Refine Your Search

Search Results

Viewing 1 to 15 of 15
Technical Paper

Improvement of the Oxygen-Storage Capacity of an Intelligent Catalyst

Ba(Ce,Zr,Pt)O3-perovskite is a new intelligent catalyst that shows self-regeneration of the precious metal. We previously reported that a Pd-perovskite catalyst, La(Fe,Pd)O3, regenerates itself through solid solution and segregation of Pd into and out of the perovskite crystal. We investigated the improvement of the oxygen-storage capacity (OSC) of an intelligent catalyst by means of suppressing the grain growth of the precious metal. The new intelligent catalyst is a composite comprising Ba(Ce,Zr,Pt)O3 perovskite formed on a CeZr oxide. We examined the self-regenerative function of the new material and tested its OSC and catalytic activity after engine aging at high temperature. The new intelligent catalyst was shown to have excellent durability of OSC and excellent catalytic activity.
Technical Paper

Development of a Rh-Intelligent Catalyst

We have developed a Pd-intelligent catalyst with a self-regenerative function that is realized by the passage of Pd through consecutive solid solution and segregation states in and out of a perovskite crystal, and commercialized it for the first time in the world [1, 2, 3, 4, 5, 6, 7, 8 and 9]. In this study, we investigated the self-regenerative function of Rh as an alternative for Pd, in two types of Rh-perovskite (LaFeRhO3 and CaTiRhO3), and found that a CaTiRhO3 perovskite has an excellent capacity for the self-regenerative function of Rh. In a LaFeRhO3 perovskite with a composition similar to the Pd-perovskite (LaFePdO3), Rh was fixed so stably in the perovskite structure that it hardly segregated from the perovskite even in high temperature reduction atmospheres. However, in the CaTiRhO3 perovskite, with its A2+B4+O3 formula, the amount of Rh that actually segregated increased greatly in reduction atmospheres.
Technical Paper

Thermal Properties of the Intelligent Catalyst

We have developed a revolutionary automotive catalyst that maintains high activity by the suppression of grain growth of precious metals. This catalyst contains Pd-perovskite crystal which has shown a capacity for self-regeneration of Pd in a cycle of solid solution and segregation in perovskite crystals [1, 2, 3, 4, 5 and 6]. We named this catalyst the “Intelligent Catalyst” and first commercialized it in the Japanese market in October 2002 [7, 8]. In this study, we investigated the activity of Pd at various temperatures to confirm that the self-regenerative mechanism worked well at low temperatures like those right after engine starting. We also examined the durability of perovskite structure at high temperatures and tested its catalytic activity after engine aging at high temperatures above 1000 °C up to 1100 °C. It is proved that the intelligent catalyst has both excellent activity and durability under practical conditions.
Technical Paper

Research on the Co-free Intelligent Catalyst

We have already reported that a LaFeCoPdO3 perovskite catalyst has the function for self-regeneration of Pd [1, 2, 3, 4, 5 and 6]. But cobalt was recognized as an environmental burden. In order to prepare for its practical application, we examined the composition of perovskite without cobalt. In this paper, we have investigated the catalytic activity, the structural durability and the regenerative ability of Co-free perovskites LaFePdO3, in comparison with LaFeCoPdO3 and Pd/Al2O3. As a result, the structural durability of LaFePdO3 is high, and the light-off performance is excellent even after aging. “Co-free Intelligent Catalyst” is regarded as the next technology for practical use especially as it is efficient in the reduction of emissions at cold starting.
Technical Paper

Design of a Practical Intelligent Catalyst

We have reported the innovation of “An Intelligent Catalyst” which has the function for self-regeneration of Pd realized through the solid solution and segregation of Pd in a perovskite crystal [1, 2, 3, 4 and 5]. We have looked for a design configuration for LaFePdO3 perovskite in the washcoat by comparing single and double layer washcaots as well as different loading locations for precious metals in order to maximize the Intelligent Catalyst's function in the practical conditions. The catalysts were attached to an engine exhaust system and subjected to an accelerated aging. The bed temperature of the catalysts reached to 1050 °C. The performance of the catalysts was evaluated on the engine dynamometer. Catalytic activity and long durability were improved by development of the washcoat configuration. The optimum design of the washcoat was double-layer with a tri-metal (Pt, Rh and Pd) system. The perovskite was located in the lower layer.
Technical Paper

A Hexa-Aluminate Automotive Three-Way Catalyst

With emission regulations getting tighter and tighter, catalysts will need to be active at ever lower temperatures in order to meet future standards. To meet this need, automotive catalysts are being installed closer to the engine so as to be active immediately after start-up. In this location, catalysts must have high temperature durability. In this paper, we examined a heat-resistant support material, “hexa-aluminate”, for possible use in future automotive catalysts. Catalytic activity of hexa-aluminate was more better than La added γ - alumina after redox treatment in model gas and after engine aging. Since hexa-aluminate had the excellent thermal durability, and Pd, which are supported on it, maintains finer particles than those on La added γ-alumina. We suggest that hexa-aluminate is a effective support material for automotive catalysts. More specifically, hexa-aluminate is expected to be a key technology for meeting the stringent emission standards of the future.
Technical Paper

Regeneration of Precious Metals in Various Designed Intelligent Perovskite Catalysts

We have reported the innovation of “An Intelligent Catalyst” which has the function for self-regeneration of Pd realized through the solid solution and segregation of Pd in a perovskite crystal. In this study, we did further research on regeneration for three different precious metals (Rh, Pd and Pt) in two types of perovskite systems (LaCeFeO3 and LaCeCoO3). In perovskite catalysts loaded with precious metals, the durability of the perovskite structure in redox fluctuation at high temperature is indispensable to suppression of the grain growth of precious metals. The key technology for the development of intelligent catalysts is considered to be the affinity of precious metals to durable perovskite oxides. In the six kinds of perovskite catalysts investigated here, only the Pd loaded LaCeFeO3 catalyst was considered “intelligent”.
Technical Paper

An Intelligent Catalyst

The catalyst of the crystalline ceramics known as a perovskite-type oxide was designed and controlled at the atomic level in order to create a new function for self-regeneration of precious metals in a usage ambience without auxiliary treatment. We have already reported that a catalyst with Pd supported on the perovskite-type oxide has higher activity than a catalyst with Pd supported on alumina. It was also found that Pd supported on the perovskite catalyst is finely dispersed [1, 2 and 3] The object of this study was to investigate the mechanism of self-regeneration by using hyper-analytical facilities. XAFS analysis, at SPring-8 (8 GeV), revealed that Pd is in six-fold coordinations with oxygen in a perovskite crystal, which indicating that Pd occupies the B site of the unit formula of ABO3 in the perovskite crystal structure under oxidation atmosphere.
Technical Paper

Influence of Oxygen Storage Characteristics on Automobile Emissions

The catalytic performance and On-Board Diagnostics (OBD) of the manifold catalyst having high Oxygen Storage Capacity (OSC) are described in this paper. First of all, we compared the performance of three-way catalysts containing Cerium - Zirconium - Yttrium oxide with Cerium - Zirconium oxide. Three-way catalysts dispersed Pt, Rh and Pd on Cerium - Zirconium - Yttrium oxide showed excellent catalytic performance especially at cold starting and at transient states, after high temperature aging at 1050°C. The performance of these catalysts was studied using the Driving Mode Simulation Dynamometer, which was developed in-house, and oxygen storage and release responses were compared in actual gas. Then we investigated the possibility of on-board diagnostics of catalyst deactivation with high OSC in manifold and close-coupled positions, a diagnostic which is usually assumed to be difficult to attain with present conventional technology.
Technical Paper

Influence of Support Materials on Durability of Palladium in Three-Way Catalyst

In this paper, we studied the influence of support materials on Pd in three-way catalysts for the aim of enhancing the durability of Pd, particularly CO and NOx conversion efficiencies which are usually seriously damaged after aging. Since the durability of precious metals was found to be strongly influenced by the support material chosen, it should be possible to optimize catalyst performance by finding the appropriate support. The performance of Pd three-way catalysts with different support materials (Aluminum oxide, Cerium - Zirconium Oxide, Cerium - Zirconium -Yttrium Oxide, Zirconium Oxide, or Titanium Oxide) was compared after high temperature agings under various gas conditions. To assess Pd deterioration, the crystallite size of Pd was measured with XRD and the micro surface was observed by FE-SEM. The performance of the catalysts was evaluated.
Technical Paper

Oxygen Storage Capacity on Cerium Oxide - Precious Metal System

Cerium oxide (CeO2) is known to have good oxygen storage capacity (OSC) and is used widely in three-way catalysts for automobiles, but it has a problem of inferior heat stability. In our previous work, cerium-zirconiumyttrium (Ce Zr-Y) oxide systems were investigated with the aim of improving the heat stability of CeO2-based oxide systems, and we found an optimum composition of Ce-Zr-Y oxide with platinum (Pt) showed good OSC even after high temperature aging. In this study OSC and thermal stability of Ce-Zr-Y oxide with varying the types of precious metals were investigated to evaluate the effect of precious metals. The results show that, Palladium (Pd) and Rhodium (Rh) are also available for Ce-Zr-Y oxide with precious metal system to improve OSC after thermal aging. In particular, Rh exhibited higher improvement than others at the composition of lower Ce content.
Technical Paper

Improvement in Oxygen Storage Capacity

Cerium oxide (Ceria) is known to have good oxygen storage capacity (OSC) and is used widely in three-way catalysts for automobiles, but it has a problem of heat stability since it is less stable than aluminium oxide (Alumina). In the present work, cerium-zirconiumyttrium (Ce-Zr-Y) oxide systems were investigated with the aim of improving the heat stability of CeO2-based oxide systems, which would result in great improvement in OSC. We found an optimum composition of Ce-Zr-Y oxide with platinum (Pt) dispersed in it at a quantity of 0.1 % in weight, which showed good OSC starting from 100°C upwards even after thermal aging at 1000°C for 2 hours under variable atmospheric conditions of rich-lean fluctuations.
Technical Paper

Durability of Three-Way Catalysts with Precious Metals Loaded on Different Location

It is necessary to mount a three-way catalyst at a place near the engine such as a close coupled converter or manifold converter to decrease cold-start emission. Naturally, in that case the catalyst of course is used under considerable A/F fluctuations at higher temperatures. We have developed a catalyst with excellent durability under such severe conditions. Three types of catalysts, made with different loading locations of precious metals, were evaluated using model gases. Durability was found to strongly depend on the loading location, and thus it should be possible to design an optimal catalyst for close coupled and manifold converters.
Technical Paper

Excellent Oxygen Storage Capacity of Perovskite-PD Three way Catalysts

Increasingly stringent emissions controls have led to a greater emphasis on strategies designed to minimize emission during cold start. One strategy employed is that of close-coupling the catalyst to the exhaust manifold of the engine in an effort to minimize catalyst light-off time. In this configuration, the catalyst must exhibit a high degree of thermal stability. Further, since the catalyst is situated nearer to the engine, it is more liable to sense cylinder-to-cylinder variations in exhaust gas composition and thus needs to possess a wider operating window than a catalyst positioned further underbody. We have previously reported that Perovskite-Pd catalysts exhibit excellent heat resistance and have three-way catalyst activity comparable with or superior to that of Pt-Rh/ Al2O3 catalysts and Pd/Al2O3 catalysts [1]*. Durability at high temperatures and oxygen storage capacity under large air/fuel (A/F) ratio fluctuation conditions have now been tested.
Technical Paper

Perovskite-Pd Three-Way Catalysts for Automotive Applications

Three-way catalysts which remove different kinds of pollutants, such as CO, THC(total hydro-carbon) and NOx, simultaneously from the automotive exhaust gas employ Rhodium(Rh) in combination with Platinum(Pt) and Palladium(Pd). Rh is the most effective for reducing NOx to N2, but Rh is the most expensive of these precious metals. The ratio of Rh to Pt applied for automobiles frequently exceeds the natural production. The gap between supply and demand of Rh sometimes causes the big price fluctuation. Accordingly, many attempts to reduce the amount of Rh loaded or to develop non-Rh three-way catalysts have been made. Although Pd catalysts are considered to be promising candidates for non-Rh automotive three-way catalysts, some performance are still inferior to Pt-Rh catalysts. We have found that an excellent three-way catalytic activity appears by compounding new Perovskite-structured oxides with Pd and auxiliary oxides.