Method for reducing waste liquid generated in platinum black catalyst preparation process

Abstract

The invention relates to a method for reducing waste liquid generated in a platinum black catalyst preparation process, which comprises the following steps: dissolving chloroplatinic acid in a small amount of water, adding solid sodium hydroxide, stirring to form a solution, and adding the solution into an organic solvent. The volume ratio of the organic solvent to the aqueous solution is 15: 1, and the organic solvent comprises but is not limited to benzene, cyclohexane, ethanol, isopropanol, ethylene glycol, acetone, methyl butanone, acetonitrile and the like. And adding a formaldehyde solution (35% by mass) according to the chemical reaction stoichiometric ratio of chloroplatinic acid to formaldehyde of 1: 1.5. And finally, transferring the whole solution into a high-pressure kettle to react at 200 DEG C for 4 hours. And calculating the mass of the mother liquor, and detecting the granularity of the sample by using a scanning electron microscope. According to the method, under the condition that the catalyst with the same granularity and the same mass is prepared, the waste liquid discharge amount is only 1 / 35 of that of a used aqueous solution, and due to the fact that the used organic solvent is low in boiling point, the organic solvent can be recycled in a fractionation mode. The particle size of the prepared sample is about 5nm.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of platinum black catalysts, and particularly relates to a method for reducing waste liquid discharge during a preparation process. Background Art

[0002] Platinum black is a catalyst with a high specific surface area, usually in powder form. It is widely used in various catalytic reactions in the chemical industry, such as hydrogenation reactions, oxidation reactions, etc. There are many methods for preparing platinum black catalysts. The following are some common preparation methods: Reduction method: This is one of the most commonly used methods for preparing platinum black. First, a soluble platinum salt (such as chloroplatinic acid H2PtCl6 or tetraammine platinum (II) nitrate) is dissolved in water, and then a reducing agent (such as formaldehyde, hydrazine hydrate, sodium borohydride NaBH4, etc.) is added to reduce the platinum ions to metallic platinum. This process can be carried out under certain temperature and pH conditions to control the size and distribution of platinum black particles.

[0003] Thermal decomposition method: By heating organic compounds or complexes of platinum (such as acetylacetone complex of platinum), these compounds will decompose into pure platinum at high temperature. This method can obtain relatively pure platinum black with small particle size.

[0004] Electrodeposition method: In an electrochemical environment, platinum is deposited from its salt in solution onto a conductive substrate by applying an electric current to form a platinum black layer. This method allows precise control of the thickness and structure of the platinum black.

[0005] Precipitation-calcination method: Platinum salt is mixed with alkaline substances to form an insoluble platinum hydroxide precipitate, which is then dried and calcined at high temperature to decompose the platinum hydroxide into metallic platinum.

[0006] Microemulsion method: A microemulsion system is used in which the platinum precursor is encapsulated in nanoscale aqueous droplets and undergoes a reduction reaction under appropriate conditions to form small-sized platinum black particles of uniform size.

[0007] Template synthesis method: Using a specific template material (such as mesoporous silica) as a support, a platinum precursor is introduced by impregnation or other means, followed by reduction, and finally the template is removed to obtain platinum black with a special morphology.

[0008] The method to be chosen depends on the specific properties of the required platinum black (such as particle size, specific surface area, morphology, etc.), cost considerations, and application requirements. Each method has its own characteristics, and the experimental conditions can be adjusted according to actual needs to optimize the performance of platinum black.

[0009] Patent CN 111745164 A discloses a method for preparing ultrafine platinum nanoparticles, which belongs to the technical field of precious metal material preparation. The present invention uses polyethylene glycol as a reducing agent to reduce platinum in a platinum precursor solution, and prepares ultrafine spherical platinum powder with a particle size of 200-400nm by controlling the amount of the reducing agent, the reaction temperature and the time. The platinum powder prepared by the present invention is spherical or nearly spherical, and the method is simple and safe to operate, has low production cost, is easy to wash, and can be applied to industrial production.

[0010] Patent CN 112517001 A provides a method for preparing a platinum black catalyst and a platinum black catalyst. The method for preparing a platinum black catalyst comprises: dissolving a halogen-containing platinum precursor in a strong acid, reacting it with silver ions, and removing the precipitate to obtain a reaction solution. The pH of the reaction solution is adjusted at a temperature of 35 to 95° C. to form a platinum hydroxide or a platinum oxide. The platinum hydroxide or the platinum oxide is reduced by hydrogen or a mixed gas containing hydrogen at a temperature of 100 to 600° C. The platinum metal particles in the platinum black catalyst have a particle size of 3.9 to 5.5 nm.

[0011] The current problem in the market is that in order to prepare nanomaterials, in order to prevent particle aggregation, the concentration of raw materials such as chloroplatinic acid needs to be reduced to below 0.1g / L. Such a low concentration of preparing a large number of platinum metal nanoparticles will produce a large amount of wastewater. The preparation of 1g of catalyst will produce more than 4L of mother liquor wastewater. Therefore, it is particularly important to find a method for producing catalysts that reduces wastewater generation. Summary of the invention

[0012] Under the above circumstances, the present invention provides a method for reducing waste liquid generation and efficiently preparing a large amount of platinum black catalyst, that is, using an organic solvent as a dispersant, even if the concentration of the raw material is increased, the particle size of the platinum metal particles will not increase. This organic solvent has a low boiling point and can be recycled by simple fractionation. DETAILED DESCRIPTION

[0013] First, dissolve chloroplatinic acid in a small amount of water, add solid NaOH, and form a solution under stirring, and then add it to an organic solvent. The volume ratio of the organic solvent to the aqueous solution is 15:1, and the organic solvent includes but is not limited to benzene, cyclohexane, alcohols such as ethanol, isopropanol, ketones such as acetone, methyl butyl ketone, acetonitrile, etc. Then add a formaldehyde solution (35% mass ratio) according to the chemical reaction ratio of chloroplatinic acid and formaldehyde at 1:1.5. Finally, transfer the entire solution to an autoclave and react at 200°C for 4 hours. Take out, filter, calculate the mass of the mother liquor, and use a scanning electron microscope to detect the sample particle size, which can represent the product performance.

[0014] Comparative experiment 1: First, weigh 2.66 g of H2PtCl6·6H2O and dissolve it in 10 mL of water. Add 1.24 g of NaOH and stir to form a solution. Then add it to 150 mL of water, and then add 3.08 g of formaldehyde solution (35% mass ratio) in a chemical reaction ratio of 1:1.5 between chloroplatinic acid and formaldehyde. Finally, transfer the entire solution to an autoclave and react at 200°C for 4 h. Take it out, filter it, and weigh the mother liquor to be 147 g. The particle size of the sample is 15 μm when detected by scanning electron microscopy.

[0015] Comparative experiment 2: First, weigh 2.66 g of H2PtCl6·6H2O and dissolve it in 10 mL of water. Add 1.24 g of NaOH and stir to form a solution. Then add it to 4.5 L of water, and then add 3.08 g of formaldehyde solution (35% mass ratio) in a chemical reaction ratio of 1:1.5 between chloroplatinic acid and formaldehyde. Finally, transfer the entire solution to an autoclave and react at 200°C for 4 h. Take it out, filter it, and weigh the mother liquor to be 4487 g. The particle size of the sample is 6.7 nm when detected by scanning electron microscopy. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a scanning electron microscope photograph of the prepared platinum black, corresponding to Specific Implementation 2. DETAILED DESCRIPTION Specific implementation method 1 First, weigh 2.66 g of H2PtCl6·6H2O and dissolve it in 10 mL of water. Add 1.24 g of NaOH and stir to form a solution. Then add it to the organic solvent acetone. The volume ratio of acetone to aqueous solution is 15:1. Then add 3.08 g of formaldehyde solution (35% mass ratio) according to the chemical reaction ratio of chloroplatinic acid and formaldehyde of 1:1.5. Finally, transfer the entire solution to an autoclave and react at 200°C for 4 hours. Take it out, filter it, weigh the mother liquor mass to be 126 g, and use a scanning electron microscope to detect the sample particle size of 5 nm. Specific implementation method 2 First, weigh 2.66 g of H2PtCl6·6H2O and dissolve it in 10 mL of water. Add 1.24 g of NaOH and stir to form a solution, then add it to acetonitrile. The volume ratio of acetonitrile to aqueous solution is 15:1, and then add 3.08 g of formaldehyde solution (35% mass ratio) according to the chemical reaction ratio of chloroplatinic acid and formaldehyde of 1:1.5. Finally, transfer the entire solution to an autoclave and react at 200℃ for 4h. Take it out, filter it, weigh the mother liquor mass to be 162 g, and use a scanning electron microscope to detect the sample particle size of 4.5 nm. Specific implementation method 3 First, weigh 2.66 g of H2PtCl6·6H2O and dissolve it in 10 mL of water. Add 1.24 g of NaOH and stir to form a solution, then add it to isopropanol. The volume ratio of isopropanol to aqueous solution is 15:1, and then add 3.08 g of formaldehyde solution (35% mass ratio) according to the chemical reaction ratio of chloroplatinic acid and formaldehyde 1:1.5. Finally, transfer the entire solution to an autoclave and react at 200℃ for 4 h. Take it out, filter it, weigh the mother liquor mass to be 124 g, and use a scanning electron microscope to detect the sample particle size of 5.2 nm.

Claims

1. A method for reducing wastewater generated during the preparation of platinum black catalyst, characterized in that: The following steps are involved: First, 2.66 g H2PtCl6·6H2O was dissolved in a small amount of water, and 1.24 g NaOH was added to form a solution under stirring, and then added to the organic solvent. The volume ratio of the organic solvent to the aqueous solution was 10:1, and then a formaldehyde solution (35% by mass) was added according to the chemical reaction ratio of chloroplatinic acid and formaldehyde of 1:1.

5. Finally, the entire solution was transferred to an autoclave and reacted at 200℃ for 4 h. Take out, filter, and calculate the mass of the mother liquor.

2. A method for reducing wastewater generated during the preparation of a platinum black catalyst as claimed in claim 1, characterized in that: An organic solvent is used, which includes but is not limited to benzene, cyclohexane, ethanol, isopropanol, acetone, methyl butyl ketone, acetonitrile, etc.

3. A method for reducing wastewater generated during the preparation of a platinum black catalyst as claimed in claim 1, characterized in that: Use organic solvents, which have a low boiling point and can be recovered and reused by simple distillation.

4. The method for reducing wastewater generated in the preparation process of platinum black catalyst as claimed in claim 3, characterized in that: The preparation of about 1 gram of platinum black catalyst produces about 150 g of waste liquid, while using only aqueous solution produces 4487 g of waste water.

5. The method for reducing wastewater generated in the preparation process of platinum black catalyst as claimed in claim 4, characterized in that: The prepared platinum black catalyst particles are only about 5 nm.

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