CN108975345B - A kind of two-dimensional ultrathin SAPO-34 molecular sieve sheet material and preparation method thereof - Google Patents

Abstract

A two-dimensional ultra-thin SAPO-34 molecular sieve sheet material, the thickness is 1-25 nanometers, the crystal structure is SAPO-34 molecular sieve, and the silicon/aluminum atomic ratio is 0.05-0.3. The technical point of the present invention lies in: using cheap and easily available aluminum phosphate, silicon source and organic amine as reactants, peeling off the layered precursor by chemical method, and then gas phase crystallization to prepare a two-dimensional ultra-thin SAPO-34 molecular sieve material . The two-dimensional ultra-thin SAPO-34 molecular sieve material has a huge external surface area, the content of silicon can be adjusted within a certain range, and the method is universal. The material has many advantages and can be mass-produced by industrialization. The inventive method has less template agent dosage, is suitable for industrial mass production, has low cost, and basically has no environmental pollution. The invention discloses its preparation method.

Description

A kind of two-dimensional ultrathin SAPO-34 molecular sieve sheet material and preparation method thereof

Technical field:

The invention relates to a two-dimensional ultrathin SAPO-34 molecular sieve sheet material and a preparation method thereof.

Background technique:

SAPO-34 is the most eye-catching type of SAPO series molecular sieves (aluminosilicate molecular sieves). Due to its unique CHA-type molecular sieve channel structure, suitable adjustable acidity, good thermal stability and hydrothermal stability, it is widely used in many The reaction showed excellent catalytic activity. Among them, the C2-C4 product in the catalytic conversion of methanol to light olefins (MTO) has high selectivity and is recognized as the best catalyst for the MTO reaction. In addition, it also exhibits excellent catalytic performance in catalytic selective reduction of NOx and purification of automobile exhaust gas. At the same time, it was found that SAPO-34 molecular sieves with different morphologies and structures have great differences in their catalytic performance.

Therefore, the synthesis and properties of SAPO-34 molecular sieves with different morphologies have attracted extensive attention. A large number of literature reports and patent applications related to the synthesis of SAPO-34 molecular sieves are continuously published and published. For example, literature reports include: In 2018, an article published by the research group of Yu Jihong from Jilin University in Chemical Communications in the United Kingdom reported the synthesis of SAPO-34 molecular sieves with hierarchical pore structure and their application in MTO reaction. Dalian Compound In an article published in Chemical Communications in the United Kingdom, the research group of Liu Zhongmin of the Institute reported the synthesis of SAPO-34 molecular sieve with core-shell structure and its application in the MTO reaction. An article published on andmesoporous materials reported a SAPO-34 molecular sieve material formed by stacking a sheet-like structure; the patents for the sheet-like structure of SAPO-34 molecular sieve are: In 2013, a sheet-like nano-SAPO- 34 molecular sieve, preparation method and application thereof (application number: 201310670278.5), in 2014, a synthesis method of sheet-like nano-SAPO-34 molecular sieve (application number: 201410557543.3), in 2015, a nano-sheet self-assembly SAPO-34 molecular sieve and preparation method thereof (application number: 201510061554.7), in 2016, a solid-phase synthesis method of sheet-like SAPO-34 (application number: 201610371179.0), in 2016, a preparation method of sheet-like SAPO-34 molecular sieve and application (application number: 201610874619.4), in 2017, nanosheet vortex self-assembled SAPO-34 hierarchical porous molecular sieve and its preparation method (application number: 201710111759.0). In these reports, people's research can be mainly attributed to: (1) a new synthesis method of SAPO-34 molecular sieve with hierarchical structure, (2) the synthesis of sheet-like self-assembled SAPO-34 molecular sieve, (3) the synthesis of SAPO-34 molecular sieve application.

Summarizing the results of the literature on the preparation of SAPO-34 molecular sieves over the years, it can be found that there is no method to prepare a two-dimensional ultra-thin SAPO-34 molecular sieve sheet material with adjustable Si-Al ratio and thickness below 25 nm.

Invention content:

The technical scheme of the present invention is as follows:

A two-dimensional ultra-thin SAPO-34 molecular sieve sheet material has a thickness of 1-25 nanometers, a crystal structure of SAPO-34 molecular sieve, and a silicon/aluminum atomic ratio of 0.05-0.3.

A method for preparing the above-mentioned two-dimensional ultrathin SAPO-34 molecular sieve sheet material, which comprises the following steps:

Step 1. Preparation of aluminum phosphate nanoroll powder material with layered structure. The described preparation method is based on literature (Chem. Commun., 2009, 3443-3445). The structure of the aluminum phosphate nano-roll is similar in appearance to rolled paper, with an inner diameter of about 80 nanometers, a thickness of about 120 nanometers, and a height of about 100 nanometers to 120 nanometers. The microstructure of aluminum phosphate nanorolls is a layered structure with inorganic-organic composite, and the interlayer spacing is about 2.9 nanometers.

The synthesis method of aluminum phosphate nanorolls is as follows: at 50 °C, 20 ml of an ethanol solution containing 4.165 g of dodecylamine and 0.500 g of hexadecylamine is slowly added to a solution containing 1.690 g of AlCl ₃ 6H ₂ O and 1.404 g of NaH ₂ In the solution of PO ₄ ·2H ₂ O, a white suspension was obtained, which was transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, and heated at 120° C. for 48 hours. After cooling, the white precipitate was filtered off, washed several times with water and ethanol, and dried in vacuo at 40°C overnight.

Step 2. Add the alcohol solution of silicon source to the aluminum phosphate nano-roll powder material in step 1, the amount of silicon source added is 10% to 50% of the mass of the aluminum phosphate nano-roll, stir at room temperature to form a paste, and then leave it for 24 hours .

Step 3. To the paste obtained in step 2, add tetraethylammonium hydroxide solution in an amount of 20% to 40% of the mass of the aluminum phosphate nano-roll, stir at room temperature to form a paste, and then stand for 24 hours.

Step 4. Add water, tetraethylammonium hydroxide solution and triethylamine to the polytetrafluoroethylene lining of the hydrothermal kettle, and the addition amounts of the three are successively 20% to 40% of the mass of the aluminum phosphate nano-roll, 40～80% and 80%-200%.

Step 5. Transfer the paste obtained in step 3 to the polytetrafluoroethylene lining in step 4, seal, and heat with water at 160-200° C. for 20-72 hours. After that, it was naturally cooled to room temperature, and the precipitate was obtained by filtration. The precipitate was washed with water and absolute ethanol for several times, and it was preferably dried at 60° C. for 24 hours to obtain a dry white powder.

Step 6. Put the white powder obtained in Step 5 into a muffle furnace, and in an air atmosphere, raise the temperature from room temperature to 550° C., preferably for 5 hours. After that, it was naturally cooled to room temperature to obtain a white sample powder.

In the above preparation method, the silicon source described in step 2 is preferably tetraethyl orthosilicate, tetrapropyl orthosilicate or tetrabutyl orthosilicate.

In the above preparation method, the alcohols described in step 2 include methanol or ethanol.

In the above-mentioned preparation method, the tetraethylammonium hydroxide solution is a 25% aqueous solution.

The technical point of the present invention lies in: using cheap and easily available aluminum phosphate, silicon source and organic amine as reactants, peeling off the layered precursor by chemical method, and then gas phase crystallization to prepare a two-dimensional ultra-thin SAPO-34 molecular sieve material . The two-dimensional ultrathin SAPO-34 molecular sieve material has a huge external surface area, the content of silicon can be adjusted within a certain range, and the method is universal. The material has many advantages and can be mass-produced by industrialization. The inventive method has less template agent dosage, is suitable for industrial mass production, has low cost, and basically has no environmental pollution. The invention discloses its preparation method.

Description of drawings:

FIG. 1 is an X-ray powder diffraction pattern of the flake SAPO-34 molecular sieve material prepared in Example 1 of the present invention.

2 is a TEM transmission electron microscope photograph of the flake SAP5-34 molecular sieve material prepared in Example 1 of the present invention.

3 is an X-ray powder diffraction pattern of the flake SAPO-34 molecular sieve material prepared in Example 2 of the present invention.

4 is a TEM transmission electron microscope photograph of the flake SAPO-34 molecular sieve material prepared in Example 2 of the present invention.

5 is a TEM transmission electron microscope photograph of the flake SAPO-34 molecular sieve material prepared in Example 3 of the present invention.

6 is a TEM transmission electron microscope photograph of the flake SAPO-34 molecular sieve material prepared in Example 4 of the present invention.

7 is a TEM transmission electron microscope photograph of the flake SAPO-34 molecular sieve material prepared in Example 5 of the present invention.

8 is a TEM transmission electron microscope photograph of the flake SAPO-34 molecular sieve material prepared in Example 6 of the present invention.

Detailed ways:

The present invention is further described below in conjunction with the examples.

Example 1:

Take 0.500 g of aluminum phosphate nano-roll powder, add 0.050 g of tetraethyl orthosilicate and 0.550 g of methanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 0.100 g of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 0.100 g of water, 0.200 g of tetraethylammonium hydroxide (25%) solution and 0.400 g of triethylamine were added. After that, it was heated with water at 160 °C for 72 hours; after that, it was cooled to room temperature naturally, and the precipitate was obtained by filtration, washed with water and absolute ethanol for many times, and dried at 60 °C for 24 hours. , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction (see Figure 1), and the morphology of the product detected by TEM electron microscope was a flake with a thickness of 1 nanometer (see Figure 2). The atomic ratio is 0.05.

Example 2:

Take 1.000 grams of aluminum phosphate nano-roll powder, add 0.500 grams of tetraethyl orthosilicate and 0.700 grams of ethanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 0.400 grams of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 0.400 g of water, 0.800 g of tetraethylammonium hydroxide (25%) solution and 2.000 g of triethylamine were added. After that, it was heated with water at 180 °C for 48 hours; after that, it was cooled to room temperature naturally, and the precipitate was obtained by filtration, washed with water and absolute ethanol for many times, and dried at 60 °C for 24 hours. , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction (see Figure 3), and the morphology of the product detected by TEM electron microscope was a flake with a thickness of 4 nanometers (see Figure 4). The atomic ratio is 0.30.

Example 3:

Take 2.000 grams of aluminum phosphate nano-roll powder, add 0.40 grams of tetrapropyl orthosilicate and 2.000 grams of methanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 0.500 grams of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 0.600 g of water, 1.000 g of tetraethylammonium hydroxide (25%) solution and 2.400 g of triethylamine were added. After that, it was heated with water at 200°C for 20 hours; after that, it was cooled to room temperature naturally, filtered to obtain the precipitate, washed with water and absolute ethanol for many times, and dried at 60°C for 24 hours , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction. The morphology of the product was detected by TEM electron microscope as a flake with a thickness of 10 nanometers (see Figure 5). X-ray fluorescence spectrum analysis showed that the silicon/aluminum atomic ratio of the sample was 0.1.

Example 4:

Take 3.000 grams of aluminum phosphate nano-roll powder, add 0.750 grams of tetrabutyl orthosilicate and 2.850 grams of ethanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 0.900 grams of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 1.050 g of water, 1.800 g of tetraethylammonium hydroxide (25%) solution and 4.400 g of triethylamine were added. After that, it was heated with water at 180 °C for 48 hours; after that, it was cooled to room temperature naturally, and the precipitate was obtained by filtration, washed with water and absolute ethanol for many times, and dried at 60 °C for 24 hours. , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction. The morphology of the product was detected by TEM electron microscope as a flake with a thickness of 20 nanometers (see Figure 6). X-ray fluorescence spectrum analysis showed that the silicon/aluminum atomic ratio of the sample was 0.14.

Example 5:

Take 4.000 grams of aluminum phosphate nano-roll powder, add 1.500 grams of tetraethyl orthosilicate and 3.300 grams of methanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 1.300 grams of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 1.100 grams of water, 2.200 grams of tetraethylammonium hydroxide (25%) solution and 3.800 grams of triethylamine were added. After that, it was heated with water at 180 °C for 48 hours; after that, it was cooled to room temperature naturally, and the precipitate was obtained by filtration, washed with water and absolute ethanol for many times, and dried at 60 °C for 24 hours. , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction. The morphology of the product was detected by TEM electron microscope as a flake with a thickness of 25 nanometers (see Figure 7). X-ray fluorescence spectrum analysis showed that the silicon/aluminum atomic ratio of the sample was 0.2.

Example 6:

Take 5.000 grams of aluminum phosphate nano-roll powder, add 0.750 grams of tetraethyl orthosilicate and 5.250 grams of ethanol, stir into a uniform paste at room temperature, and leave it for 24 hours; after that, add 1.400 grams of tetraethylammonium hydroxide (25% ) solution, stirred into a uniform paste, and left for 24 hours; after that, it was transferred to a hydrothermal kettle to which 1.500 grams of water, 2.200 grams of tetraethylammonium hydroxide (25%) solution and 5.500 grams of triethylamine were added. After that, it was heated with water at 180 °C for 48 hours; after that, it was cooled to room temperature naturally, and the precipitate was obtained by filtration, washed with water and absolute ethanol for many times, and dried at 60 °C for 24 hours. , to obtain a dry white powder; then, the obtained white powder was put into a muffle furnace, and the temperature was raised from room temperature to 550° C. under an air atmosphere, and kept for 5 hours. Finally, it was naturally cooled to room temperature to obtain a white sample powder.

The product was identified as SAPO-34 molecular sieve by X-ray powder diffraction. The morphology of the product was detected by TEM electron microscope as a flake with a thickness of 15 nanometers (see Figure 8). X-ray fluorescence spectrum analysis showed that the silicon/aluminum atomic ratio of the sample was 0.22.

Claims (4)

1. A preparation method of a two-dimensional ultrathin SAPO-34 molecular sieve flake material is characterized by comprising the following steps of:

step 1, preparing an aluminum phosphate nano coil powder material with a laminated structure;

step 2, adding an alcoholic solution of a silicon source into the aluminum phosphate nano coil powder material obtained in the step 1, wherein the adding amount of the silicon source is 10-50% of the mass of the aluminum phosphate nano coil, stirring at room temperature to form a paste, and then standing for 24 hours;

step 3, adding tetraethyl ammonium hydroxide solution into the paste obtained in the step 2, wherein the adding amount of tetraethyl ammonium hydroxide solution is 20-40% of the mass of the aluminum phosphate nanocolloid, stirring at room temperature to form a paste, and then standing for 24 hours;

step 4, adding water, tetraethyl ammonium hydroxide solution and triethylamine into a polytetrafluoroethylene lining of the hydrothermal kettle, wherein the adding amount of the water, the tetraethyl ammonium hydroxide solution and the triethylamine is 20-40%, 40-80% and 80-200% of the mass of the aluminum phosphate nanocoil in sequence;

step 5, transferring the paste obtained in the step 3 into the polytetrafluoroethylene lining in the step 4, sealing, and performing hydrothermal treatment at 160-200 ℃ for 20-72 hours; then naturally cooling to room temperature, filtering to obtain a precipitate, washing the precipitate by using water and absolute ethyl alcohol, and drying to obtain white powder;

step 6, putting the white powder obtained in the step 5 into a muffle furnace, heating the white powder to 550 ℃ from room temperature in an air atmosphere, keeping the temperature, and naturally cooling the white powder to room temperature to obtain white sample powder;

the silicon source in the step 2 is tetraethyl orthosilicate, tetrapropyl orthosilicate or tetrabutyl orthosilicate;

the crystal structure of the product obtained by the preparation method is an SAPO-34 molecular sieve, the thickness is 1-25 nanometers, and the atomic ratio of silicon to aluminum is 0.05-0.3.

2. The method for preparing the two-dimensional ultrathin SAPO-34 molecular sieve flake material as claimed in claim 1, wherein the method comprises the following steps: the alcohol in the step 2 is methanol or ethanol.

3. The method for preparing the two-dimensional ultrathin SAPO-34 molecular sieve flake material as claimed in claim 1, wherein the method comprises the following steps: the tetraethyl ammonium hydroxide solution is 25% aqueous solution.

4. The method for preparing the two-dimensional ultrathin SAPO-34 molecular sieve flake material as claimed in claim 1, wherein the method comprises the following steps: the drying temperature in the step 5 is 60 ℃, the drying time is 24 hours, and the temperature in the step 6 is increased from room temperature to 550 ℃ and then is kept for 5 hours.

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