Alkali-modified double metal oxide catalyst, preparation method and application thereof in organic sulfur hydrolysis

Abstract

This invention discloses an alkali-modified bimetallic oxide catalyst, its preparation method, and its application in the hydrolysis of organic sulfur, belonging to the field of gaseous sulfide removal technology. This invention first involves Al... 2 O 3 and TiO 2 Grind into powder and mechanically mix evenly in proportion, then impregnate Al with alkali metal salt solution. 2 O 3 and TiO 2 The catalyst is obtained by ultrasonic homogenization and drying of a mixed powder followed by calcination in air. The preparation method of this invention is simple, eliminates the need for washing and wastewater generation, and significantly reduces environmental and production costs; TiO₂ 2 With Al 2 O 3 Mechanical mixing does not damage Al 2 O 3 The porous structure and surface hydroxyl groups of TiO2 2 The introduction of [a specific ingredient] can also improve the catalyst's resistance to poisoning. The catalyst of this invention [is effective] in COS and CS [context missing]. 2 It exhibits excellent catalytic activity and good stability in hydrolysis reactions, and is effective even in the presence of water vapor and O2. 2 and CO 2 It still exhibits high hydrolysis activity under operating conditions with impurity gases, and its desulfurization performance is higher than that of similar catalysts, with broad prospects for industrial application.

Description

An alkali-modified bimetallic oxide catalyst, its preparation method, and its application in the hydrolysis of organic sulfur. Technical Fields

[0001] This invention belongs to the field of gaseous sulfide removal technology, specifically relating to an alkali-modified bimetallic oxide catalyst, its preparation method, and its application in the hydrolysis of organic sulfur. Background Technology:

[0002] With the rapid pace of modernization in my country, the demand for key raw materials in manufacturing industries such as steel has increased dramatically. Blast furnace gas, a combustible byproduct produced during steel smelting, is also an important secondary energy source. Its main components include 6–12% CO2, 28–33% CO, 55–60% N2, 1–4% H2, 0.2–0.5% hydrocarbons, and 200–300 mg / m³ of nitrogen. 3 Sulfides, over 90% of which are organic sulfur compounds, are primarily COS, with smaller amounts of CS2, etc. COS and other sulfides are toxic and harmful gases that not only severely impact air quality and threaten human health, but also corrode equipment and poison catalysts in industrial applications. Therefore, to achieve high-value utilization of blast furnace gas, it is necessary to completely remove sulfur-containing gases. Currently, the main methods for COS and CS2 removal include hydrogenation reduction, organic amine adsorption, oxidation, hydrolysis, and photolysis. Hydrolysis (CS2 + H2O → COS + H2S, COS + H2O → CO2 + H2S) has advantages such as low reaction temperature, no hydrogen consumption, and few side reactions, making it one of the most promising organic sulfur removal technologies. Catalysts are crucial for the large-scale application of hydrolysis. Simultaneously achieving high specific surface area, high hydrolysis catalytic activity, and high resistance to sulfation is a challenge for hydrolysis catalysts. The development trend of organic sulfur hydrolysis catalysts is to prepare composite catalysts by mixing different types of active components and supports.

[0003] Currently, low-temperature hydrolysis catalysts for COS and CS2 mainly use metal oxides such as Al2O3 as supports to support active alkali metals, alkaline earth metals, transition metal oxides, and rare earth metal oxides. Meanwhile, extensive research has shown that hydrotalcite, spinel, and activated carbon also possess certain hydrolysis activities. Hydrotalcite is an anionic inorganic metal material with a layered structure and abundant surface hydroxyl groups, providing numerous basic sites for COS and CS2 hydrolysis. Spinel possesses both acidic and basic active centers, exhibits stable properties, and has also been found to be a good catalyst for COS and CS2 hydrolysis. Activated carbon, after surface modification (using active precursors such as Mn, Fe, K, Cu, and Ce, or non-metallic elements such as N, S, and P), increases the number of basic functional groups on its surface, which can serve as active sites for COS and CS2 hydrolysis. Although these novel catalysts all exhibit certain COS and CS2 hydrolysis activities, they all suffer from the problem of easy deactivation under high water vapor concentrations and high space velocities, and the industrial production cost of these novel catalysts is also higher than that of traditional Al2O3-based catalysts. Therefore, it is believed that modified Al2O3-based catalysts are low-cost and efficient catalysts for COS and CS2 hydrolysis that meet current industrial needs.

[0004] Al₂O₃, as a porous material, not only possesses advantages such as large specific surface area, good thermal stability, and high mechanical strength, but also exhibits catalytic activity in the hydrolysis of COS and CS₂. Therefore, Al₂O₃-based catalysts have become the most extensively studied and widely used type of COS and CS₂ hydrolysis catalyst. However, the catalytic activity of these Al₂O₃-based hydrolysis catalysts significantly decreases at temperatures below 100℃. Furthermore, the presence of impurities such as CO and CO₂ in the feed gas also leads to a substantial reduction in their desulfurization efficiency. Therefore, designing a catalyst with high efficiency in COS and CS₂ hydrolysis and high resistance to impurity gases at low temperatures is currently a primary goal in industrial production. Invention content:

[0005] To overcome the above problems, the present invention aims to provide an alkali-modified bimetallic oxide catalyst, a preparation method thereof, and its application in the hydrolysis of organic sulfur. The alkali-modified bimetallic oxide catalyst is prepared by a simple method. The catalyst can efficiently remove COS and CS2 even when impurity gases such as CO and CO2 are present, further improving the hydrolysis performance of the catalyst.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing an alkali-modified bimetallic oxide catalyst, characterized by comprising the following steps:

[0008] (1) Grind Al2O3 and TiO2 into powder and mechanically mix them evenly in a certain proportion;

[0009] (2) Impregnate the mixed powder obtained in step (1) with a certain amount of alkali metal salt solution and mix it evenly by ultrasonication;

[0010] (3) Dry the powder obtained in step (2) in an oven overnight;

[0011] (4) The powder obtained in step (3) is heated to 300-500°C in air and calcined to obtain alkali-modified TiO2-Al2O3 bimetallic catalyst.

[0012] Based on the above technical solution, further, in step (1), the mass ratio of Al2O3 to TiO2 is in the range of 80:20 to 98:2, and the grinding time is 10 min to 30 min.

[0013] Based on the above technical solution, further, the alkali metal salt in step (2) is one or a combination of two or more of potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonate; the amount of alkali metal is 2% to 10% of the total mass of Al2O3 and TiO2, and the ultrasonic time is 10 min to 30 min.

[0014] Based on the above technical solution, further, in step (3), the drying temperature is 60-120℃ and the drying time is 12-24h.

[0015] Based on the above technical solution, further, in step (4), the calcination time is 2 to 10 hours and the heating rate is 2 to 10 °C / min.

[0016] In another aspect, the present invention provides an alkali-modified bimetallic oxide catalyst prepared by the above-described preparation method.

[0017] The present invention also provides the application of the above-mentioned alkali-modified bimetallic oxide catalyst in the hydrolysis of organic sulfur.

[0018] Based on the above technical solution, the alkali-modified bimetallic oxide catalyst is further applied to the COS and CS2 hydrolysis reaction or to the COS and CS2 hydrolysis reaction under operating conditions containing impurity gases.

[0019] Based on the above technical solution, the impurity gas further includes O2 and CO2.

[0020] The significant advantages of this invention compared to the prior art are as follows:

[0021] (1) The synthesis method of the alkali-modified bimetallic oxide catalyst of the present invention is simple, the raw materials are readily available, only a small amount of water is needed in the preparation process, and no wastewater is generated by washing, which can greatly reduce environmental protection and production costs.

[0022] (2) In this invention, TiO2 is introduced by mechanical mixing, which will not destroy the porous structure and surface hydroxyl groups of Al2O3, will not destroy the intrinsic activity of Al2O3 catalyst, and will make the alkali metal after loading have high dispersibility. The surface of the synthesized catalyst also has more alkaline sites, which is conducive to the hydrolysis reaction. Furthermore, the introduction of TiO2 significantly improves the catalyst's resistance to poisoning.

[0023] (3) The advantages of the catalyst prepared by the present invention are that it exhibits excellent catalytic activity and good stability in the hydrolysis reaction of COS and CS2, and still has high hydrolysis activity under working conditions containing impurity gases such as water vapor, O2 and CO2. Figure description:

[0024] Figure 1 shows K in Example 2. + Scanning electron microscope (SEM) images of the supported 5% TiO2-Al2O3 bimetallic catalyst, where a: SEM image with a scale bar of 5 μm, and b: SEM image with a scale bar of 2 μm.

[0025] Figure 2 shows scanning electron microscope (SEM) images of the commercial Al2O3 catalyst of Comparative Example 1, where a: SEM image with a scale bar of 5 μm, and b: SEM image with a scale bar of 2 μm. Detailed implementation method:

[0026] The specific implementation methods of the present invention will be described in detail below. The specific implementation methods described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] Example 1

[0028] 0.95g of Al2O3 catalyst and 0.05g of TiO2 catalyst were mechanically ground and mixed evenly to prepare a bimetallic oxide catalyst containing TiO2 and Al2O3 (5% TiO2-Al2O3), which was denoted as sample A.

[0029] Example 2

[0030] 0.95 g of Al₂O₃ catalyst and 0.05 g of TiO₂ catalyst were mechanically ground and mixed evenly to prepare a bimetallic oxide catalyst (5% TiO₂-Al₂O₃) containing TiO₂ and Al₂O₃. Then, 0.0734 g of K₂CO₃ was completely dissolved in 5 mL of deionized water and uniformly impregnated onto the 5% TiO₂-Al₂O₃ catalyst. The mixture was then sonicated for 30 min to ensure uniform dispersion, and then dried overnight in an oven at 60 °C. The dried sample was then heated to 450 °C at a rate of 5 °C / min and held for 3 h under air conditions to obtain 5% K₂CO₃ catalyst. + The supported 5% TiO2-Al2O3 catalyst is designated as sample B.

[0031] Figure 1 shows the 5% K in Example 2. + The SEM image of the supported 5% TiO2-Al2O3 catalyst shows an irregular blocky structure.

[0032] Example 3

[0033] 0.95 g of Al₂O₃ catalyst and 0.05 g of TiO₂ catalyst were mechanically ground and mixed evenly to prepare a bimetallic oxide catalyst (5% TiO₂-Al₂O₃) containing TiO₂ and Al₂O₃. Then, 0.1174 g of K₂CO₃ was completely dissolved in 5 mL of deionized water and uniformly impregnated onto the 5% TiO₂-Al₂O₃ catalyst. The mixture was then sonicated for 30 min to ensure uniform dispersion, and then dried overnight in an oven at 60 °C. The dried sample was then heated to 450 °C at a rate of 5 °C / min and held for 3 h under air conditions to obtain 8% K₂CO₃ catalyst. + The supported 5% TiO2-Al2O3 catalyst is denoted as sample C.

[0034] Comparative Example 1

[0035] The commercial Al2O3 catalyst is denoted as sample D.

[0036] Figure 2 shows the SEM image of the commercial Al2O3 catalyst of Comparative Example 1, which has an irregular blocky structure.

[0037] Comparative Example 2

[0038] Commercial TiO2 catalyst, denoted as sample E.

[0039] Example 4

[0040] The catalyst prepared above was used for the hydrolysis of COS and CS2. The catalyst loading was 200 mg, the total flow rate of the reaction gas was 20 mL / min, and the reaction temperature was 170 °C. COS and CS2 with a concentration of 100 ppm were used as feed gases. The feed gases also contained impurities of 0.5% O2, 2.5% CO2, and 30% water vapor. Ar was used as the equilibrium gas. The conditions and results of the COS and CS2 hydrolysis reactions are shown in Tables 1 and 2.

[0041] The formulas for calculating COS conversion rate (%) and CS2 conversion rate (%) are as follows:

[0042] COS conversion rate (%) = (COS concentration in feed gas - COS concentration in discharge gas) / COS concentration in feed gas × 100%;

[0043] CS2 conversion rate (%) = (CS2 concentration in feed gas - CS2 concentration in discharge gas) / CS2 concentration in feed gas × 100%.

[0044] Table 1. Conversion rate (%) of COS hydrolysis of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2

[0045]

[0046] Table 1 shows that the commercial Al2O3 catalyst exhibits certain COS hydrolysis performance due to the presence of surface hydroxyl groups. However, its performance significantly declines after 25 hours of reaction, with the conversion rate dropping to 68.9%. This is likely because impurities in the reaction gas disrupt the active sites of the catalyst, reducing its catalytic performance. The introduction of TiO2 improves the COS hydrolysis performance of the catalyst, and further introduction of K... + The COS hydrolysis performance of the catalyst was further improved. After 25 hours of reaction, the COS conversion rate remained at 100% without any decrease. After 35 hours of reaction, the COS conversion rate still reached over 95%, indicating that the COS hydrolysis activity of the organic sulfur hydrolysis catalyst for blast furnace gas prepared in this invention is more stable, and that it has a stronger ability to resist acidic gases and impurity gases, and better stability.

[0047] Table 2. Conversion rate (%) of CS2 hydrolysis of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2

[0048]

[0049] Table 2 shows that both commercial Al2O3 and commercial TiO2 catalysts possess a certain ability to hydrolyze CS2, but their overall performance is poor. Introducing 5% TiO2 into the Al2O3 catalyst can improve its CS2 hydrolysis performance, but the improvement is limited. Furthermore, adding K... + After being introduced into 5% TiO2-Al2O3, its CS2 hydrolysis performance was significantly improved. Even in the presence of various impurity gases, a CS2 conversion rate of 55% was still maintained after 25 hours of reaction. This indicates that K... + After its introduction, the catalyst's hydrolysis performance is improved, and its resistance to acidic gases and impurity gases is also effectively enhanced.

[0050] In summary, the alkali-modified bimetallic oxide catalyst prepared in this invention exhibits higher COS and CS2 hydrolysis performance than commercial Al2O3 and TiO2 catalysts. Furthermore, the introduction of TiO2 utilizes a mechanical mixing method, which is simple to synthesize, uses readily available raw materials, requires only a trace amount of water during preparation, and eliminates the need for washing to generate wastewater, significantly reducing environmental and production costs. Moreover, mechanical mixing does not damage the porous structure and surface hydroxyl groups of Al2O3, and the sulfates generated during hydrolysis are less likely to clog pores and surfaces, thus preserving the intrinsic activity of the Al2O3 catalyst. Additionally, the supported K... + Its high dispersibility results in more alkaline sites on the surface of the synthesized catalyst, which is beneficial to the hydrolysis reaction.

Claims

1. The application of an alkali-modified bimetallic oxide catalyst in the hydrolysis of organic sulfur, characterized in that, The alkali-modified bimetallic oxide catalyst is applied to the COS and CS2 hydrolysis reaction or to the COS and CS2 hydrolysis reaction under conditions containing impurity gases; the impurity gases include O2 and CO2; the preparation method of the alkali-modified bimetallic oxide catalyst includes the following steps: (1) grinding Al2O3 and TiO2 into powder and mechanically mixing them evenly in a certain proportion; (2) impregnating a certain amount of alkali metal salt solution onto the mixed powder obtained in step (1) and ultrasonically mixing it evenly; (3) placing the powder obtained in step (2) into the... (3) Dry in an oven overnight; (4) Calcine the powder obtained in step (3) at 300-500°C in air to obtain an alkali-modified TiO2-Al2O3 bimetallic catalyst; the mass ratio of Al2O3 to TiO2 in step (1) is 80:20 to 98:2; the alkali metal salt in step (2) is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonate; the amount of alkali metal is 2% to 10% of the total mass of Al2O3 and TiO2, and the ultrasonic time is 10 min to 30 min.

2. The application according to claim 1, characterized in that: The grinding time in step (1) is 10 min to 30 min.

3. The application according to claim 1, characterized in that: In step (3), the drying temperature is 60-120℃ and the drying time is 12-24h.

4. The application according to claim 1, characterized in that: In step (4), the calcination time is 2 to 10 hours and the heating rate is 2 to 10 °C / min.

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