Catalyst preparation method

Abstract

A method for preparing a catalyst comprising (i) preparing a calcined shaped calcium aluminate catalyst support, (ii) treating the calcined shaped calcium aluminate support with water, and then drying the support, (iii) impregnating the dried support with a solution containing one or more metal compounds and drying the impregnated support, (iv) calcining the dried impregnated support, to form metal oxide on the surface of the support and (v) optionally repeating steps (ii), (iii) and (iv) on the metal oxide coated support. The method provides an eggshell catalyst in which the metal oxide is concentrated in an outer layer on the support.

Claims

1. An eggshell catalyst comprising an outer eggshell layer comprising nickel oxide and having a thickness of 1000 microns or less on the surface of a calcined, shaped calcium aluminate cement support, wherein the nickel oxide is concentrated within the eggshell layer and not uniformly distributed within the calcined, shaped calcium aluminate cement support.

2. The eggshell catalyst of claim 1 wherein the calcium aluminate support comprises calcium aluminate cement powder and at least one of alumina or lime.

3. The eggshell catalyst of claim 1 further comprising an alkali metal oxide.

4. The eggshell catalyst of claim 1 wherein the support is in the form of a shaped pellet or extrudate.

5. The eggshell catalyst of claim 4 wherein the support is in the form of a cylindrical pellet having between 1 and 12 holes extending there-through.

6. The eggshell catalyst of claim 5 wherein the support is in the form of a cylindrical pellet having between 1 and 12 holes extending there-through and between 2 and 20 flutes or lobes.

7. The eggshell catalyst of claim 6 wherein the support has 4 holes extending there-though and 4 lobes.

8. The eggshell catalyst of claim 1 wherein nickel oxide content of the catalyst is in the range of from 2 wt % to 25% wt.

9. The eggshell catalyst of claim 1, wherein the outer eggshell layer comprising nickel oxide has a thickness of 800 microns or less.

10. The eggshell catalyst of claim 1, wherein the outer eggshell layer comprising nickel oxide has a thickness of 300 microns or less.

11. The eggshell catalyst of claim 4, wherein each of the length, width, and height of the shaped pellet or extrudate is in the range of from 3 mm to 50 mm.

12. The eggshell catalyst of claim 5, wherein the cylindrical pellet has a diameter in a range of from 4 mm to 40 mm, and an aspect ratio of length to width of 2 or less.

13. An eggshell catalyst comprising an outer eggshell layer of nickel oxide having a thickness of 1000 microns or less on the surface of a calcined, shaped calcium aluminate cement support, the eggshell catalyst precursor obtained by a method comprising: (i) preparing a calcined shaped calcium aluminate catalyst support by forming a calcium aluminate cement powder, optionally with additional alumina and/or lime, into a desired shape, curing the cement and subsequently calcining the shaped support; then (ii) treating the calcined shaped calcium aluminate support with water, said water being essentially free of salts, and drying the support; then (iii) impregnating the dried support with the solution containing one or more nickel compounds and drying the impregnated support; then (iv) calcining the dried impregnated support, to form the outer eggshell layer of nickel oxide on the surface of the support; and (v) optionally repeating steps (ii), (iii) and (iv); so as to form the eggshell catalyst precursor.

14. An eggshell catalyst obtained by subjecting the eggshell catalyst of claim 13 to a reducing environment, so as to produce an outer eggshell layer having a thickness of 1000 microns or less on the surface of a calcined, shaped calcium aluminate cement support, the outer eggshell layer comprising elemental nickel.

15. The eggshell catalyst of claim 14, wherein the reducing environment comprises hydrogen.

16. An eggshell catalyst obtained by subjecting the eggshell catalyst of claim 14 to a oxygen environment, so as to provide a passivating layer of nickel oxide on the elemental nickel.

17. An eggshell catalyst comprising an outer eggshell layer comprising elemental nickel and having a thickness of 1000 microns or less on the surface of a calcined, shaped calcium aluminate cement support, wherein the elemental nickel is concentrated within the eggshell layer and not uniformly distributed within the calcined, shaped calcium aluminate cement support.

18. The eggshell catalyst of claim 17, wherein the elemental nickel further comprises a passivating layer of nickel oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is also illustrated by reference to the Examples and FIGS. 1-3.

(2) FIG. 1 depicts an image of a cylindrical catalyst pellet cut in two to show an eggshell layer of catalyst prepared according to the present invention;

(3) FIG. 2 depicts an image of a similar catalyst pellet prepared according to the prior art, and

(4) FIG. 3 depicts an electron-probe micro-analyser (EMPA) image of a cross section of a lobed 4-hole cylindrical catalyst pellet with an eggshell layer of catalyst prepared according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Examples

Example 1. Preparation of a Catalyst Support

(5) a) Calcium aluminate cement was blended with alumina trihydrate and lime to obtain a mixture with a Ca:Al ratio of 10:43. Graphite (4 wt %) was added, and the resulting mixture pelleted using a hydraulic tabletting machine to give cylinders of diameter 3.3 mm and length 3.3 mm. The pellets were subjected to water-curing and calcination to obtain a calcined shaped support with the following properties.

(6) BET (Nitrogen): 5.7 m.sup.2/g

(7) Pore volume: 0.28 cm.sup.3/g

(8) Density: 1.66 g/cc

(9) b) The method of Example 1(a) was repeated to produce pellets of diameter 5.4 mm and length 3.0 mm.

(10) c) The method of Example 1(a) was repeated except that calcium aluminate cement was blended with alumina trihydrate to obtain a mixture with a Ca:Al ratio of 10:74.

Example 2. Preparation of a Ni Catalyst

(11) a) Re-hydration. The shaped calcined calcium aluminate support from Example 1(b) was treated with water by immersing the pellets in de-mineralised water at 30? C. for 40 minutes. The pellets were removed and dried at 110? C. for 16 hours.

(12) b) Incorporation of Ni. The catalyst support pellets were then immersed in a solution of nickel nitrate in de-mineralised water (200 g Ni/liter) for 5 minutes at 25? C. The impregnated pellets were then removed and allowed to drain for 10 minutes and dried at 110? C. for 6 hours. The dried impregnated pellets were then heated at 100? C./hour to 650? C. and then held at 650? C. for 4 hours to convert the nickel nitrate to nickel oxide. The re-hydrating, drying, impregnating, drying and calcining procedure was repeated on the nickel oxide containing pellets a further two times. The Ni was concentrated in a thin layer around the edge of the catalyst pellet as shown in FIG. 1. The thickness of the eggshell layer is about 800 ?m.

(13) The procedure was repeated on the support of Example 1(a), using the same water treatment conditions but carrying out the Ni impregnation each time for 5 minutes at 70? C. instead of 25? C. The weight increase after each calcination was measured on 20 pellets and an average taken. The results were as follows;

(14) TABLE-US-00001 Weight of Weight of oxidic NiO NiO loading Impregnation Support (g) catalyst (g) weight (g) (% wt) 1 0.045 0.0456 0.0009 1.974 2 0.045 0.0475 0.0028 5.895 3 0.045 0.0485 0.0038 7.835

(15) The final catalyst properties were;

(16) BET (Nitrogen): 43.6 m.sup.2/g

(17) Pore volume: 0.17 cm.sup.3/g

(18) Density: 1.84 g/cc

(19) This material was termed catalyst 2A.

(20) The procedure applied to the support of Example 1(a) was repeated on the support of Example 1(c), using the same water treatment and impregnation conditions. An egg-shell catalyst material was produced.

(21) In comparison, the shaped calcined calcium aluminate support from Example 1(b), but without the above re-hydration step, was immersed in a solution of nickel nitrate in de-mineralised water (200 g Ni/liter) for 5 minutes at 25? C. The impregnated pellets were then removed and allowed to drain for 10 minutes and dried at 110? C. for 6 hours. The dried impregnated pellets were then heated at 100? C./hour to 650? C. and then held at 650? C. for 4 hours to convert the nickel nitrate to nickel oxide. The impregnating, drying and calcining procedure was repeated on the nickel oxide containing pellets a further two times. The Ni was distributed throughout the catalyst pellet as seen in FIG. 2.

(22) As a further comparison, the shaped calcined calcium aluminate support from Example 1(a), again without the re-hydration step, was immersed in a solution of nickel nitrate in de-mineralised water (200 g Ni/liter) for 5 minutes at 70? C. The impregnated pellets were then removed and allowed to drain for 10 minutes and dried at 110? C. for 6 hours. The dried impregnated pellets were then heated at 100? C./hour to 650? C. and then held at 650? C. for 6 hours to convert the nickel nitrate to nickel oxide. The impregnating, drying and calcining procedure was repeated on the nickel oxide containing pellets a further two times. The NiO content of this material after the final calcination was about 16.5 wt %. This comparative material was termed catalyst 2B.

Example 3: Testing

(23) The catalysts 2A and 2B were tested in a laboratory scale steam reformer with a reformer tube internal diameter of 1-inch. The catalysts were diluted with fused alumina chips (sieve fraction 3.35 mm-4.74 mm) and reduced using 50 vol % H.sub.2 in N.sub.2 at 480? C. for 2 hours. After catalyst reduction, catalyst performance was assessed over the temperature range 480? C. to 750? C. The feed gas was natural gas mixed with steam at a steam:carbon ratio of 3.0:1. The exit gas composition was analysed by infra-red and gas chromatography.

(24) The results were as follows;

(25) TABLE-US-00002 Catalyst 2A 2B Ethane Ethane Improvement by conversion (%) conversion (%) egg-shelling 600? C. 77 54 41% 540? C. 66 43 53% 480? C. 44 29 50% 670? C. 83 66 26% 750? C. 88 76 16% 670? C. 82 63 31%

(26) The ethane conversion is better for the eggshell catalyst 2A across the temperature range.

Example 4. Preparation of Catalysts

(27) a) Catalyst Support. Calcium aluminate cement was blended with alumina trihydrate and lime to obtain a mixture with a Ca:Al ratio of 10:43. Graphite (4 wt %) was added, and the resulting mixture pelleted using a hydraulic tabletting machine to give cylinders of diameter 5.4 mm and length 5.4 mm. The pellets were subjected to water-curing and calcination to obtain a calcined shaped support with the same properties as example 1(a).

(28) b) Re-hydration. The shaped calcined calcium aluminate support was treated with water by immersing the pellets in de-mineralised water at 30? C. for 40 minutes. The catalyst support pellets were removed from the water and dried at 110? C. for 16 hours.

(29) c) Catalyst Preparation. The catalyst support pellets were immersed in a solution of metal nitrate in de-mineralised water as detailed below for 5 minutes at 25? C.

(30) TABLE-US-00003 Metal nitrate Concentration (g of metal/100 ml) Co 10 Cu 10 Ni 10

(31) The impregnated pellets were then removed and allowed to drain for 10 minutes and dried at 110? C. for 12 hours.

(32) The pellets were analysed by optical microscopy and in each case it was found that the metal compound was concentrated around the edge of the pellet, i.e. that an eggshell material had been formed.

(33) In comparison, the shaped calcined calcium aluminate support, without the re-hydration step (b), was immersed in the solution of metal nitrate in de-mineralised water as detailed above for 5 minutes at 25? C. The impregnated pellets were then removed and allowed to drain for 10 minutes and dried at 110? C. for 12 hours. The pellets were analysed by optical microscopy and in each case the metal was distributed throughout the catalyst.

Example 5. Preparation of Catalyst with Ni Acetate

(34) a) Catalyst Support. Calcium aluminate cement was blended with alumina trihydrate and lime to obtain a mixture with a Ca:Al ratio of 10:43. Graphite (4 wt %) was added, and the resulting mixture pelleted using a hydraulic tabletting machine to give cylinders of diameter 5.4 mm and length 5.4 mm. The pellets were subjected to water-curing and calcination to obtain a calcined shaped support with the same properties as example 1(a).

(35) b) Re-hydration. The shaped calcined calcium aluminate support from was treated with water by immersing the pellets in de-mineralised water at 30? C. for 40 minutes. The pellets were removed and dried at 110? C. for 16 hours.

(36) c) Catalyst preparation. The pellets were then immersed in a solution of Ni-acetate (2 g/100 ml) in de-mineralised water for 5 minutes at 25? C.

(37) The impregnated pellets were then removed and allowed to drain for 5 minutes and dried at 110? C. for 4 hours.

(38) The pellet was analysed by optical microscopy and it was found that the nickel was concentrated around the edge of the pellet.

Example 6: Shaped Catalyst Support with Through Holes

(39) A 4-holed, 4-lobed catalyst calcined calcium aluminate catalyst support was prepared according to the method of Example 1. The catalyst support was re-hydrated and impregnated three times at 25? C. with nickel nitrate according to the method of Example 2. Electron-probe micro-analysis (EPMA) of a cross section of the resulting dried and calcined catalyst pellet showed a thin layer of nickel oxide (lighter area) around the outside of the pellet and around the circumference of each of the through holes. The EPMA image is depicted in FIG. 3.