FeOx-M catalyst as well as preparation method and application thereof
By preparing FeOx-Cs catalysts with γ-Fe2O3 as the main crystalline phase, the problems of insufficient activity and stability of existing catalysts at medium and low temperatures are solved, realizing efficient and low-cost selective oxidation of H2S, which is suitable for tail gas treatment in industries such as steel, oil and gas processing.
Patent Information
- Application Number
- CN202510910823.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-11-11
AI Technical Summary
Existing catalysts exhibit poor selective oxidation activity and insufficient stability at medium and low temperatures for H2S, and are also costly, making it difficult to achieve high sulfur selectivity and high sulfur capacity, thus limiting their industrial applications.
FeOx-Cs catalysts with γ-Fe2O3 as the main crystalline phase were prepared by using alkali metal (Cs, Li, Na) doped FeOx catalysts through a mild co-precipitation-calcination method. The activity and stability of the catalysts under medium temperature conditions were controlled to improve desulfurization efficiency and sulfur selectivity.
It achieves efficient desulfurization at medium temperatures, with a sulfur selectivity of 94.0%, ultra-long stability, and low catalyst cost, making it suitable for industrial exhaust gas treatment in industries such as steel, oil and gas processing.
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Figure CN120920008A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst materials technology, specifically to an FeOx-M catalyst, its preparation method and application, and more particularly to a method for preparing an FeOx-Cs catalyst with high desulfurization efficiency, excellent stability and sulfur selectivity, and its application in the selective oxidation of hydrogen sulfide (H2S) at intermediate temperatures (60–200℃). Background Technology
[0002] Currently, the selective oxidation of H2S to elemental sulfur is a key reaction in industrial waste gas treatment. Traditional catalysts mainly employ α-Fe2O3, supported alumina, and noble metal systems. These materials generally suffer from the following problems:
[0003] α-Fe2O3 has poor reactivity, especially at temperatures below 150°C where it is almost inactive.
[0004] Although γ-Fe2O3 has high activity, it has poor thermal stability, rapid phase transition, and short lifespan.
[0005] Precious metal catalysts are expensive, difficult to recycle, and have unstable performance under aqueous reaction conditions.
[0006] Traditional iron oxide catalysts generally have low sulfur capacity and produce a lot of SO2 byproducts in the later stages of the reaction, resulting in poor sulfur selectivity.
[0007] The catalyst of the present invention has the following advantages:
[0008] Using Cs + Ions regulate the stability of the γ-Fe2O3 phase, achieving a balance between low-temperature thermal stability and surface activity;
[0009] Under intermediate temperature conditions, the sulfur capacity was increased to 25,489.6 mg S / g_cat.
[0010] It has a significant low-temperature activity window (100–180℃);
[0011] It exhibits high desulfurization activity in the early stage of the reaction, and the sulfur selectivity is improved in the later stage, realizing a self-regulated reaction pathway.
[0012] In summary, the FeOx-Cs catalyst technology provided by this invention is significantly superior to existing technologies in terms of performance, cost, and applicability, and has good prospects for engineering scale-up and patent protection value.
[0013] H2S, an air pollutant, is frequently found in industries such as steel, oil and gas processing, and papermaking. Selective catalytic oxidation of H2S to elemental sulfur is an important H2S degradation technology. Currently, widely used catalysts include iron oxide, manganese oxide, and noble metal-supported oxides, among which iron oxide (Fe2O3) has attracted widespread attention due to its low cost and environmental friendliness. However, the traditional α-Fe2O3 crystalline phase exhibits poor desulfurization activity, low sulfur selectivity, and poor stability in the medium- and low-temperature range, limiting its industrial application. γ-Fe2O3, as a metastable iron oxide phase, possesses high surface activity, but its preparation conditions are demanding and its thermal stability is poor. Summary of the Invention
[0014] In view of this, the present invention provides a FeOx-M catalyst, its preparation method, and its application. The present invention uses an alkali metal (Cs, Li, Na) as a dopant in the FeOx-Cs catalyst, employing a mild co-precipitation-calcination method to achieve a material structure with γ-Fe2O3 as the main crystalline phase. Simultaneously, it significantly improves its desulfurization efficiency in the intermediate-temperature H2S selective oxidation reaction, overcomes the limitations of sulfur capacity and selectivity, and possesses promising prospects for industrial application.
[0015] The technical solution provided by this invention is as follows:
[0016] <First Aspect>
[0017] A method for preparing an FeOx-M catalyst includes the following steps:
[0018] S1. Dissolve ferrous salt in water to form ferric salt solution;
[0019] S2. Iron salt solution is reacted with alkali metal hydroxide MOH at room temperature to form a suspension;
[0020] S3. Filter the suspension, wash the resulting precipitate until neutral, and dry it to obtain the precursor.
[0021] S4. The precursor is calcined in air at a certain heating rate to 250-550℃ and held at that temperature for a period of time to obtain FeOx-M catalyst; wherein M includes at least one of Cs, Li, and Na; X represents the number of oxygen (O) atoms, x = 1-1.5.
[0022] Preferably, M is Cs.
[0023] In S1, the ferrous salt is FeSO4·7H2O, and the molar concentration of the ferrous salt solution is 0.1-0.3 mol / L.
[0024] In S2, the molar ratio of the alkali metal hydroxide to the ferrous salt is (2.0-4.0):1.
[0025] In S2, the alkali metal hydroxide is selected from at least one of LiOH, NaOH, and CsOH.
[0026] In S3, the drying temperature is 100-110℃; the drying time is 10-15 hours.
[0027] In S4, the heating rate is 3-10℃ / min; the holding time is 2-4 hours.
[0028] Preferably, in S4, the calcination temperature is 250-350℃.
[0029] <Second aspect>
[0030] The FeOx-M catalyst prepared by the method described above also falls within the scope of protection of this invention.
[0031] <Third aspect>
[0032] The application of the FeOx-M catalyst in the selective oxidation of H2S at medium temperature is also within the scope of protection of this invention.
[0033] The reaction temperature is 60-200℃, and the reaction atmosphere is a mixture of 100-200ppm H2S and 0.5-1.5vol% O2, with the remainder being N2.
[0034] This invention achieves phase ratio regulation of α / γ-Fe2O3 by controlling the calcination temperature, adapting to different reaction requirements:
[0035] When M is Cs and the calcination temperature is 250–350℃, the catalyst is mainly composed of γ-Fe2O3 crystalline phase.
[0036] When M is Cs, and the calcination temperature is raised to 450℃, the γ-Fe2O3 peak weakens, the α-Fe2O3 characteristic peak begins to strengthen, and the crystalline phase partially transforms.
[0037] When M is Cs and the calcination temperature is raised to 550℃, the main characteristic peaks are α-Fe2O3, while γ-Fe2O3 basically disappears.
[0038] Catalysts based on γ-Fe2O3 (such as FeOx-Cs-350 and FeOx-Cs-250) exhibit excellent desulfurization efficiency at low temperatures (<120℃); catalysts based on α-Fe2O3 (such as FeOx-Cs-550) perform even better at high temperatures (>120℃).
[0039] This invention represents the first systematic development of a FeOx-Cs catalyst based on the γ-Fe2O3 main crystalline phase, which not only exhibits excellent desulfurization performance but also achieves a synergistic breakthrough in ultra-long lifetime and high selectivity within the mid-temperature range. This material is suitable for H2S treatment of industrial waste gases from industries such as steel, oil and gas processing, and papermaking, and has significant industrial application prospects and promotional value.
[0040] Compared with the prior art, the present invention has the following beneficial effects:
[0041] 1. High desulfurization efficiency: The γ-Fe2O3 main crystalline phase structure exhibits excellent H2S oxidation activity at medium temperatures;
[0042] 2. High sulfur selectivity: It inhibits the formation of SO2 byproducts, with an average sulfur selectivity of 94.0%;
[0043] 3. Ultra-long stability: It can operate continuously for more than 1600 hours at a desulfurization efficiency of over 90%;
[0044] 4. Selective oxidation to S instead of SO2 / SO3 avoids secondary pollution and corrosion problems, contributing to the green development of gas purification processes. Raw materials are inexpensive and the preparation process is simple: using FeSO4 and MOH as starting materials, no precious metals or special atmospheres are required, and scale-up synthesis can be achieved in the laboratory or pilot-scale; the catalyst product is elemental sulfur, which is easy to recover and reuse or re-commercialize, promoting the high-value utilization of industrial by-products; good compatibility with existing processes: it can directly replace traditional Fe2O3 or alumina-supported desulfurizing agents without significant modifications to the original equipment structure.
[0045] In summary, the FeOx-Cs material of this invention possesses significant practical and commercial potential, and is particularly suitable for continuous gas-phase desulfurization systems at high and medium temperatures, applicable to multiple important industries such as steel, oil and gas processing, and papermaking. The FeOx-Cs catalyst provided by this invention is suitable for various sulfur-containing gas purification scenarios: H2S pollution is widespread in industries such as steel, oil and gas processing, and papermaking. This catalyst exhibits highly efficient and selective oxidation capabilities in the medium-temperature range, effectively converting H2S into elemental sulfur. It can significantly reduce operating and maintenance costs: its high breakthrough sulfur capacity reduces the frequency of catalyst replacement, extends the operating cycle of the unit, and lowers industrial operating expenses.
[0046] This invention innovatively incorporates alkali metals (such as Cs) + Li+, Na +By introducing an iron oxide system, a FeOx-Cs catalyst with γ-Fe2O3 as the main phase was prepared, exhibiting excellent desulfurization activity, selectivity, and ultra-long-term stability, providing a novel solution for gas desulfurization under intermediate temperature conditions. It possesses advantages such as high reproducibility, ease of operation, and wide applicability, demonstrating extremely high technological value and promising prospects for industrial transformation. Attached Figure Description
[0047] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0048] Figure 1 The XRD patterns are of the FeOx-Cs catalysts prepared at different calcination temperatures in Example 1.
[0049] Figure 2 XRD patterns of different alkali metal modified catalysts prepared under calcination conditions at 350℃;
[0050] Figure 3 The graph shows a comparison of the desulfurization performance and stability of different catalysts in the selective oxidation of H2S, where (a) is the stability graph of H2S conversion rate; (b) is the breakthrough sulfur capacity (mg S / g_cat); and (c) is the sulfur selectivity (%).
[0051] Figure 4 The desulfurization efficiency and selectivity curves of FeOx-Cs catalysts prepared at different calcination temperatures at different temperatures; where (a) is the H2S removal rate (%); and (b) is the sulfur selectivity (%). Detailed Implementation
[0052] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.
[0053] Example 1: Preparation of FeOx-Cs catalyst
[0054] The preparation steps are as follows:
[0055] (1) Preparation of iron salt solution: Weigh 2.780g FeSO4·7H2O (0.01mol), dissolve it in 50mL of deionized water, and stir until completely dissolved to obtain a light green iron salt solution.
[0056] (2) Coprecipitation reaction: Weigh 3.359g MOH·H2O (0.02mol) and add it to the above iron salt solution; stir magnetically for 60 minutes at room temperature (25℃) to form a light brown suspension.
[0057] (3) Washing and drying: Filter the suspension and wash the resulting precipitate repeatedly with deionized water until the filtrate is neutral (pH≈7). Place the precipitate in an oven and dry it at 105°C for 12 hours to obtain the precursor powder.
[0058] (4) Calcination and activation: The dried precursor powder was placed in a muffle furnace and heated to different temperatures (250℃, 350℃, 450℃, 550℃, 650℃) at a heating rate of 5℃ / min in an air atmosphere. See Table 1 for details. After calcination for 3 hours, the powder was naturally cooled and then ground to obtain the FeOx-Cs catalyst.
[0059] Table 1
[0060] Calcination temperature Corresponding FeOx-Cs catalyst number 250℃ FeOx-Cs-250 350℃ FeOx-Cs-350 450℃ FeOx-Cs-450 550℃ FeOx-Cs-550 650℃ FeOx-Cs-650
[0061] The crystal phase analysis of FeOx-Cs catalyst samples calcined at different temperatures (FeOx-Cs-250, FeOx-Cs-350, FeOx-Cs-450, FeOx-Cs-550) was performed by X-ray diffraction (XRD), and the results are as follows:
[0062] FeOx-Cs-250 and FeOx-Cs-350 samples: The diffraction peak positions are consistent with the JCPDS#39-1346 (γ-Fe2O3) standard card, indicating that the γ-Fe2O3 main crystalline phase can be stably obtained at this temperature;
[0063] FeOx-Cs-450 sample: The γ-Fe2O3 peak weakened and the α-Fe2O3 characteristic peak (JCPDS#33-0664) began to strengthen in the XRD pattern, indicating that a partial phase transformation occurred;
[0064] FeOx-Cs-550 sample: mainly α-Fe2O3 characteristic peaks, high crystallinity, γ-Fe2O3 basically disappeared.
[0065] Conclusion: Calcination temperature is a key factor in regulating the crystal phase of Fe2O3. Cs element can inhibit the transformation of γ-Fe2O3 to α-Fe2O3, keeping it in a metastable phase below 350℃ and improving its low-temperature activity.
[0066] like Figure 1As shown, with the calcination temperature increasing from 250℃ to 550℃, the crystal phase of the Cs-T catalyst gradually transforms from γ-Fe2O3 to α-Fe2O3, and the crystallinity of the catalyst gradually increases. Furthermore, even when the calcination temperature is reduced to 250℃, the characteristic peaks of α-Fe2O3 can still be observed, making it difficult to prepare a catalyst with a pure γ-Fe2O3 phase.
[0067] Example 2: Preparation of FeOx-Li-350 catalyst
[0068] (1) Weigh 0.01 mol FeSO4·7H2O (2.78 g), dissolve it in 50 mL of deionized water, and stir until completely dissolved to obtain a light green iron salt solution;
[0069] (2) Weigh 0.02 mol LiOH (0.480 g) and add it to the above iron salt solution. Stir magnetically for 60 minutes at room temperature to form a light-colored suspension.
[0070] (3) After filtering the suspension, the precipitate was washed with deionized water until the pH of the filtrate was ≈7; the precipitate was dried at 105℃ for 12 hours to obtain the precursor powder.
[0071] (4) The precursor powder was placed in a muffle furnace and heated to 350°C at 5°C / min in air atmosphere. It was calcined for 3 hours, cooled naturally, and then ground to obtain the FeOx-Li catalyst.
[0072] Example 3: Preparation of FeOx-Na-350 catalyst
[0073] (1) Weigh 0.01 mol FeSO4·7H2O (2.78 g), dissolve it in 50 mL of deionized water, and stir until completely dissolved to obtain a light green iron salt solution;
[0074] (2) Weigh 0.02 mol NaOH (0.800 g) and add it to the above iron salt solution. Stir magnetically for 60 minutes at room temperature to form a light-colored suspension.
[0075] (3) After filtering the suspension, the precipitate was washed with deionized water until the pH of the filtrate was ≈7; the precipitate was dried at 105℃ for 12 hours to obtain the precursor powder.
[0076] (4) The precursor powder was placed in a muffle furnace and heated to 350°C at 5°C / min in air atmosphere. It was calcined for 3 hours, cooled naturally, and then ground to obtain the FeOx-Li catalyst.
[0077] X-ray diffraction, such as Figure 2 .
[0078] Preparation of Comparative Example 1: FeOx-K-350 Catalyst
[0079] (1) Weigh 0.01 mol FeSO4·7H2O (2.78 g), dissolve it in 50 mL of deionized water, and stir until completely dissolved to obtain a light green iron salt solution;
[0080] (2) Weigh 0.02 mol KOH (1.120 g) and add it to the above iron salt solution. Stir magnetically for 60 minutes at room temperature to form a light-colored suspension.
[0081] (3) After filtering the suspension, the precipitate was washed with deionized water until the pH of the filtrate was ≈7; the precipitate was dried at 105℃ for 12 hours to obtain the precursor powder.
[0082] (4) The precursor powder was placed in a muffle furnace and calcined at 350°C at a rate of 5°C / min under air atmosphere for 3 hours. After natural cooling, it was ground to obtain the FeOx-K catalyst. X-ray diffraction was performed as follows: Figure 2 .
[0083] from Figure 2 From this, we can obtain FeO x The -K-350 sample exhibits an α-Fe2O3 crystalline phase, while the samples modified with FeOx-Cs-350, FeOx-Li-350, and FeOx-Na-350 are predominantly γ-Fe2O3 crystalline phases. However, a small number of characteristic peaks corresponding to α-Fe2O3 can be observed in the spectrum, indicating that these are mixed crystalline phase samples.
[0084] Performance testing (desulfurization performance testing)
[0085] The FeOx-Cs-350 series catalysts prepared in Example 1 and the FeOx-Li-350, FeOx-Na-350, and FeOx-K-350 catalysts prepared in Comparative Example 1 were subjected to desulfurization tests.
[0086] The activity test of H2S catalytic oxidation was conducted in a fixed-bed quartz flow reactor (U-shaped tube with an inner diameter of 6 mm and an outer diameter of 8 mm). This system mainly consists of four parts: 1) a simulated gas preparation device; 2) a fixed-bed reactor; 3) a sulfur-containing pollutant detection device; and 4) a tail gas absorption device. 100 mg of catalyst was added for each experiment, and the catalyst was fixed in the quartz tube reactor using quartz wool. The reaction temperature was controlled at 60-200℃ using a temperature controller. The flow rate was controlled to ensure the simulated gas consisted mainly of 200 ppm H2S, 1 vol% O2, with N2 as the equilibrium gas. The reaction was carried out at atmospheric pressure. After the entire reaction system stabilized, samples were taken at time intervals, 1-2 times each at the inlet and outlet. The collected samples were analyzed by an Agilent 7890B gas chromatograph equipped with an FPD detector to determine the concentrations of H2S and byproducts (SO2) at the inlet and outlet. The O2 concentration was analyzed by a Haixin GC-950 gas chromatograph equipped with a TCD detector. Breakthrough time (BT) is defined as the point at which the H2S outlet concentration reaches 20 ppm. Breakthrough sulfur capacity (BSC) is calculated as the total desulfurization amount per gram of catalyst before BT, using the following formula:
[0087]
[0088] Among them, F and M s V m The total flow rate of the simulated gas (mL / min) -1 ), molar mass of sulfur (32 g mol) -1 The gas was at 25℃ and 101.325 kPa (24.5 L mol). -1 Molar volume of [H2S] under the following conditions in and [H2S] out The concentrations of H2S (ppm) at the inlet and outlet are respectively, and the concentrations of M are respectively. catalyst The mass (g) represents the catalyst.
[0089] In addition, H2S removal rate (X H2S ) and sulfur selectivity (S sulfur The calculation formula is as follows:
[0090]
[0091] Among them, [SO2] out It is the SO2 concentration (ppm) at the outlet.
[0092] Table 2
[0093]
[0094] The table clearly shows the influence of alkali metal type on catalyst structure and performance. In particular, FeOx-Cs (FeOx-Cs-350) far surpasses other samples in terms of breakthrough capacity and stability, demonstrating its excellent practical performance.
[0095] like Figure 1 As shown, the desulfurization performance (60–200℃) is as follows: FeOx-Cs-350 exhibits better desulfurization efficiency than FeOx-Li-350, FeOx-Na-350, and FeOx-K-350; the desulfurization efficiency of the FeOx-Cs-350 catalyst remains above 90% throughout the entire temperature range; the γ-Fe2O3 crystal phase is superior to α-Fe2O3, and FeOx-K-350 has the worst desulfurization performance, indicating that alkali metals have a significant impact on crystal phase regulation.
[0096] like Figure 1 and Figure 3 As shown, although FeOx-K-350 has poor desulfurization performance, it has the best sulfur selectivity; FeOx-Cs-35 has a sulfur selectivity of 94%, showing high sulfur yield and low by-product formation; FeOx-Cs-350 and FeOx-Cs-250 have excellent yields at low temperatures (<120℃), while FeOx-Cs-550 has the best yield at high temperatures (>120℃).
[0097] As shown in Table 2, FeOx-Cs-350 can operate continuously for 1612 hours at a desulfurization efficiency of 90%, with a sulfur capacity of 25,489.6 mg S / gcat. Its stability is far superior to FeOx-Li-350 (67 hours) and FeOx-Na-350 (318 hours). The sulfur selectivity increases with the increase of operating time, showing self-passivation and peroxidation inhibition capabilities.
[0098] Figure 4 The desulfurization efficiency and selectivity curves of FeOx-Cs catalysts prepared at different calcination temperatures at different temperatures are shown; where (a) represents the H2S removal rate (%) and (b) represents the sulfur selectivity (%).
[0099] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.
Claims
1. A method for preparing an FeOx-M catalyst, characterized in that, Includes the following steps: S1. Dissolve ferrous salt in water to form ferric salt solution; S2. Iron salt solution is reacted with alkali metal hydroxide MOH at room temperature to form a suspension; S3. Filter the suspension, wash the resulting precipitate until neutral, and dry it to obtain the precursor. S4. The precursor is calcined in air at a certain heating rate to 250-550℃ and held at that temperature for a period of time to obtain FeOx-M catalyst; wherein M includes at least one of Cs, Li, and Na; X represents the number of oxygen (O) atoms, x = 1-1.
5.
2. The preparation method according to claim 1, characterized in that, In S1, the ferrous salt is FeSO4·7H2O, and the molar concentration of the ferrous salt solution is 0.1-0.3 mol / L.
3. The preparation method according to claim 1, characterized in that, In S2, the molar ratio of the alkali metal hydroxide to the ferrous salt is 2.0-4.0:
1.
4. The preparation method according to claim 1, characterized in that, In S2, the alkali metal hydroxide is selected from at least one of LiOH, NaOH, and CsOH.
5. The preparation method according to claim 1, characterized in that, In S3, the drying temperature is 100-110℃; the drying time is 10-15 hours.
6. The preparation method according to claim 1, characterized in that, In S3, the heating rate is 3-10℃ / min; the holding time is 2-4 hours.
7. A FeOx-M catalyst prepared by any one of claims 1-6.
8. The application of the FeOx-M catalyst as described in claim 7 in the selective oxidation reaction of H2S at intermediate temperature.
9. The application according to claim 8, characterized in that, The reaction temperature is 60-200℃, and the reaction atmosphere is a mixture of 100-200ppm H2S and 0.5-1.5vol% O2, with the remainder being N2.