Molecular sieve synthesized based on fly ash and rare earth tailings and preparation method thereof

Abstract

The present application relates to the technical field of molecular sieve, and discloses a molecular sieve synthesized based on fly ash and rare earth tailings and a preparation method thereof, wherein the molecular sieve takes the rare earth tailings and the fly ash as the basis, mixes the rare earth tailings and the fly ash with alkali in a certain proportion, and then places them in a muffle furnace for activation; the activated product is dissolved in deionized water and filtered; the silicon-aluminum activation rate in the raw material is obtained by determining the change of the mass of the raw material and the percentage content of SiO2 and Al2O3 before and after the filtration; the silicon-aluminum ratio, the reaction temperature and the reaction time of the synthesis system are regulated, and the molecular sieve is synthesized by using the low-temperature and high-pressure conditions formed by the hydrothermal method; the raw material of the molecular sieve is the rare earth tailings and the fly ash left after the operations of rare earth selection, fluorite selection and iron selection, and the minerals contain the silicon-aluminum source capable of synthesizing the molecular sieve; the molecular sieve has a large specific surface area and a uniform pore size; in addition, the molecular sieve can be used as a denitration catalyst and a carbon storage adsorbent, and realizes the industrialized production of the fly ash and rare earth tailings based molecular sieve.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, and in particular to molecular sieves synthesized from fly ash and rare earth tailings and their preparation methods. Background Technology

[0002] NH3-SCR technology has been widely used due to its superior denitrification performance. Its key core technology—the catalyst—is mainly based on vanadium-tungsten-titanium catalysts. However, these catalysts have drawbacks such as high cost, toxicity, and the potential to cause secondary pollution. To overcome these shortcomings, rare earth denitrification catalysts can be used as alternatives to vanadium-based denitrification catalysts.

[0003] Solid adsorbents have broad application prospects for CO2 adsorption. Zeolite molecular sieve solid adsorbents have significant advantages as solid adsorbents due to their high specific surface area, large pore volume, uniform pore size, and strong selectivity. As an acidic gas, CO2 is readily adsorbed by zeolite molecular sieves because the surface contains numerous alkaline sites. Furthermore, as a quadrupole molecule, CO2 possesses high polarizability, resulting in strong adsorption activity for CO2.

[0004] Chinese Patent CN202110962680.5 (CN 101475191 A) discloses a method for preparing a stepped-pore molecular sieve using natural bauxite. The reaction process involves crystallization at 140-250℃ for 12-48 hours to obtain Fe-SAPO molecular sieves, followed by crystallization at 160-180℃ for 96-144 hours to obtain stepped-pore MFI molecular sieves. This method involves high crystallization temperature and long crystallization time. Chinese Patent CN202111091535.0 discloses a method for preparing zeolite molecular sieves using fly ash as raw material. Fly ash is ground and mixed with a certain mass of NaOH solid, then activated in a muffle furnace using alkali melting. The activated clinker is then aged for 23-26 hours, adjusted to pH 7, and hydrothermally crystallized for 22-26 hours. After washing, filtration, and drying, the molecular sieve is obtained. However, this method has a long preparation cycle. Chinese patent CN202011608690.0 discloses a rare earth-based low-temperature SCR catalyst and its preparation method. This catalyst uses TiO2 as a support, rare earth metal oxides as active components, and WO3, MoO3, P2O5, and SO3 as promoters. The prepared denitrification catalyst has high denitrification efficiency, but the catalyst preparation cost is high.

[0005] The Bayan Obo rare earth deposit is rich in rare earth resources, containing significant amounts of iron, fluorite, and rare earth elements, making it China's largest comprehensive iron-fluorine-rare earth deposit. Currently, the Bayan Obo rare earth tailings have a large accumulation and a complex composition, rich in various associated elements. They contain silicate minerals that can be used as silicon sources for molecular sieve synthesis, as well as active mineral components such as hematite and bastnaesite that can serve as denitrification catalysts. The rare earth tailings remaining after beneficiation operations at the Bayan Obo mine are enormous, but they have not been properly recycled. A large amount of valuable rare earth elements are not effectively recovered and end up in the tailings, resulting in low resource utilization. Fly ash, a natural solid waste generated from coal combustion, mainly contains SiO2 and Al2O3, and its composition is similar to that of molecular sieves. Therefore, the preparation of molecular sieves using rare earth tailings / fly ash is theoretically feasible.

[0006] Therefore, in order to better utilize solid wastes such as rare earth tailings and fly ash, and to realize the industrial production of molecular sieves based on rare earth tailings and fly ash, it is necessary to provide molecular sieves synthesized from fly ash and rare earth tailings and their preparation methods, so as to overcome the limitations of existing technologies. Summary of the Invention

[0007] The purpose of this invention is to provide a molecular sieve synthesized from fly ash and rare earth tailings and its preparation method, thereby solving the problem mentioned in the background art that existing solid wastes such as rare earth tailings and fly ash cannot be better utilized as resources, making it difficult to carry out industrial production of molecular sieves based on rare earth tailings and fly ash.

[0008] The technical solution adopted in this invention is as follows: a molecular sieve synthesized based on fly ash and rare earth tailings, using fly ash and rare earth tailings as the base, and also including sodium hydroxide and sodium aluminate powder.

[0009] A method for preparing molecular sieves based on fly ash and rare earth tailings is further proposed, including the following steps:

[0010] Step (1) Mix rare earth tailings and fly ash that have passed through a 120-mesh sieve in a certain proportion. Weigh a certain mass of NaOH solid and the mixed raw material with NaOH solid in a mass ratio of (1:1.5, 1:2, 1:2.5, 1:3, or 1:3.5). Grind and mix the raw material and NaOH solid evenly and then pass them through a 120-mesh sieve. After grinding and mixing the raw material and NaOH solid evenly, place them in a muffle furnace (350, 450, or 550℃) for alkaline activation (2, 2.5, or 3 hours). After taking them out, grind the activated product into powder and pass it through a 120-mesh sieve to obtain activated rare earth tailings and fly ash powder.

[0011] Step (2) The percentage content of SiO2 and Al2O3 in the activated powder of rare earth tailings and fly ash is determined, and then they are dissolved in deionized water until completely dissolved.

[0012] Step (3) Control the silicon-to-aluminum ratio of the molecular sieve synthesis system and add a certain mass of sodium aluminate powder as an external aluminum source to the activated product that is completely dissolved in water.

[0013] Step (4) Control the crystallization time and crystallization temperature of the molecular sieve hydrothermal synthesis system, transfer the reactants into the polytetrafluoroethylene hydrothermal synthesis reactor, react them into silica-alumina gel, and then into molecular sieve crystals. After the hydrothermal reaction, take them out, wash them with water and dry them to obtain molecular sieve powder.

[0014] Furthermore, an application of molecular sieves synthesized from fly ash and rare earth tailings is proposed, which can be used as a denitrification catalyst for flue gas denitrification or as a carbon storage adsorbent for carbon dioxide adsorption.

[0015] The beneficial effects of this invention are as follows: The molecular sieve described in this invention is mainly made from rare earth tailings and fly ash remaining after rare earth, fluorite, and iron beneficiation operations. These minerals contain silicon and aluminum sources that can synthesize molecular sieves. Therefore, the recycling and reuse of rare earth tailings and fly ash not only reduces the preparation cost of molecular sieves but also realizes the high-value utilization of solid waste. Furthermore, the molecular sieve described in this invention has a large specific surface area and uniform pore size. The molecular sieve has a low synthesis crystallization temperature and short crystallization time, which shortens the preparation cycle and reduces the cost of catalyst preparation. It can also be used as a denitrification catalyst and carbon storage adsorbent, realizing the industrial production of rare earth tailings and fly ash-based molecular sieves and promoting the development of my country's environmental protection cause. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the preparation method of molecular sieves synthesized from fly ash and rare earth tailings.

[0017] Figure 2 The denitrification efficiency of molecular sieve catalysts in specific embodiments 4, 5, and 6 are shown.

[0018] Figure 3 The denitrification efficiency of molecular sieve catalysts in specific embodiments 13 and 21 is shown.

[0019] Figure 4 The N2 selectivity of molecular sieve catalysts in specific embodiments 13 and 21.

[0020] Figure 5 The microstructure of the molecular sieve surface in specific embodiments 1, 2, and 3 are shown.

[0021] Figure 6 The microstructure of the molecular sieve surface in specific embodiments 4, 5, and 7 are shown. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention is described below with reference to specific embodiments shown in the accompanying drawings; however, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the present invention; furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concept of the present invention.

[0023] Molecular sieves synthesized from fly ash and rare earth tailings, using fly ash and rare earth tailings as the base, also include sodium hydroxide and sodium aluminate powder.

[0024] Furthermore, it also includes potassium permanganate for preparing 5% wt. Mn / modified molecular sieve catalysts.

[0025] The fly ash and rare earth tailings are mixed evenly at a mass ratio of 1:2; the weight of NaOH is 9g.

[0026] A further proposed method for producing the molecular sieve synthesized from fly ash and rare earth tailings includes the following steps:

[0027] Step (1) Mix rare earth tailings and fly ash that have passed through a 120-mesh sieve in a certain proportion. Weigh a certain mass of NaOH solid and the mixed raw material with NaOH solid in a mass ratio of (1:1.5, 1:2, 1:2.5, 1:3, or 1:3.5). Grind and mix the raw material and NaOH solid evenly and then pass them through a 120-mesh sieve. After grinding and mixing the raw material and NaOH solid evenly, place them in a muffle furnace (350, 450, or 550℃) for alkaline activation (2, 2.5, or 3 hours). After taking them out, grind the activated product into powder and pass it through a 120-mesh sieve to obtain activated rare earth tailings and fly ash powder.

[0028] Step (2) The percentage content of SiO2 and Al2O3 in the activated powder of rare earth tailings and fly ash is determined, and then they are dissolved in deionized water until completely dissolved.

[0029] Step (3) Control the silicon-aluminum ratio of the molecular sieve synthesis system and add a certain mass of sodium aluminate powder as an external aluminum source to the activated product that is completely dissolved in water.

[0030] Step (4) Control the crystallization time and crystallization temperature of the molecular sieve hydrothermal synthesis system, transfer the reactants into the polytetrafluoroethylene hydrothermal synthesis reactor, react them into silica-alumina gel, and then into molecular sieve crystals. After the hydrothermal reaction, take them out, wash them with water and dry them to obtain molecular sieve powder.

[0031] The rare earth tailings in step (1) are derived from the Bayan Obo rare earth mine in Baotou. They are the tailings remaining after iron beneficiation, fluorite beneficiation, and rare earth beneficiation operations. They mainly contain Fe, Ca, F, Si, Mg, Mn, P, Al, S, K, Nd, Ti, Nb, Sr, Pr, Zn, Sc, Pb, and Co elements. The contents of Fe, Ca, F, Si, Mg, Mn, P, Al, S, K, and Nd are 32.01–38.38%, 3.45–3.73%, 4.00–5.67%, 42.04–44.84%, 4.41–5.80%, 0.73–1.98%, 0.91–2.25%, 1.26–5.70%, 0.00–1.02%, 0.74–1.45%, and 0.00–0.89%, respectively.

[0032] The fly ash in step (1) mainly contains Si, Al, Fe, Ca, Mg, S, and K elements, with the contents of these elements being 15.01–45.38%, 5.45–35.73%, 4.00–14.67%, 5.04–15.84%, 3.41–9.80%, 0.73–5.26%, and 0.11–3.25%, respectively.

[0033] The reason for choosing alkali fusion activation in step (1) is that the raw materials were subjected to thermal activation, sub-molten salt activation and alkali fusion activation. By comparing the three activation methods, it was found that alkali fusion activation requires fewer steps and is simpler to operate. Moreover, the high-polymerized silicon-aluminum species in rare earth tailings and fly ash are depolymerized into low-polymerized silicon-aluminum species to the greatest extent, which means that the dissolution rate of active silicon-aluminum species that can be used for molecular sieve synthesis is the highest. Therefore, alkali fusion activation is chosen.

[0034] The aluminum source in step (3) can also be replaced with aluminum hydroxide, aluminum sulfate, sodium aluminate, or activated alumina. The reaction equation for the reaction after the addition of sodium aluminate is NaAlO2 + 2H2O = NaOH + Al(OH)3.

[0035] The hydrothermal reaction equations in step (4) are SiO2 + 2NaOH = Na2SiO2 + H2O and Al2O3 + 2NaOH = 2NaAlO2 + H2O.

[0036] A further proposed performance testing method for the above-mentioned preparation method of molecular sieve based on fly ash and rare earth tailings is as follows: (1) The denitrification efficiency of molecular sieve based on fly ash and rare earth tailings is tested using a catalytic evaluation system. The catalytic evaluation system consists of three parts: a gas supply system, a reaction system, and a flue gas analysis system. The gas supply system is mixed with NO, NH3, N2, and O2 to simulate the industrial flue gas atmosphere. The total flow rate of the experiment is 100 mL / min, with 500 ppm NH3 and 500 ppm NO introduced, O2 volume fraction of 6%, N2 as the balance gas, and space velocity of 10000 h⁻¹.-1 The prepared catalyst sample was placed in the reaction system and brought into contact with the mixed simulated industrial flue gas to begin the reaction. The test temperature in the reactor was set at 50–400 °C, and the heating rate was 10 °C / min. The gas passing through the reaction system entered the flue gas analysis system. The gas composition and content were detected by a Fourier transform infrared spectroscopy flue gas analyzer, and the denitrification efficiency of the catalyst (Equation (1)) and the N2 selectivity (Equation (2)) could be calculated. Wherein, η is the denitrification efficiency under this condition; NO x(in) The NO inlet volume fraction under this operating condition; NO x(out) The NO outlet volume fraction under this operating condition; NH 3(in) The inlet volume fraction of NH3 under this operating condition; NH 3(out) The volume fraction of NH3 at the outlet under this operating condition; N2O (out) This represents the N2O outlet volume fraction under this operating condition.

[0037]

[0038]

[0039] (2) The specific surface area of ​​the molecular sieve prepared from fly ash and rare earth tailings was tested using a specific surface area analyzer. The experimental sample was placed in a sample tube and degassed in a degassing station for 3 hours. Then, the specific surface area, pore volume and pore size of the catalyst were tested using liquid nitrogen as the adsorption medium.

[0040] Furthermore, an application of the molecular sieve synthesized from fly ash and rare earth tailings is proposed, which can be used as a denitrification catalyst for flue gas denitrification or as a carbon storage adsorbent for carbon dioxide adsorption.

[0041] Example 1

[0042] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0043] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=1, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0044] Step 3: Performance Testing

[0045] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0046] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0047] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 61% and a specific surface area of ​​163.02 m². 2 / g.

[0048] Example 2

[0049] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0050] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0051] Step 3: Performance Testing

[0052] The denitrification efficiency of molecular sieve catalysts was measured using a catalytic evaluation system.

[0053] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0054] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 74% and a specific surface area of ​​215.46 m². 2 / g.

[0055] Example 3

[0056] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0057] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=2, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature to 100℃ and the hydrothermal time to 8h, after the hydrothermal reaction is completed, take it out, wash with water and dry to obtain molecular sieve.

[0058] Step 3: Performance Testing

[0059] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0060] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0061] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 66% and a specific surface area of ​​191.34 m². 2 / g.

[0062] Example 4

[0063] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0064] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0065] Step 3: Performance Testing

[0066] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0067] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0068] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 71% and a specific surface area of ​​221.35 m². 2 / g.

[0069] Example 5

[0070] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0071] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 120℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0072] Step 3: Performance Testing

[0073] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0074] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0075] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 68% and a specific surface area of ​​203.59 m². 2 / g.

[0076] Example 6

[0077] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0078] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 12h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0079] Step 3: Performance Testing

[0080] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0081] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0082] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 75% and a specific surface area of ​​224.70 m². 2 / g.

[0083] Example 7

[0084] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 450℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0085] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 16h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0086] Step 3: Performance Testing

[0087] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0088] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0089] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 64% and a specific surface area of ​​199.73 m². 2 / g.

[0090] Example 8

[0091] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0092] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=1, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0093] Step 3: Performance Testing

[0094] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0095] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0096] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 50% and a specific surface area of ​​137.68 m². 2 / g.

[0097] Example 9

[0098] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0099] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0100] Step 3: Performance Testing

[0101] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0102] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0103] Testing revealed that the molecular sieve catalyst achieved a denitrification efficiency of up to 54% and a specific surface area of ​​176 m². 2 / g.

[0104] Example 10

[0105] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0106] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=2, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature to 100℃ and the hydrothermal time to 8h, after the hydrothermal reaction is completed, take it out, wash with water and dry to obtain molecular sieve.

[0107] Step 3: Performance Testing

[0108] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0109] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0110] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 48% and a specific surface area of ​​129.72 m². 2 / g.

[0111] Example 11

[0112] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0113] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0114] Step 3: Performance Testing

[0115] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0116] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0117] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 57% and a specific surface area of ​​172.51 m². 2 / g.

[0118] Example 12

[0119] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0120] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 120℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0121] Step 3: Performance Testing

[0122] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0123] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0124] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 53% and a specific surface area of ​​157.51 m². 2 / g.

[0125] Example 13

[0126] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0127] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 12h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0128] Step 3: Performance Testing

[0129] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0130] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0131] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 63% and a specific surface area of ​​193.59 m². 2 / g.

[0132] Example 14

[0133] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 350℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0134] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 16h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0135] Step 3: Performance Testing

[0136] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0137] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0138] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 43% and a specific surface area of ​​123.59 m². 2 / g.

[0139] Example 15

[0140] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. Measure the changes in the mass and percentage content of the raw materials before and after filtration to obtain the activation dissolution rate of silicon and aluminum in the raw materials.

[0141] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=1, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0142] Step 3: Performance Testing

[0143] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0144] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0145] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 57% and a specific surface area of ​​153.79 m². 2 / g.

[0146] Example 16

[0147] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0148] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 100℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0149] Step 3: Performance Testing

[0150] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0151] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0152] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 67% and a specific surface area of ​​173.81 m². 2 / g.

[0153] Example 17

[0154] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0155] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3)=2, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature to 100℃ and the hydrothermal time to 8h, after the hydrothermal reaction is completed, take it out, wash with water and dry to obtain molecular sieve.

[0156] Step 3: Performance Testing

[0157] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0158] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0159] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 61% and a specific surface area of ​​161.31 m². 2 / g.

[0160] Example 18

[0161] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0162] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0163] Step 3: Performance Testing

[0164] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0165] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0166] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 72% and a specific surface area of ​​191.51 m². 2 / g.

[0167] Example 19

[0168] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0169] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 120℃ and the hydrothermal time at 8h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0170] Step 3: Performance Testing

[0171] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0172] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0173] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 62% and a specific surface area of ​​141.31 m². 2 / g.

[0174] Example 20

[0175] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0176] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 12h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0177] Step 3: Performance Testing

[0178] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0179] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0180] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 68% and a specific surface area of ​​161.21 m². 2 / g.

[0181] Example 21

[0182] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw materials before and after filtration.

[0183] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 16h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0184] Step 3: Performance Testing

[0185] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0186] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0187] Testing revealed that the molecular sieve catalyst exhibited a denitrification efficiency of up to 65% and a specific surface area of ​​151.31 m². 2 / g.

[0188] Example 22

[0189] Step 1: Mix fly ash and rare earth tailings evenly at a mass ratio of 1:2. Weigh 9g of sodium hydroxide solid and grind it thoroughly with fly ash and rare earth tailings. Place it in a muffle furnace and activate it with alkali at 550℃ for 2 hours. Dissolve the activated product in water and filter it. The activation dissolution rate of silicon and aluminum in the raw material is obtained by measuring the changes in the mass and percentage content of the raw material before and after filtration.

[0190] Step 2: Control the molecular sieve synthesis system n(SiO2):n(Al2O3) = 1.5, add a certain mass of sodium aluminate as an external aluminum source, mix evenly and transfer to a reaction vessel, control the hydrothermal temperature at 110℃ and the hydrothermal time at 16h, after the hydrothermal reaction is completed, take it out, wash it with water and dry it to obtain the molecular sieve.

[0191] Step 3: Add a certain mass (5%) of potassium permanganate to the prepared molecular sieve, and prepare a 5% wt. Mn / molecular sieve catalyst under hydrothermal conditions of 120℃ and 12h.

[0192] Step 4: Performance Testing

[0193] The denitrification efficiency of molecular sieve catalysts was tested using a catalytic evaluation system.

[0194] The specific surface area of ​​the molecular sieve catalyst was tested using a specific surface area analyzer and the nitrogen adsorption method.

[0195] Testing revealed that the Mn-modified molecular sieve catalyst exhibited a denitrification efficiency of up to 85% and a specific surface area of ​​154.1 m². 2 / g.

[0196] Table 1, derived from Examples 1-22 above, shows the specific surface area and pore structure of the catalyst.

[0197]

[0198] Table 1

[0199] Although the present invention has been described in detail with reference to the foregoing examples, those skilled in the art can still make and modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., 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 preparing molecular sieves based on fly ash and rare earth tailings, characterized in that... Includes the following steps: Step (1) Mix the sieved rare earth tailings and fly ash at a mass ratio of 1:

2. Grind the mixed raw materials with NaOH solid and then sieve them. Then, place them in a muffle furnace for activation at a temperature of 450℃ and an activation time of 2 hours. After activation, remove them and grind the activated product into powder and sieve them to obtain activated rare earth tailings and fly ash powder. The rare earth tailings are from the Bayan Obo rare earth mine in Baotou. They are the tailings remaining after iron beneficiation, fluorite beneficiation and rare earth beneficiation operations. They contain Fe, Ca, F, Si, Mg, Mn, P, Al, S, K, Nd, Ti, Nb, Sr, Pr, Zn, Sc, Pb and Co elements, of which Fe The elemental content ranges from 32.01% to 38.38%, with the contents of Ca, F, Si, Mg, Mn, P, Al, S, K, and Nd being 3.45% to 3.73%, 4.00% to 5.67%, 42.04% to 44.84%, 4.41% to 5.80%, 0.73% to 1.98%, 0.91% to 2.25%, 1.26% to 5.70%, 0.00% to 1.02%, 0.74% to 1.45%, and 0.00% to 0.89%, respectively. Fly ash contains Si, Al, Fe, Ca, Mg, S, and K, with Si being the most abundant element. The elemental content is 15.01~45.38%, the Al content is 5.45~35.73%, and the contents of Fe, Ca, Mg, S and K are 4.00~14.67%, 5.04~15.84%, 3.41~9.80%, 0.73~5.26%, and 0.11~3.25%, respectively. Step (2) Determine the percentage content of SiO2 and Al2O3 in the activated powder of rare earth tailings and fly ash, and dissolve the activated powder in deionized water until it is completely dissolved. Step (3) Control the silicon-to-aluminum ratio of the molecular sieve synthesis system by adding a certain mass of sodium aluminate powder as an external aluminum source to the activated product that is completely dissolved in water; adjust and control the molecular sieve synthesis system n(SiO2):n(Al2O3)=1.5; Step (4) The reactants are transferred into a polytetrafluoroethylene hydrothermal synthesis reactor. The hydrothermal temperature of the hydrothermal synthesis system is controlled at 110°C and the hydrothermal time is 12h. After the hydrothermal reaction, the reactants are taken out, washed with water and dried to obtain molecular sieve powder. The molecular sieve is used as a denitrification catalyst for flue gas denitrification or as a carbon storage adsorbent for carbon dioxide adsorption.

2. The preparation method according to claim 1, characterized in that... The mass ratio of the raw materials mixed in step (1) to NaOH is 1:1.5, 1:2, 1:2.5, 1:3, or 1:3.

5.

3. A molecular sieve synthesized from fly ash and rare earth tailings, prepared using the method described in any one of claims 1-2, characterized in that... Based on fly ash and rare earth tailings, it also includes sodium hydroxide and sodium aluminate powder.

4. The molecular sieve synthesized from fly ash and rare earth tailings according to claim 3, characterized in that... It also includes potassium permanganate, used to prepare 5% wt. Mn / modified molecular sieve catalysts.

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