Method for producing a sulphided copper sorbent

Abstract

A method for producing a sulphided copper sorbent includes the steps of: (i) contacting a sorbent precursor material containing one or more sulphidable copper compounds, with a sulphiding gas stream including hydrogen sulphide to form a sulphided sulphur-containing sorbent material, and (ii) subjecting the sulphided sulphur-containing sorbent material to a heating step in which it is heated to a temperature above that used in the sulphiding step and ?110? C., under an inert gas selected from nitrogen, argon, helium, carbon dioxide, methane, and mixtures thereof, the inert gas optionally including hydrogen sulphide. The method provides sulphided copper sorbents that have reduced levels of elemental sulphur.

Claims

1. A method for producing a sulphided copper sorbent, comprising the steps of: (i) contacting a sorbent precursor material containing one or more sulphidable copper compounds, with a sulphiding gas stream comprising hydrogen sulphide and an inert gas selected from nitrogen, argon, helium, carbon dioxide, methane, and mixtures thereof to form a sulphided sulphur-containing sorbent material, and (ii) subjecting the sulphided sulphur-containing sorbent material to a heating step in which it is heated to a temperature above that used in the sulphiding step and ?110? C., under a gas consisting of an inert gas selected from nitrogen, argon, helium, carbon dioxide, methane, and mixtures thereof, or a gas consisting of hydrogen sulphide and an inert gas selected from nitrogen, argon, helium, carbon dioxide, methane, and mixtures thereof.

2. A method according to claim 1 wherein the precursor is formed by combining an oxide, hydroxide, carbonate or hydroxycarbonate of copper or copper and zinc, with one or more binders or by combining an oxide, hydroxide, carbonate or hydroxycarbonate of copper or copper and zinc, with one or more binders and a support material.

3. A method according to claim 1 wherein the sorbent precursor is formed by impregnating a support material with a solution of a soluble salt of copper, followed by drying the impregnated support or by impregnating a support material with a solution of a soluble salt of copper, followed by drying and calcining the impregnated support.

4. A method according to claim 1 wherein the sorbent precursor is formed by coating a support material with a slurry of an insoluble copper compound, followed by drying the coated support or by coating a support material with a slurry of an insoluble copper compound, followed by drying and calcining the coated support.

5. A method according to claim 2 wherein the support material is selected from the group consisting of alumina, hydrated alumina, metal-aluminate, silica, titania, zirconia, zinc oxide, aluminosilicates, zeolites, or a mixture thereof.

6. A method according to claim 1 wherein the hydrogen sulphide content of the sulphiding gas stream is 0.25 to 80% by volume.

7. A method according to claim 1 where the pressure of the sulphiding gas stream is in the range 1 to 100 psig.

8. A method according to claim 1 wherein the sulphiding gas stream comprises an oxidant selected from one or more of free oxygen (O.sub.2), sulphur oxides and nitrogen oxides, and has a total oxidant content of ?1%.

9. A method according to claim 1 wherein the inlet temperature for the sulphiding step is in the range 0-150? C.

10. A method according to claim 1 wherein the sulphiding gas stream is passed through a fixed bed of the sorbent precursor at a linear velocity ?0.1 m/s but less than the fluidization velocity.

11. A method according to claim 1 wherein the sulphiding gas stream comprises water vapour.

12. A method according to claim 1 wherein the sulphiding gas stream has a water vapour level in the range 0.2 to 2.0% by volume.

13. A method according to claim 1 wherein the sulphur-containing sorbent material is heated to a temperature in the heating step that is 40 or more degrees centigrade higher than the maximum temperature in the sulphiding step.

14. A method according to claim 1 wherein the sulphur-containing sorbent material is heated to a temperature ?125? C.

15. A method according to claim 1 wherein the sorbent precursor comprises basic copper carbonate and the sulphur-containing sorbent material is heated to a temperature in the range 140 to 200? C.

16. A method according to claim 1 wherein the heating step is performed under an inert gas selected from nitrogen, argon, helium, carbon dioxide, methane, and mixtures thereof, said inert gas comprising hydrogen sulphide at a concentration lower than that used in the sulphiding step.

17. A method according to claim 1 further comprising reducing the sulphided sorbent material in a hydrogen containing gas stream to produce a reduced copper sorbent.

18. A method according to claim 1 wherein the hydrogen sulphide content of the sulphiding gas stream is 0.5 to 10% by volume.

19. A method according to claim 1 wherein the hydrogen sulphide content of the sulphiding gas stream is 0.75 to 4.5% by volume.

20. A method according to claim 1 where the pressure of the sulphiding gas stream is in the range 1 to 20 psig.

21. A method according to claim 1 wherein the sulphiding gas stream comprises an oxidant selected from one or more of free oxygen (O.sub.2), sulphur oxides and nitrogen oxides, and has a total oxidant content of ?0.01% by volume.

22. A method according to claim 1 wherein the inlet temperature for the sulphiding step is in the range 20-100? C.

23. A method according to claim 1 wherein the sulphur-containing sorbent material is heated to a temperature ?140? C.

24. A method according to claim 1 wherein the sorbent precursor comprises basic copper carbonate and the sulphur-containing sorbent material is heated to a temperature in the range 160 to 200? C.

25. A method according to claim 1 wherein the sorbent precursor comprises basic copper carbonate and the sulphur-containing sorbent material is heated to a temperature in the range 160 to 180? C.

Description

EXAMPLE 1

(1) A sorbent precursor according to WO 2009/101429 was prepared by granulating basic copper carbonate with alumina tri-hydrate and a combination of cement and clay binders. The granules were dried at 105? C. The size range of the granules was 2.00 to 4.75 mm. The details are given in Table 1.

(2) TABLE-US-00001 TABLE 1 Basic copper Alumina tri- carbonate hydrate Cement and Clay binders (% w/w) (% w/w) (% w/w) 30.7 44.7 24.6

(3) The sorbent precursor was sulphided using laboratory apparatus that allowed between 10 and 100 g of precursor to be sulphided by passing H.sub.2S in a carrier gas through a bed of the sorbent precursor disposed in a 20 mm diameter tubular sulphiding vessel at different temperatures. The total gas flow of sulphiding gas could be varied in the range 25 to 2500 Nl/hr. The carrier gas composition could be varied to include one or more of N.sub.2, CO.sub.2 and H.sub.2. High purity gases were used throughout. At least a portion of the carrier gas could be passed through a water bubbler at ambient temperate and pressure. H.sub.2S was added to the carrier gas at the reactor inlet such that the inlet H.sub.2S concentration could be set in the range 0.1 to 10% vol. The sulphur content of the sulphiding gas was determined using Drager? gas detection tubes. The temperature of the system was controlled either by a chiller unit just prior to the inlet to the reactor or by an electrically-powered radiant heating device clamped to the reactor. The temperature of the sorbent in the sulphiding vessel was measured by means of a thermo-couple in the precursor bed. In each case, the sulphiding step was carried out just above atmospheric pressure, 1 to 12 psig (6.9?10.sup.3 Pag to 8.3?10.sup.4 Pag). Before and after the sulphiding step, the sulphiding vessel was purged for at least 30 minutes with carrier gas.

(4) In a first comparative example, 4 beds of the sorbent precursor, each of 20 cm.sup.3 (18.5 g), were charged into the sulphiding apparatus. The apparatus was operated in an up-flow configuration, and it was purged with CO.sub.2 to remove residual air. A sulphiding gas mixture comprising 3% H.sub.2S in CO.sub.2 was passed over the sorbent at a flow rate of 915 I/hr at ambient temperature (20 to 25? C.) and pressure for 60 mins (sulphiding time). The concentration of H.sub.2S in the reactor inlet was checked with a Dr?ger? tube. 40% vol of the sulphiding gas stream was passed through a water bubbler upstream of the sorbent.

(5) After sulphiding, the reactor heater was turned off and the process gas was changed to a pure CO.sub.2 purge. After reaching ambient temperature, the gas was turned off and the sorbent beds were discharged. The inlet bed was tested by Soxhlet extraction and by LECO analysis, as described above.

(6) In a second comparative example the procedure was repeated except that the sulphiding step was performed for 120 minutes. Again, after sulphiding the sulphur-containing sorbent was not subjected to a heating step.

(7) The results of these experiments are shown in Table 2. The results demonstrate that elemental sulphur is formed during sulphiding of the sorbent precursor and that varying the duration of the sulphiding process results in different levels of elemental sulphur on the sorbent.

EXAMPLE 2

(8) The method of Example 1 was repeated, with an additional heating step applied to the sulphided sulphur-containing sorbent. The same sorbent precursor was subjected to the same sulphiding method with a sulphiding time of 120 minutes. Following the sulphiding step, the concentration of H.sub.2S in CO.sub.2 was lowered to 0.5%, and the total flow rate was adjusted to maintain 915 l/hr gas flow. A temperature ramp was then applied to the reactor to heat the sulphided sulphur-containing sorbent to 175? C. (thermal treatment temperature) over 90 mins (ramp time). The temperature of 175? C. was held for a further 30 mins. This period is defined as the dwell time.

(9) After the heat treatment, the reactor heater was turned off and the process gas was changed to a pure CO.sub.2 purge. After reaching ambient temperature, the gas was turned off and the sorbent beds were discharged. The inlet bed inlet was tested by Soxhlet extraction and by LECO analysis.

(10) The procedure was repeated with variation of the sulphiding time, ramp time and dwell time.

(11) The results are shown in Table 2. Comparison of the results shows that a post sulphiding temperature treatment of 175? C. is sufficient to eliminate elemental sulphur from the sulphided sorbent, down to a level below the limit of detection of the GC technique (0.1 ppm). The results also show that the thermal treatment temperature of 175? C. is very effective at reducing elemental sulphur levels for a range of processing conditions.

(12) It is observed that the shorter sulphiding time and longer dwell time for runs 5 and 6 would logically favour lower elemental sulphur compared with run 2. However it appears, surprisingly, that the thermal treatment temperature of 150? C. used in run 5 and 125? C. used in run 6 are less effective at eliminating elemental sulphur than the 175? C. used in runs 1-4.

(13) TABLE-US-00002 TABLE 2 Sul- Thermal phiding Ramp Dwell treatment Elemental Total time time time tempera- sulphur sulphur Example (min) (min) (min) ture (? C.) (ppm) (wt. %) Comparative 60 34 8.5 run 1 Comparative 120 60 8.0 run 2 2 run 1 120 90 30 175 N.D. 8.1 2 run 2 180 90 0 175 N.D. 8.5 2 run 3 60 60 0 175 N.D. 8.5 2 run 4 65 60 0 175 N.D. 8.9 2 run 5 90 90 60 150 0.4 8.3 2 run 6 65 90 150 125 1.9 8.6 (N.D.: none detected. The detection limit of the GC method was 0.1 ppm.)