Tetrahydrofuran and a process for its preparation

Abstract

The present application relates to a kind of tetrahydrofuran and its preparation method, belong to synthetic technical field.The purity of tetrahydrofuran is ≥99.990%, does not contain succinic anhydride and methyl tetrahydrofuran, and the rest is impurity;Impurity includes γ-butyrolactone, content ≤0.009%, 1,4-butanediol, content ≤0.004%.Its preparation includes the following steps: maleic anhydride solution and hydrogen are introduced into the reactor loaded with supported catalyst to carry out reaction, then after separation and purification, tetrahydrofuran is obtained;Wherein the preparation of catalyst includes the following steps: S1, to pitch and molybdenum disulfide are heat treated, and porous carbon / molybdenum disulfide carrier is obtained;S2, nickel precursor and hydrophobic compound are dispersed in water, and mixed solution is obtained;The structural formula of hydrophobic compound is n ≥6;S3, porous carbon / molybdenum disulfide carrier is immersed in mixed solution, after aging, drying and heat reduction treatment, supported catalyst is obtained, and the final goal that product purity can reach 99.99% or more is achieved.

Description

Technical Field

[0001] This invention belongs to the field of synthetic technology, and particularly relates to a tetrahydrofuran and its preparation method. Background Technology

[0002] Tetrahydrofuran (THF) is a heterocyclic organic compound with good chemical stability and solubility. It is an important raw material for organic and fine chemicals and is widely used in various organic and polymerization reactions, especially in the fields of pharmaceuticals, chemicals and daily chemical products.

[0003] Currently, the main methods for synthesizing tetrahydrofuran include the furfural method, the 1,4-butanediol dehydration method, and the maleic anhydride hydrogenation method. The furfural method involves the decarbonylation reaction of furfural to separate furan, which is then purified by hydrogenation to prepare tetrahydrofuran; however, this process is relatively complex. The 1,4-butanediol dehydration method involves the dehydration of 1,4-butanediol under acidic or alkaline catalytic conditions to form a ring, followed by separation to obtain tetrahydrofuran. This method is the most commonly used industrial method for producing tetrahydrofuran, as it is simple and has a high yield. However, this method typically uses strong acids such as concentrated sulfuric acid and phosphoric acid as catalysts, which can cause equipment corrosion. Furthermore, because 1,4-butanediol contains methylbutanediol, the dehydrated tetrahydrofuran will contain methyltetrahydrofuran impurities, resulting in higher separation costs. The maleic anhydride hydrogenation method involves hydrogenating maleic anhydride and its derivatives to prepare a mixture of succinic anhydride, tetrahydrofuran, γ-butyrolactone, and 1,4-butanediol, followed by distillation to separate the remaining components and prepare tetrahydrofuran. The advantage of this technology is that it can simultaneously produce succinic anhydride, tetrahydrofuran, γ-butyrolactone, and 1,4-butanediol, depending on the specific process conditions. The main disadvantages are the large number of hydrogenation byproducts, high separation costs, and the acidic reaction system of maleic anhydride hydrogenation. Generally, acid-sensitive systems can lead to poisoning of the active sites, making long-term production impossible.

[0004] Therefore, the directional and highly selective hydrogenation of maleic anhydride is a novel process for preparing tetrahydrofuran with high purity and no methyltetrahydrofuran, which has significant industrial production value. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a tetrahydrofuran and its preparation method. A high-strength molybdenum disulfide / porous carbon support is used, which avoids the loss of non-precious metal nickel and copper catalytic centers into the product under pressurized hydrogenation conditions, thus preventing a gradual decrease in catalyst activity and ensuring long-cycle production. Furthermore, the hydrophobic compound allows for rapid desorption of the hydrogenated product from the catalyst surface. The degree of hydrogenation of maleic anhydride C=C and its two C=O bonds can be controlled by adjusting the reaction pressure and temperature, thereby obtaining the target product.

[0006] The first objective of this invention is to provide a tetrahydrofuran having a purity ≥99.990%, free from succinic anhydride and methyltetrahydrofuran, with the remainder being impurities; the impurities include γ-butyrolactone, with a content ≤0.009%, and 1,4-butanediol, with a content ≤0.004%.

[0007] The second objective of this invention is to provide a method for preparing tetrahydrofuran, wherein maleic anhydride solution and hydrogen are introduced into a reactor containing a supported catalyst to react, and then tetrahydrofuran is obtained by separation and purification.

[0008] The preparation method of the supported catalyst includes the following steps:

[0009] S1. Heat treatment of asphalt and molybdenum disulfide yields a porous carbon / molybdenum disulfide support.

[0010] S2. Disperse the nickel precursor and the hydrophobic compound in water to obtain a mixed solution; the structural formula of the hydrophobic compound is as follows: n≥6;

[0011] S3. The porous carbon / molybdenum disulfide support described in S1 is impregnated in the mixed solution described in S2, and then aged, dried and thermally reduced to obtain the supported catalyst.

[0012] In one embodiment of the present invention, in S1, the mass ratio of the asphalt to molybdenum disulfide is 1:5-5:1; the molybdenum disulfide has a 5-20 layer nanosheet structure.

[0013] In one embodiment of the present invention, in S1, the heat treatment is performed by heating at 200°C-400°C for 3-8 hours in an oxygen atmosphere.

[0014] In one embodiment of the present invention, in S2, the nickel precursor is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate, basic nickel carbonate, nickel acetylacetone, nickel oxalate, nickel acetate, nickel citrate, nickel hypophosphite, nickel phosphate, and nickel formate.

[0015] In one embodiment of the present invention, in S3, the aging temperature is 50℃-80℃ and the time is 12h-16h; the drying temperature is 100℃-150℃ and the time is 10h-14h; the thermal reduction treatment is carried out in a hydrogen atmosphere, with the temperature increased to 160℃-200℃ at a rate of 10℃ / h-20℃ / h, and the reduction is carried out for 6h-10h.

[0016] In one embodiment of the present invention, the supported catalyst has a nickel loading of 30wt%-60wt% and a hydrophobic compound loading of 0.01wt%-0.2wt%; the porous carbon / molybdenum disulfide support has a pore volume of 0.2mL / g-0.7mL / g, a particle size of 3mm-5mm, and a bulk density of 750kg / m³. 3 -1100kg / m 3 The clusters have a length of 80nm-150nm, a width of 30nm-100nm, and a thickness of 10nm-30nm; the clusters are active centers composed of nickel, copper, and hydrophobic compounds supported on porous carbon / molybdenum disulfide supports.

[0017] In one embodiment of the present invention, the maleic anhydride solution has a mass fraction of 5wt%-30wt%; the solvent of the maleic anhydride solution is selected from one or more of tetrahydrofuran, γ-butyrolactone, diethyl ether, ethyl acetate, ethyl formate and methyl acetate; preferably, the solvent of the maleic anhydride solution is selected from tetrahydrofuran and / or γ-butyrolactone.

[0018] In one embodiment of the present invention, the reaction pressure is 5 MPa-15 MPa, the temperature is 120°C-200°C, and the space velocity is 0.6 hr. -1 -6.0hr -1 .

[0019] Preferably, the reaction pressure is 6MPa-10MPa and the temperature is 130℃-180℃.

[0020] In one embodiment of the present invention, the flow rate ratio of the maleic anhydride solution to hydrogen is (0.1-5):(0.1-100).

[0021] The porous carbon / molybdenum disulfide support of this invention, due to the layered structure of molybdenum disulfide, allows the asphalt to extend along the layered voids during high-temperature treatment. Subsequently, under certain temperatures, processes such as dehydration and removal of organic matter result in a layered carbon structure that firmly bonds with molybdenum disulfide, creating numerous porous channels that facilitate the dispersion of active metal components. Simultaneously, this composite support structure naturally possesses high mechanical strength, easily achieving a particle strength of ≥450 N / cm, which is difficult to achieve with traditional alumina particles; the mechanical strength of commercial catalyst support alumina particles typically reaches 100 N / cm.

[0022] The technical solution of the present invention has the following advantages compared with the prior art:

[0023] (1) The supported catalyst described in this invention has a strength of over 450 N / cm, and the metal is not easily lost during the reaction, which plays a key role in the synthesis of high-purity tetrahydrofuran.

[0024] (2) The supported catalyst described in this invention uses porous carbon / molybdenum disulfide as a support. The porous carbon / molybdenum disulfide support has a certain hydrogenation activity, which can promote the improvement of reaction activity, thereby reducing the reaction temperature, improving the reaction selectivity, and thus improving the purity of the product.

[0025] (3) The supported catalyst described in this invention uses hydrophobic compounds as additives, which can enable the product tetrahydrofuran to desorb from the surface of the supported catalyst as soon as possible. On the one hand, it can accelerate the reaction rate, and on the other hand, it can avoid further reaction of the product on the catalyst surface, thereby achieving the final goal of product purity of more than 99.99% and without impurities such as methyltetrahydrofuran. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0027] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0030] In this invention, unless otherwise stated, the molybdenum disulfide used in the embodiments of this invention is a 5-20 layer nanosheet structure.

[0031] Example 1

[0032] The tetrahydrofuran and its preparation method in this embodiment specifically include the following steps:

[0033] S1. Preparation of supported catalysts

[0034] S11. Preparation of porous carbon / molybdenum disulfide carrier: Asphalt and molybdenum disulfide were mixed at a mass ratio of 1:1 and heat-treated at 300℃ for 4 hours under oxygen conditions to obtain a pore volume of 0.5 mL / g, a particle size of 5 mm, and a bulk density of 850 kg / m³. 3 Porous carbon / molybdenum disulfide support;

[0035] S12. Preparation of mixed solution: Weigh 50.00g of basic nickel carbonate, 159.5mL of 5mol / L dilute nitric acid solution, 0.30g of sodium dodecyl sulfonate and 500.00g of deionized water, and stir at 45℃ until all solids are dissolved to obtain a mixed solution.

[0036] S13. Preparation of supported catalyst: A porous carbon / molybdenum disulfide support was impregnated in a mixed solution. Under stirring, it was first aged at 60°C for 14 h, then dried at 120°C for 12 h, and finally packed into a tube. The temperature was increased to 200°C for 6 h under hydrogen conditions at a heating rate of 20°C / h to obtain a supported catalyst with a cluster length of about 125 nm, a width of about 67 nm, and a thickness of about 27 nm.

[0037] Preparation of S2 and tetrahydrofuran

[0038] S21. Preparation of maleic anhydride solution: Dissolve maleic anhydride in tetrahydrofuran to obtain a maleic anhydride solution with a mass fraction of 5 wt%.

[0039] S22. Preparation of tetrahydrofuran: Maleic anhydride solution and hydrogen gas were mixed at flow rates of 0.5 mL / min and 200 mL / min, respectively, and continuously fed into a 50 mL hydrogenation tubular reactor containing a supported catalyst. The reaction was carried out at a temperature of 145 °C, a pressure of 6.8 MPa (A), and a space velocity of 0.6 hr. -1 Then, the product is continuously fed into a distillation column for separation and purification to obtain the product.

[0040] Example 2

[0041] The process is basically the same as in Example 1, except that in the preparation of the supported catalyst, basic nickel carbonate is replaced with nickel nitrate.

[0042] Example 3

[0043] The process is basically the same as in Example 1, except that in the preparation of tetrahydrofuran, the 5 wt% maleic anhydride solution is replaced with a 10 wt% maleic anhydride solution.

[0044] Example 4

[0045] The process is basically the same as in Example 1, except that in the preparation of tetrahydrofuran, the solvent tetrahydrofuran in the maleic anhydride solution is replaced with the solvent γ-butyrolactone.

[0046] Comparative Example 1

[0047] The process is basically the same as in Example 1, except that sodium dodecyl sulfonate is not added during the preparation of the supported catalyst.

[0048] Comparative Example 2

[0049] The process is basically the same as in Example 1, except that molybdenum disulfide is not added during the preparation of the supported catalyst.

[0050] Test Example 1

[0051] The supported catalysts of Examples 1-4 and Comparative Example 2 were tested for strength according to the HG / T 2782 standard, and the results are shown in Table 1:

[0052] Table 1

[0053] Sample Strength (N / cm) Example 1 453.8 Example 2 455.2 Example 3 453.8 Example 4 453.8 Comparative Example 2 200.2

[0054] As can be seen from Table 1, the strength of the supported catalyst prepared in the examples exceeds 450 N / cm. By combining high-strength molybdenum disulfide with porous carbon, the strength of the supported catalyst can be greatly improved.

[0055] Test Example 2

[0056] The purity and impurity content of the products from Examples 1-4 and Comparative Examples 1-2 were tested by gas chromatography. The gas chromatography column was HP-5 (30m × 320μm × 0.25μm), with an FID detector. The column temperature conditions were: initial temperature 60℃, first-order termination temperature 90℃, heating rate 15℃ / min, hold for 2 min, second-order termination temperature 230℃, heating rate 10℃ / min, injection port temperature 260℃, split ratio 100:1, injection volume 0.2μL, hydrogen flow rate 30mL / min, and nitrogen flow rate 25mL / min. Standard curves for maleic anhydride, succinic anhydride, methyltetrahydrofuran, tetrahydrofuran, γ-butyrolactone, and 1,4-butanediol were established using acetone as solvent. The results of the maleic anhydride conversion (%) and tetrahydrofuran selectivity (%) after 1000h of continuous hydrogenation experiments are shown in Table 2.

[0057] Table 2

[0058]

[0059]

[0060] As can be seen from Table 2, the method of the present invention can prepare high-purity tetrahydrofuran.

[0061] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing tetrahydrofuran, characterized in that, A maleic anhydride solution and hydrogen gas are introduced into a reactor containing a supported catalyst to carry out the reaction, and then tetrahydrofuran is obtained by separation and purification. The preparation method of the supported catalyst includes the following steps: S1. Heat treatment of asphalt and molybdenum disulfide yields a porous carbon / molybdenum disulfide support. S2. Disperse the nickel precursor and the hydrophobic compound in water to obtain a mixed solution; the hydrophobic compound is sodium dodecyl sulfonate; S3. The porous carbon / molybdenum disulfide support described in S1 is impregnated in the mixed solution described in S2, and then aged, dried and thermally reduced to obtain the supported catalyst.

2. The method for preparing tetrahydrofuran according to claim 1, characterized in that, In S1, the mass ratio of the asphalt to molybdenum disulfide is 1:5-5:1; the molybdenum disulfide has a 5-20 layer nanosheet structure.

3. The method for preparing tetrahydrofuran according to claim 1, characterized in that, In S1, the heat treatment is performed by heating at 200°C-400°C for 3-8 hours in an oxygen atmosphere.

4. The method for preparing tetrahydrofuran according to claim 1, characterized in that, In S2, the nickel precursor is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate, basic nickel carbonate, nickel acetylacetone, nickel oxalate, nickel acetate, nickel citrate, nickel hypophosphite, nickel phosphate, and nickel formate.

5. The method for preparing tetrahydrofuran according to claim 1, characterized in that, In S3, the aging temperature is 50℃-80℃ and the time is 12h-16h; the drying temperature is 100℃-150℃ and the time is 10h-14h; the thermal reduction treatment is carried out in a hydrogen atmosphere, with the temperature increased to 160℃-200℃ at a rate of 10℃ / h-20℃ / h, and the reduction is carried out for 6h-10h.

6. The method for preparing tetrahydrofuran according to claim 1, characterized in that, The supported catalyst has a nickel loading of 30wt%-60wt% and a hydrophobic compound loading of 0.01wt%-0.2wt%; the porous carbon / molybdenum disulfide support has a pore volume of 0.2mL / g-0.7mL / g, a particle size of 3mm-5mm, and a bulk density of 750kg / m³. 3 -1100kg / m 3 The clusters have a length of 80nm-150nm, a width of 30nm-100nm, and a thickness of 10nm-30nm.

7. The method for preparing tetrahydrofuran according to claim 1, characterized in that, The maleic anhydride solution has a mass fraction of 5wt%-30wt%; the solvent of the maleic anhydride solution is selected from one or more of tetrahydrofuran, γ-butyrolactone, diethyl ether, ethyl acetate, ethyl formate and methyl acetate.

8. The method for preparing tetrahydrofuran according to claim 1, characterized in that, The reaction was carried out at a pressure of 5-15 MPa, a temperature of 120-200°C, and a space velocity of 0.6 hr. -1 -6.0hr -1 .

9. The method for preparing tetrahydrofuran according to claim 1, characterized in that, The flow rate ratio of the maleic anhydride solution to hydrogen is (0.1-5):(0.1-100).

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