A process for the preparation of 2,4,4-trimethyl-2-pentanol

Abstract

The application discloses a preparation method of 2,4,4-trimethyl-2-pentanol and belongs to the field of organic synthesis and catalysis technology. Acidic functional ionic liquid is used as a catalyst to catalyze hydration or alcoholysis reaction of 2,4,4-trimethyl-2-pentene, the reaction condition is that the reaction is carried out at a temperature of 20-80 DEG C under normal pressure for 1-6 hours, the molar ratio of the catalyst to the raw material is 1:20-1:100, and the mass ratio of the solvent (water or C1-C4 alcohol) to the raw material is 1:1-5:1. After the reaction, the catalyst is recovered by standing and layering, liquid phase is subjected to distillation to obtain the product 2,4,4-trimethyl-2-pentanol, the product yield is 85.5%-95.5%, the purity is greater than or equal to 98.8%, the isomerization byproduct content is less than or equal to 1.5 wt%, and the catalyst can be regenerated and recycled after being washed and dried. The ionic liquid is imidazolium salt containing sulfonic acid group, carboxylic acid group and phosphoric acid group (such as [SO3H-BMIM][HSO4]), the acidic sites of the ionic liquid and the solvent synergistically activate olefins. The application replaces the traditional inorganic acid process, the wastewater discharge is reduced by more than 80%, the condition is mild, the safety is high, and the application is suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis catalysis technology, specifically relating to a method for preparing 2,4,4-trimethyl-2-pentene by hydration or alcoholysis using acidic functionalized ionic liquid catalysis. Background Technology

[0002] 2,4,4-Trimethyl-2-pentanol is a high-value-added fine chemical intermediate, possessing excellent oil solubility, low volatility, and a stable chemical structure. It is widely used in fragrance formulation, pharmaceutical synthesis, and industrial specialty solvents. Fragrance and pharmaceutical-grade products have stringent requirements regarding product purity and the content of isomer byproducts. The mainstream synthetic route for preparing this alcohol is hydration or alcoholysis of 2,4,4-trimethyl-2-pentene. However, existing industrial and laboratory processes generally suffer from catalytic system defects, resulting in high levels of isomers and etherification byproducts. Furthermore, these processes are accompanied by problems such as high pressure, high corrosion, rapid catalyst depletion, and large amounts of waste. Developing a mild, efficient, green, and low-waste catalytic synthesis process is crucial for improving the economics and quality of the product.

[0003] Currently, this synthetic route mostly uses inorganic strong acids, solid sulfonic acid resins or ordinary monofunctional ionic liquids and noble metal supported catalytic systems. Although it can achieve olefin conversion, it still has shortcomings such as harsh reaction conditions, difficulty in suppressing side reactions, poor catalyst cycle stability, high raw material costs, and high environmental treatment costs, making it difficult to adapt to the needs of large-scale continuous green production. Chinese patent CN103524702A discloses a process for the hydration of cyclohexene to cyclohexanol catalyzed by sulfonic acid-based ionic liquids. This type of monosulfonic acid ionic liquid is more suitable for straight-chain olefins. If it is applied to branched olefins (such as 2,4,4-trimethyl-2-pentene), the catalytic efficiency will decrease significantly (yield <75%), and high pressure conditions (1.5-3.0 MPa) are often required, resulting in high energy consumption. BASF's patent DE102009028021A uses a Pd / Al2O3 palladium-based noble metal catalyst to catalyze the hydration of olefins. Although the product selectivity can reach 88%-92%, the noble metal loading of the catalyst is as high as 5wt%, and the cost of noble metal raw materials accounts for more than 50% of the overall production cost, making it uneconomical. US patent US7820862B2 proposes to catalyze the hydration of long-chain olefins using sulfonic acid resins, but the resin is severely deactivated due to carbon deposition after the reaction (activity decreases by >40% after 5 cycles), requiring frequent regeneration.

[0004] In recent years, bifunctional ionic liquid catalysts have become a research hotspot due to their tunable acidity and solubility. They can simplify product separation processes while reducing the generation of saline wastewater, meeting the industrial production needs of high-quality alcohols. However, there is a lack of systematic research on the application of ionic liquids with synergistic dual-acidity effects for the atmospheric-pressure directional hydration / alcoholization of sterically hindered 2,4,4-trimethyl-2-pentene. Significant technological gaps exist, particularly in overcoming high-pressure conditions, suppressing olefin isomerization and dimerization side reactions, and simultaneously improving olefin conversion, target alcohol purity, and long-term catalyst stability. Therefore, developing a bi-acidic ionic liquid catalytic system containing sulfonic acid / carboxylic acid / phosphate side chains, leveraging the synergistic effect of dual acids to precisely control the carbocation intermediate conversion pathway, and combining atmospheric-pressure mild reaction and simple regeneration processes to achieve multiple catalyst reuses, has significant industrial value for achieving the green and efficient conversion of 2,4,4-trimethyl-2-pentene, reducing energy consumption and environmental treatment costs in chemical production, and represents a crucial technological bottleneck that urgently needs to be overcome in this field. While existing technologies have reported the use of sulfonic acid-functionalized ionic liquids for olefin hydration reactions (e.g., CN103524702A), these catalyzed reactions primarily target straight-chain olefins or cyclic olefins with low steric hindrance, and often require high-pressure conditions. For branched olefins like 2,4,4-trimethyl-2-pentene, which have tertiary carbon centers and high steric hindrance, conventional monoacidic ionic liquids suffer from significantly reduced catalytic efficiency due to their limited acid strength distribution and lack of precise control over carbocation intermediates, making it difficult to suppress isomerization and dimerization side reactions. This invention, through the dual-acidic synergistic design of side-chain acidic groups and anions, achieves for the first time highly efficient directed hydration / alcoholization of highly steric-hindrance branched olefins under ambient pressure, filling this technological gap. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient and environmentally friendly method for the catalytic preparation of 2,4,4-trimethyl-2-pentanol. This method uses functionalized ionic liquids as catalysts to replace or partially replace traditional solid acid catalysts (such as sulfuric acid and phosphoric acid) systems, solving problems such as strong catalyst corrosivity, numerous side reactions, difficult product separation, and serious environmental pollution in traditional methods. At the same time, the production cost is significantly reduced through catalyst recovery and reuse.

[0006] A method for catalytically preparing 2,4,4-trimethyl-2-pentanol is characterized by using a functionalized ionic liquid as a catalyst to catalyze the hydration or alcoholysis of 2,4,4-trimethyl-2-pentene to prepare 2,4,4-trimethyl-2-pentanol. The molar ratio of 2,4,4-trimethyl-2-pentene to the functionalized ionic liquid is 20:1-100:1, the reaction temperature is 20-80℃, the reaction pressure is atmospheric pressure, and the reaction time is 1-6 hours. After the reaction, the catalyst is recovered by filtration after static separation and the liquid phase is separated and purified by vacuum distillation to obtain the product 2,4,4-trimethyl-2-pentanol, with a yield of 85.5%-95.5% and a purity ≥98.8%. The functionalized ionic liquid is one of the following three: 1-sulfonic acid propionic-3-methylimidazolium hydrogen sulfate ([SO3H-BMIM][HSO4]), 1-carboxybutyl-3-methylimidazolium hydrogen sulfate ([COOH-BMIM][HSO4]), or 1-butyl-3-methylimidazolium phosphate hydrogen sulfate ([PO3H2-BMIM][HSO4]). Its dual acidic sites allow for precise control of the reaction pathway and suppression of byproduct formation. After being washed, vacuum dried, and regenerated by filtration, the catalyst retains >95.5% of its activity after eight cycles of reuse.

[0007] This invention solves this technical problem through the following technical solution: Taking 1-sulfonopropyl-3-methylimidazolium hydrogen sulfate ([SO3H-BMIM][HSO4]) as an example, the specific technical solution is illustrated below: 2,4,4-Trimethyl-2-pentene and [SO3H-BMIM][HSO4] catalyst were added at a molar ratio of 60:1. Deionized water and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 3:1 and added to the reactor. The mixture was stirred at 300 rpm and at 50°C under normal pressure for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 100°C and 30 kPa to obtain 2,4,4-trimethyl-2-pentanol. The product yield was 95.5%, the purity was 99.0%, and the content of isomerization byproducts in the system was 0.8 wt%. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing and separating to remove residual organic matter, it was vacuum dried at 70°C for 9 hours. After filtration through a filter membrane, it was recycled. After the catalyst was continuously recycled 8 times, the product yield was 95.1%, the activity retention rate was 95.8%, and the activity decay was 4.2%.

[0008] Compared with traditional methods, the present invention is characterized by: 1. Compared with traditional single-acidic ionic liquids or inorganic acids, the double-Brønsted acidic functionalized ionic liquid used in this invention relies on the synergistic effect of the side-chain acidic groups and the bisulfate anion—the side-chain acidic groups preferentially activate the olefin double bond to generate a carbocation intermediate, while the bisulfate anion regulates the local acid environment and stabilizes the reaction transition state. This synergistic mechanism is particularly important for sterically hindered branched-chain olefins (such as 2,4,4-trimethyl-2-pentene): the gradient acid strength distribution precisely regulates the proton transfer pathway, suppresses side reactions such as excessive isomerization and polymerization of carbocations, and at the same time, the steric effect of the ionic liquid effectively hinders the formation of macromolecular byproducts. Comparative experiments show that using ionic liquids containing only side-chain sulfonic acid groups alone (yield 72.3%, isomerization byproduct 6.8 wt%) or ionic liquids containing only anionic acids alone (yield 66.8%, isomerization byproduct 10.2 wt%) cannot achieve the catalytic effect of this invention. This confirms that the synergistic effect of the two acidic sites is the core technical feature of this invention to achieve high yield (95.5%), high purity (≥99.0%), and low byproduct (≤0.8 wt%).

[0009] 2. The entire process of this invention is carried out under normal pressure and temperature range, without the need for high pressure conditions. The reaction conditions are mild, which effectively reduces equipment corrosion and energy consumption, while taking into account both reaction conversion efficiency and product selectivity.

[0010] 3. The functionalized ionic liquid can be recovered by standing and separating after reaction, and can be regenerated and reused after simple washing, drying and filtration. The activity retention rate is >95.5% after 8 cycles, which simplifies the product separation process, reduces the generation of waste, lowers production costs, is suitable for laboratory preparation, and has the potential for continuous industrial scale-up. Detailed Implementation

[0011] The method of the present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention.

[0012] Example 1: 2,4,4-Trimethyl-2-pentene and [SO3H-BMIM][HSO4] catalyst were added at a molar ratio of 20:1. Deionized water and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 1:1 and added to a reactor. The mixture was stirred at 300 rpm and 20°C at atmospheric pressure for 1 hour. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 80°C and 10 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 60°C for 6 hours and then filtered through a filter membrane for reuse.

[0013] Comparative Example 1: This comparative example provides a method for preparing 2,4,4-trimethyl-2-pentanol. The difference between this method and the examples is that the comparative example does not use a functionalized ionic liquid as a catalyst, but instead uses concentrated sulfuric acid. The specific amounts are as follows: 10g of concentrated sulfuric acid is added to a reaction vessel, along with 20g of 2,4,4-trimethyl-2-pentene and 40g of water. The mixture is heated to 50°C, stirred at 300 rpm, and reacted for 4 hours. After the reaction is complete, the mixture is cooled to room temperature, transferred to a separation device, and the catalyst is separated by neutralization. The remaining liquid phase is distilled under reduced pressure at 80°C and 20kPa to obtain 2,4,4-trimethyl-2-pentanol, with a yield of 75.5% and a purity of 85.2%.

[0014] Comparative Example 2: This comparative example provides a method for preparing 2,4,4-trimethyl-2-pentanol. The difference between this method and the previous example is that the comparative example does not use a functionalized ionic liquid as a catalyst, but instead uses a common ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]. The specific amounts are as follows: 10 g of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] is added to a reaction vessel, along with 20 g of 2,4,4-trimethyl-2-pentene and 40 g of water. The mixture is heated to 50°C, stirred at 300 rpm, and reacted for 4 hours. After the reaction, the mixture is cooled to room temperature, transferred to a separation device, and the catalyst is recovered through simple filtration. The remaining liquid phase is distilled under reduced pressure at 80°C and 20 kPa to obtain 2,4,4-trimethyl-2-pentanol, with a yield of 78.5% and a purity of 82.5%.

[0015] Example 2: 2,4,4-Trimethyl-2-pentene and [COOH-BMIM][HSO4] catalyst were added at a molar ratio of 100:1. Ethanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 5:1 and added to a reactor. The mixture was stirred at 300 rpm and the reaction temperature was 80°C under normal pressure for 6 hours. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 120°C and 50 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was vacuum dried at 80°C for 12 hours and then filtered through a filter membrane for recycling.

[0016] Example 3: 2,4,4-Trimethyl-2-pentene and [PO3H2-BMIM][HSO4] catalyst were fed at a molar ratio of 60:1. Isopropanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 3:1 and added to a reactor. The mixture was stirred at 300 rpm and at 50°C under normal pressure for 3.5 h. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 100°C and 30 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 70°C for 9 h and then filtered through a filter membrane for recycling.

[0017] Example 4: 2,4,4-Trimethyl-2-pentene and [SO3H-BMIM][HSO4] catalyst were added at a molar ratio of 60:1. Deionized water and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 3:1 and added to a reactor. The mixture was stirred at 300 rpm and at 50°C under normal pressure for 3.5 h. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 100°C and 30 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was vacuum dried at 70°C for 9 h and then filtered through a filter membrane for reuse.

[0018] To verify the synergistic catalytic effect of the dual-acid functionalized ionic liquid of the present invention, comparative experiments were conducted using the following catalysts under the exact same reaction conditions as in Example 4 (molar ratio of 2,4,4-trimethyl-2-pentene to catalyst 60:1, mass ratio of deionized water to olefin 3:1, stirring speed 300 rpm, reaction temperature 50℃, and stirring reaction at atmospheric pressure for 3.5 h): Comparative Example 3: 1-Sulfonopropyl-3-methylimidazolium chloride ([SO3H-BMIM]Cl) was used instead of [SO3H-BMIM][HSO4] as the catalyst, with the remaining operations the same as in Example 4. The resulting product yield was 72.3%, purity was 90.5%, and the content of isomerization byproducts in the system was 6.8 wt%.

[0019] Comparative Example 4: 1-Butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO4]) was used instead of [SO3H-BMIM][HSO4] as the catalyst, and the remaining operations were the same as in Example 4. The resulting product yield was 66.8%, purity was 85.7%, and the content of isomerization byproducts in the system was 10.2 wt%.

[0020] Comparative Example 5: Using Amberlyst-15 sulfonic acid resin as a catalyst, the reaction was carried out under the optimal conditions (temperature 80°C, pressure 1.0 MPa) of the example in US7820862B2, with the remaining raw material ratios the same as in Example 4. The yield of the obtained product was 82.5%, the purity was 91.3%, and the content of isomerization byproducts in the system was 5.6 wt%.

[0021] Example 5: 2,4,4-Trimethyl-2-pentene and [COOH-BMIM][HSO4] catalyst were fed at a molar ratio of 20:1. Methanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 5:1 and added to a reactor. The mixture was stirred at 300 rpm and the reaction temperature was 80°C under normal pressure for 3.5 h. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 120°C and 30 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 60°C for 9 h and then filtered through a filter membrane for recycling.

[0022] Example 6: 2,4,4-Trimethyl-2-pentene and [PO3H2-BMIM][HSO4] catalyst were added at a molar ratio of 100:1. Deionized water and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 1:1 and added to a reactor. The mixture was stirred at 300 rpm and at 20°C under normal pressure for 3.5 h. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 80°C and 30 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 80°C for 6 h and then filtered through a filter membrane for recycling.

[0023] Example 7: 2,4,4-Trimethyl-2-pentene and [COOH-BMIM][HSO4] catalyst were fed at a molar ratio of 60:1. Ethanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 1:1 and added to a reactor. The mixture was stirred at 300 rpm and the reaction temperature was 80°C under normal pressure for 6 hours. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 100°C and 10 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 70°C for 12 hours and then filtered through a filter membrane for recycling.

[0024] Example 8: 2,4,4-Trimethyl-2-pentene and [PO3H2-BMIM][HSO4] catalyst were added at a molar ratio of 20:1. Isopropanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 3:1 and added to a reactor. The mixture was stirred at 300 rpm and at 50°C under normal pressure for 1 hour. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 120°C and 50 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 80°C for 9 hours and then filtered through a filter membrane for recycling.

[0025] Example 9: 2,4,4-Trimethyl-2-pentene and [SO3H-BMIM][HSO4] catalyst were fed at a molar ratio of 100:1. Methanol and 2,4,4-trimethyl-2-pentene were mixed at a mass ratio of 5:1 and added to a reactor. The mixture was stirred at 300 rpm and at 20°C under normal pressure for 6 hours. After the reaction, the mixture was cooled to room temperature and allowed to stand to separate into layers. The ionic liquid catalyst was then separated and recovered. The upper liquid phase was first distilled under reduced pressure to remove low-boiling impurities. The target fraction was collected at 80°C and 10 kPa to obtain 2,4,4-trimethyl-2-pentanol. The recovered ionic liquid catalyst was mixed with deionized water at a volume ratio of 1:2 and stirred. After standing to separate into layers to remove residual organic matter, the mixture was dried under vacuum at 60°C for 12 hours and then filtered through a filter membrane for recycling.

[0026] Product Testing Methods: The products and byproducts of this invention were qualitatively and quantitatively analyzed using gas chromatography (GC) combined with a flame ionization detector (FID). An HP-5 capillary column (30m × 0.32mm × 0.25μm) was used. The column temperature program was: initial temperature 60℃ for 3 min, then increased to 180℃ at 8℃ / min and held for 5 min to ensure complete separation of the target product and olefin isomerization byproducts. The injection port temperature was 260℃, the detector temperature was 290℃, high-purity nitrogen was used as the carrier gas, the column flow rate was 1.2 mL / min, and the split ratio was 25:1. Before testing, the upper organic liquid phase after the reaction was cooled to room temperature. An appropriate amount of sample was diluted evenly with anhydrous ethanol, filtered through a 0.22μm organic phase filter membrane to remove trace impurities, and then injected for detection. Component qualitative analysis was performed by comparing the retention times of 2,4,4-trimethyl-2-pentanol standards and olefin isomerization impurity standards. Quantification was performed using the external standard method. The correlation coefficient R of the standard curve was [not specified]. 2 For each sample, the purity of the target product and the content of isomerization byproducts were calculated using a value ≥0.999. The product yield was then determined using material balance. Three parallel tests were conducted on all samples, and the relative standard deviation (RSD) was controlled to be ≤2% to ensure the accuracy and reliability of the test data.

[0027] Table 1. Performance comparison of ionic liquid catalytic synthesis of 2,4,4-trimethyl-2-pentanol under different process conditions

[0028] Example 1 85.5 98.8 1.4 85.5 95.5 Example 2 88.4 98.9 1.3 88.1 95.5 Example 3 91.6 98.9 1.2 91.2 95.6 Example 4 95.5 99.0 0.8 95.1 95.8 Example 5 89.3 98.8 1.3 88.9 95.5 Example 6 87.6 98.8 1.4 87.2 95.5 Example 7 90.4 98.9 1.1 90 95.5 Example 8 92.9 98.9 1 92.5 95.7 Example 9 86.5 98.8 1.4 86.1 95.5 Comparative Example 1 75.5 85.2 8.3 72.0 95.4 Comparative Example 2 78.5 82.5 7.9 75.1 95.7 Comparative Example 3 72.3 90.5 6.8 68.5 94.8 Comparative Example 4 66.8 85.7 10.2 60.2 90.1 Comparative Example 5 82.5 91.3 5.6 —— —— Note: Comparative Example 5 only verified the performance of a single reaction and did not conduct a cyclic use test.

[0029] As can be seen from the data in Table 1: 1. Significance of the synergistic effect of dual acidity. The product yields of Comparative Example 3 (containing only side-chain sulfonic acid groups) and Comparative Example 4 (containing only anionic acid) were only 72.3% and 66.8%, respectively, far lower than the 95.5% of Example 4; the contents of isomerization byproducts were 6.8 wt% and 10.2 wt%, respectively, far higher than the 0.8 wt% of Example 4. This indicates that the synergistic effect of dual acidity between the side-chain acidic group and the bisulfate anion is the core mechanism for achieving high yield and high selectivity in this invention. The side-chain sulfonic acid group preferentially activates the olefin double bond to generate a carbocation intermediate, while the bisulfate anion regulates the local acidic environment and stabilizes the reaction transition state; both are indispensable.

[0030] 2. Breakthrough under ambient pressure conditions. Comparative Example 5 achieved a yield of 82.5% under 1.0 MPa high pressure, while this invention achieves a yield of 95.5% under ambient pressure. This difference has significant industrial value for the hydration reaction of sterically hindered olefins—high-pressure reactions not only increase equipment investment and energy consumption but also pose safety hazards. This invention effectively lowers the reaction energy barrier through precise acidity control of dual-acidic ionic liquids, making a mild ambient pressure reaction possible.

[0031] 3. Adaptability to sterically hindered substrates. Existing monosulfonic acid ionic liquids are more suitable for straight-chain olefins or cyclic olefins with low steric hindrance. For branched olefins with tertiary carbon centers, such as 2,4,4-trimethyl-2-pentene, monoacidic catalytic systems cannot precisely control the conversion pathway of the carbocation intermediate, leading to severe isomerization and dimerization side reactions. This invention regulates the proton transfer pathway through gradient acid strength distribution and, in conjunction with the steric effect of ionic liquids, suppresses the formation of large molecular byproducts, achieving for the first time an efficient atmospheric pressure conversion of this type of sterically hindered olefin.

Claims

1. A method for preparing 2,4,4-trimethyl-2-pentanol, characterized in that, The hydration or alcoholysis reaction of 2,4,4-trimethyl-2-pentene is catalyzed by a dual-acid functionalized ionic liquid, including the following steps: (1) 2,4,4-trimethyl-2-pentene, acidic functionalized ionic liquid catalyst, and solvent are mixed at a catalyst-to-raw material molar ratio of 1:20-1:100 and a solvent-to-raw material mass ratio of 1:1-5:1, and stirred at 20-80℃ under normal pressure for 1-6 hours; the acidic functionalized ionic liquid is a diacidic site imidazolium salt with the general structural formula [Y-BMIM][HSO4], wherein the cation Y is selected from propyl sulfonate (-C3H6SO3H), butyl carboxylate (-C4H8COOH), or butyl phosphate (-C4H8PO3H2), and the anion is hydrogen sulfate (HSO4). - ); (2) After the reaction is complete, the mixture is allowed to stand and separate into layers. The lower layer of ionic liquid catalyst is recovered, and the upper liquid phase is transferred to a distillation flask. (3) After removing low-boiling-point components by vacuum distillation of the upper liquid phase, the target fraction is collected under conditions of 80-120℃ and 10-50kPa to obtain 2,4,4-trimethyl-2-pentanol.

2. The method according to claim 1, characterized in that: The solvent in step (1) is water or a C1-C4 alcohol, wherein the C1-C4 alcohol is selected from methanol, ethanol or isopropanol.

3. The method according to claim 1, characterized in that: The ionic liquid catalyst recovered in step (2) is mixed with deionized water at a volume ratio of 1:2 and stirred. After standing and separating to remove residual organic matter, it is vacuum dried at 60-80℃ for 6-12 hours and then filtered for recycling. The regenerated ionic liquid catalyst can be continuously recycled 8 times. Based on the yield of the first reaction product, the product yield is still ≥85.5%, and the catalyst activity decay is ≤4.5%.