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The catalyst/biomass integration concept for the direct thermo-catalytic conversion of biomass into either syngas or added-value molecules

Richardson Y., Eibner S., Tanoh S., Broust F., Blin J., Julbe A.. 2015. La Rochelle : ISGC, 3 p.. International Symposium on Green Chemistry. 3, 2015-05-03/2015-05-07, La Rochelle (France).

A new concept of integrated catalytic biomass thermochemical conversion based on the catalyst/biomass integration is proposed as a strategy to promote process intensification for either (i) the production of syngas from biomass gasification or (ii) the production of bio-oils with targeted composition from biomass flash pyrolysis. This concept is based on the smart and controlled integration of selected transition metal nanoparticles into the biomass feedstock during the pyrolysis step [1]. It relies on the postulate that heterogeneous catalysts, used to convert solid lignocellulosic biomass directly to either syngas or bio-oil, can be made substantially more efficient by improving the catalyst/biomass contact. Specifically, the achievement of such a close contact targets both (i) changes in the mechanisms of the first biomass decomposition stages, leading to high selectivity for specific products and (ii) a substantial improvement in catalyst efficiency for solid fuel conversion, allowing lower temperatures and/or shorter reaction times. This concept, illustrated in figure 1, consists of inserting the catalyst metal precursor into the lignocellulosic biomass feedstock during an impregnation stage with aqueous metal salt solutions, ensuring good precursor dispersion in the lignocellulosic matrix. The catalytic active phases, as metal-based nanoparticles, are then in-situ generated, during thermochemical conversion of the feedstock. As highlighted in figure 1, this concept involves different key reaction steps including i) insertion of catalyst precursor in the solid biomass, ii) catalytic pyrolysis of the as-pretreated biomass, iii) catalytic gasification of the nano-composite char residue and iv) recycling and reuse of the catalyst metal species maintained in the ashes. Each of these reaction steps requires a fundamental understanding in order to further develop new high-efficiency gasification and pyrolysis processes for producing both syngas and added-value molecules from biomass. On the basis of both the cumulated expertise and recent results associated to the application of this concept, this communication will focus on key results obtained using series of selected catalyst precursor for which in situ formation of metal nanoparticles during biomass pyrolysis was demonstrated. Fundamental issues regarding the mechanisms involved during biomass impregnation with metal precursors, formation and evolution of metal-based nanoparticles during pyrolysis [2-4], pyrolysis products selectivities and kinetic data associated to the metal/char nanocomposites gasification, will be addressed to depict the promises of this concept while underlining its associated challenges and prospects. (Texte intégral)

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