CN106268936A - A kind of kieselguhr/nanometer TS 1 Ti-Si zeolite composite with multi-stage artery structure and preparation method thereof - Google Patents

Abstract

The invention discloses a diatomite/nanometer TS-1 titanium silicalite composite material with a multi-level pore structure and a preparation method thereof. In the present invention, the cheap diatomite is used as a carrier, and the nanometer TS-1 titanium silicalite is evenly loaded on the surface of the diatomite by means of electrical inversion, adsorption, nucleation and crystallization, and the nano-sized TS-1 titanium-silica zeolite is uniformly loaded on the surface of the diatomaceous earth, and the nano-sized TS‑1 titanium silicalite containing large/meso/microporous The diatomite/nano TS‑1 titanium silicalite composite material with a hierarchical pore structure has a large specific surface area and a high total pore volume. Loading nano TS-1 titanium silicalite on the surface of diatomite can not only improve the problem of single pore structure and low specific surface area of diatomite, but also the obtained composite material has excellent photocatalytic degradation ability to organic pollutants such as crystal violet , improving the application value of diatomite in the field of catalysis. At the same time, the preparation method of the diatomite/nano TS-1 titanium silicalite composite material provided by the present invention has the characteristics of simple and easy process, low cost, low energy consumption and little pollution, and has broad industrial application prospects.

Description

A diatomite/nanometer TS-1 titanium silicalite composite material with multi-level pore structure Materials and their preparation methods

Technical field:

The invention belongs to the field of organic pollutant treatment, and in particular relates to a diatomite/nano TS-1 titanium silicalite composite material with a multi-level pore structure and a preparation method thereof.

Background technique:

Diatomite is a dominant mineral resource in my country, and its proven reserves rank second in the world. It is a biological sedimentary rock formed after the remains of diatom organisms (diatom shells) are deposited and accumulated. The main mineral composition is diatom opal, which belongs to type A opal (Opal-A) in mineralogy. The surface of diatomite is rich in macropores with a wide range of pore size distribution (50-800nm), so it has excellent adsorption performance; in addition, this biomass-derived mineral has the advantages of stable skeleton structure, small bulk density, and high thermal stability. As filter aid, adsorption and heat preservation materials, it is widely used in various fields of industry. In the field of environment, besides being used as an adsorption material, diatomaceous earth can also be used as a catalytic carrier to support catalysts to degrade organic pollutants such as dyes. Photocatalytic technology has a good application prospect in the treatment of environmental organic pollutants, and _TiO2 , as the most common photocatalyst, can be immobilized on the surface of diatomite, which can increase the contact probability and The contact area improves the utilization efficiency of photocatalysts (patent number: CN200910101066.9; Chuan Xiuyun et al., Journal of Inorganic Materials, 2008; Su Yingying et al., China Environmental Science, 2009). However, diatomite has a single pore structure and a low specific surface area, so that it can limit the loading of the catalyst, and the utilization efficiency of the catalytically active component Ti is not high. lower. In addition, since the composite material only has the macropores of diatomite, the adsorption capacity is limited, and the removal of organic pollutants only depends on chemical oxidation, which limits its practical application in the industrial field.

Compared with the single chemical oxidation of traditional photocatalyst _TiO2 , TS-1 titanium silicalite has a higher utilization efficiency of titanium per unit activity, which can greatly reduce the use of expensive titanium sources and reduce costs, so it is more suitable for popularization and application. TS-1 titanium silicalite is a derivative of pure silicalite. In the heteroatom molecular sieve structure, transition metal titanium atoms that can accept electrons replace part of the silicon atoms in the silicon-oxygen tetrahedron in the original zeolite molecular sieve, making it retain pure At the same time, the microporous structure of silicalite increases the surface active sites of molecular sieves, which expands its application in the field of catalysis (Zhou Jiji et al., Progress in Chemistry, 1998). The molecular sieve was first synthesized by Taramasso et al in 1983 by hydrothermal method (patent number: US4410501). Nanoscale TS-1 titanium silicalite has high specific surface area and total pore volume, and has both high physical adsorption performance and catalytic oxidation performance for organic pollutants, so it is widely used in the field of organic pollutant treatment (such as dye molecule photocatalysis, etc.) (Zhang Juan et al., Chemical Engineering, 2012); on the other hand, as a new type of nanomaterial, it is also widely used in the field of industrial catalysis such as alcohol amine oxidation, olefin epoxidation and aromatic hydrocarbon hydroxylation, etc. (Zuo Yi et al., Petroleum Journal of the Chinese Academy of Sciences, 2015; Chen Xiaoyan et al., Shanxi Chemical Industry, 2012). However, there are still the following problems in the application of nano-TS-1 titanium silicalite in the environmental and industrial fields: (1) the single pore size distribution causes nano-TS-1 titanium silicalite to only have catalytic oxidation properties for small molecule dyes of a certain size, and cannot Facilitate the catalytic degradation of macromolecular dyes such as crystal violet ( etc., Journal of Catalysis, 2001); (2) The problem of agglomeration between nano-zeolite particles will also reduce the adsorption efficiency, thereby affecting the catalytic performance and increasing the cost of pollutant treatment. Therefore, the preparation of nano TS-1 titanium silicalite composites with hierarchical pore structure and good dispersion properties is the key to solve the above problems.

Chinese invention patent "Preparation Method of Hierarchical Porous Structure Titanium-Silicon Molecular Sieve Material" (Patent No.: 201110100277), adopts gas phase crystallization method, adds phase separation inducer, structure-directing agent and catalyst, etc. into the reactor to induce titanium-silicon oxidation The crystallization of the precursor of the compound was carried out to obtain a titanium silicalite molecular sieve with a multi-level pore structure. Although the titanium-silicon molecular sieve material prepared by this method has high crystallinity, the preparation steps are cumbersome and time-consuming; the material preparation process needs to add a variety of organic reagents, such as inducers, structure-directing agents (tri-block copolymers, etc.), etc. , expensive, high cost; in addition, its preparation method gas phase crystallization needs to be carried out under high temperature and high pressure conditions, and the energy consumption is high. Chinese invention patent "Preparation method for in-situ loading and molding of titanium-silicon molecular sieve composite catalyst" (application number: 201410832823.0), using porous material as carrier, through pre-aging and hydrothermal crystallization process, prepared titanium-silicon molecular sieve composite catalyst . The composite catalyst has good cyclohexanone ammoximation activity, but it needs to be synthesized under hydrothermal conditions and roasted under an inert atmosphere, which requires high energy consumption and harsh conditions, making it difficult to popularize and apply.

Invention content:

The main purpose of the present invention is to overcome the problems of low utilization efficiency of the active components of traditional diatomite-based photocatalytic materials and the preparation of multi-level pore structure nano TS-1 titanium silicalite catalysts in the prior art. A diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure for photocatalytic degradation of organic pollutants and a preparation method thereof. The main advantage of this method is that it makes full use of the natural and abundant porous structure of the macroporous mineral diatomite, and uses cheap diatomite as a carrier to prepare a multi-level pore structure And diatomite/nanometer TS-1 titanium silicalite composite material with large specific surface area and high total pore volume, which has good photocatalytic degradation ability for macromolecular organic dyes (crystal violet, etc.). In addition, the preparation method has the advantages of mild conditions, simple process, low cost, low energy consumption, and less potential environmental damage.

The diatomite/nanometer TS-1 titanium silicalite composite material with hierarchical pore structure of the present invention is prepared by the following method:

a. Diatomite surface electrical inversion pretreatment: add diatomite powder into the polycation electrolyte solution, stir at room temperature for 2-10 hours, and then perform solid-liquid separation, and dry the obtained solid to constant weight to obtain a surface Modified diatomite powder;

b. Preparation of diatomite/nano TS-1 titanium silicalite composite material: add surface modified diatomite powder into TS-1 titanium silicalite synthesis liquid, stir and reflux reaction at 80-100°C 3 -7 days, the solid product is taken out, washed with water, centrifuged, dried, and then calcined at 550-800° C. for 3-6 hours to prepare a diatomite/nanometer TS-1 titanium silicalite composite material with a multi-level pore structure.

In the step a, adding the diatomite powder to the polycation electrolyte solution is to add the diatomite powder to a mass fraction of 0.5-1.0 according to the diatomite powder mass/polycation electrolyte solution volume ratio 1g/50-80mL % of the polycation electrolyte solution.

In the step b, adding the surface-modified diatomite powder to the TS-1 titanium silicalite synthetic liquid is based on the diatomite powder mass/TS-1 titanium silicalite synthetic liquid volume ratio 1g/15- 35 mL was added.

The polycation electrolyte solution is an aqueous solution of polydimethyldiallylammonium chloride, polyquaternary ammonium salt or chitosan.

The TS-1 titanium silicalite synthesis liquid comprises 100 parts of ethyl orthosilicate, 1-3 parts of tetrabutyl titanate, 18-32 parts of tetrapropylammonium hydroxide, 77 parts of isopropanol and 1800 parts of water.

The diatomite in the step a is diatomite with a mass percentage of diatom shells in the raw ore greater than 60%.

Advantages and positive effects of the present invention are embodied in the following points:

1. The present invention uses natural and cheap mineral diatomite with rich macroporous structure as a carrier, overcomes the problems of low utilization efficiency of active components of traditional diatomite-based photocatalytic materials and easy agglomeration of nano TS-1 particles, and prepares a large Diatomite/nano TS-1 titanium silicalite composite material with /meso/microporous hierarchical pore structure.

2. The diatomite/nanometer TS-1 titanium silicalite composite material prepared by the present invention has a large specific surface area and a high total pore volume (the specific surface area and the total pore volume of the reflux reaction reach 429.8m ² /g and 0.44 cm ³ /g); nano TS-1 titanium silicalite is uniformly dispersed on the surface of diatomite, and the utilization efficiency of the active component Ti is greatly improved; in addition, the synergistic effect of physical adsorption and chemical catalytic oxidation makes the composite material photocatalytic for crystal violet The degradation efficiency is as high as 90.4%.

3. The preparation process of the present invention adopts the method of electrical inversion adsorption nucleation and crystallization, the process is simple and easy, the conditions are mild, no high temperature and high pressure process is required, and the energy consumption is low; the natural carrier mineral diatomite used is cheap and easy to obtain , the cost is low; in addition, the surface modifier (polycation electrolyte solution) used in the preparation process can be recovered and recycled, which has advantages in reducing cost and reducing environmental pollution.

In the present invention, the cheap diatomite is used as a carrier, and the nanometer TS-1 titanium silicalite is evenly loaded on the surface of the diatomite by means of electrical inversion, adsorption, nucleation and crystallization, and a large/meso/microporous multi- The diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure has a large specific surface area and a high total pore volume. Loading nano TS-1 titanium silicalite on the surface of diatomite can not only improve the problem of single pore structure and low specific surface area of diatomite, but also the obtained composite material has excellent photocatalytic degradation ability to organic pollutants such as crystal violet , improving the application value of diatomite in the field of catalysis. At the same time, the preparation method of the diatomite/nano TS-1 titanium silicalite composite material provided by the invention has the characteristics of simple process, low cost, low energy consumption and little pollution, and has broad industrial application prospects.

Description of drawings:

Fig. 1 is an X-ray diffraction diagram of the diatomite/nano TS-1 titanium silicalite composite material with a hierarchical pore structure prepared in Example 1 of the present invention.

Fig. 2 is a scanning electron micrograph of the diatomite/nano TS-1 titanium silicalite composite material with a hierarchical pore structure prepared in Example 1 of the present invention, wherein Fig. 2b is a partially enlarged view of Fig. 2a.

Fig. 3 is a micro/mesoporous pore size distribution diagram of the diatomite/nano TS-1 titanium silicalite composite material with a hierarchical pore structure prepared in Example 1 of the present invention.

Fig. 4 is the nitrogen adsorption-desorption isotherm of the diatomite/nano TS-1 titanium silicalite composite material with hierarchical pore structure prepared in Example 1 of the present invention.

detailed description:

The following examples are to further illustrate the present invention, rather than limit the present invention.

Example 1:

1. Diatomite surface electrical property reversal pretreatment: According to the diatomite mass/polycation electrolyte solution volume ratio 1g/80mL, take 1.5g of diatomite powder and add 120mL of 0.5% polydimethyl dimethicone Allyl ammonium chloride electrolyte solution (its preparation method is that polydimethyl diallyl ammonium chloride is dissolved in water, and its mass fraction is 0.5%), the above-mentioned mixed solution is fully stirred at room temperature for 2 hours, Then, the solid-liquid separation is carried out by centrifugation, and the obtained solid is dried to a constant weight to obtain a surface-modified diatomite powder.

2. Preparation of diatomite/nanometer TS-1 titanium silicalite composite material: 1.5g of surface-modified diatomite powder prepared in step 1 was added to 52.5mL TS-1 titanium silicalite synthetic liquid (TS-1 Titanium silicalite synthesis liquid is obtained by mixing ethyl orthosilicate, tetrabutyl titanate, tetrapropylammonium hydroxide, isopropanol and water uniformly according to the mass ratio of 100:3:32:77:1800 parts ), fully stirred and refluxed at 80°C for 7 days, the solid product was taken out, washed with water, centrifuged, dried, and then calcined at 550°C for 6 hours to obtain a diatomite/nano TS-1 titanium silicalite composite with a multi-level pore structure Material.

The structure of the diatomite/nano TS-1 titanium silicalite composite material with a hierarchical pore structure prepared in this example is determined by X-ray diffraction, and the diatomite/nano TS-1 titanium with a hierarchical pore structure is obtained. X-ray diffraction patterns of silicalite composites (Figure 1). It can be seen from the figure that the prepared diatomite/nano TS-1 titanium silicalite composite material with hierarchical pore structure has the peak of the MFI zeolite phase, and the peak shape at 24.3° and 29.5° splits, indicating that Titanium elements entered the MFI-type zeolite framework, indicating that the diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure was successfully synthesized.

The diatomite/nano TS-1 titanium silicalite composite material with hierarchical pore structure was analyzed by scanning electron microscope (Fig. 2). As can be seen from the figure, the diatomite/nano TS-1 titanium silicalite composite material with multi-level pore structure has diatom shell morphology (Fig. 2a), and the macroporous structure of diatom shell remains intact. A layer of TS-1 titanium silicalite nanoparticles is evenly loaded on the surface of the shell, which is spherical in shape and about 100 nm in diameter (Fig. 2b).

The micro/mesoporous pore size distribution diagram of the diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure is shown in FIG. 3 . It can be seen from the figure that the composite material has a multi-level pore structure, containing micropores of TS-1 titanium silicalite (the pore diameter is about 0.6nm), and a large number of mesopores are formed by the accumulation of nano-zeolite particles (the pore diameter is concentrated in the 2- 18nm).

The nitrogen adsorption-desorption isotherm (Figure 4) of the diatomite/nano TS-1 titanium silicalite composite material with multi-level pore structure belongs to the type IV isotherm, and the nitrogen adsorption amount increases rapidly in the low pressure area, indicating that the composite material It contains micropores; H3 type hysteresis loops in the middle pressure region indicate that the composite contains mesopores; when the relative pressure is close to 1.0, the increase of nitrogen adsorption indicates that the composite contains macropores.

According to the BET method, the specific surface area of the diatomite/nano TS-1 titanium silicalite composite material with hierarchical pore structure is 429.8m ² /g, and the total pore volume is 0.44cm ³ /g. The zeolite loading was calculated to be 54.1%.

The diatomite/nanometer TS-1 titanium silicalite composite material prepared in this example with a multi-level pore structure was subjected to a photocatalytic reaction for 2 hours, and its degradation efficiency to crystal violet dye reached 90.4%. The degradation amount of crystal violet is 81.9 mg/g (pure phase nano TS-1 titanium silicalite).

Example 2:

1. Diatomite surface electrical property reversal pretreatment: According to the diatomite mass/polycation electrolyte solution volume ratio 1g/50mL, take 1.5g diatomite powder and add 75mL polyquaternium ammonium salt electrolyte with a mass fraction of 1.0% Solution (its preparation method is that polyquaternium salt is dissolved in water, makes its final mass fraction be 1.0%), above-mentioned mixed solution is fully stirred at room temperature for 2 hours, then solid-liquid separation is carried out by centrifugation, and the gained solid is dried to a constant weight to obtain a surface-modified diatomite powder.

2. Preparation of diatomite/nanometer TS-1 titanium silicalite composite material: 1.5g of surface-modified diatomite powder prepared in step 1 was added to 22.5mL TS-1 titanium silicalite synthetic liquid (TS-1 Titanium silicalite synthesis liquid is obtained by mixing ethyl orthosilicate, tetrabutyl titanate, tetrapropylammonium hydroxide, isopropanol and water uniformly in the ratio of 100:1:18:77:1800 ), fully stirred and refluxed at 100°C for 3 days, the solid product was taken out, washed with water, centrifuged, dried, and then calcined at 800°C for 3 hours to obtain a diatomite/nano TS-1 titanium silicalite composite material with a multi-level pore structure .

According to the BET method, the specific surface area of the diatomite/nano TS-1 titanium silicalite composite material with hierarchical pore structure prepared in this example is 180.1m ² /g, the total pore volume is 0.21cm ³ /g, and the zeolite The loading was 23.5%.

The diatomite/nanometer TS-1 titanium silicalite composite material prepared in this example with a multi-level pore structure was subjected to photocatalytic reaction for 2 hours, and its degradation efficiency to crystal violet dye reached 61.8%. The degradation amount of crystal violet was 128.9 mg/g (pure phase nano TS-1 titanium silicalite).

Example 3:

1. Diatomite surface electrical property reversal pretreatment: According to the diatomite mass/polycation electrolyte solution volume ratio 1g/80mL, take 1.5g diatomite powder and add 120mL chitosan electrolyte solution with a mass fraction of 0.5% (its preparation method is that chitosan is dissolved in water, and its final mass fraction is 0.5%), the above-mentioned mixed solution is fully stirred at room temperature for 10 hours, then solid-liquid separation is carried out by centrifugation, and the obtained solid is dried to constant temperature. Weight, to obtain surface-modified diatomite powder.

2. Preparation of diatomite/nanometer TS-1 titanium silicalite composite material: 1.5g of surface-modified diatomite powder prepared in step 1 was added to 52.5mL TS-1 titanium silicalite synthetic liquid (TS-1 Titanium silicalite synthesis liquid is obtained by mixing ethyl orthosilicate, tetrabutyl titanate, tetrapropylammonium hydroxide, isopropanol and water uniformly in the ratio of 100:2:25:77:1800 ), fully stirred and refluxed at 80°C for 5 days, the solid product was taken out, washed with water, centrifuged, dried, and then calcined at 550°C for 6 hours to obtain a diatomite/nano TS-1 titanium silicalite composite material with a multi-level pore structure .

According to the BET method, the specific surface area of the diatomite/nano TS-1 titanium silicalite composite material prepared in this example with a hierarchical pore structure is 217.9m ² /g, and the total pore volume is 0.20cm ³ /g. The loading was 37.5%.

The diatomite/nanometer TS-1 titanium silicalite composite material prepared in this example with a multi-level pore structure was subjected to photocatalytic reaction for 2 hours, and its degradation efficiency to crystal violet dye reached 82.3%. The degradation amount of crystal violet is 107.5 mg/g (pure phase nano TS-1 titanium silicalite).

Claims (10)

1. a preparation method of diatomite/nanometer TS-1 titanium silicalite composite material with multi-level pore structure, is characterized in that, comprises the following steps: a. Diatomite surface electrical inversion pretreatment: add diatomite powder into the polycation electrolyte solution, stir at room temperature for 2-10 hours, and then perform solid-liquid separation, and dry the obtained solid to constant weight to obtain a surface Modified diatomite powder; b. Preparation of diatomite/nano TS-1 titanium silicalite composite material: add surface modified diatomite powder into TS-1 titanium silicalite synthesis liquid, stir and reflux reaction at 80-100°C 3 -7 days, the solid product is taken out, washed with water, centrifuged, dried, and then calcined at 550-800° C. for 3-6 hours to prepare a diatomite/nanometer TS-1 titanium silicalite composite material with a multi-level pore structure. 2. preparation method according to claim 1, is characterized in that, adding diatomite powder in the polycation electrolyte solution of described step a is diatomite powder by diatomite powder quality/polycation electrolyte The solution volume ratio is 1g/50-80mL and added to the polycation electrolyte solution with a mass fraction of 0.5-1.0%. 3. The preparation method according to claim 1, characterized in that, adding the surface-modified diatomite powder into the TS-1 titanium silicalite synthetic liquid in the step b is based on diatomite powder Mass/TS-1 titanium silicalite synthesis liquid volume ratio 1g/15-35mL was added. 4. according to the described preparation method of claim 1,2 or 3, it is characterized in that, described polycation electrolyte solution is the aqueous solution of polydimethyldiallylammonium chloride, polyquaternium salt or chitosan . 5. The preparation method according to claim 1, 2 or 3, characterized in that, the TS-1 titanium silicalite synthetic liquid comprises 100 parts of tetraethyl orthosilicate, titanium 1-3 parts of tetrabutyl ester, 18-32 parts of tetrapropyl ammonium hydroxide, 77 parts of isopropanol and 1800 parts of water. 6. The preparation method according to claim 1, 2 or 3, characterized in that the diatomite in the step a is diatomite with a mass percentage of diatom shells in the raw ore greater than 60%. 7. A diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure prepared according to the preparation method described in claim 1, 2 or 3. 8. A diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure prepared according to the preparation method of claim 4. 9. A diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure prepared according to the preparation method of claim 5. 10. A diatomite/nanometer TS-1 titanium silicalite composite material with a hierarchical pore structure prepared according to the preparation method of claim 6.