CN114426286B - Mesoporous nano Y molecular sieve and preparation method thereof - Google Patents
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Abstract
A mesoporous nano Y molecular sieve with grain size of 20-450 nm contains two mesoporous channels with diameters of 5-20 nm and 25-50 nm. The Y molecular sieve is used for adsorbing and separating meta-xylene from mixed carbon octaaromatic hydrocarbon, 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 a type of crystalline material with a special framework structure, and are widely used in the fields of separation, catalysis and the like due to uniform micropore channels, adjustable acidity and good ion exchange performance. Currently, Y molecular sieves are used in industry as active components of m-xylene adsorption separation adsorbents, and the crystallinity, silica/alumina mole ratio, chemical composition of framework structure, grain size, internal pore structure and the like of the Y molecular sieves can significantly influence the adsorption capacity, adsorption selectivity and mass transfer performance of the adsorbents.
US4306107 discloses a process for separating meta-xylene and ethylbenzene from mixed carbon octaaromatics. According to the method, naY zeolite is used as an active component of an adsorbent, toluene is used as a desorbing agent, and mixed carbon octaarene is introduced into a simulated moving bed to perform countercurrent operation by utilizing the characteristics of the NaY zeolite that the adsorption capacity of m-xylene is strongest, the centering of p-xylene and o-xylene and the weakest of ethylbenzene, so that m-xylene, p-xylene, o-xylene and ethylbenzene are respectively obtained at different positions of the simulated moving bed.
US4326092 discloses a process for separating meta-xylene from mixed carbon octaaromatics using NaY zeolite having a silica to alumina molar ratio of 4.5 to 5.0 to prepare an adsorbent which can achieve higher meta-xylene selectivity.
CN1939883a discloses a process for separating meta-xylene from a carbon octaarene isomer, using NaY zeolite with a silica to alumina molar ratio of 5-6 to prepare an adsorbent, the zeolite containing 0-8 mass% of water and having an adsorption temperature of 25-250 ℃, the desorbent being selected from tetralin and alkylated derivatives thereof.
CN1050595C reports an adsorbent having a Y zeolite with a cation site occupied by both sodium and lithium ions as an active component, and is used for liquid-phase adsorption separation of meta-xylene from mixed carbon octaaromatics, resulting in higher meta-xylene selectivity. 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 mass percent based on the ignition quantity 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 meta-xylene from mixed carbon octaarene, and has good adsorption selectivity, mass transfer performance and higher adsorption capacity.
The invention provides a mesoporous nano Y molecular sieve, the grain size of the Y molecular sieve is 20-450 nanometers, the Y molecular sieve contains two mesoporous channels, and the diameters of the most probable pores are 5-20 nanometers and 25-50 nanometers respectively.
The mesoporous nano Y molecular sieve is a self-aggregation body formed by self-aggregation of nano Y molecular sieve crystal grains, comprises two mesoporous channels, is used for adsorbing and separating meta-xylene in mixed carbon octaarene, and can remarkably improve the adsorption selectivity of the meta-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 graph showing the pore size distribution of the mesoporous nano Y molecular sieve prepared in example 1 of the present invention.
FIG. 4 is a graph showing the pore size distribution of the mesoporous nano Y molecular sieve prepared in example 2 of the present invention.
FIG. 5 is a graph showing the pore size distribution of the mesoporous nano Y molecular sieve prepared in example 3 of the present invention.
FIG. 6 is a graph showing the pore size distribution of the mesoporous nano Y molecular sieve prepared in example 4 of the present invention.
FIG. 7 is a graph showing the pore size distribution 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.
Fig. 10 is a pore size distribution curve 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 body formed by self-assembly of nano Y molecular sieve crystal grains, the particle size of the self-assembly body is relatively large, the nano Y molecular sieve is favorable for improving mass transfer performance, and the problem of difficult solid-liquid separation caused by the generation of nano molecular sieve crystal grains during synthesis of the molecular sieve can be well solved by the large self-assembly body particle size. In addition, the self-assembled nano Y molecular sieve contains two mesoporous pore canals, so that good mass transfer performance is further provided, 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 Y molecular sieve grain self-assembly body, the grain diameter of the self-assembly body is preferably 0.5-1.5 microns, and the grain diameter of the nano Y molecular sieve in the self-assembly body is 20-400 nanometers, preferably 50-300 nanometers, and more preferably 80-250 nanometers.
SiO of the mesoporous nano Y molecular sieve 2 /Al 2 O 3 The molar ratio is preferably 4.0 to 5.5.
The specific surface area of the mesoporous nano Y molecular sieve is 740-1000 m 2 /g, youSelecting 750-900 m 2 Per gram, the total pore volume is 0.40-0.65 cm 3 Preferably 0.40 to 0.55cm 3 Per g, mesoporous volume of 0.08-0.35 cm 3 Preferably 0.10 to 0.25cm 3 /g。
The most probable pore diameter of the mesoporous nano Y molecular sieve is preferably 10-20 nanometers and 30-50 nanometers respectively.
The preparation method of the mesoporous nano Y molecular sieve comprises the following steps:
(1) Adding sodium hydroxide and water into a silicon source and an aluminum source at 0-5 ℃ to be uniformly mixed to form a molecular sieve synthesis system, wherein the molar ratio of the materials is as follows: siO (SiO) 2 /Al 2 O 3 ＝5.5～9.5、Na 2 O/SiO 2 ＝0.1～0.3、H 2 O/SiO 2 =5 to 25, the temperature of the synthesis system is 1 to 8 ℃,
(2) And (3) statically aging the molecular sieve synthesis system obtained in the step (1) at 20-40 ℃ for 10-48 hours, 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) of the invention comprises the steps of preparing a molecular sieve synthesis system at low temperature, taking a silicon source and an aluminum source 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 each material in the molecular sieve synthesis system is preferably as follows: siO (SiO) 2 /Al 2 O 3 ＝7～9、Na 2 O/SiO 2 ＝0.1～0.25、H 2 O/SiO 2 =8 to 20. The temperature of the synthesis system is preferably 1 to 5 ℃.
The method (2) of the invention is to crystallize the molecular sieve synthesis system to prepare the molecular sieve, preferably, the molecular sieve synthesis system is statically aged for 15-30 hours at 20-40 ℃, then statically crystallized for 4-9 hours at 90-120 ℃, stirred for 2-10 minutes, and continuously statically crystallized 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 to 100 ℃, more preferably 75 to 90 ℃, and the drying time is preferably 2 to 20 hours, more preferably 8 to 16 hours.
The aluminum source described in the above method is selected from the group consisting of low basicityOne or more of sodium metaaluminate solution, alumina, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum nitrate and sodium aluminate, preferably low-alkalinity sodium metaaluminate solution and/or aluminum sulfate. Al in the low-alkalinity sodium metaaluminate solution 2 O 3 The content is preferably 17 to 28 mass percent, na 2 The O content is preferably 19 to 30 mass%.
The silicon source is preferably silica sol or water glass. SiO in the water glass 2 The content is preferably 25 to 38 mass%, na 2 The O content is preferably 9 to 15 mass%.
The Y molecular sieve provided by the invention is suitable for adsorbing and separating meta-xylene from mixed carbon octaarene. The desorbant used for the adsorption separation is preferably toluene.
The adsorption selectivity and the adsorption and desorption rate for the adsorption target component are important indexes for evaluating the performance of the adsorbent. The selectivity is the ratio of the two component concentrations in the adsorption phase to the ratio of the two component concentrations in the non-adsorption phase at adsorption equilibrium. The adsorption equilibrium refers to a state when no net transfer of components occurs between the adsorption phase and the non-adsorption phase after the mixed carbon octaarene contacts with the adsorbent. The adsorption selectivity is calculated as follows:
wherein C and D represent two components to be separated, A C And A D Respectively represent the concentration of C, D components in the adsorption phase at the adsorption equilibrium, U C And U D The concentrations of the two components in the non-adsorbed phase C, D at adsorption equilibrium are shown, respectively. When the selectivity β of the two components is approximately 1.0, it is shown that the adsorption capacity of the adsorbent for the two components is equivalent, and there is no component to be preferentially adsorbed. When β is greater or less than 1.0, it is indicated that one component is preferentially adsorbed. Specifically, when beta>1.0, the adsorbent preferentially adsorbs the C component; when beta is<At 1.0, the adsorbent preferentially adsorbs the D component. The greater the beta value, the easier the adsorption separation is to proceed from the viewpoint of ease of separation. The rapid adsorption and desorption rate is beneficial to reducing the dosage of the adsorbent and the desorbent, and the extractionHigh product yield and low operation cost of the adsorption separation device.
The invention uses a dynamic pulse experimental device to measure the adsorption selectivity and the adsorption and desorption rate of meta-xylene. The device consists of 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 adsorbent loading is 50 milliliters. 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 of the adsorption column is connected with a pressure control valve and then connected with an effluent collector. The desorbent composition used in the experiment was 30% by volume toluene (T) and 70% by volume n-heptane (NC 7 ) The pulse liquid composition was 5% by volume of Ethylbenzene (EB), para-xylene (PX), meta-xylene (MX), ortho-xylene (OX), and n-Nonane (NC) 9 ) And 75% by volume of the above desorbent.
The method for measuring the adsorption selectivity comprises the following steps: filling the weighed adsorbent into an adsorption column, vibrating and packing, and dehydrating and activating in nitrogen flow at 160-280 ℃. Then introducing desorbent to remove gas in the system, increasing pressure to 0.8MPa, increasing temperature to 145 ℃, stopping introducing desorbent, and keeping the pressure at 1.0 hr －1 8 milliliters of pulse feed liquid is introduced into the reactor, then the introduction of the pulse liquid is stopped, and desorption is carried out by introducing desorbent into the reactor at the same space velocity, 3 drops of desorption liquid samples are taken every 2 minutes, and the desorption liquid samples are analyzed by gas chromatography. With desorbent feed volume for desorption as abscissa, NC 9 And EB, PX, MX, OX, drawing desorption curves of the components by taking the concentrations of the components as the ordinate. NC as tracer 9 Not adsorbed, peaks first, which gives the dead volume of the adsorption system. Measuring the desorbent feed volume from the midpoint of the half-peak width of each component EB, PX, MX, OX to zero, i.e. the net retention volume V, with the midpoint of the half-peak width of the tracer being taken as zero R . 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 relative to EB, denoted as beta MX/EB 。
In order to realize the cyclic continuous use of the adsorbent, the selectivity between the extracted component and the desorbent is also an important performance index, and the desorption curve of the extracted component can be obtained by pulse testOne-step parsing. The volume of desorbent required to increase the concentration of MX from 10% to 90% in the front effluent of the pulse desorption curve for MX was defined as the adsorption rate S A ] 10-90 The desorbent volume required to decrease the MX concentration from 90% to 10% along the trailing edge of the desorption curve is defined as the desorption rate S D ] 90-10 . Ratio of the two [ S D ] 90-10 /[S A ] 10-90 I.e. can be characterized as adsorption selectivity beta between MX and desorbent (T) MX/T . If beta is MX/T Much less than 1.0 indicates that the adsorbent is too strong in its ability to desorb, which is detrimental to the adsorption process if beta MX/T Far above 1.0, it means that the desorbing agent adsorption capacity is too weak, which makes the desorption process difficult, and the ideal condition is beta MX/T About 1.0.
The present invention will be described in detail 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 measured by toluene vapor phase adsorption experiments, and the specific operation method was as follows: nitrogen carrying toluene (toluene partial pressure 0.5 MPa) was contacted with a mass of molecular sieve at 35℃until the toluene reached adsorption equilibrium. The adsorption capacity of the molecular sieve to be measured is calculated from the following equation based on the mass difference between the molecular sieve before and after toluene adsorption.
Wherein, C is adsorption capacity, and the unit is milligrams/gram; m is m 1 The unit is gram of the mass of the molecular sieve to be tested before toluene adsorption; m is m 2 The unit is gram of the mass of the molecular sieve to be tested after toluene adsorption.
The specific surface area, total pore volume, microporous pore volume and mesoporous pore volume of the molecular sieve were determined according to astm d4365-95 (2008).
Example 1
(1) Preparation of aluminum 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,a clear and transparent low alkalinity sodium metaaluminate solution is formed as aluminum source 1. Al in the aluminum source 1 2 O 3 The content of Na is 21.58 mass percent 2 The O content was 23.59 mass%, na 2 O and Al 2 O 3 The molar ratio of (2) was 1.80. 87.89kg of aluminum sulfate octadecabydrate 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 2 2 O 3 The content was 6.73 mass%.
(2) Pretreatment of raw materials
Respectively water glass (SiO) 2 The content of Na was 37.17 mass%, na 2 The O content is 11.65 mass%) and the aluminum source prepared in step (1) is cooled to 0 ℃.
(3) Preparation of Y molecular sieves
Under the condition of stirring, 89.68kg of water glass with the temperature of 0 ℃ treated in the step (2), 49.79kg of aluminum sulfate solution with the temperature of 0 ℃, 18.14kg of low-alkalinity sodium metaaluminate solution with the temperature of 0 ℃ and 5.61kg of deionized water are taken and added into a reaction kettle to obtain a Y molecular sieve synthesis system, wherein the molar ratio of each material is SiO 2 /Al 2 O 3 ＝7.8，Na 2 O/SiO 2 ＝0.25，H 2 O/SiO 2 =10. The temperature of the synthesis system was 3 ℃.
Transferring the molecular sieve synthesis system into a closed reaction kettle, statically aging for 24 hours at 30 ℃, then statically crystallizing for 8 hours at the temperature of 100 ℃, stirring for 5 minutes, continuously statically crystallizing for 12 hours, filtering, washing the obtained solid with deionized water until the pH value of the filtrate is 8-9, and drying for 12 hours at 80 ℃ to obtain the nano Y molecular sieve a, wherein SiO of the nano Y molecular sieve a is prepared by the steps of 2 /Al 2 O 3 The molar ratio was 4.6 (by X-ray fluorescence spectroscopy, the same applies hereinafter), the XRD spectrum was shown in FIG. 1, the SEM photograph was shown in FIG. 2, and the pore size distribution curve was shown in FIG. 3. As can be seen from FIG. 2, the nano-scale Y molecular sieve grains self-aggregate to form self-aggregates, the particle size of the self-aggregates is 0.6 microns, 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 respectively 10 nm and 37 nm, and the specific surface area, the total pore volume, the micropore volume and the mesopore volume and the toluene adsorption capacity are shown in Table 1.
(4) Evaluation of adsorption Performance
The nano Y molecular sieve a is subjected to tabletting, shaping, crushing and screening to obtain particles with the particle size of 300-850 mu m, the particles are used as adsorbents, the adsorption selectivity of meta-xylene is evaluated by adopting a pulse test, and the results are shown in Table 2.
Example 2
A Y molecular sieve was prepared as in example 1 except that in 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 were taken and subjected to cooling treatment in step (2) under stirring to obtain a Y molecular sieve synthesis system, wherein the molar ratio of each material was SiO 2 /Al 2 O 3 ＝7.8，Na 2 O/SiO 2 ＝0.23，H 2 O/SiO 2 =10. The temperature of the synthesis system was 4 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static aging and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain nano Y molecular sieve b with SiO 2 /Al 2 O 3 The molar ratio was 4.8, the particle size of the self-assembled body formed by the nano-scale Y molecular sieve grains was 0.8 μm, the grain size of the nano-scale Y molecular sieve grains was 80 to 180 nm, the pore size distribution curve was shown in FIG. 4, the most probable pore diameters were 12 nm and 40 nm, respectively, the specific surface area, the total pore volume, the micropore pore volume, the mesopore volume and the toluene adsorption capacity were shown in Table 1, and the adsorption selectivity of meta-xylene as measured by the pulse test was shown in Table 2.
Example 3
A Y molecular sieve was prepared as in example 1 except that (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 were added to the reaction vessel under stirring to obtain a Y molecular sieve synthesis system, wherein the molar ratio of each material was SiO 2 /Al 2 O 3 ＝7.8、Na 2 O/SiO 2 ＝0.20、H 2 O/SiO 2 =10. The temperature of the synthesis system was 5 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, and performing static aging,Stirring in the middle, and washing the obtained solid with deionized water, and drying to obtain nanometer Y molecular sieve c with SiO 2 /Al 2 O 3 The molar ratio was 4.9, the particle size of the self-assembled body formed by the nano-scale Y molecular sieve grains was 1.0 μm, the grain size of the nano-scale Y molecular sieve grains was 90 to 200 nm, the pore size distribution curve was shown in FIG. 5, the most probable pore diameters were 15 nm and 42 nm, respectively, the specific surface area, the total pore volume, the micropore pore volume, the mesopore volume and the toluene adsorption capacity were shown in Table 1, and the adsorption selectivity of meta-xylene as measured by the pulse test was shown in Table 2.
Example 4
A Y molecular sieve was prepared as in example 1 except that in 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 were added to the reaction vessel under stirring to give a Y molecular sieve synthesis system, wherein the molar ratio of each material was SiO 2 /Al 2 O 3 ＝7.8、Na 2 O/SiO 2 ＝0.20、H 2 O/SiO 2 =15. The temperature of the synthesis system was 4 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static aging and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain nano Y molecular sieve d with SiO 2 /Al 2 O 3 The molar ratio was 4.9, the particle size of the self-assembled body formed by the nano-scale Y molecular sieve grains was 1.1 μm, the grain size of the nano-scale Y molecular sieve grains was 90 to 220 nm, the pore size distribution curve was shown in FIG. 6, the most probable pore diameters were 17 nm and 43 nm, respectively, the specific surface area, the total pore volume, the micropore pore volume, the mesopore volume and the toluene adsorption capacity were shown in Table 1, and the adsorption selectivity of meta-xylene as measured by the pulse test was shown in Table 2.
Example 5
A Y molecular sieve was prepared as in example 1 except that in 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 vessel under stirring to obtainTo a Y molecular sieve synthesis system, wherein the molar ratio of each material is SiO 2 /Al 2 O 3 ＝7.8、Na 2 O/SiO 2 ＝0.20、H 2 O/SiO 2 =20. The temperature of the synthesis system was 5 ℃. Transferring the molecular sieve synthesis system into a closed reaction kettle, performing static aging and two-stage static crystallization with stirring in the middle, washing the obtained solid with deionized water, and drying to obtain nano Y-molecular sieve e with SiO 2 /Al 2 O 3 The molar ratio was 5.0, the particle size of the self-assembled body formed by the nano-scale Y molecular sieve grains was 1.2 μm, the grain size of the nano-scale Y molecular sieve grains was 100 to 240 nm, the pore size distribution curve was shown in FIG. 7, the most probable pore diameters were 19 nm and 46 nm, respectively, the specific surface area, the total pore volume, the micropore pore volume, the mesopore volume and the toluene adsorption capacity were shown in Table 1, and the adsorption selectivity of meta-xylene as measured by the pulse test was shown in Table 2.
Comparative example 1
(1) Preparation of aluminum 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 a clear and transparent low-alkalinity sodium metaaluminate solution as an aluminum source. Al in the aluminum source 2 O 3 The content of Na is 11.87 mass percent 2 The O content was 16.59 mass%, na 2 O and Al 2 O 3 The molar ratio of (2) was 2.3.
(2) Preparation of a guiding agent
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) were stirred 2 The content of Na is 20.17 mass percent 2 O content of 6.32 mass%) was added to the reaction vessel at a molar ratio of SiO 2 /Al 2 O 3 ＝15、Na 2 O/SiO 2 ＝1.07、H 2 O/SiO 2 =21, and left standing at 35 ℃ for 16 hours to obtain a guiding agent.
(3) Preparation of Y molecular sieves
50.74kg of water glass, 42.51kg of deionized water, 7.56kg of the guiding agent prepared in the step (2) and 8.66kg of the guiding agent prepared in the step (2) are stirred to obtain the product of the example 1%1) Adding the aluminum sulfate solution obtained in the step (1) and 11.01kg of the low-alkalinity sodium metaaluminate solution prepared in the step (1) into a reaction kettle to obtain a Y molecular sieve synthesis system, wherein the molar ratio of each material is SiO 2 /Al 2 O 3 ＝9.5，Na 2 O/SiO 2 ＝0.43，H 2 O/SiO 2 =30, al contained in the guiding agent 2 O 3 And Al contained in the Y molecular sieve synthesis system 2 O 3 The molar ratio of (2) 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 ℃ for hydrothermal crystallization for 28 hours, filtering, washing the obtained solid with deionized water until the pH value of the filtrate is 8-9, and drying at 80 ℃ for 12 hours to obtain a Y molecular sieve f, wherein SiO of the Y molecular sieve f is obtained 2 /Al 2 O 3 The molar ratio was 4.8, the XRD spectrum was shown in FIG. 8, the SEM photograph was shown in FIG. 9, the Y molecular sieve grain size was 0.9 μm, the pore size distribution was shown in FIG. 10, and no apparent mesopores were shown, and the specific surface area, the total pore volume, the micropore volume and the mesopore volume and the toluene adsorption capacity were shown in Table 1.
The adsorption selectivity of m-xylene was evaluated by pulse test using Y molecular sieve f using the method described in step (4) of example 1, and the results are shown in Table 2.
Comparative example 2
Preparation of Y molecular sieves by conventional methods without directing agents
5.0kg of sodium aluminate (30 mass% Na) 2 O,44.1 mass% Al 2 O 3 25.9% by mass of H 2 O) and 27.3kg of sodium hydroxide were dissolved in 219kg of water and stirred for 1 hour to give a clear solution, 124.2kg of silica sol (containing 29.5% by mass of SiO) was added under stirring 2 ) Stirring continuously for 0.5 hour to obtain a uniformly mixed synthesis system, wherein the molar ratio of the materials is SiO 2 /Al 2 O 3 ＝28.2，Na 2 O/SiO 2 ＝0.6，H 2 O/SiO 2 =28.7. Transferring the synthesis system into a closed reaction kettle, heating to 120 ℃ for hydrothermal crystallization for 3 hours, filtering, washing the obtained solid with deionized water until the pH value of the filtrate is 8-9, and drying at 80 ℃ for 12 hours to obtain a Y molecular sieve g, wherein the specific surface area, the total pore volume, the micropore volume and the micropore volume of the Y molecular sieve g are equal to each otherThe mesoporous pore volume and toluene adsorption capacity are shown in Table 1.
The adsorption selectivity of m-xylene was evaluated by pulse test using Y molecular sieve g, using the method described in step (4) of example 1, and the results are shown in Table 2.
TABLE 1
TABLE 2
Claims (9)
1. A preparation method of a mesoporous nano Y molecular sieve comprises the following steps:
(1) Uniformly mixing a silicon source and an aluminum source at 0-5 ℃ with water to form a molecular sieve synthesis system, wherein the molar ratio of each material is as follows: siO (SiO) 2 /Al 2 O 3 =5.5~9.5、Na 2 O/SiO 2 =0.1~0.3、H 2 O/SiO 2 =5 to 25, the temperature of the synthesis system is 1 to 8 ℃,
(2) Static aging the molecular sieve synthesis system in the step (1) for 10-48 hours at 20-40 ℃, static crystallization for 2-10 hours at 90-150 ℃, stirring for 2-10 minutes, continuing static crystallization for 11-20 hours, washing and drying the obtained solid,
the aluminum source is low-alkalinity sodium metaaluminate solution and aluminum sulfate, and the low-alkalinity sodium metaaluminate solution contains Al 2 O 3 The content is 17-28 mass percent, na 2 The content of O is 19-30 mass%, the grain size of the Y molecular sieve is 20-450 nanometers, the Y molecular sieve contains two mesoporous channels, and the diameters of the most probable pores are 5-20 nanometers and 25-50 nanometers respectively.
2. The method of claim 1, wherein the molar ratio of the materials in the molecular sieve synthesis system of step (1) is: siO (SiO) 2 /Al 2 O 3 =7~9、Na 2 O/SiO 2 =0.1~0.25、H 2 O/SiO 2 =8~20。
3. The method according to claim 1, wherein the molecular sieve synthesis system is statically aged at 20-40 ℃ for 15-30 hours, statically crystallized at 90-120 ℃ for 4-9 hours, stirred for 2-10 minutes, and statically crystallized for 11-15 hours.
4. The method of claim 1, wherein the silicon source is selected from the group consisting of silica sol and water glass.
5. A process according to claim 4, wherein SiO in the water glass is 2 The content is 25-38 mass%, na 2 The O content is 9-15 mass%.
6. The method according to claim 1, wherein the mesoporous nano-Y molecular sieve is a self-assembled body of nano-Y molecular sieve grains, the self-assembled body has a grain size of 0.5 to 1.5 μm, and the nano-Y molecular sieve grains in the self-assembled body have a grain size of 20 to 400 nm.
7. The method according to claim 1, wherein the Y molecular sieve is SiO 2 /Al 2 O 3 The molar ratio is 4.0-5.5.
8. The method according to claim 1, wherein the specific surface area of the Y molecular sieve is 740-1000 m 2 Per gram, a total pore volume of 0.40 to 0.65cm 3 Per g, mesoporous volume of 0.08-0.35 cm 3 /g。
9. The method of claim 1, wherein the Y molecular sieve has a top pore size of 10 to 20 nm and 30 to 50 nm, respectively.
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| CN107777697A (en) * | 2016-08-30 | 2018-03-09 | 中国石油化工股份有限公司 | Y type molecular sieve and preparation method thereof |
| CN108862309A (en) * | 2017-05-11 | 2018-11-23 | 中国石油大学(北京) | A kind of NaY molecular sieve aggregation and preparation method thereof with nano-micro structure |
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