CN116730358A

CN116730358A - SBA molecular sieve encapsulated with nano metal particles, and preparation method and application thereof

Info

Publication number: CN116730358A
Application number: CN202210209214.4A
Authority: CN
Inventors: 吴凯; 任行涛; 裴庆君; 贾志光
Original assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Chemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2023-09-12

Abstract

The application relates to an SBA molecular sieve encapsulated with nano metal particles, and a preparation method and application thereof. The preparation method comprises the following steps: s1: passivating the SBA molecular sieve raw powder to obtain passivated SBA molecular sieve powder; s2: adding an alkaline solution into the SBA molecular sieve powder subjected to the passivation treatment in the step S1 to obtain an SBA molecular sieve powder intermediate; s3: adding a metal complex solution into the SBA molecular sieve powder intermediate obtained in the step S2 to obtain a product A, wherein metal particles in the metal complex are iron, cobalt or nickel particles; s4: uniformly mixing an organic template agent, water, a silicon source and acid to form glue, so as to obtain a product B; s5: and (3) mixing the product A obtained in the step (S3) with the product B obtained in the step (S4), crystallizing, washing, drying and roasting to obtain the target product. The nano particles in the molecular sieve prepared by the application are all in the pore canal of the molecular sieve, so that the catalyst performance of the catalyst is improved.

Description

SBA molecular sieve encapsulated with nano metal particles, and preparation method and application thereof

Technical Field

The application provides an SBA molecular sieve encapsulated with nano metal particles, and a preparation method and application thereof.

Background

Since the first successful synthesis of regular MCM-41 in 1992 by Mobil, mesoporous materials have shown great potential application value in the aspects of adsorbents, catalysts and catalyst carriers. In 1998, zhao Dongyuan successfully synthesized novel mesoporous materials SBA-15 and SBA-16 with larger specific surface area, regular pore size distribution, thicker pore wall and better thermal stability than the M41S molecular sieve for the first time, and the materials show larger application value in the aspect of catalysts. Compared with the conventional M41S series molecular sieves, the three-dimensional pore channels can enable reactants to enter the molecular sieves to react more easily, and the blocking of the pore channels of the molecular sieves is avoided. However, the SBA molecular sieve of pure silicon does not have any acidic, basic and redox centers, and only one functional group-silicon hydroxyl (Si-OH) exists on the surface, so that the application of the SBA molecular sieve in certain fields is greatly limited. In recent years, the introduction of impurity particles into mesoporous molecular sieves to increase their acidity and stability has attracted increasing attention. Almost all transition metals and main group elements can be introduced into the molecular sieve by hydrothermal synthesis and impregnation as catalytic active sites to increase the catalytic activity of the molecular sieve. Among these hetero particles, mesoporous iron, cobalt, nickel silicate also exhibit excellent catalytic performance in many homogeneous oxidation reactions, such as phenol hydroxylation, adsorption desulfurization, oxidative desulfurization, and the like. Wherein the state of the impurity particles in the molecular sieve will directly determine the catalytic performance of the molecular sieve.

The nano metal particle catalyst can be used for producing fine chemicals, improving fuel, producing hydrogen, utilizing solar energy, eliminating pollutants and the like. However, in some high temperature reactions, metal particles tend to undergo particle aggregation or deactivation by metal leaching. In order to solve the problem of stability of nano-metal particles, great efforts have been made, including strengthening metal-support interactions, adding promoters, adjusting the diameter or morphology of the metal particles, etc. The coating of nano-metal particles in molecular sieves can be largely divided into two strategies: post synthesis and in situ constraint. Post synthesis strategies refer to the introduction of nano-metal particles after the zeolite structure construction is completed. In contrast, in situ constraint methods require co-crystallization of zeolite and metal precursor and the in situ reduction to obtain nano-metal particles.

The in-situ constraint method is that nano metal particles or precursors can be introduced into the inside of the molecular sieve crystal by a one-step hydrothermal synthesis method. The method comprises the steps of firstly mixing synthesized nano metal particles or soluble metal precursors with synthetic gel of a molecular sieve, and then carrying out high-temperature crystallization. The synthesized product is further calcined to remove organic matters, and is reduced under the reducing agent to generate nano metal particles. The method is simple and effective, but because the metal particles are larger than the pore channels of the molecular sieve, the reduced metal can support the pore channel structure of the molecular sieve in the reduction process, so that the self structure of the molecular sieve is damaged, and the catalytic effect of the catalyst is reduced. The post synthesis method is widely used because it has the advantage of not limiting the kind of molecular sieve framework. The nano metal particles can enter the pore canal inside the molecular sieve by impregnating the molecular sieve carrier in metal colloid or soluble metal precursor. However, in practice, most of the nano metal particles are on the surface of the molecular sieve, and a small part of the nano metal particles can enter the pore channels of the molecular sieve, so that the catalysis of the nano metal particles is not exerted.

Disclosure of Invention

At least to solve one of the above problems in the prior art, the present application proposes an SBA molecular sieve encapsulated with nano-metal particles, and a preparation method and application thereof.

The aim of the application is achieved by the following technical scheme.

The inventor discovers that the silicon hydroxyl groups on the outer surface of the SBA molecular sieve are subjected to passivation treatment by using a passivating agent, the desilication reaction of the outer surface of the SBA molecular sieve after the passivation treatment cannot occur under the action of alkaline substances, so that the outer surface of the SBA molecular sieve is protected, then the desilication reaction of the alkaline substances occurs in the pore channels of the molecular sieve, new mesoporous and macroporous pore channels are formed, then metal particles are embedded into the pore channels of the molecular sieve, the size of the nano metal particles is regulated at any time according to the size of the pore channels of the molecular sieve, finally the outer pore channels etched by the alkaline substances are packaged by utilizing secondary crystallization, and therefore, the agglomeration of the nano metal particles cannot occur under the domain limiting effect in the pore channels of the molecular sieve.

In a first aspect, the present application provides a method for preparing an SBA molecular sieve encapsulated with nano-metal particles, comprising the steps of:

s1: passivating the SBA molecular sieve raw powder to obtain passivated SBA molecular sieve powder;

s2: adding an alkaline solution into the SBA molecular sieve powder subjected to the passivation treatment in the step S1 to obtain an SBA molecular sieve powder intermediate;

s3: adding a metal complex solution into the SBA molecular sieve powder intermediate obtained in the step S2 to obtain a product A, wherein metal particles in the metal complex are iron, cobalt or nickel particles;

s4: uniformly mixing an organic template agent, water, a silicon source and acid to form glue, so as to obtain a product B;

s5: and (3) mixing the product A obtained in the step (S3) with the product B obtained in the step (S4), crystallizing, washing, drying and roasting to obtain the target product.

Preferably, step S1 comprises: mixing SBA molecular sieve raw powder with a passivating agent and carrying out passivation treatment under stirring.

Preferably, the passivation treatment conditions are as follows: the temperature is 50-80℃and the time is preferably 2-6 hours.

Preferably, the passivating agent in step S1 comprises the general formula R _a R _b R _c SiR _d An organosilane as shown, wherein R _a 、R _b 、R _c And R is _d The same or different and independently selected from hydrogen, halogen, C ₁ -C ₂₀ Alkyl, C of (2) ₁ -C ₂₀ Alkoxy, C ₃ -C ₂₀ Cycloalkyl, C ₆ -C ₂₀ Aryl and C of (2) ₁ -C ₂₀ Any one of the haloalkyl groups of (2), and R _a 、R _b 、R _c And R is _d Not both hydrogen and/or halogen; preferably, R _d Is halogen, R _a 、R _b And R is _c Not both hydrogen or halogen; further preferably, the passivating agent includes at least one of diphenyldichlorosilane, trimethylchlorosilane, and dimethyldichlorosilane.

Preferably, the mass ratio of the passivating agent to the SBA molecular sieve raw powder is 4:5-1:10.

preferably, the SBA molecular sieve raw powder adopts SBA-15 molecular sieve raw powder or SBA-16 molecular sieve raw powder.

Preferably, step S2 includes: adding alkaline solution into the SBA molecular sieve powder after the passivation treatment in the step S1, and reacting for 1-2 hours at normal temperature to obtain an intermediate of the SBA molecular sieve powder;

preferably, the alkaline solution in the step S2 is sodium hydroxide solution, and the mass fraction is 1% -5%;

preferably, the mass ratio of the alkaline solution to the SBA molecular sieve powder raw powder in the step S2 is 1:20-1:10.

preferably, step S5 includes: and (3) mixing the product A obtained in the step (S3) with the product B obtained in the step (S4), crystallizing at 80-130 ℃ for 24-90 hours, filtering, washing, drying and roasting the crystallized product to obtain a target product, namely the M@SBA molecular sieve.

Preferably, the drying temperature in step S5 is 100-140 ℃.

Preferably, the calcination temperature in step S5 is 400-700℃and the calcination time is 5-8 hours.

Preferably, the mass ratio of the metal complex solution to the SBA molecular sieve powder raw powder is 0.5-1:5.

preferably, the metal complex is a complex of at least one iron source complex selected from potassium ferricyanide, potassium ferrocyanide and ferric nitrate with ethylenediamine tetraacetic acid or a complex of ferric chloride with ethylenediamine tetraacetic acid.

Preferably, step S4 includes: in the step S4, the organic template agent, water, a silicon source and an alkali source are uniformly mixed into glue, and the product B is provided with SiO ₂ ：a H ₂ O：b R：c H ⁺ Wherein R is an organic template, a has a value of 80 to 200, preferably 80 to 120, b has a value of 0.005 to 0.030, and c has a value of 0.10 to 0.25.

Preferably, the organic templating agent in step S4 is an amphiphilic nonionic triblock surfactant F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ )、F108(EO ₁₃₂ PO ₅₀ EO ₁₃₂ ) Hexamethylenetetramine (HMTA), P123 (EO ₂₀ PO ₇₀ EO ₂₀ ) Or P104 (EO) ₂₇ PO ₆₁ EO ₂₇ ) One or a combination of two or more of them. When the SBA molecular sieve raw powder is SBA-15 molecular sieve raw powder, the organic template agent is one or the combination of more than two of P123 and P104; and/or when the SBA molecular sieve raw powder adopts the SBA-16 molecular sieve raw powder, the organic template agent adopts one or the combination of more than two of F127, F108 or HMTA.

Preferably, the silicon source is one or more of white carbon black, tetraethoxysilane, sodium silicate or silica sol, and the acid is one of hydrochloric acid, sulfuric acid or nitric acid.

In a second aspect, the present application provides a nano-metal particle encapsulated SBA molecular sieve prepared by the nano-metal particle encapsulated SBA molecular sieve preparation method.

In the application, nano metal particles in the SBA molecular sieve encapsulated with nano metal particles exist in the SBA molecular sieve in a simple substance form.

Preferably, the specific surface area is 940-1100m ² And/or the size of the nano metal particles can be controlled between 5 and 50 nm.

Preferably, wherein when the metal particle is Fe, XPS of the Fe atom is 706eV; when the metal particles are Co, XPS of Co atoms is 778eV; when the metal particle is Ni, XPS of the Ni atom is 852eV.

In a third aspect, the present application provides the use of the nano-metal particle encapsulated SBA molecular sieve for adsorbing arsenic in water.

The application has the following advantages:

in the preparation method and the prepared molecular sieve, firstly, the silicon hydroxyl outside the molecular sieve is protected by passivation treatment, in particular by adopting a passivating agent, alkaline substances can enter the pore canal of the molecular sieve to etch from the inside without damaging the outer surface of the molecular sieve, two independent pore canal structures of the internal molecular sieve are mutually connected to form new macroporous and mesoporous structures due to the etching of the alkaline substances, the size of the pore canal structure of the molecular sieve is regulated according to the concentration and the quantity of the alkaline substances, then nano metal particles are introduced into the pore canal of the molecular sieve, the nano metal particles cannot exceed the size of the pore canal of the molecular sieve to damage the internal structure of the molecular sieve due to the domain limiting effect of the pore canal structure of the molecular sieve, and finally, the etched pore canal is repackaged by secondary crystallization, so that the nano metal particles are thoroughly packaged in the pore canal of the molecular sieve.

Drawings

FIG. 1 is a HRTEM diagram of the Fe@SBA-16 molecular sieve obtained in example 1;

FIG. 2 is a small angle XRD pattern of the Fe@SBA-16 molecular sieve obtained in example 3;

FIG. 3 is a HRTEM diagram of the Fe@SBA-16 molecular sieve obtained in example 3;

FIG. 4 is an XPS chart of the Fe@SBA-16 molecular sieve obtained in example 3;

FIG. 5 is a HRTEM image of the Fe@SBA-16 molecular sieve obtained in example 4.

Detailed Description

The application is further illustrated below in connection with specific embodiments.

The present application will be more fully understood by those skilled in the art by the following examples, which are not intended to limit the scope of the present application in any way.

In the examples, XRD was carried out by using Philips X-Pert series X-ray diffractometer, HRTEM was carried out by using Rigku model Jem-3010 high resolution transmission electron microscope to measure the regularity of the molecular sieve, XPS was carried out by using Thermo ESCALAB 250spectrometer type X-ray photoelectron spectrometer to measure the bonding condition of metal particles, and BET was carried out by using Micromeritics model ASAP2020 full-automatic specific surface analyzer. The silicon source of the application adopts SiO ₂ The iron source is calculated as Fe, the cobalt source is calculated as Co, the nickel source is calculated as Ni, and the acid is calculated as H ⁺ The solvent is calculated as H ₂ O is calculated, and the organic template agent is calculated as R.

Example 1

Taking 5.0g of SBA-16 molecular sieve raw powder and 2.1g of trimethylchlorosilane, stirring for 2 hours at 50 ℃, uniformly mixing the product with 0.4g of sodium hydroxide solution with mass fraction of 1%, stirring for 1 hour at normal temperature, filtering and washing the product to obtain solution D, and adding 2.0g of potassium ferrocyanide to obtain solution A.

Sequentially adding 1.6g of F127 and 34.5g of deionized water into a reactor, uniformly stirring, adding 24.1mL of 0.1mol/L hydrochloric acid solution, continuously stirring, slowly and dropwise adding 5g of tetraethyl orthosilicate (TEOS), wherein the molar ratio of the obtained reaction mixture is SiO ₂ ：80H ₂ O：0.005R：0.1H ⁺ And (3) mixing the solution B and the solution A, transferring the mixture into a crystallization kettle, heating to 90 ℃, and crystallizing at constant temperature for 40h. After crystallization is completed, cooling to room temperature, separating, washing and drying the reacted mixture at 100 ℃, and finally roasting at 400 ℃ for 8 hours to obtain the Fe@SBA-16 molecular sieve. The specific surface area of the product obtained by BET analysis of the sample is shown in Table 1, the high-power transmission electron microscope image of the sample is shown in FIG. 1, and the obtained sample is used for arsenic adsorption experiments, and the result is shown in Table 1.

Arsenic adsorption test, dispersing 1.0g Fe@SBA-16 molecular sieve in 50mL distilled water, adjusting pH to 7.5, and adding 10mg/L arsenic stock solution to obtain moleculesThe suspension was sieved, and the system pH was adjusted with NaOH and HCl to maintain constant. When the adsorption time is 24 hours, taking a certain amount of suspension, centrifuging for 10 minutes, removing the supernatant, filtering, and sealing for preservation to be tested. In the measurement, the arsenic concentration in the liquid phase was measured by a particle fluorescence photometer, and the detection limit was 0.1. Mu.g/L. After all glassware in the experiment was washed, it was necessary to use 1% HNO ₃ Soaking for more than 12 hours, and cleaning with distilled water.

Example 2

Substantially the same as in example 1 was conducted except that the passivating agent was changed to dimethyldichlorosilane in an amount of 0.56g, the passivating temperature was changed to 60℃for 3 hours, the sodium hydroxide solution was changed to 2% by mass, the Fe source complex was changed to a complex of ferric nitrate and ethylenediamine tetraacetic acid (molar ratio of ferric nitrate to ethylenediamine tetraacetic acid: 1:1), the template agent was changed to F108 in an amount of 4.4g, the water was changed to 54g, the silicon source was changed to white carbon black (silica content: 90% by weight), the amount was changed to 2g, the acid was changed to sulfuric acid, the amount was 44.8mL, the crystallization temperature was changed to 100℃for 50 hours, the drying temperature was changed to 110℃for 500℃for 6 hours, the molar ratio of the remaining components and the synthesis conditions were unchanged, and the resulting reaction mixture was SiO ₂ ：100H ₂ O：0.01R：0.15H ⁺ Sample the specific surface area of the product obtained by BET analysis is shown in table 1, and the obtained sample was used for arsenic adsorption experiments, and the results are shown in table 1.

Example 3

The procedure was essentially as in example 1, except that the passivating agent was changed to diphenyldichlorosilane in an amount of 1.25g, the passivating temperature was changed to 70 ℃, the passivating time was changed to 4 hours, the sodium hydroxide solution mass fraction was changed to 3%, the amount of water was 0.35g, the reaction time was changed to 2 hours, the templating agent was changed to HMTA, the amount of water was 0.15g, the amount of water was changed to 82.5g, the silicon source was changed to silica sol (SW-25, silica content 25 wt%), the amount was 10g, the acid source was changed to nitric acid, the amount was 83mL, the Fe source complex was changed to potassium ferricyanide, the amount was 1.0g, the crystallization temperature was changed to 110 ℃, the crystallization time was changed to 60 hours, the drying temperature was changed to 120 ℃, the firing time was changed to 550 ℃, the firing time was changed to 7 hours, and the remaining groupsThe molar ratio of the obtained reaction mixture is SiO ₂ ：110H ₂ O：0.025R：0.2H ⁺ The specific surface area of the product obtained by BET analysis of the sample is shown in Table 1, the small angle powder XRD diffraction of the sample is shown in FIG. 2, the high power transmission electron microscope is shown in FIG. 3, the state analysis XPS of the iron particles in the molecular sieve is shown in FIG. 4, and the obtained sample is used for arsenic adsorption experiments, and the result is shown in Table 1.

Example 4

Substantially the same procedure as in example 3 was conducted, except that the mass fraction of the sodium hydroxide solution was changed to 4%, and the remaining components and synthesis conditions were unchanged. The high-power transmission electron microscope of the sample is shown in fig. 5, the specific surface area of the product obtained by BET analysis of the sample is shown in table 1, and the obtained sample is used for arsenic adsorption experiments, and the result is shown in table 1.

Example 5

5.0g of SBA-15 molecular sieve raw powder and 2.1g of trimethylchlorosilane are stirred for 2 hours at 50 ℃, then the product is uniformly mixed with 0.4g of sodium hydroxide solution with mass fraction of 1 percent, and stirred for 1 hour at normal temperature, then the product is filtered and washed to obtain solution D, 3.6g of cobalt nitrate and 20ml (1 mol/L) of ethylenediamine tetraacetic acid solution are uniformly mixed and complexed, and then 1.0g of solution is added into the solution D to obtain solution A.

Adding 4.2g P104 and 38.9g deionized water into a reactor in turn, stirring uniformly, adding 60ml of 0.1mol/L hydrochloric acid solution, continuing stirring, slowly and dropwise adding 5g Tetraethoxysilane (TEOS), wherein the molar ratio of the obtained reaction mixture is SiO ₂ ：90H ₂ O：0.03R：0.25H ⁺ And (3) mixing the solution B and the solution A, transferring the mixture into a crystallization kettle, heating to 130 ℃, and crystallizing at constant temperature for 90 hours. After crystallization is completed, cooling to room temperature, separating, washing and drying the reacted mixture at 130 ℃, and finally roasting at 400 ℃ for 8 hours to obtain the Co@SBA-15 molecular sieve. Sample the specific surface area of the product obtained by BET analysis is shown in table 1, and the obtained sample was used for an arsenic adsorption experiment, and the result is shown in table 1.

Example 6

5.0g of SBA-15 molecular sieve raw powder and 2.1g of trimethylchlorosilane are stirred for 2 hours at 50 ℃, then the product is uniformly mixed with 0.4g of sodium hydroxide solution with the mass fraction of 1 percent, and stirred for 1 hour at normal temperature, then the product is filtered and washed to obtain solution D, 3.6g of nickel nitrate and 20ml (1 mol/L) of citric acid solution are uniformly mixed and complexed, and then 1.0g of solution is added into the solution D to obtain solution A.

Adding 4.2g P104 and 38.9g deionized water into a reactor in turn, stirring uniformly, adding 60ml of 0.1mol/L hydrochloric acid solution, continuing stirring, slowly and dropwise adding 5g Tetraethoxysilane (TEOS), wherein the molar ratio of the obtained reaction mixture is SiO ₂ ：90H ₂ O：0.03R：0.25H ⁺ And (3) mixing the solution B and the solution A, transferring the mixture into a crystallization kettle, heating to 130 ℃, and crystallizing at constant temperature for 90 hours. After crystallization is completed, cooling to room temperature, separating, washing and drying the reacted mixture at 130 ℃, and finally roasting at 400 ℃ for 8 hours to obtain the Ni@SBA-15 molecular sieve. Sample the specific surface area of the product obtained by BET analysis is shown in table 1, and the obtained sample was used for an arsenic adsorption experiment, and the result is shown in table 1.

Comparative example 1

Sequentially adding 1.6g of F127 and 34.5g of deionized water into a reactor, uniformly stirring, adding 24.1mL of 0.1mol/L hydrochloric acid solution, adding 2.0g of potassium ferrocyanide, continuously stirring, slowly and dropwise adding 5g of tetraethyl orthosilicate (TEOS), wherein the molar ratio of the obtained reaction mixture is SiO ₂ ：80H ₂ O：0.005R：0.1H ⁺ Transferring the mixed solution into a crystallization kettle, heating to 90 ℃, and crystallizing for 40h at constant temperature. After crystallization is completed, cooling to room temperature, separating, washing and drying the reacted mixture at 100 ℃, roasting at 400 ℃ for 8 hours to obtain the Fe-SBA-16 molecular sieve, placing the Fe-SBA-16 molecular sieve at the bottom of a quartz tube, introducing hydrogen, raising the temperature to 400 ℃ at a heating rate of 3 DEG/min and keeping for 2 hours, and finally obtaining the Fe@SBA-16 molecular sieve, wherein the specific surface area of a product obtained by BET analysis of a sample is shown in Table 1, and the obtained sample is used for arsenic adsorption experiments, and the result is shown in Table 1.

Comparative example 2

1.6g F127 and 34.5g deionized water were added sequentiallyIn a reactor, stirring uniformly, adding 24.1mL of 0.1mol/L hydrochloric acid solution, stirring uniformly, slowly and dropwise adding 5g of Tetraethoxysilane (TEOS), wherein the molar ratio of the obtained reaction mixture is SiO ₂ ：80H ₂ O：0.005R：0.1H ⁺ Transferring the mixed solution into a crystallization kettle, heating to 90 ℃, and crystallizing for 40h at constant temperature. After crystallization is completed, cooling to room temperature, separating, washing and drying the reacted mixture at 100 ℃, roasting at 400 ℃ for 8 hours to obtain SBA-16 molecular sieve raw powder, uniformly mixing SBA-16 molecular sieve, 2.0g of potassium ferrocyanide and 50ml of deionized water, separating, washing and drying the reacted mixture at 100 ℃, roasting at 400 ℃ for 8 hours to obtain the Fe/SBA-16 molecular sieve, analyzing the specific surface area of the product obtained by BET analysis of a sample to obtain the product, and using the obtained sample for arsenic adsorption experiments, wherein the result is shown in the table 1.

TABLE 1 arsenic adsorption experimental results

	Cyclohexane conversion (%)	Specific surface area (m) ² /g)
			Example 1	89.7	982
Example 2	90.5	1011
			Example 3	92.6	1074
Example 4	91.5	1019
			Example 5	89.2	963
Example 6	91.8	1048
			Comparative example 1	36.4	513
Comparative example 2	15.7	258

From comparative examples 1-2 and example 1, table 1 shows that comparative example 1 uses an in situ constraint method to prepare Fe@SBA-16, the process of which is quite simple and convenient, and only H is needed to be adopted finally ₂ The metal is pulled out of the framework in a reduction mode, but the method firstly can forcedly pull out the metal particles in the framework to damage the framework structure of the molecular sieve, and secondly, the metal particles precipitated from the framework are larger than the pore channels, so that the structure of the pore channels is also damaged to a certain extent, the integral structure of the molecular sieve is greatly changed, and the catalyst obtained by the method has lower catalytic performance; in comparative example 2, the post-synthesis strategy is substantially the same as the conventional loading method, and the metal is finally loaded on the surface of the molecular sieve in the form of oxide, which results in the reaction processThe integrity of the metal in the catalyst is lost, thereby affecting the performance of the catalyst.

As can be seen from FIG. 2, the Fe@SBA-16 molecular sieve obtained by the method provided by the application still has a characteristic peak of high regularity of the SBA-16 molecular sieve in small-angle XRD, which indicates that the modification of metal does not damage the structure of the molecular sieve; as can be seen from fig. 3 and fig. 4, the vanadium in the fe@sba-16 molecular sieve obtained by the method provided by the present application exists in the form of simple substance (simple substance Fe2p3/2 orbit of 706.5eV in fig. 4), and the size of the metal particles is obviously seen to be about 5nm in the electron microscope.

From fig. 1, 3 and 5, the size of the nano metal simple substance can be regulated and controlled at any time by changing the amount of alkali, and the metal simple substance is changed from 5-50 nm.

As shown in table 1, the catalytic activity is better and better with the increase of the nano metal particles, but when the nano metal particles are too large, the structure of the molecular sieve is not damaged, but the inter-connectivity of the internal pore channels of the molecular sieve is increased due to the etching of alkali, so that the strength of the molecular sieve is also reduced, and the catalytic performance is reduced to a certain extent.

In summary, the molecular sieve prepared by the method of the application firstly utilizes the passivating agent to protect the silicon hydroxyl outside the molecular sieve, alkaline substances can enter the molecular sieve pore canal to etch from the inside without damaging the outer surface of the molecular sieve, two independent pore canal structures of the internal molecular sieve are mutually connected to form new macroporous and mesoporous structures due to the etching of the alkaline substances, the size of the internal pore canal structure of the molecular sieve is regulated according to the concentration and the quantity of the alkaline substances, then nano metal particles are introduced into the molecular sieve pore canal, the nano metal particles cannot exceed the size of the molecular sieve pore canal to damage the internal structure of the molecular sieve due to the domain-limiting effect of the molecular sieve pore canal structure, and finally the internally etched pore canal is re-packaged by utilizing secondary crystallization, so that the nano metal particles are thoroughly packaged in the molecular sieve pore canal.

Compared with the conventional post-treatment method, the post-treatment method can only load most of nano metal particles on the outer surface of the molecular sieve, and meanwhile, as the nano metal particles are exposed outside and are subjected to high-temperature treatment, the nano metal particles can continuously agglomerate and even run off, so that the catalytic effect is reduced. Compared with the conventional one-step hydrothermal synthesis, the one-step hydrothermal synthesis method is simple, but the nano particles are reduced to a metal simple substance state through reduction, but the reduced nano metal particles are much larger than the pore channels of the molecular sieve, so that the internal structures of the pore channels of a part of the molecular sieve are probably damaged greatly, and the catalytic performance of the catalyst is reduced.

Any numerical value recited in this disclosure includes all values incremented by one unit from the lowest value to the highest value if there is only a two unit interval between any lowest value and any highest value. For example, if the amount of one component, or the value of a process variable such as temperature, pressure, time, etc., is stated to be 50-90, it is meant in this specification that values such as 51-89, 52-88 … …, and 69-71, and 70-71 are specifically recited. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 units may be considered as appropriate. This is only a few examples of the specific designations. In a similar manner, all possible combinations of values between the lowest value and the highest value enumerated are to be considered to be disclosed.

It should be noted that the above-described embodiments are only for explaining the present application and do not constitute any limitation of the present application. The application has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the application as defined in the appended claims, and the application may be modified without departing from the scope and spirit of the application. Although the application is described herein with reference to particular means, materials and embodiments, the application is not intended to be limited to the particulars disclosed herein, as the application extends to all other means and applications which perform the same function.

Claims

1. A method for preparing an SBA molecular sieve encapsulated with nano-metal particles, comprising the steps of:

2. The method for preparing an SBA molecular sieve encapsulated with nano-metal particles according to claim 1, wherein step S1 comprises: mixing SBA molecular sieve raw powder with a passivating agent and carrying out passivation treatment under stirring;

3. The method for preparing a nano-metal particle encapsulated SBA molecular sieve according to claim 2, wherein the passivating agent in step S1 comprises a compound of formula R _a R _b R _c SiR _d An organosilane as shown, wherein R _a 、R _b 、R _c And R is _d The same or different and independently selected from hydrogen, halogen, C ₁ -C ₂₀ Alkyl, C of (2) ₁ -C ₂₀ Alkoxy, C ₃ -C ₂₀ Cycloalkyl, C ₆ -C ₂₀ Aryl and C of (2) ₁ -C ₂₀ Any one of the haloalkyl groups of (2), and R _a 、R _b 、R _c And R is _d Not both hydrogen and/or halogen; preferably, R _d Is halogen, R _a 、R _b And R is _c Not both hydrogen or halogen; further preferably, theThe passivating agent comprises at least one of diphenyl dichlorosilane, trimethylchlorosilane and dimethyldichlorosilane;

preferably, the mass ratio of the passivating agent to the SBA molecular sieve raw powder is 4:5-1:10;

4. A method for preparing an SBA molecular sieve encapsulated with nano-metal particles according to any one of claims 1-3, wherein step S2 comprises: adding alkaline solution into the SBA molecular sieve powder after the passivation treatment in the step S1, and reacting for 1-2 hours at normal temperature to obtain an intermediate of the SBA molecular sieve powder;

5. the method for preparing an SBA molecular sieve encapsulated with nano-metal particles according to any one of claim 1 to 4,

the step S5 comprises the following steps: mixing the product A obtained in the step S3 with the product B obtained in the step S4, crystallizing at 80-130 ℃ for 24-90 hours, filtering, washing, drying and roasting the crystallized product to obtain a target product, and marking the target product as an M@SBA molecular sieve;

preferably, the drying temperature in step S5 is 100-140 ℃;

6. The method for preparing the nano-metal particle encapsulated SBA molecular sieve according to any one of claims 1 to 5, wherein the mass ratio of the metal complex solution to the raw SBA molecular sieve powder is 0.5 to 1:5, a step of;

7. The method for preparing an SBA molecular sieve encapsulated with nano-metal particles according to any one of claims 1 to 6, wherein step S4 comprises: in the step S4, the organic template agent, water, a silicon source and an alkali source are uniformly mixed into glue, and the product B is provided with SiO ₂ ：a H ₂ O：b R：c H ⁺ Wherein R is an organic template agent, a has a value of 80-200, preferably 80-120, b has a value of 0.005-0.030, and c has a value of 0.10-0.25; and/or

The organic template in step S4 is amphiphilic nonionic triblock surfactant F127 (EO ₁₀₆ PO ₇₀ EO ₁₀₆ )、F108(EO ₁₃₂ PO ₅₀ EO ₁₃₂ ) Hexamethylenetetramine (HMTA), P123 (EO ₂₀ PO ₇₀ EO ₂₀ ) Or P104 (EO) ₂₇ PO ₆₁ EO ₂₇ ) One or a combination of two or more of them; and/or when the SBA molecular sieve raw powder is SBA-15 molecular sieve raw powder, the organic template agent is one or the combination of more than two of P123 and P104; and/or when the SBA molecular sieve raw powder adopts the SBA-16 molecular sieve raw powder, the organic template agent adopts one or the combination of more than two of F127, F108 or HMTA.

8. The method for preparing an SBA molecular sieve encapsulated with nano metal particles according to any one of claims 1 to 7, wherein the silicon source is one or more of white carbon black, ethyl orthosilicate, sodium silicate or silica sol, and the acid is one of hydrochloric acid, sulfuric acid or nitric acid.

9. An SBA molecular sieve encapsulated with nano-metal particles, prepared by the method for preparing an SBA molecular sieve encapsulated with nano-metal particles according to any one of claims 1 to 8;

preferably, the specific surface area is 940-1100m ² /g, and/or the nano-metal particle size can be controlled between 5-50 nm;

preferably, wherein when the metal particle is Fe, XPS of the Fe atom is 706eV; when the metal particles are Co, XPS of Co atoms is 778eV; wherein when the metal particle is Ni, XPS of Ni atoms is 852eV.

10. Use of the nano-metal particle encapsulated SBA molecular sieve according to claim 9 for adsorbing arsenic in water.