METHOD FOR PRODUCING CATALYST MONOLITHS

Abstract

A method for producing a three-dimensional porous catalyst monolith of stacked catalyst fibers, comprising the following steps: a) Preparing a suspension paste in a liquid diluent of metal, metal alloy and/or metal oxide particles of catalytically active metal or metal alloy in which the metals, metal alloy and metal oxide particles can be supported on or mixed with inorganic oxide catalyst support particles, and which suspension can furthermore comprise a binder material, all particles in the suspension having an average particle size in the range of from 0.5 to 500 m, b) extruding the paste of step a) through one or more nozzles preferably having a maximum diameter of less than 5 mm, more preferably less than 1 mm to form fibers, and depositing the extruded fibers to form a three-dimensional porous catalyst monolith precursor, c) drying the porous catalyst monolith precursor to remove the liquid diluent, d) if necessary, reducing the metal oxide(s) in the porous catalyst monolith precursor to form the catalytically active metal or metal alloy, wherein no temperature treatment of the porous catalyst monolith precursor or porous catalyst monolith at temperatures above 1000 C. is performed.

Claims

1.-17. (canceled)

18. A method for producing a three-dimensional porous catalyst monolith of stacked catalyst fibers, in which the monolith is formed of catalytically active metal or metal alloy supported on inorganic oxide catalyst support particles starting from powders of prefabricated catalysts, comprising the following steps: a) preparing a suspension paste in a liquid diluent of powders of prefabricated supported catalysts in which metal, metal alloy and/or metal oxide particles of the catalytically active metal or metal alloy are supported on inorganic oxide catalyst support particles, and which suspension optionally further comprises a binder material, all particles in the suspension having a number average particle size in the range of from 0.5 to 500 m, measured by sieving the particles or by photographic techniques, b) extruding the paste of step a) through one or more nozzles to form fibers, and depositing the extruded fibers to form a three-dimensional porous catalyst monolith precursor, c) drying the porous catalyst monolith precursor to remove the liquid diluent, d) optionally reducing the metal oxide(s) in the porous catalyst monolith precursor to form the catalytically active metal or metal alloy, wherein no temperature treatment of the porous catalyst monolith precursor or porous catalyst monolith at temperatures above 1000 C. is performed.

19. The method of claim 18, wherein in step b) the nozzles have a maximum diameter of less than 5 mm.

20. The method of claim 19, wherein the nozzles have a maximum diameter of less than 1 mm.

21. The method of claim 18, wherein the monolith of stacked catalyst fibers is three-dimensionally structured by depositing the extruded fibers in a regular, recurring stacking pattern to form a three-dimensionally structured porous catalyst monolith precursor.

22. The method of claim 18, wherein the monolith is formed from one continuous extruded fiber or from multiple individual extruded fibers.

23. The method of claim 18, wherein the regular, recurring stacking pattern is composed of stacked layers of extruded fibers, wherein in each layer at least 50 wt % of the extruded fibers are deposited parallel to each other and spatially separated from each other, or in a cobweb pattern.

24. The method according to claim 23, wherein at least 50 wt % of the extruded fibers are deposited as linear strands parallel to each other and spatially separated from each other, or wherein multiple cobweb patterns are stacked, wherein the direction of the strands in each layer is different from the direction in neighboring layers, so that a porous structure with contact points of strands of neighboring layers results.

25. The method according to claim 18, wherein the inorganic oxide catalyst support is selected from the group consisting of silicon dioxide, aluminium oxide, titanium dioxide, zirconium dioxide, magnesium oxide, calcium oxide, mixed metal oxides, hydrotalcites, spinels, perovskites, metal phosphates, silicates, zeolites, steatite, cordierite, carbides, nitrides and mixtures or blends thereof.

26. The method according to claim 18, wherein the catalytically active metal is selected from the group consisting of 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, and Ce and mixtures or alloys thereof.

27. The method according to claim 25, wherein nickel oxide nanoparticles having a number average particle size of less than 100 nm, measured by sieving the particles or by photographic techniques, are supported on the inorganic oxide catalyst support particles.

28. The method according to claim 25, wherein the inorganic oxide catalyst support is silica, having a number average particle size in the range of from 0.05 to 200 m, measured by sieving the particles or by photographic techniques.

29. The method according to claim 18, wherein a binder material is employed, selected from the group consisting of inorganic binders.

30. The method of claim 18, wherein no organic binder material is present in the suspension.

31. The method according to claim 18, wherein the drying is performed at a temperature in the range of from 100 to 1000 C.

32. The method according to claim 18, wherein the monolith has a porosity of at least 20%, determined by Hg-PV or He-density.

33. The method according to claim 18, wherein the three-dimensional porous catalyst monolith of stacked catalyst fibers has a side crushing strength of at least 60 N.

34. The method according to claim 18, wherein the three-dimensional porous catalyst monolith of stacked catalyst fibers is for use in oxidation, hydrogenation, dehydration, desulphurization, amination or dehydrogenation reactions.

35. The method according to claim 25, wherein nickel oxide nanoparticles having a number average particle size of less than 100 nm, measured by sieving the particles or by photographic techniques, are supported on the inorganic oxide catalyst support particles in an amount of from 1 to 70 wt %, based on the inorganic oxide catalyst support particles.

36. The method according to claim 18, wherein a binder material is employed, selected from the group consisting of clays, alumina, silica and mixtures thereof.

Description

GENERAL DESCRIPTION OF 3DFD

[0064] 3D Fiber Deposition (3DFD) is used to shape the powder. The 3DFD method is an adaptive manufacturing method whereby a highly loaded paste is extruded by a moving nozzle. By computer controlling the movement of the extrusion head in x, y and z-direction, a porous material can be produced from the extruded fibers or strands layer by layer. After drying, the porous material can be thermally dried.

[0065] The main benefit of this technology is the degree of freedom with regard to the porous parameters (fiber thickness, interfiber distance and stacking design).

[0066] The typical flow chart for the 3DFD technology consists of the following subsequent steps: [0067] Prepare highly viscous ceramic (or metallic) paste [0068] Extrude through thin nozzle [0069] Computer controlled deposition of fibers to form a ceramic (or metallic) porous periodic structure [0070] Drying and if necessary reducing

[0071] The first important step is to make sure that no large particles are present in the paste. Therefore the particle size of the starting material is checked. If too large particles are present the powder is sieved to obtain the desired particle size. As a rule of thumb, the largest particle (represented by the d99 value) should preferably be at least five times smaller than the nozzle size that will be used, more preferably at least ten times smaller.

[0072] In the following step the powder is mixed together with the solvent/diluent (e.g. water), if necessary binder and additives, thus obtaining a viscous paste. A good mixing to achieve a homogenous paste (minimizing agglomerates or the incorporation of air bubbles) is a prerequisite for a smooth and reproducible process. The powder loading of the functional material depends on the specific surface area, the particle size distribution and the powder morphology. Generally, as the particle size of the powder decreases, the viscosity of the paste will increase. Therefore the solid loading needs to be lowered for these powders. Apart from organic or, preferably, inorganic binder(s), rheology modifiers can be added to control the rheological behavior of the paste. In some cases a defoamer is also added to avoid air bubbles in the paste.

[0073] After mixing and de-airing, the paste is transferred to the paste reservoir and mounted on the 3DFD set-up. The nozzle, preferably either plastic or metal (below 200 m), is attached to the paste reservoir. Paste extrusion is achieved e.g. by a displacement pump or a screw pump. During deposition, it might be necessary to control the drying conditions.

[0074] After drying at room conditions (or under controlled atmosphere and temperature), the 3DFD structure is reduced, if necessary. No calcining or sintering at temperatures above 1000 C. is necessary.

EXPERIMENTAL PROCEDURE OF 3DFD PROCESS

[0075] Obtaining a smooth process and a narrow control on the extrusion of thin filaments often requires adjustments of both the formulation of the paste and the experimental set-up. The main process parameters which have to be addressed are listed below.

[0076] Parameters [0077] Particle size distribution of starting material [0078] Preparation and mixing procedure of the paste [0079] Paste formulation [0080] De-airing & paste reservoir filling [0081] Design of deposition platform [0082] Height control of nozzle [0083] Programming of turns and transition between layers [0084] Tuning extrusion speed versus movement speed [0085] Drying conditions during deposition

[0086] For a further description of the process, reference can be made to the above-listed documents.

[0087] The stacking design is preferably as depicted in FIGS. 1 and 2 of U.S. Pat. No. 7,527,671. Most preferred is a 1-3-1 pattern.

[0088] The liquid diluent employed can be chosen from water and organic liquid diluents. Preferably, the liquid diluent contains mainly or is water.

[0089] The drying is preferably performed at a temperature in the range of from 100 to 1000 C., more preferably 0 to 300 C., most preferably 20 to 110 C.

[0090] The reducing of the metal oxide to form the catalytically active metal is performed in the presence of free hydrogen, preferably at a temperature in the range of from 1 to 1000 C., more preferably 100 to 600 C.

[0091] No treatment of the porous catalyst monolith precursor or porous catalyst monolith at temperatures above 1000 C., preferably above 900 C., more preferably above 750 C., is performed.

[0092] The monolith of stacked catalyst fibers is preferably three-dimensionally structured by depositing the extruded fibers in regular, recurring stacking pattern (periodically structured catalyst), to form a three-dimensionally structured porous catalyst monolith precursor.

[0093] The monolith can be formed from one continuous extruded fiber or from multiple individual extruded fibers.

[0094] Preferably, the regular, recurring stacking pattern is composed of stacked layers of extruded fibers, wherein in each layer at least 50% wt %, more preferably at least 90 wt % of the extruded fibers or each of the fibers are deposited parallel to each other and spatially separated from each other. The parallel deposition can be in straight or curved lines. As an alternative, they can be deposited/stacked in a circular pattern with radial interlayers, like in a cobweb pattern.

[0095] More preferably, at least 50 wt %, most preferably at least 90 wt % of the extruded fibers or each of the fibers are deposited as linear strands parallel to each other and spatially separated from each other, wherein the direction of the strands in each layer is different from the direction in neighboring layers, so that a porous structure with contact points of strands of neighboring stacks result. As an alternative, multiple cobweb pattern can be stacked, each pattern layer preferably rotated relative to its neighboring pattern layers.

[0096] One example of stacks of layers alternating by 90 in the direction is depicted in FIGS. 1 and 2 of U.S. Pat. No. 7,527,671.

[0097] The fibers or strands preferably have a thickness of 10 to 5000 m, more preferably 10 to 1000 m, most preferably 150 to 500 m.

[0098] They are preferably spatially separated from each other by 10 to 5000 m, more preferably 100 to 1000 m, most preferably 200 to 800 m.

[0099] One example is a stacking of 360 m strands being spaced by 650 m.

[0100] Typical monolith sizes are 1 cm.sup.3 to 100000 m.sup.3, more preferably 3 to 300000 cm.sup.3.

[0101] The monolith can have any desired shape. Preferably, it is in the form of a cylinder with circular or ellipsoidal cross section, a cuboid, a sphere, an ellipsoid, a tablet or a polygon.

[0102] In comparison to this, standard extrusion processes for nickel catalyst extrudates that are made on a regular basis have a minimum diameter of 1.2 mm. Depending on the formulation, these extrudates have a strength of 50 N or lower as measured by the SCS method (side crush strength).

[0103] The side crushing strength of the catalyst monolith, preferably with dimensions 1.5 cm1.5 cm1.2 cm (x,y,z axis, z being the stacking direction), according to the present invention is preferably at least 60 N, more preferably at least 100 N, most preferably at least 300 N, when yz or xy opposite planar sides are pressed.

[0104] The determination of the side crushing strength (SCS) is for examples disclosed in Oil & Gas Science and TechnologyRev. IFP, Vol. 55 (2000), No. 1, pp. 67-85, specifically section 3.1.1. An example for the determination of the Side Crushing Strength (SCS) is as follows: This method covers the resistance of a formed catalyst microstructure to a compressive force. The microstructure is subjected to a compressive load between jaws. The force required to crush the tablet is measured and recorded in Newton force. The operation is executed using the semiautomatic Schleuniger Model 6D hardness tester. The microstructure is tested with the YZ or XZ plane facing upright between the measure jaws. Press the START-button on the Schleuniger 6D. The jaws will slowly approach each other to execute the crushing test. The crushing strength is displayed on the Schleuniger and the computer monitor.

[0105] The maximum side crushing strength depends on the materials used for preparing the catalyst monolith and also on the three-dimensional structure of the catalyst monolith as well as the fiber diameter. The more contact points between the individual fiber layers are present, the higher the side crushing strength will be. Preferably, adjacent layers have at least 10 contact points, more preferably at least 20 contact points, most preferably at least 30 contact points to one neighboring layer. Thus, for a fiber layer, which has two neighboring layers, the number of contact points is twice the number stated above. Due to the contact points, the stack of fiber layers is self-supporting.

[0106] There is no upper limit for the side crushing strength of the catalyst monolith. Typically, the maximum side crushing strength is 100.000 N and often it is 10.000 N. Thus, the side crushing strength of the catalyst monolith according to the present invention is preferably in the range of from 60 to 100.000 N, more preferably 100 to 100.000 N and most preferably 300 to 100.000 N.

[0107] The maximum can also be the maximum that a machine for measuring SCS is able to measure. The maximum can depend on the size of the monolith. If the monolith is larger than the machine for measuring it allows, the monolith is cut to a suitable size, preferably 1.5 cm1.5 cm1.2 cm (xyz axis).

[0108] Structures made from 360 m fibers and 650 m interfiber distance and ABAB or ABC stacking show a side crushing strength of a 1.5 cm-1.5 cm-1.5 cm structure of 666.8 N.

[0109] Thus, the process according to the present invention leads to catalyst structures having a high strength combined with a high surface area/porosity.

[0110] The invention also relates to a three-dimensional porous catalyst monolith of stacked catalyst fibers, obtainable by the above process.

[0111] The invention furthermore relates to the use of these monoliths as catalysts in oxidation, hydrogenation, dehydration, desulphurization, amination or dehydrogenation reactions. Preferably, the reactions involve a liquid phase or mixed liquid/gas phase.

[0112] The invention furthermore relates to a control system data set containing a plurality of control instructions which when implemented on an additive production facility prompt the additive production facility to produce a three-dimensional porous catalyst monolith or three-dimensional porous catalyst monolith precursor as described above.

[0113] Additive production facilities are for example 3D fiber deposition (3DFD), 3D printing, stereolithography, fused filament fabrication (FFF) or laser sintering. These facilities or equipments are used to shape the powder or paste in order to form the three-dimensional catalyst monolith or its precursor. Thus, the additive production facility can be a 3D fiber deposition printer, 3D printer, stereolithography device or laser sintering device. These production facilities or production equipments are typically computer-controlled using a CAD file (computer aided design file). The CAD file contains the information on the three-dimensional structure of the porous catalyst monolith or its precursor and is needed to operate the additive production facility.

[0114] This CAD file which can also be described as a control system data set contains a plurality of control instructions which drive the additive production facility, for example the moving nozzle in a 3D fiber deposition apparatus. The control system data set can also be described as control system data record or data drive set. The control system data set or CAD file contains all information necessary to drive the additive production facility in order to produce the monolith or monolith precursor. This meaning is encompassed by the term prompt as used above. The control system data set and control instructions are typically electronic data stored on appropriate data storing device which can be a CD, DVD, USB stick, hard drive or SSD drive of a computer or attached to a computer.

[0115] The control system data set is typically loaded to the computer controlling the additive production facility prior to printing or extruding the 3D structure. Thus, the term implementing typically means loading the control system data or control instructions in a computer system which operates the additive production facility. Thus, the additive production facility then has the control instructions implemented thereon.

[0116] The invention will be further illustrated by the following example.

EXAMPLE OF 3D MICROEXTRUDED CATALYST

3D Microextruded Nickel Catalyst

[0117] A suspension was made from the catalyst precursor powder (nickel oxide nanoparticles on silica powder, obtained by precipitation), clay binder, and demi-water. The suspension was made by mixing the three components in the following mass percentages: 30.6% catalyst precursor, 4.4% clay, 65% demi-water. The ingredients were manually added and mixed by special mixing equipment (speedmixer) to obtain the right rheological properties for extruding through a 400 m sized nozzle. The particle size of the powder was selected to allow for this extrusion. The suspension is brought in a dispensing unit consisting of a syringe vessel and a nozzle. The unit is mounted on a microextruder machine. The microextruder is a computer numerical control (CNC) machine that is programmed to move according to a well-defined pattern and within a well-defined form. The CNC machine is programmed to continuously deposit filaments layer by layer in a predefined pattern. Depending on the thickness of the filaments foreseen in the application, a nozzle with the right diaphragm opening will be chosen, e.g. between 0.1 and 2 mm. The deposition parameters, e.g. the distance between the nozzle and the surface of the structure, the speed of the nozzle movement, the air pressure and the temperature and airflow of the environment, etc. are regulated. A 3D-structure is built in a box by depositing the filaments layer by layer according to the programmed pattern and according to the required dimensions. The 3D structures were afterwards dried at 80 C. for 2 days at 95% relative humidity. A hydrogen treatment at 350 C. was given to reduce the nickel oxide nanoparticles into nickel. The structure (ABAB stacking of 1.55 cm1.55 cm1.25 cm lbh) was tested on its side crushing strength and this was found to be 660 N in the x-x direction. The size of the nickel (oxide) nanoparticles did not change between the powder and the monolith.