Preparation method of palladium catalyst for producing hydrogen peroxide by anthraquinone method

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a palladium catalyst for hydrogen peroxide production by an anthraquinone process, which comprises the following steps: at a certain temperature, alumina powder is impregnated in a palladium salt solution for equivalent-volume impregnation for a certain time, and alumina comprises gamma-Al2O3 and alpha-Al2O3; after impregnation is completed, deionized water is added into the solid, chloride ions are removed through electro-adsorption after ultrasonic treatment, and then a filter cake is obtained through filtering; according to the preparation method of the palladium catalyst, the aluminum oxide with the crystal phase in the specific proportion is matched with the ultrasonic treatment and the electro-adsorption method, the prepared catalyst has the advantages of being high in selectivity, good in catalytic activity and mechanical property and stable in product quality, chloride ions are easy to remove, and waste of a large number of water resources is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and specifically relates to a method for preparing a palladium catalyst for producing hydrogen peroxide by an anthraquinone process. Background Art

[0002] As an important and versatile chemical product, hydrogen peroxide is widely used in medical, papermaking, textile, chemical, environmental protection and other industrial fields. At present, the main method for producing hydrogen peroxide in industry is the anthraquinone process. The anthraquinone process for producing hydrogen peroxide includes two main processes: hydrogenation and oxidation. Anthraquinone hydrogenation is an important link in the production of hydrogen peroxide, and anthraquinone hydrogenation catalyst is the key to this production link. Highly active and highly selective anthraquinone hydrogenation catalysts can increase the yield of hydrogen peroxide and reduce anthraquinone degradation. Therefore, anthraquinone hydrogenation catalysts are one of the current research focuses in the field of anthraquinone process for producing hydrogen peroxide.

[0003] The anthraquinone hydrogenation catalyst widely used in industry at present is a catalyst that uses aluminum oxide or silicon oxide as a carrier to load metal palladium. The research focuses on improving the loading method of the active component metal palladium and the improvement of the catalyst carrier. The research on the crystalline phase of aluminum oxide in the prior art, such as the British patent report of 1972 with application number GB2880370A and publication number GB1273280A, uses σ-Al2O3, θ-Al2O3 or a mixture of the two as a palladium catalyst carrier, and the U.S. patent report of 1977 with application number US05699933 and publication number US4061598A, uses γ-Al2O3 as the main crystalline phase, or alumina with a mixture of σ-Al2O3 and θ-Al2O3 as the main crystalline phase as the carrier, such as the Chinese patent application for a hydrogenation catalyst and its preparation method disclosed in application number 2016108206694. Although the above-mentioned technologies have made significant progress in some aspects, they all have defects, such as the need for impregnation with salt solution, which is cumbersome to operate, the introduction of other particles that are unevenly distributed and difficult to control, affecting the catalytic performance and increasing the cost; the process cannot guarantee that the diffusion of the palladium salt of each batch of prepared catalysts on the alumina carrier can be repeated, so it is difficult to ensure the quality of the product; after the carrier is impregnated with an equal volume of impregnation solution such as chloropalladic acid or chloroplatinic acid, the chloride ions are difficult to remove, requiring a large amount of water to be wasted, resulting in a waste of water resources and generating a large amount of wastewater. Even after a large amount of water washing, it is still difficult to remove the chloride ions because some chloride ions are attached to the catalyst and are not easy to remove. Summary of the invention

[0004] In order to solve the existing technical problems, the present invention provides a preparation method of a palladium catalyst for producing hydrogen peroxide by an anthraquinone method. The method uses alumina with a specific proportion of crystal phase, ultrasonic treatment and electrosorption method without introducing particles of silicon, nickel, iron, calcium, cerium, cobalt, etc. to prepare a catalyst with high selectivity and catalytic activity, good mechanical properties, stable product quality, easy removal of chloride ions, and avoids the waste of a large amount of water resources.

[0005] The technical solution of the present invention is as follows:

[0006] A preparation method of a palladium catalyst for producing hydrogen peroxide by an anthraquinone process, the specific preparation method comprising the following steps in sequence:

[0007] (1) at a certain temperature, the aluminum oxide powder is immersed in a palladium salt solution for a certain period of time by wet impregnation, the palladium salt solution includes a sodium tetrachloropalladate solution and a tetrachloropalladium (II) acid solution, and the aluminum oxide includes γ-Al2O3 and α-Al2O3;

[0008] (2) After the impregnation is completed, deionized water is added to the solid, and after ultrasonic treatment, chloride ions are removed by electrosorption, and then filtered to obtain a filter cake;

[0009] (3) The filter cake is dried, calcined and reduced to obtain a palladium catalyst.

[0010] Preferably, the mass ratio of γ-Al2O3 to α-Al2O3 is 80-97:3-20. Further preferably, the mass ratio of γ-Al2O3 to α-Al2O3 is 91-93:7-9. Too little addition of α-Al2O3 results in poor mechanical properties, easy pulverization and palladium removal, resulting in reduced catalytic activity. Too little addition of α-Al2O3 affects the activity of the catalyst.

[0011] Preferably, the particle size of aluminum oxide is 10-150 μm and the specific surface area is 150-200 m 2 / g.

[0012] Preferably, the temperature of step (1) is 55-65°C and the time is 20-40 min.

[0013] Further preferably, in step (1), the preparation method of sodium tetrachloropalladate solution (Na2PdCl4) is: adding palladium chloride and sodium chloride together into deionized water, and the molar ratio of palladium ions in the palladium chloride to sodium ions in the sodium chloride is 1:2; the preparation method of tetrachloropalladium (II) acid solution (H2PdCl4) is: adding palladium chloride and hydrochloric acid together into deionized water, and the molar ratio of palladium chloride to hydrochloric acid is 0.50-1.46:1.

[0014] Preferably, the amount of deionized water added in step (2) is 1-5 times the mass of the solid, and the addition of an appropriate amount of water is mainly for better removal of chloride ions.

[0015] Preferably, the ultrasonic treatment conditions in step (2) are: ultrasonic frequency of 20 to 50 kh, ultrasonic time of 5 to 10 min. After multiple experiments, the ultrasonic treatment conditions with these parameters are finally obtained, which can effectively detach the chloride ions attached to the carrier or palladium, and effectively disperse the aggregated palladium, so that the palladium is dispersed more evenly on the carrier.

[0016] Preferably, the conditions of the electrosorption method in step (2) are as follows: the power supply is a DC power supply, 0<voltage≤2.5V, the distance between the positive and negative electrodes is 1-10mm, and a DC voltage is applied to the electrodes to form a double electric layer between the positive and negative electrodes, so that capacitance is generated in the water, and the charging and discharging process is repeated without chemical reaction, so that the chloride ions are adsorbed on the electrodes, effectively avoiding the waste of a large amount of water resources, and effectively removing the chloride ions.

[0017] Alumina of different crystalline phases have different physical and chemical properties, which will affect the activity and selectivity of the catalyst. γ-Al2O3 is a commonly used carrier for preparing palladium catalysts. In its structure, oxygen ions are closely packed in cubic form, while aluminum ions are irregularly distributed in the octahedral and tetrahedral voids formed by oxygen ions. It belongs to the spinel structure and is a porous substance with a large specific surface area. The pore structure of the carrier has a great influence on the catalytic reaction, but generally an increase in pore volume will reduce its own strength, making it easy to pulverize and the palladium layer to fall off. The inventor introduced α-Al2O3. α-Al2O3 crystals are more stable than other crystalline Al2O3. The physical and chemical properties of α-Al2O3 crystals are very stable and have good mechanical properties. The combined use of γ-Al2O3 and α-Al2O3 not only guarantees the specific surface area, but also guarantees the strength, guarantees the selectivity and activity of the catalyst, and is not easy to cause pulverization and the shedding of the palladium layer, thus ensuring the stability of the catalyst quality. The inventor adopted ultrasonic treatment, on the one hand In order to separate the chloride ions attached to the catalyst, it is beneficial to the subsequent removal of the chloride ions. On the other hand, alumina as a carrier has a strong interaction with the active ingredient, and the aggregated metal palladium can be dispersed by ultrasonic treatment and better distributed on the carrier, which effectively ensures the uniformity of the distribution of palladium on the carrier. In the prior art, for the anthraquinone method of producing hydrogen peroxide, a large amount of water washing is used to remove chloride ions. Simply using water washing will cause a large amount of water resource waste. At the same time, the chloride ions attached to the carrier or metal palladium are not easy to be removed by water washing, which will cause the problem of incomplete removal of chloride ions. The inventor first uses ultrasonic treatment and then uses an electrosorption method to effectively remove the chloride ions. The electrosorption method is to apply a DC voltage to the electrode to form a double electric layer between the positive and negative electrodes, so that it generates capacitance in water, and repeatedly performs a charging and discharging process without chemical reaction, so that the chloride ions are adsorbed on the electrode, effectively avoiding a large amount of water resource waste, and effectively removing the chloride ions.

[0018] The invention provides a method for preparing a palladium catalyst for producing hydrogen peroxide by an anthraquinone process. Without introducing other particles, a palladium catalyst with high activity, high selectivity, stable mechanical properties and stable product quality is obtained. The preparation method is simple and easy to operate, which greatly shortens the process flow, avoids the waste of water resources and effectively removes chloride ions. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The raw materials described can be obtained from public commercial channels unless otherwise specified.

[0020] In the following examples and comparative examples, the particle size of aluminum oxide is 10-150 μm, and the specific surface area is 150-200 m 2 / g, which can be purchased or prepared by the prior art method. After the impregnation is completed, if there is still liquid left, it can be filtered or filtered by suction and then deionized water can be added; in the following, electrosorption is performed until no chloride ions are detected in the silver nitrate solution with a concentration of 0.1 mol / L.

[0021] Example 1

[0022] A preparation method of a palladium catalyst for producing hydrogen peroxide by anthraquinone process:

[0023] (1) At a temperature of 55° C., aluminum oxide powder is immersed in a sodium tetrachloropalladate solution for equal volume immersion for 40 minutes, the aluminum oxide comprises γ-Al2O3 and α-Al2O3, the mass ratio of γ-Al2O3 to α-Al2O3 is 4:1, and the sodium tetrachloropalladate solution (Na2PdCl4) is prepared by adding palladium chloride and sodium chloride together into deionized water, the molar ratio of palladium ions in the palladium chloride to sodium ions in the sodium chloride is 1:2;

[0024] (2) After the impregnation is completed, deionized water twice the mass of the solid is added, and after ultrasonic treatment, the ultrasonic frequency is 20kh, the ultrasonic time is 10min, and the chloride ions are removed by electrosorption. The power supply is a DC power supply, the voltage is 2V, and the distance between the positive and negative electrodes is 3mm. Then, the filter cake is obtained by filtration;

[0025] (3) The filter cake is dried at 100°C for 3 h and calcined at 300°C for 4 h. The calcined catalyst is reduced in a pure hydrogen atmosphere at a reduction temperature of 150°C for 4 h to obtain a hydrogenation reaction catalyst loaded with active metal Pd.

[0026] Example 2

[0027] A preparation method of a palladium catalyst for producing hydrogen peroxide by anthraquinone process:

[0028] (1) At a temperature of 60° C., aluminum oxide powder is immersed in a tetrachloropalladium (II) acid solution for equal volume immersion for 30 minutes, wherein the aluminum oxide comprises γ-Al2O3 and α-Al2O3, and the mass ratio of γ-Al2O3 to α-Al2O3 is 91:9; the tetrachloropalladium (II) acid solution (H2PdCl4) is prepared by adding palladium chloride and hydrochloric acid together into deionized water, wherein the molar ratio of palladium chloride to hydrochloric acid is 1:1;

[0029] (2) After the impregnation is completed, deionized water twice the mass of the solid is added, and after ultrasonic treatment, the ultrasonic frequency is 40 kh, the ultrasonic time is 8 min, and the chloride ions are removed by electrosorption. The power supply is a DC power supply, the voltage is 2.5 V, and the distance between the positive and negative electrodes is 4 mm. Then, the filter cake is obtained by filtration;

[0030] (3) The filter cake is dried at 100°C for 3 h and calcined at 300°C for 4 h. The calcined catalyst is reduced in a pure hydrogen atmosphere at a reduction temperature of 150°C for 4 h to obtain a hydrogenation reaction catalyst loaded with active metal Pd.

[0031] Example 3

[0032] A preparation method of a palladium catalyst for producing hydrogen peroxide by anthraquinone process:

[0033] (1) At a temperature of 60° C., aluminum oxide powder is immersed in a sodium tetrachloropalladate solution for equal volume immersion for 30 minutes, the aluminum oxide comprises γ-Al2O3 and α-Al2O3, the mass ratio of γ-Al2O3 to α-Al2O3 is 23:2, and the sodium tetrachloropalladate solution (Na2PdCl4) is prepared by adding palladium chloride and sodium chloride together into deionized water, the molar ratio of palladium ions in the palladium chloride to sodium ions in the sodium chloride is 1:2;

[0034] (2) After the impregnation is completed, deionized water 2.5 times the mass of the solid is added, and after ultrasonic treatment, the ultrasonic frequency is 25kh, the ultrasonic time is 9min, and the chloride ions are removed by electrosorption. The power supply is a DC power supply, the voltage is 2V, and the distance between the positive and negative electrodes is 5mm. Then, the filter cake is obtained by filtration;

[0035] (3) The filter cake is dried at 100°C for 3 h and calcined at 300°C for 4 h. The calcined catalyst is reduced in a pure hydrogen atmosphere at a reduction temperature of 150°C for 4 h to obtain a hydrogenation reaction catalyst loaded with active metal Pd.

[0036] Comparative Example 1

[0037] Compared with Example 3, except that the mass ratio of γ-Al2O3 to α-Al2O3 is adjusted to 1:1, everything else is the same as Example 1.

[0038] Comparative Example 2

[0039] Compared with Example 3, except that the aluminum oxide including γ-Al2O3 and α-Al2O3 is adjusted so that the content of α-Al2O3 in the aluminum oxide is zero, the rest is the same as Example 1.

[0040] Comparative Example 3

[0041] Compared with Example 3, except that step (2) is adjusted to the following steps, the rest are the same as Example 1;

[0042] (2) After the immersion is completed, wash with pure water until there is no Cl in the filtrate - , and obtain a filter cake.

[0043] Test example

[0044] The performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-3 was evaluated, and the specific results are shown in Table 1.

[0045] Catalyst activity evaluation method: 5 g of catalyst is loaded into a fixed bed reactor each time, and the hydrogenation efficiency is measured at 50°C, normal pressure, and a hydrogen flow rate of 20 L / h, and the hydrogenation efficiency is used as the basis for activity; wherein, the working liquid uses 2-ethylanthraquinone (EAQ) as the working medium, and heavy aromatics (AR) and trioctyl phosphate (TOP) as solvents, wherein the EAQ content is 100 g / L, and AR:TOP=3:1 (volume ratio).

[0046] Compressive strength evaluation method: The force that the sample catalyst bears when it just breaks is taken as the sample compressive strength. 20 particles are measured and the average value is taken as the sample compressive strength value, unit N / particle.

[0047] Table 1

[0048]

[0049]

[0050] As shown in the data in the above table, α-Al2O3 is added to Examples 1-3, Comparative Example 1 and Comparative Example 3, and its compressive strength is significantly higher than that of Comparative Example 2. Compared with Examples 1-3 and Comparative Example 3, Comparative Example 1 adds excessive α-Al2O3, and its activity is significantly poorer. Compared with Examples 1-3, Comparative Example 1 and Comparative Example 3, no α-Al2O3 is added, and its activity and compressive strength are the worst. Compared with Example 3, Comparative Example 3 changes the method of removing chloride ions and continues to use the traditional method of washing with water, and its activity is also significantly reduced.

[0051] The processes of Example 2 and Example 3 were repeated 20 times, and the activity of the prepared catalyst was 12.5 g / L or more, reaching 100%. The process of Example 1 was repeated 20 times, and the activity of the prepared catalyst was 11.9 g / L or more, reaching 99%. The process of the present invention can ensure that the diffusion of the palladium salt of each batch of prepared catalysts on the alumina carrier can be repeated, and the product prepared by the present invention has good quality stability.

[0052] The invention provides a preparation method of a palladium catalyst for producing hydrogen peroxide by an anthraquinone method. By using different ratios of γ-Al2O3 and α-Al2O3, combined with ultrasonic treatment and electrosorption methods, the activity and selectivity of the palladium catalyst are effectively improved, and the compressive strength and stability are improved. The palladium catalyst prepared by the preparation method of the invention has an activity of more than 11.9 g / L, a compressive strength of more than 81 N / grain, and good and stable product quality. The invention does not need to introduce additional particles, does not need to add additional processes for introducing other particles, and effectively removes chloride ions, thereby avoiding a large amount of waste of water resources.

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0054] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process, characterized in that: The specific preparation method comprises the following steps in sequence: (1) at a certain temperature, alumina powder is immersed in a palladium salt solution in equal volume for a certain period of time, the palladium salt solution includes a sodium tetrachloropalladate solution and a tetrachloropalladic acid solution, and the alumina includes γ-Al2O3 and α-Al2O3; (2) After the impregnation is completed, deionized water is added to the solid, and after ultrasonic treatment, chloride ions are removed by electrosorption, and then filtered to obtain a filter cake; (3) The filter cake is dried, calcined and reduced to obtain a palladium catalyst.

2. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The mass ratio of γ-Al2O3 to α-Al2O3 is 80-97:3-20.

3. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 2, characterized in that: The mass ratio of γ-Al2O3 to α-Al2O3 is 91-93:7-9.

4. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The particle size of the aluminum oxide is 10-150 μm, and the specific surface area is 150-200 m 2 / g.

5. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The temperature in step (1) is 55-65°C.

6. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 5, characterized in that: The time in step (1) is 20-40 min.

7. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The preparation method of the sodium tetrachloropalladate solution in step (1) is: palladium chloride and sodium chloride are added into deionized water together, and the molar ratio of palladium ions in the palladium chloride to sodium ions in the sodium chloride is 1:2; the preparation method of the tetrachloropalladic acid solution is: palladium chloride and hydrochloric acid are added into deionized water together, and the molar ratio of palladium chloride to hydrochloric acid is 0.50-1.46:

1.

8. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The amount of water added in step (2) is 1-5 times the mass of the solid.

9. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone process according to claim 1, characterized in that: The conditions of the ultrasonic treatment in step (2) are: an ultrasonic frequency of 20 to 50 kh and an ultrasonic time of 5 to 10 min.

10. The method for preparing a palladium catalyst for producing hydrogen peroxide by anthraquinone method according to claim 1 or 9, characterized in that: The conditions of the electrosorption method in step (2) are as follows: the power supply is a DC power supply, 0<voltage≤2.5V, and the distance between the positive and negative electrodes is 1-10mm.

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