid is separated is circulated in the hydrogenation reaction as an aqueous medium. Manufacturing method. 5. The method for producing succinic acid according to any one of claims 1 to 4, wherein the circulating mother liquor is treated with activated carbon.