Composite catalyst and preparation and application thereof

Abstract

The invention discloses a composite catalyst as well as preparation and application thereof. The composite catalyst comprises a metal organic framework material loaded with sulfonated graphene. The preparation method comprises the following steps: dispersing a metal organic framework material and sulfonated graphene in an alcohol solvent to obtain a first mixed solution; performing rotary evaporation on the first mixed solution and preserving heat to obtain a second mixed solution; and homogenizing the second mixed solution, and drying to obtain the composite catalyst. The composite catalyst can be applied to catalytic degradation of alpha-pinene or purification of a linalool crude product. The invention aims to develop a linalool efficient purification method based on a novel composite catalyst and a supercritical CO2 medium through collaborative innovation of the novel composite catalyst and the supercritical CO2 medium, and solves the core problems of insufficient catalyst selectivity, easy deactivation, disjunction of reaction and separation, poor environmental protection property and the like in the existing linalool chemical purification. The efficient and green industrial purification of the linalool is realized.

Description

Technical Field

[0001] This invention relates to an organic reaction catalyst, its preparation and application, and more particularly to a composite catalyst based on sulfonated graphene and metal-organic framework materials, its preparation and application. Background Technology

[0002] Linalool is a core raw material in the fragrance, cosmetic, and pharmaceutical industries, and its purity directly affects the quality and performance of these products. High-purity linalool can better exert a fresh aroma in fragrance formulation, more effectively perform bactericidal and preservative effects in cosmetics, and ensure the stability of its physiological activity in the pharmaceutical field. Therefore, efficient purification of linalool is of great significance.

[0003] Traditional chemical purification methods for linalool suffer from numerous problems. The catalysts used, such as cesium carbonate and p-toluenesulfonic acid, have limited selectivity. During purification, they not only act on the target impurities but may also affect linalool itself, causing degradation and deactivation, ultimately leading to decreased purification efficiency and increased costs. Furthermore, the reaction and separation processes in traditional methods are disconnected, requiring additional separation steps, increasing operational complexity and cost. Moreover, the large-scale use of organic solvents such as dichloromethane and ethanol not only increases purification costs but also causes environmental pollution, contradicting the trend towards green chemistry. Summary of the Invention

[0004] Objectives of this invention: The objective of this invention is to provide a composite catalyst that addresses the problems of insufficient catalyst selectivity, easy deactivation, disconnection between reaction and separation, and poor environmental performance in the existing chemical purification of linalool. A second objective is to propose a method for preparing the composite catalyst, thus solving the problem of how to prepare a composite catalyst. A third objective is to propose the application of this composite catalyst in the catalytic degradation of α-pinene or the purification of crude linalool, solving the problem of how to specifically degrade α-pinene impurities in crude linalool.

[0005] Technical solution: The composite catalyst of the present invention comprises a metal-organic framework material supported on graphene sulfonate. Preferably, the metal-organic framework material is zeolite imidazole ester framework material-8, and the sulfonic acid group loading on the zeolite imidazole ester framework material-8 is 1.2-1.5 mmol / g.

[0006] This invention utilizes zeolite imidazole ester framework material-8 (ZIF-8) within metal-organic frameworks (MOFs) as a support. ZIF-8 possesses a regular microporous structure, high specific surface area, and excellent shape selectivity. Its pore size matches the molecular size of linalool, enabling it to specifically adsorb and activate linalool while reducing the adsorption of impurities. Sulfonated graphene is selected as the solid acid, exhibiting excellent proton transfer properties that promote the selective decomposition of impurities (such as terpene byproducts). The combination of these two components constitutes a novel composite catalyst, addressing the shortcomings of traditional catalysts.

[0007] The second aspect of this invention discloses a method for preparing the above-mentioned composite catalyst, comprising the following steps: (1) The metal-organic framework material and sulfonated graphene were dispersed in an alcohol solvent to obtain a first mixture; (2) The first mixture is rotary evaporated and then kept at a constant temperature to obtain the second mixture; (3) The second mixture was homogenized and then dried to obtain the composite catalyst.

[0008] Preferably, in step (1), the preparation method of the metal-organic framework material is as follows: zinc salt and imidazole organic ligand are dissolved in alcohol solvent, and after reaction, the reaction product is obtained. Then, after centrifugation, washing and drying, zeolite imidazole ester framework material-8 with stable structure and qualified specific surface area is obtained. The method for preparing the sulfonated graphene is as follows: graphene oxide is dispersed in N,N-dimethylformamide, aminosulfonic acid is added, the reaction is heated, the reaction product is filtered, the solid is washed with water, and dried to obtain sulfonated graphene.

[0009] In some embodiments, the zinc salt may be selected from at least one of zinc nitrate, zinc sulfate, and zinc chloride, the imidazole organic ligand includes at least one of 2-methylimidazole and 4-methylimidazole, and the alcohol solvent is methanol or ethanol; the molar ratio of zinc salt to imidazole organic ligand is 1-2:2-4.

[0010] In some embodiments, graphene oxide is prepared by the Hummers method, and the ratio of graphene oxide, aminosulfonic acid and N,N-dimethylformamide is 1g:0.4-0.6g:40-60mL, and the reaction is carried out at 70-90℃ for 5-7h.

[0011] This invention introduces sulfonic acid groups into the surface of graphene oxide through a sulfonation reaction. During the reaction, the reaction temperature, time, and reactant ratio are controlled to ensure the loading and uniform distribution of sulfonic acid groups, thereby obtaining sulfonated graphene.

[0012] Based on the molecular structure and properties of linalool and its impurities, this invention screened ZIF-8 as a suitable carrier type.

[0013] Preferably, in step (1), the ratio of metal-organic framework material to sulfonic acid graphene and alcohol solvent is 1-3g: 1-2g: 50-100mL, and the dispersion method is ultrasonic dispersion at 200-400W for at least 20min.

[0014] In step (2), the rotary evaporation conditions are 60-100℃ for 1-2 hours and 110-130℃ for 1-3 hours to ensure solvent removal without damaging the material structure.

[0015] In step (3), the homogenization method is stirring or sonication.

[0016] The third aspect of this invention discloses the application of the above-mentioned composite catalyst in the catalytic degradation of α-pinene or the purification of crude linalool.

[0017] Specifically, the method for catalytic degradation of α-pinene in crude linalool using the above-mentioned composite catalyst includes the following steps: (a) Under closed conditions, crude linalool containing α-pinene was mixed with a composite catalyst and supercritical CO2 to obtain the reactants; (b) The reactants are heated and pressurized to react and obtain a mixed product; (c) After depressurizing the mixture, the liquid phase is removed to obtain pure linalool.

[0018] This invention uses supercritical CO2 as an integrated reaction and separation medium. The difference in solubility of linalool and impurities in CO2 can be precisely adjusted by controlling temperature and pressure. Moreover, it is widely available and low in cost, which can reduce the use of organic solvents.

[0019] The enclosed conditions are provided by an integrated supercritical CO2 reaction and separation unit, including a CO2 storage tank, a pressurization pump, a reaction vessel, a separation vessel, a temperature control system, and a pressure control system. This ensures the equipment's sealing and pressure resistance to meet the operating conditions of supercritical CO2.

[0020] Preferably, in step (a), the amount of composite catalyst is 3-5 wt% of the crude linalool containing α-pinene, and the amount of supercritical CO2 is 5-10 times the volume of the crude linalool containing α-pinene, to ensure mass transfer efficiency and reaction uniformity. The crude linalool is crude linalool that has had solid impurities and most of the water removed.

[0021] Preferably, in step (b), the heating and pressurizing reaction conditions are: heating to 35-50°C, pressurizing to 8-12 MPa, and reacting for 2-3 hours under supercritical CO2 flow conditions. The CO2 flow rate is adjusted to 0.0005-0.2 ml / s to ensure thorough mixing of the materials in the reactor.

[0022] Preferably, in step (c), the depressurization method is to depressurize the mixed product to 4-6 MPa.

[0023] Under the set reaction conditions, crude linalool, the composite catalyst, and supercritical CO2 were allowed to fully contact and react. During the reaction, ZIF-8 in the composite catalyst adsorbed and activated linalool, sulfonated graphene promoted the selective decomposition of impurities such as α-pinene, and supercritical CO2 enhanced the mass transfer efficiency between the catalyst and the substrate.

[0024] It should be noted that linalool itself does not react with water or CO2 in this process; supercritical CO2 is only used as a medium for reaction and separation, utilizing its solvent properties to enhance mass transfer. Most of the water has been removed during the raw material pretreatment stage, avoiding interference from water in the system. The core of the reaction is the selective decomposition of impurities (such as α-pinene) under the action of sulfonated graphene (reaction formula below), transforming them into small molecules that are easily soluble in supercritical CO2. .

[0025] Impurity separation process: After the reaction is complete, the supercritical CO2 phase containing the product is introduced into a separation vessel, and the pressure is reduced (corresponding to a supercritical CO2 density of 0.6-0.8 g / cm³). 3 This process causes a sharp drop in the solubility of linalool in supercritical CO2 (from 15 g / L in the reaction phase to below 0.5 g / L in the separation phase), while the degradation products of terpene impurities maintain a high solubility (≥5 g / L), thus achieving efficient separation of linalool from impurities. Utilizing the change in solubility of linalool and impurities in supercritical CO2, linalool is precipitated in the separation vessel, achieving separation of the product from the medium. The linalool product in the separation vessel is then collected.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. In this invention, the selective adsorption of the composite catalyst and the solvation effect of supercritical CO2 work synergistically: ZIF-8's directional capture of linalool reduces its contact loss with solid acids, and the low viscosity of supercritical CO2 enhances the mass transfer efficiency of impurities to sulfonic acid groups. The combination of these two factors increases the purification selectivity by more than 20%, with linalool purity ≥99.5% (up to 98.2% by traditional chemical methods) and separation yield ≥95% (average 82% by traditional methods). Accelerated experiments have verified that the aroma stability of the product is extended from 6 months to 18 months (under 37°C storage conditions), and the bactericidal rate against Escherichia coli is increased from 85% to 98% (24-hour contact experiment), which is 15% higher than the traditional method, fully meeting the quality control standards for pharmaceutical-grade linalool.

[0027] 2. The composite catalyst in this invention exhibits significantly improved stability: compared to traditional cesium carbonate catalysts, its service life is extended from 5 batches to 15 batches, and the cost per use is reduced by 67% (from RMB 200 / batch to RMB 65 / batch); the supercritical CO2 recycling rate reaches over 90%, replacing the 300L dichloromethane / ethanol mixed solvent consumed per ton of product in the traditional process, reducing organic solvent consumption by 92% (to a mere 25L / ton), and reducing VOC emissions in the exhaust gas from 500ppm to below 30ppm. Overall, the purification cost per ton is reduced by 28% compared to traditional methods (from RMB 4200 to RMB 3000), and zinc ions can be recovered through calcination of the spent catalyst (recovery rate ≥85%), further reducing solid waste treatment costs.

[0028] 3. This invention solves the problem of the separation between reaction and separation in existing purification methods, achieving integrated reaction and separation, simplifying the operation process, and improving production efficiency. Furthermore, the entire purification process is easy to control and exhibits good stability, laying the foundation for the industrial-scale, efficient purification of linalool. Attached Figure Description

[0029] Figure 1 The image shows the X-ray diffraction pattern of the composite catalyst prepared in Example 1. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] Example 1: A composite catalyst composed of zeolite imidazole ester framework material-8 (ZIF-8) supported on sulfonic acid graphene, wherein the sulfonic acid group loading on the zeolite imidazole ester framework material-8 in the composite catalyst is 1.35 mmol / g.

[0032] The preparation method of the above composite catalyst is as follows: (1) Preparation of ZIF-8: 0.2 mol zinc nitrate and 0.8 mol 2-methylimidazole were dissolved separately in 100 mL methanol. After thorough mixing, the 2-methylimidazole methanol solution was slowly added dropwise to the zinc nitrate methanol solution, and the mixture was stirred at 25 °C for 24 h. The mixture was then centrifuged at 8000 r / min for 15 min, the precipitate was collected, washed three times with methanol, and dried under vacuum at 60 °C for 12 h to obtain zeolite imidazole ester framework material-8 (ZIF-8), with a specific surface area ≥1800 m². 2 / g.

[0033] (2) Preparation of sulfonated graphene: Graphene oxide was prepared using the Hummers method: 1 g of graphite powder was mixed with 0.5 g of sodium nitrate, 23 mL of concentrated sulfuric acid was added, 3 g of potassium permanganate was slowly added under ice bath conditions, and the mixture was stirred at 35 °C for 2 h. Then, 46 mL of deionized water was added, the temperature was raised to 98 °C and stirred for 15 min, 100 mL of deionized water and 5 mL of 30% hydrogen peroxide were added, the mixture was filtered, washed with 5% hydrochloric acid solution until neutral, and dried under vacuum at 60 °C to obtain graphene oxide. 1 g of graphene oxide was dispersed in 50 mL of N,N-dimethylformamide, 0.5 g of aminosulfonic acid was added, the mixture was stirred at 80 °C for 6 h, filtered, washed three times with deionized water, and dried under vacuum at 60 °C to obtain sulfonated graphene.

[0034] (3) Add ZIF-8 and sulfonated graphene to ethanol according to the material-liquid ratio of ZIF-8: sulfonated graphene: alcohol solvent = 3g: 1g: 80mL, and disperse by ultrasonication at 300W for 30min to obtain the first mixture; (4) The first mixture was rotary evaporated at 80°C for 1.5 hours and then kept at 120°C for 2 hours to obtain the second mixture; (5) The second mixture is mixed evenly under stirring or ultrasonic conditions and then dried to obtain a composite catalyst. The loading of sulfonic acid groups on ZIF-8 in the composite catalyst is 1.37 mmol / g.

[0035] The composite catalyst was analyzed by X-ray diffraction (XRD) to verify the characteristic peaks of MOFs (2θ = 7.3°, 10.3°). Scanning electron microscopy was used to observe the uniformity of solid acid loading in the composite catalyst (loading rate ≥ 90%). Infrared spectroscopy confirmed the presence of sulfonic acid groups on the composite catalyst (1030 cm⁻¹). -1 Characteristic peaks) ensure the stability of the composite structure. Experimental data are as follows: Figure 1 As shown.

[0036] The method for catalytic degradation of α-pinene using the above-mentioned composite catalyst is as follows: Add 0.5 g of α-pinene standard and 0.02 g of the above composite catalyst to the reactor; seal the reactor, introduce 3 mL of supercritical CO2, and set the reaction conditions as follows: temperature 40℃, pressure 10 MPa, stirring speed 300 r / min, and reaction time 2.5 hours. After the reaction, the supercritical CO2 phase in the reactor is introduced into a separation vessel, the pressure is reduced to 5 MPa, the temperature is maintained at 35℃, and the supercritical CO2 phase containing the decomposition products is collected in the separation vessel. Liquid products are obtained by depressurization (gasification of CO2), and the volume is adjusted to 2 mL of anhydrous ethanol. The product solution after volume adjustment is analyzed by GC-MS, and the composition and relative content of the decomposition products are analyzed by comparing the retention time and mass spectrum of the α-pinene standard. Meanwhile, a blank control group was set up: only α-pinene and supercritical CO2 were added (without catalyst), and the above steps were repeated to eliminate the influence of CO2 itself on α-pinene.

[0037] The experimental results are as follows: (1) Reaction conversion rate: The remaining amount of α-pinene in the experimental group was 0.08 g, and the conversion rate was 84% ​​((0.5-0.08) / 0.5×100%). The remaining amount of α-pinene in the blank control group was 0.49 g, with almost no decomposition (conversion rate < 2%), proving that the decomposition reaction was driven by a catalyst.

[0038] (2) Product composition (GC-MS detection results): Two main small molecule products were detected: Compound A: retention time 6.2 min, mass spectrometry characteristic peak m / z=138 (molecular ion peak), combined with standard spectral library comparison, confirmed as 2,3-dimethyl-1,3-butadiene (a small molecule olefin, readily soluble in supercritical CO2). Compound B: Retention time 7.5 min, characteristic mass spectrometry peak m / z=154, confirmed as 4-methyl-3-penten-2-one. The relative contents of the two products were 62% and 35%, respectively, with the remaining 3% being unidentified trace byproducts.

[0039] The experimental results above show that: α-Pinene underwent significant selective decomposition in the above-mentioned composite catalyst and supercritical CO2 system, mainly generating two small molecule substances that are easily soluble in supercritical CO2. The method for purifying crude linalool using the above-mentioned composite catalyst is as follows: (1) In a closed supercritical CO2 reaction and separation integrated device, 100 mL of crude linalool containing α-pinene (water content of 0.5%) after solid removal was mixed with a composite catalyst and 750 mL of supercritical CO2 to obtain the reactant; the amount of composite catalyst used was 4 wt% of the crude linalool containing α-pinene; (2) The reactants were heated to 41°C and pressurized to 10 MPa. The mixture was reacted for 2.5 h under the condition of supercritical CO2 flow rate of 0.01 mL / s to obtain the mixed product. (3) After depressurizing the mixed product to 5 MPa, the liquid phase was removed to obtain pure linalool.

[0040] Example 2: A method for preparing a composite catalyst is as follows: (1) Preparation of ZIF-8: 0.1 mol zinc nitrate and 0.4 mol 2-methylimidazole were dissolved separately in 50 mL of methanol, stirred thoroughly, and then mixed. The mixture was stirred at 30 °C for 18 h. After centrifugation at 8000 r / min for 10 min, the precipitate was washed three times with methanol and dried under vacuum at 50 °C for 10 h to obtain ZIF-8 with a specific surface area ≥1700 m². 2 / g.

[0041] (2) Preparation of sulfonated graphene: Following the same steps as in Example 1 for preparing sulfonated graphene, the amount of aminosulfonic acid was adjusted to 0.4g, and the mixture was stirred at 90°C for 5h to obtain sulfonated graphene.

[0042] (3) Add 1g ZIF-8 and 1g sulfonated graphene to 50mL ethanol and disperse by ultrasonication at 200W for 20min to obtain the first mixture; (4) The first mixture was rotary evaporated at 60°C for 2 hours and then kept at 110°C for 3 hours to obtain the second mixture; (5) The second mixture is mixed evenly under stirring or ultrasonic conditions and then dried to obtain a composite catalyst. The loading of sulfonic acid groups on ZIF-8 in the composite catalyst is about 1.2 mmol / g.

[0043] The method for purifying crude linalool using the above-mentioned composite catalyst is as follows: (1) In a closed supercritical CO2 reaction and separation integrated device, 10 mL of crude linalool containing α-pinene (water content of 0.4%) after solid removal was mixed with a composite catalyst and 100 mL of supercritical CO2 to obtain the reactant; the amount of composite catalyst used was 3 wt% of the crude linalool containing α-pinene; (2) The reactants were heated to 35°C and pressurized to 8 MPa. The mixture was reacted for 2 hours under the condition of supercritical CO2 flow rate of 0.0005 ml / s to obtain the mixed product. (3) After depressurizing the mixed product to 4 MPa, the liquid phase was removed to obtain pure linalool.

[0044] Example 3: A method for preparing a composite catalyst is as follows: (1) Preparation of ZIF-8: 0.3 mol zinc nitrate and 1.2 mol 2-methylimidazole were dissolved separately in 150 mL of methanol, mixed, and stirred at 28 °C for 20 h. The mixture was then centrifuged at 8000 r / min for 20 min, and the precipitate was washed three times with methanol and dried under vacuum at 65 °C for 14 h to obtain ZIF-8 with a specific surface area ≥1850 m². 2 / g.

[0045] (2) Preparation of sulfonated graphene: Following the same steps as in Example 1 for preparing sulfonated graphene, the amount of aminosulfonic acid was adjusted to 0.6g, and the mixture was stirred at 70°C for 7h to obtain sulfonated graphene.

[0046] (3) Add 3g ZIF-8 and 2g sulfonated graphene to 100mL methanol and disperse using ultrasonication at 400W for 50min to obtain the first mixture; (4) The first mixture is rotary evaporated at 100°C for 1 hour and then kept at 130°C for 1 hour to obtain the second mixture; (5) The second mixture is mixed evenly under stirring or ultrasonic conditions and then dried to obtain a composite catalyst. The loading of sulfonic acid groups on the zeolite imidazole ester skeleton material-8 in the composite catalyst is about 1.5 mmol / g. The method for purifying crude linalool using the above-mentioned composite catalyst is as follows: (1) In a closed supercritical CO2 reaction and separation integrated device, 10 mL of crude linalool containing α-pinene (water content of 0.3%) after solid removal was mixed with a composite catalyst and 80 mL of supercritical CO2 to obtain the reactant; the amount of composite catalyst used was 5 wt% of the crude linalool containing α-pinene; (2) The reactants were heated to 50°C and pressurized to 12 MPa. The mixture was reacted for 3 hours under the condition of supercritical CO2 flow rate of 0.2 ml / s to obtain the mixed product. (3) After depressurizing the mixed product to 6 MPa, the liquid phase was removed to obtain pure linalool.

[0047] Comparative Example 1: Everything else is the same as in Example 1, except that: Replace ZIF-8 with ZIF-67.

[0048] Comparative Example 2: Everything else is the same as in Example 1, except that: Replace the sulfonated graphene in step (3) with graphene oxide.

[0049] Comparative Example 3: Everything else is the same as in Example 1, except that: Replace the sulfonic acid graphene in step (3) with phosphotungstic acid.

[0050] The composite catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 were used to catalytically degrade α-pinene according to the method in Example 1, and the degradation conversion rate was measured.

[0051] Linalool purity detection and analysis: The purity of linalool purified in Examples 1-3 and Comparative Examples 1-3 was determined by high performance liquid chromatography (HPLC), and the results are as follows: Table 1. Catalytic degradation and purification capabilities of different catalysts for α-pinene.

[0052] In Table 1, the results show that after changing the organometallic framework material in Comparative Example 1, the degradation effect of the composite catalyst on pure α-pinene decreased significantly, and the purification effect on crude linalool also decreased drastically. This was mainly due to the reduced specific adsorption of α-pinene by ZIF-67, which failed to fully utilize the catalytic degradation effect of sulfonated graphene. Simultaneously, the non-specific adsorption and activation effect of ZIF-67 on linalool increased significantly, leading to the non-specific degradation of some linalool by the composite catalyst, while the degradation of impurities such as α-pinene was competitively inhibited. Therefore, the purity of the linalool purification product decreased significantly. In Comparative Examples 2 and 3, when sulfonated graphene was replaced with other solid acids or graphene oxide, the composite catalyst lacking sulfonic acid groups lost its selective degradation effect on α-pinene and could not degrade terpene impurities, resulting in a significant decrease in the purity of the linalool purification product. The above results indicate that the selective degradation of α-pinene by sulfonated graphene depends on the assistance of specific types of metal-organic framework materials. Using other metal-organic framework materials to support sulfonated graphene will reduce the degradation specificity of the composite catalyst and easily cause non-specific degradation of the target analyte, linalool, which will have a negative impact on the purification effect and yield.

Claims

1. A composite catalyst, characterized in that, This includes metal-organic framework materials loaded with sulfonated graphene.

2. The composite catalyst according to claim 1, characterized in that, The metal-organic framework material is zeolite imidazole ester framework material-8, and the sulfonic acid group loading on the zeolite imidazole ester framework material-8 is 1.2-1.5 mmol / g.

3. The method for preparing the composite catalyst according to claim 1 or 2, characterized in that, Includes the following steps: (1) The metal-organic framework material and sulfonated graphene were dispersed in an alcohol solvent to obtain a first mixture; (2) The first mixture is rotary evaporated and then kept at a constant temperature to obtain the second mixture; (3) The second mixture was homogenized and then dried to obtain the composite catalyst.

4. The method for preparing the composite catalyst according to claim 3, characterized in that, In step (1), the preparation method of the metal-organic framework material is as follows: zinc salt and imidazole organic ligand are dissolved in alcohol solvent, and after reaction, the reaction product is obtained. Then, after centrifugation, washing and drying, zeolite imidazole ester framework material-8 is obtained. The method for preparing the sulfonated graphene is as follows: graphene oxide is dispersed in N,N-dimethylformamide, aminosulfonic acid is added, the reaction is heated, the reaction product is filtered, the solid is washed with water, and dried to obtain sulfonated graphene.

5. The method for preparing the composite catalyst according to claim 3, characterized in that, In step (1), the ratio of metal-organic framework material to sulfonated graphene and alcohol solvent is 1-3g: 1-2g: 50-100mL, and the dispersion method is ultrasonic dispersion at 200-400W for at least 20min. In step (2), the rotary evaporation conditions are 60-100℃ for 1-2 hours and 110-130℃ for 1-3 hours. In step (3), the homogenization method is stirring or sonication.

6. The application of the composite catalyst according to claim 1 or 2 in the catalytic degradation of α-pinene or the purification of crude linalool.

7. The application according to claim 6, characterized in that, Includes the following steps: (a) Under closed conditions, crude linalool containing α-pinene was mixed with a composite catalyst and supercritical CO2 to obtain the reactants; (b) The reactants are heated and pressurized to react and obtain a mixed product; (c) After depressurizing the mixture, the liquid phase is removed to obtain pure linalool.

8. The application according to claim 7, characterized in that, In step (a), the amount of composite catalyst used is 3-5 wt% of the crude linalool containing α-pinene, and the amount of supercritical CO2 used is 5-10 times the volume of the crude linalool containing α-pinene.

9. The application according to claim 7, characterized in that, In step (b), the heating and pressurizing reaction conditions are heating to 35-50°C, pressurizing to 8-12 MPa, and reacting for 2-3 hours under supercritical CO2 flow conditions.

10. The application according to claim 7, characterized in that, In step (c), the depressurization method is to depressurize the mixture to 4-6 MPa.

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