Method for preparing tetrahydrofuran by degrading poly (butylene succinate) in subcritical water

Abstract

The invention discloses a method for preparing tetrahydrofuran by degrading poly (butylene succinate) in subcritical water, which comprises the following steps: by taking poly (butylene succinate) as a raw material and deionized water as a solvent, mixing the poly (butylene succinate) and the deionized water, putting the mixture into a reactor, heating to a subcritical state, and carrying out hydrolysis reaction on the poly (butylene succinate) to generate tetrahydrofuran. The method provided by the invention has the advantages of high efficiency, greenness, mild reaction conditions and the like, can hydrolyze the poly (butylene succinate) to generate tetrahydrofuran and recycle the waste polymer, and has higher industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of waste plastic utilization, and particularly relates to a method for preparing tetrahydrofuran by degrading polybutylene glycol ester in subcritical water. Background Art

[0002] Polybutylene succinate (PBS) is a high-performance bio-based plastic derived from the polycondensation reaction of succinic acid and 1,4-butanediol. Due to its excellent physical and mechanical properties and biodegradability, it has been widely used in many fields such as food packaging, agricultural films and pesticide carriers. With the rapid development of social economy, the demand for PBS materials has risen sharply, and the amount of waste has increased significantly. 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 efforts to reduce carbon emissions. It also means that the original material resources are not fully utilized. In view of this, the development of efficient chemical conversion pathways to convert waste PBS into valuable chemicals or materials has become an urgent problem to be solved.

[0003] Supercritical fluid technology, especially the use of supercritical carbon dioxide and water, is leading the field of polymer resource utilization into a new stage. These media show extraordinary performance under specific conditions (such as the critical point of water is 374℃, 22.1MPa), which not only exceeds the limits of traditional chemical treatment, but also opens up new ways to transform environmentally friendly materials. Especially in the "near-critical" range of 200-374℃ and 10-22MPa, water, as a representative of green solvents, has outstanding characteristics: non-toxic, stable, and excellent physical and chemical properties, including strong solubility, high-speed diffusion, low dielectric constant and low viscosity, which greatly optimizes the chemical reaction kinetics and mass transfer efficiency, and becomes an efficient and eco-friendly solution for converting 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-toxic, cyclic heterocyclic ether compound with a slight ether smell. Its molecular structure is abbreviated as C4H8O. Its characteristics include low viscosity, high volatility and excellent solvent ability. It can be easily dissolved in water and a variety of organic solvents. In chemical synthesis and polymer manufacturing, THF occupies a core position due to its unique physical and chemical properties and plays a role that cannot be underestimated. As a medium-polar aprotic solvent, THF has shown high flexibility and applicability in the synthesis of fine chemicals, pharmaceutical processes, polymer science, and even the extraction and purification of biochemical products. It not only promotes the efficient progress of chemical reactions and ensures the high quality of products, but also serves as a key intermediate in the preparation of advanced materials such as polyurethane and synthetic fibers, promoting the progress of materials science. The preparation technology of THF continues to evolve, aiming to improve production efficiency and environmental performance, including traditional hydrogenation furan method and innovative green production process to meet the growing market demand for sustainable development solutions. Its wide application in the industry, coupled with continuous research and improvement, further consolidates the cornerstone position of tetrahydrofuran in the field of basic chemicals. Summary of the invention

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

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

[0007] The invention discloses a method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water. The method comprises the following steps: using polybutylene succinate as a raw material and deionized water as a solvent, mixing the two materials and placing them in a reactor, heating them to a subcritical state, performing a hydrolysis reaction of the polybutylene succinate, and generating tetrahydrofuran.

[0008] Furthermore, the subcritical heating temperature is 160-250° C., and the pressure is 0.61-3.91 MPa.

[0009] Furthermore, the subcritical heating temperature is 240-250° C., and the pressure is 3.2-3.91 MPa.

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

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

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

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

[0014] The beneficial effects achieved by the present invention are: the present invention gives specific properties through the reasonable design of different factors, and can carry out relevant technical research and development of preparing tetrahydrofuran by hydrolyzing polybutylene succinate with subcritical water. The method provided by the present invention has the advantages of high efficiency, greenness, mild reaction conditions, etc., can hydrolyze polybutylene succinate to generate tetrahydrofuran, and has strong industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a graph showing the yield change 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° C., a pressure of 1.52-3.91 MPa, and different reaction times (0, 15, 30, 60, 120 min). DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

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

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

[0019]

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

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

[0022]

[0023] The average molecular weight of the polybutylene succinate in the embodiment of the present invention is 10,000.

[0024] Example 1: A qualitative method for tetrahydrofuran in a liquid phase product of polybutylene succinate hydrolysis provided in this example

[0025] 3g of polybutylene succinate and 30g of water were placed in a reactor, and hydrolysis reaction was carried out under the conditions of stirring speed of 100r / min, reaction temperature of 210℃, and pressure of 1.8MPa, and the reaction time was 30min; after the reaction was completed, 5ml of liquid product was taken into a 10ml colorimetric tube, 5ml of ethyl acetate was used as an extractant, and the extract was mixed evenly to take the extract as the test liquid; the test liquid was analyzed by gas-mass spectrometry, and the analysis conditions were HB-5 (30m×0.25mm×0.25μm) quartz capillary column, injection volume of 1μL, carrier gas of helium, and carrier gas flow rate of 1ml·min -1 , injection port temperature was 250℃, detector temperature was 280℃, column temperature was 60℃(3min)~280℃, heating rate was 30℃·min -1 The ion source is 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 Succinic acid 1,4-Butanedioic acid

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

[0029] Example 2: Method for hydrolyzing polybutylene succinate to generate tetrahydrofuran at different stirring speeds provided in this example

[0030] 3 g of polybutylene succinate (PBS) and 30 g of water (i.e., the mass ratio of the two is 1:10) are placed in a reactor, and a hydrolysis reaction is carried out under different stirring speeds (0, 100, 200, 300, 400, 500 r / min), a reaction temperature of 230° C., a pressure of 2.93 MPa, and a reaction time of 60 min. After the reaction is completed, sampling and analysis are performed to determine the yield of tetrahydrofuran. The results are shown in Table 2. The optimal stirring speed is 100 r / min, and the maximum yield is 64%.

[0031] Table 2

[0032]

[0033] Example 3: Method for hydrolyzing polybutylene succinate to generate tetrahydrofuran at different mass ratios provided in this example

[0034] 3 g of polybutylene succinate was mixed with 18-42 g of water (the mass ratio of polybutylene succinate to deionized water was 1:6, 1:8, 1:10, 1:12, and 1:14, respectively) and placed in a reactor for hydrolysis reaction at a stirring speed of 100 r / min, a reaction temperature of 220° C., and a pressure of 2.33 MPa for 60 min. After the reaction was completed, sampling and analysis were performed to determine the yield of tetrahydrofuran, and the results are shown in Table 3.

[0035] Table 3

[0036] Quality 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 optimal mass ratio of polybutylene succinate to deionized water is 1:10, and the maximum yield of tetrahydrofuran is 46.14%

[0038] Example 4: Method for hydrolyzing polybutylene succinate to generate tetrahydrofuran at different temperatures provided in this example

[0039] 3 g of polybutylene succinate and 30 g of water (i.e., the mass ratio of the two is 1:10) are placed in a reactor, and a hydrolysis reaction is carried out under the conditions of a stirring speed of 100 r / min and different reaction temperatures (190, 200, 210, 220, 230, 240, 250° C.) for 30 min. After the reaction is completed, sampling and analysis are performed to determine the yield of tetrahydrofuran, and the results are shown in Table 4.

[0040] Table 4

[0041] Temperature(℃) 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] It can be seen from Table 4 that the optimal temperature for the supercritical reaction is 240°C and the maximum yield is 61.66%.

[0043] It can be seen from Table 4 above that according to the TOC concentration after the reaction, the liquid after the reaction of this experiment is low molecular weight compounds (oligomers and small molecular weight compounds) generated by the reaction of solid PBS and water. Secondly, the TOC concentration reaches the maximum value at 220°C, indicating that the carbon conversion rate in PBS reaches the maximum value at 220°C, that is, most of the PBS has been converted into carbon-containing organic matter. Finally, PBS begins to gradually decrease after 220°C, which indicates that as the temperature increases, some low molecular weight compounds are converted into inorganic compounds (water and carbon dioxide).

[0044]

[0045] According to the experimental conditions of Example 4, the yield of tetrahydrofuran under the conditions of stirring speed of 100 r / min, mass ratio of polybutylene succinate to water of 1:10, reaction temperature of 200-250°C, pressure of 1.52-3.91 MPa, and different reaction times (0, 15, 30, 60, 120 min) is as follows: Figure 1 shown. Figure 1 The yield at a reaction time of 0 min refers to the yield of tetrahydrofuran when the temperature is heated to the desired reaction temperature and kept warm for 0 min, that is, when the temperature is heated to the desired temperature.

[0046] Example 5: Method for hydrolyzing polybutylene succinate to generate tetrahydrofuran at different times provided in this example

[0047] 3 g of polybutylene succinate and 30 g of water were placed in a reactor, and hydrolysis was carried out under the conditions of a stirring speed of 100 r / min, a reaction temperature of 240°C, and a pressure of 3.2 MPa. Samples were taken and analyzed at different reaction times (0, 15, 30, 60, and 120 min) to determine the yield of tetrahydrofuran. The results are as follows: Figure 1 As shown. Under the conditions of stirring speed of 100r / min, mass ratio of 1:10, reaction temperature of 240℃ and reaction time of 60min, the yield of tetrahydrofuran is the highest, and its yield is 83%.

[0048] Example 6: This example provides a method for separating and hydrolyzing liquid products to prepare tetrahydrofuran

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

[0050] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with conventional techniques known in the art.

Claims

1. A method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water, characterized in that Polybutylene succinate is used as a raw material and deionized water is used as a solvent. The two are mixed and placed in a reactor, and heated to a subcritical state to perform a hydrolysis reaction of the polybutylene succinate to generate tetrahydrofuran.

2. The method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water as claimed in claim 1, characterized in that The subcritical heating temperature is 160-250° C., and the pressure is 0.61-3.91 MPa.

3. A method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water as claimed in claim 2, characterized in that The subcritical heating temperature is 240-250° C., and the pressure is 3.2-3.91 MPa.

4. The method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water as claimed in claim 1, characterized in that The hydrolysis reaction time is 30-150 min, preferably 60-120 min.

5. The method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water as claimed in claim 1, characterized in that The mass ratio of the polybutylene succinate to deionized water is 1:6 to 1:16, preferably 1:8 to 1:

10.

6. The method for preparing tetrahydrofuran by degrading polybutylene succinate in subcritical water as claimed in claim 1, characterized in that The hydrolysis reaction is carried out under stirring at a stirring rate of 50-300 rpm, preferably 100-200 rpm.

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

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