WO2014020626A1 - Process for recovering rare earth metals - Google Patents
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- WO2014020626A1 WO2014020626A1 PCT/IT2013/000211 IT2013000211W WO2014020626A1 WO 2014020626 A1 WO2014020626 A1 WO 2014020626A1 IT 2013000211 W IT2013000211 W IT 2013000211W WO 2014020626 A1 WO2014020626 A1 WO 2014020626A1
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- WIPO (PCT)
- Prior art keywords
- process according
- acid
- leaching
- carried out
- solution
- Prior art date
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 20
- 150000002910 rare earth metals Chemical class 0.000 title claims description 10
- 239000003054 catalyst Substances 0.000 claims abstract description 25
- 238000002386 leaching Methods 0.000 claims description 25
- 229910052684 Cerium Inorganic materials 0.000 claims description 24
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 24
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 23
- 229910052746 lanthanum Inorganic materials 0.000 claims description 20
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 18
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 13
- 238000001556 precipitation Methods 0.000 claims description 13
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 9
- 229910017604 nitric acid Inorganic materials 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 9
- 238000000605 extraction Methods 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 4
- 235000006408 oxalic acid Nutrition 0.000 claims description 4
- LJKDOMVGKKPJBH-UHFFFAOYSA-N 2-ethylhexyl dihydrogen phosphate Chemical compound CCCCC(CC)COP(O)(O)=O LJKDOMVGKKPJBH-UHFFFAOYSA-N 0.000 claims description 3
- OFGFUPAXBMLHGP-UHFFFAOYSA-N bis(2,4,4-trimethylpentyl)phosphane Chemical compound CC(C)(C)CC(C)CPCC(C)CC(C)(C)C OFGFUPAXBMLHGP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 150000002739 metals Chemical class 0.000 claims description 3
- FGUUSXIOTUKUDN-IBGZPJMESA-N C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 Chemical compound C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 FGUUSXIOTUKUDN-IBGZPJMESA-N 0.000 claims description 2
- 238000007792 addition Methods 0.000 claims description 2
- 239000008346 aqueous phase Substances 0.000 claims description 2
- 238000001354 calcination Methods 0.000 claims description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 239000003350 kerosene Substances 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 239000012074 organic phase Substances 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims 2
- 239000007788 liquid Substances 0.000 claims 1
- 239000000243 solution Substances 0.000 description 21
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 239000004411 aluminium Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910000421 cerium(III) oxide Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000000638 solvent extraction Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910021536 Zeolite Inorganic materials 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910000420 cerium oxide Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 239000004567 concrete Substances 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- DRVWBEJJZZTIGJ-UHFFFAOYSA-N cerium(3+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[Ce+3].[Ce+3] DRVWBEJJZZTIGJ-UHFFFAOYSA-N 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000005202 decontamination Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000013538 functional additive Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- OXHNIMPTBAKYRS-UHFFFAOYSA-H lanthanum(3+);oxalate Chemical class [La+3].[La+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O OXHNIMPTBAKYRS-UHFFFAOYSA-H 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/009—General processes for recovering metals or metallic compounds from spent catalysts
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B59/00—Obtaining rare earth metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- Some exhausted catalysts of the petroleum industry that are used for catalytic cracking processes contain elements such as nitrogen, sulphur, and high amounts of alumina and silicon oxides.
- the oxides that are present in larger amounts are Si0 2 (-48%) and Al 2 0 3 (-43%); other oxides are La 2 0 3 (-2.5%), P 2 0 5 ( ⁇ 1.5%), Fe 2 0 3 (-1%), V 2 0 5 (-1%), NiO ( ⁇ 1%) and Ce 2 0 3 ( ⁇ 0.5%).
- Such catalysts have, by virtue of the high content of Al and Si oxides, a good pozzolanic activity, which advances their use as additives in concretes.
- cerium oxide is a chromophore compound, and as such, it finds wide use in the ceramic industry.
- rare earth oxides such as lanthanum and cerium oxides
- the extraction and refining of rare earth elements is concentrated in a few countries, including China, which holds the record for production.
- the demand for such elements has already exceeded the offer, and it is expected that the recovery of rare earth elements from secondary raw materials, such as exhausted catalysts, will be more and more necessary in the future.
- the European Union also classifies the rare earth elements as a critical, strategically important material, since they are essential raw materials both for high-tech products and routinely used materials, such as, for example, cell phones, thin-layer photovoltaic elements, lithium ion accumulators, optic fiber cables, synthetic fuels, etc. It is believed that within 2030, the request of a series of fundamental raw materials could even triplicate compared to that of 2006. The main risk related to their provision is further related to the fact that they have a low degree of replaceability and a reduced degree of recycling.
- the object of the present invention is to provide a process for recovering rare earth elements from exhausted catalysts containing rare earth elements, and particularly Lanthanum and Cerium, which at least partially overcome the limitations of the known processes.
- FIG. 1 is a schematic representation of the process according to an embodiment of the present invention
- Fig. 2 is a schematic representation of the process according to an alternative embodiment of the present invention.
- a catalyst used for recovering rare earth elements comprises a gel of an inorganic oxide, such as a silica-aluminium gel, and/or a crystalline zeolite dispersed (10-50% by weight) in an inorganic matrix (50-90% by weight) having excellent mechanical properties and some catalytic properties. The remainder (0-10% by weight) is composed of additives, such as platinum, rare earth elements, antimony, and other elements.
- a typical composition of a catalyst object of the present invention is as follows:
- binders may be present.
- the process of the present invention is carried out on a raw material represented by a powder catalyst.
- the process for recovering rare earth metals comprises a first step a) of subjecting the powder of such catalysts to leaching with a strong mineral acid.
- Such acid may be sulfuric acid, hydrochloric acid, or nitric acid.
- such acid is selected from hydrochloric acid and nitric acid.
- the concentration of the acid may range between 1-4 M, so as to bring the pH to values lower than 1.
- sulfuric acid will preferably be in a concentration of 1-2 M, while hydrochloric acid and nitric acid will have a concentration of about 1-4 M, and preferably 2-3 M.
- step a) is carried out for a time ranging between 1-4 hours, and preferably about 2-3 hours at a temperature of 10-100° C and preferably 25- 80° C.
- the ratio between the leaching solution and the solid is about 20-30%, and preferably about 10-20% (weight/volume) .
- the leaching step a) according to the present invention allows the passage of Lanthanum and Cerium into the solution with very high yields, above 50% even at room temperature, and even above 80% at high temperatures.
- the leaching step may be carried out in countercurrent with 2-6 stages, in order to concentrate the solution.
- step b a precipitation step
- Such step b) is carried out by increasing the pH of the solution previously obtained by adding a base.
- sodium hydroxide is added in concentrations ranging between 4.5-5.5 M and until reaching a pH of about 0.7-2.
- the precipitation step is carried out for a period of 1-2 hours.
- the process providing the precipitation step b) comprises a leaching . step a) carried out by sulfuric acid.
- the yields of the precipitation step according to the present invention are very high, and allow an almost quantitative recovery of Lanthanum and Cerium.
- the overall yield of the process of the present invention is above 80% and ranges between 85-95%.
- the process for recovering rare earth metals from catalysts according to the present invention comprises, after the leaching step a), a solvent extraction step.
- step a) is preferably carried out using hydrochloric acid or nitric acid.
- the ratio between leaching solution and the solid is about 20-30%, and preferably about 10-20% (weight/volume) .
- step a) is carried out for 1-3 hours, preferably for about 2 hours and at a temperature of 50-80° C.
- the leaching step may take place in countercurrent with 2-6 stages, in order to concentrate the solution.
- the pH of the leaching solution is preferably increased up to 4 by adding NaOH.
- an optional filtration step b'l may be provided, so as to separate the solid from the solution, which is subsequently processed.
- such extracting agent is selected from (2- ethylhexyl) phosphoric acid (for example, available as D2EHPA) , or the di (2, 4 , 4-trimethylpentyl) phosphine acid (available as CYANEX 72) .
- such extracting agent is in an organic solvent, for example, represented by n-heptane or kerosene, at about 20% (vol/vol) .
- aqueous phase/organic phase ratio is preferably about 1:1.
- the stripping (removal) step d' is performed, wherein Cerium and Lanthanum are extracted from the solution previously obtained by adding a solution of the same acid used for the leaching step, i.e., hydrochloric acid or nitric acid.
- the organic solution/added acid (hydrochloric acid or nitric acid) ratio preferably ranges between 1:1 and 4:1.
- the stripping step is preferably repeated on the obtained aqueous solution up to 4 times, in cascade, before going through the step e' ) .
- a precipitation step e' ) follows the step d' ) .
- Cerium and Lanthanum are precipitated from the aqueous solution previously obtained with a concentrated oxalic acid solution (for example, 100 g/1) .
- concentrated NaOH is added to the precipitation solution in order to maintain the pH between about 0.5-3.
- Cerium and Lanthanum (Ce2(C20 4 ) 3 ) and (La 2 (C 2 0 ) 3) oxalate thus precipitated comprise about 45-50% Lanthanum and 3% Cerium.
- the oxalate is subjected to a temperature of about 600° C for at least 1 hour, so as to obtain a mixed Lanthanum and Cerium trioxide, the purity of which is about 98%.
- the powder sample of the point a) is subjected to a leaching step during 3 hours with a 2 M sulfuric acid solution.
- the following Table shows the leaching percentages for each element comprised in the initial sample and the percentage that is present in the solid residue.
- the leaching step allows recovering a high percentage of Lanthanum and Cerium.
- the Lanthanum and Cerium-rich solution obtained according to the point b) is subjected to precipitation, by adding 5 M sodium hydroxide and bringing the pH to below 2.
- a leaching of 20 g catalyst in 100 mL 2M HN0 3 at 30° C for 2 hours is set forth by way of example.
- the extraction yield was equal to 55% for La and 47% for Ce.
- the precipitate was then analyzed.
- the main contaminant turns out to be aluminium, since silicon, the other most concentrated element in the exhausted catalysts, is not leached by strong acids.
- the salt is composed of Cerium and Lanthanum oxalates having a purity of about 97.5%, which may be baked at 600° C for at least 1 hour, thus obtaining La 2 0 3 and Ce 2 0 3 in a high purity (>98%) .
- the waste material for example, non-leached material, may be subjected to decontamination procedures provided for by the law in order to be subsequently used again in other application fields, for example, as an additive in cement plants, due to its high pozzolanic activity, or in the ceramic industry.
- a further advantage is represented by the possibility to separate Aluminium, which is notoriously difficult to separate from the other elements, which is in fact recovered in a percentage lesser than 1% in the final product, from the rare earth metals, and particularly Lanthanum and Cerium, and still more particularly Cerium.
Abstract
The present invention relates to a process for recovering rare earth elements from exhausted industrial catalysts.
Description
"Process for recovering rare earth metals"
DESCRIPTION
[0001] Some exhausted catalysts of the petroleum industry that are used for catalytic cracking processes contain elements such as nitrogen, sulphur, and high amounts of alumina and silicon oxides. The oxides that are present in larger amounts are Si02 (-48%) and Al203 (-43%); other oxides are La203 (-2.5%), P205 (~ 1.5%), Fe203 (-1%), V205 (-1%), NiO (<1%) and Ce203 (~ 0.5%). Such catalysts have, by virtue of the high content of Al and Si oxides, a good pozzolanic activity, which advances their use as additives in concretes. In fact, it has been shown that the natural zeolite or pozzolanic materials can improve the physical and mechanical properties of concrete by virtue of the silicon oxides that react with calcium hydroxide. Furthermore, cerium oxide is a chromophore compound, and as such, it finds wide use in the ceramic industry.
Moreover, in these catalysts there are rare earth oxides (such as lanthanum and cerium oxides), of a great strategic importance for both the development and production of the new electronic technologies, and for their economic value. The extraction and refining of rare earth elements is concentrated in a few Countries, including China, which holds the record for production. However, the demand for such elements has
already exceeded the offer, and it is expected that the recovery of rare earth elements from secondary raw materials, such as exhausted catalysts, will be more and more necessary in the future.
The European Union also classifies the rare earth elements as a critical, strategically important material, since they are essential raw materials both for high-tech products and routinely used materials, such as, for example, cell phones, thin-layer photovoltaic elements, lithium ion accumulators, optic fiber cables, synthetic fuels, etc. It is believed that within 2030, the request of a series of fundamental raw materials could even triplicate compared to that of 2006. The main risk related to their provision is further related to the fact that they have a low degree of replaceability and a reduced degree of recycling.
[0002] Currently, processes for recovering rare earth elements, and particularly Lanthanum and Cerium, from catalysts, are known, but these have some drawbacks that limit their application.
OBJECT OF THE INVENTION
[0003] Therefore, the object of the present invention is to provide a process for recovering rare earth elements from exhausted catalysts containing rare earth elements, and particularly Lanthanum and
Cerium, which at least partially overcome the limitations of the known processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Fig. 1 is a schematic representation of the process according to an embodiment of the present invention, while Fig. 2 is a schematic representation of the process according to an alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0005] For the purposes of the present invention, a catalyst used for recovering rare earth elements comprises a gel of an inorganic oxide, such as a silica-aluminium gel, and/or a crystalline zeolite dispersed (10-50% by weight) in an inorganic matrix (50-90% by weight) having excellent mechanical properties and some catalytic properties. The remainder (0-10% by weight) is composed of additives, such as platinum, rare earth elements, antimony, and other elements. A typical composition of a catalyst object of the present invention is as follows:
Compounds % by
weight:
A1203 >20
Si02 >20
S 0-5
Ti 0-5
Fe 0-5
Zr 0-5
La 0-15
Ce 0-15
Other rare earth 0-15
elements
from which it is inferred that such catalysts comprise a substantial portion of Aluminium.
Similarly, binders, filler agents, and other functional additives may be present.
[0006] In particular, the process of the present invention is carried out on a raw material represented by a powder catalyst.
[0007] The process for recovering rare earth metals, preferably Lanthanum and Cerium, and still more preferably Cerium, according to the present invention, comprises a first step a) of subjecting the powder of such catalysts to leaching with a strong mineral acid.
Particularly, such acid may be sulfuric acid, hydrochloric acid, or nitric acid.
In a preferred aspect, such acid is selected from hydrochloric acid and nitric acid.
The concentration of the acid may range between 1-4 M, so as to bring the pH to values lower than 1.
Particularly, sulfuric acid will preferably be in a concentration of 1-2 M, while hydrochloric acid and
nitric acid will have a concentration of about 1-4 M, and preferably 2-3 M.
Particularly, such step a) is carried out for a time ranging between 1-4 hours, and preferably about 2-3 hours at a temperature of 10-100° C and preferably 25- 80° C.
It has been noticed that the temperature increase promotes the dissolution of the elements present in the starting powder.
[0008] Particularly, the ratio between the leaching solution and the solid (represented by the catalyst powder) is about 20-30%, and preferably about 10-20% (weight/volume) .
Advantageously, the leaching step a) according to the present invention allows the passage of Lanthanum and Cerium into the solution with very high yields, above 50% even at room temperature, and even above 80% at high temperatures.
[0009] In a particular aspect, the leaching step may be carried out in countercurrent with 2-6 stages, in order to concentrate the solution.
[0010] In a first embodiment of the process of the present invention, after the leaching step a) , a precipitation step (step b) is carried out.
Such step b) is carried out by increasing the pH of the solution previously obtained by adding a base.
In a preferred aspect, sodium hydroxide is added in
concentrations ranging between 4.5-5.5 M and until reaching a pH of about 0.7-2.
Therefore, the precipitation step is carried out for a period of 1-2 hours.
[0011] From the precipitation step:
• an exhausted solution, intended to undergo treatments provided for the waste waters;
• a concentrated solid comprising Lanthanum and Cerium plus aluminium and other impurities are obtained.
[0012] According to a preferred aspect of the present invention, the process providing the precipitation step b) comprises a leaching . step a) carried out by sulfuric acid.
[0013] Advantageously, the yields of the precipitation step according to the present invention are very high, and allow an almost quantitative recovery of Lanthanum and Cerium.
Therefore, on the whole, the overall yield of the process of the present invention is above 80% and ranges between 85-95%.
[0014] According to a particularly preferred aspect of the invention, in an alternative form illustrated for example in Fig. 2, the process for recovering rare earth metals from catalysts according to the present invention comprises, after the leaching step a), a solvent extraction step.
To this aim, step a) is preferably carried out using hydrochloric acid or nitric acid.
In this case also, the ratio between leaching solution and the solid (represented by the catalyst powder) is about 20-30%, and preferably about 10-20% (weight/volume) .
Preferably, such step a) is carried out for 1-3 hours, preferably for about 2 hours and at a temperature of 50-80° C.
[0015] In a particular aspect, the leaching step may take place in countercurrent with 2-6 stages, in order to concentrate the solution.
[0016] Next, in a step b' ) , the pH of the leaching solution is preferably increased up to 4 by adding NaOH.
[0017] At this point, an optional filtration step b'l) may be provided, so as to separate the solid from the solution, which is subsequently processed.
[0018] Subsequently, it is then proceeded with the solvent extraction step c'), in which the leaching solution is contacted under vigorous stirring with an organic extracting agent.
Preferably, such extracting agent is selected from (2- ethylhexyl) phosphoric acid (for example, available as D2EHPA) , or the di (2, 4 , 4-trimethylpentyl) phosphine acid (available as CYANEX 72) .
According to a preferred aspect, such extracting agent
is in an organic solvent, for example, represented by n-heptane or kerosene, at about 20% (vol/vol) .
Furthermore, the aqueous phase/organic phase ratio is preferably about 1:1.
[0019] After the extraction step, the stripping (removal) step d' ) is performed, wherein Cerium and Lanthanum are extracted from the solution previously obtained by adding a solution of the same acid used for the leaching step, i.e., hydrochloric acid or nitric acid.
The organic solution/added acid (hydrochloric acid or nitric acid) ratio preferably ranges between 1:1 and 4:1.
In an aspect of the present invention, the stripping step is preferably repeated on the obtained aqueous solution up to 4 times, in cascade, before going through the step e' ) .
[0020] A precipitation step e' ) follows the step d' ) .
Particularly, Cerium and Lanthanum are precipitated from the aqueous solution previously obtained with a concentrated oxalic acid solution (for example, 100 g/1) .
In a preferred aspect, concentrated NaOH is added to the precipitation solution in order to maintain the pH between about 0.5-3.
[0021] Cerium and Lanthanum (Ce2(C204) 3) and
(La2(C20 ) 3) oxalate thus precipitated comprise about 45-50% Lanthanum and 3% Cerium.
[0022] With the calcination step f' ) , the oxalate is subjected to a temperature of about 600° C for at least 1 hour, so as to obtain a mixed Lanthanum and Cerium trioxide, the purity of which is about 98%. Experimental section
[0023] In the following experimental section, some examples of processes implemented according to the present invention are described.
EXAMPLE 1
a) Characterization of a catalyst powder containing rare earth elements
A sample of a powder obtained from exhausted catalysts was characterized by XRF analysis as having the following composition:
Element % by
weight
Al 17.35
Si 12.75
S 0.013
Ti 0.43
Fe 0.33
Ni 0.02
Zr 0.16
La 3.02
Ce 0.23
b) Leaching
The powder sample of the point a) is subjected to a leaching step during 3 hours with a 2 M sulfuric acid solution.
The following Table shows the leaching percentages for each element comprised in the initial sample and the percentage that is present in the solid residue.
From the data set forth above, it shall be apparent that the leaching step allows recovering a high percentage of Lanthanum and Cerium.
c) Precipitation
The Lanthanum and Cerium-rich solution obtained according to the point b) is subjected to precipitation, by adding 5 M sodium hydroxide and bringing the pH to below 2.
In the following Table, the % composition of the precipitate after XRF analysis, and the precipitation
yields are set forth.
EXAMPLE 2
Solvent extraction process
A leaching of 20 g catalyst in 100 mL 2M HN03 at 30° C for 2 hours is set forth by way of example.
The extraction yield was equal to 55% for La and 47% for Ce.
50 mL leaching solution were treated with an organic solution at 20% vol. D2EHPA in n-heptane in a 1:1 volumetric ratio, under constant stirring for a few minutes .
The results of the extraction are reported in the following Table.
0.7 0.5 2.729 0.135631 0.012119 8.2
0.75 2.5 2.441 0.124979 0.022771 15.4
1 2.5 1.944 0.102449 0.045301 30.7
1.43 1 1.357 0.071514 0.076236 51.6
1.9 0.5 0.545 0.028449 0.119301 80.7
2.3 0.5 0.1028 0.005315 0.142435 96.4
3.7 0.5 0.02226 0.00114 0.14661 99.2
Cerium extraction
Once it has been separated, the organic step was contacted with 25 mL 4 M HN03 solution for 30 minutes under constant stirring.
LANTHANUM
Init . 4.47 0.11175 0.03486 76.2
15' 4.653 0.116325 0.030285 79.4
30' 4.819 0.120475 0.026135 82.2
CERIUM
Init. 0.2955 0.007388 0.0020625 78.2
15' 0.2965 0.007413 0.0020375 78.4
30' 0.2979 0.007448 0.0020025 78.8
To the aqueous solution, 5 mL of a solution of 40 g/L oxalic acid were added, and the pH was brought to 40% by weight with 10 mL NaOH. At pH 0.66, the formation of a cosiderable white precipitate is observed, which is separated by filtration and dried at 105° C for 24 hours .
The precipitate was then analyzed.
The concentration of the major elements is set forth in the following Table.
The main contaminant turns out to be aluminium, since silicon, the other most concentrated element in the exhausted catalysts, is not leached by strong acids.
The salt is composed of Cerium and Lanthanum oxalates having a purity of about 97.5%, which may be baked at 600° C for at least 1 hour, thus obtaining La203 and Ce203 in a high purity (>98%) .
[0024] The advantages provided by the process of the present invention are clear, since, as it has been shown, it allows recovering rare earth metals in a highly pure form.
For example, it is sufficient to note how, from the leaching and precipitation steps, percentages of Lanthanum and Cerium of 90% and 82% are obtained, respectively.
Furthermore, it allows recovering material, which otherwise would be disposed of, however losing a valuable source of important elements, such as Lanthanum and Cerium, which are metals for which a strong request increase in the market is expected. On the other hand, the waste material, for example, non-leached material, may be subjected to decontamination procedures provided for by the law in order to be subsequently used again in other application fields, for example, as an additive in
cement plants, due to its high pozzolanic activity, or in the ceramic industry.
A further advantage is represented by the possibility to separate Aluminium, which is notoriously difficult to separate from the other elements, which is in fact recovered in a percentage lesser than 1% in the final product, from the rare earth metals, and particularly Lanthanum and Cerium, and still more particularly Cerium.
[0025] From the description provided above of the process of the invention for recovering rare earth metals, and particularly Lanthanum and Cerium, and still more particularly Cerium, from catalysts, those skilled in the art, in order to meet contingent, specific needs, will be able to make a number of modifications, additions, or replacements of elements with other functionally equivalent ones, without however departing from the scope of the appended claims. Each of the characteristics described as belonging to a possible embodiment may be implemented independently from the other embodiments described.
Claims
A process for recovering rare earth metals from catalysts containing said metals, comprising the steps of:
a) subjecting to leaching with a mineral acid said catalyst, thus obtaining a leaching solution;
b' ) adding a base;
c' ) carrying out an extraction step by adding a solvent selected from (2-ethylhexyl ) phosphoric acid and di (2, 4, 4-trimethylpentyl) phosphine acid.
The process according to the preceding claim, wherein said catalyst is in the form of a powder.
The process according to any of the preceding claims, wherein the leaching step is carried out according to a solid/liquid ratio ranging between 10-30% (weight/volume) .
The process according to the preceding claim, wherein said leaching step a) is carried out with an acid selected from hydrochloric acid and nitric acid.
The process according to the preceding claim, wherein the acid is added until reaching a pH lower than 1.
The process according to claim 4 or 5, wherein
said leaching step a) is carried out for a period of time of about 1-4 hours, preferably 2- 3 hours.
7. The process according to any of the claims 4-6, wherein said leaching step a) is carried out at a temperature of about 10-100° C, preferably about 25-80° C.
8. The process according to any of the preceding claim, wherein a pH of about 4 is obtained in said step b' ) .
9. The process according to any of the preceding claim, wherein in said step c' ) the extracting agent is in a n-heptane or kerosene solution.
10. The process according to the preceding claim, wherein said extracting agent is in a solution of about 20% (volume/volume) .
11. The process according to claim 9 or 10, wherein in said step c' ) the aqueous phase/organic phase ratio is about 1:1.
12. The process according to any of the preceding claim, wherein, after said step c' ) , a stripping step d' ) is carried out by adding hydrochloric acid or nitric acid.
13. The process according to the preceding claim, wherein the organic solution/hydrochloric acid or nitric acid ratio ranges between 1:1 and 4:1.
14. The process according to claim 12 or 13, wherein
said step d' ) is repeated up to 4 times.
15. The process according to claim 12, 13, or 14, wherein, after said step d' ) , a precipitation step e' ) is carried out by adding oxalic acid.
16. The process according to the preceding claim, wherein in said step e' ) the oxalic acid has a concentration of about 100 g/1.
17. The process according to claim 15 or 16, wherein in the precipitation step e' ) it is proceeded with the addition of a base up to a pH of about 0.5-3.
18. The process according to the preceding claim, wherein said base is NaOH.
19. The process according to any of the claims 15 to 18, wherein, after the step e' ) it is proceeded with the calcination step f' ) .
20. The process according to any of the preceding claim, for the extraction of Lanthanum and Cerium.
21. The process according to any of the preceding claim, wherein said catalyst has the following average composition:
22. An oxide comprising Lanthanum and/or Cerium, which is obtained by the process of any of the preceding claims.
23. Use of a solvent selected from (2- ethylhexyl) phosphoric acid and di (2,4,4- trimethylpentyl) phosphine acid, for recovering rare earth metals from catalysts containing said metals .
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Cited By (3)
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US20160251739A1 (en) * | 2015-02-27 | 2016-09-01 | The Jamaica Bauxite Institute Limited | Method of recovering rare-earth elements |
CN111151236A (en) * | 2020-01-17 | 2020-05-15 | 北京诺维新材科技有限公司 | Treatment method of waste catalyst of silicon dioxide loaded alkali metal cesium |
US11155897B2 (en) | 2017-11-09 | 2021-10-26 | University Of Kentucky Research Foundation | Low-cost selective precipitation circuit for recovery of rare earth elements from acid leachate of coal waste |
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EP2439293A1 (en) * | 2010-10-06 | 2012-04-11 | Ferro Duo GmbH | Method for recovering lanthane from zeolites containing lanthane |
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EP0489494A1 (en) * | 1990-11-22 | 1992-06-10 | The British Petroleum Company P.L.C. | Catalyst recovery process |
US6455018B1 (en) * | 1993-05-12 | 2002-09-24 | Rhone-Poulenc Chimie | Recovery of precious metal and other values from spent compositions/materials |
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WO2011151519A2 (en) * | 2010-06-02 | 2011-12-08 | Kemira Oyj | Catalyst recovery process |
EP2439293A1 (en) * | 2010-10-06 | 2012-04-11 | Ferro Duo GmbH | Method for recovering lanthane from zeolites containing lanthane |
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US20160251739A1 (en) * | 2015-02-27 | 2016-09-01 | The Jamaica Bauxite Institute Limited | Method of recovering rare-earth elements |
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US11155897B2 (en) | 2017-11-09 | 2021-10-26 | University Of Kentucky Research Foundation | Low-cost selective precipitation circuit for recovery of rare earth elements from acid leachate of coal waste |
CN111151236A (en) * | 2020-01-17 | 2020-05-15 | 北京诺维新材科技有限公司 | Treatment method of waste catalyst of silicon dioxide loaded alkali metal cesium |
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