Catalysts

Abstract

A catalyst precursor suitable for the Fischer Tropsch reaction is described comprising cobalt oxide supported on a porous support wherein the porous support is a ceramic foam comprising a closed cell structure.

Claims

1. A Fischer Tropsch reaction catalyst precursor, comprising cobalt oxide supported on a porous support that is a ceramic foam comprising a closed cell structure, wherein the ceramic foam has a cell fraction in the range of from 50 to 95 vol % relative to the volume of the ceramic foam.

2. The catalyst precursor of claim 1, wherein the cobalt content, expressed as Co, is in the range of 5-50% by weight of the total precursor.

3. The catalyst precursor of claim 1, wherein up to 20% by volume of the cell volume is interconnected.

4. The catalyst precursor of claim 1, wherein the closed cell structure comprises cells having an average cell diameter in a size range of from 10 to 150 m.

5. The catalyst precursor of claim 1, wherein the ceramic foam contains cells having cell walls, where the cell wall thicknesses is up to 500 m with an average cell wall thickness in the range of 10-100 m.

6. The catalyst precursor of claim 1, wherein the ceramic foam comprises titania.

7. The catalyst precursor of claim 1, that has been subjected to a heating step at a temperature in the range of 500-1600 C.

8. A catalyst comprising elemental cobalt supported on a porous ceramic foam support having a closed cell structure, wherein the ceramic foam support has a cell fraction in the range of from 50 to 95 vol % relative to the volume of the ceramic foam support.

9. The catalyst of claim 8, wherein the cobalt content, expressed as Co, is in the range of 5-50% by weight of the total precursor.

10. The catalyst of claim 8, wherein up to 20% by volume of the cell volume is interconnected.

11. The catalyst of claim 8, wherein the closed cell structure comprises cells having an average cell diameter in a size range of from 10 to 150 m.

12. The catalyst of claim 8, wherein the ceramic foam contains cells having cell walls, where the cell wall thicknesses is up to 500 m with an average cell wall thickness in the range of 10-100 m.

13. The catalyst of claim 8, wherein the ceramic foam comprises titania.

14. The catalyst of claim 8, prepared by applying a reducing gas stream to a Fisher Tropsch reaction catalyst precursor comprising cobalt oxide supported on a porous support that is a ceramic foam comprising a closed cell structure, wherein the ceramic foam has a cell fraction in the range of from 50 to 95 vol % relative to the volume of the ceramic foam.

15. A Fisher-Tropsch reaction process for producing hydrocarbons, comprising contacting a synthesis gas comprising carbon monoxide and hydrogen with a catalyst of claim 8.

Description

EXAMPLE 1

Titania Foam Preparation

[0067] A) A ceramic foam was prepared using a titania suspension containing 30% wt solids. 128 g titania powder (P25 available from Evonik) were added slowly to 300 ml demineralised water in a stirred vessel. Then, without pH adjustment, 0.36 mmol DL-phenylalanine were added per gram of titania (7.6 g DL-phenylalanine). The pH of the suspension was 4.59. Air was then introduced into the suspension to form bubbles using a gas inducing impeller for 30 minutes. The foam was cast into a tray and dried at room temperature and at atmospheric pressure. It was then calcined with a nitrogen purge by heating at 2 C./min to 600 C. After 45 minutes at 600 C. the nitrogen flow was replaced by air. The total dwell at 600 C. was 4 hours. The resulting ceramic foam support was crushed and sieved to 0.5 mm.

[0068] A porosity measurement was made by immersing the ceramic foam in demineralised water at room temperature for 4 days and measuring the water up-take by the increase in weight. The porosity measured in this way includes the volume of the cells and accessible pores and indicates the volume of cobalt solution that may be used to prepare the catalyst. The porosity of the foamed titania was 0.8 cm.sup.3/g after 4 days.

[0069] B) The method was repeated for different titania contents in the suspension as follows;

TABLE-US-00001 Titania DL-phenylalanine Porosity weight % mmol/g titania pH cm.sup.3g.sup.1 17.5 0.82 4.65 2.2 20.0 0.36 4.50 1.6 20.0 0.54 4.52 1.5 20.0 0.72 4.56 1.4 25.0 0.39 4.56 0.9 25.0 0.54 4.58 1.0

[0070] D) The method was repeated, replacing the phenyl alanine with n-butyric acid. pH adjustment was required before air entrainment using potassium hydroxide.

TABLE-US-00002 Butyric Acid pH Titania mmol/g after butyric pH after KOH Porosity weight % titania acid addition Foaming addition cm.sup.3g.sup.1 20 0.36 3.86 Not 4.65 2.3 Observed 20 0.54 3.71 4.65 2.2 20 0.72 3.66 4.40 1.8 25 0.36 3.71 4.50 1.8 25 0.54 3.68 4.50 1.5 25 0.72 3.56 4.00 1.4 30 0.36 3.66 4.30 1.2 30 0.54 3.60 4.30 1.4 30 0.72 2.46 3.20* 1.1 *pH was not increased further since an increase in viscosity was observed

[0071] D) The method was repeated, replacing the phenylalanine with other alpha-amino acids. Unless otherwise indicated, no pH adjustment was performed prior to air entrainment.

TABLE-US-00003 Titania DL-amino acid Porosity Example weight % mmol/g titania pH cm.sup.3g.sup.1 1(d)(i) 30 0.21 DL-leucine 3.66 0.62 1(d)(ii) 30 0.54 DL-valine 4.02 0.47 1(d)(iii) 30 0.43 DL-phenyl alanine 1.60* 0.45 1(d)(iv) 25 0.36 DL-Leucine 0.93* 0.52 1(d)(v) 20 0.22 DL-tryptophan 3.25 0.50 1(d)(vi) 20 0.74 DL-leucine 3.96 2.84 1(d)(vii) 25 0.72 DL-isoleucine 1.28* 0.63 1(d)(viii) 25 0.72 DL-methionine 1.21* 0.44 *pH adjusted by addition of nitric acid

EXAMPLE 2

Catalyst Precursor Preparation

[0072] A) Cobalt nitrate impregnation of titania foam of Example 1(a).

[0073] 7 g of cobalt nitrate hexahydrate (Co(NO.sub.3).sub.2.6H.sub.2O) and 2.2 ml demineralised water were heated until the melting and dissolution of the salt were complete. This was added in aliquots to 15 g of the ceramic foam product of Example 1(a) in a plastic bag. After each addition the material was kneaded into the support. The impregnated foam was dried for 2 hours at 105 C. and calcined for 2 hours at 300 C. The process was then repeated. 5.5 g Co(NO.sub.3).sub.2.6H.sub.2O and 2.74 ml demineralised water were heated until the melting and dissolution of the salt were complete. This was added in aliquots to 16.5 g of the impregnated ceramic foam product from the first impregnation in a plastic bag. After each addition the material was kneaded into the support. The resulting material was dried for 2 hours at 105 C. and calcined for 2 hours at 300 C. The cobalt content of the catalyst precursor by ICPAES was 10.8% wt. The cobalt surface area as determined by hydrogen chemisorption was 1.0 m.sup.2/g catalyst.

[0074] B) Cobalt ammine-carbonate impregnation of titania foam of Example 1(a).

[0075] A cobalt ammine carbonate solution was prepared as follows; 198 ml of a 28% ammonia solution was added to 20.4 g ammonium carbonate in a round bottomed flask and diluted with 193.4 ml demineralised water. The resulting solution was stirred for 20 minutes then 23.7 g of cobalt basic carbonate was added over 15 minutes and the solution stirred at 150 rpm for a further 2.5 hr to give a purple solution. 30% hydrogen peroxide solution was added drop wise while the solution was stirred at 234 rpm until the Oxido-reduction potential (Metier Toledo transmitter M 700) was near to 100 mV. Stirring was continued for a further 10 minutes and then the solution was filtered.

[0076] 385 ml of the Co ammine carbonate solution (2.6% w/w Co) was added to a 2 L four-necked round bottom flask. A stirrer, temperature probe, lute and condenser were fitted to the flask. 52 g of the ceramic foam product of Example 1(a) was added. This mixture was then diluted with 385 mL water and 165 mL ammonia before being heated and agitated for 80 minutes to cause evolution of the ammonia and deposition of cobalt oxide in the cells and pores of the ceramic foam. The mixture was filtered and washed with 80 ml demineralised water. The catalyst precursor was dried at 105 C. for 8 hours. It was not calcined. The cobalt content of the catalyst precursor by ICPAES was 11.2% wt. The cobalt surface area as determined by hydrogen chemisorption was 1.1 m.sup.2/g catalyst.

[0077] C) Cobalt ammine-carbonate impregnation of titania foams of Examples 1(d) (i)-(iv).

[0078] The method of Example 2(b) was repeated using instead the titania foams obtained in Examples 1(d) (i)-(iv). The target cobalt content in each case was 13% by weight. The cobalt surface areas for the catalyst precursors, as determined by hydrogen chemisorption, are set out below.

TABLE-US-00004 Foam Cobalt Surface Area (m.sup.2/g catalyst) 1(d)(i) 3.9 1(d)(ii) 1.6 1(d)(iii) 1.5 1(d)(iv) 1.5

Example 3

Catalyst Testing

[0079] 0.5 g of the catalyst from Example 2(a) was tested for catalytic performance in Fischer-Tropsch synthesis. The reaction conditions were syngas (H.sub.2:CO of 2:1) flow rate 30 ml.sub.N/min, 20 bar and 210 C. with GHSV 3590 ml.sub.N sygas.Math.g catalyst.sup.1.Math.h.sup.1 and a target conversion of 50%. The selectivity to C5+ was 92%.

[0080] 0.25 g of the catalyst from Example 2(b) was tested for catalytic performance in Fischer-Tropsch synthesis. The reaction conditions were syngas (H.sub.2:CO 2:1) flow rate 44 ml.sub.N/min, 20 bar and 210 C. with GHSV 10338 ml.sub.N sygas.Math.g catalyst.sup.1.Math.h.sup.1 and a target conversion of 50%. The selectivity to C5+ was 91%.

[0081] 0.25 g of each of the catalysts from Example 2(c) was tested for catalytic performance in Fischer-Tropsch synthesis. The reaction conditions were syngas (H.sub.2:CO of 2:1), 20 bar and 210 C. and a target conversion of 50%. The remaining reaction conditions and selectivity to C5+ for the catalysts based on the different foam materials were as follows;

TABLE-US-00005 GHSV Flow (ml.sub.N Rate Pressure Temperature syngas .Math. g Selectivity Foam (ml.sub.N/min) (bar) ( C.) catalyst.sup.1 .Math. h.sup.1) to C5+ 1(d)(i) 49.48 20 210 12082 89.51 1(d)(ii) 33.98 20 210 7816 89.90 1(d)(iii) 15.20 20 210 3461 86.71 1(d)(iv) 15.13 20 210 3642 90.02