A method for recovering a homogeneous catalyst for hydrogenated nitrile rubber synthesis

Abstract

The present application relates to the field of platinum group metal catalyst recovery technology, and in particular to a recovery method for a homogeneous catalyst for hydrogenated nitrile rubber synthesis. A recovery method for a homogeneous catalyst for hydrogenated nitrile rubber synthesis, which uses a complexing extractant and an alkaline aqueous solution for continuous extraction, separates the catalyst from the hydrogenation reaction liquid through a multi-stage countercurrent extraction process, and a large amount of complexing extractant can coordinate with the platinum group metal ions in the catalyst, causing the original ligand to fall off, achieving ligand exchange, extracting the catalyst into a new phase, and finally obtaining a pure platinum group metal catalyst through distillation and incineration. At the same time, the extraction solvent after simple distillation collection and purification is recycled, which can reduce the overall recovery cost. The recovery method of the present application has the advantages of low cost, high recovery rate, and high efficiency, solves the problem of catalyst recovery, and is a catalyst recovery technology with broad application prospects.

Description

Technical Field

[0001] The present application relates to the technical field of platinum group metal catalyst recovery, and in particular to a method for recovering a homogeneous catalyst used in hydrogenated nitrile rubber synthesis. Background Art

[0002] Hydrogenated nitrile rubber (HNBR) is a highly saturated, high-performance synthetic rubber derived from nitrile rubber (NBR) through catalytic hydrogenation. It inherits the excellent oil resistance of NBR while also exhibiting excellent resistance to heat, differential pressure, acids, alkalis, and ozone. It is widely used in the petrochemical, automotive, and aerospace industries.

[0003] The production process of hydrogenated nitrile butadiene rubber (HBR) mainly includes solution hydrogenation, emulsion hydrogenation and ethylene-acrylonitrile copolymerization. The most widely used industrial process is solution hydrogenation, and the related process is described in detail in Chinese Patent CN 104610471A. This method is to first crush the nitrile butadiene rubber, then dissolve it in a solvent, and then use triphenylphosphine rhodium chloride as a catalyst and hydrogen reaction under high temperature and high pressure to obtain hydrogenated nitrile butadiene rubber. The advantage of the homogeneous solution hydrogenation process is that the catalyst and reactants are all dissolved in the same solvent, and the two molecules are fully in contact, avoiding the diffusion and mass transfer problem, thereby eliminating the need for higher reaction pressure and temperature. However, the biggest drawback of homogeneous catalysts is that they are difficult to recycle or reuse, and the recovery rate is very low, making the preparation cost of hydrogenated nitrile butadiene rubber very high and causing metal contamination, hindering its large-scale development.

[0004] Chinese Patent CN103588911A describes a method for adding triaminosilane to a solution, reacting with rhodium ions in the solution to absorb 75%-85% of the residual rhodium, which is then filtered and recovered. However, silane is unstable in the presence of water and easily reacts with the surface of the reactor. Chinese Patent CN101704926A describes a method for removing precious metal catalysts from hydrogenated copolymer solutions by extracting them with an aqueous solution of stannous chloride (SnCl2). However, the separation of stannous chloride from the precious metals is extremely difficult, and the amount used is very large. Sinopec Corporation has applied for a patent entitled "Functional Magnetic Composite Microspheres, Their Preparation Method and Application, and Method for Removing Precious Metal Catalysts from Hydrogenated Nitrile-Butadiene Rubber Latex," Publication No. CN119140057A. The patent utilizes functional magnetic composite microspheres, their preparation method, and application, to remove precious metal catalysts from hydrogenated nitrile-butadiene rubber latex. However, the magnetic composite microspheres are very expensive and difficult to industrialize, thus requiring a new, efficient, and low-cost technical solution to address the above-mentioned issues. Summary of the Invention

[0005] In view of the problems of difficulty and high cost in catalyst recovery in the prior art, the present application provides a recovery method for a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis, which is used for the preparation process of hydrogenated nitrile butadiene rubber. The present application adopts a complexing extractant and an alkaline aqueous solution for continuous extraction, and separates the catalyst from the hydrogenation reaction liquid through a multi-stage countercurrent extraction process. A large amount of complexing extractant can coordinate with the platinum group metal ions in the catalyst, promote the original ligand to fall off, realize ligand exchange, extract the catalyst to a new phase, and finally obtain a pure platinum group metal catalyst by distillation and incineration. At the same time, the extraction solvent after purification is collected by simple distillation and recycled, which can reduce the overall recovery cost. The recovery method of the present application has the advantages of low cost, high recovery rate and high efficiency, solves the catalyst recovery problem, and is suitable for industrial production.

[0006] In a first aspect, the present application provides a method for recovering a homogeneous catalyst for hydrogenated nitrile rubber synthesis, which adopts the following technical solution:

[0007] A method for recovering a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis comprises the following steps:

[0008] S1, the hydrogenation reaction liquid after the hydrogenation reaction of the nitrile rubber containing a platinum group metal compound homogeneous catalyst is collected in a temporary storage tank, then imported into the heavy phase inlet of the extraction centrifuge, mixed with the complexing extractant and the alkaline aqueous solution entering through the light phase inlet in the extraction centrifuge cavity, and phase transfer of the catalyst occurs at a suitable extraction temperature and centrifugal speed; the hydrogenation reaction liquid after extraction is imported from the heavy phase outlet into the heavy phase inlet of the next stage extraction centrifuge or exported to the reaction liquid temporary storage tank after extraction; meanwhile, the complexing extractant and the alkaline aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then imported from the light phase outlet into the light phase inlet of the next stage extraction centrifuge or exported to the extract temporary storage tank containing the platinum group metal compound homogeneous catalyst;

[0009] S2. After neutralizing the solution in the temporary storage tank of the extract containing the platinum group metal compound homogeneous catalyst, the solution is sent to a distillation tower for atmospheric or reduced pressure distillation. After the water is removed, the purified extraction solvent is collected and used;

[0010] S3. The concentrated liquid containing the complex of the platinum group metal in the distillation tower kettle is distilled and then incinerated to obtain a pure platinum group metal catalyst.

[0011] By adopting the above technical solution, catalyst recovery and separation (step S1): This step mainly involves the reaction of a complexing extractant and an alkaline aqueous solution with the homogeneous catalyst of the platinum group metal compound in the hydrogenation reaction liquid to achieve effective catalyst separation. The complexing extractant forms a stable complex with the platinum group metal ions, promoting the transfer of the catalyst from the reaction liquid to the extractant phase. At the same time, the alkaline aqueous solution helps stabilize the formation of the complex and may participate in further metal ion precipitation or conversion processes. The multi-stage countercurrent extraction process ensures efficient recovery of the platinum group metal catalyst. The continuous extraction process can minimize catalyst loss while improving extraction efficiency and catalyst recovery rate. The alkaline aqueous solution serves to increase the solubility of the platinum group metal compound in the complexing extractant. Catalyst purification (step S2): The extract containing the platinum group metal catalyst is further purified through neutralization and distillation. The neutralization process may involve adjusting the solution pH to promote metal ion precipitation or conversion. The distillation process is used to separate the solvent and water, ensuring purity for subsequent processing. The neutralization and distillation steps work together to ensure the removal of impurities and unreacted substances in the extract while retaining effective platinum group metal catalyst components. In addition, the extraction solvent is recovered by simple distillation, which reduces solvent consumption and processing costs. Final treatment of the catalyst (step S3): The concentrated liquid in the distillation tower kettle is further distilled and incinerated to obtain a pure platinum group metal catalyst. This step ensures the high purity of the catalyst and the quality of the recovered product. The distillation and incineration steps work together to completely remove all non-platinum group metal impurities while ensuring a high recovery rate of platinum group metals. The incineration process ensures that any possible residual organic extractant and impurities are completely removed. Overall, the present application achieves efficient recovery and purification of platinum group metal catalysts through carefully designed extraction, purification and incineration steps. This method not only improves the recovery rate and purity of the catalyst, but also significantly reduces processing costs, and has important industrial application value.

[0012] Preferably, in step S1, the amount of the complexing extractant used is 25-300%, preferably 50-100%, of the volume of the hydrogenation reaction liquid.

[0013] Preferably, in step S1, the complexing extractant is at least one of triethylamine, tripropylamine, triethanolamine and pyridine.

[0014] Preferably, the complexing extractant is triethylamine.

[0015] By adopting the above technical solution, triethylamine plays an important role in the recovery method of the homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis. As a complexing extractant, triethylamine undergoes a coordination reaction with platinum group metal ions, causing the original ligand to fall off, achieving ligand exchange, and thus extracting the catalyst into a new phase. This process helps to improve the recovery rate and purity of the catalyst. On the interaction between triethylamine and alkaline aqueous solution. During the extraction process, triethylamine and alkaline aqueous solution work together to help improve the extraction efficiency. Specifically, triethylamine can better form complexes with platinum group metal ions in an alkaline environment, thereby promoting phase transfer of the catalyst. In general, triethylamine plays an important role in the recovery method of the homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis, not only reducing the recovery cost, but also improving the recovery efficiency and catalyst quality.

[0016] Preferably, in step S1, the alkaline aqueous solution is one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution; the mass concentration of the alkaline aqueous solution can be 5 to 20%, preferably 10 to 15%; the amount of the alkaline aqueous solution used is 0-100% of the volume of the hydrogenation reaction liquid, preferably 10-20%; the function of the alkaline aqueous solution is to increase the solubility of the platinum group metal compound in the complexing extractant.

[0017] By adopting the above technical solution, the role of the alkaline aqueous solution is to increase the solubility of the platinum group metal compound in the complexing extractant. Specifically, the hydroxide ions in the alkaline aqueous solution will react with the platinum group metal ions to form a water-soluble complex. In this way, when the complexing extractant is mixed with the hydrogenation reaction solution, the platinum group metal ions can be more effectively extracted from the reaction solution. In addition, the amount and concentration of the alkaline aqueous solution also need to be properly controlled. If the amount is too much, the reaction solution may become too alkaline, affecting the activity and stability of the catalyst. If the concentration is too high, the complex may become too stable and difficult to separate and recover by methods such as distillation. Therefore, in step S1, it is necessary to select a suitable alkaline aqueous solution according to the specific circumstances, and strictly control its amount and concentration to ensure the recovery effect and purity of the catalyst.

[0018] Preferably, in step S1, the extraction temperature is 20 to 180°C, preferably 80 to 120°C; the centrifugal speed is 1400 to 2800 rpm, preferably 2400 to 2800 rpm.

[0019] Preferably, in step S1, the platinum group metal in the platinum group metal compound is one of ruthenium, rhodium, palladium, osmium, iridium and platinum, preferably ruthenium or palladium.

[0020] Preferably, in step S1, the extraction centrifuge is connected in a multi-stage countercurrent manner to perform continuous extraction, and the number of stages is specifically 3 to 10, preferably 5 to 6.

[0021] By employing the above-mentioned technical solution, multi-stage countercurrent extraction increases contact opportunities between the extractant and the extracted material, thereby improving extraction efficiency. Each stage of extraction transfers some catalyst from the heavy phase to the light phase, gradually reducing the catalyst concentration as the extraction process progresses. Due to the continuous and efficient nature of multi-stage countercurrent extraction, the amount of extractant used can be reduced while maintaining extraction efficiency. This reduces costs and potential environmental impacts. Multi-stage countercurrent extraction enables more efficient separation and recovery of platinum group metal catalysts. Each stage of extraction improves catalyst recovery, ultimately yielding higher-purity platinum group metal catalysts. Multi-stage countercurrent extraction allows for precise control of extraction conditions at each stage, including extractant type, concentration, and pH, thereby optimizing the extraction process and enhancing extraction efficiency. Using a multi-stage countercurrent extraction centrifuge simplifies the process flow, reduces subsequent processing steps and equipment requirements, and thus reduces overall process complexity and cost. Each stage of extraction in a multi-stage countercurrent extraction centrifuge complements and synergizes with each other, ensuring efficient and uniform separation of the catalyst from the reaction solution. This synergistic effect enhances the stability and reliability of the entire extraction process. In summary, the application of the multi-stage countercurrent extraction centrifuge in step S1 not only improves the extraction efficiency and catalyst recovery rate, but also reduces costs and environmental impact, and is an efficient and economical catalyst recovery method.

[0022] Preferably, in step S3, the incineration temperature is 550 to 600° C., and the incineration time is 5 to 7 hours.

[0023] In summary, the beneficial technical effects of this application are:

[0024] 1. Cost-effectiveness: Using low-cost complexing extractants (such as triethylamine, triethanolamine, etc.) for extraction and recovering these extractants through a simple distillation method significantly reduces the overall cost of catalyst recovery.

[0025] 2. Environmentally friendly: The complex formed by the complexing extractant and the platinum group metal ions can be removed by incineration, avoiding pollution to the environment while ensuring a high recovery rate of platinum group metals.

[0026] 3. High efficiency: The continuous countercurrent multi-stage extraction process improves extraction efficiency and catalyst recovery. This process design ensures the effective separation of the catalyst from the hydrogenation reaction liquid.

[0027] 4. Industrial applicability: This recovery method solves the problem of difficult catalyst recovery and is suitable for industrial production processes, helping to improve the overall efficiency and economic benefits of hydrogenated nitrile rubber production.

[0028] 5. Safety: By incinerating the complex, the problem of handling and emission of hazardous substances can be effectively reduced, and the safety of the production process can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings used in the embodiments:

[0030] Figure 1 Schematic diagram of the metal ligand formed in Example 1;

[0031] Figure 2 Schematic diagram of the metal ligand formed in Example 2;

[0032] Figure 3 Schematic diagram of the extraction step of the homogeneous catalyst for hydrogenated nitrile rubber synthesis in Example 1. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0034] Example 1

[0035] A method for recovering a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis comprises the following steps:

[0036] S1, the hydrogenation reaction liquid after the completion of the hydrogenation reaction of the acrylonitrile-butadiene rubber containing 5ppm palladium homogeneous catalyst of 100L is collected in the temporary storage tank, then imported into the heavy phase inlet of the extraction centrifuge, and simultaneously with the 60L triethylamine and 10L mass concentration of the light phase inlet entering are mixed in the extraction centrifuge cavity with 20% sodium hydroxide aqueous solution, and the phase transfer of catalyst occurs under the extraction temperature of 100 ℃ and the centrifugal speed of 2400rpm; The hydrogenation reaction liquid after the extraction is imported into the heavy phase inlet of the next stage extraction centrifuge from the heavy phase outlet; Meanwhile, triethylamine and sodium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then the light phase inlet of the next stage extraction centrifuge is imported from the light phase outlet; The number of extraction stages is 5; Finally, the hydrogenation reaction liquid after the extraction is exported from the heavy phase outlet to the reaction liquid temporary storage tank after the extraction; Meanwhile, triethylamine and sodium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then exported from the light phase outlet to the extract temporary storage tank containing the platinum group metal compound homogeneous catalyst;

[0037] S2. After neutralizing the solution in the temporary storage tank of the extract containing the platinum group metal compound homogeneous catalyst, the solution is sent to a distillation tower for atmospheric distillation. After the water is discharged, the purified extraction solvent is collected and used;

[0038] S3. The concentrated liquid containing the complex of the platinum group metal in the distillation tower kettle is distilled and then incinerated at a temperature of 550° C. for 7 hours to obtain a pure platinum group metal catalyst, which is then sent to the catalyst manufacturer for recycling.

[0039] Example 2

[0040] A method for recovering a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis comprises the following steps:

[0041] S1, the hydrogenation reaction liquid after the hydrogenation reaction of nitrile rubber containing 3ppm rhodium homogeneous catalyst is collected in a temporary storage tank, then imported into the heavy phase inlet of the extraction centrifuge, and simultaneously mixed with 100L pyridine and 10L mass concentration of 15% potassium hydroxide aqueous solution entering the light phase inlet in the extraction centrifuge cavity, and the phase transfer of the catalyst occurs at an extraction temperature of 120°C and a centrifugal speed of 2800rpm; the hydrogenation reaction liquid after extraction is imported into the heavy phase inlet of the next stage extraction centrifuge from the heavy phase outlet; at the same time, pyridine and potassium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then imported into the light phase inlet of the next stage extraction centrifuge from the light phase outlet; the number of extraction stages is 6; finally, the hydrogenation reaction liquid after extraction is exported from the heavy phase outlet to the reaction liquid temporary storage tank after extraction; at the same time, pyridine and potassium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then exported from the light phase outlet to the extract temporary storage tank containing the platinum group metal compound homogeneous catalyst;

[0042] S2. After neutralizing the solution in the temporary storage tank of the extract containing the platinum group metal compound homogeneous catalyst, the solution is sent to a distillation tower for atmospheric distillation. After the water is discharged, the purified extraction solvent is collected and used;

[0043] S3. The concentrated liquid containing the complex of the platinum group metal in the distillation tower kettle is distilled and then incinerated at a temperature of 600° C. for 5 hours to obtain a pure platinum group metal catalyst, which is then sent to the catalyst manufacturer for recycling.

[0044] Example 3

[0045] A method for recovering a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis comprises the following steps:

[0046] S1, the hydrogenation reaction liquid after the completion of the hydrogenation reaction of nitrile rubber containing 100L of 4ppm ruthenium homogeneous catalyst is collected in a temporary storage tank, then imported into the heavy phase inlet of the extraction centrifuge, and simultaneously mixed with 80L tripropylamine and 15L mass concentration of 12% sodium hydroxide aqueous solution entering the light phase inlet in the extraction centrifuge cavity, and the phase transfer of the catalyst occurs when the extraction temperature is 80°C and the centrifugal speed is 2600rpm; the hydrogenation reaction liquid after extraction is imported from the heavy phase outlet into the heavy phase inlet of the next-stage extraction centrifuge; at the same time, the tripropylamine and the sodium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then imported from the light phase outlet into the light phase inlet of the next-stage extraction centrifuge; the number of extraction stages is 5; finally, the hydrogenation reaction liquid after extraction is exported from the heavy phase outlet to the reaction liquid temporary storage tank after extraction; at the same time, the tripropylamine and the sodium hydroxide aqueous solution are imported into the light phase outlet of the extraction centrifuge, and then exported from the light phase outlet to the extract liquid temporary storage tank containing the platinum group metal compound homogeneous catalyst;

[0047] S2. After neutralizing the solution in the temporary storage tank of the extract containing the platinum group metal compound homogeneous catalyst, the solution is sent to a distillation tower for vacuum distillation. After the water is removed, the purified extraction solvent is collected and used again;

[0048] S3. The concentrated liquid containing the complex of the platinum group metal in the distillation tower kettle is distilled and then incinerated at a temperature of 580° C. for 6 hours to obtain a pure platinum group metal catalyst, which is then sent to the catalyst manufacturer for recycling.

[0049] Example 4

[0050] The same as Example 1, except that the amount of triethylamine added was changed from 60 L to 80 L.

[0051] Example 5

[0052] The same as Example 1, except that the amount of triethylamine added was changed from 60 L to 100 L.

[0053] Performance Testing

[0054] The metal content and metal removal rate in the extraction complexing agent phase in Examples 1 to 5 were tested respectively; the metal content in the extraction complexing agent phase in Examples 1, 4 and 5 refers to the content of palladium after palladium is extracted and complexed with triethylamine; the metal content in the extraction complexing agent phase in Example 2 refers to the content of rhodium after rhodium is extracted and complexed with pyridine; the metal content in the extraction complexing agent phase in Example 3 refers to the content of ruthenium after ruthenium is extracted and complexed with tripropylamine; the results are shown in Table 1.

[0055] Table 1 Test results

[0056]

[0057] Analyzing the data in Table 1, we can see that:

[0058] 1) Examples 1-5 describe a method for recovering a homogeneous catalyst for hydrogenated nitrile rubber synthesis. The method employs a complexing extractant and an alkaline aqueous solution for continuous extraction, followed by a multi-stage countercurrent extraction process to separate the catalyst from the hydrogenation reaction solution. A large amount of the complexing extractant coordinates with the platinum group metal ions in the catalyst, causing the original ligands to fall off, achieving ligand exchange, and extracting the catalyst into a new phase. Finally, the catalyst is distilled and then incinerated to obtain a purified platinum group metal catalyst. The metal removal rate is ≥95%.

[0059] 2) The performance comparison analysis of the recovery method of the homogeneous catalyst for hydrogenated nitrile rubber synthesis using Examples 1 and 4-5 shows that increasing the amount of the complexing extractant can effectively improve the removal efficiency of the metal. This method not only has a high catalyst recovery rate, but also recycles the purified extraction solvent by simple distillation, significantly reducing the overall production cost.

[0060] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present application may still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A method for recovering a homogeneous catalyst for hydrogenated nitrile rubber synthesis, characterized in that: The following steps are involved: S1. The hydrogenation reaction liquid after the hydrogenation reaction of nitrile rubber containing a platinum group metal compound homogeneous catalyst is collected into a temporary storage tank, and then introduced into the heavy phase inlet of the extraction centrifuge, mixed with the complexing extractant and alkaline aqueous solution entering from the light phase inlet in the extraction centrifuge cavity, and the catalyst phase transfer occurs at 20-180°C and 1400-2800rpm; 5-6 stage countercurrent extraction centrifuge is used for continuous extraction, and the extracted hydrogenation reaction liquid is introduced from the heavy phase outlet into the heavy phase inlet of the next stage extraction centrifuge or exported to the extraction centrifuge. The reaction liquid is temporarily stored in a tank; at the same time, a complexing extractant and an alkaline aqueous solution are introduced into the light phase outlet of the extraction centrifuge, and then introduced from the light phase outlet into the light phase inlet of the next-stage extraction centrifuge or discharged to an extract liquid temporary storage tank containing a platinum group metal compound homogeneous catalyst; wherein the alkaline aqueous solution is one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution; the mass concentration of the alkaline aqueous solution is 5 to 20%; the amount of the alkaline aqueous solution used is 10-20% of the volume of the hydrogenation reaction liquid; and the complexing extractant is triethylamine; S2. After neutralizing the solution in the temporary storage tank of the extract containing the platinum group metal compound homogeneous catalyst, the solution is sent to a distillation tower for atmospheric or reduced pressure distillation. After the water is removed, the purified extraction solvent is collected and used; S3. The concentrated liquid containing the platinum group metal complex in the distillation tower kettle is distilled and incinerated at 550-600° C. for 5-7 hours to obtain a pure platinum group metal catalyst.

2. A method for recovering a homogeneous catalyst for hydrogenated nitrile rubber synthesis according to claim 1, characterized in that: In step S1, the amount of the complexing extractant used is 25-300% of the volume of the hydrogenation reaction liquid.

3. A method for recovering a homogeneous catalyst for hydrogenated nitrile butadiene rubber synthesis according to claim 1, characterized in that: In step S1, the platinum group metal in the platinum group metal compound is ruthenium or palladium.

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