Method for recovering ruthenium from spent ruthenium-based catalyst carried on aluminum oxide

Abstract

A method for recovering ruthenium from a spent ruthenium-based catalyst carried on aluminum oxide includes: drying, calcining, and cooling a spent catalyst; grinding the spent catalyst into black powder; placing the black powder in a fluidized bed reactor, purging the reactor with hydrogen and heating the black powder to obtain ruthenium metal, then heating the black powder in a mixed atmosphere of oxygen and ozone to obtain RuO.sub.4 gas; absorbing the RuO.sub.4 gas with a sufficient amount of hydrochloric acid to obtain a H.sub.3RuCl.sub.6 solution; adding an excess oxidant to the H.sub.3RuCl.sub.6 solution to oxidize the H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6; adding excess NH.sub.4Cl to the H.sub.2RuCl.sub.6 and then filtering, and washing the filter cake to obtain solid (NH.sub.4).sub.2RuCl.sub.6; and reducing the solid (NH.sub.4).sub.2RuCl.sub.6 by hydrogen to obtain ruthenium metal.

Claims

1. A method for recovering ruthenium from a spent ruthenium-based catalyst carried on aluminum oxide, the method comprising: 1) drying a spent ruthenium-based catalyst carried on aluminum oxide at 100-150° C. in a nitrogen atmosphere for 1-2 hours, calcining the spent ruthenium-based catalyst carried on aluminum oxide at 300-500° C. for 2-4 hours, cooling the spent ruthenium-based catalyst carried on aluminum oxide to room temperature, and grinding the spent ruthenium-based catalyst carried on aluminum oxide into a black powder; 2) transferring the black powder to a fluidized bed reactor, purging the fluidized bed reactor with nitrogen for 20-40 minutes and then purging the fluidized bed reactor with hydrogen, and heating the black powder in a hydrogen atmosphere at a temperature of 200-400° C. and a pressure of 1-2 MPa for 2-3 hours to obtain a powder comprising ruthenium; 3) purging the fluidized bed reactor with nitrogen for 20-40 minutes, and then heating the powder comprising ruthenium in a mixed atmosphere of oxygen and ozone at a temperature of 500-750° C. and a pressure of 1-2 MPa for 1-8 hours to obtain a RuO.sub.4 gas; 4) absorbing the RuO.sub.4 gas with 3-8 mol/L hydrochloric acid to obtain a H.sub.3RuCl.sub.6 solution; 5) adding an excess oxidant to the H.sub.3RuCl.sub.6 solution, stirring the H.sub.3RuCl.sub.6 solution for 0.5-1.5 hours to completely oxidize H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6 to obtain a H.sub.2RuCl.sub.6 solution, adding excess NH.sub.4Cl to the H.sub.2RuCl.sub.6 solution and stirring at 60-90° C. for 1-3 hours to obtain a mixture, filtering the mixture to obtain a filter cake, and washing the filter cake to obtain solid (NH.sub.4).sub.2RuCl.sub.6, wherein the oxidant is a soluble chlorate; and 6) reducing the solid (NH.sub.4).sub.2RuCl.sub.6 at a temperature of 450-800° C. in a mixed atmosphere of hydrogen and nitrogen to obtain ruthenium, wherein a volume fraction of hydrogen in the mixed atmosphere of hydrogen and nitrogen is 1-15%.

2. The method of claim 1, wherein in 3), a space velocity of the mixed atmosphere of oxygen and ozone is 1000-4000 h.sup.−1.

3. The method of claim 1, wherein in 3), a volume fraction of the ozone in the mixed atmosphere of oxygen and ozone is 1-20%.

4. The method of claim 1, wherein in 4), a concentration of the hydrochloric acid is 6 mol/L.

5. The method of claim 1, wherein in 5), 1.2-2.5 times the theoretical weight of the NH.sub.4Cl that is required to completely react with the H.sub.2RuCl.sub.6 solution is added to the H.sub.2RuCl.sub.6 solution.

6. The method of claim 1, wherein in 5), the oxidant is selected from the group consisting of ammonium chlorate, potassium chlorate, sodium chlorate, and magnesium chlorate.

7. The method of claim 1, wherein in 5), the filter cake is washed with an ethanol solution.

8. The method of claim 1, wherein in 5), the H.sub.2RuCl.sub.6 solution is stirred at 100-400 revolutions per minute for 1-3 hours.

9. The method of claim 8, wherein in 5), the H.sub.2RuCl.sub.6 solution is stirred at 200 revolutions per minute for 1.5-2.5 hours.

10. The method of claim 2, wherein in 3), a volume fraction of the ozone in the mixed atmosphere of oxygen and ozone is 1-20%.

11. The method of claim 2, wherein in 4), a concentration of the hydrochloric acid is 6 mol/L.

12. The method of claim 2, wherein in 5), 1.2-2.5 times the theoretical weight of the NH.sub.4Cl that is required to completely react with the H.sub.2RuCl.sub.6 solution is added to the H.sub.2RuCl.sub.6 solution.

13. The method of claim 2, wherein in 5), the oxidant is selected from the group consisting of ammonium chlorate, potassium chlorate, sodium chlorate, and magnesium chlorate.

14. The method of claim 2, wherein in 5), the filter cake is washed with an ethanol solution.

15. The method of claim 2, wherein in 5), the H.sub.2RuCl.sub.6 solution is stirred at 100-400 revolutions per minute for 1-3 hours.

16. The method of claim 15, wherein in 5), the H.sub.2RuCl.sub.6 solution is stirred at 200 revolutions per minute for 1.5-2.5 hours.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The invention is explained in further detail below. It should be noted that the following examples are intended to describe and not to limit the invention.

Example 1

(2) 1) 90 g of spent ruthenium-based catalyst carried on aluminum oxide which contains by weight 5% ruthenium was placed in a crucible. The crucible was transferred to a muffle furnace. The muffle furnace was purged with nitrogen. After that, the spent ruthenium-based catalyst carried on aluminum oxide was dried at 100-150° C. in the nitrogen atmosphere for 1-2 hours, then calcined at 300-500° C. for 2-4 hours to remove the organic residue in the spent catalyst. Then, the muffle furnace was cooled down to room temperature to obtain 81.2 g of black solid, and the black solid was ground into powder.

(3) 2) 60 g of the obtained black powder was transferred to a fluidized bed reactor. The fluidized bed reactor was purged with nitrogen for 30 minutes. Next, the black powder was heated in a hydrogen atmosphere at 300° C. and a pressure of 1.0 MPa for 2 hours so that the ruthenium oxide in the spent catalyst was reduced into ruthenium metal.

(4) 3) The fluidized bed reactor was purged with nitrogen again for 20 minutes. Next, the spent catalyst was heated in a mixed atmosphere of oxygen and ozone containing ozone at a volume fraction of 20% at a temperature of 600-650° C., a pressure of 1 MPa, and a space velocity of 1200 h.sup.−1 for 4 hours to obtain RuO.sub.4 gas.

(5) 4) the RuO.sub.4 gas was absorbed by 6 mol/L hydrochloric acid under stirring to obtain a H.sub.3RuCl.sub.6 solution;

(6) 5) 0.63 g of NaClO.sub.3 powder (1.2 times the stoichiometric amount of 0.525 g NaClO.sub.3 required for complete reaction) was added to the H.sub.3RuCl.sub.6 solution and stirred for 0.5 hour to completely oxidize H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6. Then, 3.81 g of NH.sub.4Cl (1.2 times the stoichiometric amount of 3.18 g NH.sub.4Cl required for complete reaction) was added to the H.sub.2RuCl.sub.6 solution, and then heated at 90° C. under stirring at 200 revolutions per minute for 1.5 hours to obtain a (NH.sub.4).sub.2RuCl.sub.6 precipitate. The reaction product was filtered and the obtained filter cake was washed with an ethanol solution to remove the impurities and the hydrochloric acid in the filter cake. The filter cake was then dried to obtain solid (NH.sub.4).sub.2RuCl.sub.6; and

(7) 6) The solid (NH.sub.4).sub.2RuCl.sub.6 was heated at 650° C. in a mixed atmosphere of hydrogen and nitrogen which contains hydrogen at a volume fraction of 5% to obtain 2.941 g of ruthenium metal.

(8) In Example 1, the recovery rate of ruthenium was 98.03%.

Example 2

(9) The process of step 1) of Example 2 was identical to that of Example 1.

(10) In step 2), 60 g of the black powder obtained in 1) was transferred to a fluidized bed reactor. The fluidized bed reactor was purged with nitrogen for 20 minutes. Next, the black powder was heated in a hydrogen atmosphere at 200° C. and a pressure of 1.5 MPa for 3 hours so that the ruthenium oxide in the spent catalyst was reduced into ruthenium metal.

(11) In step 3), the fluidized bed reactor was purged with nitrogen again for 30 minutes. Next, the spent catalyst was heated in a mixed atmosphere of oxygen and ozone containing ozone at a volume fraction of 10% at a temperature of 600° C., a pressure of 1.5 MPa, and a space velocity of 3000 h.sup.−1 for 4 hours to obtain RuO.sub.4 gas.

(12) In step 4), the RuO.sub.4 gas was absorbed by 3 mol/L hydrochloric acid under stirring to obtain a H.sub.3RuCl.sub.6 solution;

(13) In step 5), 0.72 g of KClO.sub.3 powder (1.2 times the stoichiometric amount of KClO.sub.3 required for complete reaction) was added to the H.sub.3RuCl.sub.6 solution and stirred for 1 hour to completely oxidize H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6. Then, 4.77 g of NH.sub.4Cl (1.5 times the stoichiometric amount of NH.sub.4Cl required for complete reaction) was added to the H.sub.2RuCl.sub.6 solution, and then heated at 80° C. under stirring at 200 revolutions per minute for 1.5 hours to obtain a (NH.sub.4).sub.2RuCl.sub.6 precipitate. The reaction product was filtered and the obtained filter cake was washed with an ethanol solution to remove the impurities and the hydrochloric acid in the filter cake. The filter cake was then dried to obtain solid (NH.sub.4).sub.2RuCl.sub.6; and

(14) In step 6), the solid (NH.sub.4).sub.2RuCl.sub.6 was heated at 800° C. in a mixed atmosphere of hydrogen and nitrogen which contains hydrogen at a volume fraction of 10% to obtain 2.976 g of ruthenium metal.

(15) In Example 2, the recovery rate of the ruthenium was 99.2%.

Example 3

(16) The process of step 1) of Example 3 was identical to that of Example 1.

(17) In step 2), 60 g of the black powder obtained in 1) was transferred to a fluidized bed reactor. The fluidized bed reactor was purged with nitrogen for 40 minutes. Next, the black powder was heated in a hydrogen atmosphere at 400° C. and a pressure of 2 MPa for 2.5 hours so that the ruthenium oxide in the spent catalyst was reduced into ruthenium metal.

(18) In step 3), the fluidized bed reactor was purged with nitrogen again for 40 minutes. Next, the spent catalyst was heated in a mixed atmosphere of oxygen and ozone containing ozone at a volume fraction of 15% at a temperature of 650° C., a pressure of 2 MPa, and a space velocity of 4000 h.sup.−1 for 5 hours to obtain RuO.sub.4 gas.

(19) In step 4), the RuO.sub.4 gas was absorbed by 5 mol/L hydrochloric acid under stirring to obtain a H.sub.3RuCl.sub.6 solution;

(20) In step 5), 1.13 g of Mg(ClO.sub.3).sub.2 powder (1.2 times the stoichiometric amount required for complete reaction) was added to the H.sub.3RuCl.sub.6 solution and stirred for 1.5 hours to completely oxidize H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6. Then, 6.36 g of NH.sub.4Cl (twice the stoichiometric amount required for complete reaction) was added to the H.sub.2RuCl.sub.6 solution, and then heated at 90° C. under stirring at 100 revolutions per minute for 2.5 hours to obtain a (NH.sub.4).sub.2RuCl.sub.6 precipitate. The reaction product was filtered and the obtained filter cake was washed with an ethanol solution to remove the impurities and the hydrochloric acid in the filter cake. The filter cake was then dried to obtain solid (NH.sub.4).sub.2RuCl.sub.6; and

(21) In step 6), the solid (NH.sub.4).sub.2RuCl.sub.6 was heated at 650° C. in a mixed atmosphere of hydrogen and nitrogen which contains hydrogen at a volume fraction of 15% to obtain 2.946 g of ruthenium metal.

(22) In Example 3, the recovery rate of the ruthenium was 98.2%.

Example 4

(23) The process of step 1) of Example 4 was identical to that of Example 1.

(24) In step 2), 60 g of the black powder obtained in 1) was transferred to a fluidized bed reactor. The fluidized bed reactor was purged with nitrogen for 25 minutes. Next, the black powder was heated in a hydrogen atmosphere at 350° C. and a pressure of 2 MPa for 3 hours so that the ruthenium oxide in the spent catalyst was reduced into ruthenium metal.

(25) In step 3), the fluidized bed reactor was purged with nitrogen again for 35 minutes. Next, the spent catalyst was heated in a mixed atmosphere of oxygen and ozone containing ozone at a volume fraction of 5% at a temperature of 600° C., a pressure of 2 MPa, and a space velocity of 4000 h.sup.−1 for 6 hours to obtain RuO.sub.4 gas.

(26) In step 4), the RuO.sub.4 gas was absorbed by 6 mol/L hydrochloric acid under stirring to obtain a H.sub.3RuCl.sub.6 solution;

(27) In step 5), 0.63 g of NaClO.sub.3 powder (1.2 times the stoichiometric amount required for complete reaction) was added to the H.sub.3RuCl.sub.6 solution and stirred for 1.5 hours to completely oxidize H.sub.3RuCl.sub.6 into H.sub.2RuCl.sub.6. Then, 7.94 g of NH.sub.4Cl (2.5 times the stoichiometric amount required for complete reaction) was added to the H.sub.2RuCl.sub.6 solution, and then heated at 70° C. under stirring at 400 revolutions per minute for 1 hour to obtain a (NH.sub.4).sub.2RuCl.sub.6 precipitate. The reaction product was filtered and the obtained filter cake was washed with an ethanol solution to remove the impurities and the hydrochloric acid in the filter cake. The filter cake was then dried to obtain solid (NH.sub.4).sub.2RuCl.sub.6; and

(28) In step 6), the solid (NH.sub.4).sub.2RuCl.sub.6 was heated at 800° C. in a mixed atmosphere of hydrogen and nitrogen which contains hydrogen at a volume fraction of 15% to obtain 2.901 g of ruthenium metal.

(29) In Example 4, the recovery rate of the ruthenium was 96.7%.

(30) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.