Shinichi Matsumoto

The new concept 3-way catalyst for automotive lean-burn engine : NOx storage and reduction catalyst

The new concept 3-way catalysts for a lean-burn engine have been developed, and their NOx purification mechanisms have been studied. The catalysts consist of precious metals, aluminum oxide and some other metal compounds such as NOx, storage compounds. NOx is oxidized over the precious metals and stored as nitrate ion combined with NOx storage compounds under oxidizing conditions. The stored NOx, is reduced to N2 under stoichiometric and reducing conditions. The NOx, storage capacity is deteriorated by sulfur. The improved catalysts showed sufficient NOx, conversion durability in the Japanese 10–15 mode test.

DeNOx catalyst for automotive lean-burn engine☆

Abstract The performance and durability of Cu-ZSM-5 were studied. Cu-ZSM-5 has fairly high NOx reduction activity but its durability is insufficient for practical use. We developed a new deNOx catalyst. In this catalyst, we call NOx storage reduction catalyst (NSR-catalyst), NOx emitted from an engine at lean A F operation is stored and this stored NOx is reduced at stoichiometric or rich operation. This catalyst has been used on the Toyota CARINA with a lean-burn engine in Japan since 1994. This report outlines the results of our study on Cu-ZSM-5 and NSR-catalyst.

Research on new DeNOx catalysts for automotive engines

Abstract The performance and durability of Cu-ZSM-5 catalysts for selective reduction of NOx in an oxidizing atmosphere were studied. These catalysts exhibited substantial NOx conversion performance in a leanburn engine exhaust and the simulated gas. However, the temperature dependence, SV performance, and thermal stability must still be improved.

In Situ Redispersion of Platinum Autoexhaust Catalysts: An On-Line Approach to Increasing Catalyst Lifetimes?†

Supported precious metals, such as platinum (Pt), rhodium (Rh), and palladium (Pd), are used to facilitate many industrial catalytic processes. Pt in particular is found at the core of catalysts used throughout the petrochemical industry: from bifunctional catalysts (isomerization/dehydrogenation) used for refining of hydrocarbon fuel stocks, to three-way (CO and hydrocarbon oxidation/NOx reduction) conversions within car exhausts. In this latter, ubiquitous application— commercialized in the USA and Japan in 1977—Pt has always been a pivotal component in the abatement of harmful gas emissions from gasolineor diesel-driven engines. The ever-increasing appreciation of the damage that noxious gas emissions are doing to our environment and the finite availability of noble metals provide strong drivers for the continued study and optimization of the behavior of Pt-based three-way catalysts (TWCs). Central to technological progress in this area is a fundamental understanding of how these materials behave, which may allow us to stop them degrading or deactivating during operation. A longstanding problem, affecting many applications that use highly dispersed metal nanoparticles, is loss of active surface area in the metal components as a result of “sintering”. This is a particularly pernicious problem in applications in which catalysts have to experience high temperatures—in excess of 800 8C in the case of modern car catalysts. This deleterious process causes the particle size of the metal to increase massively—through either particle diffusion or agglomeration or through “ripening” processes. The result is that a large fraction of the active metal is effectively “hidden away” within the bulk of these larger particles where it cannot be used to affect the desired chemical conversions that occur on the particle surface. This central issue of exhaust catalyst deactivation has long been recognized in the hydrocarbon reforming and emission abatement industries. In the former industry, “oxidative redispersion” has been utilized to reverse the effects of sintering and regenerate spent Pt-based reforming catalysts. However, whereas other noble metal particles such as Pd or Rh can be effectively redispersed by gaseous oxygen at certain temperatures, this method is efficient for Pt catalysts only when Cl is present either in the catalyst formulation or as an adjunct added during the redispersion process: in the absence of Cl, redispersion in Pt/Al2O3 by oxygen is limited both to a narrow temperature window (of around 500 8C) and a low level of redispersion. 6] Further, a continuous oxidative treatment over time is required for this redispersion process. Exhaust gases exiting from gasoline engines change quickly and dramatically during operation. Temperatures can rise transiently to around 1000 8C, and the exhaust gas composition itself fluctuates quickly between oxidative and reductive compositions. Clearly, the conventional approach to redispersion and reactivation is highly unsuitable on many counts for “on-board” redispersion and regeneration of TWCs. Other regeneration phenomena have recently been shown in some related cases. The “intelligent” catalyst system of Daihatsu shows in-built structural reversibility of the noble metal component. In this case, it is the structure of the perovskite support that provides the foundation for this extremely elegant piece of applied catalyst design. The possibility of forming very large particles is intrinsically reduced and, under some circumstances, this technology has been successfully commercialized. However, this approach is very much dependent upon the structure of a particular and low surface area support material and is limited in this sense. [*] Dr. Y. Nagai, K. Dohmae, T. Tanabe, Dr. H. Shinjoh TOYOTA Central R&D Labs., Inc. Nagakute, Aichi 480-1192 (Japan) Fax: (+ 81)561-63-6150 E-mail: e1062@mosk.tytlabs.co.jp

NOx Storage-Reduction Three-Way Catalyst with Improved Sulfur Tolerance

The NOx storage-reduction catalyst (NSR catalyst) is poisoned by SO2 caused by fuel sulfur, thus its activity is reduced. In order to improve the NSR catalyst, the sulfur poisoning phenomenon has been analyzed. Based on this result, we developed TiO2 and Rh/ZrO2 to promote the sulfur desorption. The developed catalyst has made remarkable progress in its sulfur tolerance, about 50% improvement in NOx purification performance compared with the conventional one.

Pt3Ti Nanoparticles: Fine Dispersion on SiO2 Supports, Enhanced Catalytic CO Oxidation, and Chemical Stability at Elevated Temperatures

A platinum-based intermetallic phase with an early d-metal, Pt(3)Ti, has been synthesized in the form of nanoparticles (NPs) dispersed on silica (SiO(2)) supports. The organometallic Pt and Ti precursors, Pt(1,5-cyclooctadiene)Cl(2) and TiCl(4)(tetrahydrofuran)(2), were mixed with SiO(2) and reduced by sodium naphthalide in tetrahydrofuran. Stoichiometric Pt(3)Ti NPs with an average particle size of 2.5 nm were formed on SiO(2) (particle size: 20-200 nm) with an atomically disordered FCC-type structure (Fm3m; a = 0.39 nm). A high dispersivity of Pt(3)Ti NPs was achieved by adding excessive amounts of SiO(2) relative to the Pt precursor. A 50-fold excess of SiO(2) resulted in finely dispersed, SiO(2)-supported Pt(3)Ti NPs that contained 0.5 wt % Pt. The SiO(2)-supported Pt(3)Ti NPs showed a lower onset temperature of catalysis by 75 degrees C toward the oxidation reaction of CO than did SiO(2)-supported pure Pt NPs with the same particle size and Pt fraction, 0.5 wt %. The SiO(2)-supported Pt(3)Ti NPs also showed higher CO conversion than SiO(2)-supported pure Pt NPs even containing a 2-fold higher weight fraction of Pt. The SiO(2)-supported Pt(3)Ti NPs retained their stoichiometric composition after catalytic oxidation of CO at elevated temperatures, 325 degrees C. Pt(3)Ti NPs show promise as a catalytic center of purification catalysts for automobile exhaust due to their high catalytic activity toward CO oxidation with a low content of precious metals.

Dynamic behavior and characterization of automobile catalysts

Abstract Automotive catalyst technology is now faced with very difficult problems. The recent progress of research on the dynamic behavior and characterization of automobile catalysts, and their development to solve these problems are reviewed in this chapter. The oxygen storage and release phenomena under the non-steady atmosphere are investigated in terms of the oxygen storage capacity, the oxygen mobility and the local structure of oxygen storage materials. These parameters are in good correlation with each other. The sintering and re-dispersion phenomena of Platinum Group Metals (PGM) on metal oxides are studied by X-ray absorption analysis. The sintering of Pt is suppressed by making a bond between Pt and surface oxygen of oxides such as CeO 2 under the oxygen rich atmosphere, and sintered Pt particles on CeO 2 are re-dispersed under appropriate conditions. The NO x storage-reduction (NSR) catalyst, which was developed for automotive lean-burn engines, can reduce NO x under the oxygen-rich atmosphere. The NO x reduction phenomena are investigated by four steps. NO is oxidized on Pt under the oxygen-rich atmosphere. NO 2 reacts with basic materials and then is stored in the NSR as nitrate. The stored NO x is released after the decomposition of nitrate under the oxygen deficient atmosphere. The released NO x is reduced into N 2 on PGM by the reaction with a reducing component such as HC, CO and H 2 . The main cause of deterioration for the NSR is sulfur poisoning. The sulfur-poisoning mechanism and the way for an NSR with high tolerance to sulfur poisoning is studied in storage materials, support materials, substrate structures and the arrangement of catalysts.

Development of Thermal Resistant Three-Way Catalysts

Automotive catalysts with a good thermal durability have been developed by modifying the composition of additives. On the basis of the experimental results, the authors have designed optimal Pt/Rh/Ce three-way catalysts, which have showed significantly improved thermal durability and performance

The Development of an Automotive Catalyst using a Thin Wall (4 mil/400cpsi) Substrate

Since the monolithic ceramic substrate was introduced for automotive catalytic converters, the reduction of the substrate wall thickness has been a continuing requirement to reduce pressure drop and improve catalytic performance. The thin wall substrate of 0.10 mm (4mil) thick wall/400cpsi cell density has been introduced to production by achieving mechanical strength equivalent to a conventional 0.15 mm (6mil)/400 cpsi substrate. Although a round cross-section substrate can have a reduced catalyst volume compared to an oval cross-section substrate because section of the round substrate increases pressure drop. The thin wall technology was applied to the round substrate to offset the pressure drop increase and to further improve catalytic performance. The 1290 cm{sup 3} catalytic converter with a round thin wall substrate demonstrated pressure drop and catalytic performance equivalent to the 1,650 cm{sup 3} converter made with an oval type conventional substrate. The thin wall substrate also demonstrated improvement in thermal shock resistance compared to the original oval catalyst.

Tetraplatinum cluster complexes bearing hydrophilic anchors as precursors for γ-Al2O3-supported platinum nanoparticles

Tetraplatinum cluster complexes bearing hydrophilic anchors, [Pt4(μ-OCOCH3)4(μ-OCOC6H4OH-4)4] (2a), [Pt4(μ-OCOCH3)4(μ-OCOC6H4B(OH)2-4)4] (2b), and [Pt4(μ-OCOCH3)4(μ-OCOC6H4NH2-4)4] (2c), were successfully prepared by a selective substitution reaction of four in-plane acetates of [Pt4(μ-OCOCH3)8] (1) with the corresponding p-substituted benzoic acids. Solid-state structure determination of 2a revealed the 3D network structure through intermolecular hydrogen bonding between the hydroxy group of the p-hydroxybenzoate ligand and the oxygen atom of the carboxylate ligand of 2a. UV-vis analysis of 2a–c in CH3CN or CH3CN–H2O in the presence of γ-Al2O3 clearly indicated the adsorption efficiency of these platinum clusters on γ-Al2O3: 2a bearing a hydroxyl group and 2b bearing a B(OH)2 group were effectively deposited onto γ-Al2O3 from CH3CN solution, whereas less than 40% of 1 and 2c were chemically adsorbed onto γ-Al2O3. Highly dispersed and very small platinum nanoparticles (less than 1 nm) on γ-Al2O3 were obtained by thermal treatment of Pt4-deposited γ-Al2O3 at 500 °C.