Method for removing harmful metals in waste FCC (fluid catalytic cracking) catalyst by ultrasonic-assisted ammonium persulfate-ammonia water step leaching

Abstract

The invention relates to a method for removing harmful metals in a waste FCC (fluid catalytic cracking) catalyst by ultrasonic-assisted ammonium persulfate-ammonia water gradient leaching, and belongs to the technical field of comprehensive recycling of secondary resources. The method comprises the following steps: adding the waste FCC catalyst into an ammonium persulfate solution, carrying out primary oxidation leaching under the ultrasonic action, carrying out solid-liquid separation, and washing the solid with deionized water; the waste FCC catalyst obtained after oxidation leaching is added into an ammonia water solution, secondary complexing leaching is carried out under the ultrasonic effect, solid-liquid separation is carried out, solids are washed with deionized water and dried, and the regenerated waste FCC catalyst is obtained; the ultrasonic power of the second-stage complexing leaching is 20-80% of the ultrasonic power of the first-stage oxidizing leaching, and the temperature of the second-stage complexing leaching is 10-25 DEG C lower than that of the first-stage oxidizing leaching. According to the method, a mild leaching solvent is adopted, a cascade oxidation-complexing mechanism is combined, and differentiated ultrasonic power and frequency are designed in different leaching stages, so that harmful metals in the waste FCC catalyst are effectively removed, and meanwhile, the integrity of a molecular sieve framework structure is kept.

Description

Technical Field

[0001] The invention relates to a method for removing harmful metals in a waste FCC catalyst by ultrasound-assisted ammonium persulfate-ammonia water step leaching, belonging to the technical field of comprehensive recycling of secondary resources. Background Art

[0002] Fluidized catalytic cracking (FCC) catalysts are core materials in the oil refining process, and their performance directly affects the efficiency and economy of oil refining. However, during long-term operation, harmful metals such as V, Ni, and Fe in the feedstock will be deposited on the catalyst surface and in the pores. The presence of harmful metals will destroy the catalyst zeolite structure, reduce the activity of acid sites, promote dehydrogenation reactions, increase the amount of coke generated, form refractory phases, block the catalyst pores, and significantly reduce its catalytic activity, leading to catalyst deactivation. With the tightening of environmental protection regulations and the increase in demand for resource recycling, the development of efficient and low-consumption waste FCC catalyst regeneration technology has become an urgent need in the industry.

[0003] At present, the regeneration methods for spent FCC catalysts mainly include acid leaching, alkaline leaching, high-temperature roasting, bioleaching, etc. However, it is difficult for a single leaching system to efficiently remove multiple metals at the same time (such as the coexistence of Ni metal and oxide, and the conversion of different valence states of V). Strong acid / strong base or high-temperature processes cause the catalyst skeleton structure (Al) to dissolve, and the spherical structure of the particles is severely damaged and cannot be used again. The bioleaching treatment cycle is long and difficult to apply industrially. In view of the above problems, the development of an efficient, low-consumption, and environmentally friendly cascade leaching technology to improve the removal efficiency of harmful metals while retaining the catalyst skeleton structure is the key to be solved urgently. Summary of the invention

[0004] In view of the problems of low harmful metal removal rate and easy destruction of molecular sieve framework structure in the regeneration of waste FCC catalyst, the present invention proposes a method for removing harmful metals in waste FCC catalyst by ultrasound-assisted ammonium persulfate-ammonia step leaching. A mild leaching solvent is used, combined with a step oxidation-complexation mechanism, and differentiated ultrasonic power and frequency are designed in different leaching stages, so as to effectively remove harmful metals in the waste FCC catalyst while maintaining the integrity of the molecular sieve framework structure.

[0005] A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, the specific steps are as follows:

[0006] (1) Oxidative leaching: The spent FCC catalyst is added to an ammonium persulfate solution and subjected to primary oxidative leaching under ultrasonication, followed by solid-liquid separation, and the solid is washed with deionized water;

[0007] (2) Complex leaching: adding the spent FCC catalyst after oxidation leaching in step (1) into an aqueous ammonia solution, performing secondary complex leaching under ultrasonic action, solid-liquid separation, washing the solid with deionized water, and drying to obtain the regenerated spent FCC catalyst;

[0008] The ultrasonic power of the secondary complex leaching in step (2) is 20-80% of the ultrasonic power of the primary oxidation leaching in step (1), and the temperature of the secondary complex leaching in step (2) is 10-25° C. lower than the temperature of the primary oxidation leaching in step (1).

[0009] Measured in mass percentage, the spent FCC catalyst in step (1) contains 25-28% Al, 18-21% Si, and a total content of 0.5-2.0% Ni, V, and Fe, wherein Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

[0010] Preferably, the concentration of the ammonium persulfate solution in step (1) is 0.1-0.6 mol / L, the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution is 12-20:1 g:mL, the ultrasonic power is 80-200 W, the frequency is 20-24 kHz, the primary oxidation leaching temperature is 50-65° C., and the time is 5-20 min.

[0011] Preferably, the concentration of the aqueous ammonia solution in step (2) is 0.05-0.5 mol / L, the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution is 5-10:1 g:mL, the ultrasonic power is 40-100 W, the frequency is 40 kHz, the temperature of the secondary complex leaching is 40-55° C., and the time is 10-30 min.

[0012] The step oxidation-complexation leaching principle of the present invention:

[0013] Step leaching mechanism: ammonium persulfate solution is used as a first-stage leaching agent, using ammonium persulfate (S2O8 2- ) generates strong oxidative free radicals (SO4 - ·、·OH), low-valent metals (such as V 2+ 、Ni 0 ) is oxidized to a soluble high-valent state (V 5 + 、Ni 2+ ), while avoiding strong acid corrosion on the molecular sieve framework; using ammonia water as the second-stage leaching agent, ammonia water forms a stable complex with high-valent metal ions (such as [Ni(NH3)6] 2+ , [VO2(NH3)4] + ), to achieve deep removal;

[0014] Ultrasonic synergistic enhancement: In the primary oxidation leaching process, low-frequency and high-power ultrasound (20-24kHz, 80-200W) is used to enhance free radical generation and improve oxidation efficiency; in the secondary complexation leaching process, high-frequency and low-power ultrasound (40kHz, 40-100W) is used to promote mass transfer and enhance complexation effect;

[0015] A constraint relationship between key parameters such as the ultrasonic power ratio of the two-stage leaching (the ultrasonic power of the secondary complex leaching is 20-80% of the ultrasonic power of the primary oxidation leaching) and the temperature gradient (the temperature of the secondary complex leaching is 10-25°C lower than that of the primary oxidation leaching) is established to ensure the high efficiency and controllability of the regeneration process.

[0016] The beneficial effects of the present invention are:

[0017] (1) The present invention adopts a step-by-step oxidation-complexation mechanism. The primary ammonium persulfate oxidizes low-valent harmful metal impurities into high-valent states that are easier to remove under the action of ultrasound, and the secondary ammonia water complexes and dissolves the high-valent harmful metal impurities, thereby achieving high-efficiency removal of harmful metals.

[0018] (2) The present invention designs differentiated ultrasonic power and frequency for different leaching stages, thereby enhancing the removal of harmful metals while avoiding the destruction of the molecular sieve framework structure;

[0019] (3) The present invention addresses the bottleneck of leaching efficiency caused by the complex occurrence forms of harmful metals, utilizes ultrasound to enhance oxidation-complexation synergistic leaching, and significantly improves the removal efficiency of Ni, V, and Fe while ensuring the integrity of the molecular sieve framework carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The SEM images of the spent FCC catalyst in Example 1 before (a) and after (b) the two-stage treatment are shown;

[0021] Figure 2 These are SEM images of the spent FCC catalyst in Example 2 before (a) and after (b) the two-stage treatment. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0023] Example 1: The spent FCC catalyst in this example contains 25.8% Al, 19.3% Si, and a total content of 1.21% Ni, V, and Fe. Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

[0024] A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, the specific steps are as follows:

[0025] (1) Oxidation leaching: the waste FCC catalyst was added to a 0.5 mol / L ammonium persulfate solution, and primary oxidation leaching was performed for 20 min at a temperature of 60°C under ultrasound (power 180 W, frequency 20-24 kHz), solid-liquid separation, and the solid was washed with deionized water; the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution was 15:1 g:mL;

[0026] (2) Complex leaching: the waste FCC catalyst after oxidation leaching in step (1) was added to an aqueous ammonia solution with a concentration of 0.5 mol / L, and secondary complex leaching was performed for 30 min at a temperature of 45° C. under the action of ultrasound (power 80 W, frequency 40 kHz), solid-liquid separation was performed, the solid was washed with deionized water, and dried to obtain the regenerated waste FCC catalyst; the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution was 8:1 g:mL;

[0027] After two-stage treatment, the removal rates of Fe, V and Ni were 43.6%, 50.3% and 32.1% respectively. The SEM images of the spent FCC catalyst before and after two-stage treatment (b) are shown in Figure 1 , (a) before treatment, (b) after treatment, Figure 1 It can be seen that the spherical structure of the spent FCC catalyst remains basically intact after treatment.

[0028] Comparative Example 1: This comparative example performs oxidation leaching alone, and basically adopts the oxidation leaching process parameters of step (1) of Example 1, except that: the oxidation leaching time is 60 min;

[0029] After single ammonium persulfate leaching treatment, the removal rates of Fe, V and Ni were 28.8%, 39.2% and 23.1%, respectively; the spherical structure of the spent FCC catalyst remained basically intact after treatment.

[0030] Comparative Example 2: This comparative example performs a single complex leaching, and basically adopts the complex leaching process parameters of step (2) of Example 1, except that: the spent FCC catalyst is directly added to the ammonia solution for a single complex leaching for 60 minutes;

[0031] After separate complex leaching treatment, the removal rates of Fe, V and Ni were 30.4%, 41.2% and 20.1% respectively; the spherical structure of the spent FCC catalyst remained basically intact after treatment.

[0032] Comparative Example 3: This comparative example adopts a stepwise oxidation-complexation leaching mechanism without ultrasound enhancement, and basically adopts the leaching process parameters of Example 1, except that: ultrasound is not introduced in step (1) and step (2);

[0033] After the step-by-step oxidation-complexation leaching treatment, the removal rates of Fe, V and Ni were 26.2%, 35.6% and 20.1%, respectively; the spherical structure of the spent FCC catalyst remained basically intact after treatment.

[0034] Example 2: The spent FCC catalyst in this example contains 25.8% Al, 19.3% Si, and a total content of 1.21% Ni, V, and Fe. Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

[0035] A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, the specific steps are as follows:

[0036] (1) Oxidation leaching: the waste FCC catalyst was added to an ammonium persulfate solution with a concentration of 0.3 mol / L, and primary oxidation leaching was performed for 20 min at a temperature of 50°C and under the action of ultrasound (power 80 W, frequency 20-24 kHz), solid-liquid separation was performed, and the solid was washed with deionized water; the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution was 18:1 g:mL;

[0037] (2) Complex leaching: the waste FCC catalyst after oxidation leaching in step (1) was added to an aqueous ammonia solution with a concentration of 0.4 mol / L, and secondary complex leaching was performed for 20 min at a temperature of 40° C. under the action of ultrasound (power 50 W, frequency 40 kHz), solid-liquid separation was performed, the solid was washed with deionized water, and dried to obtain the regenerated waste FCC catalyst; the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution was 6:1 in g:mL;

[0038] After two-stage treatment, the removal rates of Fe, V and Ni were 41.4%, 48.1% and 30.6% respectively. The SEM images of the spent FCC catalyst before and after two-stage treatment (b) are shown in Figure 2 , (a) before treatment, (b) after treatment, Figure 2 It can be seen that the spherical structure of the spent FCC catalyst remains basically intact after treatment.

[0039] Example 3: The spent FCC catalyst in this example contains 27.8% Al, 20.5% Si, and a total content of 1.6% Ni, V, and Fe. Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

[0040] A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, the specific steps are as follows:

[0041] (1) Oxidation leaching: the waste FCC catalyst was added to an ammonium persulfate solution with a concentration of 0.6 mol / L, and primary oxidation leaching was performed at a temperature of 55°C and under the action of ultrasound (power 200 W, frequency 20-24 kHz) for 10 min, solid-liquid separation was performed, and the solid was washed with deionized water; the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution was 12:1 g:mL;

[0042] (2) Complex leaching: the waste FCC catalyst after oxidation leaching in step (1) was added to an aqueous ammonia solution with a concentration of 0.25 mol / L, and secondary complex leaching was performed at a temperature of 40° C. and under the action of ultrasound (power 100 W, frequency 40 kHz) for 10 min, solid-liquid separation was performed, the solid was washed with deionized water, and dried to obtain the regenerated waste FCC catalyst; the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution was 10:1 in g:mL;

[0043] After two-stage treatment, the removal rates of Fe, V and Ni were 45.6%, 47.3% and 30.1% respectively, and the spherical structure of the spent FCC catalyst remained basically intact after treatment.

[0044] Example 4: The spent FCC catalyst in this example contains 26.2% Al, 20.5% Si, and a total content of 0.7% Ni, V, and Fe. Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

[0045] A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, the specific steps are as follows:

[0046] (1) Oxidation leaching: the waste FCC catalyst was added to an ammonium persulfate solution with a concentration of 0.6 mol / L, and primary oxidation leaching was performed for 10 min at a temperature of 65°C and under the action of ultrasound (power 160 W, frequency 20-24 kHz), solid-liquid separation, and the solid was washed with deionized water; the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution was 20:1 g:mL;

[0047] (2) Complex leaching: the waste FCC catalyst after oxidation leaching in step (1) was added to an aqueous ammonia solution with a concentration of 0.2 mol / L, and secondary complex leaching was performed for 20 min at a temperature of 45° C. under the action of ultrasound (power 50 W, frequency 40 kHz), solid-liquid separation was performed, the solid was washed with deionized water, and dried to obtain the regenerated waste FCC catalyst; the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution was 8:1 in g:mL;

[0048] After two-stage treatment, the removal rates of Fe, V and Ni were 44.6%, 54.3% and 33.1% respectively, and the spherical structure of the spent FCC catalyst remained basically intact after treatment.

[0049] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia step leaching, characterized in that: The specific steps are as follows: (1) Oxidative leaching: the spent FCC catalyst is added to an ammonium persulfate solution, and primary oxidative leaching is performed under ultrasonic action, followed by solid-liquid separation, and the solid is washed with deionized water; (2) Complex leaching: adding the spent FCC catalyst after oxidation leaching in step (1) into an aqueous ammonia solution, performing secondary complex leaching under ultrasonic action, solid-liquid separation, washing the solid with deionized water, and drying to obtain the regenerated spent FCC catalyst; The ultrasonic power of the secondary complex leaching in step (2) is 20-80% of the ultrasonic power of the primary oxidation leaching in step (1), and the temperature of the secondary complex leaching in step (2) is 10-25° C. lower than the temperature of the primary oxidation leaching in step (1).

2. The method for removing harmful metals from spent FCC catalysts by ultrasound-assisted ammonium persulfate-ammonia stepwise leaching according to claim 1, characterized in that: Measured in mass percentage, the spent FCC catalyst in step (1) contains 25-28% Al, 18-21% Si, and a total content of 0.5-2.0% Ni, V, and Fe, wherein Ni mainly exists in the form of NiO and metallic Ni phases, Fe mainly exists in the form of Fe3O4, Fe2O3, and Fe2SiO4 phases, and V mainly exists in the form of VO2 and VO phases.

3. The method for removing harmful metals from spent FCC catalyst by ultrasound-assisted ammonium persulfate-ammonia step leaching according to claim 1, characterized in that: In step (1), the concentration of the ammonium persulfate solution is 0.1-0.6 mol / L, the solid-liquid ratio of the waste FCC catalyst to the ammonium persulfate solution is 12-20:1 g:mL, the ultrasonic power is 80-200 W, the frequency is 20-24 kHz, the primary oxidation leaching temperature is 50-65° C., and the time is 5-20 min.

4. The method for removing harmful metals from spent FCC catalyst by ultrasound-assisted ammonium persulfate-ammonia step leaching according to claim 1, characterized in that: In step (2), the concentration of the aqueous ammonia solution is 0.05-0.5 mol / L, the solid-liquid ratio of the waste FCC catalyst to the aqueous ammonia solution is 5-10:1 g:mL, the ultrasonic power is 40-100 W, the frequency is 40 kHz, the temperature of the secondary complex leaching is 40-55° C., and the time is 10-30 min.

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