CN114558610B - A kind of confined type Pd-based catalyst and its preparation method and application - Google Patents

Abstract

The invention relates to the technical field of Pd-based catalyst preparation, in particular to a finite field type Pd-based catalyst, and a preparation method and application thereof; the preparation method comprises the steps of exchanging positively charged Pd precursor with cations in an HY type molecular sieve framework, limiting Pd particles in HY type molecular sieve pore channels, inhibiting Pd agglomeration into large particles by utilizing the strict limitation of the HY type molecular sieve pore channels on the Pd particle size and the binding effect of nano pore channels, thereby obtaining Pd particles with the particle size range of 2.2-3.1 nm and high dispersity, and generating partial positively charged metal Pd (Pd ⁿ⁺ ) Thereby improving the catalytic efficiency of the 2,4, 6-trichloroanisole. Moreover, the Pd-based catalyst prepared by the method can avoid the competition problem of humic acid molecules and 2,4, 6-trichloroanisole on Pd active sites in a humic acid environment, thereby improving the resistance of the catalyst to humic acid.

Description

A kind of confined type Pd-based catalyst and its preparation method and application

technical field

The invention relates to the technical field of Pd-based catalyst preparation, in particular to a confined Pd-based catalyst and its preparation method and application.

Background technique

The sensory quality (color, smell, and taste) of drinking water is the water quality index that consumers and water supply organizations are most concerned about, and smell and taste are people's most intuitive judgments on the quality of drinking water. Earthy musty smell is the most widespread and unpleasant odor in water, and 2,4,6-trichloroanisole, as a typical disinfection by-product, has a strong earthy musty smell and its odor threshold is extremely low. It not only affects the sensory perception of the water body, but also directly endangers human health.

The 2,4,6-trichloroanisole in drinking water can be effectively removed by the liquid phase hydrogenation reduction method. For this dechlorination reaction, the Pd catalyst shows a higher performance, which is due to the fact that Pd has normal pressure and normal temperature conditions. The ability to dissociate hydrogen and promote the breaking of C-X bonds. Currently commonly used Pd catalysts are supported, such as the following:

Chinese patent CN201811556633.5 discloses a Pd-containing catalyst and its preparation method. In this method, Pd is added to the catalytic material through the method of step-by-step infiltration, which improves the dispersion of Pd in the catalytic material and increases the concentration of Pd and catalytic material. Contact surfaces.

Chinese patent CN200910304443.9 discloses a method for preparing eggshell-type Pd catalyst by reactive deposition method. The method is to add the carrier to the Pd metal salt solution, and control the deposition of Pd on the surface of the carrier through a rapid reduction reaction. After filtering and washing , Heat and dry in an inert atmosphere to form a stable eggshell-type Pd catalyst.

In the above-mentioned materials, no matter whether Pd is loaded on the surface of the carrier in multiple layers by impregnation method or loaded by overall deposition, Pd exists on the surface of the carrier, and the interaction between Pd and the carrier is weak. Pd is easy to fall off, and the actual natural water environment contains a large amount of humic acid, which constitutes most of the organic matter in the source water. However, the reactant molecules will compete with the humic acid molecules for the Pd active sites on the surface of the carrier, occupy the Pd surface, and inhibit The dechlorination reaction of chlorine-containing organic matter reduces the catalytic activity of the catalyst, which is not conducive to the application of the catalyst in actual water bodies.

In order to solve the above problems, the present invention designs a confined Pd-based catalyst, a preparation method thereof and a hydrogenation reduction method for 2,4,6-trichloroanisole based on the catalyst.

Contents of the invention

In order to achieve the above objectives, the present invention provides a confinement type Pd-based catalyst and its preparation method, the preparation method is by exchanging the positively charged Pd precursor with the cation in the HY type molecular sieve framework, so that the Pd particles Confined in the HY-type molecular sieve channels, using the strict restriction of the HY-type molecular sieve channels on the size of Pd particles and the binding effect of nano-scale channels, the agglomeration of Pd into large particles is suppressed, thereby obtaining smaller-sized, higher-dispersion Pd particles , and generate partially positively charged metal Pd(Pd ⁿ⁺ ), thereby improving the catalytic removal efficiency of 2,4,6-trichloroanisole.

Technical scheme of the present invention is as follows:

A confinement type Pd-based catalyst, the catalyst includes a catalyst carrier and active metal particle clusters confined in the pores of the catalyst carrier;

The catalyst carrier is a molecular sieve accounting for 100% of the mass of the catalyst carrier, and the content of the catalyst carrier in the catalyst is 98.27-99.6wt.%.

The active metal particle group accounts for 0.4-1.73wt.% of the mass of the catalyst.

Further, the molecular sieve is a HY type molecular sieve; in the HY type molecular sieve, SiO ₂ :Al ₂ O ₃ =30:1 by molar ratio.

Further, the active metal particles in the active metal particle group are Pd particles.

Further, the particle size range of the Pd particles in the pores of the HY type molecular sieve is 2.0-3.25 nm.

The present invention also discloses a specific preparation method of the above-mentioned confined Pd-based catalyst:

SA1, first disperse the HY type molecular sieve in deionized water, then add Pd(OAc) ₂ solution to obtain a mixed solution;

SA2, heating and stirring the mixed solution prepared in step SA1 in a water bath to realize the exchange between the Pd precursor and the cations in the pores of the HY molecular sieve;

SA3, filtering step SA2 to obtain a filter residue from the mixed solution, washing the filter residue with deionized water until the filtrate is neutral, and then drying at 70°C;

SA4. Reducing the dried filter residue in step SA3 under H ₂ atmosphere at 300° C. for 2 hours to obtain a confined Pd-based catalyst.

Further, in the step SA1, the content of HY type molecular sieve in the deionized water is 2 g/L.

Further, in the step SA2, the heating temperature in the water bath is 80° C., and the heating and stirring time in the water bath is 10 h.

Further, constraining the process conditions of the step SA2 to be constant, by changing the amount of Pd(OAc) _solution added in the step SA1, the particle size of the Pd particles in the confinement type Pd-based catalyst obtained in the step SA4 can be directionally adjusted. The relationship is as follows:

When the Pd(OAc) solution is added in the step _SA1 so that the content of Pd in the catalyst ranges from 0.4 to 0.43wt.%, the particle diameter of the Pd particles in the confined Pd-based catalyst obtained in step SA4 is 2.21 to 2.3 nm;

When the Pd(OAc) ₂ solution is added in the step SA1 so that the content of Pd in the catalyst ranges from 0.87 to 0.90wt.%, the particle diameter of the Pd particles in the confined Pd-based catalyst obtained in step SA4 is 2.92 to 3.01 nm;

When the Pd(OAc) ₂ solution is added in the step SA1 so that the content of Pd in the catalyst ranges from 1.7 to 1.73wt.%, the particle diameter of the Pd particles in the confined Pd-based catalyst obtained in step SA4 is 3.11 to 3.21 nm.

The present invention also discloses the application of the above-mentioned confined Pd-based catalyst in catalyzing 2,4,6-trichloroanisole. The application method includes the following steps:

SB1. Add a confined Pd-based catalyst to deionized water with a pH value of 6±0.1 at 23±5°C;

SB2, continuously electromagnetically stirring the deionized water in step SB1, and passing _H2 into the deionized water for 30 minutes to obtain hydrogen-saturated water;

SB3. In a closed environment, add 2,4,6-trichloroanisole to the container containing the hydrogen-saturated water prepared in step SB2, and take samples at regular intervals until 2,4,6-trichloroanisole Chloroanisole was completely converted to anisole.

Further, in the step SB1, the content of the confinement-type Pd-based catalyst in the deionized water is 1/24g/L; in the step SB2, the rotating speed of the electromagnetic stirring is 1000-1500rpm, and the flow range of the _H2 150-200mL/min.

Compared with existing supported Pd-based catalysts, the beneficial effects of the present invention are:

(1) In the confinement type Pd-based catalyst prepared by the present invention, the size of the Pd particles in the pores of the HY type molecular sieve is restricted within the range of 2.2 to 3.1 nm, that is, the agglomeration of the Pd particles is suppressed, the active metal Pd is stabilized, and the metal The loss of Pd further enhances the interaction between metal Pd and HY molecular sieve carrier.

(2) The confinement type Pd-based catalyst prepared by the present invention, HY type molecular sieve as an ordered porous material can enhance the enrichment ability of the catalyst to 2,4,6-trichloroanisole, and then synergistically improve the confinement type Catalytic performance of Pd-based catalysts.

(3) Compared with the traditional supported Pd-based catalyst, the confined Pd-based catalyst prepared by the present invention confines the Pd particles in the HY-type molecular sieve channels, and utilizes the strict restriction of the Pd particle size by the HY-type molecular sieve channels and The confinement effect of nano-scale pores inhibits the agglomeration of Pd into large particles, thereby obtaining smaller-sized, higher-dispersion Pd particles, and producing partially positively charged metal Pd, thereby improving the sensitivity of 2,4,6-trichlorobenzene Catalytic efficiency of methyl ether.

(4) Compared with traditional supported Pd-based catalysts, the confinement-type Pd-based catalyst prepared by the present invention has a sieving effect that HY-type molecular sieves can prevent humic acid macromolecules from entering the confinement-type Pd-based catalyst pores, avoiding Humic acid molecules compete with 2,4,6-trichloroanisole for active sites, thereby improving the resistance of the catalyst to humic acid, that is, improving the stability of the confined Pd-based catalyst, which has Potential for application in real water bodies.

Description of drawings

Fig. 1 is the demonstrative figure of confinement type Pd-based catalyst anti-humic acid in the 5th section of the experimental example of the present invention;

Fig. 2 is the demonstrative figure of load-type Pd-based catalyst anti-humic acid in the 5th section of the experimental example of the present invention;

Fig. 3 is the XPS spectrum of Pd@Y and im-Pd/Y in the 2nd section of the experimental example of the present invention;

Fig. 4 is a comparison diagram of the catalytic degradation effect of Pd@Y and im-Pd/Y on 2,4,6-trichloroanisole in Section 4 of the experimental example of the present invention;

Fig. 5 is a comparison diagram of the catalytic degradation effect of Pd@Y and im-Pd/Y on 2,4,6-trichloroanisole in humic acid environment in section 5 of the experimental example of the present invention;

Fig. 6 is the catalytic effect data of Pd@Y and im-Pd/Y on 2,4,6-trichloroanisole in humic acid environment in section 5 of the experimental example of the present invention.

In Figure 1 and Figure 2: 1-confined Pd-based catalyst, 2-supported Pd-based catalyst, 3-HY molecular sieve, 4-channel, 5-Pd particles, 6-2,4,6-trichlorobenzene Methyl ether molecule, 7-humic acid molecule.

Detailed ways

In order to further illustrate the methods and effects of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

Example 1

The main purpose of Example 1 is to illustrate the specific method for preparing a confined Pd-based catalyst under specific process parameters in the present invention, as well as the specific performance parameters of the prepared confined Pd-based catalyst, as follows.

1. Preparation method

In this embodiment, all the following experimental processes are carried out in a laboratory environment, and the temperature range of the laboratory is 23±5°C.

First, disperse 1 g of HY molecular sieve in 500 mL of deionized water, and then add Pd(OAc) ₂ solution to obtain a mixed solution; in the HY molecular sieve, SiO ₂ :Al ₂ O ₃ =30:1 by molar ratio Heating and stirring the above mixed solution in a water bath at 80°C for 10 hours to realize the exchange between the Pd precursor and the cations in the pores of the HY molecular sieve; filtering the mixed solution to obtain a filter residue, washing the filter residue with deionized water until the filtrate is neutral, Dry at 70°C; reduce the dried filter residue in H ₂ atmosphere at 300°C for 2 hours to obtain a confined Pd-based catalyst.

2. Component content of confined Pd-based catalyst

The content of Pd in the prepared confined Pd-based catalyst is 0.42wt.%, and the content of HY type molecular sieve is 99.58wt.%, which is recorded as Pd(0.42)@Y.

Example 2

The narration basis of embodiment 2 is the scheme recorded in embodiment 1, which aims to illustrate the specific performance parameters of the confinement type Pd-based catalyst prepared under different experimental parameters. The specific content is as follows:

1. Preparation method

Disperse 1 g of HY-type molecular sieve in 500 mL of deionized water, and then add Pd(OAc) ₂ solution to obtain a mixed solution; in the HY-type molecular sieve, SiO ₂ :Al ₂ O ₃ =30:1 by molar ratio; Heat and stir the mixture in a water bath at 80°C for 10 hours to exchange the Pd precursor with the cations in the pores of the HY-type molecular sieve; filter the mixture to obtain a filter residue, wash the filter residue with deionized water, and dry at 70°C dry; the dried filter residue was reduced in H ₂ atmosphere at 300°C for 2 hours to obtain a confined Pd-based catalyst.

2. Confined Pd-based catalyst

Restricting the above-mentioned preparation method, all the other process conditions except the following content remain unchanged:

Change the adding amount of Pd(OAc) ₂ solution, directionally adjust the particle size of the Pd particles in the obtained confinement type Pd-based catalyst, and get the following relational table.

Table 1 Relationship between Pd content and Pd particle size in confined Pd-based catalysts

From the data in Table 1, it can be seen that the content and size of Pd particles in the pores of the confined Pd-based catalyst increase nonlinearly and uniformly due to the confinement effect of the pores in the HY-type molecular sieve on the Pd particles and the agglomeration of the Pd particles themselves. , but it grows by leaps and bounds in stages, and there is an upper limit:

With the increase of the addition of Pd(OAc) ₂ solution, the content of Pd particles in the pores of confined Pd-based catalysts is divided into three distribution intervals: 0.4～0.43wt.%, 0.87～0.90wt.% and 1.7～1.73wt.% .%;

The size of Pd particles in the pores of the confined Pd-based catalyst corresponding to the Pd particle content in the above three distribution intervals is also divided into three distribution intervals: 2.21-2.3nm, 2.92-3.01nm and 3.11-3.21nm. It can be seen that the size range of Pd particles in the pores of confined Pd-based catalysts is restricted to 2.2-3.1 nm, that is, the agglomeration of Pd particles is suppressed, and the interaction between metal Pd and HY-type molecular sieve support is enhanced.

Experimental example

The basis of the description of this experimental example is the scheme described in Example 2, aiming to clarify the performance difference between the confined Pd-based catalyst prepared in the present invention and the traditional supported Pd-based catalyst.

1. Experimental design

In order to clarify the specific performance of the confined type Pd-based catalyst prepared by the present invention, the following experimental groups are designed:

Control group 1:

As a comparison, supported im-Pd/Y catalysts with different Pd loadings were synthesized by the impregnation method. The specific catalyst preparation process is as follows:

Disperse 1 g of HY-type molecular sieve in 100 mL of deionized water, and then add chloropalladium acid solution to obtain a mixed solution. In the HY-type molecular sieve, SiO ₂ : Al ₂ O ₃ =30:1; after immersing and stirring the above mixed solution for 2 hours , evaporate the solution to dryness at 90°C to obtain the product, then bake the product at 70°C until the weight of the product does not change; reduce the dried product at 300°C under H ₂ atmosphere for 2 hours to obtain a supported Pd base catalyst.

The content of Pd in the prepared supported Pd-based catalyst is 0.86wt.%, and the content of HY type molecular sieve is 99.14wt.%, recorded as im-Pd(0.86)/Y.

Control group 2: Control group 2 is the same as control group 1 except that the addition amount of chloropalladium acid solution is different, and other process parameters are the same.

The content of Pd in the prepared supported Pd-based catalyst is 1.72wt.%, and the content of HY type molecular sieve is 98.28wt.%, recorded as im-Pd(1.72)/Y.

Experimental group 1: Select the confinement type Pd-based catalyst whose Pd particle content in Example 2 is the median value of the range of 0.4-0.43wt.% as the experimental object of experimental group 1, denoted as Pd(0.42)@Y;

Experimental group 2: Select the confinement type Pd-based catalyst whose Pd particle content in Example 2 is the median value of the range of 0.87-0.9wt.% as the experimental object of experimental group 2, denoted as Pd(0.89)@Y;

Experimental group 3: Select the confining Pd-based catalyst whose Pd particle content is the median value in the range of 1.7-1.73wt.% in Example 2 as the experimental object of experimental group 3, denoted as Pd(1.71)@Y.

2. X-ray photoelectron spectroscopy (XPS)

ESCALAB 250 X-ray photoelectron spectroscopy (XPS) from Thermo Scientific, USA was used to characterize the valence state of the sample elements. The instrument uses Al Kα as the excitation source (hv=1486.6eV), and uses C1s=284.6eV to calibrate the binding energy of other elements. XPS peak 4.1 software was used to analyze the XPS spectra of the samples in the Pd 3d region. The Shirley background and %Lorentzian-Gaussian=80 were applied to make the peak fitting error (∑x ² ) less than 6. The test results are shown in FIG. 2 .

Figure 3 shows the XPS spectra of the prepared confinement-type Pd@Y catalysts with different Pd contents and the supported im-Pd/Y catalysts with different Pd contents in the Pd 3d region. It can be seen from the figure that Pd was successfully supported on HY molecular sieve, and the confined catalyst Pd@Y has a higher Pd ⁿ⁺ content, which is beneficial to the formation of C-Cl bond of 2,4,6-trichloroanisole. Activation to promote its hydrodechlorination.

3. High-resolution transmission electron microscopy (HRTEM)

The supported Pd-based catalysts in control group 1 and control group 2, and the confined Pd-based catalysts in experimental group 1, experimental group 2, and experimental group 3 were used as experimental objects.

A high-resolution transmission electron microscope model JEOL JEM-200CX was used to study the morphology, crystal structure and particle size distribution of the catalyst active components. Put a small amount of powder samples of the above-mentioned experimental objects in absolute ethanol, and ultrasonically treat them at 200-350W for 15-30 minutes to fully disperse them. Take a small amount of fully dispersed sample and drop it on the surface of the copper mesh, and test it after the ethanol is completely volatilized. The test results are shown in Table 2.

Table 2 Pd particle size in Pd@Y and im-Pd/Y

From the data in Table 2, it can be seen that the Pd particle size in the confined Pd-based catalyst Pd@Y is smaller, and the size range is limited to 2.2–3.1 nm, which is much smaller than the supported Pd-based catalyst im-Pd/ Y. The smaller the active metal Pd particles, the larger their surface area (the larger the contact area with the object to be catalyzed), the higher the content of the exposed Pd active sites, the more conducive to the improvement of catalytic activity, and then it is inferred that: the present invention prepares The catalytic performance of the confined Pd-based catalyst Pd@Y should be higher than that of the supported Pd-based catalyst Pd/Y.

4. Comparison of catalytic degradation effects of Pd@Y and im-Pd/Y on 2,4,6-trichloroanisole.

In order to verify the inference in Section 3 that "the catalytic performance of the confinement-type Pd-based catalyst Pd@Y prepared by the invention should be higher than that of the supported Pd-based catalyst Pd/Y", the following experiments are now designed:

Considering the volatility of 2,4,6-trichloroanisole, hydrogen saturated reduction was used in the experiment.

At 23±5°C, use 0.1M HCl and 0.1M NaOH to adjust the pH value of deionized water to 6±0.1; after adjusting the pH, add the catalyst; stir at a speed of 1000rpm, and the flow rate of _H2 is 150mL/min, aeration time of 30min, to obtain hydrogen-saturated water; then the glass reaction vial is tightly sealed with a bottle cap equipped with a polytetrafluoroethylene gasket; inject 1mg/L of 2, 4,6-Trichloroanisole starts catalytic hydrogenation reduction reaction; during the reaction, samples are taken with glass needles at fixed intervals for testing. In order to ensure the validity of the data, each experiment was repeated three times, and the data results were averaged.

Five groups of catalysts in Table 2 were used as the added catalysts, and the catalyst content was 1/24g/L. The test results after hydrodechlorination and reduction of 2,4,6-trichloroanisole are shown in FIG. 4 .

Figure 4 shows the catalytic degradation effect of Pd@Y and im-Pd/Y on 2,4,6-trichloroanisole within 120 min. When the reaction time was 30 min, the removal rate of 2,4,6-trichloroanisole for all loadings of confined Pd-based catalysts Pd@Y was above 95.5% (Pd(0.42)@Y was 95.5 %, Pd(0.89)@Y is 98.3%, Pd(1.71)@Y is 100%), while the supported catalyst im-Pd/Y is only 49.4% (im-Pd(0.86)/Y) and 68.7% ( im-Pd(1.72)/Y), indicating that the activity of the confined Pd-based catalyst Pd@Y is significantly better than that of the supported Pd-based catalyst im-Pd/Y, which verifies the inference in Section 3 of the experimental example.

The principle of the above phenomenon is explained as follows: because the confinement type Pd-based catalyst Pd@Y confines the Pd particles in the pores of the HY-type molecular sieve, which inhibits the agglomeration and growth of the active metal Pd particles, and the Pd particles are smaller in size, more uniform and dispersed. and the confined Pd-based catalyst Pd@Y has a higher Pd ⁿ⁺ content, and the interaction between the metal Pd and the HY-type molecular sieve support is stronger, which is beneficial to the activation of 2,4,6-trichloroanisole , and its hydrodechlorination, so the catalytic activity of the confined Pd-based catalyst Pd@Y is significantly higher than that of the supported Pd-based catalyst im-Pd/Y.

5. Effect of humic acid on catalytic reduction of 2,4,6-trichloroanisole by Pd@Y and im-Pd/Y

With reference to the experimental method in the experimental example section 4, the difference is: the humic acid (HA) of 5mgC/L has been added in the reaction system, and the following control experiments are designed according to the different catalysts:

im-Pd(0.86)/Y, im-Pd(0.86)/Y+HA, Pd(0.89)@Y, Pd(0.89)@Y+HA.

The test results of the above catalysts after hydrogenation-reductive dechlorination of 2,4,6-trichloroanisole are shown in FIG. 5 .

Referring to Figure 5 and Figure 6, after adding 5mgC/L of humic acid to the reaction system, the supported Pd-based catalyst im-Pd(0.86)/Y can react with 2,4,6-trichloroanisole within 120min The removal rate of Pd(0.89)@Y decreased by 53.0%, while the confined Pd-based catalyst Pd(0.89)@Y only decreased by 3.7%, which indicates that the confined Pd-based catalyst Pd@Y has better humic acid resistance and stronger stability .

The reason for the above phenomenon is that, referring to Figure 1 and Figure 2, since the Pd active sites of the supported catalyst are located on the surface of the carrier, the reactant molecules and the humic acid molecules will compete for limited active sites, resulting in a decrease in catalytic activity, while limited The domain-type catalyst restricts the Pd active particles inside the carrier pores, and the sieving effect of the molecular sieve carrier can prevent humic acid macromolecules from entering the catalyst pores to occupy the active Pd sites, avoiding competition problems, and protecting the active sites, thereby improving The resistance of the catalyst to humic acid improves the stability of the catalyst.

Claims (2)

1. The domain-limited Pd-based catalyst is characterized by comprising a catalyst carrier and active metal particle groups limited in pore channels of the catalyst carrier;

the mass ratio of the catalyst carrier in the catalyst is 98.27-99.6 wt%, and the active metal particle groups account for 0.4-1.73 wt% of the mass of the catalyst;

the catalyst carrier is an HY type molecular sieve, wherein in the HY type molecular sieve, siO (silicon dioxide) is calculated according to the molar ratio ₂ ：Al ₂ O ₃ ＝30：1；

The active metal particles in the active metal particle group are Pd particles;

the preparation method of the domain-limited Pd-based catalyst comprises the following steps:

SA1, dispersing HY type molecular sieve in deionized water, adding Pd (OAc) ₂ Obtaining a mixed solution;

SA2, heating and stirring the mixed solution prepared in the step SA1 in a water bath;

SA3, filtering the mixed solution processed in the step SA2 to obtain filter residues, washing the filter residues with deionized water until the filter liquor is neutral, and drying at 70 ℃;

SA4, drying the filter residue obtained in the step SA3 at 300 ℃ H ₂ Reducing for 2 hours in the atmosphere to prepare a finite field Pd-based catalyst;

constraining the process conditions of step SA2 to be unchanged by changing Pd (OAc) in step SA1 ₂ The addition amount of the solution can directionally adjust the particle size range of Pd particle groups in the limited-domain Pd-based catalyst prepared in the step SA4Enclose and be three-section ladder type distribution:

pd (OAc) in step SA1 ₂ When the solution is added in such an amount that the content of Pd in the catalyst ranges from 0.4 to 0.43 wt%, the particle size range of Pd particle groups in the finite field Pd-based catalyst prepared in the step SA4 is 2.21-2.3 nm, and positive correlation is shown;

pd (OAc) in step SA1 ₂ When the addition amount of the solution is such that the content of Pd in the catalyst is in the range of 0.87-0.90 wt%, the particle size range of Pd particle groups in the finite field Pd-based catalyst prepared in step SA4 is 2.92-3.01 nm, and positive correlation is presented;

pd (OAc) in step SA1 ₂ When the addition amount of the solution is such that the Pd content in the catalyst is in the range of 1.7-1.73 wt%, the Pd particle size in the finite field Pd-based catalyst prepared in step SA4 is in the range of 3.11-3.21 nm, and positive correlation is shown.

2. Use of a limited-area Pd-based catalyst as claimed in claim 1, wherein the limited-area Pd-based catalyst is capable of catalyzing 2,4, 6-trichloroanisole, the process comprising:

SB1, adding a domain-limited Pd-based catalyst into deionized water with the pH value of 6+/-0.1 at the temperature of 23+/-5 ℃; the content of the domain-limited Pd-based catalyst in deionized water is 1/24g/L;

SB2, continuously electromagnetic stirring deionized water in the step SB1, and introducing H for 30min into the deionized water ₂ Obtaining hydrogen saturated water; the rotating speed of electromagnetic stirring is 1000-1500 rpm, and H is introduced ₂ The flow range of the catalyst is 150-200 mL/min;

SB3, adding 2,4, 6-trichloroanisole into a container containing the hydrogen saturated water prepared in the step SB2 under a closed environment, sampling and detecting at fixed intervals until the 2,4, 6-trichloroanisole is completely converted into anisole.