CN102101677B - Preparation method of AlPO4-9 aluminum phosphate molecular sieve - Google Patents

Abstract

The invention relates to a method for preparing a AlPO4-9 aluminium phosphate molecular sieve, and a crystal structure. The chemical formula is [C2H7Al5.50NO25P6]. Piperazine is taken as a template, water and glycol are mixed to serve as a solvent, and the molecular sieve is synthesized by a hydrothermal process. The molecular sieve comprises three basic structural units, has one-dimensional curved octatomic ring pores in the [101] direction, has high stability and is widely applied to catalysis, ion exchange, gas separation and the like.

Description

Preparation method of AlPO4-9 aluminum phosphate molecular sieve

technical field

The invention relates to the preparation and structure of AlPO ₄ -9 aluminum phosphate molecular sieve. Using piperazine as template and water and ethylene glycol as solvent, AlPO ₄ -9 aluminum phosphate molecular sieve with high stability is synthesized by hydrothermal method, and there is a [101] direction in the structure of AlPO ₄ -9 Dimensional curved eight-membered ring channels.

technical background

The synthesis of aluminum phosphate molecular sieves with a microporous structure began with the report of Wilson et al. in 1982, and templates must be involved in all synthesis systems. This type of material has a rich and diverse structure, and most of them have open pore systems, which can increase the diffusion rate of molecules in chemical reactions, so they have potential application prospects in catalysis, ion exchange, and gas separation.

The first report on the synthesis of AlPO ₄ -9 also appeared in 1982 (author STWilson, S.Oak, BMLok, U.S. Patent 4310440), using 1,4-diazabicyclo[2.2.2]octane (DABCO ) as template for hydrothermal synthesis of AlPO ₄ -9. However, only its X-ray diffraction pattern (XRD) is given in the patent, and its crystal structure has not been reported so far. Therefore, the present invention applies for a new synthesis method of AlPO ₄ -9 aluminum phosphate molecular sieve and obtains a large single crystal, and analyzes the crystal structure. Compared with most aluminum phosphate microporous crystals, AlPO ₄ -9 has higher thermal stability, so this kind of material will have a wide range of applications in adsorption, catalysis, ion exchange, gas separation, etc.

Contents of the invention

The purpose of the present invention is to provide a preparation method of microporous aluminum phosphate molecular sieve AlPO ₄ -9.

The molecular sieve of the present invention is synthesized through the following steps: first take a certain amount of low-concentration piperazine solution, then add non-aqueous solvent ethylene glycol, aluminum source, phosphorus source and mix uniformly to make a synthetic colloid, and then the synthetic colloid is heated at 170- Hydrothermal crystallization at 180°C and autogenous pressure for 5-9 days, finally collected, washed and dried at room temperature to obtain the product.

In the method of the invention, the phosphorus source is phosphoric acid, the aluminum source is aluminum isopropoxide or pseudo-boehmite, the solvent is a mixed solvent of water and ethylene glycol, and the organic template is piperazine.

In the present invention, the phosphorus source is calculated by P ₂ O ₅ , the aluminum source is calculated by Al ₂ O ₃ , the solvent is calculated by a mixture of ethylene glycol (EG) and H ₂ O, and the organic template piperazine is represented by R. Then the reaction materials synthesize colloids according to the following molar ratio: 0.78R:Al ₂ O ₃ :P ₂ O ₅ :4.3EG:100H ₂ O.

α＝γ＝90°，β＝119.87(4)°。该晶体的不对称结构单元(图3)中包含44个非氢原子。特点之一为分子图中存在两种不同配位的铝原子，其中Al1是六配位的，Al1到A16是四配位的，整个结构是由严格交替的PO₄和AlO₄(AlO₆)共用氧原子连接而成；另一个中分子图中存在两个自由水分子和一个哌嗪分子。The crystal synthesized by the present invention is a polyhedron-like crystal (FIG. 1), and its powder XRD is completely consistent with the XRD of single crystal fitting (FIG. 2). According to the results of single crystal analysis and elemental analysis, its chemical formula is C ₂ H ₇ Al _5.50 N O ₂₅ P ₆ , which belongs to the monoclinic crystal system, the space group is C2/c, and the unit cell parameters are

α=γ=90°, β=119.87(4)°. The crystal contains 44 non-hydrogen atoms in the asymmetric structural unit (Fig. 3). One of the characteristics is that there are two differently coordinated aluminum atoms in the molecular diagram, among which Al1 is six-coordinated, Al1 to A16 are four-coordinated, and the entire structure is composed of strictly alternating PO ₄ and AlO ₄ (AlO ₆ ) Shared oxygen atoms are connected; there are two free water molecules and a piperazine molecule in the other molecular diagram.

The crystal structure of the molecular sieve of the present invention contains three basic structural units: unit I (4 ⁵ 6 ⁴ 8 ⁵ cage is composed of 5 four-membered rings, 4 six-membered rings and 5 eight-membered rings); unit II (6 ¹² The cage is composed of 12 six-membered rings) and unit III (4 ⁴ 6 ² 8 ² cages are formed by connecting 2 six-membered rings and 4 four-membered rings, that is, double eight-membered rings). First, unit I and unit III are connected strictly alternately along the a-axis to form a chain, and adjacent units I along the b-axis are connected end-to-end to form a chain, and these chains are connected to each other on the plane perpendicular to the c-axis to form a layer. Between units I and II are connected to each other through a shared six-membered ring to form the entire three-dimensional structure of AlPO ₄ -9. Among them, there is a curved eight-membered ring channel in the [101] direction (Figure 4), which is formed by the alternate connection of unit I and unit III.

The product obtained in the present invention is an open skeleton aluminum phosphate microporous crystal with a one-dimensional curved eight-membered ring channel, and the skeleton structure does not completely collapse at 550°C for 2 hours (Fig. 2), so it has higher thermal stability. Generate new wide-ranging applications.

Description of drawings

Figure 1 is a scanning electron microscope image of the molecular sieve.

Figure 2 shows the single crystal fitting XRD (top), powder XRD (middle), and XRD after calcination at 550°C for 2 hours (bottom) of the molecular sieve.

Figure 3 is a diagram of the asymmetric structural unit of the molecular sieve.

Figure 4 is the channel diagram of the eight-membered ring along the [101] direction of the molecular sieve.

Detailed ways

Example 1, at first prepare the piperazine solution of 0.434 mol/liter. In a 100 ml beaker, mix 2 ml of ethylene glycol with 15 ml of piperazine solution, stir for 10 minutes, add 1.702 g of aluminum isopropoxide, stir for another 30 minutes, then add 1.14 ml of 85% _H3 dropwise PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 180°C for 5 days to obtain colorless transparent crystals, washed with distilled water and suction filtered , to obtain the target product after drying at room temperature. The product was characterized using the following instruments and methods:

1. Use the SHIMADZU SS-550 scanning electron microscope to obtain the morphology of the crystal (Figure 1)

2. Use a Bruker-D8 type X-ray diffractometer to measure the X-ray powder diffraction spectrum of the product to obtain the XRD pattern of the product (Fig. 2).

1.75°≤θ≤27.96°。属于单斜晶系，空间群C2/c，

α＝γ＝90°，β＝119.87(4)°，

Z＝8，T＝113(2)K，R(F)＝0.0773，wR(F²)＝0.1805。单晶数据及参数见表1、2，晶体结构见图4，(使用SHELXTL 97、Diamond 2软件绘制)。由单晶衍射数据拟合的XRD图与粉末XRD图相符(图2)。3. Select a crystal with a size of 0.20×0.18× ^0.12mm3 for single crystal structure analysis. The single crystal diffraction data is collected on a BrukerSmart 1000 CCD diffractometer, and the Mokα ray is monochromated with a graphite monochromator

1.75°≤θ≤27.96°. Belongs to the monoclinic crystal system, space group C2/c,

α=γ=90°, β=119.87(4)°,

Z=8, T=113(2)K, R(F)=0.0773, wR(F ² )=0.1805. The single crystal data and parameters are shown in Tables 1 and 2, and the crystal structure is shown in Figure 4 (drawn using SHELXTL 97 and Diamond 2 software). The XRD pattern fitted from the single crystal diffraction data is consistent with the powder XRD pattern (Fig. 2).

Table 1 Crystal data table of AlPO ₄ -9

和键角(°)Table 2 Some bond lengths in AlPO ₄ -9 crystal structure

and bond angle (°)

Symmetry transformations used to generate equivalent atoms:

#1 -x, -y, -z; #2 -x, y, -z+1/2; #3 -x, -y+1, -z; #4 -x+1/2, y+1 /2, -z+1/2;

#5 -x+1/2, -y+1/2, -z; #6 -x+1/2, y-1/2, -z+1/2; #7 -x+2, y, -z+3/2;

#8 -x+1/2, -y+1/2, -z+1.

Example 2, at first prepare the piperazine solution of 0.434 mol/liter. In a 100 ml beaker, mix 2 ml of ethylene glycol with 15 ml of piperazine solution, stir for 10 minutes, add 1.702 g of aluminum isopropoxide, stir for another 30 minutes, then add 1.14 ml of 85% _H3 dropwise PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 170°C for 5 days to obtain colorless transparent crystals, washed with distilled water and filtered with suction , to obtain the target product after drying at room temperature. Every characterization and result are identical with example 1.

Example 3, at first prepare the piperazine solution of 0.451 mol/liter. In a 100 ml beaker, mix 2 ml of ethylene glycol with 15 ml of piperazine solution, stir for 10 minutes, add 1.702 g of aluminum isopropoxide, stir for another 30 minutes, then add 1.14 ml of 85% _H3 dropwise PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 180°C for 9 days to obtain colorless transparent crystals, washed with distilled water and suction filtered , to obtain the target product after drying at room temperature. Every characterization and result are identical with example 1.

Example 4, at first prepare the piperazine solution of 0.451 mol/liter. In a 100 ml beaker, mix 2 ml of ethylene glycol with 15 ml of piperazine solution, stir for 10 minutes, add 1.702 g of aluminum isopropoxide, stir for another 30 minutes, then add 1.14 ml of 85% _H3 dropwise PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 170°C for 9 days to obtain colorless transparent crystals, washed with distilled water and suction filtered , to obtain the target product after drying at room temperature. Every characterization and result are identical with example 1.

Example 5, at first prepare the piperazine solution of 0.451 mol/liter. In a 100 ml beaker, mix 2 ml of ethylene glycol and 15 ml of piperazine solution evenly, stir for 10 minutes, add 1.303 g of pseudo-boehmite, stir for another 30 minutes, and then add 1.14 ml of 85% H ₃ PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, and then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 180°C for 9 days to obtain colorless transparent crystals, washed with distilled water and pumped filtered, and dried at room temperature to obtain the target product. Every characterization and result are identical with example 1.

Example 6, at first prepare the piperazine solution of 0.434 mol/liter. In a 100 ml beaker, mix 2 ml of 7-diol and 15 ml of piperazine solution, stir for 10 minutes, add 1.303 g of pseudo-boehmite, stir for another 30 minutes, then add 1.14 ml of 85% H ₃ PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, and then transferred to a stainless steel reactor with a polytetrafluoroethylene liner, crystallized at 180°C for 9 days to obtain colorless transparent crystals, washed with distilled water and pumped filtered, and dried at room temperature to obtain the target product. Every characterization and result are identical with example 1.

Example 7, at first prepare the piperazine solution of 0.451 mol/liter. In a 100 ml beaker, mix 4 ml of ethylene glycol and 15 ml of piperazine solution evenly, stir for 10 minutes, add 1.303 g of pseudoboehmite, stir for another 30 minutes, then add 1.14 ml of 85% H ₃ PO ₄ , after stirring for 1 hour, a homogeneous mixture was formed, and then transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, and crystallized at 170°C for 9 days to obtain colorless transparent crystals, which were washed with distilled water and pumped. filtered, and dried at room temperature to obtain the target product. Every characterization and result are identical with example 1.

Claims (3)

1. A kind of AlPO _4-9 aluminum phosphate molecular sieve, it is characterized in that synthetic method comprises the steps: first get the organic template agent solution that concentration is 0.434-0.451 mol/liter, then add non-aqueous solvent, aluminum source, phosphorus source and mix uniformly The synthetic colloid is made, and then the synthetic colloid is hydrothermally crystallized at 170-180°C and autogenous pressure for 5-9 days, and finally collected, washed and dried at room temperature to obtain the product; the phosphorus source is phosphoric acid, The aluminum source is aluminum isopropoxide or pseudoboehmite, the solvent is a mixed solvent of water and ethylene glycol, and the organic template is _piperazine ; the phosphorus source is calculated as _P2O5 , and the aluminum source In terms of Al ₂ O ₃ , the solvent is in terms of a mixture of ethylene glycol (EG) and H ₂ O, and the organic template piperazine is represented by R, then the reaction materials are synthesized into a colloid according to the following molar ratio: 0.78R: _{P 2} O ₅ : Al ₂ O ₃ : 4.3EG: 100H ₂ O. 2. According to the AlPO ₄ -9 aluminum phosphate molecular sieve described in claim 1, its chemical composition is expressed as C ₂ H ₇ Al _5.50 NO ₂₅ P ₆ , belongs to the monoclinic system, the space group is C2/c, and the unit cell parameter is

α=γ=90°, β=119.87(4)°. 3. according to the described AlPO _4-9 aluminum phosphate molecular sieve of claim 1, it is characterized in that this structure contains three basic structural unit 4 ⁵ 6 ⁴ 8 ⁵ cages, 6 ¹² cages and 4 ⁴ 6 ² 8 ² cages, at first The 4 ⁵ 6 ⁴ 8 ⁵ cages and the 4 ⁴ 6 ² 8 ² cages are strictly alternately connected along the a-axis direction to form a chain, and the adjacent 4 ⁵ 6 ⁴ 8 ⁵ cages are also connected end-to-end along the b-axis to form a chain, and these chains The layers are connected to each other on the plane perpendicular to the c-axis, and the layers are connected to each other through the 4 ⁵ 6 ⁴ 8 ⁵ cage and the 6 ¹² cage through the shared six-membered ring to form the entire three-dimensional structure of AlPO ₄ -9, in which [101] There is a curved eight-membered ring channel in the direction, which is formed by alternate connections of 4 ⁵ 6 ⁴ 8 ⁵ cages and 4 ⁴ 6 ² 8 ² cages.

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