CN113086989B - Preparation method of hierarchical pore NaY molecular sieve - Google Patents
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- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
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Abstract
The invention provides a preparation method of a hierarchical porous NaY molecular sieve, which comprises the following steps: (1) Preparing kaolin into kaolin microspheres, and activating the kaolin microspheres by calcining to obtain activated kaolin microspheres; (2) preparing a Y-type molecular sieve guiding agent; (3) Mixing activated kaolin microspheres, water, a silicon source, naOH, sodium alginate, an auxiliary template agent and a Y-type molecular sieve guiding agent to prepare mixed gel, wherein the mixed gel comprises the following components in molar ratio: (1-30) Na 2 O:(2‑20)SiO 2 :Al 2 O 3 :(200‑500)H 2 O: (1.5-3) R, wherein R is sodium alginate; (4) And (4) aging, hydrothermal crystallizing and calcining the mixed gel prepared in the step (3) to obtain the hierarchical porous NaY molecular sieve.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a method for preparing a hierarchical pore NaY molecular sieve by kaolin in-situ crystallization.
Background
The in-situ crystallization technology was first reported by Engelhard corporation, and the basic principle is to grow NaY molecular sieve in situ on the surface and in the channels of kaolin by activating silica-alumina species in kaolin and using it as a raw material for synthesizing the molecular sieve. The molecular sieve is connected with the substrate by chemical bonds so as to improve the anti-attrition performance of the catalyst; the grain size of the molecular sieve is smaller than that of the conventional synthesized molecular sieve, so that the active center of the outer surface is increased, the diffusion resistance is reduced, the probability of the molecules approaching the active center is increased, and the catalytic reaction is facilitated; in the process of synthesizing the molecular sieve, a part of modified kaolin matrix with rich mesoporous structure is generated at the same time, which is beneficial to catalytic reaction.
The catalyst factory of Lanzhou petrochemical company in China utilizes kaolin as a raw material to synthesize the NaY molecular sieve in situ, and the content and the granularity of the molecular sieve can be adjusted. The Y/kaolin composite material is synthesized by adopting kaolin fine powder as a raw material, and the surface area of the Y/kaolin composite material is more than 800m 2 ·g -1 And the composite material has good FCC catalytic cracking performance. On the basis of the synthesis of the NaY molecular sieve, the synthesis of other molecular sieves on kaolin is also explored. Zhu et al (Chinese Journal of Chemical Engineering,2010,18 (6): 979) synthesized SAPO-34 molecular sieves by in situ crystallization on kaolin microspheres using TEA as a template, with about 22% wt of molecular sieve in the composite and with most of the molecular sieve being nano-sized, exhibiting high catalytic activity and better olefin selectivity in the MTO reaction. Wang (Industrial and Engineering Chemistry Research,2011,50 (17): 12-41) synthesized SAPO-34 molecular sieves on fully calcined kaolin microspheres treated with varying concentrations of sodium hydroxide using TEA and TEAOH composite templating agents. CN103818921B reports a method for preparing a TS-1 molecular sieve using a composite template agent, which is characterized by introducing aOr more than one auxiliary template agent, wherein the auxiliary template agent is one or a mixture of a fiber material or an organic alkali compound; the auxiliary template agent is added to reduce the dosage of expensive tetraalkylammonium hydroxide and reduce the production cost of the catalyst; on the other hand, the size of the molecular sieve can be adjusted by changing the auxiliary template agent and the using amount thereof.
The patent at home and abroad also reports the in-situ crystallization technology of kaolin, and CN201610429466.2 discloses a method for preparing a molecular sieve catalyst with a composite pore structure by kaolin in-situ crystallization.
CN200810084124.7 reports a preparation method of kaolin in-situ crystallization ZSM-5 molecular sieve, which is characterized in that the modified kaolin contains ZSM-5 molecular sieve by in-situ crystallization on the inner and outer surfaces, and the relative content of the ZSM-5 molecular sieve in the kaolin is 30-80% by relative crystallinity. The in-situ crystallized ZSM-5 molecular sieve has the characteristics of high crystallinity, small crystal grains, high activity and good stability.
CN200710054290.8 reports a method for synthesizing an L zeolite molecular sieve by in-situ crystallization by using kaolin as a raw material. The method is characterized in that a part of kaolin is calcined at high temperature to obtain high-temperature calcined clay, called high clay for short, and the other part of kaolin is calcined at lower temperature to obtain metakaolin, called metaclay for short. Mixing the two kinds of materials in a certain proportion, adding crystal seed or guiding agent, and crystallizing in situ in an alkaline system to obtain the L molecular sieve, wherein the L molecular sieve prepared by the method has a characteristic spectrogram of X-ray powder diffraction of the L molecular sieve.
CN200810084129.X reports a fixed bed catalyst containing kaolin in-situ crystallized ZSM-5 and Y-type molecular sieve and a preparation method thereof, wherein the preparation process comprises the steps of roasting kaolin at 1000-1400 ℃, mixing the roasted kaolin with a seed crystal molecular sieve, a binder, a structural auxiliary agent and water, carrying out extrusion forming, carrying out secondary roasting at 600-900 ℃ after forming, then carrying out hydrothermal crystallization according to the synthesis conditions of a NaY molecular sieve or a ZSM-5 molecular sieve, and carrying out modification treatment on a crystallized product to obtain a catalyst product. The catalyst prepared by the invention contains both ZSM-5 and Y-type molecular sieves, and has the advantages of high molecular sieve content, high activity and good stability.
CN201810359136.X reports preparation of SiO from low-grade kaolin 2 /Al 2 O 3 Stirring and mixing low-grade kaolin and hydrochloric acid in a stirring kettle to obtain kaolin slurry, filtering and washing to obtain washing water and a mixture; reacting the mixture with a nitric acid solution, filtering to obtain an aluminum nitrate solution and a silicon dioxide solid, mixing hydrofluoric acid with the silicon dioxide solid, and collecting the silicon fluoride gas generated by the reaction by using a gas collecting bag; mixing and stirring an aluminum nitrate solution and a hydroxide solution in a reaction kettle, introducing the collected hydrogen fluoride gas into the reaction kettle for reaction, filtering and washing to obtain a mixed solution of hydrofluoric acid and sodium nitrate and a silicon-aluminum precursor, and calcining the precursor to obtain the silicon-aluminum composite material.
CN201810357940.4 reports a small-grain-grade-hole SAPO #34 molecular sieve kaolin microspherical catalyst and preparation and application thereof. The preparation method comprises the following steps: preparing kaolin microspheres, and roasting to obtain activated kaolin microspheres; mixing the active kaolin microspheres, water, a phosphorus source, a microporous template and a mesoporous template to prepare reactant gel; crystallizing the reactant gel, and performing centrifugal separation to obtain a small-grain-grade-hole SAPO #34 molecular sieve kaolin microsphere composite material; and roasting the small-grain-grade-hole SAPO #34 molecular sieve kaolin microsphere composite material to obtain the small-grain-grade-hole SAPO #34 molecular sieve kaolin microsphere catalyst. The SAPO #34 molecular sieve kaolin microsphere catalyst has the advantages that the SAPO #34 molecular sieve content is high, the crystal grain is small, and the SAPO #34 molecular sieve kaolin microsphere catalyst has graded pores; compared with the product obtained without adding the mesoporous template agent, the product has higher yield of in-situ products.
Although the kaolin in-situ crystallization synthesis of molecular sieves is reported in a large number, besides NaY molecular sieves, other molecular sieves adopt expensive organic templates, and for in-situ synthesis of the hierarchical pore NaY molecular sieves on kaolin microspheres, the expensive organic templates are also adopted, for example, amphiphilic organosilane such as hexadecyl dimethyl trimethoxy silicon propyl ammonium chloride is adopted as a template to generate mesopores.
The inventor of the application adopts cheap natural sodium alginate to synthesize the hierarchical pore NaY molecular sieve in situ, but the sodium alginate can effectively guide the generation of mesopores under lower concentration, however, the specific surface area of the mesopores can not be improved when the hierarchical pore molecular sieve is synthesized due to the lower concentration of the sodium alginate, so that the specific surface area of the mesopores of the obtained hierarchical pore molecular sieve is generally lower than 150m 2 (iv) g. Although the method for synthesizing the hierarchical pore molecular sieve by adopting the high-concentration sodium alginate template system is an effective way for improving the specific surface area of mesopores of the hierarchical pore molecular sieve, when the molar ratio of the addition amount of the sodium alginate to the aluminum source is higher than 1.33, the agglomeration of the sodium alginate is caused due to the high concentration of the sodium alginate in the system, and the generation effect of the guided mesopores of the hierarchical pore molecular sieve is influenced. Therefore, how to adopt high-concentration sodium alginate to synthesize the hierarchical pore NaY molecular sieve with higher mesoporous specific surface area in situ is an urgent problem to be solved by the synthesis system.
Disclosure of Invention
In view of the problems and defects of the prior art, the invention aims to use high-concentration natural sodium alginate as a mesoporous template and introduce an auxiliary template into a system to realize the synthesis of the mesoporous specific surface area of 200m by using the high-concentration sodium alginate template 2 The hierarchical pore NaY molecular sieve with the specific surface area of the mesoporous is prepared on the kaolin microspheres in situ.
Therefore, the invention provides a preparation method of a hierarchical pore NaY molecular sieve, which comprises the following steps:
(1) Preparing kaolin into kaolin microspheres, and activating the kaolin microspheres by calcining to obtain activated kaolin microspheres;
(2) Preparing a Y-type molecular sieve guiding agent;
(3) Mixing activated kaolin microspheres, water, a silicon source, naOH, sodium alginate, an auxiliary template agent and a Y-type molecular sieve guiding agent to prepare mixed gel, wherein the mixed gel comprises the following components in molar ratio: (1-30) Na 2 O:(2-20)SiO 2 :Al 2 O 3 :(200-500)H 2 O: (1.5-3) R, wherein R is a biological template agent sodium alginate;
(4) Aging, hydrothermal crystallizing and calcining the mixed gel prepared in the step (3) to obtain the hierarchical porous NaY molecular sieve, wherein the specific surface area of mesopores of the hierarchical porous NaY molecular sieve is 200m 2 More than g.
In the step (3), the molar ratio of the sodium alginate to the aluminum source is higher than 1.33, and the sodium alginate has higher concentration in the template system and is easy to agglomerate, so that the auxiliary template is added into the template system. The hydrophobic group of the auxiliary template agent can interact with sodium alginate to form the composite template agent, and the existence of the hydrophilic group can greatly improve the hydrophilicity of the composite template agent, so that the agglomeration of the composite template agent taking the sodium alginate as a main body is prevented, the generation of the hierarchical pore molecular sieve in a high-concentration template agent sodium alginate system is realized, and the purpose of improving the mesoporous specific surface area is achieved. The addition amount of the sodium alginate in the invention can be embodied.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (3), preferably, the auxiliary template agent is: one or more of Sodium Dodecyl Sulfate (SDS), sodium fatty alcohol polyoxyethylene ether sulfate (AES), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and glycine.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (3), preferably, the addition sequence of each component is as follows: and (2) adding part of water, naOH, silicon source, Y-type molecular sieve guiding agent, sodium alginate and auxiliary template agent, supplementing the rest water, uniformly mixing, and adding the activated kaolin microspheres prepared in the step (1).
In the preparation method of the hierarchical pore NaY molecular sieve, in the step (3), preferably, the mass ratio of the activated kaolin microspheres to the mixed gel is 1: (5-20).
In the preparation method of the hierarchical pore NaY molecular sieve, in the step (1), the calcination temperature is preferably 600-950 ℃ and the calcination time is preferably 1-7h.
In the preparation method of the hierarchical pore NaY molecular sieve, in the step (1), the calcination time is preferably 2 to 4 hours.
In the preparation method of the hierarchical pore NaY molecular sieve, in the step (1), the particle size of the kaolin microspheres is preferably 80-100 μm.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (2), it is preferable that the Y-type molecular sieve directing agent comprises the following components in a molar ratio: (2-20) Na 2 O:(2-25)SiO 2 :Al 2 O 3 :(200-500)H 2 O。
In the step (2), preferably, in the preparation process of the hierarchical pore NaY molecular sieve directing agent, the aluminum source is completely derived from kaolin, 20-80% of the silicon source is derived from kaolin, and the balance is an additional silicon source.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (4), preferably, the aging conditions are: the temperature is 40-70 ℃ and the time is 2-5h.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (4), preferably, the hydrothermal crystallization conditions are as follows: the temperature is 90-120 ℃, and the time is 24-72h.
In the preparation method of the hierarchical pore NaY molecular sieve of the present invention, in the step (4), preferably, the calcination conditions are as follows: the temperature is 550-650 ℃, and the time is 2-24h.
The preparation method of the invention uses silicon-aluminum in the kaolin microspheres as one of the raw materials for synthesizing the hierarchical pore Y-shaped molecular sieve, and simultaneously needs to supplement partial silicon source.
According to the invention, sodium alginate is taken as a mesoporous template, when the concentration of the template sodium alginate is higher, the number of micelles is increased sharply, and due to the hydrophobic effect, the effect between the micelles begins to be enhanced, the micelles are agglomerated to form aggregates with larger volume, and on the contrary, the effect between aluminosilicate and the micelles is weakened, and finally the mesoporous molecular sieve with poorer regularity and stability is formed. The auxiliary template agent added in the invention can improve the hydrophilicity of the sodium alginate micelle and inhibit the agglomeration of the micelle. Therefore, the auxiliary template agent is added into a high-concentration sodium alginate solution system to synthesize the mesoporous molecular sieve, so that the specific surface area of mesopores can be greatly improved. The invention can synthesize mesoporous specific surface area up to 200m 2 A hierarchical pore NaY molecular sieve with more than g.
The kaolin microspheres used in the present invention may be prepared by conventional techniques, such as spray drying.
The preparation method of the hierarchical pore NaY molecular sieve provided by the invention has the following advantages:
the invention provides all aluminum sources and partial silicon sources required by molecular sieve synthesis by using kaolin microspheres, and sodium alginate and an auxiliary template agent are added in the synthesis process to form a composite template agent. The technology combines the advantages of an in-situ crystallization technology and a composite template agent technology, so that the NaY molecular sieve with the hierarchical pores grows on microspheres and the surface of the kaolin in situ and is uniformly dispersed on the surface. In addition, the method can modulate the content of mesopores in the composite material by modulating the addition amount of the sodium alginate, further modulate the pore structure of the composite material, avoid the defect that the molecular sieve pore channel is blocked by a matrix and a binder in a semi-synthesis method, and fully play the synergistic effect of the hierarchical pore molecular sieve and the matrix pore channel structure, thereby playing the advantages of the two materials. In addition, the addition of the auxiliary template agent in the method realizes the generation of mesopores in a high-concentration template agent system, thereby greatly increasing the mesopore specific surface area of the molecular sieve product.
In conclusion, the invention adopts the sodium alginate and the auxiliary template agent as the mesoporous composite template agent, the addition of the auxiliary template agent improves the hydrophilicity of the sodium alginate under high concentration, realizes the synthesis of the hierarchical pore molecular sieve in a high concentration template agent system, and greatly improves the specific surface area of mesopores. Meanwhile, the multi-level pore NaY molecular sieve can be synthesized in situ in kaolin, and the pore volume of the product is higher.
Drawings
FIG. 1 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in example 3;
FIG. 2 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in example 4;
FIG. 3 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in example 5;
FIG. 4 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in example 6;
FIG. 5 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in example 7;
FIG. 6 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in comparative example 1;
FIG. 7 is an XRD spectrum of the hierarchical pore NaY molecular sieve obtained in comparative example 2.
Detailed Description
The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.
The test methods in the following examples are all conventional methods unless otherwise specified; the reagents are commercially available, unless otherwise specified.
The invention adopts XRD to determine the crystal phase structure of the sample, and adopts Scanning Electron Microscope (SEM) to determine the crystal appearance structure of the sample. The content of the hierarchical pore NaY molecular sieve NaY improved by the method is calculated according to relative crystallinity data, and the relative crystallinity refers to the ratio of the peak area of a diffraction peak with the 2 theta of 23.5 degrees in an in-situ crystallized product to the peak area of a diffraction peak with the 2 theta of 23.5 degrees in a standard sample. The molecular sieve as a standard sample is a sample provided by petrochemical company in Lanzhou petroleum of China, and the crystallinity of the molecular sieve is 100 percent.
Measuring the adsorption-desorption isotherm of a sample at the liquid nitrogen temperature by adopting an ASAP2020M full-automatic adsorption instrument produced by Metromeritics USA, calculating the specific surface area of the sample according to the adsorption equilibrium isotherm between the relative pressure of 0.05 and 0.25 by adopting a Brunauer-Emmett-Teller (BET) equation, and distinguishing the internal surface area and the external surface area of the sample by adopting a t-plot model; and (3) measuring the pore volume and pore size distribution by adopting a static volumetric method, thereby calculating the pore structure parameters.
The raw material sources are as follows: the raw materials of water glass, aluminum sulfate, sodium metaaluminate, sodium hydroxide and the like are all industrial products from petrochemical company of Lanzhou petroleum of China.
Example 1
Preparation of activated kaolin microspheres: a slurry of kaolin was spray formed into microspheres of 80-100 microns (for consistency with the claims) and calcined at 650 ℃ for 4 hours to provide activated kaolin microspheres.
Example 2
Preparation of directing agent
Targeting agent 1: preparing gel from water glass, high-alkali sodium metaaluminate, deionized water and NaOH, wherein the molar ratio of the materials is as follows: 16Na 2 O:17SiO 2 :Al 2 O 3 :320H 2 O, aging at 50 ℃ for 6 h.
And (3) a guiding agent 2: preparing gel from water glass, high-alkali sodium metaaluminate, deionized water and NaOH, wherein the molar ratio of the materials is as follows: 15Na 2 O:14SiO 2 :Al 2 O 3 :220H 2 O, aging at 45 ℃ for 8 h.
And (3) a directing agent: preparing gel from water glass, high-alkali sodium metaaluminate, deionized water and NaOH, wherein the molar ratio of the materials is as follows: 18Na 2 O:20SiO 2 :Al 2 O 3 :400H 2 O, aging at 32 ℃ for 8 h.
And 4, a guiding agent: preparing gel from water glass, high-alkali sodium metaaluminate, deionized water and NaOH, wherein the molar ratio of the materials is as follows: 20Na 2 O:25SiO 2 :Al 2 O 3 :450H 2 O, aging at 60 ℃ for 4h.
And (5) a directing agent: preparing gel from water glass, high-alkali sodium metaaluminate, deionized water and NaOH, wherein the molar ratio of the materials is as follows: 16Na 2 O:17SiO 2 :Al 2 O 3 :289H 2 O, aging at 25 ℃ for 18 h.
Example 3:
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a 50 ℃ water bath; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 3h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 5, stirring and reacting for 3h at 80 ℃, adding 24g of sodium alginate and 2g of SDS, wherein the molar ratio of the sodium alginate to the aluminum source is 1.5. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 92 ℃ for 18h, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining at 550 ℃ for 6h to obtain the hierarchical porous NaY molecular sieve, wherein the hierarchical porous NaY molecular sieve is marked as F1.
Example 4:
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 4h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 6, stirring and reacting for 3h at 80 ℃, adding 32g of sodium alginate and 2g of AES, wherein the molar ratio of the sodium alginate to the aluminum source is 2. And (3) putting the materials into a crystallization kettle, dynamically crystallizing for 24 hours at 96 ℃, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining for 6 hours at 550 ℃ to obtain the hierarchical pore NaY molecular sieve, wherein the molecular sieve is marked as F2.
Example 5:
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 4h at 35 ℃, then heating to 80 ℃, adding 10g of guiding agent 6, stirring and reacting for 3h at 80 ℃, adding 40g of sodium alginate and 2g of PEG, wherein the molar ratio of the sodium alginate to the aluminum source is 2.5. And (3) putting the materials into a crystallization kettle, dynamically crystallizing for 24 hours at 96 ℃, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining for 6 hours at 550 ℃ to obtain the hierarchical pore NaY molecular sieve, wherein the molecular sieve is marked as F3.
Example 6:
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 4h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 6, stirring and reacting for 3h at 80 ℃, adding 45g of sodium alginate and 2g of glycine, wherein the molar ratio of the sodium alginate to the aluminum source is 2.8. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 96 ℃ for 24 hours, after the reaction is finished, washing the obtained filter cake to be neutral, performing suction filtration and drying, and calcining at 550 ℃ for 6 hours to obtain the hierarchical pore NaY molecular sieve, wherein the hierarchical pore NaY molecular sieve is marked as F4.
Example 7:
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a 50 ℃ water bath; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 4h at 35 ℃, then heating to 80 ℃, adding 10g of guiding agent 6, stirring and reacting for 3h at 80 ℃, and adding 48g of sodium alginate and 2g of PVA, wherein the molar ratio of the sodium alginate to the aluminum source is 3. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 96 ℃ for 24 hours, after the reaction is finished, washing the obtained filter cake to be neutral, performing suction filtration and drying, and calcining at 550 ℃ for 6 hours to obtain the hierarchical pore NaY molecular sieve, wherein the hierarchical pore NaY molecular sieve is marked as F5.
Comparative example 1:
the same conditions as in example 3 were used except that no mesoporous templating agent was added.
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 3 hours at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 5, and stirring and reacting for 3 hours at 80 ℃. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 92 ℃ for 18h, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining at 550 ℃ for 6h to obtain the hierarchical porous NaY molecular sieve, wherein the hierarchical porous NaY molecular sieve is marked as D1.
Comparative example 2:
the same conditions as in example 3 were used, except that the concentration of sodium alginate was lower and no auxiliary template agent was added.
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 3h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 5, stirring and reacting for 3h at 80 ℃, and adding 13g of sodium alginate, wherein the molar ratio of the sodium alginate to the aluminum source is 0.8. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 92 ℃ for 18h, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining at 550 ℃ for 6h to obtain the hierarchical porous NaY molecular sieve, wherein the hierarchical porous NaY molecular sieve is marked as D2.
Comparative example 3:
the same conditions as in example 3 were used, except that the concentration of sodium alginate was lower and no auxiliary template agent was added.
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a 50 ℃ water bath; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 3h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 5, stirring and reacting for 3h at 80 ℃, and adding 16g of sodium alginate, wherein the molar ratio of the sodium alginate to the aluminum source is 1. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 92 ℃ for 18 hours, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining at 550 ℃ for 6 hours to obtain the hierarchical porous NaY molecular sieve, wherein the molecular sieve is marked as D3.
Comparative example 4:
the same conditions as in example 3 were used except that no auxiliary templating agent was added.
190g of water glass and 25g of 650 ℃ calcined kaolin are stirred in a water bath at 50 ℃; adding 3g of NaOH solution with the mass fraction of 10%, stirring and reacting for 3h at 35 ℃, then heating to 80 ℃, adding 10g of directing agent 5, stirring and reacting for 3h at 80 ℃, and adding 22g of sodium alginate, wherein the molar ratio of the sodium alginate to the aluminum source is 1.4. And (3) putting the materials into a crystallization kettle, dynamically crystallizing at 92 ℃ for 18h, washing the obtained filter cake to be neutral after the reaction is finished, performing suction filtration and drying, and calcining at 550 ℃ for 6h to obtain the hierarchical porous NaY molecular sieve, wherein the hierarchical porous NaY molecular sieve is marked as D4.
TABLE 1 Structure and physical parameters of the resulting seeds and final products of examples 3-7 and comparative examples 1-4
As can be seen from the figure, the materials obtained in examples 3-7 and comparative examples 1-4 all have typical characteristic peaks of the Y-type molecular sieve, which indicates that the Y-type molecular sieve is successfully grown in situ on the surface of kaolin.
As can be seen from Table 1, the hierarchical pore NaY molecular sieve can be synthesized in situ in kaolin by using high-concentration sodium alginate as a mesoporous template and assisting a template agent, and the specific surface area of mesopores is 200m 2 More than g, up to 235m 2 (ii) in terms of/g. As can be seen from comparative examples 1 to 3, sodium alginate and Al 2 O 3 When the molar ratio of (2) is less than 1, the surface area of the mesopores is gradually increased along with the increase of the using amount of the sodium alginate; the method of the invention can realize the in-situ synthesis of the hierarchical porous NaY molecular sieve on the kaolin microspheres. However, as shown in comparative example 4, when the concentration of the template is high (sodium alginate and Al) 2 O 3 The molar ratio of (1.4), the number of micelles increases, and due to the enhanced interaction between the hydrophobic micelles, the micelles aggregate to form aggregates with a larger volume, and the effective generation of mesopores cannot be guided.
From the results of examples 3-7 and comparative examples 1-4, it can be seen that, with the addition of the template agent, the hydrophobic group of the template agent can interact with sodium alginate to form a composite template agent, and the presence of the hydrophilic group can greatly improve the hydrophilicity of the composite template agent, thereby preventing the agglomeration of the composite template agent mainly composed of sodium alginate, and further realizing the generation of the hierarchical pore molecular sieve in a high-concentration template agent system, and achieving the purpose of improving the mesoporous specific surface area.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.
Claims (11)
1. A preparation method of a hierarchical pore NaY molecular sieve is characterized by comprising the following steps:
(1) Preparing kaolin into kaolin microspheres, and activating the kaolin microspheres by calcining to obtain activated kaolin microspheres;
(2) Preparing a Y-type molecular sieve guiding agent;
(3) Mixing activated kaolin microspheres, water, a silicon source, naOH, sodium alginate, an auxiliary template agent and a Y-type molecular sieve guiding agent to prepare mixed gel, wherein the mixed gel comprises the following components in molar ratio: (1-30) Na 2 O:(2-20)SiO 2 :Al 2 O 3 :(200-500)H 2 O: (1.5-3) R, wherein R is sodium alginate;
(4) Aging, hydrothermal crystallization and calcining the mixed gel prepared in the step (3) to obtain the hierarchical porous NaY molecular sieve;
in the step (3), the auxiliary template agent is: one or more of Sodium Dodecyl Sulfate (SDS), sodium fatty alcohol polyoxyethylene ether sulfate (AES), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and glycine.
2. The method according to claim 1, wherein in the step (2), the molar ratio of each component of the Y-type molecular sieve directing agent is as follows: (2-20) Na 2 O:(2-25)SiO 2 :Al 2 O 3 :(200-500)H 2 O。
3. The method of claim 1, wherein in step (2), the Y-type molecular sieve guiding agent is prepared by using 20-80% of the aluminum source from kaolin and the rest from external silicon source.
4. The method of claim 1, wherein the components are added in step (3) in the order: a silicon source, activated kaolin microspheres, naOH-Y type molecular sieve guiding agent, sodium alginate and an auxiliary template agent.
5. The method according to claim 1, wherein in the step (3), the mass ratio of the activated kaolin microspheres to the mixed gel is 1: (5-20).
6. The method according to claim 1, wherein in the step (1), the calcining temperature is 600-950 ℃ and the time is 1-7h.
7. The method according to claim 1, wherein in step (1), the calcination time is 2-4h.
8. The method according to claim 1, wherein in step (1), the kaolin microspheres have a particle size of 80-100 μm.
9. The method according to claim 1, wherein in step (4), the aging condition is: the temperature is 40-70 ℃ and the time is 2-5h.
10. The method according to claim 1, wherein in the step (4), the hydrothermal crystallization conditions are as follows: the temperature is 90-120 ℃, and the time is 24-72h.
11. The method according to claim 1, wherein in step (4), the calcination conditions are: the temperature is 550-650 ℃, and the time is 2-24h.
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