CN114985017B

CN114985017B - Tungsten-doped polyaniline supported palladium catalyst and preparation method and application thereof

Info

Publication number: CN114985017B
Application number: CN202210646034.2A
Authority: CN
Inventors: 孙红; 李颢菲; 俞磊; 石尧成
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2022-06-09
Filing date: 2022-06-09
Publication date: 2023-05-16
Anticipated expiration: 2042-06-09
Also published as: CN114985017A

Abstract

The invention discloses a tungsten-doped polyaniline supported palladium catalyst and a preparation method and application thereof in the technical field of catalysts, wherein the catalyst is prepared by uniformly mixing an acid solution of aniline, a PdCl2 solution and a sodium tungstate solution, dropwise adding hydrogen peroxide, and oxidizing and polymerizing aniline in the presence of palladium and tungsten salts. The catalyst can be used for catalyzing Suzuki coupling reaction. The invention uses palladium chloride and sodium tungstate as palladium source and tungsten source, and polyaniline as carrier of catalyst. The material cost can be significantly reduced compared to conventional palladium-based catalyst materials due to the reduced palladium content.

Description

Tungsten-doped polyaniline supported palladium catalyst and preparation method and application thereof

Technical Field

The invention belongs to the fields of material chemistry and catalytic chemistry, and particularly relates to the technical fields of polyaniline supported metal catalysts and Suzuki coupling reactions.

Background

The tungsten content in China is very rich, and the tungsten is dominant in the global scope, and meanwhile, tungsten is also called strategic metal in China. Tungsten is a transition metal with high density and high melting point, and is widely used in daily life and military fields. With the development of society, people gradually start to develop and research on the catalytic chemical reaction of metal tungsten, tungsten is taken as a catalyst to participate in the chemical reaction, so that the reaction cost can be reduced, compared with other transition metal tungsten, the toxicity is lower, the waste after the reaction is convenient to treat and is more friendly to the environment, and the requirement of current industrial application is met. The tungsten-based catalyst is a novel catalyst which is gradually developed in recent years, and has been widely applied in the fields of manufacturing hard alloy, catalysis, refractory materials, corrosion-resistant materials and the like.

On the other hand, the Suzuki coupling reaction plays a very important role in organic synthesis. It is widely used in the fields of synthesizing fine chemicals, natural products, medicines and the like. To date, palladium-based catalysts remain highly efficient catalysts for catalyzing the Suzuki coupling reaction. In recent years, many researchers coordinate palladium with different ligands to enhance the catalytic activity of palladium. However, these ligands and palladium are expensive and cause contamination of ligand residues after the reaction is completed, so that such catalysts are difficult to be used for mass production, and the amount of palladium used in such catalysts is usually 1 to 5 mol%. It is therefore highly desirable to develop a low cost and environmentally friendly catalyst.

In recent years, bimetallic catalysts have been a research hotspot in the field of catalytic chemistry, and by incorporating another relatively inexpensive component into noble metal catalysts, it is expected to improve the catalyst activity, so that the use of noble metals can be reduced, and the catalyst cost can be reduced. Is a research subject with industrial application value.

Disclosure of Invention

The invention aims to provide a tungsten-doped polyaniline supported palladium catalyst which is used for efficiently catalyzing Suzuki coupling reaction. By doping tungsten into the polyaniline-supported palladium catalyst, the catalytic performance of the metal palladium can be improved, so that palladium required by the reaction is reduced, and the cost of the catalyst is reduced.

Therefore, the invention provides a tungsten doped polyaniline supported palladium catalyst, which is prepared by mixing an acid solution of aniline and PdCl ₂ Mixing the solution with sodium tungstate solution, dripping hydrogen peroxide to make aniline undergo the process of oxidative polymerization in the presence of palladium and tungsten saltIs prepared.

The invention also discloses a preparation method of the tungsten-doped polyaniline-supported palladium catalyst, which comprises the following steps:

(1) Acid solution of aniline and PdCl ₂ After the solution and the sodium tungstate solution are uniformly mixed, dropwise adding hydrogen peroxide into the mixed solution; wherein, the molar ratio of the aniline, the palladium chloride, the sodium tungstate and the hydrogen peroxide is as follows: 1: (0.0005 to 0.002): (0.005-0.03): (1-5); the acid solution of aniline is obtained by adding hydrochloric acid into aniline solution;

(2) Standing for 12-72 h at room temperature, carrying out oxidative polymerization on aniline in the presence of palladium and tungsten salts, and then regulating the pH value to be neutral; then centrifugally separating the precipitate;

(3) Washing the separated precipitate with deionized water and ethanol respectively, and drying to obtain the tungsten doped polyaniline supported palladium catalyst.

As a further improvement of the invention, in the step (1), the molar concentration of the aniline in the mixed solution is 0.05-0.3 mol/L; preferably 0.1 mol/L. Polyaniline is polymerized in the concentration range, so that high-concentration agglomeration into a large block can be avoided, and the problem that the polymerization reaction speed is too slow due to too low concentration can be avoided.

As a preferable scheme of the invention, the molar ratio of the aniline, the palladium chloride, the sodium tungstate and the hydrogen peroxide is as follows: 1:0.0006:0.009:3. in this ratio, metallic palladium can be used as fully as possible, and too high a palladium amount does not improve the activity, but increases the cost. The tungsten doping has the most obvious effect on improving the catalytic activity of the catalyst at the ratio; h of the ratio of ₂ O ₂ Can fully polymerize aniline without damaging the catalytic effect of the catalyst due to the addition of excessive oxidant.

It is further preferred that the polymerization reaction is allowed to stand at room temperature for 24 hours. The reaction yield is higher.

The washing in the present invention was 3 times. Repeated experiments prove that if the washing times are too high, the material loss is serious, and if the washing times are too low, the salt on the surface of the material cannot be thoroughly eliminated, so that the catalytic activity of the material is reduced.

The invention also discloses an application of the tungsten-doped polyaniline supported palladium catalyst, which is used for catalyzing the Suzuki coupling reaction. The catalyst amount is 0.002-0.004mol% of the compound A.

According to the invention, palladium chloride and sodium tungstate are respectively used as a palladium source and a tungsten source of the materials, the polyaniline material is used as a carrier of the catalyst, the catalyst can catalyze the Suzuki coupling reaction, the content of the used metal palladium is extremely low, and the catalytic Suzuki coupling reaction under mild conditions can be realized; the tungsten doping can improve the catalytic activity of palladium, thereby obviously reducing the dosage of palladium in the catalyst, and the whole material has simple synthesis process and low price and is beneficial to industrial application. In a word, the invention uses palladium chloride and sodium tungstate as palladium source and tungsten source respectively, and polyaniline material as carrier of catalyst. The material cost can be significantly reduced compared to conventional palladium-based catalyst materials due to the reduced palladium content.

Drawings

FIG. 1 is an infrared spectrum of Pd@PANI and Pd/W@PANI prepared.

Fig. 2 is a scanning electron microscope image of the prepared pd@pani.

FIG. 3 is a scanning electron microscope image of the prepared Pd/W@PANI.

FIGS. 4 and 5 are transmission electron microscopy images of the prepared Pd/W@PANI.

FIG. 6 and high resolution transmission electron microscopy images of the prepared Pd/W@PANI, respectively.

FIG. 7 is an electron diffraction pattern of the prepared Pd/W@PANI.

Fig. 8 is an energy dispersive X-ray spectroscopy (EDX) diagram of the preparation.

FIG. 9 is an XPS spectrum of Pd after Pd/W@PANI and Pd@PANI are reacted.

FIG. 10 is an XPS spectrum of W after Pd/W@PANI and W@PANI are reacted.

Detailed Description

Example 1:

1. Pd/W@PANI material is prepared:

to a 250 mL beaker was added 1.0 mL aniline and 58 mL of 1mol/L HCl solution and stirred for 30 minutes. Then 25 mL of PdCl is added in turn ₂ Aqueous solution (1 mg PdCl) ₂ Dissolved in 25 mL 1mol/L HCl) and 25 mL Na ₂ WO ₄ Aqueous solution (25 mg Na) ₂ WO ₄ Dissolve in 25 mL 1mol/L HCl), stir well, then add 1mL 30 wt.% H dropwise to a beaker ₂ O ₂ Polymerization of aniline was initiated (in this reaction, the molar concentration of aniline was calculated to be about 0.1 mol/L). Standing at room temperature for 24h, adjusting pH to neutrality with 1mol/L NaOH solution, centrifuging, washing precipitate with deionized water and ethanol for 3 times, respectively, and standing at 60 ^o C vacuum drying 24h. And obtaining the tungsten doped polyaniline supported palladium catalyst (Pd/W@PANI).

Comparative example 1:

other procedure is as in example 1 except Na is not added ₂ WO ₄ And (3) directly polymerizing the solution to obtain Pd@PANI.

Comparative example 2:

other procedures were the same as in example 1 except that PdCl was not added ₂ And (3) directly polymerizing the solution to obtain the W@PANI.

2. Characterization of materials

In the Fourier transform infrared spectrum (FT-IR), 1569 cm of the material ^-1 And 1483 cm ^-1 The left and right absorption peaks are caused by c=c stretching vibration of the quinone ring and the benzene ring, respectively, which are the fundamental molecular units of PANI, thus proving the existence of PANI carrier. 1450 cm ^-1 The left and right absorption peaks are caused by stretching vibration of C=N bond on quinone ring, 1313 cm ^-1 And 1308 cm ^-1 The absorption peak is related to the secondary aromatic amine c=n stretching vibration of polyaniline, 1157 cm ^-1 The absorption peak is attributed to C-N stretching vibration 752 cm ^-1 And 746 cm ^-1 The absorption peak is caused by N-H wobble vibration, 3239 cm ^-1 And 3235 cm ^-1 The left and right absorption peaks are caused by N-H stretching vibration. Pd/W@PANI is 3239 cm compared with Pd@PANI ^-1 The left and right absorption peaks are weakened, which indicates that the metals Pd and W form more coordination bonds with N than the metals Pd, and the stretching vibration of the N-H bonds is further reduced. In addition, the infrared spectrum of Pd/W@PANI is 1842 cm ^-1 And 1809 cm ^-1 Two unique small absorption peaks are added (as shown in figure 1).

Microscopic morphology of the material was observed from a Scanning Electron Microscope (SEM), and it was found that the surface of the pd@pani material was bulk-packed (as shown in fig. 2), and after the metal W was introduced into the pd@pani, the surface of the material was formed by a number of rod-like piles (as shown in fig. 3). Thereby providing a plurality of active sites and being beneficial to the efficient and orderly reaction. Transmission electron microscopy studies showed that the Pd/w@pani internal structure was a rod-like stack (as shown in fig. 4, 5), and no crystal particles were observed in the high resolution transmission electron microscope (HR-TEM) image (as shown in fig. 6), since the Pd palladium content in the Pd/w@pani material was only 0.060% (as determined by inductively coupled plasma, ICP-MS), no crystal particles of Pd could be observed. Whereas the tungsten content was 0.25% as measured by ICP-MS, possibly in an amorphous state, relative to the higher W content, this was further demonstrated by electron diffraction patterns (as shown in fig. 7). Energy dispersive X-ray spectroscopy (EDX) indicates the presence of metals Pd and W in the material and that both are present in very small amounts in the material (as shown in fig. 8).

The electron binding energy change after the metal Pd and the metal W in the material act together with the single metal respectively to react is studied by X-ray photoelectron spectroscopy (XPS). In the spectrum of Pd 3d, the binding energies at 342.5 eV and 337.5 eV correspond to Pd 3d, respectively _3/2 And Pd 3d _5/2 Binding energy corresponds to Pd 3d at 340.3 eV and 334.5 eV, respectively _3/2 And Pd 3d _5/2 Indicating that Pd is present in the material after the reaction ²⁺ And Pd (Pd) ⁰ Two valence states (as shown in fig. 9). In the spectrum of W4 f, the binding energies at 34.1 eV and 33.5 eV correspond to W4 f, respectively _5/2 And W4 f _7/2 Indicating the presence of W after the material has reacted ⁴⁺ (as shown in fig. 10). From FIG. 9, it can be seen that Pd/W@PANI reacted Pd ⁰ Valence ratio Pd@PANI Pd after participating in reaction ⁰ The valence state content is increased.

3. Application:

the Pd/W@PANI bimetallic material prepared in example 1 above was applied to a Suzuki coupling reaction.

The iodibenzene and phenylboronic acid are selected to react as model reaction to test the performance of the material.

1 mmol phenylboronic acid, 5 mg Pd/W@PANI,2 mmol K ₂ CO ₃ After putting into a 25 mL Schlenk tube and nitrogen protection, 4 mL of an absolute ethanol solution containing 1 mmol of iodobenzene was injected into the reaction tube, and the mixture was magnetically stirred at 100℃for 48 h. The product was isolated by thin layer chromatography in 89% yield. The amount of palladium added in this reaction was calculated to be 0.000028mmol, and thus 0.0028mol% of the reactant was used. The conversion of the reaction catalyst was 3.2 x 10 ⁴ 。

Similarly, the comparative example was used to prepare Pd@PANI to catalyze the reaction (the catalyst had a Pd@PANI content of 0.062% and the same reaction was carried out with Pd@PANI having an equivalent Pd content), reaction 48 h was carried out, and the yield was calculated to be 64%. Calculated to be 2.3 x 10 conversion of the reaction catalyst ⁴ . Comparative example preparation w@pani was used to catalyze this reaction, reaction 48 h, with no product formation. The above results indicate that the incorporation of metallic tungsten in the material pd@pani enhances the catalytic activity of the catalyst.

Example 2:

other conditions were the same as in example 1, and the effect of different concentrations of aniline on material properties (the overall aniline polymerization reaction liquid volume was controlled by scaling the amount of hydrochloric acid solution in each reagent used in the experiment, thus controlling the aniline concentration), and the experimental results are shown in table 1.

TABLE 1 Performance of materials prepared from different concentrations of aniline

From the above results, it was found that the effect was optimal when the aniline concentration was 0.1 mol/L.

Example 3:

other conditions are the same as in example 1, the molar ratio of aniline to palladium chloride in the material is changed, and the experimental results are shown in table 2.

TABLE 2 Performance of materials prepared with different molar ratios of aniline to palladium chloride

From the above results, it can be seen that when the molar ratio of aniline to palladium chloride is 1: the effect is best at 0.0006. Increasing the palladium level does not provide gadolinium catalyst activity but increases cost.

Example 4:

other conditions are the same as in example 1, the molar ratio of aniline to sodium tungstate in the material is changed, and the experimental results are shown in table 3.

TABLE 3 Performance of materials prepared with different molar ratios of aniline to sodium tungstate

From the above results, when the molar ratio of aniline to sodium tungstate is 1: the effect is best at 0.0009.

Example 5:

other conditions are the same as in example 1, the molar ratio of aniline to hydrogen peroxide in the material is changed, and the experimental results are shown in table 4.

Table 4 table of properties of materials prepared with different molar ratios of aniline to hydrogen peroxide

From the above results, it can be seen that when the molar ratio of aniline to hydrogen peroxide is 1: the effect of 3 times is optimal, therefore, the molar ratio of aniline to hydrogen peroxide is 1: the catalyst material is preferably prepared at 3.

Example 6:

other conditions are the same as in example 1, the influence of different polymerization times of aniline on the material properties is shown in table 5.

TABLE 5 Performance of materials with aniline at different polymerization times

From the above results, it is clear that the productivity of the catalyst material prepared by aniline polymerization 24h is the highest, and after 72 hours, the productivity is substantially unchanged, and from the economical point of view, the productivity is preferably 12 to 72 hours.

Example 7:

as shown in table 6. The tungsten-doped polyaniline-supported palladium catalyst obtained in example 1 can be used in the cross-coupling reaction of aryl or alkenyl boric acid or boric acid ester and chlorine, bromine, iodo-aromatic hydrocarbon or olefin, under the catalysis of palladium complex, the compounds A and B undergo Suzuki coupling reaction, and the palladium content in the catalyst is 0.002-0.004mol% of the compound A. The metal palladium dosage is extremely low.

TABLE 6 suitability of different substrates for catalysts

As can be seen from the table above, the catalyst has good applicability to different substrates and can be successfully used for developing various medicaments.

The invention is not limited to the above embodiments, and based on the technical solution disclosed in the invention, a person skilled in the art may make some substitutions and modifications to some technical features thereof without creative effort according to the technical content disclosed, and all the substitutions and modifications are within the protection scope of the invention.

Claims

1. A tungsten doped polyaniline supported palladium catalyst is characterized in that: the catalyst is an acid solution of aniline and PdCl ₂ The solution and the sodium tungstate solution are uniformly mixed, hydrogen peroxide is dripped, and aniline is subjected to oxidative polymerization in the presence of palladium and tungsten salts to prepare the catalyst.

2. The method for preparing the tungsten-doped polyaniline supported palladium catalyst according to claim 1, comprising the steps of:

(1) Acid solution of aniline and PdCl ₂ After the solution and the sodium tungstate solution are uniformly mixed, dropwise adding hydrogen peroxide into the mixed solution; wherein, the molar ratio of the aniline, the palladium chloride, the sodium tungstate and the hydrogen peroxide is as follows: 1: (0.0005 to 0.002): (0.005-0.03): (1-5); the acid solution of aniline is prepared from aniline solutionAdding hydrochloric acid to obtain;

3. The method for preparing the tungsten-doped polyaniline supported palladium catalyst according to claim 2, comprising the steps of: in the step (1), the molar concentration of the aniline in the mixed solution is 0.05-0.3 mol/L.

4. The method for preparing the tungsten-doped polyaniline supported palladium catalyst according to claim 3, wherein the method comprises the following steps: the molar concentration of the aniline in the mixed solution is 0.1 mol/L.

5. The method for preparing the tungsten-doped polyaniline supported palladium catalyst according to claim 2, comprising the steps of: the molar ratio of the aniline to the palladium chloride to the sodium tungstate to the hydrogen peroxide is as follows: 1:0.0006:0.009:3.

6. the method for preparing the tungsten-doped polyaniline supported palladium catalyst according to claim 2, comprising the steps of: the polymerization reaction was allowed to stand at room temperature for 24 hours.

7. The use of a tungsten doped polyaniline supported palladium catalyst according to claim 1, wherein: the catalyst is used for catalyzing Suzuki coupling reaction.