A catalyst for hcl oxidation reaction, its preparation method and use
By introducing carboxylic acid groups onto the surface of the catalyst support and preparing a composite oxide support using the sol-gel method, the problem of poor binding of the active components of the catalyst was solved, achieving a highly efficient conversion of hydrogen chloride to chlorine gas and improving the stability and activity of the catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WANHUA CHEM GRP CO LTD
- Filing Date
- 2023-12-15
- Publication Date
- 2026-07-10
AI Technical Summary
Existing catalysts suffer from incomplete metal loading, low dispersion, and poor bonding between active components and the support during the conversion of hydrogen chloride to chlorine, resulting in insufficient activity and stability. Catalysts prepared by traditional impregnation methods are prone to sintering during long-term reactions and cannot maintain high conversion rates.
A composite oxide support was prepared by the sol-gel method, and carboxylic acid groups were introduced on its surface. Metal salts were then loaded by impregnation. The anchoring effect of the carboxylic acid groups was used to improve the binding strength of the metal active components, prevent metal loss, and enhance the stability of the catalyst.
The catalyst's reactivity and stability were improved, achieving a high conversion rate of hydrogen chloride to chlorine. The catalyst maintained good activity during long-term operation, reducing metal loss and sintering.
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a catalyst for producing chlorine from hydrogen chloride, its preparation method, and its application. Background Technology
[0002] The development of the chlor-alkali industry generates a large amount of hydrogen chloride as a byproduct. Neutralizing and discharging this byproduct would waste a significant amount of alkaline solution and pollute the environment. If the byproduct hydrogen chloride could be converted into chlorine gas, it would turn waste into treasure, generating economic benefits while simultaneously solving environmental problems.
[0003] Currently, the industry uses electrolysis, catalytic oxidation, and direct oxidation technologies to convert hydrogen chloride into chlorine gas, thereby achieving the recycling of chlorine. Electrolysis suffers from drawbacks such as high energy consumption, low chlorine purity, and short electrode lifespan. Direct oxidation faces challenges such as difficult wastewater treatment and incomplete hydrogen chloride conversion. Catalytic oxidation, using oxygen to oxidize hydrogen chloride and produce chlorine gas under the action of a catalyst, is a method with low energy consumption and simple operation, and is currently widely used in industrial applications. Therefore, developing highly active and stable catalytic oxidation catalysts is of great significance.
[0004] Catalysts with the same chemical composition can exhibit significant differences in performance. This is due not only to variations in preparation methods and conditions but also to differences in the catalyst's microstructure, resulting in substantial differences in activity and stability. Traditional impregnation methods for preparing catalysts suffer from incomplete metal loading, low dispersion, and poor bonding between the active component and the support, ultimately affecting performance release. CN1272238C uses rutile titanium dioxide and alumina as supports to impregnate and load Ru-based catalysts; however, these catalysts exhibit poor stability, requiring temperature increases to maintain conversion during the reaction. CN1182717A, a catalyst prepared by loading Ru and Si onto TiO2, demonstrates superior reaction performance at low temperatures. However, prolonged exothermic reactions lead to sintering of the active component, preventing the maintenance of high conversion rates over extended periods. Therefore, there is a need to develop catalysts with high activity and good stability for the production of chlorine from hydrogen chloride. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a catalyst for HCl oxidation and its preparation method. The resulting catalyst exhibits high reactivity and good stability. By impregnating a noble metal onto a support containing carboxylic acid groups, the carboxylic acid groups on the support surface have a strong anchoring effect on metal ions, facilitating the adsorption of active components on the support. Simultaneously, the strong chemical bond energies also increase the stability of the catalyst during operation.
[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a catalyst for HCl oxidation includes the following steps:
[0007] Step 1: The composite oxide support is prepared by sol-gel method. Two of the titanium source, aluminum source and silicon source are dissolved in the first alcohol solvent, and then the second alcohol solvent, water and carboxylic acid mixture are added dropwise. The mixture is stirred, allowed to stand and age, dried and then calcined in ozone atmosphere to obtain the oxide support.
[0008] Step 2: The metal salt is impregnated onto the oxide support using an impregnation method, and then dried and calcined to obtain the desired catalyst.
[0009] As a preferred embodiment, a method for preparing a catalyst for HCl oxidation includes the following steps:
[0010] Step 1: The composite oxide support is prepared by sol-gel method. Two of the titanium source, aluminum source and silicon source are dissolved in a first alcohol solvent such as methanol, ethanol, isopropanol, etc. at a stoichiometric ratio (1 to 3:1). Then, a second alcohol solvent, water and carboxylic acid mixture (volume ratio of 10 to 5:3 to 5:1) are added dropwise. The mixture is stirred for 3 to 7 hours, allowed to stand and age for 8 to 12 hours, dried at 80 to 100°C for 2 to 5 hours, and then calcined in an oven at 200 to 300°C under an ozone atmosphere for 12 to 20 hours to obtain the oxide support.
[0011] Step 2: The metal salt is impregnated onto the oxide support using the impregnation method, dried at 80-100℃ for 2-5 hours, heat-treated for 2-5 hours, and then calcined at 250-450℃ for 12-24 hours to obtain the desired catalyst.
[0012] In step two, after the metal ions are anchored, the carboxylic acid groups on the oxide support can be removed by low-temperature heat treatment at a temperature of 120–180°C. This heat treatment typically occurs after the drying step.
[0013] Preferably, the selected metal salt is a soluble salt of ruthenium, copper, chromium, or bismuth, preferably one or more of chloride, sulfate, or nitrate, with a metal loading of 0.5–5 wt%. The titanium source is one or two of tetrabutyl titanate and titanium tetrachloride, the silicon source is one or two of methyl orthosilicate and tetraethyl orthosilicate, and the aluminum source is one or two of aluminum isopropoxide and aluminum sec-butoxide.
[0014] Preferably, in step one, the carboxylic acid is one or more of formic acid, acetic acid, peroxy acid, malonic acid, benzoic acid, and succinic acid.
[0015] The volume ratio of the mixture of the second alcohol solvent, water, and carboxylic acid to the first alcohol solvent is 1:3 to 8.
[0016] Preferably, in step one, the alcohol solvent added is an alcohol corresponding to a carboxylic acid.
[0017] Preferably, the catalyst prepared by the present invention has the following characteristics: metal loading of 0.5-5 wt%, the support is any two of Al2O3, SiO2, and TiO2; the mass ratio of the composite oxide support based on the metal is 1-3:1, and the metal is selected from one or more of ruthenium, copper, chromium, and bismuth; and it has good catalytic performance and stability.
[0018] In a second aspect of the invention, the catalyst is used in the catalytic oxidation of hydrogen chloride to chlorine, at a reaction temperature of 250°C to 420°C, a hydrogen chloride to oxygen volume ratio of 1:2 to 4:1, and a space velocity of 0.5 to 0.8 h⁻¹. -1 The reaction pressure is 1 to 2.5 atm.
[0019] The positive effects of this invention:
[0020] 1. The catalyst preparation method of the present invention introduces carboxylic acid groups on the surface of the support oxide, which can anchor the metal active component during the impregnation process, avoid metal loss, increase the surface active sites, and improve the reaction activity.
[0021] 2. The presence of carboxylic acid groups on the support surface increases the bond energy between the metal active component and the oxide support, thereby improving the stability of the catalyst. Detailed Implementation
[0022] The following examples illustrate the effects of this catalyst. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0023] The examples used HCl and O2 as reactants to evaluate the catalytic performance of the prepared catalyst, wherein V HCl :V O2 The ratio of HCl to water is 1 to 2:1, the reaction pressure is atmospheric pressure, the reaction temperature is 250 to 420°C, and the mass hourly space velocity (HHSV) of HCl is 0.5 to 0.8 h⁻¹. -1 The reaction evaluation platform consists of a raw material gas cylinder, a high-temperature furnace, and a tail gas absorption tank. Potassium iodide solution is used to absorb the product gas after the reaction, and titration is used to analyze the product composition and calculate the conversion rate of the HCl oxidation reaction.
[0024] Example 1: Preparation of Ru-TiO2 / Al2O3 catalyst
[0025] Tetrabutyl titanate and aluminum isopropoxide powder were dissolved in anhydrous ethanol at a mass ratio of 1:1 at room temperature. A mixture of ethanol, water, and acetic acid (volume ratio of 10:5:1) was added dropwise, with the volume ratio of ethanol to anhydrous ethanol being 1:7.5. The mixture was stirred for 3 hours, allowed to stand for 8 hours, dried at 100℃ for 4 hours, and then calcined at 320℃ for 19 hours in an ozone atmosphere in an oven to obtain an oxide support. Next, 26.7 ml of ruthenium chloride was weighed to prepare an aqueous solution with a concentration of 0.15 mol / L, and then the aqueous solution was impregnated onto 13.5 g of the calcined titanium oxide / alumina support. The support was then dried at 80℃ for 2 hours in an oven and then heat-treated at 120℃ for 5 hours to remove the carboxylic acid groups. Finally, the powder was transferred to a muffle furnace and calcined at 400℃ for 12 hours to obtain the desired catalyst with a mass percentage of 3% Ru / (TiO2 / Al2O3=14:13).
[0026] The prepared catalyst was used to catalyze the oxidation of HCl and O2, and its catalytic performance was investigated. The catalyst prepared in this invention performed well under the reaction conditions (V... HCl :V O2 = 2:1, atmospheric pressure, HCl mass hourly space velocity 0.6h -1 The conversion rate was 90% at 290℃, and the catalyst activity did not decrease significantly after a long-term operation of 150h.
[0027] Comparative Example 1
[0028] A Ru-TiO2 / Al2O3 catalyst was prepared using a traditional impregnation method as a control group. Tetrabutyl titanate and aluminum isopropoxide were dissolved in anhydrous ethanol at a stoichiometric ratio of 1:1 at room temperature. Water was added and stirred for 3 hours, allowed to stand for 8 hours, dried at 100℃ for 4 hours, and then calcined in an oven at 500℃ to obtain the oxide support. Next, 26.7 ml of a 0.15 mol / L aqueous solution of ruthenium chloride was prepared, and then the aqueous solution was impregnated onto 13.5 g of the calcined titanium oxide / alumina support. After drying in an oven at 80℃ for 2 hours, the powder was transferred to a muffle furnace and calcined at 400℃ for 12 hours to obtain the desired catalyst with a mass percentage of 3% Ru / (TiO2 / Al2O3 = 14:13). Under the reaction conditions (V... HCl :V O2 = 2:1, atmospheric pressure, HCl mass hourly space velocity 0.6h -1 To achieve a 90% conversion rate, the reaction temperature needs to be raised to 350℃, and the catalyst activity decreases by 5% after 150 hours of operation.
[0029] Example 2 Preparation of Ru-TiO2 / Si2O catalyst
[0030] Titanium tetrachloride and methyl orthosilicate were dissolved in anhydrous ethanol at a mass ratio of 1.2:1 at room temperature. A mixture of methanol, water, and formic acid (volume ratio of 7:3:1) was added dropwise, with a volume ratio of 1:5 to anhydrous ethanol. The mixture was stirred for 3 hours, allowed to stand for 10 hours, dried at 100°C for 3 hours, and then calcined at 270°C for 20 hours in an ozone atmosphere to obtain an oxide support. Next, 50.5 ml of 0.08 mol / L ruthenium chloride was weighed to prepare an aqueous solution, which was then used to impregnate 20.2 g of the calcined titanium oxide / silica support. The support was then dried at 85°C for 3 hours and then heat-treated at 140°C for 4 hours to remove carboxylic acid groups. Finally, the powder was transferred to a muffle furnace and calcined at 450°C for 12 hours to obtain the desired catalyst with a mass percentage of 2% Ru / (Ti / Si = 5:3).
[0031] The prepared catalyst was used to catalyze the oxidation of HCl and O2, and its catalytic performance was investigated. The catalyst prepared in this invention performed well under the reaction conditions (V... HCl :V O2 = 2:1, atmospheric pressure, HCl mass hourly space velocity 0.6h -1 The conversion rate was 90% at 302℃, and the catalyst activity did not decrease significantly after 120 hours of long-term operation, but decreased by 1% after 150 hours of operation.
[0032] Example 3: Preparation of Cu-TiO2 / SiO2 catalyst
[0033] Tetrabutyl titanate and tetraethyl orthosilicate were dissolved in isopropanol at a mass ratio of 2.5:1 at room temperature. A mixture of methanol, water, and benzoic acid (volume ratio of 6:4:1) was added dropwise, with a volume ratio of 1:5.3 to isopropanol. The mixture was stirred for 5 hours, allowed to stand for 9 hours, dried at 90°C for 4 hours, and then calcined at 280°C for 23 hours in an ozone atmosphere to obtain the oxide support. Next, 23 ml of a 0.38 mol / L aqueous solution of copper chloride was prepared, and then the aqueous solution was immersed in 16.1 g of the calcined titanium oxide / silica support. The support was then dried at 92°C for 4 hours and then heat-treated at 160°C for 2 hours to remove the carboxylic acid groups. Finally, the powder was transferred to a muffle furnace and calcined at 430°C for 17 hours to obtain the desired catalyst with a mass percentage of 3.5% Cu / (Ti / Si = 2.7:1).
[0034] The prepared catalyst was used to catalyze the oxidation of HCl and O2, and its catalytic performance was investigated. The catalyst prepared in this invention performed well under the reaction conditions (V... HCl :V O2 = 2:1, atmospheric pressure, HCl mass hourly space velocity 0.6h -1 The conversion rate was 90% at 315℃, and the catalyst activity did not decrease significantly after 130 hours of long-term operation, but decreased by 2% after 150 hours of operation.
[0035] Example 4: Preparation of Cr-TiO2 / Al2O3 catalyst
[0036] Tetrabutyl titanate and aluminum isopropoxide were dissolved in methanol at a mass ratio of 1.5:1 at room temperature. A mixture of butanediol, water, and succinic acid (volume ratio 6:3:1), with a volume ratio of 1:5.3 to methanol, was added dropwise. The mixture was stirred for 6 hours, allowed to stand for 11 hours, dried at 95°C for 3 hours, and then calcined at 300°C for 22 hours in an ozone atmosphere to obtain the oxide support. Next, 40 ml of a 0.43 mol / L aqueous solution of chromium nitrate was prepared. This solution was then impregnated onto 15 g of the calcined titanium oxide / alumina support, dried at 100°C for 5 hours, and then heat-treated at 130°C for 10 hours to remove the carboxylic acid groups. Finally, the powder was transferred to a muffle furnace and calcined at 440°C for 12 hours to obtain the desired catalyst with a mass percentage of 6% Cr / (Ti / Al = 1.6:1).
[0037] The prepared catalyst was used to catalyze the oxidation of HCl and O2, and its catalytic performance was investigated. The catalyst prepared in this invention performed well under the reaction conditions (V... HCl :V O2 = 2:1, atmospheric pressure, HCl mass hourly space velocity 0.6h -1 The conversion rate was 90% at 324℃, and the catalyst activity did not decrease significantly after 120 hours of long-term operation, but decreased by 3% after 150 hours of operation.
[0038] Table 1. Metal loading, high conversion (90%) reaction temperature, and catalyst stability in different examples and comparative examples.
[0039] catalyst catalyst High conversion reaction temperature Catalyst activity reduction after 150 hours of operation Example 1 3% Ru / (Ti / Al = 14:13) 290 0％ Comparative Example 1 3% Ru / (Ti / Al = 14:13) 350 5％ Example 2 2% Ru / (Ti / Si = 5:3) 302 1％ Example 3 3.5% Cu / (Ti / Si = 2.7:1) 315 2％ Example 4 6% Cr / (Ti / Al = 1.6:1) 324 3％
Claims
1. A method for preparing a catalyst for HCl oxidation, characterized in that, Includes the following steps: Step 1: A composite oxide carrier is prepared using the sol-gel method. Two of the titanium source, aluminum source, and silicon source are dissolved in a first alcohol solvent. Then, a mixture of a second alcohol solvent, water, and carboxylic acid is added dropwise. The mixture is stirred, allowed to stand for aging, dried, and then calcined under an ozone atmosphere to obtain the oxide carrier. The volume ratio of the second alcohol solvent, water, and carboxylic acid is 10-5:3-5:1, and the volume ratio of the prepared mixture to the first alcohol solvent is 1:3-8. The carboxylic acid is selected from one or more of formic acid, acetic acid, peroxy acid, malonic acid, benzoic acid, and succinic acid. Step 2: The metal salt is impregnated onto the oxide support using an impregnation method, and then dried and calcined to obtain the desired catalyst. The selected metal salt is one of the soluble salts of ruthenium, copper, and chromium.
2. The preparation method according to claim 1, characterized in that, Two of the titanium source, aluminum source, and silicon source are dissolved in a first alcohol solvent at a stoichiometric ratio of (1 to 3):1; and / or, the first alcohol solvent is one or more of methanol, ethanol, and isopropanol.
3. The preparation method according to any one of claims 1-2, characterized in that, The second alcohol solvent is an alcohol corresponding to a carboxylic acid.
4. The preparation method according to claim 3, characterized in that, In step one, stir for 3–7 hours and / or let stand and age for 8–12 hours.
5. The preparation method according to claim 4, characterized in that, In step one, the drying temperature is 80-100℃ and the drying time is 2-5 hours, and / or the calcination temperature is 200-300℃ and the calcination time is 12-20 hours.
6. The preparation method according to claim 3, characterized in that, In step two, the drying temperature is 80–100℃ and the time is 2–5 h, and / or the calcination temperature is 250–450℃ and the calcination time is 12–24 h.
7. The preparation method according to claim 6, characterized in that, Step two includes a heat treatment step after drying, with a temperature of 120–180°C and a time of 2–10 hours.
8. The preparation method according to claim 1, characterized in that, The titanium source is one or both of tetrabutyl titanate and titanium tetrachloride; the silicon source is one or both of methyl orthosilicate and ethyl orthosilicate; and the aluminum source is one or both of aluminum isopropoxide and aluminum sec-butoxide.
9. The catalyst prepared by the method according to any one of claims 1-8, characterized in that, The catalyst consists of a metal and a support, with the metal loading being 0.5–5 wt% and the support being any two of Al2O3, SiO2, and TiO2.
10. The use of the catalyst prepared by any one of claims 1-8 for the catalytic oxidation of hydrogen chloride to chlorine.