SHAPED CATALYST PARTICLE

Abstract

The invention concerns particles which may include a catalytically active component, in the form of a three-dimensional ellipsoidal shape having three major axes at least two of which axes are of different lengths. Beds of such particles are useful for forming particle beds through which a fluid may flow.

Claims

1. A catalyst particle in the form of a three-dimensional ellipsoidal shape having three major axes at least two of which axes are of different lengths.

2. A catalyst particle according to claim 1, wherein all three of the major axes are of different lengths.

3. A catalyst particle having the general shape of a sphere and comprising at least one intra-particle channel extending from a first location on the surface of the particle through the interior of the particle to a second location on the surface of the particle.

4. A catalyst particle according to claim 1, comprising at least one intra-particle channel extending from a first location on the surface of the particle through the interior of the particle to a second location on the surface of the particle.

5. A catalyst particle according to claim 3, comprising from 1 to 24 channels.

6. A catalyst particle according to claim 3, comprising from 1 to 100 channels per cm.sup.2 of the particle's cross-section.

7. A catalyst particle according to claim 3, comprising a cavity that is in communication with the at least one intra-particle channel extending from a first location on the surface of the particle through the interior of the particle to said cavity.

8. A catalyst particle according to claim 3, wherein the at least one of said channels has a cross-section which varies along the length of the channel.

9. A catalyst particle according to claim 3, comprising at least two channels, wherein each channel has a different dimension.

10. A catalyst particle according to claim 1 which is solid having no void space within the particle.

11. A catalyst particle according to claim 1, comprising a catalytically active composition having catalytic properties for at least one chemical reaction.

12. A catalyst particle according to claim 11, wherein said catalytically active composition comprises at least one metal or metal compound is selected from Na, K, Mg, Ca, Ba, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Hf, W, Re, Ir, Pt, Au, Pb, or Ce and compounds thereof.

13. A catalyst particle according to claim 11, wherein the catalytically active composition is distributed on the surface of the catalyst particle and/or beneath the surface of the catalyst particle.

14. A catalyst particle according to claim 11, wherein the catalytically active composition is distributed throughout or substantially throughout the catalyst particle.

15. A catalyst bed comprising a plurality of catalyst particles according to claim 1 which are packed together within a vessel, the catalyst bed comprising void spaces between and within the catalyst particles, wherein the void spaces between particles form inter-particle channels through which a fluid may flow.

16. A catalyst bed according to claim 15, wherein the volume of the void space within the particles equals the volume of void space between particles +/50%.

17. A catalyst bed according to claim 15, wherein the average minimum cross sectional area of the intra-particle channels through the particles is matched with the average cross sectional area of the inter-particle channels +/50.

18. A method of performing a chemical reaction, comprising the step of contacting at least one starting chemical compound with a catalyst bed comprising a plurality of catalyst particles according to claim 15 to form at least one product chemical compound.

19. A method according to claim 18, wherein said chemical reaction comprises hydrogenation, dehydrogenation, oxidation, hydrodesulphurisation, steam reforming, catalytic steam reforming, autothermal reforming, secondary reforming, reforming for direct reduction of iron, catalytic partial oxidation, water-gas shift, sour shift, low-temperature shift, intermediate temperature shift reactions, medium temperature shift reactions, high temperature shift reactions, methanation, a Fischer-Tropsch reaction, methanol synthesis, ammonia synthesis, ammonia oxidation, nitrous oxide decomposition, selective oxidation or reduction reaction of internal combustion engine or power station exhaust gas.

20. A method according to claim 18, wherein said starting chemical compound is a hydrocarbon, a nitrogen oxide, a substituted hydrocarbon, an alcohol, an amine, an ether, an aromatic hydrocarbon, or a substituted aromatic hydrocarbon.

21. A method of treating a fluid mixture to selectively remove one or more target components of said mixture comprising contacting said fluid with a packed bed comprising a catalyst bed according to claim 15, wherein at least a portion of said one or more target components are transferred from said fluid mixture to said catalyst particles.

22. A method according to claim 21, wherein said target components comprise a material that is sulphur, a compound of sulphur, a metal, a metal compound, or a carbonaceous particulate material.

23. A method according to claim 19, wherein the steam reforming is steam pre-reforming or the water-gas shift is an isothermal-shift reaction.

Description

[0051] The invention will be further described, by way of example only, with reference to the accompanying drawings, which are:

[0052] FIGS. 1-9: wireframe model drawings of catalyst particles according to the invention. Each A view is a perspective sketch of the particle. Each B view is an elevation perpendicular to the shortest axis, and each C view is a plan view, perpendicular to the longest axis.

[0053] FIGS. 1-6 all illustrate examples of spheroidal particles, i.e. ellipsoids having two axes (or diameters) x and y-of the same length and the third, major, axis z which is shorter than the other two axes. FIG. 1 shows a particle which has three channels 12 extending through the particle, each being angled, or dog-legged. The six channel openings 14 are chamfered. FIGS. 2 and 3 show particles with twelve and eighteen channels respectively, each channel extending from the surface of the particle to join with a central cavity 16 within the particle. The particle of FIG. 4 includes a first ring of eight dog-legged channels 12 extending through the particle and a second ring of four smaller channels 18 inside the first ring of channels, the smaller channels having a different dog-legged shape. FIGS. 5 and 6 show particles having seven and nine channels respectively. The centrally positioned channel 20 in the particle of FIG. 6 is larger than the other channels and has a bore which is narrower towards the centre of its length than at each end, i.e. the central channel is waisted.

[0054] FIGS. 7-9 show ellipsoidal particles in which all three major axes are of different lengths. The particle of FIG. 7 has a single channel, whereas the particle of FIG. 8 has seven channels. The particle shown in FIG. 9 is a solid particle having no channels or openings.

[0055] The geometric properties of the particles are shown in Table 1. In Table 1 the shell thickness is shown where the particle includes a cavity. Shell thickness represents the average distance between the cavity wall and the outer surface of the particle in a region where there is no channel present. The geometric volume is the volume of the particle, if it was solid without channels. The material volume is the volume of material forming the particle, i.e. excluding channels or cavities. The pellets/m.sup.3 and SA/m.sup.3 shows the number of pellets and the surface area of pellets packed into one cubic metre of space. The relative channel size represents a numerical comparison of the predicted inter-particulate spacing for the catalyst particles of the demonstration geometries, within the fixed catalyst bed compared with a prior art catalyst particle in the form of a cylinder of length 3 mm and diameter 3.2 mm.

[0056] FIG. 10 is a photograph of the particles shown in FIG. 6.

[0057] FIG. 11 is test data from Example 2.

[0058] FIG. 12 is a photograph of an oblate spheroid having a complex internal structure formed by 3D printing the inverse of two, overlapping hexagonally packed spheres.

[0059] FIG. 13 is the test data from Example 3.

EXAMPLES

Example 1

[0060] A catalyst comprising particles having the shape and dimensions shown in FIG. 1 and Table 1 was formed from a catalyst support material (alumina) and manufactured using an additive layer manufacturing method using a 3D printer. The particles were then coated with a slurry of a particulate commercial base metal catalyst composition. The coating method used was by adding the formed catalyst particles to a beaker of the slurry, mixing, filtering off the excess slurry and then drying the coated particles at 110 C. for 16-22 hours. The particles were then sieved and weighed.

[0061] A catalyst was tested to perform oxidation of ammonia. In these tests, a reactor basket of 40 mm internal diameter was charged with approximately 40 g of catalyst. A woven stainless steel gauze was clamped into the lower basket flange to support the catalyst. The catalyst bed was 54 mm deep and 40 mm in diameter. The catalysts were tested over 3 days under the following process conditions: 10 Nm.sup.3h.sup.1 air, 10% vol NH.sub.3, 200 C. preheat and 4 bara (0.4 MPa). The evolved gases were analysed and the conversion efficiency (for NH.sub.3 to NO, expressed as a percentage) and amount of N.sub.2O by-product in the product gas stream recorded. The pressure drop was recorded once the reactor had achieved steady state operation as 14.25 mbar (1425 Pa). A similar reaction was run for comparison, using a bed of cylindrical catalyst particles 3.2 mm diameter3 mm in length. The pressure drop was recorded as 23.75 mbar (2375 Pa).

Example 2A

[0062] catalyst comprising particles having the shape depicted in FIG. 6 was manufactured. The particles were formed from alumina and manufactured using an additive layer manufacturing method using a 3D printer. A metal cylinder with an inner diameter of 48 mm and a fine wire mesh with 3.3 mm apertures were manufactured. This was loaded with the catalyst particles and subjected to back pressure measurements. Pressure measurements were taken at flow rates of air at 50 m.sup.3/h and 80 m.sup.3/h. The results comparing the bare (unloaded) cylinder to the particle loaded cylinder are shown in FIG. 11.

Example 3

[0063] A catalyst comprising particles having the shape depicted in FIG. 6 as well as a solid version to the same dimensions were manufactured. The particles were formed from alumina and manufactured using an additive layer manufacturing method using a 3D printer. The particles were separately subjected to heat transfer measurements. The rig consists of a 136 cm long brass tube with a diameter of 10 cm. Prior to the start of the run, low pressure steam is delivered to the steam jacket which surrounds a 60 cm section of the reactor tube, heating this section to a temperature of 100 C. Air is then passed through the rig at different flow-rates and at a constant pressure. The desired air flow-rate is controlled by the flow controller and is measured upstream by the flow-meter. A feedback loop between the flow controller and flow-meter enables precise flow-control to be achieved. The temperature of the air is measured before and after the steam jacket using Platinum Resistance Thermocouples (PRTs) and from these values a heat transfer co-efficient can be calculated at each flow-rate. PRTs are assumed to have an error of 0.1 C. The results are depicted in FIG. 13.

TABLE-US-00001 TABLE 1 Major Secondary Third Shell Number Geometric Material Surface Relative Particle Diameter Diameter Diameter Thickness of Volume Volume area Pellets/m.sup.3 SA/m.sup.3 Channel Fig (mm) (mm) (mm) (mm) channels (mm.sup.3) (mm.sup.3) (mm.sup.2) (million) (m.sup.2) Size 1 5 2.5 2.5 3 33 19 67 20.8 1390 1.2 2 8 5 5 1.3 12 168 105 315 4.1 1279 2.1 3 8 4 4 1.3 18 134 65 282 5.1 1429 2.0 4 12 6 6 12 452 316 556 1.5 830 3.0 5 12 6 6 7 452 292 511 1.5 773 3.0 6 9 4.7 4.7 9 199 66 348 3.4 1187 2.3 7 12 5 7 1 220 197 206 3.09 638 2.3 8 12 5 7 7 220 133 264 3.09 816 2.3 9 12 5 7 0 223 223 194 3.09 599 2.2