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Kinetic modeling of catalytic lignin hydroconversion for aromatic production

Abstract : Nowadays, due to the fossil fuels depletion and environmental concerns, transformation of lignocellulosic biomass is becoming a great challenge in order to provide biofuels and biochemicals in a near future. Lignin, which accounts for nearly 30 wt% of lignocellulosic biomass, is the most relevant and abundant bio-resource to produce aromatic compounds because of its original polymeric structure composed by phenylpropane units with ether linkages. In this context, the use of lignin as a precursor of aromatic compounds attracts lots of attention thanks to its low cost and high availability in pulp industry or bio-refinery. In the literature, it appears that an interesting thermochemical method for obtaining high yields of liquid products was the catalytic hydroconversion of lignin. The aim of this work was to investigate the reaction scheme of the catalytic process and develop a kinetic model for catalytic lignin hydroconversion over a sulfided CoMoS/Al2O3. In the first part of this work, kinetic measurements were carried out in a H-donor solvent (tetralin) at 350 °C and 80 bar using a semi-continuous batch reactor, which is opened for gas phase with continuous supply of H2 and equipped with a condensing reflux followed by cooled traps. The recovered products were isolated in four fractions: gases (methane, carbon dioxide, light hydrocarbons, etc.), organic liquid (phenols, aromatics, naphthenes, etc.), THF-soluble and THF-insoluble residues. Thanks to several appropriate analytical tools (GPC, NMR, GCXGC, etc.), the evolution of these different fractions as a function of reaction time was followed in order to understand the transformations occurring during the conversion. Accordingly, a lumped reaction network was established based on the observed reaction schemes. The second part of this work was dedicated to the development of a parameterized kinetic model allowing to have a mathematical description for each reaction step involved in the lignin hydroconversion. Firstly, physical phenomena involved (the gas hydrodynamic behavior of our set-up, the vapor-liquid equilibrium of mixtures and the liquid-gas mass transfer) were characterized. Subsequently, a complete reactor model was constructed by coupling the suitable chemical kinetics and these physical characterizations. Taking the gathered experimental data as a basis, reliable kinetic parameters (rate constants and stoichiometric coefficients) for each reaction step were obtained by means of non-linear regression technique. The resulting model allows us to have an in-depth understanding of the lignin conversion process
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  • HAL Id : tel-02426001, version 1

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Junjie Pu. Kinetic modeling of catalytic lignin hydroconversion for aromatic production. Catalysis. Université de Lyon, 2018. English. ⟨NNT : 2018LYSE1216⟩. ⟨tel-02426001⟩

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