Regeneration catalyst for working solution used in hydrogen peroxide synthesis

Abstract

The present invention relates to a regeneration catalyst for a working solution used in the synthesis of hydrogen peroxide, a method for manufacturing the regeneration catalyst, and a method for regenerating the working solution. In particular, the present invention relates to a palladium catalyst using a spinel support as a catalyst used in the regeneration process of a working solution for hydrogen peroxide production, a method for manufacturing the catalyst, and a regeneration technique for the working solution using the catalyst. The catalyst of the present invention exhibits high efficiency and high physical / chemical durability in the regeneration reaction and the hydrogenation reaction.

Description

Technical Field

[0001] The present invention relates to a regeneration catalyst for a working solution used in the synthesis of hydrogen peroxide, a method for manufacturing the regeneration catalyst, and a method for regenerating the working solution. In particular, the present invention relates to a palladium catalyst using a spinel support as a catalyst used in the regeneration process of a working solution for manufacturing hydrogen peroxide, a method for manufacturing the catalyst, and a regeneration technique for the working solution using the catalyst. The catalyst of the present invention exhibits high efficiency and high physical / chemical durability in the regeneration reaction and the hydrogenation reaction. Background Art

[0002] Hydrogen peroxide is a compound used in various fields such as the synthesis of semiconductors, pharmaceuticals, and chemical substances. Hydrogen peroxide can be manufactured by a direct synthesis method using hydrogen and oxygen or an anthraquinone method that continuously performs hydrogenation and oxidation processes using anthraquinone compounds. The hydrogen peroxide manufacturing technology using the anthraquinone method is as follows.

[0003]

[0004] That is, hydrogen peroxide is manufactured by repeatedly performing hydrogenation and oxidation processes on a working solution (WS, Working Solution) in which an alkyl anthraquinone (usually 2-ethyl-anthraquinone, referred to as EAQ) is dissolved in an appropriate organic solvent. When the hydrogenation and oxidation processes are repeatedly performed as described above, by-products such as tetrahydroanthraquinone (THAQ) accumulate in the working solution, and coke deposited inside the catalyst causes the catalyst to deactivate, resulting in a decrease in the manufacturing and regeneration efficiency of hydrogen peroxide. Summary of the Invention

[0005] In particular, when manufacturing a palladium-based catalyst used in the process of regenerating a by-product, tetrahydroanthraquinone (THAQ), into anthraquinone, a promoter such as magnesium is added simultaneously to control the acidic sites of the support. However, as the catalytic reaction is repeatedly performed, the promoter fixed to the support gradually detaches from the catalyst, resulting in a gradual decrease in the activity of the regeneration reaction. Therefore, in order to ensure the durability of the catalyst, the adhesion of the metal supported on the support becomes crucial. Therefore, the technical problem to be achieved by the present invention is to provide a palladium catalyst having acid resistance and durability that can be used in the regeneration reaction of a hydrogen peroxide working solution or the manufacturing process of hydrogen peroxide, and a method for manufacturing the catalyst.

[0006] To solve the above problems, the inventors of the present invention used, in particular, a support for controlling the acidic sites and pore structure of the catalyst, increased the density of the active metal in the support by including a cyclic palladium active layer inside the support, and also increased the dispersion of palladium particles by introducing a co-metal, thereby achieving an improved reaction activity. In addition, the catalyst of the present invention contains the active metal inside the support, thereby reducing the loss of the active metal caused by abrasion during the reaction process, and thus improving the durability of the catalyst.

[0007] Therefore, the above problems can be solved by using a palladium catalyst with acid resistance and heat resistance of a support having a spinel structure. In addition, the above problems can be solved by using a palladium catalyst with a co-metal supported on a support having a spinel structure to improve palladium dispersion. In addition, the durability / activity stability can be improved by a palladium catalyst having a cyclic structure inside the support.

[0008] The present invention provides a working solution regeneration for hydrogen peroxide synthesis or a hydrogen peroxide synthesis catalyst in the form of palladium and a co-metal supported on a support of a spinel structure. Non-limitingly, the spinel structure can be selected from MgAl2O4, ZnAl2O4, CaAl2O4, FeAl2O4, (Mg,Zn)Al2O4, and (Mg,Fe)Al2O4 as aluminum-based spinel structures. In addition, the spinel structure can be an alumina-spinel composite oxide further containing alumina. In the catalyst of the present invention, the co-metal can be selected from the group consisting of cerium, calcium, barium, strontium, zirconium, titanium, radium, silicon, and aluminum. The catalyst support of the present invention may further contain one or more halogen components selected from the group consisting of chlorine, phosphorus, and fluorine. In the present invention, the palladium inside the support can be present in a cyclic form at a certain interval from the surface of the support. Specifically, the palladium inside the support can be present at a distance of 5 to 10 μm from the surface of the support. In the catalyst of the present invention, palladium as an active component can be present in the support at an active density of 0.005 to 0.16 wt% / m2, the co-metal can be uniformly present in the support at a density of 0.0001 to 0.002 wt% / m2, and optionally, the halogen component can be uniformly present in the support at a density of 0.004 to 0.04 wt% / m2. In the catalyst of the present invention, the support can have a pore size of 7 to 14 nm, a pore volume of 0.2 to 0.5 m3 / g, and a specific surface area of 70 to 200 m2 / g.

[0009] The catalyst according to the present invention can improve the reaction selectivity by suppressing the acidic sites that induce side reactions inside the carrier. Moreover, the active metal has a concentrated ring structure inside the carrier, and the high dispersion of palladium can be induced by introducing auxiliary metals. The catalyst according to the present invention uses a magnesium aluminate spinel structure that can prevent magnesium from detaching during the reuse of the catalyst by including magnesium inside the carrier framework. Moreover, the dispersion degree can be improved and the number of active sites of palladium can be increased by using an auxiliary metal and placing palladium above it, thereby maximizing the reaction activity. In addition, the palladium active metal can be preserved when physical wear of the catalyst occurs during the reaction, thus ensuring high durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is the general structure of the catalyst according to the present invention.

[0011] Figure 2 is the X-ray diffraction (XRD) pattern of the catalyst carrier used in Examples 1 to 3 of the present invention.

[0012] Figure 3 is the scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) images of the catalyst according to Example 1 of the present invention. DETAILED DESCRIPTION

[0013] Next, the present invention will be described in detail. The catalyst with durability / acid resistance disclosed in the present invention was developed as a catalyst for working solution regeneration, but it can also be applied as a hydrogenation catalyst for hydrogen peroxide production. In the present invention, the catalyst for working solution regeneration will be mainly described, but its application field is not limited to the regeneration reaction. In the present invention, the catalyst active component is supported on a carrier, and the carrier is also called a support.

[0014] The present invention relates to a palladium catalyst using a carrier suitable for controlling acidic sites as a spinel structure body. The spinel structure used in the present invention generally refers to a cubic crystal form having XY 2 O 4 , in which oxygen anions are arranged in a cubic close-packed lattice form, and the cationic metals X and Y occupy part or all of the octahedral and tetrahedral sites in the lattice. In the present invention, as the spinel structure body that can be applied to the catalyst for hydrogen peroxide production or working solution regeneration, in particular, an aluminum-based spinel structure body having acid resistance and heat resistance and having surface basic properties, namely MgAl 2 O 4 , ZnAl 2 O 4 , CaAl 2O 4 、FeAl 2 O 4 、(Mg,Zn)Al 2 O 4 and (Mg,Fe)Al 2 O 4 morphological particles. Preferably, AI 2 O 3 -XY 2 O 4 composite oxide form can be used to apply to both the relatively wide surface area of alumina and the basicity of the spinel structure at the same time.

[0015] In the palladium catalyst according to the present invention, a promoter metal can be applied to the spinel-structured support to improve palladium dispersion. It is judged that the promoter metal can improve its dispersion by having the catalyst active component located thereon and thereby increase the number of active sites of palladium, thus maximizing the reaction activity. Preferably, cerium can be taken as an example of the promoter metal, which can induce high dispersion of palladium. As the promoter metal, calcium, barium, strontium, zirconium, titanium, radium, silicon or aluminum can also be applied.

[0016] In the palladium catalyst according to the present invention, palladium as the catalyst active component forms a ring structure inside the support. The ring structure generally refers to a structure in which the catalyst active component is concentrated inside at a certain interval from the outer contour in a circular-structured catalyst, and there is no active component at the outer contour and the center of the catalyst. The formation and thickness of the ring will change according to the type and concentration of the reagents used in the synthesis process. The ring structure can preserve the active metal during physical abrasion of the catalyst in the reaction process, thus maintaining a high durability.

[0017] The present invention relates to a palladium catalyst obtained by loading cerium onto a magnesium aluminate support with a spinel structure manufactured by heat-treating a mixture of aluminum and alumina, firing to fix cerium, then impregnating with palladium and reducing it, and a manufacturing method thereof. When it is used in the regeneration process of the working solution, the regeneration conversion rate can be effectively ensured.

[0018] Example 1

[0019] Support manufacturing step: Using magnesium nitrate (Mg(NO 3 ) 2 ·6H 2 O, Aldrich Co., Ltd.), aluminum nitrate (Al(NO 3 ) 3 ·9H 2 O, Aldrich Co., Ltd.) and ammonia water (28wt% NH 4OH, DAEJUNG Chemical & Metals Co., Ltd. manufactured a support. First, magnesium nitrate was dissolved in distilled water, and then aluminum nitrate was dissolved according to a Mg / Al molar ratio of 0.5 to produce an aqueous solution. The pH of the aqueous solution was adjusted to 10.5 by adding ammonia water and stirred at room temperature for 12 minutes. Next, beads of approximately 100 μm in size with water removed by a spray dryer were produced. Then, it was sufficiently dried at 105 °C for 12 hours using a dryer, and then heat-treated at 900 °C for 10 hours to obtain a spinel-crystalline oxide support (magnesium aluminate).

[0020] Catalyst manufacturing step: Regarding cerium used as an auxiliary metal, cerium nitrate (Ce(NO 3 ) 3 ·6H 2 O) was used as a precursor, and regarding palladium used as an active metal, (H 2 PdCl 4 ) was used as a precursor. First, the magnesium aluminate support was mixed into ionized water containing 0.25% cerium equivalent to the total weight of the catalyst. Next, the metal was fixed by performing a heat treatment process on the cerium-supported composition at 550 °C for 2 hours in an air environment. Next, 1.0% palladium precursor, 1.0% hydrogen peroxide (H 2 O 2 ) equivalent to the total weight of the catalyst, and 0.2% HCl were added, stirred, and heated to 80 °C, and then maintained at that temperature for 1 hour.

[0021] Catalyst reduction step: It was performed by introducing a reducing agent into the cerium-palladium composite support. Sodium formate (NaCOOH) was used as the reducing agent. The temperature was raised to 60 °C to ionize Na and generate sufficient hydrogen during the reduction process, and it was maintained at that temperature for 1 hour to produce the catalyst as shown in Figure 1 .

[0022] Physical properties of the catalyst: Cerium was uniformly distributed inside the support, and palladium mainly presented a ring-shaped structure with a certain interval from the outer contour of the support and a thickness of 15 μm. By calculation, the palladium activity density in the catalyst was 0.1559 wt% / m 2 . The activity density mentioned in the present invention refers to the amount of active metal per unit support surface area where the active metal is located. A higher value indicates a larger number of metal active sites that can react in a certain volume of the support, and it can be understood as being proportional to the activity of the catalyst.

[0023] Example 2

[0024] A catalyst was manufactured by performing in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 700 °C in the carrier manufacturing step of Example 1.

[0025] Catalyst physical properties: The carrier crystal phase is a mixed form of alumina phase and magnesium aluminate phase, and the active metal exhibits the same ring shape as in Example 1. Palladium mainly presents a ring-shaped structure spaced at a certain interval from the outer contour of the carrier and distributed with a thickness of 16 μm. Moreover, the palladium activity density in the manufactured catalyst was calculated to be 0.0679 wt% / m 2 。

[0026] Example 3

[0027] A catalyst was manufactured by performing in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 500 °C in the carrier manufacturing step of Example 1.

[0028] Catalyst physical properties: The carrier crystal phase is alumina phase, and the active metal exhibits the same ring shape as in Example 1. Palladium mainly presents a ring-shaped structure spaced at a certain interval from the outer contour of the carrier and distributed with a thickness of 14 μm. Moreover, the palladium activity density in the manufactured catalyst was calculated to be 0.0646 wt% / m 2 。

[0029] Comparative Example 1

[0030] A pure alumina carrier using a carrier with a non-spinel structure was used, and magnesium was supported on the alumina carrier by an impregnation method. First, magnesium nitrate equivalent to 4.5% and cerium nitrate equivalent to 0.25% compared to the total weight of the catalyst were mixed into ionized water. The manufactured magnesium-cerium composite solution was impregnated into the alumina carrier by the wet-dry method. The metal was fixed by performing a heat treatment process on the magnesium-cerium-supported composition at 550 °C for 2 hours in an air environment. Next, 100 g of the magnesium-cerium-supported alumina composition was added to 200 ml of water, and a palladium precursor equivalent to 1.0%, hydrogen peroxide equivalent to 1.0%, and HCl equivalent to 0.2% compared to the total weight of the catalyst were added, stirred, and heated to 80 °C, and then maintained at that temperature for 30 minutes.

[0031] The catalyst reduction process was carried out by introducing a reducing agent into the magnesium-cerium-palladium-supported complex. Sodium formate (NaCOOH) was used as the reducing agent. The temperature was raised to 60 °C to ionize Na and generate sufficient hydrogen during the reduction process, and maintained at that temperature for 1 hour.

[0032] Physical properties of the catalyst: Magnesium and cerium are uniformly distributed inside the carrier, while palladium mainly presents a ring-shaped structure with a certain interval from the outer contour of the carrier and a thickness of 16 μm. The palladium activity density in the manufactured catalyst is calculated to be 0.0491 wt% / m 2 .

[0033] Comparative Example 2

[0034] A catalyst was manufactured by performing in the same manner as Comparative Example 1, except that hydrogen peroxide was not used when loading palladium.

[0035] Physical properties of the catalyst: Magnesium, cerium, and palladium are all uniformly distributed inside the carrier. The palladium activity density in the manufactured catalyst is calculated to be 0.005 wt% / m 2 .

[0036] Comparative Example 3

[0037] A catalyst was manufactured by performing in the same manner as Comparative Example 2, except that cerium was not loaded.

[0038] Physical properties of the catalyst: Magnesium and palladium are both uniformly distributed inside the carrier. The palladium activity density in the manufactured catalyst is calculated to be 0.0051 wt% / m 2 .

[0039] Test Example: Carrier Characteristics

[0040] The crystal phase and pore structure of the carriers manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 and Figure 2 as shown.

[0041]

Table 1

[0042]

[0043]

[0044] From Table 1 and Figure 2 it can be confirmed that the spinel structure of Examples 1 to 3 depends on the firing temperature of the carrier. When the temperature increases, the specific surface area and pore volume decrease, but the pore size shows a gradually increasing result. As Figure 2As shown, the diffraction peaks of Example 3 only have the crystallinity of alumina, indicating that no spinel structure is formed. In the support heat-treated at 700 degrees in Example 2, both alumina and spinel crystalline phases coexist. In the case of heat treatment at a temperature above 900 degrees by raising the heat treatment temperature as in Example 1, a pure spinel crystalline phase is finally obtained. Moreover, as shown in the results in Table 1, the pore size of the support increases significantly. Therefore, it can be predicted that when it is actually applied to the catalyst reaction, the diffusion and movement of reactants and products in the catalyst can be ensured smoothly.

[0045] Test Example 2: Physicochemical Properties of Palladium Inside the Support

[0046] Table 2 shows the results of measuring the palladium dispersion, particle size, and the distribution of palladium inside the particles of the catalysts of Examples 1 to 3 and Comparative Examples 1 to 3 using a chemisorption analyzer and an electron probe micro analyzer (EPMA).

[0047]

Table 2

[0048]

[0049]

[0050] From the analysis content in Table 2, it can be confirmed that the palladium dispersion of Comparative Example 3 without cerium loading decreased sharply compared with Examples 1 to 3 and Comparative Examples 1 to 3. Moreover, except for Comparative Example 3, relatively high palladium dispersion and low palladium particle size were generally shown. Based on the above results, it can be confirmed that cerium located on the surface of the support plays a role in uniformly dispersing palladium metal into smaller particles. The distribution of palladium inside the catalyst particles can be adjusted by hydrogen peroxide and hydrochloric acid, whereby palladium particles can exist in a ring shape on the surface of the catalyst. It can be confirmed that in Examples 1 to 3 and Comparative Example 1, the palladium metal is distributed at a position 5 - 8 μm away from the outer contour of the catalyst, and the thickness of the ring is distributed between 10 - 12 μm. The scanning electron microscope (SEM) and electron probe micro analyzer (EPMA) images of Example 1 are as Figure 3 shown.

[0051] Test Example 3: Catalyst Regeneration Efficiency

[0052] A regeneration evaluation reaction was carried out to measure the regeneration efficiency of the catalysts in the examples and comparative examples, and the evaluation was performed using a stirred reaction system made of stainless steel (SUS) as the reactor. A magnetic bar was put into the circular stirred reactor, and the regeneration efficiency was measured by putting 10 g of the catalyst into 50 g of the by-product working solution generated during the hydrogenation reaction. The catalyst activity was expressed by the conversion rate, and its calculation formula is as follows.

[0053] Conversion rate (%) = [(Area value of tetrahydroanthraquinone (THAQ) in the working solution - Area value of tetrahydroanthraquinone (THAQ) in the reactant) / (Area value of tetrahydroanthraquinone (THAQ) in the working solution)] * 100

[0054] The activity analysis was measured using a liquid chromatography (LC) analyzer, and the palladium content was measured using an inductively coupled plasma spectrometer (ICP) analyzer. The results are shown in Table 3. Table 3 is the evaluation result of the tetrahydroanthraquinone (THAQ) -> 2-ethylanthraquinone (EAQ) conversion rate of the catalysts manufactured in the examples and comparative examples.

[0055]

Table 3

[0056]

[0057] Regarding the evaluation results of the catalyst activity, compared with Comparative Examples 2 and 3 where palladium was uniformly supported, the results of Examples 1 to 3 and Comparative Example 1 supported in a ring shape were more excellent. From the above results, it can be confirmed that when the metal active sites are concentrated on the catalyst surface, the contact frequency with the reactants can be increased and the catalyst reaction can be completed more quickly. Among the ring-shaped catalysts, especially Example 1 showed the highest activity, from which it can be confirmed that the larger the pore size of the carrier, the easier the diffusion and movement of the reactants and products in the catalyst, and thus the reaction rate can be increased. Next, to confirm the durability of the catalyst, it was found that by repeating the catalyst reaction - catalyst regeneration 50 times (heat treatment at 550 °C for 6 hours), although the value decreased compared with the initial activity, the order was still the same as that of the initial activity. Regarding the magnesium content, there was almost no loss in Example 1, but there was some loss in other examples and comparative examples, indicating a correlation between the loss amount of magnesium and the activity results.

[0058] Finally, after applying physical impact with a ball mill for 24 hours, a catalyst of a certain size after removing fine powder was selected for reaction evaluation. When continuously applying impact to the outside of the catalyst using a ball mill, the catalyst will cause fragmentation and loss of surface particles due to external physical impact, and the same tendency will also be presented in commercial engineering. As a result, it can be confirmed that when evaluating after grinding for 24 hours, the catalyst in which palladium exists in a ring shape can maintain performance similar to the initial performance. This indicates that since there is no palladium on the outermost contour of the catalyst in the ring shape, even when surface particles are lost, the loss of palladium active substances can be minimized. In a catalyst with a uniform shape where there is no gap between the palladium active layer and the surface, the loss of surface particles of the catalyst will directly lead to the loss of palladium active substances. The above results can be confirmed through the analysis results of the loss rate of palladium content in the catalyst.

Claims

1. A catalyst, As a regeneration catalyst for the working solution used in hydrogen peroxide synthesis, it is in the form of palladium and auxiliary metals supported on a carrier. The palladium is spaced at a certain interval from the surface of the carrier and exists in a ring shape inside the carrier. The carrier contains a spinel structure body, and the auxiliary metal is cerium.

2. The catalyst according to claim 1, characterized in that: The spinel structure is selected from MgAl 2 O 4 、ZnAl 2 O 4 、CaAl 2 O 4 、FeAl 2 O 4 、(Mg,Zn)Al 2 O 4 and (Mg,Fe)Al 2 O 4 among them.

3. The catalyst according to claim 1, characterized in that: The spinel structure body is an alumina-spinel composite oxide further containing alumina.

4. The catalyst according to claim 1, characterized in that: The carrier further contains one or more halogen components selected from the group consisting of chlorine and fluorine.

5. The catalyst according to claim 1, characterized in that: The palladium inside the carrier exists at a distance of 5 to 10 μm from the surface of the carrier.

6. The catalyst according to claim 1, characterized in that: The palladium exists in the carrier at an active density of 0.005 to 0.16 wt% / m 2 .

7. The catalyst according to claim 1, characterized in that: The auxiliary metal is uniformly present in the carrier at a density of 0.0001 to 0.002 wt% / m 2 .

8. The catalyst according to claim 4, characterized in that: The halogen component is uniformly present in the carrier at a density of 0.004 to 0.04 wt% / m 2 .

9. The catalyst according to claim 1, characterized in that: The carrier has a pore size of 7 to 14 nm, a pore volume of 0.2 to 0.5 m 3 / g, and a specific surface area of 70 to 200 m 2 / g.

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