A method for preparing a titanium dioxide catalyst and its application in catalyzing polyester synthesis
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PEKING UNIV
- Filing Date
- 2026-05-29
- Publication Date
- 2026-06-30
AI Technical Summary
Existing titanium dioxide catalysts in polyester synthesis suffer from problems such as easy particle agglomeration, low specific surface area, imbalanced crystal structure ratio, high environmental pollution risk, high energy consumption and high cost, making it difficult to achieve green, simple, controllable and highly active and selective preparation.
The morphology and crystal form of TiO2 were synergistically controlled by tartaric acid complexation and nitrogen calcination, combined with low-temperature solvothermal reaction, to prepare a nanoscale homogeneous titanium dioxide catalyst with a particle size of 50-200 nm, a specific surface area of 50-200 m2/g, and anatase phase as the main component. This avoided the use of strong acids/bases and formed a porous carbon structure.
It achieves highly active and selective catalytic performance, reduces metal usage, improves the intrinsic viscosity and purity of polyester, reduces environmental pollution risks, and lowers energy consumption and costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic material preparation and catalysis technology, specifically relating to a method for preparing a titanium dioxide catalyst and its application in polyester synthesis. Background Technology
[0002] Titanium dioxide is a key catalyst in polyester synthesis, and its performance optimization has always been a focus of industrial catalysis research. Traditional antimony-based (such as Sb2O3), germanium-based (such as GeO2), and organotin catalysts are gradually being replaced due to problems such as high toxicity and poor selectivity. While nano-TiO2 catalysts have environmental advantages, existing technologies still face significant bottlenecks: On the one hand, TiO2 particles prepared by conventional sol-gel methods are prone to agglomeration, have low specific surface area, and an imbalance in the ratio of crystal forms (anatase / rutile), leading to dispersed active sites. For example, although high-temperature calcination (>500℃) can improve crystallinity, it will destroy the nanostructure and reduce surface activity. On the other hand, existing processes mostly rely on strong acids (such as HCl), strong bases (such as NH3·H2O), or organic solvents (such as toluene), posing environmental pollution risks. Furthermore, the products have low intrinsic viscosity and high ether bond content (>3%), which seriously affects the thermal stability and mechanical properties of polyester. For example, microwave-assisted methods require high temperature and high pressure conditions (>120℃, 500W), resulting in high energy consumption and demanding equipment requirements. The preparation of supported catalysts (such as graphene-TiO2 composites) involves complex steps (such as chemical vapor deposition) and noble metal precursors, leading to high costs and difficulty in large-scale production. Therefore, developing a green, simple, controllable method for preparing TiO2 catalysts with both high activity and selectivity has become a key requirement for overcoming the bottlenecks in polyester catalysis technology. Summary of the Invention
[0003] To achieve the above-mentioned technical objectives, this invention synergistically regulates the morphology and crystal form of TiO2 through tartaric acid complexation and nitrogen calcination, combined with low-temperature solvothermal reaction to inhibit particle agglomeration, thereby realizing a nanoscale homogeneous structure (particle size 50-200 nm, specific surface area 50-200 m²). 2 / g), and precisely control the crystal phase ratio (anatase-based), significantly improving its catalytic activity.
[0004] Specifically, the present invention adopts the following technical solution:
[0005] A method for preparing a titanium dioxide catalyst includes the following steps:
[0006] (1) Add titanium tetrachloride to a mixed solution of anhydrous ethanol and cyclohexane containing tartaric acid, and control the molar ratio of titanium tetrachloride to tartaric acid to be 0.2~4, and stir at 5~30℃ until a transparent solution is formed.
[0007] (2) Heat the solution from step (1) to reflux and react for a period of time until the solution becomes a white homogeneous system;
[0008] (3) After cooling the system to room temperature, centrifuge, wash, and vacuum dry to obtain a white powder precursor;
[0009] (4) The precursor was calcined in a nitrogen atmosphere at 350~450℃ to obtain a titanium dioxide catalyst.
[0010] Further, in step (1) above, the volume ratio of anhydrous ethanol to cyclohexane is 0.01 to 1. Preferably, the volume ratio of the anhydrous ethanol and cyclohexane mixed solution to titanium tetrachloride is 0.1:9.9 to 9.9:0.1.
[0011] Furthermore, the reflux reaction time in step (2) is 0.5 to 12 hours.
[0012] Further, after centrifugation in step (3), the precursor is washed with deionized water and ethanol in sequence, and then dried under vacuum at 60~100℃ to obtain a powdered precursor.
[0013] Furthermore, in step (4), the calcination temperature is 350~450℃ and the calcination time is 0.5~8 hours.
[0014] The above preparation method uses TiCl4 as the titanium source and tartaric acid as the complexing agent to form a homogeneous solution at 5-30℃, avoiding the use of strong acids / bases in the traditional hydrolysis method; the dispersion of TiO2 particles is controlled by a mixed solvent of ethanol / cyclohexane, and uniform nucleation is promoted by reflux reaction; finally, calcination is carried out at 350-450℃ under nitrogen protection to carbonize tartaric acid to form a porous structure, while inhibiting the transition of crystal form to rutile phase and retaining highly active crystal faces.
[0015] The titanium dioxide catalysts obtained by the above preparation method have a particle size of 20-200 nm and a specific surface area of 50-200 m². 2 / g, the titanium dioxide crystal form is mainly anatase phase (≥60%), and its surface is loaded with a thin layer of porous carbon.
[0016] The titanium dioxide catalyst prepared in this invention can be applied to the condensation polymerization of polyols and polyacids to form polyesters, exhibiting high activity and high selectivity. For example, it can be used to catalyze the condensation polymerization of terephthalic acid and ethylene glycol to form PET (polyethylene terephthalate), or to catalyze the condensation polymerization of terephthalic acid and 1,3-propanediol to form PTT (polypropylene terephthalate), or to catalyze the condensation polymerization of terephthalic acid and 1,4-butanediol to form PBT (polybutylene terephthalate), or to catalyze the condensation polymerization of 1,4-succinic acid and 1,4-butanediol to form PBS (polybutylene succinate).
[0017] Preferably, the amount of titanium dioxide catalyst used in polyester synthesis is 0.01% to 1.0% of the molar amount of the raw material polybasic acid.
[0018] The beneficial effects of this invention include:
[0019] This invention utilizes tartaric acid complexation and nitrogen calcination to synergistically regulate the morphology and crystal structure of titanium dioxide catalysts, offering significant advantages over traditional processes: **Green and Environmentally Friendly Process:** Anhydrous ethanol / cyclohexane mixed solvent replaces strong acids, strong bases, and organic solvents (toluene), avoiding the generation of toxic byproducts and meeting green chemistry requirements. Tartaric acid, as a bio-based complexing agent, carbonizes after the reaction to form a porous structure, significantly improving catalyst activity. **Precise Control of Particle Size and Crystal Form:** Nucleation is achieved at low temperatures of 5-30℃ using the sol-gel method, combined with ethanol / cyclohexane mixed solvent (volume ratio 0.01-1) to regulate dispersibility, resulting in nanoparticles with a diameter of 20-200 nm. Nitrogen calcination at 350-450℃ inhibits the transformation of the crystal form to the rutile phase, significantly enhancing the density of surface active sites. **Breakthrough in Catalytic Performance:** In PET synthesis, with 0.01% catalyst, the intrinsic viscosity of the product reaches 0.85 dL / g, and the ether bond content is <1.5%. Compared to traditional Sb2O3 catalysts, the amount of metal used is more than 80% less. Detailed Implementation
[0020] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.
[0021] Unless otherwise specified, the raw materials and catalysts used in the embodiments and comparative examples of this invention were all purchased commercially.
[0022] The testing method in the embodiments of the present invention is as follows:
[0023] The intrinsic viscosity was tested using the capillary viscometer method (Ubbelohde viscometer), and the diethylene glycol content in the polyester was analyzed using the methanol ester degradation method, referring to the GB / T 14190-2017 standard.
[0024] Example 1
[0025] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane containing 4 mol of tartaric acid (volume ratio of anhydrous ethanol to cyclohexane 0.1, total volume 100 mL). The solution was stirred at 5 °C to form a transparent solution. The mixture was refluxed for 12 h, and the solution gradually turned white to form a homogeneous system. After centrifugation, the solution was dried at 100 °C to obtain the precursor. The precursor was calcined at 350 °C under nitrogen for 8 h to obtain the TiO2-S1 catalyst.
[0026] Using 0.1 mol of terephthalic acid and 0.14 mol of ethylene glycol as raw materials (alkyd-acid molar ratio of 1.4), and TiO2-S1 as catalyst (TiO2-S1 amount was 0.01% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 5 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PET were tested, and the results are shown in Table 1.
[0027] Example 2
[0028] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane containing 0.2 mol of tartaric acid (volume ratio of anhydrous ethanol to cyclohexane: 1, total volume: 100 mL). The solution was stirred at 30 °C to form a transparent solution. The mixture was refluxed for 6 h, and the solution gradually turned white to form a homogeneous system. After centrifugation, the solution was dried at 100 °C to obtain the precursor. The precursor was calcined at 450 °C under nitrogen for 0.5 h to obtain the TiO2-S2 catalyst.
[0029] Using 0.1 mol of terephthalic acid and 0.15 mol of 1,4-butanediol as raw materials (alcohol-acid molar ratio of 1.5), and TiO2-S2 as catalyst (TiO2-S2 amount was 0.05% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 5 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PBT were tested, and the results are shown in Table 1.
[0030] Example 3
[0031] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane containing 0.2 mol of tartaric acid (volume ratio of anhydrous ethanol to cyclohexane 0.5, total volume 100 mL). The solution was stirred at 30 °C to form a transparent solution. The mixture was refluxed for 6 h, and the solution gradually turned white to form a homogeneous system. After centrifugation, the solution was dried at 100 °C to obtain the precursor. The precursor was calcined at 450 °C under nitrogen for 0.5 h to obtain the TiO2-S3 catalyst.
[0032] Using 0.1 mol of terephthalic acid and 0.13 mol of 1,3-propanediol as raw materials (alcohol-acid molar ratio of 1.3), and TiO2-S3 as catalyst (TiO2-S3 amount was 0.02% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 5 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PTT were tested, and the results are shown in Table 1.
[0033] Example 4
[0034] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane containing 2 mol of tartaric acid (volume ratio of anhydrous ethanol to cyclohexane 0.5, total volume 100 mL). The solution was stirred at 5 °C to form a transparent solution. The refluxed reaction solution gradually turned white to form a homogeneous system. The reaction was refluxed for 2 h, centrifuged, and dried at 100 °C to obtain the precursor. Calcination under nitrogen at 450 °C for 4 h yielded the TiO2-S4 catalyst.
[0035] Using 0.1 mol of 1,4-succinic acid and 0.12 mol of 1,4-butanediol as raw materials (alcohol-acid molar ratio of 1.2), and TiO2-S4 as catalyst (TiO2-S4 amount was 0.05% of the molar amount of 1,4-succinic acid), the esterification reaction was carried out under nitrogen protection at 160℃~215℃ for 3 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 230℃ for 2.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PBS were tested, and the results are shown in Table 1.
[0036] Comparative Example 1
[0037] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane (volume ratio of anhydrous ethanol to cyclohexane 0.1, total volume 100 mL), and stirred at 5 °C to form a transparent solution. The solution was refluxed for 12 h, gradually turning white to form a homogeneous system. After centrifugation, the solution was dried at 100 °C to obtain the precursor. The precursor was calcined at 350 °C under nitrogen for 8 h to obtain the TiO2-D1 catalyst.
[0038] Using 0.1 mol of terephthalic acid and 0.14 mol of ethylene glycol as raw materials (alkyd-acid molar ratio of 1.4), and TiO2-D1 as catalyst (TiO2-D1 amount was 0.05% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 9 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PET-D1 were tested, and the results are shown in Table 1.
[0039] Comparative Example 2
[0040] 1 mol of TiCl4 was dissolved in a mixed solution of anhydrous ethanol and cyclohexane containing 4 mol of tartaric acid (volume ratio of anhydrous ethanol to cyclohexane 0.1, total volume 100 mL). The solution was stirred at 5 °C to form a transparent solution. After reflux for 12 h, the solution gradually turned white to form a homogeneous system. The solution was then centrifuged and dried at 100 °C to obtain the TiO2-D2 catalyst.
[0041] Using 0.1 mol of terephthalic acid and 0.14 mol of ethylene glycol as raw materials (alkyd-acid molar ratio of 1.4), and TiO2-D2 as catalyst (TiO2-D2 dosage was 0.05% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 7.5 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.0 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PET-D2 were tested, and the results are shown in Table 1.
[0042] Comparative Example 3
[0043] Using 0.1 mol of terephthalic acid and 0.14 mol of ethylene glycol as raw materials (alkyd-acid molar ratio of 1.4), and Sb2O3 as catalyst (Sb2O3 amount was 0.5% of the molar amount of terephthalic acid), the esterification reaction was carried out under nitrogen protection at 180℃~240℃ for 7.5 h. Then, under vacuum conditions, the polycondensation reaction was stopped at 260℃ for 1.5 h. The intrinsic viscosity and diethylene glycol content of the obtained polycondensation product PET-D3 were tested, and the results are shown in Table 1.
[0044] Table 1
[0045]
[0046] Note: PET – Polyethylene terephthalate; PBT – Polybutylene terephthalate; PTT – Polypropylene terephthalate; PBS – Polybutylene succinate.
[0047] In the catalytic synthesis of polyesters, the titanium dioxide catalyst prepared in this invention exhibits high activity and low dosage: In Example 1, a catalyst dosage of 0.01% (based on the molar amount of terephthalic acid) is sufficient to achieve an intrinsic viscosity of 0.862 dL / g for PET, significantly higher than that of Comparative Example 1 (0.05% dosage, intrinsic viscosity 0.301 dL / g), indicating significantly higher catalytic activity and a reduction in catalyst metal dosage by more than 80%. High selectivity: In all examples, the diethylene glycol content of PET, PBT, PTT, and PBS is less than 1.5% (e.g., 1.06% in Example 1 and 0.73% in Example 2), significantly lower than that of Comparative Example 1 (3.73%) and Comparative Example 2 (2.12%), indicating its effective suppression of side reactions and improvement of product purity. Strong process adaptability: Applicable to the synthesis of various polyesters (PET, PBT, PTT, PBS), it can operate stably under different alcohol-acid molar ratios (1.2~1.5), with intrinsic viscosity indicators meeting expectations, demonstrating good versatility. In summary, this catalyst achieves high activity and high selectivity through synergistic regulation of tartaric acid complexation and nitrogen calcination.
[0048] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the present invention using the disclosed technical content are equivalent to equivalent implementations and fall within the scope of the present invention.
Claims
1. A method for preparing a titanium dioxide catalyst, characterized in that, Includes the following steps: 1) Add titanium tetrachloride to a mixed solution of anhydrous ethanol and cyclohexane containing tartaric acid, and control the molar ratio of tetrabutyl titanate to tartaric acid to be 0.2~4, and stir at 5~30℃ until a transparent solution is formed. 2) Heat the solution from step 1) to reflux and react for a period of time until the solution becomes a white homogeneous system; 3) After cooling to room temperature, centrifuge, wash, and vacuum dry to obtain a white powder precursor; 4) The precursor was calcined in a nitrogen atmosphere at 350~450℃ to obtain a titanium dioxide catalyst.
2. The preparation method according to claim 1, characterized in that, The volume ratio of anhydrous ethanol to cyclohexane in step 1) is 0.01~1; the volume ratio of the mixed solution of anhydrous ethanol and cyclohexane to titanium tetrachloride is 0.1:9.9~9.9:0.
1.
3. The preparation method according to claim 1, characterized in that, In step 2), the reflux reaction time is 0.5 to 12 hours.
4. The preparation method according to claim 1, characterized in that, Step 4) Calcine at 350~450℃ for 0.5~8 hours.
5. The titanium dioxide catalyst obtained by the preparation method according to any one of claims 1 to 4.
6. The titanium dioxide catalyst according to claim 5, characterized in that, The titanium dioxide catalyst has a particle size of 20-200 nm and a thin porous carbon layer supported on its surface, with a specific surface area of 50-200 m². 2 / g.
7. The application of the titanium dioxide catalyst according to claim 5 or 6 in polyester synthesis, characterized in that, The titanium dioxide catalyst is used to catalyze the condensation polymerization of polyols and polyacids into polyesters.
8. The application as described in claim 7, characterized in that, The polyacid is selected from at least one of terephthalic acid and 1,4-succinic acid, and the polyol is selected from at least one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.
9. The application as described in claim 8, characterized in that, The titanium dioxide catalyst is used to catalyze the polycondensation of terephthalic acid and ethylene glycol to produce PET, or to catalyze the polycondensation of terephthalic acid and 1,3-propanediol to produce PTT, or to catalyze the polycondensation of terephthalic acid and 1,4-butanediol to produce PBT, or to catalyze the polycondensation of 1,4-succinic acid and 1,4-butanediol to produce PBS.
10. The application as described in claim 7, characterized in that, The titanium dioxide catalyst is used in polyester synthesis at a rate of 0.01% to 1.0% of the molar amount of the raw material polybasic acid.