A method for green recycling of rare earths from waste FCC catalysts based on a high-concentration aluminum salt system

Abstract

The present invention relates to a method for green recovery of rare earths from spent FCC catalysts using a high-concentration aluminum salt system. The method comprises the following steps: first, a high-concentration aluminum salt solution-hydrogen peroxide system is used to reduce and leach the spent FCC catalyst in a two-step process to obtain a leachate containing rare earth elements lanthanum and cerium; second, the rare earth-containing leachate is subjected to P204 extraction and hydrochloric acid stripping to separate and purify the rare earths, obtaining a purified rare earth solution; and finally, precipitation with oxalic acid to obtain a high-purity lanthanum oxalate-cerium mixed product. This method achieves green, clean, and efficient recovery of rare earth elements lanthanum and cerium from spent FCC catalysts. The method achieves an extraction efficiency of over 90% for rare earths from spent FCC catalysts, a purity of over 99%, and environmentally friendly reagents such as the aluminum salt and hydrogen peroxide used.

Description

Technical Field

[0001] The present invention relates to a method for recycling rare earths in waste FCC catalysts, and in particular to a method for greenly recycling rare earths in waste FCC catalysts based on a high-concentration aluminum salt system. Background Art

[0002] Rare earths are a crucial strategic resource. Against the backdrop of my country's declining reserves due to over-exploitation of primary rare earth ores, the development of secondary rare earth resources has become a hot topic in this field. Fluid catalytic cracking catalysts (FCC catalysts) are widely used in the petroleum refining industry due to their high catalytic activity, good selectivity, high stability, and excellent hydrothermal stability. However, over the long term, FCC catalysts can deactivate and fail due to factors such as sintering, contamination with heavy metals such as nickel, vanadium, and iron, pulverization, and hydrothermal reactions, ultimately resulting in the generation of large quantities of spent FCC catalyst. According to statistics, my country generates approximately 80,000 tons of spent FCC catalyst annually. While spent FCC catalysts contain heavy metals and are classified as hazardous solid waste, they also contain 2% to 5% of the strategic rare earth metals lanthanum and cerium. Therefore, the recovery and utilization of rare earths from spent FCC catalysts not only reduces rare earth resource waste and generates significant economic value, but can also replace primary mineral resources to a certain extent, effectively reducing the environmental impact of primary ore mining.

[0003] Chinese patent CN 102586606A discloses a method for recovering rare earths from spent FCC / ROC catalysts. This method uses a strong acid such as sulfuric acid as a dissolving medium, performs strong acid leaching at 90-95°C, and then precipitates the rare earths in the rich solution by double salt precipitation. Chinese patent CN 111378842 A discloses a method for comprehensive recovery of spent FCC catalysts using a hydrochloric acid system. The method first involves soaking the spent FCC catalyst in a 4-12 mol / L hydrochloric acid solution and filtering to obtain a rare earth-containing leachate. Chinese patent CN 115924955 A discloses a process for recycling spent FCC catalysts. The process uses a hydrochloric acid-hydrogen peroxide system to reduce and leach the rare earths from the spent FCC catalysts. While these methods can effectively separate and extract rare earth elements from spent FCC catalysts and achieve the purpose of recovering rare earth elements, they are not only complex but also generate large amounts of strong acid-containing waste liquid, making subsequent waste liquid treatment difficult and causing secondary environmental pollution.

[0004] Therefore, in view of the problems and defects of the existing rare earth extraction technology in spent FCC catalysts, it is necessary to find a method for green recovery of rare earths from spent FCC catalysts based on a high-concentration aluminum salt system with high rare earth extraction efficiency and cleanliness. Summary of the Invention

[0005] The present invention addresses the shortcomings of existing rare earth recovery technologies from spent FCC catalysts by providing a method for separating, extracting, and recovering rare earths from spent FCC catalysts using a green, reductive leaching system using a high-concentration aluminum salt-hydrogen peroxide solution. This method eliminates the need for environmentally harmful strong acids such as hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, and offers advantages such as simplicity, high rare earth recovery, and a clean, environmentally friendly process.

[0006] A method for green recovery of rare earths from spent FCC catalysts based on a high-concentration aluminum salt system comprises the following steps:

[0007] (1) Calcination pretreatment: The spent FCC catalyst is calcined at 600-700°C for 2-4 hours to obtain a calcined material;

[0008] (2) Primary reduction leaching with a high-concentration aluminum salt solution: the roasted material obtained in step (1) is mixed with a high-concentration aluminum salt solution, and then hydrogen peroxide is added to perform a primary reduction leaching reaction under heating and stirring. After the reaction is completed, solid-liquid separation is performed, and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration;

[0009] (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with a high-concentration aluminum salt solution, and then hydrogen peroxide is added to carry out a secondary reduction leaching reaction under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovery of aluminum, silicon, etc.;

[0010] (4) Extraction-strip extraction separation and enrichment of rare earths: combining the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) to obtain a combined solution, extracting rare earths from the combined solution using a P204 extractant saponified with ammonia water, and then stripping the rare earth-loaded organic phase with a hydrochloric acid solution to obtain a rare earth-enriched solution;

[0011] (5) Recovering the lanthanum oxalate cerium mixed product by oxalic acid precipitation: adding an oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 2.5:1 to 1.5:1, stirring and adding ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.5 to 1.9, precipitating at 80 to 90° C. for 30 to 60 minutes, then aging at room temperature for 12 to 24 hours, and filtering to obtain the lanthanum oxalate cerium mixed product.

[0012] The aluminum salt in step (2) is one of aluminum nitrate, aluminum chloride or aluminum sulfate.

[0013] The reaction conditions for the primary reduction leaching of the high-concentration aluminum salt solution in step (2) are as follows: the mass ratio of aluminum salt to roasting material is 20:1-30:1, the mass ratio of water to aluminum salt is 1:3-1:4, the concentration of hydrogen peroxide in the reaction system is 1.5-2.0 mol / L, the reaction temperature is 75-85°C, the reaction time is 2-6 hours, and the stirring rate is 500-700 rpm.

[0014] The aluminum salt described in step (3) is one of aluminum nitrate, aluminum chloride or aluminum sulfate.

[0015] The reaction conditions for the secondary reduction leaching of the high-concentration aluminum salt solution in step (3) are as follows: the mass ratio of aluminum salt to leached residue 1 is 5:1-10:1, the mass ratio of water to aluminum salt is 1:3-1:4, the concentration of hydrogen peroxide in the reaction system is 1.2-1.5 mol / L, the reaction temperature is 75-85°C, the reaction time is 2-4 hours, and the stirring rate is 500-700 rpm.

[0016] The reaction conditions for the extraction, separation and enrichment of rare earth in step (4) are as follows: the number of extractions is 2, the P204 concentration is 0.6-1.0 mol / L, the organic phase and the aqueous phase ratio (O / A) in the first extraction is 1:1-1:2, the organic phase and the aqueous phase ratio (O / A) in the second extraction is 1:3-1:4, the saponification rate is 30%-40%, the extraction pH value is 3.5-4.5, and the extraction time is 6-8 minutes.

[0017] The reaction conditions for the stripping separation and enrichment of rare earth in step (4) are: hydrochloric acid concentration of 0.8-1.0 mol / L, the organic phase and aqueous phase ratio (O / A) of 1:4-1:6, and stripping time of 6-10 minutes.

[0018] Compared with the existing rare earth recovery process from spent FCC catalysts, the process of the present invention uses a high-concentration aluminum salt solution to reduce and leach rare earths from spent FCC catalysts in two steps, which can efficiently leach the rare earth elements lanthanum and cerium. The recovered lanthanum oxalate and cerium mixed product has high purity, and uses green leaching reagents such as aluminum salt and hydrogen peroxide, which will not cause secondary pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart of a method for green recovery of rare earths from spent FCC catalysts based on a high-concentration aluminum salt system is shown.

[0020] Figure 2 Typical scanning electron microscope images and energy spectrum diagrams of the finally recovered lanthanum oxalate cerium mixed product. DETAILED DESCRIPTION

[0021] Example 1

[0022] Follow the steps below to process:

[0023] The main components of the spent FCC catalyst are as follows: rare earth components are CeO2 (0.7124 wt.%) and La2O3 (1.34 wt.%), and the total rare earth oxide REO is 2.0524 wt.%; the main impurity components are SiO2 (43.5155 wt.%), Al2O3 (49.0451 wt.%), Na2O (1.007 wt.%), P2O5 (1.5123 wt.%) and Fe2O3 (1.0597 wt.%), and the rest are unavoidable impurities and have no substantial effect on the present invention.

[0024] (1) Calcination pretreatment: The spent FCC catalyst was calcined at 600°C for 4 hours to obtain a calcined material;

[0025] (2) Primary reduction leaching with a high-concentration aluminum salt solution: the roasted material obtained in step (1) is mixed with a high-concentration aluminum sulfate solution, and then hydrogen peroxide is added, and a primary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration; wherein the mass ratio of aluminum sulfate to roasted material is 20:1, the mass ratio of water to aluminum sulfate is 1:3, the concentration of hydrogen peroxide in the reaction system is 2.0 mol / L, the reaction temperature is 85°C, the reaction time is 6 hours, and the stirring rate is 700 rpm.

[0026] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in the spent FCC catalyst is 75% during the single reduction leaching process of high-concentration aluminum sulfate.

[0027] (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with a high-concentration aluminum sulfate solution, and then hydrogen peroxide is added, and a secondary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovering valuable elements such as aluminum and silicon; wherein the mass ratio of aluminum sulfate to leaching residue 1 is 10:1, the mass ratio of water to aluminum sulfate is 1:4, the concentration of hydrogen peroxide in the reaction system is 1.5 mol / L, the reaction temperature is 85°C, the reaction time is 4 hours, and the stirring rate is 700 rpm.

[0028] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in the spent FCC catalyst during the secondary reduction leaching process of high-concentration aluminum sulfate is 15%.

[0029] (4) Extraction-strip extraction separation and enrichment of rare earths: the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) are combined to obtain a combined liquid, the rare earth in the combined liquid is extracted using a P204 extractant saponified with ammonia water, and then the rare earth-loaded organic phase is stripped with a hydrochloric acid solution to obtain a rare earth-enriched liquid; wherein the extraction conditions are: the number of extractions is 2, the P204 concentration is 1.0 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase in the first extraction is 1:2, the phase ratio (O / A) of the organic phase to the aqueous phase in the second extraction is 1:4, the saponification rate is 30%, the extraction pH value is 4.5, and the extraction time is 6 minutes; the stripping reaction conditions are: the hydrochloric acid concentration is 0.8 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase is 1:4, and the stripping time is 6 minutes.

[0030] ICP test results showed that the extraction efficiencies of rare earth lanthanum and cerium were 99.07% and 99.68% respectively; the stripping efficiencies of rare earth lanthanum and cerium were 98.89% and 99.36% respectively.

[0031] (5) Recovering the lanthanum oxalate cerium mixed product by oxalic acid precipitation: Adding an oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 2.5:1, stirring and adding ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.5, precipitating at 90°C for 30 minutes, then aging at room temperature for 24 hours, and filtering to obtain the lanthanum oxalate cerium mixed product.

[0032] XRF test results show that the purity of the recovered lanthanum oxalate cerium mixed product is as high as 99.24%.

[0033] Example 2

[0034] Follow the steps below to process:

[0035] The main components of the spent FCC catalyst are as follows: rare earth components are CeO2 (1.1053 wt.%) and La2O3 (2.0146 wt.%), and the total rare earth oxide REO is about 3.1199 wt.%; the main impurity components are SiO2 (43.2312 wt.%), Al2O3 (48.7518 wt.%), Na2O (1.0257 wt.%), P2O5 (1.4161 wt.%) and Fe2O3 (0.9876 wt.%), and the rest are unavoidable impurities and have no substantial effect on the present invention.

[0036] (1) Calcination pretreatment: The spent FCC catalyst was calcined at 650°C for 3 hours to obtain a calcined material;

[0037] (2) Primary reduction leaching with a high-concentration aluminum salt solution: the roasted material obtained in step (1) is mixed with a high-concentration aluminum chloride solution, and then hydrogen peroxide is added to perform a primary reduction leaching reaction under heating and stirring. After the reaction is completed, solid-liquid separation is performed and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration; wherein the mass ratio of aluminum chloride to roasted material is 30:1, the mass ratio of water to aluminum chloride is 1:4, the concentration of hydrogen peroxide in the reaction system is 1.5 mol / L, the reaction temperature is 80°C, the reaction time is 4 hours, and the stirring rate is 650 rpm.

[0038] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in the spent FCC catalyst is 78.8% during the single reduction leaching process of high-concentration aluminum salt.

[0039] (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with a high-concentration aluminum chloride solution, and then hydrogen peroxide is added, and a secondary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovering valuable elements such as aluminum and silicon; wherein the mass ratio of aluminum chloride to leaching residue 1 is 5:1, the mass ratio of water to aluminum chloride is 1:3, the concentration of hydrogen peroxide in the reaction system is 1.2 mol / L, the reaction temperature is 75°C, the reaction time is 4 hours, and the stirring rate is 600 rpm.

[0040] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in spent FCC catalyst during the secondary reduction leaching process of high-concentration aluminum chloride is 13.5%.

[0041] (4) Extraction-strip extraction separation and enrichment of rare earths: the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) are combined to obtain a combined liquid, the rare earth in the combined liquid is extracted using a P204 extractant saponified with ammonia water, and then the rare earth-loaded organic phase is stripped with a hydrochloric acid solution to obtain a rare earth-enriched liquid; wherein the extraction conditions are: the number of extractions is 2, the P204 concentration is 0.6 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase in the first extraction is 1:1, the phase ratio (O / A) of the organic phase to the aqueous phase in the second extraction is 1:3, the saponification rate is 40%, the extraction pH value is 3.5, and the extraction time is 8 minutes; the reaction conditions of the stripping are: the hydrochloric acid concentration is 1.0 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase is 1:6, and the stripping time is 8 minutes.

[0042] ICP test results showed that the extraction efficiencies of rare earth lanthanum and cerium were 98.12% and 99.25% respectively; the stripping efficiencies of rare earth lanthanum and cerium were 98.54% and 99.13% respectively.

[0043] (5) Recovering the lanthanum oxalate cerium mixed product by oxalic acid precipitation: Adding an oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 1.5:1, stirring and adding ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.9, precipitating at 80°C for 60 minutes, then aging at room temperature for 12 hours, and filtering to obtain the lanthanum oxalate cerium mixed product.

[0044] XRF test results show that the purity of the recovered lanthanum oxalate cerium mixed product is as high as 99.02%.

[0045] Example 3

[0046] Follow the steps below to process:

[0047] The main components of the spent FCC catalyst are as follows: rare earth components are CeO2 (1.1053 wt.%) and La2O3 (2.0146 wt.%), and the total rare earth oxide REO is about 3.1199 wt.%; the main impurity components are SiO2 (43.2312 wt.%), Al2O3 (48.7518 wt.%), Na2O (1.0257 wt.%), P2O5 (1.4161 wt.%) and Fe2O3 (0.9876 wt.%), and the rest are unavoidable impurities and have no substantial effect on the present invention.

[0048] (1) Calcination pretreatment: The spent FCC catalyst was calcined at 700°C for 2 hours to obtain a calcined material;

[0049] (2) Primary reduction leaching with a high-concentration aluminum salt solution: the roasted material obtained in step (1) is mixed with a high-concentration aluminum nitrate solution, and then hydrogen peroxide is added to perform a primary reduction leaching reaction under heating and stirring. After the reaction is completed, solid-liquid separation is performed and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration; wherein the mass ratio of aluminum nitrate to roasted material is 25:1, the mass ratio of water to aluminum nitrate is 1:3.5, the concentration of hydrogen peroxide in the reaction system is 1.7 mol / L, the reaction temperature is 80°C, the reaction time is 5 hours, and the stirring rate is 600 rpm.

[0050] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in the spent FCC catalyst is 76.3% during the single reduction leaching process of high-concentration aluminum salt.

[0051] (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with a high-concentration aluminum nitrate solution, and then hydrogen peroxide is added to carry out a secondary reduction leaching reaction under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovering valuable elements such as aluminum and silicon; wherein the mass ratio of aluminum nitrate to leaching residue 1 is 8:1, the mass ratio of water to aluminum nitrate is 1:3.5, the concentration of hydrogen peroxide in the reaction system is 1.65 mol / L, the reaction temperature is 80°C, the reaction time is 3 hours, and the stirring rate is 650 rpm.

[0052] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in spent FCC catalyst during the secondary reduction leaching process of high-concentration aluminum chloride is 14.7%.

[0053] (4) Extraction-strip extraction separation and enrichment of rare earths: the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) are combined to obtain a combined liquid, the rare earth in the combined liquid is extracted using a P204 extractant saponified with ammonia water, and then the rare earth-loaded organic phase is stripped with a hydrochloric acid solution to obtain a rare earth-enriched liquid; wherein the extraction conditions are: the number of extractions is 2, the P204 concentration is 0.8 mol / L, the organic phase and the aqueous phase ratio (O / A) in the first extraction is 1:1.5, the organic phase and the aqueous phase ratio (O / A) in the second extraction is 1:3.5, the saponification rate is 35%, the extraction pH value is 4, and the extraction time is 10 minutes; the reaction conditions of the stripping are: the hydrochloric acid concentration is 0.8 mol / L, the organic phase and the aqueous phase ratio (O / A) is 1:5, and the stripping time is 10 minutes.

[0054] ICP test results showed that the extraction efficiencies of rare earth lanthanum and cerium were 98.54% and 99.38% respectively; the stripping efficiencies of rare earth lanthanum and cerium were 98.23% and 99.46% respectively.

[0055] (5) Oxalic acid precipitation of lanthanum oxalate cerium mixed product: add oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 2:1, stir and add ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.6, precipitate at 85°C for 40 minutes, then age at room temperature for 16 hours, and filter to obtain the lanthanum oxalate cerium mixed product.

[0056] XRF test results show that the purity of the recovered lanthanum oxalate cerium mixed product is as high as 99.15%.

[0057] Example 4

[0058] Follow the steps below to process:

[0059] The main components of the spent FCC catalyst are as follows: rare earth components are CeO2 (0.7124 wt.%) and La2O3 (1.34 wt.%), and the total rare earth oxide REO is 2.0524 wt.%; the main impurity components are SiO2 (43.5155 wt.%), Al2O3 (49.0451 wt.%), Na2O (1.007 wt.%), P2O5 (1.5123 wt.%) and Fe2O3 (1.0597 wt.%), and the rest are unavoidable impurities and have no substantial effect on the present invention.

[0060] (1) Calcination pretreatment: The spent FCC catalyst was calcined at 650°C for 3 hours to obtain a calcined material;

[0061] (2) Primary reduction leaching with a high-concentration aluminum salt solution: the roasted material obtained in step (1) is mixed with a high-concentration aluminum sulfate solution, and then hydrogen peroxide is added, and a primary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration; wherein the mass ratio of aluminum sulfate to roasted material is 30:1, the mass ratio of water to aluminum nitrate is 1:3.5, the concentration of hydrogen peroxide in the reaction system is 1.8 mol / L, the reaction temperature is 85°C, the reaction time is 6 hours, and the stirring rate is 700 rpm.

[0062] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in the spent FCC catalyst is 79.3% during the single reduction leaching process of high-concentration aluminum salt.

[0063] (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with a high-concentration aluminum nitrate solution, and then hydrogen peroxide is added, and a secondary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovering valuable elements such as aluminum and silicon; wherein the mass ratio of aluminum nitrate to leaching residue 1 is 10:1, the mass ratio of water to aluminum nitrate is 1:3, the concentration of hydrogen peroxide in the reaction system is 2 mol / L, the reaction temperature is 70°C, the reaction time is 4 hours, and the stirring rate is 500 rpm.

[0064] ICP test results show that the total leaching efficiency of rare earth lanthanum and cerium in spent FCC catalyst during the secondary reduction leaching process of high-concentration aluminum chloride is 12.6%.

[0065] (4) Extraction-strip extraction separation and enrichment of rare earths: the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) are combined to obtain a combined liquid, the rare earth in the combined liquid is extracted using a P204 extractant saponified with ammonia water, and then the rare earth-loaded organic phase is stripped with a hydrochloric acid solution to obtain a rare earth-enriched liquid; wherein the extraction conditions are: the number of extractions is 2, the P204 concentration is 1.0 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase in the first extraction is 1:1, the phase ratio (O / A) of the organic phase to the aqueous phase in the second extraction is 1:3, the saponification rate is 30%, the extraction pH value is 3.5, and the extraction time is 6 minutes; the reaction conditions of the stripping are: the hydrochloric acid concentration is 0.8 mol / L, the phase ratio (O / A) of the organic phase to the aqueous phase is 1:6, and the stripping time is 6 minutes.

[0066] ICP test results showed that the extraction efficiencies of rare earth lanthanum and cerium were 99.02% and 99.13% respectively; the stripping efficiencies of rare earth lanthanum and cerium were 98.47% and 99.23% respectively.

[0067] (5) Recovering the lanthanum oxalate cerium mixed product by oxalic acid precipitation: Adding an oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 2.5:1, stirring and adding ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.5, precipitating at 90°C for 30 minutes, then aging at room temperature for 12 hours, and filtering to obtain the lanthanum oxalate cerium mixed product.

[0068] XRF test results show that the purity of the recovered lanthanum oxalate cerium mixed product is as high as 99.37%.

Claims

1. A method for green recovery of rare earth from spent FCC catalysts based on a high-concentration aluminum salt system, characterized in that: The specific steps are as follows: (1) Calcination pretreatment: The spent FCC catalyst is calcined at 600-700°C for 2-4 hours to obtain a calcined material; (2) Single reduction leaching with a high-concentration aluminum salt solution: the calcined material obtained in step (1) is mixed with a high-concentration aluminum salt solution, and then hydrogen peroxide is added, and a single reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 1 and rare earth-containing leachate 1 are obtained by filtration; the reaction conditions of the single reduction leaching of the high-concentration aluminum salt are as follows: the mass ratio of aluminum salt to calcined material is 20:1 to 30:1, the mass ratio of water to aluminum salt is 1:3 to 1:4, the concentration of hydrogen peroxide in the reaction system is 1.5 to 2.0 mol / L, the reaction temperature is 75 to 85°C, the reaction time is 2 to 6 hours, and the stirring rate is 500 to 700 rpm; (3) secondary reduction leaching with high-concentration aluminum salt solution: the leaching residue 1 obtained in step (2) is mixed with the high-concentration aluminum salt solution, and then hydrogen peroxide is added, and a secondary reduction leaching reaction is carried out under heating and stirring. After the reaction is completed, solid-liquid separation is carried out, and leaching residue 2 and rare earth-containing leachate 2 are obtained by filtration. The leaching residue 2 is centrally processed for recovering aluminum or silicon. The reaction conditions of the secondary reduction leaching of high-concentration aluminum salt are as follows: the mass ratio of aluminum salt to leaching residue 1 is 5:1-10:1, the mass ratio of water to aluminum salt is 1:3-1:4, the concentration of hydrogen peroxide in the reaction system is 1.2-1.5 mol / L, the reaction temperature is 75-85°C, the reaction time is 2-4 hours, and the stirring rate is 500-700 rpm; (4) Extraction-strip extraction separation and enrichment of rare earth: the rare earth-containing leachate 1 obtained in step (2) and the rare earth-containing leachate 2 obtained in step (3) are combined to obtain a combined liquid, the rare earth in the combined liquid is extracted using a P204 extractant saponified with ammonia water, and then the rare earth-loaded organic phase is stripped with a hydrochloric acid solution to obtain a rare earth-enriched liquid; the reaction conditions of the extraction are: the number of extractions is 2, the P204 concentration is 0.6-1.0 mol / L, the volume ratio of the organic phase to the aqueous phase in the first extraction is 1:1-1:2, the volume of the organic phase to the aqueous phase in the second extraction is 1:3-1:4, the saponification rate is 30%-40%, the extraction pH value is 3.5-4.5, and the extraction time is 6-8 minutes; the reaction conditions of the stripping are: the hydrochloric acid concentration is 0.8-1.0 mol / L, the volume ratio of the organic phase to the aqueous phase is 1:4-1:6, and the stripping time is 6-10 minutes; (5) Recovering the lanthanum oxalate cerium mixed product by oxalic acid precipitation: adding an oxalic acid solution with a molar concentration of 2 mol / L to the rare earth enriched solution obtained in step (4), with the volume ratio of the combined solution to the oxalic acid solution being 2.5:1 to 1.5:1, stirring and adding ammonia water with a mass percentage concentration of 25% until the pH value of the solution is 1.5 to 1.9, precipitating at 80 to 90° C. for 30 to 60 minutes, then aging at room temperature for 12 to 24 hours, and filtering to obtain the lanthanum oxalate cerium mixed product.

2. The method for green recovery of rare earths from spent FCC catalysts based on a high-concentration aluminum salt system according to claim 1, characterized in that: The aluminum salt is one of aluminum nitrate, aluminum chloride or aluminum sulfate.

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