Application of 1-butyl-2, 3-dimethylimidazole trifluoromethanesulfonate in direct esterification synthesis of PET (Polyethylene Terephthalate)
By leveraging the synergistic effect of cation and anion catalysts such as 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate, the problems of slow esterification reaction rate and high energy consumption in PET synthesis were solved, achieving efficient and low-energy PET synthesis and improving product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 重庆万凯新材料科技有限公司
- Filing Date
- 2026-01-29
- Publication Date
- 2026-05-15
AI Technical Summary
The existing esterification process in PET synthesis is slow, energy-intensive, and has many side reactions, making it difficult to meet the quality requirements of high-end PET products.
1-Butyl-2,3-dimethylimidazolium trifluoromethanesulfonate was used as a cocatalyst. Through the synergistic effect of its anions and cations, the esterification reaction was promoted, the solubility of PTA in ethylene glycol was increased, a polar environment was formed, and side reactions were suppressed.
The esterification reaction temperature was lowered, saving energy and improving the intrinsic viscosity and quality of PET products, thus meeting the performance requirements of bottle-grade or fiber-grade PET.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate in the direct esterification synthesis of PET. Background Technology
[0002] Polyethylene terephthalate (PET) is one of the world's most produced and widely used synthetic polymer materials. PET is composed of rigid benzene rings, flexible methylene groups, and polar ester groups. The polar ester groups connect the rigid and flexible segments, creating a conjugated effect that gives PET a highly stereoregular structure. This results in superior properties, including excellent mechanical strength, good transparency, excellent gas barrier properties, recyclability, and relatively low cost, making it an indispensable basic material in fields such as fibers, bottle packaging, films, and engineering plastics.
[0003] In polyester synthesis, direct esterification offers significant overall advantages and has completely replaced transesterification, becoming the dominant process for PET production globally. Direct esterification mainly comprises two core stages: esterification and polycondensation. Specifically, purified terephthalic acid (PTA) and excess ethylene glycol (EG) first undergo esterification to produce diethyl terephthalate (BHET) and its oligomers; subsequently, BHET undergoes polycondensation under high temperature and high vacuum to produce high-molecular-weight PET.
[0004] For a long time, because polycondensation is the key step determining the molecular weight (intrinsic viscosity) of the final product, research has focused primarily on polycondensation catalysts such as antimony-based and titanium-based catalysts. In recent years, with the increasingly stringent requirements for PET quality (such as the stringent requirements for the content of byproducts acetaldehyde and diethylene glycol in high-end bottle PET) and the urgent need for green and environmentally friendly production, the importance of the esterification stage has been re-examined. Although the esterification reaction of PTA and EG theoretically can proceed without a catalyst (the carboxyl groups of PTA act as autocatalysis), this reaction is a heterogeneous solid-liquid reaction. PTA has low solubility in EG, resulting in a slow reaction rate and demanding conditions (high temperature and high pressure). To improve the esterification reaction rate, reduce energy consumption, and suppress side reactions at the source, the research and development of esterification catalysts has become a new hot topic and a key technological breakthrough in the field of PET synthesis. Summary of the Invention
[0005] The purpose of this invention is to provide an application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate in the direct esterification synthesis of PET, in order to reduce the energy consumption of PET synthesis, increase the rate of esterification reaction in PET synthesis, and improve the quality of PET products.
[0006] To achieve the above objectives, the present invention provides the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate in the direct esterification synthesis of PET.
[0007] The working principle and beneficial effects of this scheme are as follows: This scheme utilizes the synergistic effect of the anions and cations of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate to achieve a three-in-one function of "solventizing-catalyzing-suppressing side reactions".
[0008] (1) The cationic Lewis acid properties promote esterification: the cationic form of 1-butyl-2,3-dimethylimidazolium ([BDMIM]) + The nitrogen atom on the imidazole ring and the methyl substituent form an electron-deficient structure, possessing a Lewis acid active site. In esterification reactions, this active site can coordinate with the carbonyl oxygen in purified terephthalic acid (PTA), increasing the positive charge of the carboxyl carbon and enhancing its nucleophilic reactivity with the hydroxyl group (-OH) in ethylene glycol (EG), thereby accelerating the esterification rate. [BDMIM] + It is weakly acidic and has difficulty combining with the hydroxyl oxygen of EG, which has a low electron cloud density. Therefore, it avoids the side reactions of catalyzing the dehydration of EG to produce acetaldehyde, diethylene glycol and other substances, and can greatly improve the selectivity of the esterification reaction.
[0009] (2) Synergistic solubilizing effect of weak hydrogen bonding and strong electron-withdrawing properties of anions: Trifluoromethanesulfonic acid anion ([OTf]) - It has a strong electron-withdrawing ability and can form weak hydrogen bonds with hydrogen atoms in PTA molecules through electrostatic interactions, thereby breaking the hydrogen bonds between terephthalic acid molecules. Additionally, [BDMIM] has a relatively large volume. + It can form a spatial barrier around the dissociated PTA molecules, preventing the PTA molecules from re-aggregating, thereby increasing the solubility of PTA in EG, expanding the reaction interface, and thus accelerating the esterification reaction rate.
[0010] (3) Polar environment inhibits side reactions: At the reaction temperature (222~227℃), [BDMIM] + [OTf] - The dielectric constant of the ionic liquid (ε=18.5, 25℃) is significantly higher than that of pure EG (ε=37.7, 25℃, the dielectric constant of EG decreases more rapidly at high temperatures), which can form a stable polar environment. This environment can stabilize the positive charge of the carboxyl carbon of PTA through electrostatic interactions, promote the esterification reaction, and inhibit the bimolecular nucleophilic substitution reaction of EG—intermolecular dehydration (diethylene glycol), thus suppressing the occurrence of side reactions.
[0011] Compared with existing technologies, this method reduces the esterification reaction temperature from 230–233℃ (under single antimony trioxide catalysis) to 222–227℃. For every ton of PET produced, approximately 80 kg of steam consumption can be saved (calculated based on a steam enthalpy of 2700 kJ / kg). A PET production line with an annual capacity of 100,000 tons can save approximately 300 tons of standard coal annually, thereby reducing production costs. Furthermore, the PET product obtained using this method has an intrinsic viscosity of 0.70–0.75 dL / g, terminal carboxyl group content ≤50 mmol / kg, L value ≥60, and b value ≤4.5, exhibiting high product quality and meeting the performance requirements of bottle-grade or fiber-grade PET.
[0012] Optionally, the above application includes the following steps: adding purified terephthalic acid, ethylene glycol, 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate and polycondensation catalyst into a reactor, replacing the air in the reactor with an inert gas, controlling the pressure in the reactor to be 0.20-0.24 MPa, heating to 222-227°C, stirring to carry out the esterification reaction for 80-110 min, depressurizing to atmospheric pressure, then heating to 260-280°C, carrying out the polycondensation reaction under negative pressure, and obtaining PET product after the polycondensation reaction is completed.
[0013] Optionally, the amount of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate used is 0.02 to 0.5% of the mass of purified terephthalic acid.
[0014] Optionally, the 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate has a purity of ≥98%, a water content of ≤0.5%, and a mass loss rate of ≤0.3% after 4 hours of constant temperature at 250°C.
[0015] Optionally, the polycondensation catalyst is antimony trioxide, and the amount of antimony trioxide used is 220 ppm of antimony as a percentage of the mass of purified terephthalic acid.
[0016] Optionally, the polycondensation reaction includes a pre-polycondensation reaction and a final polycondensation reaction. During the pre-polycondensation reaction, the pressure inside the reactor is reduced to -0.09 MPa, the reaction time is 30 to 40 min, and the reaction temperature is 260 to 265 °C. During the final polycondensation reaction, the vacuum degree inside the reactor is increased to ≤100 Pa, the reaction temperature is 270 to 280 °C, the stirring rate is 80 r / min, and the stirring power is increased from 32 W to more than 60 W to terminate the reaction.
[0017] Optionally, the molar ratio between purified terephthalic acid and ethylene glycol is 1:1.4 to 1.6.
[0018] Optionally, the heating rate during the esterification reaction is controlled at 2–3 °C / min. Such a heating rate can avoid local overheating that could lead to EG dehydration to acetaldehyde or etherification to diethylene glycol (DEG), and the amount of DEG generated can be controlled to ≤1.2%. Detailed Implementation
[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0020] This invention provides the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate as a co-catalyst in the direct esterification synthesis of PET, specifically including the following steps: (1) Esterification stage: Purified terephthalic acid and ethylene glycol are added to the reactor at a molar ratio of 1:1.4 to 1.6, and 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate and polycondensation catalyst (antimony trioxide) are added at the same time. The amount of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate is 0.02 to 0.5% of the mass of purified terephthalic acid. The purity of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate is ≥98%, the water content is ≤0.5%, and the mass loss rate at 250℃ for 4 hours is ≤0.3%. The amount of antimony trioxide is 200 to 220 ppm of antimony as a percentage of the mass of purified terephthalic acid. High-purity nitrogen is used to replace the air in the reactor to ensure that the oxygen content in the reactor is ≤0.1%. Then, the initial pressure in the reactor is controlled at 0.2 MPa, and the reactor is heated to 222-227℃ at a heating rate of 2-3℃ / min. The pressure is controlled between 0.20-0.24 MPa, and the esterification reaction is carried out by stirring. During the reaction, the generated esterified water is separated in real time (collected through a water separator) until the column top temperature (the temperature measured by the thermocouple at the top of the water separator is the column top temperature) begins to drop. The pressure in the reactor is gradually reduced to atmospheric pressure, and the esterification reaction ends.
[0021] (2) Pre-polymerization stage: After the esterification reaction is completed, the pressure in the reactor is slowly reduced to -0.09 MPa, the reaction time is 30 to 40 min, and the reaction temperature is 260 to 265℃.
[0022] (3) Final polycondensation stage: The vacuum degree in the reactor is increased to ≤100 Pa, the reaction temperature is 270~280℃, the stirring rate is 80 r / min, and the stirring power is increased from 32W to above 60W to terminate the reaction, thus obtaining the PET product. The intrinsic viscosity of this PET product is 0.70~0.75 dL / g, the end carboxyl group content is ≤50 mmol / kg, the L value is ≥60, and the b value is ≤4.5.
[0023] The following specific examples illustrate the present invention in detail. It should also be understood that the following examples are only for specific illustrative purposes and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values in the examples below.
[0024] Example 1 This embodiment provides the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate as a cocatalyst in the direct esterification synthesis of PET, which includes the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.4. Then, 3.75 g of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate ([BDMIM] OTf, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 222℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 110 min and the amount of esterified water was 179 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0025] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 280°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70.6 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this example had an esterification rate of 98.5%, a terminal carboxyl group content of 46.3 mmol / kg, and a b-value of 4.2. Furthermore, in this example, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used, and the stirring rate and stirring power were adjusted and displayed using a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0026] Example 2 This embodiment provides the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate as a cocatalyst in the direct esterification synthesis of PET, which includes the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.6. Then, 0.15 g of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate ([BDMIM] OTf, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 225℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 90 min, and the amount of esterified water was 171 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0027] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 270°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70.6 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this example had an esterification rate of 98.7%, a terminal carboxyl group content of 49.7 mmol / kg, and a b-value of 4.2. Furthermore, in this example, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used, and the stirring rate and stirring power were adjusted and displayed using a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0028] Example 3 This embodiment provides the application of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate as a cocatalyst in the direct esterification synthesis of PET, which includes the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate ([BDMIM] OTf, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Second, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 80 min, and the amount of esterified water was 167 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0029] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 275°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 68.4 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this example had an esterification rate of 98.2%, a terminal carboxyl group content of 49.7 mmol / kg, and a b-value of 2.8. Furthermore, in this example, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used, and the stirring rate and stirring power were adjusted and displayed using a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0030] Comparative Example 1 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-n-butyl-3-methylimidazolium trifluoromethane sulfonate ([BMIM] OTf, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 135 min and the amount of esterified water was 191 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0031] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 97.3%, a terminal carboxyl group content of 40.7 mmol / kg, and a b-value of 11.5. In addition, in this embodiment, a miniature DC geared motor (Zibo Boshan Yabo Micro Motor Co., Ltd.) of model J110SZ52PX4A1 was used, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0032] Comparative Example 2 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-hexyl-2,3-dimethylimidazolium trifluoromethane sulfonate ([HDMIM] OTf, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 110 min and the amount of esterified water was 210 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0033] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 98.2%, a terminal carboxyl group content of 46.9 mmol / kg, and a b-value of 5.3. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0034] Comparative Example 3 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM] BF4, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 110 min and the amount of esterified water was 201 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0035] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 97.6%, a terminal carboxyl group content of 46.3 mmol / kg, and a b-value of 8.9. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0036] Comparative Example 4 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ([BDMIM] PF6, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 110 min and the amount of esterified water was 185 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0037] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 98.3%, a terminal carboxyl group content of 45.7 mmol / kg, and a b-value of 9.9. In addition, in this embodiment, a miniature DC geared motor (Zibo Boshan Yabo Micro Motor Co., Ltd.) of model J110SZ52PX4A1 was used, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0038] Comparative Example 5 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of 1-butyl-3-methylimidazolium methanesulfonate ([BMIM] MS, purity ≥98%, water content ≤0.5%, mass loss rate ≤0.3% after 4 hours of isothermal treatment at 250℃) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced 3 times to ensure oxygen content ≤0.1%). Then, the initial pressure inside the polymerization reactor was controlled at 0.2 MPa, and the reactor was heated to 227℃ at a heating rate of 2℃ / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the esterification reaction was carried out by stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to drop. At this point, the reaction duration was 135 min and the amount of esterified water was 189 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0039] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 71.6 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 97.7%, a terminal carboxyl group content of 46.7 mmol / kg, and a b-value of 9.5. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0040] Comparative Example 6 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3 L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of zinc oxide (ZnO) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced three times to ensure the oxygen content inside the reactor was ≤0.1%). The initial pressure inside the polymerization reactor was then controlled at 0.2 MPa, and the reactor temperature was raised to 227 °C at a rate of 2 °C / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the reaction was carried out with stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to decrease. At this point, the reaction duration was 100 min, and the amount of esterified water was 171 mL. Gradually reduce the pressure to atmospheric pressure, and the esterification reaction ends. The product at this stage is bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0041] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70.3 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 98.4%, a terminal carboxyl group content of 45.9 mmol / kg, and a b-value of 10.6. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0042] Comparative Example 7 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3 L polymerization reactor at a molar ratio of 1:1.5. Then, 0.25 g of titanium dioxide (TiO2) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced three times to ensure the oxygen content inside the reactor was ≤0.1%). The initial pressure inside the polymerization reactor was then controlled at 0.2 MPa, and the reactor temperature was raised to 227 °C at a rate of 2 °C / min. During the reaction, the pressure inside the polymerization reactor was controlled between 0.20 and 0.24 MPa, and the reaction was carried out with stirring at 80 r / min. During the process, the generated esterified water was separated in real time (collected through a water separator) until the column top temperature began to decrease. At this point, the reaction duration was 118 min, and the volume of esterified water was 212 mL. Gradually reduce the pressure to atmospheric pressure, and the esterification reaction ends. The product at this stage is bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0043] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 98.1%, a terminal carboxyl group content of 46.5 mmol / kg, and a b-value of 9.4. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0044] Comparative Example 8 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3 L polymerization reactor at a molar ratio of 1:1.5. Then, 1.25 g of aluminum isopropoxide (Al(OPri)3) and 0.2 g of antimony trioxide polycondensation catalyst were added. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced three times to ensure an oxygen content ≤0.1%). The initial pressure inside the reactor was controlled at 0.2 MPa, and the reactor temperature was raised to 227 °C at a rate of 2 °C / min. During the reaction, the pressure inside the reactor was controlled between 0.20 and 0.24 MPa, and the reactor was stirred at 80 r / min for esterification. During the process, the generated esterified water was separated in real time (collected using a water separator) until the column top temperature began to decrease. At this point, the reaction duration was 107 min, and the amount of esterified water was 172 mL. Gradually reduce the pressure to atmospheric pressure, and the esterification reaction ends. The product at this stage is bis(hydroxyethyl) terephthalate (BHET) prepolymer.
[0045] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 81.2 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 98.8%, a terminal carboxyl group content of 43.9 mmol / kg, and a b-value of 7.8. In addition, in this embodiment, a miniature DC geared motor (Zibo Boshan Yabo Micro Motor Co., Ltd.) of model J110SZ52PX4A1 was used, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0046] Comparative Example 9 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5, followed by 0.2 g of antimony trioxide polycondensation catalyst. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced three times to ensure an oxygen content ≤0.1%). The initial pressure inside the reactor was then controlled at 0.2 MPa, and the reactor temperature was raised to 227°C at a rate of 2°C / min. During the reaction, the pressure inside the reactor was maintained between 0.20 and 0.24 MPa, and the reactor was stirred at 80 r / min for esterification. During the process, the generated esterified water was separated in real time (collected using a water separator) until the column top temperature began to decrease. At this point, the reaction duration was 120 min, and the esterified water volume was 175 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was diethyl terephthalate (BHET) prepolymer.
[0047] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 97.4%, a terminal carboxyl group content of 41.2 mmol / kg, and a b-value of 3.6. In addition, in this embodiment, a miniature DC geared motor (Zibo Boshan Yabo Micro Motor Co., Ltd.) of model J110SZ52PX4A1 was used, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0048] Comparative Example 10 This comparative example provides a method for the direct esterification synthesis of PET, including the following steps: First, purified terephthalic acid (PTA, 750 g) and ethylene glycol (EG) were added to a 3L polymerization reactor at a molar ratio of 1:1.5, followed by 0.2 g of antimony trioxide polycondensation catalyst. Next, high-purity nitrogen was introduced into the polymerization reactor to replace the air (replaced three times to ensure an oxygen content ≤0.1%). The initial pressure inside the reactor was then controlled at 0.2 MPa, and the reactor temperature was raised to 233℃ at a rate of 2℃ / min. During the reaction, the pressure inside the reactor was maintained between 0.20 and 0.24 MPa, and the reactor was stirred at 80 r / min for esterification. During the process, the generated esterified water was separated in real time (collected via a water separator) until the column top temperature began to decrease. At this point, the reaction duration was 89 min, and the esterified water volume was 182 mL. The pressure was gradually reduced to atmospheric pressure, and the esterification reaction ended. The product at this stage was diethyl terephthalate (BHET) prepolymer.
[0049] After the esterification reaction was completed, the vacuum pump was turned on, and the pressure inside the polymerization reactor was slowly reduced to -0.09 MPa, while the temperature was raised to 260–265°C. The reaction was stirred for 30–40 min. Then, the vacuum level inside the polymerization reactor was increased to ≤100 Pa, the temperature was raised to 277°C, and the stirring rate was 80 r / min until the stirring power increased from 32 W to 70 W, at which point the reaction was terminated, yielding the PET product. The PET product obtained in this comparative example had an esterification rate of 97.7%, a terminal carboxyl group content of 43.5 mmol / kg, and a b-value of 2.7. In addition, a miniature DC geared motor (model J110SZ52PX4A1, Zibo Boshan Yabo Micro Motor Co., Ltd.) was used in this embodiment, and the stirring rate and stirring power were adjusted and displayed through a reactor controller (purchased from Weihai Xingyu Chemical Machinery Co., Ltd.).
[0050] The main parameters in Examples 1-3 and Comparative Examples 1-10 are shown in Tables 1 and 2.
[0051] Table 1
[0052] Table 2
[0053] The intrinsic viscosity, terminal carboxyl group content, color value L, and color value b in Tables 1 and 2 were tested according to GB / 17931 standard.
[0054] As shown in Tables 1 and 2, compared to the cocatalysts selected in Comparative Examples 1-8, the cocatalysts selected in Examples 1-3 significantly reduced the color value b of PET. Simultaneously, the intrinsic viscosity of PET remained at 0.70–0.75 dL / g, the terminal carboxyl group content was ≤50 mmol / kg, and the L value was ≥60, indicating good PET product quality. Furthermore, a comparison between Example 3 and Comparative Example 9 shows that the intrinsic viscosity of PET in Example 3 was higher than that in Comparative Example 9, while the color value b of PET in Example 3 was lower than that in Comparative Example 9. This demonstrates that 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate, as a cocatalyst, can increase the intrinsic viscosity of PET while reducing its color value b, thereby improving PET quality. A comparison of Example 3 and Comparative Example 10 shows that the esterification temperature in Example 3 was 6°C lower than that in Comparative Example 10. The intrinsic viscosity of PET in Example 3 was higher than that in Comparative Example 10, the end carboxyl group content was slightly higher than that in Comparative Example 10, and the color value L was slightly lower than that in Comparative Example 10. The color values b of the two were very similar. Therefore, it can be seen that the addition of the co-catalyst 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate in this invention can reduce the esterification reaction temperature and ensure that the quality of the synthesized PET meets the basic performance requirements of bottle-grade or fiber-grade PET, thereby reducing the production cost of PET.
[0055] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can improve and implement this solution based on the guidance provided in this application and their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness or practicality of the invention. The scope of protection claimed in this application should be determined by the content of its claims. The specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
Application of 1,1-Butyl-2,3-dimethylimidazolium trifluoromethanesulfonate as a co-catalyst in the direct esterification synthesis of PET.
2. The application according to claim 1, characterized in that: Includes the following steps: Purified terephthalic acid, ethylene glycol, 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate, and a polycondensation catalyst are added to a reactor. The air inside the reactor is replaced with an inert gas, and the pressure inside the reactor is controlled at 0.20–0.24 MPa. The reactor is heated to 222–227°C and stirred for esterification reaction for 80–110 min. The pressure is then released to atmospheric pressure, and the temperature is raised to 260–280°C. Polycondensation reaction is carried out under negative pressure. After the polycondensation reaction is completed, PET product is obtained.
3. The application according to claim 2, characterized in that: The amount of 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate used is 0.02 to 0.5% of the mass of purified terephthalic acid.
4. The application according to claim 2, characterized in that: The 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate has a purity of ≥98%, a water content of ≤0.5%, and a mass loss rate of ≤0.3% after 4 hours of constant temperature at 250℃.
5. The application according to claim 2, characterized in that: The polycondensation catalyst is antimony trioxide, and the amount of antimony trioxide used is 220 ppm of antimony as a percentage of the mass of purified terephthalic acid.
6. The application according to claim 2, characterized in that: The polycondensation reaction includes a pre-polycondensation reaction and a final polycondensation reaction. During the pre-polycondensation reaction, the pressure inside the reactor is reduced to -0.09 MPa, the reaction time is 30 to 40 min, and the reaction temperature is 260 to 265℃. During the final polycondensation reaction, the vacuum degree inside the reactor is increased to ≤100 Pa, the reaction temperature is 270 to 280℃, the stirring rate is 80 r / min, and the stirring power is increased from 32W to over 60W to terminate the reaction.
7. The application according to claim 2, characterized in that: The molar ratio between purified terephthalic acid and ethylene glycol is 1:1.4 to 1.
6.
8. The application according to claim 2, characterized in that: The heating rate is controlled at 2-3℃ / min during the esterification reaction.
9. The application according to claim 2, characterized in that: The intrinsic viscosity of the PET product is 0.70–0.75 dL / g, the end carboxyl group content is ≤50 mmol / kg, the L value is ≥60, and the b value is ≤4.5.