CN114426286A - Mesoporous nano Y molecular sieve and preparation method thereof - Google Patents
Mesoporous nano Y molecular sieve and preparation method thereof Download PDFInfo
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Abstract
A mesoporous nanometer Y molecular sieve is provided, the grain diameter of the Y molecular sieve is 20-450 nanometers, the Y molecular sieve contains two mesoporous channels, and the most probable pore diameters are 5-20 nanometers and 25-50 nanometers respectively. The Y molecular sieve is used for adsorbing and separating m-xylene from mixed carbon octa-arene and has good adsorption selectivity, mass transfer performance and higher adsorption capacity.
Description
Technical Field
The invention relates to a silicon-aluminum molecular sieve and a preparation method thereof, in particular to a nano Y molecular sieve and a preparation method thereof.
Background
Molecular sieves are crystalline materials with special framework structures, and are widely used in the fields of separation, catalysis and the like due to uniform microporous pore passages, adjustable acidity and good ion exchange performance. At present, a Y molecular sieve is mostly used as an active component of a meta-xylene adsorption separation adsorbent in industry, and the crystallinity, the silica/alumina molar ratio, the framework structure chemical composition, the grain size, the internal pore structure and the like of the Y molecular sieve can obviously influence the adsorption capacity, the adsorption selectivity and the mass transfer performance of the adsorbent.
US4306107 discloses a process for separating meta-xylene and ethylbenzene from mixed carbon octa-aromatics. The method adopts NaY zeolite as an active component of an adsorbent, toluene as a desorbent, and utilizes the characteristics of the NaY zeolite that the adsorption capacity to m-xylene is strongest, p-xylene and o-xylene are medium, and ethylbenzene is weakest to introduce mixed carbon-eight aromatic hydrocarbon into a simulated moving bed for countercurrent operation, so that m-xylene, p-xylene, o-xylene and ethylbenzene are respectively obtained at different positions of the simulated moving bed.
US4326092 discloses a method for separating meta-xylene from mixed carbon-eight aromatics, wherein a NaY zeolite with a molar ratio of silica to alumina of 4.5-5.0 is used to prepare an adsorbent, so that higher meta-xylene selectivity can be obtained.
CN1939883A discloses a method for separating m-xylene from a carbon eight aromatic hydrocarbon isomer, which comprises the step of preparing an adsorbent by using NaY zeolite with the molar ratio of silicon oxide to aluminum oxide being 5-6, wherein the water content of the zeolite is 0-8% by mass, the adsorption temperature is 25-250 ℃, and the adsorbent is selected from tetralin and alkylated derivatives thereof.
CN1050595C reports an adsorbent using Y zeolite with cation sites occupied by sodium and lithium ions as active components, and is used for liquid phase adsorption separation of meta-xylene from mixed carbon eight aromatic hydrocarbons, and higher meta-xylene selectivity is obtained. Wherein, lithium ions occupy 5 to 35 percent of exchangeable sites of the zeolite, and the water content of the adsorbent is 1.5 to 3.0 percent by mass calculated by the ignition loss at 500 ℃.
Disclosure of Invention
The invention aims to provide a mesoporous nano Y molecular sieve and a preparation method thereof, wherein the Y molecular sieve is used for adsorbing and separating m-xylene from mixed carbon-eight aromatic hydrocarbons, and has good adsorption selectivity, mass transfer performance and higher adsorption capacity.
The invention provides a mesoporous nanometer Y molecular sieve, wherein the grain diameter of a Y molecular sieve is 20-450 nanometers, the Y molecular sieve contains two mesoporous pore canals, and the most probable pore diameter is respectively 5-20 nanometers and 25-50 nanometers.
The mesoporous nano Y molecular sieve is a self-assembly formed by self-aggregation of nano Y molecular sieve grains, comprises two mesoporous channels, is used for adsorbing and separating m-xylene in mixed carbon-eight aromatic hydrocarbons, and can remarkably improve the adsorption selectivity of the m-xylene, and the adsorption capacity and mass transfer rate of materials in the Y molecular sieve.
Drawings
Fig. 1 is an X-ray diffraction (XRD) spectrum of the mesoporous nano Y molecular sieve prepared in example 1 of the present invention.
Fig. 2 is a Scanning Electron Microscope (SEM) photograph of the mesoporous nano Y molecular sieve prepared in example 1 of the present invention.
Fig. 3 is a pore size distribution curve of the mesoporous nano Y molecular sieve prepared in example 1 of the present invention.
Fig. 4 is a pore size distribution curve of the mesoporous nano Y molecular sieve prepared in example 2 of the present invention.
FIG. 5 is a pore size distribution curve of the mesoporous nano Y molecular sieve prepared in example 3 of the present invention.
FIG. 6 is a pore size distribution curve of the mesoporous nano Y molecular sieve prepared in example 4 of the present invention.
FIG. 7 is a pore size distribution curve of the mesoporous nano Y molecular sieve prepared in example 5 of the present invention.
Fig. 8 is an XRD spectrum of the Y molecular sieve prepared in comparative example 1.
Fig. 9 is an SEM photograph of the Y molecular sieve prepared in comparative example 1.
Figure 10 is a plot of the pore size distribution of the Y molecular sieve prepared in comparative example 1.
Detailed Description
The mesoporous nano Y molecular sieve provided by the invention is a self-assembly formed by self-assembly of nano Y molecular sieve grains, the particle size of the self-assembly is relatively large, the nano Y molecular sieve is favorable for improving mass transfer performance, and the large particle size of the self-assembly can better solve the problem of difficult solid-liquid separation caused by the generation of the nano molecular sieve grains during the synthesis of the molecular sieve. In addition, the self-assembly of the nano Y molecular sieve comprises two mesoporous channels, so that the self-assembly of the nano Y molecular sieve further endows the self-assembly of the nano Y molecular sieve with good mass transfer performance, and the improvement of the mass transfer performance can improve the adsorption selectivity of the mesoporous nano Y molecular sieve to m-xylene.
The mesoporous nano Y molecular sieve is a nano-grade Y molecular sieve crystal particle self-assembly substance, the particle size of the self-assembly substance is preferably 0.5-1.5 micrometers, and the particle size of the nano-grade Y molecular sieve crystal particles in the self-assembly substance is 20-400 nanometers, preferably 50-300 nanometers, and more preferably 80-250 nanometers.
SiO of the mesoporous nano Y molecular sieve2/Al2O3The molar ratio is preferably 4.0 to 5.5.
The specific surface area of the mesoporous nano Y molecular sieve is 740-1000 m2(ii)/g, preferably 750 to 900m2(ii) a total pore volume of 0.40 to 0.65cm3A/g, preferably 0.40 to 0.55cm3Per gram, the mesoporous pore volume is 0.08-0.35 cm3A/g, preferably 0.10 to 0.25cm3/g。
The most probable pore diameters of the mesoporous nano Y molecular sieve are preferably 10-20 nanometers and 30-50 nanometers respectively.
The preparation method of the mesoporous nano Y molecular sieve comprises the following steps:
(1) taking a silicon source and an aluminum source at 0-5 ℃, adding sodium hydroxide and water, and uniformly mixing to form a molecular sieve synthesis system, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3＝5.5～9.5、Na2O/SiO2＝0.1～0.3、H2O/SiO2The temperature of the synthesis system is 5-25 ℃, the temperature of the synthesis system is 1-8 ℃,
(2) statically aging the molecular sieve synthesis system obtained in the step (1) at 20-40 ℃ for 10-48 hours, then statically crystallizing at 90-150 ℃ for 2-10 hours, stirring for 2-10 minutes, continuously statically crystallizing for 11-20 hours, and washing and drying the obtained solid.
The method (1) comprises the steps of preparing a molecular sieve synthesis system at a low temperature, taking a silicon source and an aluminum source which are at 0-5 ℃ and preferably at 0-4 ℃, and adding sodium hydroxide and water to prepare the molecular sieve synthesis system, wherein the molar ratio of the materials in the molecular sieve synthesis system is preferably as follows: SiO 22/Al2O3＝7～9、Na2O/SiO2＝0.1～0.25、H2O/SiO28-20. The temperature of the synthesis system is preferably 1-5 ℃.
The method (2) comprises the step of crystallizing a molecular sieve synthesis system to prepare the molecular sieve, preferably, statically aging the molecular sieve synthesis system at 20-40 ℃ for 15-30 hours, then statically crystallizing at 90-120 ℃ for 4-9 hours, stirring for 2-10 minutes, and continuously statically crystallizing for 11-15 hours. And washing and drying the solid obtained after crystallization to obtain the mesoporous nano Y molecular sieve. The drying temperature is preferably 70-100 ℃, more preferably 75-90 ℃, and the drying time is preferably 2-20 hours, more preferably 8-16 hours.
The aluminum source in the method is selected from one or more of low-alkalinity sodium metaaluminate solution, alumina, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum nitrate and sodium aluminate, and the low-alkalinity sodium metaaluminate solution and/or aluminum sulfate are preferred. Al in the low-alkalinity sodium metaaluminate solution2O3The content is preferably 17 to 28 mass%, and Na is contained2The O content is preferably 19 to 30 mass%.
The silicon source is preferably silica sol or water glass. SiO in the water glass2The content is preferably 25 to 38 mass%, and Na is2The preferable O content is 9 to 15 mass%.
The Y molecular sieve is suitable for adsorbing and separating meta-xylene from mixed carbon octa-arene. The desorbent used for adsorptive separation is preferably toluene.
The adsorption selectivity and the adsorption and desorption rates of the components of the adsorption purpose are important indexes for evaluating the performance of the adsorbent. The selectivity is the ratio of the concentrations of the two components in the adsorption phase to the concentrations of the two components in the non-adsorption phase at adsorption equilibrium. The adsorption equilibrium refers to the state when no component net transfer occurs between the adsorption phase and the non-adsorption phase after the mixed carbon-eight aromatic hydrocarbon contacts with the adsorbent. The adsorption selectivity is calculated as follows:
wherein C and D represent the number to be dividedTwo separate components, ACAnd ADRespectively represents the concentrations of C, D two components in the adsorption phase at the adsorption equilibrium, UCAnd UDRespectively, the concentrations of C, D in the non-adsorbed phase at adsorption equilibrium. When the selectivity beta of the two components is approximately equal to 1.0, the adsorption capacity of the adsorbent to the two components is equivalent, and the components which are preferentially adsorbed are not present. When β is greater or less than 1.0, it indicates that one component is preferentially adsorbed. Specifically, when beta is>At 1.0, the adsorbent preferentially adsorbs the C component; when beta is<At 1.0, the adsorbent preferentially adsorbs the D component. In terms of ease of separation, adsorption separation is easier to perform as β value is larger. The absorption and desorption speed is high, the dosage of the absorbent and the desorbent is reduced, the product yield is improved, and the operation cost of the absorption and separation device is reduced.
The invention uses a dynamic pulse experimental device to measure the adsorption selectivity and the adsorption and desorption rates of the m-xylene. The device comprises a feeding system, an adsorption column, a heating furnace, a pressure control valve and the like. The adsorption column is a stainless steel tube with phi 6 multiplied by 1800 mm, and the loading of the adsorbent is 50 ml. The inlet at the lower end of the adsorption column is connected with a feeding and nitrogen system, and the outlet at the upper end is connected with a pressure control valve and then connected with an effluent collector. The desorbent composition used for the experiment was 30 vol% toluene (T) and 70 vol% n-heptane (NC)7) The pulse liquid composition was 5 vol% each of Ethylbenzene (EB), Paraxylene (PX), Metaxylene (MX), Orthoxylene (OX), and n-Nonane (NC)9) And 75% by volume of the desorbent described above.
The method for measuring the adsorption selectivity comprises the following steps: and filling the weighed adsorbent into an adsorption column, vibrating, filling, and dehydrating and activating at 160-280 ℃ in nitrogen flow. Then introducing a desorbent to remove gas in the system, increasing the pressure to 0.8MPa and the temperature to 145 ℃, stopping introducing the desorbent, and stopping introducing the desorbent when the pressure is 1.0 hour－1The pulse feeding liquid of 8 ml is introduced at the volume space velocity, then the introduction of the pulse liquid is stopped, the desorption agent is introduced at the same space velocity for desorption, 3 drops of desorption liquid samples are taken every 2 minutes, and the composition is analyzed by gas chromatography. Taking the feed volume of the desorbent for desorption as the abscissa, NC9And the concentrations of EB, PX, MX and OX are plotted as ordinateAnd (4) preparing a desorption curve of each component. NC as tracer9Not adsorbed, the first peak, which gives the dead volume of the adsorption system. Using the midpoint of the half-peak width of the tracer as zero point, and determining the feed volume of the desorbent from the midpoint of the half-peak width of each component of EB, PX, MX and OX to the zero point, i.e. net retention volume VR. The ratio of the net retention volumes of the two components is the adsorption selectivity beta. For example, the ratio of the net retention volume of MX to the net retention volume of EB is the adsorption selectivity of MX to EB, and is recorded as betaMX/EB。
In order to realize the cyclic continuous use of the adsorbent, the selectivity between the extraction component and the desorbent is also an important performance index, and can be determined by further analyzing the desorption curve of the extraction component in a pulse test. The volume of desorbent required to raise the MX concentration in the effluent from 10% to 90% at the leading edge of the pulsed desorption profile for MX is defined as the adsorption rate SA]10-90The volume of desorbent required to decrease the MX concentration from 90% to 10% after the desorption curve is defined as the desorption rate [ S ]D]90-10. Ratio of the two [ S ]D]90-10/[SA]10-90I.e. can be characterized as the adsorption selectivity beta between MX and desorbent (T)MX/T. If beta isMX/TA value of less than 1.0 means that the adsorbent has too high an adsorption capacity for the desorbent, which is disadvantageous for the adsorption process, if beta isMX/TA value of more than 1.0 means that the adsorption capacity for the desorbent is too weak, which makes the desorption process difficult, and the ideal condition is βMX/TApproximately equal to 1.0.
The present invention is illustrated in detail below by way of examples, but the present invention is not limited thereto.
In the examples and the comparative examples, the adsorption capacity of the molecular sieve is determined by adopting a toluene gas phase adsorption experiment, and the specific operation method comprises the following steps: 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.
The specific surface area, total pore volume, micropore volume and mesopore pore volume of the molecular sieve were measured according to astm d4365-95 (2008).
Example 1
(1) Preparation of an aluminium source
200kg of aluminum hydroxide, 181.52kg of sodium hydroxide and 214.84kg of deionized water are added into a reaction kettle, heated to 100 ℃, and stirred for 6 hours to form a clear and transparent low-alkalinity sodium metaaluminate solution serving as an aluminum source 1. Al in the aluminum source 12O3The content was 21.58 mass% and Na2The O content was 23.59 mass%, and Na2O and Al2O3Is 1.80. 87.89kg of aluminum sulfate octadecahydrate was dissolved in 112.11kg of water, and stirred for 1 hour to obtain a clear and transparent aluminum sulfate solution as an aluminum source 2. Al in the aluminum source 22O3The content was 6.73% by mass.
(2) Pretreatment of raw materials
Respectively mixing water glass (SiO)2The content was 37.17 mass% and Na2The O content is 11.65 mass percent) and the aluminum source prepared in the step (1) is cooled to 0 ℃.
(3) Preparation of Y molecular sieves
Under the condition of stirring, 89.68kg of 0 ℃ water glass subjected to cooling treatment in the step (2), 49.79kg of 0 ℃ aluminum sulfate solution, 18.14kg of 0 ℃ low-alkalinity sodium metaaluminate solution and 5.61kg of deionized water are added into a reaction kettle to obtain a Y molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3＝7.8，Na2O/SiO2＝0.25，H2O/SiO 210. The temperature of the synthesis system was 3 ℃.
Transferring the molecular sieve synthesis system into a closed reaction kettle, statically aging at 30 ℃ for 24 hours, then heating to 100 ℃ for static crystallization for 8 hours, and stirring for 5 minutesContinuously statically crystallizing for 12 hours, filtering, washing the obtained solid with deionized water until the pH of the filtrate is 8-9, and drying at 80 ℃ for 12 hours to obtain the nano Y molecular sieve a, SiO of which2/Al2O3The molar ratio was 4.6 (by X-ray fluorescence spectroscopy, the same applies below), the XRD spectrum is shown in FIG. 1, the SEM photograph is shown in FIG. 2, and the pore size distribution curve is shown in FIG. 3. As can be seen from FIG. 2, the nano-scale Y molecular sieve grains are self-polymerized to form a self-assembly substance, the particle size of the self-assembly substance is 0.6 micron, and the particle size of the nano-scale Y molecular sieve grains is 60-150 nanometers. Fig. 3 shows that the most probable pore diameters of the nano Y molecular sieve a are 10 nm and 37 nm, respectively, and the specific surface area, total pore volume, micropore volume, mesopore pore volume, and toluene adsorption capacity are shown in table 1.
(4) Evaluation of adsorption Properties
Tabletting, forming, crushing and screening the nano Y molecular sieve a to obtain particles with the particle size of 300-850 mu m, and evaluating the xylene adsorption selectivity by using a pulse test by using the particles as an adsorbent, wherein the results are shown in Table 2.
Example 2
A Y molecular sieve was prepared as in example 1 except that in the step (3), 89.68kg of 0 ℃ water glass, 53.29kg of 0 ℃ aluminum sulfate solution, 17.04kg of 0 ℃ low alkalinity sodium metaaluminate solution and 3.50kg of deionized water which had been subjected to the temperature reduction treatment in the step (2) were added to a reaction vessel under stirring to obtain a Y molecular sieve synthesis system in which the molar ratio of the materials was SiO2/Al2O3＝7.8，Na2O/SiO2＝0.23，H2O/SiO 210. The temperature of the synthesis system was 4 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static ageing and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain the nano Y molecular sieve b, SiO2/Al2O3The molar ratio is 4.8, the particle size of a self-assembly substance formed by nano-scale Y molecular sieve crystal grains is 0.8 micron, the particle size of the nano-scale Y molecular sieve crystal grains is 80-180 nanometers, the pore size distribution curve is shown in figure 4, the most probable pore diameters are respectively 12 nanometers and 40 nanometers, the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity are shown in table 1, and the adopted pulse isThe m-xylene adsorption selectivity measured by the impact test is shown in Table 2.
Example 3
A Y molecular sieve was prepared as in example 1 except that in the step (3), 89.68kg of 0 ℃ water glass, 58.56kg of 0 ℃ aluminum sulfate solution, 15.04kg of 0 ℃ low alkalinity sodium metaaluminate solution and 0.32kg of deionized water which had been subjected to the temperature reduction treatment in the step (2) were added to a reaction kettle under stirring to obtain a Y molecular sieve synthesis system in which the molar ratio of the materials was SiO2/Al2O3＝7.8、Na2O/SiO2＝0.20、H2O/SiO 210. The temperature of the synthesis system was 5 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static ageing and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain the nano Y molecular sieve c, SiO2/Al2O3The molar ratio is 4.9, the particle size of a self-assembly substance formed by nano-scale Y molecular sieve grains is 1.0 micron, the particle size of the nano-scale Y molecular sieve grains is 90-200 nanometers, the pore size distribution curve is shown in figure 5, the most probable pore diameters are respectively 15 nanometers and 42 nanometers, the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity are shown in table 1, and the m-xylene adsorption selectivity measured by adopting a pulse test is shown in table 2.
Example 4
A Y molecular sieve was prepared as in example 1 except that in the step (3), 59.79kg of 0 ℃ water glass, 39.05kg of 0 ℃ aluminum sulfate solution, 10.27kg of 0 ℃ low alkalinity sodium metaaluminate solution and 33.54kg of deionized water which had been subjected to the temperature reduction treatment in the step (2) were added to a reaction vessel under stirring to obtain a Y molecular sieve synthesis system in which the molar ratio of the materials was SiO2/Al2O3＝7.8、Na2O/SiO2＝0.20、H2O/SiO215. The temperature of the synthesis system was 4 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static ageing and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain the nano Y molecular sieve d, SiO2/Al2O3The molar ratio is 4.9, composed ofThe particle size of a self-assembly substance formed by the meter-level Y molecular sieve crystal grains is 1.1 micron, the particle size of the crystal grains of the nano-level Y molecular sieve is 90-220 nanometers, the pore diameter distribution curve is shown in figure 6, the most probable pore diameters are respectively 17 nanometers and 43 nanometers, the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity are shown in table 1, and the m-xylene adsorption selectivity measured by adopting a pulse test is shown in table 2.
Example 5
A Y molecular sieve was prepared as in example 1 except that in the step (3), 44.84kg of 0 ℃ water glass, 29.29kg of 0 ℃ aluminum sulfate solution, 7.7kg of 0 ℃ low alkalinity sodium metaaluminate solution and 50.16kg of deionized water were added to the reaction kettle under stirring in the cooling treatment of the step (2) to obtain a Y molecular sieve synthesis system in which the molar ratio of the materials was SiO2/Al2O3＝7.8、Na2O/SiO2＝0.20、H2O/SiO 220. The temperature of the synthesis system was 5 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static ageing and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain the nano Y molecular sieve e, SiO thereof2/Al2O3The molar ratio is 5.0, the particle size of a self-assembly substance formed by nano-scale Y molecular sieve grains is 1.2 microns, the particle size of the nano-scale Y molecular sieve grains is 100-240 nanometers, the pore size distribution curve is shown in figure 7, the most probable pore diameters are respectively 19 nanometers and 46 nanometers, the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity are shown in table 1, and the m-xylene adsorption selectivity measured by adopting a pulse test is shown in table 2.
Comparative example 1
(1) Preparation of an aluminium source
200kg of aluminum hydroxide, 232.15kg of sodium hydroxide and 652.33kg of deionized water are added into a reaction kettle, heated to 100 ℃, and stirred for 6 hours to form clear and transparent low-alkalinity sodium metaaluminate solution serving as an aluminum source. Al in the aluminum source2O3The content was 11.87 mass%, Na2O content 16.59 mass% and Na2O and Al2O3Is 2.3.
(2) Preparation of directing agent
Under stirring, 3.81kg of sodium hydroxide, 8.86kg of deionized water, 4.48kg of the aluminum source prepared in step (1) and 23.24kg of water glass (SiO in water glass)2The content of Na was 20.17 mass%2O content of 6.32 mass%) is added into a reaction kettle, and the molar ratio of the materials is SiO2/Al2O3＝15、Na2O/SiO2＝1.07、H2O/SiO2Standing at 35 ℃ for 16 hours to obtain the directing agent, wherein the temperature is 21 ℃.
(3) Preparation of Y molecular sieves
Under the condition of stirring, 50.74kg of water glass, 42.51kg of deionized water, 7.56kg of the directing agent prepared in the step (2), 8.66kg of the aluminum sulfate solution prepared in the step (1) in the example 1 and 11.01kg of the low-alkalinity sodium metaaluminate solution prepared in the step (1) are added into a reaction kettle to obtain a Y molecular sieve synthesis system, wherein the molar ratio of the materials is SiO2/Al2O3＝9.5，Na2O/SiO2＝0.43，H2O/SiO 230% of Al contained in the directing agent2O3Al contained in the synthesis system with Y molecular sieve2O3The molar ratio of (A) to (B) was 5%, and the temperature of the synthesis system was 35 ℃.
Transferring the molecular sieve synthesis system into a closed reaction kettle, heating to 100 ℃, carrying out hydrothermal crystallization for 28 hours, filtering, washing the obtained solid with deionized water until the pH of the filtrate is 8-9, and drying at 80 ℃ for 12 hours to obtain the Y molecular sieve f, wherein SiO is the molecular sieve2/Al2O3The molar ratio is 4.8, an XRD spectrogram is shown in figure 8, an SEM photograph is shown in figure 9, the grain diameter of the Y molecular sieve is 0.9 micrometer, a pore size distribution curve is shown in figure 10, no obvious mesopores are shown, and the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity are shown in table 1.
A pulse test was carried out on the Y molecular sieve f by the method described in the step (4) in example 1 to evaluate the m-xylene adsorption selectivity, and the results are shown in Table 2.
Comparative example 2
Preparing Y molecular sieve by conventional method without using directing agent
5.0kg of sodium aluminate (containing 30 mass% of Na) was added2O, 44.1 mass% Al2O325.9% by mass of H2O) and 27.3kg of sodium hydroxide were dissolved in 219kg of water, stirred for 1 hour to give a clear solution, and 124.2kg of silica sol (containing 29.5 mass% SiO) was added under stirring2) Stirring for 0.5 hr to obtain uniformly mixed synthetic system with molar ratio of each material being SiO2/Al2O3＝28.2，Na2O/SiO2＝0.6，H2O/SiO228.7. And (3) transferring the synthesis system into a closed reaction kettle, heating to 120 ℃, carrying out hydrothermal crystallization for 3 hours, filtering, washing the obtained solid with deionized water until the pH value of the filtrate is 8-9, drying at 80 ℃ for 12 hours to obtain the Y molecular sieve g, wherein the specific surface area, the total pore volume, the micropore volume, the mesopore pore volume and the toluene adsorption capacity of the Y molecular sieve g are shown in table 1.
A pulse test was carried out using Y molecular sieves g in the same manner as in the step (4) in example 1 to evaluate the m-xylene adsorption selectivity, and the results are shown in Table 2.
TABLE 1
TABLE 2
Claims (12)
1. A mesoporous nanometer Y molecular sieve is provided, wherein the grain diameter of the Y molecular sieve is 20-450 nanometers, the Y molecular sieve contains two mesoporous channels, and the most probable pore diameters are respectively 5-20 nanometers and 25-50 nanometers.
2. The Y molecular sieve of claim 1, wherein the mesoporous nano Y molecular sieve is a self-assembly of nano Y molecular sieve grains, the particle size of the self-assembly is 0.5-1.5 microns, and the particle size of the nano Y molecular sieve grains in the self-assembly is 20-400 nanometers.
3. According to the claims1 the Y molecular sieve is characterized in that SiO of the Y molecular sieve2/Al2O3The molar ratio is 4.0-5.5.
4. The Y molecular sieve of claim 1, wherein the specific surface area of the Y molecular sieve is 740 to 1000m2(ii) a total pore volume of 0.40 to 0.65cm3Per gram, the mesoporous pore volume is 0.08-0.35 cm3/g。
5. The Y molecular sieve of claim 1, wherein the Y molecular sieve has a mode pore size of 10 to 20 nm and a mode pore size of 30 to 50 nm, respectively.
6. A preparation method of the mesoporous nano Y molecular sieve of claim 1 comprises the following steps:
(1) taking a silicon source and an aluminum source at 0-5 ℃, adding sodium hydroxide and water, and uniformly mixing to form a molecular sieve synthesis system, wherein the molar ratio of the materials is as follows: SiO 22/Al2O3＝5.5～9.5、Na2O/SiO2＝0.1～0.3、H2O/SiO2The temperature of the synthesis system is 5-25 ℃, the temperature of the synthesis system is 1-8 ℃,
(2) statically aging the molecular sieve synthesis system obtained in the step (1) at 20-40 ℃ for 10-48 hours, then statically crystallizing at 90-150 ℃ for 2-10 hours, stirring for 2-10 minutes, continuously statically crystallizing for 11-20 hours, and washing and drying the obtained solid.
7. The method according to claim 6, wherein the molar ratio of the materials in the molecular sieve synthesis system in step (1) is: SiO 22/Al2O3＝7～9、Na2O/SiO2＝0.1～0.25、H2O/SiO2＝8～20。
8. The method according to claim 6, wherein the molecular sieve synthesis system is statically aged at 20-40 ℃ for 15-30 hours, then statically crystallized at 90-120 ℃ for 4-9 hours, stirred for 2-10 minutes, and continuously statically crystallized for 11-15 hours in step (2).
9. The method of claim 6, wherein the aluminum source is selected from the group consisting of low alkalinity sodium metaaluminate solution, alumina, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum nitrate and sodium aluminate.
10. The method of claim 9, wherein the Al in the low alkalinity sodium metaaluminate solution2O317 to 28 mass% of Na2The O content is 19 to 30 mass%.
11. The method of claim 6, wherein the silicon source is selected from the group consisting of silica sol and water glass.
12. The method of claim 11, wherein the SiO in the water glass225 to 38 mass% of Na2The content of O is 9 to 15 mass%.
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