Extruded titania-based material comprising mesopores and macropores

Abstract

Porous, extruded titania-based materials further comprising mesopores and macropores and/or prepared using one or more porogens, Fischer-tropsch catalysts comprising them, uses of the foregoing, processes for making and using the same and products obtained from such processes.

Claims

1. A Fischer-Tropsch synthesis catalyst comprising a porous, extruded titania-based material comprising mesopores having a pore diameter of 2 to 50 nm and macropores having a pore diameter of greater than 50 nm, and further comprising at least one metal selected from a group of consisting of cobalt, iron, nickel, ruthenium, and rhodium.

2. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the at least one metal is present in an amount of from 5 wt % to 30 wt %.

3. A Fischer-Tropsch synthesis catalyst according to claim 1, further comprising one or more promoters.

4. A Fischer-Tropsch synthesis catalyst according to claim 3, wherein the one or more promoters is selected from a group of consisting of rhenium, ruthenium, platinum, palladium, molybdenum, tungsten, boron, zirconium, gallium, thorium, manganese, lanthanum, cerium, and mixtures thereof.

5. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the at least one metal is cobalt.

6. A Fischer-Tropsch synthesis catalyst according to claim 5, wherein cobalt is present in an amount of from 5 wt % to 30 wt %.

7. A Fischer-Tropsch synthesis catalyst according to claim 5, wherein the mesopores have a pore diameter of 25 to 40 nm and the macropores have a pore diameter in the range of 100 to 850 nm.

8. A Fischer-Tropsch synthesis catalyst according to claim 5, wherein the total pore volume is at least 0.30 ml/g.

9. A Fischer-Tropsch synthesis catalyst according to claim 5, wherein the surface area is at least 30 m.sup.2/g.

10. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the mesopores have a pore diameter of 15 to 45 nm.

11. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the macropores have a pore diameter in the range of 60 to 1000 nm.

12. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the mesopores have a pore diameter of 15 to 45 nm and the macropores have a pore diameter in the range of 100 to 850 nm.

13. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the total pore volume is at least 0.30 ml/g.

14. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the surface area is at least 30 m.sup.2/g.

15. A Fischer-Tropsch synthesis catalyst according to claim 1, wherein the porous, extruded titania-based material is in the form of symmetrical cylinders, dilobes, trilobes, quadralobes or hollow cylinders.

16. A process for the preparation of a Fischer-Tropsch synthesis catalyst according to claim 1, said process comprising: a) mixing titanium dioxide and one or more porogens to form a homogeneous mixture; b) adding a solution of at least one thermally decomposable cobalt, iron, nickel, ruthenium or rhodium compound to the mixture, and mixing to form a homogeneous paste; c) extruding the paste to form an extrudate; d) optionally, drying the extrudate; e) calcining the extrudate at a temperature sufficient to decompose the one or more porogens and to convert the at least one thermally decomposable cobalt, iron, nickel, ruthenium or rhodium compound to an oxide thereof, or to the metal form, and, where an oxide is formed, optionally f) heating the calcined extrudate under reducing conditions to convert the at least one cobalt, iron, nickel, ruthenium or rhodium oxide to the metal form.

17. A process for the preparation of a Fischer-Tropsch synthesis catalyst according to claim 1, said process comprising: a) impregnating a porous, extruded titania-based material comprising mesopores and macropores with a solution of at least one thermally decomposable cobalt, iron, nickel, ruthenium or rhodium compound; b) drying and/or calcining the impregnated porous extruded titania-based material at a temperature sufficient to convert the at least one thermally decomposable cobalt, iron, nickel, ruthenium or rhodium compound to an oxide thereof, or to the metal form; and, wherein an oxide is formed, optionally c) heating the dried and/or calcined porous extruded titania-based material under reducing conditions to convert the at least one cobalt, iron, nickel, ruthenium or rhodium oxide to the metal form.

18. A process for converting a mixture of hydrogen and carbon monoxide gases to hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide with a Fischer-Tropsch synthesis catalyst according to claim 1.

19. A composition, preferably a fuel composition, comprising hydrocarbons prepared by a process according to claim 18.

20. A process for producing a fuel composition, said process comprising blending hydrocarbons prepared by a process according to claim 18 with one or more fuel components to form the fuel composition.

Description

(1) The present invention will now be illustrated by way of the following Examples and with reference to the following Figures:

(2) FIG. 1: graphical representation of pore size distribution of a titania extrudate prepared without using a porogen (Comparative Example 1),

(3) FIG. 2: graphical representation of pore size distribution of a titania extrudate prepared using cellulose as a porogen at a mass ratio of cellulose to titania of 1:0.5 (Example 1);

(4) FIG. 3: scanning electron microscope images at various magnifications of a titania extrudate prepared using cellulose as a porogen at a mass ratio of titania to cellulose of 1:0.5 (Example 1),

EXAMPLES

Comparative Example 1

(5) Titania Extrudate Comprising Mesopores

(6) Titanium dioxide (BASF P25) was formulated with distilled water in a mechanical mixer (Vinci MX 0.4) and then extruded using a mechanical extruder (Vinci VTE 1) through a die with an array of 1/16 inch diameter orifices to obtain extrudates with cylindrical geometry,

(7) The extrudates were dried at a temperature of 100 to 120 C. overnight, followed by calcination in air flow at 500 C. for four hours, via a ramp of 2 C./min.

(8) The resultant extrudate was characterised using nitrogen porosimetry (Quantachrome, Quadrasorb SI), mercury porosimetry (Micromeritics, AutoPore IV) and scanning electron microscopy.

(9) FIG. 1 depicts the pore size distribution (PDS) of the extrudate prepared in Comparative Example 1 estimated from the mercury intrusion data using the Washburn equation with a contact angle of 130 and a surface tension of bulk mercury of 485 mN/m. This sample exhibits only mesopores, with mean pore diameters of 28 nm. The pore volume and surface area of this material is shown in Table 1. The total pore volume of this material is approximately 0.36 ml/g as determined from the mercury intrusion data. The surface area of this material analysed from the nitrogen adsorption isotherm using the Brunaeur-Emmett-Teller (BET) model is 51 m.sup.2/g.

Example 1

(10) Titania Extrudate Comprising Mesopores and Micropores Prepared Using a Cellulose Porogen

(11) A porous, titania-based extrudate was prepared by mixing a predetermined amount of titanium oxide (BASF P25) and a cellulose (Aldrich, Sigmacell Type 101) in a 360 rotating mixer (Turbula) and then formulating with distilled water in a mechanical mixer to obtain a paste with a mass ratios of titania to cellulose and water of 1.0:0.5:1.17. The resulting paste was extruded through a die with 1/16 inch diameter holes to obtain extrudates with cylindrical rod geometry.

(12) The extrudate was dried at 110 C. overnight, followed by calcination at 500 C. for four hours, via a ramp of 2 C./min.

(13) The resultant extrudate was characterised using nitrogen porosimetry, mercury porosimetry, and scanning electron microscopy, as described in Comparative Example 1.

(14) FIG. 2 depicts the pore size distribution of the material of Example 1, and shows a bimodal pore distribution centred at 40 nm (mesopores) and 825 nm (macropores).

(15) FIG. 3 shows scanning electron micrographs of samples of the extrudate formed in Example 1 at various magnifications, and clearly demonstrates the presence of uniform wormhole-like macropores in the extrudate.

(16) Total pore volume and surface area values for the material of Example 1 are shown in Table 1. Owing to the formation of macropores, this material exhibits a mercury intrusion pore volume of 0.85 ml/g, which is substantially higher than the value (0.36 ml/g) of the material formulated without using porogen (Comparative Example 1). BET surface area of the material of Example 1 is 50 m.sup.2/g, which is very similar to the extrudate formed without using the porogen in Comparative Example 1.

Example 2

(17) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose Porogen

(18) A porous, titania-based extrudate was prepared according to the procedure set out in Example 1, with the exception that the mass ratio of titanium oxide to cellulose was adjusted to 1:0.4. The mixture of titanium oxide and cellulose was homogenised with a Turbula mixer, formulated with water in the trough of a Vinci mixer, extruded using a Vinci extruder, and dried and calcined as set out in Example 1.

(19) The extrudate of Example 2 was characterised using nitrogen porosimetry, mercury porosimetry and scanning electron microscopy as described in Comparative Example 1, and the results are shown in Table 1.

(20) The material of Example 2 exhibited a bi-modal pore size distribution with peaks at 32 nm and 674 nm, respectively. Total pore volume was 0.67 ml/g, and the BET surface area of the sample was 51 m.sup.2/g.

Example 3

(21) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose Porogen

(22) The procedure of Example 1 was repeated, with the exception that the mass ratio of titania to cellulose was adjusted to 1:0.3. The resulting mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1

(23) The extrudate of Example 3 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(24) The calcined extrudate of Example 3 exhibited a bi-modal pore size distribution with peaks at 33 nm and 675 nm, respectively. The total pore volume was 0.6 ml/g, and the BET surface area was 51 m.sup.2/g.

Example 4

(25) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose Porogen

(26) The procedure of Example 1 was repeated, with the exception that the mass ratio of titania to cellulose was adjusted to 1:0.2. The resulting mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1.

(27) The extrudate of Example 4 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(28) The calcined extrudate of Example 4 exhibited a bi-modal pore size distribution with peaks at 33 nm and 283 nm, respectively. The total pore volume was 0.53 ml/g, and the BET surface area was 52 m.sup.2/g.

Example 5

(29) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose Fibre as the Porogen

(30) The procedure of Example 1 was repeated, with the exception that an alternative form of cellulose (Aldrich Cellulose Fibre) was used as the porogen at a mass ratio of titania to cellulose of 1:0.5.

(31) The mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1.

(32) The calcined extrudate of Example 5 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(33) The calcined extrudate of Example 5 exhibited a bi-modal pore size distribution with peaks at 30 nm and 227 nm, respectively. The total pore volume was 0.63 ml/g, and the BET surface area was 48 m.sup.2/g.

Example 6

(34) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose as the Porogen

(35) The procedure of Example 1 was repeated, with the exception that an alternative form of cellulose (Aldrich Sigmacell Type 20) was used as the porogen at a mass ratio of titanium oxide to cellulose of 1:0.5.

(36) The mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1.

(37) The calcined extrudate of Example 6 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(38) The calcined extrudate of Example 6 exhibited a bi-modal pore size distribution with peaks at 34 nm and 183 nm, respectively. The total pore volume was 0.64 ml/g, and the BET surface area was 48 m.sup.2/g;

Example 7

(39) Titania Extrudate Comprising Mesopores and Macropores Prepared Using a Cellulose as the Porogen

(40) The procedure of Example 1 was repeated, with the exception that an alternative cellulose (Aldrich Sigmacell Type 50) was used as the porogen at a mass ratio of titanium oxide to cellulose of 1:0.5.

(41) The mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1.

(42) The calcined extrudate of Example 7 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(43) The calcined extrudate of Example 7 exhibited a bi-modal pore size distribution with peaks at 30 nm and 139 nm, respectively. The total pore volume was 0.61 ml/g, and the BET surface area was 49 m.sup.2/g.

Example 8

(44) Titania Extrudate Comprising Mesopores and Macropores Prepared Using Alginic Acid as the Porogen

(45) The procedure of Example 1 was repeated, with the exception that alginic acid (Aldrich) was used as the porogen at a mass ratio of titanium dioxide to alginic acid of 1:0.5.

(46) The mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example 1.

(47) The calcined extrudate of Example 8 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(48) The calcined extrudate of Example 8 exhibited a bi-modal pore size distribution with peaks at 36 nm and 504 nm, respectively. The total pore volume was 0.68 ml/g, and the BET surface area was 50 m.sup.2/g.

Example 9

(49) Titania Extrudate Comprising Mesopores and Macropores Prepared Using Cellulose Fibre as the Porogen at Pilot Plant Scale

(50) The materials set out in Example 5 were used to prepare a porous, extruded titania-based material comprising mesopores and macropores on a pilot scale. The titanium oxide (BASF P25) and cellulose fibre (Aldrich Cellulose Fibre) were mixed at a mass ratio of titanium oxide to cellulose of 1:0.5.

(51) The mixture was homogenised and formulated with water in a Simpson Muller, and the subsequent paste was extruded using a Bonnet Extruder. The extrudate was dried and calcined as set out in Example 1.

(52) The calcined extrudate of Example 9 was characterised as set out in Comparative Example 1, and the results are shown in Table 1.

(53) The calcined extrudate of Example 9 exhibited a bi-modal pore size distribution with peaks at 30 nm and 125 nm, respectively. The total pore volume was 0.52 ml/g, and the BET surface area was 47 m.sup.2/g.

(54) TABLE-US-00001 TABLE 1 Porogen Pore Mesopore Macropore Surface Ratio Volume Distribution Distribution Area Sample Porogen (g/g) (ml/g) (nm) (nm) (m2/g) Comparative None 0 0.36 28 51 Example 1 Example 1 Cellulose 0.5 0.85 40 825 50 Sigmacell Type 101 Example 2 Cellulose 0.4 0.67 32 674 51 Sigmacell Type 101 Example 3 Cellulose 0.3 0.60 33 675 51 Sigmacell Type 101 Example 4 Cellulose 0.2 0.53 33 283 52 Sigmacell Type 101 Example 5 Cellulose 0.5 0.63 30 227 48 Fiber Example 6 Cellulose 0.5 0.64 34 183 48 Sigmacell Type 20 Example 7 Cellulose 0.5 0.61 30 139 49 Sigmacell Type 50 Example 8 Alginic 0.5 0.68 36 504 50 Acid Aldrich Example 9 Cellulose 0.5 0.52 30 125 47 Fiber (pilot plant scale)

(55) A comparison of the results for Comparative Example 1 and Examples 1 to 9, as shown in Table 1, clearly shows that the inclusion of a porogen before the extrusion stage, and the subsequent removal thereof, allows the preparation of a porous, extruded titania-based material comprising mesopores and macropores. The resulting materials also have significantly increased total pore volume, but without any effect on BET surface area.

Comparative Example 2

(56) Fischer-Tropsch Catalyst Prepared from a Porous, Extruded Titania-Based Material Comprising Mesopores

(57) A Fischer-Tropsch catalyst was prepared by loading the porous, extruded titania-based material comprising mesopores of Comparative Example 1 with a loading of 10% cobalt and 1% manganese; for example, by impregnation with an aqueous solution of cobalt nitrate and manganese acetate using an incipient wetness procedure, followed by drying in air at 60 C. for 5 hours and 120 C. for 5 hours, and calcining at 300 C. for 2 hours with a ramp rate between soaking steps of 2 C./min.

(58) The Fischer-Tropsch catalyst of Comparative Example 2 was characterised as set out in Comparative Example 1, and the material was found to comprise only mesopores, with mean pore diameters of 24 nm.

Example 10

(59) Fischer-Tropsch Catalyst Comprising Mesopores and Macropores

(60) A Fischer-Tropsch catalyst comprising mesopores and macropores was prepared by loading the porous, extruded titania-based material comprising mesopores and macropores of Example 6 with 10% cobalt and 1% manganese, using the method set out in Comparative Example 2.

(61) The Fischer-Tropsch catalyst of Example 10 was characterised as set out in Comparative Example 1, and was found to exhibit a bi-modal pore distribution having peaks at 36 nm and 181 nm, respectively.

Example 11

(62) Comparison of Performance of Fischer-Tropsch Catalysts of Comparative Example 2 and Example 10

(63) The Fischer-Tropsch catalysts of Comparative Example 2 and Example 10 were tested to determine their activity and selectivity in a Fischer-Tropsch process as follows.

(64) The catalysts were each loaded into a fixed bed testing reactor, then reduced in-situ in hydrogen flow at 300 C. for 15 hours. Synthesis gas (a mixture of carbon monoxide and hydrogen) was passed over the catalyst bed using the following conditions:

(65) Temperature: 188 C.

(66) Pressure: 42 barg

(67) Synthesis gas: H.sub.2/CO=1.8, with 10% nitrogen

(68) GHSV: 1250 h.sup.1

(69) Each catalyst was run for a sufficient period to obtain steady state conditions and the temperature was adjusted to provide a particular level of carbon monoxide conversion (typically between about 60 and 65%). The temperature and pressure were stabilised at 188 C. and 42 barg respectively.

(70) Exit gases were sampled by on-line gas chromatography, and analysed for gaseous products. The degree of carbon monoxide conversion, methane selectivity and selectivity for C.sub.5+ hydrocarbons were determined for each catalyst. The results are shown in Table 2.

(71) As will be seen from Table 2, the Fischer-Tropsch catalyst of Example 10 comprising mesopores and macropores has improved carbon monoxide conversion and improved selectivity to C.sub.5+ hydrocarbons compared to the Fischer-Tropsch catalyst of Comparative Example 2 (comprising only mesopores). Additionally, the Fischer-Tropsch catalyst of Example 10 has significantly reduced selectivity to methane compared to the Fischer-Tropsch catalyst of Comparative Example 2, which is particularly advantageous because methane is one of the major components in typical synthesis gas feeds, and the conversion of synthesis gas back to methane is highly undesirable in Fischer-Tropsch processes.

(72) TABLE-US-00002 TABLE 2 CH.sub.4 C.sub.5+ Pore size (nm) Temp. Pressure CO conv. select. select. Catalyst Mesopores Macropores ( C.) (barg) (%) (%) (%) Mesopore 24 No 188 42 42.3 9.7 83.3 10% Co 1% Mn/TiO.sub.2 Comparative Example 2 Meso- 36 181 188 42 47.4 4.8 85.8 macropore 10% Co 1% Mn/TiO.sub.2 Example 10

(73) The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as 40 mm is intended to mean about 40 mm.

(74) Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

(75) While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope and spirit of this invention.