CATALYST PREPARATION METHOD

Abstract

A method is described for preparing an eggshell catalyst comprising the steps of: (i) preparing a calcined shaped alkaline earth metal aluminate catalyst support, (ii) treating the calcined shaped alkaline earth metal aluminate support with a gas containing water vapour to form a hydrated support, (iii) with or without an intervening drying step, impregnating the hydrated support with an acidic solution containing one or more catalytic metal compounds and drying the impregnated support, (iv) calcining the dried impregnated support, to form a calcined catalyst having a catalytic metal oxide concentrated at the surface of the support and (v) optionally repeating steps (ii), (iii) and (iv).

Claims

1-18. (canceled)

19. A method for preparing an eggshell catalyst comprising the steps of: (i) preparing a calcined shaped alkaline earth metal aluminate catalyst support, (ii) treating the calcined shaped alkaline earth metal aluminate support with a gas containing water vapour to form a hydrated support, (iii) with or without an intervening drying step, impregnating the hydrated support with an acidic solution containing one or more catalytic metal compounds and drying the impregnated support, (iv) calcining the dried impregnated support, to form a calcined catalyst having a catalytic metal oxide concentrated at the surface of the support and (v) optionally repeating steps (ii), (iii) and (iv).

20. The method according to claim 19 wherein the alkaline earth metal aluminate is selected from calcium aluminate, magnesium aluminate and mixtures thereof.

21. The method according to claim 19 wherein the calcined shaped alkaline earth metal aluminate support is prepared by forming a calcium aluminate cement powder and/or a magnesium aluminate powder, optionally with additional alumina and/or lime, into a shape and subsequently calcining the shape.

22. The method according to claim 21 wherein the calcined shaped alkaline earth metal aluminate support is alkalised by impregnation with a solution of an alkali metal or an alkaline earth metal prior to the calcination step.

23. The method according to claim 19 wherein the calcined shaped alkaline earth metal aluminate support is in the form of a cylindrical pellet having between 1 and 12 holes extending there-though and optionally between 2 and 20 flutes or lobes.

24. The method according to claim 19 wherein the humid gas is humid air.

25. The method according to claim 19 wherein the gas containing water vapour has an absolute humidity in the range of 45 to 300 g/m.sup.3.

26. The method according to claim 25 wherein the absolute humidity is ≥75 g/m.sup.3.

27. The method according to claim 19 wherein the treatment of the calcined shaped alkaline earth metal aluminate support with the gas containing water vapour is performed at a temperature in the range of 40 to 99° C.

28. The method according to claim 19 wherein the gas containing water vapour has a relative humidity in the range of 60 to 100%.

29. The method according to claim 19 wherein the acidic solution containing one or more catalytic metal compounds comprises one or more transition metals.

30. The method according to claim 19 wherein the metal concentration in the acidic solution containing one or more catalytic metal compounds is in the range 100-300 g metal/litre.

31. The method according to claim 19 wherein the metal impregnation step (iii) is performed at a temperature in the range 40-90° C.

32. The method according to claim 19 wherein the calcined catalyst has a catalytic metal oxide content in the range of from 1 to 25% be weight.

33. The method according to claim 19 wherein one or more promoter compounds are impregnated into the hydrated support, the dried impregnated support and/or the calcined catalyst.

34. The method according to claim 19 wherein the calcination of the dried impregnated support to form the calcined catalyst is performed at a temperature in the range of 250-850° C.

35. The method according to claim 19, wherein the catalytic metal oxide is a reducible metal oxide, further comprising the step of reducing at least a portion of the catalytic metal oxide to elemental form with a hydrogen-containing gas mixture to form a reduced catalyst.

36. The method according to claim 35 further comprising a step of passivating the reduced catalyst, containing metal in elemental form with an oxygen-containing gas.

37. The method according to claim 26 wherein the absolute humidity is ≥100 g/m.sup.3.

38. The method according to claim 26 wherein the absolute humidity is ≥150 g/m.sup.3.

39. The method according to claim 26 wherein the absolute humidity is ≥200 g/m.sup.3.

40. The method according to claim 19 wherein the acidic solution containing one or more catalytic metal compounds comprises one or more of chromium, manganese, nickel, cobalt, iron, copper or zinc.

41. The method according to claim 19 wherein the acidic solution containing one or more catalytic metal compounds comprises one or more of nickel, cobalt, iron or copper.

42. The method according to claim 19 wherein the acidic solution containing one or more catalytic metal compounds comprises nickel.

Description

EXAMPLE 1. PREPARATION OF A CALCINED CATALYST SUPPORT

[0036] (a) Calcium aluminate cement was blended with alumina trihydrate and lime to obtain a mixture with a Ca:Al ratio of 10:56 (molar basis). Graphite (4 wt %) was added, and the resulting mixture pelleted using a 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.

[0037] BET Surface Area: 4.5 m.sup.2/g

[0038] Pore volume: 0.24 cm.sup.3/g

[0039] Density: 1.79 g/cc

[0040] (b) The method of Example 1(a) was repeated to produce symmetrical 4-hole quadralobe cylindrical pellets as depicted in FIG. 3 of WO2010125369 having a diameter of 13 mm and a length in the range of 16.7-17.3 mm.

[0041] BET Surface Area: 4.4 m.sup.2/g

[0042] Pore volume: 0.23 cm.sup.3/g

EXAMPLE 2. PREPARATION OF EGGSHELL Ni CATALYSTS

[0043] a) Treatment of the calcined catalyst support with water vapour

[0044] The bottom of a laboratory desiccator (with the desiccant removed) was filled with demineralised water, then a dish containing the calcined shaped calcium aluminate support pellets of Example 1(b) was placed on the mesh above and the desiccator sealed. The desiccator was then placed in an oven set at 55° C. ensuring 100% relative humidity in air at 55° C. for the duration of the treatment. The pellets were treated as follows:

[0045] Example 2(a)—1 day (24 hours),

[0046] Example 2(b)—3 days

[0047] Example 2(c)—7 days

[0048] b) Impregnation of the hydrated support with Ni nitrate

[0049] After treatment, the hydrated supports were, without an intermediate drying step, dipped in 140 g of nickel nitrate solution (approximately 220 g Ni per 1000 ml, pH 1.5) at 80° C. for 20 minutes without stirring, then drained.

[0050] c) Calcination to form a calcined catalyst

[0051] The impregnated pellets were placed in a furnace and calcined in air with the following program: 100° C./h ramp to 120° C. and dwell for 10 hours, followed by 100° C./h ramp to 640° C. with a 4-hour dwell. Once the furnace had cooled to below 200° C., the samples were removed. All of the samples, Examples 2(a), 2(b), 2(c) had an eggshell layer comprising NiO.

[0052] Alternatively, following the treatment with the humid air, portions of each of the treated supports were dried at 120° C. for 17 hours before impregnation. The impregnation and calcination were then performed on the dried samples in the same manner as described above. These examples are marked 2(d), 2(e), and 2(f).

[0053] The results are set out in the following table.

TABLE-US-00001 Treatment Average eggshell layer NiO % wt Example time (h) thickness (mm) (loss free, 900° C.) 2(a) 24 0.587 Not measured 2(b) 72 0.260 Not measured 2(c) 168 0.172 1.03 2(d) 24 1.151 Not measured 2(e) 72 0.274 Not measured 2(f) 168 0.175 0.98

[0054] The results above suggest that it is not at all necessary to dry the treated catalyst supports in order to obtain an eggshell catalyst. Moreover, the humid gas treatment provided control over the eggshell layer thickness and was able to provide thinner, so more efficient eggshell layers.

EXAMPLE 3: PREPARATION OF EGGSHELL Ni CATALYSTS

[0055] Approximately 50 g of the pelleted support of Example 1(a) were weighed into a crucible before being placed in a humidity chamber. The humidity chamber was used to treat the pellets with humid air at specific temperatures and humidities for different durations. Once the treatment was complete, the pellets were removed, then without drying, dipped in aqueous nickel nitrate solution (210 g Ni per 1000 ml, pH 1.5) at 80° C. for 20 minutes without stirring, then separated from the liquid with gentle shaking to remove excess solution. The impregnated pellets were then calcined as set out in Example 2. Once the furnace had cooled to room temperature, the samples were removed and analysed for eggshell thickness and NiO content. The results are set out in the following table.

TABLE-US-00002 Relative Absolute Average NiO % wt Treatment Temperature Humidity Humidity eggshell layer (loss free, Example Time (h) (° C.) (%) (g m.sup.−3) thickness (mm) 900° C.) 3(a) A 12 90 60 251 0.659 7.47 3(b) A 24 90 60 251 0.475 6.43 3(c) A 12 70 70 138 0.47 6.57 3(d) A 12 55 95 98.9 0.378 5.26 3(e) A 12 80 70 205 0.368 5.17 3(f) A 12 90 60 251 0.595 7.14 3(g) A 12 40 95 48.7 1.07 8.43

[0056] The Experiment was repeated for the support of Example 1(b).

TABLE-US-00003 Relative Absolute Average NiO % wt Treatment Temperature Humidity Humidity eggshell layer (loss free, Example Time (h) (° C.) (%) (g m.sup.−3) thickness (mm) 900° C.) 3(a) B 12 90 60 251 0.709 6.77 3(b) B 12 80 70 205 0.451 4.68 3(c) B 12 90 60 251 0.590 Not measured 3(d) B* 12 90 60 251 0.712 Not measured *100 g of pellets were used rather than 50 g.

[0057] A cross-section of the Example 3(b) B is depicted in FIG. 1.

[0058] A cross-section of the Example 3(f) A is depicted in FIG. 2.

[0059] Both FIGS. 1 and 2 depict eggshell catalysts prepared by the method of the present invention.

EXAMPLE 4: TESTING

[0060] The eggshell catalysts of Example 3(b) A and 3(g) A were tested as natural gas steam reforming catalysts. To perform this test, the catalysts were first ‘aged’ by treating them to a temperature of 750° C. at 28 barg, under a flow of hydrogen and steam (ca. 1:7 molar ratio) for 20 days. They were then cooled, discharged, blended with an alpha alumina grit, then recharged into the natural gas steam reforming test reactor. For the Example 3(b) A test, 20.8 g of catalyst was diluted to 105 cm.sup.3 with alpha alumina grit. For the Example 3(g) A test, 22.2 g catalyst was diluted to 105 cm.sup.3 with alpha alumina grit. The charges were reduced in a flow of nitrogen (300 NL h.sup.−1) and hydrogen (300 NL h.sup.−1) at 600° C., 27 barg for 2 hours. The natural gas steam reforming test then commenced by changing the gas stream to natural gas (1400 NL h.sup.−1) and steam at a steam to carbon molar ratio of 3.0 at 27 barg. A range of temperatures were tested and the conversion of the ethane component of the natural gas was quantified as a measure of catalyst activity. Ethane conversion is a useful indicator of overall activity as unlike methane conversion, ethane conversion is irreversible.

[0061] The results are set out in the following Table:

TABLE-US-00004 Tube wall temperature (° C.) Catalyst 800 735 685 610 565 Example 3(g) A 49 33 25 18 13 ethane conversion (%) Example 3(b) A 52 38 29 20 14 ethane conversion (%)

[0062] The results show good ethane conversion from both eggshell Ni catalysts in the steam reforming reaction.