HTPB hydrogenation modification method based on unsaturation controllable regulation of supported palladium catalyst

Abstract

This invention relates to the field of polymer material modification technology, and discloses a method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst. This method uses a supported palladium catalyst as the catalytically active component, dissolving hydroxyl-terminated polybutadiene (HTPB) in a specific solvent to form a reaction solution. Catalytic hydrogenation is carried out under optimized conditions such as hydrogenation pressure, reaction temperature, and stirring speed. The unsaturation of hydrogenated HTPB is directionally controlled by precisely adjusting the reaction parameters. The supported palladium catalyst used in this invention has significantly higher activity than traditional nickel-based catalysts and offers advantages such as easy separation from the product, no residue, and reusability, significantly reducing the cost of hydrogenation modification. Simultaneously, the hydroxyl retention rate of the hydrogenated product can reach 80%–95%, and the hydrogenation rate can be precisely controlled within the range of 40%–99.5%, effectively solving the technical pain points of low catalyst activity, difficult separation, high cost, and poor controllability of product performance in existing HTPB hydrogenation technologies.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification technology, specifically relating to a method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst. Background Technology

[0002] Hydroxyl-terminated polybutadiene (HTPB) is a liquid rubber with a linear structure. Its molecular chains contain active hydroxyl groups at their ends, allowing it to react with crosslinking agents such as isocyanates and epoxy resins to form a cured product with a three-dimensional network structure. Due to its excellent flexibility, adhesion, low-temperature resistance, and good processability, HTPB has been widely used in adhesives, sealants, coatings, elastomers, and solid propellants, becoming an indispensable and important variety in the field of polymer materials.

[0003] However, HTPB molecules contain numerous carbon-carbon unsaturated double bonds, which result in poor aging resistance, thermal stability, and chemical stability. Under prolonged exposure to light, high temperatures, or chemical media, these unsaturated double bonds are prone to oxidation, cross-linking, or degradation, leading to a significant decline in key properties such as mechanical and adhesive properties. This severely limits the application of HTPB in high-end fields such as aerospace, advanced equipment manufacturing, and long-term corrosion protection. Therefore, modifying HTPB to improve its aging resistance and thermal stability while retaining the reactivity of its terminal hydroxyl groups has become a key technological direction for expanding its application range.

[0004] Hydrogenation modification is one of the effective means to improve the performance of HTPB. By selectively hydrogenating the unsaturated double bonds in the molecular chain, the aging resistance, thermal stability, and chemical stability of HTPB can be significantly improved, while retaining the reactivity of its terminal hydroxyl groups, enabling it to meet the requirements of high-end applications. Currently, the commonly used methods for HTPB hydrogenation modification are mainly divided into two categories: homogeneous catalytic hydrogenation and heterogeneous catalytic hydrogenation.

[0005] In homogeneous catalytic hydrogenation technology, commonly used catalysts are noble metal complexes, such as triphenylphosphine rhodium chloride and palladium dichloride complexes with ligands. These catalysts have the advantages of high catalytic activity and mild reaction conditions, but they also have the following significant drawbacks: First, the catalysts are expensive, leading to high hydrogenation modification costs; second, the catalyst and reaction products form a homogeneous system, making effective separation of the catalyst and product difficult after the reaction, preventing catalyst recovery and reuse, resulting in resource waste and potentially leaving catalyst residues in the product, affecting its performance; third, the separation process requires complex extraction and distillation operations, increasing process complexity and environmental pressure.

[0006] In heterogeneous catalytic hydrogenation technology, nickel-based catalysts, such as Raney nickel and supported nickel catalysts, are traditionally widely used. While these catalysts are relatively inexpensive, they suffer from insufficient catalytic activity, requiring high temperatures (above 150°C) and high pressures (above 8 MPa) to achieve effective hydrogenation reactions. This not only increases equipment investment and energy consumption but may also lead to the degradation of hydroxyl groups at the ends of HTPB molecular chains, reducing the product's reactivity. Furthermore, nickel-based catalysts exhibit poor selectivity, making it difficult to precisely control the product's unsaturation and failing to meet the diverse performance requirements of hydrogenated HTPB for different applications. In addition, some nickel-based catalysts are prone to aggregation after the reaction, increasing separation difficulties, and their poor reusability further limits their industrial application.

[0007] In addition to the problems mentioned above, existing HTPB hydrogenation modification technologies also suffer from poor product performance stability and significant batch-to-batch variations. Due to limitations in catalyst performance and imperfections in the reaction parameter control system, it is difficult to achieve precise control of the hydrogenation rate, resulting in large fluctuations in the unsaturation of the product. This, in turn, affects the consistency of key indicators such as the mechanical properties and thermal stability of the material, failing to meet the stringent requirements for material performance stability in high-end applications.

[0008] Therefore, developing a hydrogenation modification method for HTPB with high catalyst activity, simple separation, low cost, and precise control of product unsaturation has become an urgent need to solve the pain points of existing technologies and promote the high-end development of HTPB materials. Summary of the Invention

[0009] To address the problems of low catalyst activity, difficult separation, high cost, poor controllability of product unsaturation, and insufficient performance stability in existing HTPB hydrogenation modification technologies, this invention provides a method for HTPB hydrogenation modification with controllable unsaturation based on a supported palladium catalyst. By optimizing the catalyst system, reaction process parameters, and post-processing procedures, the method achieves efficient hydrogenation, convenient catalyst recovery and reuse, and precise control of the unsaturation of hydrogenated HTPB, ensuring the retention rate of hydroxyl groups in the product, reducing production costs, and meeting the needs of industrial production and various application scenarios.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst, comprising the following steps:

[0011] (1) Raw material preparation: Dissolve HTPB in a solvent to prepare a reaction solution with an HTPB concentration of 1-20%;

[0012] (2) Catalytic hydrogenation: Add the reaction solution obtained in step (1) to the reactor, and then add the supported palladium catalyst. The amount of the supported palladium catalyst is 0.1-5% of the mass of HTPB. After sealing the reactor, replace the air with N2 three times, control the stirring speed at 700 r / min, raise the temperature to 60-130℃, introduce hydrogen gas to 2-6 MPa, and react for 0.5-8 h.

[0013] (3) Product post-processing: After the reaction is completed, the pressure is released by cooling, the supported palladium catalyst is separated by filtration, and the filtrate is desolventized to obtain hydrogenated HTPB with controllable unsaturation.

[0014] Preferably, the solvent in step (1) is one or more of cyclohexane, chlorobenzene, ethyl acetate, toluene, and xylene, and the mass percentage of each component in the mixed solvent is arbitrary.

[0015] Preferably, the HTPB concentration of the reaction solution in step (1) is 5-15%.

[0016] Preferably, the support for the supported palladium catalyst in step (2) is one or more composite supports selected from activated carbon, titanium dioxide, silicon dioxide, molecular sieve, and silica gel, and the mass ratio of each component in the composite support is 1:0.5 to 3.

[0017] Preferably, the loading of palladium metal in the supported palladium catalyst in step (2) is 0.5-10%.

[0018] Preferably, the reaction temperature of the catalytic hydrogenation in step (2) is 70-100°C, the hydrogenation pressure is 3-5 MPa, and the reaction time is 1-4 h.

[0019] Preferably, the operating conditions for N2 replacement of air in step (2) are: N2 introduction rate of 0.5 to 2 L / min, and replacement time of 5 to 10 min each time.

[0020] Preferably, the solvent removal process in step (3) is carried out by vacuum distillation, with a distillation pressure of -0.06 to -0.1 MPa, a distillation temperature of 60 to 100°C, and a distillation time of 1 to 3 hours.

[0021] Preferably, the supported palladium catalyst obtained by filtration and separation in step (3) is reused after solvothermal washing and drying, and the number of reuses is not less than 5 times, and the catalytic activity retention rate of the catalyst after each reuse is not less than 85% of the initial activity.

[0022] Preferably, the hydroxyl group retention rate of hydrogenated HTPB is 80-95%, and the hydrogenation rate is 40-99.5%.

[0023] The preparation method of the present invention has the following beneficial effects:

[0024] 1. Excellent catalyst performance and good separation and reuse: This invention uses a supported palladium catalyst. Palladium metal, as a highly active hydrogenation catalytic component, exhibits catalytic activity far exceeding that of traditional nickel-based catalysts. It can achieve efficient hydrogenation of HTPB under relatively mild temperature (60–130℃) and pressure (2–6 MPa) conditions, significantly reducing equipment investment and energy consumption compared to the high temperature and high pressure conditions required by traditional nickel-based catalysts. Simultaneously, the catalyst is a solid multiphase system, forming a heterogeneous system with the reaction liquid. After the reaction, the catalyst and product can be separated by simple filtration, resulting in high separation efficiency and no catalyst residue in the product, ensuring product purity and performance. The separated catalyst can be reused after solvothermal washing and drying, with a reuse rate of at least 5 times. High catalytic activity retention significantly reduces the cost of catalyst use.

[0025] 2. Significantly Reduced Hydrogenation Modification Costs: Compared to homogeneous palladium catalysts, the supported palladium catalyst of this invention significantly reduces the amount of palladium metal used by immobilizing the active component on a support, thereby lowering the catalyst preparation cost. Simultaneously, the catalyst can be recycled and reused, avoiding the complex operations and raw material losses associated with the separation process of homogeneous catalysts, reducing process steps and environmental pressure. Furthermore, the reaction solvent can be efficiently recovered through vacuum distillation, with a recovery rate exceeding 90%, achieving recycling and further reducing solvent consumption costs. Overall, the hydrogenation modification cost of the method of this invention is 30%–50% lower than existing technologies, demonstrating excellent economic efficiency.

[0026] 3. Precise and controllable product performance with high stability: This invention, through the construction of a multi-parameter synergistic regulation system, can achieve precise control of the hydrogenation rate of hydrogenated HTPB within the range of 40% to 99.5%. By adjusting the combination of parameters such as HTPB concentration, catalyst dosage, reaction temperature, hydrogenation pressure, and reaction time, hydrogenated HTPB products with different degrees of unsaturation can be prepared in a targeted manner, meeting the differentiated material performance requirements of various application scenarios such as adhesives, sealants, coatings, and solid propellants. Simultaneously, the reaction conditions are mild, effectively avoiding the degradation of hydroxyl groups, and the hydroxyl retention rate of the product can reach 80% to 95%, preserving the reactivity of HTPB and ensuring its normal reaction with crosslinking agents to form a three-dimensional network structure. Furthermore, the method of this invention exhibits strong process stability, with batch-to-batch fluctuations in hydrogenation rate not exceeding ±2% and hydroxyl retention rate fluctuations not exceeding ±1.5%, demonstrating good product performance consistency and meeting the stringent requirements for material performance stability in high-end application fields.

[0027] 4. Simple and environmentally friendly process with broad industrialization prospects: The HTPB hydrogenation modification method of this invention includes only three core steps: raw material preparation, catalytic hydrogenation, and product post-processing. The process flow is simple, easy to operate, and readily automated. No toxic or harmful gases are generated during the reaction, the solvent can be recycled, there is no catalyst residue, and pollutant emissions are low, aligning with the development concept of green chemistry. Furthermore, this method has relatively low equipment requirements; existing high-pressure reactors and other chemical equipment can be easily modified to meet production needs, resulting in low investment costs and suitability for large-scale industrial production. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the description and claims of this application are intended to cover non-exclusive inclusion.

[0030] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] Furthermore, the terms "first," "second," etc., in the specification and claims of this application are used to distinguish different objects, rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0032] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, "connection" or "joining" in mechanical structures can refer to a physical connection, such as a fixed connection, for example, a connection fixed by fasteners, such as a connection fixed by screws, bolts, or other fasteners; a physical connection can also be a detachable connection, such as a snap-fit ​​or interlocking connection; a physical connection can also be an integral connection, such as a connection formed by welding, bonding, or integral molding. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0034] (1) Raw material preparation

[0035] Dissolve HTPB in a solvent, stir well, and prepare a reaction solution with an HTPB concentration of 1-20%.

[0036] The solvent is selected from one or more of cyclohexane, chlorobenzene, ethyl acetate, toluene, and xylene, and the mass ratio of each component in the mixed solvent can be flexibly adjusted according to actual needs. This type of solvent has the following advantages: First, it has good solubility for HTPB, ensuring complete dissolution of HTPB and forming a homogeneous reaction solution; second, it is chemically stable under the reaction conditions specified in this invention, and does not react chemically with HTPB, hydrogen, or the hydrogenated HTPB product, thus avoiding the introduction of impurities; third, it has a moderate boiling point, allowing for convenient separation from the product via vacuum distillation, and the solvent has a high recovery rate and can be reused.

[0037] The choice of HTPB concentration has a significant impact on reaction efficiency and product quality. If the concentration is too low, the number of HTPB molecules in the reaction system is small, resulting in low reaction efficiency and high solvent consumption, increasing the energy consumption and cost of subsequent solvent removal. If the concentration is too high, the viscosity of the reaction solution increases significantly, leading to reduced hydrogen solubility, poor mass transfer, and affecting the uniformity of the hydrogenation reaction, potentially causing uneven hydrogenation distribution of the product. Therefore, an HTPB concentration of 5–15% is preferred. This concentration range ensures both high reaction efficiency and good fluidity and mass transfer in the reaction system, achieving uniform hydrogenation.

[0038] (2) Catalytic hydrogenation

[0039] Add the reaction solution obtained in step (1) to the high-pressure reactor, and then add the supported palladium catalyst. The amount of the supported palladium catalyst is 0.1 to 5% of the mass of HTPB.

[0040] Supported palladium catalysts consist of a support and a palladium metal active component. The support is one or more composite supports selected from activated carbon, titanium dioxide, silica, molecular sieves, and silica gel, with a mass ratio of 1:0.5 to 3 for each component in the composite support. The selection of the support and the design of the composite ratio are mainly based on the following considerations: First, the support has a large specific surface area and a suitable pore structure, which can provide sufficient loading sites for palladium metal and improve the dispersion of palladium metal. Second, there is a strong interaction between the support and palladium metal, which can enhance the stability of the catalyst, inhibit the agglomeration of palladium metal particles during the reaction, and extend the catalyst's lifespan. Third, the composite support can combine the advantages of each individual support, such as the high specific surface area of ​​activated carbon, the electron transfer performance of titanium dioxide, and the mechanical stability of silica gel, further improving the catalytic activity and selectivity of the catalyst.

[0041] The loading of palladium metal in catalysts ranges from 0.5% to 10%. Too low a loading results in insufficient active sites, hindering efficient hydrogenation; too high a loading not only increases catalyst cost but may also lead to palladium particle agglomeration, reducing catalytic efficiency. Optimizing the loading allows for minimizing palladium metal usage while maintaining catalytic activity, thus controlling costs.

[0042] After sealing the reactor, nitrogen gas is introduced for air purging, and this process is repeated three times. The operating conditions for nitrogen purging are: N2 introduction rate of 0.5–2 L / min, and each purging time of 5–10 min. Nitrogen purging completely removes air from the reactor, preventing the formation of an explosive mixture of oxygen and hydrogen, thus ensuring reaction safety. Simultaneously, it prevents oxygen from inhibiting catalyst activity, ensuring efficient catalytic reaction.

[0043] After the displacement is completed, start the stirring device and control the stirring speed at 700 r / min. This speed ensures that the reaction system is fully mixed, promotes the dissolution and mass transfer of hydrogen in the reaction liquid, and avoids uneven local reaction. Then, raise the temperature to 60-130℃, introduce hydrogen gas to 2-6 MPa, and maintain this condition for 0.5-8 h.

[0044] Reaction temperature, hydrogenation pressure, and reaction time are key parameters affecting the effectiveness of hydrogenation reactions.

[0045] Reaction temperature: Increasing the temperature can activate the active sites of the catalyst and accelerate the hydrogenation reaction rate. However, excessively high temperatures (above 130°C) will cause the hydroxyl groups at the ends of the HTPB molecular chains to degrade, reducing the hydroxyl retention rate of the product. Conversely, excessively low temperatures (below 60°C) will result in insufficient catalyst activity, a slow reaction rate, and difficulty in achieving the expected hydrogenation rate. Therefore, the preferred reaction temperature is 70–100°C, which ensures both high catalyst activity and effective protection against hydroxyl degradation.

[0046] Hydrogenation pressure: Higher pressure increases the solubility of hydrogen in the reaction solution, strengthens the driving force of the hydrogenation reaction, and leads to a higher double bond conversion rate. However, excessively high pressure increases equipment investment and operational difficulty, and may cause side reactions. Insufficient pressure results in insufficient hydrogen solubility, a slow reaction rate, and difficulty in improving the hydrogenation rate. Therefore, a hydrogenation pressure of 3–5 MPa is preferred, ensuring reaction efficiency while reducing equipment costs and operational risks.

[0047] Reaction time: As the reaction time is extended, the hydrogenation rate gradually increases, but after a certain time, the hydrogenation rate tends to stabilize. Further extending the time will increase energy consumption and production costs. If the reaction time is too short, the hydrogenation of the double bond will be insufficient, resulting in a low hydrogenation rate. Therefore, the preferred reaction time is 1 to 4 hours, which can be flexibly adjusted according to the target hydrogenation rate.

[0048] By adjusting a combination of parameters such as HTPB concentration, catalyst dosage, reaction temperature, hydrogenation pressure, and reaction time, the hydrogenation rate of hydrogenated HTPB can be precisely controlled within the range of 40% to 99.5%, meeting the differentiated requirements of product unsaturation for different application scenarios.

[0049] (3) Post-processing of products

[0050] After the reaction is complete, turn off the heating device, cool the reactor to room temperature, and then slowly depressurize to avoid product splashing or system fluctuations caused by a sudden pressure drop.

[0051] Supported palladium catalysts are separated by filtration, which can be performed under normal pressure, reduced pressure, or pressurized conditions, making the process simple and efficient. The separated catalyst can be reused after solvothermal washing and drying. Solvothermal washing uses the same solvent as the reaction solvent at 40–60°C for 10–30 minutes to remove adsorbed products and impurities from the catalyst surface. Drying is performed at 80–120°C for 2–4 hours to remove solvent and moisture. The treated catalyst can be reused at least five times, with each reuse retaining at least 85% of its initial catalytic activity, significantly reducing the cost of catalyst use.

[0052] The filtrate obtained from filtration is subjected to solvent removal treatment using vacuum distillation at a pressure of -0.06 to -0.1 MPa, a temperature of 60 to 100°C, and a distillation time of 1 to 3 hours. Vacuum distillation lowers the boiling point of the solvent, achieving solvent-product separation at a lower temperature and avoiding hydroxyl degradation or molecular chain cross-linking of the product caused by high temperatures. Simultaneously, under these conditions, the solvent recovery rate can reach over 90%. The recovered solvent can be purified by distillation and reused in the raw material preparation step, achieving solvent recycling, reducing production costs, and mitigating environmental impact.

[0053] After solvent removal, hydrogenated HTPB products with controllable unsaturation are obtained, with hydroxyl group retention of 80%–95% and hydrogenation rate of 40%–99.5%. The products have high purity and stable performance.

[0054] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0055] Example 1

[0056] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0057] (1) Raw material preparation: Dissolve 10g HTPB in 200g toluene and stir at 25℃ for 30min until HTPB is completely dissolved to prepare a reaction solution with HTPB concentration of 5%;

[0058] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.2 g of supported palladium catalyst (3% Pd / C, i.e., palladium metal loading is 3%, and the support is activated carbon). After sealing the reactor, purge with nitrogen gas at a rate of 1 L / min three times, each time for 8 min. After the purging is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 90 °C, purge with hydrogen gas to 5 MPa, and maintain this condition for 4 h.

[0059] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by vacuum filtration. The obtained catalyst was washed with toluene at 50°C for 20 min, and then dried at 100°C for 3 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.09 MPa, the distillation temperature was 90°C, and the distillation time was 2 h to remove the solvent toluene and obtain the hydrogenated HTPB product.

[0060] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 99.3%, the hydroxyl group retention rate was 84.3%, and the product purity was 99.5%.

[0061] Example 2

[0062] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0063] (1) Raw material preparation: Dissolve 10g HTPB in 100g cyclohexane and stir at 30℃ for 25min until HTPB is completely dissolved to prepare a reaction solution with HTPB concentration of 10%.

[0064] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.3 g of supported palladium catalyst (5% Pd-TiO2 / macroporous silica gel, i.e., palladium metal loading is 5%, the support is a composite support of titanium dioxide and macroporous silica gel, and the mass ratio of the two is 1:1). After sealing the reactor, purge with nitrogen gas at a rate of 1.5 L / min three times, each purge time is 6 min. After the purge is completed, start the stirring device, control the stirring speed to 700 r / min, raise the temperature to 100 °C, purge with hydrogen gas to 5 MPa, and maintain this condition for 4 h.

[0065] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by pressure filtration. The obtained catalyst was washed with cyclohexane at 45°C for 25 min, and then dried at 110°C for 2.5 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.09 MPa, the distillation temperature was 80°C, and the distillation time was 1.5 h to remove the solvent cyclohexane, thus obtaining the hydrogenated HTPB product.

[0066] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 95.2%, the hydroxyl group retention rate was 82.3%, and the product purity was 99.2%.

[0067] Example 3

[0068] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0069] (1) Raw material preparation: Dissolve 10g HTPB in 100g ethyl acetate and stir at 28℃ for 35min until HTPB is completely dissolved to prepare a reaction solution with HTPB concentration of 10%;

[0070] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.3 g of supported palladium catalyst (3% Pd-TiO2 / macroporous silica gel, i.e., palladium metal loading is 3%, the support is a composite support of titanium dioxide and macroporous silica gel, and the mass ratio of the two is 1:2). After sealing the reactor, purge with nitrogen gas at a rate of 0.8 L / min three times, each purge lasting 10 min. After the purge is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 90 °C, purge with hydrogen gas to 5 MPa, and maintain this condition for 4 h.

[0071] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by atmospheric pressure filtration. The obtained catalyst was washed with ethyl acetate at 55°C for 15 min, and then dried at 90°C for 3.5 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.09 MPa, the distillation temperature was 90°C, and the distillation time was 2.5 h to remove the solvent ethyl acetate and obtain the hydrogenated HTPB product.

[0072] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 83.7%, the hydroxyl group retention rate was 85.1%, and the product purity was 99.4%.

[0073] Example 4

[0074] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0075] (1) Raw material preparation: Dissolve 10g HTPB in 200g toluene and stir at 22℃ for 40min until HTPB is completely dissolved to prepare a reaction solution with a HTPB concentration of 5%;

[0076] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.2 g of supported palladium catalyst (3% Pd-TiO2 / macroporous silica gel, i.e., palladium metal loading is 3%, the support is a composite support of titanium dioxide and macroporous silica gel, and the mass ratio of the two is 1:1.5). After sealing the reactor, purge with nitrogen gas at a rate of 1.2 L / min three times, each time for 7 min. After the purging is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 70 °C, purge with hydrogen gas to 5 MPa, and maintain this condition for 2 h.

[0077] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by vacuum filtration. The obtained catalyst was washed with toluene at 40°C for 30 min, and then dried at 120°C for 2 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.09 MPa, the distillation temperature was 80°C, and the distillation time was 1 h to remove the solvent toluene and obtain the hydrogenated HTPB product.

[0078] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 61.3%, the hydroxyl group retention rate was 93.5%, and the product purity was 99.6%.

[0079] Example 5

[0080] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0081] (1) Raw material preparation: Dissolve 50g HTPB in 250g toluene and stir at 32℃ for 30min until HTPB is completely dissolved to prepare a reaction solution with HTPB concentration of 20%;

[0082] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 1.0 g of supported palladium catalyst (3% Pd-TiO2 / macroporous silica gel, i.e., palladium metal loading is 3%, the support is a composite support of titanium dioxide and macroporous silica gel, and the mass ratio of the two is 1:1). After sealing the reactor, purge with nitrogen gas at a rate of 1.8 L / min three times, each purge lasting 5 min. After the purge is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 70 °C, purge with hydrogen gas to 5 MPa, and maintain this condition for 1 h.

[0083] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by pressure filtration. The obtained catalyst was washed with toluene at 60°C for 10 min, and then dried at 80°C for 4 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.09 MPa, the distillation temperature was 80°C, and the distillation time was 3 h to remove the solvent toluene and obtain the hydrogenated HTPB product.

[0084] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 41.2%, the hydroxyl group retention rate was 95.1%, and the product purity was 99.3%.

[0085] Example 6

[0086] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0087] (1) Raw material preparation: Dissolve 15g HTPB in a mixed solvent of 100g toluene and xylene (mass ratio of the two is 1:1), stir at 26℃ for 35min until HTPB is completely dissolved, and prepare a reaction solution with HTPB concentration of 13%.

[0088] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.45 g of supported palladium catalyst (8% Pd-silica / molecular sieve, i.e., palladium metal loading is 8%, the support is a composite support of silica and molecular sieve, and the mass ratio of the two is 1:3). After sealing the reactor, purge with nitrogen gas at a rate of 2.0 L / min three times, each purge lasting 6 min. After the purge is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 110 °C, purge with hydrogen gas to 4 MPa, and maintain this condition for 3 h.

[0089] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by vacuum filtration. The obtained catalyst was washed with the above mixed solvent at 50°C for 20 min, and then dried at 105°C for 3 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.08 MPa, the distillation temperature was 95°C, and the distillation time was 2 h to remove the mixed solvent and obtain the hydrogenated HTPB product.

[0090] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 92.5%, the hydroxyl group retention rate was 88.7%, and the product purity was 99.4%.

[0091] Example 7

[0092] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0093] (1) Raw material preparation: Dissolve 8g HTPB in 100g chlorobenzene and stir at 24℃ for 40min until HTPB is completely dissolved to prepare a reaction solution with an HTPB concentration of 7.4%;

[0094] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.16 g of supported palladium catalyst (2% Pd-activated carbon / silica gel, i.e., the palladium metal loading is 2%, and the support is a composite support of activated carbon and silica gel, with a mass ratio of 1:0.5). After sealing the reactor, purge with nitrogen gas at a rate of 0.5 L / min three times, with each purging time being 10 min. After the purging is completed, start the stirring device, control the stirring speed to 700 r / min, raise the temperature to 65 °C, purge with hydrogen gas to 3 MPa, and maintain this condition for 5 h.

[0095] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by atmospheric pressure filtration. The obtained catalyst was washed with chlorobenzene at 45°C for 25 min, and then dried at 95°C for 3 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.07 MPa, the distillation temperature was 75°C, and the distillation time was 2.5 h to remove the solvent chlorobenzene and obtain the hydrogenated HTPB product.

[0096] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 72.8%, the hydroxyl group retention rate was 91.2%, and the product purity was 99.5%.

[0097] Example 8

[0098] A method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst includes the following steps:

[0099] (1) Raw material preparation: Dissolve 20g HTPB in a mixed solvent of 180g ethyl acetate and cyclohexane (mass ratio of the two is 2:1), stir at 29℃ for 30min until HTPB is completely dissolved, and prepare a reaction solution with HTPB concentration of 10%.

[0100] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.6 g of supported palladium catalyst (6% Pd-titanium dioxide / silica, i.e., palladium metal loading is 6%, the support is a composite support of titanium dioxide and silica, and the mass ratio of the two is 1:2). After sealing the reactor, purge with nitrogen gas at a rate of 1.4 L / min three times, each purge lasting 8 min. After the purge is completed, start the stirring device, control the stirring speed at 700 r / min, raise the temperature to 120 °C, purge with hydrogen gas to 6 MPa, and maintain this condition for 6 h.

[0101] (3) Product post-processing: After the reaction was completed, the heating device was turned off, the reactor was cooled to room temperature, and the pressure was slowly released to atmospheric pressure. The supported palladium catalyst was separated by pressure filtration. The obtained catalyst was washed with the above mixed solvent at 55°C for 18 min, and then dried at 115°C for 2.5 h for later use. The filtrate was subjected to vacuum distillation to remove the solvent. The distillation pressure was -0.1 MPa, the distillation temperature was 98°C, and the distillation time was 1.8 h to remove the mixed solvent and obtain the hydrogenated HTPB product.

[0102] Analysis showed that the hydrogenation rate of the obtained hydrogenated HTPB was 98.7%, the hydroxyl group retention rate was 83.5%, and the product purity was 99.2%.

[0103] Example 9

[0104] The catalyst reuse experiment was conducted using the supported palladium catalyst (5% Pd-TiO2 / macroporous silica gel) separated and treated in Example 2. The reuse experiment was carried out under the process conditions of Example 2. After each reuse, the hydrogenation rate and hydroxyl retention rate of the product were measured. The results are shown in Table 1. 1 95.2 82.3 100 2 94.8 82.1 99.6 3 94.5 81.8 99.3 4 93.9 81.5 98.6 5 93.2 81.2 97.9 6 92.5 80.8 97.2 Table 1

[0105] As shown in Table 1, after six reuses, the hydrogenation rate of the supported palladium catalyst can still reach 92.5%, the catalytic activity retention rate is 97.2%, and the hydroxyl group retention rate is 80.8%, indicating that the catalyst has good reusability and can effectively reduce production costs.

[0106] Example 10

[0107] For process stability testing, five parallel batches were conducted according to the process conditions of Example 3. The hydrogenation rate and hydroxyl retention rate of each batch of product were measured, and the results are shown in Table 2. 1 83.7 85.1 - - 2 84.2 85.8 +0.5 +0.7 3 83.5 84.9 -0.2 -0.2 4 84.5 85.5 +0.8 +0.4 5 83.9 85.3 +0.2 +0.2 Table 2

[0108] As shown in Table 2, in the five batches of parallel experiments, the maximum fluctuation of the product hydrogenation rate was ±0.8%, and the maximum fluctuation of the hydroxyl retention rate was ±0.7%, indicating that the method of the present invention has good process stability and can ensure the consistency of product performance.

[0109] Comparative experiment

[0110] Comparative Example 1

[0111] The hydrogenation modification of HTPB using Raney nickel catalyst is carried out in the following steps:

[0112] (1) Raw material preparation: Dissolve 10g of HTPB in 100g of cyclohexane to prepare a reaction solution with an HTPB concentration of 10%;

[0113] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 1.0 g of Raney nickel catalyst. After sealing the reactor, purge with nitrogen three times, stir at 700 r / min, heat to 160 °C, introduce hydrogen to 9 MPa, and react for 8 h;

[0114] (3) Product post-processing: Cool and depressurize, filter to separate the catalyst, and desolvent the filtrate by vacuum distillation to obtain hydrogenated HTPB.

[0115] Testing revealed that the product hydrogenation rate was 78.5%, the hydroxyl group retention rate was 65.3%, and the catalyst exhibited severe agglomeration after separation, making it unusable.

[0116] Comparative Example 2

[0117] The hydrogenation modification of HTPB using a homogeneous catalyst of triphenylphosphine rhodium chloride is carried out in the following steps:

[0118] (1) Raw material preparation: Dissolve 10g of HTPB in 100g of toluene to prepare a reaction solution with an HTPB concentration of 10%;

[0119] (2) Catalytic hydrogenation: Add the above reaction solution to a 500 mL high-pressure reactor, and then add 0.5 g of triphenylphosphine rhodium chloride catalyst. After sealing the reactor, purge with nitrogen three times, stir at 700 r / min, heat to 90 °C, introduce hydrogen to 5 MPa, and react for 4 h;

[0120] (3) Product post-processing: Cool and depressurize, and separate the catalyst and product by distillation to obtain hydrogenated HTPB.

[0121] The product hydrogenation rate was 92.3%, the hydroxyl group retention rate was 81.5%, the catalyst separation and recovery rate was only 35%, and the hydrogenation modification cost was 3.2 times that of Example 2 of this invention.

[0122] Comparative analysis

[0123] Compared with Comparative Example 1, Example 2 of the present invention uses a supported palladium catalyst, which reduces the reaction temperature by 60°C, the reaction pressure by 4 MPa, and the reaction time by 4 h. The product hydrogenation rate is increased by 16.7 percentage points, the hydroxyl retention rate is increased by 17 percentage points, and the catalyst can be reused, which is significantly better than traditional nickel-based catalysts.

[0124] Compared with Comparative Example 2, the hydrogenation rate and hydroxyl retention rate of the product in Example 2 of the present invention are comparable, but the catalyst is easier to separate, has a higher recovery rate, and the cost of hydrogenation modification is significantly reduced, which has obvious economic advantages.

[0125] The hydrogenation modification method for HTPB with controllable unsaturation based on supported palladium catalysts provided by this invention solves the core problems of low catalyst activity, difficult separation, high cost, and poor controllability of product performance in existing technologies, and has the following advantages in industrial applications:

[0126] The product has wide applicability: By precisely controlling the hydrogenation rate, hydrogenated HTPB products with different degrees of unsaturation can be prepared to meet the application needs of multiple fields such as adhesives, sealants, coatings, elastomer materials, and solid propellants. For example, low hydrogenation rate (40%–60%) products can be used in general adhesives and sealants, medium hydrogenation rate (60%–80%) products can be used in anti-corrosion coatings and elastomer materials, and high hydrogenation rate (80%–99.5%) products can be used in solid propellants and high-end equipment sealing materials in the aerospace field.

[0127] Low production cost: The catalyst can be reused more than 5 times, the solvent recovery rate is over 90%, and the overall cost is reduced by 30% to 50% compared with the existing technology, which can significantly improve the market competitiveness of the product.

[0128] The process is environmentally friendly and safe: no toxic or harmful pollutants are generated during the reaction process, the solvent is recycled, which meets the requirements of green chemical development; the reaction conditions are mild and the operation is safe, reducing the safety risks of industrial production.

[0129] Low equipment requirements: Existing high-pressure reactors and other chemical equipment can be easily modified to meet production needs, without the need for large-scale new equipment investment, making it easy to promote industrialization.

[0130] In summary, the method of this invention has significant technical and economic advantages, broad prospects for industrial application, and can promote the high-end development of HTPB materials, providing high-performance modified materials support for related industries.

[0131] The HTPB described in this invention is a commercially available conventional product with a number-average molecular weight of 1000-5000 and a hydroxyl value of 0.8-1.2 mmol / g. Its specific source does not affect the implementation effect of this invention.

[0132] The supported palladium catalyst described in this invention can be prepared by impregnation, precipitation or ion exchange. The specific preparation method does not affect the implementation effect of this invention, as long as the limiting conditions such as the type of support and the amount of palladium metal loaded are met.

[0133] In this invention, the hydrogenation rate of the product was determined by ¹H-NMR spectroscopy, the hydroxyl retention rate was calculated by measuring the hydroxyl value of the product and comparing it with the hydroxyl value of the raw material HTPB, and the purity of the product was determined by gel permeation chromatography (GPC).

[0134] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0135] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for the controlled hydrogenation modification of HTPB based on the regulation of the unsaturation degree by means of supported palladium catalysts, characterized in that, Includes the following steps: (1) Raw material preparation: Dissolve HTPB in a solvent to prepare a reaction solution with an HTPB concentration of 1-20%; (2) Catalytic hydrogenation: Add the reaction solution obtained in step (1) to the reactor, and then add the supported palladium catalyst. The amount of the supported palladium catalyst is 0.1-5% of the mass of HTPB. After sealing the reactor, replace the air with N2 three times, control the stirring speed at 700 r / min, raise the temperature to 60-130℃, introduce hydrogen gas to 2-6 MPa, and react for 0.5-8 h. (3) Product post-processing: After the reaction is completed, the pressure is released by cooling, the supported palladium catalyst is separated by filtration, and the filtrate is desolventized to obtain hydrogenated HTPB with controllable unsaturation.

2. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The solvent in step (1) is one or more of cyclohexane, chlorobenzene, ethyl acetate, toluene, and xylene, and the mass ratio of each component in the mixed solvent is arbitrary.

3. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The HTPB concentration of the reaction solution in step (1) is 5-15%.

4. The method for hydrogenation modification of HTPB with controllable unsaturation based on supported palladium catalyst according to claim 1, characterized in that: The supported palladium catalyst in step (2) is supported by one or more composite supports selected from activated carbon, titanium dioxide, silicon dioxide, molecular sieve, and silica gel, and the mass ratio of each component in the composite support is 1:0.5 to 3.

5. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The loading of palladium metal in the supported palladium catalyst in step (2) is 0.5-10%.

6. The method for hydrogenation modification of HTPB with controllable unsaturation based on supported palladium catalyst according to claim 1, characterized in that: The reaction temperature for catalytic hydrogenation in step (2) is 70–100°C, the hydrogenation pressure is 3–5 MPa, and the reaction time is 1–4 h.

7. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The operating conditions for N2 air replacement in step (2) are: N2 introduction rate of 0.5-2 L / min, and replacement time of 5-10 min each time.

8. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The solvent removal process in step (3) is carried out by vacuum distillation, with a distillation pressure of -0.06 to -0.1 MPa, a distillation temperature of 60 to 100°C, and a distillation time of 1 to 3 hours.

9. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The supported palladium catalyst obtained by filtration and separation in step (3) is repeatedly reused after solvothermal washing and drying. The number of reuses is not less than 5 times, and the catalytic activity retention rate of the catalyst is not less than 85% of the initial activity after each reuse.

10. The method for hydrogenation modification of HTPB with controllable unsaturation based on a supported palladium catalyst according to claim 1, characterized in that: The hydrogenated HTPB has a hydroxyl retention rate of 80-95% and a hydrogenation rate of 40-99.5%.