Fischer-Tropsch Process, Supported Fischer-Tropsch Synthesis Catalyst and Uses Thereof

Abstract

A process for converting a mixture of hydrogen and carbon monoxide gases to a composition comprising alcohols and liquid hydrocarbons by means of a Fischer-Tropsch synthesis reaction, said process comprising contacting a mixture of hydrogen and carbon monoxide gases, preferably in the form of synthesis gas mixture, with a supported CoMn Fischer-Tropsch synthesis catalyst, wherein: the support material of the supported CoMn Fischer-Tropsch synthesis catalyst comprises a material selected from titania, zinc oxide, zirconia, and ceria; the supported synthesis catalyst comprises at least 2.5 wt % of manganese, on an elemental basis, based on the total weight of the supported synthesis catalyst; the weight ratio of manganese to cobalt, on an elemental basis, is 0.2 or greater; the molar ratio of hydrogen to carbon monoxide is at least 1; and, the Fischer-Tropsch synthesis reaction is conducted at a pressure in the range of from 1.0 to 10.0 MPa absolute.

Claims

1. A process for converting a mixture of hydrogen and carbon monoxide gases to a composition comprising alcohols and liquid hydrocarbons by means of a Fischer-Tropsch synthesis reaction, said process comprising contacting a mixture of hydrogen and carbon monoxide gases with a supported CoMn Fischer-Tropsch synthesis catalyst, wherein: the support material of the supported CoMn Fischer-Tropsch synthesis catalyst comprises a material selected from titania, zinc oxide, zirconia, and ceria; the supported synthesis catalyst comprises at least 2.5 wt % of manganese, on an elemental basis, based on the total weight of the supported synthesis catalyst; the weight ratio of manganese to cobalt, on an elemental basis, is 0.2 or greater; the molar ratio of hydrogen to carbon monoxide is at least 1; and the Fischer-Tropsch synthesis reaction is conducted at a pressure in the range of from 1.0 to 10.0 MPa absolute.

2. A process according to claim 1, wherein the support material comprises titania.

3. A process according to claim 2, wherein the support material is titania.

4. A process according to claim 1, wherein the weight ratio of manganese to cobalt present in the supported CoMn Fischer-Tropsch synthesis catalyst, on an elemental basis, is in the range of from 0.2 to 3.0.

5. A process according to claim 1, wherein the supported CoMn Fischer-Tropsch synthesis catalyst contains from 5 wt. % to 35 wt. % of cobalt, on an elemental basis, based on the total weight of the supported synthesis catalyst

6. A process according to claim 1, wherein the supported CoMn Fischer-Tropsch synthesis catalyst contains from 2.5 wt. % to 15 wt. % of manganese, on an elemental basis, based on the total weight of the supported synthesis catalyst.

7. A process according to claim 1, wherein the combined amount of cobalt and manganese in the supported CoMn Fischer-Tropsch synthesis catalyst is less than 30 wt. %, on an elemental basis, based on the total weight of the supported synthesis catalyst.

8. A process according to claim 1, wherein the synthesis catalyst comprises Co.sub.3O.sub.4 crystallites having a particle size of less than 100 Angstroms.

9. A process according to claim 1, wherein the Fischer-Tropsch synthesis reaction is conducted at a temperature of less than or equal to 300 C.

10. A process according to claim 1, wherein the Fischer-Tropsch synthesis reaction is conducted at a pressure of less than 7.5 MPa absolute.

11. A process according to claim 1, wherein the alcohols are C.sub.5+ alcohols.

12. A supported CoMn Fischer-Tropsch synthesis catalyst comprising at least 2.5 wt % of manganese, on an elemental basis, based on the total weight of the supported synthesis catalyst; and wherein the weight ratio of manganese to cobalt present, on an elemental basis, is 0.3 or greater, the support material of the supported CoMn Fischer-Tropsch synthesis catalyst comprises a material selected from titania, zinc oxide, zirconia, and ceria, and wherein the supported CoMn Fischer-Tropsch synthesis is prepared by impregnation.

13. A supported CoMn Fischer-Tropsch synthesis catalyst comprising Co.sub.3O.sub.4 crystallites having a particle size of less than 100 Angstroms and comprising at least 2.5 wt % of manganese, on an elemental basis, based on the total weight of the supported synthesis catalyst; and wherein the weight ratio of manganese to cobalt, on an elemental basis, is 0.2 or greater, and the support material of the supported CoMn Fischer-Tropsch synthesis catalyst comprises a material selected from titania, zinc oxide, zirconia, and ceria.

14. A process for preparing a supported CoMn Fischer Tropsch synthesis catalyst as defined in claim 12 the process comprising the steps of: (a) impregnating a support material with: a cobalt-containing compound and a manganese-containing compound in a single impregnation step to form an impregnated support material; and (b) drying and calcining the impregnated support material to form the supported CoMn Fischer-Tropsch synthesis catalyst.

15. A process according to claim 14, wherein the support material is impregnated with a solution or suspension comprising both the cobalt-containing compound and the manganese-containing compound.

16. A process according to claim 14, further comprising a step of reducing the supported CoMn Fischer-Tropsch synthesis catalyst to form a reduced supported CoMn Fischer-Tropsch synthesis catalyst by contacting with a hydrogen-containing gas stream.

17. A process according to claim 16, wherein reduction is performed at a temperature of from 200 C. to 400 C.

18. A process for converting a mixture of hydrogen and carbon monoxide gases to a composition comprising alcohols and liquid hydrocarbons by means of a Fischer-Tropsch synthesis reaction, the process comprising contacting a mixture of hydrogen and carbon monoxide gases with a supported CoMn Fischer-Tropsch synthesis catalyst as defined in claim 12.

19. A process according to claim 1, wherein the mixture of hydrogen and carbon monoxide gases is in the form of synthesis gas mixture.

20. A process for preparing a supported CoMn Fischer Tropsch synthesis catalyst as defined in claim 13, the process comprising the steps of: (a) impregnating a support material with: a cobalt-containing compound and a manganese-containing compound in a single impregnation step to form an impregnated support material; and (b) drying and calcining the impregnated support material to form the supported CoMn Fischer-Tropsch synthesis catalyst.

21. A process for converting a mixture of hydrogen and carbon monoxide gases to a composition comprising alcohols and liquid hydrocarbons by means of a Fischer-Tropsch synthesis reaction, the process comprising contacting a mixture of hydrogen and carbon monoxide gases with a supported CoMn Fischer-Tropsch synthesis catalyst as defined in Claim 13.

Description

EXAMPLES

Example 1Catalyst Preparation

[0084] Co(NO.sub.3).sub.2.6H.sub.2O and Mn(OAc).sub.2.4H.sub.2O were mixed in a solution with a small amount of water in varying amounts (see Table 1 below). This mixture was then added slowly to 100 g P25 TiO.sub.2 powder and mixed to obtain a homogeneous mixture. The Co(NO.sub.3).sub.2.6H.sub.2O was used in an amount so as to give 10 wt. % elemental Co on TiO.sub.2. The resultant paste/dough was extruded to form extrudate pellets and then dried and calcined at 300 C. Average size of Co3O4 crystallites on the TiO.sub.2 support of each catalyst were determined using X-ray diffraction and verified by hydrogen chemisorption on the reduced catalyst and the results are also shown in Table 1 below.

TABLE-US-00001 TABLE 1 Mass of Mass of cobalt manganese Co.sub.3O.sub.4 nitrate Cobalt acetate Manganese crystallite hexahydrate loading tetrahydrate Loading Mn/Co size (g) (wt. %) (g) (wt. %) ratio () 62 10 55 10 1 <30 60 10 40 7.5 0.75 <30 58 10 25 5 0.5 <30 57 10 16.2 3 0.30 34 56 10 10.8 2 0.20 49 56 10 7.6 1.5 0.15 57 56 10 5.4 1 0.10 81 55 10 0 0 107

[0085] The X-ray diffraction technique used to determine the Co.sub.3O.sub.4 crystallite size has a limit of detection of around 30 Angstroms, and as such crystallite size measurements of less than 30 Angstroms are reported as <30 Angstroms due to potentially significant margins of error in the measured crystallite sizes.

[0086] The results in Table 1 show a trend of reduction in the size of Co.sub.3O.sub.4 crystallites formed in the supported catalysts prepared in Example 1 as the Mn/Co ratio increases.

Example 2General Procedure for Fischer-Tropsch Reactions

[0087] 10 g of catalyst extruded pellets were loaded into a reactor and reduced under a H.sub.2 stream (15 h, 300 C., 100% H.sub.2, atmospheric pressure). The gaseous supply was switched to a mixture of hydrogen and carbon monoxide (H.sub.2/CO=1.8) comprising 18% nitrogen and the pressure maintained at 4.3 MPa. The temperature was raised to achieve conversion and maintained throughout the Fischer-Tropsch reaction.

Example 3Effect of Co/Mn Ratio on Selectivity in Fischer-Tropsch Reactions

[0088] The catalysts prepared in Example 1 were employed in Fischer-Tropsch synthesis reactions according to the general procedure of Example 2. CO conversion; alcohol and liquid hydrocarbons productivities; and CH.sub.4 selectivity data were compiled and results for the above Examples are provided in Table 2 below. Exit gasses were sampled by on-line gas chromatography and analysed for alcohol, olefin, iso and normal parafins from their GC peaks. The productivity of the catalyst is defined as the weight in grams of products formed over the catalyst per litre of packed catalyst volume per hour of reaction time. Values for CO conversion, CH.sub.4 selectivity, and productivity are average values obtained at steady state.

TABLE-US-00002 TABLE 2 Catalyst Mn/Co CO % % % liquid 10% Co+ ratio Conversion Alcohols Olefins hydrocarbons CH.sub.4 Sel 0% Mn 66 1 1.5 6.1 12.6 1% Mn 0.10 64 1 2.2 7.2 8.6 1.5% Mn 0.15 63 2 2.8 8.1 6.6 2% Mn 0.20 64 2.6 3.3 9.6 9.4 3% Mn 0.30 51 19.6 20.9 37.1 11.4

[0089] Table 3 below shows the alcohol selectivity by carbon number achieved for longer carbon chain lengths (i.e. the percentage of each carbon length that is present as an alcohol).

TABLE-US-00003 TABLE 3 Alcohol carbon 10% 10% Co, 10% Co, 10% Co, 10% Co, chain length Co 1% Mn 2% Mn 3% Mn 5% Mn C1 3.19% 5.39% 9.34% 12.95% 22.21% C2 0.00% 0.00% 0.00% 0.00% 0.00% C3 1.77% 2.25% 2.39% 4.25% 2.26% C4 1.34% 3.37% 7.52% 20.04% 8.63% C5 0.80% 2.92% 6.11% 17.57% 6.86% C6 0.89% 3.10% 6.40% 20.86% 9.16% C7 2.62% 4.95% 9.53% 24.99% 16.26% C8 3.29% 6.22% 10.49% 28.09% 21.76% C9 3.71% 6.96% 11.37% 29.88% 25.23% C10 4.41% 7.51% 11.98% 31.17% 28.97% C11 4.50% 7.58% 12.09% 31.49% 31.24% C12 4.28% 6.81% 11.69% 30.99% 33.25%

[0090] The results provided in Tables 2 and 3 is online data, and as a result does not include the alcohols contained in the wax product collection; offline analysis of the wax product collected showed a higher level of alcohol selectivity. The results in Table 2 and 3 demonstrate a dramatic increase in alcohol productivity as the Mn/Co ratio is increased from 0.20 to 0.30. These results are unexpected since the small Co.sub.3O.sub.4 crystallite size observed for the catalyst having a Mn/Co ratio of 0.3 used in accordance with the invention (34 ) would be expected to be too far below the optimum of 8 nm reported in the literature in order for the productivity of any particular FT product to be favourable.

[0091] Further analysis of the alcohols produced in the above Fischer-Tropsch reactions also demonstrates the increase in alcohol production when the Mn/Co ratio is in accordance with the present invention applies to a wide range of carbon numbers, including long carbon chains of C.sub.5-C.sub.15 and higher.

Example 4Catalyst Preparation

[0092] An amount of Co(NO.sub.3).sub.2.6H.sub.2O and an amount of Mn(OAc).sub.2.4H.sub.2O were mixed in a solution with a small amount of water. This mixture was then added slowly to 100 g P25 TiO.sub.2 powder and mixed to obtain a homogeneous mixture. Co(NO.sub.3).sub.2.6H.sub.2O was used in an amount so as to give approximately 10 wt. % elemental Co on TiO.sub.2. The resultant paste/dough was extruded to form extrudate pellets and then dried and calcined at 300 C. Characterization was complete on the resulting catalysts using X-ray diffraction, H.sub.2 chemisorption, elemental analysis, temperature programmed reduction and BET surface area techniques.

[0093] Several catalysts were made with between 55 and 62g of cobalt hydrate hexahydrate, and between 0 and 55g of manganese acetate tetrahydrate to give different manganese loadings and different Mn:Co ratios as detailed in Table 4.

TABLE-US-00004 TABLE 4 Mass of cobalt Cobalt Mass of manganese Manganese Mn/ nitrate hexahydrate loading acetate tetrahydrate Loading Co (g) (wt. %) (g) (wt. %) ratio 62 10 55 10 1.00 60 10 40 7.5 0.75 58 10 25 5 0.50 57 10 16.2 3 0.30 56 10 10.8 2 0.20 56 10 7.6 1.5 0.15 56 10 5.4 1 0.10 55 10 0 0 0.00

Example 5General Procedure for Fischer-Tropsch Reactions

[0094] 1 ml samples of catalyst in the form of a powder were loaded into a high throughput parallel reactor and reduced under a H.sub.2 stream (15 h, at 300 C., 100% H.sub.2, atmospheric pressure). The gaseous supply was switched to a mixture of hydrogen and carbon monoxide (H.sub.2/CO=1.8) comprising 18% nitrogen and the pressure maintained at 4.3 MPa. The temperature was raised to achieve conversion of 55-65% and maintained throughout the Fischer-Tropsch reaction. On line analytics were completed by GC. A second series of catalyst test were performed in a similar manner, except that 1 ml samples of catalyst in the form of extrudates were used instead of powders, and the H.sub.2/CO ratio was 1.5. The results are presented in Tables 5 and 6.

TABLE-US-00005 TABLE 5 CO Methane C5+ % OH % OH % OH Conversion/ Selectivity Selectivity/ fraction fraction fraction % % % of C8 of C10 of C12 0% Co 5% Mn 0.2 10% Co 62.6 4.1 89.9 5.7 6.2 4.2 (comparative) 10% Co/1% Mn 59.1 4.1 88.4 9.6 10.8 7.0 (comparative) 10% Co/3% Mn 55.5 6.6 68.1 31.7 44.7 27.3 10% Co/5% Mn 66.8 10.5 63.8 36.0 48.9 26.8 10% Co/7.5% Mn 57.6 9.9 64.5 36.0 50.6 30.7 10% Co/10% Mn 53.2 10.9 61.4 34.6 52.4 31.1 catalysts tested at 42barg, 1.8 H2:CO, 1500 hr.sup.1 GHSV, tested as powders (125-160 um), conversion levels between 53 and 66%.

TABLE-US-00006 TABLE 6 CO Methane C5+ % OH % OH % OH Conversion/ Selectivity Selectivity/ fraction fraction fraction % % % of C8 of C10 of C12 0% Co 5% Mn 0.0 10% Co 33.3 4.9 90.3 3.8 3.8 1.8 (comparative) 10% Co/1% Mn 32.0 3.5 89.1 7.8 8.6 6.2 (comparative) 10% Co/3% Mn 37.5 5.5 70.5 26.9 40.9 27.7 10% Co/5% Mn 35.1 10.9 60.2 32.6 54.4 35.0 10% Co/7.5% Mn 32.2 10.6 59.4 32.4 56.8 36.7 catalysts tested at 42barg, 1.5 H2:CO, 1500 hr-1 GHSV, tested as extrudates (1.25-3.5 mm), conversion levels between 32 and 37%

[0095] Analysis of the wax product was also performed and 2-dimensional GC analysis and is presented as FIG. 1. This clearly showed the high intensity response associated with the oxygenate material that is produced in the long chain wax product. The size of the C17OH response is similar or larger than the C20 alkane response.

[0096] Compositional analysis of waxes produced using the powder form catalyst for 0, 1, 3 and 5 wt. % Mn loadings are presented in Table 7.

TABLE-US-00007 TABLE 7 Total Average Total alcohol n-paraffin 10% Co/TiO2+ Carbon Number (% w/w) (% w/w) 0% Mn 28 4.6 91.4 (comparative) 1% Mn 28 10.2 89.8 (comparative) 3% Mn 25 37.4 62.6 5% Mn 27 44.2 55.6

Example 7Higher Loading Catalysts Two catalysts having higher cobalt loadings 19 wt. % and 25 wt. % cobalt, with 4 wt. %

[0097] and 6 wt. % manganese respectively, were prepared in a similar way as those described in Example 5. The Co.sub.3O.sub.4 crystal size was measure using XRD as 87 (8.7 nm) for the 25% Co, 6% Mn/TiO.sub.2 catalyst, and 88 (8.8nm) for the 19% Co/4% Mn/TiO.sub.2.

[0098] These catalyst were tested using the method as described in Example 6 and the results are presented in Tables 8 and 9.

TABLE-US-00008 TABLE 8 CO Methane C5+ % OH % OH % OH Conversion/ Selectivity Selectivity/ fraction fraction fraction % % % of C8 of C10 of C12 19% Co/4% Mn 57.0 14.3 59.9 31.1 33.0 30.9 25% Co/6% Mn 64.5 17.5 56.5 34.1 38.5 35.1 catalysts tested at 42barg, 1.8 H2:CO, 1500 hr-1 GHSV, tested as powders (125-160 um), conversion levels between 53 and 66%.

TABLE-US-00009 TABLE 9 CO Methane C5+ % OH % OH % OH Conversion/ Selectivity Selectivity/ fraction fraction fraction % % % of C8 of C10 of C12 19% Co/4% Mn 31.5 14.9 57.4 33.3 32.7 33.8 25% Co/6% Mn 32.8 17.8 53.2 31.6 36.5 37.2 catalysts tested at 42barg, 1.5 H2:CO, 1500 hr-1 GHSV, tested as extrudates (1.25-3.5 mm), conversion levels between 32 and 37%