Extraction of selected platinum-group metals from supported catalyst
View Patent ↗Disclosed herein is a method for extracting precious metals from supported catalysts. The precious metal in one embodiment is rhodium. The supported catalyst may be from equipment, such as a used catalytic converter. The method is carried out at low temperature, and does not require harsh conditions, such as the use of a strong acid. The method involves contacting the catalytic material with a polar molecule and a reactive gas.
1. A method of extracting a selected platinum group metal from a composite, the method comprising:
immersing in a liquid comprising a polar molecule at a pH of greater than 2 a composite comprising a supported catalyst comprising a particulate catalyst bonded to a support, the particulate catalyst comprising the selected platinum group metal and the support comprising a support material; and
while the composite is immersed in the liquid comprising the polar molecule at a pH greater than 2, exposing the composite to a reactive gas to extract the selected platinum group metal therefrom.
2. The method of claim 1 , wherein the selected platinum group metal comprises one of rhodium, rhenium, ruthenium, palladium, or platinum.
3. The method of claim 1 , wherein the selected platinum group metal comprises rhodium.
4. The method of claim 1 , wherein the polar molecule is an organic solvent.
5. The method of claim 1 , wherein the reactive gas comprises one of carbon monoxide or nitric oxide.
6. The method of claim 1 , wherein the exposure of the composite to the reactive gas occurs at a pressure between 1 bar and 25 bar.
7. The method of claim 1 , wherein the exposure to the reactive gas occurs at a temperature below 80 degrees Celsius.
8. The method of claim 1 , wherein the reactive gas is generated by reaction of a liquid precursor in contact with the composite.
9. The method of claim 8 , wherein the liquid precursor comprises one of formic acid, formaldehyde, and chloroform.
10. The method of claim 1 , wherein the polar molecule comprises at least one of acetonitrile, ethyldimethylamine, dimethylformamide, or trimethylamine.
11. The method of claim 1 , wherein at least 90% of the selected platinum group metal is extracted from the composite after 24 hours.
12. The method of claim 1 , further comprising pretreating the composite at an elevated temperature and under a flow of pretreatment gas.
13. The method of claim 1 , wherein the selected platinum group metal is in oxidized form in the composite.
14. The method of claim 1 , wherein the selected platinum group metal is in reduced form in the composite.
15. A method of extracting a quantity of rhodium from a composite, the method comprising:
immersing the composite into an aqueous liquid comprising an organic solvent at a pH of greater than 2, the composite comprising a supported catalyst comprising a particulate catalyst bonded to a support, the particulate catalyst comprising the selected platinum group metal and the support comprising a support material; and
while the composite is immersed in the aqueous liquid comprising the organic solvent at a pH greater than 2, exposing the composite to one of nitric oxide or carbon monoxide at a temperature below 80 degrees Celsius to extract the quantity of rhodium.
16. The method of claim 15 , wherein extraction is conducted at a pressure between 1 bar and 25 bar and at a temperature between 25 degrees Celsius and 70 degrees Celsius.
17. The method of claim 15 , wherein the organic solvent comprises at least one of acetonitrile, ethyldimethylamine, dimethylformamide, or trimethylamine.
18. The method of claim 15 , wherein at least 90% of the rhodium is extracted after 24 hours.
19. A method of separating rhodium from a supported catalyst, the method comprising:
immersing a supported catalyst comprising rhodium and a catalytically inert support material into an aqueous liquid comprising at least one of acetonitrile, ethyldimethylamine, dimethylformamide, or trimethylamine at a pH of greater than 2; and
while the supported catalyst is immersed in the aqueous liquid comprising the at least one of acetonitrile, ethyldimethylamine, dimethylformamide, or trimethylamine at a pH greater than 2, exposing the supported catalyst to one of nitric oxide and carbon monoxide at a temperature below 80 degrees Celsius and at a pressure between 1 bar and 25 bar to extract the rhodium, such that at least 90% of the rhodium is extracted after 24 hours.