High-stability zinc oxide coal gas desulfurizer with core-shell structure and preparation method of high-stability zinc oxide coal gas desulfurizer

Abstract

The invention discloses a high-stability core-shell structure zinc oxide coal gas desulfurizer and a preparation method thereof, and belongs to the technical field of coal chemical desulfurizer preparation.The preparation method of the high-stability core-shell structure zinc oxide coal gas desulfurizer comprises the following steps that a zinc source, CTAB, a silicon source and an aluminum source are mixed, and sequentially carrying out microwave hydrothermal treatment, cold press molding and oxidation treatment to obtain the high-stability core-shell structure zinc oxide coal gas desulfurizer. The preparation process is simple, industrial production of the desulfurizer is easy to realize, the desulfurizer adopts a molecular sieve material with high strength and rich porosity as a carrier, the desulfurizer has a core-shell structure, the durability of the desulfurizer can be improved, and the pulverization and caking phenomena of the desulfurizer are remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical desulfurization agent preparation technology, and particularly relates to a highly stable core-shell structure zinc oxide coal gas desulfurization agent and its preparation method. Background Technology

[0002] Coal gasification technology is one of the important technical means for the clean and efficient utilization of coal. During the coal gasification process, sulfur in coal is converted into hydrogen sulfide in a high-temperature reducing environment and released, causing problems such as corrosion of subsequent process equipment, affecting product quality, and causing environmental pollution. Therefore, it is necessary to remove hydrogen sulfide from the coal gas before it enters the subsequent processes.

[0003] Dry desulfurization technology uses solid-phase desulfurizing agents or catalysts to remove and convert hydrogen sulfide from coal gas. Compared with traditional wet desulfurization technology, dry desulfurization technology has advantages such as simple process flow, convenient operation, low equipment cost, and high thermal efficiency. The essence of the sulfidation reaction in dry desulfurization is a sulfur-oxygen replacement process. Single or combined metal oxides react with hydrogen sulfide gas in the coal gas, and the sulfur ions in the hydrogen sulfide replace the oxygen ions in the metal oxides, forming metal sulfides to achieve desulfurization. Therefore, as the sulfidation reaction proceeds, the active components gradually transform from smaller oxide molecules to larger sulfides. The pore structure of the desulfurizing agent collapses and becomes blocked due to the volume expansion of the active components, causing the desulfurizing agent to pulverize and significantly reduce its performance. Frequent replacement of the desulfurizing agent also increases production costs, which restricts the development of dry desulfurization technology. Therefore, studying the sulfidation regeneration behavior of desulfurizing agents and reducing their usage loss is of great significance for the industrial application of desulfurization technology.

[0004] While dry desulfurization technology boasts high desulfurization precision and thermal efficiency, and features no waste generation and easy product recovery, the desulfurizing agent experiences pulverization and agglomeration during use due to factors such as active component migration and carrier structure collapse. This reduces desulfurization efficiency, increases agent loss, and raises production costs, thus hindering the development of dry desulfurization technology.

[0005] The present invention aims to provide a core-shell type coal gas desulfurizer and its preparation method. By utilizing the microstructural characteristics of the core-shell structure, the internal space can be efficiently configured, reducing the migration and aggregation of active components, enhancing the mechanical strength of the desulfurizer, and improving the durability and reactivity of the desulfurizer. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a highly stable core-shell structured zinc oxide coal gas desulfurizer and its preparation method. By scientifically designing the core-shell structure and precisely controlling the synthesis parameters, this invention successfully solves the problem of pulverization and deactivation caused by the migration and aggregation of active components and carrier collapse in traditional dry desulfurizers. While ensuring high desulfurization efficiency, it significantly extends the material's service life, reduces replacement frequency and operating costs, and provides a practical and feasible technical path for efficient, stable, and economical sulfur pollution control in coal gasification processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a highly stable core-shell structured zinc oxide gas desulfurizer includes the following steps:

[0009] The highly stable core-shell structured zinc oxide desulfurizer for coal gas was prepared by mixing zinc source, CTAB, silicon source and aluminum source, and then sequentially performing microwave hydrothermal treatment, cold pressing and oxidation treatment.

[0010] Core-shell structured materials, as carrier materials with composite hierarchical pores, integrate the structural properties of both the core and shell materials. The microstructure of the carrier can be precisely controlled by changing the core type and controlling the shell thickness, which helps to improve the dispersion of active components and enhances the carrier's strength. This invention, through the combination of the core and shell, creates a composite porous carrier with a pore structure conducive to molecular diffusion, enabling efficient configuration of the internal space and improving the utilization rate of internal active components. Simultaneously, the hierarchical pore structure, through differences in pore structure construction, prevents the outward migration and aggregation of active components during the sulfidation reaction, acting as a confinement mechanism and reducing the performance degradation of the desulfurizer caused by the agglomeration and expansion of active components. In other words, this invention significantly improves the overall service performance of dry desulfurization materials in high-temperature reducing gas environments by constructing a zinc oxide coal gas desulfurizer with a highly stable core-shell structure. Its preparation process integrates three key technical aspects: molecular sieve carrier design, microwave hydrothermal controllable synthesis, and precise oxidation treatment. This not only features a simple process, clear parameters, and ease of industrial scale-up, but also achieves effective confinement and protection of the behavior of active components at the microstructure control level.

[0011] The formation mechanism of the core-shell structure of this invention is as follows: the core of the desulfurizing agent of this invention is a ZnO active phase; the shell is a porous framework of silicon-aluminum molecular sieve; in the initial stage of microwave hydrothermal synthesis, Zn... 2+In the NH3·H2O-NH4Cl buffer system at pH=10.0, zinc hydroxide or basic zinc species are first formed and serve as nucleation centers. Subsequently, silicon sources (sodium metasilicate nonahydrate) and aluminum sources (sodium aluminate) are gradually deposited and condensed on its surface to form an aluminosilicate framework. The active component precursor is "encased" inside a porous network composed of aluminosilicates, forming a highly stable core-shell structure zinc oxide desulfurizing agent for coal gas with ZnO as the core.

[0012] Optionally, the zinc source is selected from any one of zinc chloride, zinc nitrate, and zinc acetate.

[0013] Furthermore, the zinc source needs to be dissolved in an NH3·H2O-NH4Cl buffer solution before use;

[0014] The pH of the NH3·H2O-NH4Cl buffer solution is 9.0-10.0.

[0015] Furthermore, the pH of the NH3·H2O-NH4Cl buffer solution is 10.0.

[0016] Optionally, the silicon source is sodium metasilicate nonahydrate (Na2Si2O3·9H2O);

[0017] The aluminum source is sodium aluminate (NaAlO2).

[0018] Furthermore, the zinc-silicon molar ratio of the zinc salt and the silicon source is 0.21-0.43:1;

[0019] The silicon-aluminum molar ratio of the silicon source and the aluminum source is 20-40:1.

[0020] Furthermore, the zinc-silicon molar ratio of the zinc salt and the silicon source is 0.32:1;

[0021] The silicon-aluminum molar ratio of the silicon source and the aluminum source is 30:1.

[0022] Optionally, the microwave hydrothermal conditions are: microwave power 200-600W, microwave reaction temperature 70-90℃, and microwave reaction time 1-3h.

[0023] Furthermore, the conditions for microwave hydrothermal treatment are: microwave power 400W, microwave reaction temperature 80℃, and microwave reaction time 2h.

[0024] Optionally, the cold pressing conditions are: the forming pressure is 2.0 MPa.

[0025] Optionally, the oxidation treatment conditions are: oxidation temperature 550-750℃, oxygen concentration 4-12%, and space velocity 2-6 L·g. -1 ·h -1 The oxidation time was 4 hours.

[0026] Furthermore, the oxidation treatment conditions are: oxidation temperature 550℃, oxygen concentration 8%, and space velocity 4 L·g⁻¹. -1 ·h -1 The oxidation time was 4 hours.

[0027] A highly stable core-shell structured zinc oxide gas desulfurizer is prepared by the above-described preparation method.

[0028] The process of this invention is simple and easy to realize the industrial production of desulfurizing agents. The desulfurizing agent prepared uses high-strength, porous molecular sieve material as a carrier and has a core-shell structure, which can improve the durability of the desulfurizing agent and significantly reduce the pulverization and agglomeration phenomenon of the desulfurizing agent.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] This invention significantly improves the overall performance of coal gas desulfurizers by constructing a zinc oxide-based desulfurizer with a core-shell structure. Using molecular sieves as a carrier, and combining optimized zinc-silicon and silicon-aluminum ratios with a microwave hydrothermal synthesis process, this desulfurizer forms a multi-level porous and confined structure. This effectively inhibits the migration, agglomeration, and volume expansion of active components during the sulfidation-regeneration process, thereby significantly reducing the pulverization rate and maintaining high sulfur capacity. Simultaneously, the core-shell structure enhances the material's mechanical strength, ensuring its structural stability under high-temperature and high-gas-velocity conditions.

[0031] Furthermore, the process of this invention is simple, the parameters are controllable, and it is easy to scale up industrially. The desulfurizing agent produced has high desulfurization efficiency, excellent cycle stability, and long service life. It effectively solves the technical bottlenecks of traditional zinc oxide desulfurizing agents, such as easy pulverization, short life, and poor regeneration performance, and provides a high-performance and low-cost solution for dry desulfurization of coal gas. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 The image shows the microstructure of the desulfurizing agent prepared under the optimal conditions of this invention under a transmission electron microscope at a scale of 20 μm. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0040] All raw materials used in this invention were purchased from the market.

[0041] The technical solution of the present invention will be further illustrated by the following embodiments.

[0042] Example 1

[0043] A method for preparing a highly stable core-shell structured zinc oxide gas desulfurizer includes the following steps:

[0044] (1) Dissolve a certain amount of zinc salt (zinc acetate) in deionized water, and use a peristaltic pump to add a certain pH of NH3·H2O-NH4Cl buffer solution at a rate of 1.0 mL / min. Stir the solution thoroughly at room temperature.

[0045] (2) Dissolve hexadecyltrimethylammonium bromide (CTAB) completely in deionized water. When the solution is clear and transparent, slowly add the solution obtained in step (1) and stir. Add the mixed solution of sodium metasilicate nonahydrate and sodium aluminate (NaAlO2) at a rate of 1.0 mL / min to the above solution. Stir and mix thoroughly and continuously for a certain period of time. During this period, use a pH meter to monitor the pH value in real time to keep it constant (i.e., keep the pH of the reaction system constant based on the pH of the aforementioned NH3·H2O-NH4Cl buffer solution).

[0046] (3) The solution is transferred to a microwave synthesizer for microwave hydrothermal synthesis. The microwave power, reaction temperature and time are adjusted for reaction. After the reaction, the obtained solution is repeatedly washed with deionized water until the filtrate is neutral. The obtained product is placed in a drying oven to dry, thus obtaining the desulfurizing agent precursor. Then the obtained precursor is cold-pressed in a mold at a pressure of 2.0 MPa to form a cube of 3 mm × 3 mm × 3 mm. It is then oxidized under predetermined conditions of different oxidation temperatures, oxygen concentrations and space velocities for 4 h. After cooling to room temperature, the high-temperature coal gas desulfurizing agent is obtained.

[0047] The parameters and performance tests involved in the above preparation process were as follows: the optimal conditions were a zinc-silicon molar ratio of 0.32:1, a buffer solution pH of 10.0, a silicon-aluminum molar ratio of 30:1, a microwave power of 400W, a microwave reaction temperature of 80℃, a microwave reaction time of 2h, an oxidation temperature of 550℃, an oxygen concentration of 8%, and a space velocity of 4 L·g⁻¹. -1 ·h -1 Table 1 shows the results of single-factor experiments and performance tests with different parameters (when a certain parameter condition is specified in the table, the other parameter conditions correspond to the optimal condition parameters).

[0048] The sulfidation performance test was conducted at a temperature of 500 ℃. The desulfurizing agent was in cubic blocks of 3×3×3 mm. 3.0 g of desulfurizing agent was used in each experiment, and the inlet gas space velocity was 4 L·g⁻¹. -1 ·h -1 The sulfurization atmosphere was simulated Texaco gas.

[0049] After vulcanization is complete, the desulfurizing agent is used at 650℃, oxygen concentration of 8%, and space velocity of 4 L·g⁻¹. -1 ·h -1 Regeneration was carried out under certain conditions, followed by a second vulcanization performance test.

[0050] The radial compressive strength conforms to the GB-T 44750-2024 standard for measuring the compressive strength of granules.

[0051] The formula for calculating sulfur capacity is:

[0052] (1)

[0053] Wherein, SC represents the breakthrough sulfur capacity of the desulfurizing agent (g S / 100 g desulfurizing agent); WHSV represents the mass hourly space velocity of the inlet reactant gas (L·g -1 ·h -1 ); M s The molar mass of sulfur is expressed as 32.06 g mol. -1 ); V m The molar volume of the gas at standard temperature and atmospheric pressure (24.5 L·mol⁻¹) -1 ); C in and C out These represent the concentrations (ppm) of sulfur-containing gases in the inlet and outlet gases, respectively; t represents the sulfidation reaction time (h) of the desulfurizing agent.

[0054] The formula for calculating the pulverization rate (the ratio of the mass of pulverized desulfurizer after ten sulfidation processes to the mass of the original desulfurizer) is as follows:

[0055] (2)

[0056] The sieving process uses a 40-mesh sieve.

[0057] Table 1

[0058]

[0059] As can be seen from the single-factor experiment and performance test results shown in Table 1:

[0060] Among all process parameters, the zinc-silicon molar ratio of 0.32:1 exhibited the best overall performance: the initial sulfur capacity was as high as 11.6%, and it still maintained 11.3% after ten sulfidation-regeneration cycles, with a pulverization rate of only 2.51% and a radial compressive strength of 126 N / cm. In contrast, a zinc-silicon ratio that was too low (0.21:1) resulted in insufficient active components and a low sulfur capacity; while a ratio that was too high (0.43:1) increased the initial sulfur capacity to 14.2%, but the sulfur capacity significantly decreased to 9.3% after cycling, and the pulverization rate rose sharply to 13.20%, indicating that excessive zinc damaged the stability of the carrier structure.

[0061] The pH value of the buffer solution has a significant impact on the performance of the desulfurizer. When the pH is 10.0, all indicators reach their peak values; when the pH drops to 9.0, the sulfur capacity drops sharply to 4.2% after ten cycles, and the pulverization rate is as high as 16.82%, indicating that insufficient alkalinity is not conducive to the formation and stability of the porous shell; while pH=9.5 shows some improvement, it is still not as good as the overall performance of pH=10.0.

[0062] The performance is optimal when the silicon-aluminum molar ratio is 30:1, with stable sulfur capacity, low pulverization rate, and high strength. Both excessively high (40:1) and excessively low (20:1) silicon-aluminum ratios lead to structural imbalance. Although the pulverization rate is slightly lower at 20:1 (1.74%), the circulating sulfur capacity decreases significantly, indicating that excessive aluminum content may inhibit pore development or affect zinc species dispersion.

[0063] Optimization of microwave synthesis conditions showed that 400 W power, 80℃ reaction temperature, and 2 h reaction time were the optimal combination. Under these conditions, the desulfurizer exhibited high sulfur capacity, excellent cycle stability, and low pulverization rate. Excessive power (600 W) or excessive temperature (90℃) led to structural densification or grain coarsening, reducing reactivity; insufficient time (1 h) resulted in incomplete formation of the porous carrier and poor cycle performance.

[0064] The oxidation treatment parameters are 550℃, 8% oxygen concentration, and space velocity of 4 L·g. -1 ·h -1 The optimal conditions are as follows. Increasing the oxidation temperature to 650℃ or 750℃ significantly aggravates the sintering of the desulfurizer, resulting in a pulverization rate of 10.31% and 19.22% respectively, and a significant decrease in circulating sulfur capacity. Excessive oxygen concentration or excessive space velocity will cause a large amount of heat to be released during the formation of the desulfurizer, increasing the internal temperature gradient and weakening the structural stability.

[0065] Of particular note is that, compared with pure zinc oxide (sulfur capacity of only 4.5%, which drops to 1.3% after ten cycles), the core-shell structured desulfurizer prepared in this invention not only has significantly improved initial activity, but also exhibits excellent cycle durability and mechanical strength, fully verifying the key role of the core-shell structure in inhibiting the migration and aggregation of active components, alleviating volume expansion stress, and maintaining the integrity of the pores.

[0066] Figure 1 The image shows the microstructure of the desulfurizer prepared under the optimal conditions of this invention using a transmission electron microscope at a scale of 20 nm. As can be seen from the image, the desulfurizer prepared by this invention has a clear core-shell structure, and the shell layer has a rich and uniform pore structure. The desulfurizer plays a supporting and confining role in the sulfurization reaction process, thereby reducing the pulverization phenomenon of the desulfurizer caused by the aggregation and migration of active components, and promoting the dispersion of active components. Therefore, the desulfurizer has high reactivity and durability.

[0067] In summary, by precisely controlling the zinc-silicon ratio, pH, silicon-aluminum ratio, and microwave-oxidation process parameters, this invention successfully constructed a core-shell zinc oxide desulfurizer with high reactivity, strong structural stability, and excellent anti-pulverization ability, providing reliable material support for the long-term, low-cost operation of dry gas desulfurization technology.

[0068] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly stable core-shell structured zinc oxide coal gas desulfurizing agent, characterized in that, Includes the following steps: The highly stable core-shell structured zinc oxide desulfurizer for coal gas was prepared by mixing zinc source, CTAB, silicon source and aluminum source, and then sequentially performing microwave hydrothermal treatment, cold pressing and oxidation treatment.

2. The preparation method of a highly stable core-shell structured zinc oxide gas desulfurizer according to claim 1, characterized in that, The zinc source is selected from any one of zinc chloride, zinc nitrate, and zinc acetate; The zinc source needs to be dissolved in an NH3·H2O-NH4Cl buffer solution with a pH of 9.0-10.0 before use.

3. The preparation method of a highly stable core-shell structure zinc oxide gas desulfurizer according to claim 2, characterized in that, The pH of the NH3·H2O-NH4Cl buffer solution is 10.

0.

4. The preparation method of a highly stable core-shell structured zinc oxide gas desulfurizer according to claim 1, characterized in that, The silicon source is sodium metasilicate nonahydrate, and the aluminum source is sodium aluminate; The zinc salt and silicon source have a zinc-silicon molar ratio of 0.21-0.43:1; The silicon-aluminum molar ratio of the silicon source and the aluminum source is 20-40:

1.

5. The preparation method of a highly stable core-shell structure zinc oxide gas desulfurizer according to claim 4, characterized in that, The zinc salt and silicon source have a zinc-silicon molar ratio of 0.32:1; The silicon-aluminum molar ratio of the silicon source and the aluminum source is 30:

1.

6. The preparation method of a highly stable core-shell structured zinc oxide gas desulfurizer according to claim 1, characterized in that, The conditions for microwave hydrothermal treatment are: microwave power 200-600W, microwave reaction temperature 70-90℃, and microwave reaction time 1-3h.

7. The preparation method of a highly stable core-shell structure zinc oxide gas desulfurizer according to claim 6, characterized in that, The conditions for microwave hydrothermal treatment are: microwave power 400W, microwave reaction temperature 80℃, and microwave reaction time 2h.

8. The preparation method of a highly stable core-shell structured zinc oxide gas desulfurizer according to claim 1, characterized in that, The oxidation treatment conditions are: oxidation temperature 550-750℃, oxygen concentration 4-12 vol%, space velocity 2-6 L·g -1 ·h -1 .

9. The preparation method of a highly stable core-shell structured zinc oxide gas desulfurizer according to claim 8, characterized in that, The oxidation treatment conditions were: oxidation temperature 550℃, oxygen concentration 8%, and space velocity 4 L·g⁻¹. -1 ·h -1 .

10. A highly stable core-shell structured zinc oxide gas desulfurizer, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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