WO2009108356A1

WO2009108356A1 - Method for sealing cells in extruded monoliths and devices resulting

Info

Publication number: WO2009108356A1
Application number: PCT/US2009/001266
Authority: WO
Inventors: Paulo G Marques; Keyan Schultes; James S Sutherland
Original assignee: Corning Incorporated
Priority date: 2008-02-29
Filing date: 2009-02-27
Publication date: 2009-09-03
Also published as: KR20100129309A; CN102036935A; EP2262749A1; CN102036935B; TW200948748A; JP2011514856A

Abstract

Disclosed is a method for sealing selected cells in an extruded monolith at an end face of the monolith by providing an extruded monolith having a plurality of cells extending along a common direction and one or more end faces at which one or more of the cells are open, the open cells including some to be sealed and some to remain open, and by filling the open end of one of the cells to be sealed with a plug comprising a glass frit, such that an exterior portion the plug extends beyond the end of the cell, and such that the exterior portion of the plug also extends beyond the width of the cell; and by heating the extruded monolith together with the plug sufficiently to cause the glass frit to consolidate and flow sufficiently to seal the respective cell.

Description

METHOD FOR SEALING CELLS IN EXTRUDED MONOLITHS AND DEVICES RESULTING

PRIORITY

[0001] This application claims priority to United States Patent Application number 61/067752, filed February 29, 2008, titled "Method For Sealing Cells In Extruded Monoliths and Devices Resulting".

RELATED CASES

[0002] The present application is related to U.S. Provisional Application Serial No. 60/921,053, filed 31 March 2007 entitled Honeycomb Continuous Flow Reactor and to U.S. Provisional application 61/018,1 19 filed 31 December 2007 entitled Devices and Methods for Honeycomb Continuous Flow Reactors.

SUMMARY

[0003] According to one aspect of the present invention, a method for sealing selected cells in an extruded monolith at an end face of the monolith is disclosed. The method includes providing an extruded monolith having a plurality of cells extending along a common direction and one or more end faces at which one or more of the cells are open, the open cells including some to be sealed and some to remain open. The method also includes filling the open end of at least one of the cells to be sealed with a plug comprising a glass frit, such that an exterior portion the plug extends beyond the end of the cell, and such that the exterior portion of the plug also extends beyond the width of the cell, then heating the extruded monolith together with the plug sufficiently to cause the glass frit to consolidate and flow sufficiently to seal the respective cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 is a perspective view of an extruded monolith 20 having a path 30 formed therein in part by plugs or continuous plugging material 40 at one or more end faces 70 thereof.

[0005] Figure 2 is a cross section of a portion of a monolith 20 like that of Figure 1 , showing an arrangement of plugs or plug material 40.

[0006] Figure 3 is a cross section of a portion of a monolith 20 like that of Figure 1, showing another arrangement of plugs or plug material 40.

[0007] Figures 4A-4D are plan views of an extruded monolith 20 having a path formed therein in part by plugs or continuous plugging material 40 at one or more end faces 70 thereof, with varying arrangements of plugging material 40.

[0008] Figure 5 is perspective view of an extruded monOlith 20 showing side access to the path 30 corresponding to Figure 4B.

[0009] Figure 6A and 6B show a cross section of an individual plug 40 or row of plug material 40 being formed according to the methods of the present invention.

[0010] Figures 7A-7C are cross sections like those of Figures 6A-6B illustrating plug formation as presently understood according to the methods of the present invention.

[0011] Figures 8A-8B are cross sections like those of figures 6A-6B showing a plug 40 being formed according to another embodiment of the methods of the present invention.

[0012] Figures 9A-9D are cross sections like those of figures 6A-6B showing a plug 40 being formed according to yet another embodiment of the methods of the present invention.

[0013] Figure 10 is a digital photograph of a cross section of a plug 40 formed according to the methods of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Reference will now be made in detail to the presently preferred embodiments of the invention, instances of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0015] The present inventors and colleagues have various techniques for fabricating low-cost high-robustness chemical reactors based on honeycomb extrusion technology. In the chemical reactors of this type, reactant fluids flow in a path 30 comprised millimeter-scale channels formed along the cells of and extruded monolith 20, as shown generally in Figure 1. The path is desirably formed by shortening selected walls at the face 70 of the extruded monolith 20, selectively plugging with individual or essentially continuous plug material 40 to form a typically serpentine path 30.

[0016] Examples of two plugging schemes in a plane along the path 30 are shown in Figures 2 and 3. As may be seen in Figures 2 and 3, by shortening selected walls between adjacent cells of the monolith 20, and positioning plugs 40 appropriately, a generally serpentine 30 may be formed, lying in a direction mainly along the lengths of the cells of the monolith 20, with lateral connections between cells only near the end faces of the monolith. For lower pressure resistance along the path 30, the path 30 may follow more than one cell at a time in parallel, as shown in Figure 3. [0017] For maximum surface area, the path 30, generally following the pattern of the plugs or continuous plugging material 40 in the plan views of Figures 4A-4D, is desirably doubly serpentine, as in Figure 4B. For maximum surface area and further reduced pressure resistance, the path may be parallel with internal manifolding, as in Figure 4C, or parallel with external manifolding, if any, as in Figure 4D. [0018] Regardless of the type of path in the direction along the cells, two variations of which are shown in Figures 2 and 3, and regardless of the type of path in the plane perpendicular to the direction of the cells of the monolith 20, four variations of which are shown in Figures 4A-4D, it is desirable that width of the path in the plane perpendicular to the direction of the cells is generally only one cell wide, as in each of Figures 4A-4D. This allows relatively easy fabrication of one or more very high surface-area channel paths, with a high-flow path, in the form of the path direct through the open cells of the monolith, in very close contact. [0019] The path shown in Figure 4B, in particular, allows long fluid channels to be formed, useful for reactants requiring significant dwell time, while heat exchange fluids flow parallel to the extrusion direction through many millimeter-scale heat exchange channels adjacent to the reactant fluid channels. As shown in Figure 5, side access can be provided the path or paths 30 through one or more holes 50 formed in a side, preferably a flat side or flattened side face 60 of the extruded monolith 20. The side is flat, or flattened by removing the outer walls down to a flat wall formerly within the extruded monolith, a wider variety of fluid porting options may be available, including, for example the use of O-rings against the flat 60. [0020] Various processes and compositions may be used for forming the plugs 40 or continuous plug material 40 to plug the cells of the monoliths 20. What is desirable is a robust and simple process to provide plugs that are leak-free at pressures up to 55 bar or even higher, and are chemically resistant to a wide range of acids, bases and solvents. The present invention provides such a process, an embodiment of which may be described with reference to Figure 6.

[0021] Given an extruded monolith 20 having a plurality of cells extending along a common direction and one or more end faces 70 at which one or more of the cells are open, and given that the open cells include some to be sealed and some to remain open, the method further includes filling the open end of one or more of the cells to be sealed with a plug 40 comprising a glass frit, typically with an organic binder, such that an exterior portion 42 of the plug extends beyond the end of the cell, and such that the exterior portion 42 of the plug also extends beyond the width W of the cell, as shown in Figure 6A for one cell of a monolith 20. The monolith and the plug are then heated together sufficiently to cause the glass frit to consolidate and flow sufficiently to seal the respective cell, as shown in Figure 6B, which shows a representative plug profile after heating.

[0022] Although not wishing or intending to be bound by theory, the inventors offer the following as their current understanding of the basic operation of the process: Starting with a plug 40 of the form shown in Figure 7A, as the plug is first heated, debinding of the glass frit and binder mixture, and/or consolidation of the frit cause shrinkage of the plug 40 without significant flow or deformation of the glass. This results in the plug 40 pulling away from one or more of the walls of the cell to be plugged, leaving a gap 44 represented in Figure 7B. Because the exterior portion 42 of the plug 40 extends sufficiently beyond the width W of the cell, the plug 42 remains in contact with the top surface of the wall where the gap 44 is opened. This allows the plug to flow, as it softens and begins to round, under the influence of surface forces, back against the wall where the gap was opened, sealing the gap closed and providing a robust and leak-free seal in a single heating step. [0023] It is also possible, according to another aspect of the present invention, to utilize the flow properties of the softened glass in order to provide a large margin of error in the sealing process. This may be accomplished by filling the open end of one or more of the cells to be sealed with a plug 40 comprising a glass frit, such that an exterior portion 42 of the plug extends beyond the end of the cell, and such that the exterior portion 42 of the plug also extends beyond the outward surface of the walls of the cell, as shown in Figure 8A for one cell of a monolith 20, where the position of the outward surface of the walls of the cell is shown by the dotted lines extending upward therefrom. The depth of the unheated plug may also be adjusted as desired, with deeper plugs, such as the one in Figure 8, typically providing a more robust seal, at the expense of somewhat reduced internal volume. The monolith and the plug are then heated together sufficiently to cause the glass frit to consolidate and flow sufficiently to seal the respective cell, as shown in Figure 8B, which shows a representative plug profile after heating. Because the glass tends to contract and to pull into itself, the adjacent cells intended to remain open are not plugged, but the finished plug 40 of figure 8B covers the potentially sharp corners of the monolith walls, reducing the likelihood of forming stress-concentrating geometry in the wall plus finished plug structure.

[0024] One useful way of efficiently producing the pre-fired plugs described above is illustrated in Figure 9. Fig. 9A shows a cross-section view of a monolith 20 at an end face thereof where all cells but the one in the middle are covered by a thick mask 80, such as a tape mask. The thick mask 80 may be 1-2 mm thick, and may be formed by one or two layers of a thick pressure sensitive tape material or a flexible molded mask material such as silicone, for example. The edges of the mask 80 are positioned so that they do not completely cover the tops of monolith walls on either side of the end channel to be plugged.

[0025] Glass-based plug material is then applied to the monolith end face so that it flows between the two parts of the mask 80 and into the ends of the cells of monolith 20, as shown in Figure 9B. The plug material can be a paste at room temperature that is spread over the mask with a spatula so that excess plug material is removed. Alternatively the plug material can be suspended in a wax binder, and a layer of plug material may be spread over a hot plate so that it forms a uniform thin layer (1-2 mm thick), and then the monolith end face with the thick mask 80 may be is pushed into the thin layer of melted plug material. The hot plate may then be cooled or allowed to cool, so that the plug material solidifies and adheres to the monolith and mask. [0026] The thick mask 80 is then removed from the monolith end face, leaving the glass-based plug material with an exterior portion 42 of the plug 40 extending beyond the end of the cell, that is, beyond the monolith end face, as shown in Figure 9C. The exterior portion 42 of the plug 40 extends beyond the width W of the cell to be plugged so that it contacts at least a portion of the tops of the monolith walls that are adjacent to the cell.

[0027] Next the monolith is heated to bond the glass-based plug material to the monolith and form a leak-free seal as represented by the plug of Figure 9D. During the initial heating portion of sintering cycle the plug material polymer binder is burned off, as described above with respect to Figure 7. This results in a partial shrinkage of the plug material. It is important that the plug material remains in contact or close proximity to the monolith walls during this and any subsequent plug shrinkage as the sintering cycle continues. This contact or proximity is required so that when the plug material is heated to an elevated temperature so that it flows, it is close enough to wet all four adjacent monolith walls, or at least all of the adjacent walls that remain after any previous machining or other process to selectively remove walls. This wall wetting prevents the formation of gaps and provides a robust seal.. [0028] Surface tension effects can also work to coax plug materials into closer contact with the monolith walls. For example, the initially square corners on the plug material are rounded during sintering, resulting in limited transport of plug material downward to locations near the plug-wall interface.

Experimental

[0029] Alumina extruded monoliths were selected for study because of their strength, inertness, and reasonably good thermal conductivity. A glass composition was developed and selected for use because of its excellent CTE match to alumina and its very good chemical resistance. The glass composition is given in Table 1 below: Table 1

Material mol%

SiO2 76.5

B2O3 3.2

A12O3 3.0

Na2O 14.4

ZrO2 2.9

[0030] The glass composition was joined with a wax-based binder (MX4462) (17% by weight), by to form the final plug composition. Next a mask was applied to the end face of an alumina monolith with machined end walls. The tape mask was positioned so that two long channel regions were not masked by the tape. Meanwhile the plug material was heated on a hot plate at 125⁰C so that it melted and spread into a thin layer 1-2 mm thick. The alumina monolith end face was then applied onto the molten plug material so that the plug material flowed through the gaps in the mask and into the ends of the cells of the monolith. After the plug material and the alumina monolith cooled, the mask was removed.

[0031] The alumina monolith was then sintered at 875⁰C for 30 minutes. The monolith was placed in the furnace horizontally (on its side) so that the two plug ridges were oriented parallel to the floor of the furnace. During sintering the plug material slumped such that it remained in contact with the walls of the alumina monolith. Long bond lines between the resulting plug and the alumina monolith were produced on both of the non-shortened sidewalls. Some asymmetry of the plug shape resulted from the alumina monolith being sintered resting on one side, but the targeted cells were successfully sealed. Figure 10 is a cross-sectional view of a sintered plug 40 showing a good bond with the cell sidewalls of an alumina monolith 20. Visual inspection of the interface between the glass plug material and the alumina monolith sidewall at the end face confirmed good wetting all along both sides of the plug ridge. The 116 plug material extended over the alumina monolith sidewall tops, with no gaps visible along the plug-sidewall interface. Also, the CTE match with the alumina monolith was excellent, and no shrinkage cracks or other defects appeared within the plug material along its entire length. Applications

[0032] The process described herein and the resulting selectively plugged extruded monolith structures may form a fluid processing device or a portion of such a device potentially useful for a wide range of fluid processes and chemical reactions, such as any process that involves mixing, separation, extraction, crystallization, precipitation, or otherwise processing fluids or mixtures of fluids, including multiphase mixtures of fluids — and including fluids or mixtures of fluids including multiphase mixtures of fluids that also contain solids. The processing may include a physical process, a chemical reaction defined as a process that results in the interconversion of organic, inorganic, or both organic and inorganic species, a biochemical process, or any other form of processing. The following non-limiting list of reactions may be performed with the disclosed methods and/or devices: oxidation; reduction; substitution; elimination; addition; ligand exchange; metal exchange; and ion exchange. More specifically, reactions of any of the following non-limiting list may be performed with the disclosed methods and/or devices: polymerisation; alkylation; dealkylation; nitration; peroxidation; sulfoxidation; epoxidation; ammoxidation; hydrogenation; dehydrogenation; organometallic reactions; precious metal chemistry/ homogeneous catalyst reactions; carbonylation; thiocarbonylation; alkoxylation; halogenation; dehydrohalogenation; dehalogenation; hydroformylation; carboxylation; decarboxylation; amination; arylation; peptide coupling; aldol condensation; cyclocondensation; dehydrocyclization; esterification; amidation; heterocyclic synthesis; dehydration; alcoholysis; hydrolysis; ammonolysis; etherification; enzymatic synthesis; ketalization; saponification; isomerisation; quaternization; formylation; phase transfer reactions; silylations; nitrile synthesis; phosphorylation; ozonolysis; azide chemistry; metathesis; hydrosilylation; coupling reactions; and enzymatic reactions.

[0033] The rounded upper surfaces of the plugs formed by the disclosed process are particularly pressure resistant to pressure on the rounded side. Thus high fluid pressure may be applied at an end face of a selectively plugged monolith plugged as disclosed herein, allowing for high flow into the channels unplugged at that face. By adjusting the thickness of the mask 80 or by other suitable means, the portion of an unsintered plug extending beyond the monolith end face may be adjusted to optimize the after-sintering profile of the rounded upper surface for maximum pressure resistance.

Claims

What is claimed is:

1. A method for sealing selected cells in an extruded monolith at an end face of the monolith, the method comprising: providing an extruded monolith having a plurality of cells extending along a common direction and one or more end faces at which one or more of the cells are open, the open cells including some to be sealed and some to remain open; filling the open end of one of the cells to be sealed with a plug comprising a glass frit, such that an exterior portion the plug extends beyond the end of the cell, and such that the exterior portion of the plug also extends beyond the width of the cell; heating the extruded monolith together with the plug sufficiently to cause the glass frit to consolidate and flow sufficiently to seal the respective cell.

2. The method of claim 1 further comprising filling the open end of one of the cells such that the exterior portion 42 of the plug extends beyond the outward surface of the walls of the cell.

3. The method of claim 1 further comprising covering the cells to remain open with a mask at least about lmm thick, with the edges of the mask positioned so that they do not completely cover the tops of monolith walls on either side of the cell to be plugged.

4. The method of claim 3 further comprising applying glass-based plug material to the monolith end face so that it flows through the mask and into the ends of the cells of monolith.

5. The method of claim 4 wherein the plug material can be a paste at room temperature that is spread over the mask with a spatula or doctor blade so that excess plug material is removed.

6. The method of claim 4 wherein the plug material is suspended in a wax binder, and the monolith end face with the mask thereon is pushed into a layer of melted plug material.

7. The method of any of claims 3-6, further comprising removing the mask from the monolith end face and heating the monolith to bond the glass-based plug material to the monolith and form a leak-free seal.

8. A device for treating or reacting one or more fluids made by the process of any of claims 1-7.