In-situ crystallization of solid waste coal gangue to synthesize aluminum-based hydrotalcite, its preparation method and application

Abstract

This invention relates to the field of solid waste resource utilization technology, specifically to the in-situ crystallization synthesis of aluminum-based hydrotalcite from solid waste coal gangue, its preparation method, and its application. The preparation method includes: (1) mixing coal gangue with acid and water, stirring at 80-95℃ for 0.5-3h to remove impurities, filtering, washing, and drying to obtain impurity-removed coal gangue; (2) calcining the impurity-removed coal gangue at 600-850℃ for 0.5-5h to obtain calcined coal gangue microspheres; (3) reacting the calcined coal gangue microspheres with calcium / magnesium salts, acid, and water, adjusting the pH to 7-9 with alkali, aging, adding solid phase seed crystals, adjusting the pH to 10-12 with alkali again, crystallizing at 100-150℃ for 12-72h, and then processing to obtain the product. This method uses coal gangue as the aluminum source, improves the crystallinity of aluminum-based hydrotalcite, reduces costs, and realizes solid waste resource utilization. The product can be used for flue gas desulfurization or as an FCC sulfur transfer agent. It has excellent desulfurization and sulfur transfer performance and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to the in-situ crystallization of solid waste coal gangue to synthesize aluminum-based hydrotalcite, its preparation method, and its application. Background Technology

[0002] Flue gas generated during industrial production and energy consumption contains sulfur oxides (SOx), which are key pollutants causing air pollution, acid rain, and other environmental problems. Therefore, flue gas desulfurization has become a core component of environmental governance. Current mainstream dry desulfurization technologies rely on the reaction of solid alkaline adsorbents with SOx to achieve removal. Among these, calcium aluminum hydrotalcite (CAL) exhibits superior desulfurization performance compared to traditional calcium-based adsorbents due to its excellent surface alkalinity, large specific surface area, and high thermal stability. Furthermore, in fluidized catalytic cracking (FCC) units, FCC sulfur transfer agents with magnesium aluminum hydrotalcite as the core active component are crucial materials for controlling SOx emissions from regenerated flue gas, and their demand is becoming increasingly urgent, especially given the increasing processing of high-sulfur crude oil.

[0003] However, the widespread application of calcium aluminum hydrotalcite (CAH) and FCC sulfur transfer agents faces two major bottlenecks: First, traditional synthesis processes rely on high-priced aluminum sources, resulting in high preparation costs; second, existing in-situ crystallization technologies using solid waste coal gangue (abundant, inexpensive, and rich in Al2O3, making it an ideal low-cost aluminum source) as raw material generally produce CAH or MgAH with low crystallinity. This problem stems from two aspects: First, in a strongly alkaline environment (pH>10), the precipitation rates of calcium / magnesium ions and aluminum ions differ significantly, making it difficult to precisely control the atomic ratio of co-precipitated species, which is detrimental to subsequent crystallization and the formation of highly crystalline crystals; second, the crystallization process lacks crystal structure guiding components, hindering crystal nucleation, growth, and complete crystallization.

[0004] Furthermore, coal gangue, a major solid waste from coal mining and washing, not only occupies land resources when stored for a long time, but may also cause secondary pollution such as heavy metal leakage. Its resource utilization has always been a challenge for the industry. How to use coal gangue as a low-cost aluminum source, break through the bottleneck of in-situ crystallization technology, improve the crystallinity of hydrotalcite, and at the same time reduce the preparation cost of calcium aluminum hydrotalcite and FCC sulfur transfer agent, so as to achieve the dual goals of "solid waste reduction" and "low-cost environmental protection materials", has become an urgent technical problem to be solved in the field of solid waste resource utilization and environmental protection materials. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an aluminum-based hydrotalcite synthesized from solid waste coal gangue in situ, which has a high sulfur removal rate in flue gas desulfurization, can efficiently control SOx emissions from FCC unit regeneration flue gas, and meet the environmental regulations for high-sulfur crude oil processing.

[0006] Another objective of this invention is to provide a method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue. This method replaces traditional high-priced aluminum sources with abundant and inexpensive solid waste coal gangue. At the same time, it achieves efficient activation and extraction of aluminum elements in coal gangue through spray drying and calcination parameter optimization, thereby significantly reducing the raw material costs of calcium-aluminum hydrotalcite and FCC sulfur transfer agent.

[0007] The third objective of this invention is to provide an application of in-situ crystallization of solid waste coal gangue to synthesize aluminum-based hydrotalcite for flue gas desulfurization or as an FCC sulfur transfer agent.

[0008] This invention is achieved using the following technical solution:

[0009] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0010] (1) Mix coal gangue, acid and water and stir at 80-95℃ for 0.5-3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0011] (2) The impurity-free coal gangue obtained in step (1) is roasted to obtain roasted coal gangue microspheres.

[0012] (3) Mix the roasted coal gangue microspheres, calcium or magnesium salts, acid and water obtained in step (2), and stir continuously at 65-95℃ for 0.5-5h; then add alkaline solution dropwise until the slurry pH=7-9, and let it stand for aging for 0.5-5h; then add solid seed crystals to the obtained slurry, and add alkaline solution dropwise while stirring continuously until the slurry pH=10-12, and transfer the slurry to a high pressure reactor for crystallization; after crystallization, cool to room temperature, filter, wash and dry to obtain aluminum-based hydrotalcite synthesized from solid waste coal gangue in situ crystallization.

[0013] The acid is at least one of hydrochloric acid, nitric acid and sulfuric acid, preferably hydrochloric acid. In step (2), before roasting, the impurity-removed coal gangue, the curing agent and water are mixed and then spray-dried.

[0014] In step (1), the mass ratio of coal gangue, acid and water is 1:(0.05-0.15):(5-10).

[0015] In step (2), the curing agent is at least one of silica sol, sodium silicate, potassium silicate, and water glass, preferably silica sol. The mass ratio of coal gangue, curing agent and water is 1:(0-0.15):(0-4), the calcination temperature is 600-850℃ and the calcination time is 0.5-5h.

[0016] In step (3), the calcium salt is at least one of calcium chloride, calcium nitrate, calcium acetate and calcium lactate, preferably calcium chloride, and the magnesium salt is at least one of magnesium chloride, magnesium nitrate and magnesium sulfate, preferably magnesium chloride.

[0017] In step (3), the alkaline solution is at least one of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate solution with a concentration of 1 mol / L, preferably sodium hydroxide.

[0018] In step (3), the mass ratio of roasted coal gangue microspheres, calcium salt (calculated as CaO), magnesium salt (calculated as MgO), acid and water is 1:(0-3):(0-3):(0.1-0.3):(4-8).

[0019] In step (3), the mass ratio of roasted coal gangue to solid seed crystal is 1:(0.01-0.1), the solid seed crystal is calcium aluminum hydrotalcite or magnesium aluminum hydrotalcite, the crystallinity of calcium aluminum hydrotalcite is ≥85%, the crystallinity of magnesium aluminum hydrotalcite is ≥85%, the crystallization temperature is 100-150℃, and the crystallization time is 12-72h.

[0020] The aluminum-based hydrotalcite synthesized from solid waste coal gangue is prepared by the above-mentioned method for preparing aluminum-based hydrotalcite synthesized from solid waste coal gangue.

[0021] The application of the in-situ crystallization of solid waste coal gangue to synthesize aluminum-based hydrotalcite is for flue gas desulfurization or as an FCC sulfur transfer agent.

[0022] The in-situ crystallization of solid waste coal gangue to synthesize aluminum-based hydrotalcite is one of calcium-aluminum hydrotalcite or FCC sulfur transfer agent.

[0023] In the above in-situ crystallization process, calcium and aluminum ions first co-precipitate in a strongly alkaline environment (pH>10), and the co-precipitated species generate calcium aluminum hydrotalcite crystals through a further crystallization process. Therefore, the low crystallinity of existing in-situ crystallization synthesis of calcium aluminum hydrotalcite is mainly due to the following two reasons: (1) The precipitation rates of calcium and aluminum ions in a strongly alkaline environment are quite different, making it difficult to accurately control the ratio of calcium to aluminum atoms in the co-precipitated species under strongly alkaline conditions, which is not conducive to obtaining highly crystalline calcium aluminum hydrotalcite crystals in the subsequent crystallization process; (2) The crystallization process lacks crystal structure guiding components, which is not conducive to the nucleation, growth and crystal formation of calcium aluminum hydrotalcite crystals. To address the aforementioned two issues, the method of this invention uses solid waste coal gangue as the aluminum source. First, heavy metals and other impurities in the solid waste coal gangue structure are removed through acid treatment. Then, aluminum elements in the coal gangue structure are activated through roasting. Subsequently, aluminum elements are extracted from the roasted coal gangue structure using acid extraction. Using the removed aluminum elements as the aluminum source and calcium salts as the calcium source, calcium and aluminum ions in the system are co-precipitated under weakly alkaline conditions by adding an external alkaline solution. This effectively reduces the difference in co-precipitation rates between calcium and aluminum ions, resulting in uniform co-precipitated species. Furthermore, the alkalinity of the system is increased to strong alkalinity, and solid-phase calcium-aluminum hydrotalcite seed crystals are introduced as crystal structure guiding components for high-temperature hydrothermal crystallization. This greatly promotes the nucleation, growth, and crystallization process of the co-precipitated species, resulting in highly crystalline in-situ crystallized calcium-aluminum hydrotalcite, which imparts excellent flue gas desulfurization performance to the synthesized in-situ crystallized calcium-aluminum hydrotalcite. In addition, magnesium and aluminum ions first co-precipitate in a strongly alkaline environment (pH>10), and the co-precipitated species are further crystallized to form magnesium aluminum hydrotalcite crystals. Therefore, the low crystallinity of existing in-situ crystallization synthesis of magnesium aluminum hydrotalcite is mainly due to the following two reasons: (1) The precipitation rates of magnesium and aluminum ions in a strongly alkaline environment are quite different, making it difficult to accurately control the ratio of magnesium to aluminum atoms in the co-precipitated species under strongly alkaline conditions, which is not conducive to obtaining highly crystalline magnesium aluminum hydrotalcite crystals in the subsequent crystallization process; (2) The crystallization process lacks crystal structure guiding components, which is not conducive to the nucleation, growth and crystal formation of magnesium aluminum hydrotalcite crystals.To address the aforementioned two issues, the method of this invention uses solid waste coal gangue as the aluminum source. First, heavy metals and other impurities in the solid waste coal gangue structure are removed through acid treatment. Then, aluminum elements in the coal gangue structure are activated by roasting. Subsequently, aluminum elements are extracted from the roasted coal gangue structure using acid extraction. Using the removed aluminum elements as the aluminum source and magnesium salts as the magnesium source, magnesium and aluminum ions in the system are co-precipitated under weakly alkaline conditions by adding an external alkaline solution. This effectively reduces the difference in co-precipitation rates between magnesium and aluminum ions, resulting in uniform co-precipitated species. Furthermore, the alkalinity of the system is increased to strong alkalinity, and solid-phase magnesium-aluminum hydrotalcite seed crystals are introduced as crystal structure guiding components for high-temperature hydrothermal crystallization. This greatly promotes the nucleation, growth, and crystallization process of the co-precipitated species, obtaining highly crystalline in-situ crystallized magnesium-aluminum hydrotalcite, which endows the prepared in-situ crystallized FCC sulfur transfer agent with excellent sulfur transfer performance.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) This invention uses an innovative process of “weakly alkaline pre-coprecipitation + strong alkaline seed crystal-induced crystallization” to first regulate the precipitation rate of calcium / magnesium ions and aluminum ions in a weakly alkaline environment to obtain coprecipitated species with uniform atomic ratio; then introduce calcium aluminum / magnesium aluminum hydrotalcite solid-phase seed crystals to provide structural guidance for crystal growth. Combined with high-temperature hydrothermal crystallization, the crystallinity of calcium aluminum hydrotalcite is finally increased to 79%-86%, and the crystallinity of magnesium aluminum hydrotalcite in FCC sulfur transfer agent reaches 81%-88%, which is far higher than the existing technology, laying the foundation for excellent flue gas desulfurization performance and sulfur transfer performance.

[0026] (2) This invention replaces the traditional high-priced aluminum source with abundant and inexpensive solid waste coal gangue. At the same time, it achieves efficient activation and extraction of aluminum elements in coal gangue through spray drying and roasting parameter optimization, which greatly reduces the raw material cost of calcium aluminum hydrotalcite and FCC sulfur transfer agent. In addition, the efficient utilization of coal gangue effectively reduces solid waste stockpiling pollution, realizes "waste treatment", and has both economic and environmental benefits.

[0027] (3) The highly crystalline calcium aluminum hydrotalcite prepared in this invention achieves a sulfur removal rate of 84%-94% in flue gas desulfurization, which is significantly better than the 70%-75% of traditional materials. The FCC sulfur transfer agent based on highly crystalline magnesium aluminum hydrotalcite can efficiently control SOx emissions from FCC regeneration flue gas, meeting the stringent environmental regulations for high-sulfur crude oil processing. At the same time, the raw materials such as acids, alkalis, and curing agents in the process are widely available and easy to select, and the reaction parameters are easy to control, making it suitable for industrial-scale production. It has extremely high application value in the fields of flue gas treatment in power, oil refining, and chemical industries. Attached Figure Description

[0028] Figure 1 The image shows the XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (C1) prepared in Example 1.

[0029] Figure 2 The image shows the XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (C3) prepared in Example 3.

[0030] Figure 3 The image shows the XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (D1) prepared in Comparative Example 1.

[0031] Figure 4 The image shows the XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (D3) prepared in Comparative Example 3.

[0032] Figure 5 The image shows the XRD pattern of the in-situ crystallized FCC sulfur transfer agent (C7) prepared in Example 7.

[0033] Figure 6 The image shows the XRD pattern of the in-situ crystallized FCC sulfur transfer agent (D4) prepared in Comparative Example 4. Detailed Implementation

[0034] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below.

[0035] Coal gangue: SiO2 45.2%; Al2O3 52.1%; Inner Mongolia Mengtai Group Co., Ltd.

[0036] Silica sol: SiO2 content 30wt%, Grace Company;

[0037] Calcium aluminum hydrotalcite: YN type, Shandong Jinshengtai Chemical Co., Ltd.;

[0038] Magnesium aluminum hydrotalcite: Mg4Al2(OH) 12 CO3·3.5H2O, hydrotalcite (Shandong) Technology Development Co., Ltd.;

[0039] Calcium chloride, sodium hydroxide, and hydrochloric acid, analytical grade reagents, were purchased from Sinopharm Group.

[0040] Analysis and Testing

[0041] The crystallinity of the sample was analyzed and tested using a D / max-2200PC X-ray diffractometer manufactured by Rigaku Corporation of Japan: the X-ray diffractometer operating voltage was 40 kV, the current was 20 mA, CuKα radiation was used, the phase scanning angle was 5~50 °, and the scanning rate was 10 ° / min.

[0042] The flue gas desulfurization performance of the samples was tested on a fixed fluidized bed reactor. SO₂ levels before and after desulfurization were analyzed by gas chromatography. x Content, calculate desulfurization rate, SO2 content in sample flue gas is 700-4500 mg / m³ 3Reaction temperature: 40-60℃; space velocity: 3.5 ~ 5.5 m / s.

[0043] Example 1

[0044] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0045] (1) Mix 500g of coal gangue powder (dry basis), 25g of hydrochloric acid and 2500g of water and stir at 80℃ for 3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0046] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (850℃, 0.5h) to obtain roasted coal gangue.

[0047] (3) Mix 100g of roasted coal gangue obtained in step (2), 100g of calcium chloride, 10g of hydrochloric acid and 400g of water, and stir continuously at 95℃ for 0.5h; then add 1mol / L sodium hydroxide solution dropwise until the slurry pH=7, and let it stand for 5h; then add 1g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the slurry pH=10, and transfer the slurry to an autoclave for crystallization (100℃, 72h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallized calcium aluminum hydrotalcite C1 from solid waste coal gangue. The XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (C1) prepared in Example 1 is shown in the figure. Figure 1 As shown.

[0048] Example 2

[0049] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0050] (1) Mix 500g of coal gangue powder (dry basis), 35g of hydrochloric acid and 3000g of water and stir at 83℃ for 2.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0051] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (800℃, 1h) to obtain roasted coal gangue.

[0052] (3) Mix 100g of roasted coal gangue obtained in step (2), 198g of calcium chloride, 14g of hydrochloric acid and 480g of water, and stir continuously at 89℃ for 1h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 7.4, and let it stand for 4h; then add 3g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 10.4, and transfer the slurry to a high pressure vessel for crystallization (110℃, 60h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to synthesize calcium aluminum hydrotalcite C2.

[0053] Example 3

[0054] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0055] (1) Mix 500g of coal gangue powder (dry basis), 45g of hydrochloric acid and 3500g of water and stir at 86℃ for 2h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0056] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (750℃, 2h) to obtain roasted coal gangue.

[0057] (3) Mix 100g of roasted coal gangue obtained in step (2), 297g of calcium chloride, 18g of hydrochloric acid and 560g of water, and stir continuously at 83℃ for 2h; then add 1mol / L sodium hydroxide solution dropwise until the slurry pH=7.8, and let it stand for 3h; then add 5g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the slurry pH=10.8, and transfer the slurry to a high-pressure reactor for crystallization (120℃, 48h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallized calcium aluminum hydrotalcite C3 from solid waste coal gangue. The XRD pattern of the in-situ crystallized calcium aluminum hydrotalcite (C3) prepared in Example 3 is shown in the figure. Figure 2 As shown.

[0058] Example 4

[0059] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0060] (1) Mix 500g of coal gangue powder (dry basis), 55g of hydrochloric acid and 4000g of water and stir at 89℃ for 1.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0061] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (700℃, 3h) to obtain roasted coal gangue.

[0062] (3) Mix 100g of roasted coal gangue obtained in step (2), 396g of calcium chloride, 22g of hydrochloric acid and 640g of water, and stir continuously at 77℃ for 3h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 8.2, and let it stand for 2h; then add 7g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 11.2, and transfer the slurry to a high pressure vessel for crystallization (130℃, 36h); after crystallization, cool to room temperature, filter, wash and dry to obtain the calcium aluminum hydrotalcite C4 synthesized from the solid waste coal gangue in situ crystallization.

[0063] Example 5

[0064] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0065] (1) Mix 500g of coal gangue powder (dry basis), 65g of hydrochloric acid and 4500g of water and stir at 92℃ for 1h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0066] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (650℃, 4h) to obtain roasted coal gangue.

[0067] (3) Mix 100g of roasted coal gangue obtained in step (2), 495g of calcium chloride, 26g of hydrochloric acid and 720g of water, and stir continuously at 71℃ for 4h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 8.6, and let it stand for 1h; then add 9g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 11.6, and transfer the slurry to a high pressure vessel for crystallization (140℃, 24h); after crystallization, cool to room temperature, filter, wash and dry to obtain the calcium aluminum hydrotalcite C5 synthesized from the solid waste coal gangue in situ crystallization.

[0068] Example 6

[0069] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0070] (1) Mix 500g of coal gangue powder (dry basis), 75g of hydrochloric acid and 5000g of water and stir at 95℃ for 0.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0071] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (600℃, 5h) to obtain roasted coal gangue.

[0072] (3) Mix 100g of roasted coal gangue obtained in step (2), 594g of calcium chloride, 30g of hydrochloric acid and 800g of water, and stir continuously at 65℃ for 5h; then add 1mol / L sodium hydroxide solution dropwise until the slurry pH=9, and let it stand for aging for 0.5h; then add 10g of calcium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the slurry pH=12, and transfer the slurry to a high pressure reactor for crystallization (150℃, 12h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to synthesize calcium aluminum hydrotalcite C6.

[0073] Example 7

[0074] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0075] (1) Mix 500g of coal gangue powder (dry basis), 25g of hydrochloric acid and 2500g of water and stir at 80℃ for 3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0076] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 15g of silica sol and 600g of water, and then spray dry and calcine (850℃, 0.5h) to obtain calcined coal gangue microspheres.

[0077] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 100g of magnesium chloride, 10g of hydrochloric acid and 400g of water, and stir continuously at 95℃ for 0.5h; then add 1mol / L sodium hydroxide solution dropwise until the slurry pH=7, and let it stand for 5h for aging; then add 1g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the slurry pH=10, and transfer the slurry to a high-pressure reactor for crystallization (100℃, 72h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C7. The XRD pattern of the in-situ crystallized FCC sulfur transfer agent (C7) prepared in Example 7 is shown in the figure. Figure 5 As shown.

[0078] Example 8

[0079] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0080] (1) Mix 500g of coal gangue powder (dry basis), 35g of hydrochloric acid and 3000g of water and stir at 83℃ for 2.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0081] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 21g of silica sol and 720g of water, and spray dry and calcine (800℃, 1h) to obtain calcined coal gangue microspheres.

[0082] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 198g of magnesium chloride, 14g of hydrochloric acid and 480g of water, and stir continuously at 89℃ for 1h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 7.4, and let it stand for 4h; then add 3g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 10.4, and transfer the slurry to a high pressure vessel for crystallization (110℃, 60h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C8.

[0083] Example 9

[0084] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0085] (1) Mix 500g of coal gangue powder (dry basis), 45g of hydrochloric acid and 3500g of water and stir at 86℃ for 2h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0086] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 27g of silica sol and 840g of water, and spray dry and calcine (750℃, 2h) to obtain calcined coal gangue microspheres.

[0087] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 297g of magnesium chloride, 18g of hydrochloric acid and 560g of water, and stir continuously at 83℃ for 2h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 7.8, and let it stand for 3h; then add 5g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 10.8, and transfer the slurry to a high pressure vessel for crystallization (120℃, 48h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C9.

[0088] Example 10

[0089] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0090] (1) Mix 500g of coal gangue powder (dry basis), 55g of hydrochloric acid and 4000g of water and stir at 89℃ for 1.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0091] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 33g of silica sol and 960g of water, and spray dry and calcine (700℃, 3h) to obtain calcined coal gangue microspheres.

[0092] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 396g of magnesium chloride, 22g of hydrochloric acid and 640g of water, and stir continuously at 77℃ for 3h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 8.2, and let it stand for 2h; then add 7g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 11.2, and transfer the slurry to a high pressure vessel for crystallization (130℃, 36h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C10.

[0093] Example 11

[0094] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0095] (1) Mix 500g of coal gangue powder (dry basis), 65g of hydrochloric acid and 4500g of water and stir at 92℃ for 1h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0096] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 39g of silica sol and 1080g of water, and spray dry and calcine (650℃, 4h) to obtain calcined coal gangue microspheres.

[0097] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 495g of magnesium chloride, 26g of hydrochloric acid and 720g of water, and stir continuously at 71℃ for 4h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 8.6, and let it stand for 1h; then add 9g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the pH of the slurry is 11.6, and transfer the slurry to a high pressure vessel for crystallization (140℃, 24h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C11.

[0098] Example 12

[0099] The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue includes the following steps:

[0100] (2) Mix 500g of coal gangue powder (dry basis), 75g of hydrochloric acid and 5000g of water and stir at 95℃ for 0.5h to remove impurities. Then filter, wash and dry to obtain cleaned coal gangue.

[0101] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 45g of silica sol and 1200g of water, and spray dry and calcine (600℃, 5h) to obtain calcined coal gangue microspheres.

[0102] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 594g of magnesium chloride, 30g of hydrochloric acid and 800g of water, and stir continuously at 65℃ for 5h; then add 1mol / L sodium hydroxide solution dropwise until the slurry pH=9, and let it stand for aging for 0.5h; then add 10g of magnesium aluminum hydrotalcite to the obtained slurry, and add 1mol / L sodium hydroxide solution dropwise while stirring continuously until the slurry pH=12, and transfer the slurry to a high pressure vessel for crystallization (150℃, 12h); after crystallization, cool to room temperature, filter, wash and dry to obtain the in-situ crystallization of solid waste coal gangue to prepare FCC sulfur transfer agent C12.

[0103] Comparative Example 1

[0104] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0105] (1) Mix 500g of coal gangue powder (dry basis), 25g of hydrochloric acid and 2500g of water and stir at 80℃ for 3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0106] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (850℃, 0.5h) to obtain roasted coal gangue.

[0107] (3) Mix 100g of roasted coal gangue obtained in step (2), 100g of calcium chloride, 10g of hydrochloric acid and 400g of water, and stir continuously at 95℃ for 0.5h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 10, and transfer the slurry to an autoclave for crystallization (100℃, 72h); after crystallization, cool to room temperature, filter, wash and dry to obtain calcium aluminum hydrotalcite D1 synthesized from comparative solid waste coal gangue in situ. The XRD pattern of the in situ crystallized calcium aluminum hydrotalcite (D1) prepared in Comparative Example 1 is shown in the figure. Figure 3 As shown.

[0108] Comparative Example 2

[0109] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0110] (1) Mix 500g of coal gangue powder (dry basis), 45g of hydrochloric acid and 3500g of water and stir at 86℃ for 2h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0111] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (750℃, 2h) to obtain roasted coal gangue.

[0112] (3) Mix 100g of roasted coal gangue obtained in step (2), 297g of calcium chloride, 18g of hydrochloric acid and 560g of water, and stir continuously at 83℃ for 2h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 10.8, and transfer the slurry to a high pressure vessel for crystallization (120℃, 48h); after crystallization, cool to room temperature, filter, wash and dry to obtain calcium aluminum hydrotalcite D2 synthesized from comparative solid waste coal gangue in situ crystallization.

[0113] Comparative Example 3

[0114] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0115] (1) Mix 500g of coal gangue powder (dry basis), 65g of hydrochloric acid and 4500g of water and stir at 92℃ for 1h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0116] (2) Roast 300g of the cleaned coal gangue obtained in step (1) (650℃, 4h) to obtain roasted coal gangue.

[0117] (3) Mix 100g of roasted coal gangue obtained in step (2), 495g of calcium chloride, 26g of hydrochloric acid and 720g of water, and stir continuously at 71℃ for 4h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 11.6, and transfer the slurry to an autoclave for crystallization (140℃, 24h); after crystallization, cool to room temperature, filter, wash and dry to obtain calcium aluminum hydrotalcite D3 synthesized from comparative solid waste coal gangue in situ. The XRD pattern of the in situ crystallized calcium aluminum hydrotalcite (D3) prepared in Comparative Example 3 is shown in the figure. Figure 4 As shown.

[0118] Comparative Example 4

[0119] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0120] (1) Mix 500g of coal gangue powder (dry basis), 25g of hydrochloric acid and 2500g of water and stir at 80℃ for 3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0121] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 15g of silica sol and 600g of water, and then spray dry and calcine (850℃, 0.5h) to obtain calcined coal gangue microspheres.

[0122] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 100g of magnesium chloride, 10g of hydrochloric acid and 400g of water, and stir continuously at 95℃ for 0.5h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 10, and transfer the slurry to an autoclave for crystallization (100℃, 72h); after crystallization, cool to room temperature, filter, wash and dry to obtain the FCC sulfur transfer agent D4 prepared by in-situ crystallization of comparative solid waste coal gangue. The XRD pattern of the in-situ crystallized FCC sulfur transfer agent (D4) prepared in Comparative Example 4 is shown in the figure. Figure 6 As shown.

[0123] Comparative Example 5

[0124] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0125] (1) Mix 500g of coal gangue powder (dry basis), 45g of hydrochloric acid and 3500g of water and stir at 86℃ for 2h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0126] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 27g of silica sol and 840g of water, and spray dry and calcine (750℃, 2h) to obtain calcined coal gangue microspheres.

[0127] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 297g of magnesium chloride, 18g of hydrochloric acid and 560g of water, and stir continuously at 83℃ for 2h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 10.8, and transfer the slurry to a high pressure vessel for crystallization (120℃, 48h); after crystallization, cool to room temperature, filter, wash and dry to obtain the FCC sulfur transfer agent D5 prepared by in-situ crystallization of solid waste coal gangue.

[0128] Comparative Example 6

[0129] The method for preparing the aluminum-based hydrotalcite includes the following steps:

[0130] (1) Mix 500g of coal gangue powder (dry basis), 65g of hydrochloric acid and 4500g of water and stir at 92℃ for 1h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue.

[0131] (2) Mix 300g of the cleaned coal gangue obtained in step (1), 39g of silica sol and 1080g of water, and spray dry and calcine (650℃, 4h) to obtain calcined coal gangue microspheres.

[0132] (3) Mix 100g of roasted coal gangue microspheres obtained in step (2), 495g of magnesium chloride, 26g of hydrochloric acid and 720g of water, and stir continuously at 71℃ for 4h; then add 1mol / L sodium hydroxide solution dropwise until the pH of the slurry is 11.6, and transfer the slurry to a high pressure vessel for crystallization (140℃, 24h); after crystallization, cool to room temperature, filter, wash and dry to obtain FCC sulfur transfer agent D6 prepared by in-situ crystallization of solid waste coal gangue.

[0133] The crystallinity of the in-situ crystallized calcium aluminum hydrotalcite synthesized in Examples 1-6 and Comparative Examples 1-3 is shown in Table 1.

[0134] The crystallinity of the FCC sulfur transfer agents prepared in Examples 7-12 and Comparative Examples 4-6 is shown in Table 2.

[0135] The flue gas desulfurization performance of the in-situ crystallized calcium aluminum hydrotalcite synthesized in Examples 1-6 and Comparative Examples 1-3 is shown in Table 3.

[0136] Table 1: Crystallinity of in-situ crystallized calcium aluminum hydrotalcite synthesized in the examples and comparative examples

[0137]

[0138] As shown in Table 1, compared with the existing in-situ crystallization methods, the in-situ crystallized calcium aluminum hydrotalcite synthesized by the method of the present invention has a significantly higher degree of crystallinity. This indicates that the method of the present invention can significantly improve the crystallinity of calcium aluminum hydrotalcite synthesized by in-situ crystallization of solid waste coal gangue, thereby endowing the synthesized in-situ crystallized calcium aluminum hydrotalcite with excellent flue gas desulfurization performance.

[0139] Table 2: Crystallinity of FCC sulfur transfer agents prepared in Examples 7-12 and Comparative Examples 4-6

[0140]

[0141] As shown in Table 2, compared with the existing in-situ crystallization method, the FCC sulfur transfer agent prepared by the method of the present invention has a significantly higher degree of magnesium aluminum hydrotalcite crystallinity. This indicates that the method of the present invention can significantly improve the crystallinity of the FCC sulfur transfer agent prepared by in-situ crystallization of solid waste coal gangue, thereby endowing the prepared FCC sulfur transfer agent with excellent FCC flue gas sulfur transfer performance.

[0142] Table 3: Flue gas desulfurization performance of in-situ crystallized calcium aluminum hydrotalcite synthesized in Examples 1-6 and Comparative Examples 1-3

[0143]

[0144] As shown in Table 3, compared with existing in-situ crystallization methods, the in-situ crystallized calcium aluminum hydrotalcite synthesized by the method of the present invention showed significantly better flue gas desulfurization performance, with a sulfur removal rate significantly higher than the former.

Claims

1. A method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue, characterized in that, Includes the following steps: (1) Mix coal gangue, acid and water and stir at 80-95℃ for 0.5-3h to remove impurities. Then filter, wash and dry to obtain impurity-removed coal gangue. (2) The impurity-removed coal gangue obtained in step (1) is roasted to obtain roasted coal gangue microspheres; (3) Mix the roasted coal gangue microspheres, calcium or magnesium salts, acid and water obtained in step (2), and stir continuously at 65-95℃ for 0.5-5h; then add alkaline solution dropwise until the slurry pH=7-9, and let it stand for aging for 0.5-5h; then add solid seed crystals to the obtained slurry, and add alkaline solution dropwise while stirring continuously until the slurry pH=10-12, and transfer the slurry to a high pressure reactor for crystallization; after crystallization, cool to room temperature, filter, wash and dry to obtain aluminum-based hydrotalcite synthesized from solid waste coal gangue in situ crystallization. In step (2), the roasting temperature is 600-850℃ and the roasting time is 0.5-5h; In step (3), the mass ratio of roasted coal gangue to solid seed crystal is 1:(0.01-0.1), the solid seed crystal is calcium aluminum hydrotalcite or magnesium aluminum hydrotalcite, the crystallization temperature is 100-150℃, and the crystallization time is 12-72h.

2. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, The acid is at least one of hydrochloric acid, nitric acid and sulfuric acid. In step (2), before roasting, the impurity coal gangue, the curing agent and water are mixed and then spray dried.

3. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, In step (1), the mass ratio of coal gangue, acid and water is 1:(0.05-0.15):(5-10).

4. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 2, characterized in that, In step (2), the curing agent is at least one of silica sol, sodium silicate, potassium silicate, and water glass, except that the mass ratio of coal gangue, curing agent and water is 1:(0-0.15):(0-4).

5. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, In step (3), the calcium salt is at least one of calcium chloride, calcium nitrate, calcium acetate and calcium lactate, and the magnesium salt is at least one of magnesium chloride, magnesium nitrate and magnesium sulfate.

6. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, In step (3), the alkaline solution is at least one of the following: ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate solution with a concentration of 1 mol / L.

7. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, In step (3), the mass ratio of roasted coal gangue microspheres, calcium or magnesium salts, acid and water is 1:(0-3):(0.1-0.3):(4-8).

8. The method for preparing aluminum-based hydrotalcite by in-situ crystallization of solid waste coal gangue according to claim 1, characterized in that, In step (3), the crystallinity of calcium aluminum hydrotalcite is ≥85%, and the crystallinity of magnesium aluminum hydrotalcite is ≥85%.

9. A method for synthesizing aluminum-based hydrotalcite through in-situ crystallization of solid waste coal gangue, characterized in that, It is prepared by the method of in-situ crystallization synthesis of aluminum-based hydrotalcite from solid waste coal gangue as described in any one of claims 1-8.

10. An application of the in-situ crystallization synthesis of aluminum-based hydrotalcite from solid waste coal gangue as described in claim 9, characterized in that, Used for flue gas desulfurization or as a sulfur transfer agent in FCC.

Images