Supported acidic catalyst, method of preparation and use in diels-alder reactions
By supporting acidic metal oxide catalysts with acid-modified mesoporous molecular sieves and supercritical carbon dioxide solvent, the problems of complex catalyst application, high temperature, long reaction time and low yield in the Diels-Alder reaction were solved, and efficient and stable catalytic effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG NHU PHARMA
- Filing Date
- 2024-02-20
- Publication Date
- 2026-06-12
AI Technical Summary
The existing Diels-Alder reaction has difficulties in using catalysts, the preparation process is complex, and the reaction temperature is high, the time is long, and the yield is low.
Acid-modified mesoporous molecular sieves were used as supports to load acidic metal oxide catalysts, combined with supercritical carbon dioxide solvent, and the reaction conditions were optimized to improve catalytic activity and stability.
The catalyst preparation process is simplified, the reaction temperature and time are reduced, the yield of cyclized fragrances is improved, and the catalyst can be reused multiple times to maintain high efficiency and selectivity.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, and in particular to a supported acidic catalyst, its preparation method, and its application in the Diels-Alder reaction. Background Technology
[0002] The Diels-Alder reaction, also known as diene addition, involves the reaction of a conjugated diene with a dienophile to form a six-membered cyclic olefin. This reaction is difficult to carry out at room temperature or low temperatures, and Lewis acid catalysts are commonly used to accelerate it. The Diels-Alder reaction is widely used in the research and production of synthetic fragrances, such as leaf alcohol, privet aldehyde, heterocyclic citral, and citric acid aldehyde, and is a very important class of organic chemical reactions.
[0003] Leaf alcohol, also known as cis-3-hexenol, is a colorless, oily liquid with a strong, fresh, herbaceous aroma. It is a prized fragrance ingredient used in flavor formulations, cosmetics, and food flavorings. Leaf alcohol can be synthesized from isoprene and formaldehyde via the Diels-Alder reaction to form 2-methyl-5,6-dihydro-2H-pyran, followed by ring-opening catalyzed by lithium metal.
[0004] Privet aldehyde, a colorless or very pale yellow liquid, is an important organic fine chemical and intermediate. It is also a green fragrance product with a strong, fresh, and grassy aroma. Its fragrance has strong diffusion, making it effective as a top note in floral, fresh, and fruity fragrances. It is suitable for formulating fragrances in soaps, cosmetics, detergents, and other products. Privet aldehyde can be obtained by the Diels-Alder reaction of 2-methyl-1,3-pentadiene with acrolein.
[0005] Heterocyclic citral is a colorless to pale yellow liquid with a fresh and strong aroma, reminiscent of citrus and verbena. It is relatively diffuse and primarily used in the formulation of floral fragrances, and can also be used to add fragrance to household cleaning products. Heterocyclic citral can be synthesized from 2-methyl-1,3-pentadiene and crotonaldehyde via the Diels-Alder reaction.
[0006] Citrus aldehyde is a colorless to slightly yellow liquid with a fresh and strong aroma, reminiscent of the green peel of citrus fruits like oranges and tangerines. When diluted, it has a floral scent, a fresh aroma with hints of aldehydes like citrus aldehyde, and a long-lasting, consistent fragrance. It is mainly used in the formulation of cosmetic fragrances. Citrus aldehyde can be produced by the Diels-Alder reaction of myrcene and acrolein.
[0007] Patent CN1244518A discloses a method for synthesizing 2-methyl-5,6-dihydro-2H-pyran from isoprene under reaction conditions of 0-200 atm and 0-400℃ in the presence of a catalyst, but the method does not disclose the catalyst composition or report the reaction conversion and selectivity.
[0008] Patent CN104689824B discloses a method for catalytically synthesizing 2-methyl-5,6-dihydro-2H-pyran using isoprene as a raw material, Fe / Mo as the active component, γ-Al₂O₃ as the support, and formaldehyde or acetaldehyde as the solvent under heating and stirring conditions. In Example 3, using this catalyst, the reaction was carried out at 300°C for 3 hours, with an isoprene conversion rate of 61.5% and a 2-methyl-5,6-dihydro-2H-pyran selectivity of 28%. This method suffers from problems such as low isoprene conversion, low 2-methyl-5,6-dihydro-2H-pyran selectivity, high reaction temperature, and long reaction time.
[0009] Patent CN100540545C describes a method for preparing 5,6-dihydro-pyran and its derivatives from conjugated dienes and anhydrous formaldehyde. In this method, the anhydrous formaldehyde, obtained by depolymerizing paraformaldehyde, triformaldehyde, or polyformaldehyde in a separate reactor, is introduced into the synthesis reactor in gaseous form. The Lewis acid catalyst used is a solution of ZnCl2, SnCl4, AlCl3, or BF3 diethyl ether. In Example 6, using ZnCl2 as a catalyst and tetrahydrofuran as a solvent, the yield of 2-methyl-5,6-dihydro-2H-pyran produced by the reaction of pentadiene and formaldehyde at 80°C reaches 78.5%. This method separates depolymerization and synthesis, increasing the number of equipment sets required and presenting the problem of difficult catalyst recovery and reuse.
[0010] Patent CN116943710B reports a method for obtaining a cyclized product (2-methyl-5,6-dihydro-2H-pyran / private aldehyde) by reacting conjugated dienes and aldehydes at a reaction temperature of 60-100℃ for 2.0-6.0 h under the action of a metal-supported catalyst. The conversion rate of dienes can reach 99.5%, and the selectivity of the cyclized product can reach 99.6%. However, this method has a long reaction time and requires the catalyst to be prepared first as a layered nanomaterial before being loaded onto a support material, and then the first metal salt and the second metal salt are loaded, which presents a problem of complex catalyst preparation process.
[0011] In summary, the existing Diels-Alder reaction has various problems, such as low yield, high reaction temperature, long reaction time, difficulty in applying catalysts, and complex process. Summary of the Invention
[0012] In view of this, the present invention provides a supported acidic catalyst, a preparation method thereof, and its application in the Diels-Alder reaction, to solve the technical problems of existing catalysts being difficult to apply and having complex preparation processes, as well as the high temperature, long time, and low yield of the Diels-Alder reaction. The present invention simplifies the catalyst preparation process and improves the stability of the applied catalyst, reduces the reaction temperature and shortens the reaction time, and increases the yield of cyclized fragrances.
[0013] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0014] In a first aspect, the present invention provides a supported acidic catalyst, comprising a support and an active component; the support is an acid-modified mesoporous molecular sieve; the active component is an acidic metal oxide, and the loading of the acidic metal oxide is 3.0 wt%-15.0 wt%.
[0015] Preferably, in the above-mentioned supported acidic catalyst, the mesoporous molecular sieve is any one of MCM-41, SBA-15, and MSU-X.
[0016] Preferably, in the above-mentioned supported acidic catalyst, the acidic metal oxide is any one of vanadium pentoxide, chromium trioxide, or tungsten trioxide.
[0017] Secondly, the present invention provides a method for preparing a supported acidic catalyst, comprising the following steps:
[0018] (1) After the mesoporous molecular sieve is added to an acidic solution for adsorption, it is dried and calcined to obtain an acid-modified mesoporous molecular sieve.
[0019] (2) The acid-modified mesoporous molecular sieve is impregnated in a soluble salt solution of the active component for adsorption, and then dried and calcined to obtain a supported acid catalyst.
[0020] Preferably, in the above-mentioned method for preparing the supported acidic catalyst, the acidic solution in step (1) is a 2-4 mol / L sulfuric acid solution, the adsorption temperature is 20-50℃, the adsorption time is 12-24h, the calcination temperature is 400-600℃, and the calcination time is 2-5h.
[0021] Preferably, in the above-mentioned method for preparing the supported acidic catalyst, the adsorption temperature in step (2) is 20-50℃, the adsorption time is 12-24h, the calcination temperature is 400-600℃, and the calcination time is 2-5h; the soluble salt is any one of ammonium salt or chloride.
[0022] Thirdly, the present invention provides an application of the above-mentioned supported acidic catalyst in the Diels-Alder reaction for the synthesis of cyclized fragrances using conjugated dienes and aldehydes as raw materials and supercritical carbon dioxide as a solvent.
[0023] Preferably, in the application of the above-mentioned supported acidic catalyst, the molar ratio of the aldehyde to the conjugated diene is 0.95-1.05:1.
[0024] Preferably, in the application of the above-mentioned supported acidic catalyst, the mass ratio of the supported acidic catalyst to the conjugated diene is 0.05%-0.5%:1.
[0025] Preferably, in the application of the above-mentioned supported acidic catalyst, the Diels-Alder reaction time is 10-30 min; the supercritical pressure is 7.5-10 MPa; and the temperature is 35-50 °C.
[0026] Preferably, in the application of the above-mentioned supported acidic catalyst, after the Diels-Alder reaction is completed, the supported acidic catalyst can be reused after filtration and separation.
[0027] This invention provides a supported acidic catalyst, its preparation method, and its application in the Diels-Alder reaction. Compared with the prior art, its advantages are as follows:
[0028] (1) The supported acid catalyst support of the present invention is a mesoporous molecular sieve after acid modification, which improves its acidity. At the same time, after loading the acid metal oxide active component, the support and the active component work together to greatly improve the catalytic activity of the supported acid catalyst, which is beneficial to improving the rate and yield of the Diels-Alder reaction.
[0029] (2) The preparation method of the supported acid catalyst of the present invention is simple. It utilizes the regular pores and large specific surface area of the mesoporous molecular sieve to promote the diffusion of conjugated dienes, aldehydes and cyclic fragrance molecules, thereby reducing carbon deposition, improving the life of the supported acid catalyst, maintaining the stability of the supported acid catalyst, and allowing it to be reused multiple times, thus reducing production costs.
[0030] (3) The application of the supported acid catalyst of the present invention in the Diels-Alder reaction, by using a supported acid catalyst with high catalytic activity and good reaction selectivity, achieves a reaction yield of up to 99.6% at a lower temperature and a shorter reaction time, and has fewer side reactions in the reaction process, which greatly improves the utilization rate of raw materials and the yield of products, and improves economic benefits.
[0031] (4) In the application of the supported acid catalyst of the present invention in the Diels-Alder reaction, supercritical carbon dioxide is also used as a solvent, which has good solubility for the materials in the reaction, which is beneficial to improving the reaction rate. At the same time, the solvent is easy to separate from the system, which is beneficial to reducing the post-processing cost. Detailed Implementation
[0032] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.
[0033] Some embodiments of the present invention provide a supported acidic catalyst, comprising a support and an active component; wherein the support is an acid-modified mesoporous molecular sieve, the mesoporous molecular sieve being any one of MCM-41, SBA-15, and MSU-X, preferably MCM-41; the active component is an acidic metal oxide, the acidic metal oxide being any one of vanadium pentoxide, chromium trioxide, or tungsten trioxide, preferably vanadium pentoxide, and the loading of the acidic metal oxide is 3.0 wt%-15.0 wt%, preferably 10 wt%.
[0034] Other embodiments of the present invention provide a method for preparing a supported acidic catalyst, comprising the following steps:
[0035] (1) Add the mesoporous molecular sieve to a sulfuric acid solution of 2-4 mol / L, preferably 2 mol / L, and adsorb it at a temperature of 20-50℃, preferably 25-40℃, more preferably 30℃ for 12-24h, preferably 16h. Dry it and calcine it at a temperature of 400-600℃, preferably 500℃ for 2-5h, preferably 3h, to obtain an acid-modified mesoporous molecular sieve.
[0036] (2) The acid-modified mesoporous molecular sieve is impregnated in a soluble salt solution of the active component and adsorbed at 20-50°C, preferably 30°C, for 12-24 hours, preferably 16 hours. After drying, it is calcined at 400-600°C, preferably 500°C, for 2-5 hours, preferably 3 hours, to obtain a supported acidic catalyst.
[0037] In some embodiments of the present invention, the soluble salt is any one of ammonium salt or chloride, preferably an ammonium salt.
[0038] Some embodiments of the present invention provide an application of the above-mentioned supported acidic catalyst in the Diels-Alder reaction, using conjugated diene and aldehyde as raw materials and supercritical carbon dioxide as solvent to synthesize cyclized fragrances, wherein the molar ratio of aldehyde to conjugated diene is 0.95-1.05:1, preferably 1-1.05:1, more preferably 1.01:1, and the mass ratio of supported acidic catalyst to conjugated diene is 0.05%-0.5%:1, preferably 0.05%-0.1%:1, more preferably 0.1%:1.
[0039] In some embodiments of the present invention, the Diels-Alder reaction time is 10-30 min, preferably 20 min; the supercritical pressure is 7.5-10 MPa, preferably 8 MPa; and the temperature is 35-50 °C, preferably 40 °C.
[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0041] Example 1: Preparation of supported acidic catalyst:
[0042] 9.0 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 1.86 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 10% V2O5 / MCM-41.
[0043] Example 2: Preparation of supported acidic catalyst:
[0044] 9.0 g of mesoporous molecular sieve MCM-41 was adsorbed in 3 mol / L sulfuric acid solution at 50 °C for 12 h, dried, and calcined at 400 °C for 5 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 1.26 g (NH4)2Cr2O7, adsorbed at 50 °C for 12 h, dried, and calcined at 400 °C for 5 h to obtain supported acid catalyst 10% CrO3 / MCM-41.
[0045] Example 3: Preparation of supported acidic catalyst:
[0046] 9.0 g of mesoporous molecular sieve MCM-41 was adsorbed in 4 mol / L sulfuric acid solution at 20 °C for 24 h, dried, and calcined at 600 °C for 2 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 1.71 g WCl6, adsorbed at 20 °C for 24 h, dried, and calcined at 600 °C for 2 h to obtain supported acid catalyst 10% WO3 / MCM-41.
[0047] Example 4: Preparation of supported acidic catalysts:
[0048] 9.7 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 0.56 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 3% V2O5 / MCM-41.
[0049] Example 5: Preparation of supported acidic catalyst:
[0050] 9.5 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 0.93 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 5% V2O5 / MCM-41.
[0051] Example 6: Preparation of supported acidic catalyst:
[0052] 8.5 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 2.79 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 15% V2O5 / MCM-41.
[0053] Example 7: Preparation of supported acidic catalyst:
[0054] 9.0 g of mesoporous molecular sieve SBA-15 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 1.86 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 10% V2O5 / SBA-15.
[0055] Example 8: Preparation of supported acidic catalyst:
[0056] 9.0 g of mesoporous molecular sieve MSU-X was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 1.86 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 10% V2O5 / MSU-X.
[0057] Comparative Example 1: Preparation of Supported Acidic Catalyst
[0058] 9.9 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 0.19 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 1% V2O5 / MCM-41.
[0059] Comparative Example 2: Preparation of Supported Acidic Catalysts
[0060] 8.0 g of mesoporous molecular sieve MCM-41 was adsorbed in 2 mol / L sulfuric acid solution at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain acid-modified mesoporous molecular sieve MCM-41; then it was impregnated in an aqueous solution containing 3.72 g (NH4)3VO4, adsorbed at 30 °C for 16 h, dried, and calcined at 500 °C for 3 h to obtain supported acid catalyst 20% V2O5 / MCM-41.
[0061] The specific process parameters for preparing the supported acid catalysts in Examples 1-8 and Comparative Examples 1-2 are shown in Table 1 below.
[0062] Table 1
[0063]
[0064]
[0065] Example 9: Application of supported acidic catalysts in the Diels-Alder reaction:
[0066] 340.6 g of isoprene, 151.5 g of paraformaldehyde, and 0.34 g of supported acidic catalyst 10% V2O5 / MCM-41 were added to a 1 L high-pressure reactor and reacted for 20 min at a supercritical carbon dioxide pressure of 8.0 MPa and a reaction temperature of 40 °C. The liquid product was analyzed by gas chromatography, and the conversion rate of isoprene was 99.9%, and the selectivity of 2-methyl-5,6-dihydro-2H-pyran was 99.7%.
[0067] The difference between Examples 10-16 and Example 9 is the type of catalyst. The obtained liquid products were analyzed by gas chromatography to obtain the conversion rate of isoprene and the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran. The results are shown in Table 2.
[0068] Table 2
[0069]
[0070]
[0071] Note: Molar ratio represents the molar ratio of aldehyde to conjugated diene, and mass ratio represents the mass ratio of supported acid catalyst to conjugated diene.
[0072] Data from the above examples and comparative examples show that the catalytic activity of the catalyst changes with the type of acidic metal oxide. When vanadium pentoxide is used as the acidic metal oxide, the conversion rate of isoprene is the highest, and the selectivity of the resulting 2-methyl-5,6-dihydro-2H-pyran is the best. The higher the loading of the acidic metal oxide, the higher the catalytic activity of the catalyst. However, when the loading of the acidic metal oxide exceeds 15.0 wt%, the catalytic activity of the catalyst decreases. A comparison of the data from Examples 9 and 10-16 shows that when the type of mesoporous molecular sieve is changed, there is no significant change in the conversion rate of the feedstock isoprene and the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran.
[0073] The difference between Examples 17-27 and Example 9 is that the conditions of the Diels-Alder reaction are different. The liquid products obtained are analyzed by gas chromatography to obtain the conversion rate of isoprene and the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran. The results are shown in Table 3.
[0074] Table 3
[0075]
[0076] Note: Molar ratio represents the molar ratio of aldehyde to conjugated diene, and mass ratio represents the mass ratio of supported acid catalyst to conjugated diene.
[0077] Table 3 shows that the conversion of the feedstock isoprene and the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran did not change significantly when the mass ratio of the supported acid catalyst to the conjugated diene and the supercritical pressure in the Diels-Alder reaction changed. With the increase of the molar ratio of aldehyde to conjugated diene, the conversion of the feedstock isoprene and the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran increased accordingly. It should be noted that when the molar ratio of aldehyde to conjugated diene exceeded 1.05:1, the conversion of the feedstock isoprene did not change significantly, but the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran decreased. Changes in temperature and time in the Diels-Alder reaction had little effect on the conversion of the feedstock isoprene, but the selectivity of the product 2-methyl-5,6-dihydro-2H-pyran decreased significantly when the temperature was above 70℃ or the time was less than 10 min.
[0078] The difference between Examples 28-30 and Example 9 is that the raw materials of the Diels-Alder reaction and the resulting liquid products were analyzed by gas chromatography to obtain the conversion rate of conjugated dienes and the selectivity of cyclic flavorings. The results are shown in Table 4.
[0079] Table 4
[0080]
[0081] As shown in Table 4, when 10% V2O5 / MCM-41 is used as a catalyst and the raw materials are changed in the Diels-Alder reaction, the conversion rate of conjugated dienes and the selectivity of cyclized fragrance products are both high. This catalyst has a good catalytic effect on the reaction of dienes and aldehydes.
[0082] Example 31: Application of supported acidic catalysts:
[0083] The supported acidic catalyst used in Example 9 was recovered and reused, with the same reaction conditions and operation as in Example 9. The results are shown in Table 5 below.
[0084] Table 5
[0085] Number of times to apply catalyst Temperature / °C Time / min Conversion rate / % Selectivity / % 0 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.7 1 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.8 99.6 2 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.7 3 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.8 99.6 4 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.6 5 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.8 99.7 6 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.6 7 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.5 8 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.7 99.6 9 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.9 99.6 10 <![CDATA[10%V2O5 / MCM-41]]> 40 20 99.8 99.7
[0086] As shown in Table 5, the supported acid catalyst used in this invention still exhibits high catalytic activity after 10 consecutive applications, with the conversion rate of conjugated dienes remaining above 99.7% and the product selectivity remaining above 99.5%, indicating that the catalyst has excellent stability.
[0087] The supported acidic catalysts used in Examples 10-30 were recovered and reused. Fifty batches were reused under the corresponding Diels-Alder reaction feedstocks and reaction conditions. The resulting liquid products were analyzed by gas chromatography, and the conversion rate of conjugated dienes was 99.7-99.9%, and the selectivity of cyclic fragrances was 99.5-99.7%.
[0088] As can be seen from the above embodiments, after 50 consecutive batches of use, the conversion rate of conjugated dienes and the selectivity of cyclic fragrances provided by the present invention fluctuated by ±0.2%, indicating that the supported acid catalyst provided by the present invention has excellent stability and still has high efficiency after multiple cycles of use.
[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for synthesizing a cyclized flavoring agent, characterized in that, include: In the presence of a supported acidic catalyst, conjugated dienes and aldehydes undergo a Diels-Alder reaction in a supercritical carbon dioxide solvent to yield cyclized fragrances; The supported acid catalyst includes a support and an active component; The carrier is an acid-modified mesoporous molecular sieve; the preparation method of the acid-modified mesoporous molecular sieve is as follows: after adding the mesoporous molecular sieve to an acidic solution for adsorption, it is dried and calcined to obtain the acid-modified mesoporous molecular sieve. The acidic solution is a 2-4 mol / L sulfuric acid solution; The active component is an acidic metal oxide, and the loading of the acidic metal oxide is 3.0 wt%-15.0 wt%. The mesoporous molecular sieve is either MCM-41 or SBA-15; The acidic metal oxide is any one of vanadium pentoxide, chromium trioxide, or tungsten trioxide.
2. The method for synthesizing cyclic flavorings according to claim 1, characterized in that, The preparation process of the supported acidic catalyst includes the following steps: (1) After the mesoporous molecular sieve is added to an acidic solution for adsorption, it is dried and calcined to obtain an acid-modified mesoporous molecular sieve. (2) The acid-modified mesoporous molecular sieve is impregnated in a soluble salt solution of the active component for adsorption, and then dried and calcined to obtain a supported acid catalyst.
3. The method for synthesizing cyclic flavorings according to claim 2, characterized in that, The adsorption temperature in step (1) is 20-50℃ and the adsorption time is 12-24h. The calcination temperature is 400-600℃ and the calcination time is 2-5h.
4. The method for synthesizing cyclic flavorings according to claim 2, characterized in that, The adsorption temperature in step (2) is 20-50℃, the adsorption time is 12-24h, the calcination temperature is 400-600℃, and the calcination time is 2-5h. The soluble salt is either an ammonium salt or a chloride.
5. The method for synthesizing cyclic flavorings according to claim 1, characterized in that, The molar ratio of the aldehyde to the conjugated diene is 0.95-1.05:1; The mass ratio of the supported acidic catalyst to the conjugated diene is 0.05%-0.5%:
1.
6. The method for synthesizing cyclic flavorings according to claim 1, characterized in that, The Diels-Alder reaction time is 10-30 min; The supercritical pressure is 7.5-10 MPa and the temperature is 35-50℃.
7. The method for synthesizing cyclic flavorings according to claim 1, characterized in that, After the reaction is complete, the supported acidic catalyst is filtered and separated for reuse.