Confined Pd@CeZr-MOF catalyst and its preparation method and use

Abstract

In the field of water pollution treatment technology, a confined Pd@CeZr-MOF catalyst and a preparation method for said catalyst are provided. First, the CeZr-MOF support is prepared, and then the free Pd as the active precursor is restricted in the channel of the CeZr-MOF support by the dual solvent method, and then reduced to form active Pd particles. The confinement effect of the MOF channel and the strong metal-support interaction between Ce and Pd inhibit the aggregation and growth of Pd particles, and limit the loading position of Pd particles in the Pd@CeZr-MOF catalyst. In the Pd@CeZr-MOF catalyst prepared by the present invention, the particle size range of Pd particles is restricted to 1.95±0.6 nm, which effectively improves the dispersion of Pd, exposes more active sites, and improves the catalytic activity. In addition, due to the fixing effect of Ce on Pd, the spatial distribution of Pd particles is positively correlated with the spatial position of Ce, i.e., macroscopically, it shows a uniform distribution state.

Description

[Technical field]

[0001] The present invention relates to the technical field of water pollution treatment, in particular to the confined Pd@CeZr-MOF The present invention relates to a catalyst and its production method and use. [Background technology]

[0002] Odor pollution is a common water pollution problem worldwide, and 2,4,6-trimethylphenyl 2,4,6-tri ... The odor threshold of chloroanisole (TCA) is low, and its irritating odor and toxicity are strong, so its efficiency The development of efficient processing methods is of great practical significance. TCAs are chlorine-substituted organic contaminants that could theoretically be removed by liquid-phase hydrodechlorination. However, metallic palladium (Pd) dissociates hydrogen under normal pressure and temperature conditions, promoting the cleavage of CX bonds. It has the ability to promote the synthesis of TCA, and therefore shows relatively high activity in the reaction of treating TCA. Palladium nanoparticles (Pd NPs) have a relatively high surface energy and are easy to prepare and catalyze. During the catalytic reaction, traditional supported Pd catalysts suffer from aggregation, washing away, and surface contamination of active Pd particles. This leads to the problem of catalyst deactivation. Previous studies have used metal-organic frameworks (MOFs) as supports to stabilize precious metal nanoparticles. It is described that a composite material of noble metal nanoparticles / MOFs is obtained by the above-mentioned technique. It is essential to suppress the overgrowth of metal particles by the channel confinement protection action of MOFs. When the above techniques are used to support Pd NPs on MOFs, the following techniques have not been developed at present: There are technical difficulties. How Pd NPs can be supported on the MOFs surface to nullify the channel confinement protection How to design the channel shape and diameter on the MOFs surface to ensure that there are no defects and to achieve high molecular weight How to prepare Pd NPs with small size and dispersion? and ensure the bonding strength between the MOFs. In order to solve the above problems, the inventors have devised the conventional technology to achieve the confinement type Pd@Ce We have devised a Zr-MOF catalyst and its manufacturing method. Summary of the Invention

[0003] In order to achieve the above object, the present invention provides a confined Pd@CeZr-MOF catalyst and its This aspect is based on the optimization of the manufacturing method and parameters to produce Pd The particle size is strictly limited within the support channel size range, and the Ce position within the support is used as the basis for the determination of the particle size. Moreover, the above phenomenon can be described and examined in the embodiment. We also present a verifiable mathematical model, which will be useful for future research into composite materials made of noble metal nanoparticles and MOFs. Research data and theoretical support are provided, and the content of this embodiment is as follows. CeZr-MOF support and a CeZr-MOF supported on the inner wall of the channel of the CeZr-MOF support. The confined Pd@CeZr-Pd particles consist of Pd particles aggregated and reduced by free Pd on the surface. A MOF catalyst comprising: Explanation: The term "confinement" in the confined Pd@CeZr-MOF catalyst refers to the control of the region in which the catalyst is located. In this application, this has two meanings: the first is the loading position of the Pd particles. The position is restricted to the channels of the CeZr-MOF support and supported on the surface of the CeZr-MOF support. The second point is that the Pd particles are not trapped in the channels of the CeZr-MOF support. The more specific loading position is the CeZr-MOF support. These are Ce active sites exposed on the inner wall of the channel. The fully functional periodic structure of the Pd@CeZr-MOF catalyst is a single octahedral cage. The eight inorganic brick structures are composed of a tetrahedral cage and two adjacent tetrahedral cages. The CeZr-MOF support with square units and the strong metal-support interactions P is supported on the Ce active sites exposed on the inner walls of the channels of the CeZr-MOF support. d particle. The distribution position of Pd particles on the inner wall of the channel of the CeZr-MOF support is expressed by the following formula (1): (2) is satisfied, JPEG0007678974000002.jpg941(1) JPEG0007678974000003.jpg922(2) During the ceremony: JPEG0007678974000004.jpg814 is the particle size of Pd particles, JPEG0007678974000005.jpg819 is the average pore size of the CeZr-MOF support, and h is the distance from the Pd particle core to the Ce. can be, JPEG0007678974000006.jpg89 is the limit distance at which free Pd can be captured by Ce, Explanation: In the process of free Pd being supported on the CeZr-MOF support, the first free Pd After being attracted and captured by Ce due to the strong interaction, it is connected to Ce by oxygen bridges, and the subsequent The free Pd is successively captured, aggregated, and then reduced to form Pd particles. JPEG0007678974000007.jpg89 means the limit distance at which free Pd can be captured by Ce, Free Pd is the amount of free Pd in ​​solution. JPEG0007678974000008.jpg920, and Pd particles refer to single Pd particles formed after free Pd is aggregated and reduced. death, Confinement is the effect of restricting the flow of gas through a particular channel structure due to spatial restrictions. In this embodiment, the term "confinement" refers to a restriction or promotion effect on the behavior of molecules or ions confined in the liquid. The binding effect refers to the binding effect of the cage in the CeZr-MOF support on free Pd. In the formula (2), JPEG0007678974000009.jpg89 is determined by the following formulas (3) to (6): JPEG0007678974000010.jpg1431(3) JPEG0007678974000011.jpg884(4) JPEG0007678974000012.jpg1465(5) JPEG0007678974000013.jpg17150(6) During the ceremony: JPEG0007678974000014.jpg89 is the interaction force between Pd and Ce, d is the differential operation sign, JPEG0007678974000015.jpg810 is the total interaction energy between Ce and Pd particles, JPEG0007678974000016.jpg815 is the interaction free energy of Pd particles in n-hexane hydrophobic solution, JPEG0007678974000017.jpg826 is the interaction free energy when the distance between Ce and Pd particles is h, JPEG0007678974000018.jpg810 is the electrostatic repulsion energy between Ce and Pd particles, JPEG0007678974000019.jpg1026 is the Hamaker value of Pd particles in n-hexane hydrophobic solution, and λ is the half-attenuation Diameter, λ=h- JPEG0007678974000020.jpg89 and h> JPEG0007678974000021.jpg89, JPEG0007678974000022.jpg1443 is the equilibrium distance JPEG0007678974000023.jpg89 is the polar surface energy between Ce and Pd particles in n-hexane hydrophobic solution, and e xp represents the natural exponential function, explanation: JPEG0007678974000024.jpg815The official name is Lifshitz-van der Waals interaction free energy In this embodiment, the mutual attraction action energy of Pd particles in n-hexane hydrophobic solution is Ghee, JPEG0007678974000025.jpg826The official name is Lewis acid-base interaction free energy, and this embodiment So, the mutual polar interaction energy between Ce and Pd particles when the distance between them is h is, JPEG0007678974000026.jpg810The official name is electrostatic repulsion energy. In this embodiment, it is the electrostatic repulsion energy between Ce and Pd particles, JPEG0007678974000027.jpg1443 Polar surface energyThe official name is Polar Surface Energy, and This is caused by the electric dipole moment interaction due to the asymmetric charge distribution on the material surface. In this embodiment, the equilibrium distance is is the polar surface energy between Ce and Pd particles in n-hexane hydrophobic solution at 89, The particle size range of the CeZr-MOF support is 100-200 nm, and the specific surface area is 11 00~1108 JPEG0007678974000029.jpg1023, The average particle size range of Pd particles is 1.95 ± 0.6 nm. Based on the above microstructure, the range of metallic Pd loading in the Pd@CeZr-MOF catalyst is , 0.80-0.85 wt.%. In another aspect of the present invention, there is provided a method for producing Pd @We further provide a method for preparing CeZr-MOF catalyst, Step S1 of producing a CeZr-MOF support, S1-1, JPEG0007678974000030.jpg828, JPEG0007678974000031.jpg857 and 1,4-phthalic acid were added to N,N-dimethylformamide, and then the volume concentration was 98 % formic acid was added and mixed uniformly with ultrasonic waves to obtain a first mixture. In the first mixture, JPEG0007678974000032.jpg828, JPEG0007678974000033.jpg857, 1,4-phthalic acid, N,N-dimethylformamide and formic acid added at a ratio of 0.746 g: 0.298 g: 0.664 g: 45 mL: 9.21 g, The first mixture obtained in S1-2 and S1-1 was reacted at 110 to 120°C for 24 hours, and then at room temperature. After cooling to room temperature, the mixture was centrifuged and washed with DMF and acetone to remove any residual material. to obtain a first solid product; The first solid product obtained in S1-3 and S1-2 was vacuum dried at 80°C for 24 h to obtain CeZr- Obtaining a MOF support, JPEG0007678974000034.jpg669 A step S2 for producing a catalyst, S2-1 and S1 were prepared by dissolving the CeZr-MOF support in n-hexane at a volume concentration of 95%. Disperse in a hydrophobic solution, mix uniformly with ultrasonic waves, and increase Pd mass concentration while maintaining the ultrasonically mixed state. The concentration is 2 g / L. JPEG0007678974000035.jpg940 solution was added dropwise and homogenized to obtain a second mixed solution. In the second mixture, the CeZr-MOF support, the n-hexane hydrophobic solution, and The ratio of the 940 solution added was 200 mg:40 mL:1 mL. S2-2, the second mixed liquid obtained in S2-1 is dried to obtain a second solid product; The flow rate is 20 mL / min. JPEG0007678974000037.jpg89 Reduced at 100℃ for 2 hours under atmospheric conditions. JPEG0007678974000038.jpg669 Obtain the catalyst. Description: The present invention provides a method for the synthesis of a specific regular channel structure and a high specific surface area by a one-pot synthesis method. The CeZr-MOF support with a high molecular weight was prepared, and the active metal Pd was attached to the CeZr -After being introduced into the channel of MOF, The high specific surface area of ​​the CeZr-MOF support allows Pd activity to be increased. The CeZr-MOF support is favorable for the dispersion of the sites, and the channel confinement effect and the interaction between Pd and CeZr The strong metal-support interactions between the r-MOF support and the Pd particles limit the overgrowth of both. At the same time, the spatial position of the Pd particles is fixed by the Ce in the support, which results in high Stable, highly dispersible Pd particles with extremely small and uniform particle size and uniform distribution can be obtained. In one aspect of the present invention, the parameters of ultrasonic mixing in S1-1 and S2-1 are both The ultrasonic power is 100-120 W, and the ultrasonic time is 30-40 min. In one aspect of the present invention, the parameters of the centrifugation process in S1-2 are a centrifugation speed of 8000 to 8 The centrifugation time is 10 to 15 minutes at 500 r / min. In one aspect of the present invention, the room temperature in S1-2 is 24 to 25°C. In another aspect of the present invention, the above Pd@CeZr-MOF catalyst is used for the decomposition of TCA. The use of the d@CeZr-MOF catalyst is further provided. The Pd@CeZr-MOF catalyst produced in this invention supports a large amount of extremely small Pd particles. And cationic Pd( The high content of 920) can effectively increase the decomposition rate of TCA, and the catalytic mechanism The mechanism is as follows: The length of the Pd particles is restricted by the channel confinement effect of the CeZr-MOF support, and the Pd The particles are highly dispersed, exposing more active sites, and the Pd and CeZr- It has a strong metal-support interaction with the MOF support, and transfers electrons from Pd to the support. Form JPEG0007678974000041.jpg920, JPEG0007678974000042.jpg920 favors the activation of C-Cl bonds in TCA and promotes the cleavage of C-Cl bonds . Therefore, the Pd@CeZr-MOF catalyst prepared in this invention can effectively decompose TCA. TCA can be decomposed into low-toxicity, odorless anisole by catalytic hydrogenation reduction. This also shows that the Pd@CeZr-MOF catalyst is an It can be applied to the efficient decomposition of halogenated odorous pollutants including TCA, which is a typical example of CA. I realized it was possible. Compared with conventional TCA decomposition catalysts, the beneficial effects of the present invention are as follows: (1) The present invention uses a dual solvent method to insert active Pd particles into the channels of a CeZr-MOF support. The confinement effect of the MOF channel effectively suppresses the aggregation and growth of Pd particles, d) Promote particle dispersion, obtain Pd particles with a particle size of only 1.95 nm, and effectively improve the dispersion degree of Pd. The smaller the particle size of the active Pd particles, the more active sites are exposed, and the greater the catalytic activity. This is beneficial for improving sexual function. (2) The Pd@CeZr-MOF catalyst produced by this invention has a high molecular weight and a low molecular weight. - Strong metal-support interaction with the MOF support, transferring electrons from Pd to the support JPEG0007678974000043.jpg920 can be formed, JPEG0007678974000044.jpg920 favors the activation of C-Cl bonds in TCA and promotes the cleavage of C-Cl bonds . (3) The Pd@CeZr-MOF catalyst produced in this invention is a Pd-CeZr-MOF supported Due to the strong metal-support interaction between Ce and Pd in ​​the matrix, Ce can support Pd at the support center position. Since Ce is a uniform part in the CeZr-MOF support, The Pd particles supported on the F support are also uniformly distributed, i.e., the supported positions of the Pd particles are The spatial location of Ce shows a positive correlation with the position of the nucleus. [Brief description of the drawings]

[0004] [Figure 1] 1 is a schematic diagram of the fully functional periodic structure of the Pd@CeZr-MOF catalyst prepared in the present invention, in which 1 is Pd particle, 2 is Ce, and 3 is the channel of the CeZr-MOF support. [Diagram 2] Schematic diagram of the fully functional periodic structure of the Pd@CeZr-MOF catalyst from another angle. [Diagram 3] FIG. 2 is a Pd K-edge XANES spectrum of the catalyst and reference sample in Experimental Example 3.1. [Figure 4] FIG. 3 is a SEM image of the Pd(0.82)@CeZr-MOF catalyst in Experimental Example 3.2, with Mag of 160,000. [Diagram 5]FIG. 3 is a SEM image of the Pd(0.82)@CeZr-MOF catalyst in Experimental Example 3.2, with Mag of 300,000. [Figure 6] FIG. 3 is a HR-TEM image of the Pd(0.82)@CeZr-MOF catalyst at 50 nm in Example 3.2. [Figure 7] FIG. 3 is a HR-TEM image of the Pd(0.82)@CeZr-MOF catalyst at 10 nm in Experimental Example 3.2. [Figure 8] 1 is a histogram of the particle size distribution of Pd in ​​the Pd(0.82)@CeZr-MOF catalyst in Experimental Example 3.2. [Figure 9] FIG. 3 shows the HAADF-STEM image and corresponding EDX elemental mapping (C, O, Zr, Ce, Pd) of the Pd(0.82)@CeZr-MOF catalyst in Example 3.2. [Figure 10] 3 shows the TCA removal kinetics of each group of catalysts in Experimental Example 3.3, where Ct is the concentration of TCA when the reaction time is t, and C0 is the initial concentration of TCA. [Figure 11] FIG. 2 is an initial activity diagram of catalytic hydrodechlorination TCA removal of each group of catalysts in Experimental Example 3.3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] To further illustrate the embodiments of the present invention and the advantages thereof, reference is now made to the following experiments. The technical solutions of the present invention are clearly and completely explained. Example 1: This example describes a confined Pd@CeZr-MOF catalyst. The confined Pd@CeZr-MOF catalyst designed in this invention is shown in Figs. 1 and 2. A fully functional periodic structure is formed by one octahedral cage and two adjacent tetrahedral cages. A composite CeZr-MOF with eight inorganic bricks as cubic units The support and the channels of the CeZr-MOF support are formed by the confinement effect and the strong metal-support interactions. Ce is supported on the active sites exposed on the inner wall of the filter and is aggregated and reduced by a small amount of free Pd. The Pd particles are The distribution position of Pd particles on the inner wall of the channel of the CeZr-MOF support is expressed by the following formula (1): (2) is satisfied, JPEG0007678974000045.jpg941(1) JPEG0007678974000046.jpg922(2) During the ceremony: JPEG0007678974000047.jpg814 is the particle size of Pd particles, JPEG0007678974000048.jpg819 is the average pore size of the CeZr-MOF support, and h is the distance from the Pd particle core to the Ce. can be, JPEG0007678974000049.jpg89 is the limit distance at which free Pd can be captured by Ce, Explanation: The above formula means that the particle size of Pd particles is the MOF catalyst on the CeZr-MOF support. The Ce-Zr-MOF support is supported by the Pd particles, and the Pd particles are trapped in the support. The area is within the utility barrier and the macrotopography shown is shown in FIG. In the formula (2), JPEG0007678974000050.jpg89 is determined by the following formulas (3) to (6): JPEG0007678974000051.jpg1431(3) JPEG0007678974000052.jpg884(4) JPEG0007678974000053.jpg1465(5) JPEG0007678974000054.jpg17150(6) During the ceremony: JPEG0007678974000055.jpg89 is the interaction force between Pd and Ce, d is the differential operation sign, JPEG0007678974000056.jpg810 is the total interaction energy between Ce and Pd particles, JPEG0007678974000057.jpg815 is the interaction free energy of Pd particles in n-hexane hydrophobic solution, JPEG0007678974000058.jpg826 is the interaction free energy when the distance between Ce and Pd particles is h, JPEG0007678974000059.jpg810 is the electrostatic repulsion energy between Ce and Pd particles, JPEG0007678974000060.jpg1026 is the Hamaker value of Pd particles in n-hexane hydrophobic solution, and λ is the half-attenuation Diameter, λ=h- JPEG0007678974000061.jpg89 and h> JPEG0007678974000062.jpg89, JPEG0007678974000063.jpg1443 is the equilibrium distance JPEG0007678974000064.jpg89 is the polar surface energy between Ce and Pd particles in n-hexane hydrophobic solution, and e xp represents the natural exponential function, The particle size range of the CeZr-MOF support is 100-200 nm, and the specific surface area is 11 00~1108 JPEG0007678974000065.jpg1023, The average particle size range of Pd particles is 1.95±0.6 nm, and the lattice spacing is 0.23 nm. which corresponds to the (111) plane of a typical Pd face-centered cubic (fcc) structure. Based on the above microstructure, the Pd@CeZr-MOF catalyst of this example was measured. The amount of metallic Pd supported on the catalyst was 0.8 wt.%. Example 2: This example is another group of the confined Pd@CeZr-MOF catalysts in Example 1. The measurement data of the loop. In the measurement results of this example, the 5Pd@CeZr-MOF catalyst The amount of metallic Pd supported in the catalyst was 0.85 wt.%. Example 3: This example describes the preparation of the confined Pd@CeZr-MOF catalyst in Example 1. The method is as follows: S1, Preparation of CeZr-MOF support; S1-1, 0.746 g JPEG0007678974000066.jpg828, 0.298 g JPEG0007678974000067.jpg857 and 0.664 g 1,4-phthalic acid were added to 45 mL of N,N-dimethylformamide. Add 98% volumetric concentration of formic acid to the mixture and mix uniformly with ultrasonic waves to form the first mixture. Obtain the liquid, The ultrasonic mixing parameters were ultrasonic power 100W, ultrasonic time 30 min, The first mixture obtained in S1-2 and S1-1 was placed in a reactor, and the reactor was heated to 110°C. The mixture was placed in an oven for 24 hours, cooled to 24°C, centrifuged, and the remaining material was removed. Sequentially wash with DMF and acetone until removal to obtain a first solid product. The parameters of the centrifugation process were: centrifugation speed 8000-8500 r / min, centrifugation time 10 min, is 10 to 15 minutes, S1-3, the first solid product obtained in S1-2 was vacuum dried at 80 °C for 24 hours, and Ce Obtaining a Zr-MOF support, S2, JPEG0007678974000068.jpg669 Catalyst production, S2-1: 200 mg of the CeZr-MOF support obtained in S1 was dissolved in water at a volume concentration of 95%. The mixture was dispersed in 40 mL of n-hexane hydrophobic solution, mixed uniformly by ultrasonication for 30 min, and then subjected to ultrafiltration. The Pd mass concentration is 2 g / L while maintaining the sonic mixing state. JPEG0007678974000069.jpg1 mL of 940 solution was added dropwise, and the mixture was stirred for 3 hours until homogenized to obtain a second mixture. The ultrasonic mixing parameters were: ultrasonic power 100 W, ultrasonic time 100 min, 30 min, S2-2. The second mixed liquid obtained in S2-1 is dried to obtain a second solid product. The flow rate of the composition is 20 mL / min. JPEG0007678974000070.jpg89 Reduced at 100℃ for 2 hours in the atmosphere. JPEG0007678974000071.jpg669A catalyst was obtained. Example 4: The description premise of this example is the contents described in Example 3. Specifically, This is a manufacturing method with the parameters. S1, Preparation of CeZr-MOF support; S1-1, 0.746 g JPEG0007678974000072.jpg828, 0.298 g JPEG0007678974000073.jpg857 and 0.664 g 1,4-phthalic acid in 45 mL of N,N-dimethylformamide Then, formic acid having a volume concentration of 98% is added and mixed uniformly by ultrasonication to obtain the first mixture. Gain, The parameters of ultrasonic mixing were ultrasonic power 120W, ultrasonic time 1000s, and ultrasonic mixing time 100s. 40 minutes, S1-2, the first mixed solution obtained in S1-1 is put into the reactor, and then the reactor is heated to 120°C. The mixture was then placed in an oven for 24 hours, cooled to 25°C, centrifuged, and the residual material was removed. and washing successively with DMF and acetone until the solid is removed to obtain a first solid product. The centrifugation parameters were a centrifugation speed of 8500 r / min and a centrifugation time of 15 min. n, The first solid product obtained in S1-3 and S1-2 was vacuum dried at 80°C for 24 h and then treated with CeZ Obtaining an r-MOF support, S2, JPEG0007678974000074.jpg669 Catalyst production, S2-1: 200 mg of the CeZr-MOF support obtained in S1 is mixed with the CeZr-MOF support at a volume concentration of 95%. Disperse in 40mL of n-hexane hydrophobic solution, mix uniformly with ultrasonic for 30mi, and ultrasonicate The Pd mass concentration is 2 g / L while maintaining the mixed state. JPEG0007678974000075.jpg1 mL of 940 solution was added dropwise, and the mixture was stirred for 3 hours until homogenized to obtain a second mixture. The parameters of ultrasonic mixing were ultrasonic power 120W and ultrasonic time 40min. the law of nature, S2-2. The second mixed liquid obtained in S2-1 is dried to obtain a second solid product. The flow rate of the composition is 20 mL / min. JPEG0007678974000076.jpg89 Reduced at 100℃ for 2 hours in the atmosphere. JPEG0007678974000077.jpg669A catalyst was obtained. Experimental Example: The description of this experimental example is based on the contents described in Examples 1 and 4. The purpose of this document is to clarify the effect of the application of the 1. Experimental procedure Considering the volatility of TCA, hydrogen saturation reduction was adopted in the experiment. The Pd@CeZr-MOF catalyst was placed in a glass headspace vial containing 240 mL of deionized water. Add the solution to the deionized water and pre-adjust the pH to 6.00 ± 0.05 with 0.1 M NaOH. The headspace vial was placed under vigorous stirring for 30 minutes. JPEG0007678974000078.jpg89Then, the glass headspace vial was aerated to obtain hydrogen-saturated water. The container was sealed with a cap cover fitted with a polyethylene gasket. The contaminant TCA was injected into the vial using a microsampling syringe, and the contact water was analyzed. The oxidation reaction is started. During the reaction, the reaction time is 0, 5, 10, 30, 60, 90 and 120 min. At the nth time point, a glass needle was used to sample the sample, and the sample was mixed with n-hexane (1:1, v:v) and extracted TCA and its dechlorination product anisole. n-Hexane was isolated using a gas chromatograph (6890N, Agilent, USA) The concentration of TCA in the extract was measured, and the TCA dechlorination product anisole was analyzed by gas chromatography. Mass spectrometry (Thermo Fisher Scientific, USA) was used. The reaction completely reduced TCA to anisole within 60 min. In the above liquid-phase catalytic hydrogenation reduction reaction, the amount of Pd@CeZr-MOF catalyst added was 20 mg. the liquid phase volume is 240 mL, and the initial mass concentration of TCA is 1 mg / L; The flow rate of JPEG0007678974000079.jpg89 was 150 mL / min, and the rotation speed of the stirring was 1000-1500 rpm. The reaction was carried out at room temperature, and the initial pH of the reaction was 6.0. 2. Experimental design In order to clarify the properties of the Pd@CeZr-MOF catalyst prepared in the present invention, Based on the preparation method in 1, the following experimental groups were designed. Experimental group 1: The support was replaced with pure Zr-MOF material without Ce, and other processes were Without any changes, a Pd-based catalyst was produced using Zr-MOF as a support, and the Pd loading mass% was 0.84 wt.% and is denoted as Pd(0.84)@Zr-MOF. Experimental group 2: The other processes were unchanged, and the Ce:Zr in the CeZr-MOF support was The molar ratio was adjusted to 1:1 to prepare a catalyst, and the mass% of Pd supported was 0.82 wt.%. It is denoted as Pd(0.82)@CeZr-MOF(1:1). Experimental group 3: The other processes were unchanged, and the Ce:Zr in the CeZr-MOF support was The molar ratio was adjusted to 1:4 to prepare a catalyst, and the mass% of Pd supported was 0.82 wt.%. It is denoted as Pd(0.82)@CeZr-MOF(1:4). III. Characterization 3.1. XAFS characterization To identify the chemical state of Pd in ​​the catalyst, X-ray absorption fine structure (XAFS) studies were performed. Figure 3 shows the Pd K-edge X-ray absorption spectra of two types of catalysts and a reference sample (Pd, PdO). The structure (XANES) spectrum. As is clear from the figure, Pd(0.84)@Zr The Pd K-edge positions of the Pd(0.82)@CeZr-MOF and Pd(0.82)@CeZr-MOF are both in the metallic state P d, and the amount of cationic Pd( JPEG0007678974000080.jpg920) exists and the Pd K-side position of Pd(0.82)@CeZr-MOF is Pd(0.8 4)@Zr-MOF and close to the standard PdO reference, Pd(0.82)@C The metal-support interaction in eZr-MOF is stronger, and the electrons transferred from Pd to the support are The more Pd has a higher valence and degree of cationization, the more This characteristic is due to the high C content in the TCA catalytic hydrogenation reaction. It is favorable for activating the -Cl bond, improving the catalytic activity, and promoting its hydrodechlorination. do. 3.2. Shape evaluation Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), High Angle Annular High-energy-dispersive X-ray (ED) and dark-field scanning transmission electron microscope (HAADF-STEM) X) The shape and microstructure of the catalyst were observed using elemental mapping. See Figures 4 to 7. In comparison, HR-TEM and EDX images show that Pd was successfully supported on the CeZr-MOF support. It was clear that the particles were highly uniformly dispersed in the carrier. As can be seen in Figure 8, Pd(0.82)@CeZ nanoparticles were clearly observed. The particle size distribution of the Pd particles in the r-MOF was concentrated between 1.95±0.6 nm, and the particle size distribution The average particle size was 1.95 nm, and these results indicate that the particle size of the Pd catalyst is This further illustrates the small size and high dispersion of Pd particles, which are constrained by the support MOF channels. The catalyst is This is to prevent uncontrolled aggregation and growth of Pd particles during the reduction process. The smaller the active metal Pd particles are, the higher the degree of dispersion, and the more exposed Pd active centers are, the higher the catalytic activity. This is advantageous for improving the 3.3. Evaluation of TCA removal effect 10 and 11 show the effectiveness of hydrodechlorination for TCA removal by different Pd-based catalysts. Two CeZr-MOF supports with different e:Zr ratios were synthesized. were similar. The reaction conditions were designed as follows: initial mass concentration of TCA was 1 mg / L, catalyst loading was 20 mg, and The reaction was carried out at 25°C, and the initial pH of the reaction was 6.0. When the reaction time was 60 min, the Pd(0.82)@CeZr-MOF(1:1) reaction with TCA was The removal rate of Pd(0.82)@CeZr-MOF(1:4) for TCA was 86.9%. The removal rate of 99.6% was due to the better catalytic activity of Ce:Zr=1:4. In addition, the activity of the Pd(0.82)@CeZr-MOF catalyst was This was superior to Pd(0.84)@Zr-MOF, and the Pd The removal rate of (0.84)@Zr-MOF was only 45.5%. Compared with the Pd-based catalyst supported on CeZr-MOF, the Pd-based catalyst supported on CeZr-MOF (0.82 )@CeZr-MOF(1:4) improved the removal rate of TCA by 54.1% within 60 min. He made him do so. Figure 6 shows the initial activity at 5 min for different catalytic hydrodeoxygenation TCA removal, Pd (0. The initial activity of the Pd(0.84)@Zr-MOF was 0.78; The catalytic activity of Pd(0.82)@CeZr-MOF is improved by 10 times. The excellent catalytic activity of the (1:4) is due to the effective confinement effect of the CeZr-MOF channel. The aggregation and growth of metallic Pd particles is suppressed, resulting in smaller Pd particle size and higher dispersion. , many Pd active centers are exposed, and Pd(0.82)@CeZr-MOF(1:4) Okeru JPEG0007678974000083.jpg920 content is higher, the metal-support interaction is stronger, and it is favorable for the activation of TCA, and C-Cl It is speculated that this promotes the cleavage of bonds and significantly improves catalytic activity.

Claims

1. A confined Pd@CeZr MOF catalyst comprising: The Pd@CeZr-MOF catalyst is composed of a CeZr-MOF support and a Pd particles are supported on the inner walls of the channels of the body and are aggregated and reduced with a small amount of free Pd. and wherein the Pd@CeZr-MOF catalyst is used to decompose TCA; The distribution position of the Pd particles on the inner wall of the channel of the CeZr-MOF support is expressed by the following formula (1 ), (2) is satisfied, （１） （２） During the ceremony: is the particle size of the Pd particles, is the average pore size of the CeZr-MOF support, and h is the distance from the Pd particle core to the Ce. can be, is the limit distance at which free Pd can be captured by Ce, In the formula (2), is determined by the following equations (3) to (6), （３） （４） （５） （６） During the ceremony: is the interaction force between Pd and Ce, d is the differential operation sign, is the total interaction energy between Ce and Pd particles, is the interaction free energy of a Pd particle in n-hexane hydrophobic solution, is the interaction free energy when the distance between the Ce and Pd particles is h, is the electrostatic repulsion energy between Ce and Pd particles, is the Hamaker value of Pd particles in n-hexane hydrophobic solution, and λ is the half-attenuation Diameter, λ=h- And h> and is the equilibrium distance is the polar surface energy between Ce and Pd particles in n-hexane hydrophobic solution, and e xp represents the natural exponential function, The average particle size range of the Pd particles is 1.95±0.6 nm; The particle size range of the CeZr-MOF support is 100 to 200 nm, and the specific surface area is １１００～１１０８ and The range of the amount of metal Pd supported in the Pd@CeZr-MOF catalyst is 0.80 to 0.85 The confined Pd@CeZr-MOF catalyst is characterized in that it is 0.01 wt. %.

2. A method for producing the confined Pd@CeZr MOF catalyst of claim 1, comprising the steps of: The steps include: （１） 、 and 1,4-phthalic acid were added to N,N-dimethylformamide, and then the volume concentration was 98 % formic acid is added and mixed uniformly by ultrasonic waves to obtain a first mixed liquid, and the ultrasonic mixing performance is The parameters are: ultrasonic power is 100-120W, ultrasonic time is 30-40min; In the first mixture, 、 , 1,4-phthalic acid, N,N-dimethylformamide and formic acid in a ratio of 0.746 g:0 .298g:0.664g:45mL:9.21g, (2) The first mixture is reacted at 110 to 120° C. for 24 hours, cooled to room temperature, and then centrifuged. The mixture was washed with DMF and acetone to obtain a first solid product. The centrifuge was rotated at a speed of 8000. 8500 r / min, centrifugation time is 10 to 15 min, and the room temperature is 24 to 25° C. (3) The first solid product is vacuum dried at 80° C. for 24 h to obtain a CeZr-MOF support; (4) The CeZr-MOF support was dispersed in a hydrophobic n-hexane solution having a volume concentration of 95%. , and uniformly mixed with ultrasonic waves. While maintaining the ultrasonic mixed state, the Pd mass concentration is 2 g / L. The solution is dropped and homogenized to obtain a second mixed solution, and the parameters of the ultrasonic mixing are: The ultrasonic power is 100-120W, and the ultrasonic time is 30-40min. In the second mixture, a CeZr-MOF support, an n-hexane hydrophobic solution, and The ratio of the solution is 200 mg: 40 mL: 1 mL, (5) drying the second mixture to obtain a second solid product; and subjecting the second solid product to a flow rate of 20 mL / min The mixture was reduced under atmospheric conditions at 100°C for 2 hours. Obtaining a catalyst A manufacturing method comprising the steps of:

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