A method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water

Abstract

The application discloses a method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water, and the method comprises the following steps: taking polybutylene succinate as raw material, deionized water as solvent, mixing the two, and then placing the mixture in a reactor to generate tetrahydrofuran by heating to a subcritical state for hydrolysis reaction of the polybutylene succinate. The method has the advantages of high efficiency, greenness, mild reaction condition and the like, can make polybutylene succinate hydrolyze to generate tetrahydrofuran, realizes resource utilization of waste polymers, and has strong industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste plastic utilization, and particularly relates to a method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water. BACKGROUND

[0002] Polybutylene succinate (PBS) is a high-performance bio-based plastic derived from the polycondensation of succinic acid and 1,4-butanediol. Due to its excellent physical and mechanical properties and biodegradability, PBS has been widely used in food packaging, agricultural films, pesticide carriers and many other fields. With the rapid development of social economy, the demand for PBS materials has increased dramatically, leading to a significant increase in waste. Although PBS has the ability to biodegrade in the natural environment, this process is quite slow, and the final degradation products are carbon dioxide and water, which is not conducive to the current global effort to reduce carbon emissions, and also means that the original material resources are not fully utilized. Therefore, developing an efficient chemical conversion route to convert waste PBS into valuable chemicals or materials has become a pressing problem.

[0003] Supercritical fluid technology, particularly the use of supercritical carbon dioxide and water media, is leading the polymer resource utilization field into a new era. These media exhibit extraordinary properties under specific conditions (such as the critical point of water at 374℃ and 22.1MPa), not only surpassing the boundaries of traditional chemical processing, but also opening up new ways for the conversion of environmentally friendly materials. In particular, in the "near-critical" range of 200-374℃ and 10-22MPa, water as a representative of green solvents has particularly outstanding characteristics: non-toxic, stable, superior physical and chemical properties, including strong solubility, high diffusion rate, low dielectric constant and low viscosity, greatly optimizing chemical reaction kinetics and mass transfer efficiency, becoming an efficient and eco-friendly solution for the conversion of waste plastics into high-value resources. This not only accelerates the reaction process, but also significantly improves the economic value of waste plastic recycling and the feasibility of circular economy.

[0004] Tetrahydrofuran (THF) is a colorless, transparent, low-toxicity, and slightly ethereal compound with a faint odor of ether. Its molecular structure is represented by the formula C4H8O. It is characterized by low viscosity, high volatility, and excellent solvent capacity, easily dissolving in water and various organic solvents. In the chemical synthesis and polymer manufacturing industries, THF plays a crucial role due to its unique physical and chemical properties. As a moderately polar aprotic solvent, THF exhibits high flexibility and applicability in fine chemical synthesis, pharmaceutical processes, polymer science, and even the extraction and purification of biochemical products. It not only promotes efficient chemical reactions and ensures high-quality products but also serves as a key intermediate in the production of advanced materials such as polyurethane and synthetic fibers, driving progress in material science. The preparation technology of THF is continuously evolving to improve production efficiency and environmental performance, including traditional hydrogenation of furan and innovative green production processes to meet the growing demand for sustainable solutions in the market. Its wide range of industrial applications, combined with ongoing research and improvement, further solidifies the position of tetrahydrofuran as a cornerstone in the field of basic chemicals. SUMMARY

[0005] The purpose of the present application is to provide a method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water.

[0006] The technical solution adopted by the present application is:

[0007] A method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water, using polybutylene succinate as raw material and deionized water as solvent. After mixing, the mixture is placed in a reactor and heated to a subcritical state to carry out the hydrolysis reaction of polybutylene succinate, generating tetrahydrofuran.

[0008] Further, the heating temperature of the subcritical state is 160-250℃, and the pressure is 0.61-3.91MPa.

[0009] Further, the heating temperature of the subcritical state is 240-250℃, and the pressure is 3.2-3.91MPa.

[0010] Further, the hydrolysis reaction time is 30-150min, preferably 60-120min.

[0011] Further, the mass ratio of polybutylene succinate to deionized water is 1:6-1:16, preferably 1:8-1:10.

[0012] Further, the hydrolysis reaction is carried out under stirring, and the stirring rate is 50-300rpm, preferably 100-200rpm.

[0013] Further, the average molecular weight of the polybutylene succinate is 8000-12000.

[0014] The present application has the advantages that: the present application is designed by different factors, and has specific performance, and can be used for the research and development of the technology of preparing tetrahydrofuran by hydrolysis of polybutylene succinate in subcritical water. The method provided by the present application has the advantages of high efficiency, green, mild reaction conditions, etc., can make polybutylene succinate hydrolysis to generate tetrahydrofuran, and has strong industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The yield of tetrahydrofuran under the conditions of a stirring speed of 100 r / min, a mass ratio of 1:10, a reaction temperature of 200-250 DEG C, a pressure of 1.52-3.91 MPa, and different reaction times (0, 15, 30, 60, and 120 min) is shown in the figure. DETAILED DESCRIPTION

[0016] The present application is further described in detail below with reference to the specific embodiments, and the examples are given only to illustrate the present application, and are not intended to limit the scope of the present application. The examples provided below can be used as a guide for further improvement by those skilled in the art, and do not constitute any limitation on the present application.

[0017] In the following examples, the experimental methods are conventional methods, and are performed according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0018] The yield of tetrahydrofuran in the examples of the present application is calculated according to the following formula:

[0019]

[0020] The theoretical amount of tetrahydrofuran generated when PBS is completely converted is the amount of tetrahydrofuran generated when PBS is completely converted into butanediol, and then butanediol is completely converted into tetrahydrofuran.

[0021] The reaction formula of the PBS conversion reaction is as follows:

[0022]

[0023] The average molecular weight of the polybutylene succinate in the examples of the present application is 10000.

[0024] Example 1, the example provides a qualitative method for tetrahydrofuran in a polybutylene succinate hydrolysis liquid product

[0025] Put 3g of polybutylene succinate and 30g of water in a reaction kettle, and carry out a hydrolysis reaction under the conditions of a stirring speed of 100r / min, a reaction temperature of 210℃, and a pressure of 1.8MPa, and a reaction time of 30min; after the reaction is completed, take 5ml of a liquid-phase product in a 10ml colorimetric tube, mix 5ml of ethyl acetate as an extractant, and take the extracted liquid as a to-be-tested liquid; the to-be-tested liquid is analyzed by gas-liquid chromatography, and the analysis conditions are as follows: an HB-5(30m x 0.25mm x 0.25μm) quartz capillary column, a sample injection amount of 1μL, a carrier gas of helium, a carrier gas flow rate of 1ml·min -1 , a sample injection port temperature of 250℃, a detector temperature of 280℃, a column temperature of 60℃(3min) to 280℃, a temperature rising rate of 30℃·min -1 , and an ion source of an EI source. The analysis results are shown in Table 1.

[0026] Table 1

[0027] No. RetentionTime / min CAS Name Chinese name 1 2.492 109-99-9 Tetrahydrofuran Tetrahydrofuran 2 5.227 110-63-4 1,4-Butanediol 1,4-Butanediol 3 6.045 108-30-5 Succinicanhydride Succinic anhydride 4 7.458 110-15-6 Succinicacid 1,4-Butyric acid

[0028] As can be seen from Table 1, the liquid product after the reaction contains tetrahydrofuran and some other products.

[0029] Example 2, the example provides a method for hydrolyzing polybutylene succinate to generate tetrahydrofuran under different stirring speeds

[0030] Put 3g of polybutylene succinate (PBS) and 30g of water (i.e., the mass ratio of the two is 1:10) in a reaction kettle, and carry out a hydrolysis reaction under different stirring speeds (0, 100, 200, 300, 400, 500r / min), a reaction temperature of 230℃, and a pressure of 2.93MPa, and a reaction time of 60min; after the reaction is completed, take a sample for analysis to determine the yield of tetrahydrofuran, and the results are shown in Table 2, the optimal stirring speed is 100r / min, and the maximum yield is 64%.

[0031] Table 2

[0032]

[0033] Example 3, the example provides a method for hydrolyzing polybutylene succinate to generate tetrahydrofuran under different mass ratios

[0034] Take 3g of polybutylene succinate, mixed with 18-42g of water (so that the mass ratio of polybutylene succinate to deionized water is 1:6, 1:8, 1:10, 1:12, 1:14 in turn) and placed in a reaction kettle, under the conditions of stirring speed of 100r / min, reaction temperature of 220℃, pressure of 2.33MPa, the hydrolysis reaction is carried out for 60min; after the reaction is completed, the yield of tetrahydrofuran is determined by sampling analysis, and the results are shown in Table 3.

[0035] Table 3

[0036] mass ratio 1:6 1:8 1:10 1:12 1:14 Yield (%) 32.45 42.47 46.14 40.58 38.57

[0037] As can be seen from Table 3, the best mass ratio of polybutylene succinate to deionized water is 1:10, and the maximum yield of tetrahydrofuran is 46.14%

[0038] Example 4, the different temperature polybutylene succinate hydrolysis to generate tetrahydrofuran method provided by this embodiment

[0039] Take 3g of polybutylene succinate, mixed with 18-42g of water (so that the mass ratio of polybutylene succinate to deionized water is 1:6, 1:8, 1:10, 1:12, 1:14 in turn) and placed in a reaction kettle, under the conditions of stirring speed of 100r / min, reaction temperature of 220℃, pressure of 2.33MPa, the hydrolysis reaction is carried out for 60min; after the reaction is completed, the yield of tetrahydrofuran is determined by sampling analysis, and the results are shown in Table 3.

[0040] Table 4

[0041] Temperature (°C) 190 200 210 220 230 240 250 Tetrahydrofuran yield (%) 0.37 1.11 3.32 31.63 58.25 61.66 59.98 TOC concentration (mg / L) 3.62 4.86 34.86 45.15 44.95 42.76 40.98 PBS conversion rate (%) 3.82 9.65 88.14 98.96 99.09 99.25 99.49 Carbon conversion rate (%) 6.49 8.71 62.46 80.9 80.54 76.67 73.43

[0042] As can be seen from Table 4, the best temperature of supercritical reaction is 240℃, and the maximum yield is 61.66%.

[0043] From the above Table 4, according to the TOC concentration after the reaction, it can be seen that the liquid after the reaction is the low molecular compounds (oligomers and small molecular compounds) generated by the reaction of solid PBS and water, secondly, the TOC concentration reaches the maximum value at 220℃, which indicates that the carbon conversion rate in PBS reaches the maximum value at 220℃, that is, PBS has been mostly converted into carbon-containing organic matter, finally, PBS begins to gradually decrease after 220℃, which indicates that with the increase of temperature, a part of low molecular compounds is converted into inorganic compounds (water and carbon dioxide).

[0044]

[0045] The yield of tetrahydrofuran under different reaction time (0, 15, 30, 60, 120 min) is shown in Table 2. The yield of tetrahydrofuran under the condition of stirring speed of 100 r / min, mass ratio of 1:10, reaction temperature of 200-250 °C, pressure of 1.52-3.91 MPa and reaction time of 60 min is the highest, and the yield of tetrahydrofuran is 83%. Figure 1 Figure 1 The yield of tetrahydrofuran under reaction time of 0 min refers to the yield of tetrahydrofuran when the temperature is heated to the required reaction temperature and kept for 0 min, i.e. the yield of tetrahydrofuran when the temperature is heated to the required temperature.

[0046] Example 5, the present embodiment provides a method for preparing tetrahydrofuran by hydrolysis of polybutylene succinate under different time

[0047] The 3 g of polybutylene succinate and 30 g of water are placed in a reaction kettle, and the hydrolysis reaction is carried out under the condition of stirring speed of 100 r / min, reaction temperature of 240 °C and pressure of 3.2 MPa. The sample is analyzed under different reaction time (0, 15, 30, 60, 120 min) to determine the yield of tetrahydrofuran, and the results are shown in Table 3. Under the condition of stirring speed of 100 r / min, mass ratio of 1:10, reaction temperature of 240 °C and reaction time of 60 min, the yield of tetrahydrofuran is the highest, and the yield of tetrahydrofuran is 83%. Figure 1

[0048] Example 6, the present embodiment provides a method for preparing tetrahydrofuran by separating the hydrolysis liquid phase product

[0049] The liquid phase product containing tetrahydrofuran generated under the condition of stirring speed of 100 r / min, mass ratio of 1:10, reaction temperature of 240 °C, pressure of 3.2 MPa and reaction time of 60 min is placed in a 50 ml distillation flask, and tetrahydrofuran is collected by distillation at 80 °C. The yield of tetrahydrofuran is 83%, and the recovery rate is 81%.

[0050] The present application has been described in detail. For those skilled in the art, without departing from the purpose and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wider range under the same parameters, concentrations and conditions. Although the present application provides a special example, it should be understood that further improvements can be made to the present application. In summary, according to the principle of the present application, the present application intends to include any change, use or improvement of the present application, including changes made by conventional techniques known in the art, which deviates from the scope disclosed in the present application.​​

Claims

1. A method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water, characterized in that... Using polybutylene succinate as raw material and deionized water as solvent, the two are mixed and placed in a reactor. The mixture is heated to a subcritical state to carry out the hydrolysis reaction of polybutylene succinate, generating tetrahydrofuran. The subcritical heating temperature is 240~250℃ and the pressure is 3.2~3.91MPa.

2. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 1, characterized in that... The hydrolysis reaction takes 30-150 minutes.

3. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 2, characterized in that... The hydrolysis reaction takes 60-120 minutes.

4. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 1, characterized in that... The mass ratio of polybutylene succinate to deionized water is 1:6 to 1:

16.

5. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 4, characterized in that... The mass ratio of polybutylene succinate to deionized water is 1:8 to 1:

10.

6. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 1, characterized in that... The hydrolysis reaction is carried out under stirring at a speed of 50-300 rpm.

7. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 6, characterized in that... The hydrolysis reaction is carried out under stirring at a speed of 100-200 rpm.

8. The method for preparing tetrahydrofuran by subcritical water degradation of polybutylene succinate as described in claim 1, characterized in that... The average molecular weight of the polybutylene succinate is 8000-12000.

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