CN107954850A - The preparation method of M-phthalic acid - Google Patents

Abstract

The invention discloses a preparation method of isophthalic acid. The preparation method comprises the following steps: under the action of a catalyst and a catalytic additive, m-xylene is oxidized in a solvent to obtain isophthalic acid; the catalyst is Co -Mn-Br catalyst, described catalytic additive comprises one or more in rare earth metal acetate, alkali metal acetate and transition metal acetate, the add-on of described catalytic additive in m-xylene oxidation system 50-1500ppm. The preparation method of the invention has the effects of low content of m-carboxybenzaldehyde and weakening of manganese precipitation, bromine oxidation and equipment corrosion.

Description

The preparation method of isophthalic acid

technical field

The present invention relates to a kind of preparation method of isophthalic acid.

Background technique

Iso-phthalic acid (IPA) is a fast-growing organic chemical intermediate raw material, mainly used as a modified monomer for PET resin to improve the processing and product performance of PET resin; used to replace phthalic anhydride Produce high-strength, chemical-resistant unsaturated resins; replace phthalic anhydride to produce high-performance, high-solid alkyd resins. IPA has been widely used in foreign countries, and its development prospects are promising. Many large companies are preparing to expand production capacity and build new IPA devices. With the continuous expansion of device scale, its cost will continue to decrease, and its application fields and market share will continue to expand. The application of IPA in my country has a certain basis. At present, it has been applied in the field of bottle-grade polyester resin and polyester cationic dyeable fiber, unsaturated resin, and alkyd resin high-grade coatings, but its source is mainly solved by imports. As many large foreign companies adopt advanced technologies to expand production capacity and build new IPA plants, there will be major problems in the competitiveness of these plants.

The MX high-temperature catalytic oxidation process uses the Co-Mn-Br ternary composite system as the catalyst, and its catalytic mechanism has been described in detail in relevant literature. Co is the main catalyst in the oxidation process of MX. Among all the transition metals, Co has the highest catalytic activity for the air oxidation process of MX; The effect is far less than that of Co, but Mn can produce a synergistic effect with Co, and the catalytic activity of the combination of the two is much greater than that of pure Co or Mn; bromine is a good free radical reaction accelerator, and can be combined with high-valence Co(III), Rapid electron transfer between Mn(III) generates bromine radicals, which accelerate the reaction.

During the high-temperature catalytic oxidation of MX to prepare IPA, the precipitation of catalyst Mn occurs. This precipitation reaction not only consumes the content of catalyst Mn, reduces the reaction rate, but also affects the color of the product. In a high-temperature aerobic environment, accompanied by the oxidation of the catalyst Br, the oxidation reaction consumes the content of the catalyst Br and reduces the oxidation reaction rate. Therefore, adding a fourth metal or non-metallic compound as a catalytic additive to the original Co-Mn-Br catalytic system to improve the catalytic performance of the system is very important for the technical transformation and production expansion of the IPA device.

The above-mentioned method of adding a fourth metal or metalloid compound as a catalytic additive in the original Co-Mn-Br catalytic system may accelerate the reaction and reduce side reactions, but it cannot effectively reduce the meta-carboxyl group in the crude isophthalic acid. Benzaldehyde (3-CBA) content. Generally, too high a content of 3-CBA in crude isophthalic acid will lead to poor color of the product, which requires further hydrofining. Therefore, it is very necessary to optimize the adjustment of catalyst, catalytic additive, acetic acid and water content in the MX oxidation reaction system.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problems such as the crude isophthalic acid intermediate carboxyl benzaldehyde content of the crude isophthalic acid produced by the oxidation of m-xylene in the prior art is too high, the combustion side reaction is serious, manganese precipitation, bromine oxidation, equipment corrosion, etc., And a kind of preparation method of isophthalic acid is provided. The preparation method of the invention has the characteristics of low content of meso-carboxybenzaldehyde in crude isophthalic acid produced by oxidizing m-xylene, and weakening of manganese precipitation, bromine oxidation and equipment corrosion.

The present invention provides a kind of preparation method of isophthalic acid, described preparation method comprises the following steps: under the action of catalyst and catalytic additive, m-xylene is oxidized in solvent, reacts to obtain isophthalic acid; Said catalyst is Co -Mn-Br catalyst, described catalytic additive comprises one or more in rare earth metal acetate, alkali metal acetate and transition metal acetate, the addition amount of described catalytic additive in m-xylene oxidation system 50-1500ppm.

Wherein, the rare earth metal acetate is preferably composed of acetate of one or more rare earth metals in Ce, Nd, Pr, Gd, Dy, Sm and La, more preferably, the rare earth metal Acetate is prepared by dissolving rare earth metal oxides or rare earth metal salts in acetic acid. The alkali metal acetate is preferably composed of one or more alkali metal acetates in KAc, KOH and NaOH, more preferably prepared by dissolving the alkali metal in acetic acid, or preparing the alkali as Acetate, wherein said alkali metal includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). The transition metal acetate is preferably composed of one or more of Hf, Zr, Fe acetate and organic molybdenum acetate. Among the transition metal acetates, Hf acetate has a better effect than Zr.

The inventors have shown through experiments that: Zr, Hf, K, Na, Ce, etc. all have an accelerating effect on oxidation, but Zr is easy to precipitate, and the residual Zr in the crude IPA will poison the subsequent hydrofining catalyst. While Ce and the like have the effect of preventing manganese precipitation, Zr is not suitable for large-scale industrial applications in terms of industrial feasibility. Therefore, rare earth metal acetates and alkali metal acetates should be given priority, and transition metal acetates can only be used as an auxiliary, using rare earth metal acetates, alkali metal acetates, etc., or in combination with transition metal acetates , which weakens the precipitation phenomenon and accelerates the oxidation reaction.

In the present invention, the addition amount of the catalytic additive in the m-xylene oxidation system is preferably 100-300ppm. In the present invention, the m-xylene oxidation system has a conventional meaning in the field, including a collection of all reaction raw materials.

In the present invention, considering the overall index of effect data, the catalytic additive is preferably rare earth metal acetate and/or alkali metal acetate, more preferably La(Ac) ₃ , NaAc and Dy(Ac) ₆ A mixture formed at a mass ratio of 2:1:1. From the perspective of the inhibition effect on combustion side reactions alone, there are the following preferred relationships: Dy(Ac) ₆ >La(Ac) ₃ >Ce(Ac) ₃ ; Hf(Ac) ₄ >Ce(Ac) ₃ ; NaAc>Ce( Ac) ₃ .

In the present invention, the preferred range of the addition amount of the rare earth metal acetate in the m-xylene oxidation system is 50 ppm to 500 ppm.

In the present invention, the preferred range of the addition amount of the alkali metal acetate in the m-xylene oxidation system is 50 ppm to 500 ppm.

In the present invention, the preferred range of the addition amount of the transition metal acetate in the m-xylene oxidation system is 50ppm-500ppm. In the present invention, if it is based on the added amount of transition metal ions, its content is preferably 20-350 ppm.

In the present invention, in the catalyst, the concentration ranges of Co ions, Mn ions, and Br ions of cobalt acetate, manganese acetate, and sodium bromide are conventional ranges in this field, preferably 100-2000ppm, 100-2000ppm, and 100ppm respectively. ~2000ppm.

In the present invention, preferably, the catalyst and the catalytic additive are uniformly mixed before the reaction.

In the reaction system of the present invention, the oxidizing agent is generally air, and the solvent is a conventional solvent in the field, preferably a liquid composed of water and acetic acid. Wherein, the content of water in the reaction system is preferably 3%-12%.

In the reaction system of the present invention, the solvent ratio ((HAc+H ₂ O)/MX) is preferably 3-20.

In the present invention, the temperature of the reaction is conventional in the field, preferably 150-250° C.; the pressure of the reaction is conventional in the field, preferably 0.5-2.5 MPa. The reaction time is conventional in the art, preferably 20-60 min.

On the basis of conforming to common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain preferred examples of the present invention.

The reagents and raw materials used in the present invention are all commercially available.

The positive progress effect of the present invention is that: the specially selected catalytic additive of the present invention effectively improves the reaction effect of isophthalic acid produced by oxidation of m-xylene, and can be applied in the industrial production of isophthalic acid. Moreover, the preparation method of the present invention has the characteristics of low meso-carboxybenzaldehyde content in crude isophthalic acid produced by m-xylene oxidation, and weakened phenomena of manganese precipitation, bromine oxidation and equipment corrosion.

Description of drawings

Fig. 1 is the liquid chromatogram that the embodiment of the present application measures.

Fig. 2 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 1.

Fig. 3 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 2.

Fig. 4 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 3.

Fig. 5 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 4.

Fig. 6 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 5.

Fig. 7 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 6.

Fig. 8 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 7.

Fig. 9 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 8.

Fig. 10 is a schematic diagram of fitting of CO ₂ and CO generation rates in Example 9.

Fig. 11 is a schematic diagram of the fitting comparison of CO generation rate in Example 10.

Fig. 12 is a schematic diagram of the fitting comparison of the CO ₂ generation rate in Example 10.

13 is a schematic diagram of the reaction process of Example 6.

Detailed ways

The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples. For the experimental methods that do not specify specific conditions in the following examples, select according to conventional methods and conditions, or according to the product instructions.

In the following examples, the instrument and test conditions of high performance liquid chromatography analysis:

The HPLC detection method adopts the American Agilent 1120 high performance liquid chromatograph, automatic sample injector, Agilent 1120 UV/Vis detector, Empower 2 data processing system.

Chromatographic conditions:

Chromatographic column: Agilent TC-C18 chromatographic column (4.6×250mm, 5μm); mobile phase A is 100% acetonitrile, mobile phase B is 17% methanol + 83% water; gradient elution conditions: A from 30% in 0-20min to 100%, B from 100% to 30% in 20-25min, B from 70% to 0% in 0-20min, B from 0% to 70% in 20-25min; flow rate: 1ml·min ^-1 ; column temperature : 30°C; detection wavelength: 260nm; injection volume: 20μL. Under this condition, the retention time of the main peak of isophthalic acid is about 5.3min, and the retention time of the main peak of m-carboxybenzaldehyde is about 6.5min, and the retention time of the main peak of m-toluic acid is about 9.5min, and the retention time of the main peak of m-methylbenzaldehyde is about 9.5min. The retention time is about 11.4min, and the retention time of the main peak of m-xylene is about 16.8min. Please refer to Figure 1 for details. Wherein, peak 1-isophthalic acid, peak 2-m-carboxybenzaldehyde, peak 3-benzoic acid, peak 4-m-toluic acid, peak 5-m-tolualdehyde, peak 6-m-xylene.

For Figure 1, the following two points need to be explained:

First, by making standard curves for different substances, the absorption peak areas of different substances in the product are measured in the experiment, and the concentrations of different substances can be calculated correspondingly. Since the absorption intensity of each substance is different, the corresponding absorption peak area is also different. Therefore, the peak area size of different substances cannot directly determine the content.

In addition, in the examples, the yield of IPA is calculated according to the calculation method routinely used in the art, specifically: yield=concentration of IPA in the product/concentration of MX in the raw material. It should be noted that the concentration of IPA in the product refers to the concentration after configuring the sample required for liquid phase detection in liquid chromatography analysis.

The detection equipment and test conditions of the infrared gas analyzer are as follows:

The concentration analysis of _CO2 and CO adopts the GXH-510 infrared gas analyzer produced by Xibi Instruments. This analyzer belongs to the non-dispersive infrared analyzer. Its optical system consists of three parts: light source, gas chamber and detector. The electrical system consists of three parts: preamplifier, temperature control and power supply. Its working principle is based on the characteristics of selective absorption of infrared rays by specific gases, and is obtained through certain functional correlation conversion. The instrument adopts an advanced single light source, a single-tube half-air chamber and a new pyroelectric detector with high stability and reliability. The light source component modulates the continuous infrared radiation to 6.25Hz to continue to radiate and alternately pass through the analysis side and reference side of the gas cell, and finally absorbed by the detector.

Oxygen analysis (the formula for calculating CO ₂ and CO generation rate requires the concentration of oxygen, so the oxygen analysis instrument is used to measure the concentration of O ₂ in the tail gas) EN-560 magnetic oxygen analyzer (Shanghai Yingsheng Instrument is preferred) company), the EN-560 magnetic oxygen analyzer is an integrated fixed-installation online analysis instrument. The working principle of the instrument is based on the paramagnetic properties of oxygen, which has a very high magnetic susceptibility. Under the action of a non-uniform magnetic field, a "magnetic wind" is formed, which generates thermomagnetic convection in the sensitive element, thereby producing a "cooling" effect on the sensitive element. , so that its resistance value changes to work.

In the following examples, suitable experimental conditions are selected as reference conditions, and rare earth metals, alkali metals, and transition metal catalytic additives are added under reference conditions, and the _CO and CO generation curves obtained are consistent with the _CO and Compared with the CO curve, the effect of the catalytic additive on the combustion reaction can be judged by the reaction end time, and the effect of the catalytic additive on the main reaction can be judged by the content of 3-CBA in the reaction product, thereby confirming the effect of the catalytic additive.

The raw material conditions used in the following examples are all MX:HAc=1:3, H ₂ O/HAc=5%, the converted solvent ratio ((HAc+H ₂ O)/MX) is 3.15, and water is in The content in the reaction system is specifically 3.61%, and the percentage is a mass percentage.

Mechanistically speaking, the combustion side reaction is the process in which MX and acetic acid are oxidized to generate _CO2 and CO. In the experiment, the reaction time (within 15 min) is mainly used to integrate the _CO2 production rate to obtain the combustion equivalent of acetic acid (approximately using the value below the curve area for comparison) to evaluate the inhibitory effect. If the combustion equivalent is similar, the formation rate at the end of the reaction is used as the evaluation standard. In this application, due to the addition of each type of catalytic additive, the oxidation rate is different, resulting in different oxidation degrees of different catalytic systems at the end. Therefore, some of them showed an upward trend at 15 minutes, while others tended to be stable.

Example 1

Weigh 1.5g Ce ₂ O ₃ , first dissolve it completely with a small amount of acetic acid, then transfer all of it into a 250ml volumetric flask, and dilute to the mark with acetic acid at 20°C to obtain the acetate solution corresponding to the oxide . Prepare the MX oxidation system according to the following ratio of catalyst, reactant and solvent: catalytic additive Ce(Ac) ₃ is 300ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1 , H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 191 ° C and a pressure of 1.3 MPa, MX was oxidized for 20 minutes to obtain crude IPA. Even if the reaction time reaches 60 minutes, the color of the IPA product remains white, and when there is no Ce ³⁺ in the system, even if there is a trace of Br ^- in the system, the product still appears black. Experiments have proved that adding Ce to the Co-Mn-Br catalytic system can indeed inhibit the precipitation of MnO ₂ . After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 96.5%, and the content of 3-CBA in the crude IPA is 491ppm. By analyzing the _CO2 and CO change curves in the tail gas by an infrared gas analyzer, it can be seen (specifically shown in Figure 2) that the combustion side reactions are suppressed.

Example 2

Weigh 1.0g La ₂ O ₃ , first dissolve it completely with a small amount of acetic acid, then transfer all of it into a 250ml volumetric flask, and dilute to the mark with acetic acid at 20°C to obtain the acetate solution corresponding to the oxide . Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additive La(Ac) ₃ is 200ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1 , H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 191 ° C and a pressure of 1.3 MPa, MX was oxidized for 20 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 97%, and the content of 3-CBA in the crude IPA is 500ppm. By analyzing the _CO2 and CO change curves in the tail gas by an infrared gas analyzer, it can be seen that compared with Figure 2 obtained in Example 1, the combustion side reactions of this embodiment are suppressed to a certain extent, as shown in Figure 3.

Example 3

Prepare the catalytic additive La(Ac) ₃ according to the above-mentioned Example 1, mix it uniformly with the Co-Mn-Br catalyst, and add it to the MX oxidation system. Prepare the MX oxidation system according to the following ratio of catalyst, reactant and solvent: catalytic additive La(Ac) ₃ is 200ppm, MX:HAc=1:3, Co addition is 350 ppm, Co:Mn:Br=1:1: 1. H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 210°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. After analyzing the product by high-performance liquid chromatography, it can be known that the yield of IPA reaches 98.1%, and the content of 3-CBA in the crude IPA is 300ppm. The _CO2 and CO change curves in the tail gas were analyzed by an infrared gas analyzer, as shown in Figure 4. The combustion equivalent in Fig. 4 is obviously lower than that in Fig. 2, that is, the suppression effect of the combustion side reaction in this embodiment is better than that in Embodiment 1.

Example 4

Accurately weigh 1.0g of DyO ₃ , add 10ml of distilled water, and add 1M ammonium carbonate solution dropwise while stirring on the magnetic stirrer. In order to make all the rare earth metals turn into carbonate precipitates, the amount of ammonium carbonate should be slightly excessive (based on the solution pH> 10), then filter and wash the precipitate for 3 to 5 times, dissolve the precipitate with acetic acid after drying to obtain a rare earth acetate solution, and crystallize the solution to obtain the rare earth acetate. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additive Dy(Ac) ₆ 200 ppm, MX:HAc=1:3, Co addition 350ppm, Co:Mn:Br=1:1:1 , H ₂ O/HAc=5%, the intake air volume is 10L/min. Under the condition of temperature of 191° C. and pressure of 1.3 MPa, MX was oxidized for 42 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 97.1%, and the content of 3-CBA in the crude IPA is 450ppm. By analyzing the _CO2 and CO change curves in the tail gas by an infrared gas analyzer, it can be seen that compared with Figure 2 obtained in Example 1, the combustion side reactions of this embodiment are suppressed to a certain extent, as shown in Figure 5.

Example 5

Prepare the catalytic additive Dy(Ac) ₆ according to the above-mentioned Example 4, mix it uniformly with the Co-Mn-Br catalyst, and add it to the MX oxidation system. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additive Dy(Ac) ₆ is 200ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1 , H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 200°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 97.6%, and the content of 3-CBA in the crude IPA is 365 ppm. Analysis of the _CO2 and CO change curves in the tail gas by an infrared gas analyzer shows that, as shown in Figure 6, the combustion equivalent in Figure 6 is significantly lower than that in Figure 4, and the formation rate at the end of the reaction is also significantly lower than Figure 4. Illustrate that in the present embodiment, the suppression effect of the combustion side reaction is better than that of Embodiment 3.

Example 6

Hf(Ac) ₄ was prepared by precipitation method using HfOCl ₂ as raw material, and the specific process is shown in Figure 13 .

Prepare the MX oxidation system according to the following ratio of catalyst, reactant and solvent: catalytic additive is Hf(Ac) ₄ 200ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1 , H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 191°C and a pressure of 1.3 MPa, MX was oxidized for 42 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be seen that the yield of IPA reaches 96.5%, and the content of 3-CBA in the crude IPA is 600ppm. By analyzing the _CO2 and CO change curves in the tail gas by an infrared gas analyzer, it can be seen that compared with Figure 2 obtained in Example 1, the combustion side reactions of this embodiment are suppressed to a certain extent, as shown in Figure 7.

Example 7

Prepare the catalytic additive NaAc according to the above-mentioned Example 1, mix it uniformly with the Co-Mn-Br catalyst, and add it to the MX oxidation system. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additive NaAc is 250ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1, H ₂ O /HAc=5%, the intake air volume is 10L/min. At a temperature of 200°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 98.1%, and the content of 3-CBA in the crude IPA is 343ppm. Analysis of the _CO in the tail gas by an infrared gas analyzer and the change curve of CO can be seen, specifically as shown in Figure 8, the combustion equivalent of Figure 8 is significantly lower than that of Figure 2, indicating that the combustion side reaction is better than the suppression effect of Example 1.

Example 8

Prepare the catalytic additive NaAc according to the above-mentioned Example 1, mix it uniformly with the Co-Mn-Br catalyst, and add it to the MX oxidation system. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additive NaAc is 250ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn:Br=1:1:1, H ₂ O /HAc=5%, the intake air volume is 10L/min. At a temperature of 220°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. After analyzing the product by high-performance liquid chromatography, it can be known that the yield of IPA reaches 98.5%, and the content of 3-CBA in the crude IPA is 303ppm. The _CO2 and CO change curves in the tail gas were analyzed by an infrared gas analyzer. As shown in Figure 9, the combustion equivalent in Figure 9 is significantly lower than that in Figure 2, and the formation rate at the end of the reaction in Figure 9 is also significantly lower than that in Figure 2. Illustrate that the combustion side reaction of this embodiment is better than embodiment 1 suppression effect.

Example 9

Catalyst additives La(Ac) ₃ , NaAc, and Dy(Ac) ₆ were prepared according to the above-mentioned Example 1, mixed evenly with the Co-Mn-Br catalyst, and added to the MX oxidation system. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: the catalytic additives La(Ac) ₃ , NaAc, and Dy(Ac) ₆ are 100ppm, 50ppm, and 50ppm respectively, MX:HAc=1:3, and the amount of Co added is 350ppm, Co:Mn:Br=1:1:1, H2O/HAc=5%, intake air volume is 10L/min. At a temperature of 220°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. After analyzing the product by high performance liquid chromatography, it can be known that the yield of IPA reaches 99.1%, and the content of 3-CBA in the crude IPA is 251ppm. Analysis of the _CO2 and CO change curves in the tail gas by an infrared gas analyzer shows that the suppression effect of the combustion side reaction is better than that of Example 1, as shown in Figure 10, reaching the best reaction conditions. Through comparison, it is found that under this condition, the combustion equivalent is not high, but the product yield reaches the highest. Therefore, under the condition of low combustion loss, high yield and purity are guaranteed, so it can be considered that the conditions at this time are the optimal reaction conditions.

Example 10

The acetates of Zr, Na, Hf, and Dy were respectively prepared according to the above-mentioned Example 1 as catalytic additives, mixed evenly with the Co-Mn-Br catalyst, and added to the MX oxidation system. Prepare the MX oxidation system according to the following catalyst, reactant, and solvent ratios: catalytic additives Zr, Na, Hf, and Dy acetate are all added at 100ppm, MX:HAc=1:3, Co addition is 350ppm, Co:Mn: Br=1:1:1, H ₂ O/HAc=5%, the intake air volume is 10L/min. At a temperature of 220°C and a pressure of 1.3 MPa, MX was oxidized for 25 minutes to obtain crude IPA. Through high performance liquid chromatography analysis product as can be known, under the condition of above-mentioned four kinds of catalytic additives, the yield of IPA has reached 97.8%, 98.1%, 97.9%, 98.3% respectively, and 3-CBA content is respectively 381ppm, 365ppm in the thick IPA , 375ppm, 355ppm. Analyzing the change curves of _CO2 and CO in the exhaust gas by an infrared gas analyzer shows that when Zr acetate is used as a catalytic additive, the combustion side reactions are the most serious, as shown in Figures 11 and 12. It can be seen from Figures 11 and 12 that when Zr acetate is used as a catalytic additive, the combustion equivalent of acetic acid and the formation rate at the end of the reaction are the largest, and the combustion side reaction is the most serious at this time. That is to say, starting from the inhibition effect on combustion side reactions alone, the preferred relationship of acetates of several elements is as follows: Dy>Hf>Na>Zr.

Example 11

In this embodiment, the type of catalytic additive added is LiAc, and its content, other raw material types, content and process conditions are the same as in Example 7. This embodiment can realize the IPA yield value and the 3-CBA content value in the thick IPA that are equivalent to embodiment 7, and the effect of suitable suppression combustion side reaction.

Example 12

In this embodiment, the type of catalytic additive added is KAc, and its content, other raw material types, content and process conditions are all the same as in Example 7. This embodiment can realize the IPA yield value and the 3-CBA content value in the crude IPA which are equivalent to those of the embodiment 7, and the effect of inhibiting the combustion side reaction is equivalent.

Example 13

In this embodiment, the type of catalytic additive added is RbAc, and its content, other raw material types, content and process conditions are the same as in Example 7. This embodiment can realize the IPA yield value and the 3-CBA content value in the thick IPA that are equivalent to embodiment 7, and the effect of suitable suppression combustion side reaction.

Example 14

In this embodiment, the type of catalytic additive added is CsAc, and its content, other raw material types, content and process conditions are the same as in Example 7. This embodiment can realize the IPA yield value and the 3-CBA content value in the thick IPA that are equivalent to embodiment 7, and the effect of suitable suppression combustion side reaction.

Example 15

In this embodiment, the type of catalytic additive added is FrAc, and its content, other raw material types, content and process conditions are the same as in Example 7. This embodiment can realize the IPA yield value and the 3-CBA content value in the thick IPA that are equivalent to embodiment 7, and the effect of suitable suppression combustion side reaction.

Example 16

In this embodiment, the type of catalytic additive added is Nd(Ac) ₃ , and its content, other raw material types, content and process conditions are the same as in Example 1. This embodiment can realize the equivalent IPA yield value and the 3-CBA content value in the crude IPA of embodiment 1, and the effect of corresponding inhibition combustion side reaction.

Example 17

In this embodiment, the type of catalytic additive added is Pr(C ₂ H ₃ O ₂ ) ₃ ·4H ₂ O, and its content, types, content and process conditions of other raw materials are the same as in Example 1. This embodiment can realize the equivalent IPA yield value and the 3-CBA content value in the crude IPA of embodiment 1, and the effect of corresponding inhibition combustion side reaction.

Example 18

In this embodiment, the type of catalytic additive added is Gd(C ₂ H ₃ O ₂ ) ₃ ·4H ₂ O, and its content, types, content and process conditions of the other raw materials are the same as in Example 1. This embodiment can realize the equivalent IPA yield value and the 3-CBA content value in the crude IPA of embodiment 1, and the effect of corresponding inhibition combustion side reaction.

Example 19

In this embodiment, the type of catalytic additive added is Sm(C ₂ H ₃ O ₂ ) ₃ ·4H ₂ O, and its content, types, content and process conditions of the other raw materials are the same as in Example 1. This embodiment can realize the equivalent IPA yield value and the 3-CBA content value in the crude IPA of embodiment 1, and the effect of corresponding inhibition combustion side reaction.

Example 20

In this embodiment, the type of catalytic additive added is Fe(Ac) ₃ , and its content, types, content and process conditions of the other raw materials are the same as in Example 6. This embodiment can realize the IPA yield value and the 3-CBA content value in the crude IPA that are equivalent to those of Embodiment 6, and the effect of suppressing the combustion side reaction.

Example 21

In this embodiment, the type of catalytic additive added is Mo ₂ (Ac) ₄ , and its content, other raw material types, content and process conditions are the same as in Example 6. This embodiment can realize the IPA yield value and the 3-CBA content value in the crude IPA that are equivalent to those of Embodiment 6, and the effect of suppressing the combustion side reaction.

Claims (10)

1. a kind of preparation method of isophthalic acid, it is characterized in that, described preparation method comprises the steps: under the effect of catalyzer and catalytic additive, m-xylene is oxidized in solvent, reacts and obtains isophthalic acid; Described catalyst It is a Co-Mn-Br catalyst, and the catalytic additive includes one or more of rare earth metal acetate, alkali metal acetate and transition metal acetate, and the catalytic additive in the m-xylene oxidation system The amount added is 50-1500ppm. 2. preparation method as claimed in claim 1, is characterized in that, described rare earth metal acetate comprises the acetic acid of one or more rare earth metals in Ce, Nd, Pr, Gd, Dy, Sm and La Salt; And/or, the alkali metal acetate comprises one or more alkali metal acetates in Li, Na, K, Rb, Cs and Fr; And/or, the transition metal acetate includes acetate of one or more transition metals in Hf, Zr, Fe and Mo. 3. The preparation method according to claim 1, characterized in that, the addition amount of the catalytic additive in the m-xylene oxidation system is 100-300 ppm. 4. The preparation method according to claim 1, characterized in that, the catalytic additive is a rare earth metal acetate and/or an alkali metal acetate. 5. The preparation method according to claim 4, wherein the catalytic additive is a mixture of La(Ac) ₃ , NaAc and Dy(Ac) ₆ in a mass ratio of 2:1:1. 6. The preparation method according to claim 1, characterized in that, the addition amount of the rare earth metal acetate in the m-xylene oxidation system is 50ppm～500ppm; And/or, the addition amount of the alkali metal acetate in the m-xylene oxidation system is 50ppm-500ppm; And/or, the addition amount of the transition metal acetate in the m-xylene oxidation system is 50ppm-500ppm. 7. The preparation method according to claim 6, characterized in that, the addition of the rare earth metal acetate in the m-xylene oxidation system is 200 to 300 ppm; And/or, the addition amount of the alkali metal acetate in the m-xylene oxidation system is 200-300ppm; And/or, the addition amount of the transition metal acetate in the m-xylene oxidation system is 200-300 ppm. 8. The preparation method according to claim 1, characterized in that, the addition amount of the transition metal acetate is 20-350 ppm based on the addition amount of transition metal ions. 9. the preparation method as claimed in claim 1 is characterized in that, in described catalyzer, the Co ion of cobalt acetate, manganese acetate, sodium bromide, Mn ion, Br ion concentration range are respectively 100～2000ppm, 100～ 2000ppm, 100～2000ppm; And/or, the catalyst and catalytic additive are mixed uniformly before reacting. 10. The preparation method according to claim 1, wherein, in the m-xylene oxidation system, the oxidizing agent is air, and the solvent is a liquid composed of water and acetic acid; wherein the content of water in the reaction system is 3% ~12%; solvent ratio (HAc+H ₂ O)/MX is 3~20; And/or, the reaction temperature is 150-250° C.; the reaction pressure is 0.5-2.5 MPa; the reaction time is 20-60 min.