Supported MCM-41 molecular sieve and preparation method thereof
By pretreating fly ash with acid-soluble pretreatment and preparing loaded MCM-41 molecular sieve by using a multi-step process, the problems of low comprehensive utilization rate and high preparation cost are solved, and the separation and reuse of elements in fly ash are achieved. Reduced preparation costs.
Patent Information
- Application Number
- CN202411637755.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-02-18
AI Technical Summary
In the prior art, the comprehensive utilization rate of fly ash is low and the preparation cost of MCM-41 molecular sieve is high.
Pretreatment of fly ash by acid dissolution, the valuable metal elements in fly ash enter the liquid phase, and silicon enters the solid phase, achieving separation and reuse of different elements. Multi-step processes include dissolution reaction, drying, roasting, The activation reaction and crystallization treatment were carried out to prepare a loaded MCM-41 molecular sieve.
The comprehensive utilization rate of fly ash is improved, the preparation cost of MCM-41 molecular sieve is reduced, and the effective separation and reuse of different elements in fly ash is achieved.
Abstract
Description
Technical Field
[0001] The invention relates to the field of comprehensive utilization of solid waste, and in particular to a supported MCM-41 molecular sieve and a preparation method thereof. Background Art
[0002] As a highly ordered mesoporous material, MCM-41 molecular sieve has large and uniform pore size, large specific surface area, large adsorption capacity and high thermal stability. MCM-41 molecular sieve has not only received considerable attention in the fields of adsorption, drug transport systems, extraction and catalytic applications, but can also be regarded as a good hydrogen storage medium. It is also widely used in the fields of catalysis and petrochemicals, such as in acid catalysis such as catalytic cracking of residual oil, hydrogenation of heavy oil, hydrogenation of lubricating oil, alkylation, olefin polymerization, separation of CO2 and CH4, etc. In addition, MCM-41 molecular sieve also has high application value in environmental applications, heterogeneous catalysis, ion exchange, guest chemistry, sensor technology and optoelectronic devices.
[0003] Fly ash is one of the largest industrial solid wastes in my country. According to statistics, 0.25-0.30 tons of fly ash are usually produced for every ton of coal burned, and the large amount of fly ash accumulation will inevitably cause serious environmental problems. Summary of the invention
[0004] The main purpose of the present invention is to provide a supported MCM-41 molecular sieve and a preparation method thereof, so as to solve the problems of low comprehensive utilization rate of fly ash and high preparation cost of MCM-41 molecular sieve in the prior art.
[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a supported MCM-41 molecular sieve is provided, and the method comprises: step S1, subjecting a raw material comprising fly ash and an acid solution to a dissolution reaction and a first solid-liquid separation in sequence to obtain a first solid phase and a first liquid phase; step S2, subjecting the first solid phase to a first drying and a first roasting in sequence to obtain an acid slag; step S3, subjecting a raw material comprising an acid slag and an alkaline solution to an activation reaction and a centrifugal separation in sequence to obtain a precipitate and a supernatant; step S4, subjecting a raw material comprising a supernatant, a surfactant, water and an aluminum source to a crystallization treatment and a second solid-liquid separation in sequence to obtain a second solid phase and a second liquid phase; step S5, subjecting the second solid phase to a second drying and a second roasting in sequence to obtain a supported MCM-41 molecular sieve.
[0006] Furthermore, in the above step S1, the temperature of the dissolution reaction is 160-200° C., and / or the time of the dissolution reaction is 4-6 hours.
[0007] Furthermore, in the above step S1, the liquid-to-solid ratio of the acid solution to the fly ash is 3-5 mL / g, and / or the mass concentration of the acid solution is 20-35%, and the acid solution is preferably a hydrochloric acid solution.
[0008] Furthermore, in the above step S2, the temperature of the first drying is 80-100°C, and the insulation time of the first drying is 12-24h; and / or the temperature of the first roasting is 700-800°C, and the insulation time of the first roasting is 2-4h.
[0009] Furthermore, in the above step S3, the liquid-to-solid ratio of the acid slag to the alkaline solution is 3-6 mL / g; and / or the mass concentration of the alkaline solution is 100-130 g / L, and the alkaline solution is preferably a NaOH solution and / or a KOH solution.
[0010] Furthermore, in the above step S3, the temperature of the activation reaction is 100-200° C., and / or the time of the activation reaction is 4-10 h.
[0011] Furthermore, in the above step S4, the pH of the mixture of raw materials including the supernatant, surfactant, water and aluminum source is adjusted to 10-11, and the mixture is continuously stirred for 2-3 hours before crystallization treatment; preferably, the temperature of the crystallization treatment is 100-140°C, and / or the time of the crystallization treatment is 24-72 hours; preferably, the surfactant is hexadecyltrimethylammonium bromide; and / or the aluminum source is NaAlO2; and / or the mass concentration of Si element in the supernatant is 20-70 g / L, and / or the mass concentration of Al element in the supernatant is 0.05-0.5 g / L; and / or the amount of supernatant, aluminum source, surfactant and water is calculated according to the molar ratio of n(Si):n(Al):n(surfactant):n(water)=1:0.01-0.1:0.1-0.5:120-180.
[0012] Furthermore, in the above step S5, the temperature of the second drying is 100-120° C., and the insulation time of the second drying is 12-24 hours; and / or the temperature of the second roasting is 500-700° C., and the insulation time of the second roasting is 4-8 hours.
[0013] According to another aspect of the present invention, a supported MCM-41 molecular sieve is provided. The supported MCM-41 molecular sieve is prepared by the aforementioned preparation method.
[0014] Furthermore, the specific surface area of the supported MCM-41 molecular sieve is 850 to 1050 m 2 / g, and / or the average particle size of the supported MCM-41 molecular sieve is 3 to 5 nm.
[0015] By applying the technical solution of the present invention, fly ash is rich in silicon, so it can be used as a high-quality raw material for silicon-based materials. The use of fly ash as a raw material to prepare MCM-41 molecular sieve can not only solve the problem of serious environmental pollution caused by fly ash, but also improve the comprehensive utilization rate of fly ash, and at the same time reduce the preparation cost of MCM-41 molecular sieve. Specifically, the present invention uses acid dissolution to pretreat fly ash, so that the valuable metal elements in the fly ash enter the liquid phase, and silicon enters the solid phase, thereby realizing the separation and reuse of different elements in the fly ash. The liquid phase can be used to extract metal elements such as aluminum, lithium, and gallium. DETAILED DESCRIPTION
[0016] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.
[0017] As analyzed in the background technology of this application, the prior art has the problems of low comprehensive utilization rate of fly ash and high preparation cost of MCM-41 molecular sieve. In order to solve the above problems, this application provides a loaded MCM-41 molecular sieve and a preparation method thereof.
[0018] In a typical embodiment of the present application, a method for preparing a supported MCM-41 molecular sieve is provided, the method comprising: step S1, subjecting a raw material comprising fly ash and an acid solution to a dissolution reaction and a first solid-liquid separation in sequence to obtain a first solid phase and a first liquid phase; step S2, subjecting the first solid phase to a first drying and a first roasting in sequence to obtain an acid slag; step S3, subjecting a raw material comprising an acid slag and an alkaline solution to an activation reaction and a centrifugal separation in sequence to obtain a precipitate and a supernatant; step S4, subjecting a raw material comprising a supernatant, a surfactant, water and an aluminum source to a crystallization treatment and a second solid-liquid separation in sequence to obtain a second solid phase and a second liquid phase; step S5, subjecting the second solid phase to a second drying and a second roasting in sequence to obtain a supported MCM-41 molecular sieve.
[0019] The present invention uses acid dissolution to pretreat fly ash, so that valuable metal elements in the fly ash enter the liquid phase and silicon enters the solid phase, thereby realizing the separation and utilization of different elements in the fly ash. The liquid phase can be used to extract metal elements such as aluminum, lithium, gallium, etc., and the solid phase can be used to prepare a loaded MCM-41 molecular sieve. The preparation method not only improves the comprehensive utilization rate of the fly ash, but also reduces the preparation cost of the loaded MCM-41 molecular sieve.
[0020] In one embodiment of the present application, in the above step S1, the temperature of the dissolution reaction is 160-200° C., and / or the time of the dissolution reaction is 4-6 hours.
[0021] The above preferred dissolution temperature and time help to make the fly ash dissolve more fully in the acid solution, thereby facilitating the separation and utilization of different elements in the fly ash.
[0022] In one embodiment of the present application, in the above step S1, the liquid-to-solid ratio of the acid solution to the fly ash is 3-5 mL / g, and / or the mass concentration of the acid solution is 20-35%, and the acid solution is preferably a hydrochloric acid solution.
[0023] The above preferred conditions are helpful to improve the dissolution efficiency and effect of fly ash in acid solution, and can further improve the utilization rate of fly ash.
[0024] In one embodiment of the present application, in the above step S2, the first drying temperature is 80-100°C, and the first drying insulation time is 12-24h; and / or the first calcination temperature is 700-800°C, and the first calcination insulation time is 2-4h.
[0025] The above preferred drying conditions are helpful to fully remove the moisture in the first solid phase, and the above preferred roasting conditions are helpful to form the acid slag into a desired microstructure.
[0026] In one embodiment of the present application, in the above step S3, the liquid-to-solid ratio of the acid slag to the alkaline solution is 3-6 mL / g; and / or the mass concentration of the alkaline solution is 100-130 g / L, and the alkaline solution is preferably a NaOH solution and / or a KOH solution.
[0027] The above preferred conditions are helpful to make the acid slag react more fully with the alkaline solution, thereby removing the elements in the acid slag that are unfavorable to the formation of MCM-41 molecular sieve and making them enter the precipitate, thereby separating the favorable elements and unfavorable elements for forming the MCM-41 molecular sieve, thereby improving the quality of the MCM-41 molecular sieve.
[0028] In one embodiment of the present application, in the above step S3, the temperature of the activation reaction is 100-200° C., and / or the time of the activation reaction is 4-10 hours.
[0029] The above preferred activation reaction conditions are helpful to improve the efficiency and effect of the activation reaction between the acid slag and the alkaline solution, thereby separating the elements in the acid slag as much as possible.
[0030] In one embodiment of the present application, in the above step S4, the pH of the mixture of raw materials including the supernatant, surfactant, water and aluminum source is adjusted to 10-11, and the mixture is continuously stirred for 2-3 hours before crystallization treatment; preferably, the temperature of the crystallization treatment is 100-140°C, and / or the time of the crystallization treatment is 24-72 hours; preferably, the surfactant is hexadecyltrimethylammonium bromide; and / or the aluminum source is NaAlO2; and / or the mass concentration of Si element in the supernatant is 20-70 g / L, and / or the mass concentration of Al element in the supernatant is 0.05-0.5 g / L; and / or the amount of supernatant, aluminum source, surfactant and water is calculated by molar ratio n(Si):n(Al):n(surfactant):n(water)=1:0.01-0.1:0.1-0.5:120-180.
[0031] The above-mentioned supernatant, aluminum source, amount of surfactant and water, crystallization treatment conditions, surfactant, aluminum source, and mass ratio of Si element to Al element in the supernatant are preferably within the above ranges, which are helpful to control the purity, crystallinity, size and morphology of the supported MCM-41 molecular sieve crystals, and promote the formation of molecular sieve framework units of specific structures by elements such as silicon and aluminum, and at the same time help to improve the thermal stability of the supported MCM-41 molecular sieve.
[0032] In one embodiment of the present application, in the above step S5, the temperature of the second drying is 100-120°C, and the insulation time of the second drying is 12-24h; and / or the temperature of the second roasting is 500-700°C, and the insulation time of the second roasting is 4-8h.
[0033] The above preferred drying conditions are helpful to fully remove the moisture in the second solid phase, and the above preferred calcining conditions are helpful to form a supported MCM-41 molecular sieve with large and uniform pore size.
[0034] In another typical embodiment of the present application, a supported MCM-41 molecular sieve is provided. The supported MCM-41 molecular sieve is prepared by the aforementioned preparation method.
[0035] The preparation method of the present application utilizes fly ash to prepare the loaded MCM-41 molecular sieve, which not only improves the comprehensive utilization rate of fly ash, but also reduces the preparation cost of the loaded MCM-41 molecular sieve, and the prepared loaded MCM-41 molecular sieve has excellent catalytic and loading effects.
[0036] Preferably, the specific surface area of the supported MCM-41 molecular sieve is 850 to 1050 m 2 / g, and / or the average particle size of the supported MCM-41 molecular sieve is 3 to 5 nm, which is more conducive to using it as a supported molecular sieve.
[0037] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.
[0038] The fly ash raw material of the following examples is fly ash from the power plant of the State Energy Group Corporation, and its chemical composition is shown in Table 1.
[0039] Table 1 Chemical composition of fly ash from power plant of China Energy Group Co., Ltd. (wt%)
[0040] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> other 34.51 46.80 2.49 2.37 0.18 0.65 1.48 11.52
[0041] Example 1
[0042] A method for preparing a supported MCM-41 molecular sieve comprises the following steps:
[0043] (1) 100 g of fly ash (density of fly ash is 1.010 g / cm 3 , bulk density is 0.540g / cm 3 The average particle size is 29.32 μm and the specific surface area is 14.93 m 2 / g, water content is 2%) and 400mL of HCl (mass concentration is 25%) are uniformly mixed, dissolved at 200°C for 4h, and then solid-liquid separation is performed; the solid phase obtained by solid-liquid separation is first dried at a temperature of 80°C and a heat preservation time of 24h, and then first calcined at 800°C for 4h to obtain acid slag.
[0044] (2) 25 g of the acid residue was uniformly mixed with 100 mL of NaOH solution (mass concentration of 130 g / L), activated at 200°C for 4 h, then stirred for 4 h, and centrifuged to obtain a supernatant. ICP-MS analysis showed that the mass concentration of Si in the supernatant was 65.64 g / L and the mass concentration of Al was 0.49 g / L.
[0045] (3) The required amount of raw materials is calculated according to n(Si):n(Al):n(surfactant):n(water)=1:0.01~0.1:0.1~0.5:120~180, i.e., 20 mL of supernatant, 0.0087 g of NaAlO2, 3.42 g of CTBA (hexadecyltrimethylammonium bromide), and 107 g of deionized water. The required raw materials are uniformly mixed, the pH is adjusted to 10.5 with hydrochloric acid, and stirring is continued for 2 h. Then, the mixture is placed in an oven for crystallization treatment at 120°C for 72 h. After the crystallization treatment is completed, solid-liquid separation is performed. The solid phase obtained by the solid-liquid separation is subjected to a second drying, the second drying temperature is 80°C, and the second drying insulation time is 12 h to obtain a pre-product.
[0046] (4) The pre-product was second calcined at 550°C for 6 h to obtain a supported MCM-41 molecular sieve.
[0047] After the above step (4) was completed, the specific surface area and pore size were measured by N2 adsorption-desorption. The specific surface area was 1028m 2 / g, and the pore size is 3.65nm.
[0048] Example 2
[0049] The difference from Example 1 is that for 100 g of fly ash, the liquid-solid ratio of HCl (mass concentration of 20%) to fly ash is 5 mL / g, and finally a supported MCM-41 molecular sieve is obtained.
[0050] Example 3
[0051] The difference from Example 1 is that the temperature of the first drying is 100° C., the insulation time of the first drying is 12 h, and finally the supported MCM-41 molecular sieve is obtained.
[0052] Example 4
[0053] The difference from Example 1 is that the temperature of the first calcination is 700° C., and the supported MCM-41 molecular sieve is finally obtained.
[0054] Example 5
[0055] The difference from Example 1 is that 25 g of acid slag, the liquid-to-solid ratio of the acid slag to the NaOH solution is 6 mL / g, and finally a supported MCM-41 molecular sieve is obtained.
[0056] Example 6
[0057] The difference from Example 1 is that the activation reaction temperature is 150° C., the activation reaction time is 10 h, and finally a supported MCM-41 molecular sieve is obtained.
[0058] Example 7
[0059] The difference from Example 1 is that n(Si):n(Al):n(surfactant):n(water)=1:0.01:0.3:150, and finally the supported MCM-41 molecular sieve is obtained.
[0060] Example 8
[0061] The difference from Example 1 is that the mass concentration of Si element in the supernatant is 58.19 g / L, and the mass concentration of Al element in the supernatant is 0.24 g / L, and finally a supported MCM-41 molecular sieve is obtained.
[0062] Example 9
[0063] The difference from Example 1 is that the mass concentration of Si element in the supernatant is 34.39 g / L, and the mass concentration of Al element in the supernatant is 0.39 g / L, and finally a supported MCM-41 molecular sieve is obtained.
[0064] Example 10
[0065] The difference from Example 1 is that the temperature of the second calcination is 700° C., and the supported MCM-41 molecular sieve is finally obtained.
[0066] The specific surface area and average particle size values of the above examples and the commercially available MCM-41 molecular sieve (Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) are listed in Table 2.
[0067] Table 2
[0068] Implementation / Comparative Example <![CDATA[Specific surface area (m 2 / g)]]> Average particle size (nm) Example 1 1028 3.65 Example 2 1013 3.57 Example 3 1023 3.71 Example 4 996 3.73 Example 5 987 3.81 Example 6 1019 3.69 Example 7 969 3.82 Example 8 981 3.81 Example 9 940 3.86 Example 10 988 3.92 Commercially available MCM-41 molecular sieve 800 3～5
[0069] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
[0070] Fly ash is rich in silicon, so it can be used as a high-quality raw material for silicon-based materials. The preparation of MCM-41 molecular sieve using fly ash as raw material can not only solve the problem of serious environmental pollution caused by fly ash, but also improve the comprehensive utilization rate of fly ash, and at the same time reduce the preparation cost of MCM-41 molecular sieve. Specifically, the present invention uses acid dissolution to pretreat fly ash, so that the valuable metal elements in the fly ash enter the liquid phase, and silicon enters the solid phase, thereby achieving the separation and reuse of different elements in the fly ash. The liquid phase can be used to extract metal elements such as aluminum, lithium, and gallium.
[0071] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for preparing a supported MCM-41 molecular sieve, characterized in that: The preparation method comprises: Step S1, subjecting the raw materials including fly ash and acid solution to dissolution reaction and first solid-liquid separation in sequence to obtain a first solid phase and a first liquid phase; Step S2, performing a first drying and a first calcination on the first solid phase in sequence to obtain an acid slag; Step S3, subjecting the raw materials including the acid slag and the alkaline solution to activation reaction and centrifugal separation in sequence to obtain a precipitate and a supernatant; Step S4, sequentially performing crystallization treatment and second solid-liquid separation on the raw materials including the supernatant, the surfactant, the water and the aluminum source to obtain a second solid phase and a second liquid phase; Step S5, subjecting the second solid phase to a second drying and a second calcination in sequence to obtain a supported MCM-41 molecular sieve.
2. The preparation method according to claim 1, characterized in that: In the step S1, the temperature of the dissolution reaction is 160-200° C., and / or the time of the dissolution reaction is 4-6 hours.
3. The preparation method according to claim 1 or 2, characterized in that: In the step S1, the liquid-to-solid ratio of the acid solution to the fly ash is 3-5 mL / g, and / or the mass concentration of the acid solution is 20-35%. Preferably, the acid solution is a hydrochloric acid solution.
4. The preparation method according to any one of claims 1 to 3, characterized in that In the step S2, the temperature of the first drying is 80-100°C, and the insulation time of the first drying is 12-24 hours; and / or the temperature of the first calcination is 700-800°C, and the insulation time of the first calcination is 2-4 hours.
5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step S3, the liquid-to-solid ratio of the acid slag to the alkaline solution is 3-6 mL / g; and / or the mass concentration of the alkaline solution is 100-130 g / L, and preferably the alkaline solution is a NaOH solution and / or a KOH solution.
6. The preparation method according to any one of claims 1 to 5, characterized in that In the step S3, the temperature of the activation reaction is 100-200° C., and / or the time of the activation reaction is 4-10 hours.
7. The preparation method according to any one of claims 1 to 6, characterized in that In the step S4, the pH of the mixture including the supernatant, the surfactant, the water and the raw material of the aluminum source is adjusted to 10-11, and the mixture is continuously stirred for 2-3 hours before the crystallization treatment is performed; Preferably, the temperature of the crystallization treatment is 100 to 140° C., and / or the time of the crystallization treatment is 24 to 72 hours; Preferably, the surfactant is hexadecyltrimethylammonium bromide; And / or the aluminum source is NaAlO2; and / or the mass concentration of Si element in the supernatant is 20-70 g / L, and / or the mass concentration of Al element in the supernatant is 0.05-0.5 g / L; And / or the amount of the supernatant, the aluminum source, the surfactant and the water is calculated according to the molar ratio of n(Si):n(Al):n(surfactant):n(water)=1:0.01-0.1:0.1-0.5:120-180.
8. The preparation method according to any one of claims 1 to 7, characterized in that In step S5, the temperature of the second drying is 100-120° C., and the insulation time of the second drying is 12-24 hours; and / or the temperature of the second roasting is 500-700° C., and the insulation time of the second roasting is 4-8 hours.
9. A supported MCM-41 molecular sieve, characterized in that: The supported MCM-41 molecular sieve is prepared by the preparation method described in any one of claims 1 to 8.
10. The supported MCM-41 molecular sieve according to claim 9, characterized in that: The specific surface area of the supported MCM-41 molecular sieve is 850 to 1050 m 2 / g, and / or the average particle size of the supported MCM-41 molecular sieve is 3 to 5 nm.