Preparation method and application of ruthenium-based catalyst for producing chlorine by hydrogen chloride oxidation in fixed bed

Abstract

This invention discloses a method for preparing a ruthenium-based catalyst for the catalytic oxidation of hydrogen chloride to chlorine in a fixed-bed reactor and its application. The active component RuO2 of the catalyst is loaded onto the surface of a TiO2 support through precursor salt adsorption-deposition-calcination, and then shaped into a ruthenium-based catalyst that can be directly used in a fixed-bed reactor by adding structural and molding aids. The ruthenium-based catalyst exhibits high low-temperature activity when used for the catalytic oxidation of hydrogen chloride to chlorine: at 280°C and a space velocity of 0.75 g-HCl / (g-cat·h), the conversion rate of hydrogen chloride can reach 90% to 95%. Compared with the current operating temperature of industrial fixed-bed reactors, the reaction temperature can be reduced by at least 20°C, while the conversion rate of hydrogen chloride can be increased by 5% to 10%.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology and relates to a catalyst used in the catalytic oxidation of hydrogen chloride to produce chlorine using a fixed-bed process. More specifically, it relates to a method for preparing a low-temperature, highly active ruthenium-based catalyst for chlorine production. Background Technology

[0002] Chlorine is a key component in the manufacture of important industrial chemicals and consumer products, widely used in the production processes of inorganic non-metallic oxides, metal oxides, silicon materials, phosgene, chlorinated hydrocarbons, and chlorinated aromatic hydrocarbons. However, the application of chlorine typically generates an equimolar amount of hydrogen chloride gas as a byproduct. The utilization rate of chlorine atoms is generally less than 50%, and in some cases, as much as one-third, chlorine derivatives contain no chlorine at all, resulting in a chlorine atom utilization rate of 0%. A prime example is the production of isocyanates, a crucial precursor in polyurethane production. In the phosgenation step, every mole of isocyanate produces 4 moles of hydrogen chloride, and the same applies to polycarbonate production. If these unusable hydrogen chloride waste gases cannot be converted into chlorine for utilization, the treatment of large quantities of byproduct hydrogen chloride will incur significant costs, causing severe environmental pollution and a substantial waste of chlorine resources.

[0003] Converting the byproduct hydrogen chloride into chlorine gas to achieve chlorine resource recycling is the most effective, economical, and environmentally friendly method for solving the problems of hydrogen chloride emissions, recovery, and utilization. Compared to the drawbacks of electrolysis and direct oxidation methods, catalytic oxidation stands out due to its low energy consumption, simple equipment, and environmental friendliness. It has been a research hotspot in recent years, and industrial chlorine production itself begins with a catalytic process. Catalytic oxidation refers to the method of producing Cl2 and H2O from HCl under the action of a catalyst. The chemical equation is as follows:

[0004] 4HCl + O2 == 2Cl2 + 2H2O, Δ r H m = -59kJ / mol

[0005] Typical processes include the Deacon process, the MT-Chlor process, the Shell-Chlor process, and the SUMITOMO (Sumitomo, Japan) process, and each process uses different types of catalysts.

[0006] The Deacon process uses CuO / CuCl2 as the main catalyst component. Based on this, many researchers have improved the co-catalyst and catalyst support to enhance the catalyst's activity and stability. For example, patent CN103920507 uses a composite material formed by rare earth sulfate oxysalts and auxiliary materials such as alumina and silica as the catalyst support; patent CN103920500 uses attapulgite as the catalyst material; and patent CN103920499 uses activated clay as the support. All of these patents use transition metal elements such as Cr, Ru, La, Ce, and Yr as co-catalysts added to the catalyst. However, while the addition of co-catalysts can lower the reaction temperature and improve catalyst stability to some extent, the high activation barrier of Cu-based catalysts requires a high reaction temperature (700K). Since CuCl2 has a melting point of 770K, CuCl2 volatilizes, leading to the loss of active components, decreased catalyst stability, and shortened lifespan. Furthermore, CuCl2 is a highly corrosive substance, posing significant challenges in the selection of reaction equipment and piping materials.

[0007] The Shell-Chlor process was the first fluidized bed reactor process to be industrially applied, developed by Shell Oil Company in the 1960s using a CuCl2-KCl / SiO2 catalyst. Later, Minet et al. improved it into a two-stage fluidized bed process: (1) at a low temperature of 200–280°C, HCl gas flows through a fluidized bed supported on a copper oxide catalyst, reacting to form a composite chloride; (2) at a high temperature of 340–380°C, the composite chloride catalyst is transferred to a second fluidized bed reactor to undergo dechlorination with oxygen. Compared to the Deacon process, the Shell-Chlor process significantly reduces the reaction temperature and separates the two different reaction stages in two reactors, allowing both reactions to proceed under optimal conditions. The two fluidized bed reactors are connected via a circulating catalyst, ultimately improving the conversion rate of hydrogen chloride and reducing the difficulty of product separation. However, the catalyst in this process still exhibits a tendency to deactivate. Currently, many research institutions in China are conducting extensive research on this process, with the main goal of improving catalyst lifespan. Patent WO2015 / 109587 A1 discloses a method for preparing a Cu-based catalyst support and catalyst for fluidized bed reactors. The catalyst prepared by this method exhibits excellent performance due to its good mechanical strength and stability, coupled with high activity. It achieves a single-pass average conversion rate of 80%–85% in a fluidized bed reactor, and after 1000 hours of reaction, there is no mutual adhesion between catalyst particles, maintaining good fluidity. Patent CN 109718789 discloses a method for preparing a core-shell structured supported catalyst. This catalyst support consists of an Al2O3-ZrO2 composite core and a shell, both of which contain active components. This design improves the catalyst's wear resistance and thus extends its lifespan. However, the reaction temperature in fluidized bed catalytic oxidation processes still cannot be reduced below 340℃. Although the conversion rate can reach 85%, the reaction operation cost is high, the catalyst is rapidly depleted, and continuous regeneration is required, offering little advantage over fixed-bed processes.

[0008] The MT-Chlor process was first proposed by Mitsui Toatsu Chemicals in 1980, primarily using amorphous Cr2O3 catalyst supported on a SiO2 support in a fluidized bed. This reaction equipment is relatively simple, and the catalyst does not melt under the reaction conditions, eliminating the need for the chloride-oxide reaction cycle of the copper-based catalyst in the Deacon process. However, this process also suffers from the problem of active component loss due to the in-situ formation of volatile CrO2Cl2 species during the reaction, which severely deactivates the catalyst. Furthermore, the high toxicity of chromium metal limits its industrial application to some extent.

[0009] Sumitomo Chemicals, Inc. of Japan has developed a Ru-based catalyst with RuO2 as the active center, representing a significant breakthrough in the catalytic oxidation of hydrogen chloride. In 2002, they built a 10 kt / a industrial-scale plant, subsequently adding three more, marking the true industrialization of the catalytic oxidation of hydrogen chloride to chlorine. The Sumitomo process utilizes a fixed-bed tubular reactor with a RuO2 / TiO2 supported particulate catalyst, conducting the catalytic oxidation of hydrogen chloride to chlorine at relatively low temperatures, down to below 330°C. Because the active component ruthenium is easily volatilized and lost at high temperatures (400°C), leading to gradual catalyst deactivation, and high temperatures also reduce the equilibrium conversion rate of hydrogen chloride, achieving a higher conversion rate (such as the 85% hydrogen chloride conversion rate in the Sumitomo process) at lower temperatures (below 330°C) significantly extends catalyst life and reduces energy consumption considerably. The industrial production of chlorine gas from hydrogen chlorination requires a catalytic temperature between 300 and 420°C. However, this reaction is highly exothermic, leading to the formation of localized hot spots in the catalyst bed. These hot spots have temperatures significantly higher than the average temperature distribution of the bed. If the hot spot temperature is too high, the active components are prone to sintering and deactivation. In the temperature range below 280°C, conventional catalysts exhibit very low activity, with hydrogen chloride conversion rates below 60%. Sumitomo Chemicals of Japan, in patent CN102131731B, discloses a ruthenium-based catalyst that achieves a hydrogen chloride conversion rate of up to 10% at temperatures as low as 282°C. Patent CN116550321A discloses a method for improving the metal dispersion of ruthenium catalysts in the hydrogen chlorination-to-chlorine production process. This method yields crystallites with particle sizes of 1–10 nm and ruthenium metal surface areas of 120–410 m². 2 Ru, in a highly dispersed state, can achieve a hydrogen chloride conversion rate of 68% at 300°C. No Ru-based catalysts have been reported in currently available patents and literature to achieve a hydrogen chloride conversion rate of 85% at or below 300°C.

[0010] The ruthenium catalyst preparation methods disclosed in the aforementioned patent documents are mainly based on impregnation. Impregnation is very suitable for large-scale industrial catalyst production and is also the most direct method to load the active component onto a prepared support. Especially for noble metal catalysts, the performance of the support largely determines the performance of the catalyst and has a high tolerance for error; if a batch of supports is found to be substandard, the waste of the entire batch of noble metals can be avoided. However, this method cannot prepare supported catalysts with special structures. Numerous research papers indicate that the catalytic oxidation of hydrogen chloride on the RuO2 catalyst surface follows the Langmuir-Hinshelwood mechanism. That is, during the catalytic reaction, HCl molecules first adsorb and bind to the O(top) sites on the RuO2-{110} crystal face, undergoing heterogeneous cleavage to form adsorbed Cl* and OH*. The adsorbed Cl* collide and combine to produce Cl2 molecules, and the OH* combine to generate H2O molecules and O(top) sites, and the entire process repeats. This process occurs only on the outermost atoms of the RuO2 crystal, preventing deep chlorination of RuO2 to form volatile RuCl3, which would lead to rapid catalyst deactivation. Simultaneously, because RuO2 and rutile TiO2 have the same crystal structure and similar cell size, RuO2 can be epitaxially grown on the TiO2 surface to form an oxide film several atomic layers thick. This structure significantly improves the dispersibility of RuO2, and the self-limiting chlorination property of the surface also enhances the catalyst's stability. Clearly, conventional impregnation methods are insufficient to prepare catalysts with this structure. This is because the internal pore structure of the support is complex; the impregnation solution first occupies all the vacant positions in the support pores through capillary action. Then, during the drying-calcination process, as the solvent in the impregnation solution continuously evaporates, the active component gradually precipitates and crystallizes, forming unevenly sized microcrystals. These microcrystals are unstable and will quickly collapse into sintered ruthenium compounds in the presence of hydrogen chloride gas and under the reaction conditions, leading to rapid catalyst deactivation. Therefore, it is necessary to change the traditional catalyst preparation method to solve these problems. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the impregnation method for preparing ruthenium catalysts and to provide a method for preparing a ruthenium-based catalyst with good low-temperature activity for fixed-bed catalytic hydrogen chlorination to chlorine, as well as the application of the ruthenium-based catalyst prepared by this method for catalytic hydrogen chlorination to chlorine.

[0012] To achieve the aforementioned objective, the ruthenium-based catalyst provided by this invention is a granular catalyst with a diameter of 1.0–5.0 mm and a length of 2.0–10.0 mm. The active component is RuO2, the support is TiO2, and the structural aid is any one or a combination of α-Al2O3, quartz, and zirconium oxide. The mass content of metallic ruthenium in the catalyst is 0.1%–10.0%, preferably 1.0%–5.0%. The preparation method of this catalyst includes the following steps:

[0013] Step 1: Disperse titanium dioxide with D50 = 5-25μm in deionized water, and adjust the pH of the resulting slurry to between 2.0 and 7.0 with 0.1-1.0mol / L inorganic acid;

[0014] Step 2: Dissolve the water-soluble ruthenium-containing compound in deionized water and add it to the slurry from Step 1. After adsorption and aging at 40–80°C for 30 minutes to 12 hours, add 0.01–0.1 mol / L alkali solution to the aged slurry, adjust the pH to between 7.0 and 12.0, and raise the temperature to 60–100°C for aging for 30 minutes to 12 hours. Then filter the slurry, dry it at 80–150°C for 4–12 hours, and then pulverize it.

[0015] Step 3: Mix the structural additive with D50 = 5-25μm and the powder obtained in Step 2 at a mass ratio of 1:9 to 9:1, add a tableting agent, and press into cylindrical particles using a tablet press; or mix the structural additive with D50 = 5-25μm and the powder obtained in Step 2 at a mass ratio of 1:9 to 9:1, add an extrusion agent, knead evenly, and then extrude and cut into strip-shaped particles in a mold; calcine the cylindrical particles or strip-shaped particles at 250-450℃ for 2-24 hours in air or oxygen atmosphere to obtain the formed ruthenium-based catalyst.

[0016] In step one above, the titanium dioxide used can be a pure rutile phase or a mixed rutile and anatase phase. If a mixed rutile phase titanium dioxide is used, the mass content of the rutile phase should not be less than 50%, preferably pure rutile phase titanium dioxide. The particle size distribution of the titanium dioxide is preferably D50 of 10 μm. The inorganic acid can be hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid, with hydrochloric acid being preferred.

[0017] Preferably, in step one above, pure rutile titanium dioxide with D50 = 10 μm is dispersed in deionized water, and the resulting slurry is adjusted to a pH value between 3.0 and 5.0 with 0.1 to 1.0 mol / L hydrochloric acid.

[0018] In step two above, the water-soluble ruthenium-containing compound is derived from any one or more combinations of the following components, but not limited to: RuCl3, RuCl3·xH2O, RuBr3, RuBr3·xH2O, ruthenium chloride (such as K3RuCl6, (NH4)3RuCl3, K2RuCl6), ruthenium chloride hydrate (such as K2[RuCl5(H2O)4], [RuCl2(H2O)4]Cl), ruthenium chloride (such as K2RuO4 or Na2RuO4), ruthenium oxychloride (such as Ru2OCl4, Ru2OCl5, Ru2OCl6), and ruthenium oxychloride salt (such as K2Ru2OCl). 10 The alkaline solution can be an aqueous solution of an inorganic base, such as Na₂CO₃, K₂CO₃, KOH, NaOH, LiOH, or ammonia water, or an organic base, such as ethylamine, ethanolamine, diethylamine, ethylenediamine, tetrapropylammonium hydroxide, or urea. The alkaline solution can be an aqueous solution of an inorganic base, such as Na₂CO₃, K₂CO₃, KOH, NaOH, LiOH, or ammonia water, or an organic base, such as ethylamine, ethanolamine, diethylamine, ethylenediamine, tetrapropylammonium hydroxide, or urea.

[0019] Preferably, in step two above, the water-soluble ruthenium-containing compound is dissolved in deionized water and then added to the slurry in step one. After adsorption aging at 60-80°C for 2-4 hours, 0.01-0.1 mol / L alkali solution is added to the aged slurry to adjust the pH value to 9.0-11.0, and the temperature is raised to 80-100°C for aging for 2-4 hours. Then, the slurry is filtered, dried at 100-120°C for 8-12 hours, and then pulverized.

[0020] In step three above, the extrusion molding aid is selected from any one or a combination of silica sol, aluminum sol, silica-alumina sol, titanium sol, phosphorus-aluminum sol, guar gum, and boehmite. The amount of extrusion molding aid added is calculated based on the mass of the solid, and the amount added is 1.0% to 5.0% of the catalyst mass. The tableting molding aid is selected from any one or a combination of graphite powder, PEG1000-8000, magnesium stearate, sodium stearate, stearic acid, talc, macroporous boehmite, and fumed silica, and its amount added is 1.0% to 5.0% of the catalyst mass.

[0021] Preferably, in step three above, the structural additive with D50 = 10 μm is mixed evenly with the powder obtained in step two at a mass ratio of 4:6 to 6:4, and a tableting agent is added. The mixture is then pressed into cylindrical particles using a tablet press. Alternatively, α-Al2O3 with D50 = 10 μm is mixed evenly with the powder obtained in step two at a mass ratio of 4:6 to 6:4, and an extrusion agent is added. After kneading evenly, the mixture is extruded and cut into strip-shaped particles in a mold. The cylindrical particles or strip-shaped particles are then calcined at 300 to 400°C for 12 to 18 hours in an air or oxygen atmosphere to obtain the formed ruthenium-based catalyst.

[0022] The method for producing chlorine from hydrogen chloride using the ruthenium-based catalyst prepared in this invention is as follows: the catalyst is loaded into a fixed-bed reactor, and oxygen and hydrogen chloride gas are introduced to carry out the reaction. The reaction temperature is 250–420°C, preferably 280–390°C; the reaction pressure is not particularly limited, and atmospheric pressure of 1.0 bar is generally used. Pure oxygen, air, or pure oxygen diluted with an inert gas can be used, with pure oxygen being preferred as the oxygen feedstock. Further, according to the stoichiometry of the chemical reaction formula, the theoretical molar ratio of hydrogen chloride to oxygen in the reaction is 4:1, and the actual molar ratio of hydrogen chloride to oxygen in the reactor is between 4:1 and 1:1, preferably 2:1. The amount of catalyst added is calculated using the mass hourly space velocity (WHSV) of hydrogen chloride gas (g-HCl / (g-cat·h), which ranges from 0.5 to 5.0 h⁻¹. -1 Preferably 0.75–2.0 h -1 .

[0023] The beneficial effects of this invention are as follows:

[0024] This invention is based on a deposition-precipitation method, in which RuO2 is loaded onto the surface of TiO2 through precursor salt adsorption-deposition-calcination to obtain RuO2 / TiO2 composite nanoparticles. These nanoparticles are then shaped into ruthenium-based catalysts that can be directly used in a fixed-bed reactor by adding structural and molding aids. The composite nanoparticles formed by the active component RuO2 and TiO2 powder exhibit high catalytic activity at low temperatures. The structural aids increase both the catalyst's strength and its thermal conductivity. The ruthenium-based catalyst of this invention exhibits very high initial activity at low temperatures. When used for the catalytic oxidation of hydrogen chloride to chlorine at a hot spot temperature of 280°C, it can achieve a conversion rate of no less than 90%. Compared to the operating temperature of current industrial fixed-bed reactors, this reduces the reaction temperature by at least 20°C, while simultaneously increasing the hydrogen chloride conversion rate by 5%–10%. Detailed Implementation

[0025] The present invention will be further described below with reference to the embodiments. However, the scope of protection of the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0026] Example 1

[0027] Step 1: Take 60g of rutile titanium dioxide powder with D50=10μm and 600g of deionized water. Use an emulsifier to evenly disperse the rutile titanium dioxide powder into the deionized water to form a slurry. Adjust the pH of the slurry to 4.3 with 0.1mol / L hydrochloric acid.

[0028] Step 2: Dissolve 11.63g of potassium chlororuthenate in 100g of deionized water, add it to the slurry prepared in Step 1, raise the temperature to 60℃, and adsorb and age for 2 hours. Then adjust the pH of the slurry to 9.2 with 0.01mol / L KOH aqueous solution, raise the temperature to 80℃, and age for 4 hours. Then filter and wash the slurry, and dry it in a forced-air drying oven at 120℃ for 12 hours to obtain 62g of dried powder.

[0029] Step 3: After crushing and grinding the powder obtained in Step 2, add 36g of α-Al2O3 powder with D50 = 10μm, 1.5g of graphite powder and 3.0g of macroporous pseudoboehmite powder. Mix evenly in a powder mixer and press into cylindrical particles with a diameter of 3.0mm and a length of 4.5mm using a tablet press. Then calcine in air at 350℃ for 12 hours to obtain the formed ruthenium-based catalyst.

[0030] Theoretically, the mass percentage of the active component Ru in the catalyst is: RuO2 wt.% = [m RuO2 / (m RuO2 +m TiO2 +m Al2O3 []×100%=3.95% (The mass of alumina consists of two parts: the mass of α-Al2O3 powder and macroporous pseudoboehmite powder), of which the mass percentage of metallic ruthenium is: Ru wt.%=RuO2 wt.%×0.7595=3.0%.

[0031] Example 2

[0032] Step 1: Take 60g of rutile titanium dioxide powder with D50=10μm and 600g of deionized water. Use an emulsifier to evenly disperse the rutile titanium dioxide powder into the deionized water to form a slurry. Adjust the pH of the slurry to 4.3 with 0.1mol / L hydrochloric acid.

[0033] Step 2: Dissolve 5.82g of potassium chlororuthenate in 50g of deionized water, add it to the slurry prepared in Step 1, raise the temperature to 60℃, and adsorb and age for 2 hours. Then adjust the pH of the slurry to 9.2 with 0.01mol / L KOH aqueous solution, raise the temperature to 80℃, and age for 4 hours. Then filter and wash the slurry, and dry it in a forced-air drying oven at 120℃ for 12 hours to obtain 61g of dried powder.

[0034] Step 3: After crushing and grinding the powder obtained in Step 2, add 38g of α-Al2O3 powder with D50 = 10μm, 1.5g of graphite powder and 3.0g of macroporous pseudoboehmite powder. Mix evenly in a powder mixer and press into cylindrical particles with a diameter of 3.0mm and a length of 4.5mm using a tablet press. Then calcine in air at 350℃ for 12 hours to obtain the formed ruthenium-based catalyst.

[0035] Theoretically, the mass percentage of the active component Ru in the catalyst is: RuO2 wt.% = [m RuO2 / (m RuO2 +m TiO2 +m Al2O3 []×100%=1.97% (The mass of alumina consists of two parts: the mass of α-Al2O3 powder and pseudoboehmite (macroporous) powder), of which the mass percentage of metallic ruthenium is: Ru wt.%=RuO2 wt.%×0.7595=1.5%.

[0036] Example 3

[0037] Step 1: Take 60g of rutile titanium dioxide powder with D50=10μm and 600g of deionized water. Use an emulsifier to evenly disperse the rutile titanium dioxide powder into the deionized water to form a slurry. Adjust the pH of the slurry to 4.3 with 0.1mol / L hydrochloric acid.

[0038] Step 2: Dissolve 11.63g of potassium chlororuthenate in 100g of deionized water, add it to the slurry prepared in Step 1, raise the temperature to 60℃, and adsorb and age for 2 hours. Then adjust the pH of the slurry to 9.2 with 0.01mol / L KOH aqueous solution, raise the temperature to 80℃, and age for 4 hours. Then filter and wash the slurry, and dry it in a forced-air drying oven at 120℃ for 12 hours to obtain 62g of dried powder.

[0039] Step 3: After crushing and grinding the powder obtained in Step 2, add 36g of α-Al2O3 powder with D50 = 10μm, 1.5g of guar gum and 30mL of silica sol with a mass concentration of 10%. After kneading evenly, extrude the mixture using an extruder and cut it into strip-shaped particles with a diameter of 1.5mm and a length of 4.5-8.0mm. Dry the particles in a forced-air drying oven at 120℃ for 6 hours, and then calcine them in air at 350℃ for 12 hours to obtain the formed ruthenium-based catalyst.

[0040] Theoretically, the mass percentage of the active component Ru in the catalyst is: RuO2 wt.% = [m RuO2 / (m RuO2 +m TiO2 +m Al2O3 +m SiO2[]×100%=3.95%, of which the mass percentage of ruthenium is: Ru wt.%=RuO2wt.%×0.7595=3.0%.

[0041] Example 4

[0042] Step 1: Take 60g of rutile titanium dioxide powder with D50=10μm and 600g of deionized water. Use an emulsifier to evenly disperse the rutile titanium dioxide powder into the deionized water to form a slurry. Adjust the pH of the slurry to 4.3 with 0.1mol / L hydrochloric acid.

[0043] Step 2: Dissolve 5.82g of potassium chlororuthenate in 100g of deionized water, add it to the slurry prepared in Step 1, raise the temperature to 60℃, and adsorb and age for 2 hours. Then adjust the pH of the slurry to 9.2 with 0.01mol / L KOH aqueous solution, raise the temperature to 80℃, and age for 4 hours. Then filter and wash the slurry, and dry it in a forced-air drying oven at 120℃ for 12 hours to obtain 61g of dried powder.

[0044] Step 3: After crushing and grinding the powder obtained in Step 2, add 38g of α-Al2O3 powder with D50=10μm, 1.5g of guar gum and 30mL of silica sol with a mass concentration of 10%. After kneading evenly, extrude the mixture using an extruder and cut it into strip-shaped particles with a diameter of 1.5mm and a length of 4.5-8.0mm. Dry the particles rapidly at 120℃ for 6 hours in a forced-air drying oven, and then calcine them in air at 350℃ for 12 hours to obtain the formed ruthenium-based catalyst.

[0045] Theoretically, the mass percentage of the active component Ru in the catalyst is: RuO2 wt.% = [m RuO2 / (m RuO2 +m TiO2 +m Al2O3 +m SiO2 The mass percentage of ruthenium is: Ru wt.% = RuO2wt.% × 0.7595 = 1.5%.

[0046] Comparative Example 1

[0047] Based on the technical solution disclosed in the catalyst section of the example of Sumitomo Chemical's patent CN102791620A, a supported ruthenium catalyst was prepared. The catalyst is prepared by a typical impregnation method. The preparation process is as follows: 60g of rutile titanium dioxide (STR-60R, manufactured by Sakai Chemical Co., Ltd., 100% rutile form), 38g of α-Al2O3 powder (AES-12, manufactured by Sumitomo Chemical Co., Ltd.), 8g of titanium dioxide sol (CSB, manufactured by Sakai Chemical Co., Ltd., titanium dioxide content 38wt.%), and 1.2g of methylcellulose (Metolose 65SH-4000, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed, and then 33g of deionized water was added and kneaded evenly. The resulting mixture was extruded and cut into strip-shaped particles with a diameter of 3.0 mm and a length of 4.5–8.0 mm using an extruder. These particles were then calcined in air at 800 °C for 3 hours to obtain a support composed of a mixture of titanium oxide and α-Al₂O₃. The support was then immersed in an aqueous solution of ruthenium trichloride, dried, and subsequently calcined in air at 250 °C for 2 hours to obtain a light blue-gray supported ruthenium oxide catalyst. The volume of the impregnation solution was controlled according to the concentration of the ruthenium trichloride solution and the actual Ru content therein, so that the final Ru loading on the catalyst surface was 1.5 wt.%.

[0048] Comparative Example 2

[0049] 60g of rutile titanium dioxide (STR-60R, manufactured by Sakai Chemical Co., Ltd., 100% rutile form), 38g of α-Al₂O₃ powder (AES-12, manufactured by Sumitomo Chemical Co., Ltd.), 8g of titanium dioxide sol (CSB, manufactured by Sakai Chemical Co., Ltd., titanium dioxide content 38wt.%), and 1.2g of methylcellulose (Metolose 65SH-4000, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed, followed by the addition of 33g of deionized water and kneading until homogeneous. The resulting mixture was extruded using an extruder and cut into strips with a diameter of 1.5mm and a length of 4.5–8.0mm. These strips were then calcined in air at 800°C for 3 hours to obtain a carrier composed of a mixture of titanium dioxide and α-Al₂O₃. The support was immersed in an aqueous solution of ruthenium trichloride, dried, and then calcined in air at 250°C for 2 hours to obtain a light blue-gray supported ruthenium oxide catalyst. The volume of the impregnation solution was controlled according to the concentration of the ruthenium trichloride solution and the actual Ru content therein, so that the final Ru loading on the catalyst surface was 3.0 wt.%.

[0050] Comparative Example 3

[0051] 60g of rutile titanium dioxide powder with a D50 of 10μm, 38g of α-Al₂O₃ powder with a D50 of 10μm, 33g of silica sol with a mass concentration of 10%, and 1.5g of guar gum were mixed and kneaded until homogeneous. The resulting mixture was extruded using an extruder and cut into strips with a diameter of 1.5mm and a length of 4.5–8.0mm. These strips were then calcined in air at 800℃ for 3 hours to obtain a support composed of a mixture of titanium dioxide and α-Al₂O₃. The support was then immersed in an aqueous solution of ruthenium trichloride, dried, and subsequently calcined in air at 250℃ for 2 hours to obtain a light blue-gray supported ruthenium oxide catalyst. The volume of the impregnation solution was controlled according to the concentration of the ruthenium trichloride solution and the actual Ru content therein, so that the final Ru loading on the catalyst surface was 3.0 wt.%.

[0052] Example 5

[0053] Fixed-bed chlorination to chlorine production

[0054] The activity of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3 was evaluated in a fixed-bed reactor. The fixed-bed reactor was heated and heat-transferred using a molten salt medium in the outer layer. The reactor had an inner diameter of 22 mm and a height of 1800 mm. The catalyst loading volume was 300 mL, and the catalyst and inert packing were packed in four layers: 56.58 mm of inert ceramic rings, a 160 mL mixed layer (ceramic ring to catalyst ratio = 42:58), a 197.2 mm catalyst layer, and a 56.58 mL inert ceramic ring layer. Oxygen and hydrogen chloride gases were introduced, and the reaction space velocity was 0.75 h⁻¹. -1 (The mass hourly space velocity (WHSV) of hydrogen chloride gas is g-HCl / (g-cat·h)), which translates to flow rates of 3.1 L / min for hydrogen chloride gas and 1.55 L / min for oxygen, with a pressure of 0.1 MPa. The conversion rate of hydrogen chloride during the reaction was determined by sampling with quantitative potassium iodide solution absorption. The amount of chlorine gas generated and the amount of unreacted hydrogen chloride were measured using iodine titration and neutralization titration methods, respectively, and the conversion rate was calculated accordingly. The conversion rates of hydrogen chloride for different catalysts at different temperatures are shown in Table 1.

[0055] Table 1 Comparison of hydrogen chloride conversion rates of different catalysts at different temperatures

[0056]

[0057] As shown in Table 1, the catalysts prepared by this special adsorption-deposition-calcination method in the examples generally have higher initial low-temperature activity than the catalysts prepared by the reported ordinary impregnation method (Comparative Examples 1, 2, and 3). The high-activity temperature range can be extended from 280°C to above 390°C. Moreover, the activity of the catalyst mainly depends on the loading method of the active component RuO2 and is not significantly related to the final molding process.

[0058] Industrial practicality

[0059] This catalyst can efficiently produce chlorine from hydrogen chloride gas. Compared with the current operating temperature of industrial fixed-bed devices, it can reduce the reaction temperature by at least 20°C, while increasing the hydrogen chloride conversion rate by 5% to 10%.

Claims

1. A method for preparing a ruthenium-based catalyst for the production of chlorine gas by hydroxyl chloride in a fixed-bed process, characterized in that: The catalyst is a granular catalyst with a diameter of 1.0–5.0 mm and a length of 2.0–10.0 mm. The active component is RuO2, the support is TiO2, and the structural aid is any one or a combination of several of α-Al2O3, quartz, and zirconium oxide. The mass content of ruthenium in the catalyst is 0.1%–10.0%. The preparation method of the catalyst includes the following steps: Step 1: Disperse titanium dioxide with D50 = 5~25μm in deionized water, and adjust the pH of the resulting slurry to between 3.0 and 5.0 with 0.1~1.0mol / L inorganic acid; Step 2: Dissolve the water-soluble ruthenium-containing compound in deionized water and add it to the slurry from Step 1. After adsorption and aging at 40–80°C for 30 minutes to 12 hours, add 0.01–0.1 mol / L alkali solution to the aged slurry, adjust the pH to between 9.0 and 11.0, and raise the temperature to 60–100°C for aging for 30 minutes to 12 hours. Then filter the slurry, dry it at 80–150°C for 4–12 hours, and then pulverize it. Step 3: Mix the structural additive with D50 = 5-25μm and the powder obtained in Step 2 at a mass ratio of 1:9-9:1, add a tableting agent, and press into cylindrical particles using a tablet press; or mix the structural additive with D50 = 5-25μm and the powder obtained in Step 2 at a mass ratio of 1:9-9:1, add an extrusion agent, knead evenly, and then extrude and cut into strip particles in a mold; calcine the cylindrical particles or strip particles at 250-450℃ for 2-24 hours in air or oxygen atmosphere to obtain the formed ruthenium-based catalyst.

2. The method for preparing the ruthenium-based catalyst for chlorination with hydrogen chlorination in a fixed bed according to claim 1, characterized in that: The catalyst contains 1.0% to 5.0% ruthenium by mass.

3. The method for preparing the ruthenium-based catalyst for chlorination by hydrogen chlorination in a fixed bed according to claim 1 or 2, characterized in that: In step one, the titanium dioxide has a pure rutile phase or a mixed rutile and anatase phase, wherein the mass content of the rutile phase is ≥50%; the inorganic acid is selected from any one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

4. The method for preparing the ruthenium-based catalyst for chlorination by hydrogen chlorination in a fixed bed according to claim 1 or 2, characterized in that: In step one, pure rutile phase titanium dioxide with D50 = 10μm is dispersed in deionized water, and the resulting slurry is adjusted to a pH value between 3.0 and 5.0 with 0.1 to 1.0 mol / L hydrochloric acid.

5. The method for preparing the ruthenium-based catalyst for chlorination to chlorine using hydrogen chlorination in a fixed bed according to claim 1, characterized in that: In step two, the water-soluble ruthenium-containing compound is selected from any one or more of ruthenium trichloride or its hydrate, ruthenium chloride, ruthenium salt, ruthenium oxychloride, ruthenium ammonia complex, ruthenium chloride ammonia complex, and ruthenium bromide ammonia complex; the alkaline solution is selected from any aqueous solution of Na2CO3, K2CO3, KOH, NaOH, LiOH, ammonia, ethylamine, ethanolamine, diethylamine, ethylenediamine, tetrapropylammonium hydroxide, and urea.

6. The method for preparing the ruthenium-based catalyst for chlorination by hydrogen chlorination in a fixed bed according to any one of claims 1, 2, and 5, characterized in that: In step two, the water-soluble ruthenium-containing compound is dissolved in deionized water and then added to the slurry from step one. After adsorption aging at 60–80°C for 2–4 hours, 0.01–0.1 mol / L alkali solution is added to the aged slurry to adjust the pH to 9.0–11.0, and the temperature is raised to 80–100°C for aging for 2–4 hours. Then the slurry is filtered, dried at 100–120°C for 8–12 hours, and then pulverized.

7. The method for preparing the ruthenium-based catalyst for chlorination to chlorine using hydrogen chlorination in a fixed bed according to claim 1, characterized in that: In step three, the extrusion molding aid is selected from any one or a combination of silica sol, aluminum sol, silica-alumina sol, titanium sol, phosphorus-aluminum sol, guar gum, and boehmite. The amount of extrusion molding aid added is calculated based on the mass of the solid and is 1.0% to 5.0% of the catalyst mass. The tableting molding aid is selected from any one or a combination of graphite powder, PEG 1000-8000, magnesium stearate, sodium stearate, stearic acid, talc, macroporous boehmite powder, and fumed silica. Its amount added is 1.0% to 5.0% of the catalyst mass.

8. The method for preparing a ruthenium-based catalyst for chlorination by hydrogen chlorination in a fixed bed according to any one of claims 1, 2, and 7, characterized in that: The structural additive with D50 = 10 μm is mixed with the powder obtained in step two at a mass ratio of 4:6 to 6:4, and a tableting agent is added. The mixture is then pressed into cylindrical particles using a tablet press. Alternatively, α-Al2O3 with D50 = 10 μm is mixed with the powder obtained in step two at a mass ratio of 4:6 to 6:4, and an extrusion agent is added. After kneading the mixture evenly, it is extruded and cut into strip-shaped particles in a mold. The cylindrical particles or strip-shaped particles are calcined at 300 to 400 °C for 12 to 18 hours in air or an oxygen atmosphere to obtain the formed ruthenium-based catalyst.

9. The use of the ruthenium-based catalyst prepared by the method of claim 1 for the catalytic oxidation of hydrogen chlorination to chlorine gas, characterized in that: The catalyst was loaded into a fixed-bed reactor, and oxygen and hydrogen chloride gases were introduced. The molar ratio of hydrogen chloride to oxygen was 4:1 to 1:1, and the mass hourly space velocity (HHSV) of the hydrogen chloride gas was 0.5 to 5.0 h⁻¹. -1 The reaction occurs at 250–420°C under normal pressure.

10. The use of the ruthenium-based catalyst for catalytic hydrogen chloride oxidation to chlorine gas production according to claim 9, characterized in that: The catalyst was loaded into a fixed-bed reactor, and oxygen and hydrogen chloride gases were introduced. The molar ratio of hydrogen chloride to oxygen was 2:1, and the mass hourly space velocity (WHSV) of the hydrogen chloride gas was 0.75–2.0 h⁻¹. -1 The reaction occurs at 280–390°C under normal pressure.

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