A heterogeneous catalyst for selective hydrogenation of nitrile rubber and its preparation method and application

Abstract

The application discloses a kind of heterogeneous catalyst for selective hydrogenation of nitrile rubber and its preparation method and application, the catalyst includes carrier and is supported on carrier noble metal and magnesium salt, the loading of noble metal in catalyst is 1-10%, the mass ratio of noble metal and Mg element is 0.5-1.5:1, the content of noble metal in catalyst is 40-70% of the total amount of noble metal element, the noble metal is Pd, the particle size of noble metal particle is 1-20 nm, catalyst is Pd as active center, with Mg as second metal to stabilize Pd valence, the carrier is ceria, titania, zirconium dioxide, aluminium oxide or indium trioxide.The heterogeneous catalyst of the application can carry out rapid hydrogenation reaction under mild conditions when used for catalyzing selective hydrogenation reaction of nitrile rubber, and the hydrogenation selectivity is as high as 99.9%, and the hydrogenation activity is more than 99%.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a heterogeneous catalyst for the selective hydrogenation of nitrile rubber, its preparation method, and its application. Background Technology

[0002] Hydrogenated nitrile butadiene rubber (HNBR) is a synthetic elastic material with excellent oil resistance, chemical stability, and heat resistance. It is produced by hydrogenating nitrile butadiene rubber (NBR) in the presence of hydrogen and a metal catalyst. Nitrile butadiene rubber was initially developed for the automotive industry, used in seals, protective sleeves, and pipes. However, due to its limitations in high-temperature environments, researchers sought to improve its properties. Hydrogenation provides superior thermal stability, dimensional stability, and mechanical strength, making it suitable for a wider range of applications.

[0003] The catalytic hydrogenation process of nitrile rubber solution is divided into homogeneous and heterogeneous types. Homogeneous catalysts involve the reactants and catalyst in the same phase, eliminating mass transfer issues and exhibiting high reactivity. However, a common problem with homogeneous catalysts is that noble metals tend to remain in the reactants and solvent after the reaction, making complete separation difficult. This not only increases the cost of using the catalyst but also leads to a decrease in product quality. Heterogeneous catalysts, compared to homogeneous catalysts, have the significant advantage of easy separation. Simple filtration or centrifugation can separate the catalyst from the reaction solvent phase, making catalyst recovery easier. Commonly used heterogeneous catalysts involve supporting noble metal nanoparticles such as Ru, Rh, and Pd on supports such as AC, SiO2, TiO2, PS resin, and some porous mesoporous materials. Although heterogeneous catalysts are increasingly being studied, several problems remain to be solved, primarily the low cyclic stability of the catalysts. DeBoer, JE, et al., used a palladium / carbon catalyst in their research on the hydrogenation of nitrile rubber. While the reaction could proceed at lower temperatures and pressures, the degree of hydrogenation was low, and the catalyst could not be recycled. In industrial production, large-scale enterprises such as Bayer in Germany also use palladium / carbon catalysts for the hydrogenation reaction of nitrile butadiene rubber (NBR). After a period of reaction, the activity of the catalyst gradually decreases. This is because the hydrogenated NBR molecules have a certain degree of viscosity, forming a thin film on the catalyst surface and covering the active sites. This not only reduces the contact opportunities between hydrogen and rubber molecules and the catalyst, but may also lead to physical blockage of the catalyst, thereby reducing its efficiency and lifespan. Summary of the Invention

[0004] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a heterogeneous catalyst for selective hydrogenation of nitrile rubber and its application. When the catalyst of the present invention is applied to the selective hydrogenation reaction of nitrile rubber, it can react rapidly under mild conditions and exhibit high hydrogenation activity and selectivity.

[0005] The technical solution adopted in this invention is as follows:

[0006] A heterogeneous catalyst for the selective hydrogenation of nitrile rubber includes a support and a noble metal and a magnesium salt supported on the support. The loading of the noble metal in the catalyst is 1-10%, the mass ratio of the noble metal to Mg is 1-3:3-1, the content of the positive valence noble metal in the catalyst accounts for 40-70% of the total noble metal content, the noble metal is Pd, the particle size of the noble metal is 1-20 nm, the catalyst has Pd as the active center and Mg as the second metal to stabilize the valence state of Pd, and the support is cerium dioxide, titanium dioxide, zirconium dioxide, aluminum oxide or indium oxide.

[0007] Furthermore, the support is indium trioxide or aluminum trioxide, the loading of noble metal in the catalyst is 4-5%, and the mass ratio of noble metal to Mg is 1:1.

[0008] Furthermore, the catalyst contains 60-70% of the total amount of noble metals in the positive valence state, and the particle size of the noble metal particles is 1-5 nm.

[0009] The method for preparing a heterogeneous catalyst for selective hydrogenation of nitrile rubber includes the following steps:

[0010] 1) Weigh the precious metal Pd salt and magnesium salt according to the mass ratio, dissolve them in deionized water, and prepare a solution with a total salt concentration of 0.05-0.25 mol / L;

[0011] 2) Add the carrier to the solution prepared in step 1) and mix and stir. The resulting slurry is then poured into a porcelain boat, which is then placed in a muffle furnace at 400-500℃ for rapid heating and boiling. The product was then removed and rapidly cooled at room temperature to obtain the calcined solid product.

[0012] 3) Wash the calcined product obtained in step 2) with water and then dry it to obtain the catalyst product.

[0013] Furthermore, in step 1), the precious metal Pd salt is sodium tetrachloropalladium (sodium tetrachloropalladium decomposes at high temperatures to produce some chlorine gas, which partially reduces Pd to Pd). 0 Make Pd 0 With Pd 2+Coexistence: After palladium atoms are loaded onto the support surface, they can be stabilized on the support through strong interactions, so some palladium will exist in the form of zero-valent palladium. The magnesium salt is magnesium chloride. The temperature of the muffle furnace in step 2) is 400-450℃.

[0014] This invention also provides the application of the heterogeneous catalyst in the selective hydrogenation reaction of nitrile rubber, specifically: nitrile rubber is dissolved in an organic solvent to prepare a rubber solution, the rubber solution is added to a high-pressure reactor, then the heterogeneous catalyst is added, hydrogen gas is introduced, and the hydrogenation reaction is carried out under stirring conditions. The organic solvent is acetone, the concentration of nitrile rubber in the rubber solution is 5 mg / mL-25 mg / mL, the mass ratio of catalyst to nitrile rubber is 0.1-0.6:1, preferably 0.4-0.5:1, and the stirring rate is 500-1000 r / min.

[0015] Furthermore, the hydrogen pressure is 0.1 MPa to 3 MPa, the reaction temperature is 20 to 120 °C, and the reaction time is 0.5 to 12 h.

[0016] Furthermore, the reaction temperature is 60-80℃, and the reaction time is 1.5-3h, preferably 2h.

[0017] Compared with existing technologies, the technical effects achieved by this invention are as follows:

[0018] 1) This invention uses indium trioxide or aluminum trioxide, sodium tetrachloropalladate, and magnesium chloride as raw materials to prepare a palladium-supported heterogeneous catalyst via a one-step calcination method, with the addition of a second metallic magnesium. After high-temperature calcination, the resulting heterogeneous catalyst is uniformly prepared. This preparation method is simple, quick, low-cost, and energy-efficient, and the support is inexpensive.

[0019] 2) In the prior art, conventional heterogeneous catalysts require high reaction temperatures and long reaction times for the selective hydrogenation of nitrile rubber. In contrast, the heterogeneous catalyst of the present invention can carry out rapid hydrogenation reactions under mild conditions, with a hydrogenation selectivity of up to 99.9% and a hydrogenation activity exceeding 99%.

[0020] 3) The active site of the NBR hydrogenation catalyst of this invention is Pd. 0 With Pd 2+ Pd 0 Pd is responsible for activating hydrogen. 2+ Pd is responsible for increasing the hydrogen coverage on the catalyst surface. 0 With Pd 2+ The catalyst synergistically lowers the reaction energy barrier, jointly promoting the selective hydrogenation of NBR. Compared with catalysts commonly used for the hydrogenation reaction of nitrile butadiene rubber, the catalyst of this invention contains Pd... 2+ Higher content of Pd is more conducive to the hydrogenation of double bonds. 2+A content of 40-70% is required for good activity, Pd 2+ If the content is too low, the catalyst activity will be poor. Furthermore, the preparation method of the catalyst of this invention is simple, the supported metal Pd is uniform and has a small particle size, and its most significant feature is the addition of the second metal Mg, which makes Pd... 2+ The valence state is stabilized, the catalyst can be recovered after the reaction and carried out in the next reaction, and it can also have good activity.

[0021] This invention does not limit the preparation method of nitrile butadiene rubber (NBR). NBR can be an alternating copolymer or a random copolymer, wherein the mass content of acrylonitrile is 15%-50%. Attached Figure Description

[0022] Figure 1 The images show the infrared spectra of the NBR before and after hydrogenation.

[0023] Figure 2 This is a TEM image of the catalyst in Example 1.

[0024] Figure 3 The image shows XPS images of the catalyst before and after the reaction in Example 1. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1: PdMg / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd

[0027] 1) Using indium trioxide, sodium tetrachloropalladium, and magnesium chloride as raw materials, sodium tetrachloropalladium and magnesium chloride are mixed according to the mass ratio of Pd to Mg of 1:1, dissolved in deionized water, and prepared into an aqueous solution with a total salt concentration of 0.1 mol / L.

[0028] 2) Based on the feed amount, the Pd loading in the catalyst is 5%. Add the corresponding mass of indium trioxide support to the aqueous solution described in step 1), mix and stir for 1 hour. Then transfer the mixed slurry to a ceramic boat and put it into a muffle furnace at 450°C for rapid heating and boiling. After 30 minutes, take it out and cool it rapidly at room temperature. Then scrape off the solid from the surface of the ceramic boat, stir and wash it in deionized water at room temperature for 1 hour, then filter it and put it in an oven to dry overnight to obtain the PdMg / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd.

[0029] TEM characterization of the catalyst obtained in Example 1 showed that the average particle size of Pd in ​​the catalyst was 2.27 nm.

[0030] Acrylonitrile rubber (NBR) was dissolved in acetone at a concentration of 20 mg / mL to prepare a slurry, which was then added to a high-pressure reactor. Catalyst was added at a mass ratio of 0.5:1 to NBR. Hydrogen gas was then introduced, and the reactor was purged and vented three times with hydrogen (i.e., the air inside the high-pressure reactor was replaced with hydrogen to purge it; the following examples are equivalent). The reactor was then purged with hydrogen to 2 MPa and sealed. The reaction temperature was set to 60°C, and the magnetic stirring speed was 1000 r / min. After 2 hours of reaction, heating and stirring were stopped, and the sample was cooled to room temperature. The sample was then filtered, and a small amount of the filtrate was pipetted onto a potassium bromide slab. The filtrate was then dried using an infrared lamp, forming a rubber film on the potassium bromide slab. The degree of hydrogenation of the product was measured and analyzed using an infrared spectrometer. The calculated double bond selectivity of the nitrile rubber was 99.9%, and the degree of hydrogenation was 99%.

[0031] Infrared spectra of the NBR before and after hydrogenation in Example 1 are shown below. Figure 1 As shown, the initial reaction is NBR, and the reaction after hydrogenation is HNBR. Figure 1 The following conclusion can be drawn: 970cm -1 and 920cm -1 These peaks correspond to 1,4-C=C- and 1,2-C=C-, respectively. The significant disappearance of these two peaks after the reaction indicates that the unsaturated double bonds in the NBR have been hydrogenated. (723 cm⁻¹) -1 Corresponding to -(CH2)n- obtained after hydrogenation of carbon-carbon double bonds, it can be seen from the infrared spectrum that HNBR no longer has double bond peaks, indicating that hydrogenation is complete.

[0032] TEM image of the catalyst used in Example 1 is shown below. Figure 2 It can be seen that the Pd particles are small in size and uniformly dispersed on the catalyst. XPS images of the catalyst used in Example 1 before and after the reaction are shown below. Figure 3 ( Figure 3 The upper and middle sections correspond to the state before the reaction, and the lower section corresponds to the state after the reaction. It can be seen that the oxidation state of Pd does not change much before and after the reaction, and Mg is also in the Mg2+ state. 2+ The presence of this form indicates that the addition of Mg stabilized the valence state of Pd.

[0033] Infrared spectroscopy calculation methods are existing technologies, and can be found in the following literature: Ind. Eng. Chem. Res. 2019, 58, 11821-11830.

[0034] Example 2: PdMg / TiO2 heterogeneous catalyst based on titanium dioxide supported Pd

[0035] Example 2: The catalyst preparation conditions were the same as in Example 1, except that "the indium trioxide support was replaced with an equal mass of titanium dioxide support". All other conditions remained the same, and a PdMg / TiO2 heterogeneous catalyst based on titanium dioxide supported Pd was finally obtained.

[0036] The catalyst of Example 2 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 70.1%.

[0037] Example 3: PdMg / CeO2 heterogeneous catalyst based on cerium dioxide-supported Pd

[0038] The preparation conditions of the catalyst in Example 3 were the same as those in Example 1, except that the indium trioxide support was replaced with an equal mass of cerium dioxide support. All other conditions remained the same, and a PdMg / CeO2 heterogeneous catalyst based on cerium dioxide supported on Pd was finally obtained.

[0039] The catalyst of Example 3 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 65.5%.

[0040] Example 4: PdMg / ZrO2 heterogeneous catalyst based on zirconium dioxide-supported Pd

[0041] Example 4: The catalyst preparation conditions were the same as in Example 1, except that "the indium trioxide support was replaced with an equal mass of zirconium dioxide support". All other conditions remained the same, and a PdMg / ZrO2 heterogeneous catalyst based on zirconium dioxide supported on Pd was finally obtained.

[0042] The catalyst of Example 4 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 61.6%.

[0043] Example 5: PdMg / Al2O3 heterogeneous catalyst based on Pd supported by alumina

[0044] Example 5: The catalyst preparation conditions were the same as in Example 1, except that the indium trioxide support was replaced with an equal mass of aluminum trioxide support. All other conditions remained the same, and a PdMg / Al2O3 heterogeneous catalyst based on zirconium dioxide supported on Pd was finally obtained.

[0045] The catalyst of Example 5 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 96%.

[0046] Comparing the experimental results of Examples 1-5, it can be seen that using aluminum oxide and indium oxide as carriers yields better experimental results.

[0047] Example 6: Pd3Mg1 / In2O3 heterogeneous catalyst based on indium trioxide supported Pd

[0048] Example 6 The preparation conditions of the catalyst were the same as in Example 1, except that in "step 1) when preparing the aqueous solution, the amount of magnesium chloride was reduced so that the mass ratio of Pd to Mg was 3:1". Other conditions remained unchanged, and finally, a Pd3Mg1 / In2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0049] The catalyst of Example 6 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 92%.

[0050] Example 7: Pd2Mg1 / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd

[0051] Example 7 The catalyst preparation conditions were the same as in Example 1, except that in "step 1) when preparing the aqueous solution, the amount of magnesium chloride was reduced so that the mass ratio of Pd to Mg was 2:1". Other conditions remained unchanged, and finally, a Pd2Mg1 / In2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0052] The catalyst of Example 7 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 94%.

[0053] Example 8: Pd1Mg2 / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd

[0054] Example 8 The preparation conditions of the catalyst were the same as in Example 1, except that in "step 1) when preparing the aqueous solution, the amount of magnesium chloride was increased so that the mass ratio of Pd to Mg was 1:2". Other conditions remained unchanged, and finally a Pd1Mg2 / In2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0055] The catalyst of Example 8 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 93%.

[0056] Example 9: Pd1Mg3 / In2O3 heterogeneous catalyst based on indium trioxide supported Pd

[0057] Example 9 The preparation conditions of the catalyst were the same as in Example 1, except that in "step 1) when preparing the aqueous solution, the amount of magnesium chloride was increased so that the mass ratio of Pd to Mg was 1:3". Other conditions remained unchanged, and finally a Pd1Mg3 / In2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0058] The catalyst of Example 9 was used in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 91%.

[0059] Comparing the experimental results of Examples 5-9, it can be seen that the catalyst has the best experimental effect when the mass ratio of palladium to magnesium is 1:1.

[0060] Examples 10-13 Hydrogenation activity of the catalyst prepared in Example 1 at different temperatures

[0061] Examples 10-13 were tested according to the method of Example 1 for selective hydrogenation reaction of nitrile rubber, with the difference being that the reaction temperature was changed to 80℃, 60℃, 40℃ and 25℃ respectively, while the other conditions were the same as in Example 1. The experimental results are shown in Table 1.

[0062] Table 1

[0063]

[0064] As shown in Table 1, the degree of hydrogenation increases with increasing temperature. This is because nitrile rubber dissolves better in acetone at higher temperatures, and the number of activated molecules increases. At a reaction temperature of 60℃, the double bond selectivity of nitrile rubber is 99.9%, and the degree of hydrogenation is 99%.

[0065] Examples 14-17 Hydrogenation activity of the catalyst prepared in Example 1 under different pressures

[0066] Examples 14-17 were conducted according to the method of Example 1 for the selective hydrogenation reaction of nitrile rubber, with the difference being that the hydrogen pressure was changed to 0.1 MPa, 0.2 MPa, 0.5 MPa, 1 MPa and 2 MPa respectively, and the reaction temperature was set to 60℃. The other conditions were the same as in Example 1. The experimental results are shown in Table 2.

[0067] Table 2

[0068]

[0069] As can be seen from Table 2, the hydrogen pressure has virtually no effect on the reaction results. This is because the molecular weight of nitrile rubber is nearly 30,000, while the molecular weight of hydrogen is 2. Therefore, the molar fraction of nitrile rubber compared to hydrogen is very small. Under these circumstances, even if hydrogen is introduced at atmospheric pressure for the reaction, the amount of hydrogen will be far in excess.

[0070] Example 18 Hydrogenation activity of the catalyst prepared in Example 1 under cyclic reuse

[0071] Example 18 tested the selective hydrogenation reaction of nitrile rubber according to the method of Example 1, except that the catalyst after the reaction was recovered before the next hydrogenation reaction. The catalyst recovery step was to separate the catalyst after the reaction from the solution, add an appropriate amount of ethyl acetate and stir at 60°C for 20 hours to remove the nitrile rubber attached to the catalyst, and then filter to recover the catalyst. The catalyst was recycled for a total of 4 times. The reaction temperature, pressure and other conditions were the same as in Example 1. The experimental results are shown in Table 3.

[0072] Table 3

[0073]

[0074] As can be seen from Table 3, PdMg / In2O3 has good stability in the cyclic reuse, and still has a hydrogenation degree of 62% in the fourth reaction.

[0075] Comparative Example 1: Pd / In₂O₃ heterogeneous catalyst based on indium trioxide-supported Pd

[0076] The preparation conditions of the catalyst in Comparative Example 1 were the same as those in Example 1, except that magnesium chloride was not added when preparing the aqueous solution in step 1). All other conditions remained the same, and a Pd / In2O3 heterogeneous catalyst based on indium trioxide supported on Pd was finally obtained.

[0077] Comparative Example 1 catalyst was tested in the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The difference was that the catalyst was recovered after the reaction and then used for the next hydrogenation reaction. The catalyst recovery step was to separate the catalyst after the reaction from the solution, add an appropriate amount of ethyl acetate and stir at 60°C for 20 hours to remove the nitrile rubber attached to the catalyst, and then filter to recover the catalyst. The catalyst was recycled for a total of 4 times. The reaction temperature, pressure and other conditions were the same as in Example 1. The experimental results are shown in Table 4.

[0078] Table 4

[0079]

[0080] As shown in Table 4, Pd / In₂O₃ exhibits a high degree of hydrogenation in the first reaction but poor cycle stability, nearly deactivating in the second reaction. This indicates that the addition of the second metal, Mg, improves the catalyst's cycle stability. The addition of Mg stabilizes the valence state of Pd, allowing the catalyst to maintain its cyclic stability. 2+ The content remains stable, thus resulting in high hydrogenation activity.

[0081] Comparative Example 2: PdMg / In2O3-dry heterogeneous catalyst based on indium trioxide-supported Pd

[0082] The preparation conditions of the catalyst in Comparative Example 2 were the same as those in Example 1, except that the mixed slurry was poured into a ceramic boat instead of being dried in an oven to remove moisture. All other conditions remained the same, and a PdMg / In2O3-dry heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0083] The catalyst of Comparative Example 2 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 70%.

[0084] Comparative Example 2 shows that retaining moisture and directly calcining it in a muffle furnace can rapidly raise the temperature and bring it to a boil at high temperatures, achieving a more uniform catalyst preparation and thus resulting in higher hydrogenation activity.

[0085] Comparative Example 3: PdZn / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd

[0086] The preparation conditions of the catalyst in Comparative Example 3 were the same as those in Example 1, except that in "step 1), magnesium chloride was replaced with zinc chloride, sodium tetrachloropalladium and zinc chloride were mixed according to the mass ratio of Pd to Zn elements of 1:1, dissolved in deionized water, and prepared into an aqueous solution with a total salt concentration of 0.1 mol / L". Other conditions remained unchanged, and finally, a PdZn / Al2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0087] The catalyst of Comparative Example 3 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 50.7%.

[0088] Comparative Example 4: PdZr / In2O3 heterogeneous catalyst based on indium trioxide-supported Pd

[0089] The preparation conditions of the catalyst in Comparative Example 4 were the same as those in Example 1, except that in "step 1), magnesium chloride was replaced with zirconium chloride, sodium tetrachloropalladate and zirconium chloride were mixed according to the mass ratio of Pd to Zr of 1:1, dissolved in deionized water, and prepared into an aqueous solution with a total salt concentration of 0.1 mol / L". Other conditions remained unchanged, and finally, a PdZr / Al2O3 heterogeneous catalyst based on indium trioxide supported on Pd was obtained.

[0090] The catalyst of Comparative Example 4 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 99.9% and the degree of hydrogenation was 60.3%.

[0091] Comparative Examples 3-4 show that magnesium is the most effective second metal. This is because magnesium is among the most reactive metals and can better stabilize the valence state of palladium. Zirconium and zinc, on the other hand, do not play a good role, and their hydrogenation degree is lower than that of the Pd / Al2O3 catalyst without a second metal. This may be because their interaction with the support causes changes in the valence state and loading of palladium, reducing the reactivity.

[0092] The above examples of hydrogenation of nitrile rubber are exemplary. This invention is a novel supported hydrogenation catalyst with high activity and high selectivity, capable of achieving near-100% hydrogenation of nitrile rubber under mild conditions and in a short time. Appropriate modifications to this invention by those skilled in the art, such as changing the hydrogenation matrix (small molecules or polymers containing carbon-carbon double bonds), increasing or decreasing the catalyst dosage, changing the precursor, changing the added second metal, and appropriately altering the reaction pressure, temperature, and solution concentration, are all within the scope of this invention.

[0093] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A heterogeneous catalyst for the selective hydrogenation of nitrile rubber, characterized in that... The catalyst includes a support and a noble metal and magnesium salt supported on the support. The loading of the noble metal in the catalyst is 1-10%, the mass ratio of the noble metal to Mg is 1-3:3-1, the content of the positive valence noble metal in the catalyst accounts for 40-70% of the total noble metal content, the noble metal is Pd, the particle size of the noble metal is 1-20 nm, the catalyst is Pd as the active center and Mg as the second metal to stabilize the valence state of Pd, and the support is cerium dioxide, titanium dioxide, zirconium dioxide, aluminum oxide or indium oxide. The catalyst preparation method includes the following steps: 1) Weigh the precious metal Pd salt and magnesium salt according to the mass ratio, dissolve them in deionized water, and prepare a solution with a total salt concentration of 0.05-0.25 mol / L; 2) Add the carrier to the solution prepared in step 1), mix and stir for 30-60 min, then pour the resulting slurry into a porcelain boat, and then put the porcelain boat into a muffle furnace at 400-500℃ for rapid heating and boiling. After 30-60 min, take it out and cool it rapidly at room temperature to obtain the calcined solid product. 3) Wash the calcined product obtained in step 2) with water and then dry it to obtain the catalyst product; In step 1), the precious metal Pd salt is sodium tetrachloropalladium, and the magnesium salt is magnesium chloride.

2. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... The support is indium trioxide or aluminum trioxide, and the loading of noble metals in the catalyst is 4-5%, with a mass ratio of noble metals to Mg of 1:

1.

3. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... The catalyst contains 60-70% positively valence noble metals, and the particle size of the noble metal particles is 1-5 nm.

4. The application of the heterogeneous catalyst as described in claim 1 in the selective hydrogenation reaction of nitrile rubber.

5. The application as described in claim 4, characterized in that... Nitrile rubber is dissolved in an organic solvent to prepare a rubber solution. The rubber solution is added to a high-pressure reactor, a heterogeneous catalyst is added, hydrogen gas is introduced, and a hydrogenation reaction is carried out under stirring conditions.

6. The application as described in claim 5, characterized in that... The organic solvent is acetone, the concentration of nitrile rubber in the adhesive solution is 5 mg / mL-25 mg / mL, the mass ratio of catalyst to nitrile rubber is 0.1~0.6:1, and the stirring rate is 500-1000 r / min.

7. The application as described in claim 6, characterized in that... The mass ratio of catalyst to nitrile rubber is 0.4~0.5:

1.

8. The application as described in claim 6, characterized in that... The hydrogen pressure is 0.1 MPa to 3 MPa, the reaction temperature is 20 to 120℃, and the reaction time is 0.5 h to 12 h.

9. The application as described in claim 8, characterized in that... The reaction temperature is 60-80℃, and the reaction time is 1.5-3h.

10. The application as described in claim 9, characterized in that... The reaction temperature is 60-80℃, and the reaction time is 2 hours.

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