JPH09271671A - Hydrogenating catalyst used in production of hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrogenating catalyst of anthraquinones high in selectivity without damaging the strength, activity and life of the catalyst by adding a specific amt. of an alkali metal to silica. SOLUTION: An alkali metal is added to silica in an amt. of 0.1-5% by wt. of silica., As silica, silica used as a usual catalyst carrier may be used. The content of palladium is usually 0.1-10% by wt. of silica and, as an alkali metal, group Ia alkali metals may be used but sodium or potassium is pref. This catalyst is prepared by supporting palladium and alkali metal on silica. An ion exchange method is excellent in the supporting of palladium. The alkali metal is supported by bringing silica or silica having palladium supported thereon into contact with a soln. of an alkali metal compd. and washing the obtained impregnated silica if necessary before drying or baking the same.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrogenation catalyst for anthraquinones used in the production of hydrogen peroxide by the anthraquinone method and a method for producing hydrogen peroxide using the catalyst.

[0002]

2. Description of the Related Art The main method for producing hydrogen peroxide which is industrially used at present is a method using anthraquinones as a reaction medium and is called an anthraquinone method. Generally, anthraquinones are used by dissolving them in a suitable organic solvent. The organic solvent is used alone or as a mixture, but usually a mixture of two kinds of organic solvents is used. A solution prepared by dissolving anthraquinones in an organic solvent is called a working solution.

In the anthraquinone method, anthraquinones in the working solution are reduced with hydrogen in the presence of a catalyst in the reduction step (hereinafter referred to as hydrogenation) to produce corresponding anthrahydroquinones. Next, in the oxidation step, the anthrahydroquinones are converted into anthraquinones again by oxidizing them with air or a gas containing oxygen, and at the same time hydrogen peroxide is produced. The hydrogen peroxide formed in the working solution is usually extracted with water in the extraction process and separated from the working solution. The working solution from which hydrogen peroxide has been extracted is returned to the reduction step again, forming a circulation process. This process essentially produces hydrogen peroxide from hydrogen and air and is a very efficient process. Hydrogen peroxide has already been industrially produced using this circulation process.

Raney nickel catalysts, palladium black catalysts, and palladium catalysts supported on carriers are known as catalysts used for hydrogenation of anthraquinones in the reduction step of the above circulation process. The Raney nickel catalyst has many drawbacks such as high activity, but it is significantly deteriorated by a small amount of hydrogen peroxide in the working solution, is dangerous in handling because it is an ignition metal, and has low selectivity. . Further, the palladium black catalyst is excellent in activity and selectivity,
Separation from the working solution is difficult, and it has a fatal drawback for industrial production of hydrogen peroxide, which is easily decomposed in the presence of palladium. On the other hand, the palladium catalyst supported on the carrier is slightly inferior in activity and selectivity to palladium black, but can be separated from the working solution and is a catalyst suitable for industrially producing hydrogen peroxide.

As the palladium catalyst supported on the carrier, catalysts supported on various carriers such as silica, alumina, silica-alumina, aluminosilicate and carbonates of alkaline earth metals have been proposed, but all are industrially supported. It does not satisfy the conditions of low cost, high catalyst strength, high activity and selectivity required as a catalyst for use in the catalyst, and only a part of the above catalysts can be actually used industrially.

A palladium catalyst supported on alumina is
It is one of the few catalysts that can be industrially used, and has the advantages of relatively high activity and easy regeneration by calcination. However, there are many by-products generated in the hydrogenation of anthraquinones, and there is a disadvantage that the activity in the working solution is significantly reduced (US Pat. No. 2,862).
7,507).

As a catalyst for compensating for the disadvantages of the palladium catalyst supported on alumina, Japanese Patent Publication No. 49-5120 discloses a catalyst in which an alumina carrier is impregnated with copper or silver in addition to palladium, and the catalyst in a gas containing hydrogen. At 1
Catalysts treated at 50-650 ° C have been proposed. The treatment with the added metal and hydrogen improves the hydrogenation selectivity of the anthraquinones to some extent. On the other hand, however, this catalyst has a complicated manufacturing method and has a drawback that the activity is lowered by water.

Further, in Japanese Examined Patent Publication No. 63-29588, as a catalyst superior to the alumina-supported palladium catalyst, at least one metal selected from zirconium, thorium, cerium, titanium and aluminum is used in addition to palladium on silica as a carrier. The added catalyst is proposed.
It is claimed that the addition of the metal improves the activity, and the use of silica as a carrier also suppresses the deterioration due to the water content in the working solution.

In the above-mentioned circulation process for producing hydrogen peroxide, since the working solution is recycled and reused, the alkyloxanthrone produced by hydrogenation of anthraquinones,
Alkyltetrahydroanthraquinone and other byproducts that can no longer produce hydrogen peroxide will gradually accumulate in the working solution as hydrogen peroxide production continues. The production of these by-products is an unfavorable reaction that increases the production cost of hydrogen peroxide because not only the supplied hydrogen is lost but also expensive anthraquinones are lost. Further, some of these by-products can be returned to the original anthraquinones by an appropriate treatment, but the production cost of hydrogen peroxide increases. Therefore, the selectivity of the catalyst is as important as the strength, activity and life of the catalyst, or even more important than the hydrogenation catalyst of anthraquinones. However, as described above, the conventional catalyst has been improved in strength, activity and life, but it cannot be said to be sufficient in selectivity.

[0010]

The object of the present invention is to eliminate the drawbacks of the prior art as described above, and to hydrogenate anthraquinones having high selectivity without impairing the strength, activity and life of conventional catalysts. It is an object of the present invention to provide a catalyst and an economically excellent method for producing hydrogen peroxide using the catalyst.

[0011]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a silica-supported palladium catalyst containing an alkali metal does not impair strength, activity and life of anthraquinones. The present inventors have found that it is possible to suppress the production of by-products in the hydrogenation of, and have reached the present invention.

That is, the present invention provides a hydrogenation catalyst for anthraquinones which is used in the production of hydrogen peroxide by the anthraquinone method, in an amount of 0.1 to 5 relative to the weight of silica.
TECHNICAL FIELD The present invention relates to a palladium catalyst supported on silica, which comprises an alkali metal in a weight percentage, and a method for producing hydrogen peroxide using the catalyst. When the content of the alkali metal is less than 0.1% by weight, the effect of suppressing the production of by-products becomes small, and the content of more than 5% by weight impairs the strength, activity and life of the catalyst.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The silica used in the catalyst of the present invention is not particularly limited as long as it is a silica usually used as a catalyst carrier. The palladium content of the catalyst of the present invention is not critical to the effect of the present invention, but is usually 0.1 to 10% by weight based on the weight of silica. Further, although palladium of the catalyst is usually supported in a metal state,
It may be supported in the form of a compound such as an oxide that is easily reduced to palladium metal under the reaction conditions.

The alkali metal of the catalyst of the present invention may be any alkali metal of Group Ia of the periodic table, but sodium or potassium is preferred. It is necessary that the content of the alkali metal is 0.1 to 5% by weight based on the weight of silica.

To produce the catalyst of the present invention, silica is loaded with palladium and an alkali metal. The palladium and the alkali metal may be loaded at the same time or one of them may be loaded first.

The palladium can be supported by an ion exchange method or an impregnation method in which a palladium compound ion is absorbed by silica by ion exchange. The ion exchange method is a particularly excellent palladium supporting method.

In order to support palladium by the ion exchange method, silica is brought into contact with a solution containing ammonium ions to be ion-exchanged with ammonium ions, and then is brought into contact with a solution of a palladium compound to obtain ions containing palladium and ions. Replace. The ion exchange with the ammonium ion and the ion exchange with the ion containing palladium may be sequentially performed in different solutions, but may be simultaneously performed in the same solution. After the ions containing palladium are carried by ion exchange, firing is performed to decompose the ions containing palladium, and in some cases, further reduction treatment is performed to obtain palladium metal.

The above-mentioned ammonium ion-containing solution may contain ammonium ions necessary to support a desired amount of palladium. Further, the palladium compound used may be a compound which becomes a cation containing palladium in a solution, and specifically, a salt of a palladium complex cation such as tetraamminepalladium (II) chloride monohydrate, or Palladium chloride and palladium nitrate, which become complex cations in a solution of ammonia, are exemplified.

To carry palladium by the impregnation method, silica particles or silica particles carrying an alkali metal are dipped in a solution of a palladium compound to evaporate the solvent. Then, firing is performed, and further reduction treatment is performed in some cases to convert the palladium compound into palladium metal.

The palladium compound used for supporting palladium by this method may be any palladium compound which is soluble in a solvent such as water or an organic solvent. Specific examples include palladium salts such as palladium chloride, palladium nitrate, palladium acetate and palladium (II) acetylacetonate, and palladium complex salts such as ammonium tetrachloropalladate and tetraamminepalladium (II) chloride monohydrate. To be done.

To carry an alkali metal, silica or silica carrying palladium is brought into contact with a solution of an alkali metal compound, preferably a solution of a sodium or potassium compound, and if necessary, washed with water and then dried or calcined. Done. At that time, the finally prepared catalyst is loaded with 0.1 to 5% by weight of an alkali metal based on the weight of silica.

The method of contacting the silica with the solution of the alkali metal compound includes a method of filling the column with the silica and circulating the solution, or a method of immersing the silica in the solution. Further, the solution of the above-mentioned alkali metal compound only needs to contain an amount of the alkali metal compound capable of supporting 0.1 to 5% by weight of the alkali metal on the above-mentioned silica. Some silica may dissolve, in which case it is preferable to use a dilute solution. However, even in a high-concentration aqueous solution, the dissolution of silica can be suppressed by shortening the contact time or lowering the contact temperature.

The most important point in producing the catalyst of the present invention is to carry 0.1 to 5% by weight of alkali metal with respect to the weight of silica. The amount of supported metal is quantified by fluorescent X-ray.

The anthraquinones used in the present invention are preferably alkylanthraquinone, alkyltetrahydroanthraquinone or a mixture thereof. The alkyl anthraquinone and the alkyl tetrahydro anthraquinone may each be a plurality of alkyl anthraquinones or a mixture of alkyl tetrahydro anthraquinones. Examples of the alkyl anthraquinone include ethyl anthraquinone, t-butyl anthraquinone and amyl anthraquinone. Examples of alkyltetrahydroanthraquinone include ethyltetrahydroanthraquinone, t-butyltetrahydroanthraquinone, amyltetrahydroanthraquinone and the like.

The solvent used for preparing the working solution in the present invention is not particularly limited, but preferable solvents are a combination of aromatic hydrocarbon and higher alcohol, aromatic hydrocarbon and cyclohexanol. Alternatively, a combination of alkylcyclohexanol with a carboxylic acid ester, tetra-substituted urea and the like are exemplified.

[0026]

EXAMPLES The invention will be further understood by the following examples. In the examples,% is by weight unless otherwise specified. In addition, the content of the alkali metal is shown by weight% with respect to silica.

The production amount of the by-products of the catalyst was evaluated by using a circulation device in which the working solution circulates through the reduction process, the oxidation process and the extraction process to produce hydrogen peroxide. The method for carrying out the evaluation test will be described below.

150 g of the catalyst to be tested was charged into the hydrogenation reactor in the reduction step of the above-mentioned circulation apparatus, and the anthraquinones were continuously hydrogenated to produce hydrogen peroxide. The working solution in the hydrogenation reactor was kept at about 4 liters, and 0.25 liter / min of working solution and 1.8 liter / min of hydrogen were supplied. The working solution in which the anthraquinones were hydrogenated was separated from the catalyst through a candle filter and withdrawn from the hydrogenation reactor. Stirring was carried out with an inclined turbine blade so that sufficient mixing could be obtained by a baffle attached to the inner wall of the reactor. The reaction temperature of the hydrogenation reaction was 40 ° C.

The working solution comprises 60% by volume of 1,2,4-trimethylbenzene and 40% by volume of diisobutylcarbinol.
Amyl anthraquinone was dissolved in a mixed solvent consisting of 1) so that the concentration was 0.60 mol / l. The total volume of working solution in the circulator was about 50 liters.

The activity of the catalyst was evaluated by the hydrogen partial pressure 24 hours after the reaction was started (hereinafter referred to as the initial hydrogen partial pressure), and the deterioration of the catalyst activity was evaluated by the rate of increase of the hydrogen partial pressure.
In this evaluation, the higher the activity of the catalyst, the lower the initial hydrogen partial pressure, and the less the activity of the catalyst, the lower the hydrogen partial pressure increasing rate. Moreover, after producing hydrogen peroxide in a circulation reactor for 200 hours, the concentrations of amylanthraquinone, amyloxanthrone, and amyltetrahydroanthraquinone in the working solution were measured by liquid chromatography. From the obtained concentration, the amount of amyloxanthrone, amyltetrahydroanthraquinone and other by-products produced in the reduction step was calculated, and the ratio to the amount of main product produced was calculated.

Example 1 Silica gel CARiACT Q- manufactured by Fuji Silysia Chemical Ltd.
No. 10 was sieved and classified to 200 to 350 mesh. 200 g of this silica gel was added to 25% aqueous ammonia 68 at room temperature.
It was suspended in 0 ml. While stirring this suspension,
3.35 g of palladium chloride in 120 ml of aqueous ammonia.
The solution in which was dissolved was added dropwise. Then, this suspension was filtered, washed with 2000 ml of pure water, and then dried at 120 ° C. for 12 hours. Furthermore, it baked at 600 degreeC for 3 hours. Next, the calcined catalyst was suspended in 680 ml of pure water, and a 4% sodium hydroxide solution was added until pH 9 was reached. Then, 20 ml of 37% formaldehyde solution was added, the temperature of the suspension was raised to 60 ° C., and stirring was continued for 30 minutes. During this period, a 4% sodium hydroxide solution was added so that the pH was 9. Then, the suspension is filtered and purified water 200
After washing with 0 ml, it was dried at 120 ° C. for 12 hours. The sodium content of the catalyst was 0.56% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure was 0.6 kgf / cm ² , and there was almost no increase in the hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Example 2 Palladium was carried, dried and calcined in the same manner as in Example 1. Then 0.5% sodium hydroxide solution 200
After suspending in 0 ml and stirring at 60 ° C. for 30 minutes, it was filtered and washed with 1000 ml of pure water. Then, at 120 ° C, 1
Dried for 2 hours. The sodium content of the catalyst is 0.4
It was 1% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure is 0.6 kgf / cm ² ,
There was almost no increase in hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Example 3 Palladium was carried, dried and calcined in the same manner as in Example 1. Next, the calcined catalyst was packed in a glass column and placed in a 3% aqueous solution of sodium carbonate (4000 ml and 40 ml).
00 ml of pure water was circulated at room temperature. Then, it dried at 120 degreeC for 12 hours. The sodium content of the catalyst is 0.6
7% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure is 0.6 kgf / cm ² ,
There was almost no increase in hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Example 4 Palladium was carried, dried and calcined in the same manner as in Example 1. Then 400 ml of 0.1% sodium hydroxide
It was dipped in and heated to dryness on a hot water bath. Then, at 120 ° C, 1
Dried for 2 hours. Sodium content of the catalyst is 0.13
% By weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure is 0.6 kgf / cm2, and 2
There was almost no increase in the hydrogen partial pressure in the operation for 00 hours.
The results of the production ratio of by-products are shown in Table 1.

Example 5 A catalyst was prepared in the same manner as in Example 1. However, 4% potassium hydroxide was used instead of the 4% sodium hydroxide solution. The potassium content of the catalyst was 0.43% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure was 0.6 kgf / cm ² , and there was almost no increase in the hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Example 6 A catalyst was prepared in the same manner as in Example 1. However, 4% potassium carbonate was used instead of the 4% sodium hydroxide solution. The potassium content of the catalyst was 0.52% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure was 0.6 kgf / cm ² , and there was almost no increase in the hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Comparative Example 1 As a control, a silica-supported palladium catalyst having an alkali metal content of less than 0.1% by weight was produced. Palladium was loaded, dried and calcined in the same manner as in Example 1, then immersed in 400 ml of 0.05% sodium hydroxide and heated to dryness on a water bath. Then, it dried at 120 degreeC for 12 hours. The sodium content of the catalyst was 0.07% by weight. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure was 0.6 kgf / cm ² , and there was almost no increase in the hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Comparative Example 2 As a control, palladium was loaded in the same manner as in Example 1,
A silica-supported palladium catalyst which was dried and calcined and was not further treated was produced. The content of alkali metal in the catalyst was 0.01% by weight. The produced catalyst was evaluated by the above evaluation test. Initial hydrogen partial pressure is 0.6 kgf /
It was cm ² , and there was almost no increase in hydrogen partial pressure after 200 hours of operation. The results of the production ratio of by-products are shown in Table 1.

Comparative Example 3 As a control, a standard alumina-supported palladium catalyst was prepared as follows. 200 g of γ-alumina classified to 200 to 350 mesh is immersed in 400 ml of pure water and stirred, and 3.35 g of palladium chloride is added to 65N of 0.5N hydrochloric acid.
The solution dissolved in ml was added dropwise. After the dropping was completed, the temperature was raised to 80 ° C. and stirring was continued for 30 minutes, then, the mixture was filtered and washed with water. Then, after drying at 120 ° C. for 12 hours, it was baked at 600 ° C. for 3 hours. The produced catalyst was evaluated by the above evaluation test. The initial hydrogen partial pressure is 0.7 kgf / cm ² ,
The hydrogen partial pressure became 1.0 kg / cm ^{2 after} 0 hours of operation. The results of the production ratio of by-products are shown in Table 1.

[0040]

When the catalyst of the present invention is used for hydrogenation of anthraquinones in the production of hydrogen peroxide by the anthraquinone method, the loss of hydrogen and expensive anthraquinones is reduced as compared with the conventional catalysts.

Table 1 ───────────────────────────────── Example No. Alkali metal by -product formation ratio * 1 wt% * 2 OX * 3 TH * 4 Others * 5 ────────────────────────────────── Example 1 Na: 0.56 1/1300 1/3000-* 6 Example 2 Na: 0.41 1/1400 1/3000-* 6 Example 3 Na: 0.67 1/1000 1/2500-* 6 Example Example 4 Na: 0.13 1/1050 1/2000-* 6 Example 5 K: 0.43 1/1200 1/3000-* 6 Example 6 K: 0.52 1/1200 1/3500-* 6 Comparative Example 1 Na: 0.07 1/900 1/850-* 6 Comparative Example 2 Na: 0.01 1/850 1/600-* 6 Comparative Example 3 Na: 0.26 1/300 1/800 1 / 3000 ───────────────────────────────── * 1 Production ratio of by-product to main product * 2 To carrier Alkaline gold % By weight of genus * 3 Amyloxanthrone * 4 Amyltetrahydroanthraquinone * 5 By-products * 6 − other than amyloxanthrone and amyltetrahydroanthraquinone represent production within the analysis error of liquid chromatography.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenji Kato 6-1-1, Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory

Claims (6)

[Claims] 1. A hydrogenation catalyst for anthraquinones used for the production of hydrogen peroxide by the anthraquinone method, characterized by containing 0.1 to 5% by weight of an alkali metal with respect to the weight of silica. Palladium catalyst supported on. 2. The catalyst according to claim 1, wherein the content of palladium is 0.1 to 10% by weight based on the weight of silica. 3. The catalyst according to claim 1, wherein the alkali metal is sodium or potassium. 4. In the production of hydrogen peroxide by the anthraquinone method, hydrogenating anthraquinones with a palladium catalyst supported on silica containing 0.1 to 5% by weight of alkali metal based on the weight of silica. A method for producing hydrogen peroxide, which is characterized. 5. The content of palladium in the palladium catalyst supported on silica is 0.1 to 10 relative to the weight of silica.
The manufacturing method according to claim 4, wherein the manufacturing method is wt%. 6. The method according to claim 4, wherein the alkali metal contained is sodium or potassium.