Catalyst for preparing chlorine through HCl oxidation and preparation method and application thereof

Abstract

The invention discloses a catalyst for preparing chlorine through HCl oxidation and a preparation method and application of the catalyst, the catalyst is an aluminum oxide supported Cu-based catalyst, and the mass ratio of particles with the particle size smaller than 5 micrometers is 0.005-8 wt%. The catalyst has the advantages of simple preparation process, high activity, high stability and the like, and can be used in the technical field of preparation of chlorine through hydrogen chloride oxidation.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing chlorine by hydrogen chloride oxidation, and particularly relates to a catalyst for HCl oxidation to chlorine, a preparation method thereof, and an application thereof. Background Art

[0002] In the production processes of many bulk chemicals such as polyurethane intermediates, polyvinyl chloride, organic chlorine intermediates (chlorobenzene, chloroacetic acid, benzyl chloride, chlorotoluene), epoxy resins, etc., chlorine is often required as a raw material, and a large amount of hydrogen chloride is by-produced. The by-produced hydrogen chloride is difficult to handle. The simplest way to handle the by-produced hydrogen chloride is to directly absorb it with an alkali, but this will produce a large amount of waste brine that is difficult to recycle. The catalytic oxidation of hydrogen chloride to chlorine can not only treat the by-produced hydrogen chloride on a large scale, but also the generated chlorine can continue to be used as a raw material, which is the best solution to achieve nearly 100% chlorine cycle. The key to this solution lies in the development of highly efficient catalysts.

[0003] In the reported literature, catalysts obtained by using transition metals such as gold, ruthenium, chromium, and copper as active components have good activity for the oxidation of hydrogen chloride to chlorine. However, the noble metal gold and ruthenium-based catalysts among them have high costs and high requirements for the purity of reaction raw materials, and it is difficult to directly use them in industrial devices with complex tail gas components. The chromium-based catalyst has high toxicity and causes great environmental pollution. Therefore, the copper-based catalyst has received extensive attention due to its cost advantage and environmental friendliness.

[0004] In order to obtain a copper-based catalyst with high activity and high stability, researchers have conducted in-depth research.

[0005] CN114904561A reports a catalyst obtained by adding arsenic to a copper-based catalyst, modifying the catalyst, and improving the catalyst preparation method. It overcomes the problems that the catalyst used in the fluidized bed reaction process has poor abrasion resistance and the active components are easily peeled off and pulverized during long-term operation, resulting in a decrease in catalyst activity. However, there are multiple impregnation operations in its preparation process, the preparation process is relatively complex, and the production cost of the catalyst is high.

[0006] CN114713250B reports a new catalyst that adds fluorine elements during the catalyst preparation process and uses at least one of CuClF, selectively containing CuF2, and CuCl2 as the active component. The new catalyst has excellent catalytic activity and tolerance stability under high temperature and high acid conditions. However, the introduction of fluorine elements during the catalyst preparation process brings great safety risks to catalyst production.

[0007] CN108097232A reported a catalyst prepared by mixing two different formulations of powders, which has good comprehensive performance and an HCl conversion rate of 85% at a reaction temperature of 350 - 360 °C. However, the preparation process of this catalyst is relatively complex, and the catalyst strength still needs to be further improved.

[0008] Based on the above research background, it is necessary to develop a catalyst with a simple preparation process, high activity, and high stability. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the present invention provides a catalyst for the oxidation of HCl to chlorine and a preparation method. The catalyst has the advantages of a simple preparation process, high activity, high stability, etc., and can be used in the technical field of preparing chlorine by the oxidation of hydrogen chloride.

[0010] During the research on the catalyst for the oxidation of HCl to chlorine, the inventors unexpectedly found that for a Cu-based catalyst with alumina as the carrier, its particle size distribution affects the activity, especially the content of fine particles has a significant impact. Further discovery shows that by adjusting the content of fine particles in the catalyst within a certain range, a catalyst with higher activity and better stability can be obtained.

[0011] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0012] The present invention provides a catalyst for the oxidation of HCl to chlorine, which is an alumina-supported Cu-based catalyst, wherein the mass ratio of particles with a particle size < 5 μm is 0.005 - 8 wt%, such as 0.005, 0.01, 0.05, 0.1, 0.5, 1, 2, 4, 6, 8 wt%, preferably 0.005 - 5 wt%, more preferably 0.01 - 4 wt%.

[0013] The alumina-supported Cu-based catalyst of the present invention is further loaded with an alkali metal element, a rare earth metal element, and optionally other metal elements;

[0014] Preferably, the alkali metal element is selected from at least one of potassium, sodium, and lithium;

[0015] Preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, samarium, and europium, more preferably at least one of cerium, lanthanum, and praseodymium;

[0016] Preferably, the other metal element is selected from at least one of magnesium, iron, calcium, titanium, zinc, cobalt, and nickel, more preferably at least one of magnesium, calcium, zinc, and iron.

[0017] For the catalyst for HCl oxidation to produce chlorine gas according to the present invention, based on the total mass of the catalyst being 100%, the mass content of the Cu element is 2-18%, such as 2, 4, 6, 8, 10, 12, 14, 16, 18%, preferably 3-15%, and more preferably 3.5-11%; the Cu element is supported on the alumina support in the form of an oxide or a copper salt such as copper chloride;

[0018] Preferably, the mass content of the alkali metal element is 0.5-8%, such as 0.5, 1, 2, 4, 6, 8%, preferably 1-7%, and more preferably 2-6%; the mass content of the rare earth metal element is 0.5-12%, such as 0.5, 2, 4, 6, 8, 10, 12%, preferably 1-11%, and more preferably 2-8.5%; the mass percentage of the other metal element is 0-8%, such as 0, 0.1, 0.5, 1, 2, 4, 6, 8%, preferably 0.5-7%, and more preferably 1-5%; the alkali metal element, the rare earth metal element, and the other elements are all supported on the alumina support in the form of an oxide or a metal salt such as a chloride.

[0019] For the catalyst for HCl oxidation to produce chlorine gas according to the present invention, its average particle size is 40-80 μm, such as 40, 50, 60, 70, 80 μm, preferably 45-75 μm.

[0020] For the catalyst for HCl oxidation to produce chlorine gas according to the present invention, its loose bulk density is 0.5-1.4 g / ml, such as 0.5, 0.6, 0.8, 1.0, 1.2, 1.4 g / ml, preferably 0.7-1.35 g / ml.

[0021] The present invention also provides a preparation method of the above-mentioned catalyst for HCl oxidation to produce chlorine gas, and the steps include:

[0022] (1) Crushing the alumina support raw material to obtain solid powder with an average particle size of 1-5 μm, dispersing it in water, stirring and mixing evenly, and then adding an acidic liquid to obtain a slurry support;

[0023] (2) Mixing the mixed salt solution containing copper, alkali metal element, rare earth metal element, and optionally other metal elements evenly with the slurry support in step (1) to obtain a paste;

[0024] (3) Drying and roasting the paste in step (2), and then regulating the particle size of the roasted solid particles so that the proportion of particles with a particle size <5 μm is 0.005-8 wt%, such as 0.005, 0.01, 0.05, 0.1, 0.5, 1, 2, 4, 6, 8 wt%, to prepare the catalyst for HCl oxidation to produce chlorine gas.

[0025] In the present invention, the alumina support raw material in step (1) is selected from at least one of alumina and alumina hydrate.

[0026] In the present invention, the concentration of the solid powder dispersed in water in step (1) is 13-55 wt%, such as 13, 15, 25, 35, 45, 55 wt%.

[0027] In the present invention, for the acidic liquid in step (1), the acid therein is selected from at least one of nitric acid, phosphoric acid, and hydrochloric acid;

[0028] Preferably, the acidic liquid is an aqueous solution of an acid, and the concentration is 30-68 wt%, such as 30, 40, 50, 60, 68 wt%;

[0029] Preferably, the mass ratio of the acidic liquid to the solid powder is 0.05-0.2:1, such as 0.05:1, 0.1:1, 0.15:1, 0.2:1.

[0030] In the present invention, for the mixed salt solution containing copper, alkali metal elements, rare earth metal elements, and optionally other metal elements in step (2), the salt therein is selected from at least one of nitrates, chlorides, and carbonates;

[0031] Preferably, in the mixed salt solution, the concentration of the copper salt is 2-13 wt%, such as 2, 4, 6, 8, 10, 13 wt%; the concentration of the alkali metal element salt is 0.5-6 wt%, such as 0.5, 1, 2, 4, 6 wt%; the concentration of the rare earth metal element salt is 0.5-10 wt%, such as 0.5, 1, 2, 4, 6, 8, 10 wt%; the concentration of the optionally other metal element salt is 0-6 wt%, such as 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6 wt%, preferably 2-6 wt%;

[0032] Preferably, the alkali metal element is selected from at least one of potassium, sodium, and lithium;

[0033] Preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, samarium, and europium, more preferably at least one of cerium, lanthanum, and praseodymium;

[0034] Preferably, the other metal element is selected from at least one of magnesium, iron, calcium, titanium, zinc, cobalt, and nickel, more preferably at least one of magnesium, calcium, zinc, and iron.

[0035] In the present invention, the mass ratio of the mixed salt solution containing copper, alkali metal elements, rare earth metal elements, and optionally other metal elements in step (2) to the slurry carrier in step (1) is 0.4-4:1, such as 0.4:1, 1:1, 2:1, 3:1, 4:1.

[0036] In the present invention, the roasting in step (3) is carried out in an air atmosphere;

[0037] For the roasting, the temperature is 450 - 680 °C, such as 450, 500, 550, 600, 650, 680 °C, and the time is 1 - 7.5 h, such as 1, 3, 5, 7, 7.5 h.

[0038] In the present invention, when regulating the particle size of the solid particles after roasting in step (3), the regulating means is a conventional operation in the art, and it is only necessary to make the catalyst meet the particle size distribution requirements described in the present invention. There are no special requirements in the present invention. The methods include but are not limited to conventional screening, partial mixing, ball milling, crushing, blending after grinding, or controlling process parameters during drying, etc.

[0039] The catalyst described in the present invention is applicable to the field of hydrogen chloride oxidation to chlorine, especially the fluidized bed process route.

[0040] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0041] Through the alumina-supported Cu-based catalyst of the present invention, by controlling the proportion of particles with a particle size < 5 μm in the catalyst particles, the catalyst has the characteristics of high activity and high stability during the reaction of hydrogen chloride oxidation to chlorine. Specific Embodiments

[0042] In order to better understand the technical solution of the present invention, the content of the present invention will be further elaborated below in combination with embodiments, but the content of the present invention is not limited to the following embodiments only.

[0043] The main raw material sources in each embodiment and comparative example of the present invention are as follows:

[0044] Aluminum oxide was purchased from Zibo Chaoke Aluminum Oxide Materials Co., Ltd.;

[0045] Aluminum oxide hydrate was purchased from Shanxi Juhua New Materials Technology Co., Ltd.;

[0046] Unless otherwise specified, other raw materials and reagents were obtained through commercial channels on the market.

[0047] The following is the method for testing the activity of the hydrogen chloride oxidation catalyst used in the examples or comparative examples:

[0048] Catalyst Performance Testing Method

[0049] 1 kg of catalyst was placed in a fluidized bed reactor with an inner diameter of 40 mm and a height of 1700 mm. Using hydrogen chloride / oxygen = 2 / 1 in molar ratio as raw materials, the reaction of hydrogen chloride oxidation to chlorine was carried out under the conditions of HCl mass space velocity of 0.40 h-1, reaction temperature of 340 - 350 °C, and reaction pressure of 0.3 MPa (absolute pressure). During the catalyst reaction performance test, samples were taken 3 times every 24 h for analysis, and the average conversion rate during the whole operation process was taken as the conversion rate of the catalyst for hydrogen chloride.

[0050] 2. Calculation method of hydrogen chloride conversion rate:

[0051] After the above reaction of hydrogen chloride oxidation to chlorine ended, the product gas was introduced into an aqueous potassium iodide solution with a mass fraction of 15% for absorption. The iodine in the absorption solution was titrated with an aqueous sodium thiosulfate solution of 0.1 mol / L, and the residual HCl amount in the absorption solution was titrated with an aqueous sodium hydroxide solution of 0.1 mol / L, so as to calculate the amount of chlorine generated and the amount of residual HCl.

[0052] 3. Elemental analysis of the catalyst sample was carried out by ICP test.

[0053] 4. Particle size and its distribution test method: Particle size analysis of the catalyst sample was carried out using a laser particle size analyzer.

[0054] 5. Loose bulk density: Loose bulk density analysis of the catalyst sample was carried out using a loose density tester.

[0055] Example 1

[0056] (1) Catalyst preparation:

[0057] 1600 g of alumina hydrate was crushed to obtain a solid powder with an average particle size of 1 - 5 μm, dispersed in 7811.8 g of water, stirred and mixed evenly, and then 288 g of a nitric acid aqueous solution with a concentration of 65 wt% was added to obtain 9.699 kg of a slurry carrier;

[0058] 181.83 g of copper chloride, 86.72 g of potassium chloride, 76.25 g of sodium chloride, 93.37 g of praseodymium nitrate, 141.4 g of lanthanum nitrate, 114.8 g of cerium chloride, 59.24 g of magnesium chloride, 68.81 g of zinc nitrate were mixed with 4000 g of water to prepare 4.8225 kg of a mixed brine solution, and mixed evenly with 9.699 kg of the slurry carrier in step (1) to obtain a paste;

[0059] Then it is spray-dried and calcined at 480 °C for 6 h in an air atmosphere. The particle size is adjusted by ball milling, screening, etc. to obtain a catalyst for HCl oxidation to chlorine gas. The proportion of particles with a particle size <5 μm is 0.1 wt%, the average particle size is 45 μm, and the loose bulk density is 1.25 g / ml.

[0060] For the prepared catalyst, using alumina as the carrier and taking the total mass of the catalyst as 100%, the content of copper element loaded is 4.5 wt%, the alkali metal is potassium element with a content of 3% and sodium element with a content of 2%, the rare earth metal is praseodymium element with a content of 2%, lanthanum element with a content of 3%, and cerium element with a content of 3%. The other active metals are magnesium element with a content of 1% and zinc element with a content of 1%. Each element is loaded on the alumina carrier in the form of oxide or chloride.

[0061] (2) Catalyst performance test:

[0062] According to the above method for catalyst activity evaluation, the HCl conversion rate is 86.1% after continuous reaction for 100 h, and the HCl conversion rate is 85.7% after continuous reaction for 3000 h.

[0063] Example 2

[0064] (1) Catalyst preparation:

[0065] 1600 g of alumina hydrate is crushed to obtain a solid powder with an average particle size of 1 - 5 μm, dispersed in 1600 g of water, stirred and mixed evenly, and then 96 g of hydrochloric acid aqueous solution with a concentration of 32 wt% is added to obtain 3.296 kg of a slurry carrier.

[0066] 543.7 g of copper nitrate, 27.53 g of potassium chloride, 36.31 g of sodium chloride, 89.8 g of lanthanum nitrate, 36.4 g of cerium chloride, 56.42 g of magnesium chloride, 59.08 g of calcium nitrate, 98.3 g of zinc nitrate, 104.2 g of iron nitrate are mixed with 9000 g of water to prepare 10.051 kg of a mixed brine solution, which is mixed evenly with 3.296 kg of the slurry carrier in step (1) to obtain a paste.

[0067] Then it is spray-dried and calcined at 650 °C for 2 h in an air atmosphere. The particle size is adjusted by ball milling, screening, etc. to obtain a catalyst for HCl oxidation to chlorine gas. The proportion of particles with a particle size <5 μm is 4 wt%, the average particle size is 70 μm, and the loose bulk density is 0.7 g / ml.

[0068] The prepared catalyst uses alumina as the carrier. Based on 100% of the total mass of the catalyst, the copper element content is 10 wt%, the alkali metal potassium element content is 1%, the sodium element content is 1%, the rare earth metal lanthanum element content is 2%, the cerium element content is 1%, and the other active metals magnesium element content is 1%, calcium element content is 1%, zinc element content is 1.5%, and iron element content is 1%. Each element is loaded on the alumina carrier in the form of oxide or chloride.

[0069] (2) Catalyst performance test:

[0070] According to the above method for catalyst activity evaluation, the HCl conversion rate is 84.9% after continuous reaction for 100 h, and the HCl conversion rate is 83.9% after continuous reaction for 3000 h.

[0071] Example 3

[0072] (1) Catalyst preparation:

[0073] 1600 g of alumina hydrate is crushed to obtain solid powder with an average particle size of 1 - 5 μm, dispersed in 2971.4 g of water, stirred and mixed evenly, and then 160 g of nitric acid aqueous solution with a concentration of 55 wt% is added to obtain 4.731 kg of slurry carrier.

[0074] 462.13 g of copper nitrate, 29.25 g of potassium chloride, 135 g of sodium chloride, 38.6 g of praseodymium chloride, 116.75 g of lanthanum chloride, 47.42 g of cerium nitrate, 59.94 g of magnesium chloride, 42.46 g of calcium chloride, 74.05 g of iron nitrate are mixed with 3000 g of water to prepare 4.005 kg of mixed brine solution, and mixed evenly with 4.731 kg of the slurry carrier in step (1) to obtain a paste.

[0075] Then it is spray-dried and calcined at 550 °C for 4 h in an air atmosphere, and the particle size is adjusted by ball milling, screening, etc. to obtain a catalyst for HCl oxidation to chlorine gas. The proportion of particles with a particle size < 5 μm is 2.8 wt%, the average particle size is 65 μm, and the loose bulk density is 0.85 g / ml.

[0076] The prepared catalyst uses alumina as the carrier. Based on 100% of the total mass of the catalyst, the copper element content is 8 wt%, the alkali metal potassium element content is 1%, the sodium element content is 3.5%, the rare earth metal lanthanum element content is 3%, the cerium element content is 1%, the praseodymium element content is 1%, and the other active metals magnesium element content is 1%, calcium element content is 1%, and iron element content is 1%. Each element is loaded on the alumina carrier in the form of oxide or chloride.

[0077] (2) Catalyst performance test:

[0078] The catalyst activity was evaluated by the above method. After continuous reaction for 100 h, the HCl conversion rate was 85.3%, and after continuous reaction for 3000 h, the HCl conversion rate was 84.8%.

[0079] Comparative Example 1

[0080] (1) Catalyst preparation:

[0081] Referring to Example 1, the difference is only that: after calcination, the proportion of particles with a particle size <5 μm was adjusted to 0%, the average particle size was 45 μm, and the loose bulk density was 1.25 g / ml.

[0082] (2) Catalyst performance test:

[0083] The catalyst activity was evaluated by the above method. After continuous reaction for 100 h, the HCl conversion rate was 78.6%, and after continuous reaction for 3000 h, the HCl conversion rate was 75.6%.

[0084] Comparative Example 2

[0085] Referring to Example 1, the difference is only that: after calcination, the proportion of particles with a particle size <5 μm was adjusted to 9 wt%, the average particle size was 44.5 μm, and the loose bulk density was 1.28 g / ml.

[0086] (2) Catalyst performance test:

[0087] The catalyst activity was evaluated by the above method. After continuous reaction for 100 h, the HCl conversion rate was 76.7%, and after continuous reaction for 3000 h, the HCl conversion rate was 73.2%.

Claims

1. A catalyst for the oxidation of HCl to chlorine, characterized in that, The catalyst is an alumina-supported Cu-based catalyst, wherein the mass fraction of particles with a particle size < 5 μm is 0.005 - 8 wt%, preferably 0.005 - 5 wt%, and more preferably 0.01 - 4 wt%.

2. The catalyst for oxidizing HCl to chlorine according to claim 1, characterized in that, The alumina-supported Cu-based catalyst further supports an alkali metal element, a rare earth metal element, and optionally other metal elements; Preferably, the alkali metal element is selected from at least one of potassium, sodium, and lithium; Preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, samarium, and europium, and more preferably at least one of cerium, lanthanum, and praseodymium; Preferably, the other metal element is selected from at least one of magnesium, iron, calcium, titanium, zinc, cobalt, and nickel, and more preferably at least one of magnesium, calcium, zinc, and iron.

3. The catalyst for HCl oxidation to chlorine according to claim 2, wherein Based on 100% of the total mass of the catalyst, the mass content of the Cu element is 2 - 18%, preferably 3 - 15%, and more preferably 3.5 - 11%; Preferably, the mass content of the alkali metal element is 0.5 - 8%, preferably 1 - 7%, and more preferably 2 - 6%; the mass content of the rare earth metal element is 0.5 - 12%, preferably 1 - 11%, and more preferably 2 - 8.5%; the mass percentage of the other metal element is 0 - 8%, preferably 0.5 - 7%, and more preferably 1 - 5%.

4. The catalyst for the oxidation of HCl to chlorine according to any one of claims 1-3, characterized in that The average particle size is 40 - 80 μm, preferably 45 - 75 μm; and / or The loose bulk density is 0.5 - 1.4 g / ml, preferably 0.7 - 1.35 g / ml.

5. The preparation method of the catalyst for HCl oxidation to chlorine according to any one of claims 1-4, characterized in that the steps It includes: (1) Crushing the alumina carrier raw material to obtain a solid powder with an average particle size of 1 - 5 μm, dispersing it in water, stirring and mixing evenly, and then adding an acidic liquid to obtain a slurry carrier; (2) Mixing a mixed salt solution containing copper, an alkali metal element, a rare earth metal element, and optionally other metal elements evenly with the slurry carrier in step (1) to obtain a paste; (3) Drying and roasting the paste in step (2), and then adjusting the particle size of the roasted solid particles so that the proportion of particles with a particle size < 5 μm is 0.005 - 8 wt% to prepare a catalyst for the oxidation of HCl to chlorine.

6. The preparation method according to claim 5, characterized in that, The alumina carrier raw material in step (1) is selected from at least one of alumina and alumina hydrate; and / or The concentration of the solid powder dispersed in water in step (1) is 13 - 55 wt%; and / or The acidic liquid in step (1), wherein the acid is selected from at least one of nitric acid, phosphoric acid, and hydrochloric acid; Preferably, the acidic liquid is an aqueous solution of an acid with a concentration of 30 - 68 wt%; Preferably, the mass ratio of the acidic liquid to the solid powder is 0.05 - 0.2:

1.

7. The preparation method according to claim 5, wherein The mixed salt solution containing copper, an alkali metal element, a rare earth metal element, and optionally other metal elements in step (2), wherein the salt is selected from at least one of nitrates, chlorides, and carbonates; Preferably, in the mixed salt solution, the concentration of the copper salt is 2 - 13 wt%; the concentration of the alkali metal element salt is 0.5 - 6 wt%; the concentration of the rare earth metal element salt is 0.5 - 10 wt%; the concentration of the other metal element salt is 0 - 6 wt%, preferably 2 - 6 wt%. Preferably, the alkali metal element is selected from at least one of potassium, sodium, and lithium; Preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, samarium, and europium, more preferably at least one of cerium, lanthanum, and praseodymium; Preferably, the other metal element is selected from at least one of magnesium, iron, calcium, titanium, zinc, cobalt, and nickel, more preferably at least one of magnesium, calcium, zinc, and iron.

8. The preparation method according to claim 5, characterized in that, The mixing mass ratio of the mixed salt solution containing copper, alkali metal element, rare earth metal element, and optionally other metal elements in step (2) to the slurry carrier in step (1) is 0.4 - 4:

1.

9. The preparation method according to claim 5, characterized in that, The roasting in step (3) is carried out in an air atmosphere; For the roasting, the temperature is 450 - 680 °C and the time is 1 - 7.5 h.

10. The application of the catalyst for HCl oxidation to chlorine gas described in any one of claims 1 - 4 or the catalyst for HCl oxidation to chlorine gas prepared by the method described in any one of claims 5 - 9 in the field of HCl oxidation to chlorine gas is particularly suitable for the fluidized bed process route.