A method for hydrogenating indigo to indigo white

Abstract

The present invention relates to the field of fine chemical technology, and in particular to a method for hydrogenating indigo to form indigo white; the method comprising, in an alkaline environment, hydrogenating and reducing indigo to form hydrogenated indigo; wherein, a single-atom platinum-carbon catalyst is used, in which platinum metal is loaded on a carbon support in the form of a single atom or a cluster; and the platinum content in the platinum-carbon catalyst is 0.2-10wt%. The present invention adopts a catalytic hydrogenation reduction method to reduce indigo to hydrogenated indigo, which can ensure the continuous production of indigo leuco-body, has high efficiency, short reduction time, no wastewater during the production process, and effectively reduces environmental pollution; relative to the use of a sulfur-containing reducing agent, it has greater production flexibility, effectively reduces the amount of wastewater in the dyeing process, reduces the cost of wastewater treatment, saves resources, and protects the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, in particular to a method for hydrogenating indigo to produce indigo white. Background Art

[0002] Indigo is a vat dye widely used to color fabrics such as cotton, linen, and viscose. Before dyeing, vat dyes must be reduced to their leuco form, which is then impregnated and oxidized to achieve the desired color.

[0003] Currently, the commonly used indigo reduction methods include fermentation, hydrosulfite method, thiourea dioxide method, and electrochemical reduction method.

[0004] Patent CN103842448A discloses a method for reducing indigo using yeast. Yeast is sensitive to temperature and the pH of the reducing solution and is only effective at 25-35°C and pH <11.

[0005] Patent CN104088173A discloses a method for dyeing polyester-cotton fabric with indigo dye in a homochromatic manner. Indigo is reduced with sodium hydrosulfite under alkaline conditions of 40-80°C, and then added to the fabric for dyeing. The addition of sodium hydrosulfite in this system causes environmental pollution due to sulfur-containing substances, which increases the difficulty of wastewater treatment.

[0006] Patent CN104294671A discloses a reducing agent for vat dyeing, which contains 5-10% thiourea dioxide, 5-30% sodium hydrosulfite, 10-40% reducing sugars, and 20-50% salts. The reducing agent of this system is superior to sodium hydrosulfite, and the leuco form after reduction has a longer existence time. However, the addition of sulfur-containing substances will still cause certain pollution to the environment.

[0007] The catalytic hydrogenation method is to generate free hydrogen on the catalyst surface by hydrogen gas, which directly reacts with indigo in the reaction system, converting the hydroxyl group on the indigo molecule into a carbonyl group, and generating a leuco-sodium salt in an alkaline environment.

[0008] Patent CN1120357 discloses a method for preparing leuco indigo using Raney nickel as a catalyst for the catalytic hydrogenation of indigo, and dyeing fiber-containing textile materials. During the dyeing process, the oxidized leuco indigo is electrochemically reduced using a dielectric system, which increases the source of wastewater.

[0009] However, there are many disadvantages in using Raney nickel catalysts. Raney nickel catalysts are extremely unstable and oxidize and burn in the air. The chemical composition of Raney nickel is complex, and the comprehensive recovery of waste Raney nickel is low and the cost is high. Summary of the Invention

[0010] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for hydrogenating indigo to indigo white.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for hydrogenating indigo to indigo white is designed; the method comprises: in an alkaline environment, hydrogenating indigo to form hydrogenated indigo;

[0013] Among them, a single-atom platinum-carbon catalyst is used, in which the platinum metal is supported on a carbon support in the form of a single atom or cluster;

[0014] The platinum content in the platinum-carbon catalyst is 0.2-10 wt%.

[0015] Preferably, the platinum content in the platinum carbon is 0.5-2 wt%.

[0016] Preferably, the amount of catalyst used is 0.2-1.0 wt%.

[0017] Preferably, the alkaline environment is an alkaline aqueous solution environment, and the alkaline aqueous solution is obtained by adding a metal hydroxide salt into water.

[0018] Preferably, the alkaline aqueous solution is selected from a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or a mixed solution of the two alkalis.

[0019] Preferably, hydrogen is used in the hydrogenation process, and the hydrogen pressure is 0.1 MPa-10 MPa.

[0020] Preferably, the hydrogen pressure is 0.2-2 MPa.

[0021] Preferably, after the reaction is completed, the solid and liquid are separated to obtain a liquid product, and the solid obtained by separation is a catalyst.

[0022] Preferably, the recovered catalyst can be returned to the aforementioned reaction system after cleaning and reused as a catalyst.

[0023] Preferably, the liquid product is a solution containing hydrogenated indigo, and the content of hydrogenated indigo in the solution is 5-40%.

[0024] The present invention provides a method for hydrogenating indigo to indigo white, which has the following beneficial effects: the method uses a catalytic hydrogenation reduction method to reduce indigo to hydrogenated indigo, can ensure the continuous production of indigo leuco form, has high efficiency, short reduction time, and no wastewater during the production process, effectively reducing environmental pollution;

[0025] Compared with the use of sulfur-containing reducing agents, it has greater production flexibility, effectively reduces the amount of wastewater in the dyeing process, reduces the cost of wastewater treatment, saves resources and protects the environment. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] A method for hydrogenating indigo to indigo white; the method comprises, in an alkaline environment, hydrogenating and reducing indigo to hydrogenated indigo;

[0028] Among them, a single-atom platinum-carbon catalyst is used, in which the platinum metal is supported on a carbon support in the form of a single atom or cluster;

[0029] The platinum content in the platinum-carbon catalyst is 0.2-10 wt%.

[0030] The platinum content in the platinum carbon is 0.5-2wt%.

[0031] The amount of catalyst used is 0.2-1.0 wt%.

[0032] The alkaline environment is an alkaline aqueous solution environment, and the alkaline aqueous solution is obtained by adding a metal hydroxide salt into water.

[0033] The alkaline aqueous solution is selected from a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or a mixed solution of the two alkalis.

[0034] Hydrogen is used in the hydrogenation process, and the hydrogen pressure is 0.1Mpa-10Mpa.

[0035] The hydrogen pressure is 0.2-2 MPa.

[0036] After the reaction is completed, the solid and liquid are separated to obtain a liquid product, and the solid obtained by separation is a catalyst.

[0037] The recovered catalyst can be returned to the aforementioned reaction system after cleaning and reused as a catalyst.

[0038] The liquid product is a solution containing hydrogenated indigo, and the content of hydrogenated indigo in the solution is 5-40%.

[0039] The catalyst of the present invention uses a 10% platinum-carbon catalyst, and two control groups are set up. The types of catalysts are Raney nickel and 1% platinum-carbon catalyst respectively. The test results and data are shown in Table 1:

[0040] The present invention: The catalyst uses 10% platinum carbon as the catalyst:

[0041] In a 350 ml reactor, 7.5 g of flaky sodium hydroxide, 100 ml of water, 0.015 g of a 10% platinum carbon catalyst, and 25 g of powdered indigo raw material were added in sequence. The atmosphere was replaced with nitrogen three times and then with hydrogen three times. The reaction temperature was 85 ° C, the hydrogen pressure was 0.5 MPa, the reaction time was 6 hours, and the reaction was completed.

[0042] Control group 1: using Raney nickel as catalyst;

[0043] In a 350 ml reactor, 7.5 g of flaky sodium hydroxide, 100 ml of water, 1.25 g of Raney nickel, and 25 g of powdered indigo raw material were added in sequence. The atmosphere was replaced with nitrogen three times and then with hydrogen three times. The reaction temperature was 85 ° C, the hydrogen pressure was 0.5 MPa, and the reaction time was 12 hours. The reaction was completed.

[0044] Control group 2: 1% platinum carbon was used as a catalyst;

[0045] In a 350 ml reactor, 7.5 g of flaky sodium hydroxide, 100 ml of water, 0.15 g of 1% platinum carbon catalyst, and 25 g of powdered indigo raw material were added in sequence. The atmosphere was replaced with nitrogen three times and then with hydrogen three times. The reaction temperature was 85 ° C, the hydrogen pressure was 0.5 MPa, the reaction time was 30 hours, and the reaction was completed.

[0046] Table 1: Test results

[0047]

[0048] Compared with nanocatalysts, the present invention shows that single-atom catalysts have better catalytic performance and lower usage costs at a low noble metal usage, and have high industrial application prospects.

[0049] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for hydrogenating indigo to indigo white, characterized in that: The method comprises, in an alkaline environment, hydrogenating and reducing indigo to form hydrogenated indigo; Among them, a single-atom platinum-carbon catalyst is used, in which the platinum metal is supported on a carbon support in the form of a single atom or cluster; The platinum content in the platinum-carbon catalyst is 0.2-10 wt %.

2. The method for hydrogenating indigo to indigo white according to claim 1, wherein: The platinum content in platinum carbon is 0.5-2wt%.

3. The method for hydrogenating indigo to indigo white according to claim 2, wherein: in, The amount of catalyst used is 0.2-1.0wt%.

4. The method for hydrogenating indigo to indigo white according to claim 3, wherein: The alkaline environment is an alkaline aqueous solution environment, and the alkaline aqueous solution is obtained by adding a metal hydroxide salt into water.

5. The method for hydrogenating indigo to indigo white according to claim 4, wherein: The alkaline aqueous solution is selected from a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or a mixed solution of the two alkalis.

6. The method for hydrogenating indigo to indigo white according to claim 5, characterized in that: Hydrogen is used in the hydrogenation process, and the hydrogen pressure is 0.1MPa-10MPa.

7. The method for hydrogenating indigo to indigo white according to claim 6, characterized in that: The hydrogen pressure is 0.2-2MPa.

8. The method for hydrogenating indigo to indigo white according to claim 7, characterized in that: After the hydrogenation reduction is completed, the solid and liquid are separated to obtain a liquid product, and the solid obtained by separation is a catalyst.

9. The method for hydrogenating indigo to indigo white according to claim 8, characterized in that: The separated catalyst can be returned to the aforementioned reaction system after cleaning and reused as a catalyst.

10. The method for hydrogenating indigo to indigo white according to claim 9, characterized in that: The liquid product is a solution containing hydrogenated indigo, and the content of hydrogenated indigo in the solution is 5-40%.

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