abstracts - Институт катализа им. Г.К. Борескова

OP-III-25EPR STUDY OF CARBON BLACK OXIDATION MECHANISM IN LOOSE ANDTIGHT CONTACT WITH Al 2 O 3 AND CeO 2 CATALYSTSSaab E., Abi-Aad E., Bokova M.N., Zhilinskaya E.A., Aboukaïs A.Laboratoire de Catalyse et Environnement E.A. 2598, Université du Littoral - Côte d’Opale,MREI-1, 145, av. M. Schumann, 59140 Dunkerque, FranceE-mail: abiaad@univ-littoral.frAn effective way for soot removal from diesel exhausts consists in the use of ceramictraps suitable for collection and subsequent combustion of trapped carbon particulate at dieselexhaust temperatures. Catalysts can be used in a number of ways to accelerate the combustionof this accumulated soot. It can be added either through the fuel, in which case it isincorporated into the soot spherules as they form, or physically mixed in after collection ofsoot. The latter would correspond to the case of a soot filter whose surface is impregnatedwith catalyst via a wash coat.The contact between soot and catalyst is a very important parameter in the catalyticoxidation of soot. Only limited information is available on the intimacy of the solid-solidcontact between the catalyst (solid) and soot (solid) under real conditions. In literature varioustypes of physical contact are used for catalytic soot oxidation. Laboratory preparation of sootcatalystmixtures by milling yields “tight” contact whereas in a particulate filter the sootcatalystcontact will typically be loose. A mechanical mill is often chosen to establish closecontact between soot and catalyst in order to define an intrinsic catalytic activity underoptimal conditions. Simply mixing with a spatula gives information with practical relevance.It was found that the intensity of contact between soot and catalyst is one of the majorparameters that determine the soot oxidation rate. It can be seen that in general the mixtureswith ‘loose contact’ have a high combustion temperature, while samples prepared with ‘tightcontact’ have lower combustion temperature. However, the information about physicochemicalmanifestation of the contact is absent in the literature. As long as the degree ofphysical contact plays an important part in the combustion process, the nature of this contactshould be analysed to understand the mechanism of the reaction. Synthetic soot (carbon black,Printex U, fullerenes…) can be used as a model compound for diesel soot during simulatedlaboratory oxidation experiments.Several studies have shown that carbon black and its derivatives show that an EPR signalconstituted by a single line at different widths depending on the carbon and on theexperimental treatment. The EPR parameters of this signal are g = 2.002-2.005 and the line-373