CN104229806A - Method for synthesizing magadiite by adopting catalytic nucleation method - Google Patents

Abstract

The invention discloses a method for synthesizing magadiite by a catalytic nucleation method. The preparation method comprises the following steps: mixing a silicon source, an alkali source, a catalytic nucleating agent and water to obtain a mixture; Source: Alkali source=3~7; Water: Alkali source=20~100; Put the mixture into a closed container under autogenous pressure, crystallize at 110~170°C for 6~72 hours; take out the crystallized product and filter , washing with water until pH = 7-8, and then drying at 60°C-100°C for 4-12 hours to prepare the two-dimensional layered structure material magadiite. Compared with the existing synthesis method without catalytic nucleating agent, the synthesis period is shortened by 12-108 hours, and the synthesis temperature is reduced by 30-40°C. The magadiite can be used as catalyst, adsorbent, pillar material, ion exchange agents, fillers for nanocomposites, etc.

Description

A method for synthesizing magadiite by catalytic nucleation method

technical field

The invention relates to a synthesis method of magadiite, in particular to a method for synthesizing magadiite by a catalytic nucleation method.

Background technique

Magadiite is a two-dimensional layered structure material. Its laminates are composed of negatively charged SiO ₄ tetrahedrons, which have good chemical and thermal stability. There are hydrated sodium ions that can be exchanged between the laminates. These properties promote the application of magadiite as cation exchangers, adsorbents, pillar materials, catalysts, nanocomposite fillers, etc. .

At present, the literature on the synthesis of magadiite mostly focuses on the different silicon sources, the different ratios of silicon sources, alkali sources, and water, and the formation of symbiotic materials with one or more of mordenite, β zeolite, and ZSM-35. The process of synthesizing magadiite by nucleation has not yet been documented.

Contents of the invention

The technical problem to be solved by the present invention is that the synthesis cycle of magadiite is longer and the synthesis temperature is higher in the prior art, and a method for synthesizing magadiite by catalytic nucleation is provided, which is characterized in that while increasing the nucleation rate It also accelerates the chemical reaction rate of forming magadiite. Compared with the existing synthesis method without catalytic nucleating agent, the synthesis cycle is shortened by 6-72 hours, and the synthesis temperature is reduced by 6-20°C.

In order to solve the above problems, the technical scheme adopted by the present invention is as follows.

A method for synthesizing magadiite by catalytic nucleation method, comprising the following steps:

(1) Mix silicon source, alkali source, catalytic nucleating agent and water to obtain a mixture; the components in the mixture meet the requirements of silicon source: alkali source=3～7 in molar ratio; water: alkali source=20～100; The volume of catalytic nucleating agent does not exceed one-half of the volume of all mixtures, and more than one-sixth of the volume of all mixtures;

(2) Put the mixture obtained in step (1) into an airtight container under autogenous pressure, and crystallize at 110-170° C. for 6-144 hours;

(3) The crystallized product is taken out, filtered, washed with water until pH = 7-8, and then dried at 60°C-100°C for 4-12 hours to obtain magadiite, a two-dimensional layered structure material.

In the above method, the silicon source described in step (1) is more than one of fumed silica or precipitated white carbon black.

In the above method, the alkali source in step (1) is a mixture of sodium hydroxide and sodium carbonate; in terms of molar ratio, Na ₂ CO ₃ :NaOH=2-5.

In the above method, in step (1), the catalytic nucleating agent is one of glass beads, ceramic beads or steel balls, and the diameter of the catalytic nucleating agent is 2 mm to 7 mm.

In the above method, in step (1), the catalytic nucleating agent does not participate in the chemical synthesis reaction and is reused.

In the above method, the specific steps of mixing the silicon source, alkali source, catalytic nucleating agent and water described in step (1) are: first mix the alkali source and water into a solution, then mix with the silicon source, and finally mix with the catalytic nucleating agent Nuclear agent mix.

In the present invention, the synthesis temperature has been reduced by 6 to 20° C., and its principle can be explained as: its catalytic action is due to the addition of a catalytic nucleating agent to make some groups of the reactant contact and react with the nucleating catalyst first to form an intermediate product. Afterwards, the nucleation reaction is carried out, and the intermediate product is reduced to the nucleation catalyst and generates the target product, so that the generation of the intermediate product changes the reaction path, reduces the activation energy of the reaction, and then reduces the reaction temperature and increases the reaction rate; nucleation It can be understood that in the absence of a catalytic nucleating agent, it is homogeneous nucleation, and the nucleation rate is:

$\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; N\&kappa;T</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; \&kappa;\; T</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&alpha;\&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; \&kappa;\; T</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;G</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}{<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

In the formula, N—the number of atoms in the liquid phase per unit volume;

κ——Boltzmann's constant;

ΔG _A ——The activation energy of an atom crossing the liquid-solid interface:

α——crystal nucleus shape factor, for spherical crystal nucleus, α=16π/3;

ΔG _v ——Volume free energy difference.

The calculation formulas of the nucleation free ΔG _s of heterogeneous nucleation and the nucleation rate μ _s per unit area of heterogeneous nuclei are:

ΔG _s = ΔG _average f(θ)

${\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\mathrm{<span\; class="notranslate">\; \&kappa;\; T</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; \&kappa;\; T</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&kappa;\; T</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>$

In the formula $f\left(\mathrm{\&theta;}\right)=\frac{1}{4}\&times;(2+\cos \mathrm{\&theta;}){(1-\cos \mathrm{\&theta;})}^2$

θ——the contact angle between the newborn crystal and the heterogeneous crystal nucleus

N _s - the number of atoms per unit area

The rest of the symbols are the same as the homogeneous nucleation formula without nucleating agent.

It can be seen from the above three formulas that unless θ=180°, f(θ) is always less than 1, so the amount of nucleation free energy required for heterogeneous nucleation is always less than the average nucleation free energy, and the nucleation rate The nucleation rate is always higher than that of homogeneous nucleation, and the smaller the θ angle, the greater the difference, that is to say, the better the wettability of the reactant solution and the nucleating agent, the higher the nucleation rate. [Xing Jiandong, Oriented Crystal Growth [M], Xi'an Jiaotong University Press, 2008.5, 5-7]. This has the effect of catalysis and nucleation at the same time, so it is called "catalytic nucleation".

Compared with the prior art, the present invention has the following advantages and technical effects:

The present invention adds the catalytic nucleating agent under the limited technological condition, synthesizes the magadiite of pure phase, and this method shortens the synthetic period by 6～96 hours compared with the existing synthetic method that does not add the catalytic nucleating agent, synthesizes The temperature dropped by 6-20°C. The prepared material has a two-dimensional layered structure with exchangeable cations between the layers, and has a wide range of applications in ion exchange, catalysis, adsorption and the like.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of gained magadiite among the embodiment 1.

Fig. 2 is the X-ray diffraction pattern of gained magadiite in embodiment 2.

Fig. 3 is the X-ray diffraction pattern of gained magadiite in embodiment 3.

Fig. 4 is the X-ray diffraction pattern of gained magadiite in embodiment 4.

Figure 5a and Figure 5b are the scanning electron micrographs of magadiite obtained in Example 4.

Detailed ways

The present invention is described in detail below through examples, but the protection scope of the present invention is not limited to these examples.

The fumed silica (SiO ₂ content wt.% ≥ 99.8) used in the following examples was purchased from Jiangxi Jiajie New Material Co., Ltd.; precipitated silica (93% SiO ₂ , 7% H ₂ O) , purchased from Shanghai Zhenjiang Chemical Co., Ltd.

Example 1

Get 0.40 gram of sodium hydroxide and 2.12 gram of sodium carbonate and dissolve successively in 53.05 gram of water and make mixed solution, add 50 ceramic beads (diameter 5mm) after mixed solution and 13.55 gram of precipitation white carbon black (water content 7wt%) fully mix and Stir for 15 minutes, stir evenly, and then add it into a high-pressure reactor to carry out hydrothermal crystallization at 110° C. for 36 hours. The product is filtered, washed with water until pH = 7-8, and then dried at 80°C for 6 hours to obtain magadiite. Carry out qualitative analysis by X-ray diffraction method (its X-ray diffraction spectrogram sees accompanying drawing 1), as can be known that this magadiite is a pure phase, and is the same as the product that does not add catalytic nucleating agent and method same condition difference, degree of crystallization Correspondingly, it can be seen that the catalytic nucleation of ceramic beads at 110°C shortens the synthesis time by approximately 108h.

Example 2

Get 0.40 gram of sodium hydroxide and 2.12 gram of sodium carbonate and dissolve successively in 42.39 gram of water and make mixed solution, add 50 ceramic beads (diameter 5mm) after mixed solution and 11.61 gram of precipitated white carbon black (water content 7wt%) fully mix and Stir for 15 minutes, stir evenly, and then add it into a high-pressure reactor to carry out hydrothermal crystallization at 110° C. for 36 hours. The product was filtered, washed with water to pH=7-8, and then dried at 80°C for 6 hours to obtain magadiite. Carry out qualitative analysis by X-ray diffraction method (its X-ray diffraction spectrogram is shown in accompanying drawing 2), as can be known that this magadiite is a single phase, and the degree of crystallization is quite, it can be known that the product synthesized under 150 ℃, 36h condition is in the ceramic bead It can be synthesized under catalytic nucleation at 110°C for 36 hours, approximately reducing the synthesis temperature by 40°C.

Example 3

Get 0.40 gram of sodium hydroxide and 2.12 gram of sodium carbonate to be dissolved in 26.32 gram of water successively and make mixed solution, add 50 glass beads (diameter 5mm) after mixed solution is fully mixed with 9.68 gram of precipitated white carbon black (moisture 7wt%) and Stir for 15 minutes, stir evenly, and then add it into a high-pressure reactor to carry out hydrothermal crystallization at 130° C. for 24 hours. The product was filtered, washed with water to pH = 7-8, and then dried at 80°C for 6 hours to obtain magadiite. Qualitative analysis is carried out by X-ray diffraction method (its X-ray diffraction spectrum is shown in accompanying drawing 3), as can be known that this magadiite is a pure phase, and is the same as the product that does not add catalytic nucleating agent and method same condition difference, and does not have Adding a catalytic nucleating agent and using the same method and different conditions are the same. It can be seen that the product synthesized at 160°C for 24 hours can be synthesized at 130°C for 24 hours under the catalytic nucleation of ceramic beads, and the synthesis temperature is approximately reduced by 30°C.

Example 4

Get 0.40 gram of sodium hydroxide and 2.12 gram of sodium carbonate to be dissolved in 10.26 gram of water successively to make mixed solution, add 50 steel balls (diameter 5mm) and stir after mixed solution is fully mixed with 7.74 gram of precipitated white carbon black (water content 7wt%) After 15 minutes, stir evenly, add to the autoclave and carry out hydrothermal crystallization at 170° C. for 6 hours. The product was filtered, washed with water to pH=7-8, and then dried at 80°C for 6 hours to obtain magadiite. As shown in Fig. 5a and Fig. 5b (Fig. 5a is hydrothermal crystallization at 170°C for 18h without adding a catalytic nucleating agent), it can be seen from magadiite scanning electron microscope soil that it has a layered rose petal-like structure, that is, it has a two-dimensional layer As can be seen by comparison, the product added with the nucleating catalyst has a more perfect crystallization structure and a more ordered layered structure, which is qualitatively analyzed by X-ray diffraction (see the attached Figure 4), it can be seen that the magadiite is a pure phase, and it is the same as the product without adding a catalytic nucleating agent and with the same method and different conditions. It can be seen that the catalytic nucleation of steel balls at 170 ° C shortens the synthesis time by approximately 12 hours.

The above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (6)

1. a method for synthesizing magadiite by catalytic nucleation method, is characterized in that, comprises the following steps: (1) Mix silicon source, alkali source, catalytic nucleating agent and water to obtain a mixture; the components in the mixture meet the requirements of silicon source: alkali source = 3-7; water: alkali source = 20-100 in terms of molar ratio; The volume of catalytic nucleating agent does not exceed one-half of the volume of all mixtures, and more than one-sixth of the volume of all mixtures; (2) Put the mixture obtained in step (1) into an airtight container and crystallize at 110-170°C for 6-144 hours under autogenous pressure; (3) The crystallized product is taken out, filtered, washed with water to pH=7-8, and then dried at 60°C-100°C for 4-12 hours to obtain magadiite, a two-dimensional layered structure material. 2. The method for synthesizing magadiite by catalytic nucleation method according to claim 1, characterized in that, the silicon source described in step (1) is more than one of fumed silica or precipitated white carbon black. 3. according to the method for the described synthetic magadiite of catalytic nucleation method of claim 1, it is characterized in that, the alkali source described in step (1) is the mixture of sodium hydroxide and sodium carbonate; In molar ratio, wherein Na ₂ CO ₃ : NaOH=2-5. 4. according to the method for the described catalytic nucleation method synthesis magadiite of claim 1, it is characterized in that, in step (1), described catalytic nucleating agent is a kind of in glass bead, ceramic bead or steel ball, and described catalytic The diameter of the nucleating agent is 2 mm to 7 mm. 5. The method for synthesizing magadiite by catalytic nucleation method according to claim 1, characterized in that, in step (1), the catalytic nucleating agent does not participate in the chemical synthesis reaction and is reused. 6. The method for synthesizing magadiite by catalytic nucleation method according to claim 1 is characterized in that, the specific steps of mixing silicon source, alkali source, catalytic nucleating agent and water as described in step (1) are: first mix alkali The source and water are mixed into a solution, then mixed with the silicon source, and finally mixed with the catalytic nucleating agent.