阅读说明：本技术 大颗粒高性能催化带 (Large-particle high-performance catalytic belt ) 是由 J·A·诺夫 F·J·谢利 Z·宋 于 2020-04-09 设计创作，主要内容包括：本公开内容涉及一种催化复合物,其包含持久地缠埋在多孔原纤化聚合物膜中的多孔负载催化剂颗粒。负载催化剂颗粒包含分散在多孔载体基材上的至少一种金属或金属氧化物催化剂。在一些实施方式中,多孔原纤化聚合物膜被穿孔或以其他方式在其中包含机械形成的孔。负载催化剂颗粒具有至少部分基于大于60微米的D90值的大颗粒群。催化膜复合物可用于过滤应用以去除空气污染物质,例如SOx、NOx、二噁英/呋喃、CO等,并将它们转化为非污染或污染较小的气体成分。此外,催化制品的形式可以是过滤袋、蜂窝体、整料或任何其他合适的几何结构形式。(The present disclosure relates to a catalytic composite comprising porous supported catalyst particles permanently embedded in a porous fibrillated polymeric film. The supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate. In some embodiments, the porous fibrillated polymeric film is perforated or otherwise contains mechanically formed pores therein. The supported catalyst particles have a population of large particles based at least in part on a D90 value greater than 60 microns. The catalytic membrane composite may be used in filtration applications to remove air pollutants such as SOx, NOx, dioxin/furan, CO, etc., and convert them into non-polluting or less-polluting gas components. In addition, the catalytic article may be in the form of a filter bag, a honeycomb, a monolith, or any other suitable geometric form.)

1. A catalytic article comprising a porous fibrillated polymeric film including supported catalyst particles permanently embedded within the porous fibrillated polymeric film, wherein the supported catalyst particles have a particle size distribution defined by a D90 value of at least 60 microns.

2. The catalytic article of claim 1, wherein the supported catalyst particles have a particle size distribution defined by a D90 value of at least 100 microns.

3. The catalytic article of claim 1 or 2, wherein the supported catalyst particles have an average particle size of greater than or equal to 20 microns.

4. The catalytic article of any of claims 1-3, wherein the supported catalyst particles have an average particle size of greater than about 20 microns.

5. The catalytic article of any of claims 1-4, wherein the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

6. The catalytic article of any of claims 1-5, wherein the porous fibrillated film includes supported catalyst particles in an amount ranging from about 30 wt% to about 98 wt% supported catalyst particles.

7. The catalytic article of any of claims 1-6, wherein the porous fibrillated polymeric film has a porosity of about 20% to about 90%.

8. The catalytic article of any of claims 1-7, wherein the porous fibrillated polymeric membrane comprises Polytetrafluoroethylene (PTFE), poly (ethylene-co-tetrafluoroethylene) (ETFE), Ultra High Molecular Weight Polyethylene (UHMWPE), parylene (PPX), polylactic acid, and any combination or blend thereof.

9. The catalytic article of any of claims 1-8, wherein the supported catalyst particles have a population of particles having a D50 value greater than or equal to 7 microns.

10. The catalytic article of any of claims 1-9, wherein at least 40% of the pores comprise a pore size greater than 9 microns.

11. The catalytic article of any of claims 1-10, wherein the porous fibrillated polymeric film includes perforations therein.

12. The catalytic article of any of claims 1-11, wherein the catalytic article is in the form of a filter bag, a honeycomb, a monolith, or any other suitable geometric form.

13. The catalytic article of any of claims 1-12, wherein the supported catalyst particles are disposed throughout the thickness of the fibrillated polymeric film.

14. A catalytic filter material comprising the catalytic article of any of claims 1-13.

15. A method of reducing NOx from a gas stream, comprising:

a) providing a gas stream comprising a concentration of NOx; and

b) contacting the gas stream with a catalytic article of any preceding claim, thereby reducing the NOx concentration.

16. A NOx reaction system, comprising:

a catalytic article; and

a fluid stream comprising NOx.

17. The reaction system of claim 16, wherein the fluid stream is flue gas or automobile exhaust.

18. A reaction system according to claim 16 or claim 17 wherein the catalytic article is in the form of a filter bag, honeycomb, monolith or any other suitable geometric form.

19. The reaction system of any of claims 16-18, wherein the catalytic article comprises a porous fibrillated polymeric film comprising supported catalyst particles permanently embedded within the porous fibrillated polymeric film.

20. The reaction system of claim 19, wherein the supported catalyst particles have a particle size distribution defined by a D90 value of at least 60 microns.

21. A reaction system as claimed in claim 19 or 20, wherein the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

22. A reaction system as claimed in any one of claims 19 to 21 wherein the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

23. A reaction system as claimed in any one of claims 19 to 22 wherein the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

24. The reaction system of any of claims 19-23, wherein the supported catalyst particles are disposed throughout the thickness of the porous fibrillated polymeric film.

25. A reaction system as in any of claims 19-24 wherein the supported catalyst particles have an average particle size of greater than or equal to 20 microns.

26. A reaction system as recited in any of claims 19-25, wherein the supported catalyst particles have an average particle size of greater than about 20 microns.

27. The reaction system of any of claims 19-26, wherein the porous fibrillated film includes supported catalyst particles in an amount ranging from about 30 wt% to about 98 wt% supported catalyst particles.

28. The reaction system of any of claims 19-27, wherein the porous fibrillated polymeric film has a porosity of about 20% to about 90%.

29. The reaction system of any one of claims 19-28, wherein the porous fibrillated polymeric membrane comprises Polytetrafluoroethylene (PTFE), poly (ethylene-co-tetrafluoroethylene) (ETFE), Ultra High Molecular Weight Polyethylene (UHMWPE), parylene (PPX), polylactic acid, and any combination or blend thereof.

30. The reaction system of any of claims 19-29, wherein the porous fibrillated polymeric film includes perforations therein.

Technical Field

The present disclosure relates generally to filter materials, and more particularly, to a porous fibrillated polymeric film that includes supported catalyst particles permanently embedded in the porous fibrillated polymeric film, which can be used to filter toxic chemicals.

Background

Catalytic filters are used in a variety of fluid filtration applications. Typically, these filters incorporate a catalytic material (e.g., TiO) in a matrix₂、V₂O₅、WO₃、Al₂O₃、MnO₂Zeolites and/or transition metal compounds and their oxides). As the fluid passes over or through the substrate, contaminants within the fluid react with the catalyst particles, converting the contaminants into more desirable byproducts or end products, thereby removing selected types of contaminants from the fluid stream.

During operation of the filter, the catalyst may undergo chemical and mechanical degradation. The operating life of the catalytic filter may be limited due to particulate, liquid, and gaseous contaminants (i.e., fine dust particles, metals, silica, salts, metal oxides, hydrocarbons, water, acid gases, phosphorus, basic metals, arsenic, alkali metal oxides, etc.) from the fluid stream. Catalyst deactivation may occur due to physical masking or chemical alteration of active sites on the catalyst within the filter. Unless these contaminants can fall off the catalyst, the efficiency of the filter can quickly decrease until it is unusable. In addition, in some cases, the processing aid used for the production may cause deterioration of the catalyst.

Another form of chemical degradation is due to loss of the catalyst that is buried during operation. In many cases, the catalyst particles do not adhere sufficiently strongly to the host fibers to withstand the harsh environment of normal operation. As a result, catalyst particles fall out of the filter, thereby not only reducing the efficiency of the filter, but also contaminating the clean fluid stream.

Accordingly, there is a need in the art for a catalytic article that effectively retains catalyst particles and effectively treats pollutants such as NOx and SOx.

Disclosure of Invention

According to one aspect ("aspect 1"), a catalytic article includes a porous fibrillated polymeric film including supported catalyst particles permanently embedded within the porous fibrillated polymeric film, wherein the supported catalyst particles have a particle size distribution defined by a D90 value of at least 60 microns.

According to a further another aspect of aspect 1 ("aspect 2"), the supported catalyst particles have a particle size distribution defined by a D90 value of at least 100 microns.

According to a further another aspect of aspect 1 or aspect 2 ("aspect 3"), the supported catalyst particles have an average particle size of greater than or equal to 20 microns.

According to a further aspect of any of the preceding aspects ("aspect 4"), the supported catalyst particles have an average particle size of greater than about 20 microns.

According to a further aspect of any of the preceding aspects ("aspect 5"), the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

According to a further another aspect of any of the preceding aspects ("aspect 6"), the porous fibrillated film includes supported catalyst particles in an amount ranging from about 30 wt% to about 98 wt% supported catalyst particles.

In accordance with a further another aspect of any of the preceding aspects ("aspect 7"), the porous fibrillated polymeric film has a porosity of about 20% to about 90%.

According to a further another aspect of any of the preceding aspects ("aspect 8"), the porous fibrillated polymeric membrane includes Polytetrafluoroethylene (PTFE), poly (ethylene-co-tetrafluoroethylene) (ETFE), Ultra High Molecular Weight Polyethylene (UHMWPE), parylene (PPX), polylactic acid, and any combination or blend thereof.

In accordance with a further aspect of any of the preceding aspects ("aspect 9"), the supported catalyst particles have a population of particles having a D50 value greater than or equal to 7 microns.

According to a further aspect of any of the preceding aspects ("aspect 10"), at least 40% of the pores comprise a pore size greater than 9 microns.

According to a further another aspect of any of the preceding aspects ("aspect 11"), the porous fibrillated polymeric film includes perforations therein.

According to a further aspect of any of the preceding aspects ("aspect 12"), the catalytic article is in the form of a filter bag, a honeycomb, a monolith, or any other suitable geometric form.

In accordance with a further aspect of any of the preceding aspects (aspect 13), the supported catalyst particles are distributed throughout (disposed within) the entire thickness of the fibrillated polymeric film.

According to another aspect ("aspect 14"), a catalytic filter material comprising the catalytic article of any of the preceding aspects.

According to another aspect, ("aspect 15"), a method of reducing NOx from a gas stream comprises (a) providing a gas stream comprising a concentration of NOx and (b) contacting the gas stream with a catalytic article of any preceding claim, thereby reducing the NOx concentration.

According to another aspect ("aspect 16"), a NOx reaction system includes a catalytic article and a fluid stream comprising NOx.

According to a further aspect of aspect 16 ("aspect 17"), the fluid stream is flue gas or automobile exhaust.

According to a further aspect of aspect 16 or aspect 17 ("aspect 18"), the catalytic article is in the form of a filter bag, a honeycomb, a monolith, or any other suitable geometric form.

According to a further another aspect of any of aspects 16-18 ("aspect 19"), the catalytic article includes a porous fibrillated polymeric film comprising supported catalyst particles permanently embedded within the porous fibrillated polymeric film.

According to a further another aspect of aspect 19 ("aspect 20"), the supported catalyst particles have a particle size distribution defined by a D90 value of at least 60 microns.

According to a further aspect of aspect 19 or aspect 20 ("aspect 21"), the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

According to a further aspect of any of aspects 19-21 ("aspect 22"), the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

According to a further aspect of any of aspects 19-22 ("aspect 23"), the supported catalyst particles comprise at least one metal or metal oxide catalyst dispersed on a porous support substrate.

According to a further another aspect of any of aspects 19-23 ("aspect 24"), the supported catalyst particles are distributed throughout (disposed within) the entire thickness of the porous fibrillated polymeric film.

According to a further aspect of any of aspects 19-24 ("aspect 25"), the supported catalyst particles have an average particle size of greater than or equal to 20 microns.

According to a further aspect of any of aspects 19-25 ("aspect 26"), the supported catalyst particles have an average particle size of greater than about 20 microns.

According to a further another aspect of any of aspects 19-26 ("aspect 27"), the porous fibrillated film includes supported catalyst particles in an amount ranging from about 30 wt% to about 98 wt% of the supported catalyst particles.

According to a further aspect of any one of aspects 19-27 ("aspect 28"), the porous fibrillated polymeric film has a porosity of about 20% to about 90%.

According to a further another aspect of any of aspects 19-28 ("aspect 29"), the porous fibrillated polymeric membrane includes Polytetrafluoroethylene (PTFE), poly (ethylene-co-tetrafluoroethylene) (ETFE), Ultra High Molecular Weight Polyethylene (UHMWPE), parylene (PPX), polylactic acid, and any combination or blend thereof.

According to a further another aspect of any of aspects 19-29 ("aspect 30"), the porous fibrillated polymeric film includes perforations therein.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments and together with the description serve to explain the principles of the disclosure.

FIG. 1 is a schematic illustration of a composite filter material including a perforated catalytic fluoropolymer membrane assembled with an upstream felt batt (felt batt), according to at least one embodiment;

FIG. 2 is a schematic representation of a second composite filter material comprising a perforated porous catalytic fluoropolymer membrane assembled with a scrim (script), upstream and downstream batt layers, and a protective porous membrane, in accordance with at least one embodiment;

FIG. 3 is a schematic illustration of a third composite filter material comprising a perforated catalytic fluoropolymer membrane assembled with an upstream batt layer and a protective porous membrane, according to at least one embodiment;

FIG. 4 illustrates a method for assembling a composite filter material, in accordance with at least one embodiment;

FIG. 5 illustrates particular aspects of the method for assembling a composite filter material as illustrated in FIG. 4, in accordance with at least one embodiment;

FIG. 6 is a graphical illustration showing particle size distributions for two catalyst size distributions ("small" and "large") in accordance with at least one embodiment;

FIG. 7 is a graph showing catalyst mass per unit area versus NO using two different catalyst size distributions ("small" and "large"), according to at least one embodiment_xGraphical illustration of reaction efficiency;

FIG. 8 is a graphical illustration of a mercury porosity plot showing mean pore diameter versus log differential intrusion (mL/g) for representative "large" and "small" particulate catalytic composite bands, in accordance with at least one embodiment;

FIG. 9A is a Scanning Electron Microscope (SEM) image of a composite tape prepared using "small" particle size distribution catalyst particles according to at least one embodiment;

FIG. 9B is an SEM image of a composite tape prepared using "large" particle size distribution catalyst particles according to at least one embodiment;

FIG. 10 is a graph showing catalyst mass per unit area versus NO using several different catalyst size distributions, according to at least one embodiment_xGraphical illustration of reaction efficiency;

FIG. 11 is a graph showing total flow rate and NO for representative "large" and "small" particulate catalytic composite strips, according to at least one embodiment_xGraphical illustration of reaction efficiency;

FIG. 12 is a graphical illustration of the average surface area of representative "large" and "small" particulate catalytic composite tapes at 30 wt% filler, according to at least one embodiment;

FIG. 13 is a graphical illustration of the average surface area of representative "large" and "small" particulate catalytic composite tapes at 50 wt% filler, according to at least one embodiment;

FIG. 14 is a graphical illustration of the efficiency of the reaction of large batches of catalyst particles (in wt.%) with NOx, according to at least one embodiment;

FIG. 15 is a graphical illustration of the efficiency of the reaction of large batches of catalyst particles (in vol%) with NOx, according to at least one embodiment; and

FIG. 16 is a graph of NOx reaction efficiency versus catalyst area density (g/m) at four average particle sizes (1 μm, 23 μm, 65 μm, 93 μm) in accordance with at least one embodiment²) To illustrate the same.

Detailed Description

Those skilled in the art will readily appreciate that the various aspects of the disclosure may be implemented by any number of methods and apparatus configured to perform the desired functions. It should also be noted that the drawings referred to herein are not necessarily drawn to scale, but may be exaggerated to illustrate various aspects of the disclosure, and in this regard, the drawings should not be taken as limiting. The use of the term "filtration" in this disclosure is intended to encompass any form of readily flowable material, including filtration of liquids and gases.

The present disclosure relates to a catalytic composite comprising or formed from porous supported catalyst particles permanently embedded in a porous fibrillated polymeric film. It is noted that the supported catalyst particles may be porous, non-porous or substantially non-porous. As used herein, the term "substantially nonporous" is intended to mean that there is measurable porosity, but no more than 5%. The supported catalyst particles consist of at least one metal or metal oxide catalyst dispersed on a porous support substrate. In some embodiments, the porous fibrillated polymeric film is perforated or otherwise contains mechanically formed pores therein. The catalytic membrane composite may be used in filtration applications to remove air pollutants such as, but not limited to, SOx, NOx, dioxins/furans, and CO (e.g., from flue gas or automobile exhaust) and convert them into non-polluting or less-polluting gas components. In addition, the catalytic article may be in the form of a filter bag, a honeycomb, a monolith, or any other suitable geometric form.

The supported catalyst particles comprise or are formed from at least one catalytic metal or metal oxide particle supported on and/or within a carrier substrate.Non-limiting examples of catalyst particles suitable for incorporation onto a carrier substrate include vanadium pentoxide, vanadium oxide, tungsten trioxide, titanium dioxide, iron oxide, copper oxide, molybdenum oxide, chromium oxide, and combinations thereof. In some embodiments, the metal or metal oxide catalyst is suitable for catalyzing such as NO, NO₂,NO₃NO of_XThe material is reduced to water and nitrogen or removed. The metal or metal oxide catalyst may be dispersed on and/or in the carrier substrate by known and optimized methods described in the art including, but not limited to, precipitation, plating, atomic layer deposition and molecular layer deposition. By the effective dispersion of the catalyst, the catalyst is caused to cover the carrier substrate and/or to be dispersed in the pores of the carrier substrate, thereby obtaining high catalytic activity.

The support substrate is not particularly limited so long as it does not interfere with the end use of the catalytic composite. In some embodiments, the carrier substrate is porous. Examples of materials useful as support substrates include, but are not limited to, metals, metal oxides (e.g., titania, alumina, and the like), zeolites, carbon, clays, and combinations thereof.

The supported catalyst particles comprise or are formed from at least one catalytic metal or metal oxide supported on and/or within a carrier substrate. In some embodiments, the catalyst particles are permanently embedded in the expanded polymer matrix. As used herein, the phrase "permanently embedded" is intended to describe catalyst particles that are non-covalently immobilized within the fibrillated microstructure of the polymeric film. There is no separate binder to hold the catalyst particles in the membrane. In addition, the catalyst particles are located throughout the thickness of the fibrillated polymer film. The supported catalyst particles can be present on and/or in the porous fibrillated film in an amount greater than about 30%, greater than about 40%, greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, or greater than about 90%. Further, the supported catalyst particles may be present on and/or in the porous fibrillated film in a range of from about 30 weight percent to about 98 weight percent, from about 30 weight percent to about 90 weight percent, from about 30 weight percent to about 85 weight percent, from about 30 weight percent to about 80 weight percent, from about 30 weight percent to about 75 weight percent, from about 30 weight percent to about 70 weight percent, from about 30 weight percent to about 65 weight percent, or from about 30 weight percent to about 60 weight percent of the fibrillated polymer film. Further, the porous fibrillated polymeric film has a total porosity of about 20% to about 90%, about 30% to about 90%, about 40% to about 90%, about 50% to about 90%, about 60% to about 90%, about 70% to about 90%, or about 80% to about 90%.

In some embodiments, the supported catalyst particles have a particle distribution based at least in part on a D90 value greater than 60 microns. In some embodiments, the supported catalyst particles can have a D90 value of greater than 70 microns, greater than 80 microns, greater than 90 microns, or greater than 100 microns. Further, the supported catalyst particles may have an upper limit value of 300 to 500 micrometers. In some embodiments, the supported catalyst particles have a population of particles with a D50 value of 7 microns or greater. In some embodiments, the supported catalyst particles have a D10 value of 0.3 microns or greater, or 0.5 microns or greater. Further, the supported catalyst particles have an average particle size of greater than or equal to (i.e., at least) 20 microns, 30 microns, or 40 microns. In some embodiments, the porous fibrillated polymeric membrane includes a volume fraction that satisfies the relationship wherein at least 40% of the pores include a pore size (measured by mercury porosimetry) of greater than or about 1 micron, greater than or about 2 microns, greater than or about 3 microns, greater than or about 4 microns, greater than or about 5 microns, greater than or about 6 microns, greater than or about 7 microns, greater than or about 8 microns, greater than or about 9 microns, greater than or about 10 microns, greater than or about 11 microns, greater than or about 12 microns, greater than or about 13 microns, greater than or about 14 microns, or greater than or about 15 microns.

The polymers forming the fibrillated polymeric film include or are formed from fixed catalyst particles selected to be resistant or inert to degradation by components present in the fluid stream for the intended use. In one embodiment, the polymer forming the fibrillated polymeric film is a polymer that is inert or solvent resistant to the solvent. In particular, the polymer is insoluble and inert to the solution in which it is used. In some embodiments, the fibrillated polymeric film may be perforated. As used herein, the term "perforations" refers to perforations (e.g., holes) that are spaced apart on some or all of the film. The fibrillated polymeric film may include or be formed from: polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), poly (ethylene-co-tetrafluoroethylene) (ETFE), ultra-high molecular weight polyethylene (UHMWPE), polyethylene, parylene (PPX), polylactic acid (PLLA), Polyethylene (PE), expanded polyethylene (ePE), and any combination or blend thereof. It should be understood that throughout this disclosure, the term "PTFE" includes not only polytetrafluoroethylene, but also expanded PTFE, modified PTFE, expanded modified PTFE and expanded PTFE copolymers, such as described in U.S. patent No. 5,708,044 to Branca, U.S. patent No. 6,541,589 to bailie, U.S. patent No. 7,531,611 to Sabol et al, U.S. patent No. 8,637,144 to Ford, and U.S. patent No. 9,139,669 to Xu et al. The porous fibrillated polymeric film may also be formed from one or more monomers of tetrafluoroethylene, ethylene, p-xylene, and lactic acid. In at least one embodiment, the porous fibrillated polymeric film includes or is formed from solvent inert submicron fibers of expanded fluoropolymer.

In some embodiments, the fibrillated polymeric film is a Polytetrafluoroethylene (PTFE) film or an expanded polytetrafluoroethylene (ePTFE) film having a node and fibril microstructure. The fibrils of the PTFE particles are interconnected with other PTFE fibrils and/or nodes to form a network structure within and around the supported catalyst particles, effectively immobilizing them. Thus, in one non-limiting embodiment, the fibrillated polymeric film may be formed from a network of PTFE fibrils that immobilize and embed the supported catalyst particles within the fibrillated microstructure.

Porous fibrillated polymeric films may be formed by blending fibrillated polymeric particles with supported catalyst particles, followed by uniaxial or biaxial expansion, for example, by means generally taught in the following documents: U.S. patent No. 7,710,877 to Zhong et al, U.S. patent publication No. 2010/0119699 to Zhong et al, U.S. patent No. 5,849,235 to Sassa et al, U.S. patent No. 6,218,000 to Rudolf et al, or U.S. patent No. 4,985,296 to Mortimer, jr. As used herein, the term "fibrillating" refers to the ability of a polymer to fibrillate to form nodes and fibril microstructures. Mixing can be accomplished, for example, by wet or dry mixing, by dispersion or by coagulation. The time and temperature at which mixing occurs will vary with the particle size, the materials used and the amount of particles co-mixed and can be determined by one skilled in the art. Uniaxial or biaxial expansion can be carried out in a continuous or batch process known to those skilled in the art, as generally described in U.S. Pat. No. 3,953,566 to Gore and U.S. Pat. No. 4,478,665 to Habis (Hubis).

Catalytic composite as a filter medium

Fig. 1 depicts a catalytic filter material 100. The catalytic filter material includes a catalytic composite 102 and a batt layer 104. The upstream direction 106 is defined in terms of the primary direction of incoming fluid flow 110, and the downstream direction 108 is defined in terms of the primary direction of outgoing fluid flow 112. The felt layer 104 is located upstream of the catalytic composite 102 and is operable to collect debris 120 (e.g., dust, etc.) from the incoming fluid stream 110. In some embodiments described herein, the catalytic composite is perforated therein. The perforated catalytic composite allows fluid to pass easily through the catalytic composite while still interacting sufficiently with the supported catalyst particles permanently embedded within the porous fibrillated polymeric film to dispose of contamination in the fluid stream. The catalytic material that catalyzes the fluoropolymer membrane is selected to target specific contaminant species. For example, as shown in FIG. 1, the supported catalyst particles of the catalytic composite 102 may include a material suitable for catalyzing NO_XSubstances (e.g. NO, NO)₂，NO₃) Reduction to water and nitrogen or removal of NO_XCatalytic substance of matter TiO₂、V₂O₃、WO₃Some or all of these. However, other catalytic materials suitable for converting different pollutants may be substituted or included, e.g. for the disposal of carbon monoxide (CO), dioxins/furans, ozone (O)₃) And other contaminants.

In one embodiment, catalytic composite 102 is perforated, including intact portion 116 and perforations 118. Perforations 118 may be formed in catalytic composite 102 by a needling operation and may vary in size depending on the needling operation. Suitable needle punching operations may include a needle punching operation in which a needle is pressed through a membrane while piercing and displacing material, or a needle punch operation in which a needle removes a portion of material. In one embodiment, the catalytic composite 102 is needle punched, and the perforations correspond to a needle diameter of 0.1mm to 3.0 mm. In another embodiment, the catalytic composite 102 is punched with needles, and the perforations correspond to a needle diameter of 0.1mm to 3.0 mm. In one embodiment, perforations 118 are spaced throughout catalytic composite 102. In other embodiments, perforations 118 are located only in some portions of catalytic composite 102. The perforations, in combination with the pores of the catalytic composite 102, provide the catalytic filter material 100 as a whole with gas permeability suitable for filtration applications.

In various embodiments, perforations 118 are formed in the catalytic composite 102 in a pattern. Larger perforations correspond to larger spacings between adjacent perforations and smaller perforations correspond to smaller spacings between adjacent perforations. The perforation pattern may be designed such that the airflow through the perforations is uniform across the catalytic composite 102. Some suitable patterns include a square pattern, a triangular pattern, an amorphous pattern, or any other comparable pattern that generally conforms to a minimum perforation density. In one embodiment, the patterned perforations are closely spaced.

The catalytic composite 102 facilitates the catalytic reduction or removal of the target species by the supported catalyst embedded in the porous filled polymer membrane. Perforations 118 may reduce the pressure drop across catalytic composite 102 (i.e., increase permeability) making it useful in a variety of applications. The passage of fluid through the perforations 118 does not destroy the effectiveness of the catalytic composite 102 as a catalytic structure, even if a significant portion of the fluid flows through the perforations rather than through the unperforated intact portion 116. In some embodiments, the perforations extend completely through the membrane and provide a channel for a substantial portion of the fluid to pass therethrough. However, sufficient fluid contacts the porous fibrillated polymeric film and interacts with the supported catalyst embedded therein to effectively dispose of contaminants in the fluid stream. Without wishing to be bound by theory, it is believed that the assembled combination of the catalytic composite 102 and the batt layer 104 contributes, at least in part, to the efficacy of the catalytic composite 102 as a catalytic filter. For example, the catalytic composite 102 interacts with the batt layer 104, and the internal structure 114 (e.g., staple fibers) of the batt layer 104 causes the incoming fluid stream 110 to circulate within the batt layer 104, particularly along the interface 122 of the batt layer and the catalytic composite 102. This circulation brings the incoming fluid stream 110 into sufficient contact with the catalytic composite 102 to catalyze the incoming fluid stream and reduce and/or remove chemical contaminants.

The batt 104 may comprise any suitable porous structure capable of filtering particulate contaminants 120 and/or conditioning the incoming fluid stream 110 for introduction to the catalytic composite 102. The felt batt 104 may be formed of any suitable woven or nonwoven having a highly porous internal structure such as, but not limited to, a staple fiber woven or nonwoven, a PTFE staple fiber woven or nonwoven, a fleece formed from fluoropolymer staple fibers, or a fluoropolymer staple fiber woven or nonwoven. In one embodiment, the felt layer 104 is a PTFE fiber felt or PTFE fiber fleece.

In at least one embodiment, the constituent layers of catalytic filter material 100 are joined together by a needle punching or pin punching operation, i.e., a needle or punch may be pressed through both the assembled batt layer 104 and catalytic composite 102 to locally deform the layers to hold the layers in contact with each other. Typically, the needle punching operation penetrates and deforms the material, and the needle punching operation also removes a small piece of material; both of these operations may be referred to as "needling". The layers of the catalytic filter material 100 may also be held together by lamination or applied heat treatment, by an adhesive (typically a discontinuous adhesive to maintain porosity), by an external connector, by weaving or other similar means of attachment, or by any suitable combination of the above. In one embodiment, the constituent layers of the catalytic filter material 100 are bonded by needle punching and/or pin punching, followed by a subsequent heat treatment to fix the composite and form the catalytic composite. Alternatively, the constituent layers of the catalytic filter material 100 may be bonded together by laminating the layers together after perforations have been applied to the catalytic composite 102, and then heat treating the layered assembly to form the catalytic composite.

In various embodiments, the supported catalyst particles may extend into the pores of the porous fibrillated polymeric film; and in some embodiments may extend into the perforations. In various embodiments, the catalytic article may or may not be assembled with a support layer or a felt layer as described above. In other words, it is possible to produce a catalytic filter material comprising a perforated porous polymeric membrane in which the catalytic particles are embedded, and which is free of a support or a felt layer.

The catalytic filter material 100 may also be combined with other layers. For example, fig. 2 shows a catalytic filter material 200 that includes additional layers. The catalytic filter material 200 and its components may be described with an upstream side 212 facing an incoming fluid stream 216 and a downstream side 214 from which an outgoing fluid stream 218 exits. FIG. 2 shows a catalytic article 202 similar to catalytic article 102 (FIG. 1) having a first felt layer 204 and a protective porous membrane 208 laminated in an upstream direction 212 of the fluoropolymer membrane 202; with a supporting scrim 206 and a second batt layer 210 in a downstream direction 214. The catalytic filter material 200 is capable of filtering particulates 220 that may be suspended in the incoming fluid stream 216 and also capable of reducing or removing chemical contaminants by catalytic reaction at the catalytic article 202 in the catalytic filter composite.

The catalytic article 202 is formed from the perforated catalytic article 102 as described above with reference to fig. 1, including the intact portion 222 interrupted by the perforations 224. Perforations 224 may be formed in catalytic article 202 by a needle punching operation or by a needle punching operation, as described above with reference to perforations 118 (fig. 1). Similar to the catalytic filter material 100 (fig. 1), the configuration of the adjacent catalytic article 202 and first batt layer 204 provides for the incoming fluid flow 216 to circulate within the internal structure 226 of the first batt layer and about the embedded catalytic particles of the catalytic article 202 before passing through the catalytic article 202 at the perforations 224 or via the holes in the intact portion 222. According to various embodiments, the catalytic article 202 and the first batt layer 204 may have similar thickness, permeability, and/or material properties as the catalytic article 102 and the batt layer 104 described above.

In one embodiment, the protective film 208 is located on the upstream side of the first batt layer 204 and is capable of capturing or preventing the entry of particles 220. The protective film 208 can trap particles (e.g., dust, soot, ash, etc.) to prevent the particles from entering the catalytic article 102 or the batt layer 104, thereby preventing or minimizing clogging of the perforations 118 of the film and preventing or minimizing fouling of the porous fibrillated polymer film that may impede contact with the supported catalytic particles embedded therein. The protective film 208 may collect the particles 220 in a film or cake that may be easily cleaned from the protective film 208, thereby providing easy maintenance of the catalytic filter material 200. The protective membrane 208 may be constructed of any suitable porous membrane material, such as, but not limited to, a porous woven or nonwoven membrane, a PTFE woven or nonwoven, an ePTFE membrane, a fluoropolymer membrane, and the like. The protective film 208 may be porous or microporous and may be attached to the first batt layer 204 by lamination, heat treatment, a discontinuous or continuous adhesive, or other suitable joining method.

In accordance with at least one embodiment, the catalytic article 202 is supported by a scrim 206, the scrim 206 providing structural support without significantly affecting the overall fluid permeability of the catalytic filter material 200. Scrim 206 may be any suitable porous backing material capable of supporting catalytic filter material 200. The scrim may be, for example, a fluoropolymer woven or nonwoven, a PTFE woven or nonwoven, or, in one particular embodiment, an ePTFE fiber (e.g., 440 dtex)Fibers, available from w.l. gor, elkton, maryland, Inc (WL Gore and Associates). The scrim 206 may be disposed downstream 214 of the catalytic article 202, e.g., downstream of and adjacent to the catalytic article 202, or downstream of the catalytic article 202And separated from the catalytic article 202 by one or more other layers. The scrim 206 may be attached to the catalytic article 202 by a needle punching or needle punching operation. The scrim 206 may also or alternatively be attached to the catalytic article 202 by: by heat treatment; laminating the layers together by one or more connectors; or by an adhesive, such as a thin layer of adhesive (which may be continuous or discontinuous) between the scrim 206 and the catalytic article 202; or by any suitable combination of two or more of the above methods, including needle punching or pin punching operations. Typically, the air permeability of scrim 206 is higher than the air permeability of catalytic article 202.

In one embodiment, the catalytic filter material 200 may also include a second batt layer 210, which is located in the downstream direction 214 of the catalytic article 202. The second felt batt 210 may have a similar construction and dimensions as the first felt batt 204, for example, the second felt batt may comprise or be composed of any suitable woven or non-woven, such as, but not limited to, a short fiber woven or non-woven, a PTFE short fiber woven or non-woven, or a fluoropolymer short fiber woven or non-woven. For example, the second batt layer 210 may be a PTFE fiber felt or a PTFE fiber fleece.

The catalytic article 202, scrim 206, and first and second batt layers 204 and 210 may be joined together by a needling or needle punching operation, other methods described with respect to the catalytic article 102 and batt layer 104 of fig. 1, or a combination of these techniques. In one embodiment, only the catalytic article 202 is perforated because the perforations provide suitable fluid flow through the catalytic article 202, while the other layers generally have a higher permeability than the catalytic article 202, and therefore do not require any perforations. Alternatively, a sub-assembly of the above elements, such as the catalytic article 202 and scrim 206, the catalytic article 202 and first batt layer 204, or the catalytic article 202, first batt layer 204 and scrim 206, may be perforated by a process of joining the layers together using needling or needle punching. Some or all of the layers may further be joined by heat treatment, adhesives, or other suitable joining methods. The protective film 208 may be attached to the remaining layers of the catalytic filter material 200 by adhesion, heat treatment, or other methods that do not cause the protective film 208 to perforate. Alternatively, the protective membrane 208 may be attached to the remainder of the catalytic filter material 200 by needling or pin punching.

The catalytic filter materials 100, 200 described above with reference to fig. 1 and 2 are illustrative embodiments of catalytic composites that utilize a perforated catalytic article adjacent to and downstream of a batt layer, the combination of which is capable of directing a contaminated fluid to flow along and through the catalytic article to mitigate contamination in the fluid. Various other components, such as the protective film 208, scrim 206, and second felt layer 210 described above with reference to fig. 2, enhance the strength of the catalytic filter material 200 and may provide additional advantages, such as improved filtration performance and/or reduced particle penetration.

Other combinations of the layered elements described above with respect to fig. 2 are possible and are considered within the scope of and without substantially departing from the present disclosure, and it is also possible to add other filtering or catalytic elements thereto. For example, one or more of the protective film 208, the first and second batt layers 204, 210, and the scrim 206 may have catalytic properties. Additionally, layers may be added and/or removed between the layers described above with respect to fig. 2, such as other porous fibrillated polymer films, other felt layers, other catalytic materials, such as catalytic felts (e.g., those described in U.S. patent No. 5,843,390 to Plinke et al), other support layers or scrims, or fewer layers than the above.

Additional one or more catalytic fluoropolymer membranes similar to catalytic article 202 may be provided; which are located upstream or downstream of the catalytic article 202 and contain different catalysts or catalyst groups to enable the catalytic filter material 200 to catalyze the disposal of a variety of specific contaminants in a fluid stream. In one embodiment, additional porous fibrillated polymer films and additional intermediate batt layers and/or scrims may be provided upstream and downstream of each porous fibrillated polymer film, respectively, to separate the porous fibrillated polymer films and provide space for flow communication between the porous fibrillated polymer films.

Fig. 3 shows an alternative catalytic filter material 300 comprising only a catalytic article 302, a batt layer 304 upstream of a fluoropolymer membrane, and a protective membrane 306 upstream of the batt layer. Here, the combination of protective membrane 306, felt layer 304, and catalytic article 302 functions in much the same manner as membrane 208, first felt layer 204, and catalytic article 202 described above with reference to fig. 2. The incoming air flow 314 passes through the protective membrane 306, which protective membrane 306 at least partially blocks the entry of particles 316. The incoming airflow 314 then passes through the batt 304, i.e., within the internal structure 312 of the batt, where the airflow 314 may interact with the catalytic article 302 and begin to pass through the catalytic article 302.

As described above with respect to the catalytic article 102 (fig. 1), the catalytic article 302 is perforated such that a portion of the incoming airflow 314 passes through the entire portion 308 of the catalytic article, while another, typically greater, proportion of the portion passes through the perforations 310. As described above, the perforations 318 may be formed by a needle punching or needle punching operation. Two or in some cases all three of the catalytic article 302, felt layer 304, and protective membrane 306 may be needled or needle punched together in a single operation, thus forming both the perforations 310 and connecting the layers. Additional joining steps, such as heat treatment or bonding steps, may be used to join the layers together.

Fig. 4 depicts a method of catalytic composite assembly. For example, as shown in fig. 4, a catalytic composite (e.g., catalytic filter material 100, 200, 300, fig. 1-3) may be assembled (402) by laminating together a catalytic fluoropolymer membrane and a felt layer (e.g., PTFE staple fleece or similar layer) to form a layered assembly. The first batt layer is laminated on the first upstream side of the catalytic article. Other layers may be assembled with the first batt layer and the catalytic article, such as a scrim adjacent to a downstream side of the catalytic article opposite the first batt layer (404), and a second batt layer adjacent to the downstream side of the scrim (406). A protective porous membrane layer may be added to the assembly adjacent the upstream side of the first batt layer (408). The assembly layer or a portion of the assembly layer may be subjected to a perforation step, including needle punching, or both (410). Where only a portion of the assembled layers are perforated, a needling or needling step (410) may be performed prior to one or more of the above-described stacking steps, such as needling or needling the catalytic article prior to assembly with the first batt layer, needling or needling the combined catalytic article and first batt layer prior to stacking the scrim, needling or needling the combined catalytic article, scrim, and first batt layer prior to adding other layers, and so forth. The needling or needle punching step may produce poor adhesion between the layers, may be suitable for joining the layers individually, or may supplement the use of adhesives, connectors, or heat treatment to bond the layers to form the catalytic filter material. For example, the assembly layers or a portion of the assembly layers may further be joined together by an adhesive (412), which may include a continuous or discontinuous adhesive that bonds two or more layers. The assembly layers or a portion of the assembly layers may be joined together (414) by a heat treatment that at least partially adheres the layers together. Note that as with the perforation step (410), the bonding and/or heat treatment steps (412, 414) may be performed at an intermediate stage of assembly, for example, prior to the addition of the scrim (406), second batt layer (408) or porous protective film (408). For example, prior to the needling or needling step, a layered assembly comprising a fluoropolymer membrane, a scrim, and first and second batt layers may be produced, followed by lamination of an unperforated protective membrane layer, followed by heat treatment to form a catalytic filter material. Alternatively, a layered assembly (including a protective film layer) comprising all of the above layers may be produced, subsequently needle punched or punched and then fixed by heat treatment to form a catalytic composite; alternatively, the heat treatment step (414) may be omitted or replaced with the bonding step (412).

A simplified block diagram illustrating a particular assembly process 500 is shown in fig. 5. According to one embodiment, a first carding operation may be performed on the staple fibers 502 to produce a first batt layer or fleece 504; a second carding operation is performed on the other staple fiber 510 to produce a second batt or fleece 512. These batt layers 504, 512 may be laminated on either side of the catalytic article 506 and scrim 508 to form a layered assembly that is subjected to a perforation step, such as a needle punching process or needle punching process 514. This step results in the catalytic filter material being joined together and the catalytic article 506 being perforated therein.

A heat-setting process 516 may be used to further join the layers. The heat-set material may then be wound 518, or other manufacturing steps may be performed. A layer addition process 520 may be included to add a layer to the catalytic composite, such as a protective film (e.g., protective film 208 (fig. 2) or 306 (fig. 3)). The other layers or protective films are combined with the tie layer after the needle punch/needle punch process 514 so that the other layers are not subjected to needle punching but are still attached to the assembly by the heat setting process 516. Other layers or films may be adhered or otherwise attached to the catalytic composite after the heat-setting process 516 but before winding 518. Alternatively, other layers or films may be added to the assembled layers prior to the needling or needling process 514, and thus may also be perforated.

In the above embodiments, the porous fibrillated polymeric film is effective to distribute the catalyst particles throughout the film in both the length and thickness directions. In addition, the porous nature of the fibrillated polymeric film allows for efficient and reliable transport of fluids across the catalyst surface. In addition, since the supported catalyst particles are permanently embedded within the fibrils of the porous fibrillated polymer film, the loss of catalyst is minimized.

Test method

Particle size distribution measurement

The particle size distribution of the catalyst powders in examples 2, 5 and 6 was measured using a Microtrac S3500 laser particle size analyzer. The apparatus was set up to measure the volume distribution of 64 channels with 1408 μm at the upper edge and 0.0215 μm at the lower edge. The S3000ALT run mode was used with residual disabled, filter enabled, and 20 seconds run time. The particles were set to have a reflection of the irregular particle shape with a fluid reference index of 1.3. The particle solution was prepared by adding approximately 0.6mL of the powder to 20mL of IPA test solution (isopropyl alcohol with a carrier additive of odorless mineral spirits and lecithin). The solution was then sonicated for 30 seconds. Prior to testing, the machine Setzero was performed on the tester, and then the sample solution was added and tested in the above settings. The average volume diameter, D10, D50, and D90 values used in the examples were taken directly from the output data captured in the Microtrac test report. The volume percentage of particles below 9 μm was determined by interpolating the cumulative volume distribution percentage values between the 7.78 μm and 9.25 μm channels.

The particle size distribution of the catalyst powder in example 1 was optically measured using a Horiba LA-350 particle size analyzer (Horiba, New bamboo, Taiwan). Selecting TiO in water₂As the type of sample to be analyzed. Two aqueous solutions were used in the measurement. Solution 1 was prepared by adding 0.4 g of TKPP (tetrapotassium diphosphate) to 1 liter of water. Solution 1 was used to flush the particle size analyzer and perform blank measurements. Solution 2 was prepared by adding 0.4 gram of TKPP and 0.75mL of Photolow wetting agent (Kodak Photo-Flo 200 solution; Eastman Kodak, Rochester, NY) to 1 liter of water. Solution 2 serves as a dispersion medium for the catalyst powder. To disperse the catalyst powder, approximately 20mL of solution 2 was added to 0.25g of catalyst powder. After 5 minutes of sonication, the catalyst powder dispersion was slowly added to the sampling bath in the particle size analyzer using a micropipette to obtain a light transmittance in the range of 80-90%. Particle size distribution measurements are taken when the real-time distribution window is stable.

Mercury porosity test

Porosity measurements were performed on a Micromeritics AutoPore V mercury porosimeter (mike instruments, nokros, georgia, usa) using Micromeritics MicroActive software version 2.0. Pure silver from quadruple distillation-purity 99.9995% (berthehem Apparatus, brix pennsylvania) was used as received for the test. The test uses a solid penetrometer with a bulb volume of 5cm³The volume of the rod is 0.392cm³(SN: 07-0979). The composite sample pieces were cut into 1cm X2 cm strips and enough of these strips were weighed on an analytical balance to provide a total mass of about 0.25 g. After labeling the mass, the sample piece was placed in a penetrometer.

The test parameters were as follows: (1) place the penetrometer in the low pressure port on the AutoPore and evacuate to 50 μm hg and then for 5 minutes without restriction; (2) the penetrometer was then filled with mercury at 0.5psia (-3.5 kPa) and equilibrated for 10 seconds; the capillary was then pressurized with nitrogen at a pressure that was stepped up to 30psia (-0.21 MPa), equilibrated for 10 seconds in each step, and then the intrusion volume was determined by standard capacitance measurements using a penetrometer capillary; (3) after returning to atmospheric pressure, the osmometer was removed from the low pressure port and weighed to determine the amount of mercury added; (4) the penetrometer was then placed into a high pressure port on the AutoPore and the pressure was again raised to about 60,000psia (-413.7 MPa) by a series of steps, each of which was equilibrated for 10 seconds, before intrusion volume measurements were taken.

The intrusion volume V at any pressure can be determined by capacitance measurement using a pre-calibrated capillary (i.e., a cylindrical capacitor where the external contact is a metallized coating on the outer surface of the glass capillary, the internal contact is liquid mercury, and the dielectric is the glass capillary). The total intrusion volume is divided by the sample mass to give the specific intrusion volume (in mL/g).

The volume occupied by the sample was calculated at two extreme target pressures, 0.5psia (-3.5 kPa) and 60,000psia (-413.7 MPa). Since the penetrometer has a known calibration volume, the difference between this volume and the mercury volume (determined by the mass increase after mercury addition at low pressure and the density of the mercury) gives the volume of the sample including any pores. The bulk density of the sample is obtained by dividing the mass of the sample by the volume at this low pressure. At high pressure, mercury is pushed into the pores in an amount given by the intrusion volume, and the skeletal density can be approximated by dividing the sample mass by the adjusted sample volume (e.g., low pressure volume minus total intrusion volume).

Total hole area

The total aperture area is determined by a series of intermediate calculations. First, the diameter of the filled hole at a given pressure is calculated using the walsh equation:

wherein D_iI thPore diameter of pressure point, γ ═ surface tension, θ ═ contact angle, P_iPressure. Then, the average diameter of the ith point is taken as:

Dm_i＝(D_i+D_i-1)/2

the incremental specific intrusion volume at point I is based on the total intrusion volume (I) at each point_i) And calculating to obtain:

Ii_i＝I_i–I_i-1

finally, the incremental specific pore area at point i is calculated from the incremental intrusion volume and the mean diameter according to the following formula:

Ai_i＝(4X Ii_i)/Dm_i

then, the total (i.e., cumulative) specific hole area for the ith point is calculated as follows:

A_i＝Ai_i+Ai_i-1+…+Ai_i。

bulk density

The bulk density of the sample is the density of the solid including all open pores and internal void volumes. Bulk density is calculated by dividing the sample mass by the low pressure mercury intrusion volume. The sample mass was determined by weighing on an analytical balance with a sensitivity of +/-0.01 mg.

Bulk density of M/(V)_{Low pressure})

Skeleton density

Skeletal density is the density of a solid calculated by excluding all open pores and internal void volumes. The skeletal density was calculated by dividing the sample mass by the adjusted sample volume (low pressure volume minus total intrusion volume). The sample mass was determined by weighing on an analytical balance with a sensitivity of +/-0.01 mg.

Framework density ═ M/((V)_{Low pressure})–(V_{High pressure}))

Wherein, V_{Low pressure}Is the sample volume, V, at 0.5psia (. about.3.5 kPa)_{High pressure}Is the total intrusion volume at 60,000psia (-413.7 MPa).

Total porosity

The total porosity in the substrate is the void volume of the sample divided by the total volume of the sample. Can be calculated as:

% porosity 100 (total intrusion volume at 60,000psia (413.7 MPa))/(0.5 psia)

(-sample volume at 3.5 kPa).

Thickness of

The film was placed on a Kafer FZ1000/30 gauge (kaifames scale, bardeng-tenburg, germany) (Messuhrenfabrik GmbH, Villingen-Schwenningen, Germany)) between two plates. The average of three measurements was used.

Examples

Example 1

Preparation and evaluation of composite membranes

A series of composite membranes of Polytetrafluoroethylene (PTFE) and catalyst were prepared using the general dry blending process taught in U.S. patent No. 7,791,861 to Zhong et al to form composite tapes which were then uniaxially expanded according to the teachings of gore U.S. patent No. 3,953,566. The resulting porous fibrillated expanded ptfe (ePTFE) composite membrane includes supported catalyst particles permanently embedded and fixed within the ePTFE nodes and fibril matrix. Table 1 summarizes detailed information for various ePTFE composite membranes.

TABLE 1

ePTFE composite membrane

The filler 1 being vanadium pentoxide on titanium dioxide particles

The catalytic composite comprises filler particles of 30% or 50% by weight of vanadium pentoxide (CRI Catalyst, division of Royal Shell, The Netherlands) and two different particle size variants (called "large" and "small") on titanium dioxide particles. The distribution was measured by the Horiba instrument described in the test methods section above. The raw particle size distribution data output by the Horiba instrument is shown in fig. 6.

The "small" catalyst size variation was unimodal and the weighted distribution of the raw particle size data yielded the statistical data shown in table 2.

TABLE 2

Particle distribution statistics for "small" catalyst variants

The average particle size was about 1.24 μm with a standard deviation of 1.53. mu.m.

The "large" catalyst size variant appeared to be multimodal, and the weighted distribution of the raw particle size data yielded the statistical data shown in table 3.

TABLE 3

Statistics of particle size distribution for "small" catalyst variants

The average particle size was about 28.9 μm with a standard deviation of about 49.8. mu.m.

FIG. 6 shows the actual particle size distribution of the "large" and "small" variants as measured by the Horiba instrument described above.

NO_xEfficiency of reaction

Prior to conducting the catalytic performance test, small holes were manually punched in the catalytic composite using a manual punch tool to achieve gas permeability. Testing catalytic NO of catalytic composite membranes against simulated flue gas_xThe reaction efficiency. Briefly, a 4.5 inch (. about.1.77 cm) by 4.5 inch (. about.1.77 cm) square of catalytic film (e.g., sample) was placed in a sample holder located within the reaction chamber. The sample is exposed to N at 200 deg.C₂The equilibrium simulates in the flue gas. Simulation ofThe flue gas contains 360ppm NO and 340ppm NH₃6% by volume of O₂And the total flow rate was 4.2 liters/minute. To determine NO_xEfficiency of reaction, using MKS MULTII-GAS^TM2030D FTIR Analyzer (MKS instruments Inc. of Andoft, Mass.) monitoring of NO and NH₃Upstream and downstream concentrations (i.e., relative to the catalytic membrane). Calculating NO according to the following formula_xReaction efficiency, where 'NO' represents the concentration of NO in the respective stream.

The mass of catalyst per unit area (MPA) of each catalytic composite membrane was calculated. Catalyst MPA represents the catalytic vanadium pentoxide/titanium dioxide mass per unit area (by mixing 0.1 m)²Round specimens (cut using a PS100 punch system; Karl Schroeder, Wehmem, Germany (Karl)KG, Weinheim, Germany)) divided by the known punch area and the resulting number multiplied by the mass fraction of catalyst present in the catalytic composite membrane).

Figure 7 shows that higher performance is obtained by using "larger" catalyst particles. Under the condition of constant catalyst mass per unit area (MPA), compared with a small particle catalytic composite belt, the reaction efficiency of the large particle catalytic composite membrane is about 10-15% higher. Mercury porosity measurements were performed as described in the test methods section above. Mercury porosity analysis showed that membranes made with "large" catalytic filler particles generally exhibited more pores in the 1-100 μm diameter size range, indicating that the catalytic particle size affected the structure and catalytic efficiency of the membrane. FIG. 8 shows a mercury porosity plot showing the number of pores versus pore diameter for representative "large" and "small" particulate catalytic composite membranes.

Fig. 9A and 9B show that catalytic composites prepared with "large" catalytic filler particles generally have smaller nodes, which increases the exposure of the catalytic filler particles to the reactant gases.

Example 2

Preparation of catalytic composite membranes and NO_XEvaluation of reaction efficiency as a function of catalyst particle size

5 composite membranes of Polytetrafluoroethylene (PTFE) and catalyst were prepared using the general dry blending method taught in U.S. Pat. No. 7,791,861 to Zhong et al to form composite tapes which were then uniaxially expanded according to the teachings of U.S. Pat. No. 3,953,566 to Goll. The resulting porous fibrillated expanded ptfe (ePTFE) composite membrane includes supported catalyst particles permanently embedded and fixed within the ePTFE nodes and fibril matrix. The properties of each sample are listed in table 4. The particle size was measured by the Microtrac method described in the test methods section above.

TABLE 4

¹Vanadium pentoxide on a TiO2 support

Before conducting the catalytic performance test using the method described in example 1, small holes were manually punched in the catalytic composite using a manual punching tool to achieve gas permeability. The membranes were tested for NOx reaction efficiency using the method described in example 1. The membrane efficiency results are plotted against grams per square meter of catalyst as shown in figure 10, from which it can be seen that the performance is significantly improved when using particles with a mean of 40 microns compared to an average particle size of 0.9 or 6.5 microns.

Example 3

NOx reaction efficiency of catalyst powder

The NOx reactions on the "small" and "large" catalyst powders in example 1 were carried out in a fixed bed quartz flow reactor at 200 ℃. The catalyst powder (0.2g) was mixed with 1.0g of PTFE powder before being placed in the reactor. The feed gas mixture contained 360ppm NO, 340ppm NH₃6% by volume of O₂The balance being N₂. The NOx reaction was measured at total flow rates of 1.19 and 1.78 liters/minute. To determine NO_xEfficiency of reaction, using MKS MULTII-GAS^TM2030D FTIR analyzer(MKS instruments, Andov, Mass.) upstream NO concentration (i.e., the concentration of NO entering the chamber prior to exposure to the filter media; NO)_Into) And downstream NO concentration (NO)_{Go out}). Calculating NO according to the following formula_xReaction efficiency, where 'NO' represents the total concentration of NO in the respective stream.

NO_xReaction efficiency (%) - (NO)_Into–NO_{Go out})/NO_Into×100％。

As shown in fig. 11, at each flow rate tested, the sample containing the smaller particle size powder catalyst had a higher NOx reaction (removal) efficiency relative to the larger particle size powder catalyst.

Example 4

Surface area of ePTFE composite membrane

Brunauer-Emmett-Teller (BET) surface area measurements of ePTFE composite membranes described in example 1 were derived by QuantachromeSurface area Analyzer (Anton Paar GmBH, Graz, Austria) for N₂Measurement of adsorption. All ePTFE composite membrane samples were vacuum degassed at 150 ℃ for 2 hours. The surface area was calculated using the BET method (Brunauer et al, (1938) JACS 60(2): 309-. In this method, P/P0 in the range of 0.05 to 0.35 is applied.

For an ePTFE composite membrane with a filler loading of 30 wt% and a "small" filler size, the average surface area was obtained by adding the surface areas of samples 1, 2, 3, and 12 (table 1) and dividing by 4. For an ePTFE composite membrane with a filler loading of 30 wt% and a "large" filler size, the average surface area was obtained by adding the surface areas of samples 6, 8, 15, 16, 23, and 24 (table 1) and dividing by 6. The data are shown in figure 12. It was concluded that the average surface area of the ePTFE composite containing the "larger" catalyst particles was greater at 30 wt% filler loading.

For an ePTFE composite membrane with a filler loading of 50 wt% and a "small" filler size, the average surface area was obtained by adding the surface areas of samples 19, 20, and 22 (table 1) and dividing by 3. For an ePTFE composite membrane with a filler loading of 50 wt% and a "large" filler size, the average surface area was obtained by adding the surface areas of samples 5,7, 9, 10, 13, and 14 (table 1) and dividing by 6. The data are shown in figure 13. It was concluded that the average surface area of the ePTFE composite containing the "larger" catalyst particles was greater at 50 wt% filler loading.

Example 5

Effect of percentage of large particle batch materials by weight and volume on NOx efficiency

For this example, the catalytic powder was taken from two batches, one with an average particle size of 1-2 microns (batch M) and the other with an average particle size of 69 microns (batch X), and the particle size distributions of the two samples were measured using the Microtrac system described in the test methods section above. Further, for batch X, 85% of the particles were greater than 9 microns with an average particle size of 69 microns, D90 of 149 microns and a maximum particle size of 500 microns. The bulk density of each batch was measured by weighing 300cc of sample taken from each batch in a cup. The bulk density of the 1-2 micron catalyst batch (batch M) was determined to be about 40g/cc (sample size n 7), while the bulk density of the 69 micron average particle size batch (batch X) was determined to be about 100g/cc (sample size n 7), or about 2.4 times the bulk density of the first batch (batch X). From these two batches (batch X and batch M) new batch formulations were prepared with "large" particulate filler, with a gradually increasing content of the 69 micron mean particle size batch (batch X), resulting in the following batches, as shown in table 5 below.

TABLE 5

Batch number formulation for percent of large particle filler by weight and volume

Each batch was mixed with PTFE resin at a ratio of 1 part catalytic capacity to 2 parts PTFE or 33 wt% filler, agglomerated, and converted to ePTFE tape using the methods described in the previous examples and by the methods described in Zhong et al, U.S. patent No. 7,791,861. The tape was then uniaxially expanded at 3:1 to form an ePTFE membrane according to the teachings of gore, U.S. patent No. 3,953,566. NOx efficiency of ePTFE membranes was obtained by measuring each membrane according to the method set forth in example 1. In addition, replica films containing 1-2 micron sized particles, previously fabricated and tested for NOx efficiency, are also included in the data sets shown in FIGS. 14 and 15.

Figure 14 shows that there is a transition point where the NOx efficiency increases from the 1-2 micron baseline, i.e., when the catalyst mixture contains about 33 wt% of a 69 micron average "large" particle size (batch X). The NOx efficiency continues to increase until the catalyst mixture contains about 50 wt.% or more of a 69 micron average particle size particle batch.

Similarly, fig. 15 shows that on a volume-to-volume basis, NOx efficiency increases with the addition of more "large" particles, starting from the baseline of the 1-2 micron particle mixture and increasing until about 30 volume percent of 69 micron average particle size particles (batch X) are included in the catalyst mixture. It was also observed that membranes containing higher content of 69 micron average particle size particles (batch X) exhibited higher NOx efficiency and had a more gritty texture than those of the low efficiency ePTFE membranes containing a higher percentage of "smaller" 1-2 micron average particle size particles (batch M).

Example 6

Catalytic article in the form of a catalytic felt

A series of composite filter materials (catalytic felts) were formed according to international patent application WO 2019/099025. The composite filter material includes a porous catalytic fluoropolymer membrane assembled with a scrim and upstream and downstream batt layers. Each felt layer is formed of a fleece formed of PTFE staple fibers. The filter material is joined together by a plurality of perforations formed by a needle punching process. The series of catalytic mats were tested for NOx reaction efficiency performance.

Four supported catalyst powder samples having the same catalyst/support composition but different particle size distributions were selected. The average particle size of sample A was 1 μm, the average particle size of sample B was 23 μm, the average particle size of sample C was 65 μm, and the average particle size of sample D was 93 μm (Table 6). The catalytic tape was then prepared using a 1:1 mass ratio of PTFE to catalyst powders a and B using the general dry blending process taught in U.S. patent No. 7,791,861 to Zhong et al, forming a composite tape, which was then uniaxially expanded according to the teachings of U.S. patent No. 3,953,566 to gore.

TABLE 6

Supported catalyst particle size information

Three uniaxial expansions were performed to produce membranes of 130%, 150% and 170% of their original tape length to produce ePTFE composite membranes with different catalyst area densities (amount of catalyst mass per square meter). Expanded PTFE composite membranes having the properties listed in table 7 were produced.

TABLE 7

ePTFE composite membrane

These membrane needled felts were then made into the above-described ePTFE composite membranes.

Finally, the catalytic felt/film composite was tested for NOx reaction efficiency as described in example 1, except that the initial perforation step was not performed. The results of the NOx reaction efficiency test are shown in fig. 16 (NOx reaction efficiency performance of four particle sizes versus catalyst area density). Fig. 16 illustrates that the felt samples incorporating "larger" sized particles (particles B, C and D) exhibit higher NOx reaction efficiency than the felt samples incorporating "smaller" particles (particles a). This increase in NOx reaction efficiency persists over the range of catalyst areal densities tested.

The invention of the present application has been described above generally and in conjunction with specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments without departing from the scope of the disclosure. Thus, it is intended that the embodiments cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.