Characterization of the Evolution of Noble Metal Particles in a Commercial Three-Way Catalyst: Correlation between Real and Simulated Ageing

Abstract

Ageing of automotive catalysts is associated to a loss of their functionality and ultimately to a waste of precious resources. For this reason, understanding catalyst ageing phenomena is necessary for the design of long lasting efficient catalysts. The present work has the purpose of studying in depth all the phenomena that occur during ageing, in terms of morphological modification and deactivation of the active materials: precious metal particles and oxidic support. The topic was deeply investigated using specific methodologies (FT-IR, CO chemisorption, FE-SEM) in order to understand the behavior of metals and support, in terms of their surface properties, morphology and dispersion in the washcoat material. A series of commercial catalysts, aged in different conditions, have been analyzed, in order to find correlations between real and simulated ageing conditions. The characterization highlights a series of phenomena linked to the deactivation of the catalysts. Pd nanoparticles undergo a rapid agglomeration, exhibiting a quick loss of dispersion and of active sites with an increase of particles size. The evolution of the support allows highlighting also the contribution of chemical ageing effects. These results were also correlated with performance tests executed on synthetic gas bench, underlining a good correspondence between vehicle and laboratory aged samples and the contribution of chemical poisoning to vehicle aged ones. The collected data are crucial for the development of accelerated laboratory ageing protocols, which are instrumental for the development and testing of long lasting abatement systems.

PROMETHEUS: A Copper-Based Polymetallic Catalyst for Automotive Applications. Part II: Catalytic Efficiency an Endurance as Compared with Original Catalysts

“…Vehicle ageing method is actually close to real road driving condition but, on the other hand, it is time-consuming, it takes more manpower and the cost is high. Furthermore, according to recent publications of Centre Research Fiat and University of Torino, after applying comparative tests of laboratory ageing, real on vehicle aging and engine bench aging it was proved the similar results of gases conversion (%) with no significant variations [ 34 , 35 , 36 ].…”

High Catalytic Efficiency of a Nanosized Copper-Based Catalyst for Automotives: A Physicochemical Characterization

“…The latter result is in accordance with the SEM images presented above, which revealed the sintering of the particles. Metal sintering is known to take place during the thermal treatment of three-way catalysts, leading to thermal deactivation indicated by a significant decrease in the specific surface area of the material and finally to decreased catalytic activity [ 35 , 55 ]. Moreover, according to Recommendation 2011/696/EU, revised on 10 June 2022, a material with a specific surface area by volume of less than 6 m 2 /cm 3 shall not be considered as a nanomaterial.…”

Mesoporous Ceria and Ceria‐Praseodymia as High Surface Area Supports for Pd‐based Catalysts with Enhanced Methane Oxidation Activity

“…Currently, Pd‐based catalysts are considered the best choice for reducing the methane emissions through its complete oxidation, considering their high activity at relatively low temperature [6–10] . Although these materials have already been extensively studied, further efforts are needed to limit the loss of activity around 700–800 °C due to the PdO‐Pd transition and the detrimental effects of water [11–14] .…”

“…[3][4][5] Currently, Pd-based catalysts are considered the best choice for reducing the methane emissions through its complete oxidation, considering their high activity at relatively low temperature. [6][7][8][9][10] Although these materials have already been extensively studied, further efforts are needed to limit the loss of activity around 700-800 °C due to the PdO-Pd transition and the detrimental effects of water. [11][12][13][14] In this context, the Pd deposition on CeÀ Pr supports has been investigated over the past few years, obtaining materials with a higher catalytic activity with respect to Pd/CeO 2 , a better stability of the PdO species in the high temperature range, and an interesting behavior in the presence of water.…”