Eggshell type palladium catalyst as well as preparation method and application thereof

Abstract

The invention provides an eggshell type palladium catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method comprises the following steps: modifying an alumina ball carrier by using a silicate solution and an alcohol amine solution in sequence, and carrying out isopyknic impregnation on the modified carrier by using a sodium palladate solution containing a nonionic surfactant to finally prepare the eggshell type palladium catalyst. According to the palladium catalyst prepared by the method, Pd on the surface is dispersed more uniformly, a palladium layer is thinner, and the catalyst has relatively high stability and hydrogenation efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to an eggshell type palladium catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is an important inorganic chemical raw material, which is widely used in chemical synthesis, textiles, medicine, electronics, food and metallurgy. The anthraquinone method has become the mainstream method for producing hydrogen peroxide due to its advantages such as large scale, low energy consumption, low cost and easy operation. The production of hydrogen peroxide by the anthraquinone method is mainly carried out in two steps of hydrogenation-oxidation of alkyl anthraquinone, among which the selective hydrogenation of alkyl anthraquinone is crucial to the yield of H2O2. In order to improve the activation ability of the C=O bond on the alkyl anthraquinone molecule and reduce the production of degradation products, the development of efficient hydrogenation catalysts is particularly critical.

[0003] As one of the alkyl anthraquinone hydrogenation catalyst systems, Pd catalyst has the characteristics of high activity, operation resistance, long life and easy recovery, so it has attracted widespread attention and has become the mainstream alkyl anthraquinone hydrogenation catalyst on the market. Studies have found that the preparation method of the catalyst seriously affects the interaction between the loaded metal and the carrier, which in turn affects the dispersion of the active metal, changes the crystal state and impregnation depth, and finally affects its catalytic performance.

[0004] A Chinese patent with publication number CN105582911A discloses a method for preparing an anthraquinone hydrogenation catalyst, wherein a refractory oxide, a modified macroporous pore former, a modified microporous pore former, a peptizing agent and water are kneaded and formed, and then dried and calcined to obtain an anthraquinone hydrogenation catalyst. The catalyst has high activity, low anthraquinone degradation rate and solvent loss, but does not mention the service life and stability of the catalyst, and the improvement of the hydrogenation efficiency is not obvious. It is a hydrogenation catalyst in the traditional sense.

[0005] The Chinese patent with publication number CN115430419A discloses a preparation method and application of a palladium-based catalyst for producing hydrogen peroxide by anthraquinone method, wherein the content of palladium element as the main active component is 0.5wt% to 1.9wt%, the content of titanium or zirconium element as the auxiliary active component is 0.7wt% to 4.3wt%, the carrier is amorphous silicon aluminum, wherein the content of aluminum oxide is 5.6wt% to 24.7wt%, the content of silicon dioxide is 64.6wt% to 88.6wt%, and the pH of gel aging is adjusted by using organic base and organic acid. However, the preparation process focuses on the preparation of the carrier, and the noble metal palladium source is directly added to the carrier for impregnation aging. The palladium can only adsorb a layer on the surface of the carrier and cannot enter the pores deeply, and the distribution is unstable. Once de-powdering occurs, the catalyst will be deactivated. At the same time, the system production environment applicable to the catalyst is not mentioned.

[0006] The Chinese patent with publication number CN109967132A discloses an index method for a modified alumina carrier, a palladium catalyst and a preparation method thereof, wherein the carrier is aged, dried and calcined, first the Co particles load the carrier, and then the Pd nanoparticles are replaced with Co. However, in this method, the carrier is in a colloidal state, and the colloidal state is loaded into the reaction equipment, and continuous stirring will form a slurry, which is easy to cause equipment blockage, and hydrogen peroxide is not easy to purify. Secondly, the replacement of Pd with Co is an incomplete reaction, which will reduce the activity and life of the catalyst. Summary of the invention

[0007] In view of this, an object of the present invention is to provide a palladium catalyst with more uniform surface Pd dispersion, thinner palladium layer, high catalytic stability and hydrogenation efficiency.

[0008] In order to achieve the above object, the present invention discloses the following technical solutions:

[0009] A method for preparing an eggshell type palladium catalyst comprises the following steps:

[0010] (1) pre-soaking the alumina ball carrier in deionized water at 30-70° C. for 1-6 hours, then pre-treating it in a silicate solution at 30-70° C. for 0.5-2 hours, and drying and calcining it after the pre-treatment to obtain a pre-carrier I;

[0011] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 30-70° C. for 1-6 h, then pre-treating in a 0.5-3% alcohol amine solution at 30-70° C. for 0.5-2 h, and then washing until the pH value of the pre-carrier surface is 7-8, to obtain a pre-carrier II;

[0012] (3) The sodium palladium acid solution is mixed with a nonionic surfactant to obtain a mixed solution, and the pre-support II obtained in step (2) is added to the mixed solution at 30 to 70° C., and impregnated with equal volumes for 0.5 to 2 hours, followed by drying and calcining to obtain an eggshell-type palladium catalyst.

[0013] Preferably, the particle size of the alumina ball carrier in step (1) is 2.0-2.6 mm.

[0014] Preferably, the silicate in the silicate solution in step (1) is any one of sodium silicate, potassium silicate and sodium metasilicate;

[0015] The mass concentration of silicate in the silicate solution is 0.01-1.00% calculated according to the Si content;

[0016] The mass ratio of the alumina ball carrier to the silicate solution is 1:1-5.

[0017] Preferably, the drying and roasting conditions in step (1) are: drying at 80-120° C. for 8-16 hours, and roasting at 400-500° C. for 2-6 hours.

[0018] Preferably, the alcoholamine in the alcoholamine solution of step (2) is any one of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, and triisopropanolamine;

[0019] The mass concentration of the alcoholamine in the alcoholamine solution is 1-1.5%; the mass ratio of the pre-carrier I to the alcoholamine solution is 1:1-5.

[0020] Preferably, the molar ratio of Na to Pd in ​​the sodium palladium solution of step (3) is Na:Pd=2:1, and the mass concentration of Pd in ​​the sodium palladium solution is 0.27-0.32%;

[0021] The nonionic surfactant is any one of P123, F127, polyvinyl alcohol, and polyethylene glycol;

[0022] The mass ratio of the pre-carrier II to the non-ionic surfactant is 1:0.0001-0.001.

[0023] Preferably, the drying and roasting conditions in step (3) are: drying at 80-120° C. for 8-16 hours, and roasting at 400-500° C. for 2-6 hours.

[0024] Another object of the present invention is to provide an eggshell type palladium catalyst prepared by the above method.

[0025] The present invention also provides an application of the eggshell type palladium catalyst, wherein the eggshell type palladium catalyst is used in a process for producing hydrogen peroxide by an anthraquinone method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The invention sequentially modifies an alumina ball carrier with a silicate solution and an alcohol amine solution, and then uses a sodium palladium acid solution containing a nonionic surfactant to impregnate the modified carrier in equal volumes, and finally obtains an eggshell-type palladium catalyst. The palladium catalyst obtained by the method has a more uniform Pd dispersion on the surface, a thinner palladium layer, and a higher stability and hydrogenation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The palladium layer distribution diagram of the 1# eggshell type palladium catalyst of Example 1;

[0029] Figure 2 The palladium layer distribution diagram of the 5# eggshell type palladium catalyst of Example 5;

[0030] Figure 3The palladium layer distribution diagram of the 6# eggshell type palladium catalyst of Comparative Example 1;

[0031] Figure 4 The palladium layer distribution diagram of the 7# eggshell type palladium catalyst of Comparative Example 2;

[0032] Figure 5 This is the palladium layer distribution diagram of the 8# eggshell type palladium catalyst of comparative example 3. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0034] (1) pre-soaking an alumina ball carrier with a particle size of 2.4 mm in deionized water at 30-70° C. for 1-6 h, then transferring it to a silicate solution at 30-70° C. for pretreatment for 0.5-2 h, drying it at 80-120° C. for 8-16 h, and calcining it at 400-500° C. for 2-6 h to obtain a pre-carrier I;

[0035] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 30-70° C. for 1-6 h, then pre-treating in a 0.5-3% alcohol amine solution at 30-70° C. for 0.5-2 h, and washing until the pH value of the pre-carrier surface is 7-8, to obtain a pre-carrier II;

[0036] (3) Mixing the sodium palladium acid solution with a nonionic surfactant to obtain a mixed solution, adding the pre-support II obtained in step (2) to the mixed solution at 30-70° C., and impregnating the mixed solution in equal volumes for 0.5-2 h, followed by drying at 80-120° C. for 8-16 h, and calcining at 400-500° C. for 2-6 h to obtain an eggshell-type palladium catalyst.

[0037] In a specific embodiment of the present invention, the silicate in the silicate solution in step (1) is any one of sodium silicate, potassium silicate and sodium metasilicate;

[0038] The mass concentration of silicate in the silicate solution is 0.01-1.00% calculated according to the Si content;

[0039] The mass ratio of the alumina ball carrier to the silicate solution is 1:1-5.

[0040] In a specific embodiment of the present invention, the drying and roasting conditions in step (1) are:

[0041] In a specific embodiment of the present invention, the alcoholamine in the alcoholamine solution of step (2) is any one of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, and triisopropanolamine;

[0042] The mass concentration of the alcoholamine in the alcoholamine solution is 1-1.5%; the mass ratio of the pre-carrier I to the alcoholamine solution is 1:1-5.

[0043] In a specific embodiment of the present invention, the molar ratio of Na to Pd in ​​the sodium palladium solution of step (3) is Na:Pd=2:1, and the mass concentration of Pd in ​​the sodium palladium solution is 0.27-0.32%;

[0044] The nonionic surfactant is any one of P123, F127, polyvinyl alcohol, and polyethylene glycol;

[0045] The mass ratio of the pre-carrier II to the non-ionic surfactant is 1:0.0001-0.001.

[0046] The eggshell type palladium catalyst prepared by the method has a palladium layer thickness of 0.05 mm to 0.06 mm.

[0047] The eggshell palladium catalyst was used in the anthraquinone process to produce hydrogen peroxide;

[0048] In a specific embodiment of the present invention, a glass fixed bed reactor is used, 10 g of catalyst is weighed and loaded into a glass tube reactor with an inner diameter of 20 mm and a height of 400 mm, 50 mL of working solution is loaded, the anthraquinone content in the working solution is set to 120 g / L, the reaction temperature is 50 ° C, the pressure is normal, and the working solution is subjected to a single-pass reaction for 30 min. The hydrogenation working solution is titrated and analyzed with potassium permanganate solution to test the hydrogenation efficiency of the catalyst.

[0049] The technical solution of the present invention is further described below in conjunction with the embodiments. In the specific embodiments of the present invention, the raw material ratios or concentrations are all mass ratios or mass concentrations unless otherwise specified.

[0050] Example 1

[0051] A method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0052] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to sodium silicate with a Si content of 0.5% at 60° C. for pretreatment for 1 h. The mass ratio of the carrier to the sodium silicate solution was 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I.

[0053] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 60° C. for 3 h, and then transferring it to a 1% ethanolamine solution at 60° C. for pre-treatment for 1 h, wherein the mass ratio of the pre-carrier I to the ethanolamine solution is 1:2, and washing until the pH value of the pre-carrier surface is 7, thereby obtaining a pre-carrier II;

[0054] (3) After mixing a sodium palladium acid solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to P123 is 1:0.005) evenly, the pre-carrier II obtained in step (2) is added to the mixed solution at 60°C and impregnated with an equal volume for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 1# eggshell type palladium catalyst with a palladium layer thickness of 0.05 mm. The palladium layer distribution diagram of the 1# eggshell type palladium catalyst is as follows: Figure 1 .

[0055] Example 2

[0056] A method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0057] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to potassium silicate with a Si content of 0.5% at 60° C. for pretreatment for 1 h, with the mass ratio of the carrier to the sodium silicate solution being 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I;

[0058] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 60° C. for 3 h, and then transferring it to a 1% ethanolamine solution at 60° C. for pre-treatment for 1 h, wherein the mass ratio of the pre-carrier I to the ethanolamine solution is 1:2, and washing until the pH value of the pre-carrier surface is 7, thereby obtaining a pre-carrier II;

[0059] (3) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to non-ionic surfactant is 1:0.005) evenly, the pre-carrier II obtained in step (2) is added to the mixed solution at 60°C and impregnated with equal volumes for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 2# eggshell type palladium catalyst.

[0060] Example 3

[0061] A method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0062] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to sodium silicate with a Si content of 0.5% at 60° C. for pretreatment for 1 h. The mass ratio of the carrier to the sodium silicate solution was 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I.

[0063] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 60° C. for 3 h, and then transferring it to a 1% diisopropylamine solution at 60° C. for pre-treatment for 1 h, wherein the mass ratio of the pre-carrier I to the ethanolamine solution is 1:2, and washing until the pH value of the pre-carrier surface is 7, thereby obtaining a pre-carrier II;

[0064] (3) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to P123 is 1:0.005) evenly, the pre-carrier II obtained in step (2) is added to the mixed solution at 60°C and impregnated with equal volumes for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 3# eggshell-type palladium catalyst.

[0065] Example 4

[0066] A method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0067] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to sodium silicate with a Si content of 0.5% at 60° C. for pretreatment for 1 h. The mass ratio of the carrier to the sodium silicate solution was 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I.

[0068] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 60° C. for 3 h, and then transferring it to a 1% ethanolamine solution at 60° C. for pre-treatment for 1 h, wherein the mass ratio of the pre-carrier I to the ethanolamine solution is 1:2, and washing until the pH value of the pre-carrier surface is 7, thereby obtaining a pre-carrier II;

[0069] (3) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with polyethylene glycol (the mass ratio of pre-carrier II to polyethylene glycol is 1:0.005) evenly, the pre-carrier II obtained in step (2) is added to the mixed solution at 60°C and immersed in equal volumes for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 4# eggshell type palladium catalyst.

[0070] Example 5

[0071] A method for preparing an eggshell type palladium catalyst, comprising the following steps:

[0072] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to sodium silicate with a Si content of 0.8% at 60° C. for pretreatment for 1 h. The mass ratio of the carrier to the sodium silicate solution was 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I.

[0073] (2) pre-soaking the pre-carrier I in step (1) in deionized water at 60° C. for 3 h, and then transferring it to a 1% ethanolamine solution at 60° C. for pre-treatment for 1 h, wherein the mass ratio of the pre-carrier I to the ethanolamine solution is 1:2, and washing until the pH value of the pre-carrier surface is 7, thereby obtaining a pre-carrier II;

[0074] (3) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to P123 is 1:0.005) evenly, the pre-carrier II obtained in step (2) is added to the mixed solution at 60°C and impregnated with an equal volume for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 5# eggshell type palladium catalyst with a palladium layer thickness of 0.06 mm. The palladium layer distribution diagram of the 5# eggshell type palladium catalyst is as follows: Figure 2 .

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 1 is that only silicate solution is used to modify the alumina ball carrier, and the specific steps are as follows:

[0077] (1) An alumina ball carrier with a particle size of 2.4 mm was pre-soaked in deionized water at 60° C. for 3 h, and then transferred to sodium silicate with a Si content of 0.5% at 60° C. for pretreatment for 1 h. The mass ratio of the carrier to the sodium silicate solution was 1:2. After the pretreatment, the carrier was dried at 100° C. for 10 h and calcined at 450° C. for 4 h to obtain a pre-carrier I.

[0078] (2) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to P123 is 1:0.005) evenly, the pre-carrier I obtained in step (1) is added to the mixed solution at 60°C and impregnated with equal volumes for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 6# eggshell type palladium catalyst with a palladium layer thickness of 0.10 mm. The palladium layer distribution diagram of the 6# eggshell type palladium catalyst is as follows: Figure 3 .

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 1 is that the alumina ball carrier is not modified, but the eggshell type palladium catalyst is prepared by immersing it in a sodium palladium acid solution containing a P123 nonionic surfactant when carrying palladium. The specific steps are as follows:

[0081] (1) Pre-soak the alumina ball carrier with a particle size of 2.4 mm in deionized water at 60 °C for 3 h;

[0082] (2) After mixing a sodium palladium solution with a Na:Pd ratio of 2:1 and a Pd content of 0.30% with P123 (the mass ratio of pre-carrier II to P123 is 1:0.005) evenly, the alumina ball carrier pre-impregnated in step (1) is added to the mixed solution at 60°C and impregnated with equal volume for 1 hour, followed by drying at 100°C for 10 hours and calcining at 450°C for 4 hours to obtain a 7# eggshell type palladium catalyst with a palladium layer thickness of 0.14 mm. The palladium layer distribution diagram of the 7# eggshell type palladium catalyst is as follows: Figure 4 .

[0083] Comparative Example 3

[0084] The difference between Comparative Example 3 and Example 1 is that the alumina ball carrier is not modified, and the eggshell type palladium catalyst is obtained by directly immersing it in a sodium palladium acid solution. The specific steps are as follows:

[0085] (1) Pre-soak the alumina ball carrier with a particle size of 2.4 mm in deionized water at 60 °C for 3 h;

[0086] (2) At 60°C, a sodium palladium solution with a ratio of Na:Pd = 2:1 and a Pd content of 0.30% was added to the pre-impregnated alumina ball carrier, and the solution was impregnated with equal volume for 1 hour. The catalyst was then dried at 100°C for 10 hours and calcined at 450°C for 4 hours to obtain an 8# eggshell type palladium catalyst with a palladium layer thickness of 0.18 mm. The distribution diagram of the palladium layer of the 8# eggshell type palladium catalyst is shown in FIG. Figure 5 .

[0087] The hydrogenation efficiency of the eggshell palladium catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was evaluated:

[0088] A glass fixed bed reactor was used. 10 g of catalyst was weighed and loaded into a glass tube reactor with an inner diameter of 20 mm and a height of 400 mm. 50 mL of working solution was loaded. The anthraquinone content in the working solution was set to 120 g / L. The reaction temperature was 50 ° C and the pressure was normal. The working solution was reacted for 30 minutes in a single pass. The hydrogenation working solution was titrated with potassium permanganate solution to test the hydrogenation efficiency of the catalyst.

[0089] The palladium layer thickness, palladium loading and hydrogenation efficiency of the catalyst are shown in Table 1.

[0090] Table 1 Palladium layer thickness, palladium loading and hydrogenation efficiency of different eggshell palladium catalysts

[0091] catalyst Palladium layer thickness Palladium loading Hydrogenation efficiency Example 1 0.05mm 0.303％ 12.35％ Example 2 0.05mm 0.301％ 12.27％ Example 3 0.05mm 0.301％ 12.24％ Example 4 0.05mm 0.299％ 12.22％ Example 5 0.06mm 0.300％ 12.15％ Comparative Example 1 0.10mm 0.297％ 10.07％ Comparative Example 2 0.14mm 0.296％ 9.25％ Comparative Example 3 0.18mm 0.295％ 7.88％

[0092] The catalyst prepared by the present invention is used to carry out an evaluation experiment on the anthraquinone hydrogenation ability.

[0093] Reaction conditions: The ratio of catalyst to working liquid is 1:10, and the working liquid is composed of 1,3,5-trimethylbenzene, trioctyl phosphate and tetrabutyl urea in a ratio of 2:1:1, containing 120 g / L of 2-ethylanthraquinone. The reaction temperature is 60°C, atmospheric pressure, and the hydrogenation efficiency is analyzed every 0.5 h. The evaluation of the anthraquinone hydrogenation ability of the catalyst is shown in Table 2.

[0094] Table 2 Evaluation of the ability of catalysts to hydrogenate anthraquinone

[0095]

[0096] It can be seen from Table 2 that the catalyst prepared by the present invention still has a good hydrogenation efficiency after reacting for 3.5 hours, indicating that the catalyst prepared by the present invention has high stability.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an eggshell type palladium catalyst, characterized in that: The following steps are involved: (1) pre-soaking the alumina ball carrier in deionized water at 30-70° C. for 1-6 hours, then pre-treating it in a silicate solution at 30-70° C. for 0.5-2 hours, and drying and calcining it after the pre-treatment to obtain a pre-carrier I; (2) pre-soaking the pre-carrier I in step (1) in deionized water at 30-70° C. for 1-6 h, then pre-treating in a 0.5-3% alcohol amine solution at 30-70° C. for 0.5-2 h, and then washing until the pH value of the pre-carrier surface is 7-8, to obtain a pre-carrier II; (3) The sodium palladium acid solution is mixed with a nonionic surfactant to obtain a mixed solution, and the pre-support II obtained in step (2) is added to the mixed solution at 30 to 70° C., and impregnated with equal volumes for 0.5 to 2 hours, followed by drying and calcining to obtain an eggshell-type palladium catalyst.

2. The method for preparing an eggshell type palladium catalyst according to claim 1, wherein The particle size of the alumina ball carrier in step (1) is 2.0-2.6 mm.

3. The preparation method of the eggshell type palladium catalyst according to claim 1, characterized in that, The silicate in the silicate solution of step (1) is any one of sodium silicate, potassium silicate and sodium metasilicate; The mass concentration of silicate in the silicate solution is 0.01-1.00% calculated according to the Si content; The mass ratio of the alumina ball carrier to the silicate solution is 1:1-5.

4. The preparation method of the eggshell type palladium catalyst according to claim 1, characterized in that, The drying and roasting conditions of step (1) are: drying at 80-120° C. for 8-16 hours and roasting at 400-500° C. for 2-6 hours.

5. The preparation method of the eggshell type palladium catalyst according to claim 1, characterized in that, The alcoholamine in the alcoholamine solution of step (2) is any one of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine; The mass concentration of the alcoholamine in the alcoholamine solution is 1-1.5%; the mass ratio of the pre-carrier I to the alcoholamine solution is 1:1-5.

6. The method for preparing an eggshell type palladium catalyst according to claim 1, wherein The molar ratio of Na to Pd in ​​the sodium palladium solution of step (3) is Na:Pd=2:1, and the mass concentration of Pd in ​​the sodium palladium solution is 0.27-0.32%; The nonionic surfactant is any one of P123, F127, polyvinyl alcohol, and polyethylene glycol; The mass ratio of the pre-carrier II to the non-ionic surfactant is 1:0.0001-0.

001.

7. The method for preparing an eggshell type palladium catalyst according to claim 1, wherein The drying and roasting conditions in step (3) are: drying at 80-120° C. for 8-16 hours and roasting at 400-500° C. for 2-6 hours.

8. An eggshell type palladium catalyst prepared by the above method, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

9. The use of the eggshell type palladium catalyst according to claim 8, characterized in that: The eggshell type palladium catalyst is used in the process of producing hydrogen peroxide by anthraquinone method.

Images