A method for synthesizing high content framework phosphorus-maculine zeolite

Abstract

The application relates to a synthesis method of high-content-framework phosphorus-macropotassium zeolite. A high-content-framework phosphorus-macropotassium zeolite is synthesized by taking a silicon source, an aluminum source, a phosphorus source, KOH and deionized water as raw materials. In the application, the phosphorus atoms are effectively introduced into the molecular sieve framework in a tetrahedral coordination mode, the introduced amount of phosphorus is high, the Si / P molar ratio in the product can reach 1, the product does not contain a P2O5 impurity phase, and the synthesis method has the advantages of simplicity, short crystallization time (20-36h) and high crystallinity (>90%).

Description

Technical Field

[0001] The invention relates to a method for synthesizing heteroatom molecular sieves, specifically a simple and rapid method for synthesizing high-content skeletal phosphorus-potassium zeolite. Background Technology

[0002] Zeolite is an inorganic microporous crystalline material whose basic framework is composed of shared vertices between TO4 (T = Al, Si, P, B, Ga, etc.) tetrahedra. Due to its unique pore structure, zeolite has been widely used in ion exchange, catalysis, adsorption separation, and other fields.

[0003] Potassium zeolite is a small-pore aluminosilicate zeolite belonging to the tetragonal crystal system. Its pore structure is composed of three-dimensional octagonal rings connected to each other. Potassium hydroxide zeolite is usually synthesized by hydrothermal method at 150 ℃-180 ℃. For example, Yang Xu et al. (Yang Xu, et al. Journal of Chemical Research in Chinese Universities, 2015, 36(2): 336-343.) used silicon-aluminum microspheres, potassium hydroxide and deionized water as raw materials, with a molar ratio of 0.75K2O:0.1Al2O3:SiO2:14H2O. After mixing the raw materials evenly, potassium hydroxide zeolite was synthesized by hydrothermal crystallization at 150 ℃ for 72 h. Maghsoodloorad et al. (Maghsoodloorad H, et al. Clays&ClayMinerals, 2011, 59(3): 328-335.) used aluminum hydroxide, silicon dioxide, potassium hydroxide and deionized water as raw materials, with a molar ratio of 5.6K2O:6.4SiO2:Al2O3:164.6H2O. Under certain conditions, Al(OH)3 was first dissolved in KOH solution under heating, cooled to room temperature, and then mixed with an aqueous silicic acid solution. After stirring, a uniform gel was formed, aged at room temperature for 5 hours, and then crystallized at 165℃ for 72 hours to synthesize potassium methyl methacrylate (PMMA) zeolite hydrothermally. In addition, there are reports of synthesizing PMMA zeolite through molecular sieve transformation, such as Salah (Salah, Synthesis of chamazolithium and graded porous PMMA zeolite by Y-type molecular sieve transformation [D], 2020), who obtained K-MER molecular sieves with a silica-to-alumina ratio between 1.7 and 2.1 by modifying Y-type molecular sieves with NH4F and oxalic acid. Some researchers have also used mineral raw materials to synthesize PMMA zeolite, such as Qi Yuxiang (Qi Yuxiang, Synthesis of zeolite from potassium feldspar and its use for removing lead and cadmium from aqueous solutions [D], 2018), who used potassium feldspar powder as raw material and synthesized PMMA zeolite using a hydrothermal method. Xu Jianang (Xu Jianang, Experimental study on hydrothermal synthesis of potassium zeolite from tangent green rock powder [D], 2020) synthesized potassium zeolite from tangent green rock powder using hydrothermal methods.

[0004] With the development of industrial technology and the improvement of scientific and technological level, the application fields of potassium zeolite are becoming wider and wider. For example, it can be used for the exchange of potassium ions in seawater, as a slow-release potassium fertilizer widely used in agriculture, as a potential catalyst for methanol dehydration, to remove carbon dioxide impurities contained in natural gas, to purify petroleum hydrocarbons to remove hydrogen sulfide, or to concentrate oxygen to separate nitrogen, etc.

[0005] In summary, to date, there are relatively few reported methods for synthesizing potassium zeolite molecular sieves, and the methods are generally quite complex. Furthermore, the introduction of heteroatoms into molecular sieves can effectively control the strength and density of acid centers and influence pore size, specific surface area, adsorption, and diffusion properties, thereby enabling the molecular sieves to exhibit higher activity and selectivity in many reactions, which has attracted widespread attention. Therefore, the study of heteroatom molecular sieves is of great significance, and currently, no synthetic methods for heteroatom potassium zeolite have been reported in the literature. Summary of the Invention

[0006] The purpose of this invention is to provide a simple and rapid synthesis method for high-content skeletal phosphorus-potassium zeolite. The synthesis uses silicon, aluminum, phosphorus, KOH, and water as raw materials.

[0007] The technical solution of the present invention is as follows: silicon source, aluminum source and KOH are added sequentially to phosphorus source solution, and the resulting slurry is synthesized into the framework phosphorus-potassium zeolite through a one-step hydrothermal crystallization reaction; the phosphorus source is an inorganic phosphorus compound, and the phosphorus source solution is an aqueous solution of phosphorus source.

[0008] In some specific technical solutions, the molar ratio of phosphorus source to aluminum source in the synthesis method is P2O5 / Al2O3 = 0.5~3.5:1, calculated as oxides.

[0009] In some specific technical solutions, the molar ratio of phosphorus source to aluminum source in the synthesis method is P2O5 / Al2O3 = 0.8~2.5:1, as an oxide.

[0010] In some specific technical solutions, the phosphorus source is at least one of phosphoric acid, pyrophosphate, diammonium hydrogen phosphate, and diammonium dihydrogen phosphate.

[0011] The present invention provides a one-step crystallization synthesis method for synthesizing framework phosphorus-potassium zeolite, the specific operation of which is as follows: (1) Weigh a certain amount of phosphorus source using a balance to prepare solution A, then weigh a certain amount of aluminum source and add it to solution A, and stir for 0.5~2 h. At room temperature, add a certain amount of silicon source to solution A, stir for 1~3 h, then add a certain amount of KOH solution dropwise to the solution, and continue stirring for 6~20 h to obtain sol slurry B.

[0012] (2) Transfer the obtained sol slurry B to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, seal it, crystallize it at the required temperature for the required time, filter it, wash it, transfer the filter cake to an oven at 110~150 ℃ to dry it, and then transfer it to a muffle furnace at 450~600 ℃. Phosphorus-potassium zeolite is obtained by calcining at ℃ for 4-8 hours.

[0013] Furthermore, in the above technical solution, the amounts of various raw materials used are as follows: silicon source: SiO2; OH... - The molar ratio of KOH to water to aluminum source (based on Al2O3) is 0.5~6:0.5~2:25~76:1. The water here includes the aluminum source, silicon source, water in the KOH solution, and water used to prepare solution A.

[0014] Furthermore, in the above technical solution, the amounts of various raw materials used are as follows: silicon source: SiO2; OH... - The molar ratio of KOH:water:aluminum source (based on Al2O3) is 1~5:1.0~2:28~76:1.

[0015] The silicon and aluminum sources mentioned are commonly used silicon and aluminum sources for synthesizing potassium zeolite.

[0016] Furthermore, in the above technical solution, the silicon source is at least one of water glass and silica sol; Furthermore, in the above technical solution, the aluminum source is at least one of aluminum sulfate, sodium aluminate, AlCl3, Al(NO3)3, and boehmite.

[0017] Furthermore, in the above technical solution, the hydrothermal crystallization reaction can be carried out under static, rotating, or stirring conditions.

[0018] Furthermore, in the above technical solution, the crystallization temperature is 170~220 ℃.

[0019] Furthermore, in the above technical solution, the crystallization time is 20~72 h.

[0020] The beneficial effects of this invention are: (1) The present invention utilizes conventional hydrothermal synthesis method to directly prepare high-content skeletal phosphorus-potassium zeolite in one step. The synthesized skeletal phosphorus content can reach Si / P = 1, and the synthesis process is simple and easy to operate.

[0021] (2) The one-step crystallization synthesis method of the present invention can obtain high-content skeletal phosphorus-potassium zeolite with high crystallinity (>90%).

[0022] (3) In the high-content skeletal phosphorus-potassium zeolite prepared by the present invention, phosphorus is located in the molecular sieve framework in a tetrahedral coordination manner, and the product contains only a small amount or even no P2O5 impurity phase. Attached Figure Description

[0023] Figure 1 The image shows the X-ray powder diffraction (XRD) phase diagram of the phosphorus-potassium zeolite synthesized in Example 1.

[0024] The spectrum clearly contains characteristic diffraction peaks of potassium zeolite, such as 2θ = 8.66º, 10.58º, 12.37º, and 24.30º, and has a strong diffraction peak intensity, indicating that the obtained sample is a highly ordered potassium zeolite.

[0025] Figure 2 This is a SEM image of the phosphorus-potassium zeolite synthesized in Example 1. Detailed Implementation

[0026] To further illustrate the invention, the following embodiments are provided, but they do not limit the scope of the invention as defined by the appended claims. In the specific embodiments, the phosphoric acid content is 85% by mass, the alumina content in the boehmite is 71.32% by mass, and the KOH solution concentration is 20% by mass. Example 1

[0027] (1) Weigh 10.26 g of phosphoric acid using a balance and add it to 56.30 g of deionized water to prepare solution A. Then weigh 8.37 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 13.73 g of silica sol (40% SiO2) to solution A, stir for 2 h, then add 11.34 g of KOH solution dropwise to the solution and continue stirring for 10 h to obtain sol slurry B.

[0028] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at -180 °C for 20 h. After filtration and washing, the filter cake was transferred to a 120 °C oven for drying, and then transferred to a muffle furnace for 600 °C. Phosphorus-potassium zeolite was obtained by calcination at ℃ for 6 h. The analytical results are shown in Table 1. Example 2

[0029] The steps are the same as in Example 1, except that “13.73 g silica sol (40% SiO2)” is replaced with “18.30 g water glass (30% SiO2)”. The analysis results are shown in Table 1. Example 3

[0030] The steps were the same as in Example 1, except that “8.37 g boehmite” was replaced with “15.62 g aluminum chloride”. The analysis results are shown in Table 1. Example 4

[0031] The steps are the same as in Example 1, except that “static crystallization at 180 °C for 20 h” is replaced with “stirred crystallization at 180 °C for 20 h at a rotation speed of 100 rpm”. The analysis results are shown in Table 1. Example 5

[0032] The steps are the same as in Example 1, except that “crystallization at 180 °C for 20 h” is replaced with “crystallization at 180 °C for 26 h”. The analysis results are shown in Table 1. Example 6

[0033] The steps are the same as in Example 1, except that “crystallization at 180 °C” is replaced with “crystallization at 170 °C for 30 h”. The analysis results are shown in Table 1. Example 7

[0034] (1) Weigh 8.43 g of phosphoric acid using a balance and add it to 46.46 g of deionized water to prepare solution A. Then weigh 9.68 g of boehmite and add it to solution A, and stir for 0.5 h. At room temperature, add 15.87 g of silica sol (40% SiO2) to solution A, stir for 1 h, then add 19.56 g of KOH solution dropwise to the solution and continue stirring for 6 h to obtain sol slurry B.

[0035] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at -180 °C for 20 h. After filtration and washing, the filter cake was transferred to a 120 °C oven for drying, and then transferred to a muffle furnace for 500 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 4 h. Example 8

[0036] (1) Weigh 8.27 g of phosphoric acid using a balance and add it to 48.77 g of deionized water to prepare solution A. Then weigh 10.16 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 10.78 g of silica sol (40% SiO2) to solution A, stir for 2 h, then add 13.75 g of KOH solution dropwise to the solution and continue stirring for 6 h to obtain sol slurry B.

[0037] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 200 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 500 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 8 h. Example 9

[0038] (1) Weigh 9.66 g of phosphoric acid using a balance and add it to 19.39 g of deionized water to prepare solution A. Then weigh 10.06 g of boehmite and add it to solution A, and stir for 2 h. At room temperature, add 22.21 g of silica sol (40% SiO2) to solution A, stir for 2 h, and then add 29.03 g of KOH solution dropwise to the solution. Continue stirring for 12 h to obtain sol slurry B.

[0039] (2) The obtained sol slurry B was transferred to a stainless steel crystallization vessel with a polytetrafluoroethylene liner, sealed, and statically crystallized at 170 °C for 30 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 6 h. Example 10

[0040] (1) Weigh 11.52 g of phosphoric acid using a balance and add it to 20.86 g of deionized water to prepare solution A. Then weigh 7.25 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 24.38 g of silica sol (40% SiO2) to solution A and stir for 2 h. Then add 24.47 g of KOH solution dropwise to the solution and continue stirring for 13 h to obtain sol slurry B.

[0041] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at -180 °C for 20 h. After filtration and washing, the filter cake was transferred to a 120 °C oven for drying, and then transferred to a muffle furnace for 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 6 h. Example 11

[0042] (1) Weigh 25.69 g of phosphoric acid using a balance and add it to 9.65 g of deionized water to prepare solution A. Then weigh 6.69 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 32.22 g of silica sol (40% SiO2) to solution A, stir for 3 h, then add 25.75 g of KOH solution dropwise to the solution and continue stirring for 15 h to obtain sol slurry B.

[0043] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 220 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 8 h. Example 12

[0044] (1) Weigh 16.14 g of phosphoric acid using a balance and add it to 5.85 g of deionized water to prepare solution A. Then weigh 6.10 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 38.16 g of silica sol (40% SiO2) to solution A, stir for 3 h, then add 17.60 g of KOH solution dropwise to the solution and continue stirring for 20 h to obtain sol slurry B.

[0045] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 190 °C for 25 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 8 h. Example 13

[0046] (1) Weigh 11.43 g of pyrophosphoric acid using a balance and add it to 54.36 g of deionized water to prepare solution A. Then weigh 8.57 g of boehmite and add it to solution A, and stir for 1 h. At room temperature, add 14.04 g of silica sol (40% SiO2) to solution A, stir for 2 h, then add 11.60 g of KOH solution dropwise to the solution and continue stirring for 10 h to obtain sol slurry B.

[0047] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 180 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 6 h. Example 14

[0048] (1) Weigh 7.42 g of ammonium dihydrogen phosphate using a balance and add it to 58.67 g of deionized water to prepare solution A. Then weigh 8.49 g of boehmite and add it to solution A. Stir for 1 h. At room temperature, add 13.92 g of silica sol (40% SiO2) to solution A and stir for 2 h. Then add 11.50 g of KOH solution dropwise to the solution and continue stirring for 10 h to obtain sol slurry B.

[0049] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 180 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 6 h.

[0050] Comparative Example 1 (1) Weigh 9.33 g of boehmite using a balance and add it to 62.73 g of deionized water to prepare a solution. Add the solution to solution A and stir for 1 h. At room temperature, add 15.30 g of silica sol (40% SiO2) to solution A and stir for 2 h. Then, add 12.64 g of KOH solution dropwise to the solution and continue stirring for 10 h to obtain sol slurry B.

[0051] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 180 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcination at ℃ for 6 h. The analytical results are shown in Table 1.

[0052] Comparative Example 2 (1) Weigh 9.42 g of boehmite using a balance and add it to 27.11 g of deionized water to prepare solution A. Stir for 1 h. At room temperature, add 31.67 g of silica sol (40% SiO2) to solution A and stir for 2 h. Then, add 31.79 g of KOH solution dropwise to the solution and continue stirring for 10 h to obtain sol slurry B.

[0053] (2) The obtained sol slurry B was transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene liner, sealed, and statically crystallized at 180 °C for 20 h. After filtration and washing, the filter cake was transferred to an oven at 120 °C for drying, and then transferred to a muffle furnace at 600 °C. Phosphorus-potassium zeolite was obtained by calcining at ℃ for 6 h.

[0054] Test Implementation Examples

[0055] The crystal phase structure analysis of the catalyst was performed using X Pert from PAN Analytical, Netherlands. 3 Powder-type X-ray diffractometer. Specific parameters are: Cu target Kα light source (λ = 0.1541 nm), tube voltage = 40 kV, tube current = 40 mA, scan rate = 10. o min -1 The XRD pattern obtained by ZSM-35 in Comparative Example 2 is recorded as the standard sample. The ratio of the peak area of ​​the XRD pattern of the samples in other examples to the peak area of ​​the standard sample is recorded as the relative crystallinity.

[0056] The chemical composition and proportion of ZSM-35 molecular sieve samples were determined using an X-ray fluorescence spectrometer (XRF) from PANAnalytical (Netherlands), with an excitation voltage of 40 kV and a current of 50 mA. Specific data are shown in Table 1.

[0057] The microstructure of the samples was observed using a HITACHI SU5000 scanning electron microscope from HITACHI Corporation, Japan. Specific experimental methods: A small amount of sample powder was applied evenly to the conductive adhesive on the sample plate using a toothpick. Excess powder was then blown away with a bulb syringe to avoid contaminating the instrument. Before placing the sample plate into the electron microscope chamber for analysis, it underwent gold sputtering, a process that should be performed under vacuum conditions.

[0058] Table 1 Example 1 Pure phase potassium zeolite 102% 1.00 Example 2 Pure phase potassium zeolite 94% 1.08 Example 3 Pure phase potassium zeolite 99% 1.02 Example 4 Pure phase potassium zeolite 96% 1.05 Example 5 Pure phase potassium zeolite 99% 1.03 Example 6 Pure phase potassium zeolite 92% 1.10 Example 7 Pure phase potassium zeolite 95% 1.45 Example 8 Pure phase potassium zeolite 96% 1.08 Example 9 Pure phase potassium zeolite 96% 1.82 Example 10 Pure phase potassium zeolite 94% 1.66 Example 11 Pure phase potassium zeolite 93% 1.08 Example 12 Pure phase potassium zeolite 90% 1.90 Example 13 Pure phase potassium zeolite 100% 1.01 Example 14 Pure phase potassium zeolite 96% 1.05 Comparative Example 1 Pure phase potassium zeolite 99% - Comparative Example 2 Pure phase potassium zeolite 100% - As shown in Table 1, the method of the present invention can synthesize pure-phase phosphorus-doped potassium zeolite with a Si / P molar ratio of 1 and no P2O5 impurity phase in the product.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the crystallization synthesis of a skeletal phosphorus-potassium zeolite, characterized in that: Silicon source, aluminum source, and KOH are added sequentially to phosphorus source solution, and the resulting slurry is synthesized into the framework phosphorus-potassium zeolite through a one-step hydrothermal crystallization reaction; The phosphorus source is an inorganic phosphorus compound; The molar ratio of phosphorus source to aluminum source, calculated as oxides, is P2O5 / Al2O3 = 0.8~2.5:1; The molar ratio of silicon source (SiO2): KOH (OH-): water: aluminum source (Al2O3) is 0.5~6:0.5~2:25~76:

1. The temperature of the hydrothermal crystallization reaction is 170~220℃, and the crystallization time is 20~72h.

2. The synthesis method according to claim 1, characterized in that: The phosphorus source is at least one of phosphoric acid, pyrophosphate, diammonium hydrogen phosphate, and diammonium dihydrogen phosphate.

3. The synthesis method according to claim 1, characterized in that: The molar ratio of silicon source (SiO2): KOH (OH-): water: aluminum source (Al2O3) is 1~5:1.0~2:28~76:

1.

4. The synthesis method according to any one of claims 1-3, characterized in that: The silicon source is at least one of water glass and silica sol; The aluminum source is at least one of aluminum sulfate, sodium aluminate, AlCl3, Al(NO3)3, and boehmite.

5. The synthesis method according to any one of claims 1-3, characterized in that: The stirring times for adding silicon source, aluminum source, and KOH to phosphorus source solution were 0.5~2h, 1~3h, and 6~20h, respectively.

6. The synthesis method according to any one of claims 1-3, characterized in that: The hydrothermal crystallization reaction is carried out under static, rotating, or stirring conditions.

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