Experimental Microkinetic Approach of the Catalytic Oxidation of Diesel Soot by Ceria Using Temperature-Programmed Experiments. Part 2: Kinetic Modeling of the Impact of the Ceria/Soot Contacts on the

详细信息    查看全文

• 作者：Badr Bassou ; Nolven Guilhaume ; Karine Lombaert ; Claude Mirodatos ; Daniel Bianchi
• 刊名：Energy & Fuels
• 出版年：2010
• 出版时间：September 16, 2010
• 年：2010
• 卷：24
• 期：9
• 页码：4781-4792
• 全文大小：945K
• 年卷期：v.24,no.9(September 16, 2010)
• ISSN：1520-5029

文摘

An experimental microkinetic approach of the catalytic oxidation of diesel soots is developed considering mechanical mixtures of ceria and soot (ceria/soot weight ratio R) to mimic the situation of a catalyst-coated filter. Three ceria/soot mixtures denoted as TC-R = 10, TC-R = 1, and LC-R = 10 have been prepared according to the tight and loose contacts, respectively. Temperature-programmed experiments (without O₂) performed on stabilized ceria/soot mixtures provide the rate of the CO₂ production, R_CO2(T), via the reaction between carbon defect sites C_f of the soot and oxygen species transferred by the ceria particles. The R_CO2(T) curves present two peaks at low and high temperatures. The study is dedicated to the kinetic modeling of the R_CO2(T) curves at low temperatures. According to the experimental microkinetic approach, two plausible kinetic models of the reaction have been selected on the basis of literature data; they differ from the implication or not of oxygen diffusion on the ceria surface. The mathematical kinetic formalisms, associated with the models, consider that the ceria/soot contacts constitute key kinetic parameters of the soot oxidation and their properties, such as the average number of contacts N_c between a ceria particle and the soot particles and the average surface s_c of a contact, included in the kinetic equations. Different kinetic parameters have been obtained using experimental procedures, such as the activation energy of oxidation of the carbon defect sites (187 kJ/mol) and the N_c values for the different ceria/soot mixtures (i.e., N_c = 4.3 for TC-R = 10). It is shown that the microkinetic approach permits obtaining theoretical R_CO2(T) curves consistent with the experimental data for the three mixtures, considering similar values of the kinetic parameters, except the N_c and R values. Moreover, the kinetic models have been extended to catalytic soot oxidation in the presence of O₂ by including its adsorption on ceria. This study confirms the interest of the experimental microkinetic approach for the understanding of the key kinetic parameters controlling the catalytic soot oxidation. Moreover, it provides a mathematical formalism for the comparison of the performances of different solid catalysts, in particular for the development of new formulations.