CN108636455A - It is a kind of using nucleocapsid MOF as the preparation and application of the carried noble metal base catalyst of reaction vessel - Google Patents

Abstract

It is a kind of using nucleocapsid MOF as the preparation and application of the carried noble metal base catalyst of reaction vessel, belong to catalyst technical field.Using the bimetallic Ni/Zn MOF of nucleocapsid as carrier; pass through regulation and control; noble metal nano particles can be encapsulated in the cavity between nucleocapsid; kernel can be used as carrier; evenly dispersed precious metal palladium nano particle; shell can play a protective role, and noble metal nano particles is inhibited to be lost in, and construct the Pd@Ni Zn MOF with multilevel hierarchy.In a hydrogen atmosphere, catalytic performance of its catalyst to carbon-carbon double bond and C=O bond selective hydrogenation is studied.Preparation method of the present invention is simple, easy to implement, and yield is high.The catalyst carrier Ni Zn MOF large specific surface areas of preparation, are conducive to the evenly dispersed of noble metal nano grain, abundant duct is conducive to the diffusion of reaction substrate and product, moreover it is possible to play molecular dimension selection index system, therefore have excellent catalytic activity and selectivity.

Description

A supported noble metal-based catalyst with a core-shell structure MOF as the reaction vessel Preparation and application

technical field

The invention belongs to the technical field of catalysts, and relates to a nano-reactor with a core-shell structure (NiZn-MOFs) as a carrier to construct a loaded noble metal-based multi-level structure catalyst, which is applied to carbon-carbon double bonds and carbon Selective hydrogenation of oxygen double bonds.

Background technique

The selective catalytic hydrogenation of α-β unsaturated aldehydes is one of the important reactions in the synthesis of fine chemical products, and has been widely used in modern fine organic synthesis, especially in the preparation of drugs and their intermediates, food additives, spices, etc. . The method of catalytic hydrogenation can greatly reduce product cost, improve product quality, increase yield, shorten reaction time and reduce three waste emissions, so it is widely valued by people. According to literature reports, the C=C hydrogenation selectivity of the catalyst Pd is relatively high. Bond hydrogenation selectivity. However, it is still very important and challenging to further improve the catalytic efficiency and utilization of Pd catalysts.

Metal-organic frameworks (Metal-organic frameworks, MOFs) are a new type of porous functional materials, which are porous network framework materials formed by self-assembly of metal ions or ion clusters and organic ligands. Due to their high specific surface area and porosity, adjustable pore size and pore surface function, MOFs have potential applications in the fields of adsorption separation, catalysis, and energy storage. Compared with traditional heterogeneous catalysts, porous MOFs materials have the above advantages, and their applications in the field of catalysis are increasingly favored by researchers. In particular, MOFs have a high specific surface area and an ordered pore structure, which can be used as a carrier for nanoparticle catalysts, allowing nanoparticles to be evenly dispersed in the pores or on the surface of MOFs, and the catalytic activity will be greatly improved due to the synergistic effect. At present, there are many reports on MOFs as carriers to support nanoparticles and their application in catalysis, but in contrast, there are still few reports on MOF-based core-shell structures.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a supported noble metal-based catalyst with a core-shell bimetallic Ni/Zn-MOF as a carrier and its application to the selective hydrogenation of carbon-carbon double bonds and carbon-oxygen double bonds reaction.

The synthetic method of above-mentioned composite material of the present invention mainly comprises the following steps:

(1) preparing a dispersion of noble metal nanoparticles;

(2) Preparation of noble metal @Ni/Zn-MOF:

Dissolve terephthalic acid, nickel salt and zinc salt in the mixed solution of N,N-dimethylformamide and ethylene glycol, stir for 0.5 to 1 hour, transfer to a polytetrafluoroethylene reactor, and react Temperature 140-160°C, react for 0-6 hours, then add the dispersion of noble metal nanoparticles synthesized in the previous step (1), react for 2-12 hours, then cool, centrifuge, wash, activate, and dry to obtain noble metal @Ni/Zn - Preparation of MOFs.

In step (1), the dispersion liquid for preparing noble metal nanoparticles can be prepared according to a conventional method, and the noble metal nanoparticles are selected from one or more of Pd, Pt, Au, Ag;

For example, the preparation of Pd and Pt nanoparticles: dissolve a certain amount of noble metal chloride salt and polyvinylpyrrolidone in a mixed solution of methanol and water, condense and reflux for 2 to 6 hours, and prepare the noble metal nanoparticles; the aqueous solution of noble metal chloride salt The concentration is 0.5-2mg/mL, wherein the noble metal chloride salt is selected from one of palladium chloride and chloroplatinic acid, and the volume ratio of methanol to water is 5:1-20:1.

In step (2), the molar ratio of the nickel salt to the zinc salt is 4:1˜1:1, preferably 1:1. The total molar ratio of terephthalic acid to nickel nitrate and zinc nitrate is preferably (1-5):10, more preferably 3:10. The volume ratio of N,N-dimethylformamide and ethylene glycol is (6-10):5, preferably 8:5.

In step (2), the loading capacity of the noble metal nanoparticles can be adjusted as required. Generally, the volume ratio of the added volume of the noble metal nanoparticle dispersion to the total volume of the mixed solution of N,N-dimethylformamide and ethylene glycol is 1 :15～8:13.

The Ni/Zn-MOF in the noble metal @Ni/Zn-MOF obtained in step (2) has a peanut-like core-shell structure, and the noble metal is loaded in the core, in the shell or/and in the cavity between the core and the shell. By adjusting the addition time of the dispersion of noble metal nanoparticles, that is, the time of reaction before the dispersion of noble metal nanoparticles is added, the noble metal nanoparticles are dispersed in different parts of the Ni/Zn-MOF peanut-like core-shell structure, especially After reacting for 1 to 1.5 hours, add the dispersion of noble metal nanoparticles synthesized in the previous step (1), and the noble metal nanoparticles can be loaded in the cavity between the core and the shell, and the inner core can be used as a carrier to uniformly disperse the noble metal palladium nanoparticles Particles, the shell can play a protective role, inhibiting the loss of precious metal nanoparticles.

The core-shell structure MOF obtained in the present invention is a supported noble metal-based catalyst in the reaction vessel, that is, noble metal @Ni/Zn-MOF is used for the hydrogenation reaction of carbon-carbon double bonds, especially for carbon-carbon in carbon-carbon double bonds and carbon-oxygen double bonds Selective hydrogenation of double bonds.

The method of the above-mentioned application is as follows: the hydrogenation reaction of carbon-carbon double bond in the compound containing carbon-carbon double bond and carbon-oxygen double bond, such as the hydrogenation reaction of carbon-carbon double bond in cinnamaldehyde: 0.5～1mmol compound, a small amount of catalyst Noble metal @Ni/Zn-MOF, 5-10mL of isopropanol, under the condition of hydrogen atmosphere, stir, react for 2-24 hours, the reaction temperature is 25-60℃; the amount of catalyst added is 10-50mg, preferably 20mg; Compression pressure 0.1 ~ 3MPa.

The invention prepares a bimetallic Ni/Zn-MOF with uniform size and regular morphology, which has a core-shell structure, and there is a cavity between the core and the shell, and noble metal nanoparticles can be encapsulated in the cavity, which is beneficial to the noble metal nanoparticles. Evenly dispersed, not easy to lose, improves the catalytic activity of carbon-carbon double bond hydrogenation, and has wide application in the field of fine chemical synthesis; the preparation method of the present invention is simple, easy to implement, high yield, easy to batch production, and greatly improves the utilization rate of precious metals .

Description of drawings

Fig. 1 is an X-ray powder diffraction pattern of Pd@Ni/Zn-MOF in Example 1 of the present invention.

Fig. 2 is a schematic diagram of a scanning electron microscope of Pd@Ni/Zn-MOF in Example 1 of the present invention.

Fig. 3 is a performance diagram of Pd@Ni/Zn-MOF catalyzed hydrogenation reaction of cinnamaldehyde in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

Step 1: Dissolve 15 mg of palladium chloride and 77 mg of polyvinylpyrrolidone in a mixture of 85 mL of methanol and 15 mL of deionized water, and reflux at 70°C for 4 hours to obtain a Pd nanoparticle solution.

The second step: Weigh 30mg of terephthalic acid, 60mg of nickel nitrate and 40mg of zinc nitrate and dissolve them in a mixed solution of N,N-dimethylformamide (8mL) and ethylene glycol (5mL), after stirring for 1 hour, Transfer to a polytetrafluoroethylene reactor at a reaction temperature of 150°C. After reacting for 1.5 hours, add the Pd nanoparticle solution (3.5 mL) synthesized above, and react for 4 hours. Then cool, centrifuge, wash, activate, and dry to prepare Pd@Ni/Zn-MOF, noble metal Pd nanoparticles were successfully loaded in the cavity (mainly in the cavity) between the core-shell structure of the core-shell Ni/Zn-MOF.

Step 3: Weigh 20mg of catalyst Pd@Ni/Zn-MOF, 5mL of isopropanol, 0.5mmol of cinnamaldehyde, transfer to a high-pressure reactor, feed hydrogen gas at 0.3MPa, stir with magnetic force, and react for 3 hours at a reaction temperature of 25°C .

Example 2

Step 1: Weigh 16.6 mg of polyvinylpyrrolidone and dissolve it in 45 mL of ethanol, add 5.0 mL of H ₂ PtCl ₆ (6.0 mM) aqueous solution dropwise, and reflux for 3 hours to obtain a Pt nanoparticle solution.

Second step: Weigh 30mg of terephthalic acid, 50mg of nickel nitrate and 50mg of zinc nitrate and dissolve them in a mixed solution of N,N-dimethylformamide (10mL) and ethylene glycol (5mL), stir for 1 hour, Transfer to a polytetrafluoroethylene reactor, add the above synthesized Pt nanoparticle solution (5mL), the reaction temperature is 140°C, the reaction time is 6 hours, then cooled, centrifuged, washed, activated, and dried to prepare Pt@Ni/Zn- MOF, noble metal Pd nanoparticles were successfully supported in the core (mainly in the core) of the core-shell structure Ni/Zn-MOF.

Step 3: Weigh 50mg of catalyst Pt@Ni/Zn-MOF, 5mL of isopropanol, 0.4mmol of cinnamaldehyde, transfer to a high-pressure reactor, feed hydrogen at 1.0MPa, stir with magnetic force, and react for 24 hours at a reaction temperature of 30°C .

Example 3

The first step: Weigh 100mL of HAuCl ₄ (0.01%) aqueous solution, condense and reflux, add 4.5mL of sodium citrate (1%) aqueous solution, condense and reflux for 20 minutes, drop to room temperature, add 20mL polyvinylpyrrolidone (0.5 g) an aqueous solution, stirred at room temperature for 24 hours to obtain an Au nanoparticle solution.

The second step: Weigh 30mg of terephthalic acid, 60mg of nickel nitrate and 40mg of zinc nitrate and dissolve them in a mixed solution of N,N-dimethylformamide (8mL) and ethylene glycol (5mL), after stirring for 1 hour, Transfer to a polytetrafluoroethylene reactor at a reaction temperature of 150°C. After 6 hours of reaction, add the Au nanoparticle solution (3.5 mL) synthesized above, stir at room temperature, and then centrifugally wash, activate, and dry to prepare Au@ Ni/Zn-MOF, noble metal Pd nanoparticles were successfully loaded outside the shell (mainly outside the shell) of the core-shell structure Ni/Zn-MOF.

Step 3: Weigh 50mg of catalyst Au@Ni/Zn-MOF, 5mL of isopropanol, and 0.5mmol of cinnamaldehyde, transfer it to a high-pressure reactor, inject hydrogen gas at 1MPa, stir with magnetic force, and react for 12 hours at a reaction temperature of 60°C.

The test result of the material of above-mentioned embodiment 1 gained is identical, specifically sees following:

(1) Material morphology characterization:

Figure 1 is the X-ray powder diffraction pattern of Pd@Ni/Zn-MOF; Figure 2 is the scanning electron microscope image of Pd@Ni Zn-MOF.

(2) Characterization of material catalytic performance:

Figure 3 is the performance diagram of Pd@Ni/Zn-MOF, Pt@Ni/Zn-MOF and Au@Ni/Zn-MOF catalysts in catalyzing the hydrogenation reaction of cinnamaldehyde. It can be seen from the figure that the noble metal @Ni/Zn-MOF catalyst has Excellent catalytic activity and selectivity.

The above content is only a preferred example of the present invention, but the present invention should not be limited to the content disclosed in this example. Therefore, all equivalents or modifications that do not deviate from the spirit disclosed in the present invention fall within the protection scope of the present invention.

Claims (10)

1. it is a kind of using nucleocapsid MOF as the carried noble metal base catalyst noble metal@Ni/Zn-MOF of reaction vessel, it is special Sign is that Ni/Zn-MOF is the nucleocapsid of peanut formula in noble metal@Ni/Zn-MOF, is in nucleocapsid, exists between nucleocapsid Cavity, in cavity of the noble-metal-supported in core, outside shell or/and between nucleocapsid.

2. described in accordance with the claim 1 a kind of expensive using nucleocapsid MOF as the carried noble metal base catalyst of reaction vessel Metal@Ni/Zn-MOF, which is characterized in that noble metal nano particles, wherein selected from one or more of Pd, Pt, Au, Ag.

3. preparing as claimed in claim 1 or 2 using nucleocapsid MOF as the expensive gold of carried noble metal base catalyst of reaction vessel Belong to the method for@Ni/Zn-MOF, which is characterized in that include the following steps：(1) dispersion liquid of noble metal nano particles is prepared；

(2) preparation of noble metal@Ni/Zn-MOF：

Terephthalic acid (TPA), nickel salt and zinc salt are dissolved in the mixed solution of n,N-Dimethylformamide and ethylene glycol, stirring 0.5~ It after 1 hour, is transferred in polytetrafluoroethylene reaction kettle, 140~160 DEG C of reaction temperature, reacts 0~6 hour, be added walk later Suddenly then the dispersion liquid of the noble metal nano particles of (1) synthesis, 2~12 hours reaction time cool down centrifuge washing, activation, do The dry preparation up to noble metal@Ni/Zn-MOF.

4. according to the method for claim 3, which is characterized in that in step (2), nickel salt and zinc salt be metal nitrate or One or more of metal chloride.

5. according to the method for claim 3, which is characterized in that in step (2), the molar ratio 4 of nickel nitrate and zinc nitrate:1 ~1:1, preferably 1:1；Terephthalic acid (TPA) is preferably (1-5) with the total moles ratio of nickel nitrate and zinc nitrate:10, further preferred 3: 10；The volume ratio of N,N-dimethylformamide and ethylene glycol is (6-10):5, preferably 8:5.

6. according to the method for claim 3, which is characterized in that in step (2), the load capacity of noble metal nano particles can root It is adjusted according to needs, the volume and n,N-Dimethylformamide of the addition of noble metal nano particles dispersion liquid and mixing for ethylene glycol It is 1 to close overall solution volume ratio:15~8:13.

7. according to the method for claim 3, which is characterized in that Ni/Zn- in noble metal@Ni/Zn-MOF obtained by step (2) MOF is the nucleocapsid of peanut formula, in cavity of the noble-metal-supported in core, outside shell or/and between nucleocapsid, passes through to adjust and is added The addition time of the dispersion liquid of noble metal nano particles be noble metal nano particles dispersion liquid be added before reacted when Between so that noble metal nano particles are dispersed in the different parts of the nucleocapsid of Ni/Zn-MOF peanut formulas；Especially reaction 1~ 1.5 hours, the dispersion liquid of the noble metal nano particles of upper step (1) synthesis is added later, can obtain noble metal nano In cavity of the particle loading between nucleocapsid, kernel can be used as carrier, evenly dispersed precious metal palladium nano particle, shell that can rise To protective effect, noble metal nano particles is inhibited to be lost in.

8. as claimed in claim 1 or 2 using nucleocapsid MOF as the carried noble metal base catalyst noble metal@of reaction vessel The application of Ni/Zn-MOF is used for the hydrogenation reaction of carbon-carbon double bond.

9. according to the application of claim 8, which is characterized in that the selectivity for carbon-carbon double bond in carbon-carbon double bond and C=O bond Hydrogenation reaction.

10. specific as follows according to the application of claim 9：Carbon carbon in compound simultaneously comprising carbon-carbon double bond and C=O bond The hydrogenation reaction of carbon-carbon double bond in the hydrogenation reaction such as cinnamic acid of double bond：0.5~1mmol compounds, a small amount of catalyst noble metal@ Ni/Zn-MOF, 5~10mL of isopropanol, under the conditions of hydrogen atmosphere, stirring is reacted 2~24 hours, 25~60 DEG C of reaction temperature； 10~50mg of catalyst charge, preferably 20mg；0.1~3MPa of pressurized with hydrogen pressure.