Method for preparing a sorbent

Abstract

A method is described for preparing a sorbent comprising the steps of: (i) mixing together a particulate copper sulphide material and a particulate calcined rehydratable alumina, (ii) shaping the mixture, and (iii) drying the shaped mixture to form a dried sorbent.

Claims

1. A method for preparing a sorbent comprising the steps of: (i) mixing a particulate copper sulphide material and a particulate calcined rehydratable aluminato to form a mixture, (ii) shaping the mixture, and (iii) drying the shaped mixture to form the sorbent.

2. A method according to claim 1 wherein the calcined rehydratable alumina comprises a calcined amorphous alumina or a transition alumina that is one or more of rho-alumina, chi-alumina, or pseudo gamma-alumina.

3. A method according to claim 1, wherein the particulate copper sulphide material (a) is manufactured by roasting copper or a copper compound with elemental sulphur,or (b) by precipitating copper sulphide from solution, sulphiding copper compounds using hydrogen sulphide, a mechanochemical process that is mixing powdered copper metal with elemental sulphur under conditions that cause the elemental copper and elemental sulphur to react to form one or more copper sulphides.

4. A method according to claim 1, wherein the particulate copper sulphide material comprises one or more copper sulphides that is copper (II) sulphide, CuS, and/or substoichiometric copper sulphide of formula Cu.sub.2xS where x is in a range of from 0 to 1.

5. A method according to claim 1, wherein the particulate copper sulphide material has an overall S:Cu atomic ratio of 0.8.

6. A method according to claim 1, wherein the particulate copper sulphide material is in the form of a powder with an average particle size, [D50], in the range of 5 to 100 m.

7. A method according to claim 1, wherein a copper content of the sorbent produced by the method is in a range of from 5% to 75% by weight expressed as CuS.

8. A method according to claim 1, wherein the particulate calcined rehydratable alumina is a powder with a D.sub.50 particle size in a range of 1 to 100 m.

9. A method according to claim 1, wherein a BET surface area of the calcined rehydratable alumina as determined by nitrogen adsorption is in a range of from 200 m.sup.2/g to 400.

10. A method according to claim 1, wherein the sorbent produced by the method consists essentially of the particulate copper sulphide material and the particulate calcined rehydratable alumina.

11. A method according to claim 1, wherein the shaping step comprises granulating the mixture in a granulator to produce granules of the sorbent.

12. A method according to claim 11 wherein the granulating is performed under a non-oxidising atmosphere.

13. A method according to claim 11, wherein the granules are aged for a time of from 0.5 hours to 8 hours before drying.

14. A method according to claim 1, wherein the sorbent is dried at a temperature up to 120 C. under a non-oxidising atmosphere.

15. A sorbent obtained by the method of claim 1.

16. A process for removing one or more heavy metals from a heavy metal-containing fluid stream by contacting the fluid stream with the sorbent according to claim 15.

17. A method according to claim 5, wherein the overall S:Cu atomic ratio is 0.9.

18. A method according to claim 7, wherein the copper content of the sorbent is in the range of 10 to 75% by weight expressed as CuS.

19. A method according to claim 8, wherein the particle size of the particulate calcined rehydratable alumina is in the range of from 1 m to 20.

20. A method according to claim 9, wherein the BET surface area of the calcined rehydratable alumina as determined by nitrogen adsorption is in the range of from 250 m.sup.2/g to 300 m.sup.2/g.

Description

EXAMPLE 1

Preparation of Sorbent

(1) A mixture of a copper sulphide powder and a calcined, rehydratable alumina powder was prepared as follows:

(2) TABLE-US-00001 Component Source % wt Copper sulphide (99%), Eurolub 33 Calcined, rehydratable alumina CP-5, BASF 67

(3) The properties of the calcined, rehydratable alumina powder were as follows:

(4) TABLE-US-00002 Chemical composition (wt %) Residual Moisture (dried a 250 C. for 30 minutes) 2 Total loss on ignition (250-1100 C.) 7 SiO.sub.2 <0.02 Fe.sub.2O.sub.3 <0.01 Na.sub.2O <0.4

(5) Physical Properties

(6) TABLE-US-00003 BET Surface area 270 m.sup.2/g Packed bulk density 38 lb/ft.sup.3 Particle size distribution (average size) 5 m Particle size distribution (90 wt % <) 12 m XRD Phase Amorphous

(7) The powders were pre-mixed to ensure a homogenous mixture. Granules were then formed by nodulizing the mixture in a rotating pan while water (about 0.33 ml/g mixture) was sprayed onto the mixture as a fine mist. The water was found to be about 25 wt % of the mass of the shaped agglomerates before drying. This is significantly higher than the water content of the prior granulated sorbents which typically only comprise about 15 wt % water. Following granulation, the material was aged at 45 C. Following ageing, the material was dried in a fluid bed dryer at 105 C., to produce the sorbent.

(8) The physical properties of the sorbent were determined, and are shown below compared to a sulphided copper sorbent prepared using basic copper carbonate, cement and clay binders, and an alumina trihydrate (ATH) support material, according to the method described in WO2009/101429.

(9) The tapped bulk density (TBD) was measured by pouring approximately 500 mls of sorbent granules into a 500 ml plastic measuring cylinder and tapping it until a constant volume was achieved. The TBD was calculated by dividing the mass of sorbent by the tapped volume.

(10) The drum tumbling loss (DrTL) was measured by rotating 100 g of sorbent through 1800 total revolutions at 60 rpm for 30 minutes according to the ASTM method D4058-96. The DrTL is reported as a percentage of the original mass.

(11) The mean crush strength (MCS) was determined by crushing 25 granules of each sorbent using an Engineering Systems C53 machine to calculate mean crush strength based on a normal distribution.

(12) TABLE-US-00004 Ageing time MCS Example (h) TBD (g cm.sup.3) DrTL (%) (kgF) 1(a) 1 1.04 0.00 7.61 1(b) 6 1.04 n/a 8.51 1(c) 6 1.02 0.00 8.89 1(d) 24 1.03 n/a 9.91 1(e) 24 1.04 0.00 9.55 Comparative 12 0.99 2.20 1.48

(13) The use of a calcined, rehydratable alumina provided a much stronger product when compared to the prior art material produced using mixed binders and aluminium trihydrate. The rate at which strength develops also occurs much more rapidly in the calcined, rehydratable alumina product when compared to the mixed binder product with strength achieved over 5 times higher following 1 hour of ageing.