CN112142063A - Preparation method of X molecular sieve - Google Patents
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Abstract
A preparation method of an X molecular sieve comprises (1) uniformly mixing an X molecular sieve crystallization mother liquor, inorganic base, an aluminum-containing compound and water, stirring at 90-150 ℃ for 0.1-20 hours, standing for 12-60 hours, removing solids in the mixture to obtain a recycled aluminum source, and (2) preparing the recycled aluminum source, the silicon source, the water and the inorganic base into a guiding agent, wherein the molar ratio of the materials is SiO2/Al2O3=2~25,M2O/SiO2=0.6~1.8,H2O/SiO2=10~50,K+/(K++Na+) 0-1, (3) preparing an X molecular sieve synthesis system from a silicon source, an inorganic base, a recycled aluminum source, an X molecular sieve crystallization mother liquor, water and a guiding agent, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3=2.0~3.0,M2O/SiO2=1.0~5.0,H2O/SiO2=25~100,K+/(K++Na+) And (3) obtaining the X molecular sieve by hydrothermal crystallization and drying, wherein the content of the X molecular sieve is 0-0.6. The method can synthesize the X molecular sieve by using the mother liquor, reduce the discharge of waste water and reduce the production cost.
Description
Technical Field
The invention relates to a preparation method of an X molecular sieve, in particular to a method for preparing the X molecular sieve by using molecular sieve crystallization mother liquor.
Background
The X molecular sieve has larger micropore diameter so that the X molecular sieve shows higher adsorption capacity, and the lower framework silica-alumina ratio endows the X molecular sieve with good adsorption and ion exchange performances, so the X molecular sieve is widely used in the fields of separation, catalysis, ion exchange and the like. At present, the X molecular sieve is produced by a liquid phase hydrothermal synthesis method in industry, however, the content of inorganic alkali and silicon in a large amount of molecular sieve mother liquor generated by the production method is high, and the environmental protection treatment difficulty is high.
CN106430228A discloses a method for processing molecular sieve crystallization mother liquor, which comprises the steps of sucking the molecular sieve crystallization mother liquor into a reduced pressure distillation still, introducing steam into a jacket of the distillation still to heat the distillation still, evaporating organic amine and water in the crystallization mother liquor, introducing the organic amine and the water into a condenser, introducing condensate into a solvent storage tank, arranging a stirring device in the distillation still to continuously turn evaporation materials, preventing the cavity wall from coking, and automatically discharging residues after the water content of residues in the distillation still reaches the standard. The method can completely recycle the organic amine and water in the crystallization mother liquor, and realizes no wastewater discharge.
CN105000642B discloses a method for treating silicon-containing wastewater generated in the preparation process of a molecular sieve, which comprises the steps of collecting and blending filtrate, mother liquor and washing liquor generated in the preparation process of the molecular sieve to form gel wastewater, adding 8-10% lime emulsion, stirring for a period of time, standing, wherein the content of soluble silicon in each liter of gel wastewater is 500-1000mg, recycling supernatant and discharging sludge at the bottom.
CN104556460B discloses a method for removing fluorine and phosphorus from PSRY molecular sieve production wastewater, which comprises the steps of mixing the PSRY molecular sieve production wastewater with solid waste residues generated in the treatment process of other molecular sieve production wastewater, and enabling aluminum in the solid waste residues to be Al3+Dissolving into wastewater, and adjusting pH of the mixed system to above 6 to obtain Al3+And F-、PO4 3-The reaction forms a precipitate, a coagulant aid (PAM) is added for reaction, and then solid-liquid separation is carried out, so that fluorine and phosphorus in the wastewater can be effectively removed.
Disclosure of Invention
The invention aims to provide a preparation method of an X molecular sieve, which can improve the utilization rate of mother liquor, reduce the wastewater discharge in the production process of the X molecular sieve and reduce the production cost.
The preparation method of the X molecular sieve provided by the invention comprises the following steps:
(1) uniformly mixing the X molecular sieve crystallization mother liquor, inorganic base, an aluminum-containing compound and water, stirring at 90-150 ℃ for 0.1-20 hours, standing for 12-60 hours, removing solids in the mixture to obtain a recycled aluminum source,
(2) uniformly mixing the recycled aluminum source, the silicon source, water and the inorganic base obtained in the step (1), standing and aging at 20-60 ℃ for 1-72 hours to prepare the guiding agent, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3=2~25, M2O/SiO2=0.6~1.8,H2O/SiO2=10~50,K+/(K++Na+)=0~1,
(3) Uniformly mixing a silicon source, an inorganic base, a recycled aluminum source obtained in the step (1), an X molecular sieve crystallization mother liquor, water and the guiding agent prepared in the step (2) to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3=2.0~3.0,M2O/SiO2=1.0~5.0,H2O/SiO2=25~100,K+/(K++Na+) 0 to 0.6 of Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (A) to (B) is 0.1-2.0 mass%, performing hydrothermal crystallization on the prepared X molecular sieve synthesis system at 90-150 ℃ for 1-72 hours, performing solid-liquid separation to obtain a solid and an X molecular sieve crystallization mother liquor, washing and drying the solid to obtain the X molecular sieve, wherein the inorganic base is sodium hydroxide or sodium hydroxide and potassium hydroxide, and M is Na or Na and K.
According to the invention, the crystallization mother liquor generated after crystallization in the X molecular sieve synthesis process is treated to obtain the recycled aluminum source, then the crystallization mother liquor is used as the X molecular sieve synthesis raw material, the silicon source, the recycled aluminum source and the inorganic base are added, and the X molecular sieve is synthesized under the action of the guiding agent, so that the cyclic utilization of the X molecular sieve crystallization mother liquor is realized, the production cost of the X molecular sieve is reduced, and the wastewater discharge in the X molecular sieve production process is reduced.
Drawings
FIG. 1 is an X-ray diffraction (XRD) spectrum of the molecular sieve prepared in accordance with example 1 of the present invention.
FIG. 2 is a Scanning Electron Microscope (SEM) image of the X molecular sieve prepared in example 1 of the present invention.
FIG. 3 is an XRD spectrum of the X molecular sieve prepared in example 2 of the present invention.
FIG. 4 is a scanning electron micrograph of an X molecular sieve prepared according to example 2 of the present invention.
Detailed Description
The X molecular sieve crystallization mother liquor is a liquid phase substance generated after hydrothermal crystallization and solid-liquid phase separation in the synthesis process, wherein the liquid phase substance contains Na, Si and Al, and optionally K, and the four elements are important chemical components of an X molecular sieve synthesis system. The method comprises the steps of adding inorganic alkali, water and an aluminum-containing compound into X molecular sieve crystallization mother liquor to enable the crystallization mother liquor to meet the caustic ratio and density requirements required by synthesis of the X molecular sieve, standing for separation to remove solids in the X molecular sieve, removing Si to obtain a recycled aluminum source which can be used for preparing a directing agent and an aluminum source of the X molecular sieve, and synthesizing a pure-phase X molecular sieve by utilizing the X molecular sieve crystallization mother liquor. The method can effectively utilize aluminum and alkali in the X molecular sieve crystallization mother liquor, reduce the synthesis cost of the X molecular sieve and discharge of alkali-containing wastewater, and ensure that the production of the X molecular sieve is more environment-friendly.
The method comprises the step (1) of preparing a recycled aluminum source by using an X molecular sieve crystallization mother liquor, namely supplementing an aluminum-containing compound into the crystallization mother liquor, adding an inorganic base to prepare low-alkalinity sodium metaaluminate, standing to precipitate a generated silicon-containing solid, and removing the solid to obtain the recycled aluminum source. The reaction temperature after the inorganic base and the aluminum-containing compound are added into the X molecular sieve crystallization mother liquor is preferably 95-120 ℃, the stirring time is preferably 0.3-10 hours, and the standing time is preferably 20-50 hours.
The method of the invention is characterized in that alkali metal ions M in the X molecular sieve crystallization mother liquor+The content of (A) is 5000-80000 mg/L, preferably 6000-60000 mg/L, the content of Si is 1000-10000 mg/L, preferably 1600-9000 mg/L, the content of Al is 20-200 mg/L, preferably 20-100 mg/L, and M is Na or Na and K. The density of the X molecular sieve crystallization mother liquor at 25 ℃ is preferably 1.0-1.2 g/mL.
(1) The aluminum-containing compound is at least one selected from the group consisting of metallic aluminum, aluminum oxide, aluminum hydroxide, pseudoboehmite, aluminum sulfate, aluminum chloride, aluminum nitrate and sodium aluminate.
(1) Is added step by step and containsThe aluminum compound and the inorganic base are present in amounts such that the resulting caustic ratio-M of the recycled aluminum source is obtained2O/Al2O3Al in a molar ratio of 1.5 to 2.8, preferably 1.8 to 2.62O3The content is 5.0 to 15.0 mass%, wherein the Si is substantially not contained, and the substantially not containing of Si means that the Si content is less than 30 ppm. The M is Na or Na and K, and when the M is Na and K, the M is2O is (Na)2O+K2O). (1) The density of the recycled aluminum source in the step (1) is preferably 1.3-1.7 g/mL at 25 ℃.
The step (2) of the method is to use the recycled aluminum source prepared in the step (1) to prepare the guiding agent, and the molar ratio of the materials in the guiding agent is preferably as follows: SiO 22/Al2O3=10~25,M2O/SiO2=0.6~1.2,H2O/SiO2=10~30, K+/(K++Na+)=0~1。
(2) Uniformly mixing the recycled aluminum source, the silicon source, water and the inorganic base, standing and aging at the temperature of 25-50 ℃ for 10-30 hours. When the inorganic alkali used in the step (1) is sodium hydroxide and potassium hydroxide, K in the guiding agent prepared in the step (2)+/(K++Na+) The molar ratio of (A) to (B) is preferably 0.01 to 0.6.
In the invention, the recycled aluminum source prepared in the step (1) and the crystallization mother liquor of the X molecular sieve are used for preparing the X molecular sieve in the step (3), and the molar ratio of the materials in the synthesis system of the X molecular sieve is preferably as follows: SiO 22/Al2O3=2.4~3.0, M2O/SiO2=1.0~3.0,H2O/SiO2=25~80,K+/(K++Na+) 0 to 0.6. Al contained in the introduced directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) is preferably 0.1 to 1.0 mass%.
When the inorganic alkali used in the step (1) is sodium hydroxide and potassium hydroxide, K in the X molecular sieve synthesis system prepared in the step (3)+/(K++Na+) The molar ratio of (A) is preferably 0.1 to 0.5, more preferably 0.1 to 0.3.
(3) In the step, the temperature of hydrothermal crystallization of an X molecular sieve synthesis system is preferably 90-120 ℃, the time is preferably 5-20 hours, solid-liquid separation is carried out after the hydrothermal crystallization, mother liquor is collected, and the obtained solid is washed and dried to obtain the X molecular sieve. The drying temperature is preferably 70-90 ℃, the drying time is preferably 2-20 hours, and the collected molecular sieve crystallization mother liquor is preferably used for preparing the recycled aluminum source in the step (1).
The inorganic base added in the steps (1) to (3) of the method is sodium hydroxide or sodium hydroxide and potassium hydroxide.
The silicon source in the method is selected from at least one of tetraethoxysilane, silica sol, water glass, sodium silicate, silica gel and white carbon black.
The grain diameter (average grain diameter) of the X molecular sieve prepared by the method is preferably 0.4-2.5 micrometers, more preferably 0.4-2.0 micrometers, and the cation is Na or Na and K.
The present invention is illustrated in detail below by way of examples, but the present invention is not limited thereto.
In the examples and comparative examples, the adsorption capacity of the molecular sieve was determined by a toluene gas phase adsorption experiment, and the specific operation method was: toluene-laden nitrogen (toluene partial pressure 0.5MPa) was contacted with a mass of molecular sieve at 35 ℃ until toluene reached adsorption equilibrium. And calculating the adsorption capacity of the molecular sieve to be detected according to the mass difference of the molecular sieve before and after toluene adsorption by the following formula.
Wherein C is adsorption capacity, and the unit is milligram/gram; m is1The mass of the molecular sieve to be detected before toluene adsorption is carried out, and the unit is gram; m is2The unit is the mass of the molecular sieve to be detected after toluene adsorption.
Example 1
(1) Preparation and reuse of aluminum source
Taking 170kg of X molecular sieve crystallization mother liquor, wherein the density at 25 ℃ is 1.086g/mL, and Na in the mother liquor+30440mg/L, Si, 4889mg/L, Al, 53mg/L, adding into a reaction kettle together with 50kg aluminum hydroxide, 48.70kg sodium hydroxide and 2.35kg deionized water, heating to 100 deg.CStirring for 1 hour, standing for 24 hours, removing bottom solids to obtain a clear recycled aluminum source with the density of 1.376g/mL at 25 ℃, and recycling Al in the aluminum source2O3The content was 12.77 mass%, Na2The O content was 17.56% by mass, and Si and Na were not substantially contained2O/Al2O3The molar ratio was 2.26.
(2) Preparation of directing agent
3.83kg of sodium hydroxide, 9.13kg of deionized water, 4.19kg of the recycled aluminum source prepared in the step (1) and 23.24kg of water glass (SiO in the water glass)2The content of Na was 20.17 mass%2O content of 6.32 mass%, the same applies hereinafter) is added into a reaction kettle and mixed evenly, and the molar ratio of the materials is SiO2/Al2O3=15, Na2O/SiO2=1.07,H2O/SiO2The mixture was then aged at 35 ℃ for 16 hours to obtain a directing agent.
(3) Synthesis of X molecular sieves
Adding 18kg of the X molecular sieve crystallization mother liquor, 46.09kg of deionized water, 31.97kg of the recycled aluminum source prepared in the step (1), 32.77kg of water glass and 0.46kg of the guiding agent prepared in the step (2) into a reaction kettle, and uniformly mixing to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.95, Na2O/SiO2=1.15,H2O/SiO252, Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, carrying out hydrothermal crystallization at 100 ℃ for 12 hours, carrying out solid-liquid separation by adopting a reduced pressure filtration method after crystallization is finished, collecting 107.07kg of mother liquor altogether, washing the obtained solid with deionized water until the pH of the filtrate is 8-9, drying at 80 ℃ for 12 hours to obtain an X molecular sieve A, wherein an XRD (XRD) spectrogram is shown in figure 1, a Scanning Electron Microscope (SEM) photograph is shown in figure 2, and the toluene adsorption capacity and SiO adsorption capacity are shown in figure 22/Al2O3The molar ratio, the grain size, the amount of mother liquor used and the ratio of the mother liquor used to the mother liquor produced are shown in Table 1.
Example 2
(1) Preparation and reuse of aluminum source
175kg of the X molecular sieve crystallization mother liquor described in example 1, 50kg of aluminum hydroxide, 38.79kg of sodium hydroxide and 0.79kg of deionized water are added into a reaction kettle, the mixture is heated to 100 ℃, stirred for 3 hours, then kept stand for 36 hours, and bottom solids are removed to obtain a clear recycled aluminum source, the density of the clear recycled aluminum source at 25 ℃ is 1.362g/mL, and Al in the recycled aluminum source2O3The content was 12.78 mass% and Na2The O content was 14.59 mass%, and Si and Na were substantially not contained2O/Al2O3The molar ratio was 1.88.
(2) Preparation of directing agent
Adding 3.99kg of sodium hydroxide, 8.97kg of deionized water, 4.19kg of the recycled aluminum source prepared in the step (1) and 23.24kg of water glass into a reaction kettle, and uniformly mixing, wherein the molar ratio of the materials is SiO2/Al2O3=15, Na2O/SiO2=1.07,H2O/SiO2Standing and aging at 35 ℃ for 16 hours to obtain the directing agent.
(3) Synthesis of X molecular sieves
Adding 42kg of the X molecular sieve crystallization mother liquor described in example 1, 22.79kg of deionized water, 32.52kg of the recycled aluminum source prepared in the step (1), 31.55kg of water glass and 0.47kg of the directing agent prepared in the step (2) into a reaction kettle, and uniformly mixing to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.90,Na2O/SiO2=1.15,H2O/Si2O52, Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, performing hydrothermal crystallization according to the method in the step (1) and (3) in the example, performing solid-liquid separation by adopting a reduced pressure filtration method after crystallization is completed, collecting 107.08kg of mother liquor, washing and drying the obtained solid to obtain the X molecular sieve B, wherein an XRD (X-ray diffraction) spectrogram is shown in figure 3, a Scanning Electron Microscope (SEM) picture is shown in figure 4, and the toluene adsorption capacity and SiO adsorption capacity of the X molecular sieve B are shown in figure 42/Al2O3Molar ratio, grain size, amount of mother liquor and use of mother liquor in producing mother liquorThe liquid ratios are shown in Table 1.
Example 3
(1) Preparation and reuse of aluminum source
349kg of X molecular sieve crystallization mother liquor is taken, the density at 25 ℃ is 1.126g/mL, wherein Na+60652mg/L, Si content, 8255mg/L, Al content and 66mg/L content, adding the aluminum hydroxide, 20.91kg sodium hydroxide and 0.11kg deionized water into a reaction kettle, heating to 100 ℃, stirring for 5 hours, standing for 40 hours, removing bottom solids to obtain a clear recycled aluminum source with the density of 1.342g/mL at 25 ℃, wherein Al in the recycled aluminum source2O3The content thereof was 7.18 mass%, and Na was added2An O content of 9.27 mass% and substantially no Si or Na2O/Al2O3The molar ratio was 2.12.
(2) Preparation of directing agent
Adding 3.89kg of sodium hydroxide, 5.77kg of deionized water, 7.49kg of the recycled aluminum source prepared in the step (1) and 23.24kg of water glass into a reaction kettle, and uniformly mixing, wherein the molar ratio of the materials is SiO2/Al2O3=15, Na2O/SiO2=1.07,H2O/Si2And O-21, and then standing and aging at 35 ℃ for 16 hours to obtain the directing agent.
(3) Synthesis of X molecular sieves
Adding 14kg of the X molecular sieve crystallization mother liquor, 25.20kg of deionized water, 59.23kg of the recycled aluminum source prepared in the step (1), 30.04kg of water glass and 0.48kg of the guiding agent prepared in the step (2) into a reaction kettle, and uniformly mixing to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.85,Na2O/SiO2=1.15,H2O/Si2O52, Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, performing hydrothermal crystallization according to the method in the step (3) in the example 1, performing solid-liquid separation by adopting a reduced pressure filtration method after crystallization is completed, collecting 106.76kg of mother liquor, washing and drying the obtained solid to obtain the X molecular sieve C, absorbing toluene by the X molecular sieve CAttached volume, SiO2/Al2O3The molar ratio, the grain size, the amount of mother liquor used and the ratio of the mother liquor used to the mother liquor produced are shown in Table 1.
Example 4
(1) Preparation and reuse of aluminum source
434kg of the X molecular sieve crystallization mother liquor described in example 3, 50kg of aluminum hydroxide, 9.56kg of sodium hydroxide and 0.56kg of deionized water are added into a reaction kettle, the mixture is heated to 100 ℃, stirred for 7 hours, then kept stand for 42 hours, and the bottom solid is removed to obtain a clear recycled aluminum source, the density of the clear recycled aluminum source at 25 ℃ is 1.335g/mL, and Al in the recycled aluminum source2O3The content of Na was 6.60 mass%2The O content was 8.00 mass%, and Si and Na were not substantially contained2O/Al2O3The molar ratio was 1.99.
(2) Preparation of directing agent
Adding 3.94kg of sodium hydroxide, 5.04kg of deionized water, 8.16kg of the recycled aluminum source prepared in the step (1) and 23.24kg of water glass into a reaction kettle, and uniformly mixing, wherein the molar ratio of the materials is SiO2/Al2O3=15, Na2O/SiO2=1.07,H2O/Si2And (3) standing and aging at 35 ℃ for 16 hours to obtain the guiding agent.
(3) Synthesis of X molecular sieves
Adding 18kg of the X molecular sieve crystallization mother liquor described in example 3, 15.86kg of deionized water, 65.66kg of the recycled aluminum source prepared in the step (1), 28.78kg of water glass and 0.49kg of the directing agent prepared in the step (2) into a reaction kettle, and uniformly mixing to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.80,Na2O/SiO2=1.15,H2O/Si2O52, Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, performing hydrothermal crystallization according to the method in the step (3) in the example 1, performing solid-liquid separation by adopting a reduced pressure filtration method after crystallization is completed, collecting 106.63kg of mother liquor, and washing and drying the obtained solid to obtain the molecular sieveTo X molecular sieve D, its toluene adsorption capacity, SiO2/Al2O3The molar ratio, the grain size, the amount of mother liquor used and the ratio of the mother liquor used to the mother liquor produced are shown in Table 1.
Example 5
(1) Preparation and reuse of aluminum source
170kg of X molecular sieve crystallization mother liquor is taken, the density at 25 ℃ is 1.075g/mL, wherein Na+The content is 29310mg/L, K+10350mg/L, Si content and 4862mg/L, Al content and 31mg/L content are added into a reaction kettle together with 50kg of aluminum hydroxide, 34.71kg of sodium hydroxide, 12.53kg of potassium hydroxide and 3.81kg of deionized water, the mixture is heated to 100 ℃, stirred for 10 hours, then kept stand for 48 hours, bottom solids are removed, and a clear recycled aluminum source is obtained, the density of the recycled aluminum source at 25 ℃ is 1.380g/mL, and Al in the recycled aluminum source2O3The content was 11.94 mass% and Na2O content 12.40 mass%, K2An O content of 4.70 mass%, and substantially no Si (Na)2O+K2O)/Al2O3The molar ratio was 2.12.
(2) Preparation of directing agent
Taking 8.16kg of the recycled aluminum source prepared in the step (1), preparing the guiding agent according to the method in the step (2) of the example 4, wherein the molar ratio of all materials in the guiding agent is SiO2/Al2O3=15,Na2O/SiO2=1.07,H2O/Si2O=21, K2O/SiO2=0.06。
(3) Synthesis of X molecular sieves
Adding 67kg of the X molecular sieve crystallization mother liquor, 12.52kg of deionized water, 26.48kg of the recycled aluminum source prepared in the step (1), 20.99kg of water glass and 0.36kg of the guiding agent prepared in the step (2) into a reaction kettle, and uniformly mixing to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.75, (Na2O+K2O)/SiO2=1.63,H2O/Si2O72, K/(K + Na) 0.16, Al contained in the directing agent added2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, performing hydrothermal crystallization according to the method in the step (3) in the example 1, performing solid-liquid separation by adopting a reduced pressure filtration method after crystallization is completed, collecting 107.79kg of mother liquor, washing and drying the obtained solid to obtain the X molecular sieve E with toluene adsorption capacity and SiO adsorption capacity2/Al2O3The molar ratio, the grain size, the amount of mother liquor used and the ratio of the mother liquor used to the mother liquor produced are shown in Table 1.
Comparative example 1
(1) Preparation of an aluminium source
Adding 200kg of aluminum hydroxide, 232.15kg of sodium hydroxide and 652.33kg of deionized water into a reaction kettle, heating to 100 ℃, stirring for 6 hours, taking the formed clear and transparent low-alkalinity sodium metaaluminate solution as an aluminum source, wherein the density at 25 ℃ is 1.366g/mL, and Al is contained in the solution2O3The content was 11.87 mass%, Na2O content 16.59 mass% and Na2O/Al2O3The molar ratio was 2.3.
(2) Preparation of directing agent
3.81kg of sodium hydroxide, 8.86kg of deionized water, 4.48kg of the aluminum source prepared in the step (1) and 23.24kg of water glass are added into a reaction kettle and uniformly mixed, and the molar ratio of the materials is SiO2/Al2O3=15, Na2O/SiO2=1.07,H2O/Si2And (3) standing and aging at 35 ℃ for 16 hours to obtain the guiding agent.
(3) Synthesis of X molecular sieves
73.37kg of deionized water, 25.11kg of aluminum source, 25.05kg of water glass and 0.36kg of guiding agent prepared in the step (2) are added into a reaction kettle and uniformly mixed to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3=2.90,Na2O/SiO2=1.10,H2O/Si2O72, Al contained in the introduced directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (B) was 0.15% by mass.
Transferring the molecular sieve synthesis system into a closed reaction kettle, performing hydrothermal crystallization according to the method of the step 1 and the step 3, and performing reduced pressure after crystallizationPerforming solid-liquid separation by filtering method, collecting mother liquor 104.86kg, washing the obtained solid, and drying to obtain X molecular sieve F with toluene adsorption capacity and SiO2/Al2O3The molar ratio and the grain size are shown in Table 1.
TABLE 1
The amount of mother liquor used directly and the amount of mother liquor converted from the recycled aluminum source are included.
Claims (12)
1. A preparation method of an X molecular sieve comprises the following steps:
(1) uniformly mixing the X molecular sieve crystallization mother liquor, inorganic base, an aluminum-containing compound and water, stirring at 90-150 ℃ for 0.1-20 hours, standing for 12-60 hours, removing solids in the mixture to obtain a recycled aluminum source,
(2) uniformly mixing the recycled aluminum source, the silicon source, water and the inorganic base obtained in the step (1), standing and aging at 20-60 ℃ for 1-72 hours to prepare the guiding agent, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3=2~25,M2O/SiO2=0.6~1.8,H2O/SiO2=10~50,K+/(K++Na+)=0~1,
(3) Uniformly mixing a silicon source, an inorganic base, a recycled aluminum source obtained in the step (1), an X molecular sieve crystallization mother liquor, water and the guiding agent prepared in the step (2) to obtain an X molecular sieve synthesis system, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3=2.0~3.0,M2O/SiO2=1.0~5.0,H2O/SiO2=25~100,K+/(K++Na+) 0 to 0.6 of Al contained in the added directing agent2O3With total Al contained in the molecular sieve synthesis system2O3The ratio of (A) to (B) is 0.1-2.0 mass%, subjecting the obtained X molecular sieve synthesis system to hydrothermal crystallization at 90-150 ℃ for 1-72 hours, performing solid-liquid separation to obtain a solid and an X molecular sieve crystallization mother liquor, and subjecting the solid to solid-liquid separationWashing and drying to obtain the X molecular sieve,
the inorganic alkali is sodium hydroxide or sodium hydroxide and potassium hydroxide, and M is Na or Na and K.
2. The method according to claim 1, wherein the crystallization mother liquor obtained after the solid-liquid separation in step (3) is used for preparing the recycled aluminum source in step (1).
3. The method according to claim 1, wherein when the inorganic base used in the step (1) is sodium hydroxide or potassium hydroxide, K is contained in the directing agent obtained in the step (2)+/(K++Na+) The molar ratio of (A) to (B) is 0.01 to 0.6.
4. The method of claim 1, wherein when the inorganic bases used in step (1) are sodium hydroxide and potassium hydroxide, step (3) produces K in the synthesis system of molecular sieve X+/(K++Na+) The molar ratio of (A) to (B) is 0.1 to 0.5.
5. The method of claim 1, wherein the mother liquor for crystallizing the X molecular sieve contains alkali metal ions M+The content of (A) is 5000-80000 mg/L, the content of Si is 1000-10000 mg/L, the content of Al is 20-200 mg/L, and M is Na or Na and K.
6. The method according to claim 1, wherein the density of the X molecular sieve crystallization mother liquor at 25 ℃ is 1.0-1.2 g/mL.
7. The process of claim 1 wherein the amount of aluminum-containing compound and inorganic base added in step (1) is such that M is obtained as a recycled aluminum source2O/Al2O31.5 to 2.8 mol ratio of Al2O3The content is 5.0-15.0 mass%, and M is Na or Na and K.
8. The method of claim 1, wherein the recycled aluminum source in step (1) has a density of 1.3 to 1.7g/mL at 25 ℃.
9. The process according to claim 1, wherein the aluminum-containing compound in the step (1) is at least one selected from the group consisting of metallic aluminum, alumina, aluminum hydroxide, pseudoboehmite, aluminum sulfate, aluminum chloride, aluminum nitrate and sodium aluminate.
10. The method of claim 1, wherein the silicon source is at least one selected from the group consisting of ethyl orthosilicate, silica sol, water glass, sodium silicate, silica gel, and silica white.
11. The method according to claim 1, wherein the time for the standing aging in the step (2) is 20 to 50 hours.
12. The method according to claim 1, wherein the grain size of the X molecular sieve obtained in step (3) is 0.4 to 2.5 μm.
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CN114988427A (en) * | 2022-04-19 | 2022-09-02 | 江苏国瓷新材料科技股份有限公司 | Preparation method and application of small-grain low-silicon X-type molecular sieve |
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