A method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran
By using ZSM5 molecular sieve catalyst in a continuous reactor and optimizing reaction conditions, the problems of catalyst stability and high cost in existing technologies were solved, achieving efficient and low-cost TMTHF synthesis and improving conversion rate and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI XUENTIAN TECHNOLOGY CO LTD
- Filing Date
- 2023-11-30
- Publication Date
- 2026-06-02
AI Technical Summary
In the existing technology, the synthesis of 2,2,5,5-tetramethyltetrahydrofuran (TMTHF) using Nafion-H as a catalyst has problems such as excessive acidity, poor stability, low reusability and high cost. In addition, the contact time and area between the raw material and the catalyst in the batch reactor are limited, resulting in low conversion rate.
Using ZSM5 molecular sieve as a solid acid catalyst, the continuous synthesis reaction of 2,5-dimethyl-2,5-hexanediol was carried out in a continuous reactor, especially a fixed-bed reactor. By optimizing reaction conditions such as temperature, space velocity, pressure and carrier gas flow rate, the efficient production of TMTHF was achieved.
This method achieves high-yield and low-cost TMTHF synthesis, improves production efficiency, reduces waste generation, lowers production costs, and demonstrates superior stability and renewability compared to other catalysts using ZSM5 molecular sieves.
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Figure CN117777065B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of chemical synthesis, and more specifically, to a method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran. Background Technology
[0002]
[0003] 2,2,5,5-Tetramethyltetrahydrofuran, CAS No.: 15045-43-0, abbreviated as TMTHF, is a colorless liquid with a freezing point of -92℃, a boiling point of 112℃, a relative density of 0.811 g / mL (25℃), a refractive index of 1.409, and a flash point of 39℉.
[0004] Toluene is an important solvent in the chemical industry, but its odor and toxicity cause obvious pollution and hazards during use. Research by Fergal P. Byrne et al. (Journal of Cleaner Production, Volume 240, 2019, 118-175) shows that 2,2,5,5-tetramethyltetrahydrofuran has similar characteristics to toluene, such as low polarity and low boiling point, and is more environmentally friendly and cleaner, making it a promising alternative to solvents like toluene.
[0005] Regarding the synthesis of TMTHF, according to the literature, Denney et al.'s method (J. Org. Chem. 1984, 49, p. 2831) uses DCM as a solvent to react 2,5-dimethyl-2,5-hexanediol with the catalyst pentaethoxyphosphine; Vlad et al.'s method (Synthesis 1983, p. 216) uses benzene as a solvent to react 2,5-dimethyl-2,5-hexanediol with the catalyst trimethylchlorosilane; Gillis et al.'s method (J. Org. Chem. 1963, 28, p. 1388) uses DMSO as both a solvent and a catalyst to react with 2,5-dimethyl-2,5-hexanediol.
[0006] Regarding the synthesis of TMTHF using solid acid catalysts, the method of Olah et al. (Synthesis 1981, p. 474) uses Nafion-H as a catalyst in the reaction with 2,5-dimethyl-2,5-hexanediol. Nafion-H, also known as perfluorosulfonic acid resin, is currently the strongest known solid superacid. In this reaction, compared to molecular sieve catalysts, its acidity is too strong, its stability is poor, its regeneration ability is poor, its reusability is low, and its cost is also higher. To optimize these problems, research has been conducted on molecular sieve catalysts for this reaction. Molecular sieve catalysts, also known as zeolite catalysts, are widely used in chemical synthesis due to their unique structure, excellent renewability, and low cost. H-type molecular sieves have also become widely used solid acid catalysts.
[0007] The study by Fergal B et al. (Green Chemistry, 2017, 19(15)) showed that HBEA from β-zeolite was the most effective in the synthesis of TMTHF from 2,5-dimethyl-2,5-hexanediol. CN 109790134 A also indicated that the yield of TMTHF could reach more than 95% by using β-zeolite HBEA-25 and HCZB-25, while the yield using ZSM5-80 was only 28%. All of the above reactions are batch reactions. This application aims to use the more widely used and lower-cost ZSM5 molecular sieve in a continuous reactor to achieve a higher yield of TMTHF and improve production efficiency. Summary of the Invention
[0008] Technical issues
[0009] This application provides a method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran. The method involves reacting a raw material in a continuous reactor in the presence of a catalyst. The raw material is 2,5-dimethyl-2,5-hexanediol, and the catalyst is a solid acid catalyst, preferably a ZSM5 molecular sieve. The continuous reactor is preferably a fixed-bed reactor.
[0010] Technical solution
[0011] A method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran involves reacting the starting material 2,5-dimethyl-2,5-hexanediol in a continuous reactor in the presence of a catalyst to obtain 2,2,5,5-tetramethyltetrahydrofuran. The catalyst is a solid acid catalyst, and the reaction formula is as follows:
[0012]
[0013] Furthermore, the solid acid catalyst is selected from one or more of activated carbon, ion exchange resin, γ-Al2O3, SiO2, ZrO2, CeO2, WO3, Nb2O5, and zeolite molecular sieves;
[0014] The zeolite molecules were selected from one or more of ZSM5, HY, and β zeolite.
[0015] The preferred molecular sieve is ZSM5, with a Si / Al ratio of 25:1-500:1, preferably 25:1-100:1.
[0016] Furthermore, the continuous reactor is selected from any one of the following reactors: continuous stirred tank reactor, plug flow reactor, fixed bed reactor, and fluidized bed reactor, or a mixed reactor consisting of two or more of these reactors connected together, preferably a fixed bed reactor.
[0017] The method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran specifically includes the following steps:
[0018] (1) Add a solid acid catalyst to the reactor and heat it to the reaction temperature under an inert gas atmosphere;
[0019] (2) After the temperature stabilizes, liquid 2,5-dimethyl-2,5-hexanediol is introduced into the reactor to carry out the reaction.
[0020] Furthermore, the reaction temperature in step (1) is in the range of 50-250°C, preferably 100-200°C;
[0021] Furthermore, the inert gas in step (1) is one or more of nitrogen atmosphere, helium atmosphere and argon atmosphere.
[0022] Furthermore, in step (2), the space velocity of 2,5-dimethyl-2,5-hexanediol is in the range of 0.02-3.00 h⁻¹. -1 Preferably, it is 0.05-0.80h. -1 ;
[0023] Furthermore, the reaction in step (2) is carried out at atmospheric pressure -2 MPa, preferably atmospheric pressure -0.5 MPa.
[0024] Furthermore, in step (2), the reaction carrier gas flow rate is 5-80 mL / min, preferably 10-50 mL / min.
[0025] Further, in step (2), the raw material 2,5-dimethyl-2,5-hexanediol is reacted in the presence of a solvent or in the presence of a solvent, wherein the solvent is one or more of tetrahydrofuran, 1,4-dioxane, and acetonitrile, preferably tetrahydrofuran or 1,4-dioxane.
[0026] Beneficial effects
[0027] 1. The synthesis method of this application can achieve a very high yield of the product by adjusting the reaction conditions (reaction temperature, space velocity, pressure, carrier gas flow rate, etc.).
[0028] 2. The synthesis method of this application can achieve continuous reaction.
[0029] 3. A reaction temperature above 90℃ is more suitable for fixed-bed reactions, which is beneficial to production efficiency.
[0030] 4. The method described in this application can use ZSM5 molecular sieve, which is more widely used and less expensive than β zeolite, to synthesize 2,2,5,5-tetramethyltetrahydrofuran (TMTHF) in a continuous reaction with yields comparable to or even higher than those using β zeolite. This method is less expensive, more efficient, has higher yields, and is more environmentally friendly. Attached Figure Description
[0031] Figure 1 The graph shows the reaction results after 500 hours of continuous reaction under optimal conditions. The optimal reaction conditions are: 10g of 20-40 mesh ZSM5 molecular sieve catalyst, molten 2,5-dimethyl-2,5-hexanediol, atmospheric pressure, nitrogen gas at 20 mL / min, reaction temperature at 110℃, and space velocity at 0.120 h⁻¹. -1 The reaction is a continuous process in a fixed-bed reactor. In the figure: Con.: conversion of 2,5-dimethyl-2,5-hexanediol; Sel.-TMTHF: selectivity for 2,2,5,5-tetramethyltetrahydrofuran.
[0032] Figure 2 This is a schematic diagram of a continuous reaction fixed-bed reactor.
[0033] Figure 3 This is a schematic diagram of a batch reactor. Detailed Implementation
[0034] In the method for synthesizing 2,2,5,5-tetramethyltetrahydrofuran according to this application, 2,5-dimethyl-2,5-hexanediol is used as a starting material, and the product is obtained through a dehydration reaction. The product is analyzed and detected using gas chromatography (GC). Qualitative analysis of the low-boiling-point product is performed by GC-MS and comparison with the GC retention time of a standard, confirming that the starting material involved in the reaction is 2,5-dimethyl-2,5-hexanediol. Quantitative determination of the low-boiling-point substance is performed using a Shimadzu-GC 2020 gas chromatograph, and quantitative analysis is performed by comparing the retention time with that of a standard and the peak area. The relevant calculation formulas are as follows:
[0035]
[0036]
[0037] Yield of 2,2,5,5-tetramethyltetrahydrofuran
[0038] =Conversion of 2,5-dimethyl-2,5-hexanediol *Selectivity of 2,2,5,5-tetramethyltetrahydrofuran
[0039]
[0040]
[0041] The flow rate of 2,5-dimethyl-2,5-hexanediol is expressed in g / min, and the amount of catalyst is expressed in g.
[0042] The preferred catalyst used in this method is ZSM5 molecular sieve. ZSM5 molecular sieves are widely used in chemical synthesis due to their low cost. The acidity of ZSM5 molecular sieves varies depending on the Si / Al ratio; a higher Si / Al ratio results in weaker acidity and slower deactivation. The Si / Al ratio can be flexibly selected according to production needs to match suitable reaction conditions. Furthermore, ZSM5 molecular sieves exhibit high stability and slow deactivation. Deactivation can be resolved through catalyst regeneration via calcination, resulting in high reusability and further reducing production costs. The following examples demonstrate its excellent stability and regenerability; the reaction conversion rate increases with catalyst usage time. The conversion rate began to decline after about 350 hours, with no significant change in product selectivity. When the conversion rate dropped below 90%, calcination regeneration was performed. The calcination conditions were 550℃, air flow rate 200 mL / min, and calcination for 5 hours. After calcination regeneration, the catalyst activity recovered to a level similar to that of fresh catalyst. Experimental results show that not all solid catalysts can catalyze this reaction. As can be seen in the examples below, the reaction using γ-Al₂O₃ did not proceed towards the formation of the target product. However, using acidic molecular sieves of the same type as ZSM5, such as β-zeolite and Y-type molecular sieves, achieved comparable results to ZSM5. The advantage of ZSM5 lies in its wide applicability and lower cost.
[0043] This method utilizes a continuous reactor, preferably a fixed-bed reactor. Traditional batch reactors involve a large amount of feedstock and a small amount of catalyst in contact, thus limiting the contact time and area between the feedstock and catalyst, resulting in insufficient catalyst to improve feedstock conversion. This method, using a fixed-bed reactor, allows for continuous feed and discharge. The contact time between the feedstock and catalyst can be flexibly adjusted by changing the space velocity of the feedstock entering the fixed bed, allowing a small amount of feedstock to contact a large amount of catalyst, thereby improving feedstock conversion. Furthermore, a certain amount of catalyst can be reused for extended periods and regenerated within the fixed bed, reducing production and labor costs, minimizing waste generation, and making it more environmentally friendly. The continuous production mode of the continuous reactor improves production efficiency. Experimental results show that the reaction yields better results in a continuous reactor than in a batch reactor, as illustrated in the following examples.
[0044] The raw material, 2,5-dimethyl-2,5-hexanediol, is a white crystalline solid at room temperature with a melting point of 86-88℃. A reaction temperature above 90℃ allows the reaction to proceed as a liquid-solid phase reaction, making it more suitable for fixed-bed reactions. The reaction can be carried out with or without a solvent. The raw material can be dissolved in a solvent before being introduced into the fixed-bed reaction, or it can be preheated to 90℃ before being introduced into the fixed-bed reaction. The choice can be flexibly adjusted according to actual production needs.
[0045] CN109790134A clearly states that using β-zeolite can achieve a TMTHF yield of over 95%, while using ZSM5 results in a very low yield of only 28%. Considering these advantages, the method described in this application can utilize ZSM5 molecular sieves, which are more widely used and less expensive than β-zeolite, to achieve a yield comparable to or even higher than that using β-zeolite in a continuous reaction to synthesize 2,2,5,5-tetramethyltetrahydrofuran (TMTHF). This method offers lower cost, higher production efficiency, greater yield, and is more environmentally friendly.
[0046] Example
[0047] 2,2,5,5-Tetramethyltetrahydrofuran is prepared by the following steps:
[0048] Continuous reaction: 10g of 20-40 mesh catalyst is added to a fixed-bed reactor. The temperature is raised to the reaction temperature under N2 atmosphere. After the temperature stabilizes, molten 2,5-dimethyl-2,5-hexanediol or 2,5-dimethyl-2,5-hexanediol dissolved in a solvent is introduced into the fixed-bed reactor at a certain space velocity under a certain pressure to carry out the reaction. If a solvent is used for dissolution, the solvent is preferably tetrahydrofuran and 1,4-dioxane. The mass concentration of 2,5-dimethyl-2,5-hexanediol is (10±5)%.
[0049] Batch reaction: Install a spherical condenser above a three-necked flask, with a condensation temperature of 0-5℃. Add a certain mass of solid 2,5-dimethyl-2,5-hexanediol to the flask and heat it to melt it. When all the raw materials have become molten, add a certain mass of catalyst powder, heat to the reaction temperature, and stir the reaction for 5 hours.
[0050] The reaction results under different reaction conditions are shown in Table 1.
[0051] Table 1. Reaction results using different catalysts and reaction conditions
[0052]
[0053]
[0054] In Table 1, rows 2 and 3 compare batch reactions using β-zeolite and ZSM5 molecular sieves under the conditions described in CN109790134A; rows 4-9 compare continuous and batch reactions using ZSM5 molecular sieves under different raw material forms, pressures, carrier gas flow rates, reaction temperatures, and space velocities. It can be seen that the yield under continuous reaction conditions is significantly better than that under batch reaction conditions.
[0055] The rows in Table 1 numbered 10-13 compare the continuous and batch reactions using β-zeolite and HY molecular sieves, showing that the yield of the continuous reaction is better than that of the batch reaction. In addition, it can be seen that the yield of the continuous reaction using ZSM5 molecular sieve is better than that of β-zeolite and HY under the same conditions.
[0056] Table 1, rows 14-16, compares the continuous reactions using γ-Al₂O₃, A35, and A15. It also shows that under the same conditions, the yield using ZSM5 molecular sieve is superior to that of γ-Al₂O₃, A35, and A15 in the continuous reaction. In conclusion, the method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran described in this application is significantly superior to the batch reaction.
[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran, characterized in that, The raw material 2,5-dimethyl-2,5-hexanediol and a catalyst are reacted in a continuous reactor to obtain 2,2,5,5-tetramethyltetrahydrofuran. The catalyst is a solid acid catalyst, and the reaction formula is as follows: ； The solid acid catalyst is a zeolite molecular sieve selected from ZSM5 and HY, wherein the Si / Al value of the ZSM5 molecular sieve is 25:1-500:
1. The method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran specifically includes the following steps: (1) Add a solid acid catalyst to the reactor and heat it to the reaction temperature under an inert gas atmosphere; (2) After the temperature stabilizes, liquid 2,5-dimethyl-2,5-hexanediol is introduced into the reactor to carry out the reaction; The continuous reactor is selected from any one of the following reactors: continuous stirred tank reactor, plug flow reactor, fixed bed reactor, and fluidized bed reactor; or a mixed reactor consisting of two or more of these reactors connected together is a continuous reactor. In step (2), the space velocity of 2,5-dimethyl-2,5-hexanediol is in the range of 0.02-3.00 h⁻¹. -1 .
2. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The solid acid catalyst is a ZSM5 molecular sieve with a Si / Al ratio of 25:1-100:
1.
3. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The continuous reactor is a fixed-bed reactor.
4. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The reaction temperature in step (1) is in the range of 50-250℃.
5. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The reaction temperature in step (1) is in the range of 100-200℃.
6. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, In step (1), the inert gas is one or more of nitrogen atmosphere, helium atmosphere and argon atmosphere.
7. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, In step (2), the space velocity of 2,5-dimethyl-2,5-hexanediol is in the range of 0.05-0.80 h⁻¹. -1 .
8. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The reaction in step (2) is carried out at atmospheric pressure -2 MPa.
9. A method for the continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, The reaction in step (2) is carried out at a reaction pressure of atmospheric pressure -0.5 MPa.
10. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, In step (2), the reaction carrier gas flow rate is 5-80 mL / min.
11. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, In step (2), the reaction carrier gas flow rate is 10-50 mL / min.
12. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 1, characterized in that, In step (2), the raw material 2,5-dimethyl-2,5-hexanediol is reacted in the presence of a solvent or in the presence of a solvent, wherein the solvent is one or more of tetrahydrofuran, 1,4-dioxane, and acetonitrile.
13. The method for continuous synthesis of 2,2,5,5-tetramethyltetrahydrofuran according to claim 12, characterized in that, The solvent is tetrahydrofuran or 1,4-dioxane.