A nano-silicoaluminophosphate molecular sieve material and a method for synthesizing the same

Abstract

The application discloses a nano aluminophosphate molecular sieve and a synthesis method thereof. The crystal structure of the aluminophosphate molecular sieve is an aluminophosphate-A type crystal structure, the crystal morphology is similar to a cube, and the crystal edge length is 30-110 nm. The crystal outer surface has irregular step lines, and with the decrease of the crystal size, the crystal morphology tends to be a sphere. The synthesis method of the nano aluminophosphate molecular sieve comprises the following steps: (1) preparing initial gel materials; (2) performing crystallization treatment on the gel obtained in the step (1) under crystallization reaction conditions; (3) further separating after the crystallization treatment, and then treating under drying conditions and calcination conditions to obtain the nano aluminophosphate molecular sieve. The synthesis method adopts a novel structure directing agent to synthesize the nano aluminophosphate molecular sieve, and the synthesis process is simple and operable, and the target product can be obtained without harsh conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of porous crystalline material and its preparation method, belong to inorganic porous material synthesis technical field, specifically it is related to a kind of nano silicon aluminum phosphate molecular sieve material and its synthesis method. BACKGROUND

[0002] Porous solid material is widely used in chemical field basic material, including the zeolite molecular sieve that has been realized industrialized use in catalytic field, and phosphaluminate, alumina, silica, organic porous material, MOF material etc..These porous materials are mainly used as catalyst carrier or catalyst, and gas-liquid separation adsorbent, chromatographic packing, electrode etc. functional materials, indispensable key material in chemical reaction and chemical process.

[0003] CN109179449 discloses a synthesis method of silicon aluminum phosphate molecular sieve SAPO-42, comprising the following steps: (1) uniformly mixing the initial reactants: aluminum source, phosphorus source, fluorine source, structure directing agent and silicon source in a mortar, and manually grinding for 20 min; (2) transferring the mixture obtained in step (1) into a high-pressure reaction kettle with polytetrafluoroethylene lining, and performing crystallization at 150-170℃ for 8-24h; (3) naturally cooling to room temperature after the crystallization reaction is completed, sequentially using deionized water and acetone for centrifugal washing until the upper liquid is clear, and drying at 110℃ for 150min to obtain molecular sieve raw powder; (4) calcining the molecular sieve raw powder obtained in step (3) at 550℃ for 4h to obtain silicon aluminum phosphate molecular sieve SAPO-42 powder.

[0004] CN106629759A discloses a synthesis method of AEL-type silicon aluminum phosphate molecular sieve, comprising the following steps: (1) accurately weighing the reaction raw materials aluminum source, phosphorus source, fluorine source, template agent and silicon source according to a specific molar ratio, then uniformly mixing in a mortar and manually grinding for 10-20min; (2) placing the precursor after grinding in a small reaction kettle for activation pretreatment, constant temperature at 80℃ for 8-12h, then adjusting the temperature to 160-200℃, starting crystallization, and crystallization time is 10-20h; (3) naturally cooling to room temperature after the crystallization reaction is completed, sequentially using deionized water and acetone for centrifugal washing until the upper liquid is clear, and drying at 110℃ for 150min to obtain molecular sieve raw powder; (4) calcining the molecular sieve raw powder obtained in step (3) at 550-600℃ for 3-5h to obtain AEL-type silicon aluminum phosphate molecular sieve powder.

[0005] "Multidirectionality of hydrothermal crystallization of P2O5-Al2O3-triethanolamine system" (Petroleum Science and Technology, September 1989, Vol. 5, No. 3) discloses the synthesis of phosphorus aluminum molecular sieve. By changing the preparation conditions of P2O5-Al2O3-triethanolamine (TEA) system, 10 different structure types of crystalline products are obtained. Phosphoric acid, pseudo-boehmite and triethanolamine are used as raw materials, and the synthesis is carried out under the conditions of P2O5 / Al2O3=1.0; TEA / Al2O3=0.1-1.0; H2O / Al2O3=40; gel pH≥4.5; crystallization temperature 150℃. The crystal framework of the material is composed of aluminum, phosphorus and oxygen, and the crystal structure is aluminophosphate-A. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a nano-silicon aluminum phosphate molecular sieve material and a synthesis method thereof. The synthesis method synthesizes nano-silicon aluminum phosphate molecular sieve by using a new type of structure directing agent, and the synthesis process is simple and has strong operability. The target product can be obtained without harsh conditions.

[0007] One of the technical solutions of the present application is to provide a nano-silicon aluminum phosphate molecular sieve. The crystal structure of the silicon aluminum phosphate molecular sieve is aluminophosphate-A type crystal structure, the crystal morphology is approximately cubic, and the crystal edge length is 30-110nm. The crystal outer surface has irregular step lines, and as the crystal size decreases, the crystal morphology tends to be spherical.

[0008] Further, the nano-silicon aluminum phosphate molecular sieve skeleton structure includes four elements of silicon, phosphorus, aluminum and oxygen, and specifically includes silicon-oxygen structure, aluminum-oxygen structure and phosphorus-oxygen structure as basic structural units to further form a networked porous structure.

[0009] Further, the nano-silicon aluminum phosphate molecular sieve includes the XRD diffraction data listed in the following table:

[0010]

[0011] The second technical solution of the present application is to provide a synthesis method of nano-silicon aluminum phosphate molecular sieve. The synthesis method of nano-silicon aluminum phosphate molecular sieve includes the following steps:

[0012] (1) preparing initial gel material: uniformly mixing phosphoric acid, silicon-containing compound, aluminum-containing compound, triethylamine, glycine and water under contact conditions to obtain a gel;

[0013] (2) crystallization treatment: crystallizing the gel obtained in step (1) under crystallization reaction conditions;

[0014] (3) Post-treatment: After the crystallization treatment, the product is further separated, and then treated under drying and calcination conditions to obtain the nano-sized aluminophosphate-silica molecular sieve.

[0015] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, the triethylamine and glycine in step (1) play the role of structure directing agent; during the hydrothermal synthesis, the triethylamine and glycine interact with the silicon-containing compound, the aluminum-containing compound and the phosphoric acid to form the aluminophosphate-A framework structure.

[0016] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, the silicon-containing compound in step (1) can be selected from one or more of white carbon black, silica gel, methyl orthosilicate, ethyl orthosilicate, silica sol and water glass, and is preferably selected from one or more of methyl orthosilicate and ethyl orthosilicate. The silicon-containing compound forms the aluminophosphate-A material framework with silicon-oxygen microstructure in the hydrothermal crystallization reaction.

[0017] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, the aluminum-containing compound can be selected from one or more of aluminum isopropoxide, aluminum butoxide and aluminum sec-butoxide. The aluminum-containing compound forms the aluminophosphate-A material framework with aluminum-oxygen microstructure in the hydrothermal crystallization reaction.

[0018] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, when preparing the initial gel material in step (1), the molar ratio of the various materials is as follows: the molar ratio of phosphoric acid (calculated based on P element), silicon-containing compound (calculated based on SiO2), aluminum-containing compound (calculated based on Al2O3), water, triethylamine and glycine is 2-7P: 0.5-3SiO2: Al2O3: 100-700H2O: 3.5-12.5 triethylamine: 1.5-8.5 glycine, and is preferably 2.5-6P: 1-2.5SiO2: Al2O3: 250-650H2O: 4-10 triethylamine: 2-8 glycine.

[0019] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, the crystallization reaction conditions in step (2) are generally as follows: the crystallization reaction temperature is 150-210°C, and the crystallization reaction time is 40-160h; preferably, the crystallization reaction temperature is 160-200°C, and the crystallization reaction time is 50-150h.

[0020] Preferably, in the synthesis method of the nano-sized aluminophosphate-silica molecular sieve, the separation in step (3) is at least one of any of the existing solid-liquid separation methods, such as filtration and centrifugal separation. Since the particle size of the product is in the nanometer scale, it is difficult to collect, and therefore centrifugal separation is preferably used.

[0021] Preferably, in the synthesis method of the nano-sized aluminophosphate molecular sieve, the drying condition in step (3) is generally as follows: the drying temperature is 100-150°C, and the drying time is 1-10h.

[0022] Preferably, in the synthesis method of the nano-sized aluminophosphate molecular sieve, the calcination condition in step (3) is generally as follows: the calcination is carried out in an oxygen-containing atmosphere, the oxygen content in the oxygen-containing atmosphere is 10%-100%, and the oxygen-containing atmosphere can be at least one of oxygen and air; the calcination temperature is generally 400-600°C; and the calcination time is generally 1-10h.

[0023] The third aspect of the present application provides a nano-sized aluminophosphate molecular sieve obtained by the above synthesis method.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] 1. The present application provides a nano-sized aluminophosphate molecular sieve. The molecular sieve structure belongs to aluminophosphate-A type in crystallographic classification, and the molecular sieve crystal morphology can be approximately regarded as a cube, the edge length of the crystal is 30-110nm, the outer surface of the crystal has irregular step lines, and as the crystal size decreases, the crystal morphology tends to be a sphere; the size of the crystal changes with the change of the synthesis condition, and the change of the synthesis reaction parameters can change the size of the crystal in the above range, and accordingly the adsorption performance will also change. The molecular sieve provided by the present application has good molecular transport capacity, and can be used as an adsorbent or a catalyst carrier, and can be further used after modification treatment, and the modification treatment can adopt any one of the existing modification methods for molecular sieve materials in the art. Specifically, the aluminophosphate molecular sieve can be used for separating and purifying one or several components from a gas phase or a liquid phase raw material, and can also be used as a carrier of a hydrogenation catalyst.

[0026] 2. The application provides a new method for synthesizing nano-sized aluminophosphate-silica molecular sieves, in particular, a method for synthesizing nano-sized aluminophosphate-silica molecular sieves under the action of a new structure directing agent composed of triethylamine and glycine. The method is simple and easy to operate, and has strong operability. In the synthesis method, the structure directing agent used is triethylamine and glycine, which belongs to a composite structure directing agent. During the hydrothermal synthesis process, triethylamine and glycine form a complex structure with a silicon source, an aluminum source and a phosphorus source, and finally form an aluminophosphate-A framework. Moreover, single triethylamine or single glycine cannot act as a structure directing agent for the aluminophosphate-A framework in the synthesis system of the application. The use of triethylamine or glycine alone cannot induce the synthesis of the aluminophosphate-A framework. Moreover, the use of the structure directing agent of the application can reduce the crystal size of the aluminophosphate-silica molecular sieve, and nano-sized aluminophosphate-silica molecular sieves can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 XRD spectrum of the nano-sized aluminophosphate-silica molecular sieve synthesized in Example 1.

[0028] Figure 2 Transmission electron microscope photo of the nano-sized aluminophosphate-silica molecular sieve synthesized in Example 1. DETAILED DESCRIPTION

[0029] The technical solutions and implementation technical effects of the application are further illustrated below in combination with examples, comparative examples and the drawings, but are not limited to the following examples.

[0030] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and should be understood as including values approximately near to the stated values. For ranges of values, the endpoints of the ranges are combined with the individual points to form new ranges of values that are not specifically disclosed.

[0031] In the present text, percentages, percentage contents are by mass, unless otherwise explicitly stated.

[0032] In the present text, the phase structure of the aluminophosphate-silica molecular sieve is characterized by X-ray diffraction, and is tested by using a Japan Rigaku D / max2500 type X-ray diffractometer, a Cu target, a Kα radiation source, a graphite monochromator, a tube voltage of 40 kV, a tube current of 80 mA, a scanning range of 5°-40°, a step size of 0.1° and a scanning speed of 1 ° / min.

[0033] In the present text, the pore structure of the silicoaluminophosphate molecular sieve is measured by N2 adsorption-desorption, using an ASAP 2420 physical adsorption instrument from Micromeritics, USA. Before measurement, the sample is treated in vacuum at 300°C for more than 4 h. The total specific surface area and other parameters are calculated according to the BET isotherm equation.

[0034] In the present text, the microstructure of the silicoaluminophosphate molecular sieve is characterized by high-resolution electron microscopy. The sample morphology is observed and electron diffraction analysis is performed using a JEM-2100 LaB6 high-resolution transmission electron microscope from JEOL, Japan. The images and electron diffraction spectra are collected using a Gatan 832 CCD camera, USA.

[0035] Example 1

[0036] 7.5 g of phosphoric acid, 9 g of aluminum isopropoxide, 11.8 g of triethylamine, 8 g of glycine are added to 150 g of distilled water, then 7 g of tetraethyl orthosilicate is added, mixed uniformly, and then treated at 180°C for 120 h; the liquid-solid product obtained is then collected by centrifugation at a centrifugal rate of 10,000 rpm for 1 h; then placed in an oven at 110°C for drying for 12 h, and finally calcined in air at 550°C for 5 h. The sample obtained is numbered A1.

[0037] Example 2

[0038] 5.4 g of phosphoric acid, 9 g of aluminum isopropoxide, 9 g of triethylamine, 3.5 g of glycine are added to 100 g of distilled water, then 4.6 g of tetraethyl orthosilicate is added, mixed uniformly, and then treated at 160°C for 50 h; the liquid-solid product obtained is then collected by centrifugation at a centrifugal rate of 10,000 rpm for 1 h; then placed in an oven at 110°C for drying for 12 h, and finally calcined in air at 550°C for 5 h. The sample obtained is numbered A2.

[0039] Example 3

[0040] 12.3 g of phosphoric acid, 9 g of aluminum isopropoxide, 22 g of triethylamine, 13 g of glycine are added to 255 g of distilled water, then 11 g of tetraethyl orthosilicate is added, mixed uniformly, and then treated at 180°C for 150 h; the liquid-solid product obtained is then collected by centrifugation at a centrifugal rate of 10,000 rpm for 1 h; then placed in an oven at 110°C for drying for 12 h, and finally calcined in air at 550°C for 5 h. The sample obtained is numbered A3.

[0041] Example 4

[0042] Example 1

[0043] Example 2

[0044] Example 3

[0045] Comparative Example 1

[0046] Comparative Example 2

[0047] Comparative Example 3

[0048] Comparative Example 4

[0049] Comparative Example 5

[0050] Example 4 7.5 g of phosphoric acid, 0.8 g of triethylamine, 1 g of glycine, 9 g of aluminum isopropoxide were added to 150 g of distilled water, and then 7 g of tetraethyl orthosilicate was added, mixed well, and then treated at 180°C for 120 h. The liquid-solid product obtained was then collected by centrifugation at a rate of 10,000 rpm for 1 h. Then, it was dried in an oven at 110°C for 12 h, and finally calcined in air at 550°C for 5 h. The sample obtained was numbered A8, and the product obtained was amorphous, and no silico-aluminum phosphate molecular sieve was synthesized.

[0051] Comparative Example 4

[0052] 7.5 g of phosphoric acid, 50 g of triethylamine, 50 g of glycine, 9 g of aluminum isopropoxide were added to 150 g of distilled water, and then 7 g of tetraethyl orthosilicate was added, mixed well, and then treated at 180°C for 120 h. The liquid-solid product obtained was then collected by centrifugation at a rate of 10,000 rpm for 1 h. Then, it was dried in an oven at 110°C for 12 h, and finally calcined in air at 550°C for 5 h. The sample obtained was numbered A9, and the product obtained was amorphous, and no silico-aluminum phosphate molecular sieve was synthesized.

[0053] Table 1. Physico-chemical properties of the samples of the examples and comparative examples

[0054] Note: In the present application, the crystallinity of the sample in Example 1 is defined as 100%, specifically, the height of the peak with the strongest diffraction intensity in the XRD spectrum of the sample in Example 1 is defined as 100%. The crystallinity of all other samples is obtained by comparing the height of the peak with the strongest diffraction intensity in the XRD spectrum of the sample to be compared with the sample in Example 1.

Claims

1. A nano-aluminophosphate-silica molecular sieve, wherein the crystal structure of the aluminophosphate-silica molecular sieve is an aluminophosphate-A type crystal structure, the crystal morphology is approximately a cube, and the crystal edge length is 30-110 nm; and the crystal outer surface has irregular step patterns, and the crystal morphology tends to be a sphere as the crystal size decreases.

2. The nanosilicoaluminophosphate molecular sieve according to claim 1, characterized by: The framework structure of the aluminophosphate-silica molecular sieve comprises four elements of silicon, phosphorus, aluminum and oxygen, and the basic structural units are formed by a silicon-oxygen structure, an aluminum-oxygen structure and a phosphorus-oxygen structure, and further form a network porous structure.

3. A synthesis method of a nano-aluminophosphate-silica molecular sieve, comprising the following steps: (1) preparing an initial gel material: uniformly mixing phosphoric acid, a silicon-containing compound, an aluminum-containing compound, triethylamine, glycine and water under a contact condition to obtain a gel; (2) crystallization treatment: performing crystallization treatment on the gel obtained in step (1) under a crystallization reaction condition; (3) post-treatment: further separating after the crystallization treatment is completed, and then treating under a drying condition and a calcination condition to obtain the nano-aluminophosphate-silica molecular sieve; The triethylamine and the glycine in step (1) play a role of a structure directing agent; during the hydrothermal synthesis process, the triethylamine and the glycine interact with the silicon-containing compound, the aluminum-containing compound and the phosphoric acid to form an aluminophosphate-A framework structure.

4. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: The silicon-containing compound in step (1) is selected from one or more of white carbon black, silica gel, methyl orthosilicate, ethyl orthosilicate, silica sol and water glass.

5. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: The silicon-containing compound in step (1) is selected from one or more of methyl orthosilicate and ethyl orthosilicate.

6. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: The aluminum-containing compound is selected from one or more of aluminum isopropoxide, aluminum butoxide and aluminum sec-butoxide.

7. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: When the initial gel material is prepared in step (1), the molar ratio of the various materials is as follows: phosphoric acid is calculated based on P element, the silicon-containing compound is calculated based on SiO2, the aluminum-containing compound is calculated based on Al2O3, water, triethylamine and glycine, and the molar ratio is 2-7P:0.5-3SiO2:Al2O3:100-700H2O:3.5-12.5 triethylamine:1.5-8.5 glycine.

8. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: When the initial gel material is prepared in step (1), the molar ratio of the various materials is as follows: phosphoric acid is calculated based on P element, the silicon-containing compound is calculated based on SiO2, the aluminum-containing compound is calculated based on Al2O3, water, triethylamine and glycine, and the molar ratio is 2.5-6P:1-2.5SiO2:Al2O3:250-650H2O:4-10 triethylamine:2-8 glycine.

9. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: The crystallization reaction condition in step (2) is that the crystallization reaction temperature is 150-210°C, and the crystallization reaction time is 40-160 h.

10. The method of synthesizing nanosilicoaluminophosphate molecular sieve according to claim 3, characterized in that: The crystallization reaction condition in step (2) is that the crystallization reaction temperature is 160-200°C, and the crystallization reaction time is 50-150 h.

11. The method of synthesizing nanosilicoaluminophosphatic molecular sieves according to claim 3, characterized in that: The drying condition in step (3) is that the drying temperature is 100-150°C, and the drying time is 1-10 h.

12. The method of synthesizing nanosilicoaluminophosphates molecular sieves according to claim 3, characterized in that: The calcining conditions in step (3) are as follows: the calcining is carried out in an oxygen-containing atmosphere, the oxygen volume content in the oxygen-containing atmosphere is 10% to 100%, the oxygen-containing atmosphere is at least one of oxygen and air; the calcining temperature is 400 to 600 ℃; and the calcining time is 1 to 10 h.

13. A nano-silicoaluminophosphate molecular sieve obtained by the synthesis method according to any one of claims 3 to 12.

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