Method for recovering high-purity silicon aluminum from waste catalyst

Abstract

The invention relates to the technical field of resource recovery, and discloses a method for recovering high-purity silicon aluminum from a waste catalyst, which comprises the following steps: (1) the waste catalyst comprises SiO2, Al2O3 and other metal oxides, the content of SiO2 is greater than 30wt%, and the content of Al2O3 is greater than 20wt%; the method comprises the following steps: ball-milling and mixing the waste catalyst and sodium carbonate, and carrying out aerobic roasting to obtain a mixture; (2) adding the mixture into water for water immersion treatment, and filtering to obtain a crude sample; (3) adding the crude sample into a hydrochloric acid solution for acid leaching treatment, filtering and roasting to obtain high-purity silicon; and (4) adding alkali into the filtrate obtained in the step (3) until the pH value is 7.5-9.5, precipitating, filtering and roasting to obtain an aluminum oxide product. Through sodium salt activation roasting and a multi-stage separation process, mutual interference of metal impurities, silicon and aluminum is avoided, and efficient separation of silicon and aluminum is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recovery, and in particular to a method for recovering high-purity silicon and aluminum from waste catalysts. Background Art

[0002] Fluidized catalytic cracking (FCC) catalysts are high in silicon and aluminum. Automobile exhaust catalysts also contain high levels of silicon and aluminum. The resource utilization of high-content silicon and aluminum catalysts faces the following challenges: First, pyrometallurgical regeneration results in high energy consumption and secondary pollution, requiring high-temperature decarbonization above 800°C (energy consumption > 1000kWh / ton), and activity recovery after regeneration is only 60-80%. Second, the multi-stage acid-base treatment during wet recovery produces high-salt wastewater (Cl - >5%, SO4 2- >10%), which increases the burden of post-processing; third, during alkali fusion activation, high-temperature calcination above 700°C is required, and the amount of alkali agent is 1:1, which is costly and releases CO2 / NO x Therefore, the above resource utilization methods seriously restrict their industrial applications.

[0003] In addition, in the process of resource recycling, the silicon-aluminum separation technology still has the following limitations: (1) Acid-preferential aluminum dissolution method: For example, the invention patent with publication number CN 103332715A discloses a method for recovering aluminum oxide from waste FCC catalyst. The main active component of FCC catalyst is zeolite molecular sieve, which has a highly ordered pore structure and a silicon-aluminum oxide skeleton. This structure gives the catalyst good stability. Hydrochloric acid is used to dissolve aluminum to generate AlCl3, but silicon remains in the slag due to its dense structure (purity ≤85%), and a secondary alkali dissolution is required to extract silicon (the process is increased to 6 steps); (2) Alkali-preferential silicon dissolution method: For example, the invention patent with publication number CN Patent No. 101705380A discloses a method for recovering rare earths from aluminum-silicon materials containing rare earths. NaOH dissolves silicon at high temperature (>90°C) to produce Na2SiO3, but aluminum is lost due to co-dissolution (recovery rate <80%), and the strong alkaline waste liquid is difficult to treat (pH>12); (3) combined acid-base method: first acid leaching is used to extract aluminum, and then alkaline dissolution is used to extract silicon. The process is lengthy (the process is increased to 8 steps) and the reagent consumption is doubled (HCl+NaOH>300L / ton of waste reagent). Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for recovering high-purity silicon and aluminum from waste catalysts. Through sodium salt activation roasting and multi-stage separation process, the mutual interference of metal impurities, silicon and aluminum is avoided, and the efficient separation of silicon and aluminum is achieved. Finally, more than 95% high-purity silicon and more than 90% high-purity aluminum are obtained, which are significantly higher than the recovery purity of traditional processes, thereby realizing efficient resource utilization of high-content silicon and aluminum catalysts.

[0005] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for recovering high-purity silicon and aluminum from waste catalysts, comprising the following steps: (1) The spent catalyst comprises SiO2, Al2O3 and other metal oxides, wherein the SiO2 content is greater than 30 wt% and the Al2O3 content is greater than 20 wt%; the spent catalyst is ball-milled with sodium carbonate and then aerobic calcined to obtain a mixture; (2) adding the mixture into water for water immersion treatment, and filtering to obtain a crude sample; (3) adding the crude sample to a hydrochloric acid solution for acid leaching, filtering, and then calcining to obtain a silica product; (4) Adding alkali to the filtrate obtained in step (3) to a pH of 7.5-9.5, performing precipitation, filtering, and then roasting to obtain an alumina product.

[0006] First, by subjecting the spent catalyst and sodium carbonate (Na2CO3) to an oxygen roasting treatment, other metals are converted into water-soluble salts, while SiO2 and Al2O3 are converted into aluminosilicates that are not easily soluble in water. Then, through water leaching treatment, the preferential separation of other metals can be achieved, and aluminosilicates are obtained in the filter residue. After that, acid leaching treatment is carried out. Aluminosilicates are easily soluble in acid and a silicon-containing precipitate is generated (mainly a silicic acid precipitate, but since silicic acid is unstable in solution, some silicon dioxide may also be present). Then, high-purity silicon dioxide is obtained by roasting. The filtrate obtained after acid leaching and filtration is added with ammonia water to obtain aluminum hydroxide precipitate, which is then roasted to obtain high-purity alumina. Therefore, the present invention can avoid the mutual interference of metal impurities, silicon and aluminum, and achieve efficient separation of silicon and aluminum through a multi-stage separation process, ultimately obtaining more than 95% high-purity silicon and more than 90% high-purity aluminum, which are significantly higher than the recovery purity of traditional processes.

[0007] Preferably, in step (1), the other metals include one or more of Ni, V, La, Fe, Ce, Mg, Ti, Ni, Sb, Y, K, and Nb.

[0008] Preferably, in step (1), the amount of sodium carbonate added is 70-110% of the mass of the waste catalyst.

[0009] Preferably, in step (1), the ball milling mixing time is 0.5-2h.

[0010] Preferably, in step (1), the temperature of the aerobic roasting is 500-600°C, the heating rate is 5-10°C / min, and the holding time is 1-2 hours. Alternatively, a two-stage roasting is adopted, wherein the first roasting is heated to 400°C (oxidation of organic matter), the heating rate is 5-10°C / min, and the holding time is 0.5-1 hour; and the second roasting is heated to 550°C (enhanced sodium salt formation), the heating rate is 5-10°C / min, and the holding time is 0.5-1 hour.

[0011] Preferably, in step (2), the mass ratio of the mixture to water is 1:6-8.

[0012] Preferably, in step (2), the water immersion treatment is carried out at 80-90° C. for 30-60 minutes.

[0013] Preferably, in step (3), the mass concentration of the hydrochloric acid solution is 15-20%.

[0014] Preferably, in step (3), the mass ratio of the crude sample to the hydrochloric acid solution is 1:8-12.

[0015] Preferably, in step (3), the acid leaching treatment is carried out at 90-100° C. for 10-16 hours.

[0016] Preferably, in step (3), the calcination temperature is 500-600°C, the heating rate is 5-10°C / min, and the holding time is 1-2h.

[0017] Preferably, in step (4), aqueous ammonia is added to the filtrate to adjust the pH to 7.5-9.5.

[0018] Preferably, in step (4), the calcination temperature is 500-600°C, the heating rate is 5-10°C / min, and the holding time is 1-2h.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) High-efficiency separation and high-purity products: Through sodium salt activation roasting and multi-stage separation process (including water leaching of nickel and vanadium, acid washing to obtain silicon and precipitation to obtain aluminum), the mutual interference of heavy metal impurities, silicon and aluminum is avoided, and high-efficiency separation of silicon and aluminum is achieved. Ultimately, more than 95% high-purity silicon and more than 90% high-purity aluminum are obtained, which are significantly higher than the recovery purity of traditional processes.

[0020] (2) The overall process is green and environmentally friendly: no toxic gas emissions: sodium carbonate is used instead of sodium chloride / sodium sulfate to eliminate the generation of Cl2 / SO3 (compared with the traditional process, the toxicity of waste gas is reduced by 100%); heavy metal recovery throughout the entire process: water extraction is used to recover metal impurities, and the comprehensive recovery rate of heavy metals is >95% (traditional process ≤70%); near-zero wastewater pollution discharge: after neutralization treatment, the process wastewater has a heavy metal concentration of <1ppm and a SO42 / Cl concentration of <0.1%, and can be directly reused or discharged in compliance with standards (national standard limit: heavy metals <5ppm).

[0021] (3) Versatility and ease of operation of equipment: The equipment used in this process (such as ball mill, roasting furnace, reactor, etc.) are all conventional chemical equipment and do not require special customization. The process is easy to implement and the operating conditions are mild, which is suitable for large-scale production and reduces equipment investment and operating difficulty.

[0022] (4) Strong adaptability to raw materials: This process has low requirements on the type and composition of waste catalysts and can be applied to various types of waste catalysts (such as petroleum cracking catalysts, automobile exhaust catalysts, fly ash, etc.), and has wide applicability. DETAILED DESCRIPTION

[0023] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0024] Example 1 (1) 20 g of spent catalyst (containing 44.5 wt% SiO2, 41.4 wt% Al2O3, 4.31 wt% La2O3, 1.61 wt% V2O5, 1.51 wt% Fe2O3, 1.43 wt% CeO2, 1.22 wt% MgO, 1.07 wt% TiO2, 0.84 wt% NiO, 0.55 wt% Sb2O3, 0.47 wt% Y2O3, 0.46 wt% P2O5, 0.44 wt% K2O, and 0.19 wt% Nb2O5) was ball-milled with 17 g Na2CO3 for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in air atmosphere, calcined for 1 h, and cooled to obtain a mixture (white-gray powder). (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0025] Example 2 Comparative Example 1, other processes remained unchanged, the acid concentration was changed to 15wt%, and the leaching time was extended to 16h.

[0026] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 15 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir for 16 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0027] Example 3 Comparative Example 1, other processes remain unchanged, and a two-stage roasting method is adopted, with the first roasting at 400°C (oxidation of organic matter) and the second roasting at 550°C (enhanced sodium salt formation).

[0028] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 400°C at a rate of 5°C / min in air atmosphere and calcined for 30 min. The mixture was then heated to 550°C at a rate of 5°C / min and calcined for 30 min. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0029] Example 4 Compared with Example 1, the other processes remain unchanged, and the roasting temperature is increased to 650°C.

[0030] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 650°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0031] Example 5 Comparative Example 1, other processes remain unchanged, and the precipitant in the aluminum precipitation process is changed to 10wt% ammonia water.

[0032] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 10 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0033] Example 6 Comparative Example 1, other processes remained unchanged, and during the aluminum precipitation process, the pH was adjusted to 9.5.

[0034] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 9.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0035] Comparative Example 1 Comparative Example 1, other processes remain unchanged, 17g Na2CO3 is changed to 22.78g Na2SO4 (keeping the molar equivalent of Na the same as in Example 1).

[0036] (1) 20 g of spent catalyst was ball-milled with 22.78 g of Na2SO4 for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0037] Comparative Example 2 Comparative Example 1, other processes remain unchanged, 17g Na2CO3 is replaced by 18.76g NaCl (molar equivalent is the same as in Example 1).

[0038] (1) 20 g of spent catalyst was ball-milled with 18.76 g of NaCl for 30 min. The mixture was heated to 550 °C at a rate of 5 °C / min in air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0039] Comparative Example 3 Comparative Example 1, other processes remain unchanged, and the amount of Na2CO3 is increased to 30g.

[0040] (1) 20 g of spent catalyst was mixed with 30 g of Na2CO3 by ball milling for 30 min; the mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere, calcined for 1 h, and cooled to obtain a mixture (white-gray powder); (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0041] Comparative Example 4 Comparative Example 1, other processes remain unchanged, and direct calcination is performed without adding Na2CO3.

[0042] (1) Take 20 g of spent catalyst, heat it to 550 °C at 5 °C / min in air atmosphere, calcine it for 1 h, and cool it to obtain a mixture (gray powder); (2) Add 200 g of deionized water (the mass ratio of the mixture to water is 1:6) to 33 g of the mixture, heat to 80 ° C, stir and leach for 30 min, filter to obtain the filtrate and filter residue, wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0043] Comparative Example 5 Comparative Example 1, other processes remain unchanged, and the roasting temperature is changed to 450°C.

[0044] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 450°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0045] Comparative Example 6 Comparative Example 1, the other processes remain unchanged, and the concentration of hydrochloric acid used in the acid leaching silicon stage is changed to 30wt%.

[0046] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) 255 g of 30 wt% HCl solution was added to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution was 1:10), the temperature was raised to 100 ° C. and stirred for reaction for 12 h. After filtration, the solid was washed with deionized water until neutral, dried, and heated to 550 ° C. at 5 ° C. / min in an air atmosphere and calcined for 1 h to obtain the product. Since the concentration of HCl solution was too high, the silicon-aluminum mixture was difficult to react, and the obtained product still contained a high proportion of silicon and aluminum.

[0047] Comparative Example 7 Comparative Example 1, other processes remain unchanged, and the concentration of hydrochloric acid used in the acid leaching silicon stage is changed to 10wt%.

[0048] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 10 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0049] Comparative Example 8 As in Example 1, other processes remained unchanged, and the temperature for acid leaching of silicon was lowered to 50°C.

[0050] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 50 ° C, stir and react for 12 h, filter, wash the solid with deionized water until neutral, dry, and heat to 550 ° C at 5 ° C / min in air atmosphere, and calcine for 1 h to obtain silica product; (4) Add 28 wt% ammonia water to the acid leaching filtrate obtained in step (3), adjust the pH to 7.5, and generate Al(OH)3 precipitate. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550°C at 5°C / min in an air atmosphere, and calcined for 1 hour to obtain an alumina product.

[0051] Comparative Example 9 Comparative Example 1, other processes remain unchanged, and the ammonia water in the aluminum precipitation process is replaced with a 20wt% sodium hydroxide solution with a pH of 14.

[0052] (1) 20 g of spent catalyst was mixed with 17 g of Na2CO3 by ball milling for 30 min. The mixture was heated to 550°C at a rate of 5°C / min in an air atmosphere and calcined for 1 h. After cooling, a mixture (white-gray powder) was obtained. (2) Add 200 g of deionized water (mass ratio of mixture to water is 1:6) to 33 g of the mixture, heat to 80 °C, stir and leach for 30 min, filter to obtain the filtrate and filter residue (aluminosilicate), wash the filter residue with deionized water, and dry to obtain a crude sample; (3) Add 255 g of 20 wt% HCl solution to 25.5 g of crude sample (the mass ratio of crude sample to HCl solution is 1:10), heat to 100 ° C and stir to react for 12 h. After filtering, the solid is washed with deionized water until neutral, dried, and heated to 550 ° C at 5 ° C / min in air atmosphere and calcined for 1 h to obtain silica product; (4) 20 wt% sodium hydroxide solution was added to the acid leaching filtrate obtained in step (3) to adjust the pH to 14. Due to the mismatch in the pH control range, aluminum could not be precipitated.

[0053] Table 1 Case Changes in process conditions Silicon purity / % Aluminum purity / % Example 1 Standard process 98.4 94.8 Example 2 HCl concentration 15% + leaching time 16h 95.8 90.5 Example 3 Two-stage roasting: 400℃ (oxidation of organic matter) + 550℃ (enhanced sodium salt formation) 98.1 93.5 Example 4 Calcination temperature 650℃ 98.8 95.2 Example 5 Aluminum precipitation uses 10wt% ammonia water (2.8 times the amount required) 98.1 94.5 Example 6 Aluminum precipitation pH adjusted to 9.5 98.2 93.9 Comparative Example 1 <![CDATA[Replacement of Na2CO3 with Na2SO4]]> 94.2 91.5 Comparative Example 2 <![CDATA[Replacement of Na2CO3 with NaCl]]> 84.5 79.1 Comparative Example 3 <![CDATA[Excess Na2CO3 (30 g)]]> 90.5 91.3 Comparative Example 4 <![CDATA[Direct roasting without adding Na2CO3]]> 85 80 Comparative Example 5 Calcination temperature 450℃ 88.2 82.5 Comparative Example 6 Acid leaching HCl concentration 30wt% Unable to extract Unable to extract Comparative Example 7 Acid leaching HCl concentration 10wt% 78.4 70 Comparative Example 8 Acid leaching temperature 50℃ 80.3 78 Comparative Example 9 Aluminum precipitation was replaced with 20wt% NaOH solution 98.1 Unable to extract Note: Silicon purity refers to the mass percentage of silicon dioxide in the silicon dioxide product; aluminum purity refers to the mass percentage of aluminum oxide in the aluminum oxide product.

[0054] As shown in Table 1, the following conclusions are drawn through a large number of experiments: (1) Temperature control during the calcination stage and the addition of sodium salt flux are the basis for efficient separation of silicon and aluminum. In the standard process, the calcination temperature of 550°C is combined with the addition of sodium carbonate (Example 1). Through the solid-phase reaction of sodium salt with the waste catalyst, the nickel, vanadium and other components therein are formed into soluble salts, which are preferentially separated in the water leaching part. At the same time, the inert waste molecular sieve components are also activated, which significantly improves the separation efficiency of the subsequent acid leaching. The effect of heavy metal removal can be verified by the purity of silicon and aluminum. If sodium carbonate is replaced with sodium sulfate (Comparative Example 1), it will lead to the formation of salts that are difficult to dissolve in acid, resulting in a decrease in the silicon recovery rate. If sodium carbonate is replaced with sodium chloride (Comparative Example 2), it can be concluded from the purity of silicon and aluminum that sodium chloride cannot activate the impurity heavy metals at low temperatures, and introduces chloride ions that interfere with the separation process. If sodium carbonate is not added (Comparative Example 4) or the calcination temperature is insufficient (Comparative Example 5), the role of sodium salt in activating impurities is lost, which not only leads to the introduction of heavy metal impurities into aluminum, but also greatly reduces the silicon and aluminum separation effect (the purity of silicon and aluminum is less than 85%). Excessive addition of sodium carbonate (Comparative Example 3) not only causes the remaining sodium salt to enter the acid leaching stage, but also causes the hydrochloric acid solution to react with the remaining sodium salt and be consumed, resulting in incomplete reaction in the acid leaching stage, resulting in reduced recovery purity. It also forms more soluble sodium silicate during the high-temperature roasting stage, resulting in a reduced silicon recovery rate. The purity of silicon and aluminum recovered using the two-stage roasting process (Example 3) is essentially the same as that obtained using the standard process, and appropriately increasing the roasting temperature (Example 4) can slightly improve the recovered purity, but energy consumption and material sintering risks must be considered comprehensively.

[0055] (2) Refined regulation of acid leaching conditions is crucial. Using 20% ​​hydrochloric acid at 100°C for 12 hours (Example 1) can effectively dissolve aluminum while retaining silicon, achieving the recovery of high-purity silicon (98.4%). Lowering the hydrochloric acid concentration and extending the acid leaching time (Example 2) will result in a decrease in silicon purity and aluminum purity, but still maintain a high level. If the acid concentration (Comparative Example 7) or the temperature (Comparative Example 8) is reduced beyond the specified range of the present invention, the aluminum will not be fully dissolved due to limited reaction kinetics. The use of higher concentrations, temperatures, time and other parameters is to increase the activity of the reaction, thereby allowing the aluminum-containing components in the waste catalyst to be completely dissolved and increasing the aluminum recovery rate. The silicon purity dropped sharply to below 80%. However, excessively high acid concentrations (Comparative Example 6) will induce passivation, making it difficult for the silicon-aluminum mixture to react, resulting in the inability to separate silicon and aluminum by acid leaching.

[0056] (3) The choice of pH and precipitant in the aluminum precipitation step is extremely sensitive to the precipitation effect. When 28% ammonia water is used to accurately adjust the pH to 7.5 (Example 1), aluminum is selectively precipitated in the form of aluminum hydroxide, and the purity reaches 94.8% after further roasting. When the pH is appropriately raised (Example 6), the purity of aluminum will decrease slightly due to the introduction of impurities for co-precipitation. In addition, although low-concentration ammonia water (Example 5) can achieve similar purity, it consumes more reagents and is less economical. When a high-concentration sodium hydroxide solution is used instead (Comparative Example 9), aluminum cannot be precipitated due to the mismatch of the pH control range.

[0057] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for recovering high-purity silicon and aluminum from spent catalysts, characterized in that: The steps include: (1) The waste catalyst includes SiO2, Al2O3 and other metal oxides, with SiO2 content greater than 30wt% and Al2O3 content greater than 20wt%. The waste catalyst is mixed with sodium carbonate by ball milling and then aerobic calcination is performed to obtain a mixture; (2) Add the mixture to water for soaking, and filter to obtain a crude sample; (3) The crude sample is added to a hydrochloric acid solution for acid leaching, filtered, and then calcined to obtain a silica product; (4) Add alkali to the filtrate obtained in step (3) to a pH of 7.5-9.5, perform precipitation, filter, and then calcine to obtain an alumina product.

2. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1, characterized in that: In step (1), the amount of sodium carbonate added is 70-110% of the mass of the waste catalyst.

3. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1 or 2, characterized in that: In step (1), the ball milling mixing time is 0.5-2h.

4. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1 or 2, characterized in that: In step (1), the temperature of the oxygen roasting is 500-600°C and the time is 1-2 hours.

5. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1, characterized in that: In step (2), the mass ratio of the mixture to water is 1:6-8.

6. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1 or 5, characterized in that: In step (2), the water immersion treatment is carried out at 80-90° C. for 30-60 minutes.

7. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1, characterized in that: In step (3), the mass concentration of the hydrochloric acid solution is 15-20%.

8. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1 or 7, characterized in that: In step (3), the mass ratio of the crude sample to the hydrochloric acid solution is 1:8-12.

9. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1 or 7, characterized in that: In step (3), the acid leaching treatment is carried out at 90-100°C for 10-16 hours.

10. The method for recovering high-purity silicon and aluminum from waste catalyst according to claim 1, characterized in that: In step (4), aqueous ammonia is added to the filtrate to adjust the pH to 7.5-9.5.