Method for preparing alkali-free accelerator from waste catalytic cracking catalyst and application of alkali-free accelerator

Abstract

The invention provides a method for preparing an alkali-free accelerator from a waste catalytic cracking catalyst and application of the alkali-free accelerator, and the method comprises the following steps: adding aluminum mud into a fluosilicic acid solution, stirring to react for 1-3 hours, then adding the waste catalytic cracking catalyst, and stirring to react for 1-2.5 hours to obtain the alkali-free accelerator; the waste catalytic cracking catalyst comprises the following main components: Al2O3 and SiO2; wherein the molar ratio of the fluosilicic acid solution to the aluminum mud to the waste catalytic cracking catalyst is (1-3): (2-4): (0.5-2) according to the content of fluosilicic acid in the fluosilicic acid solution, the content of Al2O3 in the aluminum mud and the content of Al2O3 in the waste catalytic cracking catalyst. The problems existing in a traditional alkali accelerator are solved, efficient utilization of resources is achieved, and the prepared accelerator does not contain harmful alkali components and can promote rapid setting of concrete.

Description

Technical Field

[0001] This invention relates to the field of waste catalyst recycling, specifically to a method and application for preparing alkali-free accelerators from waste catalytic cracking catalysts. Background Technology

[0002] Concrete admixtures are indispensable materials in modern engineering construction, and their performance directly affects the construction efficiency and service life of concrete. Among various admixtures, accelerators are widely used in complex construction scenarios such as tunnels, mine shafts, and urban underground spaces because they can significantly shorten the setting time of concrete and improve early strength.

[0003] Meanwhile, the resource utilization of spent catalysts has received increasing attention. Spent catalysts, as solid waste generated during industrial production, mainly originate from petrochemical, fine chemical, and environmental remediation fields. The composition of spent catalysts is complex, typically containing precious metals (such as platinum, palladium, and rhodium), metal oxides (such as alumina and silicon oxide), and other impurities. Currently, the main approaches to resource utilization of spent catalysts include metal recovery, regeneration, and use as raw materials to prepare other functional materials. However, research on the use of spent catalysts in the preparation of alkali-free rapid-setting agents is still in its early stages, with significant research gaps.

[0004] Waste catalysts contain a large amount of useful components such as aluminum and silicon. If they can be effectively recovered and applied to the preparation of accelerators, not only can resources be recycled, but the potential environmental hazards of waste can also be reduced. Therefore, developing a new type of alkali-free accelerator that meets engineering needs while also taking into account environmental protection has become an urgent research task. Summary of the Invention

[0005] The technical objective of this invention is to address the shortcomings of the prior art by providing a method and application for preparing an alkali-free accelerator from waste catalytic cracking catalyst, thereby solving the problems of traditional alkali-containing accelerators and achieving efficient resource utilization. The accelerator prepared by this invention does not contain harmful alkaline components and can promote the rapid setting of concrete.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for preparing an alkali-free accelerator from spent catalytic cracking catalyst, comprising the following steps: Aluminum sludge is added to a fluorosilicic acid solution and stirred for 1-3 hours. Then, pretreated waste catalytic cracking catalyst is added and stirred for 1-2.5 hours to obtain an alkali-free quick-setting agent. The main components of the waste catalytic cracking catalyst include Al2O3 and SiO2. The molar ratio of the amounts of the fluorosilicic acid solution, aluminum sludge, and waste catalytic cracking catalyst added is (1-3):(2-4):(0.5-2), based on the fluorosilicic acid content, the Al2O3 content, and the Al2O3 content.

[0007] Furthermore, the spent catalytic cracking catalyst is an amorphous aluminum silicate catalyst.

[0008] Furthermore, the pretreatment includes heating the waste catalyst at 110-130°C for 0.75-1.25 h, and then calcining it at 480-520°C for 1.5-2.5 h.

[0009] Furthermore, the pretreated spent catalytic cracking catalyst has a particle size of 10-50 μm and a specific surface area of ​​100-300 m². 2 / g.

[0010] Furthermore, by mass percentage, the spent catalytic cracking catalyst comprises the following components: Al2O3: 50%-56%; SiO2: 35%-40%.

[0011] Furthermore, when the pH value of the reaction solution of fluorosilicic acid and spent catalytic cracking catalyst is 1.3-2, spent catalytic cracking catalyst is added.

[0012] Furthermore, after adding the waste catalytic cracking catalyst, when the pH value of the reaction solution is ≥2.5, the reaction yields an alkali-free quick-setting agent.

[0013] Furthermore, the preferred molar ratio of the fluorosilicic acid solution (based on its fluorosilicic acid content), the aluminum sludge (based on its Al2O3 content), and the waste catalytic cracking catalyst (based on its Al2O3 content) is 2:3:1.

[0014] Furthermore, the aluminum sludge is in a semi-solid state and is preferably white in color.

[0015] Furthermore, the stirring rate is 60 r / min-120 r / min.

[0016] The present invention also provides an alkali-free quick-setting agent prepared based on the above method and its application. Specifically, the alkali-free quick-setting agent is used in shotcrete to adjust the concrete setting time, wherein the dosage of the alkali-free quick-setting agent is 3-9 wt% of the cement mass in the concrete.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses treated waste catalytic cracking catalyst as raw material to prepare an alkali-free accelerator. By accelerating the cement hydration process, it reduces the initial setting time to less than 4 minutes and the final setting time to less than 8 minutes, both exceeding the standards specified in GB / T35159-2017. It can promote the initial setting and early strength of concrete within minutes, ensuring rapid construction. The accelerator prepared by this invention meets the requirements for alkali-free accelerators specified in the national standard GB / T35159-2017 (sodium oxide equivalent content not exceeding 1%). Therefore, the accelerator prepared by this invention is an alkali-free accelerator. Compared with traditional alkali-based accelerators, its significant advantages include the absence of harmful alkaline components, effectively preventing steel corrosion and reducing the risk of later strength reduction, thus significantly improving the durability and safety of concrete. Furthermore, the low-corrosion characteristics of the alkali-free accelerator minimize its impact on construction equipment and the environment, meeting the requirements of modern engineering for green building materials.

[0018] The alkali-free quick-setting agent of this invention can promote the formation of hydrated calcium silicate (CSH) gel, silicate gel, and aluminate gel in silicate cement / slag silicate cement. The three-dimensional network structure formed by the gel products significantly improves the mechanical properties of concrete. The microporous structure of the waste catalytic cracking catalyst is conducive to catalyzing the hydration reaction of cement particles, accelerating the hardening process of concrete, achieving rapid setting, and enhancing the strength and durability of cement stone. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] A method for preparing an alkali-free accelerator from spent catalytic cracking catalyst includes the following steps: Take a fluorosilicic acid solution and place it in a beaker. Add aluminum sludge. The reaction is exothermic, with an exothermic temperature of 30-60℃. Stir at a rate of 60-120 r / min for 1-3 hours and measure the pH value. When the pH value is 1.3-2, add the spent catalytic cracking catalyst and stir at a rate of 60-120 r / min for 1-2.5 hours. Measure the pH value again. When the pH value is 2.5-3.5, an alkali-free quick-setting agent is obtained. The molar ratio of the fluorosilicic acid solution (based on its fluorosilicic acid content), the aluminum sludge (based on its Al2O3 content), and the spent catalytic cracking catalyst (based on its Al2O3 content) is (1-3):(2-4):(0.5-2).

[0021] The spent catalytic cracking catalyst is a pretreated amorphous aluminosilicate catalyst. The pretreatment includes heating the spent catalyst at 120°C for 1 hour, then calcining it at 500°C for 2 hours, and finally sieving it. Pretreatment removes oil, water, gums, and organic matter from the spent catalytic cracking catalyst and improves its activity.

[0022] The pretreated spent catalytic cracking catalyst, by mass percentage, comprises the following components: Al₂O₃: 53.16%; SiO₂: 39.82%; NiO: 2.28%; Fe₂O₃: 1.06%; P₂O₅: 0.73%; TiO₂: 0.62%; CeO₂: 0.42%; La₂O₃: 0.34%; Sb₂O₃: 0.28%; K₂O: 0.25%; CaO: 0.25%; Na₂O: 0.11%; Co₂O₃: 0.11%; V₂O₅: 0.10%; with a particle size of 10-50 μm and a specific surface area of ​​100-300 m². 2 / g.

[0023] The preferred molar ratio of the amounts of the fluorosilicic acid solution, aluminum sludge, and waste catalytic cracking catalyst added is 2:3:1, based on the fluorosilicic acid content, the Al2O3 content, and the Al2O3 content.

[0024] The aluminum sludge is in a semi-solid state, with an aluminum content of 13-16 wt% and a water content of ≤70 wt%, and the aluminum exists in the form of aluminum hydroxide or aluminum oxide.

[0025] The fluorosilicic acid solution is a commercially available fluorosilicic acid solution with a concentration of 30%.

[0026] The aforementioned alkali-free accelerator can be used in wet-mixed shotcrete to adjust the concrete setting time. Specifically, the alkali-free accelerator is mixed evenly with cement in a certain proportion, wherein the dosage of the alkali-free accelerator is 3-9 wt% of the cement mass in the concrete. Then, setting time and strength tests are conducted. Specific examples are as follows:

[0027] Example 1 First, a fluorosilicic acid solution was placed in a beaker, and aluminum sludge was added. The reaction was exothermic, with a temperature of 40℃. After stirring for 2 hours, the pH value was measured to be 1.7. The reaction was then complete. Waste catalytic cracking catalyst was added, and the mixture was stirred for 2 hours, at which point the pH value was measured to be 3, resulting in an alkali-free quick-setting agent. The amounts of the fluorosilicic acid solution (based on its fluorosilicic acid content), the aluminum sludge (based on its Al2O3 content), and the waste catalytic cracking catalyst (based on its Al2O3 content) added were 1 mol, 1.5 mol, and 0.5 mol, respectively.

[0028] Example 2 First, a fluorosilicic acid solution was placed in a beaker, and aluminum sludge was added. The reaction was exothermic, with a temperature of 50°C. After stirring for 2 hours, the pH value was measured to be 1.3. The reaction was then complete. Waste catalytic cracking catalyst was added, and the mixture was stirred again for 2 hours. The pH value was measured to be 2.5, thus generating an alkali-free quick-setting agent. The amounts of the fluorosilicic acid solution (based on its fluorosilicic acid content), the aluminum sludge (based on its Al2O3 content), and the waste catalytic cracking catalyst (based on its Al2O3 content) added were 2 mol, 1.5 mol, and 0.5 mol, respectively.

[0029] Example 3 First, a fluorosilicic acid solution was placed in a beaker, and aluminum sludge was added. The reaction was exothermic, with a temperature of 30°C. After stirring for 2 hours, the pH value was measured to be 2. The reaction was then complete. Waste catalytic cracking catalyst was added, and the mixture was stirred again for 2 hours. The pH value was measured to be 3.5, resulting in an alkali-free quick-setting agent. The amounts of the fluorosilicic acid solution (based on its fluorosilicic acid content), the aluminum sludge (based on its Al2O3 content), and the waste catalytic cracking catalyst (based on its Al2O3 content) added were 1 mol, 3 mol, and 0.5 mol, respectively.

[0030] Comparative Example First, a fluorosilicic acid solution was placed in a beaker, and aluminum sludge was added. The reaction was exothermic, with a temperature of 40°C. After stirring for 1 hour, the pH value was measured to be 1. The reaction was then complete. Waste catalytic cracking catalyst was added, and the mixture was stirred again for 1 hour. The pH value was measured to be 1.9, thus generating an alkali-free quick-setting agent. The amounts of the fluorosilicic acid solution, aluminum sludge, and waste catalytic cracking catalyst added were 1 mol, 1.5 mol, and 0.5 mol, respectively, based on their fluorosilicic acid content, Al2O3 content.

[0031] Testing showed that the accelerators prepared in Examples 1-3 met the requirements for alkali-free accelerators specified in the national standard GB / T35159-2017 (sodium oxide equivalent content not exceeding 1%). Setting time is one of the important indicators for evaluating the performance of alkali-free accelerators; initial and final setting times directly affect construction efficiency and project quality. Compressive strength is the core indicator for measuring the effect of accelerators on cement strength development. Based on relevant standards (such as GB / T 35159—2017), this invention determined the setting time of cement paste containing accelerators and the compressive strength of cement mortar containing accelerators at different ages, evaluating the influence of accelerators on the mechanical properties of cement. The test results of the setting time of cement paste containing alkali-free liquid accelerators are shown in Table 1.

[0032] Table 1. Cement setting time of the examples and comparative examples with added accelerators.

[0033] The results showed that the initial setting time of the comparative example was 3 min 30 s, and the final setting time was negligible. This did not meet the national standard requirements, and verification observation indicated that the reaction in this experiment was incomplete and did not meet the expected requirements. The cement paste with the accelerators from Examples 1-3 exceeded the national standard requirements of an initial setting time ≤ 5 min and a final setting time ≤ 12 min. Furthermore, tests showed that the 1-day compressive strength of the cement mortar with the accelerators from Examples 1-3 was greater than or equal to 7 MPa, and the 28-day compressive strength ratio was greater than or equal to 90%, meeting the national standard requirements. Through these examples, the data from Example 1 without the accelerator met the national standard requirements and was the best compared to other examples, saving raw materials.

[0034] To further verify the compatibility of the accelerator with different types of cement, seven common PSA32.5 slag silicate cements produced in different regions were selected for testing. Using the accelerator prepared in Example 1, at a dosage of 8 wt%, the test results of the setting time of cement paste from different brands with added alkali-free liquid accelerator are shown in Table 2.

[0035] Table 2 Setting Time of Cement with Accelerators of Different Brands

[0036] The results show that, despite the differences in mineral composition and admixture types among different cements, the prepared alkali-free accelerator, at a dosage of 8%, can achieve good results with an initial setting time of less than 3 minutes and a final setting time of no more than 6 minutes. The cement mortar with the accelerator was tested to have a 1-day compressive strength greater than or equal to 7 MPa and a 28-day compressive strength ratio greater than or equal to 90%, which meets the national standard requirements. This indicates that the accelerator has the potential for widespread application in practical engineering.

[0037] The above technical solutions illustrate the technical concept of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any modifications or alterations made to the above technical solutions based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for preparing an alkali-free accelerator from spent catalytic cracking catalyst, characterized in that: Includes the following steps: Aluminum sludge is added to a fluorosilicic acid solution and stirred for 1-3 hours. Then, pretreated waste catalytic cracking catalyst is added and stirred for 1-2.5 hours to obtain an alkali-free quick-setting agent. The main components of the waste catalytic cracking catalyst include Al2O3 and SiO2. The molar ratio of the amounts of the fluorosilicic acid solution, aluminum sludge, and waste catalytic cracking catalyst added is (1-3):(2-4):(0.5-2), based on the fluorosilicic acid content, the Al2O3 content, and the Al2O3 content.

2. The method for preparing alkali-free accelerators from spent catalytic cracking catalysts according to claim 1, characterized in that: The spent catalytic cracking catalyst is an amorphous aluminum silicate catalyst.

3. The method for preparing an alkali-free accelerator from spent catalytic cracking catalyst according to claim 1, characterized in that: The pretreatment includes heating the waste catalyst at 110-130℃ for 0.75-1.25h, and then calcining it at 480-520℃ for 1.5-2.5h.

4. The method for preparing an alkali-free accelerator from spent catalytic cracking catalyst according to claim 3, characterized in that: The pretreated spent catalytic cracking catalyst has a particle size of 10-50 μm and a specific surface area of ​​100-300 m². 2 / g.

5. The method for preparing an alkali-free accelerator from spent catalytic cracking catalyst according to claim 1, characterized in that: The spent catalytic cracking catalyst comprises the following components by mass percentage: Al2O3: 50%-56%; SiO2: 35%-40%.

6. The method for preparing an alkali-free accelerator from spent catalytic cracking catalyst according to claim 1, characterized in that: When the pH of the reaction solution of fluorosilicic acid and spent catalytic cracking catalyst is 1.3-2, the spent catalytic cracking catalyst is added; when the pH of the reaction solution is ≥2.5, the reaction yields an alkali-free quick-setting agent.

7. The method for preparing an alkali-free accelerator from spent catalytic cracking catalyst according to claim 1, characterized in that: The molar ratio of the amounts of fluorosilicic acid solution, aluminum sludge, and waste catalytic cracking catalyst added is 2:3:1, based on the fluorosilicic acid content, Al2O3 content, and Al2O3 content.

8. The method for preparing alkali-free accelerators from spent catalytic cracking catalysts according to claim 1, characterized in that: The aluminum sludge is semi-solid and white in color; the stirring rate is 60 r / min-120 r / min.

9. An alkali-free quick-setting agent prepared by the method according to any one of claims 1-8.

10. The application of an alkali-free quick-setting agent prepared according to any one of claims 1-8 in shotcrete.

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