Method for synthesizing MCM-41 mesoporous molecular sieve by using coal gasification slag
MCM-41 mesoporous molecular sieves were prepared by acid-base leaching of coal gasification slag combined with hydrothermal reaction, which solved the problem of direct synthesis of MCM-41 from gasification slag, realized low-cost and high-efficiency molecular sieve preparation, and improved catalytic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH
- Filing Date
- 2024-03-15
- Publication Date
- 2026-06-09
Smart Images
Figure CN118145671B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid waste utilization technology, specifically relating to a method for synthesizing MCM-41 mesoporous molecular sieves using coal gasification slag. Background Technology
[0002] As a core technology in the development of modern coal chemical industry, coal gasification technology has made rapid progress, but it has also resulted in serious industrial solid waste emissions. Gasification slag is a new type of solid waste generated during coal gasification, formed by the incomplete combustion of coal and oxygen or oxygen-enriched air. Its main components are residual carbon and inorganic minerals, with impurities primarily including calcium, magnesium, and iron. To address the enormous environmental pressure from gasification slag inventory and achieve "zero emissions" from gasification slag technology, developing gasification slag resource utilization technologies is essential. The preparation of high-value-added materials has been explored as a research hotspot in the utilization of gasification slag resources. For example, Xu et al. (Xu, YC, XL Characterization of coal gasification slag-based activated carbon and its potential application in lead removal. ENVIRONMENTALTECHNOLOGY, 2018. 39(3): p. 10.) studied industrial solid waste-based catalysts, and Gu et al. (Gu, YY and X.C. Qiao, A carbon silica composite prepared from water slurry coalgasification slag. Microporous and Mesoporous Materials, 2019. 276: p. 303-307.) developed carbon-silicon composite materials. These studies have further broadened the utilization directions and improved the utilization of carbon and ash in coal gasification slag to the nanoscale. The utilization value of industrial solid wastes such as gasification slag has been significantly enhanced, and the preparation of high-value-added materials will become an advanced technology for the resource utilization of gasification slag.
[0003] Mesoporous zeolite molecular sieves possess highly ordered pore structures and large specific surface areas, supporting a variety of surface groups. They are excellent adsorbents and separators, catalysts, supports, ion exchangers, and microreactors, and have been widely used in petrochemicals, gas separation, and other fields. The preparation of molecular sieves using gasification slag has been reported. Currently, the main techniques for synthesizing molecular sieves using gasification slag focus on alkaline leaching and hot alkaline leaching to increase the leaching amount of silicon components. Patent CN112250085A discloses a method for synthesizing ZSM-5 molecular sieves using coal gasification slag under caustic soda-free conditions, providing an alkaline environment for the reaction by supplementing insufficient silicon and sodium sources. However, the main technical challenge in preparing molecular sieves from gasification slag lies in the leaching of silicon and aluminum, as these methods struggle to flexibly control the silicon-to-aluminum ratio.
[0004] MCM-41 mesoporous silica molecular sieves, characterized by their highly ordered pore structure, large specific surface area, and ability to load various surface functional groups, are excellent adsorbents and catalysts. However, the gaseous silica and tetraethyl orthosilicate (TEOS) used in the current technology for synthesizing MCM-41 are very expensive. There are no reports on using gasification slag as a more affordable silicon source alternative for preparing MCM-41, and due to the lack of an effective method for adjusting the silicon-aluminum molar ratio in MCM-41, existing technologies are difficult to use directly for manufacturing MCM-41.
[0005] How to use gasification slag as a green synthetic raw material to synthesize MCM-41 is a technical problem that needs to be solved. Summary of the Invention
[0006] To solve the above-mentioned technical problems, the present invention provides a method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag.
[0007] The technical means employed in this invention are as follows:
[0008] A method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag includes the following steps:
[0009] S1. The coal gasification slag is ground to a particle size of less than 45μm and then acid-leached. After acid leaching, the coal gasification slag is washed until neutral to obtain acid-leached slag and acid-leaching solution.
[0010] S2. The acid leaching residue is further subjected to alkaline leaching, and filtered to obtain alkaline leaching solution;
[0011] S3. Add acidic and alkaline solutions to a CTAB solution of a set concentration, and stir at room temperature for 10 minutes to obtain a gel material;
[0012] S4. The obtained gel material was subjected to a hydrothermal reaction at 110°C for 48 hours. The reactants were washed and filtered, and the solid products were collected and dried in air at 50°C.
[0013] S5. After drying, the solid product is placed in a muffle furnace and calcined in air at 550°C for 6 hours to obtain the desired MCM-41 mesoporous molecular sieve.
[0014] Preferably, the acid leaching uses a 4-6 mol / L hydrochloric acid solution, with a solid-liquid ratio of 1 g to 4 ml for the coal gasification slag and hydrochloric acid solution, and is carried out in an 80°C water bath for 3-6 hours.
[0015] Preferably, the alkaline leaching uses a sodium hydroxide solution of 40-70 g / L, with a solid-liquid ratio of 1 g for the acid leaching residue to 4 ml for 2-4 hours in a 95°C water bath.
[0016] Preferably, in step S3, the concentration of the CTAB solution is 0.1 mol / L.
[0017] Preferably, the molar ratio of each component in the gel material is: 1SiO2:YAl2O3:0.2CTAB:120H2O, the volume ratio of the alkaline leaching solution to the CTAB (hexadecyltrimethylammonium bromide) solution is 3:4, and the amount of acid leaching solution is calculated based on the Si content in the alkaline leaching solution and the required silicon-aluminum ratio of 1:Y.
[0018] The beneficial effects of this invention are as follows:
[0019] This invention provides a method for synthesizing MCM-41 using gasification slag as a raw material. The inorganic silicon and aluminum components in the gasification slag are used to replace the high-cost reagents (gaseous silicon dioxide, tetraethyl orthosilicate (TEOS) and aluminum sulfate) used in the synthesis of MCM-41. The synthesis process results in zero waste gas emissions, achieving green and low-cost synthesis of MCM-41 and efficient utilization of solid waste chemical components.
[0020] Coal gasification slag, as a low-cost industrial waste, contains a high amount of aluminosilicate minerals, providing ample silicon and aluminum for the production of valuable mesoporous aluminosilicate materials. However, the leaching of silicon and aluminum is relatively difficult. The synthesis method of this invention includes two steps: first, an efficient aluminum and silicon leaching process; and second, the preparation of MCM-41. Firstly, to reduce particle size and increase the number of active sites, the gasification slag is crushed and dissociated through grinding. Reducing the particle size of the coal gasification slag allows for the full exposure of the components within the particles, promoting the effective dissociation of the carbon phase and inorganic mineral phases, which is beneficial for the removal of silicon and aluminum in subsequent processing. Then, hydrochloric acid is used to leach the metal elements in the obtained solid. The coordinated aluminum in the amorphous aluminosilicate and the iron in the form of hematite in the gasification slag are removed during the acid activation process, thus the resulting acid leaching solution is rich in Al. 3+ and Fe 3+As an aluminum source for synthesizing molecular sieves, the reactivity of amorphous silica is also improved. The acid-activated gasification slag is then mixed with a dilute alkaline solution to completely leach out the amorphous silica. The resulting alkaline leachate serves as the silicon source for synthesizing Al-MCM-41. Finally, the acid and alkaline leachates are used to replace high-cost reagents such as tetraethyl orthosilicate (TEOS) in the synthesis of MCM-41, significantly reducing the production cost of MCM-41.
[0021] This invention prepares MCM-41 using coal gasification slag as raw material, which not only realizes the preparation of high value-added materials and provides a technical foundation for the development and utilization of MCM-41, but also reduces the solid waste emissions of coal gasification slag by disposing of solid waste resources, thereby reducing environmental pollution and providing a new approach for the promotion of resource utilization of gasification slag.
[0022] Experiments show that the MCM-41 molecular sieve prepared by this invention using gasification slag as raw material not only has a distinct hexagonal mesoporous structure but also a high degree of mesoporous order, approaching the level of MCM-41 synthesized from pure reagents. The MCM-41 molecular sieve prepared by this invention possesses larger pore size and pore volume, thus exhibiting catalytic ability for large-diameter molecules; the presence of uniformly distributed metal ions such as Mg and Fe within the molecular sieve particles further enhances its catalytic performance. Attached Figure Description
[0023] Figure 1 The XRD patterns of the MCM-41 molecular sieves synthesized in Examples 2-4 are shown below.
[0024] Figure 2 XRD comparison of the MCM-41 molecular sieve prepared in Example 4 and the MCM-41 molecular sieve prepared according to the standard method;
[0025] Figure 3 The images show EDS scans of the MCM-41 molecular sieves prepared in Examples 2-4, with the distributions of Mg, Ca, and Fe ions displayed. Detailed Implementation
[0026] The technical solution of the present invention will be described in more detail below with reference to the embodiments.
[0027] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.
[0028] Example 1
[0029] Using coal gasification slag as raw material, a planetary ball mill with steel balls as the grinding media was used to grind 80g of raw material for 30 minutes at a grinding frequency of 50Hz. After grinding, the raw material was subjected to the following optimal conditions (based on the concentration of aluminum ions in the leaching solution): 25g of the ground raw material and 100mL of 5.5mol / L hydrochloric acid solution were added to a reaction vessel and heated in a water bath at 80℃ for 4 hours. After the leaching process was completed, the acid leaching solution was obtained, and the acid leaching residue was washed until neutral.
[0030] Continue to remove amorphous silica from the raw material using alkaline leaching: Add 80 ml of 50 g / L NaOH solution and 20 g of acid leaching residue to a digestion tank, heat in a 95°C water bath for 2 hours, and collect the alkaline leaching solution.
[0031] The collected acid and alkaline leaching solutions were used as the sources of aluminum and silicon for the synthesis of MCM-41, respectively. The ion concentrations of aluminum and silicon in the leaching solutions were measured using inductively coupled plasma optical emission spectrometry (ICP-OES).
[0032] Molecular sieve synthesis process:
[0033] Add 30 ml of alkaline leaching solution (as silicon source) and a calculated amount of acidic leaching solution (as aluminum source) to 40 ml of 0.2 mol / L CTAB solution. Stir at room temperature for 10 min to obtain a gel material, maintaining the pH value at around 12 during stirring. The molar ratio of each component in the obtained gel material can be recorded as: 1SiO2:YAl2O3:0.2CTAB:120H2O (Y varies with the Si / Al ratio).
[0034] After the gel was transferred to the reactor, a hydrothermal reaction was carried out at 110°C for 48 hours. The resulting reactant was repeatedly filtered, washed with deionized water until neutral, dried in air at 50°C for 8 hours, and finally calcined in a muffle furnace at 550°C in air for 6 hours to remove the template agent CTAB, yielding the desired MCM-41 molecular sieve.
[0035] Example 2
[0036] The synthesis conditions in this embodiment are the same as in Example 1. The difference is that, during the molecular sieve synthesis process, by adjusting the acid leaching solution, the silicon-aluminum molar ratio Y in the obtained gel material is 20.
[0037] Example 3
[0038] The synthesis conditions in this embodiment are the same as in Example 1. The difference is that, during the molecular sieve synthesis process, by adjusting the acid leaching solution, the silicon-aluminum molar ratio Y in the obtained gel material is 40.
[0039] Example 4
[0040] The synthesis conditions in this embodiment are the same as in Example 1. The difference is that, during the molecular sieve synthesis process, by adjusting the acid leaching solution, the silicon-aluminum molar ratio Y in the obtained gel material is 60.
[0041] XRD analysis was performed on the MCM-41 molecular sieves obtained in Examples 2-4, and the results are as follows: Figure 1 As shown, all three exhibit a relatively obvious 100 diffraction peak. The 100 diffraction peak corresponds to the hexagonal mesoporous structure of MCM-41, and its presence proves that the molecular sieve has a basic mesoporous structure, indicating that MCM-41 with a distinct hexagonal mesoporous structure was successfully synthesized.
[0042] The 110, 200, and 210 diffraction peaks are standards for the degree of order in the mesoporous structure of molecular sieves. Figure 2 This shows a comparison between the MCM-41 molecular sieve prepared in Example 4 and that synthesized according to the standard method (pharmaceutical synthesis, see J.S. Beck, J.C., J.C., W.J. Roth, M.E. Leonowicz, J.T. K. Resge, J.S. D.S. Chrnitt, J.T. W. Chu, D.H. Holson, E.W. Sheppard, S.B. McCullen, J.B. Higgins, J.S. Chrnitter, A new family of mesoporous molecular sieves prepared with liquid crystal template. Journal of the American Chemical Society, 1992, 114: pp. 10834-10843.). From Figure 2 As can be seen, MCM-41 synthesized from gasification slag not only has a distinct two-dimensional hexagonal mesoporous structure, but the presence of diffraction peaks such as 110 and 210 also indicates that the mesoporous structure of this sample is highly ordered.
[0043] like Figure 3 The image shown is an EDS scan of the prepared MCM-41 molecular sieve. It can be seen that metal ions such as Mg and Fe are uniformly distributed within the molecular sieve particles. Molecular sieves synthesized from pharmaceutical reagents are difficult to load with a large number of metal ions, while the molecular sieve prepared using solid waste raw materials in this invention contains a variety of metal ions in high concentrations. The presence of these metal ions provides more acidic sites for the molecular sieve, thereby enhancing its catalytic performance.
[0044] Table 1 compares the performance of MCM-41 prepared by the present invention with that synthesized by existing methods. In the table, GS-20, GS-40, and GS-60 correspond to the MCM-41 molecular sieves obtained in Examples 2-4, respectively, and RS-20, RS-40, and RS-60 are synthesized by existing methods. 20, 40, and 60 all represent the silicon-aluminum molar ratio.
[0045] Table 1. Nitrogen adsorption test data of samples
[0046]
[0047] It can be seen that the molecular sieve prepared from gasification slag has a larger pore size and pore volume, thus possessing the catalytic ability of large-diameter molecules; while its specific surface area is only slightly lower than that of the control group, which may be due to the presence of more impurities in the raw materials.
[0048] The above experiments show that the present invention successfully synthesizes MCM-41 molecular sieve using gasification slag as raw material. The synthesized molecular sieve has a distinct hexagonal mesoporous structure with high mesoporous order, larger pore size and pore volume. At the same time, the molecular sieve particles contain uniformly distributed metal ions such as Mg and Fe, which can improve the catalytic performance of the molecular sieve.
[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag, characterized in that, Includes the following steps: S1. The coal gasification slag is ground to a particle size of less than 45μm and then acid-leached. After acid leaching, the coal gasification slag is washed until neutral to obtain acid-leached slag and acid-leaching solution. S2. The acid leaching residue is further subjected to alkaline leaching, and filtered to obtain alkaline leaching solution; S3. Add acidic and alkaline solutions to a CTAB solution of a set concentration, and stir at room temperature for 10 minutes to obtain a gel material; S4. The obtained gel material was subjected to a hydrothermal reaction at 110°C for 48 hours. The reactants were washed and filtered, and the solid products were collected and dried in air at 50°C. S5. After drying, the solid product is placed in a muffle furnace and calcined in air at 550°C for 6 hours to obtain the desired MCM-41 mesoporous molecular sieve.
2. The method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag as described in claim 1, characterized in that, The acid leaching process uses a 4-6 mol / L hydrochloric acid solution, with a solid-liquid ratio of 1 g to 4 ml for the coal gasification slag and hydrochloric acid solution, and is carried out in an 80°C water bath for 3-6 hours.
3. The method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag as described in claim 2, characterized in that, The alkaline leaching uses a sodium hydroxide solution of 40-70 g / L, with a solid-liquid ratio of 1 g for the acid leaching residue to 4 ml for 2-4 hours in a 95°C water bath.
4. The method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag as described in claim 3, characterized in that, In step S3, the concentration of the CTAB solution is 0.1 mol / L.
5. The method for synthesizing MCM-41 mesoporous molecular sieve using coal gasification slag as described in claim 4, characterized in that, The molar ratio of each component in the gel material is: 1SiO2:YAl2O3:0.2CTAB:120H2O. The volume ratio of the alkaline leaching solution to the CTAB solution is 3:
4. The amount of acid leaching solution is calculated based on the Si content in the alkaline leaching solution and the required silicon-aluminum ratio of 1:Y.