Method for preparing terephthalate plasticizer through low-temperature esterification

Abstract

The invention discloses a method for preparing a terephthalate plasticizer through low-temperature esterification. According to the method, the cucurbit [6] urea-modified Oxyma catalyst is used for activating terephthalic acid to form an active intermediate, the esterification reaction energy barrier is reduced, the terephthalate plasticizer is prepared at low temperature, and meanwhile, the cucurbit [6] urea-Oxyma catalyst subjected to the esterification reaction is directionally recovered through a competitive guest under the host-guest action. The method realizes preparation of the terephthalate plasticizer through low-temperature esterification, has high product yield, can directionally recover the catalyst Oxyma, and accords with the green and environmental protection concept.

Description

Technical Field

[0001] The invention relates to a method for preparing terephthalate plasticizer by low-temperature esterification, belonging to the technical field of organic chemical industry. Background Art

[0002] Plasticizers are widely used polymer material additives in industry, which can effectively give polymers good ductility and flexibility. The traditional plasticizer market is dominated by phthalic plasticizers, but in recent years, studies have found that phthalic plasticizers have human reproductive toxicity safety issues, so the development of non-toxic and harmless plasticizers is the current mainstream development trend. Benzene plasticizers are a type of plasticizer with good application prospects. They have the advantages of high plasticizing efficiency and environmental protection. At present, the Fischer esterification method is mainly used in the preparation of terephthalate plasticizers in industry. This method uses terephthalic acid and alcohol as raw materials, concentrated sulfuric acid as a catalyst, and reacts at 180~230℃ for 8~12 hours to prepare terephthalate plasticizer products. However, this method has problems such as catalyst corrosion equipment and high process energy consumption. Based on this, researchers developed the Steglich esterification method. This method can form active intermediates between raw materials and catalysts, reduce the reaction energy barrier, and thus achieve efficient reaction, and terephthalate plasticizers can be synthesized under mild conditions. However, although the Steglich esterification method can effectively reduce process energy consumption, its catalyst is difficult to recover. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the existing methods and to provide a method for preparing terephthalate plasticizers by low-temperature esterification, which is characterized in that the process steps and conditions of the method are as follows, and the parts of the following materials are all parts by weight: (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 120-180 parts of potassium persulfate are dispersed in 1000 parts of water, and reacted at 70-90°C under nitrogen protection for 7-9 hours. After the reaction, the mixture is cooled and filtered. The filtrate is dried under vacuum, and the obtained solid is reacted with 300-500 parts of cyanoacetic acid at 70-90°C for 3-5 hours. The obtained product is then dispersed with 400-600 parts of nitrous acid in 1000 parts of 5% sulfuric acid, and reacted at 60-80°C for 2-4 hours. Finally, the mixture is cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of alcohol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform are mixed evenly, and reacted at 20°C~40°C for 4~8 hours. After the reaction is completed, the reaction liquid is filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and the catalyst: add 5 to 10 parts of silica microspheres with a competitive guest immobilized on the surface to the organic phase obtained in step (2), stir at 20 to 25°C for 30 to 60 minutes, then filter and collect the organic phase, spin-dry it to obtain the terephthalate plasticizer product; heat the filtered solid in 10 parts of acetonitrile at 60°C for 1 to 3 hours, collect the supernatant and remove the solvent, and recover the cucurbit[6]uril-Oxyma catalyst; The alcohol in step (2) is one or more of n-butanol, isooctyl alcohol, n-hexyl alcohol, n-octanol, and isodecanol; The competitive guest immobilized on the surface of the silica microspheres in step (2) is one or more of diamine, pentamethylenediamine and hexamethylenediamine.

[0004] The principle involved in the present invention is: (1) In the present invention, the carboxyl group of terephthalic acid is first activated by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, i.e., by EDC, to generate an O-acylisourea active intermediate, which then undergoes acyl transfer with Oxyma to form an Oxyma active ester, and then undergoes alcoholysis to obtain the product ester. This method greatly reduces the reaction energy barrier and effectively solves the problem of high energy consumption in traditional Fischer esterification.

[0005] (2) The present invention utilizes the characteristic that the tertiary hydrocarbon at the equatorial position of cucurbit[6]uril can be oxidized, first prepares hydroxycucurbit[6]uril, then converts the hydroxyl group into cyanoacetate group, and finally obtains cucurbit[6]uril-Oxyma catalyst by nitrosation. The applicant has found through a large number of experiments that the grafting density of hydroxycucurbit[6]uril is affected by the number of potassium persulfate and the reaction time. When the potassium persulfate is greater than 120-180 parts and the reaction time is greater than 7-9 hours, the hydroxyl substitution degree is high and the Oxyma grafting density is greater than 10, thereby forming a large steric hindrance, affecting the formation of activated intermediates and reducing the esterification yield (see Comparative Example 1); when the potassium persulfate is less than 120-180 parts and the reaction time is less than 7-9 hours, the Oxyma grafting density is less than 5, the formation of activated intermediates is relatively small, resulting in an increase in esterification time and a decrease in the yield of terephthalate plasticizer (see Comparative Example 2).

[0006] (3) When synthesizing terephthalate plasticizers by the general Steglich esterification method, the oxyma catalyst is often difficult to recover, resulting in increased production costs. For this reason, the present invention uses a cucurbit[6]uril-oxyma catalyst. The cucurbit[6]uril in the present invention is a rigid macrocyclic compound composed of six glycoside urea units bridged by methylene groups, having a hydrophobic cavity and two electron-rich holes surrounded by carbonyl groups. The cavity can selectively include fatty amine compounds by hydrophobic interaction. The present invention uses the host-guest interaction between cucurbit[6]uril-oxyma and the competitive guest to directional adsorb the catalyst in the solution after the esterification reaction, and then desorbs the catalyst by increasing the temperature, thereby recovering the catalyst. In the present invention, Oxyma can only be modified at the waist of cucurbit [6] uril, and cucurbit [7] uril and cucurbit [8] uril cannot be used. This is mainly because as the cavity structure of cucurbit uril becomes larger, terephthalic acid and alcohol will also combine with cucurbit uril, interfering with the adsorption of competitive guests, not only reducing the recovery rate of Oxyma, but also reducing the yield of terephthalate plasticizer (see Comparative Example 3).

[0007] (4) The present invention has found through a large number of experiments that the competitive guest for adsorbing cucurbit[6]uril-Oxyma must be one or more of butanediamine, pentanediamine, and hexanediamine. If short-chain amines such as propylenediamine and the like are grafted, the host-guest interaction is weak and it is difficult to effectively adsorb cucurbit[6]uril-Oxyma (see Comparative Example 4); if spermine is grafted, the combined adsorption is too strong and it is difficult to remove and recover the catalyst (see Comparative Example 5).

[0008] Compared with the prior art, the present invention has the following positive effects: The present invention prepares a cucurbit [6] uril-oxygen catalyst, and the raw material and the catalyst form an active intermediate to reduce the reaction energy barrier, thereby mildly preparing a terephthalate plasticizer, and through the host-guest interaction between the cucurbit [6] uril-oxygen and the competitive guest, the catalyst in the solution after the esterification reaction is directional adsorbed, and then desorption is achieved by increasing the temperature, thereby recovering the catalyst. The present invention realizes the preparation of the terephthalate plasticizer under mild conditions, and at the same time solves the problem that the catalyst is difficult to recover in the general Steglich esterification method, and realizes the directional recovery of the catalyst. DETAILED DESCRIPTION

[0009] The present invention is specifically described below through embodiments, which are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical engineers in this field can make some non-essential improvements and adjustments to the present invention based on the contents of the above invention. Example 1

[0010] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 120 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 7 hours. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 300 parts of cyanoacetic acid at 70°C for 3 hours. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 hours. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of alcohol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 8 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and catalyst: 5 parts of silica microspheres with a competitive guest immobilized on the surface are added to the organic phase obtained in step (2), and the mixture is stirred at 20° C. for 60 minutes. The organic phase is then filtered, collected, and spin-dried to obtain a terephthalate plasticizer product. The filtered solid is heated in 10 parts of acetonitrile at 60° C. for 1 hour, and the supernatant is collected and the solvent is removed to recover the cucurbit[6]uril-Oxyma catalyst. The above-mentioned dibutyl terephthalate yield was 94.8%, and the cucurbit[6]uril-Oxyma catalyst recovery rate was 97.4%. Example 2

[0011] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 180 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 90°C under nitrogen protection for 9 hours. After the reaction, the mixture was cooled and filtered. The filtrate was dried under vacuum, and the obtained solid was reacted with 500 parts of cyanoacetic acid at 90°C for 5 hours. The obtained product was then co-dispersed with 600 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 80°C for 4 hours. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of alcohol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 40°C for 4 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and catalyst: add 10 parts of silica microspheres with competitive guests immobilized on the surface to the organic phase obtained in step (2), stir at 25°C for 30 minutes, then filter and collect and spin-dry the organic phase to obtain the terephthalate plasticizer product; heat the filtered solid in 10 parts of acetonitrile at 60°C for 3 hours, collect the supernatant and remove the solvent to recover the cucurbit[6]uril-Oxyma catalyst; The yield of the above dibutyl terephthalate product was 96.1%, and the recovery rate of the cucurbit[6]uril-Oxyma catalyst was 96.5%. Comparative Example 1

[0012] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 200 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 12 h. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 3000 parts of cyanoacetic acid at 70°C for 3 h. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 h. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of alcohol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 4 hours. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and catalyst: add 5 parts of silica microspheres with competitive guests immobilized on the surface to the organic phase obtained in step (2), stir at 20°C for 30 minutes, then filter and collect and spin-dry the organic phase to obtain the terephthalate plasticizer product; heat the filtered solid in 10 parts of acetonitrile at 60°C for 1 hour, collect the supernatant and remove the solvent, and then recover the cucurbit[6]uril-Oxyma catalyst; The above-mentioned dibutyl terephthalate product yield was 42.8%, and the cucurbit[6]uril-Oxyma catalyst recovery rate was 90.9%. Comparative Example 2

[0013] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 100 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 4 h. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 300 parts of cyanoacetic acid at 70°C for 3 h. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 h. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of n-butanol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 4 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and the catalyst: 5 parts of silica microspheres with pentamethylenediamine competitive guest immobilized on the surface are added to the organic phase obtained in step (2), and the mixture is stirred at 20° C. for 30 minutes. The organic phase is then filtered, collected, and dried to obtain the terephthalate plasticizer product; the filtered solid is heated in 10 parts of acetonitrile at 60° C. for 1 hour, and the supernatant is collected and the solvent is removed to recover the cucurbit[6]uril-Oxyma catalyst; The yield of the above dibutyl terephthalate product was 26.3%, and the recovery rate of the cucurbit[6]uril-Oxyma catalyst was 95.5%. Comparative Example 3

[0014] (1) Preparation of catalyst: 100 parts of cucurbit[7]uril and 120 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 7 hours. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 300 parts of cyanoacetic acid at 70°C for 3 hours. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 hours. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[7]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of n-butanol, 40 parts of cucurbit[7]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 4 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[7]uril-Oxyma and benzene products; (3) Separation and recovery of the product and catalyst: 5 parts of silica microspheres with pentamethylenediamine competitive guest immobilized on the surface are added to the organic phase obtained in step (2), and the mixture is stirred at 20° C. for 30 minutes. The organic phase is then filtered, collected, and dried to obtain the terephthalate plasticizer product; the filtered solid is heated in 10 parts of acetonitrile at 60° C. for 1 hour, and the supernatant is collected and the solvent is removed to recover the cucurbit[7]uril-Oxyma catalyst; The above-mentioned dibutyl terephthalate product yield was 50.8%, and the cucurbit[7]uril-Oxyma catalyst recovery rate was 43.7%. Comparative Example 4

[0015] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 120 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 7 hours. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 300 parts of cyanoacetic acid at 70°C for 3 hours. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 hours. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of n-butanol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 4 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and the catalyst: 5 parts of silica microspheres with propylenediamine competitive guest immobilized on the surface are added to the organic phase obtained in step (2), and the mixture is stirred at 20° C. for 30 minutes. The organic phase is then filtered, collected, and dried to obtain the terephthalate plasticizer product; the filtered solid is heated in 10 parts of acetonitrile at 60° C. for 1 hour, and the supernatant is collected and the solvent is removed to recover the cucurbit[6]uril-Oxyma catalyst; The above-mentioned dibutyl terephthalate product yield was 95.9%, and the cucurbit[6]uril-Oxyma catalyst recovery rate was 30.1%. Comparative Example 5

[0016] (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 120 parts of potassium persulfate were dispersed in 1000 parts of water, and reacted at 70°C under nitrogen protection for 7 hours. After the reaction, the mixture was cooled and filtered. The filtrate was vacuum dried, and the obtained solid was reacted with 300 parts of cyanoacetic acid at 70°C for 3 hours. The obtained product was then co-dispersed with 400 parts of nitrous acid in 1000 parts of 5% sulfuric acid and reacted at 60°C for 2 hours. Finally, the mixture was cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of n-butanol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform were mixed evenly and reacted at 20°C for 4 h. After the reaction was completed, the reaction solution was filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and the catalyst: 5 parts of silica microspheres with spermine competitive guest immobilized on the surface are added to the organic phase obtained in step (2), and the mixture is stirred at 20° C. for 30 minutes. The organic phase is then filtered, collected, and dried to obtain the terephthalate plasticizer product; the filtered solid is heated in 10 parts of acetonitrile at 60° C. for 1 hour, and the supernatant is collected and the solvent is removed to recover the cucurbit[6]uril-Oxyma catalyst; The above-mentioned dibutyl terephthalate product yield was 96.7%, and the cucurbit[6]uril-Oxyma catalyst recovery rate was 14.3%.

Claims

1. A method for preparing terephthalate plasticizer by low temperature esterification, characterized in that The process steps and conditions of the method are as follows, and the parts of the following materials are all parts by weight: (1) Preparation of catalyst: 100 parts of cucurbit[6]uril and 120-180 parts of potassium persulfate are dispersed in 1000 parts of water, and reacted at 70-90°C under nitrogen protection for 7-9 hours. After the reaction, the mixture is cooled and filtered. The filtrate is dried under vacuum, and the obtained solid is reacted with 300-500 parts of cyanoacetic acid at 70-90°C for 3-5 hours. The obtained product is then dispersed with 400-600 parts of nitrous acid in 1000 parts of 5% sulfuric acid, and reacted at 60-80°C for 2-4 hours. Finally, the mixture is cooled, filtered and dried to obtain the cucurbit[6]uril-Oxyma catalyst. (2) Low-temperature esterification: 100 parts of terephthalic acid, 300 parts of alcohol, 40 parts of cucurbit[6]uril-Oxyma, 30 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 120 parts of sodium bicarbonate, and 1000 parts of chloroform are mixed evenly, and reacted at 20°C~40°C for 4~8 hours. After the reaction is completed, the reaction solution is filtered and washed with water to obtain an organic phase containing cucurbit[6]uril-Oxyma and benzene products; (3) Separation and recovery of the product and the catalyst: add 5 to 10 parts of silica microspheres with a competitive guest immobilized on the surface to the organic phase obtained in step (2), stir at 20 to 25°C for 30 to 60 minutes, then filter and collect the organic phase, spin-dry it to obtain the terephthalate plasticizer product; heat the filtered solid in 10 parts of acetonitrile at 60°C for 1 to 3 hours, collect the supernatant and remove the solvent, and recover the cucurbit[6]uril-Oxyma catalyst; The alcohol in step (2) is one or more of n-butanol, isooctyl alcohol, n-hexyl alcohol, n-octanol, and isodecanol; The competitive guest immobilized on the surface of the silica microspheres in step (2) is one or more of diamine, pentamethylenediamine and hexamethylenediamine.