CN113952983B - A kind of preparation method of paper-supported noble metal nanoparticle catalyst - Google Patents

Abstract

The invention belongs to the field of synthesis of catalyst materials, and provides a preparation method of a paper-supported noble metal nanoparticle catalyst. The invention can prepare a novel catalyst with the characteristics of easy separation of a heterogeneous catalyst and high activity of a homogeneous catalyst, and the performance of the catalyst is investigated by respectively using dehydrogenation oxidation reaction and hydrogenation reduction reaction.

Description

A kind of preparation method of paper-supported noble metal nanoparticle catalyst

technical field

The invention belongs to the field of synthesis of catalyst materials, in particular to a synthesis method of a paper-supported noble metal nanoparticle catalyst.

Background technique

Catalysis and catalyst play a pivotal role in the development of human society. At present, more than 90% of chemical industrial processes are inseparable from catalysis and catalysts. In the catalytic reaction, the catalyst interacts with the reactants to change the reaction pathway, thereby reducing the activation energy of the reaction, which is the reason why the catalyst can increase the reaction rate. Catalysis plays a very crucial role in the development of world civilization and the progress of human society. It can chemically transform readily available and cheap raw materials into high value-added chemical products and high energy density fuels in a cost-effective, high-efficiency, green and environmentally friendly way. It also involves modern high-tech fields, such as network technology, information transmission, bioengineering, aerospace and military industries, so catalysis is called "the heart of modern industry". There are three main types of catalysts: heterogeneous catalysts, homogeneous catalysts and enzyme catalysts. Heterogeneous catalysts are widely used in industrial production due to their easy separation and high stability, while homogeneous catalysts and enzyme catalysts are difficult to be applied in industry due to their high cost and difficult separation. However, heterogeneous catalysts do not have homogeneous catalysts. High selectivity and high activity. It is very challenging to establish a bridge between heterogeneous catalysis and homogeneous catalysis/enzymatic catalysis, so that heterogeneous catalysts have the excellent performance of homogeneous catalysts and enzymatic catalysts. Therefore, the development of green, high-efficiency, low-cost, high-selectivity, and environmentally friendly new heterogeneous catalysts is the core of the development of chemistry, chemical industry, catalysis and other disciplines.

It is known that noble metal catalysts exhibit high catalytic activity and selectivity in many reactions. Therefore, noble metal catalysts have been widely used, and it is very important to find suitable noble metal supports to make noble metal catalysts break through their original performance. Paper catalysts can integrate the characteristics of easy separation of heterogeneous catalysts, independent single clear active centers and high selectivity and high activity of stable and homogeneous catalysts. This is because in the liquid-phase chemical reaction system, the paper catalyst can have the characteristics of a homogeneous catalyst by forming the state of pulp, and exists in the state of paper during separation and recovery, and can also have the characteristics of a heterogeneous catalyst. At the same time, the separation and recovery of the paper catalyst is simpler than the traditional heterogeneous catalyst separation. Therefore, the research on the preparation of paper catalysts is very important, and it is even hopeful to establish a unified theory of catalysis.

In summary, when we use some special papers, such as porous chromatography paper, filter paper, etc., as catalyst carriers, in addition to supporting noble metal nanoparticles, due to the abundant hydroxyl groups on the surface, it does not require functionalization, and can be well combined with noble metal nanoparticles. Also cheap and easy to get. Using paper as a catalyst support can take advantage of the unique phase transition properties of paper, allowing easy and reversible transitions between liquid and solid phases. At the same time, the colloid method is used to colloid and deposit the precious metal on the paper, and the hydroxyl group indicated by the paper is used to adsorb the precious metal, and the particle size of the precious metal can be adjusted by adjusting the concentration of the protective agent and the reaction time of preparing the colloid, and uniform precious metal nanoparticles can be obtained. When the noble metal/paper catalyst is formed into pulp state, its structure and performance are similar to homogeneous catalysts or even enzyme catalysts.

At present, there are some deficiencies in the preparation methods of paper catalysts:

Chinese patent, application number: CN201910955378.X, introduces a polyimide composite paper with catalytic properties and SERS properties and its preparation. Use the metal nanoparticle-loaded precipitating fiber to directly make paper; or mix the metal nanoparticle-loaded precipitating fiber and the polyimide chopped fiber to make a polyimide composite paper. However, the preparation conditions are cumbersome and the raw materials are relatively expensive, especially the price of polyimide has even reached 9000-15000 yuan/kg, and the economic benefit is not obvious.

Chinese patent, application number: CN201610569319.5, introduces a process of M(salen) catalytic paper catalyzing liquefaction of biomass in ionic liquid. In the presence of ionic liquid and M(salen) catalytic paper, the catalytic liquefaction of biomass compounds is carried out. Because of the introduction of ionic liquid catalysis, the difficult separation of ionic liquid from pulp makes its catalyst difficult to recycle, which limits its application.

Chinese patent, application number: CN201510130919.7, introduces the application of Co(salen) catalyzed paper in lignin oxidation. This patent synthesizes Co complexes and mixes them with ceramic fibers, polyacrylamide, etc. to obtain catalyst-ceramic fiber-polymer composite paper by papermaking. It also has the problems of cumbersome process and high cost, and the morphology and particle size of Co cannot be control, affecting its performance.

Chinese patent, application number: CN202110485155.9, introduces a photocatalytic paper and its preparation method. A photocatalytic paper has been prepared for photocatalysis. Although its process is simple and low in cost, it is limited to the application of photocatalysis and has limitations.

Chinese patent, application number: CN200420022026.8, introduces a transfer catalytic paper for cotton printing. The utility model is composed of paper and a dye layer. The processing device includes a pressure rubber roller, an expansion balance roller, a catalytic padding rubber roller and other components. An isolation layer is arranged on the surface of the printed paper, and a catalyst layer is arranged on the back. The layer is provided with or coated with a transfer catalyzed paper gravure printed dye layer. It is an environmentally friendly and green technology, but the process is cumbersome and difficult to achieve large-scale production.

SUMMARY OF THE INVENTION

The invention discloses a preparation method of a paper-supported noble metal nanoparticle catalyst, which belongs to the field of synthesis of catalyst materials. The present invention aims to provide a novel catalyst preparation method, in order to communicate heterogeneous catalysis and homogeneous catalysis, and to make use of the characteristics of paper that can undergo reversible phase transition, so that it has the characteristics of easy separation and high activity.

The technical scheme of the present invention is as follows:

Use water or alcoholic organic solvent to dissolve the precursor salt of the precious metal to obtain a solution of the precious metal precursor salt with a concentration of 0.001-0.1mol/L, stir to completely dissolve the precursor salt of the precious metal, and then add a protective agent to control the protective agent in the system. The solubility of the solution is 0.01-0.1 mol/L. After stirring and dissolving, the solution is heated at a temperature of 100-140° C. for 5-120 minutes to obtain a precious metal colloid solution. Then add the paper to the precious metal colloid solution, adjust the pH to less than 3, then heat to 100-140°C, and keep the constant temperature for 5-120 minutes; at this time, the solution is in a pulp state, then cooled to room temperature, filtered and washed until neutral, at 60-100 Drying at a temperature of ℃ for 6-12 hours to prepare a paper-supported noble metal nanoparticle catalyst; wherein the weight percentage of the noble metal in the paper is 0.01-10 wt %. Water or alcohol organic solvent, alcohol organic solvent is water-methanol, water-ethanol, water-ethylene glycol, water-n-propanol or water-n-butanol, wherein the volume fraction of organic solvent is not more than 100%. The precious metal is one or a mixture of two or more precious metals such as platinum, palladium, gold, rhodium and iridium. The metal salt solution is a mixture of one or more of nitrates, chlorides, acetates and chlorohydrochloric acid. The protective agents are inorganic salts such as sodium acetate, polymers such as polyvinylpyrrolidone and the like. The paper used as the catalyst carrier is a paper-based material having a fibrous or paper-like structure, such as chromatography paper, filter paper, and carbon paper. The physical and chemical properties of the paper can also be adjusted by irradiating the paper with an external lamp or electromagnetic wave at a power of 0-2w·m ^-2 for 12-100 hours. The external light source is one or a combination of two or more common light sources such as mercury lamps, xenon lamps, and metal halide lamps. The electromagnetic wave is one or more combinations of visible light, ultraviolet light, infrared light, X-ray and other invisible light.

Compared with the known paper catalyst preparation technology, the present invention has the following advantages:

1. There is no need to use ceramic fibers, a large number of high molecular polymers and other expensive materials, and the cost is low.

2. There is no need to carry out tedious paper technology such as paper making.

3. Not limited to photoelectric catalysis, it can be used in the field of thermal catalysis and has potential industrial application prospects.

4. During the catalytic reaction, the catalyst exists in the state of pulp in the solution, so that its active center is uniform. In theory, its catalytic performance can be comparable to that of a homogeneous catalyst or even an enzyme catalyst. After the reaction, the catalyst can be re-formed into paper by a simple separation method, and the heterogeneous catalyst can be recycled.

5. It is cheap and easy to obtain, and at the same time, due to the abundant hydroxyl groups on its surface, no carrier pretreatment is required. It combines the advantages of homogeneous catalysts and heterogeneous catalysts, and even has the hope of establishing a unified theory of catalysis.

Detailed ways

In order to further illustrate the present invention, the following examples are given without limiting the scope of the invention as defined by the appended claims.

Embodiment 1: get a certain amount of chloroplatinic acid and dissolve it in 10mL ethylene glycol solution, make its concentration be 0.0025mol/L, fully stir until completely dissolved, then add a certain amount of sodium acetate, so that the concentration of sodium acetate is 0.04mol/L. L. After stirring and dissolving, heat at 120 degrees for 20 minutes to obtain a Pt colloidal solution. Then, 8 sheets of chromatographic paper (1cm×1cm, 97.5mg) were added to the colloid solution, and the acid-base environment was adjusted with dilute hydrochloric acid to make the pH less than 3, and then heated to 120 degrees and kept at a constant temperature for 60 minutes. At this time, the solution was in pulp state, then cooled to room temperature, filtered and washed for 5 times, and dried at 80 degrees for 12 hours to obtain a Pt/paper catalyst, wherein the mass percentage of noble metal in the carrier was 5wt%.

Embodiment 2: get a certain amount of chloroplatinic acid and dissolve it in 10mL of ethylene glycol solution, make its concentration be 0.0025mol/L, fully stir until completely dissolved, then add a certain amount of sodium acetate, so that the concentration of sodium acetate is 0.04mol/L. L. After stirring and dissolving, heat at 120 degrees for 20 minutes to obtain a Pt colloidal solution. Then, 97.5 mg of activated carbon was added to the colloid, and the acid-base environment was adjusted to pH less than 3 with dilute hydrochloric acid, and then heated to 120 degrees for 60 minutes at a constant temperature. Filtration and washing 5 times, drying at 80 degrees for 12 hours to obtain a Pt/activated carbon catalyst, wherein the mass percentage of noble metal in the carrier is 5 wt%.

Embodiment 3: use ultraviolet light to irradiate chromatographic paper: use UVA-340 type ultraviolet lamp tube, ultraviolet light wavelength selection 340nm; irradiance is 0.76w m ^-2 ; temperature is (30 ± 3) ℃; humidity is not controlled; Directly irradiate the front of the paper for 12 hours and then irradiate the back of the paper for 12 hours. The catalyst was then prepared according to the method of Example 1. Denoted as Pt/L paper catalyst.

Example 4: take 50mL methanol-water solution, wherein the ratio of alcohol to water is 1:1, add 0.15g polyvinylpyrrolidone, add a certain amount of chloroplatinic acid, make the concentration of chloroplatinic acid 0.0005ml/L, stir and dissolve in Heating at 120 degrees for 180 minutes to obtain a Pt colloidal solution. Then, 8 sheets of chromatographic paper (1cm×1cm, 97.5mg) were added to the colloid solution, and the acid-base environment was adjusted with dilute hydrochloric acid to make the pH less than 3, and then heated to 120 degrees and kept at a constant temperature for 60 minutes. At this time, the solution was in pulp state, then cooled to room temperature, filtered and washed for 5 times, and dried at 80 degrees for 12 hours to obtain Pt/paper catalyst-4, in which the mass percentage of precious metals in the carrier was 5wt%.

Embodiment 5: take 50mL ethanol-water solution, wherein the ratio of alcohol and water is 1:1, add 0.15g polyvinylpyrrolidone, add a certain amount of chloroplatinic acid, make the concentration of chloroplatinic acid be 0.0005ml/L, stir and dissolve in Heat at 120 degrees for 120 minutes to obtain a Pt colloidal solution. Then, 8 sheets of chromatographic paper (1cm×1cm, 97.5mg) were added to the colloid solution, and the acid-base environment was adjusted with dilute hydrochloric acid to make the pH less than 3, and then heated to 120 degrees and kept at a constant temperature for 60 minutes. At this time, the solution was in pulp state, then cooled to room temperature, filtered and washed for 5 times, and dried at 80 degrees for 12 hours to obtain Pt/paper catalyst-5, wherein the mass percentage of noble metal in the carrier was 5wt%.

Embodiment 6: take 50mL n-propanol-water solution, wherein the ratio of alcohol to water is 1:1, add 0.146g polyvinylpyrrolidone, add a certain amount of chloroplatinic acid, make the concentration of chloroplatinic acid be 0.0005ml/L, stir and dissolve After heating at 120 degrees for 120 minutes, a Pt colloid solution was obtained. Then, 8 sheets of chromatographic paper (1cm×1cm, 97.5mg) were added to the colloid solution, and the acid-base environment was adjusted with dilute hydrochloric acid to make the pH less than 3, and then heated to 120 degrees and kept at a constant temperature for 60 minutes. At this time, the solution was in pulp state, then cooled to room temperature, filtered and washed for 5 times, and dried at 80 degrees for 12 hours to obtain Pt/paper catalyst-6, wherein the mass percentage of noble metal in the carrier was 5wt%.

Embodiment 7: take 50mL n-butanol-water solution, wherein the ratio of alcohol and water is 1:1, add 0.15g polyvinylpyrrolidone, add a certain amount of chloroplatinic acid, make the concentration of chloroplatinic acid be 0.0005ml/L, stir and dissolve After heating at 120 degrees for 120 minutes, a Pt colloid solution was obtained. Then, 8 sheets of chromatographic paper (1cm×1cm, 97.5mg) were added to the colloid solution, and the acid-base environment was adjusted with dilute hydrochloric acid to make the pH less than 3, and then heated to 120 degrees and kept at a constant temperature for 60 minutes. At this time, the solution was in pulp state, then cooled to room temperature, filtered and washed for 5 times, and dried at 80 degrees for 12 hours to obtain Pt/paper catalyst-7, wherein the mass percentage of precious metals in the carrier was 5wt%.

Example 8: Comparison of the performance of Pt/paper catalyst and Pt/activated carbon catalyst. The catalysts prepared in Example 1-Example 3 were used to catalyze the reaction of dehydrogenation of glucose. Firstly, 0.4324g glucose was dissolved in 40mL water-methanol solution, the volume fraction of water was 40%, 0.7405g KOH was added, the gas in the reactor was replaced with Ar atmosphere, the reaction temperature was 30℃, the reaction pressure was normal pressure, and the dehydrogenation was carried out. The catalyst is Pt/activated carbon, Pt/paper, Pt/L paper catalyst, the product gas is collected and analyzed by gas chromatography, the detector is a thermal conductivity detector, the chromatographic column is TDX-01, the gas chromatography shows the generation of hydrogen, and the reaction results are shown in the table 1.

Example 9: Comparison of the performance of Pt/paper catalysts prepared with different solvents. The catalysts prepared in Examples 4 to 7 were used in the reductive hydrogenation of nitrobenzene. First, 5 mmol of nitrobenzene was dissolved in 20 mL of cyclohexane solution, the hydrogenation reduction catalyst was Pd/paper catalyst 4-7, and the amount of catalyst added was 20 mg, and then the solution was transferred to a tank reactor. The air in the reactor was replaced 5 times with hydrogen, and the reactor was heated to 60 degrees at 700 rpm, and then filled with hydrogen with a set pressure of 1 Mpa. The product composition was analyzed by gas chromatography, and the reaction results were shown in Table 2.

Example 10: Evaluation of catalyst recycling. In Example 8, the three catalysts after the reaction for 4 h were centrifuged and recovered by vacuum drying. Dissolve 0.4324g glucose in 40mL water-methanol solution, the volume fraction of water is 40%, add 0.7405g KOH, replace the gas in the reactor with Ar atmosphere, the reaction temperature is 30 ℃, the reaction pressure is normal pressure, deoxidation catalyst It is Pt/activated carbon, Pt/paper, and Pt/L paper catalyst. The product gas is collected and analyzed by gas chromatography. The detector is a thermal conductivity detector, and the chromatographic column is TDX-01. The gas chromatography shows the generation of hydrogen. The reaction results are shown in Table 1. . The catalyst was recycled 5 times, and the reaction results are shown in Table 3.

Table 1 Performance Evaluation of Catalysts of Examples 1-3

catalyst Hydrogen yield (mol%) Pt/Paper 90 Pt/Activated carbon 84 Pt/L paper 93

Table 2 Performance Evaluation of Catalysts of Examples 4-7

Table 3 Catalyst stability test

catalyst Cycles Hydrogen yield (mol%) Pt/Paper 1 89 Pt/Paper 2 88 Pt/Paper 3 87 Pt/Paper 4 88 Pt/Paper 5 86 Pt/L paper 1 93 Pt/L paper 2 90 Pt/L paper 3 85 Pt/L paper 4 80 Pt/L paper 5 78 Pt/Activated carbon 1 82 Pt/Activated carbon 2 83 Pt/Activated carbon 3 83 Pt/Activated carbon 4 83 Pt/Activated carbon 5 82

Claims (6)

1. a preparation method for the paper-loaded precious metal nanoparticle catalyst of catalyzing dehydrogenation glucose reaction, is characterized in that, step is as follows: Use water-methanol, water-ethanol, water-ethylene glycol, water-n-propanol or water-n-butanol to dissolve the precursor salt of the precious metal to obtain the concentration of the precious metal precursor salt solution is 0.001-0.1mol/L, stir Completely dissolve the precious metal precursor salt, then add a protective agent to control the solubility of the protective agent in the system to 0.01-0.1mol/L, after stirring and dissolving, then heat the solution at a temperature of 100-140 ℃ for 5-120 minutes to obtain a precious metal colloidal solution; then add paper to the precious metal colloidal solution, adjust the pH to less than 3, and then heat to 100-140 ° C for 5-120 minutes at a constant temperature; at this time, the solution is in the state of pulp, then cooled to room temperature, filtered and Washing to neutrality, drying at 60-100°C for 6-12 hours to obtain a paper-supported noble metal nanoparticle catalyst; wherein the mass percentage of noble metal in the paper is 0.01-10wt%; the paper used as the catalyst carrier is chromatography paper, filter paper or carbon paper. 2. preparation method according to claim 1, is characterized in that, described precious metal is one or more mixing in platinum, palladium, gold, rhodium, iridium; The precursor salt of precious metal is nitrate, chlorine One or two or more of hydrochloric acid salts, acetate salts, and chlorohydrochloric acid are mixed. 3. preparation method according to claim 1 and 2 is characterized in that, described protective agent is sodium acetate or polyvinylpyrrolidone. 4. The preparation method according to claim 1 or 2, characterized in that, using an external lamp or electromagnetic wave to irradiate the paper with a power of 0-2w∙m ^-2 for 12-100 hours, wherein the power is not zero, adjusting the paper Physicochemical properties of catalysts. 5. The preparation method according to claim 3, characterized in that, using an external lamp or electromagnetic wave to irradiate the paper with a power of 0-2w∙m ^-2 for 12-100 hours, wherein the power is not zero, adjusting the amount of the paper catalyst. Physical and chemical properties. 6. preparation method according to claim 4 is characterized in that, described external lamp source is one or both in mercury lamp, xenon lamp, metal halide lamp combined use; Described electromagnetic wave is visible light, ultraviolet, One or a combination of infrared and X-ray.