Thermal stability and decomposition kinetics of NdNiO3− δ at 1 bar of O2

Despite the interest in rare-earth nickelates for applications, their processing under 1 bar of oxygen pressure is still challenging. In this work, we report the co-precipitation synthesis, thermal stability and thermally driven decomposition of NdNiO3 phase, in order to determine the synthesis parameters towards a pure perovskite phase. We concluded that using a 1% molar excess of Nd during preparation and posterior annealing at around 900 °C at 1 bar of O2 yields an almost pure NdNiO3−δ phase (with a hexagonal Nd2O3 phase below 0.6% molar), with an oxygen deficiency of δ = 0.082 ± 0.001. The decomposition of the NdNiO3−δ phase into Nd4Ni3O10 and NiO was found to start above 900 °C. On further heating, above 1050 °C, the Nd4Ni3O10 decomposes into Nd2NiO4 and NiO phases. Structural parameters and Raman spectra are provided for the NdNiO3, Nd4Ni3O10 and Nd2NiO4 compounds.The authors would like to acknowledge Fundacao para a Ciencia e Tecnologia (FCT) through projects NORTE/01/0145/FEDER/028538, CERN/FIS-PAR/0005/2017, CERN/FIS-TEC/0003/2019, PTDC/FIS-MAC/29454/2017 and when appropriate co-financed by FEDER under PT2020 Partnership Agreement: CQVR: UIDB/QUI/00616/2020; IFIMUP-IN: Norte-070124-FEDER-000070; NECL: NORTE-01-0145-FEDER-022096, UID/NAN/50024/2019. P. Machado and J. Oliveira acknowledge FCT through Ph.D. Grants SFRH/BD/108509/2015 and SFRH/BD/146886/2019 respectively. A special acknowledgment is made to CEMUP for XPS measurements

Comparaison du filtre adaptatif RIF et du filtre a base de reseau de neurones pour le filtrage du courant de reference pour la commande du filtre actif parallele

No Abstract. Technologies Avancees Vol. 17 2005: pp. 29-

Mechanistic study of Diesel soot combustion over an AgMnOx catalyst

International @ INGENIERIE+NOG:DBI:CMIInternational audienceNon

Impact of potassium on the heats of adsorption of adsorbed CO species on supported Pt particles by using the AEIR method

International audienceThe heats of adsorption at several coverages of the linear and bridged CO species (denoted L and B, respectively) adsorbed on the Pt0 sites of the 2.9 wt% Pt/10% K/Al2O3 catalyst are determined using the Adsorption Equilibrium Infrared spectroscopy method. The addition of K on 2.9% Pt/Al2O3 modifies significantly the adsorption of CO on the Pt particles: (a) the ratio L/B is decreased from 8.4 to 1, (b) a new adsorbed CO species is detected with an IR band at 1763 cm−1, (c) the heats of adsorption of L and B CO species are significantly altered and the positions of their IR bands are shifted. The heats of adsorption of L CO species are decreased: i.e. 206 and 105 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively. Two B CO species denoted B1 and B2, with different heats of adsorption are observed on Pt/K/Al2O3. The heats of adsorption of B2 CO species (major B CO species) are significantly larger than those measured in the absence of K: i.e. 94 and 160 kJ/mol at low coverages on Pt/Al2O3 and Pt/K/Al2O3 respectively, whereas those of B1 CO species (minor species) are similar: 90 kJ/mol at low coverages. These values are consistent with the qualitative High Resolution Electron Energy Loss Spectrometry literature data on Pt(1 1 1) modified by potassium

Mechanistic study of diesel soot combustion over an AgMnOx catalyst

AIR:INGENIERIE:SURFACES+NOG:BBA:DBI:CM

Mechanistic study of diesel soot combustion over an AgMnOx catalyst

AIR:INGENIERIE:SURFACES+NOG:BBA:DBI:CM

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 Rate of Oxidation

Bassou, Badr Guilhaume, Nolven Lombaert, Karine Mirodatos, Claude Bianchi, DanielAn 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 O-2) 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(7) 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 O-2 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

Experimental Microkinetic Approach of the Catalytic Oxidation of Diesel Soot by Ceria Using Temperature-Programmed Experiments. Part 1: Impact and Evolution of the Ceria/Soot Contacts during Soot Oxidation

Bassou, Badr Guilhaume, Nolven Lombaert, Karine Mirodatos, Claude Bianchi, DanielThe present study is dedicated to an experimental microkinetic approach of the catalyst oxidation of the diesel soot using a filter coated with ceria. To mimic the situation encountered in this process, mechanical ceria/soot mixtures have been prepared according to the tight and loose contact concepts described in the literature with ceria/soot ratio R > 1. Diesel soots prepared on an engine test bench and commercial soot have been used. The evolution of the ceria/soot contacts (via the amount of oxygen transferred from ceria to soot) with the progressive oxidation of the soot is followed using temperature-programmed experiments (denoted as TPEs) that provide the rate of CO2 and CO productions [denoted as R-CO2(T) and R-CO(T)] during the increase in the temperature in helium in the range of 300-1100 K. During the first TPE, different surface processes implying pure soot and ceria contribute to R-CO2(T) and R-CO(T), making the evaluation of the oxygen transfer difficult. It is shown that these difficulties are suppressed by performing, on the same ceria/soot sample, successive cycles constituted by a TPE followed by adsorption of O-2 at 300 K that leads to the progressive oxidation of the soot. After three cycles, it is shown that, whatever the ceria/soot mixtures, the amount of oxygen that can be transferred from ceria to soot remains constant. This indicates that the ceria/soot surface contacts do not change during the soot oxidation, which is a conclusion consistent with recent literature data on environmental transmission electron microscopy (TEM). However, the amount of oxygen provided by ceria and available for the soot oxidation is dependent upon the type of ceria/soot mixtures, and this controls the performances of the catalyst evaluated by the decrease of the light-off temperature of the soot in a flow rate of 30% O-2/He. These conclusions are used in part 2 (10.1021/ef100582w) to provide a detailed kinetic modeling of the TPE experiments for the different ceria/soot mixtures, focusing on the key role of the ceria/soot contacts on the rate of soot oxidation. This provides a consistent formalism to understand the impact of the types of catalyst/soot mixtures on the performances

In situ investigation of Diesel soot combustion over an AgMnOx catalyst

AIR:BIOVERT:MATERIAUX:INGENIERIE:SURFACES+NOG:BBA:GBR:DBI:FBS:ADS:BJO:CMIAn AgMnOx catalyst (3.5 wt.% Ag) incorporating silver ions in a Mn2O3 phase exhibits high performances for soot oxidation below 300 degrees C. Its structural and redox properties have been investigated under reaction conditions using in situ XRD and DTA-TGA measurements. The catalyst appears unmodified during soot combustion experiments under oxygen, but in the absence of oxygen the soot is stoichiometrically oxidised by lattice oxygen leading to catalyst bulk reduction according to the steps Mn2O3 -> Mn3O4 -> MnO. The isotopic reaction product composition ((CO2)-O-16, (COO)-O-18-O-16, (CO2)-O-16, (CO)-O-16 and (CO)-O-18) obtained during soot combustion experiments under O-18(2) reveals that the reaction follows a redox mechanism, in which the transfer of lattice oxygen from the catalyst to the soot is responsible for the soot ignition at low temperature. (C) 2012 Elsevier B.V. All rights reserved

High-throughput approach to the catalytic combustion of diesel soot II: Screening of oxide-based catalysts

AIR:INGENIERIE:SURFACES+BBA:NOG:EIO:DFA:DBI:CM