A composite purification method for improving the light transmittance of coal-based tetrahydrofuran HPLC grade and simultaneously removing peroxides

Abstract

The application provides a composite purification method for improving the light transmittance of coal-based tetrahydrofuran HPLC grade and simultaneously removing peroxides, and belongs to the field of tetrahydrofuran purification; the method comprises the steps of catalytic reduction pretreatment, composite refining, azeotropic rectification, and ultrafiltration and sterile filling; in the catalytic reduction pretreatment step, an organic phosphorus reducing agent or a metal catalyst is added to coal-based crude tetrahydrofuran raw materials, and a circulating reaction is carried out under a nitrogen atmosphere, the pressure is 0.1-0.3 MPa, the temperature is 30-50 DEG C, the single circulating reaction time is 0.5-1.0 h, the number of cycles is 3-5 times, and a pretreated raw material is obtained; the product obtained by using the purification method has low peroxide content, high light transmittance, and meets the HPLC grade standard.

Description

Technical Field

[0001] This invention belongs to the field of tetrahydrofuran purification, specifically relating to a composite purification method that improves the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removes peroxides. Background Technology

[0002] Tetrahydrofuran (THF) is an important polar aprotic solvent, widely used in polymer synthesis, pharmaceutical intermediate production, and chromatographic analysis. With the development of the coal chemical industry, the production of THF using coal-based routes such as the calcium carbide acetylene method or maleic anhydride hydrogenation method has become an important source. However, compared with petroleum-based routes, coal-based THF feedstocks often contain a more complex impurity profile, including trace amounts of unsaturated aldehydes and ketones, conjugated dienes, sulfur-containing compounds, and peroxides generated during storage or production.

[0003] For HPLC-grade solvents, the core indicators are not only chemical purity (usually required to be ≥99.9%), but more importantly, optical performance, namely ultraviolet transmittance (absorbance) at low wavelengths (such as 200 nm, 210 nm, 254 nm). Even at the ppb level, trace conjugated impurities (such as furan derivatives and unsaturated aldehydes) remaining in coal-based THF can significantly reduce transmittance at low wavelengths, resulting in high baseline noise and numerous ghost peaks in the chromatogram, which seriously affects the accuracy of the analytical results.

[0004] In addition, THF readily generates explosive peroxides (such as 2-hydroperoxytetrahydrofuran) under the influence of light and oxygen; traditional purification methods usually employ "alkali treatment + distillation" or "single adsorbent treatment"; However, simple distillation is difficult to completely remove conjugated impurities with boiling points close to THF and cannot effectively destroy peroxides; although adsorption with ordinary activated carbon can remove some colored impurities, its effect on removing peroxides is limited and it is easy to introduce new particulate contamination; although treatment with reducing agents (such as sulfites) can remove peroxides, it will introduce inorganic ions, requiring subsequent complex water washing and drying, which increases the difficulty of moisture control.

[0005] Currently, there is a lack of an integrated green purification process on the market that can simultaneously address the two major pain points of "peroxide safety hazards" and "insufficient low-wavelength transmittance" in coal-based THF.

[0006] Therefore, developing a composite purification method that integrates chemical reduction, selective adsorption, and precision fractionation has significant industrial application value. Summary of the Invention

[0007] The purpose of this invention is to provide a composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran while simultaneously removing peroxides. This method, through multi-stage synergistic action, reduces the peroxide content below the detection limit without introducing new impurities, significantly improves the ultraviolet transmittance in the 200-260 nm wavelength range, and strictly controls moisture and evaporation residue, producing HPLC-grade coal-based tetrahydrofuran that meets international high-end standards.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides includes the following steps: Step 1: Catalytic Reduction Pretreatment An organophosphorus reducing agent or a metal catalyst is added to a coal-based crude tetrahydrofuran feedstock, and a cyclic reaction is carried out under a nitrogen atmosphere at a pressure of 0.1-0.3 MPa and a temperature of 30-50℃. The single cycle reaction time is 0.5-1.0 h, and the number of cycles is 3-5 times to obtain a pretreated feedstock. The coal-based crude tetrahydrofuran feedstock has a peroxide content of 30-45 ppm, a transmittance of 70-75% at 200 nm, and a transmittance of 84-88% at 254 nm. The organophosphorus reducing agent is triphenylphosphine, and the dosage is 0.05-0.10 wt% of the coal-based crude tetrahydrofuran feedstock. Preferably, the amount of the organic reducing agent is 0.08 wt% of the coal-based crude tetrahydrofuran feedstock; The metal catalyst is Pd / C (palladium / carbon), and the dosage is 0.5-2.0 wt% of the coal-based crude tetrahydrofuran feedstock. The Pb content in the Pb / C catalyst is 4-6%. Preferably, the amount of the metal catalyst is 1.0 wt% of the coal-based tetrahydrofuran feedstock, the metal catalyst is Pd / C (palladium / carbon), the amount of which is 0.5-2.0 wt% of the coal-based crude tetrahydrofuran feedstock, and the Pb content in the Pb / C catalyst is 5%. The catalytic reduction pretreatment step aims to quantitatively reduce unstable peroxides to the corresponding alcohols, eliminate the risk of explosion, and saturate some unsaturated carbonyl impurities, thereby reducing their ultraviolet absorption coefficient.

[0009] Step Two: Compound Refining The pretreated raw material is passed sequentially through two adsorption column systems connected in series to obtain the adsorption-purified material. The adsorption column system consists of two stages of adsorbents with different functions. The first stage is for deep deoxygenation and removal of polar impurities. The first adsorption column is filled with the first adsorbent to adsorb alcohols, trace acidic substances, and residual moisture generated during reduction. The flow rate of the pretreated raw material entering the first adsorption column is 9-11 L / h. The height of the first adsorption column is 1.2-1.5 m, the inner diameter is Φ0.2 m, and the filling rate of the first adsorbent is 80-85%. The height of the second adsorption column is 1.2-1.4 m, the inner diameter is Φ0.2 m, and the filling rate of the second adsorbent is 80-85%. The second stage is ultraviolet absorption for impurity removal. The second adsorption column is filled with a second adsorbent, which can specifically adsorb conjugated dienes, aromatic impurities, and macromolecular polymer precursors, thereby significantly improving the low-wavelength transmittance while avoiding excessive adsorption of the THF host.

[0010] The preparation method of the first adsorbent is as follows: alkaline alumina and molecular sieve are mixed evenly at a volume ratio of 1:2-3. The alkaline alumina neutralizes trace acidic substances and adsorbs alcohols. The molecular sieve is deeply dehydrated. Then, it is activated at high temperature at 250-300℃ for 3-4 hours to completely remove the crystal water and strongly polar residues in the pores and restore the maximum specific surface area and adsorption sites. After the high temperature activation is completed, high-purity nitrogen is introduced as a protective atmosphere, and the temperature is naturally reduced to 30-45℃ with the furnace to obtain the first adsorbent. The alkaline alumina is γ-alumina, with a sodium oxide mass fraction of 0.25-0.35% and a specific surface area of ​​220-250 m². 2 / g; The molecular sieve is either 3A or 4A molecular sieve, with a particle size of 1.6-2.5 mm. The method for preparing the porous carbon material is as follows: Phenolic resin is added to anhydrous ethanol and stirred to dissolve. Then, 6-10 wt% sulfuric acid solution is added while stirring. After the sulfuric acid solution is added, phytic acid and ferric ammonium citrate are added and stirred until homogeneous to obtain the impregnation solution. SBA-15 powder was added to the impregnation solution and ultrasonically dispersed for 30-40 min at an ultrasonic power of 210-220 W and an ultrasonic frequency of 34-36 kHz to ensure that the precursor components fully entered the silicon-based channels. The solid product was collected by centrifugation, washed, and kept at 95-105℃ for 5.5-6.0 h. After naturally returning to room temperature, it was placed in a nitrogen atmosphere and the temperature was increased to 300-320℃ at a rate of 1.0-1.5℃ / min, and then increased to 850-880℃ at a rate of 2.5-3.0℃ / min. The temperature was held for 1.8-2.2 h and then naturally returned to room temperature to obtain the carbonized product. The carbonized product was completely immersed in a 1.5-2.0 mol / L sodium hydroxide solution and stirred at 78-82℃ and 120-150 rpm for 4-6 h. The product was washed until the filtrate was neutral and then dried to obtain the porous carbon material. The mass-to-volume ratio of the SBA-15 powder, phenolic resin, sulfuric acid solution, phytic acid, and ferric ammonium citrate is 1g:1.22-1.25g:14-18mL:0.3-0.5g:0.3-0.5g.

[0011] Step 3: Azeotropic distillation After adsorption and purification, the light components and moisture have been removed. The material then enters a distillation column. The entire distillation process is carried out under nitrogen or argon protection, with the pressure controlled at 800-900 kPa, the bottom temperature at 142.8-153.7℃, the top temperature at 105-127℃, and the reflux ratio controlled at 20-50:1. The distilled product is collected from the top of the column. Preferably, the pressure of the distillation column is 830-850 kPa, the bottom temperature is 143.5-146.5℃, the top temperature is 107-114℃, and the reflux ratio is 30-40:1.

[0012] Step 4: Ultrafiltration and Aseptic Filling The distilled product is then filtered through a polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) membrane filter with a pore size ≤0.22μm to remove micron-sized particles. The purified product is then filled into the container under nitrogen protection in a clean environment.

[0013] Compared with the prior art, the present invention has the following significant advantages: 1. This invention is adapted to the characteristics of coal-based raw materials: Addressing the complex THF impurity spectrum in coal-based materials, a multi-stage cascade process was designed, demonstrating excellent removal effects on unsaturated aldehydes, ketones, sulfides, etc. It innovatively combines mild chemical reduction with physical adsorption, completely eliminating peroxides while specifically removing conjugated impurities that cause increased absorbance at low wavelengths. The transmittance at 200 nm can reach over 90%, and the organophosphorus reducing agent can be easily separated through adsorption or distillation, avoiding the introduction of inorganic salt ions. This invention destroys peroxides at the source, avoiding the explosion risk caused by the accumulation of peroxides in the still residue during traditional distillation, and improving the overall stability of the product. 2. The purified product obtained by the method of the present invention has a content of 99.992-99.995%, a peroxide content of 0.2-0.3 ppm, a transmittance of 91-92% at a wavelength of 210 nm, a transmittance of 94-96% at a wavelength of 210 nm, and a transmittance of 98.5-99% at a wavelength of 254 nm. Detailed Implementation

[0014] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0015] Example 1 Raw material: Industrial-grade coal-based crude tetrahydrofuran (THF) produced by the coal-based maleic anhydride hydrogenation method, with a peroxide content of 45 ppm, a transmittance of 75% at 200 nm, a transmittance of 81% at 210 nm, and a transmittance of 88% at 254 nm.

[0016] 1. Catalytic reduction pretreatment 0.08 wt% triphenylphosphine was added to crude coal-based tetrahydrofuran (THF) and the mixture was subjected to a cyclic reaction under a nitrogen atmosphere at a pressure of 0.3 MPa and a stirring temperature of 50°C for 0.5 hours. The reaction was repeated 3 times to obtain a pretreated raw material. The peroxide content was found to be reduced to below 1 ppm.

[0017] 2. Compound refining The pretreated raw material is passed sequentially through two adsorption columns connected in series to obtain the purified material. The flow rate of the pretreated raw material into the first adsorption column is 11 L / h, the height of the first adsorption column is 1.5 m, the inner diameter is 0.2 m, and the filling rate of the first adsorbent is 80%. The height of the second adsorption column is 1.4 m, the inner diameter is 0.2 m, and the filling rate of the second adsorbent is 80%. (1) Preparation method of the first adsorbent Alkaline alumina and molecular sieve were mixed evenly at a volume ratio of 1:4, and then activated at 300℃ for 2 hours. After the high-temperature activation was completed, high-purity nitrogen was introduced as a protective atmosphere, and the furnace temperature was naturally reduced to 38℃ to obtain the first adsorbent. The alkaline alumina is γ-alumina, with a sodium oxide mass fraction of 0.35% and a specific surface area of ​​220 m². 2 / g; The molecular sieve is a 3A molecular sieve with a particle size of 1.6 mm.

[0018] (2) Preparation method of the second adsorbent Phenolic resin was added to anhydrous ethanol and stirred until dissolved. Then, 10 wt% sulfuric acid solution was added while stirring. After the sulfuric acid solution was added, phytic acid and ferric ammonium citrate were added and stirred until homogeneous to obtain the impregnation solution. SBA-15 powder was added to the impregnation solution and ultrasonically dispersed for 40 min at an ultrasonic power of 210 W and an ultrasonic frequency of 34 kHz to ensure that the precursor components fully entered the silicon-based channels. The solid product was collected by centrifugation, washed, and kept at 105 °C for 5.5 h. After naturally returning to room temperature, it was placed in a nitrogen atmosphere and the temperature was increased to 320 °C at a rate of 1.0 °C / min and then to 850 °C at a rate of 2.5 °C / min. The temperature was held for 2.2 h and then naturally returned to room temperature to obtain the carbonized product. The carbonized product was completely immersed in a 2.0 mol / L sodium hydroxide solution and stirred at 82 °C and 120 rpm for 4 h. The product was washed until the filtrate was neutral and then dried to obtain the porous carbon material. The mass-to-volume ratio of the SBA-15 powder, phenolic resin, sulfuric acid solution, phytic acid, and ferric ammonium citrate is 1g:1.25g:18mL:0.5g:0.5g.

[0019] 3. Azeotropic distillation After adsorption purification, the material enters the distillation column. The entire distillation process is carried out under an argon protective atmosphere, with a controlled pressure of 850 kPa, a bottom temperature of 146.5℃, a top temperature of 114℃, and a reflux ratio of 30:1. The distilled product is collected from the top of the column.

[0020] 4. Ultrafiltration and Aseptic Filling The distilled product is then filtered through a polytetrafluoroethylene (PTFE) membrane filter with a pore size ≤0.22μm, and filled into a nitrogen-protected container in a clean environment to obtain the purified product.

[0021] The purified product obtained by the method of Example 1 has a content of 99.995%, a peroxide content of 0.3 ppm, a transmittance of 92% at 200 nm, a transmittance of 96% at 210 nm, and a transmittance of 99% at 254 nm.

[0022] Example 2 Raw material: Industrial-grade crude tetrahydrofuran THF produced by the calcium carbide acetylene method, with a peroxide content of 30 ppm, a transmittance of 70% at 200 nm, a transmittance of 76% at 210 nm, and a transmittance of 84% at 254 nm.

[0023] Step 1: Catalytic Reduction Pretreatment 0.5 wt% metal catalyst was added to the coal-based crude tetrahydrofuran feedstock, and a cyclic reaction was carried out under a nitrogen atmosphere at a pressure of 0.1 MPa and a temperature of 30 °C. The single cycle reaction time was 12 min, and the number of cycles was 5 to obtain the pretreated feedstock. The metal catalyst is Pd / C (palladium / carbon), and the amount used is 1.0 wt% of the coal-based crude tetrahydrofuran feedstock. The Pb content in the Pb / C catalyst is 5%.

[0024] 2. Compound refining The pretreated raw material is passed sequentially through two adsorption columns connected in series to obtain the purified material. The flow rate of the pretreated raw material into the first adsorption column is 9 L / h, the height of the first adsorption column is 1.2 m, the inner diameter is 0.2 m, and the loading rate of the first adsorbent is 85%. The height of the second adsorption column is 1.2 m, the inner diameter is 0.2 m, and the loading rate of the second adsorbent is 85%. (1) Preparation method of the first adsorbent Alkaline alumina and molecular sieve were mixed evenly at a volume ratio of 1:2, and then activated at 250°C for 4 hours. After the high-temperature activation was completed, high-purity nitrogen was introduced as a protective atmosphere, and the furnace temperature was naturally reduced to 30°C to obtain the first adsorbent. The alkaline alumina is γ-alumina, with a sodium oxide mass fraction of 0.25% and a specific surface area of ​​220 m². 2 / g; The molecular sieve is a 4A molecular sieve with a particle size of 2.5 mm.

[0025] (2) Preparation method of the second adsorbent Phenolic resin was added to anhydrous ethanol and stirred to dissolve. Then, 6 wt% sulfuric acid solution was added while stirring. After the sulfuric acid solution was added, phytic acid and ferric ammonium citrate were added and stirred until homogeneous to obtain the impregnation solution. SBA-15 powder was added to the impregnation solution and ultrasonically dispersed for 30 min at an ultrasonic power of 2320 W and an ultrasonic frequency of 36 kHz to ensure that the precursor components fully entered the silicon-based channels. The solid product was collected by centrifugation, washed, and kept at 95 °C for 6.0 h. Then, it was placed in a nitrogen atmosphere and the temperature was increased to 300 °C at a rate of 1.5 °C / min and then increased to 880 °C at a rate of 3.0 °C / min. The temperature was kept for 1.8 h and allowed to naturally return to room temperature to obtain the carbonized product. The carbonized product was completely immersed in a 1.5 mol / L sodium hydroxide solution and stirred at 78 °C and 150 rpm for 6 h. The product was washed until the filtrate was neutral and then dried to obtain the porous carbon material. The mass-to-volume ratio of the SBA-15 powder, phenolic resin, sulfuric acid solution, phytic acid, and ferric ammonium citrate is 1g:1.22g:14mL:0.3g:0.3g.

[0026] 3. Azeotropic distillation The adsorption-refined material enters the distillation column. The entire distillation process is carried out under an argon protective atmosphere, with a controlled pressure of 820 kPa, a bottom temperature of 143.5℃, a top temperature of 107℃, and a reflux ratio of 40:1. The distilled product is collected from the top of the column.

[0027] 4. Ultrafiltration and Aseptic Filling The distilled product is then filtered through a polyvinylidene fluoride (PVDF) membrane filter with a pore size ≤0.22μm, and filled into a nitrogen-protected container in a clean environment to obtain the purified product.

[0028] The purified product obtained by the method in Example 2 had a content of 99.992%, a peroxide content of 0.2 ppm, a transmittance of 91% at 200 nm, a transmittance of 94% at 210 nm, and a transmittance of 98.5% at 254 nm.

[0029] Comparative Example 1 Based on Example 1, the catalytic reduction pretreatment and compound purification steps are omitted; Coal-based crude tetrahydrofuran (THF) is directly subjected to azeotropic distillation, and all other operations are the same.

[0030] In Comparative Example 1, peroxides accumulated in the residue during the purification process, posing a safety hazard. The purified product obtained in Comparative Example 1 had a content of 92.11% and a peroxide content of 37 ppm. Its transmittance at 200 nm wavelength was only 78%, which could not meet the requirements for low-wavelength detection in HPLC. The transmittance at 210 nm wavelength was 87%, and the transmittance at 254 nm wavelength was 90%.

[0031] Comparative Example 2 is based on Example 1, with the following changes: (1) The catalytic reduction pretreatment step is omitted; (2) The compound refining step is as follows: The pretreated raw material is passed sequentially through two adsorption columns connected in series to obtain the purified material. The flow rate of the pretreated raw material into the first adsorption column is 11 L / h, the height of the first adsorption column is 1.5 m, the inner diameter is 0.2 m, and the filling rate of the first adsorbent is 80%. The height of the second adsorption column is 1.4 m, the inner diameter is 0.2 m, and the filling rate of the second adsorbent is 80%. The preparation method of the first adsorbent is exactly the same as that in Example 1; The second adsorbent is activated carbon with a particle size of 250 nm. The rest of the operations are exactly the same.

[0032] Using the method of Comparative Example 2, the removal of peroxides was incomplete, and there was a risk of slow decomposition on the adsorption column. The purified product obtained in Comparative Example 2 had a content of 94.68%, a peroxide content of 15 ppm, and a transmittance of 82% at a wavelength of 200 nm, because some conjugated impurities were not effectively converted or adsorbed. The transmittance at a wavelength of 210 nm was 90%, and the transmittance at a wavelength of 254 nm was 93%.

[0033] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0034] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides, characterized in that it includes catalytic reduction pretreatment, composite purification, azeotropic distillation, ultrafiltration and aseptic filling steps; The catalytic reduction pretreatment step involves adding an organophosphorus reducing agent or a metal catalyst to the coal-based crude tetrahydrofuran feedstock, conducting a cyclic reaction under a nitrogen atmosphere at a pressure of 0.1-0.3 MPa and a temperature of 30-50°C, with a single cycle reaction time of 0.5-1.0 h and a cycle count of 3-5 times, to obtain the pretreated feedstock. The organophosphorus reducing agent is triphenylphosphine, and the metal catalyst is Pd / C; The composite refining step involves passing the pretreated raw material sequentially through a system of two adsorption columns connected in series to obtain the adsorbed and refined material. The first adsorption column is filled with a first adsorbent, and the second adsorption column is filled with a second adsorbent, which is a porous carbon material. The method for preparing the porous carbon material is as follows: phenolic resin is added to anhydrous ethanol and stirred until dissolved. Sulfuric acid solution is then added, followed by phytic acid and ferric ammonium citrate. After stirring until homogeneous, an impregnation solution is obtained. SBA-15 powder is added to the impregnation solution and ultrasonically dispersed for 30-40 minutes. The solid product is collected, washed, and then kept at 95-105℃ for 5.5-6.0 hours. After naturally returning to room temperature, it is placed in a nitrogen atmosphere and kept at 850-880℃ for 1.8-2.2 hours to obtain a carbonized product. The carbonized product is then completely immersed in a sodium hydroxide solution and stirred at 78-82℃ for 4-6 hours to obtain the porous carbon material.

2. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 1, characterized in that, The amount of the organophosphorus reducing agent used is 0.05-0.10 wt% of the coal-based crude tetrahydrofuran feedstock; The amount of the metal catalyst is 0.5-2.0 wt% of the coal-based crude tetrahydrofuran feedstock, and the Pd content in the Pd / C catalyst is 4-6%.

3. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 1, characterized in that, In the composite refining step, the flow rate of the pretreated raw material entering the first adsorption column is 9-11 L / h, the height of the first adsorption column is 1.2-1.5 m, the inner diameter is Φ0.2 m, and the filling rate of the first adsorbent is 80-85%. The height of the second adsorption column is 1.2-1.4 m, the inner diameter is Φ0.2 m, and the filling rate of the second adsorbent is 80-85%.

4. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 3, characterized in that, The preparation method of the first adsorbent is as follows: alkaline alumina and molecular sieve are mixed evenly at a volume ratio of 1:2-3. The alkaline alumina neutralizes trace acidic substances and adsorbs alcohols. The molecular sieve is deeply dehydrated. Then, it is activated at high temperature at 250-300℃ for 3-4 hours to completely remove the crystal water and strongly polar residues in the pores and restore the maximum specific surface area and adsorption sites. After the high temperature activation is completed, high-purity nitrogen is introduced as a protective atmosphere, and the temperature is naturally reduced to 30-45℃ with the furnace to obtain the first adsorbent. The alkaline alumina is γ-alumina, with a sodium oxide mass fraction of 0.25-0.35% and a specific surface area of ​​220-250 m². 2 / g; The molecular sieve is either 3A or 4A molecular sieve, with a particle size of 1.6-2.5 mm.

5. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 1, characterized in that, In the preparation method of the porous carbon material, the mass-volume ratio of SBA-15 powder, phenolic resin, sulfuric acid solution, phytic acid, and ferric ammonium citrate is 1g:1.22-1.25g:14-18mL:0.3-0.5g:0.3-0.5g.

6. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 1, characterized in that, The azeotropic distillation step is as follows: after adsorption purification, light components and moisture have been removed, and the material enters the distillation column. The entire distillation process is carried out under nitrogen or argon protection, with the pressure controlled at 800-900 kPa, the bottom temperature at 142.8-153.7℃, the top temperature at 105-127℃, and the reflux ratio controlled at 20-50:

1. The distilled product is collected from the top of the column.

7. The composite purification method for improving the HPLC transmittance of coal-based tetrahydrofuran and simultaneously removing peroxides according to claim 1, characterized in that, The ultrafiltration and aseptic filling steps are as follows: the distilled product is filtered through a membrane filter for terminal filtration, and then filled with nitrogen protection in a clean environment to obtain the purified product.