CN100512960C - Method for preparing modified MCM-41/aluminium oxide composite carrier - Google Patents

Abstract

A method for preparing a modified MCM-41/alumina composite carrier material, belonging to the technical field of new composite materials, using F ^- modified alumina as an aluminum source, water glass as a silicon source, cetyl trimethyl bromide Ammonium is used as a template to hydrothermally synthesize MCM-41/alumina composites. Modified alumina is obtained by impregnating alumina in a solution of soluble fluoride. In F ^- modified alumina, it is prepared by mixing with water glass Mixed with template agent, hydrothermally synthesized MCM-41/alumina composite material, which further improved the structural stability of MCM-41, adjusted the surface pH of the composite material, and made the MCM-41/alumina composite material more suitable for diesel fuel Support for hydrodesulfurization, hydrodenitrogenation, aromatics hydrosaturation and heavy distillate hydrotreating catalysts.

Description

A preparation method of modified MCM-41/alumina composite carrier material

technical field

The invention belongs to the technical field of composite new materials, relates to a preparation method of a composite carrier material, and particularly designs a preparation method of an MCM-41/alumina composite material prepared by F ^- modified alumina.

Background technique

Composite materials synthesized by surfactants as templates have broad application prospects and academic research value in the fields of macromolecule conversion, catalysis, catalyst support, adsorption separation, and separation and purification of biomacromolecules.

U.S. Patent US 5098684 provides a kind of method for preparing mesoporous molecular sieve MCM-41, 100g cetyltrimethylammonium hydroxide solution is mixed with 100g tetramethylammonium hydroxide solution (25%), stirs, adds 25g0 .02 microns of silicon oxide hydrate (containing 6wt.% of free water and 4.5wt.% of bound water), the mixture was hydrothermally crystallized overnight at 150 ° C in an autoclave, the solid product was separated, washed, and dried at room temperature, 540 °C for 1 h in N ₂ , followed by 6 h in air. The specific surface area of the mesoporous molecular sieve is 993m ² /g, 72% of the specific surface area is retained in 100% steam at 676°C for 2 hours, and 55% of the specific surface area is maintained in 100% steam at 788°C for 2 hours, and it is treated in zeolite for 12

The h structure is completely destroyed, indicating that the hydrothermal stability is poor. After mesoporous molecular sieves were calcined at 550°C for 6 hours, the unit cells shrank by 25%, and the structure was rapidly destroyed by heat treatment above 750°C, indicating that the thermal stability was also poor.

In order to overcome the problem of poor hydrothermal stability, U.S. Patent US 5942208 adopted three methods of adjusting pH and adding salts: (1) mixing ammonium salt solution, silicate, aluminate, and alkyltrimethylammonium halide (2) use this mixture to carry out hydrothermal crystallization reaction, adjust the pH value, and carry out hydrothermal crystallization reaction again; (3) add one or more water-soluble organic or organic compounds that can form bonds with monovalent cations in the mixture Inorganic salts, including CH ₃ COONa, LiCl, NaCl, KCl, NaNO ₃ , Na ₂ SO _{4 ,} etc.; (4) repeating step (2); (5) performing hydrothermal crystallization reaction at an appropriate temperature for an appropriate time to obtain The mesophase of mesoporous molecular sieve; (6) filtering, washing and drying; (7) roasting at 500-600°C. Mesoporous molecular sieves are calcined at 500°C for 2 hours in oxygen containing 2.3kPa water vapor or treated in boiling water for 12 hours, and the structure is not damaged. However, the process is complicated, the repeatability is poor, and the cycle is long, so it is difficult to apply on a large scale.

Jin Yingjie et al. (Petrochemical Industry, 1999, 28: 524) used sodium silicate and activated alumina as the silicon and aluminum sources, and CTMAB as the structural template agent. By optimizing the synthesis conditions, a pore size of 3.18nm and a specific surface area of ^1103m2 were synthesized. /g, MCM-41 mesoporous molecular sieve with pore wall thickness of 2.82nm can improve the stability of MCM-41 mesoporous molecular sieve.

Dou Tao et al. (Journal of Fuel Chemistry, 1998, 26(3): 243) synthesized pure silicon MCM-41 mesoporous molecular sieve materials with surfactants 1631 and 1831, room temperature method and hydrothermal crystallization method. Compared with 1831, the molecular sieve samples prepared by using 1631 have faster crystallization rate and better thermal stability, while using 1831 can obtain larger unit cell parameters and good hydrothermal stability and Acid-resistant pure silicon MCM-41 product.

MCM-41 molecular sieve of pure silicon has good stability but weak acidity. Adding aluminum is the main way to increase acidity, but after adding aluminum, the stability of AlMCM-41 molecular sieve will drop a lot. Chinese patent CN 03134883.1 introduces the MCM-41/alumina composite material with high stability synthesized by using alumina as the aluminum source, water glass as the silicon source, and 1831 as the template agent. But the structural stability of MCM-41 is not very good. In order to further improve the stability of aluminum-containing AlMCM-41 and have good acidity, surface treatment of alumina is an effective means to solve this problem.

The invention carries out F ^- ion modification on aluminum oxide, mixes it with water glass and template agent, and synthesizes high-stability MCM-41/alumina composite material by hydrothermal method. The structural stability of the synthesized MCM-41 molecular sieve is improved even more.

Contents of the invention

The average pore diameter of the MCM-41/alumina composite material of the present invention is 3-10nm, the pore volume is 0.5-1.1ml/g, and the specific surface area is ^180-500m2 /g. The purpose of preparing the MCM-41/alumina composite material is Provide a hydrorefining and hydrotreating catalyst carrier with higher stability, which is more suitable as a carrier for diesel hydrodesulfurization, hydrodenitrogenation, aromatics hydrosaturation and heavy distillate oil hydrotreating catalyst .

General idea of composite material preparation: the present invention impregnates aluminum oxide with a certain mesh number (20-100 mesh) with fluoride aqueous solution, then adds silicon source such as water glass, adds template agent, adjusts pH value with dilute acid, hydrothermal crystallization After melting, it is washed with water, dried, roasted and sieved.

Implementation steps of the present invention are as follows:

1. Alumina pretreatment: impregnate 20-100 mesh alumina with fluoride aqueous solution, and form a sodium fluoride layer on its surface, which is conducive to the crystallization of MCM-41. The immersion temperature is room temperature to 80°C, the immersion time is 2 to 48 hours, stirring is required during the immersion, and the stirring rate is 50 to 500 rap/min.

2. Mix the 20-100 mesh aluminum oxide in step 1 with the silicon source aqueous solution to form the precursor of the composite material.

3. Obtaining the composite material gel: adding the mixture obtained in step 2 into the templating agent and water mixing and stirring to form a jelly system, adding dilute acid to adjust the pH value to 9-13.

4. Obtaining the composite carrier material: the product obtained in step 3 is hydrothermally crystallized at 90-150°C for 12-144 hours, washed with water, dried at 90-130°C for 5-40 hours, and calcined at 450-650°C for 3-20 hours, namely A composite material was obtained in the form of a white powder.

Concrete invention content is as follows:

A preparation method of modified MCM-41/alumina composite carrier material, using F ^- modified alumina as aluminum source, water glass as silicon source, cetyltrimethylammonium bromide as template agent, hydrothermal Synthesis of MCM-41/alumina composites.

Modified alumina is obtained by impregnating alumina in a solution of soluble fluoride. Soluble fluoride is sodium fluoride. The weight concentration of fluorine in the soluble fluoride solution is 0.05-0.15 g/mL. The particle size of alumina is 20-200 mesh.

Its preparation method comprises the following steps,

a) The modified alumina is mixed with the silicon source aqueous solution, and then added to the colloidal system formed by mixing and stirring the templating agent and water to form a slurry of the composite material, wherein the molar ratio of each component in the slurry is (3.0-6.0) Na ₂ O: (7.0~25) SiO ₂ : (1) Al ₂ O ₃ : (0.85~2.5) F: (0.01~0.1) CTAB: (350~400) H ₂ O, add acid to adjust the pH value to 9 ~13;

b) crystallize the slurry obtained in step a) at 90-150°C for 12-144 hours, filter and wash the obtained material, dry it at 80-130°C for 5-40 hours, and bake it at 450-650°C for 3-4 hours 20h, the material was obtained.

The loading amount of fluoride in the modified MCM-41/alumina composite carrier material is 1.0-5.0% by weight. The average pore diameter is 3-10nm, the pore volume is 0.5-1.1ml/g, and the specific surface area is 180-500m ² /g.

In F ^- modified alumina, by mixing with water glass and template agent, hydrothermal synthesis of MCM-41/alumina composite material can further improve the structural stability of MCM-41, adjust the surface pH of the composite material, and make MCM-41/alumina composite material is more suitable as the carrier of diesel hydrodesulfurization, hydrodenitrogenation, aromatics hydrosaturation and heavy distillate hydrotreating catalyst. Meet the needs of production.

Description of drawings

Fig. 1. XRD pattern of composite material 1

Figure 2. XRD pattern of composite material 2

Fig. 3. XRD pattern of composite material 3

Figure 4. XRD pattern of composite material 4

Fig. 5. XRD pattern of composite material 5

Fig. 6. XRD pattern of composite material 6

Figure 7. XRD spectrum of sample 7 (pure MCM-41)

Fig.8 XRD spectrum of MCM-41/Al ₂ O ₃ composites prepared from alumina without F adsorption

Figure 9. XRD spectrum of composite material 1 after calcination at 900 °C

Figure 10. XRD spectrum of pure MCM-41 after roasting at 900°C

Figure 11. XRD spectrum of MCM-41/Al ₂ O ₃ prepared from alumina without F adsorption after calcination at 900°C

Detailed ways

Example 1

Dissolve 6.6g of sodium fluoride in 50ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F-modified alumina. Then add 352ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and immerse for 6h. Take 6g of cetyltrimethylammonium bromide and mix it with 100ml of water, stir to form a slurry, mix the two, stir for 1h, and adjust the pH value to 11.0 with 2mol/L dilute sulfuric acid. The composition of the mixture is: _4.5Na2O : _8.3SiO2 : _Al2O3 : _0.67F : 0.07CTAB: _380H2O . Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and roasted at 550°C for 5h to obtain white MCM-41/γ - Al ₂ O ₃ composite material 1. The XRD results are shown in Figure 1.

Example 2

Dissolve 6.6g of sodium fluoride in 50ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F ^- modified alumina. Then add 352ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and immerse for 6h. Take 6g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is: _4.5Na2O : _8.3SiO2 : _Al2O3 : _0.67F : 0.07CTAB: _380H2O . Hydrothermal crystallization at 140°C for 48h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ -Al ₂ O ₃ composite material 2. The XRD results are shown in Figure 2.

Example 3

Dissolve 6.6g of sodium fluoride in 50ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F ^- modified alumina. Then add 704ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and soak for 6h. Take 6g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is: _4.5Na2O : _16.6SiO2 : _Al2O3 : _0.67F : 0.07CTAB: _380H2O . Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ - Al ₂ O ₃ composite material 3. The XRD results are shown in Figure 3.

Example 4

Dissolve 6.6g of sodium fluoride in 50ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F ^- modified alumina. Then add 704ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and soak for 6h. Get 2.57g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is : 4.5Na ₂ O: 16.6SiO ₂ : Al ₂ O ₃ : 0.67F: 0.03CTAB: 380H ₂ O. Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ -Al ₂ O ₃ composite material 4, XRD results are shown in Figure 4.

Example 5

Dissolve 13g of sodium fluoride in 50ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F ^- modified alumina. Then add 704ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and soak for 6h. Get 2.57g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is : 4.5Na ₂ O: 16.6SiO ₂ : Al ₂ O ₃ : 1.3F: 0.03CTAB: 380H ₂ O. Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ -Al ₂ O ₃ composite material 5. The XRD results are shown in Figure 5.

Example 6

Dissolve 25g of sodium fluoride in 100ml of water, add 24g of γ-Al ₂ O ₃ , and soak for 24 hours to obtain F ^- modified alumina. Add 1018ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above-mentioned F-modified γ-Al ₂ O ₃ and immerse for 6h. Get 7.62g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is : 6.0Na ₂ O : 24.0SiO ₂ : Al ₂ O ₃ : 2.5F: 0.09CTAB: 400H ₂ O. Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ -Al ₂ O ₃ composite material 5. The XRD results are shown in Figure 6.

Comparative example 1

Mix 6g of cetyltrimethylammonium bromide with 100ml of water, stir to form a jelly, take 352ml of water glass and add it to the mixture of cetyltrimethylammonium bromide and water, stir for 1h, then use 2mol/ L dilute sulfuric acid to adjust the pH to 12.0, the composition of the mixture is: 4.5Na ₂ O: 8.3SiO ₂ 0.07CTAB: 380H ₂ O. Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, take out the product, wash 5 times with 100ml of distilled water, dry at 110°C for 12h, and roast at 550°C for 5h to obtain white MCM-41, XRD The results are shown in Figure 7.

Comparative example 2

Take 100ml of water and add 24g of γ-Al ₂ O ₃ , and stir to form a slurry. Then add 1018ml of water glass (modulus 3.0, SiO ₂ content 26m%) into the above gamma-Al ₂ O ₃ and soak for 6h. Get 7.62g of cetyltrimethylammonium bromide and mix with 100ml of water, stir to form a slurry, mix the two, after stirring for 1h, adjust the pH value to 12.0 with 2mol/L dilute sulfuric acid, the composition of the mixture is : 6.0Na ₂ O: 24.0SiO ₂ : Al ₂ O ₃ : 0.09CTAB: 400H ₂ O. Hydrothermal crystallization at 140°C for 24h in an autoclave lined with Teflon, the product was taken out, washed 5 times with 100ml of distilled water, dried at 110°C for 12h, and calcined at 550°C for 5h to obtain white MCM-41/γ -Al ₂ O ₃ composite material 5. The XRD results are shown in Figure 8.

Comparative example 3

After the materials of Example 1 and Comparative Example 1 and Comparative Example 2 were calcined at 900° C. for 1 hour, the XRD results were measured, as shown in FIG. 9 , FIG. 10 and FIG. 11 . The material of Example 1 still maintains a high crystallinity (see Figure 9), while the XRD crystallinity of the materials of Comparative Example 1 and Comparative Example 2 is greatly reduced (see Figure 10), indicating that the alumina modified by F is re- The MCM-41/γ-Al ₂ O ₃ composite obtained by hydrothermal synthesis has good thermal stability.

Table 1 Physical parameters of prepared MCM-41/γ-Al ₂ O ₃ composites

composite material Specific surface area m²/g Pore volumeml/g Average pore size nm 1 400.0 0.82 3.12 2 180.5 0.54 4.55 3 320.4 0.78 4.79 4 192.8 0.59 4.27 5 290.6 0.57 3.23 6 498.2 0.84 3.15

Claims (8)

1, the preparation method of a kind of modified MC M-41/ aluminium oxide composite carrier is characterized in that: with F ^-Modified aluminas as aluminium source, waterglass as silicon source, softex kw as the template agent, hydro-thermal is synthesized MCM-41/ alumina composite material.

2, preparation method according to claim 1 is characterized in that: described modified aluminas is that aluminium oxide makes by infusion process in the solution of soluble fluoride.

3, preparation method according to claim 2 is characterized in that: described soluble fluoride is a sodium fluoride.

4, preparation method according to claim 2 is characterized in that: the weight concentration of fluorine is 0.05～0.15g/mL in the described soluble fluoride solution.

5, preparation method according to claim 1 is characterized in that: F ^-Adopting the granularity of aluminium oxide before the modified aluminas modification is 20～200 orders.

6, preparation method according to claim 1 is characterized in that: may further comprise the steps,

A) aluminium oxide of modification and silicon source aqueous solution join in the gluey system that template agent and water is mixed into again, form the slurries of composite, and wherein the mol ratio of each component is (3.0～6.0) Na in the slurries ₂O:(7.0～25) SiO ₂: (1) Al ₂O ₃: (0.85～2.5) F:(0.01～0.1) softex kw: (350～400) H ₂O adds acid for adjusting pH value to 9～13;

B) slurries that step a) is obtained are at 90～150 ℃ of following crystallization 12～144h, and the material that obtains after filtration, after the washing, at 80～130 ℃ of down dry 5～40h, at 450～650 ℃ of following roasting 3～20h, obtain described material.

7, according to claim 1 or 6 described preparation methods, it is characterized in that: the load capacity of the fluoride of described modified MC M-41/ aluminium oxide composite carrier is weight percentage 1.0～5.0%.

8, according to claim 1 or 6 described preparation methods, it is characterized in that: described modified MC M-41/ aluminium oxide composite carrier average pore size is 3～10nm, and pore volume is 0.5～1.1ml/g, and specific area is 180～500m ²/ g.

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