Preparation method of Pd-based catalyst and application of Pd-based catalyst in catalytic synthesis of biphenyltetracarboxylic dianhydride

Abstract

The invention relates to a preparation method of a Pd-based catalyst and application of the Pd-based catalyst in catalytic synthesis of biphenyltetracarboxylic dianhydride. According to the method, an alkaline substance is added, and nickel oxide is modified and regulated through hydroxyl, so that the specific surface area of the Pd / NiO catalyst is increased, and the effect between Pd and NiO is enhanced; the obtained catalyst can promote coupling of halogenated phthalic anhydride, and the synthesis efficiency of biphenyl tetracarboxylic dianhydride is improved. The catalyst is simple in preparation process and excellent in performance and is applied to synthesis of biphenyltetracarboxylic dianhydride, and esterification and ester hydrolysis steps do not need to be added.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst material preparation, in particular to a Pd-based catalyst and its application in catalytic synthesis of diphthalic dianhydride. BACKGROUND

[0002] Polyimide is widely used in aerospace, electronic storage, new energy and other fields due to its excellent mechanical properties and flexibility, excellent dielectric properties and chemical resistance. Among them, polyimide synthesized from diphthalic dianhydride (BPDA) is one of the super heat-resistant resins with the highest heat-resistant temperature. In addition, the polyimide film prepared by polymerization of BPDA and specific amines is light, flexible, thin and transparent, which is used in folding display screen and other applications. This film not only has scratch-resistant and heat-resistant properties, but also can withstand hundreds of thousands of folds without creases, showing great application value. Therefore, the synthesis of BPDA has also attracted the attention of researchers. At present, the main method for industrial production of BPDA is dehalogenation coupling method, which has mild conditions, simple preparation process and relatively single product. However, the conversion rate and selectivity of the palladium-carbon (Pd / C) catalyst used in the dehalogenation coupling method are relatively low, resulting in low yield of the target product. At the same time, the service life of Pd / C catalyst is short and it is difficult to reuse, which increases the production cost of BPDA. Therefore, in order to solve the above problems, it is urgent to develop a new type of Pd-based catalyst with high efficiency to improve the conversion rate of the reaction and the number of catalyst reuse, and solve the problem of low conversion rate of traditional Pd / C catalyst.

[0003] The patent of Dalian University of Technology (CN 117486843A) discloses a method for preparing diphthalic dianhydride using anhydrous nickel chloride coordinated with triphenylphosphine as a catalyst. First, 4-halophthalic anhydride is esterified with concentrated sulfuric acid, and then a coupling reaction is realized using a nickel catalyst to obtain phthalic ester. After ester hydrolysis and dehydration, diphthalic dianhydride is finally obtained. Due to the need for esterification and ester hydrolysis steps, the complexity of the synthesis process is increased. The patent of Tianjin University (CN 115805070A) discloses a method for preparing diphthalic dianhydride using graphene oxide supported Pd nanoparticles as a catalyst. Partially reduced graphene is used as a template to support Pd nanoparticles to obtain Pd particles with uniform particle size distribution, and the dominant crystal face is controlled to improve the catalytic activity. However, the production process of graphene oxide requires the use of strong acid and strong oxidizing agent, which increases the complexity and cost of the process. SUMMARY

[0004] The application aims at the limitations of the prior art, and provides a preparation method of a Pd-based catalyst and application of the Pd-based catalyst in catalytic synthesis of biphthalic dianhydride. The method provides hydroxyl groups by adding alkaline substances to modify and enhance the interaction between Pd and NiO, so that the obtained catalyst has a higher specific surface area and a stronger metal support interaction, which can promote the coupling of halogenated phthalic anhydride and improve the synthesis efficiency of BPDA. The catalyst preparation process is simple and has excellent performance, and the catalyst is applied to the synthesis of biphthalic dianhydride, without the need to add esterification and ester hydrolysis steps.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] A preparation method of a Pd-based catalyst, comprising the following steps.

[0007] (1) dispersing a nickel precursor and an alkaline substance in a solvent, ultrasonic mixing for 10-60 minutes, then hydrothermal reaction at 100-200℃ for 8-24h to obtain a reaction liquid;

[0008] The alkaline substance is sodium formate, sodium methoxide or sodium hydroxide; 0.1-1.0g of the nickel precursor is added per 50mL of the solvent, and the amount of the alkaline substance is 1-3 times the molar amount of the nickel precursor;

[0009] The solvent is one or two of water, ethanol, ethylene glycol and N’N-dimethylformamide;

[0010] (2) filtering and washing the reaction liquid obtained in the above step, then heating to 200-600℃ and calcining for 1-12h to obtain a nickel oxide carrier;

[0011] (3) loading a palladium precursor onto the nickel oxide carrier obtained in the above step, then heating to 200-600℃ and calcining for 1-12h to obtain a Pd-based catalyst;

[0012] The mass ratio of Pd element to the carrier is 1-10wt%;

[0013] In step (1), the nickel precursor is selected from nickel chloride, nickel nitrate and nickel acetate, preferably nickel chloride;

[0014] The solvent is preferably water and N’N-dimethylformamide;

[0015] In step (2), the heating rate is 2-10℃

[0016] The palladium precursor can be at least one of palladium chloride, palladium acetate, palladium nitrate and sodium palladate;

[0017] In step (3), the loading method can be co-precipitation or impregnation;

[0018] The co-precipitation method comprises the following steps: dispersing NiO in water, adding a Pd precursor solution, adding a basic compound solution to adjust the pH value of the solution to 7-9, stirring for 1-4 hours, and then centrifuging and drying.

[0019] The basic compound is sodium hydroxide, potassium hydroxide or ammonia water.

[0020] In step (3), the heating rate is 1-5 DEG C.

[0021] The Pd-based catalyst prepared by the method is applied to catalyzing the synthesis of biphenyl tetracarboxylic dianhydride.

[0022] The method comprises the following steps:

[0023] (1) coupling reaction is carried out by heating halogenated phthalic anhydride, the Pd-based catalyst, a sodium hydroxide solution and a reducing substance to 30-110 DEG C for 4-8 hours to obtain the sodium salt of biphenyl tetracarboxylic acid;

[0024] The mass of the Pd-based catalyst is 0.5-1.5 wt% of the mass of the halogenated phthalic anhydride; the amount of the sodium hydroxide is 3-6 times the molar amount of the halogenated phthalic anhydride; and the amount of the reducing substance is 0.5-3 times the molar amount of the halogenated phthalic anhydride.

[0025] The reducing substance is hydroxylamine hydrochloride or hydroxylamine sulfate.

[0026] The halogenated phthalic anhydride is chlorinated phthalic anhydride or brominated phthalic anhydride.

[0027] The mass concentration of the sodium hydroxide solution is 5-30%.

[0028] (2) the obtained sodium salt of biphenyl tetracarboxylic acid is acidified by hydrochloric acid until the pH value is 2-3, and white precipitate, i.e. biphenyl tetracarboxylic acid, is precipitated, and then the biphenyl tetracarboxylic acid is heated at 150-250 DEG C for 1-4 hours to obtain biphenyl tetracarboxylic dianhydride.

[0029] The concentration of the hydrochloric acid is 10-20%.

[0030] The substantial features of the application are:

[0031] The application provides hydroxyl groups by using a basic substance to obtain a Pd / NiO catalyst modified by hydroxyl groups. The modification by hydroxyl groups not only increases the specific surface area of the catalyst, but also enhances the interaction between Pd and NiO and improves the catalytic capacity of Pd active sites, so that the reaction efficiency of halogenated phthalic anhydride coupling to form BPDA is high.

[0032] The application has the following beneficial effects:

[0033] 1. The present invention provides a method for synthesizing biphenyltetracarboxylic dianhydride using a Pd-based catalyst. The active metal Pd is loaded on a nickel oxide carrier to prepare a Pd / NiO catalyst, which is then used in the synthesis reaction of biphenyltetracarboxylic dianhydride. The catalytic activity of the Pd / NiO catalyst is significantly superior to that of a conventional Pd / C catalyst (at 110° C., using 4-chlorophthalic anhydride as a raw material, the reaction conversion rate is 69% when using Pd / NiO; while the reaction conversion rate when using Pd / C is only 15%, resulting in a 4.6-fold increase in the reaction conversion rate). This method greatly broadens the application of the Pd-based catalyst in the synthesis of biphenyltetracarboxylic dianhydride.

[0034] 2. In the preparation method of the Pd-based catalyst provided by the present invention, nickel oxide is regulated by modifying with hydroxyl groups, which not only increases the specific surface area of ​​the Pd / NiO catalyst, but also enhances the interaction between Pd and NiO, significantly improving its catalytic performance in the synthesis reaction of biphenyltetracarboxylic dianhydride. Specifically, compared with the traditional Pd / NiO catalyst, the hydroxyl-modified Pd / NiO-OH catalyst has a higher specific surface area, exposes more active sites, and improves the catalyst's catalytic conversion ability for halogenated phthalic anhydride, thereby showing a higher conversion rate and selectivity (at 110°C, using 4-chlorophthalic anhydride as raw material, the optimal reaction conversion rate and selectivity can reach 94% and 87%, respectively), achieving efficient synthesis of biphenyltetracarboxylic dianhydride.

[0035] 3. The high-efficiency Pd-based catalyst provided by the present invention not only has excellent catalytic activity and outstanding cyclic stability, but also has a simple preparation method and low cost, and has obvious industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Figure 2 is the XRD pattern of Pd / NiO-OH and Pd / NiO catalysts.

[0037] Figure 2 The infrared spectra of Pd / NiO-OH and Pd / NiO.

[0038] Figure 3 is the N2 physical adsorption result of Pd / NiO-OH and Pd / NiO, where Figure 3 a is the N2 isothermal adsorption-desorption curve, Figure 3 b is the pore size distribution result.

[0039] Figure 4 The reaction performance results of the methods of Examples 1-3 are shown in FIG. Figure 4 a is the conversion and selectivity results of the methods of Examples 1-3; Figure 4 b is the cyclic stability result of the method in Example 1.

[0040] Figure 5 This is the cyclic stability result of the method in Example 4.

[0041] Figure 6 1 is a high performance liquid chromatogram of BPDA synthesized using the method of Example 1. DETAILED DESCRIPTION

[0042] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0043] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0044] Preparation of Pd / NiO-OH

[0045] 0.5 g of nickel chloride and 0.5 g of sodium formate were weighed and dissolved in 50 mL of a mixed solvent of deionized water and N'N-dimethylformamide (volume ratio 1:4). After sonication for 30 minutes, the mixture was transferred to a Teflon-lined autoclave and treated at 170°C for 10 hours. After cooling to room temperature, the mixture was filtered, washed (until the pH remained constant), and then dried at 80°C overnight. The mixture was then heated to 400°C (at a heating rate of 2°C / min) and calcined in air for 2 hours to obtain the NiO support. 0.5 g of the prepared NiO was dispersed in 50 mL of water, followed by the addition of a Na2PdCl4 solution (55 mg in 5 mL, Pd loading 4 wt% of the support). The pH of the suspension was adjusted to 8 with a 0.01 mol / L aqueous NaOH solution and stirred for 3 hours. The precipitate was obtained by centrifugal separation, washed with distilled water, centrifuged, and dried at 60° C. overnight, and then calcined at 300° C. for 2 h to obtain the catalyst hydroxyl-modified Pd / NiO-OH.

[0046] Preparation of Pd / NiO

[0047] 0.5 g of nickel acetate tetrahydrate was weighed and dissolved in a mixed solvent of 8 mL of ethanol and N'N-dimethylformamide (volume ratio 3:1). After ultrasonication for 30 minutes until complete dissolution, the mixture was placed in a 60°C oil bath and stirred to dryness. After cooling to room temperature, it was then calcined in air at 400°C for 2 hours to obtain the NiO support. 0.5 g of the prepared NiO was dispersed in 50 mL of water, and then Na2PdCl4 solution (55 mg, 5 mL) was added. The pH of the suspension was adjusted to 8 with an aqueous NaOH solution and stirred for 3 hours. The precipitate was obtained by centrifugation, thoroughly washed with distilled water, dried at 60°C overnight, and then calcined at 300°C for 2 hours to obtain the catalyst Pd / NiO.

[0048] Preparation of Pd / C

[0049] Weigh 1.0g of activated carbon and disperse it in 20% dilute nitric acid solution, reflux and stir at 80℃ for 8h. Wash the activated carbon powder with deionized water until neutral, then dry it at 120℃ for 12h. -1 The temperature was raised to 850°C at a rate of 1000 ℃ and kept at this temperature for 2 hours to obtain modified activated carbon. Metal Pd was loaded on the modified activated carbon by impregnation. 13.5 mg of PdCl2 was dissolved in 6-8 mL of deionized water, 0.2 g of modified activated carbon was mixed with the PdCl2 solution, and ultrasonic treatment was performed for 90 minutes. Transferred to an infrared lamp for drying, and the dried sample was placed in an 80°C oven and dried for 12 hours. Then, the sample was placed in a tubular furnace, heated to 300°C at 2°C / min in a 10% H2 / Ar atmosphere, and reduced for 2 hours to obtain a Pd / C catalyst.

[0050] Example 1

[0051] (1) 10 mmol (i.e., 1.8 g) of 4-chlorophthalic anhydride and Pd / NiO-OH catalyst (22.5 mg) were uniformly dispersed in 20 mL of 10% sodium hydroxide solution (i.e., 0.05 mol) under stirring. After heating to 110° C., a peristaltic pump was controlled to slowly add hydroxylamine hydrochloride solution at a rate of 1.6 mL / h (finally, 5 mL was added, with a concentration of 1.4 g / mL, i.e., 10 mmol). The addition time was 6 h (i.e., the addition was continued throughout the entire reaction process) to obtain disodium biphenyltetracarboxylate.

[0052] (2) After the reaction is completed, the filtrate is filtered to obtain a filtrate, and a hydrochloric acid solution with a concentration of 10-20% is added to the filtrate to acidify until the pH reaches 2-3, and a white precipitate is precipitated, which is filtered to obtain biphenyltetracarboxylic acid.

[0053] (3) The temperature of biphenyltetracarboxylic acid was gradually increased to 200° C. and heated for 2 h to obtain biphenyltetracarboxylic dianhydride, wherein the amount of Pd / NiO-OH used was 1.25 wt% of the halogenated phthalic anhydride.

[0054] Example 2 is different only in that the catalyst is Pd / NiO, and the remaining steps are the same as Example 1.

[0055] Example 3, the only difference is that the catalyst is Pd / C catalyst, and the rest of the steps are the same as Example 1

[0056] Example 4 differs only in that the substrate is 4-chlorophthalic anhydride replaced by 4-bromophthalic anhydride, the reaction temperature is 50° C., and the remaining steps are consistent with Example 1, and biphenyltetracarboxylic dianhydride is also obtained.

[0057] Example 5, the difference is only the catalytic reaction temperature of the substrate is 100°C, the rest of the steps are consistent with example 1, the catalytic reaction obtained diphenyl tetracarboxylic dianhydride.

[0058] Example 6, the difference is only the amount of catalyst is changed to 1wt%, the rest of the steps are consistent with example 1; the catalytic reaction obtained diphenyl tetracarboxylic dianhydride.

[0059] Example 7, the difference is only the substrate will be 4-chlorophthalic anhydride instead of 4-bromophthalic anhydride, the reaction temperature is 30°C, the rest of the steps are consistent with example 1; the catalytic reaction obtained diphenyl tetracarboxylic dianhydride.

[0060] Example 8, the other steps are the same as example 1, the difference is that the catalyst used is changed, that is, in the preparation of Pd / NiO-OH catalyst, the basic substance is changed, sodium formate is replaced by sodium hydroxide, and the same Pd / NiO-OH catalyst with the same Pd loading is prepared; the catalytic reaction obtained diphenyl tetracarboxylic dianhydride.

[0061] Catalyst performance evaluation

[0062] Figure 1 Pd / NiO-OH and Pd / NiO XRD patterns, from the figure, the characteristic peaks of Pd / NiO-OH, Pd / NiO correspond to the diffraction peaks of NiO crystal face.

[0063] Figure 2 Pd / NiO-OH and Pd / NiO infrared spectra, from the figure, Pd / NiO-OH has hydroxyl structure, and Pd / NiO does not detect hydroxyl structure.

[0064] Figure 3 Pd / NiO-OH and Pd / NiO N2 physical adsorption diagram, the specific surface area of Pd / NiO-OH is 59cm 3 / g, significantly higher than Pd / NiO (18cm 3 / g). Figure 3 b is the pore size distribution results, from the figure, the pore size of Pd / NiO-OH is significantly higher than that of Pd / NiO catalyst. The increased specific surface area and pore size promote the catalytic synthesis of diphenyl tetracarboxylic dianhydride.

[0065] Using the method of example 1-3, the conversion rate and selectivity of the reaction are calculated as Figure 4 a shown, at 110°C, with chlorophthalic anhydride as the substrate, using Pd / NiO-OH catalyst, the conversion rate and selectivity of the product are 94% and 87% respectively, which is significantly higher than Pd / NiO (69% and 83%) and Pd / C (15% and 80%). Figure 4b is the result of the cycling stability obtained according to the method of Example 1, as Figure 4 As shown in b, the conversion and selectivity of the reaction still remain 81% and 90% respectively after Pd / NiO-OH is used for 5 times, which indicates that Pd / NiO-OH has good cycling reuse ability.

[0066] Figure 5 The result of the catalytic cycling performance tested according to the method of Example 4, at 50℃, using brominated phthalic anhydride as the substrate and Pd / NiO-OH as the catalyst, the conversion of the reaction is 100%, the selectivity of the target product, biphenyl tetracarboxylic dianhydride, reaches 98%, and after being used for 20 times, it still has excellent catalytic activity (the conversion and selectivity both remain above 94%), which shows good potential for industrial application.

[0067] Figure 6 The high performance liquid chromatogram of biphenyl tetracarboxylic dianhydride obtained according to the method of Example 1. The analysis result of the liquid chromatogram is shown in Table 1, and the synthesized biphenyl tetracarboxylic dianhydride has high purity, which is 99%.

[0068] Table 1. The result of liquid chromatography analysis

[0069]

[0070] The above describes the embodiments of the present application. However, the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0071] The details of the present application are known technologies.

Claims

1. A method for preparing a Pd-based catalyst, characterized in that: The method includes the following steps. (1) dispersing a nickel precursor and an alkaline substance in a solvent, ultrasonically mixing for 10 to 60 minutes, and then hydrothermally reacting at 100 to 200° C. for 8 to 24 hours to obtain a reaction solution; The alkaline substance is sodium formate, sodium methoxide or sodium hydroxide; 0.1 to 1.0 g of nickel precursor is added to every 50 mL of solvent, and the amount of the alkaline substance is 1 to 3 times the molar amount of the nickel precursor; The solvent is one or two of water, ethanol, ethylene glycol, and N'N-dimethylformamide; (2) filtering and washing the reaction solution obtained in the previous step, heating it to 200-600° C., and calcining it for 1-12 hours to obtain a nickel oxide support; (3) loading the palladium precursor onto the nickel oxide support obtained in the previous step, and then heating to 200-600° C. and calcining for 1-12 hours to obtain a Pd-based catalyst; The mass ratio of the Pd element to the carrier is 1 to 10 wt %, and the palladium precursor is at least one of palladium chloride, palladium acetate, palladium nitrate, and sodium palladate.

2. The method for preparing a Pd-based catalyst as claimed in claim 1, wherein In step (1), the nickel precursor is selected from nickel chloride, nickel nitrate or nickel acetate; The solvents are water and N'N-dimethylformamide.

3. The method for preparing a Pd-based catalyst as claimed in claim 1, wherein In step (2), the heating rate is 2 to 10°C; in step (3), the heating rate is 1 to 5°C.

4. The method for preparing a Pd-based catalyst as claimed in claim 1, wherein In step (3), the loading method is a co-precipitation method or an impregnation method.

5. The method for preparing a Pd-based catalyst as claimed in claim 4, wherein The coprecipitation method comprises the following steps: dispersing NiO in water, adding a Pd precursor solution, adding an alkaline compound solution to adjust the pH value of the solution to 7-9, stirring for 1-4 hours, and then centrifuging and drying; The alkaline compound is sodium hydroxide, potassium hydroxide or ammonia water.

6. the application of the Pd-based catalyst obtained by the method as claimed in claim 1, for catalytic synthesis of biphenyltetracarboxylic dianhydride as catalyst.

7. The use according to claim 6, characterized in that The following steps are involved: (1) heating the halogenated phthalic anhydride, the Pd-based catalyst, a sodium hydroxide solution, and a reducing substance to 30 to 110° C. for 4 to 8 hours to perform a coupling reaction to obtain the sodium salt of biphenyltetracarboxylic acid; The mass of the Pd-based catalyst is 0.5 to 1.5 wt% of the mass of the halogenated phthalic anhydride; the amount of sodium hydroxide used is 3 to 6 times the molar amount of the halogenated phthalic anhydride; and the amount of the reducing substance used is 0.5 to 3 times the molar amount of the halogenated phthalic anhydride; Wherein, the reducing substance is hydroxylamine hydrochloride or hydroxylamine sulfate; the halogenated phthalic anhydride is chlorophthalic anhydride or bromophthalic anhydride; (2) The obtained sodium salt of biphenyltetracarboxylic acid is acidified with hydrochloric acid until the pH is 2-3, and a white precipitate, i.e., biphenyltetracarboxylic acid, is precipitated. The mixture is then heated at 150-250° C. for 1-4 hours to obtain biphenyltetracarboxylic dianhydride.

8. The use according to claim 7, characterized in that The mass concentration of the sodium hydroxide solution is 5-30%; the concentration of the hydrochloric acid is 10-20%.

Images