Description : This project gathers researchers working on a wide range of disciplinary fields: physicist, chemist, process and materials engineering. Our goal is to develop a novel process of lignin valorisation to produce high added-value chemicals. In biorefineries, lignin could produce aromatic compounds which are important building blocks currently produced from crude oil. Here, a novel process will be developed by using a multi-scale approach: from molecular scale with ab-initio modelling to the synthesis of new tailored catalysts and the optimisation of the most efficient catalysts in a representative process. This project is part of an important projects’ dynamic (in Lorraine and at an international level) on biomass valorisation and notably on lignin.
Porteur : Anthony DUFOUR
Participants L2CM: Nadia Canilho, Andreea Pasc
Results : Y. Berro, S. Gueddida, Y. Bouizi, C. Bellouard, El-E. Bendeif, A. Gansmuller, A. Celzard, V. Fierro, D. Ihiawakrim, O. Ersen, M. Kassir, F. El Haj Hassan, S. Lebegue, M. Badawi, N. Canilho, A. Pasc, Imprinting isolated single iron atoms onto mesoporous silica by templating with metallosurfactants, Journal of Colloid and Interface Science, 573, 2020, 193-203. https://doi.org/10.1016/j.jcis.2020.03.095.
One of the main drawbacks of metal-supported materials, traditionally prepared by the impregnation of metal salts onto pre-synthesized porous supports, is the formation of large and unevenly dispersed particles. Generally, the larger are the particles, the lower is the number of catalytic sites. Maximum atom exposure can be reached within single-atom materials, which appear therefore as the next generation of porous catalysts.
Herein, we designed single iron atom-supported silica materials through sol-gel hydrothermal treatment using mixtures of a non-ionic surfactant (Pluronic P123) and a metallosurfactant (cetyltrimethylammoniumtrichloromonobromoferrate, CTAF) as porogens. The ratio between the Pluronic P123 and the CTAF enables to control the silica structural and textural properties. More importantly, CTAF acts as an iron source, which amount could be simply tuned by varying the non-ionic/metallo surfactants molar ratio.
The fine distribution of iron atoms onto the silica mesopores results from the iron distribution within the mixed micelles, which serve as templates for the polymerization of the silica matrix. Several characterization methods were used to determine the structural and textural properties of the silica material (XRD, N2 sorption isotherms and TEM) and the homogeneous distribution and lack of clustering of iron atoms in the resulting materials (elemental analysis, magnetic measurements, pair distribution function (PDF), MAS-NMR and TEM mapping). The oxidation and spin state of single-iron atoms determined from their magnetic properties were confirmed by DFT calculations. This strategy might find straightforward applications in preparing versatile single atom catalysts, with improved efficiency compared to nanosized ones.
Keywords: Single iron atom catalysts; Mesoporous silica; Metallosurfactants; Density functional theory; Spin state; Pair distribution