CN112958065A - Composite catalyst for producing dioctyl terephthalate, preparation method and application thereof - Google Patents
Composite catalyst for producing dioctyl terephthalate, preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a composite catalyst for producing plasticizer dioctyl terephthalate in the technical field of chemical production, a preparation process and application thereof, wherein the catalyst comprises loose and porous gamma-Al2O3And the kernel is soaked in an alcoholic solution of tetraisopropyl titanate and graphene oxide, and is repeatedly soaked and evaporated to remove alcohol to obtain the composite catalyst. The connection between the inside carbon atom of graphite alkene is very pliable and tough, and the structure is very stable, can protect the tetraisopropyl titanate of participating in the reaction effectively, makes it more stable, is difficult for hydrolysising, promotes catalytic ability. The composite catalyst has the advantages of simple preparation, excellent catalytic performance and great reduction of reactionThe method is applied to the production of plasticizer dioctyl terephthalate, and has extremely high catalytic function and cost advantage.
Description
Technical Field
The invention relates to a composite catalyst for producing plasticizer dioctyl terephthalate, a preparation method and application thereof, and belongs to the technical field of chemical production.
Background
Plasticizers are a class of polymeric material aids that are widely used in industrial production. The use of a plasticizer, on the one hand, can improve the toughness of the base material of the product, increase the elongation at break of the product, and make the product softer during processing, such as reducing the brittleness of the film, reducing the dead folds of the film product, and rejecting the waste products generated thereby; on the other hand, the method can greatly improve the processability of plastics, and has important significance for realizing industrial production of certain plastic varieties which are particularly difficult to process, such as PVC (40 percent of plasticizer is added in PVC industrial processing). Since 1868 Haite cloth used camphor as a plasticizer for cellulose nitrate, the plasticizer developed rapidly, and it produced the greatest amount and consumed the most in all rubber and plastic processing aids, and the variety was the greatest.
DOTP is short for dioctyl terephthalate, is a plasticizer with excellent performance, has the advantages of low high insulation, volatility, heat resistance, cold resistance, extraction resistance, good flexibility, good compatibility with PVC resin and the like, is widely used for cables and PVC products, can also be used as a plasticizer, a coating additive, a lubricant for precise instruments and the like of synthetic rubber, and has wide application range and market potential.
DOTP is a plasticizer with particular potential for development today when environmental protection is advocated. China also carries out industrial production in the 90 s and has more researches on related synthesis processes, but the method only provides more feasible catalysts except for methods of increasing reaction temperature, enhancing diffusion and the like, and the method is not actually improved and consumes too long of production process. The development of a composite catalyst which is efficient and has an enhanced catalytic effect at high temperature becomes a necessary trend in the production industry of diisooctyl terephthalate.
Disclosure of Invention
The invention provides a composite catalyst for producing plasticizer dioctyl terephthalate, a preparation method and application thereof.
The specific technical scheme is as follows:
a composite catalyst for preparing dioctyl terephthalate contains loose and porous gamma-Al2O3And the kernel is soaked in an alcoholic solution of tetraisopropyl titanate and graphene oxide, and is repeatedly soaked and evaporated to remove alcohol to obtain the composite catalyst.
The preparation method of the composite catalyst for producing the plasticizer dioctyl terephthalate comprises the following steps:
s1, selecting Al (OH)3The xerogel is calcined at the temperature of 410-450 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the step S2, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: (20-40);
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 70-90 ℃, and continuously stirring until the volume of the solution is reduced to 20-25% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 90-110 deg.C, oven-drying to remove volatile ethanol, oven-drying, taking out, soaking in vacuum again, and soaking in water againReleasing the vacuum, and drying again for 6-8 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3Continuously drying for 30-60min at the temperature of 120-130 ℃ in a vacuum-pumping environment, and cooling to the normal temperature to obtain the composite catalyst.
The Graphene Oxide (GO) is prepared by the following steps:
s3-1, sequentially weighing (2-3) g of natural graphite powder and (1-2) g of sodium nitrate, adding into a 500mL reaction bottle, placing in an ice-water bath at 0 ℃, then weighing (60-90) mL of concentrated sulfuric acid, and slowly adding into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is completed, weighing (8-10) g of potassium permanganate, adding the potassium permanganate into a reaction bottle in several times, controlling the reaction temperature to be not more than 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 35-40 ℃, slowly adding 100mL of deionized water, then adding a 30% hydrogen peroxide aqueous solution, and continuing to stir for 120 min;
s3-4, heating to 95-98 ℃, slowly adding 100mL of deionized water, adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
The composite catalyst is used for producing plasticizer dioctyl terephthalate, wherein the production raw materials are phthalic acid and isooctanol, the phthalic acid and the isooctanol are subjected to catalytic esterification reaction to generate the dioctyl terephthalate, and the addition amount of the composite catalyst is 0.01-0.08% of the total mass of the production raw materials.
The graphene oxide has the beneficial effects that a large number of functional groups such as carboxyl, hydroxyl and epoxy groups are arranged on the surface of the graphene oxide, so that the graphene oxide is easy to combine with organic matters for reaction and becomes graphene after reduction; the connection between the carbon atoms in the graphene is flexible, the structure is very stable, the tetraisopropyl titanate participating in the reaction can be effectively protected, the tetraisopropyl titanate is more stable and not easy to hydrolyze, and the catalytic capability can be improved. gamma-Al2O3The solution dipped in the vacuum environment is sucked into gamma-Al when the vacuum is released2In O3, the effective components of the composite catalyst can be slowly released, so that the activity of the catalyst can be maintained for a long time, the used catalyst is the composite catalyst, the conversion efficiency of raw materials can be improved, and the prepared dioctyl terephthalate (DOTP) has the characteristics of high content, no color, transparency and stable quality. The composite catalyst is simple to prepare, has excellent catalytic performance, greatly shortens the reaction time, is applied to the production of plasticizer dioctyl terephthalate, and has extremely high catalytic function and cost advantage.
Detailed Description
Example 1
Composite catalyst for producing dioctyl terephthalate, which has loose and porous gamma-Al2O3And the kernel is soaked in an alcoholic solution of tetraisopropyl titanate and graphene oxide, and is repeatedly soaked and evaporated to remove alcohol to obtain the composite catalyst.
The preparation method of the composite catalyst comprises the following steps:
s1, selecting Al (OH)3The xerogel is calcined at 410 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the step S2, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 20;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 70 ℃, and continuously stirring until the volume of the solution is reduced to 20% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 90 deg.C, oven-drying, removing volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 6 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying the catalyst for 30min at 120 ℃ in a vacuum-pumping environment, and cooling the dried catalyst to normal temperature to obtain the composite catalyst.
The Graphene Oxide (GO) in step S3 is prepared as follows:
s3-1, sequentially weighing 2g of natural graphite powder and 1g of sodium nitrate, adding the natural graphite powder and the 1g of sodium nitrate into a 500mL reaction bottle, placing the reaction bottle in ice-water bath at 0 ℃, weighing 60mL of concentrated sulfuric acid, and slowly adding the concentrated sulfuric acid into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is finished, weighing 8g of potassium permanganate, adding the potassium permanganate into the reaction bottle in several times, controlling the reaction temperature not to exceed 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 35 ℃, slowly adding 100mL of deionized water, then adding aqueous hydrogen peroxide solution with the mass concentration of 30%, and continuing to stir for 120 min;
s3-4, heating to 95 ℃, slowly adding 100mL of deionized water, then adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
Example 2
The composite catalyst of example 1 can be prepared as follows:
s1, selecting Al (OH)3The xerogel is calcined at 450 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 40;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 90 ℃, and continuously stirring until the volume of the solution is reduced to 25% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 110 deg.C, oven-drying to remove volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 8 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying for 60min at 130 ℃ in a vacuum-pumping environment, and cooling to normal temperature to obtain the composite catalyst.
The Graphene Oxide (GO) in step S3 is prepared as follows:
s3-1, sequentially weighing 3g of natural graphite powder and 2g of sodium nitrate, adding into a 500mL reaction bottle, placing in an ice-water bath at 0 ℃, weighing 90mL of concentrated sulfuric acid, and slowly adding into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is finished, weighing 10g of potassium permanganate, adding the potassium permanganate into the reaction bottle in several times, controlling the reaction temperature not to exceed 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 40 ℃, slowly adding 100mL of deionized water, then adding aqueous hydrogen peroxide solution with the mass concentration of 30%, and continuing to stir for 120 min;
s3-4, heating to 98 ℃, slowly adding 100mL of deionized water, then adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
Example 3
The composite catalyst of example 1 can be prepared as follows:
s1, selecting Al (OH)3The xerogel is calcined at 420 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 30, of a nitrogen-containing gas;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 80 ℃, and continuously stirring until the volume of the solution is reduced to 20% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 110 deg.C, and oven-dryingRemoving volatilized ethanol, drying, taking out, soaking in vacuum environment again, releasing vacuum, drying again, and repeating the steps for 6 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying the catalyst for 30min at 130 ℃ in a vacuum-pumping environment, and cooling the dried catalyst to normal temperature to obtain the composite catalyst.
The Graphene Oxide (GO) in step S3 is prepared as follows:
s3-1, sequentially weighing 2g of natural graphite powder and 2g of sodium nitrate, adding the natural graphite powder and the sodium nitrate into a 500mL reaction bottle, placing the reaction bottle in an ice-water bath at 0 ℃, weighing 60mL of concentrated sulfuric acid, and slowly adding the concentrated sulfuric acid into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is finished, weighing 10g of potassium permanganate, adding the potassium permanganate into the reaction bottle in several times, controlling the reaction temperature not to exceed 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 35 ℃, slowly adding 100mL of deionized water, then adding aqueous hydrogen peroxide solution with the mass concentration of 30%, and continuing to stir for 120 min;
s3-4, heating to 98 ℃, slowly adding 100mL of deionized water, then adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
Example 4
The composite catalyst of example 1 can be prepared as follows:
s1, selecting Al (OH)3The xerogel is calcined at 410 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 40;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 70 ℃, and continuously stirring until the volume of the solution is reduced to 25% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 100 deg.C, oven-drying, removing volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 6-8 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying for 45min at the temperature of 120-130 ℃ in a vacuum-pumping environment, and cooling to the normal temperature to obtain the composite catalyst.
The Graphene Oxide (GO) in step S3 is prepared as follows:
s3-1, sequentially weighing 2.5g of natural graphite powder and 1.5g of sodium nitrate, adding into a 500mL reaction bottle, placing in an ice-water bath at 0 ℃, weighing 75mL of concentrated sulfuric acid, and slowly adding into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is finished, weighing 9g of potassium permanganate, adding the potassium permanganate into the reaction bottle in several times, controlling the reaction temperature not to exceed 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 40 ℃, slowly adding 100mL of deionized water, then adding aqueous hydrogen peroxide solution with the mass concentration of 30%, and continuing to stir for 120 min;
s3-4, heating to 95 ℃, slowly adding 100mL of deionized water, then adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
Example 5
The composite catalyst of example 1 can be prepared as follows:
s1, selecting Al (OH)3The xerogel is calcined at 420 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 35;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 80 ℃, and continuously stirring until the volume of the solution is reduced to 25% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 95 deg.C, oven-drying, removing volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 7 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying for 60min at 125 ℃ in a vacuum-pumping environment, and cooling to normal temperature to obtain the composite catalyst.
Example 6
The composite catalyst of example 1 can be prepared as follows:
s1, selecting Al (OH)3The xerogel is calcined at 450 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving Tetraisopropyl Titanate (TTIP) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with mass-volume concentration of 1 mg/mL;
s3, dissolving Graphene Oxide (GO) in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: 25;
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 70-90 ℃, and continuously stirring until the volume of the solution is reduced to 22% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 110 deg.C, oven-drying, removing volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 6-8 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3And continuously drying the catalyst for 60min at the temperature of 120-130 ℃ in a vacuum-pumping environment, and cooling the catalyst to the normal temperature to obtain the composite catalyst.
The composite catalyst obtained in the above examples 1 to 6 can be used for the production of plasticizer dioctyl terephthalate, the production raw materials are phthalic acid and isooctanol, the two are subjected to catalytic esterification reaction to generate dioctyl terephthalate, and the addition amount of the composite catalyst is 0.01 to 0.08 percent of the total mass of the production raw materials.
When the dioctyl terephthalate is produced, the production method comprises the following steps:
the reaction is carried out in an esterification kettle, terephthalic acid and isooctyl alcohol with the molar ratio of 1:3 are taken as raw materials, and the raw materials and a composite catalyst are subjected to a mono-esterification reaction, the adding amount of the composite catalyst is 0.01-0.08 percent of the total mass of the raw materials, the mixture is continuously stirred, the temperature is raised to 205-210 ℃, and the esterification reaction is carried out for 1-2 hours; in the reaction process, water is divided once every 20min, so that the hydrolysis of the composite catalyst is avoided; and continuously carrying out neutralization and water washing, dealcoholization and stripping, decoloring and filtering on the mixture obtained by the reaction to finally obtain the dioctyl terephthalate.
The surface of the graphene oxide is provided with a large number of functional groups such as carboxyl, hydroxyl and epoxy, so that the graphene oxide is easy to combine with organic matters for reaction and becomes graphene after reduction; the connection between the carbon atoms in the graphene is flexible, the structure is very stable, the tetraisopropyl titanate participating in the reaction can be effectively protected, the tetraisopropyl titanate is more stable and not easy to hydrolyze, and the catalytic capability can be improved. gamma-Al2O3The solution dipped in the vacuum environment is sucked into gamma-Al when the vacuum is released2In O3, the effective components of the composite catalyst can be slowly released, so that the activity of the catalyst can be maintained for a long time, the used catalyst is the composite catalyst, the conversion efficiency of raw materials can be improved, and the prepared dioctyl terephthalate (DOTP) has the characteristics of high content, no color, transparency and stable quality.
In the above embodiment, the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: (20-40); the composite catalyst prepared according to the following proportion is used for producing dioctyl terephthalate according to the method, wherein the mass of the composite catalyst is 0.05 percent of the total mass of terephthalic acid and isooctanol raw materials, and the data listed in the following table are obtained:
| serial number | Volume usage amount of graphene oxide-ethanol solution | Volumetric usage of tetraisopropyl titanate-ethanol solution | Reaction time (h) | Conversion (%) |
| 1 | 1 | 5 | 2 | 87.58 |
| 2 | 1 | 10 | 2 | 92.33 |
| 3 | 1 | 15 | 2 | 95.14 |
| 4 | 1 | 20 | 2 | 99.35 |
| 5 | 1 | 25 | 2 | 99.92 |
| 6 | 1 | 30 | 2 | 99.95 |
| 7 | 1 | 35 | 2 | 99.31 |
| 8 | 1 | 40 | 2 | 99.32 |
| 9 | 1 | 45 | 2 | 96.24 |
| 10 | 1 | 50 | 2 | 95.63 |
| 11 | 1 | 55 | 2 | 95.33 |
| 12 | 1 | 60 | 2 | 95.34 |
The data in the table show that the volume dosage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: (20-40), the conversion rate is high, when the dosage of the graphene oxide is too large, the conversion rate is reduced sharply, when the dosage of the graphene oxide is too small, tetraisopropyl titanate is used as a main catalytic component in the reaction, and the reaction conversion rate is basically maintained at about 95.35%, so that the volume dosage ratio of the preferential graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: (20-40).
The complex catalyst obtained in the above example 1 was subjected to multiple dioctyl terephthalate preparations, obtaining the data listed in the following table:
| serial number | Catalyst mass amount (%) | Reaction temperature (. degree.C.) | Time (h) | Conversion (%) |
| 1 | 0.006 | 210 | 1 | 85.38 |
| 2 | 0.008 | 210 | 1 | 92.14 |
| 3 | 0.01 | 210 | 1 | 97.35 |
| 4 | 0.02 | 210 | 1 | 98.90 |
| 5 | 0.04 | 210 | 1 | 99.26 |
| 6 | 0.06 | 210 | 1 | 99.32 |
| 7 | 0.08 | 210 | 1 | 99.56 |
| 8 | 0.10 | 210 | 1 | 99.55 |
| 9 | 0.12 | 210 | 1 | 99.35 |
| 10 | 0.2 | 210 | 1 | 99.42 |
The data in the table show that when the dosage of the conforming catalyst is 0.01-0.08% of the total mass of the production raw materials, the preferable scheme is adopted, and when the dosage of the catalyst is less than 0.01%, the conversion rate is reduced sharply, and the conversion rate is not changed obviously when the dosage of the catalyst is more than 0.08%.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described above, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A composite catalyst for producing dioctyl terephthalate is characterized in that: comprising gamma-Al having a loose porosity2O3A core impregnated with tetraisopropyl titanate and oxygenAnd (3) after the alcoholic solution of the graphene is dissolved, repeatedly dipping and evaporating to remove the alcohol to obtain the composite catalyst.
2. The preparation method of the composite catalyst for the production of plasticizer dioctyl terephthalate according to claim 1, characterized by comprising the steps of:
s1, selecting Al (OH)3The xerogel is calcined at the temperature of 410-450 ℃ in a vacuum environment to obtain the gamma-Al with a loose porous structure2O3；
S2, dissolving tetraisopropyl titanate in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent to prepare tetraisopropyl titanate-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s3, dissolving graphene oxide in absolute ethyl alcohol by taking the absolute ethyl alcohol as a solvent, and performing ultrasonic dispersion to prepare a graphene oxide-ethyl alcohol solution with the mass-volume concentration of 1 mg/mL;
s4, gradually dripping the S3 graphene oxide-ethanol solution into the tetraisopropyl titanate-ethanol solution prepared in the S2 step by step, and continuously stirring to obtain a mixed solution, wherein the volume usage ratio of the graphene oxide-ethanol solution to the tetraisopropyl titanate-ethanol solution is 1: (20-40);
s5, placing the mixed solution in a continuous vacuum-pumping environment, heating to 70-90 ℃, and continuously stirring until the volume of the solution is reduced to 20-25% of the volume of the mixed solution, so as to obtain a concentrated mixed solution;
s6, and then mixing the gamma-Al prepared in the step S12O3Completely soaking in the concentrated mixed solution in a vacuum environment, releasing the vacuum, and filtering to obtain soaked gamma-Al2O3Then impregnating the gamma-Al2O3Placing in a continuously vacuum-pumping environment, heating to 90-110 deg.C, oven-drying to remove volatile ethanol, oven-drying, taking out, soaking in vacuum environment again, releasing vacuum, oven-drying again, and repeating for 6-8 times;
s7, dipping and drying the gamma-Al obtained in the S6 for multiple times2O3Continuously drying at 120-130 deg.C for 30-60min under vacuum-pumping environment, cooling to normal temperature to obtainA composite catalyst.
3. The preparation method of the composite catalyst for the production of dioctyl terephthalate according to claim 2, wherein:
the graphene oxide is prepared by the following steps:
s3-1, sequentially weighing (2-3) g of natural graphite powder and (1-2) g of sodium nitrate, adding into a 500mL reaction bottle, placing in an ice-water bath at 0 ℃, then weighing (60-90) mL of concentrated sulfuric acid, and slowly adding into the reaction bottle under the condition of stirring;
s3-2, after the slow addition is completed, weighing (8-10) g of potassium permanganate, adding the potassium permanganate into a reaction bottle in several times, controlling the reaction temperature to be not more than 20 ℃, stirring for 30min, and uniformly mixing;
s3-3, heating to 35-40 ℃, slowly adding 100mL of deionized water, then adding a 30% hydrogen peroxide aqueous solution, and continuing to stir for 120 min;
s3-4, heating to 95-98 ℃, slowly adding 100mL of deionized water, adding a hydrogen peroxide solution with the mass concentration of 30%, and continuously stirring for 60 min;
and S3-5, cooling the reactor to room temperature, washing the product twice with a hydrochloric acid solution with the mass concentration of 5%, then washing with deionized water and absolute ethyl alcohol, and drying to obtain the graphene oxide.
4. Use of a hybrid catalyst according to claim 1, characterized in that: the composite catalyst is used for producing plasticizer dioctyl terephthalate, wherein the production raw materials are phthalic acid and isooctanol, the phthalic acid and the isooctanol are subjected to catalytic esterification reaction to generate the dioctyl terephthalate, and the addition amount of the composite catalyst is 0.01-0.08% of the total mass of the production raw materials.
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