Patent Application
20160305031
The invention relates generally to apparatuses and methods for decomposing nitrogen oxide.
Nitrogen oxide (NOx, including NO and/or NO2) is undesirable for the environment and has to be controlled. Some approaches have been proposed to decompose nitrogen oxide into nitrogen and oxygen. However, these approaches use hazardous compound such as ammonia or rigid ceramic materials, and/or cause secondary pollution by producing ammonium sulfate, besides being complex and expensive.
Therefore, while some of the proposed approaches have general use in various industries, it is desirable to provide new apparatuses and methods for decomposing nitrogen oxide.
In one aspect, the invention relates to an apparatus including a first stack having: a porous metallic current collector; a first electrode layer on the porous metallic current collector; a second electrode layer; a first electrolyte layer between the first electrode layer and the second electrode layer; a third electrode layer on the porous metallic current collector, the third electrode layer sandwiching the porous metallic current collector therebetween with the first electrode layer; a fourth electrode layer; and a second electrolyte layer between the third and the fourth electrode layers.
In another aspect, the invention relates to a method comprising: providing an apparatus described in the paragraph above; applying a first electric field between the first electrode layer and the second electrode layer; applying a second electric field between the third and the fourth electrode layers; and introducing nitrogen oxide to the apparatus to be decomposed into nitrogen and oxygen in the apparatus.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The use of “including”, “comprising” or ing” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
In the specification and the claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Moreover, the suffix “(s)” as used herein is usually intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term.
As used herein, the term “or” is not meant to be exclusive and refers to at least one of the referenced components (for example, a material) being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise.
As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances, an event or capacity can he expected, while in other circumstances, the event or capacity cannot occur. This distinction is captured by the terms “may” and “may be”.
Reference throughout the specification to “some embodiments”, “other embodiments”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the invention is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described inventive features may be combined in any suitable manner in the various embodiments.
Embodiments of the present invention relate to apparatuses and methods for decomposing nitrogen oxide.
As used herein the term “nitrogen oxide” refers to nitrogen monoxide, nitrogen dioxide, or a combination thereof. The nitrogen oxide may be from a variety of sources, such as gas turbines, internal combustion engines, and combustion devices.
Please refer to
The porous metallic current collector 102, 202 may be made of any metals or metal alloys and be in any porous forms suitable for use in apparatuses and methods for decomposing/converting nitrogen oxide to nitrogen and oxygen. In some embodiments, the porous metallic current collector 102, 202 is made of nickel. In some embodiments, the porous metallic current collector 102, 202 is in the form of mesh, porous film, foam, or any combination thereof. In some embodiments, the porous metallic current collector 102, 202 is nickel foam. In some embodiments, a porosity of the porous metallic current collector 102, 202 in a range from about 25% to about 99%.
In some embodiments, the porous metallic current collector 102, 202 is mechanical support for the first, the second, the third and the fourth electrode layers 103, 203, 104, 204, 106, 206, 107, 207 and the first and the second electrolyte layers 105, 205, 108, 208.
The porous metallic current collector may be a single layer or has more than one layer. In the embodiments of the porous metallic current collector having more than one layer, different layers may be electrically and/or mechanically connected with each other in suitable ways.
In some embodiments, as is shown in
In other embodiments, as is shown in
In some embodiments, the first stack 101, 201 includes a blocking layer 109, 209 configured to block nitrogen oxide from entering the anode layers 103. 106, 204, 207, the electrolyte layers 105, 108, 205, 208 and the porous metallic current collector 102. The blocking layer may be made of any material that blocks gas in some embodiments, the blocking layer is a glass layer. In some embodiments, the first stack 101, 201 has other layers (not shown) as is needed for the specific application environment.
The apparatus may include more than one stack, the same as or different from each other. In some embodiments, as is shown in
Each of the layers may be a single layer or comprise more than one layer depending on the needed flexibility, gas diffusion capability, and porosity. Multiple layers may be the same as or different from each other and connected in suitable ways. In each single layer, the composition may be the same or different through at least one dimension thereof.
The anode layers may be the same as or different from each other. Any of the anode layers may include any material that oxidizes oxygen ions to oxygen and any other materials that can be used in the anode layers. In some embodiments, the anode layer comprises (La0.8Sr0.2)0.95MnO3 (LSM), a combination of platinum and yttria stabilized zirconia, a combination of platinum and Gd addition ceria, or any combination thereof. In sonic embodiments, the anode layer includes materials that catalyze the oxidization of oxygen ions to oxygen. In some embodiments, the anode layer has materials that improve the discharge of oxygen.
The cathode layers may be the same as or different from each other. Any of the cathode layers may include any material that decomposes nitrogen oxide to nitrogen and oxygen and any other materials that can be used in the cathode layers. In some embodiments, the cathode layer has materials that adsorb nitrogen oxide, in some embodiments, the cathode layer includes catalysts catalyzing the decomposition of nitrogen oxide. In some embodiments, the cathode layer comprises catalysts catalyzing the decomposition of nitrogen oxide with little or no impact by the presence of oxygen. The oxygen coexisting the nitrogen oxide may be discharged from the cathode layer.
In some embodiments the cathode layer comprises La0.6Sr0.4Ni0.3Mn0.7O3 (LSNM), a combination of LSNM and Gd0.1Ce0.9O1.95 (GDC), LSNM-Zr0.89Sc0.1Ce0.01O2-x(SSZ) (50 wt % ratio), LSNM-NliO-SSZ (40 wt %, 30 wt %, 30 wt. %). NiO-SSZ (50 wt %), a combination of platinum and yttria stabilized zirconia, a combination of platinum and Gd addition ceria, or any combination thereof.
The electrolyte layers may be the same as or different from each other. The electrolyte layers may include any material that has the oxygen ion conductivity and any other suitable material. In some embodiments, the electrolyte layer comprises Gd0.1Ce0.9O1.95 (GDC), Zr0.89Sc0.1Ce0.01O2-x(SSZ), BaZr0.7Ce0.2Y0.1O3, or any combination thereof. In some embodiments, the electrolyte layer includes zeolite, alumina, silica, nitriding aluminum, SiC, nickel oxide, iron oxide, copper oxide, a calcium oxide, magnesium oxide, a zinc oxide, aluminum, yttria stabilized zirconia, scandia stabilized zirconia, perovskite oxides, such as samarium or a gadolinium addition ceria, lanthanum strontium calcium manganese, iron oxide, lanthanum silicate, Nd9.33(SiO4)6O2, AlPO4, B2O3, and R2O3, (R stands for an alkaline metal), AlPO4—B2O3—R2O glass which carries out the main component of Na and the K, porous SiO2—P2O5 system glass, Y addition BaZrO3, Y addition SrZrO3 and Y addition SrTiO3, strontium doping lanthanum manganite, a lanthanum strontium cobalt iron oxide (La—Sr—Co—Fe system perovskite type oxide), a La—Sr—Mn—Fe system perovskite type oxide, a Ba—Sr—Mn—Fe system perovskite type oxide, or any combination thereof.
When the first and the second electric fields are respectively applied between the anode layer and the cathode layer, nitrogen oxide is decomposed in the cathode layer in a reaction such as NO+2e→1/2N2+O2', nitrogen is discharged from the cathode layer, and the porous metallic current collector, if not being blocked. A porous structure for the cathode layer can increase the active surface area, the reaction rate for NO reduction and the diffusion of nitrogen oxide and nitrogen.
A dense electrolyte layer is preferred for mitigating the mixing of the gases of the cathode layer and the anode layer and reducing the ohmic resistance of the electrolyte layer. Low ohmic resistance is preferred for energy saving in NO reduction process.
Oxygen ions travel from the cathode layer through the electrolyte layer into the anode layer to be oxidized into oxygen in a reaction such as O2−−2e→1/2O2. The produced oxygen is discharged from the anode layer, and the porous metallic current collector, if not being blocked.
In some embodiments, a total reaction in one stack includes: NO=1/2N2+1/2O2.
The decomposition of nitrogen oxide may be at any suitable temperature. In some embodiments, the temperature is in a range from about 400° C. to about 800° C.
The stack described herein may be prepared by providing a porous metallic current collector and applying sequentially different layers on both sides thereof, or providing any of other layers and laminating different layers on either/both sides thereof. The layers may be applied/laminated by any suitable means such as dip coating, spray and printing.
The apparatus transmits gases separately in electrode layers and the porous metallic current collector, so there is no need for special design of gas channels. The porous metallic current collector is flexible, cheap and comparatively easy to manufacture.
The following examples are included to provide additional guidance to those of ordinary skill in the art in practicing the claimed invention. These examples do not limit the invention as defined in the appended claims.
La2O3, SrCO3, and Mn(AC)2.4H2O & NiO were ball milled in Et0H. and calcine at 1300° C. for 8 hours to prepare LSNM. X--ray diffraction (XRD) analyses confirmed that a pure phase of LSNM was obtained.
A slurry with the formula in table I below was prepared, screen printed on Ni foam (95% porosity), and sintered in argon for 6 hours to obtain a first electrode layer on the porous nickel foam. V006 was obtained from Heraeus Materials Technology LLC, 24 Union Hill Road, West Conshohocken, Pa. 19428 USA.
The temperature, the temperature change speed, and time of the sintering are shown in
A slurry with the formula in table 2 below was prepared, screen printed on the first electrode layer, and sintered in Argon for 6 hours to obtain a first electrolyte layer on the first electrode layer. The temperature, the temperature change speed, and tune of the sintering are shown in FIG-. 4. SEM analysis reveals a high density pore free electrode layer was obtained.
Four 7.5 cm long one-end open (La0.8Sr0.2)0.95MnO1 (LSM) tubes were fabricated by extruding. The outer diameter of each tube was about 1 cm, and the inner diameter was about 0.7 cm. A dense Zr0.89Sc0.1Ce0.01O2-x(SSZ) electrolyte film was then coated on each LSM tube and was co-sintered with the LSM tube at 1250° C. La0.6Sr0.4Ni0.3Mn0.7O3 (LSNM), LSNM-SSZ (50 wt % ratio), LSNM-NiO-SSZ. (40, 30, 30 wt %), and NiO-SSZ (50 wt %) layers were then deposited on SSZ electrolyte film and sintered at around 900-1100° C. to obtain reactors. The active catalyst area of each of La0.6Sr0.4Ni0.3Mn0.7O3, (LSNM), LSNM-SSZ (50 wt % ratio), LSNM-NiO-SSZ (40 wt %, 30 wt %, 30 wt %), and NiO-SSZ (50 wt %) layers was about 10 cm2. A layer of porous platinum paste was applied to each of La0.6Sr0.4Ni0.3Mn0.7O3 (LSNM), LSNM-SSZ (50 wt % ratio), LSNM-NiO-SSZ (40 wt %, 30 wt %, 30 wt %), and NiO-SSZ (50 wt %) layers to act as a porous metallic current collector.
The microstructures of the reactors were analyzed. As a typical example, SEM images of LSM/SSZ/NiO-SSZ reactor show that three layers could be observed on the cross section of the tube, the LSM layer had a porous structure with low porosity, SSZ had a dense structure, while NiO-SSZ had a porous structure with high porosity.
The reactors were each put inside an alumina tube. The inner diameter of the alumina tube was about 2 cm. Gases containing NO (80 ml/min gas containing 400 ppm NO balanced with He or 200 ml/min gas containing 2.0 ppm NO balanced with He) were fed into the alumina tube passing through the outer surface of the reactor in the temperature range of 600-800° C. Direct current (DC) electric field was applied on the LSM/SSZ/NiO-SSZ reactor with a range about 0-200 mA. The NiO-SSZ layer was assigned as cathode, where electrochemical NO reduction took place. The LSM layer was the anode, where the oxidation of oxygen ions took place. The corresponding voltage between anode and cathode was in the range of 1 1.5 V. Gas chromatography equipped with a PQ column and a RAE7800 gas sensor were used to detect NC) and NO2 with an accuracy of I ppm and 0.1 ppm, respectively. Effects of O2 in the feeding gas on the conversion of NO were tested on typical catalysts by using a gas containing 20 ppm NO and 2000 ppm O2.
NO conversion rates of NO (80 ml/min 400 ppm NO balanced with He) under 50 ml at some typical temperatures in reactors using NiO-SSZ, LSM-SSZ, and LSNM-SSZ as cathode layers are summarized in
NO conversion rate as a function of the electric current on LSNM-SSZ was tested on 20 ppm NO, and 80% NC) conversion was achieved at 600° C., suggesting that the catalyst is more efficient for the removal of low concentration NO effluent. Significant NO conversion rate without the electric current was observed, suggesting that direct NO decomposition plays an important role in present electrochemical NO reduction process.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310687068.7 | Dec 2013 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/066636 | 11/20/2014 | WO | 00 |
