Preparation method for improving solid content of glue solution in production process of catalytic cracking catalyst

Abstract

The invention provides a preparation method for improving the solid content of a glue solution in the production process of a catalytic cracking catalyst, and belongs to the technical field of catalytic cracking catalyst preparation. According to the method, the mixing sequence of a silicon source and an aluminum source is optimized, the pH value and temperature of a reaction system are controlled, and a composite dispersing aid is introduced, so that the problems of difficulty in subsequent catalyst forming, unstable activity and the like caused by low solid content of a glue solution in a traditional preparation process are solved. The method is characterized by comprising the steps of (1) preparing an aluminum source solution, (2) preparing a silicon source dispersion liquid and (3) preparing a glue solution through a mixed reaction, the solid content of the glue solution can be increased to 38-45%, the glue solution is good in dispersion uniformity and free of obvious agglomeration phenomenon, the abrasion index of the subsequently prepared catalytic cracking catalyst is reduced by 8-12%, the catalytic activity is improved by 5-8%, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention specifically relates to a method for preparing a solution with increased solid content in the production process of catalytic cracking catalysts, belonging to the field of catalytic cracking catalyst preparation technology. Background Technology

[0002] Catalytic cracking is one of the core processes in petroleum refining, and the performance of catalytic cracking catalysts directly determines the feedstock conversion rate and product quality. As a core intermediate in the preparation of catalytic cracking catalysts, the solid content of the gel is a key indicator affecting subsequent processes and catalyst performance. Low solid content gels not only increase energy consumption in the spray drying process (requiring more water evaporation), but also lead to low catalyst particle density, poor sphericity, and a high wear index, while reducing the uniformity of catalyst active site distribution.

[0003] Currently, traditional silica sol preparation processes often employ simultaneous mixing of silicon and aluminum sources without the addition of dedicated dispersants. This leads to localized agglomeration in the reaction system, making it difficult to exceed 35% solid content in the sol. For example, existing technologies often directly mix silica sol with aluminum salt solutions. During the reaction, large pH fluctuations cause the resulting aluminum-silicon complex to aggregate into large particles, limiting solid content improvement and affecting compatibility with molecular sieves, ultimately resulting in unstable catalyst performance. Therefore, developing a preparation method that can significantly improve the solid content of the sol while ensuring its dispersibility is of great significance for the industrial production of catalytic cracking catalysts. Summary of the Invention

[0004] This invention provides a method for preparing a solution with increased solid content in the production of catalytic cracking catalysts, aiming to overcome the shortcomings of low solid content and poor dispersibility in existing technologies. The technical solution of this invention is characterized by the following steps: 1. The preparation method includes: 1) Preparing an aluminum source solution: Add boehmite to deionized water, stir until completely dissolved, add nitric acid to adjust the pH to 2.0-2.5, heat to 50-70 ℃, and stir for 20-50 min to obtain an aluminum source solution; 2) Preparing a silicon source dispersion: Mix silica sol with a composite dispersant, the composite dispersant being polyethylene glycol 400 and sodium dodecylbenzene sulfonate in a mass ratio of 1:0.3-0.5, the amount of composite dispersant added being 1.2-1.8% of the silica sol mass, and stir at 300-500 r / min for 10-30 min to obtain a silicon source dispersion; 3) Preparing a colloid solution through mixing reaction: Add the aluminum source solution obtained in step 1) dropwise to the silicon source dispersion obtained in step 2) at a rate of 5-8 mL / min, maintaining the reaction system temperature at 50-70 ℃ and the rotation speed at 400-600 r / min during the dropwise addition. After adding the solution at a constant speed of r / min, adjust the pH of the system to 3.5-4.0, continue stirring for 60-90 min, and then let it stand for 2-3 h to obtain a high solids content solution.

[0005] 2. The preparation method according to claim 1, characterized in that the particle size of the pseudoboehmite in step 1) is 50~80 μm and the purity is ≥98%; the mass concentration of the nitric acid is 65~68%.

[0006] 3. The preparation method according to claim 1, wherein the SiO2 content of the silica sol in step 2) is 25-30% and the particle size is 10-20 nm.

[0007] 4. The preparation method according to claim 1, wherein the volume ratio of the aluminum source solution to the silicon source dispersion in step 3) is 1:1.5~2.0.

[0008] 5. The preparation method according to claim 1, characterized in that, in step 3), the pH is adjusted using a sodium hydroxide solution with a mass concentration of 10-15% or a nitric acid solution with a mass concentration of 65-68%.

[0009] 6. The preparation method according to claims 1-5, characterized in that the high solid content adhesive has a solid content of 35-42% and a viscosity of 800-1200 mPa·s (25℃).

[0010] 7. The application of the preparation method according to claims 1-5 in the production of catalytic cracking catalyst, characterized in that the high solid content colloid is mixed with molecular sieve and clay at a mass ratio of 1:0.8~1.2:0.3~0.5, and the catalytic cracking catalyst is obtained after spray drying, calcination and water washing.

[0011] Compared with existing technologies, this invention has the following advantages: 1) Precise preparation of the aluminum source solution: Selecting small-particle-size and high-purity boehmite reduces the interference of impurities on the reaction; adjusting the pH with nitric acid promotes the full dissolution of boehmite into Al³⁺; constant-temperature stirring avoids premature hydrolysis of Al³⁺ to form aluminum hydroxide precipitate, laying the foundation for the subsequent uniform reaction with the silicon source. 2) Polyethylene glycol 400 in the composite dispersant can prevent particle agglomeration through steric hindrance, while sodium dodecylbenzenesulfonate can reduce the surface tension of silica sol and improve the uniformity of silicon source dispersion; the amount of additives added ensures the dispersion effect while avoiding excessive additive residue that affects catalyst activity. 3) Stepwise dropwise addition and control of reaction parameters: Adding the aluminum source solution to the silicon source dispersion at a low speed avoids excessively high local Al³⁺ concentrations that lead to rapid polymerization; constant temperature and medium-speed mixing promote full contact and reaction of aluminum and silicon ions; and a suitable pH can stably generate an aluminum-silicon gel structure, reducing particle agglomeration.

[0012] The above technologies can increase the solid content of the gel solution during catalytic cracking catalyst production to 38-45%, significantly reducing energy consumption in the spray drying process (saving approximately 150 kg of steam per ton of catalyst produced). The resulting gel solution exhibits excellent dispersibility; the combination of composite dispersants and a stepwise dripping process prevents particle agglomeration and facilitates subsequent mixing with molecular sieves, clay, and other components. Catalysts prepared using this gel solution can have their wear index reduced by 8-12%, catalytic activity increased by 5-8%, and batch-to-batch performance fluctuations less than 3%, making it suitable for large-scale industrial production. Detailed Implementation Example

[0013] 1) Preparation of aluminum source solution: Take 100 g of boehmite with a particle size of 50 μm and a purity of 98%, add 500 mL of deionized water, and stir until completely dissolved; add 65% nitric acid to adjust the pH to 2.0, heat to 50 ℃, and keep warm and stir for 20 min to obtain aluminum source solution.

[0014] 2) Preparation of silicon source dispersion: Take 300 g of silica sol with SiO2 content of 25% and particle size of 10 nm, add 3.6 g of composite dispersion aid (polyethylene glycol 400: sodium dodecylbenzene sulfonate = 1: 0.3), stir at 300 r / min for 15 min to obtain silicon source dispersion.

[0015] 3) Preparation of the adhesive solution through mixing and reaction: The aluminum source solution was added dropwise to the silicon source dispersion at a rate of 5 mL / min, maintaining the reaction temperature at 50 ℃ and the rotation speed at 400 r / min. After the addition was complete, the pH was adjusted to 3.5 with a 10% sodium hydroxide solution, and stirring was continued for 60 min. The solution was then allowed to stand for 2 h to age, yielding the adhesive solution. Testing showed that the solid content of the adhesive solution was 38%, and the viscosity was 967 mPa·s (25℃).

[0016] Example 2 1) Preparation of aluminum source solution: Take 120 g of boehmite with a particle size of 65 μm and a purity of 99%, add 600 mL of deionized water, and stir until completely dissolved; add 67% nitric acid to adjust the pH to 2.3, heat to 60 ℃, and keep warm and stir for 35 min to obtain aluminum source solution.

[0017] 2) Preparation of silicon source dispersion: Take 400 g of silica sol with SiO2 content of 28% and particle size of 15 nm, add 6.4 g of composite dispersion aid (polyethylene glycol 400: sodium dodecylbenzene sulfonate = 1: 0.4), stir at 400 r / min for 18 min to obtain silicon source dispersion.

[0018] 3) Preparation of the adhesive solution through mixing and reaction: The aluminum source solution was added dropwise to the silicon source dispersion at a rate of 6.5 mL / min, maintaining the reaction temperature at 65 ℃ and the rotation speed at 500 r / min. After the addition was complete, the pH was adjusted to 3.8 with 67% nitric acid, and stirring was continued for 70 min. The solution was then allowed to stand for 2.5 h to obtain the adhesive solution. The solid content of the adhesive solution was found to be 40%, and the viscosity was 1018 mPa·s (25℃).

[0019] Example 3 1) Preparation of aluminum source solution: Take 150 g of boehmite with a particle size of 80 μm and a purity of 98.5%, add 750 mL of deionized water, and stir until completely dissolved; add 68% nitric acid to adjust the pH to 2.5, heat to 70 ℃, and keep warm and stir for 50 min to obtain aluminum source solution.

[0020] 2) Preparation of silicon source dispersion: Take 500 g of silica sol with SiO2 content of 30% and particle size of 20 nm, add 9 g of composite dispersion aid (polyethylene glycol 400: sodium dodecylbenzene sulfonate = 1: 0.5), stir at 500 r / min for 20 min to obtain silicon source dispersion.

[0021] 3) Preparation of the adhesive solution through mixing and reaction: The aluminum source solution was added dropwise to the silicon source dispersion at a rate of 8 mL / min, maintaining the reaction temperature at 70 ℃ and the rotation speed at 600 r / min. After the addition was complete, the pH was adjusted to 4.0 with a 15% sodium hydroxide solution, and stirring was continued for 90 min. The mixture was then allowed to stand for 3 h to age, yielding the adhesive solution. Testing showed that the solid content of the adhesive solution was 42%, and the viscosity was 1286 mPa·s (25℃).

[0022] Comparative Example The traditional "simultaneous mixing" process was adopted: 100g of pseudoboehmite was dissolved in 500mL of deionized water (pH 2.0, 55℃), and directly mixed with 300g of silica sol without dispersing agents. The mixture was stirred at 400 r / min for 100 min and allowed to stand for 2 hours for aging. Testing revealed that the solid content of the solution was only 30%, the viscosity was 700 mPa·s (25℃), and significant particle agglomeration was observed.

[0023] Effect verification The colloids prepared in Examples 1-3 and the comparative example were mixed with molecular sieves and kaolin at a mass ratio of 1:1:0.4, respectively. After spray drying (inlet air temperature 280 ℃, outlet air temperature 120 ℃), calcination (550 ℃, 2 h), and water washing (catalyst to water liquid-solid ratio 5:1, room temperature), a catalytic cracking catalyst was obtained. The performance test results are as follows: The results above show that the high solids content colloid prepared by this invention can significantly reduce the catalyst wear index, improve catalytic activity, and meet the needs of industrial applications.

Claims

1. A process for improving the solids content of a colloidal solution in the production of a catalytic cracking catalyst characterized by Includes the following steps: 1) Preparation of aluminum source solution: Add boehmite to deionized water and stir until completely dissolved. Add nitric acid to adjust the pH to 2.0~2.5, heat to 50~70 ℃, and keep warm and stir for 20~50 min to obtain aluminum source solution; 2) Preparation of silicon source dispersion: The silica sol and the composite dispersion aid are mixed evenly. The composite dispersion aid is polyethylene glycol 400 and sodium dodecylbenzene sulfonate in a mass ratio of 1:0.3~0.

5. The amount of composite dispersion aid added is 1.2~1.8% of the mass of silica sol. Stir at 300~500 r / min for 10~30 min to obtain the silicon source dispersion. 3) Preparation of adhesive solution by mixing reaction: The aluminum source solution obtained in step 1) is added dropwise to the silicon source dispersion obtained in step 2) at a rate of 5~8 mL / min. During the dropwise addition, the temperature of the reaction system is maintained at 50~70 ℃ and the rotation speed is 400~600 r / min. After the dropwise addition is completed, the pH of the system is adjusted to 3.5~4.0, and stirring is continued for 60~90 min. Then, the system is allowed to stand for 2~3 h to obtain a high solid content adhesive solution.

2. The production method according to claim 1, characterized by, The particle size of the pseudoboehmite mentioned in step 1) is 50~80 μm and the purity is ≥98%; the mass concentration of the nitric acid is 65~68%.

3. The production method according to claim 1, characterized by, The silica sol described in step 2) has a SiO2 content of 25-30% and a particle size of 10-20 nm.

4. The method of claim 1, wherein, The volume ratio of the aluminum source solution to the silicon source dispersion in step 3) is 1:1.5~2.

0.

5. The production method according to claim 1, characterized by, In step 3), the pH is adjusted using a sodium hydroxide solution with a mass concentration of 10-15% or a nitric acid solution with a mass concentration of 65-68%.

6. The production method according to claims 1 to 5, characterized in that, The high-solids content adhesive has a solids content of 38-45% and a viscosity of 800-1200 mPa·s (25℃).

7. Use of the production process according to claims 1-5 in the production of catalytic cracking catalysts, characterized by, The high-solids content colloid is mixed with molecular sieve and clay at a mass ratio of 1:0.8~1.2:0.3~0.5, and then spray-dried, calcined and washed with water to obtain a catalytic cracking catalyst.