The Smartcat project is dedicated to the development of novel catalytic post-treatment systems based on two complementary approaches : - the development of self-regenerative materials as support, to stabilize the active elements, exhibiting perovskite and spinelle type structures and - the application of the dual bed concept with the aim to create more active reaction intermediates particularly singlet oxygen to lower running temperature for an efficient methane conversion. Accordingly, one of the objectives will be to slower thermal aging in order to preserve the production of active singlet oxygen species. Different steps have been envisioned to fullfill this general objectives.
– (i) The development of hard templating methods for obtaining thermally resistant hierarchical porous structures for improving oxygen mobility and related oxygen storage capacity (OSC), specific surface area and mass transfer diffusion.
– (ii) The development of innovative strategies for the introduction of more resistant palladium species to thermal sintering and poisoning effects (one pot sol gel synthesis or post-thermal treatment) and to implement advanced techniques for ex situ and in situ characterization of the catalytic functionalities of those systems, i.e. redox and OSC properties.
– (iii) The development of advanced spectroscopic tools and appropriate in situ methodologies for the characterization of reactive oxygen species and reactive intermediate carbidic species implying steady-state transient kinetic analysis.
– (iv) The investigation of the kinetics of methane combustion at various richness and the establishment of more relevant surface-reactivity relationships in agreement with a selected reaction mechanism that would allow a better optimization of the catalytic functionalities.
– (v) The selection of appropriate compositions and structures that allow the verification of the concept of catalytic dual-bed reactor.
First the perovskite struture has been chosen. Two strategies have been implemented. The first one consisted in optimizing the textural and structural properties of a parent composition. In a second stage, palladium has been incorporated according to two different methods leading to a surface distribution or an homogeneous dispersion in the bulk structure. Afterwards, the catalytic properties of these different catalytic samples have been evaluated in methane oxidation and compared to the rates measured from isotopic exchange of oxygen. It was found that palladium improves the performances. On the other hand the mode of incorporation seems important. Indeed, a better stability is observed when Pd is stabilized inside the perovskite lattice preserving higher activity after several catalytic testings. The study of the structural features and surface analysis have been planned in order to explain such changes in thermal stability.
The second option consisted in optimizing a parent LaMnO3 structure through partial substitution in B-site. La has been partly substituted by potassium and strontium. The substitution of La3+ by divalent (Sr2+) or monovalent cations (K+) is able to create structural distorsions and electronic imbalance that can promote oxygen mobility. X-ray diffraction, temperature-programmed reduction experiments and oxygen desorption showed higher oxygen mobility and improved redox properties for intermediaite K and Sr content. On the other hand at high content, partial segregation of impurities induce a loss of specific surface area as well as reducibility. Palladium has also been incorporated through a conventional wet impregnation revealing improved reducibility. Physicochemical characterization are in progress to understand the nature of interaction between palladium and the perovkite support materials.
Work plan for the next period
Particular attention will be paid to Pd-doped catalysts with the aim to reduce the metal loading. The evaluation of their catalytic properties will be carry out in representative inlet gas compositions close to real exhaust gas conditions. IC2MP will contribute significantly to check the dual bed concept in these operating conditions and finally when the catalyst will be subjected to deactivation. Most of the solids prepared at the LSFC will be tested in order to select a short list that could be potentially developed. A better understanding of their physicochemical properties and oxygen storage capacity through isotopic exchange measurements will clarify their catalytic functionalities with the aim the establish relevant structure-activity relationship.
UCCS will continue to get a direct evidence of singlet oxygen production through spectral characterization. Probably, this study will be restricted to few samples among those exhibiting the best properties and will provide relevant information to optimize the dual bed reactor. An important aspect will be relate to the use of the Realcat platform on simple inlet composition for the characterization of : (i) catalyst functionalities in methane oxidation for a single bed technology – (ii) behaviour towards deactivation – (iii) reaction mechanism. Regarding this latter point complementary information will be provided by SSITKA analysis which could be useful to identified real intermediates after methane activation on palladium.
1. Synthesis of catalysts for total oxidation of methane suited for alternative fuels , M. Delporte, H. Kaper, X. Courtois, F. Can, N. Bion, 17th International Congress on Catalysis, San Diego, USA, 14-19 juin 2020 (reporté suite à la crise du COVID 19)
2. Synthèse de catalyseurs pérovskites pour l’oxydation totale du méthane, M. Delporte, H. Kaper, S. Bouchet, X. Courtois, F. Can, N. Bion, GECAT, Hendaye, France, 25-28 mai 2020 (reprogrammé au 3-6 novembre 2020
3. Dual substitution of stoichiometric and La-deficient manganite perovskites : Criteria for gasoline and Natural Gas Vehicle Three-Way-Catalysts developments. J. Wu, Y. Zheng, J.P. Dacquin, C. Cordier, C. Dujardin, P. Granger, 11th International Conference on Environmental Catalysis, september 6-9th, 2020 Manchester, UK
A review article in preparation
«New opportunities in the development of Natural Gas Vehicle engines and related catalytic postcombustion end-of-pipe technologies : Concept and practices«
An invitation to a technical paper : «Les techniques de l'ingénieur« for writting a contribution dedicated to aftertreatment systems for natural gas fuelled vehicles - CRMT will managed this contribution.
Exhaust gas treatment catalysts for mobile sources are becoming more and more sophisticated with an extensive use of critical materials of strategic importance such as precious metals and rare earths. The diversification of energy sources open new opportunities with the implementation of more simple and cost-efficient end-of-pipe technologies. By way of illustration, new combustion modes and natural gas powered engines (NGV) have the advantages to lower NOx emissions with nearly no particulate matter formation and also to lessen greenhouse gas emissions. In this latter case, the treatment of unburnt methane traces in the exhaust gas is requested because of its much higher global warming potential than CO2. Methane is recognized as refractory molecule due to its chemical stability. As a consequence, its abatement currently induces high running temperature and highly loaded PGM catalysts to compensate the loss of performance due to strong deactivation. Hence, the development of low loaded precious metal based catalysts, thermally stable and resistant to poisoning effects in the presence of sulfur contaminant, represents important scientific and technological issues. A gradual approach, from the nanoscopic description of the catalyst to the implementation of new reactor concept, is developed in this project which should match with the future recommendations in terms of methane abatement classified as greenhouse gas.
The goal of the SmartCat project is to propose innovative scientific and technological responses to reach higher efficiency in methane abatement at lower temperature than conventional catalytic technologies, with lower platinum group metal (PGM) loading. In practice, it consists in improving both on the generation of very active oxygen species and the reactivity of carbidic species. In order to fulfill those objectives, two complementary approaches will be implemented : (i) Introduction of new concepts with hard templating methods for the preparation of perovskites ABO3 and mixed ion-electronic conductors (MIEC) to get higher specific surface area with independent control of the macropore and mesopore sizes, improved OSC properties and higher catalytic efficiency. (ii) The second option resides in the development of an innovative approach based on a dual-bed configuration composed of ABO3-MIEC catalysts association. The first bed is composed of palladium free materials for the production of active singlet oxygen species, suggested as the intermediate active species for methane activation at low temperature. The second bed contains catalysts with low Pd loading dedicated to methane activation and oxidation. This new concept will be tentatively demonstrated in real exhaust gas conditions in the absence and in the presence of sulfur contaminant. The consortium is composed of three academic laboratories working in the field of environmental catalysis and materials sciences. They will closely collaborate in order to get a complete description of the systems at the nanoscale. Through this approach, a sharp gain in efficiency is expected compared to current end-of-pipe technologies.
Monsieur Pascal GRANGER (Unité de Catalyse et de Chimie du Solide)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
UCCS Unité de Catalyse et de Chimie du Solide
L.S.F.C. laboratoire de synthèse et fonctionnalisation des céramiques
IC2MP Institut de Chimie des Milieux et des Matériaux de Poitiers
Help of the ANR 445,532 euros
Beginning and duration of the scientific project: October 2018 - 42 Months