The Promoting Role of Noble Metals on NOxStorage Catalyst and Mechanistic Study of NOxStorage under Lean-Burn Conditions

2001 ◽  
Vol 15 (1) ◽  
pp. 205-213 ◽  
Author(s):  
H. Y. Huang ◽  
R. Q. Long ◽  
R. T. Yang
Keyword(s):  
Noble Metals ◽  
Mechanistic Study ◽  
Lean Burn

Technical Considerations for Catalysts for the European Market

1988 ◽  
Vol 202 (4) ◽  
pp. 227-234
Author(s):  
H S Gandhi
Keyword(s):  
Noble Metals ◽  
Modulation Frequency ◽  
Lean Burn ◽  
Active Metal ◽  
Metal Support ◽  
Temperature Ageing ◽  
Lead Levels ◽  
Higher Temperature ◽  
In The Beginning

The durability of automotive catalysts for European applications were investigated as a function of higher temperatures encountered in autobahn driving over extended periods of time, potentially higher lead levels anticipated in the beginning in European unleaded fuels and occasional misfuelling with leaded fuels. Increasing residual lead levels from 3 mg Pb/L to 10 mg Pb/L in laboratory experiments at 1000°C peak temperature substantially decreased three-way catalyst (TWC) performance. Higher temperature ageing conditions from 730 to 1000°C resulted in 50 per cent loss of BET area and increased stoichiometric light-off temperatures. The paper also reviews briefly the role of noble metals, rare earth oxides and base metal oxides in the formulation of practical TWCs. The operation of a TWC and the effects of A/F modulation frequency and amplitude on its performance are also discussed. Important thermal and chemical modes of TWC deactivation are discussed with specific examples. The importance of matching the active metal component to the support material to achieve the desired metal-support interactions and how this understanding has led to the development of practical TWC with proper utilization of noble metals is emphasized. Finally, the lean-burn versus stoichiometric combustion approach as it relates to catalyst requirements is also discussed.

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

scholarly journals Ag/CeO2 Composites for Catalytic Abatement of CO, Soot and VOCs

Catalysts ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 285 ◽  
Author(s):  
M. Grabchenko ◽  
N. Mikheeva ◽  
G. Mamontov ◽  
M. Salaev ◽  
L. Liotta ◽  
...  
Keyword(s):  
Noble Metals ◽  
Chemical Properties ◽  
Soot Oxidation ◽  
Catalytic Performance ◽  
Defective Structure ◽  
Metal Support Interaction ◽  
Key Factor ◽  
Metal Support ◽  
Vocs Abatement

Nowadays catalytic technologies are widely used to purify indoor and outdoor air from harmful compounds. Recently, Ag–CeO2 composites have found various applications in catalysis due to distinctive physical-chemical properties and relatively low costs as compared to those based on other noble metals. Currently, metal–support interaction is considered the key factor that determines high catalytic performance of silver–ceria composites. Despite thorough investigations, several questions remain debating. Among such issues, there are (1) morphology and size effects of both Ag and CeO2 particles, including their defective structure, (2) chemical and charge state of silver, (3) charge transfer between silver and ceria, (4) role of oxygen vacancies, (5) reducibility of support and the catalyst on the basis thereof. In this review, we consider recent advances and trends on the role of silver–ceria interactions in catalytic performance of Ag/CeO2 composites in low-temperature CO oxidation, soot oxidation, and volatile organic compounds (VOCs) abatement. Promising photo- and electrocatalytic applications of Ag/CeO2 composites are also discussed.

Investigation of the Role of Carbonylchemistry to Pattern Platinum Electrodes

2001 ◽  
Vol 688 ◽  
Author(s):  
St. Schneider ◽  
H. Kohlstedt ◽  
R. Waser
Keyword(s):  
Carbon Monoxide ◽  
Etch Rate ◽  
Noble Metals ◽  
Electrode Materials ◽  
In Situ Monitoring ◽  
Platinum Electrodes ◽  
Process Chemistry ◽  
Dimension Control ◽  
Axis Position

AbstractNoble metals like platinum or irdium are used as electrode materials in DRAM or FRAM devices. Their etch process is a challenge as conventional, sputter driven etch processes either result in redeposition problems (fences) or in a severe sloping (loss of dimension control) and are not acceptable for high density integration architectures. The high temperature etch regime offers a solution by increasing the chemical etch component and thus the volatility of the etch products.As previously reported, the platinum etch rate increases exponentially for a chlorine etch process with increasing wafer temperature. In this study we investigate the particular role of carbon monoxide in a Cl2/CO etch process. We find that carbon monoxide additions to a chlorine process boost the chemical component of the platinum etch rate very significantly, exceeding the effects in the chlorine only process regime by far. Additionally we compare these results with a Cl2/O2 and a Cl2/CO2 process chemistry, which are not found to be particularly beneficial.To better understand the etch process we use an energy dispersive quadrupole mass spectrometer for in situ monitoring, attached to the chamber at two different locations. We are able to position the probe orifice at the place of the wafer electrode, to record ion energy and ion mass spectra of species impinging on the wafer plane. A second off axis position allows for etch product monitoring.

Mechanistic Study of the Role of One-Component Resins in Rubber-to-Brass Bonding in Tires

2004 ◽  
Vol 77 (5) ◽  
pp. 891-913 ◽  
Author(s):  
Pankaj Y. Patil ◽  
William J. van Ooij
Keyword(s):  
Reaction Time ◽  
Secondary Ion Mass Spectrometry ◽  
Gel Permeation Chromatography ◽  
Mechanistic Study ◽  
Coated Steel ◽  
Adhesion Promoters ◽  
Steel Cords ◽  
Adhesion Performance ◽  
Secondary Ion

Abstract Adhesion between rubber and brass-coated steel cords is enhanced by using resins as adhesion promoters. Experiments were carried out using a squalene liquid rubber modeling approach to study the effect of resins on the chemistry of the vulcanization reaction. The formation of new intermediates during vulcanization and changes in chemical concentrations with reaction time was studied using Gel Permeation Chromatography (GPC) analysis of the reacted squalene mixtures. Also, the effect of presence of resins on the surface of sulfidized brass cords was studied by analyzing the adhesion layer's elemental composition using the Electron Dispersive X-ray Spectroscopy (EDX) and Secondary Ion Mass Spectrometry (SIMS) characterization techniques. The changes in surface morphology of the adhesion layer with reaction time was noted by taking micrographs using the Scanning Electron Microscopy (SEM) technique. In this paper, a new mechanism is proposed for the role of resins in the improvement of initial and aged adhesion performance between rubber and brass-coated steel tire cords.

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