WO2019087132A1

WO2019087132A1 - Phosphorus-modified zirconia material as catalyst support

Info

Publication number: WO2019087132A1
Application number: PCT/IB2018/058598
Authority: WO
Inventors: Fudong Liu; Michel Deeba
Original assignee: Basf Corporation
Priority date: 2017-11-02
Filing date: 2018-11-01
Publication date: 2019-05-09

Abstract

This invention is directed to catalyst compositions, catalytic articles for purifying exhaust gas emissions and methods of making and using the same. In particular, the invention relates to a catalytic article including a catalytic material on a substrate, wherein the catalytic material has a first layer and a second layer. The first layer contains a rhodium component impregnated on a support material and a phosphorus component, which is either impregnated on the support material or is in a physical mixture with the rhodium component impregnated on the support material.

Description

PHOSPHORUS-MODIFIED ZIRCONIA MATERIAL AS CATALYST SUPPORT

FIELD OF THE INVENTION

This invention is directed to catalyst compositions and catalytic articles for purifying exhaust gas emissions, as well as methods of making and using the same.

BACKGROUND OF THE INVENTION

Various catalysts have been developed for purifying the exhaust gas emitted from internal combustion engines by reducing harmful components contained in the exhaust gas such as hydrocarbons (HCs), nitrogen oxides (NO_x) and carbon monoxide (CO). These catalysts are usually part of an exhaust gas treatment system, which may further comprise catalytic converters, evaporative emissions devices, scrubbing devices (e.g., for removal of hydrocarbon, sulfur, and the like), particulate filters, traps, adsorbers, absorbers, non-thermal plasma reactors, and the like, as well as combinations of at least two of the foregoing devices. Each of these devices individually or in combination may be rated in terms of its ability to reduce the concentration of any one of the harmful component(s) in an exhaust gas stream under various conditions.

Catalytic converters, for example, are one type of an exhaust emission control device used within an exhaust gas treatment system, and comprise one or more catalytic materials disposed on one or more substrates. The composition of the catalytic matenal(s), the type of substrate(s), and the method by which the catalytic material is disposed on the substrate are ways in which catalytic converters are differentiated from one another. For example, three-way conversion (TWC) catalysts located in catalytic converters typically comprise one or more platinum group metals (PGMs) (e.g., platinum, palladium, rhodium, and/or iridium) located upon one or more supports such as high surface area, refractory oxide supports (e.g., high surface area aluminas or mixed metal oxide composite supports). The supported PGMs are carried on a suitable substrate, such as a monolithic substrate comprising a refractory ceramic or metal honeycomb structure. Many TWC catalysts are manufactured with at least two separate catalyst coating compositions (washcoats) that are applied in the form of aqueous dispersions as successive layers on a substrate. For example, PGMs such as palladium and rhodium, which typically represent the main catalytically active species in a TWC catalyst, are often applied as separate washcoats. Separation of palladium and rhodium into individual washcoat layers has been shown to prevent the formation of alloys, which are known to be less catalytically active. Generally, a TWC catalyst promotes oxidation by oxygen in the exhaust gas stream of unburned hydrocarbons (HCs) and carbon monoxide (CO) as well as the reduction of nitrogen oxides (NO_x) to nitrogen. Oxidization of CO and HCs and reduction of NO_x occur substantially simultaneously.

Many catalyst components, including TWC catalysts, used to treat the exhaust gas of internal combustion engines are less effective during periods of low temperature operation (e.g., lower than 200 °C), such as the initial cold-start period of engine operation. During this time period, the operating temperatures of catalyst components are generally too low for treating engine exhaust gas efficiently. This is particularly true for downstream catalyst components of an engine exhaust gas treatment system, which are further removed from the engine, and often take several minutes to reach a suitable operating temperature. As emission standards for treating engine exhaust gas continue to become more stringent, particularly during the initial cold start period, there is a continuing need in the art to provide catalyst compositions exhibiting catalytic activity at low operating temperatures. However, many catalyst compositions currently exhibiting catalytic activity at low operating temperatures are sensitive to sulfur poisoning of the PGM components within the catalyst compositions. As such, it would be highly desirable to provide catalyst compositions that are resistant to sulfur poisoning.

SUMMARY OF THE INVENTION

The invention relates to a three-way conversion (TWC) catalytic material and catalytic article with low light-off temperature for the conversion of NO_x, CO, and HC. The invention also relates to using such TWC materials and articles to treat exhaust gas streams. In particular, the TWC catalytic material of the invention contains a phosphorus component-impregnated support material having one or more catalytically active metals (e.g., platinum group metals (PGMs)) disposed thereon. Although not intending to be limited by theory, it is believed that impregnating the support material with a phosphorus component modifies the surface of the TWC catalytic material, resulting in better conversion of CO, HC, and NO_x at lower operating temperatures. The HC, CO, and NO_x light-off performance of the TWC catalytic material of the invention is maintained even after aging (e.g., at temperatures of 950 °C or 1050 °C).

The disclosed TWC catalytic material can optionally include a phosphorus trap material to absorb at least a portion of phosphorus-containing impurities which would otherwise poison the TWC catalytic article. Although not limited thereto, a TWC catalytic article containing a phosphorus trap material as disclosed herein is particularly effective in reducing poisoning associated with phosphorus-containing impurities when it is the first catalytic component within the catalytic converter exposed to engine exhaust gas.

One aspect of the invention is a TWC catalytic article comprising a catalytic material on a substrate, the catalytic material comprising a first layer and a second layer, wherein the first layer comprises a rhodium component impregnated on a support material, and a phosphorus component, wherein the phosphorus component is impregnated on the support material or is in a physical mixture with the rhodium component impregnated on the support material, wherein the catalytic material is effective for three-way conversion to oxidize carbon monoxide and hydrocarbons and reduce nitrogen oxides. In some embodiments, the support material is a zirconia-based support material. In some embodiments, the zirconia-based support material is zirconia, lanthana-zirconia, titania-zirconia, titania-lanthana-zirconia, alumina-zirconia, baria-zirconia, strontia-zirconia, neodymia-zirconia, praseodymia-zirconia, tungsten oxide -zirconia, niobia-zirconia, yttria- zirconia, or any combination thereof. In some embodiments, the zirconia-based support material is lanthana- zirconia. In some embodiments, the lanthana-zirconia comprises zirconia in an amount from about 80 to about 99 wt.%.

In some embodiments, the phosphorus component is present in an amount ranging from about 0.1% to about 10 wt.% based on the total weight of the support material, the rhodium component, and the phosphorus component; or the total weight of the physical mixture of the rhodium impregnated on the support material and the phosphorus component. In some embodiments, the phosphorus component is impregnated on the support material.

In some embodiments, the TWC catalytic article further comprises a phosphorus trap material in the first layer, wherein the phosphorus trap material comprises an alkaline earth metal component and a metal oxide. In some embodiments, the alkaline earth metal component is supported on the metal oxide or is in the form of a composite with the metal oxide. In some embodiments, the alkaline earth metal component is a composite of barium oxide and alumina. In some embodiments, the alkaline earth metal component is present in an amount of about 1 to about 20 wt.% of the first layer. In some embodiments, the first layer is zoned into an upstream zone and a downstream zone, wherein the upstream zone comprises the phosphorus trap material. In some embodiments, the upstream zone has a length of about 20 to about 60% that of the substrate. In some embodiments, the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof. In some embodiments, the alkaline earth metal component is barium oxide. In some embodiments, barium oxide is present in an amount from about 1 to about 40 wt.% based on the weight of the phosphorus trap material.

In some embodiments, the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof.

In some embodiments, the metal oxide is alumina. In some embodiments, the phosphorus component is impregnated on the support material, the support material is lanthana-zirconia, and wherein the phosphorus trap material comprises barium oxide and alumina. In some embodiments, the second layer comprises barium oxide and a palladium component impregnated on ceria-zirconia and lanthana-alumina.

In some embodiments, the TWC catalytic article further comprises a refractory metal oxide in the first layer selected from alumina, lanthana-alumina, ceria-alumina, zirconia-alumina, cena-zirconia-alumina, lanthana-zirconia-alumina, lanthana-neodymia-alumina, and combinations thereof. In some embodiments, the refractory metal oxide is lanthana-alumina. In some embodiments, the first layer contains the rhodium component in an amount from about 0.05 to about 5 wt.%.

In some embodiments, the second layer comprises a platinum group metal (PGM) component impregnated on a porous support material. In some embodiments, at least a portion of the porous support material comprises an oxygen storage component selected from ceria, zirconia, lanthana, yttria, neodymia, praseodymia, niobia, and combinations thereof. In some embodiments, the oxygen storage component is ceria-zirconia, comprising ceria in an amount from about 5 to about 75 wt.%. In some embodiments, at least a portion of the porous support material is a refractory metal oxide support selected from alumina, lanthana- alumina, ceria-alumina, zirconia-alumina, ceria-zirconia-alumina, lanthana-zirconia-alumina, lanthana- neodymia-alumina, and combinations thereof. In some embodiments, the PGM component is a palladium component

In some embodiments, the second layer further comprises barium oxide, magnesium oxide, calcium oxide, strontium oxide, lanthanum oxide, cerium oxide, zirconium oxide, manganese oxide, copper oxide, iron oxide, praseodymium oxide, yttrium oxide, neodymium oxide, or any combination thereof. In some embodiments, the second layer comprises barium oxide and a palladium component impregnated on ceria- zirconia and lanthana-alumina. In some embodiments, the first layer is directly disposed on the substrate and the second layer is disposed on top of the first layer. In some embodiments, the second layer is directly disposed on the substrate and the first layer is disposed on top of the second layer.

In some embodiments, the substrate is a metal or ceramic monolithic honeycomb substrate. In some embodiments, the substrate is a wall flow filter substrate or a flow through substrate.

Another aspect of the invention is a method of making the TWC catalytic article as disclosed herein, comprising: disposing the first layer and the second layer on the substrate to yield a catalytic material -coated substrate, and calcining the catalytic material -coated substrate to render the TWC catalytic article. A further aspect of the invention is a method of making a TWC catalytic article comprising a catalytic material disposed on a substrate, wherein the catalytic material comprises a first layer composition and a second layer composition, the method comprising: (a) combining a support material with a phosphorus component precursor and a rhodium component precursor so as to impregnate at least the rhodium component on the support material; (b) calcining the product obtained from step (a) to afford a dried rhodium

component/phosphorus component-containing material; and (c) disposing the first layer composition comprising the dried rhodium component/phosphorus component-containing material and the second layer composition onto the substrate. In some embodiments, step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor or impregnating the support material with the rhodium component precursor to give a rhodium component-impregnated support material and mixing the rhodium component-impregnated support material with the phosphorus component precursor. In some embodiments, step (a) comprises impregnating the support material with the phosphorus component precursor to obtain a phosphorus component-impregnated support material, and then impregnating the phosphorus component-impregnated support material with the rhodium component precursor to obtain the rhodium component/phosphorus component-containing material. In some embodiments, step (a) comprises impregnating the support material with the rhodium component precursor to obtain a rhodium component-impregnated support material, and then impregnating the rhodium component-impregnated support material with the phosphorus component precursor or physically mixing the rhodium component-impregnated support material with the phosphorus component precursor to obtain the rhodium component/phosphorus component-containing material. In some embodiments, step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor simultaneously. In some embodiments, the phosphorus component precursor is (NH₄)₂HP0₄.

In some embodiments, the rhodium component precursor is rhodium chloride, rhodium nitrate, rhodium acetate, or a combination thereof. In some embodiments, the support material is a zirconia-based support material. In some embodiments, the zirconia-based support material is lanthana-zirconia. In some embodiments, the phosphorus trap material is a composite of barium oxide and alumina. In some embodiments, mixing of the dried rhodium component/phosphorus component-containing material with a phosphorus trap material affords the first layer composition. In some embodiments, the phosphorus trap material comprises an alkaline earth metal component and a metal oxide. In some embodiments, the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof. In some embodiments, the alkaline earth metal component is barium oxide. In some embodiments, the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof. In some embodiments, the metal oxide is alumina. In some embodiments, the phosphorus trap material is a composite of barium oxide and alumina. In some embodiments, the second layer composition comprises a platinum group metal component impregnated on a porous support material.

Another aspect of the invention relates to a method for reducing CO, HC, and NO_x levels in a gas stream, comprising contacting the gas stream with a TWC catalytic article as disclosed herein for a time and at a temperature sufficient to reduce CO, HC, and NO_x levels in the gas stream. In some embodiments, the CO, HC, and NO_x levels in the gas stream are reduced by at least 50% compared to the CO, HC, and NO_x levels in the gas stream prior to contact with the TWC catalytic article.

Another aspect of the invention relates to an emission treatment system for treatment of an exhaust gas stream, the emission treatment system comprising an engine producing an exhaust gas stream; and a TWC catalytic article as disclosed herein positioned downstream from the engine in fluid communication with the exhaust gas stream and adapted for the abatement of CO and HC and conversion of NO_s to N₂. In some embodiments, the engine is a gasoline engine or diesel engine.

The invention includes, without limitation, the following embodiments.

Embodiment 1: A TWC catalytic article comprising a catalytic material on a substrate, the catalytic material comprising a first layer and a second layer, wherein the first layer comprises a rhodium component impregnated on a support matenal, and a phosphorus component, wherein the phosphorus component is impregnated on the support material or is in a physical mixture with the rhodium component impregnated on the support material.

Embodiment 2: The TWC catalytic article of the preceding embodiment, wherein the support material is a zirconia-based support material.

Embodiment 3: The TWC catalytic article of any preceding embodiment, wherein the zirconia-based support material is zirconia, lanthana-zirconia, titania-zirconia, titania-lanthana-zirconia, alumina-zirconia, baria-zirconia, strontia-zircoma, neodymia-zirconia, praseodymia-zirconia, tungsten oxide -zirconia, mobia- zirconia, yttria-zirconia, or any combination thereof.

Embodiment 4: The TWC catalytic article of any preceding embodiment, wherein the zirconia-based support material is lanthana-zirconia.

Embodiment 5: The TWC catalytic article of any preceding embodiment, wherein the lanthana-zirconia comprises zirconia in an amount from about 80 to about 99 wt.%.

Embodiment 6: The TWC catalytic article of any preceding embodiment, wherein the phosphorus component is present in an amount ranging from about 0.1% to about 10 wt.% based on the total weight of the support material, the rhodium component, and the phosphorus component; or the total weight of the physical mixture of the rhodium impregnated on the support material and the phosphorus component.

Embodiment 7: The TWC catalytic article of any preceding embodiment, wherein the phosphorus component is impregnated on the support material. Embodiment 8: The TWC catalytic article of any preceding embodiment, further comprising a phosphorus trap material in the first layer, wherein the phosphorus trap material comprises an alkaline earth metal component and a metal oxide.

Embodiment 9: The TWC catalytic article of any preceding embodiment, wherein the alkaline earth metal component is supported on the metal oxide or is in the form of a composite with the metal oxide.

Embodiment 10: The TWC catalytic article of any preceding embodiment, wherein the alkaline earth metal component is a composite of barium oxide and alumina.

Embodiment 11 : The TWC catalytic article of any preceding embodiment, wherein the alkaline earth metal component is present in an amount of about 1 to about 20 wt.% of the first layer.

Embodiment 12: The TWC catalytic article of any preceding embodiment, wherein the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof.

Embodiment 13: The TWC catalytic article of any preceding embodiment, wherein the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof.

Embodiment 14: The TWC catalytic article of any preceding embodiment, wherein the phosphorus component is impregnated on the support material, the support material is lanthana-zirconia, and wherein the phosphorus trap material comprises barium oxide and alumina.

Embodiment 15: The TWC catalytic article of any preceding embodiment, wherein the second layer comprises barium oxide and a palladium component impregnated on ceria-zirconia and lanthana-alumina. Embodiment 16: The TWC catalytic article of any preceding embodiment, further comprising a refractory metal oxide in the first layer selected from alumina, lanthana-alumina, ceria-alumina, zirconia-alumina, ceria-zirconia-alumina, lanthana-zirconia-alumina, lanthana-neodymia-alumina, and combinations thereof. Embodiment 17: The TWC catalytic article of any preceding embodiment, wherein the refractory metal oxide is lanthana-alumina.

Embodiment 18: The TWC catalytic article of any preceding embodiment, wherein the first layer contains the rhodium component in an amount from about 0.05 to about 5 wt.%.

Embodiment 19: The TWC catalytic article of any preceding embodiment, wherein the second layer comprises a platinum group metal (PGM) component impregnated on a porous support material.

Embodiment 20: The TWC catalytic article of any preceding embodiment, wherein at least a portion of the porous support material comprises an oxygen storage component selected from ceria, zirconia, lanthana, yttria, neodymia, praseodymia, niobia, and combinations thereof.

Embodiment 21: The TWC catalytic article of any preceding embodiment, wherein the oxygen storage component is ceria-zirconia, comprising ceria in an amount from about 5 to about 75 wt.%.

Embodiment 22: The TWC catalytic article of any preceding embodiment, wherein at least a portion of the porous support material is a refractory metal oxide support selected from alumina, lanthana-alumina, ceria- alumina, zirconia-alumina, ceria-zirconia-alumina, lanthana-zirconia-alumina, lanthana-neodymia-alumina, and combinations thereof. Embodiment 23 : The TWC catalytic article of any preceding embodiment, wherein the PGM component is a palladium component.

Embodiment 24: The TWC catalytic article of any preceding embodiment, wherein the second layer further comprises barium oxide, magnesium oxide, calcium oxide, strontium oxide, lanthanum oxide, cerium oxide, zirconium oxide, manganese oxide, copper oxide, iron oxide, praseodymium oxide, yttrium oxide, neodymium oxide, or any combination thereof.

Embodiment 25 : The TWC catalytic article of any preceding embodiment, wherein the second layer comprises barium oxide and a palladium component impregnated on ceria-zirconia and lanthana-alumina.

Embodiment 26: The TWC catalytic article of any preceding embodiment, wherein the first layer is directly disposed on the substrate and the second layer is disposed on top of the first layer.

Embodiment 27: The TWC catalytic article of any preceding embodiment, wherein the second layer is directly disposed on the substrate and the first layer is disposed on top of the second layer.

Embodiment 28: The TWC catalytic article of any preceding embodiment, wherein the substrate is a metal or ceramic monolithic honeycomb substrate.

Embodiment 29: The TWC catalytic article of any preceding embodiment, wherein the substrate is a wall flow filter substrate or a flow through substrate.

Embodiment 30: The TWC catalytic article of any preceding embodiment, wherein the catalytic material is effective for three-way conversion to oxidize carbon monoxide and hydrocarbons and reduce nitrogen oxides.

Embodiment 31: A method of makmg the TWC catalytic of any preceding embodiment, comprising disposing the first layer and the second layer on the substrate to yield a catalytic material-coated substrate, and calcining the catalytic material -coated substrate to render the TWC catalytic article.

Embodiment 32: A method of making a TWC catalytic article comprising a catalytic material disposed on a substrate, wherein the catalytic material comprises a first layer composition and a second layer composition, the method comprising:

(a) combining a support material with a phosphorus component precursor and a rhodium component precursor so as to impregnate at least the rhodium component on the support material;

(b) calcining the product obtained from step (a) to afford a dried rhodium

component/phosphorus component-containing material; and

(c) disposing the first layer composition comprising the dried rhodium component/phosphorus component-containing material and the second layer composition onto the substrate.

Embodiment 33: The method of any preceding embodiment, wherein step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor or impregnating the support material with the rhodium component precursor to give a rhodium component- impregnated support material and mixing the rhodium component-impregnated support material with the phosphorus component precursor.

Embodiment 34: The method of any preceding embodiment, wherein step (a) comprises impregnating the support material with the phosphorus component precursor to obtain a phosphorus component-impregnated support material, and then impregnating the phosphorus component-impregnated support material with the rhodium component precursor to obtain the rhodium component/phosphorus component-containing material. Embodiment 35: The method of any preceding embodiment, wherein step (a) comprises impregnating the support material with the rhodium component precursor to obtain a rhodium component-impregnated support material, and then impregnating the rhodium component-impregnated support material with the phosphorus component precursor or physically mixing the rhodium component-impregnated support material with the phosphorus component precursor to obtain the rhodium component/phosphorus component-containing material.

Embodiment 36: The method of any preceding embodiment, wherein step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor simultaneously.

Embodiment 37: The method of any preceding embodiment, wherein the phosphorus component precursor is (NH₄)₂HP0₄.

Embodiment 38: The method of any preceding embodiment, wherein the rhodium component precursor is rhodium chloride, rhodium nitrate, rhodium acetate, or a combination thereof.

Embodiment 39: The method of any preceding embodiment, wherein the support material is a zirconia- based support material.

Embodiment 40: The method of any preceding embodiment, wherein the zirconia-based support material is lanthana-zirconia.

Embodiment 41: The method of any preceding embodiment, wherein the phosphorus trap material is a composite of barium oxide and alumina.

Embodiment 42: The method of any preceding embodiment, wherein mixing of the dried rhodium component/phosphorus component-containing material with a phosphorus trap material affords the first layer composition.

Embodiment 43 : The method of any preceding embodiment, wherein the phosphorus trap material comprises an alkaline earth metal component and a metal oxide.

Embodiment 44: The method of any preceding embodiment, wherein the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof. Embodiment 45 : The method of any preceding embodiment, wherein the alkaline earth metal component is barium oxide.

Embodiment 46: The method of any preceding embodiment, wherein the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof.

Embodiment 47: The method of any preceding embodiment, wherein the metal oxide is alumina.

Embodiment 48: The method of any preceding embodiment, wherein the phosphorus trap material is a composite of barium oxide and alumina.

Embodiment 49: The method of any preceding embodiment, wherein the second layer composition comprises a platinum group metal component impregnated on a porous support material. Embodiment 50: A method for reducing CO, HC, and NO_x levels in a gas stream, comprising contacting the gas stream with the TWC catalytic article of any preceding embodiment for a time and at a temperature sufficient to reduce CO, HC, and NO_x levels in the gas stream.

Embodiment 51 : The method of any preceding embodiment, wherein the CO, HC, and NO_x levels in the gas stream are reduced by at least 50% compared to the CO, HC, and NO_x levels in the gas stream prior to contact with the TWC catalytic article.

Embodiment 52: An emission treatment system for treatment of an exhaust gas stream, the emission treatment system comprisingvan engine producing an exhaust gas stream; andvthe TWC catalytic article of any preceding embodiment positioned downstream from the engine in fluid communication with the exhaust gas stream and adapted for the abatement of CO and HC and conversion of NO_x to N₂.

Embodiment 53: The emission treatment system of the preceding embodiment, wherein the engine is a gasoline engine or diesel engine.

These and other features, aspects, and advantages of the disclosure will be apparent from a reading of the following detailed description together with the accompanying drawings, which are briefly described below. The invention includes any combination of two, three, four, or more of the above-noted

embodiments as well as combinations of any two, three, four, or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined in a specific embodiment description herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosed invention, in any of its various aspects and embodiments, should be viewed as intended to be combinable unless the context clearly dictates otherwise. Other aspects and advantages of the present invention will become apparent from the following.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to provide an understanding of embodiments of the invention, reference is made to the appended drawings, which are not necessarily drawn to scale, and in which reference numerals refer to components of exemplary embodiments of the invention. The drawings are exemplary only, and should not be construed as limiting the invention.

FIG. 1 is a perspective view of a honeycomb-type substrate that may be employed in certain embodiments of the present invention;

FIG. 2 is a partial cross-sectional view enlarged relative to FIG. 1 and taken along a plane parallel to the end faces of the substrate of FIG. 1 representing a monolithic flow-through substrate, which shows an enlarged view of a plurality of the gas flow passages shown in FIG. 1;

FIG. 3 is a cutaway view of a section enlarged relative to FIG. 1, wherein the honeycomb-type substrate in FIG. 1 represents a wall flow filter substrate monolith;

FIG. 4 shows a cross-sectional view of one embodiment of a zoned catalytic article of the present invention, wherein the top layer is zoned; FIG. 5 shows a cross-sectional view of one embodiment of a zoned catalytic article of the present invention, wherein the bottom layer is zoned;

FIG 6 shows a series of different catalytic articles in a layered configuration;

FIG. 7 is a line graph showing FTP-72 test results on a GVS reactor for cumulative NO_x emission of washcoated catalyst 1 and washcoated catalyst 2;

FIG. 8 is a line graph showing FTP-72 test results on a GVS reactor for cumulative HC emission of washcoated catalyst 1 and washcoated catalyst 2;

FIG. 9 is a line graph showing FTP-72 test results on a GVS reactor for cumulative CO emission of washcoated catalyst 1 and washcoated catalyst 2;

FIG. 10 is a line graph showing FTP-72 test results on a GVS reactor for cumulative NO_x emission of washcoated catalyst 3 and washcoated catalyst 4;

FIG. 11 is a line graph showing FTP-72 test results on a GVS reactor for cumulative HC emission of washcoated catalyst 3 and washcoated catalyst 4; and

FIG. 12 is a line graph showing FTP-72 test results on a GVS reactor for cumulative CO emission of washcoated catalyst 3 and washcoated catalyst 4.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

The present invention relates to a catalytic material and a three-way conversion (TWC) catalytic article incorporating such a catalytic material capable of exhibiting a low light-off temperature for the conversion of HC, CO, and NO_x in exhaust gas. The catalytic material of the TWC catalytic article comprises a first layer and a second layer disposed on a substrate. The first layer comprises a phosphorus component and a rhodium component, wherein the rhodium component is impregnated on a support material and the phosphorus component is either co-impregnated on the same support material as the rhodium component or is physically mixed with the supported rhodium component. The second layer can comprise any catalyst composition known in the art for the conversion of one or more pollutants selected from HC, CO and NO_x.

Although phosphorus is known to poison catalyst compositions, the compositions disclosed herein surprisingly demonstrate enhanced catalytic effects where certain phosphorus-containing materials are included. In particular, TWC catalyst compositions including a phosphorus component and a rhodium component show a lower light-off temperature for HC, CO, and NO_x conversion than comparable compositions without a phosphorus component. Without intending to be bound by theory, it is thought that the addition of a phosphorus component to a supported rhodium component modifies the catalytic surface of the support material to form highly efficient catalytic sites with the rhodium component impregnated thereon (e.g., Rh-O-P sites).

In particular for support materials comprising more than one metal (e.g., lanthana-zirconia), introduction of a phosphorus component can prevent interactions between the impregnated rhodium component and metal atoms present in the support to form catalytically inactive rhodate species. With a larger amount of catalytically active rhodium present on the catalyst surface a high overall reducibility of rhodium is provided (even after high aging temperatures), which contributes to the enhanced HC, CO, and NO_x light-off performance of such catalysts in TWC applications.

Thus, phosphorus components may generally be introduced into support materials exhibiting various metal contents (e.g., ratio and/or combination of metals), morphology, surface area, pore structure or other physical-chemical properties to render catalytic materials with similar beneficial catalytic properties as the catalytic materials disclosed herein. These phosphorus-modified support materials can then generally be used in catalyst compositions as support materials for PGM components to improve TWC performance, or they can be used in catalyst compositions focused on other applications, e.g., Gasoline Oxidation Catalysts (GOC), Diesel Oxidation Catalysts (DOC), or NO pre-oxidation catalysts.

As used herein, the term "catalyst" or "catalyst composition" refers to a material that promotes a reaction.

As used herein, the terms "upstream" and "downstream" refer to relative directions according to the flow of an engine exhaust gas stream from an engine towards a tailpipe, with the engine in an upstream location and the tailpipe and any pollution abatement articles such as filters and catalysts being downstream from the engine.

As used herein, the term "stream" broadly refers to any combination of flowing gas that may contain solid or liquid particulate matter. The term "gaseous stream" or "exhaust gas stream" means a stream of gaseous constituents, such as the exhaust of a combustion engine, which may contain entrained non-gaseous components such as liquid droplets, solid particulates, and the like. The exhaust gas stream of a combustion engine typically further comprises combustion products (C0₂ and H₂0), products of incomplete combustion (carbon monoxide (CO) and hydrocarbons (HC)), oxides of nitrogen (NO_x), combustible and/or carbonaceous particulate matter (soot), and un-reacted oxygen and nitrogen.

As used herein, the term "substrate" refers to the monolithic material onto which the catalyst composition is placed, typically in the form of a washcoat. For example, a honeycomb-type carrier member can be used as a substrate, which is sufficiently porous to permit the passage of the gas stream being treated.

As used herein, the term "washcoat" has its usual meaning in the art of a thin, adherent coating of a catalytic or other material applied to a substrate. A washcoat is formed by preparing a slurry containing a certain solid content (e.g., 10%-90% by weight) of particles in a liquid vehicle, which is then coated onto a substrate and dried to provide a washcoat layer. As used herein, the term "catalytic article" refers to an element that is used to promote a desired reaction. For example, a catalytic article may comprise a washcoat containing catalytic compositions on a substrate

As used herein, the term "support" refers to any high surface area material, usually a metal oxide material, upon which a catalytic metal is applied.

As used herein, "impregnated" or "impregnation" refers to permeation of the catalytic material into the porous structure of the support material.

As used herein, the term "platinum group metal component" or "PGM component" refers to a platinum group metal or an oxide thereof, such as palladium (Pd), platinum (Pt), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), oxides, or mixtures thereof.

As used herein, the term "abatement" means a decrease in the amount, caused by any means.

As used herein, the term "light-off temperature" refers to the temperature at which 50% conversion of exhaust gas is attained and is often referred to as T₅₀.

Catalytic Material

The catalytic material of the invention includes two catalyst compositions, which are disposed onto a substrate, e.g., in a layered configuration, to generate a TWC catalytic article. One of these catalyst compositions (typically used as the first/bottom layer of the article) is referred to herein as a "phosphorus- modified catalyst composition" and comprises a rhodium-containing catalyst material, a phosphorus component and optionally a phosphorus trap material and/or a refractory metal oxide. The second catalyst composition (typically used as the second/top layer of the article) comprises any catalyst composition known in the art for the conversion of HC, CO and/or NO_x (referred to herein as "the platinum group metal (PGM)- containing catalyst composition"), as described in more detail below.

Phosphorus-Modified Catalyst Composition

As noted above, the phosphorus-modified catalyst composition comprises a rhodium -containing catalyst material and a phosphorus component. The rhodium-containing catalyst material comprises a rhodium component on a support material. The rhodium component is selected from rhodium metal, rhodium oxides, and combinations thereof. Typically, the rhodium component is impregnated on a support material. The amount of the rhodium component can vary, but will typically be from about 0.05 wt.% to about 5 wt.%, from about 0.1 to about 3 wt.%, or from about 0.5 to about 2.5 wt.% relative to the weight of the support material impregnated thereon (no more than about 5%, about 4%, about 3%, about 2%, about 1%, or about 0.5%). In some embodiments, the support material comprises a zirconia-based support material. A zirconia-based support material may comprise zirconia in an amount ranging from about 50 to about 99 wt.%, from about 60 to about 99 wt.%, from about 70 to about 99 wt.%, from about 80 to about 99 wt.%, or from about 90 to about 99 wt.%.

In some embodiments, the zirconia-based support material is zirconia modified with one or more metal oxide(s) including oxides of an alkali metal, a semimetal, a Group III metal, and/or a transition metal, e.g., La, Mg, Ba, Sr, Zr, Ti, Si, Ce, Mn, Nd, Pr, Sm, Nb, W, Y, Nd, Mo, Fe, and/or Al. Exemplary zirconia- based support materials include lanthana-zirconia, titania-zirconia, titania-lanthana-zirconia, alumina- zirconia, baria-zirconia, strontia-zirconia, neodymia-zirconia, praseodymia-zirconia, tungsten oxide-zirconia, niobia-zirconia, yttria-zirconia, or a combination thereof. In some embodiments, the support material is lanthana-zirconia. In some embodiments, the amount of alkali metal, semimetal, Group III metal, and/or transition metal oxide(s) within the support material can range from about 0.5% to about 50%, about 0.5% to about 40%, about 0.5% to about 30%, about 0.5% to about 20%, about 0.5% to about 10%, or from about 5% to about 10% by weight based on the total weight of the support material. In some embodiments, the amount of alkali metal, semimetal, Group III metal, and/or transition metal oxide(s) within the support material is no more than about 50%, about 40%, about 30%, about 20%, about 10%, about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2%, or about 1 % by weight based on the total weight of the support material .

The phosphorus component can be selected from phosphorus metal, phosphorus oxides, and combinations thereof. For example, in some embodiments, the phosphorus component comprises

NH₄H₂PO₄, (NH₄)₂HP0₄, (NH₄)₃P0₄, H₃P0 or combinations thereof. In some embodiments, the phosphorus component comprises phosphorus with an oxidation state of +V. In some embodiments, the phosphorus component is impregnated on a support material, wherein the support material is a support material on which the rhodium component is impregnated, as described above giving a rhodium

component/phosphorus component-containing material. In some embodiments, the phosphorus component is not supported and is physically mixed with a support material having the rhodium component impregnated thereon. The amount of phosphorus component can vary and, in some embodiments can range from about 0.1% to about 10%, about 0.1% to about 8%, about 1% to about 5%, or from about 3% to about 5% by weight based on the total weight of the rhodium component/phosphorus component-containing material or the physical mixture of the phosphorus component with the rhodium component-impregnated support material.

The molar ratio of the rhodium component to the phosphorus component within the phosphorus- modified catalyst composition can vary and can range from about 1 :30 to at about 1: 1. In some

embodiments, the molar ratio of the rhodium component to the phosphorus component is equal to or less than about 1: 1, or equal to or less than about 1:8, but is generally greater than about 1:30. In a specific embodiment, the phosphorus-modified catalyst composition comprises a rhodium component and a phosphorus component co-impregnated on a lanthana-zirconia support.

In some embodiments, the phosphorus-modified catalyst composition further comprises a phosphorus trap material, which can be any material that is able to remove undesired phosphorus species from engine exhaust by binding (e.g., permanently binding) the undesired phosphorus species. For example, in some embodiments, the phosphorus trap material is an alkaline earth metal component supported on a metal oxide or an alkaline earth metal component in the form of a composite with a metal oxide. As used herein, an "alkaline earth metal component" is an alkaline earth metal or an oxide thereof, such as magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), oxides thereof, and mixtures thereof. In some embodiments, the alkaline earth metal component is barium oxide (BaO). The amount of alkaline earth metal component in the phosphorus trap material can vary, but will typically be from about 1 to about 50 wt.%, from about 1 to about 40 wt.%, from about 1 to about 30 wt.%, or from about 1 to about 20 wt.% based on the total weight of the phosphorus trap material. The metal oxide of the phosphorus trap material is an oxide of a metal other than an alkaline earth metal, e.g., a transition metal, Group III metal, lanthanide, or a combination thereof. Exemplary metal oxides are alumina, zirconia, titania, ceria, and combinations thereof.

The amount of phosphorus trap material, where present in the phosphorus-modified catalyst composition, can vary, but will typically be from about 1 to about 80 wt.%, from about 1 to about 70 wt.%, from about 1 to about 60 wt.%, from about 1 to about 50 wt.%, from about 1 to about 40 wt.%, from about 1 to about 30 wt.%, from about 1 to about 20 wt.%, or from about 1 to about 15 wt.% based on the total weight of the phosphorus-modified catalyst composition. In a specific embodiment, the phosphorus- modified catalyst composition comprises a rhodium component and a phosphorus component, both impregnated on lanthana-zirconia, and a phosphorus trap material comprising barium oxide supported on alumina or in the form of a composite with alumina.

In some embodiments, the phosphorus-modified catalyst composition further comprises a refractory metal oxide. As used herein, "refractory metal oxide" refers to a metal -containing oxide material exhibiting chemical and physical stability at high temperatures, such as the temperatures associated with gasoline or compressed natural gas engine exhaust. Exemplary refractory metal oxides include alumina, silica, zirconia, titania, ceria, and physical mixtures or chemical combinations thereof, including atomically-doped combinations. In some embodiments, the refractory metal oxide is modified with one or more oxides of an alkali metal, a semimetal, and/or a transition metal, e.g., La, Mg, Ba, Sr, Zr, Ti, Si, Ce, Mn, Nd, Pr, Sm, Nb, W, Y, Nd, Mo, Fe, or combinations thereof. The amount of alkali metal, semimetal, and/or transition metal oxide(s) within the refractory metal oxide can range, e.g., from about 0.5% to about 50% by weight based on the total weight of the refractory metal oxide. Exemplary refractory metal oxides include zirconia-stabilized alumina, zirconia-alumina, ceria-zirconia-alumina, lanthana-alumina, lanthana-zirconia-alumina, lanthana- neodymia-alumina, and ceria-alumina. In some specific embodiments, the refractory metal oxide material is lanthana-alumina.

In some embodiments, high surface area refractory metal oxides are used, such as high surface area alumina-based support materials, e.g., gamma alumina or activated alumina, which typically exhibit a BET surface area in excess of 60 m²/g, often up to about 200 m²/g or higher. "BET surface area" has its usual meaning of referring to the Brunauer, Emmett, Teller method for determining surface area by N₂ adsorption. In one or more embodiments, the BET surface area ranges from about 100 to about 1 0 m²/g. Useful commercial alumina includes high surface area alumina, such as high bulk density gamma-alumina, and low or medium bulk density large pore gamma-alumina.

Platinum Group Metal (PGM) -Containing Catalyst Composition

The PGM-containing catalyst composition comprises a PGM component on a porous support material. In some embodiments, the PGM component is a palladium (Pd) component. In some

embodiments, the PGM component is impregnated onto the porous support material, and the porous support material is selected from a refractory metal oxide material, an oxygen storage component (OSC), and combinations thereof. In some embodiments, at least a portion of the porous support material is a refractory metal oxide material as defined above. In some embodiments, at least a portion of the porous support material is an OSC. As used herein, "OSC" refers to an oxygen storage component that exhibits an oxygen storage capability and often is an entity that has multi-valent oxidation states and can actively react with oxidants such as oxygen (0₂) or nitric oxides (N0₂) under oxidative conditions, or can actively react with reductants such as carbon monoxide (CO), hydrocarbons (HC), or hydrogen (H₂) under reduction conditions. Certain exemplary OSCs comprise rare earth metal oxides, which are oxides of scandium, yttrium, and/or the lanthanum series defined in the Periodic Table of Elements. Examples of suitable OSCs include zirconium oxide (Zr0₂), ceria (Ce0₂), titania (Ti0₂), praseodymia (Pr₆On), yttria (Y ₂0₃), neodymia (Nd₂0₃), lanthana (La₂0₃), gadolinium oxide (Gd₂0₃), and mixtures comprising at least two of the foregoing. In some embodiments, the OSC comprises ceria. In some embodiments, the OSC comprises ceria in combination with one or more other materials including, for example, oxides of zirconium (Zr), titanium (Ta), lanthanum (La), praseodymium (Pr), neodymium (Nd), niobium (Nb), yttrium (Y), nickel (Ni), manganese (Mn), iron (Fe) copper (Cu), silver (Ag), gold (Au), samarium (Sm), gadolinium (Gd), and combinations comprising at least two of the foregoing metals. Such combinations may be referred to as mixed oxide composites. For example, a "ceria-zirconia composite" means a composite comprising ceria and zirconia, without specifying the amount of either component. Suitable ceria-zirconia composites include, but are not limited to, composites having a ceria content ranging from about 5% to about 95%, preferably from about 5% to about 75%, more preferably from about 10% to about 70% by weight based on the total weight of the ceria-zirconia composite (e.g., at least about 5%, at least about 15%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least about 95% ceria content with an upper boundary of 100%).

The amount of the PGM component (e.g., Pd component) in the PGM component-containing catalyst composition can vary. For example, the amount of the PGM component in the PGM-containing catalyst composition ranges from about 0.1 to about 10% by weight based on the total weight of the PGM component-containing catalyst composition. In some embodiments, the PGM-containing catalyst composition further comprises a metal oxide selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, lanthanum oxide, cerium oxide, zirconium oxide, manganese oxide, copper oxide, iron oxide, praseodymium oxide, yttrium oxide, neodymium oxide, and combinations thereof. The amount of metal oxide can vary, but will typically be from about 1 wt.% to about 20 wt.% based on the total weight of the PGM-containing catalyst composition. For representative PGM-containing catalyst compositions, see, for example, U.S. Pat. No. 6,764,665 to Deeba, which is hereby incorporated by reference in its entirety. Catalytic Article

The disclosure provides catalytic articles comprising catalytic compositions as disclosed above disposed on a substrate. According to one or more embodiments, the substrate of the catalytic article of the invention may be constructed of any material typically used for preparing automotive catalysts and typically comprises a metal or ceramic monolithic honeycomb structure. The substrate typically provides a plurality of wall surfaces upon which washcoats comprising the catalyst compositions described herein are applied and adhered, thereby acting as a carrier substrate for the catalyst compositions.

Exemplary metallic substrates include heat resistant metals and metal alloys, such as titanium and stainless steel as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and/or aluminum, and the total amount of these metals may advantageously comprise at least 15 wt. % of the alloy, e.g., 10-25 wt. % of chromium, 3-8 wt. % of aluminum, and up to 20 wt. % of nickel. The alloys may also contain small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium and the like. The surface of the metal substrate may be oxidized at high temperatures, e.g., 1000 °C and higher, to form an oxide layer on the surface of the substrate, improving the corrosion resistance of the alloy and facilitating adhesion of the washcoat layer to the metal surface.

Ceramic materials used to construct the substrate may include any suitable refractory material, e.g., cordierite, mullite, cordierite-a alumina, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, a alumina, aluminosilicates and the like.

Any suitable substrate may be employed, such as a monolithic flow-through substrate having a plurality of fine, parallel gas flow passages extending from an inlet to an outlet face of the substrate such that passages are open to fluid flow. The passages, which are essentially straight paths from the inlet to the outlet, are defined by walls on which the catalytic material is coated as a washcoat so that the gases flowing through the passages contact the catalytic material. The flow passages of the monolithic substrate are thin- walled channels which can be of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular, and the like. Such structures may contain from about 60 to about 1200 or more gas inlet openings (i.e., "cells") per square inch of cross section (cpsi), more usually from about 300 to 600 cpsi. The wall thickness of flow-through substrates can vary, with a typical range being between 0.002 and 0.1 inches. A representative commercially available flow-through substrate is a cordierite substrate having 400 cpsi and a wall thickness of 6 mil, or 600 cpsi and a wall thickness of 4 mil. However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry.

In alternative embodiments, the substrate may be a wall-flow substrate, wherein each passage is blocked at one end of the substrate body with a non-porous plug, with alternate passages blocked at opposite end-faces. This requires that gas flow through the porous walls of the wall-flow substrate to reach the exit. Such monolithic substrates may contain up to about 700 or more cpsi, such as about 100 to 400 cpsi and more typically about 200 to about 300 cpsi. The cross-sectional shape of the cells can vary as described above. Wall-flow substrates typically have a wall thickness between 0.002 and 0.1 inches. A representative commercially available wall-flow substrate is constructed from a porous cordierite, an example of which has 200 cpsi and 10 mil wall thickness or 300 cpsi with 8 mil wall thickness, and wall porosity between 45-65%. Other ceramic materials such as aluminum-titanate, silicon carbide and silicon nitride are also used a wall- flow filter substrates. However, it will be understood that the invention is not limited to a particular substrate type, material, or geometry. Note that where the substrate is a wall-flow substrate, the catalyst composition can permeate into the pore structure of the porous walls (i.e., partially or fully occluding the pore openings) in addition to being disposed on the surface of the walls.

FIGS. 1 and 2 illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with washcoat compositions as described herein. Referring to FIG. 1, the exemplary substrate 2 has a cylindrical shape and a cylindrical outer surface 4, an upstream end face 6 and a corresponding downstream end face 8, which is identical to end face 6. Substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As seen in FIG. 2, flow passages 10 are formed by walls 12 and extend through substrate 2 from upstream end face 6 to downstream end face 8, the passages 10 being unobstructed so as to permit the flow of a fluid, e.g., a gas stream, longitudinally through substrate 2 via gas flow passages 10 thereof. As more easily seen in FIG. 2, walls 12 are so dimensioned and configured that gas flow passages 10 have a substantially regular polygonal shape. As shown, the washcoat compositions can be applied in multiple, distinct layers if desired. In the illustrated embodiment, the washcoats consist of a discrete first washcoat layer 14 adhered to the walls 12 of the substrate member and a second discrete washcoat layer 16 coated over the first washcoat layer 14. The present invention can be practiced with one or more (e.g., 2, 3, or 4) washcoat layers and is not limited to the illustrated two-layer embodiment.

A catalytic article of the invention typically comprises a catalytic material with multiple layers, wherein each layer has a different composition. For example, in some embodiments, the first layer (e.g., layer 14 of FIG. 2) comprises the PGM-containing catalyst composition disclosed herein and the second layer (e.g., layer 16 of FIG. 2) comprises the phosphorus-modified catalyst composition disclosed herein. In another embodiment, the first layer (e.g., layer 14 of FIG. 2) comprises the phosphorus-modified catalyst composition disclosed herein and the second layer (e.g., layer 16 of FIG. 2) comprises the PGM-containing catalyst composition disclosed herein.

FIG. 3 illustrates an exemplary substrate 2 in the form a wall flow filter substrate coated with a washcoat composition as described herein. As seen in FIG. 3, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly enclosed by the internal walls 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. Alternate passages are plugged at the inlet end with inlet plugs 58 and at the outlet end with outlet plugs 60 to form opposing checkerboard patterns at the inlet 54 and outlet 56. A gas stream 62 enters through the unplugged channel inlet 64, is stopped by outlet plug 60 and diffuses through channel walls 53 (which are porous) to the outlet side 66. The gas cannot pass back to the inlet side of walls because of inlet plugs 58. The porous wall flow filter used in this invention is catalyzed in that the wall of said element has thereon or contained therein one or more catalytic materials. Catalytic materials may be present on the inlet side of the element wall alone, the outlet side alone, both the inlet and outlet sides, or the wall itself may consist all, or in part, of the catalytic material This invention includes the use of one or more layers of catalytic material on the inlet and/or outlet walls of the element.

In some embodiments, the substrate can be coated with at least two layers contained in separate washcoat slurries, wherein at least one layer is in an axially zoned configuration. For example, the same substrate can be coated with a single washcoat slurry of one layer and two different washcoat slurries of another layer, wherein each washcoat slurry is different. This may be more easily understood by reference to FIG. 4, which shows an embodiment in which the first layer comprises a washcoat zone 28 located along the entire length of the substrate 22 and a second layer comprising two washcoat zones 24 and 26 located side by side along the length of the substrate 22 on top of washcoat zone 28. The washcoat zone 24 of specific embodiments extends from the inlet end 25 of the substrate 22 through the range of about 5% to about 95%, about 10 to about 80%, about 15 to about 75%, or about 20 to about 60% of the total axial length of the substrate 22. The washcoat zone 26 extends from the outlet 27 of the substrate 22 from about 5% to about 95%, about 10 to about 80%, about 15 to about 75%, or about 20 to about 60% of the total axial length of the substrate 22.

For example, single catalyst compositions (e.g., the PGM-containing catalyst composition and/or the phosphorus-modified catalyst composition) can be separated into their individual components, although the description above focuses on these compositions in their entireties. Different washcoat slurries of one or more individual components of a composition can be prepared and applied onto the same substrate in a zoned configuration. In some embodiments, the components of the phosphorus-modified catalyst composition (e.g., rhodium -containing catalyst material and phosphorus trap material) are zoned in the same layer. For example, referring back to FIG. 4, the washcoat zone 24 can represent the phosphorus trap material, extending from the inlet end 25 of the substrate through the range of about 5% to about 95% of the length of the substrate 22 and the washcoat zone 26 comprises the rhodium-containing catalyst material. Hence, the washcoat zone 26 comprising the rhodium -containing catalyst material is located side by side with zone 24, extending from the outlet 27 of the substrate 22.

In another embodiment, a substrate 32 can be coated with a first layer comprising two washcoat zones 34 and 36 located side by side along the length of the substrate 32 and a second layer 38 located along the entire length of the substrate 32 on top of the first layer as shown in FIG. 5. The washcoat zone 34 of specific embodiments extends from the inlet end 35 of the substrate 32 through the range of about 5% to about 95%, about 10 to about 80%, about 15 to about 75%, or about 20 to about 60% of the total axial length of the substrate 32. The washcoat zone 36 extends from the outlet 37 of the substrate 32 from about 5% to about 95%, about 10 to about 80%, about 15 to about 75%, or about 20 to about 60% of the total axial length of the substrate 32. For example, the washcoat zone 34 can represent the phosphorus trap material, extending from the inlet end 35 of the substrate through the range of about 5% to about 95% of the length of the substrate 32 and the washcoat zone 36 comprises the rhodium-containing catalyst material. Hence, the washcoat zone 36 comprising the rhodium-containing catalyst material is located side by side with zone 34, extending from the outlet 37 of the substrate 32.

In describing the quantity of washcoat or catalytic metal components or other components of the composition, it is convenient to use units of weight of component per unit volume of catalyst substrate. Therefore, the units, grams per cubic inch ("g/in³") and grams per cubic foot ("g/ft³") are used herein to mean the weight of a component per volume of the substrate, including the volume of void spaces of the substrate. Other units of weight per volume such as g/L are also sometimes used. The loading of supported active metal on the catalytic article is typically from about 0.5 to about 6 g/in³, more typically from about 1 to about 5 g/in³, or from about 1 to about 3.5 g/in³. In the presently disclosed articles these values reflect the total loading of rhodium (from the phosphorus-modified catalyst composition) and the PGM (from the PGM-containing catalyst composition) taking into account the weight of the metal and the weight of the support. The total loading of the active metal without support material on the catalytic article is typically from about 0.1 to about 200 g/ft³, from about 0.1 to about 100 g/ft³, from about 1 to about 50 g/ft³, from about 1 to about 30 g/ft³, or from about 5 to about 25 g/ft³. Such values are understood in the context of the present disclosure to include both rhodium (from the phosphorus-modified catalyst composition) and PGM (from PGM-containing catalyst composition) taking into account the weight of the metal but not the weight of the support. It is noted that these weights per unit volume are typically calculated by weighing the catalyst substrate before and after treatment with the corresponding catalyst washcoat composition, and since the treatment process involves drying and calcining the catalyst substrate at high temperature, these weights represent an essentially solvent-free catalyst coating as essentially all of the water of the washcoat slurry has been removed.

Method of Making the Catalyst Compositions

Preparation of PGM-containing catalyst compositions generally involves impregnating a porous support material with a PGM component precursor (e.g., a palladium component precursor) to give a PGM component-impregnated support material. PGM component precursors are generally salts of PGM components and are typically dissolved in a solvent to form a PGM component precursor solution.

Exemplary palladium component precursors include, but are not limited to, palladium nitrate, palladium tetra amine, palladium acetate, or combinations thereof. Preparation of the PGM component-impregnated support material typically comprises impregnating the porous support material (e.g., a refractory metal oxide material, oxygen storage material, or combinations thereof) in particulate form with a PGM component precursor solution using, e.g., incipient wetness techniques as described in more detail below. In some embodiments, the PGM component-impregnated support material can be mixed with other components, e.g., a metal oxide (such as barium oxide), by conventional methods.

Preparation of the phosphorus-modified catalyst composition generally involves combining a support material with a phosphorus component precursor and a rhodium component precursor so as to impregnate at least the rhodium component on the support material. Rhodium component precursors are generally salts of the rhodium component and are typically dissolved in a solvent to form a rhodium component precursor solution. Exemplary rhodium component precursors include, but are not limited to, rhodium chloride, rhodium nitrate (e.g., Ru(NO)₃ and salts thereof), rhodium acetate, or combinations thereof. Phosphorus component precursors are also generally salts of phosphorus components include, but are not limited to, ammonium phosphate dibasic ((NH₄)₂HP0₄), ammonium dihydrogen phosphate

(NH₄H₂P0₄) or combinations thereof

In some embodiments, the support material is co-impregnated with the phosphorus component precursor and the rhodium component precursor, wherein the phosphorus component precursor and the rhodium component precursor can be impregnated into the support material at the same time or stepwise. For example, in some embodiments, the disclosed method involves impregnating the support material with a rhodium component precursor to yield a rhodium component-impregnated support material, and subsequently impregnating the rhodium component-impregnated support material with a phosphorus component precursor to obtain a rhodium component/phosphorus component-containing material. In some embodiments, the disclosed method involves impregnating the support material with a phosphorus component precursor to yield a phosphorus component-impregnated support material, and subsequently impregnating the phosphorus component-impregnated support material with a rhodium component precursor to afford a rhodium component/phosphorus component-containing material. In some embodiments, the disclosed method involves impregnating the support material with a solution containing a phosphorus component precursor and a rhodium component precursor to afford a rhodium component/phosphorus component-containing material in a single impregnation step.

In some embodiments, the disclosed method involves impregnation of the support material with a rhodium component precursor to yield a rhodium component-impregnated support material, and subsequently physically mixing the rhodium component-impregnated support material with a phosphorus component precursor (e.g., ammonium phosphate dibasic ((NH₄)₂HP0₄), ammonium dihydrogen phosphate (NH₄H₂P0₄)) to afford a rhodium component/phosphorus component-containing material.

In some embodiments, the rhodium component/phosphorus component-containing material can be mixed with other components by conventional methods. For example, in some embodiments, the rhodium component/phosphorus component-containing material can be mixed with a phosphorus trap material (e.g., an alkaline earth metal component supported on a metal oxide or as a composite with a metal oxide) and/or refractory metal oxide.

The above referenced impregnation steps can be conducted, e.g., using an incipient wetness technique. Incipient wetness impregnation techniques, also called capillary impregnation or dry impregnation, are commonly used for the synthesis of heterogeneous materials, i.e., catalysts. Typically, a precursor is dissolved in an aqueous or organic solution and then the resulting solution is added to a catalyst support containing the same pore volume as the volume of the solution that was added. Capillary action draws the solution into the pores of the support. Solution added in excess of the support pore volume causes the solution transport to change from a capillary action process to a diffusion process, which is much slower. The support material, e.g., in particulate from, is typically dry enough to adsorb substantially all of the solution to form a moist solid. The catalyst can then be dried and calcined to remove the volatile components within the solution, depositing the rhodium component and/or phosphorus component on the surface of the support material. The concentration profile of the impregnated material depends on the mass transfer conditions within the pores during impregnation and drying.

Following treatment of the support material with the active metal solution, the material is dried, such as by heat treating the material at elevated temperature (e g , 100-150°C) for a period of time (e g , 1-3 hours), and then calcined to convert the active metal to a more catalytically active form. An exemplary calcination process involves heat treatment in air at a temperature of about 400-550°C for 10 min to 3 hours. The above process can be repeated as needed to reach the desired level of metal impregnation.

The impregnated supports can be mixed with other components by conventional methods. For example, in some embodiments, the rhodium component/phosphorus component-containing material can be mixed with a phosphorus trap material (e.g., an alkaline earth metal component supported on a metal oxide or is a composite with a metal oxide) and/or refractory metal oxide.

Substrate Coating Process

The catalyst compositions, typically prepared in the form of catalyst particles as noted above, can be mixed with water to form a slurry for purposes of coating a catalyst substrate, such as a honeycomb -type substrate. In addition to the catalyst particles, the slurry may optionally contain a binder in the form of alumina, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide, associative thickeners, and/or surfactants (including anionic, cationic, non-ionic or amphoteric surfactants). Other exemplary binders include bohemite, gamma-alumina, or delta/theta alumina, as well as silica sol. When present, the binder is typically used in an amount of about 1-5 wt.% of the total washcoat loading. Addition of acidic or basic species to the slurry can be carried out to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of ammonium hydroxide, aqueous nitric acid, or acetic acid. A typical pH range for the slurry is about 3 to 12.

The slurry can be milled to reduce the particle size and enhance particle mixing. The milling can be accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry may be, e.g., about 20-60 wt.%, more particularly about 20-40 wt.%. In one embodiment, the post-milling slurry is characterized by a D90 particle size of about 10 to about 40 microns, preferably 10 to about 30 microns, more preferably about 10 to about 15 microns. The D90 is determined using a dedicated particle size analyzer. The equipment employed in this example uses laser diffraction to measure particle sizes in small volume slurry. The D90, typically with units of microns, means 90% of the particles by number have a diameter less than that value.

The slurry is coated on the catalyst substrate using any washcoat technique known in the art. In one embodiment, the catalyst substrate is dipped one or more times in the slurry or otherwise coated with the slurry. Thereafter, the coated substrate is dried at an elevated temperature (e.g., 100-150 °C) for a period of time (e.g., 10 min - 3 hours) and then calcined by heating, e.g., at 400-600 °C, typically for about 10 minutes to about 3 hours. Following drying and calcining, the final washcoat coating layer can be viewed as essentially solvent-free.

After calcining, the catalyst loading obtained by the above described washcoat technique can be determined through calculation of the difference in coated and uncoated weights of the substrate. As will be apparent to those of skill in the art, the catalyst loading can be modified by altering the slurry rheology. In addition, the coating/drying/calcining process to generate a washcoat can be repeated as needed to build the coating to the desired loading level or thickness, meaning more than one washcoat may be applied.

Method of Hydrocarbon (HQ. Carbon Monoxide (CO), and Nitrogen Oxides (N( ) Conversion

In general, hydrocarbons, carbon monoxide, and nitrogen oxides present in the exhaust gas stream of a gasoline or diesel engine can be converted to carbon dioxide, nitrogen, and water according to the equations shown below: 2CO + 0₂→ 2C0₂

C_xH_y + (x+y/2)0₂→ xC0₂ + yH₂0

2NO + 2CO→ N₂ + 2C0₂

2NO + 2H₂→ N₂ + 2H₂0

NO + C_xH_y→ N₂ + H₂0 + C0₂

Typically, hydrocarbons present in an engine exhaust gas stream comprise Ci-C₆ hydrocarbons (i.e., lower hydrocarbons), although higher hydrocarbons (greater than C₆) can also be detected.

The disclosed catalytic article can at least partially convert HC, CO, and NO_x in an exhaust gas stream. As such, methods herein generally comprise contacting the gas stream with a catalytic article as described herein. In some embodiment, the catalytic article converts hydrocarbons to carbon dioxide and water. In some embodiments, the catalytic article converts at least about 60%, at least about 70%, at least about 75%, at least about 80%, at least about 90%, or at least about 95% of the amount of hydrocarbons present in the exhaust gas stream prior to contact with the catalytic article. In some embodiments, the catalytic article converts carbon monoxide to carbon dioxide. In some embodiments, the catalytic article converts at least about 60%, at least about 70%, at least about 75%, at least about 80%, at least about 90%, or at least about 95% of the amount of carbon monoxide present in the exhaust gas stream prior to contact with the catalytic article. In some embodiment, the catalytic article converts nitrogen oxides to nitrogen. In some embodiments, the catalytic article converts at least about 60%, at least about 70%, at least about 75%, at least about 80%, at least about 90%, or at least about 95% of the amount of nitrogen oxides present in the exhaust gas stream prior to contact with the catalytic article. In some embodiment, the catalytic article converts at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 95% of the total amount of hydrocarbons, carbon dioxide, and nitrogen oxides combined present in the exhaust gas stream prior to contact with the catalytic article.

In the methods described herein, the catalytic article of the invention reduces NO_x, CO, and HC levels to levels that are lower than those provided by comparative catalytic article comprising the same catalytic material at the same loading, but containing no phosphorus component. In some embodiments, the disclosed catalytic article reduces NO_x, CO, and HC levels in the gas stream to levels that are about 5% to about 75%, about 10% to about 70%, or about 15% to about 0% lower than those provided by catalytic articles comprising the same catalytic material at the same loading, but containing no phosphorus component. For example, in some embodiments, the method provides catalytic articles capable of reducing NO_x, CO, and HC levels in a gas stream to levels that are least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 60%, or at least about 70% lower than the levels provided by a comparative catalytic article, with an upper boundary of 75%.

In some embodiments, the catalytic article of the invention reduces the NO_x level in the gas stream to a level that is about 5% to about 50%, about 10% to about 40%, or about 10% to about 30% lower than that provided by a comparative catalytic article. For example, in some embodiments, the method provides catalytic articles capable of reducing the level of NO_x levels in a gas stream to a level that is at least 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, or at least about 45% lower than that provided by a comparative catalytic article, with an upper boundary of about 50%. In some embodiments, the catalytic article of the invention reduces the HC level in a gas stream to a level that is about 5% to about 50%, about 10% to about 40%, or about 10% to about 30% lower than that provided by a comparative catalytic article. For example, in some embodiments, the method provides catalytic articles reducing the HC level in a gas stream to a level that is at least 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, or at least about 45% lower than that provided by a comparative catalytic article, with an upper boundary of about 50%. In some embodiments, the catalytic article of the invention reduces the CO level in a gas stream to a level that is about 1% to about 20%, about 3% to about 15%, or about 5% to about 12% lower than that provided by a comparative catalytic article. For example, in some embodiments, the method provides catalytic articles reducing the CO level in a gas stream to a level that is at least 1%, at least about 3%, at least about 5%, at least about 8%, at least about 12%, or at least about 15% lower than that provided by a comparative catalytic article, with an upper boundary of about 20%.

In certain methods of treating an engine exhaust gas stream with a catalytic article disclosed herein, the light-off temperature of the catalytic article for conversion of HC, CO, and NO_x is lower than that of a comparable catalytic article comprising the same catalytic material at the same loading, but containing no phosphorus component. In some embodiments, the disclosed catalytic article has a light-off temperature for the conversion of HC, CO, and NO_s that is about 1% to about 20%, or about 5% to about 15% lower than that of a catalytic article comprising the same catalytic material at the same loading but containing no phosphorus component. In some embodiments, the catalytic article of the invention has a light-off temperature for the conversion of HC that is about 1% to about 15%, or about 5% to about 10% lower (or at least about 15%, at least about 14%, at least about 13%, at least about 12%, at least about 11%, at least about 10%, at least about 9%, at least about 8%, at least about 7%, at least about 6%, at least about 5%, at least about 4%, at least about 3%, at least about 2%, or at least about 1% lower) than that of a comparative catalytic article. In some embodiments, the catalytic article of the invention has a light-off temperature for the conversion of CO that is about 1% to about 15%, or about 5% to about 10% lower (or at least about 15%, at least about 14%, at least about 13%, at least about 12%, at least about 11%, at least about 10%, at least about 9%, at least about 8%, at least about 7%, at least about 6%, at least about 5%, at least about 4%, at least about 3%, at least about 2%, or at least about 1% lower) than that of a comparative catalytic article. In some embodiments, the catalytic article of the invention has a light-off temperature for the conversion of NO_xthat is about l% to about 15%, or about 5% to about 10% lower (or at least about 15%, at least about 14%, at least about 13%, at least about 12%, at least about 11%, at least about 10%, at least about 9%, at least about 8%, at least about 7%, at least about 6%, at least about 5%, at least about 4%, at least about 3%, at least about 2%, or at least about 1% lower) than that of a comparative catalytic article. Emission Treatment System

The present invention also provides an emission treatment system generally comprising an engine producing an exhaust gas stream and a catalytic article as disclosed herein positioned downstream from the engine in fluid communication with the exhaust gas stream. The engine can be a gasoline engine and/or compressed natural gas (CNG) engine (e.g., for gasoline and compressed natural gas mobile sources such as gasoline or CNG cars and motorcycles) or can be an engine associated with a stationary source (e.g., electricity generators or pumping stations). In some embodiments, the emission treatment system further comprises one or more additional catalytic components. For example, the treatment system can include further components, such as a hydrocarbon trap, ammonia oxidation (AMOx) materials, ammonia- generating catalysts, a selective catalytic reduction (SCR) catalyst, and NO_x storage and/or trapping components (LNTs). The preceding list of components is merely illustrative and should not be taken as limiting the scope of the invention. The relative placement of the various catalytic components present within the emission treatment system can vary. For example, in some embodiments, a LNT component is positioned upstream of the catalytic article as disclosed herein. In some embodiments, a AMOx component or a SCR component is located downstream of the catalytic article as disclosed herein.

EXAMPLES

Aspects of the present invention are more fully illustrated by the following examples, which are set forth to illustrate certain aspects of the present invention and are not to be construed as limiting thereof.

Example 1 : TPR measurements of phosphorus-modified catalyst compositions.

Two phosphorus-modified catalyst compositions comprising 0.5 wt.% of a rhodium component supported on lanthana-zirconia (9% La₂0₃-Zr0₂), optionally impregnated with a phosphorus component, were analyzed by H₂ Temperature Programed Reduction (TPR) before and after exposure to lean-rich aging at 1050 °C with 10% H₂0 for 5 hours. The samples were pretreated in 4% 02/Helium at 500 °C for 30 min, and then cooled down to 50 °C. Then the samples were reduced in 1% H2/N2 up to 900 °C with 10 °C/min programed temperature ramping rate. See, for example, Zeng et al., Part I: A Comparative Thermal Aging Study on the Regenerability of Rh/Al₂0₃ and Rh/Ce_x O_y-Zr0₂ as Model Catalysts for Automotive Three Way Catalysts, Catalysts, 2015, 5, 1770-1796, which is herein incorporated by reference in its entirety. The phosphorus-modified catalyst compositions containing a phosphorus component showed a significant increase in H₂ consumption (see sample 3 and 4 in Table 1), indicating reducibility of the rhodium species on the phosphorus-modified catalyst surface may be responsible for the observed enhanced HC, CO, and NO_x performance . Table 1. H₂-TPR results of 0.5 wt% Rh/La₂0₃-Zr0₂ w/wo P before/after aging

Example 2: Preparation and evaluation of powder samples of rhodium -containing catalyst materials containing a rhodium component supported on a lanthana-zirconia support material impregnated with various amounts of phosphorus.

Rhodium -containing catalyst materials were prepared using different preparation methods and were tested for their light-off temperature performance.

Preparation Method A:

Several samples of lanthana-zirconia support material (9% La₂0₃-91% Zr0₂) containing 0%, 1%, 3%, and 5% wt. of phosphorus were prepared by employing impregnation methods (i.e., using a

(NH₄)₂HP0₄ solution as a phosphorus precursor) to first introduce phosphorus into the lanthana-zirconia support material, followed by calcination at 550 °C for 5 hours. Next, rhodium was introduced into the phosphorus-impregnated lanthana-zirconia support material using impregnation methods to afford 0.5% Rh/P-La₂0₃-Zr0₂, followed by calcination at 550 °C for 2 hours. All of the samples were aged at 950 °C or 1050 °C under lean-rich conditions with 10% steam for 5 hours. The powder test results show that HC, CO and NO light-off temperatures of the catalytic materials containing phosphorus (i.e., samples 2 and 4 in Table 2) were generally lower than those of catalyst materials containing no phosphorus (i.e., samples 1 and 3 in Table 2). Table 2. T₅₀ results of HC, CO and NO_x light-off on 0.5 wt% Rh/La₂0₃-Zr0₂ with and without (w/wo) P after 950 °C or 1050 °C aging (with phosphorus introduced first and Rh then loaded)

4 0.5 wt% Rh/5% P-La₂O₃-ZrO₂-1050

368 312 302

Aged

Preparation Method B:

A large sample of 0.5% Rh La₂0₃-Zr0₂ was prepared via impregnation methods, followed by calcination at 550 °C for 2 hours. The calcined 0.5% Rh/La₂0₃-Zr0₂ material was divided into several smaller samples.

Impregnation of a series of smaller samples of the 0.5% Rh/La₂0₃-Zr0₂ material with various amounts of phosphorus (0, 1, 3, and 5 % wt.) using a (NH₄)₂HP0₄ solution as a phosphorus source followed by calcination at 550 °C for 5 hours afforded Rh/La₂0₃-Zr0₂ impregnated with phosphorus. All of the samples were then aged at 950 °C or 1050 °C under lean-rich conditions with 10% steam for 5 hours. The powder test results show that the HC, CO and NO_x light-off temperatures of rhodium-containing catalyst materials with phosphorus (samples 2 and 4 in Table 3) were lower (meaning higher light-off performance) than those of rhodium -containing catalyst materials with no phosphorus (especially after aging at 1050 °C) (samples 1 and 3 in Table 3). For 950 °C aged samples, the HC and CO light-off performance of rhodium- containing catalyst materials containing phosphorus was lower, while the NO_x light-off performance was higher.

Table 3. T₅₀ results of HC, CO and NO_x light-off on 0.5 wt% Rh/La₂0₃-Zr0₂ w/wo P after 950 °C and 1050 °C aging (with rhodium loaded first and phosphorus then introduced by impregnation)

Preparation Method C:

A sample of (0.5% Rh-0.5% P)/La₂0₃-Zr0₂ was prepared by co-impregnation of Rh nitrate and NH H₂P0₄ (ammonium dihydrogen phosphate, acidic precursor) on lanthana-zirconia followed by calcination at 550 °C for 2 hours. The sample was then aged at 950 °C under lean-rich conditions with 10% steam for 5 hours. The powder test results show that HC, CO and NO_x light-off performance of rhodium- containing catalyst materials containing phosphorus were higher than those of rhodium -containing catalyst materials without phosphorus, even at a low phosphorus concentration level (see Table 4). This result suggests that the co-impregnation of rhodium and phosphorus onto the support is feasible for preparing the phosphorus-promoted rhodium-containing catalyst material for TWC application, and the co-impregnation step can simplify the catalyst preparation procedure. To prevent the covering of Rh species by P species resulting in less exposure of Rh active sites, the P species can be introduced into the La-Zr0₂ material first, followed by Rh introduction, or P and Rh can be co-impregnated onto the support material(s).

Table 4. T₅₀ results of HC, CO and N0_X light-off on 0.5 wt% Rh/La₂0₃-Zr0₂ w/wo P after 950 °C aging (Rh and P co-impregnated onto support)

Example 3 : Preparation and evaluation of powder samples of rhodium -containing catalyst materials containing a rhodium component supported on a lanthana-zirconia support material physically mixed with phosphorus

A sample of 0.5% Rh/La₂0₃-Zr0₂ was prepared and calcined at 550 °C for 2 hours. The calcined sample 0.5% Rh/La₂0₃-Zr0₂ was physically mixed with (NH₄)₂HP0₄ salt containing 5 wt.% phosphorus, and was calcined at 550 °C for 5 hours. The calcined sample was then aged at 950 °C or 1050 ^CC under lean- rich conditions with 10% steam for 5 hours.

The powder test results show that HC, CO and NO_x light-off performance of rhodium -containing catalyst materials with phosphorus (Samples 2 and 4 in Table 5) were higher than those of rhodium- containing catalyst materials without phosphorus (samples 1 and 3 in Table 5), especially after aging at 1050 °C. These results suggest that physically mixing Rh/La₂0₃-Zr0₂ with a phosphorus salt provides beneficial effects of the phosphorus species on the TWC performance. For 950 °C aged samples, the HC light-off performance of the rhodium-containing catalyst materials with phosphorus was lower, while the CO and NO_x light-off performance were higher. From the point of view of practical operation to avoid the spreading of phosphates onto other TWC materials, this represents a viable method for fixing the phosphates on La, Zr- material surface by impregnation/co-impregnation with Rh.

Table 5. T₅₀ results of HC, CO and NO_x light-off of 0.5 wt.% Rh/La₂0₃-Zr0₂ w/wo P after 950 and 1050 °C agmg (with rhodium loaded first and phosphorus than introduced by physical mixing)

0.5 wt% Rh/La₂O₃-ZrO₂-1050

3 379 336 332

Aged

0.5 wt% Rh/La₂0₃-Zr0₂ + 5% P-

4 348 300 294

1050 Aged

Example 4: Preparation of catalytic article and engine testing

(Rh-P)/La₂0₃-Zr0₂ material was incorporated into a fully formulated catalytic article by washcoating onto a cordierite substrate. Figure 6 shows a layered TWC catalyst design having Rh/La₂0₃- Zr0₂ with and without phosphorus present in the top layer. Washcoat Catalyst 1 is a reference catalyst with Pd in the bottom coat and Rh in the top coat, while Washcoat Catalyst 2 contains the same Pd bottom coat as Washcoat Catalyst 1 but has a different Rh-based top coat in which Rh-N and NH₄H₂P0₄ with a Rh: P molar ratio of 1:8 were co-impregnated onto La₂0₃-Zr0₂, followed by calcination at 800 °C. Catalyst samples were cored to 1.0" x 1.5" size, aged at 950 °C for 5 hours under lean-rich conditions with 10% steam, and tested on a gasoline vehicles simulator (GVS) reactor. As the GVS results show in Figures 7-9, comparing the reference Washcoat Catalyst 1 with Washcoat Catalyst 2 containing (Rh-P)/La₂0₃-Zr0₂ in the top coat, a decrease of about 10% in NO_x emission and a decrease of about 22% in THC emission was observed, although with slightly increased CO emission. This suggests the beneficial effects of having (Rh-P)/ La₂0₃- Zr0₂ incorporated into the coated catalysts with two layers.

Example 5 : Preparation of catalytic article and engine testing

Another set of catalysts with Pd in the top layer and Rh in the bottom layer was designed and prepared (Figure 6) to further elucidate the benefit from (Rh-P)/La₂0₃-Zr0₂ material in a fully formulated TWC catalyst. Washcoat Catalyst 3 was prepared as a reference catalyst without P in the Rh bottom layer, and Washcoat Catalyst 4 contained (Rh-P)/La₂0₃-Zr0₂ with a Rh: P molar ratio of 1:8 from the co- impregnation of Rh-N and NH₄H₂P0₄ onto La₂0₃-Zr0₂ followed by calcination at 800 °C. Catalyst samples were cored to 1.0" x 1.5" size, aged at 950 °C for 5 hours under lean-rich condition with 10% steam, and tested on gasoline vehicles simulator (GVS) reactor. As the GVS results show in Figures 10-12, Washcoat Catalyst 4 with (Rh-P)/La₂0₃-Zr0₂ in the Rh bottom coat showed lower emission for NO_x (about 11%),

THC (about 10%) and CO (about 14%) than those of reference Washcoat Catalyst 3. This further shows that the benefits of powder (Rh-P)/La₂0₃-Zr0₂ material can be successfully incorporated into the coated catalysts, not only in the top coat but also in the bottom coat for layered TWC catalysts. In summary, these phosphorus-modified lanthana-zirconia based materials as Rh supports incorporated in washcoated full part TWC catalysts (optionally in combination with other phosphorus trapping materials) can improve TWC light-off performance and phosphorus resistance simultaneously.

Claims

THAT WHICH IS CLAIMED:

1. A TWC catalytic article comprising a catalytic material on a substrate, the catalytic material comprising a first layer and a second layer,

wherein the first layer comprises:

a rhodium component impregnated on a support material, and

a phosphorus component, wherein the phosphorus component is impregnated on the support material or is in a physical mixture with the rhodium component impregnated on the support material.

2. The TWC catalytic article of claim 1, wherein the support material is a zirconia-based support material .

3. The TWC catalytic article of claim 2, wherein the zirconia-based support material is zirconia, lanthana-zirconia, titania-zirconia, titania-lanthana-zirconia, alumina-zirconia, baria-zirconia, strontia-zirconia, neodymia-zirconia, praseodymia-zirconia, tungsten oxide -zirconia, niobia-zirconia, yttria- zirconia, or any combination thereof.

4. The TWC catalytic article of claim 3, wherein the zirconia-based support material is lanthana-zirconia.

5. The TWC catalytic article of claim 4, wherein the lanthana-zirconia comprises zirconia in an amount from about 80 to about 99 wt.%.

6. The TWC catalytic article according to any one of the preceding claims, wherein the phosphorus component is present in an amount ranging from about 0.1% to about 10 wt.% based on the total weight of the support material, the rhodium component, and the phosphorus component; or the total weight of the physical mixture of the rhodium impregnated on the support material and the phosphorus component.

7. The TWC catalytic article of claim 6, wherein the phosphorus component is impregnated on the support material.

8. The TWC catalytic article according to any one of the preceding claims, further comprising a phosphorus trap material in the first layer, wherein the phosphorus trap material comprises an alkaline earth metal component and a metal oxide.

9. The TWC catalytic article of claim 8, wherein the alkaline earth metal component is supported on the metal oxide or is in the form of a composite with the metal oxide.

10. The TWC catalytic article of claim 9, wherein the alkaline earth metal component is a composite of barium oxide and alumina.

11. The TWC catalytic article of claim 8, wherein the alkaline earth metal component is present in an amount of about 1 to about 20 wt.% of the first layer.

12. The TWC catalytic article of claim 8, wherein the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof.

13. The TWC catalytic article of claim 8, wherein the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof.

14. The TWC catalytic article of claim 9, wherein the phosphorus component is impregnated on the support material, the support material is lanthana-zirconia, and wherein the phosphorus trap material comprises barium oxide and alumina.

15. The TWC catalytic article of claim 14, wherein the second layer comprises barium oxide and a palladium component impregnated on ceria-zirconia and lanthana-alumina.

16. The TWC catalytic article according to any one of the preceding claims, further comprising a refractory metal oxide in the first layer selected from alumina, lanthana-alumina, ceria-alumina, zirconia- alumina, ceria-zirconia-alumina, lanthana-zirconia-alumina, lanthana-neodymia-alumina, and combinations thereof.

17. The TWC catalytic article of claim 16, wherein the refractory metal oxide is lanthana- alumina.

18. The TWC catalytic article according to any one of the preceding claims, wherein the first layer contains the rhodium component in an amount from about 0.05 to about 5 wt.%.

19. The TWC catalytic article according to any one of the preceding claims, wherein the second layer comprises a platinum group metal (PGM) component impregnated on a porous support material.

20. The TWC catalytic article of claim 19, wherein at least a portion of the porous support material comprises an oxygen storage component selected from ceria, zirconia, lanthana, yttria, neodymia, praseodymia, niobia, and combinations thereof.

21. The TWC catalytic article of claim 20, wherein the oxygen storage component is ceria- zirconia, comprising ceria in an amount from about 5 to about 75 wt.%.

22. The TWC catalytic article of claim 19, wherein at least a portion of the porous support material is a refractory metal oxide support selected from alumina, lanthana-alumina, ceria-alumina, zirconia-alumina, ceria-zirconia-alumina, lanthana-zirconia-alumina, lanthana-neodymia-alumina, and combinations thereof.

23. The TWC catalytic article of claim 19, wherein the PGM component is a palladium component.

24. The TWC catalytic article of claim 19, wherein the second layer further comprises barium oxide, magnesium oxide, calcium oxide, strontium oxide, lanthanum oxide, cerium oxide, zirconium oxide, manganese oxide, copper oxide, iron oxide, praseodymium oxide, yttrium oxide, neodymium oxide, or any combination thereof.

25. The TWC catalytic article of claim 19, wherein the second layer comprises barium oxide and a palladium component impregnated on ceria-zirconia and lanthana-alumina.

26. The TWC catalytic article according to any one of the preceding claims, wherein the first layer is directly disposed on the substrate and the second layer is disposed on top of the first layer.

27. The TWC catalytic article according to any one of the preceding claims, wherein the second layer is directly disposed on the substrate and the first layer is disposed on top of the second layer.

28. The TWC catalytic article according any one of the preceding claims, wherein the substrate is a metal or ceramic monolithic honeycomb substrate.

29. The TWC catalytic article according to any one of the preceding claims, wherein the substrate is a wall flow filter substrate or a flow through substrate.

30. The TWC catalytic article according to any one of the preceding claims, wherein the catalytic material is effective for three-way conversion to oxidize carbon monoxide and hydrocarbons and reduce nitrogen oxides.

31. A method of making the TWC catalytic according to any one of the preceding claims, comprising: disposing the first layer and the second layer on the substrate to yield a catalytic material -coated substrate, and

calcining the catalytic material-coated substrate to render the TWC catalytic article.

32. A method of making a TWC catalytic article comprising a catalytic material disposed on a substrate, wherein the catalytic material comprises a first layer composition and a second layer composition, the method comprising:

(a) combining a support material with a phosphorus component precursor and a rhodium

component precursor so as to impregnate at least the rhodium component on the support material;

(b) calcining the product obtained from step (a) to afford a dried rhodium

component/phosphorus component-containing material; and

33. The method of claim 32, wherein step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor or impregnating the support material with the rhodium component precursor to give a rhodium component-impregnated support material and mixing the rhodium component-impregnated support material with the phosphorus component precursor.

34. The method of claim 32, wherein step (a) comprises impregnating the support material with the phosphorus component precursor to obtain a phosphorus component-impregnated support material, and then impregnating the phosphorus component-impregnated support material with the rhodium component precursor to obtain the rhodium component/phosphorus component-containing material.

35. The method of claim 32, wherein step (a) comprises impregnating the support material with the rhodium component precursor to obtain a rhodium component-impregnated support material, and then impregnating the rhodium component-impregnated support material with the phosphorus component precursor or physically mixing the rhodium component-impregnated support material with the phosphorus component precursor to obtain the rhodium component/phosphorus component-containing material.

36. The method of claim 32, wherein step (a) comprises impregnating the support material with the rhodium component precursor and the phosphorus component precursor simultaneously.

37. The method of claim 32, wherein the phosphorus component precursor is (NH₄)₂HP0₄.

38. The method of claim 32, wherein the rhodium component precursor is rhodium chloride, rhodium nitrate, rhodium acetate, or a combination thereof.

39. The method of claim 32, wherein the support material is a zirconia-based support material.

40. The method of claim 39, wherein the zirconia-based support material is lanthana-zirconia.

41. The method of claim 32, wherein the phosphorus trap material is a composite of barium oxide and alumina.

42. The method of claim 32, wherein mixing of the dried rhodium component/phosphorus component-containing material with a phosphorus trap material affords the first layer composition.

43. The method of claim 42, wherein the phosphorus trap material comprises an alkaline earth metal component and a metal oxide.

44. The method of claim 43, wherein the alkaline earth metal component is selected from barium oxide, magnesium oxide, calcium oxide, strontium oxide, and combinations thereof.

45. The method of claim 39, wherein the alkaline earth metal component is barium oxide.

46. The method of claim 43, wherein the metal oxide is alumina, zirconia, titania, ceria, or a combination thereof.

47. The method of claim 46, wherein the metal oxide is alumina.

48. The method of claim 43, wherein the phosphorus trap material is a composite of barium oxide and alumina.

49. The method of claim 32, wherein the second layer composition comprises a platinum group metal component impregnated on a porous support material.

50. A method for reducing CO, HC, and NO_x levels in a gas stream, comprising contacting the gas stream with the TWC catalytic article of any one of claims 1-30 for a time and at a temperature sufficient to reduce CO, HC, and NO_x levels in the gas stream.

51. The method of claim 0, wherein the CO, HC, and NO_x levels in the gas stream are reduced by at least 50% compared to the CO, HC, and NO_x levels in the gas stream prior to contact with the TWC catalytic article.

52. An emission treatment system for treatment of an exhaust gas stream, the emission treatment system comprising:

an engine producing an exhaust gas stream; and

the TWC catalytic article of any one of claims 1-30 positioned downstream from the engine in fluid communication with the exhaust gas stream and adapted for the abatement of CO and HC and conversion of ΝΟ_χΐο Ν₂.

53. The emission treatment system of claim 52, wherein the engine is a gasoline engine or diesel engine.