Three-way catalyst systems including Fe-activated Rh and Ba-Pd material compositions

Three way catalysts (TWCs) for catalyst systems are disclosed. The disclosed TWC systems include Iron (Fe)-activated Rhodium (Rh) and Barium (Ba)-Palladium (Pd) layers capable of interacting with conventional and/or non-conventional catalyst supports and additives. Variations of TWC system samples are produced including Fe-activated Rh layers deposited onto a washcoat (WC) layer having one or more of an oxygen storage material (OSM). Other TWC system samples are produced including an impregnation (IMPG) layer having loading variations of Ba within a Pd, Ce, and Nd applied onto an OSM WC layer, and a further overcoat layer including Fe-activated Rh is applied onto the IMPG layer. The catalytic performance of disclosed TWC catalysts is evaluated by performing a series of light-off tests, wide pulse perturbation tests, and standard isothermal oxygen storage capacity oscillating tests. Disclosed TWC catalysts exhibit high catalytic performance and significant oxygen storage capacity.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates in general to materials used in three-way catalytic (TWC) converters, and more specifically, to TWC catalysts systems including Fe-activated Rh and Ba—Pd material compositions employed within TWC converters.

2. Background Information

Three-way catalyst (TWC) systems are located within the exhaust systems of internal combustion gas engines to promote the oxidation of unburned hydrocarbons (HC) and carbon monoxide (CO), and the reduction of nitrogen oxides (NOX) within the exhaust gas stream.

The elevated cost of conventional TWC systems for controlling/reducing HC, CO and NOXemissions is primarily due to (a) the presence of complex groups of metal compounds within the catalyst systems and (b) the cost of obtaining said metals.

The catalysts in TWC systems typically contain platinum group metals (PGM), e.g., Platinum (Pt), Palladium (Pd), and Rhodium (Rh), amongst others. Pt and Pd are generally used for HC and CO conversion, while Rh is more effective for the reduction of NOX. Although the price of Rh tends to fluctuate, its greater performance in NOXconversion makes Rh the most common element employed in TWCs.

Accordingly, as emission standards for HC, CO and NOXcontinue to become more stringent, there is a continuing need to provide TWC systems enabled to provide enhanced conversion levels so that the emission limits can be achieved cost-effectively.

SUMMARY

The present disclosure describes three-way catalysts (TWCs) of enhanced catalytic performance. The improvements in catalytic performance are enabled by material compositions including Iron (Fe)-activated Rhodium (Rh) and Barium (Ba)-Palladium (Pd) in layers capable of interacting with conventional and/or non-conventional catalyst supports and additives. Catalysts of enhanced efficiency can be produced using a variety of Barium oxide loadings impregnated onto separate Alumina/OSM layers in interaction with different Rh—Fe loadings and other platinum group metals (PGM) material compositions.

In some embodiments, TWCs are configured to include a substrate and one or more of a washcoat (WC) layer, an impregnation (IMPG) layer, and/or an overcoat (OC) layer. In these embodiments, the WC layer is deposited onto the substrate, the IMPG layer is deposited onto the WC layer, and the OC layer is deposited onto the WC/IMPG layer.

In some embodiments, TWC catalyst samples are produced employing a 1.00 L cordierite substrate having a 4.66″ diameter, 600 cells per square inch (CPSI), and 3.5 mil wall thickness. In these embodiments, the WC layer is produced using a slurry that includes one or more of an oxygen storage material (OSM). The OSM can be a fluorite phase oxygen storage material including one or more of Cerium (Ce) oxide within a range from about 10 wt % to about 75 wt %, Zirconium-Hafnium (Zr—Hf) oxide within a range from about 25 wt % to about 90 wt %, Neodymium (Nd) oxide within a range from about 0 wt % to about 15 wt %, and Yttrium (Y) oxide within a range from about 0 wt % to about 15 wt %, and from about 0 wt % to about 15 wt % other light lanthanides.

In a set of exemplary embodiments, herein referred as TWC catalyst Types A, B, C, D, E, F, G, H, I, and J, the WC layer is implemented as a slurry having a total loading of about 60 g/L, including about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y oxides, fluorite phase OSM. In these exemplary embodiments, the WC layer is deposited onto the cordierite substrate and further calcined to achieve adhesion of the ceramic-coating layer on top of the substrate.

Further to these exemplary embodiments, one or more IMPG layers are formed using one or more of Rhodium (Rh) nitrate and Iron (Fe) nitrate applied to the coated substrate at selected loadings. Still further to these exemplary embodiments, suitable Rh loadings include loadings within a range from about 1 g/ft3to about greater than 20 g/ft3, and suitable Fe loadings include loadings within a range from about 60 g/ft3to about 630 g/ft3. In these exemplary embodiments, the IMPG layer for TWC catalyst Types A, B, C, D, E, F, G, H, I, and J is implemented including loadings of about 3.0 g/ft3Rh and about 140 g/ft3Fe in a water-based solution and applied onto the WC layer. Further to these exemplary embodiments, the IMPG layer is then calcined to generate the oxides within the porous WC layer. Still further to this exemplary embodiment, TWC catalyst Type A is a reference Fe-activated Rh catalyst which does not include an OC layer and serves as a baseline to gauge the potential effects of other common and/or non-conventional catalyst supports and additives within an OC layer as the other aforementioned TWC catalyst samples.

In these exemplary embodiments, the OC layer for TWC catalyst Types B, C, D, E, F, G, H, I, and J is implemented as a slurry including variations of one or more of an OSM, support oxides, Barium (Ba) carbonate, different doped Alumina, and Strontium (Sr) carbonate, amongst others, at selected total loadings, respectively. Further to these exemplary embodiments, the slurry is deposited onto the impregnated WC layer and subsequently calcined to achieve adhesion of the deposited layer to the top of the impregnated WC layer. All OC layers for catalyst Types B through J are PGM free catalysts. The main driver on catalytic activity is the Fe-activated Rh OSM layer underneath. This allows the detection of positive and negative influences of the other coating materials.

TWC catalyst Type B includes an OSM comprising about 30 wt % Ce, about 60% Zr—Hf, about 5% Nd, and about 5% Praseodymium (Pr) oxides. TWC catalyst Type C includes an OSM comprising about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y oxides. TWC catalyst Type D includes a high surface area Alumina oxide. TWC catalyst Type E includes a high surface area Lanthanum (La)-stabilized Alumina oxide. TWC catalyst Type F includes a specialized highly calcined, high surface area, La-stabilized Alumina oxide. TWC catalyst Type G includes a Ba carbonate powder. TWC catalyst Type H includes a La carbonate powder. TWC catalyst Type I includes a Sr carbonate powder. TWC catalyst Type J includes a Niobium (Nb) oxide powder.

In other embodiments, TWC catalyst samples are produced employing a 0.445 L cordierite substrate having a 4.16″ diameter, 600 CPSI, and 4.3 mil wall thickness. In these embodiments, the WC layer is produced using a slurry having material compositions of about 40 wt % of an OSM including about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y oxides, and about 60 wt % of a high surface area Alumina with La2O3stabilized at high temperature. Further to these embodiments, the slurry is deposited onto the cordierite substrate as a WC layer and further calcined to achieve adhesion of the ceramic-coating layer on top of the substrate.

In another set of exemplary embodiments, herein referred as TWC catalyst Types K, L, M, N, O, P, and Q, the IMPG layer is produced as a slurry including Palladium (Pd) nitrate, Ce nitrate, and Nd nitrate using loadings of about 92.6 g/ft3Pd, about 105.8 g/ft3Ce, and about 12.1 g/ft3Nd. In these exemplary embodiments, the slurry includes loading variations using a soluble Ba salt within a range of Ba loading from about 57.6 g/ft3to about 691.3 g/ft3. Further to these exemplary embodiments, the water-based solution of Pd, Ce, Nd, and Ba salts is deposited onto the WC layer and further calcined to generate the oxides within the porous WC layer.

In these exemplary embodiments, the OC layer for TWC catalyst Types K, L, M, N, O, P, and Q is implemented as a slurry including a powder batch of a Ce—Zr—Nd—Y OSM that is first impregnated with Fe nitrate and then calcined at about 750° C. Further to these exemplary embodiments, a water based slurry of the powder along with Rh nitrate is employed to form the OC layer using loadings of about 9.07 g/ft3Rh, about 210 g/ft3Fe, and a total loading of about 100 g/L. In these exemplary embodiments, the OC layer is further calcined to achieve adhesion of the coating layer to the top of the impregnated WC layer.

In some embodiments, a TWC catalyst sample, herein referred as TWC catalyst Type R, is produced including aforementioned WC layer, and cordierite substrate as within TWC catalyst Type K. In these embodiments, the IMPG layer is implemented as a slurry including water soluble salts of Pd, Ce, Nd, and Ba using loadings of about 22.0 g/ft3Pd, 115.2 g/ft3Ba, 105.8 g/ft3Ce, and 12.1 g/ft3Nd. Further to these embodiments, the slurry is deposited onto the WC layer and further calcined to generate the oxides within the porous WC layer. Still further to these embodiments, the OC layer for TWC catalyst Type R is implemented as a slurry including a powder batch of a Ce—Zr—Nd—Y OSM which is first impregnated with Fe nitrate and then calcined at about 750° C. In these embodiments, a water-based slurry of the powder along with Rh Nitrate is employed to form an OC layer using loadings of about 3.6 g/ft3Rh, about 210 g/ft3Fe, and a total loading of about 100 g/L. Further to these embodiments, the OC layer is further calcined to achieve adhesion of the coating layer to the top of the impregnated WC layer.

In other embodiments, a commercially available SULEV30 close-coupled catalyst (CCC), herein referred as reference catalyst Type 1, is employed to compare catalytic performance for TWC activity with the aforementioned TWC catalyst samples produced. In these embodiments, the reference catalyst Type 1 includes a 1.00 L cordierite substrate having a 4.16″ diameter, 400 CPSI, and 3.5 mil wall thickness, and platinum group metal (PGM) loadings of about 94.7 g/ft3Pd and about 7.3 g/ft3Rh.

In some embodiments, the catalytic performance of the aforementioned TWC catalyst samples and the reference catalyst Type 1 is evaluated by performing a series of LO tests to determine the temperature at which 50% conversion (T50) and the temperature at which 90% conversion (T90) of pollutants including Nitrogen oxides (NOX), Carbon monoxide (CO), and Hydrocarbons (HC) are achieved. In these embodiments, the LO tests are performed using a gas stream composition including CO, Hydrogen, Propene, Propane, Nitric oxide, Water, Carbon dioxide, nitrogen for the remaining amount, and a square wave-varying Oxygen (O2) concentration. Further to these embodiments, the LO tests are performed at a space velocity (SV) of about 90,000 h−1, average R-value of about 1.05 (rich condition close to stoichiometric condition), air-to-fuel (A/F) span of about 0.4, and gas temperature ramping at about 40° C./min to about 550° C.

In other embodiments, the catalytic performance of the aforementioned TWC systems is evaluated by performing a series of wide pulse perturbation tests (WPPT) to determine combinations of TWC performance and kinetically-limited reductive/oxidative storage capacity of the TWC catalyst samples, as well as to illustrate the catalyst's performance during out-of-loop A/F ratio excursions. In these embodiments, the net conversion per pollutant is calculated after the NOX, HC, and CO emissions are measured every second and averaged over about a 5 minute interval after about a 2 minute settling time. Further to these embodiments, the series of WPPTs are conducted at average R-value of about 1.05 (rich condition close to stoichiometric condition) and A/F ratio span of about 0.8 and period of about 8 seconds.

In some embodiments, a series of standard isothermal oxygen storage capacity (OSC) oscillating tests are conducted to determine the OSC property of the aforementioned TWC catalyst samples in terms of O2and CO delay times.

The TWC systems including Fe-activated Rh and Ba—Pd catalyst layers outperform conventional TWC catalysts when their LOs and catalytic performance are compared. The TWC systems, including layers of the disclosed material compositions, exhibit early light-offs than conventional TWC systems, thereby improving pollutants (e.g., NOx, CO, HC) emissions conversion efficiency. The disclosed TWC material compositions exhibiting high catalytic performance are produced employing low loadings of Rh, thereby the costs associated with the use of PGM materials within TWC systems are reduced. The disclosed TWC material compositions exhibit enhanced OSC property, thereby facilitating a highly significant transport of materials in and out of the Fe-activated Rh catalyst layers and providing improved interactions with conventional and unconventional catalyst supports and additives.

Numerous other aspects, features and benefits of the present disclosure may be made apparent from the following detailed description taken together with the drawing figures.

DETAILED DESCRIPTION

The present disclosure is described herein in detail with reference to embodiments illustrated in the drawings, which form a part hereof. Other embodiments may be used and/or other modifications may be made without departing from the scope or spirit of the present disclosure. The illustrative embodiments described in the detailed description are not meant to be limiting of the subject matter presented.

Definitions

As used here, the following terms have the following definitions:

“Air/Fuel ratio or A/F ratio” refers to the mass ratio of air to fuel present in a combustion process.

“Calcination” refers to a thermal treatment process applied to solid materials, in presence of air, to bring about a thermal decomposition, phase transition, or removal of a volatile fraction at temperatures below the melting point of the solid materials.

“Catalyst” refers to one or more materials that may be of use in the conversion of one or more other materials.

“Catalyst system” refers to any system including a catalyst, such as, a PGM catalyst or a ZPGM catalyst of at least two layers comprising a substrate, a washcoat and/or an overcoat.

“CO delay time” refers to the time required to reach to 50% of the CO concentration in feed signal during an isothermal oscillating test.

“Conversion” refers to the chemical alteration of at least one material into one or more other materials.

“Conversion efficiency” refers to the percentage of emissions passing through the catalyst that are converted to their target compounds.

“Impregnation” refers to the process of imbuing or saturating a solid layer with a liquid compound or the diffusion of some element through a medium or substance.

“Lean condition” refers to exhaust gas condition with an R value less than 1.

“Light off” refers to the time elapsed from an engine cold start to the point of 50 percent pollutant conversion.

“O2delay time” refers to the time required to reach to 50% of the O2concentration in feed signal during an isothermal oscillating test.

“Overcoat layer” refers to a catalyst layer of at least one coating that can be deposited onto at least one washcoat layer or impregnation layer.

“Oxygen storage capacity (OSC)” refers to the ability of materials used as OSM in catalysts to store oxygen at lean condition and to release it at rich condition.

“Oxygen storage material (OSM)” refers to a material that absorbs oxygen from oxygen rich gas flows and further able to release oxygen into oxygen deficient gas flows.

“R-value” refers to the value obtained by dividing the total reducing potential of the gas mixture (in Moles of Oxygen) by the total oxidizing potential of the gas mixture (in moles of Oxygen).

“Rich condition” refers to exhaust gas condition with an R value greater than 1.

“Stoichiometric condition” refers to the condition when the oxygen of the combustion gas or air added equals the amount for completely combusting the fuel, an exhaust gas condition with an R-value equal to 1.

“Substrate” refers to any material of any shape or configuration that yields a sufficient surface area for depositing a washcoat layer and/or an overcoat layer.

“Support oxide” refers to porous solid oxides, typically mixed metal oxides, which are used to provide a high surface area which aids in oxygen distribution and exposure of catalysts to reactants such as NOx, CO, and hydrocarbons.

“T50” refers to the temperature at which 50% of a material is converted.

“T90” refers to the temperature at which 90% of a material is converted.

“Three-way catalyst (TWC)” refers to a catalyst able to perform the three simultaneous tasks of reduction of nitrogen oxides to nitrogen and oxygen, oxidation of carbon monoxide to carbon dioxide, and oxidation of unburnt hydrocarbons to carbon dioxide and water.

“Washcoat layer” refers to a catalyst layer of at least one coating, including at least one oxide solid that can be deposited onto a substrate.

“Wide pulse perturbation test” refers to a catalytic performance test during which A/F ratio perturbations of longer duration and increased amplitude are used to assess catalytic performance, as compared with the light-off test.

Description of the Disclosure

Disclosed herein are materials used as support oxides within three-way catalyst (TWC) catalytic converters, said support oxides including Niobium Oxide, Zirconia, and Alumina.

Material Compositions and Production of TWC Samples According to Catalyst Structure

FIG. 1is a graphical representation illustrating a catalyst structure used for three-way catalyst (TWC) samples including a substrate, one or more of a washcoat (WC) layers, an impregnation (IMPG) layer, and/or an overcoat (OC) layer, according to an embodiment. InFIG. 1, TWC structure100includes substrate102, WC layer104, IMPG layer106, and OC layer108. In some embodiments, WC layer104is deposited onto substrate102, IMPG layer106is deposited onto WC layer104, and OC layer108is deposited onto IMPG layer106. In other embodiments, TWC structure100can include additional, fewer, or differently arranged components and layers than those illustrated inFIG. 1. In some embodiments, TWC structure100is employed to produce a set of exemplary embodiments of TWC catalyst samples.

TWC Catalyst Type A

In this exemplary embodiment, TWC catalyst Type A includes a 1.00 L cordierite substrate with a 4.66″ diameter, 600 cells per square inch (CPSI), and 3.5 mil wall thickness. Further to this embodiment, the cordierite substrate is employed as the monolith upon which a slurry is deposited as a WC layer. In this embodiment, the slurry has a total loading of about 60 g/L, including about 31 wt % Cerium (Ce), about 58.3 wt % Zirconium-Hafnium (Zr—Hf), about 5.5 wt % Neodymium (Nd), and about 5.2 wt % Yttrium (Y) oxides, and a fluorite phase oxygen storage material (OSM). Still further to this embodiment, the WC layer is calcined to achieve adhesion to the top of the cordierite substrate. In this embodiment, an IMPG layer including loadings of about 3.0 g/ft3Rhodium (Rh) and about 140 g/ft3Iron (Fe) in a water-based solution is applied onto the WC layer. Further to this embodiment, the IMPG layer is calcined to achieve adhesion to the top of the WC layer. Still further to this exemplary embodiment, TWC catalyst Type A is a reference Fe-activated Rh catalyst which does not include an OC layer.

TWC Catalyst Type B

In this exemplary embodiment, TWC catalyst Type B includes the aforementioned WC and IMPG layers as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type B additionally includes an OC layer having about 37 g/L total loading of an OSM containing about 30 wt % Ce, about 60% Zr—Hf, about 5 wt % Nd, and about 5 wt % Praseodymium (Pr) oxides. In this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type C

In this exemplary embodiment, TWC catalyst Type C includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as describe in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type C additionally includes an OC layer having about 42 g/L total loading of an OSM containing about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y oxides. In this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type D

In this exemplary embodiment, TWC catalyst Type D includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type D additionally includes an OC layer having about 32 g/L total loading of a high surface area Alumina oxide. In this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type E

In this exemplary embodiment, TWC catalyst Type E includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type E additionally includes an OC layer having about 40 g/L of a high surface area Lanthanum (La)-stabilized Alumina oxide. In this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type F

In this exemplary embodiment, TWC catalyst Type F includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type F includes an OC layer having about 37 g/L total loading of a specialized highly calcined, high surface area, high La2O3content, La-stabilized Alumina oxide. In this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type G

In this exemplary embodiment, TWC catalyst Type G includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type G includes an OC layer having about 23 g/L total loading of a Barium (Ba) carbonate powder. In This embodiment, the OC layer is applied as a slurry onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type H

In this exemplary embodiment, TWC catalyst Type H includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type H includes an OC layer having about 48 g/L total loading of a La carbonate powder. In this embodiment, the OC layer is applied as a slurry onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type I

In this exemplary embodiment, TWC catalyst Type I includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type I includes an OC layer having about 90 g/L total loading of a Strontium (Sr) carbonate powder. In this embodiment, the OC layer is applied as a slurry onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type J

In this exemplary embodiment, TWC catalyst Type J includes the aforementioned WC and IMPG layers, as well as the cordierite substrate as described in TWC catalyst Type A, above. Further to this embodiment, TWC catalyst Type J includes an OC layer having about 98 g/L total loading of a Niobium (Nb) (V) oxide powder. In this embodiment, the OC layer is applied as a slurry onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type K

In this exemplary embodiment, TWC catalyst Type K includes a 0.445 L cordierite substrate with a 4.16″ diameter, 600 CPSI, and 4.3 mil wall thickness. Further to this embodiment, the cordierite substrate is employed as the monolith upon which a slurry is deposited as a WC layer. In this embodiment, the slurry has a total loading of about 180 g/L, including about 40% by weight of OSM including about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y oxides, and about 60% by weight of a high surface area Alumina with La2O3stabilized at high temperature. Still further to this embodiment, the WC layer is calcined to achieve adhesion to the top of the cordierite substrate. In this embodiment, an IMPG layer including Palladium (Pd) nitrate, Ce nitrate, Nd nitrate, and Ba salt with loadings of about 92.6 g/ft3Pd, about 57.6 g/ft3Ba, about 105.8 g/ft3Ce, and about 12.1 g/ft3Nd in a water-based solution is applied onto the WC layer. Further to this embodiment, the IMPG layer is calcined to achieve adhesion to the top of the WC layer. Still further to this embodiment, a powder batch of the Ce—Zr—Nd—Y OSM is first impregnated with Fe nitrate to form a slurry which is then calcined at about 750° C. to produce Fe-OSM powder. In this embodiment, a water based slurry of the Fe-OSM powder and Rh nitrate is used to form an OC layer and is produced with total loading of about 100 g/L, and Rh loading of about 9.07 g/ft3and Fe loading of about 210 g/ft3. Further to this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

TWC Catalyst Type L

In this exemplary embodiment, TWC catalyst Type L includes the aforementioned OC and WC layers as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type L additionally includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K as well as a different Ba loading of about 115.2 g/ft3.

TWC Catalyst Type M

In this exemplary embodiment, TWC catalyst Type M includes the aforementioned OC and WC layers, as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type M additionally includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K, as well as a different Ba loading of about 230.4 g/ft3.

TWC Catalyst Type N

In this exemplary embodiment, TWC catalyst Type N includes the aforementioned OC and WC layers, as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type N additionally includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K, as well as a different Ba loading of about 345.7 g/ft3.

TWC Catalyst Type O

In this exemplary embodiment, TWC catalyst Type O includes the aforementioned OC and WC layers, as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type O additionally includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K, as well as a different Ba loading of about 460.9 g/ft3.

TWC Catalyst Type P

In this exemplary embodiment, TWC catalyst Type P includes the aforementioned OC and WC layers, as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type P includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K, as well as a different Ba loading of about 567.1 g/ft3.

TWC Catalyst Type Q

In this exemplary embodiment, TWC catalyst Type Q includes the aforementioned OC and WC layers, as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type Q additionally includes the aforementioned Pd nitrate, Ce nitrate, and Nd nitrate loadings as in TWC catalyst Type K, as well as a different Ba loading of about 691.3 g/ft3.

TWC Catalyst Type R

In this exemplary embodiment, TWC catalyst Type R includes the aforementioned WC layer as well as the cordierite substrate as described in TWC catalyst Type K, above. Further to this embodiment, the IMPG layer in TWC catalyst Type R additionally includes Pd nitrate, Ce nitrate, Nd nitrate, and Ba salt with loadings of about 22.0 g/ft3Pd, about 115.2 g/ft3Ba, about 105.8 g/ft3Ce, and about 12.1 g/ft3Nd, in a water-based solution. Still further to this embodiment, the IMPG layer is applied onto the WC layer and then calcined to achieve adhesion to the top of the WC layer. In this embodiment, a powder batch of the Ce—Zr—Nd—Y OSM is first impregnated with Fe nitrate to form a slurry which is then calcined at about 750° C. to produce Fe-OSM powder. Further to this embodiment, a water based slurry of the Fe-OSM powder and Rh nitrate is used to form an OC layer and is produced with total loading of about 100 g/L, and an Rh loading of about 3.6 g/ft3and Fe loading of about 210 g/ft3. Further to this embodiment, the OC layer is applied onto the impregnated-WC layer and subsequently calcined to achieve adhesion of the OC layer to the top of the impregnated-WC layer.

In other embodiments, a commercially available SULEV30 close-coupled catalyst (CCC), herein referred as reference catalyst Type 1, is employed to compare catalytic performance for TWC activity with the aforementioned TWC catalyst samples produced. In these embodiments, the reference catalyst Type 1 includes a 1.00 L cordierite substrate having a 4.16″ diameter, 400 CPSI, and 3.5 mil wall thickness, and platinum group metal (PGM) loadings of about 94.7 g/ft3 Pd and about 7.3 g/ft3 Rh.

Test Methodologies for Catalytic Performance Assessment of TWC Catalyst Samples

In some embodiments, different test methodologies are employed to assess catalytic performance of the aforementioned TWC catalysts samples. In these embodiments, the test methodologies employed are a series of light-off (LO) tests, wide pulse perturbation tests (WPPTs), and standard isothermal oxygen storage capacity (OSC) oscillating tests.

In some embodiments, for the assessment of the catalytic performance of the aforementioned TWC catalyst samples, core samples measuring about 1 inch in diameter and about 2 inches in length are taken from the coated monoliths, using a diamond core drill. In these embodiments, the core samples are aged at about 1,000° C. for about 20 hours in an atmosphere of about 10% (by mole) of water vapor, about 10% Carbon dioxide (CO2), and Nitrogen (N2) for the remaining amount. Further to these embodiments, the amounts of CO and Oxygen (O2) are varied to simulate the thermal aging associated with driving a vehicle from about 50,000 miles to about 120,000 miles. Further to these embodiments, the aging of the core samples consists of both fuel cut like events with high O2content, and rich events having an A/F ratio below 13 A/F ratio. Still further to these embodiments, the cores are cooled in the mixed gas at a temperature from about 200° C. to about 300° C. and then removed from the aging system.

In these embodiments, before standard experiments are performed on the core samples, the cores samples are conditioned within a proprietary custom built bench flow reactor employed to test performance of TWCs, diesel oxidation catalysts, catalyzed particulate filters, and selective catalytic reduction (SCR) catalysts. An example of such a proprietary custom built bench flow reactor is disclosed in US Patent Application Publications 2014/0334978, 2014/0335625, and 2014/0335626. Further to these embodiments, conditioning of the core samples is conducted on the bench reactor for about 10 minutes at about 600° C. Still further to these embodiments, for conditioning of the core samples, a gas stream, at a slightly rich R-value of about 1.05 is employed with nearly symmetric lean and rich perturbations at a frequency of about 1 Hz.

Light-off Test Methodology

In some embodiments, the catalytic performance of the TWC catalyst core samples and the reference catalyst Type 1 is evaluated by performing a series of LO tests to determine the temperature at which 50% conversion (T50) and the temperature at which 90% conversion (T90) of pollutants including Nitrogen oxides (NOX), Carbon monoxide (CO), and Hydrocarbons (HC) are achieved. In these embodiments, the LO tests are performed using a gas stream composition including about 8,000 ppm CO, about 2,000 ppm Hydrogen, about 400 ppm (C3) Propene, about 100 ppm (C3) Propane, about 1,000 ppm Nitric oxide, about 100,000 ppm water, about 100,000 ppm CO2, N2for the remaining amount, and O2concentration varying as a square wave signal within a range from about 4,234 ppm to about 8,671 ppm. Further to these embodiments, the average R-value for the gas is about 1.05 and the square wave change in O2concentration results in an air-to-fuel (A/F) span of about 0.4 units. Further to these embodiments, the LO tests are performed at a space velocity of about 90,000 h−1at the standard conditions of about 21.1° C., at about 1 atmosphere with the total volume enclosed by the monolith surface used as the volume for the space velocity (SV) calculation. Still further to these embodiments, the temperature is stabilized at about 100° C. for about 2 minutes and subsequently, the gas temperature ramps at about 40° C./min to about 550° C., while a gas blanket warms the core holder ramping at the same set point temperature. During these series of tests, the conversion of the gas species are calculated at the temperature points of 50% conversion (T50) and 90% conversion (T90) for each pollutant.

Wide Pulse Perturbation Test (WPPT) Methodology

In other embodiments, a series of WPPTs are performed at selected temperatures to assess catalytic performance of the TWC catalyst core samples. In these embodiments, the WPPT methodology tests combinations of the TWC performance along with kinetically-limited reductive/oxidative storage capacity of the aforementioned TWC catalyst samples, as well as to illustrate catalytic performance during out-of-loop A/F ratio excursions. Further to these embodiments, the A/F ratio span of the square wave used in these tests is about 0.8 units and the period is about 8 seconds, with an average R-value of about 1.05 (rich condition close to stoichiometric condition). Still further to these embodiments, the NOX, HC, and CO emissions are measured every second and averaged over about a 5 minute interval after about 2 minutes settling time. The net conversion is calculated for each pollutant with a high conversion associated with lower emissions from the catalytic converter if applied to a vehicle or stationary engine.

OSC Isothermal Oscillating Test

In some embodiments, OSC isothermal oscillating tests facilitate the determination of the O2and CO delay times for a selected number of cycles during which feed signals of O2and CO pulses are used to determine the OSC performance and verify the OSC aging stability of the aforementioned TWC catalyst samples. In these embodiments, the OSC isothermal oscillating tests are performed on the catalyst samples at a temperature of about 525° C. with a feed of either O2with a concentration of about 4,000 ppm diluted in inert N2, or CO with a concentration of about 8,000 ppm of CO diluted in inert N2. Further to these embodiments, the OSC isothermal oscillating tests are performed within the proprietary reactor using a SV of about 60,000 h−1, ramping from room temperature to a temperature of about 525° C. under a dry N2environment. When the temperature of about 525° C. is reached, the OSC isothermal oscillating test is initiated by flowing O2through the catalyst sample within the reactor. After about 240 seconds, the feed flow is switched to CO, thereby allowing CO to flow through the catalyst sample within the reactor for about another 240 seconds. The isothermal oscillating condition between CO and O2flows is enabled for about 4 cycles of about 480 seconds each, respectively. The last 3 cycles are averaged and reported.

In these embodiments, O2and CO are allowed to flow first within an empty test reactor, before the OSC isothermal oscillating test of the catalyst samples, in order to establish test reactor benchmarks. Further to these embodiments, a catalyst sample under testing is placed within the test reactor and O2and CO are allowed to flow. In these embodiments, as the catalyst sample exhibits OSC, the catalyst sample stores O2when O2flows. Further to these embodiments, when CO flows there is no O2flowing and the O2stored within the catalyst sample reacts with the CO to form CO2. Still further to these embodiments, the time during which the catalyst sample stores O2and the time during which CO is oxidized to form CO2are measured to confirm/verify the OSC performance and aging stability of the catalyst samples.

Catalytic Performance of TWC Catalyst Samples

In some embodiments, the catalytic performance of the aforementioned TWC catalyst Types A, B, C, D, E, F, G, H, I, and J is assessed using TWC catalyst core samples. In these embodiments, TWC catalyst core samples are evaluated by performing a series of LO tests to determine the temperature at which 50% conversion (T50) and the temperature at which 90% conversion (T90) of pollutants including Nitrogen oxides (NOX), Carbon monoxide (CO), and Hydrocarbons (HC) are achieved. Further to these embodiments, T50and T90values achieved per species converted are detailed in Table 1, below.

In some embodiments, the interactions between the catalyst layers of the TWC catalyst Types A, B, C, D, E, F, G, H, I, and J are observed when reviewing the data from Table 1 and the associated graphs inFIGS. 2-5. In these embodiments, these interactions result from the application of the IMPG layer of Fe-activated Rh material compositions in the production of the aforementioned TWC catalyst systems. Further to these embodiments, the Ce—Zr based OSM, including about 30 wt % Ce, about 10 wt % La dopants, and zirconia for the remaining amount, is related to a surface area decrease within a range from about 30 m2/g to about 15 m2/g, after the aforementioned TWC catalyst samples are aged under a multimode aging condition at about 1,000° C., for about 20 hours. Still further to these embodiments, under the aforementioned multimode aging condition and after adding Rh and Fe material compositions within the TWC structure, a low surface area is produced within a range from about 0.5 m2/g to about 1.5 m2/g. In these embodiments, even with this low surface area TWC catalyst Type A, which is a reference Fe-activated Rh catalyst not including an OC layer, exhibits a significantly higher TWC performance. Further to these embodiments, for TWC catalyst Type A the LO temperatures T50during NOX, CO, and HC conversions are 259.2° C., 254.4° C., and 282.2° C., respectively, while the LO temperatures T90during NOX, CO, and HC conversions are 308.8° C., 264.4° C., and 348.4° C., respectively.

In these embodiments, TWC catalyst Types B and C exhibit substantially similar catalytic performance behavior (bars206,208,306,308for NOXconversion, bars218,220,318,320for CO conversion, and bars230,232,330,332for HC conversion) as a result of the interaction between of Fe-activated Rh catalyst layer and the OC layers within both TWC catalysts, respectively, including Ce—Zr—Nd—Pr OSM (about 30 wt % Ce, about 60% Zr—Hf, about 5 wt % Nd, and about 5 wt % Pr) and Ce—Zr—Nd—Y OSM (about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y). This implies that the OC layer materials can be used freely with the Fe—Rh—Ce—Zr OSM catalyst material and may generate a large set of catalytic systems when PGM materials (Pt, Rh, Pd) are added to the support OC layer.

In these embodiments, TWC catalyst Types D, E, F, G, H, and I exhibit catalytic interactions between the Fe-activated Rh catalyst layer with the variations of conventional catalyst supports and additives within their respective OC layers.

In some embodiments, even though the catalyst interaction of TWC catalyst Types D-J are less than TWC catalyst Type A, high performance TWC catalysts can be produced by modifying the concentrations of the catalyst material compositions within the TWC structure. In these embodiments, this negative interaction can be observed when TWC catalyst Type A (reference Fe-activated Rh catalyst without OC layer) is compared with TWC catalyst Type G (OC layer including Ba carbonate). Further to these embodiments, even if the interaction of Ba with the Fe-activated Rh catalyst layer is less than TWC catalyst Type A, high performance catalysts can be produced with variations of mixed Ba oxide/carbonate impregnated onto a separate alumina/OSM layer. The co-impregnation ingredients of Ce and Nd may form a Ba perovskite and inhibit the Ba mobility.

In other embodiments, the catalytic performance of the TWC catalyst Types K, L, M, N, O, and reference catalyst Type 1 is assessed using TWC catalyst core samples. In these embodiments, TWC catalyst core samples are evaluated by performing a series of LO tests to determine the temperatures at which 50% conversion (T50) and 90% conversion (T90) of pollutants including NOX, CO, and HC are achieved. Further to these embodiments, T50and T90values achieved per species converted are detailed in Table 2, below.

In some embodiments, the catalytic performance of the TWC catalyst Types P, Q, R, and reference catalyst Type 1 is assessed using TWC catalyst core samples. In these embodiments, TWC catalyst core samples are evaluated by performing a series of LO tests to determine the temperatures at which 50% conversion (T50) and 90% conversion (T90) of pollutants including NOX, CO, and HC are achieved. Further to these embodiments, T50and T90values achieved per species converted are detailed in Table 3, below.

In some embodiments, the interactions between the catalyst layers of the TWC catalyst Types K, L, M, N, O, P, Q, and R are observed in Tables 2-3, and illustrated inFIGS. 6-9. In these embodiments, high performance catalysts can be produced with variations of mixed Ba oxide/carbonate impregnated onto a separate Alumina/OSM layer. Further to these embodiments, varying the Ba loadings enables the determination of the optimal Ba loadings that will provide the interaction with the Fe-activated Rh catalyst layer resulting in greater catalytic performance.

In these embodiments, the TWC structure for TWC catalyst Types K, L, M, N, O, P, and Q include 40% by weight of OSM including about 31 wt % Ce, about 58.3 wt % Zr—Hf, about 5.5 wt % Nd, and about 5.2 wt % Y, and about 60% by weight of a high surface area Alumina with La2O3stabilized at high temperature deposited within the WC layers. Further to these embodiments, the IMPG layers include Pd nitrate, Ce nitrate, Nd nitrate, and Ba salt with loadings of about 92.6 g/ft3Pd, about 105.8 g/ft3Ce, and about 12.1 g/ft3Nd, and variations of Ba loadings within a range from about 57.6 g/ft3to about 691.3 g/ft3. Still further to these embodiments, OC layers include Ce—Zr—Nd—Y OSM with Rh loading of about 9.07 g/ft3and Fe loading of about 210 g/ft3.

In these embodiments, TWC catalyst Type R includes a WC layer substantially similar to TWC catalyst Types K through Q. Further to these embodiments, the IMPG layer includes loadings of about 22.0 g/ft3Pd, about 115.2 g/ft3Ba, about 105.8 g/ft3Ce, and about 12.1 g/ft3Nd. Still further to these embodiments, the OC layer includes Ce—Zr—Nd—Y OSM with Rh loading of about 3.6 g/ft3and Fe loading of about 210 g/ft3.

In these embodiments, as observed in Tables 2-3, and illustrated inFIGS. 6-9, for TWC catalyst Types K through R, the LO temperatures T50and T90during NOX, CO, and HC conversions are lower than the LO temperatures T50and T90for TWC catalyst Type A (reference Fe-activated Rh catalyst not including an OC layer), TWC catalyst Types B through J, and for reference catalyst Type 1, which is a commercially available SULEV30 close-coupled catalyst (CCC), including PGM loadings of about 94.7 g/ft3 Pd and about 7.3 g/ft3 Rh. Further to these embodiments, TWC catalyst Type R exhibits a high level of catalytic performance, with lower PGM loadings, which is substantially similar to the catalytic performance for TWC catalyst Type A.

Catalytic Conversion Efficiency of TWC Catalysts Including Ba—Pd and Rh—Fe Material Compositions

In some embodiments, the catalytic conversion efficiency of the TWC catalyst core samples is evaluated by performing a series of WPPTs at a temperature of about 550° C. In these embodiments, the catalytic performance of the TWC catalyst Types A, B, C, D, E, F, G, H, I, and J are determined by performing test combinations of the TWC performance along with kinetically-limited reductive/oxidative storage capacity of the TWC catalyst core samples. Further to these embodiments, the WPPTs illustrate catalytic performance during out-of-loop A/F ratio excursions. Still further to these embodiments, % NOX, % CO and % HC conversions for TWC catalyst Types A, B, C, D, E, F, G, H, I, and J are detailed in Table 4, below.

In other embodiments, the catalytic conversion efficiency of the TWC catalyst core samples is evaluated by performing a series of WPPTs at a temperature of about 400° C. In these embodiments, the catalytic performance of the TWC catalyst Types K, L, M, N, O, P, Q and reference catalyst Type 1 are determined by performing test combinations of the TWC performance along with kinetically-limited reductive/oxidative storage capacity of the TWC catalyst core samples. Further to these embodiments, the WPPTs illustrate catalytic performance during out-of-loop A/F ratio excursions. Still further to these embodiments, % NOX, % CO and % HC conversions for TWC catalyst Types K, L, M, N, O, P, Q and reference catalyst Type 1 are detailed in Table 5, below.

FIG. 13is a graphical representation illustrating conversion comparisons1300of NOX, CO, and HC for TWC catalyst samples Types O, P, Q, and reference catalyst Type 1, under WPPT condition at 400° C., according to an embodiment. InFIG. 13, conversion comparisons1300include NOX conversion comparison1302, CO conversion comparison1310, and HC conversion comparison1318. InFIG. 13, NOX conversion comparison1302additionally include bar1304, bar1306, bar1308, and bar1212. InFIG. 13, CO conversion comparison1310also include bar1312, bar1314bar1316, and bar1224. InFIG. 13, HC conversion comparison1318further include bar1320, bar1322, bar1324, and bar1236. InFIG. 13, elements having identical element numbers from previous figures perform in a substantially similar manner

In some embodiments, bar1304, bar1306, bar1308, and bar1212illustrate % NOXconversion for TWC catalyst samples Types O, P, Q, and reference catalyst Type 1, respectively. In these embodiments, bar1312, bar1314bar1316, and bar1224illustrate % CO conversion for TWC catalyst samples Types O, P, Q, and reference catalyst Type 1, respectively. Further to these embodiments, bar1320, bar1322, bar1324, and bar1236illustrate % HC conversion for TWC catalyst samples O, P, Q, and reference catalyst Type 1, respectively, as detailed in Table 5 above.

In some embodiments, the catalytic conversion efficiencies of the TWC catalyst systems (TWC catalyst Types A through Q) are observed in Tables 4-5 and illustrated inFIGS. 10-13. In these embodiments, greater conversion efficiencies measured during WPPTs at temperatures of about 550° C. and about 400° C. are the result of the interaction of Pd and Ba oxide/carbonate impregnated onto a separate Alumina/OSM layer. Further to these embodiments, the TWC catalyst Types A through J exhibit NOX, CO, and HC conversions within ranges from about 83.6% to about 62.7%, from about 91.4% to about 76.1%, and from about 90.4% to about 80.6%, respectively. Still further to these embodiments, the TWC catalyst Types K through Q exhibit NOX, CO, and HC conversions within ranges from about 99.8% to about 91.9%, from about 97.7% to about 92.8%, and from about 99.0% to about 96.6%, respectively.

In these embodiments, TWC catalyst Type C, inFIG. 10, exhibits the greatest conversion efficiency in NOX, CO, and HC conversions of TWC catalyst Types A through J (bar1008illustrates about 83.6% NOXconversion, bar1020illustrates about 91.4% CO conversion, and bar1032illustrates about 90.1% HC conversion). Further to these embodiments, TWC catalyst Type K, inFIG. 12, exhibits the greatest conversion efficiency of all (Types A through R) the aforementioned TWC catalyst systems in NOX, CO, and HC conversions (bar1204illustrates about 99.8% NOXconversion, bar1216illustrates about 97.7% CO conversion, and bar1228illustrates about 99.0% HC conversion).

In these embodiments, the early LO temperatures of the aforementioned TWC catalyst systems indicate highly significant catalytic performance in the plurality of interactions of the Fe-activated Rh reference catalyst with both common and/or uncommon catalyst supports and additives. Further to these embodiments, catalytic samples including impregnated layers having variations of Pd, Ba, Ce, and Nd loadings exhibit improved earlier LO temperature performance when compared with the aforementioned TWC catalyst samples as well as with either the Fe-activated Rh reference catalyst (TWC catalyst Type A) or the reference catalyst Type 1 (commercially available SULEV30 CCC, including PGM loadings of about 94.7 g/ft3 Pd and about 7.3 g/ft3 Rh).

Both the LO tests and WPPTs confirm the enhanced catalytic performance of the aforementioned TWC catalyst systems. Further, performing test combinations of the TWC performance along with kinetically-limited reductive/oxidative storage capacity of the TWC catalyst core samples illustrate catalytic performance during out-of-loop A/F ratio excursions.

OSC of TWC Catalysts Including Rh—Fe Material Compositions

In some embodiments, the OSC of the TWC catalyst core samples are evaluated by performing a series of standard isothermal OSC oscillating tests at a temperature of about 525° C. In these embodiments, The OSC of the TWC catalyst Types A, B, C, D, E, F, G, H, I, and J are determined in terms of O2and CO delay times, as detailed in Table 6, below.

In some embodiments, bar1404, bar1406, bar1408, bar1410, and bar1412illustrate CO delay time in seconds for TWC catalyst samples Types A, B, C, D, and E, respectively. In these embodiments, bar1416, bar1418, bar1420, bar1422, and bar1424illustrate O2delay time in seconds for TWC catalyst samples Types A, B, C, D, and E, respectively, as detailed in Table 6 above.

In some embodiments, bar1504, bar1506, bar1508, bar1510, and bar1512illustrate CO delay time in seconds for TWC catalyst samples Types A, B, C, D, and E, respectively. In these embodiments, bar1516, bar1518, bar1520, bar1522, and bar1524illustrate O2delay time in seconds for TWC catalyst samples Types A, B, C, D, and E, respectively, as detailed in Table 6 above.

In some embodiments, as previously described, the Ce—Zr based OSM, including about 30 wt % Ce, about 10 wt % lanthanide dopants, and zirconia for the remaining amount, is related to a surface area decrease to surface area in a range from about 30 m2/g to about 15 m2/g, after multimode aging at about 1,000° C., for about 20 hours. In these embodiments, adding Rh and Fe to the material compositions produces after aging a low surface area within a range from about 0.5 m2/g to about 1.5 m2/g. Further to these embodiments, even with this low surface area the reference Fe-activated Rh catalyst without an OC layer exhibits a significant TWC performance. In these embodiments, the OSC of the TWC catalyst Types A through J (all including a Fe-activated Rh catalyst layer within the TWC structure) in terms of CO and O2delay times and measured during the OSC oscillating tests at about 525° C. are observed in Table 6, and illustrated inFIGS. 14-15. Further to these embodiments, the low surface area produced after applying the Fe-activated Rh catalyst layer results from improvements in the oxygen transport of the modified OSM, which is also consistent with TWC catalysts exhibiting highly significant OSC.

In these embodiments, the interactions of the Fe-activated Rh catalyst layer with both common and uncommon catalyst supports and additives are verified by the aforementioned LO test results and catalytic efficiencies measured using WPPTs.