IMPROVEMENT IN AND RELATING TO AN ABSORBENT COMPOSITION

Abstract

The invention provides an absorbent composition comprising an oxide or a carbonate, the oxide or carbonate comprising one or more transition and/or Group 12 metal and a hydrocolloidal polymer and/or a thermal decomposition product thereof. A method of removing materials such as sulphur containing compounds (such as hydrogen sulphide) or mercury is also provided, as is a method of making an absorbent composition.

Claims

1. An absorbent composition comprising an oxide or a carbonate, the oxide or carbonate comprising one or more transition and/or Group 12 metal, and a hydrocolloidal polymer and/or a thermal decomposition product of the hydrocolloidal polymer.

2. The composition according to claim 1 wherein the hydrocolloidal polymer comprises one or more of a polysaccharide, a glycoprotein, a proteoglycan, a polypeptide, a polyacrylic acid, a polyacrylic amide, a polyvinyl alcohol, a polyvinyl ether, a polypyrrolidone or gelatin.

3. (canceled)

4. The composition according to claim 1 comprising at least 0.5 wt %, and optionally no more than 5.0 wt %, of the hydrocolloidal polymer and/or thermal decomposition product thereof, based on the weight of the composition.

5. (canceled)

6. The composition according to claim 1 comprising from 0.5 to 4.0 wt % of the hydrocolloidal polymer and/or thermal decomposition product thereof, based on the weight of the composition.

7. The composition according to claim 1 comprising at least 80% by weight, and optionally no more than 98 wt % by weight, of said oxide or said carbonate, based on the weight of the composition.

8. (canceled)

9. The composition according to claim 1 comprising from 90 wt % to 98 wt % of said oxide or said carbonate, based on the weight of the composition.

10. The composition according to claim 1 comprising one or more additional binders, wherein the additional binder optionally comprises a clay or a mixture of clays.

11. (canceled)

12. The composition according to claim 10 comprising from 1.0 wt % to 8.0 wt % of the additional binder, based on the weight of the composition.

13. The composition according to claim 1 comprising one or more absorbent materials in addition to said oxide or said carbonate.

14. The composition according to claim 1 wherein the absorbent composition is in the form of particles, optionally sized so as not to pass through a 1 mm sieve.

15. The composition according to claim 1 wherein each transition metal and/or Group 12 metal is from Period 4 or 5 of the periodic table, optionally from Period 4 of the Periodic Table.

16. The composition according to claim 1 wherein the oxide or the carbonate is a basic oxide or basic carbonate, and/or is selected from copper carbonate, zinc carbonate, nickel carbonate, copper zinc carbonate, aluminium copper zinc oxide and copper oxide.

17. (canceled)

18. A method of making an absorbent composition, the method comprising mixing a hydrocolloidal polymer and an oxide or a carbonate, said oxide or carbonate comprising one or more transition and/or Group 12 metals.

19. The method according to claim 18 comprising mixing the hydrocolloidal polymer and said oxide or said carbonate in the presence of a liquid.

20. The method according to claim 18 further comprising adding an additional binder.

21. The method according to claim 18 further comprising forming a powder mixture comprising the oxide or the carbonate and the hydrocolloidal polymer.

22. The method according to claim 18 further comprising forming a precursor composition for an absorbent material, the precursor composition being in the form of particles comprising a liquid, and optionally removing the liquid from the precursor composition thereby providing said absorbent composition.

23. (canceled)

24. A precursor composition obtained from claim 22.

25. An absorbent composition prepared from the method of claim 18, optionally to absorb one or more target species from a fluid, the target species being one or more of sulphur, mercury and at least one sulphur-containing compound.

26. (canceled)

27. A method of removing a target species from a fluid, the method comprising contacting the absorbent composition according to claim 1 with the fluid, wherein the target species optionally comprises one or more of sulphur, mercury and at least one sulphur-containing compound.

28. (canceled)

Description

DETAILED DESCRIPTION

[0075] Examples of absorbent compositions in accordance with the present invention and comparative examples were made in accordance with the following method. In general, the metal carbonate or oxide was admixed with gelatin (if present) and Attapulgite clay in the presence of water using a high-sheer granulator. The metal carbonate or oxide, gelatin and the clay were provided as powders.

[0076] Examples of compositions in accordance with the present invention and comparative examples which are not the subject matter of the present invention were made as described below with reference to Table 1.

TABLE-US-00001 TABLE 1 mixtures used to make examples of absorbent compositions in accordance with the present invention Amount of Amount Amount Water On-size Example Oxide or oxide or of clay of gelatin volume Density Strength % yield number carbonate carbonate (g) (g) (g) (mL) (g mL.sup.−1) (N) Attrition (%) C. Ex. 1 Copper 500 70 0 138 1.38 17 2.5 — carbonate C. Ex. 2 ″ 500 60 0 134 1.45 13.7 3 — C. Ex. 3 ″ 500 60 0 130 1.38 13.1 2.8 — 1 ″ 500 50 20 130 1.40 24.6 3 — 2 ″ 500 40 10 135 1.38 33.2 2.4 — 3 ″ 500 30 10 132 1.37 22.1 6.6 — 4 ″ 500 30 20 138 1.30 22.1 0.7 71 5 ″ 500 25 25 120 1.35 35.5 1.8 74 6 ″ 500 25 15 125 1.41 32.6 2 70 7 ″ 500 20 10 140 1.43 26.2 5.1 67 8 ″ 500 20 10 138 1.35 39.4 1.7 69 9 ″ 500 20 10 136 1.42 33.7 2.9 64 10 ″ 500 15 10 142 1.32 25.6 2.9 69 11 ″ 500 15 5 140 1.26 15.0 4.09 62 12 ″ 500 10 10 130 1.40 34.6 3.2 68 C. Ex. 4 ″ 500 70 0 — 1.42 — — — 13 ″ 500 10 10 — 1.39 — — — C. Ex. 5 ″ 500 70 0 — 1.48 — — — 14 ″ 500 10 10 — 1.47 — — — 15 Aluminium 500 10 10 245 1.31 27 1.3 copper zinc carbonate C. Ex. 6 ″ 500 70 0 216 1.28 17 3.1 16 Copper zinc 500 10 10 170 1.38 23 0.2 carbonate C. Ex. 7 ″ 500 70 0 165 1.35 14 1.3 17 Copper oxide 100 2 2 N/K N/K 12.8 1.4 C. Ex. 8 ″ 100 8 0 N/K N/K 8.8 5.8 18 Zinc 408.5 8.17 8.17 150 N/K 12.8 4.3 carbonate C. Ex. 9 ″ 408.7 57.2 0 183.5 N/K 10.5 3.6 19 Nickel 170.1 3.2 3.2 96 N/K 12.3 4.8 carbonate C. Ex. 10 ″ 328.15 26.3 0 124 N/K 7.2 3.2 20 Copper 500 10 10 140 1.34 26 3.6 carbonate 21 Nickel 500 10 10 160 1.31 29 2 carbonate

[0077] All materials were used as provided without further treatment or purification. Copper carbonate was obtained from/made by William Blythe Ltd., unless indicated otherwise. Attapulgite clay was obtained from Richard Baker Ltd. Bovine gelatin was obtained from VWR. Fish gelatin was obtained from Sigma Aldrich. The zinc carbonate was a basic carbonate obtained from Alfa Aesar. The nickel carbonate was a basic carbonate and made by William Blythe Limited. The copper oxide was made by William Blythe Limited. The copper zinc carbonate and aluminium copper zinc carbonate were basic, and made by William Blythe Limited.

[0078] The Examples are in accordance with the invention of the present application. The prefix “C. Ex.” indicates that the experiment is a comparative example which is not the subject matter of the present application. The presence of a dash “-” or “N/K” indicates that no note was made of the particular attribute or the attribute was not measured.

[0079] All Examples bar numbers 20 and 21 were made using bovine gelatin. Examples 20 and 21 were made using fish gelatin.

[0080] Examples 1 to 12 and C. Ex. 1 to 3 were made using basic copper carbonate as supplied by William Blythe Limited, having a tapped density of 1.21 g cm.sup.−3 and a water absorption number (WAN) of 43.5 mL/100 g.

[0081] C. Ex. 4 and Example 13 were prepared using a low density (1.15 gcm.sup.−3) copper carbonate obtained from Taixing Smelting Plant Co., Ltd. China

[0082] C. Ex. 5 and Example 14 were prepared using a higher density (1.47 gcm.sup.−3) copper carbonate obtained from Taixing Smelting Plant Co., Ltd. China.

[0083] The amount of oxide or carbonate, clay and gelatin, and water volume indicate the amounts used in the manufacturing process described generally above and in more detail below. The final make-up of the dried particulate composition may be determined from the amount of oxide or carbonate, gelatin and clay used because the water is removed on drying.

[0084] The method of making the compositions mentioned above will now be described in more detail. An Eirich EL1 mixer was used to mix and granulate the various components. Mixing/granulation was performed at 30° C. The powdered components (the copper carbonate, the clay and the gelatin (if present)) were blended using the granulator at 2 ms.sup.−1 for two minutes. A quantity of mixed powder was removed (30%) and split into three approximately equal portions. The water in the amount shown in Table 1 was then added to remaining powder over a period of about a minute, with the mixer tool set to a speed of 15 m/s to remaining powder over a period of about a minute, with the mixer tool set to a speed of 15 ms.sup.−1. Mixing was continued for 105 seconds after the water had been added, and then the mixture was mixed at 20 ms.sup.−1 for 5 minutes. After further mixing at 10 ms.sup.−1 for 1 minute, the mixer was slowed to 5 ms.sup.−1. One of the portions of mixed powder was then added over a period of about 2 minutes. The mixture was then left to mix (roll) for 1 minute. After the tool had been slowed to 2 ms.sup.−1 a second portion of mixed powder was added over a period of about two minutes. The mixture was then rolled for 5 minutes, with the mixer being slowed to 2 ms.sup.−1 again before the third and final portion of mixed powder is added. The mixture is then rolled for 5 minutes.

[0085] The resulting wet granules were dried at 110° C. in a fluid bed drier to produce dried granules.

[0086] The resulting dried granules were sieved to a size of 2.8 mm-4.75 mm for analysis. For the purpose of strength testing, granules were further sieved to a size of 3.15 mm-4.0 mm.

[0087] The tapped density of the sieved granules was determined by loading a known mass of composition into a measuring cylinder, gently tapping the measuring cylinder to facilitate settling of the composition and then determining the volume of the composition, the density being determined from the mass and volume.

[0088] The strength was determined by measuring 25 granules on the tablet hardness instrument and then taking a mean of the result.

[0089] The percentage attrition was determined by weighing 100 g of dried granules in to the drum of a tablet friability instrument. The drum was rotated at 60 rpm for 30 minutes. The resulting granules were sieved using a 1 mm sieve with the percentage amount passing through the sieve indicating the amount lost.

[0090] On-size yield was determined based on the percentage of wet granules that were inside the 2.8-4.75 mm range (on-size).

[0091] The samples, as received, were tested using a modified procedure normally used for wet gas condition testing and modified for a dry gas input stream. The recirculating warm water scrubber was removed, test volume changed and inlet temperature reduced. The tests were run until the outlet H.sub.2S values equalled the inlet values without intermediate analyses on the breakthrough curves which indicated that the absorbent material was saturated. The analytical values therefore represent the total H.sub.2S uptake for the sample under low pressure and temperature. Analytical values for % wt. S are reported on the results from the total S combustion analyses and averaged over duplicate samples.

[0092] The conditions used for the test procedure were a nominal material volume of 125 ml, a temperature of 46-65° F., a test gas of 2800-3300 ppm H.sub.2S in nitrogen, a flow rate STP of 310-330 ml/min, feed gas water 0% wt., with a back pressure across the columns of 1 psig.

[0093] Analyses of the input and output H.sub.2S values were carried out using Draeger tubes. The runs were terminated when the H.sub.2S outlet values were greater than 2800 ppm for 24 hrs. On termination the columns were flushed with nitrogen and air, emptied. Some samples were ground down for total S % analysis.

[0094] The sulphur-absorbing capacity of an existing comparative example composition comprising 100 parts copper carbonate and 14 parts clay, with no gelatin, was measured using four samples to be 23.8±0.9% w/w.

[0095] Examples 7 and 9 above were mixed to provide sufficient material to measure sulphur-absorbing capacity. The sulphur-absorbing capacity was found to be 25.7% w/w, an increase compared to the comparative example composition.

[0096] The sulphur-absorbing capacity of Examples 13, 14 and Comparative Examples 4 and 5 were also measured and are shown in Table 2.

TABLE-US-00002 TABLE 2 sulphur-containing compound absorbing capacity measurements Sulphur compound absorbing capacity Sample (% w/w) Example 13 23.3 Comparative Example 4 21.3 Example 14 22.2 Comparative Example 5 17.1

[0097] The results of Table 2 clearly demonstrate that for a low density copper carbonate the composition of Example 13 outperforms the analogous composition of C. Ex. 4, and that for a higher density copper carbonate the composition of Example 14 outperforms the analogous composition of C. Ex. 5. The applicant has therefore demonstrated that a hydrocolloidal polymer and/or a thermal decomposition product thereof is a successful binder for different copper carbonates.

[0098] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein as well as combinations of the embodiments that have been discussed. By way of example only, certain possible variations will now be described.

[0099] The examples above illustrate the use of clay binders. Those skilled in the art will realise that other such binders may be used.

[0100] The examples above illustrate the use of Attapulgite clay. Those skilled in the art will realise that other aluminosilicate clays may be used. Those skilled in the art will realise that other clays more generally may be used, such as bentonite.

[0101] The examples above illustrate the use of gelatin. Those skilled in the art will realise that other hydrocolloidal polymer materials may be used, such as other polypeptides. Those skilled in the art will realise that polysaccharide hydrocolloidal polymer materials may be used.

[0102] The examples above illustrate a composition that uses copper carbonate as the sole absorbent material. Those skilled in the art will realise that other absorbent materials may be incorporated into the composition, such as zinc, aluminium or silicon materials, aluminium copper zinc carbonate and copper zinc carbonate.

[0103] Those skilled in the art will realise that the composition may comprise more than one oxide or carbonate of a transition metal and/or Group 12 metal.

[0104] The examples above illustrate a composition in the form of granules which are typically spherical and are sieved to a size of about 2-4 mm. Those skilled in the art will realise that the granules need not be of the size stated and need not be spherical. Furthermore, those skilled in the art will realise that, while desirable, it is not necessary for the composition to be in granular form. For example, the composition may be in powder form.

[0105] The examples above describe the removal of hydrogen sulphide from nitrogen. Those skilled in the art will realise that the hydrogen sulphide may be removed form carrier fluids other than nitrogen (such as natural gas). Those skilled in the art will also realise that sulphur-containing compounds other than hydrogen sulphide may be removed, such as mercaptans and carbonyl sulphide. It would also be possible to remove sulphur-containing compounds from a liquid (as opposed to a gas) carrier. Furthermore, other material such as mercury that is found in natural gas may be removed.

[0106] The examples above describe how the composition may be made by adding several separate charges of powder material to the mixer. Those skilled in the art will realise that the composition may be made in a different manner.

[0107] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.