Metals recovery from spent catalyst
An improved method for recovering metals from spent catalysts, particularly from spent slurry catalysts, is disclosed. The method and associated processes comprising the method are useful to recover catalyst metals used in the petroleum and chemical processing industries. The method generally involves a pyrometallurgical method and a hydrometallurgical method and includes forming a soda ash calcine of a caustic leach residue of the spent catalyst containing an insoluble Group VIII/Group VIB/Group VB metal compound combined with soda ash, and extracting and recovering soluble Group VIB metal and soluble Group VB metal compounds from the soda ash calcine.
1 . A method for recovering metals from a deoiled spent catalyst, the method comprising:
heating a deoiled spent catalyst comprising a Group VIB metal, a Group Vill metal, and a Group VB metal under oxidative conditions at a first pre-selected temperature for a first time sufficient to reduce the levels of sulfur and carbon to less than pre-selected amounts and to form a calcined spent catalyst;
contacting the calcined spent catalyst with a caustic leach solution to form a spent catalyst slurry at a pre-selected leach temperature for a pre-selected leach time and at a pre-selected leach pH;
separating and removing a first filtrate and a first solid residue from the spent catalyst slurry, the first filtrate comprising a soluble Group VIB metal compound and a soluble Group VB metal compound and the first solid residue comprising an insoluble Group VIII/Group VIB/Group VB metal compound;
drying the insoluble Group VIII/Group VIB/Group VB metal compound first solid residue;
combining the dried Group VIII/Group VIB/Group VB metal compound first solid residue with anhydrous soda ash to form a solid residue/soda ash mixture;
heating the metal compound solid residue/soda ash mixture at a second pre-selected temperature and for a second pre-selected time under gas flow conditions to form a soda ash calcine;
contacting the soda ash calcine with water to form a soda ash calcine slurry at a temperature and for a time sufficient to leach a soluble Group VIB metal compound and a soluble Group VB metal compound from the soda ash calcine;
separating and removing a second filtrate and a second solid residue from the soda ash calcine slurry, the second filtrate comprising the soluble Group VIB metal compound and the soluble Group VB metal compound and the second solid residue comprising an insoluble Group VIII metal compound; and
recovering the soluble Group VIB metal compound and the soluble Group VB metal compound from the spent catalyst slurry first filtrate and from the soda ash calcine slurry second filtrate;
wherein, the oxidative heating conditions comprise heating the deoiled spent catalyst at the first pre-selected temperature in the presence of air, or a gas mixture comprising no more than about 20 vol. % oxygen followed by heating the deoiled spent catalyst at the first pre-selected temperature under gas conditions comprising more than about 80 vol. % oxygen; or,
wherein the gas flow conditions comprise an inert gas and are sufficient to remove any off-gases.
2 . The method of claim 1 , wherein the deoiled spent catalyst is substantially devoid of residual hydrocarbons, or is devoid of residual hydrocarbons, or comprises residual hydrocarbons in an amount of less than about 1000 ppm.
3 . The method of claim 1 , wherein the deoiled spent catalyst comprises residual hydrocarbons and the process further comprises heating the catalyst under non-oxidative conditions at a pre-selected non-oxidative condition temperature for a time sufficient to reduce the level of residual hydrocarbons to an amount of less than about 1000 ppm.
4 . The method of claim 3 , wherein the pre-selected non-oxidative condition temperature is in the range of about 350° C. to 500° C.
5 . The method of claim 1 , wherein the deoiled spent catalyst is substantially devoid of catalyst support materials comprising alumina, silica, titania, or a combination thereof, or wherein a catalyst support material comprising alumina, silica, titania, or a combination thereof is not used to prepare the catalyst.
6 . The method of claim 1 , wherein the spent catalyst comprises or is a slurry catalyst.
7 . The method of claim 1 , wherein the oxidative heating conditions comprise heating in the presence of an inert gas, air, or a combination thereof.
8 . The method of claim 1 , wherein the oxidative heating conditions comprise heating the deoiled spent catalyst at the first pre-selected temperature in the presence of air, or a gas mixture comprising no more than about 20 vol. % oxygen.
9 . The method of claim 8 , wherein the oxidative heating conditions further comprise heating the deoiled spent catalyst at the first pre-selected temperature under gas conditions comprising more than about 80 vol. % oxygen.
10 . The method of claim 1 , wherein the first pre-selected temperature is greater than about 600° C.
11 . The method of claim 1 , wherein the levels of sulfur and carbon are individually or both reduced to less than pre-selected amounts, as measured by CO 2 and SO 2 off-gas analysis, of less than about 1 wt. %.
12 . The method of claim 1 , wherein the pre-selected leach temperature is greater than about 60° C.
13 . The method of claim 1 , wherein the pre-selected leach time is in the range of about 1-5 hr.
14 . The method of claim 1 , wherein the pre-selected leach pH is in the range of about 9.5 to 11.
15 . The method of claim 1 , wherein the first filtrate comprises soluble molybdate or vanadate compounds, or a mixture thereof.
16 . The method of claim 1 , wherein the first filtrate contains greater than about 80 wt. % of the Group VIB metal or greater than about 85 wt. % of the Group VB metal present in the deoiled spent catalyst, or both greater than about 80 wt. % of the Group VIB metal and greater than about 85 wt. % of the Group VB metal present in the deoiled spent catalyst.
17 . The method of claim 1 , wherein the first solid residue is dried at a temperature in the range of about 110-140° C.-for a time period in the range of 0.5-2 hr.
18 . The method of claim 1 , wherein the first solid residue is dried at a temperature and for a time sufficient to reduce the amount of water to less than about 2 wt. %.
19 . The method of claim 1 , wherein the first solid residue comprises Group VB and/or Group VIB metal compound solids.
20 . The method of claim 1 , wherein the second pre-selected temperature is in the range of about 600° C. to 650° C.
21 . The method of claim 1 , wherein the second pre-selected time is in the range of about 0.5-2 hr.
22 . The method of claim 1 , wherein the soda ash calcine is contacted with water to form the soda ash calcine slurry at a temperature greater than about 60° C.
23 . The method of claim 1 , wherein the soda ash calcine leach time is in the range of 0.5-4 hr.
24 . The method of claim 1 , wherein the soda ash calcine leach is conducted without pH modification.
25 . The method of claim 1 , wherein the second filtrate comprises sodium molybdate, sodium vanadate, or a mixture thereof.
26 . The method of claim 19 , wherein the second filtrate contains the Group VB metal present in the Group VB and/or Group VIB metal compound in an amount greater than about 90 wt. %.
27 . The method of claim 1 , wherein the second filtrate contains the Group VIB metal present in the Group VB and/or Group VIB metal compound in an amount greater than about 90 wt. %.
28 . The method of claim 1 , wherein the overall extraction of the Group VB metal present in the deoiled spent catalyst is greater than about 90 wt. %.
29 . The method of claim 1 , wherein the overall extraction of the Group VIB metal present in the deoiled spent catalyst is greater than about 90 wt. %.
30 . The method of claim 1 , wherein a Group IIA compound is excluded from the method, or wherein a calcium compound is excluded from the method, or wherein calcium carbonate is excluded from the method.