A Pt / Co3O4 catalyst, its preparation method and application

Abstract

This invention provides a Pt / Co3O4 catalyst, its preparation method, and its applications. The preparation method of the Pt / Co3O4 catalyst includes the following steps: under nitrogen protection, cobalt tetroxide, polyvinylpyrrolidone, and water are mixed uniformly, a chloroplatinic acid isopropanol solution is added, and trisodium citrate is added at 50–80°C, reacting for 0.5–2 hours. The preparation method provided by this invention is simple, and the obtained Pt / Co3O4 catalyst is a supported platinum-based catalyst. The Pt-Co3O4 catalyst provided by this invention is not only recyclable but also features small particle size, large specific surface area, easy dispersion, and high catalytic efficiency; good addition efficiency can be achieved with less than 0.1 wt% of the total raw materials.

Description

Technical Field

[0001] This invention relates to the field of platinum-based catalysts, and more specifically, to a Pt / Co3O4 catalyst, its preparation method, and its application. Background Technology

[0002] Platinum catalysts are widely used in the field of catalysts due to their advantages such as high catalytic activity, strong selectivity, and the ability to be compounded with other metals or co-catalyst active components. Currently, the catalysts used in hydrosilylation reactions are homogeneous platinum catalysts, meaning that the reactants and catalysts can coexist in the same phase.

[0003] Among the existing technologies, Speier catalysts and Karstedt catalysts have been industrialized. Supported platinum catalysts have also been studied extensively, such as platinum catalysts supported by molecular sieves or silica catalysts. The specific preparation method includes the following steps: adding molecular sieves or silica as catalyst supports to a solution of isopropanol chloroplatinate.

[0004] Existing homogeneous catalysts are difficult to recycle and have high production costs. Meanwhile, existing supported platinum-based catalysts exhibit low activity, requiring large quantities to achieve the desired catalytic effect, and have poor recyclability. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing a Pt / Co3O4 catalyst, which is simple to synthesize and yields a Pt / Co3O4 catalyst with high reactivity.

[0006] The preparation method of this Pt / Co3O4 catalyst includes the following steps:

[0007] Under nitrogen protection, cobalt tetroxide, polyvinylpyrrolidone and water are mixed evenly, and isopropanol chloroplatinate solution is added. Trisodium citrate is added at 50-80°C, and the reaction is carried out for 0.5-2 hours.

[0008] In a preferred embodiment of the present invention, the concentration of the isopropanol chloroplatinic acid solution is 0.01-0.1 mol / L. Within this concentration range, a catalyst with good performance can be obtained in the present invention.

[0009] In a preferred embodiment of the present invention, the mass ratio of cobalt tetroxide to chloroplatinic acid in the isopropanol chloroplatinic acid solution is 10:1 to 20:1.

[0010] In a specific embodiment of the present invention, after adding the isopropanol chloroplatinate solution, the mixture is usually stirred for 0.2 to 1 hour, and then trisodium citrate is added at 50 to 80°C for reaction.

[0011] In a preferred embodiment of the present invention, the amount of polyvinylpyrrolidone added is 0.1 wt% to 1 wt% of the total amount of raw materials in the system (total mass of all raw materials). Within this range, the catalyst activity is better.

[0012] In this invention, water is used as the solvent for the reaction. In a specific embodiment of this invention, the amount of water added can be 40-100 ml.

[0013] In a preferred embodiment of the present invention, the molar ratio of trisodium citrate to chloroplatinic acid in the chloroplatinic acid is (10-90):1.

[0014] In a specific embodiment of the present invention, the system after the reaction is completed can be allowed to stand and cool to room temperature, filtered, washed with ethanol, and dried to obtain the Pt / Co3O4 catalyst.

[0015] In a specific embodiment of the present invention, commercially available cobalt tetroxide can be used. To improve the activity of the obtained catalyst, in a preferred embodiment of the present invention, the preparation method of cobalt tetroxide includes the following steps:

[0016] Cobalt nitrate hexahydrate, urea, and water are mixed and reacted at 160-200℃ for 12-36 hours. The mixture is filtered, washed, and dried to obtain a solid (usually pink). The solid is then calcined at 400-430℃ in air.

[0017] The preferred mass ratio of cobalt nitrate hexahydrate to urea is 1:1 to 1:5. Water is used as the solvent in this cobalt tetroxide preparation method, and the amount used is the conventional amount of solvent. The calcination temperature in the cobalt tetroxide preparation method provided by this invention is a preferred calcination temperature; calcination below 400℃ yields a purple powder, while calcination at excessively high temperatures (e.g., 450℃) results in cobalt tetroxide with lower catalyst activity. The calcination time can be 4-5 hours.

[0018] In the preparation method of cobalt tetroxide according to a specific embodiment of the present invention, the solid after calcination is cooled to room temperature. In a preferred embodiment of the present invention, uniform cooling is used, preferably at a cooling rate of 1-10°C / min. At this cooling rate, the catalyst prepared from the cobalt tetroxide exhibits better activity.

[0019] The Pt / Co3O4 catalyst prepared by the above method has high reactivity, and it can be recycled without significant decrease in reactivity after 7 cycles.

[0020] Another object of the present invention is to provide a Pt / Co3O4 catalyst obtained by the above preparation method.

[0021] Another object of the present invention is to provide the application of the above-described preparation method or the Pt / Co3O4 catalyst obtained by the above-described preparation method in hydrosilylation reactions, particularly in the catalytic preparation of polyether-modified heptamethyltrisiloxane.

[0022] The reaction preferably uses heptamethyltrisiloxane and allyl polyether as raw materials. The Pt / Co3O4 catalyst of this invention requires a small amount, less than 0.1 wt% of the total raw materials (the Pt / Co3O4 catalyst provided by this invention) to effectively achieve good catalytic addition efficiency.

[0023] The novel Pt / Co3O4 catalyst prepared by this invention has simple steps, and the obtained Pt / Co3O4 catalyst is a supported platinum-based catalyst. Compared with catalysts given in the prior art (such as those disclosed in CN202211473009.5 and CN201910266026.3), the catalyst provided by this invention has a small particle size, large specific surface area, is easy to disperse, and has high catalytic efficiency. Using the catalyst of this invention, only a small amount is needed to achieve an effective catalytic effect, with high conversion rate and low production cost. At the same time, the catalyst can be effectively recycled and has good recyclability (no significant decrease in reaction activity after 7 cycles). Attached Figure Description

[0024] Figure 1 The NMR spectrum is shown for the polyether-modified heptamethyltrisiloxane synthesized using the catalyst provided in Example 1. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, "%" in this invention refers to a percentage by mass.

[0027] Example 1

[0028] Accurately weigh 1g of urea and 0.5g of cobalt nitrate hexahydrate, place them in a hydrothermal reactor, add 30mL of distilled water, stir for 2 hours, seal the reactor, place it in an oven at 180℃, and hydrothermally heat for 24 hours. After completion, cool to room temperature, filter, wash, and dry to obtain a pink solid. Grind the pink solid and transfer it to a porcelain boat, calcine it in air at a gas rate of 0.1L / min, a calcination temperature of 400℃, a calcination time of 5 hours, and a heating rate of 2℃ / min. After completion, cool to room temperature at a cooling rate of 5℃ / min to obtain black Co3O4 powder.

[0029] Take 0.3g Co3O4 powder, 0.1g polyvinylpyrrolidone, and 50mL distilled water into a three-necked flask, and stir for 1h under a nitrogen atmosphere. Add 2mL of 0.02mol / L HPtCl6·6H2O isopropanol solution and stir for 0.5h. Heat to 60℃, add 0.2g trisodium citrate, stir for 1h, let stand and cool to room temperature, filter, wash several times with ethanol, and dry to obtain Pt / Co3O4 catalyst.

[0030] 45g of heptamethyltrisiloxane, 80g of allyl polyether with a molecular weight of 400, and 120mg of the Pt / Co3O4 catalyst obtained in Example 1 were placed in a three-necked flask under nitrogen protection. The mixture was heated to 85°C and reacted for 6 hours. After removing low-boiling-point catalysts and filtering to recover the catalyst, polyether-modified heptamethyltrisiloxane was obtained. The NMR spectrum of the obtained polyether-modified heptamethyltrisiloxane is shown below. Figure 1 As shown. The conversion rate in this reaction is 93%. In a specific embodiment of the present invention, the conversion rate = [1 - (total feed amount - amount of product after removing low-boiling point) / feed amount of heptamethyltrisiloxane] * 100%.

[0031] The recovered catalyst was recycled and reused as a catalyst for the above reaction. The catalyst was recycled multiple times, and the conversion results are shown in Table 1 below:

[0032] Table 1

[0033] Loop count 1 2 3 4 5 6 7 Conversion rate 93％ 94％ 94％ 93％ 92％ 92％ 93％

[0034] Example 2

[0035] The Co3O4 powder in this embodiment is the Co3O4 powder from Example 1.

[0036] Take 0.27 g Co3O4 powder, 0.48 g polyvinylpyrrolidone, and 80 mL distilled water into a three-necked flask, and stir for 1 h under a nitrogen atmosphere. Add 1 mL of 0.06 mol / L HPtCl6·6H2O isopropanol solution and stir for 1 h. Heat to 60 °C, add 0.8 g trisodium citrate, stir for 2 h, let stand and cool to room temperature, filter, wash several times with ethanol, and dry to obtain Pt / Co3O4 catalyst.

[0037] 45g of heptamethyltrisiloxane, 80g of allyl polyether with a molecular weight of 400, and 120mg of the Pt / Co3O4 catalyst obtained in Example 2 were placed in a three-necked flask under nitrogen protection. The mixture was heated to 85°C and reacted for 6 hours. After removing low-boiling-point catalysts and filtering to recover the catalyst, polyether-modified heptamethyltrisiloxane was obtained. The conversion rate in this reaction was 92%.

[0038] The recovered catalyst was recycled and reused in the above reaction. The catalyst was recycled multiple times, and the conversion results are shown in Table 2 below:

[0039] Table 2

[0040] Loop count 1 2 3 4 5 6 7 Conversion rate 92％ 93％ 93％ 92％ 91％ 91％ 92％

[0041] Example 3

[0042] The preparation method of this embodiment is the same as that of Embodiment 1, except that commercially available cobalt tetroxide powder is used in this embodiment.

[0043] 45g of heptamethyltrisiloxane, 80g of allyl polyether with a molecular weight of 400, and 120mg of the Pt / Co3O4 catalyst obtained in Example 3 were placed in a three-necked flask under nitrogen protection. The mixture was heated to 85°C and reacted for 6 hours. After removing low-boiling-point catalysts and filtering to recover the catalyst, polyether-modified heptamethyltrisiloxane was obtained. The conversion rate in this reaction was 80%.

[0044] The recovered catalyst was recycled and reused as a catalyst for the above reaction. The catalyst was recycled multiple times, and the conversion results are shown in Table 3 below:

[0045] Table 3

[0046]

[0047]

[0048] Finally, the method of this invention is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. The application of Pt / Co3O4 catalyst in the catalytic preparation of polyether-modified heptamethyltrisiloxane, characterized in that, The preparation method of the Pt / Co3O4 catalyst includes the following steps: Under nitrogen protection, cobalt tetroxide, polyvinylpyrrolidone and water are mixed evenly, and isopropanol chloroplatinate solution is added. Trisodium citrate is added at 50-80℃ and the reaction is carried out for 0.5-2 hours. The concentration of the isopropanol chloroplatinic acid solution is 0.01-0.1 mol / L; The mass ratio of cobalt tetroxide to chloroplatinic acid in the isopropanol chloroplatinic acid solution is 10:1 to 20:

1. The amount of polyvinylpyrrolidone added is 0.1wt%-1wt% of the total amount of raw materials in the system; The molar ratio of trisodium citrate to chloroplatinic acid in the isopropanol chloroplatinic acid solution is (10~90):

1.

2. The application according to claim 1, characterized in that, The preparation method of the cobalt tetroxide includes the following steps: Cobalt nitrate hexahydrate, urea, and water are mixed and reacted at 160-200℃ for 12-36 hours. The mixture is then filtered, washed, dried, and calcined at 400-430℃ in air.

3. The application according to claim 2, characterized in that, The mass ratio of cobalt nitrate hexahydrate to urea is 1:1 to 1:

5.

4. The application according to claim 2, characterized in that, The calcination time is 4-5 hours.

5. The application according to claim 2, characterized in that, The method for preparing cobalt tetroxide further includes cooling the solid after calcination to room temperature, wherein the cooling rate is 1-10℃ / min.

6. The application according to claim 1, characterized in that, The reaction uses heptamethyltrisiloxane and allyl polyether as raw materials.

7. The application according to claim 6, characterized in that, The amount of the Pt / Co3O4 catalyst used is less than 0.1 wt% of the total amount of the raw materials.

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