Nanostructured platinum alloys for use as catalyst materials (original) (raw)
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Preparation, activity and durability of promoted platinum catalysts for automotive exhaust control
Applied Catalysis B-environmental, 1994
The effects of the addition of calcia, ceria and lanthana to alumina-supported platinum catalysts on the simultaneous control of hydrocarbon, carbon monoxide and nitrogen oxide automobile emissions (three-way catalyst behaviour) were analyzed. The activity of the prepared samples was determined with steady-state, reducing and oxidizing, simulated feedstreams as well as with a cycled oxidizing-reducing feedstream averaged at the stoichiometric conditions which resembled the exhaust air/fuel fluctuations in a closed-loop emission control system. Activity of the catalysts was also analyzed after conducting accelerated thermal and chemical ageing in order to test their durability. Under normal operating conditions of the automobile engine, Pt/Al2O3 catalysts promoted by rare-earth oxides are able to achieve high HC, CO and NO conversions. The behaviour of the catalysts in the cold start period was determined by analysis of light-off temperatures and a comparison was made with those corresponding to some commercial samples and others reported in the literature. The catalysts prepared in this work showed lower light-off temperatures than those of commercial and reported Pt/Al2O3 catalysts but these temperatures were not so low as with PtRh/Al2O3. In all cases, the prepared catalysts resulted in a better resistance to accelerated ageing. Samples with ceria showed the best resistance to accelerated ageing.
Gold, an alternative to platinum group metals in automobile catalytic converters
Gold Bulletin, 2011
Catalytic convertors based on the use of platinum, palladium and rhodium play a major role in the cleaning of automobile emissions. Gold, when dispersed as nano-sized particles, has demonstrated significant activity in the conversion of toxic components, including carbon monoxide, unburnt hydrocarbons and nitrogen oxides, in engine emissions and some advantages over the platinum group metals. Some research outcomes on the application of nano-sized gold for the conversion of these components are reviewed. Several key issues in relation to its performance and applicability in catalytic convertors such as low-temperature activity and thermal stability and the possibilities of substituting platinum group metals for automobile emission control with gold are discussed. Keywords Gold nanoparticles. Automotive catalytic converters. Selective reduction of nitrogen oxides. Catalytic oxidation of CO. Catalytic oxidation of hydrocarbons 1. The core, or substrate, which has a large surface area to support the catalyst and therefore is often called a catalyst support. 2. The washcoat, a very thin layer of paint or sealer on the catalyst support, is used to increase the core surface area by making it rougher and more irregular. 3. The catalyst itself. This is the key element in a catalytic converter and is composed most often of precious metals, i.e. platinum group metals (PGMs) including Pt, Pd and Rh [3]. Cerium, iron, manganese and nickel are also used, but each has its own limitations [3]. The annual global supply of Pt is only about 210 t [4]. The global Pt consumption has been doubled in the last decade, and production of automotive catalysts is the
First of Its Kind Automotive Catalyst Prepared by Recycled PGMs-Catalytic Performance
Catalysts
The production of new automotive catalytic converters requires the increase of the quantity of Platinum Group Metals in order to deal with the strict emission standards that are imposed for vehicles. The use of PGMs coming from the recycling of spent autocatalysts could greatly reduce the cost of catalyst production for the automotive industry. This paper presents the synthesis of novel automotive Three-Way Catalysts (PLTWC, Pd/Rh = 55/5, 60 gPGMs/ft3) and diesel oxidation catalysts (PLDOC, Pt/Pd = 3/1, 110 gPGMs/ft3) from recovered PGMs, without further refinement steps. The catalysts were characterized and evaluated in terms of activity in comparison with benchmark catalysts produced using commercial metal precursors. The small-scale catalytic monoliths were successfully synthesized as evidenced by the characterization of the samples with XRF analysis, optical microscopy, and N2 physisorption. Hydrothermal ageing of the catalysts was performed and led to a significant decrease of ...
Applied Catalysis B: Environmental, 2001
X-ray Absorption Near Edge Spectroscopy (XANES) shows that Pt in Pt nitrate solutions has +4 oxidation state. Extended X-ray absorption fine structure (EXAFS) reveals each Pt is coordinated to an average of 5.4(±0.5) oxygen atoms with a Pt-O bond distance of 1.99(5) Å. Each Pt center has an average of 2.9 neighboring Pt atoms with a Pt···Pt non-bonding distance of 3.08(3) Å. A Pt[-O(H)] 2 Pt ring with two Pt atoms linked by two O or OH ligands is proposed to be the primary structure moiety and building blocks for more complex oligomeric structures.
Angewandte Chemie International Edition, 2008
Dedicated to the Catalysis Society of Japan on the occasion of its 50th Anniversary 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/NO x reduction) conversions within car exhausts. In this latter, ubiquitous applicationcommercialized in the USA and Japan in 1977 [1]-Pt has always been a pivotal component in the abatement of harmful gas emissions from gasoline-or 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.
Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation
Catalysis Today, 2003
Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 • C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications.
New Strategies for the Improvement of Automobile Catalysts
International Journal of Molecular Sciences, 2001
This paper provides a review of recently obtained spectroscopic results, ab-initio calculations and catalytic activity tests from the authors´ laboratory of factors affecting the performance of materials used as automobile catalysts. Issues addressed include the preparation of (Ce,Zr)O x /Al 2 O 3 (CZA) mixed oxide supports and the use of new active metals, such as Pd and Cu, for three-way catalysts (TWCs); the performance of non-noble transition metals, such as Co or Ag, for pollution control under lean conditions; and the use of Pt/BaO x /Al 2 O 3 (PtBa) for engine exhaust gas treatment under oscillating lean-stoichiometric conditions.
Modification of Catalytic Converters Thereby Bettering their Performance and Reducing The Cost
With the invention of IC engines and their increased use in automobile industries, pollution has become a cause for major concern since the last two decades. We are not new to the destructive effects, global warming has had on the environment. Automobile exhausts contain hazardous gases like Nitrogen oxide gases, Carbon Monoxide and unburnt hydrocarbons. These poisonous gases pose a great threat to life on the planet and the environment that we thrive in. For the reduction of these exhaust emissions, catalytic converters have been introduced in automobiles which provide a medium to carry out simultaneous oxidation and reduction of these exhaust gases using selective catalysts. Catalysts are those substances which never participate in the reactions but speed up the reaction processes. Normally, noble metals such as Platinum (Pt), Palladium (Pd) and Rhodium (Rh) are used in manufacturing of catalytic converters. In this review an attempt is made, to study various materials like activa...
2005
Due to advances in nanotechnology, the approach to catalytic design is transitioning from trial-and-error to planned design and control. Expected advances should enable the design and construction of catalysts to increase reaction speed, yield, and catalyst durability while also reducing active species loading levels. Nanofabrication techniques enabling precise control over the shape, size, and position of nanoscale platinum-group metal (PGM) particles in automotive catalysts should result in reduced PGM loading levels.