Bis (hydroxyl) tetraammine palladium (II) and preparation method and application thereof

Abstract

The invention discloses bis (hydroxyl) tetraammine palladium (II) and a preparation method and application thereof, and belongs to the technical field of palladium compound preparation. According to the preparation method, tetraammine palladium sulfate ([Pd (NH3) 4] SO4) and alkaline earth metal hydroxide are taken as raw materials, and di (hydroxyl) tetraammine palladium (II) which can be applied to different fields is prepared by adjusting the relative content of the alkaline earth metal hydroxide and ammonium oxalate; and a certain amount of ammonium carboxylate is added, so that the falling condition of amino groups in the bis (hydroxyl) tetraammine palladium (II) is reduced, and the stability and water solubility of the material are improved. According to the method, chlorine-free and alkali metal ion-free tetraammine palladium sulfate is selected as a palladium source, so that the influence of elements or ions on a catalytic precursor is avoided from the source; secondly, residual alkaline earth metal ions are effectively removed by utilizing the characteristics that oxalate of alkaline earth metal is low in solubility and ammonium oxalate is easy to decompose after being heated; then, a certain amount of alkaline ammonium carboxylate is added, so that the stability of a target product and the solubility of the target product in water are improved; finally, the relative content of alkaline earth metal ions and C2O4 < 2-> is selectively controlled, and the method is suitable for synthesis of bis (hydroxyl) tetraammine palladium (II) in different application scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of palladium compound preparation, and specifically relates to di(hydroxy)tetraaminepalladium (II) and a preparation method and application thereof. Background Art

[0002] Palladium catalytic precursor refers to the palladium compound that introduces active ingredients into the carrier catalyst, and common ones include palladium chloride and palladium nitrate. A large number of studies have shown that the composition and structure of palladium compounds have an important influence on the performance of the catalyst. For example, automobile exhaust purification catalysts and VOC treatment catalysts strictly limit the chlorine content because the residual chlorine in the catalyst will significantly reduce the catalytic activity and service life of the catalyst; palladium nitrate is sold in the market in the form of nitric acid solution of more than 10%, because nitrates are difficult to prepare in solid state and are unstable in water, and only exist in nitric acid with a higher concentration. The 10% nitric acid medium is highly corrosive, dissolving the surface of the carrier material, destroying the original surface structure, reducing the dispersion and adhesion of the active ingredients on the carrier surface, and affecting the catalytic performance; at the same time, a large amount of nitric acid is introduced into the preparation process, and harmful gases are decomposed during the drying or calcination of the catalyst, which pollutes the environment and is not conducive to clean production.

[0003] At present, the preparation methods of palladium catalyst precursors mainly include anion resin exchange method. The preparation method of [Pd(NH3)4)](OH)2 reported in Chinese patent CN201410228792.8 is to use palladium chloride as the starting material to react with ammonia water to generate dichlorotetraamminepalladium, and then use anion resin exchange to convert Cl - Use OH - Instead, the target product is obtained. In this method, OH - Resin exchange Cl - , leading to Cl - It is difficult to completely remove, and requires repeated exchange and regeneration of the resin, resulting in a lot of waste liquid, low product yield, and difficult to control purity.

[0004] According to the currently developed preparation method, the conventional process for preparing di(hydroxy)tetraamminepalladium is as follows:

[0005]

[0006] The traditional method of preparing palladium catalytic precursors generally starts with a chlorine-containing palladium salt, palladium acid (such as PdCl2, N2PdCl4 (N=H, Na, K)) or a nitrate-containing palladium salt (such as Pd(NO3)2) as the starting point, first adding an excess of concentrated ammonia to form an ammonia-coordinated palladium complex intermediate, and then introducing OH -, and the final product is obtained. This method has two major drawbacks. On the one hand, the obtained product contains elements or ions such as chlorine and nitrate. The presence of chlorine will reduce the activity of the catalyst, and nitrate will form nitrogen oxides during the subsequent use of the catalytic precursor, causing damage to the environment. On the other hand, the purity of the product is not high, mainly due to the second step, OH - The source of OH is mainly alkali (such as NaOH, Ca(OH)2, KOH, etc.). Taking the palladium source as chlorine-containing PdCl2, the introduction of OH - A chloride salt (such as NaCl, CaCl2, KCl, etc.) is bound to be generated. These chloride salts are easily soluble in water, causing them to mix with the product. Even after multiple purification treatments, it is difficult to completely separate them, which results in the purity of the obtained product being not very high.

[0007] In summary, finding a method to prepare a high-purity, water-soluble palladium catalytic precursor using a palladium source that does not contain chlorine, potassium, sodium, and nitrate is of great significance for improving the activity and life of the palladium catalyst. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, the present invention provides a di(hydroxy)tetraamminepalladium(II) and a preparation method and application thereof.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A preparation method of di(hydroxy)tetraaminepalladium(II) comprises the following steps: dissolving [Pd(NH3)4](SO4) in water, then adding an aqueous solution of alkaline earth metal hydroxide to react, adding ammonium carboxylate to react after the reaction, and then separating a precipitate and a filtrate to obtain di(hydroxy)tetraaminepalladium(II)A.

[0011] A preparation method of di(hydroxy)tetraaminepalladium(II), comprising the following steps: dissolving [Pd(NH3)4](SO4) in water, then adding alkaline earth metal hydroxide to react, adding ammonium carboxylate to react after the reaction, continuously adding ammonium oxalate to the upper clear layer until no more precipitation is generated in the filtrate, standing, and then separating the lower precipitate and the upper clear liquid to obtain di(hydroxy)tetraaminepalladium(II)B.

[0012] As a preferred embodiment of the present invention, the di(hydroxy)tetraamminepalladium(II)A is a filtrate or a solid substance obtained by freeze-drying the filtrate.

[0013] As a preferred embodiment of the present invention, the di(hydroxy)tetraamminepalladium(II) B is a supernatant or a solid substance obtained by freeze-drying the supernatant.

[0014] The invention uses a conventional method of repeated recrystallization to obtain di(hydroxy)tetraaminepalladium(II) A or di(hydroxy)tetraaminepalladium(II) B to obtain di(hydroxy)tetraaminepalladium(II) with a purity of ≥99%, and a yield of more than 95%.

[0015] As a preferred embodiment of the present invention, the molar ratio of [Pd(NH3)4](SO4) to alkali metal hydroxide is 1:(1-1.5).

[0016] As a preferred embodiment of the present invention, the ammonium carboxylate is preferably ammonium acetate, and the molar ratio of the added amount to [Pd(NH3)4](SO4) is (0.1-0.5):1.

[0017] As a preferred embodiment of the present invention, the temperature of adding the alkaline earth metal hydroxide to react is 60-70° C. and the reaction time is 0.5-1 h.

[0018] As a preferred embodiment of the present invention, the temperature of the reaction of adding the ammonium carboxylate is 60-70° C. and the reaction time is 0.5 h.

[0019] The present invention also claims to protect the di(hydroxy)tetraaminepalladium(II) A prepared by the preparation method of di(hydroxy)tetraaminepalladium(II).

[0020] The present invention also claims to protect the di(hydroxy)tetraaminepalladium(II) B prepared by the preparation method of di(hydroxy)tetraaminepalladium(II).

[0021] The present invention also claims to protect the use of the di(hydroxy)tetraaminepalladium(II)A as a palladium catalyst precursor in the preparation of automobile exhaust treatment catalysts.

[0022] The present invention also claims to protect the use of the di(hydroxy)tetraaminepalladium(II)B as a palladium catalyst precursor in the preparation of a Pd / C catalyst.

[0023] Compared with the prior art, the present invention has the following beneficial effects: firstly, the present invention selects tetraamminepalladium sulfate and alkaline earth metal hydroxide as raw materials, thereby eliminating elements or ions such as chlorine, sodium, and nitrate from the source, thus avoiding the influence of these elements or ions on the product, and reducing the risk of the amino group in di(hydroxy)tetraamminepalladium (II) falling off easily by adding ammonium carboxylate, thereby improving the stability and solubility of di(hydroxy)tetraamminepalladium (II) in water, and later utilizing the property of ammonium oxalate that it is easy to decompose when heated, thereby effectively removing the residual alkaline earth metal ions while having almost no influence on the purity of the product. In addition, by controlling the alkaline earth metal ions and C2O4 -The prepared different di(hydroxy)tetraaminepalladium(II) are applied to different fields, and by controlling the content of alkaline earth metal ions and C2O4 in di(hydroxy)tetraaminepalladium(II), the - The relative content of di(hydroxy)tetraamminepalladium(II) is increased to improve the efficiency and life of the catalyst prepared during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a high performance liquid chromatogram of di(hydroxy)tetraamminepalladium prepared in Example 1 of the present invention.

[0025] Figure 2 It is a picture of the stratification of the solution after the reaction of adding ammonium oxalate and the actual picture of the filtrate after filtration in Example 1 of the present invention.

[0026] Figure 3 This is the surface oxalate ion chromatogram of di(hydroxy)tetraamminepalladium B prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] Example 1

[0029] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0030] Weigh 2.71g (10.0mmol) of tetraamminepalladium sulfate and 3.21g (10.2mmol) of Ba(OH)2·8H2O (5% excess) and dissolve them in a 100ml beaker with deionized water. Slowly add Ba(OH)2·8H2O to the tetraamminepalladium sulfate solution while stirring, and heat to 60°C. Continue stirring and keep warm for 0.5h. Cool to room temperature, add 0.38g (4.93mmol) of ammonium acetate solution, stir and react for 30min, and let stand. At this time, stratification will occur, with a clear solution on the upper layer and a white solid precipitate on the lower layer. Continue to add ammonium oxalate to the clear solution on the upper layer until no white precipitate is generated. Use a sand core funnel to separate the precipitate and the filtrate. Rinse the precipitate three times with deionized water, freeze-dry the filtrate, and finally obtain 1.99g of a light yellow solid product [Pd(NH3)4)(OH)2] (yield 95.2%). Figure 1 It can be seen that the present invention successfully prepared di(hydroxy)tetraaminepalladium B. After di(hydroxy)tetraaminepalladium B was left for 7 days, 0.5 g of di(hydroxy)tetraaminepalladium B was added into 10 mL of distilled water to obtain a light yellow clear solution.

[0031] Example 2

[0032] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0033] Weigh 40.59g (0.15mol) of tetraamminepalladium sulfate and 11.11g (0.15mol) of Ca(OH)2 and dissolve them in a 1L beaker with deionized water. Slowly add Ca(OH)2 to the tetraamminepalladium sulfate solution while stirring, heat to 60°C and stir to react for 0.5h, let stand and cool to room temperature, then add 5.77g (75mmol) of ammoniated ammonium acetate solution, stir and react for 30min, let stand, at this time, stratification will appear, the upper layer is a clear solution, and the lower layer is a white solid precipitate. Add ammonium oxalate dropwise to the upper solution until no white precipitate is generated, let stand, separate the precipitate with a sand core funnel, rinse the precipitate three times with deionized water, and freeze-dry the filtrate to finally obtain a light yellow solid product [Pd(NH3)4](OH)229.63g (yield 94.69%). After the light yellow solid product [Pd(NH3)4](OH)2 was left for 7 days, 0.5 g of the light yellow solid product [Pd(NH3)4](OH)2 was added into 10 mL of distilled water to obtain a light yellow clear solution.

[0034] Example 3

[0035] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0036] Weigh 162.39g (0.60mol) of tetraamminepalladium sulfate and 198.73g (0.63mmol) of Ba(OH)2·8H2O and dissolve them in a 2L beaker with deionized water. Slowly add Ba(OH)2·8H2O to the tetraamminepalladium sulfate solution while stirring, heat to 60℃ and stir to react for 0.5h, let stand to cool, then add 4.62g (60.0mmol) of ammonium acetate solution, stir to react for 0.5h, let stand, at this time, stratification will occur, the upper layer is a clear solution, and the lower layer is a white solid precipitate. Add ammonium oxalate solution to the upper solution until no white precipitate is generated, let stand for a while, separate the precipitate with a sand core funnel, rinse the precipitate three times with deionized water, and freeze-dry the filtrate to obtain a light yellow solid product [Pd(NH3)4](OH)2120.64g (yield 96.40%). After the light yellow solid product [Pd(NH3)4](OH)2 was left for 7 days, 0.5 g of the light yellow solid product [Pd(NH3)4](OH)2 was added into 10 mL of distilled water to obtain a light yellow clear solution.

[0037] Example 4

[0038] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0039] Weigh 8.12g (30.0mmol) of tetraamminepalladium sulfate and 10.50g (33.3mmol) of Ba(OH)2·8H2O to prepare solutions. Slowly add Ba(OH)2·8H2O to the tetraamminepalladium sulfate solution under stirring, and heat to 70°C. Stir and react for 0.5h. After cooling, add 1.15g (14.93mmol) of ammonium acetate solution and stir and react for 0.5h. Let stand. At this time, stratification will occur. The upper layer is a clear solution and the lower layer is a white solid precipitate. Add ammonium oxalate solution dropwise to the upper solution until no white precipitate is generated. Let stand. Separate the precipitate with a sand core funnel. Rinse the precipitate three times with deionized water. Make the filtrate dilute to 53ml to obtain a light yellow solution of [Pd(NH3)4](OH)2 with a Pd content of 6%. After the light yellow solution of [Pd(NH3)4](OH)2 was left for 7 days, no insoluble matter was found and the color and state did not change.

[0040] Example 5

[0041] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0042] Weigh 5.42g (20.0mmol) of tetraammine palladium sulfate and 6.50g (20.6mmol) of Ba(OH)2·8H2O and dissolve them in a 100ml beaker. Slowly add Ba(OH)2·8H2O to the tetraammine palladium sulfate solution under stirring, heat to 60°C, stir and react for 0.5h, let stand and cool, then add 0.77g (10.0mmol) of ammonium acetate solution, stir and react for 0.5h, let stand, then stratification will appear, the upper layer is a clear solution, and the lower layer is a white solid precipitate. Use a sand core funnel to separate the precipitate, rinse the precipitate three times with deionized water, and freeze-dry the filtrate to obtain a light yellow solid product [Pd(NH3)4](OH)23.87g (yield 92.8%). Ion chromatography (IC) detection shows that the Ba in the filtrate is 1.34g. 2+ The content is 0.11 mg / L. After the light yellow solid product [Pd(NH3)4](OH)2 is left for 7 days, 0.5 g of the light yellow solid product [Pd(NH3)4](OH)2 is added to 10 mL of distilled water to obtain a light yellow clear solution.

[0043] Example 6

[0044] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0045] Weigh 5.42g (20.0mmol) of tetraamminepalladium sulfate and 9.46g (30.0mmol) of Ba(OH)2·8H2O and dissolve them in a 100ml beaker respectively. Slowly add Ba(OH)2·8H2O to the tetraamminepalladium sulfate solution while stirring, heat to 60°C, stir and react for 0.5h, let stand and cool, then add 0.77g (10.0mmol) of ammonium acetate solution, stir and react for 0.5h, let stand, then stratification will appear, the upper layer is a clear solution, and the lower layer is a white solid precipitate. Use a sand core funnel to separate the precipitate, rinse the precipitate three times with deionized water, and freeze-dry the filtrate to obtain a light yellow solid product [Pd(NH3)4](OH)23.99g (yield 97.60%). After the light yellow solid product [Pd(NH3)4](OH)2 was left for 7 days, 0.5 g of the light yellow solid product [Pd(NH3)4](OH)2 was added into 10 mL of distilled water to obtain a light yellow clear solution.

[0046] Comparative Example 1

[0047] A method for preparing di(hydroxy)tetraamminepalladium comprises:

[0048] Weigh 2.71g (10.0mmol) of tetraamminepalladium sulfate and 3.21g (10.2mmol) of Ba(OH)2·8H2O (5% excess) and dissolve them in a 100ml beaker. Slowly add Ba(OH)2·8H2O to the tetraamminepalladium sulfate solution while stirring. Heat to 60°C and keep stirring for 1h. Cool to room temperature. Put the filtrate in a 100ml beaker and let it stand. Add ammonium oxalate to the upper clear solution continuously until no white precipitate is generated. Use a sand core funnel to separate the precipitate and filtrate. Rinse the precipitate three times with deionized water. Freeze-dry the filtrate to obtain 1.98g of a light yellow solid product [Pd(NH3)4)(OH)2] (yield 95.19%). Figure 1 It can be seen that the present invention successfully prepared di(hydroxy)tetraaminepalladium, but after di(hydroxy)tetraaminepalladium was left for 7 days, 0.5g of di(hydroxy)tetraaminepalladium was taken and added into 10mL of distilled water, and a small amount of white insoluble matter was found.

[0049] Effect Example 1

[0050] Test samples: products prepared in Examples 1-4.

[0051] The use of Examples 1-4 as a precursor in the preparation of a Pd / C catalyst comprises:

[0052] The activated carbon was subjected to acidification and oxidation treatment to obtain pretreated activated carbon. Then 3 g of the pretreated activated carbon was added to 20 ml of water and stirred to obtain a slurry, and then the test sample was added and stirred for 4 hours, and finally 20 ml of a reducing substance (hydrazine hydrate) was added and stirred for reduction for 4 hours, and the Pd-loaded activated carbon was taken out and washed to neutrality, and vacuum dried at 80°C to obtain a Pd / C catalyst, and the Pd loading was 4% of the total mass of the catalyst.

[0053] Effect Example 2

[0054] Test sample: the product prepared in Example 5 or Example 6.

[0055] The use of the product prepared in Example 5 or Example 6 as a catalyst for treating automobile exhaust gas includes:

[0056] The catalyst was prepared by an impregnation method with the test sample as the active component and the molecular sieve as the carrier, and the Pd loading amount was 1.91% of the total mass of the catalyst.

[0057] The prepared catalyst was used for exhaust gas treatment, namely, for the catalytic conversion of CH4 oxidation in natural gas engines (CNG). The small sample simulated gas distribution test (SGB) was used to investigate the catalyst's CH4 oxidation conversion efficiency. The simulated gas distribution conditions were CH4 1000mL / m 3 +8% O2+5% H2O+86.9% N2 (volume fraction), test air velocity is 80000h -1 The temperature when the CH4 conversion rate is 50% is about 370°C, which indicates that the product prepared in Example 5 or Example 6 can be used as a precursor to prepare a catalyst for treating automobile exhaust.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing di(hydroxy)tetraamminepalladium(II), characterized in that: The method comprises the following steps: dissolving [Pd(NH3)4](SO4) in water, then adding alkaline earth metal hydroxide solution and stirring for reaction, adding ammonium carboxylate for reaction after the reaction is completed, standing, and then separating precipitate and filtrate to obtain di(hydroxy)tetraaminepalladium(II)A; the di(hydroxy)tetraaminepalladium(II)A is a supernatant or a solid substance after freeze-drying the supernatant.

2. A method for preparing di(hydroxy)tetraamminepalladium(II), characterized in that: The method comprises the following steps: dissolving [Pd(NH3)4](SO4) in water, then adding alkaline earth metal hydroxide solution and stirring for reaction, adding ammonium carboxylate for reaction after the reaction is completed, continuously dropping ammonium oxalate to the upper clear layer until no more precipitation is generated, standing, and then separating the lower precipitation and the upper clear liquid to obtain di(hydroxy)tetraamminepalladium(II)B; the di(hydroxy)tetraamminepalladium(II)B is the upper clear liquid or a solid substance after freeze-drying the upper clear liquid.

3. The method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 1 or 2, characterized in that: The molar ratio of [Pd(NH3)4](SO4) to alkali metal hydroxide is 1:(1-1.5).

4. The method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 1 or 2, characterized in that: The ammoniated ammonium carboxylate is ammonium acetate, and the molar ratio of the ammoniated ammonium carboxylate to [Pd(NH3)4](SO4) is (0.1-0.5):

1.

5. The method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 1 or 2, characterized in that: The temperature of adding alkaline earth metal hydroxide to react is 60-70° C. and the reaction time is 0.5-1 h.

6. The method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 1 or 2, characterized in that: The reaction temperature of adding the ammonium carboxylate is 60-70° C. and the reaction time is 0.5 h.

7. Di(hydroxy)tetraaminepalladium(II)A prepared by the method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 1.

8. Di(hydroxy)tetraaminepalladium(II) B prepared by the method for preparing di(hydroxy)tetraaminepalladium(II) as claimed in claim 2.

9. Use of di(hydroxy)tetraaminepalladium(II)A as claimed in claim 7 as a palladium catalyst precursor in the preparation of an automobile exhaust treatment catalyst.

10. Use of di(hydroxy)tetraaminepalladium(II)B as claimed in claim 8 as a palladium catalyst precursor in the preparation of a Pd / C catalyst.

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