A heterogeneous catalyst for selective hydrogenation of nitrile rubber and application thereof

Abstract

This application discloses a heterogeneous catalyst for the selective hydrogenation of nitrile rubber and its application. The heterogeneous catalyst, by weight percentage, consists of 1–10% noble metal particles and 90–99% support, wherein the support is alumina, cerium oxide, titanium dioxide, zirconium oxide, or neodymium oxide. The content of positively valence noble metal in the catalyst accounts for 20–80% of the total noble metal element content, and the noble metal is uniformly loaded on the support. The noble metal is Rh, Os, Ir, Pt, Ru, or Pd, and the particle size of the noble metal particles is 1–20 nm. The heterogeneous catalyst of this invention can carry out hydrogenation reactions at room temperature and pressure, and its hydrogenation selectivity is as high as 100%, with a hydrogenation activity >99%.

Description

Technical Field

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

[0002] Hydrogenated nitrile butadiene rubber (HNBR) is produced by selectively hydrogenating the butadiene units in nitrile butadiene rubber (NBR). Compared to nitrile butadiene rubber (NBR), HNBR retains the excellent abrasion resistance and oil resistance of its unhydrogenated form, while exhibiting superior chemical stability, media resistance, heat resistance, weather resistance, compression set resistance, and tear resistance after hydrogenation. These excellent properties make HNBR widely used in various fields, such as the automotive industry, aerospace, and petrochemical industry.

[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. For example, Bhattacharjee et al. used a homogeneous palladium acetate catalyst for the selective hydrogenation of nitrile rubber, achieving a hydrogenation degree of 97% at 50℃ and 4.8 MPa for 3 hours. However, a common problem with homogeneous catalysts is that precious metals tend to remain in the reactants and solvent after the reaction, increasing the cost of catalyst use and potentially affecting 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 Ru, Rh, Pd nanoparticles on carriers such as AC, SiO2, TiO2, PS resin, and various porous mesoporous materials. Although heterogeneous catalysts are increasingly being studied by researchers, there are still some problems that need to be solved, mainly (1) low catalyst activity: there is a serious mass transfer resistance in the hydrogenation process and the utilization rate of active sites is low. (2) the catalyst preparation process is relatively complicated and the preparation time is long. 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 at room temperature and pressure and exhibit high selectivity and hydrogenation activity.

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

[0006] A heterogeneous catalyst for the selective hydrogenation of nitrile rubber comprises, by weight percentage, 1-10% noble metal particles and 90-99% support, wherein the support is alumina, cerium oxide, titanium dioxide, zirconium oxide, or neodymium oxide; the content of positively valence noble metal in the catalyst accounts for 20-80% of the total noble metal element content, and the noble metal is uniformly loaded on the support, wherein the noble metal is Rh, Os, Ir, Pt, Ru, or Pd, and the particle size of the noble metal particles is 1-20 nm.

[0007] Furthermore, the support is alumina; the content of positively valence noble metal in the catalyst accounts for 40-70% of the total noble metal element content, the noble metal is Pd, and the particle size of the noble metal particles is 2-5 nm.

[0008] The heterogeneous catalyst for selective hydrogenation of nitrile rubber is prepared by the following steps:

[0009] 1) Dissolve the precious metal salt in deionized water to prepare an aqueous solution with a concentration of 0.05–0.25 mol / L;

[0010] 2) Add the carrier to the aqueous solution prepared in step 1), mix and stir for 30-60 minutes, then transfer the resulting slurry to a porcelain boat, and then transfer the porcelain boat to a muffle furnace at 350℃-550℃ for rapid heating and boiling. After 30-60 minutes, take it out and rapidly cool it at room temperature for annealing to obtain the calcined product.

[0011] 3) Wash the calcined product obtained in step 2) with water and dry it. Then reduce it in low-temperature hot hydrogen for a period of time to obtain the catalyst product.

[0012] Further, the noble metal salt mentioned in step 1) is a Pd salt, preferably sodium tetrachloropalladium; the carrier in step 2) is aluminum oxide.

[0013] Furthermore, in step 2), the temperature of the muffle furnace is 400-450℃.

[0014] Furthermore, in step 3), the reduction temperature is 55-70℃, preferably 60℃, and the reduction time is 20-40min, preferably 30min.

[0015] The present invention also provides the application of the heterogeneous catalyst in the selective hydrogenation reaction of nitrile rubber. The application method is as follows: nitrile rubber is dissolved in an organic solvent to prepare a rubber solution. The organic solvent is one or more of acetone, cyclohexanone, ethyl acetate, chlorobenzene, and N-methylpyrrolidone. The rubber solution is added to a high-pressure reactor, and then the heterogeneous catalyst is added. Hydrogen gas is introduced to carry out the hydrogenation reaction.

[0016] Furthermore, the concentration of nitrile rubber in the adhesive solution is 5 mg / mL to 25 mg / mL, and the mass ratio of catalyst to nitrile rubber is 0.1 to 0.6:1, preferably 0.4 to 0.5:1.

[0017] Furthermore, the hydrogen pressure is 0.1 MPa to 3 MPa, the reaction temperature is 20℃ to 125℃, and the reaction time is 0.5 h to 12 h.

[0018] Compared with existing technologies, the technical effects achieved by this invention are as follows:

[0019] 1) This invention uses alumina and sodium tetrachloropalladium as raw materials, and generates a heterogeneous catalyst support composed of alumina and Pd through a one-step calcination and annealing process. High-temperature calcination yields a tightly bonded heterogeneous catalyst. The preparation method is simple, quick, energy-efficient, and inexpensive, and the support is readily available and inexpensive.

[0020] 2) In the prior art, when heterogeneous catalysts are used in the selective hydrogenation reaction of nitrile rubber, the catalytic reaction temperature is high and the reaction time is long. In contrast, the heterogeneous catalyst of the present invention can carry out the hydrogenation reaction at room temperature and pressure, and its hydrogenation selectivity is as high as 100%, and its hydrogenation activity is >99%.

[0021] 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, promoting selective hydrogenation of NBR. Compared to catalysts commonly used for the hydrogenation 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 20-80% is required for good activity, Pd 2+ If the content is too low, the catalyst activity will be poor. Moreover, the preparation method of the catalyst of this invention is simple, and the supported metal Pd is uniform and has a small particle size. Therefore, its greatest feature is that the catalyst can achieve selective hydrogenation of nitrile rubber at room temperature and pressure without side reactions.

[0022] 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% to 50%. Attached Figure Description

[0023] Figure 1 The images show the infrared spectra of the NBR before and after hydrogenation.

[0024] Figure 2 The NMR spectra of the NBR before and after hydrogenation are shown.

[0025] Figure 3 This is a TEM image of the catalyst used in Example 17. Detailed Implementation

[0026] 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.

[0027] Example 1: Heterogeneous catalyst based on Pd supported by γ-alumina

[0028] Using γ-alumina and sodium tetrachloropalladium as raw materials, sodium tetrachloropalladium was prepared into a 0.1 mol / L aqueous solution with deionized water. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of γ-alumina according to the Pd loading of 5% in the catalyst and stirred for 30 min. The mixture was then transferred to a ceramic boat and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, it was removed and rapidly cooled to room temperature. The solid on the surface of the ceramic boat was scraped off, and the mixture was washed with deionized water for 1 h. After filtration and drying, it was reduced in hydrogen at 60 °C for 30 min to obtain a heterogeneous catalyst based on Pd supported on γ-alumina.

[0029] XPS characterization of the catalyst obtained in Example 1 showed that the Pd content in the fresh catalyst was... 2+ The content of Pd in ​​the catalyst is close to 70% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 2.26 nm.

[0030] NBR was dissolved in acetone at a concentration of 10 mg / mL to prepare a gel solution, which was then added to a high-pressure reactor. Catalyst was added at a mass ratio of 0.5:1 (catalyst 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 3 MPa and sealed. The reaction temperature was set to 120°C, and the magnetic stirring speed was 800 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 slab. Infrared spectroscopy was then used for analysis. A certain amount of the filtrate was dried in a beaker, deuterated chloroform was added, and the solution was then subjected to 1H NMR spectroscopy. The structure was analyzed by infrared and NMR, and the degree of hydrogenation of the product was determined. The test results showed that the double bond selectivity of nitrile rubber was 100% and the degree of hydrogenation was 96.4%.

[0031] Infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy are existing technologies, and can be found in Ind. Eng. Chem. Res. 2019, 58, 11821-11830.

[0032] Example 2: Heterogeneous catalyst based on titanium dioxide supported Pd

[0033] Using titanium dioxide and sodium tetrachloropalladium as raw materials, sodium tetrachloropalladium was prepared into a 0.1 mol / L aqueous solution with deionized water. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of titanium dioxide according to the Pd loading in the catalyst being 5%, and stirred for 30 min. The mixture was then transferred to a ceramic boat and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, it was removed and rapidly cooled to room temperature. The solid on the surface of the ceramic boat was scraped off, and the mixture was washed with deionized water for 1 h. After filtration and drying, it was reduced in hydrogen at 60 °C for 30 min to obtain a heterogeneous catalyst based on titanium dioxide supported on Pd.

[0034] XPS characterization of the catalyst obtained in Example 2 revealed that the Pd content in the fresh catalyst was... 2+ The content of Pd in ​​the catalyst is close to 70% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 2.33 nm.

[0035] The catalyst of 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 100% and the degree of hydrogenation was 74.7%.

[0036] Example 3: Heterogeneous catalyst based on cerium dioxide supported Pd

[0037] Using cerium dioxide and sodium tetrachloropalladium as raw materials, a 0.1 mol / L aqueous solution of sodium tetrachloropalladium and deionized water was prepared. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of cerium dioxide according to a Pd loading of 5% in the catalyst, and stirred for 30 min. The mixture was then transferred to a ceramic boat and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, it was removed and rapidly cooled to room temperature. The solids on the surface of the ceramic boat were scraped off, washed with deionized water for 1 h, filtered, dried, and reduced in hydrogen at 60 °C for 30 min to obtain a heterogeneous catalyst based on cerium dioxide-supported Pd. XPS characterization showed that the Pd content in the fresh catalyst was... 2+ The content of Pd in ​​the catalyst is close to 70% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 2.08 nm.

[0038] The catalyst of Example 3 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 100% and the degree of hydrogenation was 70.2%.

[0039] Example 4: Heterogeneous catalyst based on zirconium dioxide supported Pd

[0040] Using zirconium dioxide and sodium tetrachloropalladium as raw materials, a 0.1 mol / L aqueous solution of sodium tetrachloropalladium and deionized water was prepared. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of zirconium dioxide according to a Pd loading of 5% in the catalyst, and stirred for 30 min. The mixture was then transferred to a ceramic boat and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, it was removed and rapidly cooled to room temperature. The solids on the surface of the ceramic boat were scraped off, washed with deionized water for 1 h, filtered, dried, and reduced in hydrogen at 60 °C for 30 min to obtain a heterogeneous catalyst based on zirconium dioxide supported on Pd. XPS characterization showed that the Pd content in the fresh catalyst was... 2+ The content of Pd in ​​the catalyst is close to 70% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 2.35 nm.

[0041] 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 100% and the degree of hydrogenation was 62.6%.

[0042] Examples 5-7: Heterogeneous catalysts based on Pd supported by three crystal forms of alumina (κ, θ, β).

[0043] Referring to Example 1, using κ-type alumina, θ-type alumina, β-type alumina, and sodium tetrachloropalladium as raw materials, sodium tetrachloropalladium was prepared into a 0.1 mol / L aqueous solution with deionized water. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of each alumina crystal type (κ-type, θ-type, β-type) according to a Pd loading of 5% in the catalyst, and stirred for 30 min. The mixture was then transferred to ceramic boats and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, the mixture was removed and rapidly cooled to room temperature. The solids on the surface of the ceramic boats were scraped off, washed with deionized water for 1 h, filtered, dried, and reduced in hydrogen at 60 °C for 30 min to obtain a heterogeneous catalyst based on Pd supported on each alumina crystal type. XPS characterization showed that the Pd content in the fresh catalyst was... 2+ The Pd content in these catalysts was close to 70% of the total Pd content. TEM characterization revealed that the average Pd particle sizes in the catalysts were 2.45 nm, 2.38 nm, and 2.19 nm, respectively.

[0044] The catalysts of Examples 5-7 were used to conduct experiments on the selective hydrogenation reaction of nitrile rubber according to the method of Example 1. The experimental results are shown in Table 1.

[0045] Table 1

[0046]

[0047] Comparing the experimental results of Examples 1 and 5-7, it can be seen that the experimental effect is best when γ-alumina is used as the carrier.

[0048] Examples 8-11 Hydrogenation activity of the catalyst prepared in Example 1 at different temperatures

[0049] Examples 8-11 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 120℃, 80℃, 60℃ and 25℃ respectively, while the other conditions were the same as in Example 1. The experimental results are shown in Table 2.

[0050] Table 2

[0051]

[0052] As shown in Table 2, the degree of hydrogenation decreases to some extent with increasing temperature. This is because in high-temperature reactions, the catalyst's valence state is easily reduced by the reactants and hydrogen, causing the catalyst's Pd value to decrease. 2+ The content decreased, while Pd 0 With Pd 2+ The ratio of [specific component] to [specific component] has a significant impact on catalytic activity. Therefore, as the temperature decreases, the catalyst activity actually increases to some extent.

[0053] Examples 12-16: Hydrogenation activity of the catalyst prepared in Example 1 under different pressures

[0054] Examples 12-16 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 25°C. The other conditions were the same as in Example 1. The experimental results are shown in Table 3.

[0055] Table 3

[0056]

[0057] As can be seen from Table 3, 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 hydrogen content 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 hydrogen will be in far excess.

[0058] Example 17 Hydrogenation activity of the catalyst prepared in Example 1 at room temperature and pressure

[0059] Example 17 was tested according to the method of Example 1 for the selective hydrogenation reaction of nitrile rubber, except that atmospheric pressure hydrogen gas was introduced and the reaction temperature was set to 25°C. The other conditions were the same as in Example 1. The experimental results were as follows: the double bond selectivity of nitrile rubber was 100% and the degree of hydrogenation was >99%.

[0060] As can be seen from Example 17, the catalyst can achieve selective hydrogenation of nitrile rubber at room temperature and pressure, and its activity and selectivity are extremely high.

[0061] Figure 1-2 These are the characterization results of the NBR before and after hydrogenation in Example 17. Before the reaction, it was NBR; after hydrogenation, it was HNBR. The following conclusions 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 the -(CH2)n- obtained after hydrogenation of the carbon-carbon double bond, the HNBR spectrum shows no double bond peak, indicating complete hydrogenation. In the 1H NMR spectrum, the peaks at 4.9-5.1 ppm belong to 1,2-C=C-, and the peaks at 5.3-5.6 ppm belong to 1,4-C=C-. Again, the disappearance of the double bond peaks indicates complete hydrogenation.

[0062] TEM image of the catalyst used in Example 17 is shown below. Figure 3 It can be seen that the Pd particles are small in size and uniformly dispersed on the catalyst.

[0063] Comparative Example 1: Preparation of Pd / Al2O3 catalyst for selective hydrogenation of nitrile rubber

[0064] Using γ-alumina and sodium tetrachloropalladate as raw materials, sodium tetrachloropalladate and 600 mg of γ-alumina were added to a beaker according to a Pd loading of 5% in the catalyst. 20 mL of deionized water was added for impregnation, and the mixture was stirred dry at 80 °C. The dried solid was scraped off, ground evenly in a mortar, and then placed in a porcelain boat. The boat was placed in a tube furnace, and calcined and reduced at 300 °C for 2 h under a hydrogen atmosphere at a rate of 5 °C / min. Finally, it was allowed to cool naturally to room temperature, removed, and ground evenly again in a mortar. XPS characterization revealed the Pd content in the fresh catalyst. 2+ The content of Pd in ​​the catalyst is close to 20% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 3.58 nm.

[0065] The catalyst of Comparative Example 1 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 17. The experimental results showed that the degree of hydrogenation of the double bond of nitrile rubber was 12.8%.

[0066] Comparative Example 2: Pd / Al2O3 catalyst prepared by sodium hydroxide precipitation method for selective hydrogenation of nitrile rubber

[0067] Using γ-alumina and sodium tetrachloropalladium as raw materials, sodium tetrachloropalladium and 600 mg of γ-alumina were added to a beaker according to a Pd loading of 5%, followed by 20 mL of deionized water and stirring for 30 min. Then, 0.75 mL of a 20 mg / mL sodium hydroxide solution was added, and the mixture was stirred for another 5 min. After filtration and washing, the mixture was dried overnight at 70 °C in a vacuum drying oven. Finally, it was ground evenly in a mortar to obtain the catalyst. XPS characterization showed that the Pd content in the fresh catalyst was... 2+ The content of Pd in ​​the catalyst is higher than 90% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 3.64 nm.

[0068] The catalyst of Comparative Example 2 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 17. The experimental results were as follows: the double bond selectivity of nitrile rubber was 100% and the degree of hydrogenation was 21%.

[0069] Comparative Example 3: The catalyst prepared in Example 1 was used for the reduction of nitrile rubber by hydrogen.

[0070] Using γ-alumina and sodium tetrachloropalladium as raw materials, a 0.1 mol / L aqueous solution of sodium tetrachloropalladium and deionized water was prepared. The sodium tetrachloropalladium aqueous solution was mixed with 600 mg of γ-alumina according to a Pd loading of 5% in the catalyst and stirred for 30 min. The mixture was then transferred to a ceramic boat and rapidly heated to boiling in a muffle furnace at 450 °C. After 30 min, the mixture was removed and rapidly cooled to room temperature. The solids on the surface of the ceramic boat were scraped off, washed with deionized water for 1 h, filtered, dried, and reduced in hydrogen at 60 °C for 30 min. The catalyst was then reduced in hydrogen at 150 °C for 1 h. The Pd content was determined by XPS. 2+ The content of Pd in ​​the catalyst is 46% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 2.29 nm.

[0071] The catalyst of Comparative Example 3 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 17. The experimental results were as follows: the double bond selectivity of nitrile rubber was 100% and the degree of hydrogenation was 85.3%.

[0072] Comparative Example 4 changed the catalyst preparation method of Example 1 from one-step calcination and annealing to conventional calcination.

[0073] Using γ-alumina and sodium tetrachloropalladate as raw materials, a 0.1 mol / L aqueous solution of sodium tetrachloropalladate and deionized water was prepared. The sodium tetrachloropalladate aqueous solution was mixed with 600 mg of γ-alumina according to a Pd loading of 5% in the catalyst, and stirred for 30 min. The mixture was then transferred to a ceramic boat and placed in a muffle furnace. The temperature was increased to 450℃ at 5℃ / min and maintained for 30 min. After the muffle furnace cooled naturally to room temperature, the solid was removed from the ceramic boat, scraped off the surface, and washed with deionized water for 1 h. The mixture was then filtered and dried to obtain the catalyst. The Pd content was determined by XPS. 2+ The content of Pd in ​​the catalyst is higher than 95% of the total Pd content. TEM characterization shows that the average particle size of Pd in ​​the catalyst is 5.05 nm.

[0074] The catalyst of Comparative Example 4 was used to test the selective hydrogenation reaction of nitrile rubber according to the method of Example 17. The experimental results were as follows: the double bond selectivity of nitrile rubber was 100% and the degree of hydrogenation was 8.3%.

[0075] As can be seen from the comparative examples, catalysts prepared from the same raw materials using the conventional impregnation hydrogen reduction method are difficult to hydrogenate nitrile rubber at room temperature and pressure. Catalysts obtained via sodium hydroxide precipitation are almost entirely Pd. 2+ The catalyst can perform small-scale hydrogenation of nitrile rubber at room temperature and pressure, but its activity is far less than that of the highly active catalyst described in Example 17 of this invention. In Comparative Example 3, compared to Example 1, the catalyst was further reduced by brief reduction with hydrogen to decrease its Pd. 2+ The content and activity of the precursor were significantly lower than those in Example 1. In Comparative Example 4, there was no rapid heating and boiling process, the precursor decomposition was insufficient, Pd dispersion was uneven, and the activity was low.

[0076] 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 within a short time at room temperature and pressure. Appropriate modifications made 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, and appropriately altering the reaction pressure, temperature, and solution concentration, are all within the scope of this invention.

[0077] 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... By weight percentage, it consists of 1-10% noble metal particles and 90-99% carrier, the carrier being alumina; the noble metal is uniformly loaded on the carrier, the noble metal being Pd, and the particle size of the noble metal particles being 1-20 nm. The percentage of positively valence precious metals in the catalyst is 46-70% of the total precious metal elements; The preparation method of the heterogeneous catalyst includes the following steps: 1) Dissolve the precious metal salt in deionized water to prepare an aqueous solution with a concentration of 0.05-0.25 mol / L. The precious metal salt is a Pd salt. 2) Add the carrier to the aqueous solution prepared in step 1), mix and stir for 30-60 min, then transfer the resulting slurry to a porcelain boat, and then transfer the porcelain boat to a muffle furnace at 350℃-550℃ for rapid heating and boiling. After 30-60 min, take it out and cool it rapidly at room temperature to obtain the calcined product. 3) Wash the calcined product obtained in step 2) with water and dry it. Then reduce it in low-temperature hot hydrogen for a period of time. The reduction temperature is 55-70℃ and the reduction time is 20-40min to obtain the catalyst product.

2. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... The particle size of the noble metal particles is 2–5 nm.

3. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... The noble metal salt mentioned in step 1) is sodium tetrachloropalladium.

4. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... In step 2), the temperature of the muffle furnace is 400-450℃.

5. The heterogeneous catalyst for selective hydrogenation of nitrile rubber as described in claim 1, characterized in that... In step 3), the reduction temperature is 60℃ and the reduction time is 30min.

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

7. The application as described in claim 6, characterized in that... Nitrile rubber is dissolved in an organic solvent to prepare a rubber solution. The organic solvent is one or more of acetone, cyclohexanone, ethyl acetate, chlorobenzene, and N-methylpyrrolidone. The rubber solution is added to a high-pressure reactor, a heterogeneous catalyst is added, and hydrogen gas is introduced to carry out a hydrogenation reaction.

8. The application as described in claim 7, characterized in that... The concentration of nitrile rubber in the adhesive solution is 5 mg / mL to 25 mg / mL, and the mass ratio of catalyst to nitrile rubber is 0.1 to 0.6:

1.

9. The application as described in claim 8, characterized in that... The mass ratio of catalyst to nitrile rubber is 0.4~0.5:

1.

10. The application as described in claim 7, characterized in that... The hydrogen pressure is 0.1 MPa to 3 MPa, the reaction temperature is 20℃ to 125℃, and the reaction time is 0.5 h to 12 h.

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