CN112645812A - Start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene - Google Patents
Start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene Download PDFInfo
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- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
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Abstract
The invention relates to a start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene, which mainly solves the problems of low reaction speed and high impurity content of products in the prior art. The invention relates to a start-up method for preparing terephthalic acid by adopting liquid-phase oxidation of paraxylene, which comprises the following steps: (1) the oxidation reactor is made to obtain a mixture 1 comprising paraxylene, terephthalic acid, solvent and catalyst; (2) under the condition of oxidation reaction, the mixture 1 is in contact reaction with an oxygen source containing free oxygen to generate terephthalic acid; the catalyst comprises bromide and at least one selected from the group consisting of Co salt, Mn salt, Zr salt, Hf salt, Fe salt, Ni salt, Ce salt and La salt, and can be used for preparing terephthalic acid by liquid-phase oxidation of p-xylene.
Description
Technical Field
The invention relates to a start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene.
Background
Purified terephthalic acid, commonly known as PTA, is a basic raw material for synthesizing polyethylene terephthalate (PET), the demand of which is continuously increased, and the demand of global PTA is estimated to reach 6000 million tons in 2018. At present, the PTA production technology is mainly a two-step process of Paraxylene (PX) oxidation and hydrofining developed by Amoco company, and acetic acid is used as a solvent in the oxidation step and a Co-Mn-Br catalyst system is adopted; the hydrogenation is mainly carried out by adding p-aldehyde benzoic acid (4-CBA) into p-methyl benzoic acid (p-TA) under the catalyst of palladium carbon, and then centrifuging and washing with water to remove.
The different processes are different in oxidation reaction temperature (from 160 ℃ to 225 ℃) of each process, and the corresponding process conditions, reactor forms and flow design are different. ICI and Amoco reaction temperature is highest, the three-well-Amoco temperature is intermediate, and Eastman is lowest, which are respectively called high temperature oxidation, medium temperature oxidation and low temperature oxidation process.
No matter which process is adopted, bromine is needed as a cocatalyst, the bromine has strong corrosivity, and particularly under the high-temperature condition, so all reactors adopt expensive titanium materials; at the same time, too much bromine causes side reactions to occur, resulting in loss of solvent and raw materials. Many scholars both at home and abroad are studying to reduce the bromine content or completely replace bromine. U.S. Pat. No. 4,7985875 (Process for preparing aromatic polycarboxylic acid by liquid phase oxidation) describes a Process in which a bromine-containing ionic liquid is used as a promoter to achieve the same effect as a conventional catalyst, but this does not substantially reduce the bromine content. U.S. Pat. No. 6,53790 (Method to product aromatic dicarboxylic acids using cobalt and zirconium catalysts) uses cobalt and cerium as catalysts in a 7:1 molar ratio without the use of a bromine source, with a terephthalic acid yield of greater than 95%; the reaction time is 120min, but the catalyst dosage is large and exceeds 5 wt%, the 4-CBA content in the product exceeds 1.0 wt%, and the p-TA acid exceeds 2.0 wt%.
Disclosure of Invention
The invention aims to solve the technical problems of low reaction speed and high impurity content of a product in the prior art, and provides a start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene comprises the following steps:
(1) the oxidation reactor is made to obtain a mixture 1 comprising paraxylene, terephthalic acid, solvent and catalyst;
(2) under the condition of oxidation reaction, the mixture 1 is in contact reaction with an oxygen source containing free oxygen to generate terephthalic acid;
the catalyst includes bromide and at least one selected from the group consisting of Co salt, Mn salt, Zr salt, Hf salt, Fe salt, Ni salt, Ce salt and La salt.
We have surprisingly found that not only the conversion of p-xylene is accelerated but also the oxidation product is lower in the contents of p-tolualdehyde (4-CBA), p-toluic acid (p-TA), which are the main impurities, due to the addition of terephthalic acid.
In the above technical solutions, in order to reduce the introduction of impurities into the anionic part, the salt in the catalyst component is preferably acetate.
The technical key point of the present invention is that p-dibenzoic acid is added into the oxidation reactor in step (1), and for those skilled in the art, the types of bromide and metal salt in the catalyst, and the amounts of the components are not particularly limited, and those commonly used in the art can be used, and all can achieve comparable technical effects. In order to facilitate the same ratio, the mass concentration of Co in the mixture 1 is 300-800 ppmw, and the mass ratio of Co: mn: zr: la-500: (100-300): (5-50): (5-50); the mass concentration of Br in the mixture 1 is 500-2000 ppmw.
In the above technical solution, the solvent preferably comprises a carboxylic acid of C1-C8 and water.
In the above-described embodiment, the mass ratio of water to carboxylic acid is preferably greater than 0 and 0.2 or less. For example, but not limited to, a mass ratio of water to carboxylic acid of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, and the like.
In the above technical scheme, acetic acid is preferred as the carboxylic acid.
In the above technical scheme, the mass ratio of the solvent to the p-xylene is preferably 2 to 10. Such as but not limited to a solvent to para-xylene mass ratio of 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, and the like.
In the above technical solution, the mass ratio of terephthalic acid to p-xylene in step (1) is preferably 0.01 to 0.5. Such as but not limited to terephthalic acid to para-xylene mass ratio of 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and the like.
In the above technical solution, the oxygen source of the free oxygen may be pure oxygen or air. Preferably air, the air space velocity (the ratio of the gas volume flow rate to the volume of the mixture 1 in the step (1)) is preferably 2 to 5h-1. For example, but not limited to, the air space velocity may be 2.5h-1、3h-1、3.5h-1、4h-1、4.5h-1And so on.
In the technical scheme, the reaction pressure is preferably 0.8-2 MPa. For example, but not limited to, reaction pressures of 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa, 1.6MPa, 1.7MPa, 1.8MPa, 1.9MPa, etc.
Unless otherwise specified, all pressures referred to herein are gauge pressures.
In the technical scheme, the reaction temperature is preferably 160-250 ℃. For example, but not limited to, the reaction temperature is 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃ and the like.
In the technical scheme, the reaction time is preferably 0.5-8 h. For example, but not limited to, the reaction time may be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, and the like.
In the above technical scheme, the bromide is selected from inorganic bromide and/or organic bromide.
In the above-mentioned embodiment, the inorganic bromide preferably includes at least one selected from the group consisting of hydrogen bromide and an alkali metal bromide.
In the above technical solution, the organic bromide preferably comprises polybrominated alkanes selected from the group consisting of C2 to C4. Such as tribromoalkane or tetrabromoalkane. By way of non-limiting example, the organic bromide includes at least one selected from the group consisting of tetrabromoethane, tetrabromopropane, and tetrabromobutane.
In the products of the embodiments and the comparative examples of the present invention, firstly, the sample to be analyzed is completely dissolved in dimethyl sulfoxide, PX is analyzed by gas chromatography, and the chromatographic conditions are as follows: GDX-103 packed column (2m × 4mm), FID detector, and internal standard method for product quantification; analyzing TA, 4-CBA and p-TA acid by High Performance Liquid Chromatography (HPLC), wherein the chromatographic conditions are as follows: the column temperature is 30 ℃, the wavelength of the detector is 254nm, the mobile phase comprises methanol, acetonitrile and phosphate buffer solution, and the sample injection amount is 5 ul; the mobile phase composition (V/V) is as follows: 25% of methanol, 20% of acetonitrile, 55% of phosphate buffer (1 thousandth V/V), and 3-4% of PH; the flow rate was 1 mL/min. Quantification was performed by internal standard method.
The method for preparing terephthalic acid by oxidizing p-xylene achieves the same PX conversion rate, the reaction time can be shortened by more than one time, the main impurities of p-tolualdehyde (4-CBA) and p-toluic acid (p-TA) in the product are lower, and a better effect is achieved.
The mass of TA obtained in the actual oxidation product, i.e. the mass of TA added before the reaction, was calculated by HPLC analysis.
The mass of theoretical TA obtained by complete oxidation of PX is the mass of PX added in the reaction x 166 ÷ 106.
The invention is further illustrated by the following examples.
Detailed Description
[ example 1 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 8g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixing, adding into an autoclave, and sealing.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 60min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 2 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 4g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixing, adding into an autoclave, and sealing.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 60min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 3 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 12g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixed, added into an autoclave and sealed.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 60min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 4 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 8g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixing, adding into an autoclave, and sealing.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 45min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 5 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 8g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixing, adding into an autoclave, and sealing.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 90min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 6 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture), uniformly mixing, adding into an autoclave, and sealing.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 60min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
[ example 7 ]
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 8g of terephthalic acid, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate, and 0.05g of zirconium acetate (Zr (CH)3COO)4) 0.05g of lanthanum acetate pentahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine: 1000ppmw, based on the entire mixture), mixedAfter the mixture is uniform, the mixture is added into an autoclave and sealed.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 60min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
Comparative example 1
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
80g of p-xylene, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture) are weighed, mixed uniformly, added into an autoclave and sealed.
Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
Switching with air at 186 ℃ with air airspeed of 4h-1Keeping the temperature constantAnd reacting for 60 min.
And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
Comparative example 2
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture) are weighed, mixed uniformly, added into an autoclave and sealed.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 120min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
Comparative example 3
The reaction was carried out in a 1000ml autoclave made of titanium material with a magnetic stirrer, gas feed line, reflux condenser, thermocouple, rupture disk, with a stirring speed of 400rpm, heated by circulating hot oil. The reaction steps are as follows:
1) 80g of p-xylene, 400g of acetic acid, 10g of pure water, 0.8g of cobalt acetate tetrahydrate, 0.4g of manganese acetate tetrahydrate and 0.55g of 1,1,2, 2-tetrabromoethane (bromine is 1000ppmw based on the whole mixture) are weighed, mixed uniformly, added into an autoclave and sealed.
2) Adding 2.0MPa nitrogen gas to carry out airtight test for 30min, and determining that the pressure drop is not more than 0.1MPa within 30 min.
3) Adding nitrogen at a space velocity of 4h-1And the stirrer was started at a stirring speed of 400rpm and the temperature was raised to 186 ℃ while maintaining the pressure at 1.0 MPa.
4) Switching with air at 186 ℃ with air airspeed of 4h-1The reaction was carried out for 240min while maintaining the temperature.
5) And after the reaction, switching to nitrogen again, cooling to room temperature, relieving the pressure of the reaction kettle to normal pressure, discharging, performing vacuum filtration to obtain a solid sample, washing the solid sample with pure water for 5 times, wherein the amount of the pure water is 500ml each time, performing vacuum filtration on the washed product, drying for 8 hours at 110 ℃, and cooling for analysis. The analysis method comprises the following steps: dimethyl sulfoxide was added to completely dissolve the solid, and unreacted p-xylene was taken out and analyzed by gas chromatography, and Terephthalic Acid (TA), p-toluic acid (p-TA)) and p-aldehyde benzoic acid (4-CBA) were analyzed by high performance liquid chromatography.
The experimental conditions are shown in table 1, and the product data analysis is shown in table 2.
TABLE 1
TABLE 2
| PX conversion (%) | TA yield (%) | 4-CBA(ppmw) | p-TA(ppmw) | |
| Example 1 | 100 | 98.8 | 1200 | 658 |
| Example 2 | 100 | 98.5 | 1298 | 700 |
| Example 3 | 100 | 98.7 | 1186 | 726 |
| Example 4 | 99.8 | 98.4 | 2864 | 1096 |
| Example 5 | 100 | 99.1 | 968 | 597 |
| Example 6 | 99.7 | 98.2 | 3875 | 865 |
| Example 7 | 99.7 | 98.3 | 3659 | 905 |
| Comparative example 1 | 99.3 | 95.6 | 18653 | 12659 |
| Comparative example 2 | 99.6 | 97.3 | 8699 | 8000 |
| Comparative example 3 | 99.8 | 98.1 | 2438 | 968 |
Claims (10)
1. A start-up method for preparing terephthalic acid by liquid-phase oxidation of paraxylene comprises the following steps:
(1) the oxidation reactor is made to obtain a mixture 1 comprising paraxylene, terephthalic acid, solvent and catalyst;
(2) under the condition of oxidation reaction, the mixture 1 is in contact reaction with an oxygen source containing free oxygen to generate terephthalic acid;
the catalyst includes bromide and at least one selected from the group consisting of Co salt, Mn salt, Zr salt, Hf salt, Fe salt, Ni salt, Ce salt and La salt.
2. The method according to claim 1, wherein the solvent comprises a C1-C8 carboxylic acid and water.
3. The method according to claim 2, wherein the mass ratio of water to the carboxylic acid is more than 0 and 0.2 or less.
4. The method according to claim 1, wherein the mass ratio of the solvent to p-xylene is 2 to 10.
5. The method according to claim 1, wherein the mass ratio of terephthalic acid to paraxylene in the step (1) is 0.01 to 0.5.
6. The method according to claim 1, wherein the oxygen source of the free oxygen is pure oxygen or air.
7. According to claimThe method of claim 6, wherein the air airspeed is 2-5 h-1。
8. The method according to claim 1, wherein the reaction pressure is 0.8 to 2 MPa.
9. The method according to claim 1, wherein the reaction temperature is 160 to 250 ℃.
10. A method according to claim 1, characterized in that the bromide is selected from inorganic bromides and/or organic bromides.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113311087A (en) * | 2021-05-26 | 2021-08-27 | 浙江省化工产品质量检验站有限公司 | Method for measuring content of terephthalic acid in copolyester plastic |
| CN113354533A (en) * | 2021-06-01 | 2021-09-07 | 中国科学技术大学 | Method for preparing terephthalic acid by utilizing lignocellulose biomass |
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| CN103012120A (en) * | 2011-09-27 | 2013-04-03 | 中国石油化工股份有限公司 | Method for preparing terephthalic acid by oxidation refining process |
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| JPS54130529A (en) * | 1978-04-03 | 1979-10-09 | Asahi Chem Ind Co Ltd | Preparation of terephthalic acid |
| US5122307A (en) * | 1990-07-13 | 1992-06-16 | Shell Oil Company | Process for the oxidation of alcohols to acids |
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| CN113311087A (en) * | 2021-05-26 | 2021-08-27 | 浙江省化工产品质量检验站有限公司 | Method for measuring content of terephthalic acid in copolyester plastic |
| CN113354533A (en) * | 2021-06-01 | 2021-09-07 | 中国科学技术大学 | Method for preparing terephthalic acid by utilizing lignocellulose biomass |
| CN113354533B (en) * | 2021-06-01 | 2024-03-29 | 中国科学技术大学 | Method for preparing terephthalic acid by using lignocellulose biomass |
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